DE102022133633A1 - DEVICES AND METHODS FOR SPUTTERING AT LEAST TWO ELEMENTS - Google Patents

Abstract

According to various aspects, a magnetron sputtering source (104(n)) is provided, comprising: a first target (106(n, 1)) having an annular shape or a circular shape, the first target (106(n, 1)) comprising a first material; a second target (106(n, 2)) having an annular shape, wherein the second target (106(n, 2)) comprises a second material different from the first material and is arranged concentrically to the first target (106(n, 1)); a magnet system (206(n)) configured to generate a first magnetic field through the first target (106(n, 1)) and a second magnetic field through the second target (106(n, 2)), wherein a first field strength distribution of the first magnetic field differs from a second field strength distribution of the second magnetic field.

Description

Technical part

Various aspects relate to devices and methods for sputtering at least a first element and a second element. According to various aspects, the devices and methods enable the creation of a material layer containing the first element and the second element in a predefined atomic ratio.

background

In general, material layers (e.g., thin films) can be created by a variety of physical or chemical vapor deposition processes. For example, a material layer containing two or more elements can be deposited onto a substrate by sputtering (e.g., using a magnetron). In various applications, such as memristive devices or memristors, the properties (e.g., the memristive switching properties) can strongly depend on the stoichiometry of the material, such as the atomic ratio between at least two of the two or more elements. Therefore, to achieve the desired properties, it may be necessary for the deposited material layer to have a predefined stoichiometry (e.g., a predefined atomic ratio between at least two elements). However, when sputtering the two or more elements, several factors can affect the sputtering process and thus the stoichiometry of the finally deposited material layer.

Short description of the drawings

• 1A bis 1C zeigen jeweils zumindest einen Teil eines Systems gemäß verschiedener Aspekte;
• 2A bis 2H zeigen jeweils Aspekte einer entsprechenden Konfiguration einer Sputterquelle, die in der Lage ist, von mindestens zwei Sputter-Targets gemäß verschiedenen Aspekten zu sputtern;
• 3 zeigt beispielhaft eine entsprechende Verdampfungsdruckkurve von Bismut und Eisen als Funktion von Druck und Temperatur;
• 4 zeigt beispielhaft eine funktionale Korrelation zwischen einer ersten Leistung, die zum Sputtern von Bismut angewandt wird, und einer zweiten Leistung, die zum Sputtern von Eisen angewandt wird, um beim reaktiven Sputtern in einer oxidischen Atmosphäre eine Materialschicht zu erzeugen, die im Wesentlichen aus Bismut-Ferrit besteht und ein vordefiniertes Verhältnis zwischen Bismut und Eisen von 1:1 aufweist;
• 5 zeigt beispielhaft die jeweiligen Strom-Spannungs-Charakteristiken von memristiven Bauelementen, die eine gesputterte Bismut-Ferrit-Materialschicht enthalten, abhängig von ihrer Position auf einem Wafer;
• 6 zeigt die Elementverteilung einer Bismut-Ferrit-Materialschicht, die auf ein Platin-Titan-Siliziumoxid-Substrat bei 700°C gesputtert wurde, und die Elementverteilung einer Bismut-Ferrit-Materialschicht, die auf ein Platin-Titan-Siliziumoxid-Substrat bei 600°C gesputtert wurde;
• 7 bis 18 zeigen jeweils ein Flussdiagramm eines entsprechenden Verfahrens zum Sputtern zumindest eines ersten Elements und eines zweiten Elements gemäß verschiedener Aspekte.

In the drawings, like reference characters generally refer to the same parts throughout the several views. The drawings are not necessarily to scale. Emphasis is generally placed upon illustrating the principles of the invention. In the following description, various aspects of the invention are described with reference to the following drawings, in which:

• 1A to 1C each show at least part of a system according to different aspects;
• 2A to 2H each show aspects of a corresponding configuration of a sputter source capable of sputtering from at least two sputter targets according to different aspects;
• 3 shows an example of a corresponding evaporation pressure curve of bismuth and iron as a function of pressure and temperature;
• 4 shows, by way of example, a functional correlation between a first power applied for sputtering bismuth and a second power applied for sputtering iron in order to produce, during reactive sputtering in an oxidic atmosphere, a material layer consisting essentially of bismuth ferrite and having a predefined ratio between bismuth and iron of 1:1;
• 5 shows examples of the respective current-voltage characteristics of memristive devices containing a sputtered bismuth ferrite material layer, depending on their position on a wafer;
• 6 shows the element distribution of a bismuth ferrite material layer sputtered onto a platinum-titanium-silicon oxide substrate at 700°C and the element distribution of a bismuth ferrite material layer sputtered onto a platinum-titanium-silicon oxide substrate at 600°C;
• 7 until 18 each show a flow chart of a corresponding method for sputtering at least a first element and a second element according to various aspects.

Description

The following detailed description refers to the accompanying drawings which, by way of illustration, show certain details and aspects in which the invention may be practiced. These aspects are described in sufficient detail to enable one skilled in the art to practice the invention. Other aspects may be used, and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various aspects are not necessarily mutually exclusive, as some aspects may be combined with one or more other aspects to form new aspects. Various aspects are described in the context of methods, and various aspects are described in the context of devices (e.g., assemblies). It should be understood, however, that aspects described in the context of methods may similarly apply to devices, and vice versa.

The term “element” as used here can refer to a chemical element (e.g. a chemical element of the periodic table).

In some aspects, two physical and/or chemical properties (e.g., an electrical voltage, an electrical current, an electrical conductance, a thickness, an electrical conductivity, a doping concentration) may be compared using relative terms such as "greater," "higher," "lower," "less," or "equal." It is understood that in some aspects, a comparison may include a sign (positive or negative) of a value representing the physical and/or chemical properties, or that in other aspects, the absolute values are considered for the comparison. However, a comparison of measured values representing a physical and/or chemical property may typically include a measurement of such measured values using the same measurement principle or at least using comparable measurement principles.

The term "processor" as used here can be understood as any kind of technical unit that enables the processing of data. The data can be processed depending on one or more specific functions that the processor can perform. Furthermore, a processor as used here can be understood as any kind of circuit, e.g. any kind of analog or digital circuit. A processor can therefore be an analog circuit, a digital circuit, a mixed-signal circuit, a logic circuit (e.g., a hard-wired logic circuit or a programmable logic circuit), a microprocessor (e.g., a CISC (Complex Instruction Set Computer) processor or a RISC (Reduced Instruction Set Computer) processor), a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), an integrated circuit, an ASIC (Application Specific Integrated Circuit), etc., or a combination thereof. A “processor” can also be a logic-implementing unit that executes software, e.g., any type of computer program, e.g., a computer program that uses virtual machine code such as Java. A “processor” as used here can also be any type of cloud-based processing system that enables distributed processing of data, e.g., with a variety of logic implementing units that are communicatively connected to one another (e.g. via the Internet) and each tasked with processing the data or a portion of the data. To illustrate: An application running on a server and the server can also be a "processor". Any other way of implementing the respective functions, which is described in more detail below, can also be understood as a processor. It is understood that two (or more) of the processors described herein can be realized as a single unit with equivalent functionality or the like, and conversely that each individual processor described herein can be realized as two (or more) separate units with equivalent functionality or the like.

The term "memory" as used herein may be understood as a computer-readable medium (e.g., a non-transitory computer-readable medium) in which data or information can be stored for retrieval. When referring to "memory" here, it may mean volatile or non-volatile memory, including random access memory (RAM), read-only memory (ROM), flash memory, solid-state memory, magnetic tape, hard disk drive, optical drive, among others, or any combination thereof. In addition, it goes without saying that registers, shift registers, processor registers, data buffers, among others, are also included in the term memory here. It is also clear that a single component referred to as "memory" or "a memory" may consist of more than one different type of memory and may therefore refer to a collective component that includes one or more types of memory. It is understood that any individual memory component may be divided into several collectively equivalent memory components and vice versa. Even if the memory is shown separately from one or more other components (e.g. in the drawings), the memory may also be integrated into another component, e.g. in a common integrated chip.

Various aspects relate to sputtering at least a first element and a second element to deposit on a substrate a layer of material containing the first element and the second element in a predefined atomic ratio and/or substantially homogeneous properties.

1A shows an exemplary system 100 for sputtering at least the first element and the second element according to various aspects. The system 100 may also be referred to as a sputtering system and/or a processing system.

The system 100 may include a process chamber 102 (may also be referred to as a vacuum chamber). The system may include one or more sputter sources 104(n = 1 to N) (where “N” is any integer equal to or greater than one). Each sputter source 104(n) of the one or more Each sputter source 104(n = 1 to N) may include at least one sputter target 106(n). Each sputter target (short: target) may include one or more elements. Each (eg magnetron) sputter source 104(n) may be configured to sputter the one or more elements that the corresponding at least one sputter target 106(n) includes (eg magnetron). According to various aspects, at least one (eg each) sputter source of the one or more sputter sources 104(n = 1 to N) may be a magnetron sputter source. It is understood that 1A and 1B for illustrative purposes, three sputter sources 104(1), 104(2), 104(3) are shown and that more or fewer sputter sources may be used for the aspects of the disclosure described here. Although 1A and 1B show that each sputter source 104(n) has exactly one sputter target 106(n), a sputter source can have more than one sputter target (see e.g. 2A until 2H and the corresponding description). It is understood that a sputter source 104(n) may include further components, such as electronics for supplying (eg applying) a (eg high) voltage (eg a direct current (DC) or a radio frequency (RF) voltage), a water cooling system, a shutter for blocking or releasing a flow of deposition material toward a substrate, etc. A sputter source 104(n) may, for example, be a magnetron sputter source including one or more magnets configured to generate a magnetic field through the corresponding at least one sputter target 106(n).

The system 100 may include a control system 107. The control system 107 may include one or more controllers (a controller may also be referred to as a controller and/or may include a control device). The one or more controllers of the control system 107 may be communicatively coupled to each other and/or to a master controller (e.g., a computer) configured to control the one or more controllers. Each controller of the one or more controllers may include one or more processors configured to perform the correspondingly described processing (e.g., using memory).

According to various aspects, the control system 107 may include a sputter controller 108. Therefore, the system 100 may include the sputter controller 108. The sputter controller 108 may be configured to control the one or more sputter sources 104 (n = 1 to N). The sputter controller 108 may be configured to control sputtering using the one or more sputter sources 104 (n = 1 to N). As described herein, a sputtering process may depend on a variety of (static and dynamic) parameters and the sputter controller 108 may be configured to control one or more of these parameters to produce a material layer with predefined properties. The sputter controller 108 may include a power supply. The power supply may be configured to apply a corresponding (e.g. DC or RF) (high) voltage to each sputter target of the one or more sputter sources 104 (n = 1 to N) to sputter the one or more elements from the respective sputter target. The power supply may be configured to apply a (high) voltage to a sputter source 104(n) according to a power. Although various aspects relate to applying a voltage to a sputter source 104(n), it is understood that this applies in the case that the sputter source 104(n) includes one sputter target 106(n), and that in the case that a sputter source includes two or more sputter targets, either the same voltage may be applied to the two or more sputter targets or (see e.g. 2F and 2G) the sputter source may include electronics that allow a corresponding voltage to be applied to each sputter target of the two or more sputter targets, and the power supply may be configured to apply a corresponding voltage to each of the two or more sputter targets of the sputter source according to a corresponding power. The sputter controller 108 may include a control device. The control device may be configured to control the power supply.

The system 100 may include a pumping system 110. The processing chamber 102 may be connected to the pumping system 110. The pumping system 110 may be configured to create a negative pressure (e.g., a vacuum) in the processing chamber 102. The pumping system 110 may include one or more vacuum pumps. A vacuum pump may be any type of vacuum pump, such as a high vacuum pump (e.g., a turbomolecular pump, TMP) or a fore-vacuum pump (e.g., a scroll pump, a diaphragm pump, a (e.g., multistage) Roots pump, a diffusion pump, a turbomolecular pump, etc.). The pumping system 110 may include a combination of one or more of the pumps described above (e.g., the pumping system 110 may be or include a pumping station with at least one fore-pump and at least one high vacuum pump). It is understood that the processing chamber 102 can be, for example, air-, dust- and/or vacuum-tight in the closed state in order to achieve and/or maintain the negative pressure. The control system 107 (eg a pump control control system 107) may be configured to control pumping system 110. A negative pressure, as described herein, may be a pressure in a range of about 10 mbar to about 1 mbar (ie, rough vacuum) or less, such as a pressure in a range of about 1 mbar to about 103 mbar (ie, fine vacuum) or less, such as a pressure in a range of about 10-3 mbar to about 107 mbar (ie, high vacuum) or less, such as a vacuum below 107 mbar (ie, ultra-high vacuum).

The system 100 may include one or more gas inlet devices 112. Each gas inlet device of the one or more gas inlet devices 112 may be connected to a gas reservoir (e.g., a gas bottle or cylinder). Each gas inlet device of the one or more gas inlet devices 112 may include or be connected to a mass flow controller (MFC) configured to control the mass flow of the associated gas into the process chamber 102. In various aspects, the control system 107 may include one or more mass flow controllers or be configured to control the mass flow controller(s). Therefore, by admitting one or more gases into the vacuum, an atmosphere may be created in the processing chamber 102 that includes the one or more gases in a composition dependent on the respective mass flow and that has a pressure dependent on the initial pressure of the vacuum and the mass flows of the one or more gases. The system 100 may include one or more pressure sensors configured to sense the pressure in the process chamber 102 and communicate the sensed pressure to the control system 107. Sputtering as described herein may be non-reactive sputtering or reactive sputtering. In non-reactive sputtering, each of the one or more gases may be an inert gas, such as argon (Ar), helium (He), neon (Ne), krypton (Kr), xenon (Xe), etc. In the case of reactive sputtering, at least one of the one or more gases may be an inert gas, such as argon (Ar), and at least one other of the one or more gases may be a gas, such as oxygen (O2), that reacts with at least one of the sputtered elements. The control system 107 may be configured to control the respective gas flow via the one or more gas inlet devices 112 by controlling the corresponding mass flow controller (MFC). According to various aspects, the system 100 may include a mass spectrometer configured to sense the composition of the atmosphere in the process chamber 102 to provide mass spectroscopy data representing that composition to the control system 107. The control system 107 may be configured to control the gas flow (e.g., an oxygen gas flow) based on the mass spectroscopy data. According to various aspects, the system 100 may include an oxygen sensor (e.g., a lambda probe) configured to detect an oxygen content in the atmosphere and provide oxygen data representing that oxygen content to the control system 107. The control system 107 may be configured to determine the partial pressure of oxygen based on the oxygen data and control a flow of oxygen into the processing chamber 102 based on the determined partial pressure of oxygen.

The system 100 may include a sample holder 114 (also referred to as a substrate holder in some aspects). The sample holder 114 may be configured to receive (and optionally attach) a substrate 116 thereon. The substrate 116 may be any suitable substrate having any shape, composition, structure, etc. For example, the substrate may be a wafer (e.g., a 150 mm, 200 mm, 300 mm, or 450 mm wafer). The substrate 116 may include a material layer stack having one or more material layers of different compositions. The substrate 116 may include a variety of structures (e.g., transistors, vias, etc.). Thus, the substrate 116 may be any structural component to which the material layer 122 may be applied.

As described herein, the sputter controller 108 may be configured to control sputtering by the one or more sputter sources 104(n = 1 to N). In response to applying a high voltage (RF or DC) to the sputter target 106(n), inert gas ions (e.g., Ar+) in the atmosphere are accelerated toward the sputter target 106(n), thereby extracting atoms from the sputter target 106(n). In addition, secondary electrons may be emitted from the sputter target 106(n), exciting the ions of the inert gas (e.g., Ar+), thereby igniting a discharge plasma 118(n). The extraction of the atoms from the sputter target 106(n) may create a flow of deposition material 120(n) toward the substrates 116. The atoms within the deposition material stream 120(n) may be deposited on the substrate 116, thereby (gradually) forming a layer of material 122 on the substrate 116.

The system 100 may include a heating device 124 (short: heater 124). The heating device 124 may be configured to heat the sample holder 114 and/or the substrate 116 to a certain temperature. The heating device 124 may be or include a resistive heater. The system 100 may include one or more temperature sensors 126. The one or more temperature sensors 126 may be configured to sense a temperature representing a temperature of the substrate 116 and/or the material layer 122. The temperature representing the temperature of the substrate 116 and/or the material layer 122 may be, for example, a temperature of the sample holder 114, a temperature of the heating device 124, a temperature of the substrate 116, and/or a temperature of the material layer 122. In various aspects, a temperature sensor of the one or more temperature sensors 126 may be part of the sample holder 114 and configured to contact the sample holder 114 or the substrate 116 to sense a temperature thereof. Additionally or alternatively, the one or more temperature sensors 126 may include at least one temperature sensor configured to non-contact sense a temperature of the sample holder 114 and/or the substrate 116 and/or the material layer 122 (e.g., the at least one temperature sensor may be a pyrometer). The control system 107 (e.g., a heater controller) may be configured to control the heater 124 to heat the substrate 116 and/or the material layer 122 to a particular temperature (e.g., using the temperature sensed by the one or more temperature sensors 126).

The system 100 may include one or more plasma detection sensors 128. The one or more plasma detection sensors 128 may be configured to detect plasma characteristics of at least one (e.g., each) plasma 118(n). The one or more plasma detection sensors 128 may be configured to provide data representing the detected plasma characteristics to the control system 107. In various aspects, at least one plasma detection sensor of the one or more plasma detection sensors 128 may be an optical sensor configured to detect plasma characteristics. The plasma properties may be detected using any suitable sensor and/or measurement technique, such as optical emission spectroscopy (OES) (e.g., using OES imaging), interferometry, atomic absorption spectroscopy, and/or layer-induced fluorescence, etc. The control system 107 may be configured to determine a composition of the sputtered elements within the deposition material stream based on the plasma properties (e.g., based on the plasma emission lines and/or the intensities within the detected spectra). For example, the plasma properties may enable the determination of an atomic ratio of the first element to the second element in the deposition material stream(s). In the case of the example described here of (e.g. reactive) sputtering of a BFO material layer, OES can be used, for example, to determine the respective intensities of the (optical) plasma emission lines of bismuth, iron, oxygen, the inert gas (e.g. argon) and optionally titanium. Various aspects described here relate to the control system 107 being configured to perform control aspects based on the plasma properties. In this case, the control system 107 can be configured to perform the control aspects, for example, based on the intensity (or intensities) of at least one of the (optical) plasma emission lines (e.g. more than one). The control system 107 can, for example, be configured to perform the control aspects based on a (mathematical) correlation between two or more of the intensities of the (optical) plasma emission lines. The plasma properties may include electrical properties of the plasma, such as a plasma current, a plasma voltage, a plasma power, a plasma impedance, etc. According to various aspects, the control system 107 may be configured to perform the control aspects, for example, based on the electrical properties of the plasma.

As described herein with reference to various aspects of the disclosure, the system 100 may include one or more additional components 130 (e.g., one or more pressure sensors, a manipulator for controlling the position and/or orientation of the sample holder 114, a manipulator for transporting the substrate 116 into and out of the processing chamber 102, one or more gates, etc.).

As described herein, the system 100 may be in various configurations. In various aspects, the one or more sputter sources 104 (n = 1 to N) may include two or more sputter sources. Sputtering at least a first (chemical) element and a second (chemical) element from two different sputter sources may be referred to as co-sputtering. In some aspects, the two or more sputter sources and the substrate 116 may be arranged such that the two or more sputter sources each have a different focus position on the substrate 116 than at least one other sputter source of the two or more sputter sources. In other aspects, the two or more sputter sources and the substrate 116 may be arranged such that the two or more sputter sources have a substantially have the same focus position on the substrate 116. This can be referred to as confocal co-sputtering of the first element and the second element. As in 1A , the focus position may be substantially the center of the substrate 116. As shown in 1B (showing a portion of system 100), the focus position may also be eccentric. For example, substrate 116 may be a wafer and the stream of deposition material may impinge on the wafer at approximately the center of the wafer radius.

In various aspects, the system 100 may include a motor 132. The motor 132 may be configured to drive the sample holder 114 to rotate (in a predefined direction). The control system 107 (e.g., a motor controller) may be configured to control the motor 132.

In relation to 1C the system 100 may include a linear lamp array 134 (see also bottom view 138). The linear lamp array 134 may be configured to radiate 136 toward the sample holder 114 to heat the material layer 122. It will be understood that the process chamber 102 may include the linear lamp array 134 in addition to or alternatively to the one or more sputter sources 104 (n = 1 to N). In some aspects, the linear lamp array 134 may be configured to irradiate 136 substantially the entire surface of the material layer 122. In other aspects, the linear lamp array 134 may be configured to irradiate only a portion (e.g., one half) of the surface of the material layer 122. In any case, the control system 107 may be configured to control the motor 132 to rotate the sample holder 114.

The heating device 124 may be or include one or more resistive heaters. The one or more resistive heaters may include one or more electrically conductive lines (e.g., in the form of heating coils). The one or more electrically conductive lines of the one or more resistive heaters may be configured (e.g., arranged) such that more heat is generated in an inner region of the sample holder 114 (e.g., in a central portion of the sample holder 114) than in an outer region of the sample holder 114 (e.g., closer to an edge of the sample holder 114). For example, the one or more electrically conductive lines may be configured (e.g., arranged) such that the resistance of the one or more electrically conductive lines is greater in the outer region than in the inner region. For example, the one or more electrically conductive lines may take up more space in the outer region than in the inner region. As an illustrative example, the one or more electrically conductive lines may be configured (e.g., arranged) as one or more heating coils such that more heat is generated in the outer turns than in the inner turns of the one or more heating coils (e.g., because the outer turns have a higher resistance and/or more turns per area compared to the inner turns). Generating more heat in the outer region than in the inner region of the sample holder 114 may compensate for increased cooling in an outer region of the substrate 116 (e.g., ring in the case of a wafer; the outer region of the wafer may also be referred to as the edge region of the wafer), thereby increasing the homogeneity of the material layer 122. According to various aspects, the heating device 124 may be configured to generate a temperature gradient (laterally) across the sample holder 114 (e.g., from the center of a wafer toward the edge region of the wafer). For example, the heat generated may gradually increase from the center of the sample holder 114 toward the edge. Due to the progressive cooling of the edge region of the substrate 116 (e.g., the wafer), the temperature gradient generated by the heater 124 may result in a substantially stable temperature laterally across the substrate 116 (i.e., the substrate 116 has substantially no temperature gradient).

It will be appreciated that when aspects relate to heating of the substrate 116 (e.g., described for the heater by way of example), the heating may be performed by the heater 124 and/or the linear lamp array 134. For example, the temperature of the substrate 116 may depend on both the heating by the heater 124 and the heating by the linear lamp array 134 (which may be heated simultaneously or sequentially, for example).

As described herein, a sputter source 104(n) of the one or more sputter sources 104(n = 1 to N) may include at least one sputter target 106(n). 2A until 2H each show aspects of a corresponding configuration of a sputter source 104(n) that includes at least two sputter targets. The figures show various cross-sectional views 202 (eg, of rotationally symmetric aspects of the sputter source) and various top views 204.

The sputter source 104(n) may include a first target 106(n, 1) and a second target 106(n, 2). In some aspects, the sputter source 104(n) may include more than two targets, such as the first target 106(n, 1), the second target 106(n, 2) and a third target 106(n, 3) (see e.g. 2E) . The innermost target (eg the first target 106(n, 1)) may have a ring-shaped form (see eg 2A) or a circular shape (see e.g. 2C until 2G) Each additional target may have a ring-shaped form and be arranged concentrically to the first target 106(n,1). Therefore, the second target 106(n,2) may have a ring-shaped form and be arranged concentrically around the first target 106(n,1) (see e.g. 2A and 2C until 2G) . The third target 106(n, 3) may have an annular shape and be arranged concentrically to the second target 106(n, 2) (see e.g. 2E) . Each target may contain (eg consist of) one or more elements. According to various aspects, the first target 106(n, 1) may contain at least one first element and the second target 106(n, 2) may contain at least one second element different from the first element. 2D shows, by way of example, a ring-shaped second target 106(n, 2) (in this example consisting essentially of bismuth, Bi) which is arranged concentrically around a circular first target 106(n, 1) (in this example consisting essentially of iron, Fe). In this example, the second target 106(n, 2) has four quarter ring parts. As in 2D As shown, a central portion of the circular first target 106(n,1) has a substantially metallic surface, while an outer region of the circular first target 106(n,1) is oxidized. The annular second target 106(n,2) exhibits iron oxide on an inner portion of the ring, while the central portion of the annular second target 106(n,2) exhibits metallic bismuth. This distribution may affect the composition of the deposition material stream(s) during sputtering.

The sputter source 104(n) may include a magnet system 206(n). The magnet system 206(n) may be configured to generate a first magnetic field through the first target 106(n, 1) and a second magnetic field through the second target 106(n, 2). The magnet system 206(n) may include one or more first magnets 208(n, 1) configured to generate the first magnetic field through the first target 106(n, 1). The magnet system 206(n) may include one or more second magnets 208(n, 2) configured to generate the second magnetic field through the second target 106(n, 2). In the event that the sputter source 104(n) includes more than two sputter targets, the magnet system 206(n) may include one or more magnets for each sputter target of the more than two sputter targets (e.g., one or more third magnets 208(n,3) configured to generate a third magnetic field through the third target 106(n,3), etc.). The magnets described herein may be permanent magnets. However, it is to be understood that the magnets may also be electromagnets.

According to various aspects, the one or more first magnets 208(n, 1) and/or the one or more second magnets 208(n, 2) may have an annular shape (see e.g. 2 B) .

According to various aspects, the first magnetic field may have a first field strength distribution that differs from a second field strength distribution of the second magnetic field. Similarly, the third magnetic field may have a third field strength distribution that differs from the first field strength distribution and/or the second field strength distribution.

In some aspects, the first field strength distribution and/or the second field strength distribution may be preconfigured. In this case, the field strength distributions may be static. For example, the one or more first magnets 208(n,1) may be permanent magnets with a first magnetic field strength and the one or more second magnets 208(n,2) may be permanent magnets with a second magnetic field strength that is different from the first magnetic field strength. In some aspects, the one or more first magnets 208(n,1) may have a different geometry than the one or more second magnets 208(n,2), thereby creating a different field strength distribution. In some aspects, the number of magnets of the one or more first magnets 208(n,1) may differ from the number of magnets of the one or more second magnets 208(n,2), thereby creating a different field strength distribution.

In some aspects, the first field strength distribution and/or the second field strength distribution may be controlled. It is understood that there may be a combination of control and pre-configuration of the field strength distributions. The sputter source 104(n) may include a magnet control device configured to change the position and/or orientation of one or more first magnets 208(n,1) and/or one or more second magnets 208(n,2). In some aspects, only the position and/or orientation of either the one or more first magnets 208(n,1) or the one or more second magnets 208(n,2) may be changed. In other aspects, the position and/or orientation of both the one or more first magnets 208(n,1) and the one or more second magnets 208(n,2) may be changeable. For example, the sputter source 104(n) may include a first motor 210(n, 1) configured to adjust the distance between the one or more first magnet 208(n,1) and the first target 106(n,1). Additionally or alternatively, the first motor 210(n,1) may be configured to change the orientation of the one or more first magnets 208(n,1) relative to the first target 106(n,1). The sputter source 104(n) may include a second motor 210(n,2) configured to change the distance between the one or more second magnets 208(n,2) and the second target 106(n,2). Additionally or alternatively, the second motor 210(n,2) may be configured to change the orientation of the one or more second magnets 208(n,2) relative to the second target 106(n,2). Therefore, the first field strength distribution and/or the second field strength distribution can be controlled by changing the distance to or the orientation relative to the respective target. The orientation can be changed, for example, by tilting the one or more magnets.

In some aspects, the sputter source 104(n) may be configured to apply a voltage to each sputter target (e.g., the first target 106(n,1), the second target 106(n,2), the third target 106(n,3), etc.) (see, e.g., 2A , 2C , 2E) . In other aspects, the sputter source 104(n) may be configured to apply a corresponding voltage to the sputter targets, such that a first voltage may be applied to the first target 106(n, 1), a second voltage to the second target 106(n, 2), a third voltage to the third target 106(n, 3), etc. (see, e.g., 2F and 2G) . According to various aspects, the sputter source 104(n) may be configured such that a different type of sputtering (eg, DC sputtering (eg, continuous DC sputtering or DC pulse sputtering) or RF sputtering) may be performed for the different targets. For example, the sputter source 104(n) may be configured such that the first target 106(n, 1) may be RF sputtered and the second target 106(n, 2) may be DC sputtered (eg, continuous DC sputtering or DC pulse sputtering), or vice versa. In other aspects, the sputter source 104(n) may be configured such that both the first target 106(n,1) and the second target 106(n,2) may be RF or DC sputtered (e.g., both continuously DC, both DC pulses, or one continuously DC and the other DC pulses).

In addition or alternatively to the magnet control device for changing the position and/or orientation of one or more first magnets 208(n, 1) and/or one or more second magnets 208(n, 2) and/or for generating a corresponding magnetic field through each of the sputtering targets, the sputtering source 104(n) may include a target control device configured to change a position and/or orientation of the first target 106(n, 1) and/or the second target 106(n, 2) (e.g., by means of one or more motors) and/or to rotate the first target 106(n, 1) and/or the second target 106(n, 2). In some aspects, the target control device may be configured to change the position and/or orientation of the first target 106(n, 1) and/or the second target 106(n,2) individually. In other aspects, the target control device may be configured to jointly control the position and/or orientation of the first target 106(n,1) and/or the second target 106(n,2). This may enable the first target 106(n,1) and/or the second target 106(n,2) to be moved (e.g., panned or wobbled) and/or tilted during sputtering, thereby increasing the homogeneity of the material layer 122. In various aspects, such as in the case where the sputtering source 104(n) includes a plurality of (e.g., planar) stripe-shaped or strip-like targets, the target control device may be configured to rotate the plurality of targets in the plane, thereby increasing the homogeneity of the material layer 122.

It goes without saying that 2A until 2G show exemplary configurations of a sputter source and that a sputter source 104(n) may include any combination of the components described above.

According to various aspects, the first sputtering target 106(n,1) and the second sputtering target 106(n,1) may have a shape other than an annular or circular shape. For example, the first sputtering target 106(n,1) and the second sputtering target 106(n,1) may have a linear shape. For example, the first sputtering target 106(n,1) and the second sputtering target 106(n,1) may be (e.g., planar) stripe or stripe-shaped targets. According to various aspects, the sputtering source 104(n) may include a plurality of targets in an alternating sequence of targets having at least the first element and targets having at least the second element. As in 2 As shown by way of example, the sputtering source 104(n) may include a first target 106(n, 1) having at least the first element, a second target 106(n, 2) having at least the second element, a third target 106(n, 3) having at least the first element, a fourth target 106(n, 4) having at least the second element, a fifth target 106(n, 5) having at least the first element, a sixth target 106(n, 6) having at least the second element, and a seventh target 106(n, 7) having at least the first element. It is understood that this is only an example and that the sputtering source 104(n) may include any number of sputtering targets. that is equal to or greater than two. Use of the plurality of targets in an alternating sequence of targets having at least the first element and targets having at least the second element can increase the laterally homogeneous nature of the material layer 122. As described above, the target controller can be configured to rotate the plurality of targets in-plane, thereby also increasing the homogeneity of the material layer 122.

In some aspects, the magnet system 206(n) may include one or more magnets configured to generate a magnetic field through all of the targets. In other aspects, the magnet system 206(n) may include a plurality of one or more magnets, each of the magnets configured to generate a respective magnetic field through a respective target of the plurality of targets. As described above, the field strength distribution of a respective magnetic field may be controlled, e.g., by changing the position and/or orientation of the respective magnet(s) 208(n) (e.g., relative to the respective sputtering target).

As described above, the sputter source 104(n) may include or be coupled to one or more motors configured to change the position and/or orientation of the plurality of sputter targets (e.g., together or individually).

In some cases, the same voltage may be applied to the plurality of sputtering targets. In other aspects, the sputtering source may include electronics that enable a corresponding voltage to be applied to each of the plurality of sputtering targets, and the power supply may be configured to apply a corresponding voltage to each of the plurality of sputtering targets of the sputtering source according to a corresponding power.

Several factors (pressure, oxygen partial pressure, power applied to the sputtering source, composition of the target, temperature of the substrate, etc.) may affect the sputtering process. Some of these factors may change over time. For example, the temperature of the substrate and/or the deposited material layer may increase due to atoms impacting the substrate (this is also referred to as temperature drift). For example, the composition of the sputtering target may change over time due to an inhomogeneous material distribution across the depth of the sputtering target and/or (e.g., in case the sputtering target contains two or more elements) due to selective sputtering of some elements. These factors affecting the sputtering process may consequently also affect the material layer 122 (e.g., its overall composition, its composition distribution, its electrical properties, etc.).

Various aspects relate to (actively) controlling the sputtering process to produce the material layer 122 such that it has predefined properties (e.g., a predefined atomic ratio of two elements, substantially homogeneous properties, a substantially homogeneous composition, etc.). Various aspects of controlling the sputtering are described below as an example for the system 100. It is understood that the control aspects can be implemented in any other system that is capable of sputtering at least two elements under the conditions described in each case. It is understood that the control aspects described below can be combined with each other if necessary (e.g., a temperature-based control can be combined with a control based on the plasma properties). For illustration, various aspects for producing a bismuth ferrite (BiFeO3, BFO for short) material layer with predefined properties are described. For example, the BFO material layer can be produced as part of forming one or more memristive devices. The predefined properties may be or include predefined (e.g., analog) memristive switching properties. For example, a plurality of memristive devices may be formed with the BFO material substantially having the predefined properties, resulting in homogeneous switching properties. The BFO material layer may be polycrystalline. According to various aspects, the BFO may be deposited on a wafer (as substrate 116).

According to various aspects, at least a first element (e.g. Bi) and a second element (e.g. Fe) may be sputtered using the one or more sputter sources 104 (n = 1 to N). It has been found that in case the first element has a higher temperature-dependent evaporation rate (e.g. from the substrate and/or from the material layer 122) than the second element, a characteristic temperature value exists that allows, when setting a temperature of the substrate 116 and/or the material layer 122 equal to or greater than the characteristic temperature value, to create the material layer 122 such that it has a predefined atomic ratio between a first element and a second element. It has been found that if the first element and the second element are sputtered such that their deposition material stream(s) 118(n) have an atomic ratio between a first element and a second element that is greater than the predefined atomic ratio (therefore, there may be an excess of atoms of the first element) and when the temperature of the substrate 116 and/or the material layer 122 is equal to or greater than the characteristic temperature value, the material layer 122 can be created to have the predefined atomic ratio between a first element and a second element. Due to the higher temperature-dependent evaporation rate, at temperatures equal to or greater than the characteristic temperature value, a higher number of atoms of the first element than atoms of the second element can be evaporated from the substrate 116 and/or the material layer 122, so that the material layer 122 has the predefined atomic ratio. In this case, atoms of the first element that are not incorporated into a (stable) phase of the material layer 122 can be evaporated from the surface of the material layer 122. The number of atoms evaporated from the surface can be described by the adhesion coefficient, which defines the ratio between the number of atoms/ions impacting the substrate and the number of atoms/ions remaining on the surface of the material layer (i.e., not evaporated).

The first element and the second element may be sputtered with a single sputtering target 106(n) or with two different sputtering targets attached to a common sputtering source 104(n) or to two different sputtering sources. In some aspects, when using two different targets, one target of the two different targets may consist essentially of the first element and the other target of the two different targets may consist essentially of the second element. In other aspects, when using two different targets, one target of the two different targets may include both the first element and the second element and the other target of the two different targets may consist essentially of either the first element or the second element.

The characteristic temperature may depend on the configuration of the system 100 (e.g., size of the process chamber 102, arrangement of the one or more sputter sources 104 (n = 1 to N), gas flow within the process chamber 102, whether a single target or two different targets are used, etc.), sputtering settings (e.g., a first power value of a first power used for sputtering the first element, a second power value of a second power used for sputtering the second element, an oxygen partial pressure, a mass flow, a pressure within the process chamber 102, etc.), and on the first element and the second element (e.g., their temperature dependent evaporation rate). The sputter controller 108 may be configured to control the one or more sputter sources 104 (n = 1 to N) to sputter the first element and the second element such that the deposition material stream(s) contain an atomic ratio between a first element and a second element that is greater than the predefined atomic ratio. The control system 107 may be configured to determine the characteristic temperature value based on the configuration of the system 100, the sputter settings, and/or information about the first element and the second element. The control system 107 (e.g., the heater controller) may be configured to control the heater 124 to heat the substrate 116 and/or the material layer 122 to a temperature equal to or greater than the characteristic temperature value (e.g., prior to sputtering the first element and the second element).

As described, the temperature dependent evaporation rate of the first element may be greater than the temperature dependent evaporation rate of the second element. In various aspects, at temperature values equal to or greater than the characteristic temperature value, the temperature dependent evaporation rate of the first element may be at least twice (e.g., at least three times, such as at least four times) the temperature dependent evaporation rate of the second element.

The characteristic temperature value may represent a vapor pressure (also referred to as vaporization pressure) of the first element at a (working) pressure of the atmosphere in which the deposition material stream is generated. As an example, the first element may be bismuth and the second element may be iron. 3 shows, by way of example, an evaporation pressure curve 302 of bismuth and an evaporation pressure curve 304 of iron. As shown, the temperature-dependent evaporation rate of bismuth is significantly greater than the temperature-dependent evaporation rate of iron. The evaporation pressure curve 302 of bismuth can indicate the characteristic temperature value (ie the temperature value corresponding to the pressure value described by the evaporation pressure curve 302) for a certain (working) pressure value of the atmosphere (ie the pressure of the atmosphere in which the sputtering is carried out). The evaporation pressure curve 302 of bismuth can have a non-evaporation region 306 at temperatures below the characteristic temperature value and an evaporation region 308 at temperatures equal to or greater than the characteristic temperature value. In the non-evaporation region 306, excess bismuth (i.e., bismuth that is not incorporated into the (stable) phase of the material layer 122) cannot be evaporated from the surface of the material layer 122 and thus be included in the material layer 122, resulting in a bismuth concentration that is greater than the predefined atomic ratio. In the evaporation region 308, excess bismuth (e.g., metallic bismuth) can be evaporated from the surface of the material layer 122, whereby the material layer 122 can be created with the predefined atomic ratio. As in 3 As shown, the evaporation pressure curve 304 of iron is essentially independent of temperature compared to the evaporation pressure curve 302 of bismuth. Therefore, the atomic ratio between bismuth and iron atoms can depend significantly on the evaporation of the bismuth atoms. As shown in 3 As shown, the characteristic temperature value may range from about 600°C to about 650°C (e.g., about 630°C for a working pressure of about 0.2* 10 ^-2 mbar) depending on the atmospheric pressure in the process chamber 102 (and, as described herein, depending on the configuration of the system 100).

As described herein, the sputtering may be non-reactive sputtering or reactive sputtering. For example, bismuth and iron may be reactively sputtered and the atmosphere may include oxygen (eg, in addition to the inert gas). The predefined properties of the material layer 122 may, for example, include a predefined phase, such as bismuth ferrite (BiFeO ₃ ), with a predefined atomic ratio between bismuth and iron (eg, 1:1).

According to various aspects, there may be an upper temperature threshold (a threshold may also be referred to as a limit value). For example, the substrate 116 may contain (e.g. on its surface) a layer with a material that can (unintentionally) diffuse into the material layer 122 at temperatures above the upper temperature threshold. The temperature value to which the substrate 116 or the material layer 122 is heated may thus be in a temperature range defined by a lower and an upper threshold. The characteristic temperature value may be the lower threshold value or the lower threshold value may be determined based on the characteristic temperature value.

Regarding the example of the deposition of the BFO material layer: In case the BFO material layer is deposited over a metal electrode layer (e.g. titanium and/or platinum), temperatures above the upper threshold may lead to (unintended) stresses (e.g. compressive or tensile stresses) within the metal electrode layer and/or to (unintended) diffusion of a metal material of the metal electrode layer into the BFO material layer. 6 shows the element distribution of a bismuth ferrite material layer sputtered onto a substrate 116. Here, the substrate 116 may include a silicon wafer, a silicon oxide layer over the silicon wafer, a titanium layer over the silicon oxide layer, and a platinum layer over the titanium layer. 6 shows an element distribution 602 for the deposition of the BFO material layer at 700°C and an element distribution 602 for the deposition of the BFO material layer at 600°C. As shown, when sputtering at 700°C, the platinum atoms of the platinum layer may diffuse into the BFO material layer. This may, for example, lead to a reduced breakdown voltage of a corresponding memristive device. When sputtering at 600°C, on the other hand, there is essentially no diffusion of platinum atoms into the BFO material layer. According to various aspects, a Fe2 O3 layer may be deposited over the platinum layer before the BFO material layer is deposited. This may slightly increase the deposition temperature (since the Fe2 O3 layer may serve as a diffusion barrier). As an example, the upper threshold may have a temperature value of approximately 650°C. In some aspects, diffusion of titanium atoms from the titanium layer into the BFO material layer may serve to produce titanium-doped bismuth ferrite.

Deposition of the material layer 122 at temperatures equal to or higher than the characteristic temperature may enable the material layer 122 to have a substantially homogeneous stoichiometry distribution (e.g., laterally) across the entire substrate 116 (e.g., wafer) because the excess of bismuth atoms may be provided across the entire substrate 116 and the homogeneous stoichiometry may be created by evaporating the excess bismuth atoms from the surface of the material layer 122.

It is understood that the principles are described by way of example for the first element and the second element and that one or more additional elements (from a (eg, the) common sputtering target with at least one of the first element and/or the second element and/or from another sputtering target (using the same sputtering source or a different sputtering source)) may be sputtered using the one or more sputtering sources 104 (n = 1 to N) to form the material layer 122. The temperature dependent evaporation rate of the one or more additional elements may be less than the temperature dependent evaporation rate of the first element. For example, a third element may be sputtered at a temperature dependent evaporation rate that substantially matches the temperature dependent evaporation rate of the second element. For example, in the example where the first element is bismuth and the second element is iron, the third element may be titanium (eg, to produce titanium-doped bismuth ferrite (Ti:BiFeO ₃ )).

However, using a sputtering temperature (i.e., a temperature of the substrate 116 and/or the material layer 122) that is equal to or greater than the characteristic temperature value may limit the sputtering process to using elevated temperatures and/or to a predefined temperature range (e.g., in case of a higher threshold value). Therefore, it may be desirable to create the material layer 122 with predefined properties even at temperatures below the characteristic temperature value. For example, the substrate 116 may include elements that (unintentionally) diffuse into the material layer 122 at temperatures equal to or greater than the characteristic temperature value, thereby possibly not achieving the predefined properties. As another example, the substrate 116 may include one or more components that have one or more elements that may (unintentionally) diffuse at temperatures equal to or greater than the characteristic temperature value, thereby affecting the properties of the one or more components. The substrate 116 may, for example, include a complementary metal oxide semiconductor (CMOS) structure with one or more elements. Therefore, the substrate 116 (e.g., a wafer) may be associated with a thermal budget that sets an upper limit for the temperature for sputtering the first and second elements. Therefore, in this case, it may not be possible to sputter at temperatures equal to or higher than the characteristic temperature value. Various control aspects are described below that allow to create the material layer 122 with the predefined properties below the characteristic temperature value. This may, for example, increase the flexibility of the sputtering process and allow to create the material layer 122 by sputtering when the substrate 116 includes one or more critical components that limit the thermal budget.

Regarding the example of the deposition of the BFO material layer, the deposition of the BFO material layer at temperatures below the characteristic temperature may be necessary to reduce the diffusion of platinum into the BFO material layer and thereby increase the stability of the electrode layer (e.g., the bottom electrode) and thus the memristive switching properties of the fabricated memristive device(s).

The deposition of the BFO material layer at temperatures higher than the upper threshold may lead to an (unintended) stress (e.g. compressive stress or tensile stress) within the metal electrode layer and/or to an (unintended) diffusion of a metal material of the metal electrode layer into the BFO material layer.

According to various aspects, the control system 107 may be configured to receive (eg, continuously) a temperature value representing the temperature of the substrate 116 and/or the material layer 122 via the one or more temperature sensors 126. The control system 107 may be configured to receive (eg, continuously) the plasma properties during sputtering via the one or more plasma detection sensors 128. The sputtering process may be performed using a variety of operating parameters. An operating parameter of the plurality of operating parameters may, for example, be a first power value of a first power used to sputter the first element, a second power value of a second power used to sputter the second element, a power ratio between the first power and the second power, a first sputtering rate at which the first element is sputtered, a second sputtering rate at which the second element is sputtered, a sputtering ratio between the first sputtering rate and the second sputtering rate, a pressure of the atmosphere within the process chamber 102, an oxygen mass flow (e.g., set via a corresponding mass flow controller) into the process chamber 102, the set temperature to which the heater 124 is to heat the substrate 116 and/or the material layer 122, (in the case of RF sputtering) a first power frequency used to sputter the first element, a second power frequency used to sputter the second element, a frequency ratio between the first power frequency and the second power frequency, etc. The control system 107 may be configured to control (eg continuously) one or more operating parameters of the plurality of operating parameters based on the (received) temperature value and/or the (received) plasma properties to produce the material layer 122 with the predefined properties (below the characteristic temperature value). This enables the production of BFO material layers with predefined defined memristive switching properties over the entire substrate 116 (e.g. the wafer).

As described herein, the plasma properties (as sensed by one or more plasma detection sensors 128) may enable a composition of the sputtered elements within the deposition material stream to be determined, such as an atomic ratio of the first element to the second element within the deposition material stream(s). In various aspects, the composition and/or atomic ratio may change during sputtering (e.g., due to thinning of at least one sputtering target). The control system 107 may be configured to adjust at least one of the one or more operating parameters to compensate for these changes so that the composition and/or atomic ratio may be maintained substantially stable during sputtering. For example, if the control system 107 determines from the plasma properties that the atomic ratio between a first element and a second element is increasing, the control system 107 may be configured to control the at least one operating parameter to increase the sputtering rate of the second element (e.g., by increasing the second power) and/or decrease the sputtering rate of the first element (e.g., by decreasing the first power), and vice versa. In the case of reactive sputtering, the plasma properties may indicate an oxygen content, and the control system 107 may be configured to control an oxygen flow into the processing chamber 102 if the oxygen content changes. In various aspects, the control system 107 may be configured to control the oxygen flow into the processing chamber 102 based on the one or more operating parameters. For example, if a power and/or power ratio is changed, the oxygen flow may be changed accordingly.

According to various aspects, the control system 107 (e.g., the sputter controller 108) may be configured to control the first power and/or the second power as an operating parameter of the one or more operating parameters. The control system 107 (e.g., the sputter controller 108) may be configured to control a power ratio between the first power and the second power as an operating parameter of the one or more operating parameters. Therefore, the control system 107 may be configured to determine a power ratio (in some aspects referred to as a nominal power ratio) between the first power and the second power based on the (received) temperature value and/or the (received) plasma properties and then control the first power and the second power according to the determined power ratio. Thus, the first power and/or the second power (e.g. only the first power or only the second power or both the first power and the second power) may be varied such that the ratio between the first power and the second power (i.e. a ratio between their respective values) substantially corresponds to the determined power ratio. With respect to the example of the creation of a bismuth ferrite (BFO) material layer with predefined properties, 4 a graph 400 representing (for an exemplary configuration of the system 100) a correlation 402 between the first power (i.e., the power used to sputter bismuth) and the temperature of the substrate 116 when the second power (i.e., the curve 402 thus allows one to determine, for a particular temperature value, a power ratio between the first power (i.e., a data point on the curve 402 at the particular temperature value) and the second power (i.e., 1000 W in this example).) It is illustrated that the power ratio may be a function of temperature. As shown, at a temperature value of about room temperature (about 25°C), the first power may be about 750 W (resulting in a power ratio of about 0.75), at a temperature value of about 450°C, the first power may be about 500 W (resulting in a power ratio of about 0.5), and at a temperature value of about 600°C, the first power may be about 400 W (resulting in a power ratio of about 0.4). Thus, in this example, the sputter controller 108 may be configured to control the one or more sputter sources 104 (n = 1 to N) to decrease the power ratio of the first power to the second power (e.g., by decreasing the first power and/or by increasing the second power) as the temperature of the substrate increases and/or to increase the power ratio of the first power to the second power (e.g., by increasing the first power and/or by decreasing the second power) as the temperature of the substrate decreases. As shown, a corresponding temperature value may be associated with a particular sputtering rate ratio between a sputtering rate for the first element and a sputtering rate for the second element. Therefore, one or more operating parameters may be adjusted based on the temperature of the substrate 116 to adjust the sputtering rate ratio.

Therefore, both altered plasma properties and a changed temperature can be achieved by changing the sputtering rate ratio It is therefore self-evident that the control aspects described on the basis of temperature can apply analogously to the control aspects described on the basis of plasma properties and vice versa.

According to various aspects, the one or more operating parameters may include the pressure of the atmosphere in the process chamber 102. The sputtering rate at which the first element is sputtered and/or the second sputtering rate at which the second element is sputtered may depend on the pressure of the atmosphere. Therefore, the control system 107 may be configured to control the pressure in the process chamber 102 (e.g., by changing a gas flow into the process chamber 102 and/or by changing a suction power of the pump system 110 (e.g., by opening or closing a gate connected to the pump system 110)) based on the temperature of the substrate 116 and/or based on the plasma properties (e.g., to adjust the sputtering rate ratio).

As described herein, the temperature of the substrate 116 means the temperature that represents the temperature of the substrate 116 (e.g., the temperature of the heater 124 and/or the temperature of the material layer 122).

In various aspects, the control system 107 may be configured to set a temperature to which the heater 124 is to be heated prior to sputtering and determine the power ratio based on the set temperature. Also during sputtering, the control system 107 may continuously receive the temperature sensed by the one or more temperature sensors 126 and determine a power ratio based on the temperature and then control the first power and/or the second power according to the power ratio.

According to various aspects, the first element may be sputtered at a first frequency and the second element may be sputtered at a second frequency. The control system 107 (e.g., the sputter controller 108) may be configured to control the first frequency and/or the second frequency as an operating parameter of the one or more operating parameters. The control system 107 (e.g., the sputter controller 108) may be configured to control a frequency ratio between the first frequency and the second frequency as an operating parameter of the one or more operating parameters. Therefore, the control system 107 may be configured to determine a frequency ratio (referred to as a nominal frequency ratio in some aspects) between the first frequency and the second frequency based on the (received) temperature value and/or the (received) plasma properties and then control the first frequency and/or the second frequency according to the determined frequency ratio.

According to various aspects, the first element may be sputtered with DC pulses and the second element may be sputtered with DC pulses. The control system 107 (e.g., the sputter controller 108) may be configured to control first pulse characteristics (a pulse duration, a pulse rate, and/or a pulse power) of the pulses associated with the DC pulse sputtering of the first element and/or second pulse characteristics (a pulse duration, a pulse rate, and/or a pulse power) of the pulses associated with the DC pulse sputtering of the second element as operating parameters of the one or more operating parameters. The control system 107 (e.g., the sputter controller 108) may be configured to control a ratio between the first pulse characteristics and the second pulse characteristics (e.g., a ratio between pulse durations, a ratio between pulse rates, a ratio between pulse powers, etc.) as an operating parameter of the one or more operating parameters. The control system 107 may be configured to determine the ratio based on the (received) temperature value and/or the (received) plasma characteristics and then control the first pulse characteristics and/or the second pulse characteristics according to the determined ratio.

According to various aspects, the system 100 may include a surface roughness sensor (e.g., an optical roughness sensor) configured to sense a surface roughness of the material layer 122 (e.g., during deposition). The surface roughness may depend on a stoichiometry (e.g., the atomic ratio between a first and a second element). The surface roughness sensor may be configured to provide roughness data representing the sensed surface roughness to the control system 107. The control system 107 may be configured to determine the one or more operating parameters based on the surface roughness. For example, in the event that the roughness data indicates that the atomic ratio falls below the predefined atomic ratio, the control system 107 may be configured to control the one or more sputter sources based on the adjusted one or more operating parameters to adjust at least one sputtering rate to increase the atomic ratio, and vice versa.

As in 2A until 2G As described, a (magnetron) sputtering source 104(n) of the one or more sputtering sources 104(n = 1 to N) may be configured to enable control of the first magnetic field and/or the second magnetic field. It is understood that a single target sputtering source 104(n) may also include a magnet system that enables control of the magnetic field by the single target. According to various aspects, the control system 107 (e.g., the sputter controller 108) may be configured to control the first magnetic field associated with sputtering the first element and/or the second magnetic field associated with sputtering the second element as an operating parameter of the one or more operating parameters. The control system 107 (e.g., the sputter controller 108) may be configured to control a field ratio between the first magnetic field and the second magnetic field as an operating parameter of the one or more operating parameters. Adjusting the first magnetic field and/or the second magnetic field may change the composition of the deposition material stream(s) and thus the atomic ratio between a first element and a second element. The control system 107 may be configured to control the first magnetic field and/or the second magnetic field based on the plasma properties (e.g., to adjust the sputtering rate of at least one of the first and second elements) and/or based on the temperature of the substrate (e.g., since a different temperature may require a different (e.g., optimal) sputtering rate). As described herein, a magnetic field may be changed by controlling the corresponding magnet or magnets to change the distance between the one or more magnets and the corresponding sputtering target and/or to change the orientation relative to the corresponding sputtering target (e.g., by tilting the one or more magnets). For example, the field ratio between the first magnetic field and the second magnetic field may be controlled by controlling a distance ratio between the first distance of the one or more first magnets to the first target and the second distance of the one or more second magnets to the second target. In the example of depositing the BFO material layer, the first magnetic field through the target containing bismuth may have a first magnetic field strength and the second magnetic field through the target containing iron may have a first magnetic field strength that is greater than the second magnetic field strength.

It will be appreciated that the control system 107 may be configured to control the one or more operating parameters based on both the temperature of the substrate and the plasma properties. For example, the control system 107 may be configured to control the one or more operating parameters using a first and a second control loop. Within the first control loop, the control system 107 may adjust at least one of the one or more operating parameters based on the temperature of the substrate (e.g., by controlling the power ratio, as in 4 illustrated). Within the second control loop, the control system 107 may adjust at least one operating parameter of the one or more operating parameters based on the plasma characteristics. In various aspects, a first cycle of the first control loop may differ from a second cycle of the second control loop. The first cycle may indicate a first time interval in which the operating parameters are adjusted, and the second cycle may indicate a second time interval in which the operating parameters are adjusted. As described herein, the temperature of the substrate may be set on the heater 124 and may change (slightly) due to temperature drift caused by impinging atoms. Therefore, the rate at which the one or more operating parameters are adjusted may be less than the rate of the second cycle (i.e., in a given period of time, the one or more operating parameters may be adjusted more frequently based on the plasma characteristics than on the temperature of the substrate). For example, the one or more operating parameters may be adjusted every 2 seconds based on the plasma characteristics and every 20 seconds based on the temperature of the substrate.

When a material layer is sputtered onto a substrate (e.g., a wafer) having a lateral size larger than a predefined threshold, the properties of the material layer may vary laterally. For example, the stoichiometry of the material layer 122 on the substrate 116 may vary laterally. 5 shows, by way of example, the current-voltage characteristics of memristive components that contain a sputtered bismuth ferrite material layer. Diagram a) shows the memristive switching properties for various memristive components S2, S3, S4 in a first wafer position, and diagram b) shows the memristive switching properties for various memristive components S2, S3, S4 in a second wafer position that differs from the first wafer position. As shown, the memristive switching properties (the current-voltage characteristic) of the memristive components can vary depending on the lateral position on the wafer. The memristive components at the first wafer position only show hysteresis at positive tive voltages, while the memristive components at the second wafer position exhibit a corresponding hysteresis at both positive and negative voltages.

In various aspects, the material layer 122 may be deposited using a configuration of the system 100 that includes the motor 132 for rotating the sample holder 114 and in which the one or more sputter sources are off-center focused (having the same or different focal points) (see, for example, 1B) . As an example, the first target 106(1) of the first sputtering source 104(1) may include the first element and the second element, and the focus of the first sputtering source 104(1) may be eccentric on the substrate 116. As another example, the first sputtering source 104(n) may include the first target 106(1,1) including (e.g., consisting essentially of) the first element and another target 106(1,2) including (e.g., consisting essentially of) the second element, and the focus of the first sputtering source 104(1) may be decentered on the substrate 116. As an even better example, the first target 106(1) of the first sputtering source 104(1) may include the first element and the second target 106(2) of the second sputtering source 104(2) may include the second element, and the first sputtering source 104(1) may have a first focus that is off-center on the substrate 116 and the second sputtering source 104(2) may have a second focus that is off-center on the substrate 116. The second focus may be the same as the first focus (in the case of confocal co-sputtering of the first element and the second element) or the second focus may be different from the first focus. In various aspects, the substrate 116 may be a wafer and the first focus and/or the second focus may be at a position approximately halfway along the radius of the wafer.

The control system 107 (e.g., the motor controller) may be configured to rotate the sample holder 114 at a rotation speed (may also be referred to as rotation frequency) equal to or greater than a predefined rotation speed. The predefined rotation speed may mean that upon one revolution (e.g., revolution) of the substrate 116, a sublayer of the material layer 122 is formed with a thickness of approximately one lattice constant of a crystal structure associated with a predefined phase of the material layer 122. This may make it possible to create memristive devices having substantially homogeneous properties (laterally) across the entire substrate 116. It has been shown that in case the rotation (e.g., revolution) of the substrate 116 is less than the predefined rotation speed, diffusion processes may lead to the creation of phases other than a predefined phase with the predefined properties. Therefore, the predefined rotation speed may depend on the deposition rate at which the material layer 122 is deposited. The control system 107 may be configured to determine the predefined rotation speed based on the deposition rate. According to various aspects, the control system 107 may be configured to determine the predefined rotation speed depending on the deposition rate. As described herein, the control system 107 may be configured to control and adjust one or more operating parameters of the sputtering process during sputtering. Thus, when one or more operating parameters are adjusted, e.g., to adjust the sputtering rate of the first element and/or the sputtering rate of the second element, the deposition rate may change. Therefore, the control system 107 may be configured to also adjust the predefined rotation speed (also referred to as a predefined rotation speed value) based on the one or more operating parameters. In various aspects, the control system 107 may be configured to determine a rotation speed value equal to or greater than the predefined rotation speed value and control the motor 132 to rotate the substrate 116 according to the determined rotation speed value. Additionally, the diffusion processes may depend on the temperature of the material layer 122. Therefore, the predefined rotation speed (value) may also depend on the temperature of the material layer 122. Therefore, the control system 107 may be configured to also adjust the predefined rotation speed (value) based on a temperature representing the temperature of the material layer 122 (e.g., the temperature of the substrate 116). As described herein, the temperature of the substrate 116 may vary during deposition of the material layer 122.

In an example: The control system 107 may determine the predefined rotation speed prior to sputtering and control the motor 132 to rotate the substrate 116 at a rotation speed equal to or greater than the predefined rotation speed (value). During deposition, the control system 107 may adjust the one or more operating parameters based on the temperature of the substrate 116 (and optionally further based on the plasma properties) (as described herein). This adjustment of the one or more operating parameters may affect the sputtering rate of the first element and/or the second element and thus change the deposition rate. Therefore, the control system 107 may also adjust the predefined rotation speed based on the one or more operating parameters (according to the changed deposition rate) and, since the temperature of the substrate 116 also changes the diffusion processes, also based on the temperature of the substrate 116.

According to different aspects, the rotation speed can be more than 60 revolutions per minute.

The deposition rate may have a lower threshold corresponding to a minimum required power to atomize the respective element with the corresponding power. Therefore, the deposition rate cannot be reduced to a value below the lower threshold. This simultaneously means that there may be a lower value for the predefined rotation speed. Therefore, it may be necessary to configure the system 100 so that the rotation speed is as high as possible to enable a wider range of deposition rates.

In the example of depositing the BFO material layer (ie, with bismuth ferrite as the predefined phase), the lattice constant of bismuth ferrite (BiFeO ₃ ) is approximately 0.563 nm. The control system 107 may be configured to determine the predefined rotation speed (value) such that in one rotation (eg, revolution) of the substrate 116, a layer of approximately 0.563 nm is formed at a certain (eg, current) deposition rate and may then determine a rotation speed value equal to or greater than the determined rotation speed value.

As described herein, in case the rotation (e.g., revolution) of the substrates 116 is less than the predefined rotation speed, diffusion processes may lead to the formation of phases other than the predefined phase (e.g., BFO). These other phases may have a different lattice constant than the predefined phase. According to various aspects, the control system 107 may be configured to determine the predefined rotation speed also based on the lattice constants of the other (possible) phases. Thus, the control system 107 may consider the phase with the lowest lattice constant. The control system 107 may be configured to determine the predefined rotation speed such that upon rotation (e.g., revolution) of the substrate 116, a sublayer of the material layer 122 is formed with a thickness of approximately one lattice constant of a crystal structure belonging to a (possible) phase of the material layer 122 (wherein the (possible) phase has a lowest lattice constant of the (possible) phases of the material layer 122). In the example of deposition of the BFO material layer (i.e., with bismuth ferrite as predefined phase), the lattice constant of bismuth oxide ( _Bi2O3 ) (as a possible phase) is approximately 0.566 nm and the lattice constant of iron oxide ( _Fe2O3 ) (as a possible phase) is approximately 0.84 nm. Therefore, in this example, the lattice constant of BFO may be the lowest lattice constant of the possible phases. This may prevent a monolayer of bismuth oxide or iron oxide from forming. For example, at temperatures of approximately 650°C, these monolayers can be stable and prevent the formation of the predefined BFO phase.

According to various aspects, the material layer 122 may be irradiated during and/or after sputtering using the linear lamp arrangement 134. The control system 107 may be configured to control the motor 132 to rotate the sample holder 114 at a certain speed during irradiation. It has been shown that the irradiated (e.g., temperature-treated) material layer 122 may have inhomogeneous properties due to the linear arrangement of the lamps (e.g., between a region located in the direction below the lamps and a region located between two adjacent lamps) and that rotating the material layer 122 (e.g., by rotating the sample holder 132) results in substantially homogeneous properties in the transverse direction of the material layer 122.

As described herein, the first and second elements (and optionally the third element and/or oxygen) may be sputtered from common targets and/or from different targets, and in the case of different targets, they may be applied to the same sputtering source or to different sputtering sources. In the event that a sputtering target includes one of the elements, the sputtering target may also include other elements. It is also understood that the first element and the second element may be sputtered from a common target and at the same time the first element and/or the second element may be sputtered from another sputtering source(s). The control aspects described herein may be applicable to any of these configurations unless explicitly stated otherwise. Various exemplary sputtering scenarios are described below for the example of deposition of the BFO material layer:

According to various aspects, bismuth and iron can be sputtered reactively (ie in an oxygen atmosphere) to form the BFO material layer. In some aspects, bismuth and iron may be sputtered from a common target. In other aspects, bismuth and iron may be sputtered from two different targets (attached to the same sputtering source or to different sputtering sources). Bismuth may be sputtered from a first target and iron may be sputtered from a second target. In some cases, the first target may consist essentially of bismuth and the second target may consist essentially of iron.

The simultaneous sputtering of two or more elements (e.g. from two different targets) can be referred to as co-sputtering of the two or more elements.

According to various aspects, bismuth, iron and oxygen may be sputtered to create the BFO material layer (e.g., non-reactive). Again, any suitable configuration of sputtering target(s) may be used. For example, bismuth, iron and oxygen may be sputtered from a common BFO target (e.g., with an atomic ratio between bismuth and iron that is greater than the predefined atomic ratio). Alternatively to the common target or in addition to the common target, bismuth may be sputtered from a first target and iron from a second target (different from the first target). In this case, the first target and/or the second target may further contain oxygen (e.g., the first target may be a bismuth oxide target and/or the second target may be an iron oxide target).

Further, as described herein, elements such as the third element may be sputtered. The third element may be, for example, titanium (Ti). In this case, the BFO material layer may be a titanium-doped BFO material layer (Ti:BiFeO ₃ ). The titanium-doped BFO material layer may be reactively or non-reactively deposited as described herein. In any case, at least one sputtering target may include titanium. In some cases, titanium may be sputtered from a titanium sputtering target (i.e., a target consisting essentially of titanium) or a titanium oxide sputtering target (i.e., a target consisting essentially of titanium oxide). In this case, the control system 107 may be configured to control the sputtering of titanium such that the sputtering target burns continuously, and an aperture associated with the sputtering source to which the sputtering target is attached may be opened/closed to control the titanium content in the deposition material stream. Alternatively or in addition to the sputtering target made of titanium, at least one of the other sputtering targets may also contain titanium. For example, the common BFO target may contain titanium (e.g., it may be a titanium-doped BFO target). For example, one or more of the following elements may contain titanium: a bismuth target (i.e., a target consisting essentially of (metallic) bismuth), an iron target (i.e., a target consisting essentially of (metallic) iron), a bismuth oxide (i.e., a target consisting essentially of bismuth oxide) and/or an iron oxide (i.e., a target consisting essentially of iron oxide), etc.

Various aspects relate to control aspects based on the temperature of the substrate 116 and/or the plasma properties. When adjusting one or more operating parameters of the sputtering, the sputtering rates of the first element (e.g., Bi) and/or the second element (e.g., Fe) may change, resulting in a change in the composition of the deposition material stream(s). Therefore, the control system 107 may be configured to also adjust one or more operating parameters associated with sputtering the third element (e.g., Ti) to produce the material layer 122 (e.g., the BFO material layer) having a predefined concentration of the third element (e.g., Ti).

In various aspects, the substrate 116 may include a complementary metal oxide semiconductor (CMOS) structure and a metallization structure (e.g., having one or more metallization layers) over the CMOS structure. The system 100 may be configured to form at least a portion of one or more memristive devices over the metallization structure. For example, the system 100 may include an electrode layer over the metallization structure, or the substrate 116 may already include the electrode layer. The electrode layer may include, for example, a platinum layer and a titanium layer. The system 100 may be configured to deposit the BFO material layer 122 (having predefined memristive properties) over the electrode layer (using any type of deposition described herein).

The CMOS structure may have a thermal budget that only allows temperatures below the characteristic temperature value. With one or more of the control aspects described herein, the material layer 122 with the predefined properties may also be created at temperatures below the characteristic temperature value. At these temperatures, it may not be possible to create a titanium-doped BFO material layer by diffusing titanium into the BFO material layer. Therefore, titanium may be sputtered as described herein to create the titanium-doped To produce a BFO material layer with the predefined properties (e.g. with the predefined titanium concentration).

According to various aspects, the system 100 may be configured to form a metal layer over the metallization layer prior to forming the one or more memristive devices or the substrate 116 may already contain the metal layer. The metal layer may be configured such that the metal layer reflects at least 70% (e.g., at least 90%) of the incident radiation from the linear lamp array when the material layer (e.g., the BFO material layer) is irradiated with the linear lamp array during and/or after the formation of the material layer (e.g., the BFO material layer). Therefore, the metal layer may be formed as a reflective layer. The metal layer may, for example, contain or consist essentially of a noble metal.) This may allow to increase the homogeneity of the material layer 122 after irradiation (e.g., after a thermal treatment). Optionally, a non-reflective layer (e.g. a layer that reflects at least 10% (e.g. at least 5%) of the incident radiation) can be arranged under the metal layer.

Various exemplary methods for producing a material layer (e.g., a BFO material layer) with predefined properties are described below. It is understood that these methods are illustrative and that features thereof may be combined with one another, if desired. The methods may be performed with the system 100.

7 shows a flow chart of a method 700 for depositing a material layer containing at least a first element and a second element in a predefined atomic ratio.

The method 700 may include depositing a material layer on a substrate (in 702). The material layer may include at least a first element and a second element in a predefined atomic ratio. The first element may have a higher temperature dependent reevaporation rate from the substrate and/or the material layer than the second element.

Depositing the material layer onto the substrate (in 702) may include generating a deposition material stream for depositing onto the substrate (in 702A). The deposition material stream may include an atomic ratio of the first element to the second element that is greater than the predefined atomic ratio.

Depositing the material layer onto the substrate (in 702) may include setting a temperature of the substrate to evaporate the first element from the substrate and/or the material layer such that the material layer has the predefined atomic ratio (in 702B).

8th shows a flow chart of a method 800 for setting (eg, controlling) one or more operating parameters of a sputtering process.

The method 800 may include determining a temperature value representing a temperature of a substrate on which a material layer comprising at least a first element and a second element in a predefined atomic ratio is to be deposited (in 802).

The method 800 may include determining, based on the temperature value, a nominal power ratio between a first power associated with sputtering the first element and a second power associated with sputtering the second element (in 804).

The method 800 may include setting a first power value of the first power and a second power value of the second power according to the nominal power ratio (in 806).

9 shows a flow chart of a method 900 for controlling one or more operating parameters of a sputtering process.

The method 900 may include sputtering at least a first element according to a first power and a second element according to a second power to deposit a material layer including the first element and the second element on a substrate (in 902).

The method 900 may include sensing plasma properties associated with sputtering of the first element and/or the second element (in 902A) during sputtering (in 902).

The method 900 may include controlling, during sputtering (in 902), a sputtering rate ratio between a first sputtering rate associated with sputtering the first element and a second sputtering rate associated with sputtering the second element based on the plasma properties (in 902B).

10 shows a flow chart of a dual-loop control method 1000 for con Controls of one or more operating parameters of a sputtering process.

The dual loop control method 1000 may include sputtering at least a first element according to a first power and a second element according to a second power to deposit a material layer including the first element and the second element onto a substrate (in 1002).

The dual loop control method 1000 may include controlling the first power and the second power using a first control loop (in 1002A) (a control loop may also be referred to as a closed loop) and a second control loop (in 1002B) during sputtering of the first element and the second element. The first control loop may include (in 1002A) sensing a temperature of the substrate and controlling the first power and the second power to adjust a power ratio between the first power and the second power based on the temperature of the substrate. The second control loop may include (in 1002B) sensing plasma characteristics associated with sputtering of the first element and/or the second element and controlling the first power and the second power to adjust the power ratio between the first power and the second power based on the plasma characteristics.

11 shows a flow chart of a dual-loop control method 1100 for controlling one or more operating parameters of a sputtering process.

The dual loop control method 1100 may include sputtering at least a first element according to a first power and a second element according to a second power to deposit a material layer including the first element and the second element onto a substrate (in 1102).

The dual loop control method 1100 may include controlling the first power and the second power using a first control loop (in 1102A) and a second control loop (in 1102B) during sputtering of the first element and the second element (in 1102). The first control loop may include (in 1102A) sensing a temperature of the substrate and controlling sputtering based on the temperature of the substrate. The second control loop may include (in 1102B) sensing plasma characteristics associated with sputtering of the first element and/or the second element and controlling sputtering based on the plasma characteristics.

12 shows a flowchart of a method 1200 for controlling one or more operating parameters of a sputtering process.

The method 1200 may include sputtering at least a first element according to a first power and a second element according to a second power to deposit a material layer including the first element and the second element on a substrate (in 1202).

The method 1200 may include, during sputtering (in 1202), sensing plasma properties associated with sputtering of the first element and/or the second element (in 1202A).

The method 1200 may include, during sputtering (in 1202), determining, based on the plasma characteristics, one or more operating parameters of the sputtering (in 1202B).

The method 1200 may include, during sputtering (in 1202), controlling the sputtering based on the one or more operating parameters (in 1202C).

13 shows a flowchart of a method 1300 for controlling one or more operating parameters of a sputtering process.

The method 1300 may include sputtering at least a first element according to a first power and a second element according to a second power to deposit a material layer including the first element and the second element on a substrate (in 1302).

The method 1300 may include sensing a temperature value representing a temperature of the substrate (in 1302A) during sputtering (in 1302).

The method 1300 may include, during sputtering (in 1302), determining, based on the temperature value, one or more operating parameters of the sputtering (in 1302B).

The method 1300 may include, during sputtering (in 1302), controlling the sputtering based on the one or more operating parameters (in 1302C).

14 shows a flow chart of a method 1400 for controlling a sputtering process.

The method 1400 may include radio frequency sputtering a first element according to a first power frequency value (in 1402).

The method 1400 may include radio frequency sputtering a second element according to a second power frequency value that is different from the first power frequency value (in 1404).

15 shows a flow chart of a method 1500 for controlling a sputtering process.

The method 1500 may include radio frequency sputtering a first element according to a first power frequency value (in 1502).

The method 1500 may include sputtering a second element with direct current (in 1504).

16 shows a flow chart of a method 1600 for controlling one or more operating parameters of a sputtering process.

The method 1600 may include depositing a material layer on a substrate rotating at a rotational speed equal to or greater than a predefined rotational speed (in 1602). The material layer may include at least a first element and a second element in a predefined phase. The predefined rotational speed may indicate that upon rotation of the substrate, a sublayer of the material layer is formed having a thickness of a lattice constant of a crystal structure associated with the predefined phase.

17 shows a flow chart of a method 1700 for controlling one or more operating parameters of a sputtering process.

The method 1700 may include depositing a material layer on a substrate (in 1702). The material layer may include at least a first element and a second element in a predefined phase.

The method 1700 may include irradiating the material layer using a linear lamp arrangement (in 1702A) during and/or after depositing the material layer onto the substrate (in 1702).

The method 1700 may include rotating the substrate (in 1702B) during irradiation of the material layer with the linear lamp arrangement (in 1702A).

18 shows a flow diagram of a method 1800 for forming one or more memristive devices.

The method 1800 may include forming a complementary metal-oxide-semiconductor structure at least in or on a substrate (in 1802).

The method 1800 may include forming a metallization structure over the complementary metal-oxide-semiconductor structure (in 1804).

The method 1800 may include forming one or more memristive devices over the metallization structure (in 1806). Forming the one or more memristive devices (in 1806) may include either reactively co-sputtering bismuth, iron, and titanium in an atmosphere including oxygen to create a titanium-doped bismuth ferrite material layer (in 1806A) or co-sputtering bismuth, iron, oxygen, and titanium to create a titanium-doped bismuth ferrite material layer (in 1806B).

Optionally, the method 1800 may include controlling one or more operating parameters of the sputtering according to one or more control aspects described herein (e.g., using one or more of the methods described herein).

In the following, various examples are given that illustrate one or more of the aspects described above with respect to sputtering at least the first element (e.g., Bi) and the second element (e.g., Fe) (and optionally the third element (e.g., Ti)), such as by means of the devices (e.g., the sputter controller 108, the one or more sputter sources 104(n=1 to N)) and/or systems (e.g., the sputtering system 100), and/or using one of the methods 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800. It may be intended that aspects described with respect to one of the devices (e.g., the sputter controller 108, the one or more sputter sources 104 (n = 1 to N)) and/or the system 100 may also apply to one or more of the methods 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800 and vice versa.

Example 1 is a method comprising: depositing a material layer on a substrate, the material layer comprising at least a first element (eg, Bi) and a second element (eg, Fe) in a predefined atomic ratio, the first element having a greater temperature-dependent evaporation rate from the substrate and/or the material layer than the second element wherein depositing the material layer comprises: generating a deposition material stream for depositing onto the substrate, the deposition material stream having an atomic ratio of the first element to the second element that is greater than the predefined atomic ratio, and setting a temperature of the substrate to evaporate the first element from the substrate and/or the material layer such that the material layer has the predefined atomic ratio.

In Example 2, the article of Example 1 can optionally comprise adjusting the temperature of the substrate prior to generating the deposition material stream.

In Example 3, the article of Example 1 or 2 can optionally comprise setting the temperature of the substrate to a temperature value equal to or greater than a lower limit, wherein the lower limit represents a vapor pressure of the first element at a working pressure of an atmosphere in which the deposition material stream is generated.

In Example 4, the article according to any one of Examples 1 to 3 can optionally comprise that the substrate includes a metal layer comprising a metal material and that the material layer is deposited on the metal layer; wherein the temperature of the substrate is set to a temperature value equal to or less than an upper threshold value, wherein the upper threshold value represents an upper limit of a diffusion-induced atomic concentration of the metal material within the material layer.

In Example 5, the article of any of Examples 1 to 4 can optionally include that generating the deposition material stream comprises sputtering the first element from a first sputtering target containing the first element and sputtering the second element from a second sputtering target containing the second element, wherein the second sputtering target is different from the first sputtering target.

In Example 6, the article of Example 5 can optionally include the first sputtering target being attached to a first sputtering source and the second sputtering target being attached to a second sputtering source that is different from the first sputtering source; or wherein the first sputtering target and the second sputtering target are attached to a common sputtering source.

In Example 7, the article of any of Examples 1 to 4 can optionally include that generating the deposition material stream comprises sputtering the first element and the second element from a common sputtering target containing the first element and the second element.

In Example 8, the article of any of Examples 1 to 7 can optionally include that the material layer further contains oxygen; and wherein the deposition material stream is generated in an atmosphere containing oxygen (e.g., by reactive co-sputtering the first element and the second element) (wherein the atmosphere optionally further contains an inert gas) or wherein the deposition material stream contains oxygen (e.g., in case of two sputtering targets: the first sputtering target can contain an oxide of the first element and/or the second sputtering target can contain an oxide of the second element; or in case of a single sputtering target: the common sputtering target can contain an oxide of the first element and the second element).

In Example 9, the article of any of Examples 1 to 8 can optionally comprise that in a temperature range of about 400°C to about 800°C, the temperature dependent evaporation rate of the first element from the substrate and/or the material layer is at least twice the temperature dependent evaporation rate of the second element from the substrate and/or the material layer.

In Example 10, the article of any of Examples 1 to 9 can optionally comprise that the material layer further contains a third element in a predefined atomic ratio to the first element and the second element, wherein the first element has a higher temperature dependent evaporation rate from the substrate and/or the material layer than the third element.

In Example 11, the article of Example 10 can optionally comprise that in a temperature range of about 400°C to about 800°C, the temperature dependent evaporation rate of the first element from the substrate and/or the material layer is at least twice the temperature dependent evaporation rate of the third element from the substrate and/or the material layer.

In Example 12, the article of any of Examples 1 to 11 can optionally comprise the first element being bismuth and the second element being iron.

In Example 13, the article of Example 12 may optionally comprise that the temperature of the substrate is controlled to obtain a temperature value in a range of about 600°C to about 650°C (e.g. a temperature value of approximately 630°C).

In Example 14, the article of Example 3 in combination with Example 12 or 13 can optionally have the lower threshold at a working pressure of about 0.2* 10 ^-2 mbar, being about 630°C.

In Example 14, the article of Example 4 in combination with any of Examples 12 to 14 can optionally include that the metal material is titanium and that the upper threshold is about 650°C.

In Example 16, the article of any of Examples 12 to 15 can optionally include that the predefined atomic ratio of the first element to the second element is about 1:1.

In Example 17, the article of any of Examples 12 to 16 can optionally comprise that the third element is titanium.

In Example 18, the article of any of Examples 1 to 17 can optionally comprise that the material layer includes a predefined phase comprising the first element and the second element; and that the method further comprises: while depositing the material layer onto the substrate, rotating the substrate at a rotational speed equal to or greater than a predefined rotational speed indicating that in one rotation (revolution) of the substrate, a sublayer of the material layer having a thickness of (approximately) a lattice constant of a crystal structure associated with the predefined phase is formed.

In Example 19, the article of Example 18 in combination with any of Examples 12 to 17 can optionally comprise that the predefined phase is bismuth ferrite (BiFeO ₃ ).

In Example 20, the article of Example 18 or 19 can optionally include generating the deposition material stream to impinge off-center on the substrate.

In Example 21, the article of Example 20 can optionally include that the substrate is a wafer; and that the deposition material stream is generated to impinge on the wafer at about an average radius of the wafer.

In Example 22, the article of Example 20 or 21 can optionally include that generating the deposition material stream comprises confocal co-sputtering the first element and the second element with the focus being off-center on the substrate.

In Example 23, the article of Example 20 or 21 can optionally include generating the deposition material stream comprising: generating a first deposition material stream by sputtering the first element and generating a second deposition material stream by sputtering the second element; and wherein the first deposition material stream is generated to impinge off-center on the substrate at a first focus and wherein the second deposition material stream is generated to impinge off-center on the substrate at a second focus different from the first focus.

Example 24 is a method comprising: determining a temperature value (e.g., preset or measured during deposition) representing a temperature of a substrate on which a material layer comprising at least a first element (e.g., Bi) and a second element (e.g., Fe) in a predefined atomic ratio is to be deposited; determining a nominal power ratio between a first power associated with sputtering the first element and a second power associated with sputtering the second element based on the temperature value (and optionally a desired atomic ratio between a first element and a second element); and setting a first power value of the first power and a second power value of the second power according to the nominal power ratio.

In Example 25, the method of Example 24 can optionally further comprise depositing the material layer on the substrate.

In Example 26, the article of Example 25 can optionally include depositing the material layer on the substrate comprising sputtering the first element (e.g., from a first sputtering target) according to the first power value and sputtering the second element (e.g., from a second sputtering target) according to the second power value.

In Example 27, the method of Example 25 may optionally further comprise: during the deposition of the material layer onto the substrate: detecting plasma properties associated with sputtering of the first element and/or the second element, determining an adjusted nominal power ratio between the first power and the second power based on the plasma properties, and controlling the first power and the second power according to the adjusted nominal power ratio.

In Example 28, the method of Example 25 can optionally further comprise: during depositing the material layer onto the substrate: sensing plasma properties associated with sputtering the first element and/or the second element, controlling the temperature of the substrate based on the plasma properties.

In Example 29, the article of any of Examples 24 to 28 can optionally include determining (e.g., measuring) the temperature value during deposition of the material layer onto the substrate.

In Example 30, the method of any of Examples 24 to 29 can optionally further comprise: heating the substrate to a certain temperature prior to depositing the layer of material onto the substrate.

In Example 31, the method according to any one of Examples 24 to 30 can optionally further comprise: during the deposition of the material layer onto the substrate, continuously (e.g., at predefined (e.g., regular) time intervals) detecting the temperature of the substrate and controlling the first power and the second power based on a respectively detected temperature value of the temperature of the substrate.

In Example 32, the article of any of Examples 24 to 31 can optionally include that depositing the layer of material on the substrate comprises generating a flow of deposition material in an oxygen-containing atmosphere (e.g., by reactive co-sputtering the first element and the second element) (wherein the atmosphere optionally further includes an inert gas).

In Example 33, the method of Example 32 can optionally further comprise: during depositing the material layer onto the substrate, acquiring oxygen data representing an oxygen concentration in an environment of the substrate, and controlling an oxygen supply according to an adjusted oxygen concentration based on the oxygen data.

In Example 34, the method of Example 33 can optionally further comprise: acquiring the oxygen data by: sensing an oxygen partial pressure (e.g., using mass spectrometry and/or a lambda probe); and/or provided that in combination with Example 25, determining one or more parameters representing electrical properties (e.g., a current, a voltage, a power, an impedance, etc.) of a first plasma associated with the sputtering of the first element and/or a second plasma associated with the sputtering of the second element, and determining an oxygen partial pressure based on the one or more parameters; and/or provided that in combination with Example 25, sensing (e.g., optically) a plasma emission of a first plasma associated with the sputtering of the first element and/or a second plasma associated with the sputtering of the second element, and determining, based on the plasma emission, an intensity of an oxygen characteristic.

In Example 35, the article of any of Examples 24 to 31, provided in combination with Example 25, can optionally include wherein the first element is sputtered from a first sputtering target consisting essentially of the first element, and wherein the second element is sputtered from a second sputtering target different from the first sputtering target, wherein the second sputtering target consists essentially of an oxide of the second element; or wherein the first element is sputtered from a first sputtering target consisting essentially of an oxide of the first element, and wherein the second element is sputtered from a second sputtering target different from the first sputtering target, wherein the second sputtering target consists essentially of an oxide of the second element; or wherein the first element is sputtered from a first sputtering target consisting essentially of an oxide of the first element, and wherein the second element is sputtered from a second sputtering target different from the first sputtering target, the second sputtering target consisting essentially of an oxide of the second element.

In Example 36, the method of any of Examples 24 to 35 can optionally further comprise: setting a temperature to which the substrate is to be heated.

In Example 37, the article of Example 36 can optionally include the temperature being set to a temperature value less than a threshold value representing a vapor pressure of the first element at a working pressure of an atmosphere in which the material layer is to be deposited.

In Example 38, the article of any of Examples 24 to 37 can optionally include that the material layer further includes a third element.

In Example 39, the article of Example 38 can optionally comprise that the third element is titanium.

In Example 40, the article of any of Examples 24 to 39 can optionally comprise the first element being bismuth and the second element being iron.

In Example 41, the subject matter of Examples 24 and 40 can optionally include that the temperature to which the substrate is to be heated has a temperature value below 630°C (e.g., below 600°C).

In Example 42, the article of Example 34 in combination with Example 40 or 41 can optionally have the threshold value at a working pressure of about 0.2* 10 ^-2 mbar being about 630°C.

In Example 43, the subject matter of Example 28 in combination with any of Examples 40 to 42 can optionally include controlling the power ratio comprising: decreasing the power ratio of the first power to the second power (e.g., by decreasing the first power and/or by increasing the second power) in case the temperature of the substrate increases; and/or increasing the power ratio of the first power to the second power (e.g., by increasing the first power and/or by decreasing the second power) in case the temperature of the substrate decreases.

In Example 44, the article of any of Examples 24 to 43 can optionally include the material layer including a predefined phase comprising the first element and the second element; and wherein the method further comprises: while depositing the material layer onto the substrate, rotating the substrate at a rotational speed equal to or greater than a predefined rotational speed indicating that in one rotation (revolution) of the substrate, a sublayer of the material layer having a thickness of (approximately) a lattice constant of a crystal structure associated with the predefined phase is formed.

In Example 45, the article of Example 44 in combination with any of Examples 40 to 43 can optionally include that the predefined phase is bismuth ferrite (BiFeO ₃ ).

In Example 46, the article of Example 44 or 45 can optionally include that depositing the material layer creates a deposition material stream that impinges off-center on the substrate.

In Example 47, the article of Example 46 can optionally include the substrate being a wafer; and wherein the deposition material stream is generated to impinge on the wafer at about an average radius of the wafer.

In Example 48, the article of Example 46 or 47 can optionally include that generating the deposition material stream comprises confocal co-sputtering the first element and the second element with the focus being off-center on the substrate.

In Example 49, the article of Example 46 or 47 can optionally include generating the deposition material stream comprising generating a first deposition material stream by sputtering the first element and generating a second deposition material stream by sputtering the second element; and wherein the first deposition material stream is generated to off-center impact the substrate at a first focus and wherein the second deposition material stream is generated to off-center impact the substrate at a second focus different from the first focus.

Example 50 is a sputter controller comprising: a power supply configured to: apply a first voltage according to a first power to a first sputtering source (e.g., to sputter a first element from a first target toward a substrate), and apply a second voltage according to a second power to a second sputtering source (e.g., to sputter a second element from a second target toward the substrate, the second element being different than the first element); and a controller configured to: receive temperature data representing a temperature of a substrate; determine a power ratio between the first power and the second power based on the temperature of the substrate, and control the power supply to apply the first voltage and the second voltage according to the power ratio between the first power and the second power.

In Example 51, the subject matter of Example 50 can optionally include that the temperature data comprises the temperature of the substrate; and/or that the temperature data comprises the temperature of a heating element (e.g., a resistive heating element and/or a lamp assembly) configured to heat the substrate to the set temperature.

Example 52 is a sputtering system comprising: the sputtering control according to Example 50 or 51; and a temperature sensor configured to detect a temperature representing the temperature of the substrate.

In Example 53, the subject matter of Example 52 can optionally include the temperature sensor being configured to sense the temperature of the substrate; and/or the sputtering system further comprising a heater configured to heat the substrate to a set temperature, and wherein the temperature sensor is configured to sense a temperature representative of a temperature of the substrate.

In example 54, the sputtering system of example 52 or 53 may optionally further comprise: a substrate carrier on which a substrate can be placed; and a motor configured to drive the substrate holder to rotate according to a set rotation speed; wherein the controller of the sputter controller is configured to adjust the rotation speed based on the first power and the second power.

In Example 55, the sputtering system according to any of Examples 52 to 54 can optionally further comprise: a vacuum chamber; and a device (e.g., a mass flow controller and/or a gate valve) configured to define an oxygen flow into the vacuum chamber; wherein the control device of the sputter controller is configured to control the device to define the oxygen flow depending on the power ratio between the first power and the second power.

Example 56 is a method comprising: sputtering at least a first element (e.g., Bi) according to a first power and a second element (e.g., Fe) according to a second power to deposit a layer of material including the first element and the second element on a substrate; during sputtering the first element and the second element: (e.g., continuously) sensing plasma characteristics associated with sputtering the first element and/or the second element, and controlling a sputtering rate ratio between a first sputtering rate associated with sputtering the first element and a second sputtering rate associated with sputtering the second element based on the plasma characteristics.

In Example 57, the subject matter of Example 56 can optionally include sputtering the first element and the second element comprising: sputtering the first element from a first sputtering source and sputtering the second element from a second sputtering source different from the first sputtering source, wherein the plasma characteristics comprise plasma characteristics of a first plasma associated with sputtering the first element from the first sputtering source and/or plasma characteristics of a second plasma associated with sputtering the second element from the second sputtering source; or sputtering the first element and the second element from a common target, wherein the plasma characteristics are plasma characteristics of a plasma associated with sputtering from the common target.

In Example 58, the method of Example 56 or 57 can optionally further comprise that sensing plasma properties associated with sputtering the first element and/or the second element comprises: optically sensing plasma properties associated with sputtering the first element and/or the second element (e.g., using optical emission spectroscopy (OES) (e.g., via OES imaging), interferometry, atomic absorption spectroscopy, and/or laser-induced fluorescence, etc.).

In Example 59, the method of any of Examples 56 to 58 can optionally further comprise wherein controlling the sputtering rate ratio comprises controlling a power ratio between the first power and the second power; and/or wherein controlling the sputtering rate ratio comprises controlling a first magnetic field associated with sputtering the first element and/or controlling a second magnetic field associated with sputtering the second element; and/or wherein sputtering the first element comprises radio frequency (RF) sputtering the first element, and wherein controlling the sputtering rate ratio comprises controlling a power frequency associated with radio frequency (RF) sputtering the first element; and/or wherein sputtering the second element comprises radio frequency (RF) sputtering the second element, and wherein controlling the sputtering rate ratio comprises controlling a power frequency associated with radio frequency (RF) sputtering the second element; and/or that controlling the sputtering rate ratio comprises controlling a pressure of an atmosphere in which the first element and the second element are sputtered.

In Example 60, the method of any of Examples 56 to 59 can optionally further comprise: heating the substrate to a set temperature prior to sputtering the first element and the second element.

In Example 61, the article of Example 60 can optionally include setting the temperature to a temperature value less than a threshold value representing a vapor pressure of the first element at a working pressure of an atmosphere in which the material layer is to be deposited.

In Example 62, the method according to any one of Examples 56 to 61 can optionally further comprise: during sputtering of the first element and the second element, continuously (e.g., at predefined (e.g., regular) time intervals) detecting a temperature of the substrate; wherein the sputtering rate ratio between the first sputtering rate and the second sputtering rate is controlled based on the plasma properties and based on a respectively detected temperature value of the temperature of the substrate.

In Example 63, the article of any of Examples 56 to 62 can optionally include sputtering the first element and the second element in an atmosphere containing oxygen (e.g., by reactive sputtering of the first element and the second element) (where the atmosphere optionally also contains an inert gas).

In Example 64, the method of Example 63 can optionally further comprise: during sputtering the first element and the second element, controlling an oxygen flow depending on the sputtering rate ratio between the first sputtering rate and the second sputtering rate.

In Example 65, the article of any of Examples 56 to 64 can optionally comprise the first element being bismuth and the second element being iron.

In Example 66, the article of any of Examples 60 to 65 can optionally include that the set temperature has a temperature value of less than 630°C.

In Example 67, the article of Example 61 in combination with Example 65 or 66 can optionally have the threshold value at a working pressure of about 0.2* 10 ^-2 mbar being about 630°C.

In Example 68, the article of any of Examples 56 to 67 can optionally include the material layer including a predefined phase comprising the first element and the second element; and wherein the method further comprises: during sputtering the first element and the second element, rotating the substrate at a rotational speed equal to or greater than a predefined rotational speed indicating that in one rotation (revolution) of the substrate, a sublayer of the material layer having a thickness of (approximately) a lattice constant of a crystal structure associated with the predefined phase is formed.

In Example 69, the article of Example 68 in combination with any of Examples 65 to 67 can optionally include that the predefined phase is bismuth ferrite (BiFeO ₃ ).

In Example 70, the article of Example 68 or 69 can optionally include that sputtering the first element and the second element comprises sputtering the first element and the second element off-center on the substrate.

In Example 71, the article of Example 70 can optionally include that the substrate is a wafer; and that the first element and the second element are sputtered to impinge on the wafer at approximately an average radius of the wafer.

In Example 72, the article of Example 70 or 71 can optionally include that sputtering the first element and the second element comprises confocal co-sputtering the first element and the second element with a focus off-center on the substrate.

In Example 73, the article of Example 70 or 71 can optionally include that sputtering the first element and the second element comprises sputtering the first element off-center on the substrate with a first focus, and sputtering the second element comprises off-center on the substrate with a second focus that is different from the first focus.

Example 74 is a sputter controller comprising: a power supply configured to operate a first sputter source configured to sputter bismuth and operate a second sputter source configured to sputter iron; and a controller configured to: receive plasma data representing plasma characteristics associated with sputtering bismuth and/or iron, determine, based on the plasma characteristics, a sputtering rate ratio between a bismuth sputtering rate associated with sputtering bismuth and an iron sputtering rate associated with sputtering iron, and control operation of the first sputtering source and/or the second sputtering source according to the sputtering rate ratio between between the bismuth sputtering rate and the iron sputtering rate.

In Example 75, the subject matter of Example 74 can optionally include the power supply being configured to operate the first sputtering source for radio frequency (RF) sputtering of bismuth according to a first power frequency; and the controller being configured to control operation of the first sputtering source according to the sputtering rate ratio between the bismuth sputtering rate and the iron sputtering rate by controlling the first power frequency.

In example 76, the subject matter of example 74 or 75 can optionally include the power supply being configured to operate the second sputtering source for radio frequency (RF) sputtering of iron according to a second power frequency; and the controller being configured to control operation of the second sputtering source according to the sputtering rate ratio between the bismuth sputtering rate and the iron sputtering rate by controlling the second power frequency.

In Example 77, the subject matter of any of Examples 74-76 can optionally include the power supply being configured to operate the first sputtering source for radio frequency (RF) sputtering of bismuth according to a first power frequency and to operate the second sputtering source for radio frequency (RF) sputtering of iron according to a second power frequency; and wherein the controller is configured to: determine a frequency ratio between the first power frequency and the second power frequency based on the sputtering rate ratio between the bismuth sputtering rate and the iron sputtering rate, and control operation of the first sputtering source and/or the second sputtering source according to the sputtering rate ratio between the bismuth sputtering rate and the iron sputtering rate by controlling operation of the first sputtering source and/or the second sputtering source according to the frequency ratio.

Example 78 is a sputtering system comprising: the sputter controller of any of examples 74 to 77; the first sputtering source; and the second sputtering source.

In Example 79, the sputtering system of Example 78 can optionally further comprise: an optical sensor configured to sense plasma properties.

In Example 80, the subject matter of Example 78 or 79 can optionally include that the first sputtering source is a first magnetron sputtering source comprising a bismuth target, one or more first magnets for generating a first magnetic field through the bismuth target, and a first motor configured to change a distance between the bismuth target and the one or more first magnets; wherein the controller is configured to control operation of the first sputtering source according to the sputtering rate ratio between the bismuth sputtering rate and the iron sputtering rate by controlling the first motor to change the distance between the bismuth target and the one or more first magnets.

In Example 81, the subject matter of any of Examples 78 to 80 can optionally include that the second sputtering source is a second magnetron sputtering source having an iron target, one or more second magnets for generating a second magnetic field through the iron target, and a second motor configured to change a distance between the iron target and the one or more second magnets; wherein the controller is configured to control operation of the second sputtering source according to the sputtering rate ratio between the bismuth sputtering rate and the iron sputtering rate by controlling the second motor to change the distance between the iron target and the one or more second magnets.

In Example 82, the subject matter of Example 78 or 79 can optionally include the first sputtering source being a first magnetron sputtering source including a bismuth target, one or more first magnets for generating a first magnetic field through the bismuth target, and a first motor for changing a first distance between the bismuth target and the one or more first magnets; wherein the second sputtering source is a second magnetron sputtering source including an iron target, one or more second magnets for generating a second magnetic field through the iron target, and a second motor configured to change a second distance between the iron target and the one or more second magnets; and in that the control device is configured to: determine a distance ratio between the first distance and the second distance based on the sputtering rate ratio between the bismuth sputtering rate and the iron sputtering rate, and to control the operation of the first sputtering source and/or the second sputtering source according to the sputtering rate ratio between the bismuth sputtering rate and the iron sputtering rate by controlling the operation of the first sputtering source and/or the second sputtering source according to the distance ratio.

In Example 83, the sputtering system according to any of Examples 78 to 82 can optionally further comprise: a vacuum chamber; and a device (eg, a mass flow controller and/or a gate valve) configured to control an atmospheric pressure in the vacuum chamber; wherein the control device is configured to: determine a pressure value of the atmospheric pressure based on the sputtering rate ratio, and control operation of the first sputtering source according to the sputtering rate ratio between the bismuth sputtering rate and the iron sputtering rate by controlling the device to control the atmospheric pressure according to the pressure value.

In Example 84, the sputtering system of any of Examples 78 to 83 may optionally further comprise: a substrate carrier on which a substrate can be placed; and a motor configured to drive the substrate holder to rotate according to a set rotation speed; wherein the controller of the sputter controller is configured to adjust the rotation speed based on the first power and the second power.

In Example 85, the sputtering system according to any one of Examples 78 to 84 can optionally further comprise: a vacuum chamber; and a device (e.g., a mass flow controller and/or a gate valve) configured to define an oxygen flow into the vacuum chamber; wherein the control device of the sputter controller is configured to control the device to define the oxygen flow depending on the sputter ratio.

Example 86 is a dual loop control method comprising: sputtering at least a first element (e.g., Bi) according to a first power and a second element (e.g., Fe) according to a second power to deposit a material layer including the first element and the second element on a substrate; and, during sputtering the first element and the second element, controlling the first power and the second power using a first control loop and a second control loop; wherein the first control loop comprises: (e.g., continuously (e.g., at predefined (e.g., regular) time intervals)) sensing a temperature of the substrate, and controlling the first power and the second power to adjust a power ratio between the first power and the second power based on the temperature of the substrate; wherein the second control loop comprises: (e.g., continuously (e.g., at predefined (e.g., regular) time intervals) sensing plasma properties associated with sputtering of the first element and/or the second element, and controlling the first power and the second power to adjust the power ratio between the first power and the second power based on the plasma properties.

In Example 87, the dual loop control method of Example 86 can optionally further comprise: heating the substrate to a set temperature prior to sputtering the first element and the second element.

In Example 88, the article of Example 87 can optionally include the set temperature having a temperature value that is less than a threshold value representing a vapor pressure of the first element at a working pressure of an atmosphere in which the first element and the second element are sputtered.

In Example 89, the article of any of Examples 86 to 88 can optionally include that sputtering the first element and the second element comprises: sputtering the first element and the second element in an atmosphere containing oxygen (e.g., by reactive co-sputtering the first element and the second element) (wherein the atmosphere optionally further contains an inert gas).

In Example 90, the dual-loop method of Example 89 can optionally further comprise: during sputtering of the first element and the second element, controlling an oxygen flow depending on the power ratio between the first power and the second power

In Example 91, the subject matter of any of Examples 86 to 90 can optionally include sputtering the first element and the second element comprising: co-sputtering the first element from a first sputtering target consisting essentially of the first element and the second element from a second sputtering target different from the first sputtering target, wherein the second sputtering target consists essentially of an oxide of the second element; or co-sputtering the first element from a first sputtering target consisting essentially of an oxide of the first element and the second element from a second sputtering target different from the first sputtering target, wherein the second sputtering target consists essentially of the second element; or co-sputtering the first element from a first sputtering target consisting essentially of an oxide of the first element and the second element from a second sputtering target that is different from the first sputtering target. wherein the second sputtering target consists essentially of an oxide of the second element.

In Example 92, the article of any of Examples 86 to 91 can optionally include that sputtering the first element and the second element comprises: sputtering the first element from a first sputtering source and sputtering the second element from a second sputtering source that is different from the first sputtering source; or sputtering the first element and the second element from a common target.

In Example 93, the subject matter of any of Examples 86 to 92 can optionally include the first control loop further comprising: determining whether the temperature of the substrate is changing, and in the event that it is determined that the temperature of the substrate is changing, controlling the first power and the second power to adjust the power ratio between the first power and the second power based on a change in the temperature of the substrate.

In Example 94, the article of any of Examples 86 to 93 can optionally include continuously sensing the temperature of the substrate and the plasma properties during sputtering of the first element and the second element.

In Example 95, the article of Example 94 can optionally include continuously sensing the temperature of the substrate after a first (e.g., regular) cycle and continuously sensing the plasma properties after a second (e.g., regular) cycle, wherein a length of the first cycle is greater than a length of the second cycle.

In Example 96, the subject matter of any of Examples 86 to 95 can optionally include that a cycle of the second control loop is shorter than a cycle of the first control loop.

In Example 97, the article of any of Examples 86-96 can optionally include that sensing plasma properties associated with sputtering of the first element and/or the second element comprises: optically sensing plasma properties associated with sputtering of the first element and/or the second element (e.g., using optical emission spectroscopy (OES) (e.g., via OES imaging), interferometry, atomic absorption spectroscopy, and/or laser-induced fluorescence, etc.).

In Example 98, the article of any of Examples 86 to 97 can optionally comprise the first element being bismuth and the second element being iron.

In Example 99, the subject matter of Examples 93 and 98 can optionally include controlling the power ratio within the first control loop comprising: decreasing the power ratio of the first power to the second power (e.g., by decreasing the first power and/or by increasing the second power) in the event that the temperature of the substrate increases; and/or increasing the power ratio of the first power to the second power (e.g., by increasing the first power and/or by decreasing the second power) in the event that the temperature of the substrate decreases.

In Example 100, the article of Example 87 in combination with Example 98 or 99 can optionally include that the set temperature has a temperature value less than 630°C (e.g., below 600°C).

In Example 101, the article of Example 88 in combination with any of Examples 98 to 100 can optionally have the threshold value at a working pressure of about 0.2* 10 ^-2 mbar being about 630°C.

In Example 102, the article of any of Examples 98 to 101 can optionally include that the material layer includes a predefined phase comprising the first element and the second element; and that the method further comprises: during sputtering the first element and the second element, rotating the substrate at a rotational speed equal to or greater than a predefined rotational speed indicating that in one rotation (revolution) of the substrate, a sublayer of the material layer having a thickness of (approximately) a lattice constant of a crystal structure associated with the predefined phase is formed.

In Example 103, the article of Example 102 in combination with any of Examples 98 to 101 can optionally comprise that the predefined phase is bismuth ferrite (BiFeO ₃ ).

In example 104, the article of example 102 or 103 can optionally include that sputtering the first element and the second element comprises sputtering the first element and the second element off-center on the substrate.

In Example 105, the article of Example 104 may optionally comprise that the substrate is a wafer; and that the first element and the second element are sputtered to impinge on the wafer at approximately an average radius of the wafer.

In example 106, the article of example 104 or 105 can optionally include that sputtering the first element and the second element comprises confocal co-sputtering the first element and the second element with an eccentric focus on the substrate.

In example 107, the article of example 104 or 105 can optionally include sputtering the first element and the second element comprising sputtering the first element to impinge off-center on the substrate having a first focus and sputtering the second element to impinge off-center on the substrate having a second focus different from the first focus.

Example 108 is a sputter controller comprising: a power supply configured to: apply a first voltage according to a first power to a first sputtering source (e.g., to sputter a first element from a first target toward a substrate), and apply a second voltage according to a second power to a second sputtering source (e.g., to sputter a second element from a second target toward the substrate, wherein the second element is different from the first element); and a controller configured to: (e.g., continuously (e.g., at predefined (e.g., regular) time intervals)) receive plasma data representing plasma characteristics associated with sputtering of the first element and/or the second element; determine a power ratio between the first power and the second power based on the plasma data; control the power supply to apply the first voltage and the second voltage according to the power ratio between the first power and the second power; (e.g., continuously (e.g., at predefined (e.g., regular) time intervals)) receiving temperature data representing a temperature of the material layer; determining whether the temperature of the substrate is changing; in the event that it is determined that the temperature of the substrate is changing, controlling the first power and the second power to adjust the power ratio between the first power and the second power based on a change in the temperature of the substrate.

In Example 109, the subject matter of Example 108 can optionally include that the temperature data comprises the temperature of the substrate; and/or that the temperature data comprises the temperature of a heating element (e.g., a resistive heating element and/or a lamp assembly) configured to heat the substrate to the set temperature.

Example 110 is a sputtering system comprising: the sputter controller of example 108 or 109; and a temperature sensor configured to detect a temperature representing the temperature of the substrate and to provide temperature data according to the detected temperature to the sputter controller.

In Example 111, the subject matter of Example 110 can optionally include the temperature sensor being configured to sense the temperature of the substrate; and/or the sputtering system further comprising a heater configured to heat the substrate to a set temperature, and wherein the temperature sensor is configured to sense a temperature representative of a temperature of the substrate.

In example 112, the sputtering system of example 110 or 111 can optionally further comprise: a substrate carrier on which a substrate can be placed; and a motor configured to drive the substrate holder to rotate according to a set rotation speed; wherein the controller of the sputter controller is configured to adjust the rotation speed based on the power ratio between the first power and the second power.

In Example 113, the sputtering system according to any of Examples 110 to 112 can optionally further comprise: a vacuum chamber; and a device (e.g., a mass flow controller and/or a slider) configured to define an oxygen flow into the vacuum chamber; wherein the control device of the sputter controller is configured to control the device to define the oxygen flow depending on the power ratio between the first power and the second power.

In Example 114, the sputtering system according to any one of Examples 110 to 113 can optionally further comprise: an optical sensor configured to detect plasma properties.

Example 115 is a method comprising: sputtering at least a first element (eg, Bi) and a second element (eg, Fe) to deposit on a substrate a layer of material containing the first element and the second element; during sputtering the first element and the second element: (eg continuously) detecting a temperature value representing a temperature of the substrate; determining, based on the temperature value, one or more operating parameters of the sputtering; and controlling the sputtering based on the one or more operating parameters.

In Example 116, the method of Example 115 can optionally further comprise heating the substrate to a set temperature prior to sputtering the first element and the second element.

In example 117, the article of example 115 or 116 can optionally include that a temperature value of the set temperature is less than a threshold value representing a vapor pressure of the first element at a working pressure of an atmosphere in which the material layer is deposited.

Example 118 is a method comprising: sputtering at least a first element (e.g., Bi) and a second element (e.g., Fe) to deposit a layer of material including the first element and the second element on a substrate; during sputtering the first element and the second element: (e.g., continuously) sensing plasma characteristics associated with sputtering the first element and/or the second element; determining, based on the plasma characteristics, one or more operating parameters of the sputtering; and controlling the sputtering based on the one or more operating parameters.

In Example 119, the subject matter of Example 118 can optionally include the one or more operating parameters comprising a temperature value; and wherein controlling the sputtering comprises heating or cooling the substrate to the temperature value.

In Example 120, the subject matter of Example 118 or 119 can optionally include that sensing plasma properties associated with sputtering of the first element and/or the second element comprises: optically sensing plasma properties associated with sputtering of the first element and/or the second element (e.g., using optical emission spectroscopy (OES) (e.g., via OES imaging), interferometry, atomic absorption spectroscopy, and/or laser-induced fluorescence, etc.).

In Example 121, the article of any of Examples 118-120 can optionally include sputtering the first element and the second element comprising: sputtering the first element from a first sputtering source and sputtering the second element from a second sputtering source different from the first sputtering source, wherein the plasma properties comprise plasma properties of a first plasma associated with sputtering the first element from the first sputtering source and/or plasma properties of a second plasma associated with sputtering the second element from the second sputtering source; or sputtering the first element and the second element from a common target, wherein the plasma properties comprise plasma properties of a plasma associated with sputtering from the common target.

In Example 122, the article of any of Examples 118 to 121 can optionally include sputtering the first element and the second element comprising: sputtering the first element and the second element in an atmosphere containing oxygen (e.g., by reactive co-sputtering the first element and the second element) (wherein the atmosphere optionally further contains an inert gas).

In Example 123, the method of Example 122 can optionally further comprise: wherein the one or more operating parameters comprise an oxygen partial pressure; and wherein controlling sputtering comprises controlling an oxygen supply based on the oxygen partial pressure.

In Example 124, the subject matter of Example 123 can optionally include wherein determining the oxygen partial pressure based on the plasma characteristics comprises determining one or more parameters representing electrical properties (e.g., a current, a voltage, a power, an impedance, etc.) of a first plasma associated with the sputtering of the first element and/or a second plasma associated with the sputtering of the second element and determining the oxygen partial pressure based on the one or more parameters; and/or wherein sensing the plasma characteristics comprises sensing a plasma emission of a first plasma associated with the sputtering of the first element and/or a second plasma associated with the sputtering of the second element, determining an intensity of an oxygen characteristic based on the plasma emission, wherein determining the oxygen partial pressure is performed using the oxygen characteristic.

In Example 125, the method according to any one of Examples 118 to 124 may optionally further be based on comprise: during sputtering of the first element and the second element, continuously (eg at predefined (eg regular) time intervals) detecting a temperature of the substrate; and wherein the one or more operating parameters comprise the temperature of the substrate.

In Example 126, the subject matter of any of Examples 115 to 125 can optionally include wherein sputtering the first element and the second element comprises sputtering the first element according to a first power and the second element according to a second power; and wherein the one or more operating parameters comprise a power ratio between the first power and the second power, and wherein controlling the sputtering comprises controlling the first power and the second power according to the power ratio.

In Example 127, the subject matter of any of Examples 115-126 can optionally include wherein sputtering the first element comprises radio frequency (RF) sputtering the first element according to a first power and a first power frequency; wherein sputtering the second element comprises direct current (DC) sputtering the second element according to a second power; and wherein the one or more operating parameters comprise a power ratio between the first power and the second power, and wherein controlling the sputtering comprises controlling the first power and the second power according to the power ratio, and/or wherein the one or more operating parameters comprise a frequency value of the first power frequency, and wherein controlling the sputtering comprises controlling the sputtering of the first element according to the frequency value.

In Example 128, the subject matter of any of Examples 115-126 can optionally include wherein sputtering the second element comprises radio frequency (RF) sputtering the second element according to a second power and a second power frequency; sputtering the first element comprises direct current (DC) sputtering the first element according to a first power; and wherein the one or more operating parameters comprise a power ratio between the first power and the second power, and wherein controlling the sputtering comprises controlling the first power and the second power according to the power ratio, and/or wherein the one or more operating parameters comprise a frequency value of the second power frequency, and wherein controlling the sputtering comprises controlling the sputtering of the second element according to the frequency value.

In Example 129, the subject matter of any of Examples 115-126 can optionally include wherein sputtering the first element comprises radio frequency (RF) sputtering the first element according to a first power and a first power frequency; wherein sputtering the second element comprises radio frequency (RF) sputtering the second element according to a second power and a second power frequency; and wherein the one or more operating parameters comprise a power ratio between the first power and the second power, and wherein controlling the sputtering comprises controlling the first power and the second power according to the power ratio, and/or wherein the one or more operating parameters comprise a frequency ratio between the first power frequency and the second power frequency, and wherein controlling the sputtering comprises controlling the sputtering of the first element and the second element according to the frequency ratio.

In Example 130, the article of any of Examples 115 to 129 can optionally include that sputtering the first element and the second element comprises: sputtering the first element and the second element in an atmosphere containing oxygen (e.g., by reactive co-sputtering the first element and the second element) (wherein the atmosphere optionally further contains an inert gas).

In Example 131, the subject matter of Example 130 can optionally include wherein the first element is sputtered from a first sputtering target consisting essentially of the first element, and wherein the second element is sputtered from a second sputtering target that is different from the first sputtering target, wherein the second sputtering target consists essentially of an oxide of the second element; or wherein the first element is sputtered from a first sputtering target consisting essentially of an oxide of the first element, and wherein the second element is sputtered from a second sputtering target that is different from the first sputtering target, wherein the second sputtering target consists essentially of an oxide of the second element; or wherein the first element is sputtered from a first sputtering target consisting essentially of an oxide of the first element, and wherein the second element is sputtered from a second sputtering target different from the first sputtering target, the second sputtering target consisting essentially of an oxide of the second element.

In Example 130, the article of any of Examples 115 to 129 may optionally include that the sputtering of the first element is a magnet ron sputtering of the first element from a first target, and wherein the sputtering of the second element comprises magnetron sputtering of the second element from a second target; and wherein the one or more operating parameters comprise a distance ratio between a first distance and a second distance, wherein the first distance is a distance between the first target and one or more first magnets associated with the magnetron sputtering of the first element, and wherein the second distance is a distance between the second target and one or more second magnets associated with the magnetron sputtering of the second element.

In Example 131, the article of any of Examples 115 to 130 can optionally include wherein sputtering the first element and the second element comprises sputtering the first element and the second element in an atmosphere; and wherein the one or more operating parameters comprise a pressure value representing a pressure of the atmosphere, and wherein controlling the sputtering comprises controlling the pressure of the atmosphere according to the pressure value.

In Example 132, the article of any of Examples 115 to 131 can optionally include that the material layer further includes a third element.

In Example 133, the article of Example 132 can optionally include that the third element is titanium.

In Example 134, the article of any of Examples 115 to 133 can optionally comprise the first element being bismuth and the second element being iron.

In Example 135, the method of any of Examples 116 to 134 can optionally further comprise that the temperature to which the substrate is to be heated has a value below 630°C (e.g. below 600°C).

In Example 136, the article of Example 117 in combination with Example 134 or 135 can optionally have the threshold value at a working pressure of about 0.2* 10 ^-2 mbar being about 630°C.

In Example 137, the article of any of Examples 115 to 136 can optionally include the material layer including a predefined phase comprising the first element and the second element; and wherein the method further comprises: during sputtering the first element and the second element, rotating the substrate at a rotational speed equal to or greater than a predefined rotational speed indicating that in one rotation (revolution) of the substrate, a sublayer of the material layer having a thickness of (approximately) a lattice constant of a crystal structure associated with the predefined phase is formed.

In Example 138, the article of Example 137 in combination with any of Examples 134 to 136 can optionally comprise that the predefined phase is bismuth ferrite (BiFeO ₃ ).

In Example 139, the article of Example 137 or 138 can optionally include that sputtering the first element and the second element comprises generating a stream of deposition material that impinges off-center on the substrate.

In Example 140, the article of Example 139 can optionally include the substrate being a wafer; and wherein the deposition material stream is generated to impinge on the wafer at approximately an average radius of the wafer.

In Example 141, the article of Example 139 or 140 can optionally include that generating the deposition material stream comprises confocal co-sputtering the first element and the second element with the focus being off-center on the substrate.

In example 142, the article of example 139 or 140 can optionally include generating the deposition material stream comprising generating a first deposition material stream by sputtering the first element and generating a second deposition material stream by sputtering the second element; and wherein the first deposition material stream is generated to off-center impact the substrate at a first focus and wherein the second deposition material stream is generated to off-center impact the substrate at a second focus different from the first focus.

Example 143 is a sputter controller comprising: a power supply configured to operate one or more sputter sources, the one or more sputter sources configured to sputter at least a first element and a second element; and a controller configured to: receive temperature data representing a temperature of a substrate, determine, based on the temperature of the substrate, one or more operating parameters of the one or more sputter sources; and control operation of the one or more sputter sources based on the one or more operating parameters.

In Example 144, the subject matter of Example 143 can optionally include wherein the temperature data comprises the temperature of the substrate; and/or wherein the temperature data comprises the temperature of a heating element (e.g., a resistive heating element and/or a lamp array) configured to heat the substrate to the set temperature.

Example 145 is a sputter controller comprising: a power supply configured to operate one or more sputter sources, the one or more sputter sources configured to sputter at least a first element and a second element; and a controller configured to: receive plasma data representing plasma characteristics associated with sputtering the first element and/or the second element, determine, based on the plasma characteristics, one or more operating parameters of the one or more sputter sources; and control operation of the one or more sputter sources based on the one or more operating parameters.

In example 146, the subject matter of any of examples 143 to 145 can optionally include wherein the power supply is configured to operate the one or more sputter sources for radio frequency (RF) sputtering the first element according to a first power frequency; and wherein the one or more operating parameters comprise a frequency value of the first power frequency, and wherein the controller is configured to control operation of the one or more sputter sources for radio frequency (RF) sputtering the first element according to the frequency value of the first power frequency.

In example 147, the subject matter of any of examples 143 to 145 can optionally include wherein the power supply is configured to operate the one or more sputter sources for radio frequency (RF) sputtering the second element according to a second power frequency; and wherein the one or more operating parameters include a frequency value of the second power frequency, and wherein the controller is configured to control operation of the one or more sputter sources for radio frequency (RF) sputtering the second element according to the frequency value of the second power frequency.

In Example 148, the subject matter of any of Examples 143 to 145 can optionally include the power supply being configured to operate the one or more sputtering sources for radio frequency (RF) sputtering the first element according to a first power frequency and for radio frequency (RF) sputtering the second element according to a second power frequency; wherein the one or more operating parameters comprise a frequency ratio between the first power frequency and the second power frequency; and wherein the controller is configured to control operation of the one or more sputtering sources by controlling the first power frequency and the second power frequency according to the frequency ratio.

Example 149 is a sputtering system comprising: the sputter controller of any of examples 143 to 148; and the one or more sputtering sources.

In Example 150, the sputtering system of Example 149 can optionally further comprise: a temperature sensor configured to sense a temperature representative of the temperature of the substrate.

In Example 151, the subject matter of Example 150 can optionally include wherein the temperature sensor is configured to sense the temperature of the substrate; and/or wherein the sputtering system further comprises a heater configured to heat the substrate to a set temperature, and wherein the temperature sensor is configured to sense a temperature representative of a temperature of the substrate.

In Example 152, the subject matter of any of Examples 149 to 151, provided that in combination with Example 145, can optionally comprise that the sputtering system further comprises: an optical sensor configured to detect plasma properties.

In Example 153, the subject matter of any of Examples 149 to 152 can optionally include the one or more sputter sources being configured to sputter the first element from a first target, and wherein the one or more sputter sources include one or more first magnets for generating the first magnetic field through the first target and a first motor configured to change a first distance between the first target and the one or more first magnets; and wherein the one or more operating parameters include a distance value of the first distance, and wherein the controller is configured to control operation of the one or more sputter sources by controlling the first motor to change the first distance according to the distance value.

In Example 154, the article of any of Examples 149 to 153 may optionally comprise that the one or more sputter sources are configured to sputter the second element from a second target, and that the one or more sputter sources comprise one or more second magnets for generating a second magnetic field through the second target, and a second motor is configured to change a second distance between the second target and the one or more second magnets; and wherein the one or more operating parameters include a distance value of the second distance, and wherein the controller is configured to control operation of the one or more sputter sources by controlling the second motor to change the second distance according to the distance value.

In Example 155, the subject matter of any of Examples 149-152 can optionally include the one or more sputtering sources being configured to sputter the first element from a first target, and wherein the one or more sputtering sources include one or more first magnets for generating a first magnetic field through the first target and a first motor for changing a first distance between the first target and the one or more first magnets; wherein the one or more sputtering sources being configured to sputter the second element from a second target, and wherein the one or more sputtering sources include one or more second magnets for generating a second magnetic field through the second target, and a second motor for changing a second distance between the second target and the one or more second magnets; and wherein the one or more operating parameters include a distance ratio between the first distance and the second distance, and wherein the controller is configured to control operation of the one or more sputtering sources by controlling the first distance and the second distance according to the distance ratio.

In example 156, the sputtering system of any of examples 149 to 155 can optionally further comprise: a vacuum chamber; and a device (e.g., a mass flow controller and/or a gate valve) configured to control a pressure with the vacuum chamber; wherein the one or more operating parameters comprise a pressure value of the pressure, and wherein the control device is configured to control operation of the one or more sputter sources by controlling the device to control the pressure according to the pressure value.

In example 157, the sputtering system according to any one of examples 149 to 156 can optionally further comprise: a substrate carrier on which a substrate can be placed; and a motor configured to drive the substrate holder to rotate according to a set rotation speed; wherein the controller of the sputter controller is configured to adjust the rotation speed based on the first power and the second power.

In example 158, the sputtering system according to any of examples 149 to 157 can optionally further comprise: a vacuum chamber; and a device (e.g., a mass flow controller and/or a gate valve) configured to define an oxygen flow into the vacuum chamber; wherein the control device of the sputter controller is configured to control the device to define the oxygen flow depending on the one or more operating parameters.

Example 159 is a dual loop control method comprising: sputtering at least a first element (e.g., Bi) and a second element (e.g., Fe) to deposit a material layer including the first element and the second element on a substrate; and during sputtering of the first element and the second element, controlling the sputtering using a first control loop and a second control loop; wherein the first control loop comprises: (e.g., continuously (e.g., at predefined (e.g., regular) time intervals)) sensing a temperature of the substrate, and controlling the sputtering based on the temperature of the substrate; wherein the second control loop comprises: (e.g., continuously (e.g., at predefined (e.g., regular) time intervals)) sensing plasma properties associated with sputtering of the first element and/or the second element, and controlling the sputtering based on the plasma properties.

In Example 160, the dual loop control method of Example 159 can optionally further comprise: heating the substrate to a set temperature prior to sputtering the first element and the second element.

In Example 161, the article of Example 160 can optionally include the set temperature having a temperature value that is less than a threshold value representing a vapor pressure of the first element at a working pressure of an atmosphere in which the first element and the second element are sputtered.

In Example 162, the article of any of Examples 159 to 161 can optionally include that sputtering the first element and the second element comprises: sputtering the first element and the second element in an atmosphere that Contains oxygen (e.g. by reactive co-sputtering of the first element and the second element) (wherein the atmosphere optionally further contains an inert gas).

In Example 163, the subject matter of any of Examples 159 to 162 can optionally include sputtering the first element and the second element comprising: co-sputtering the first element from a first sputtering target consisting essentially of the first element and the second element from a second sputtering target different from the first sputtering target, wherein the second sputtering target consists essentially of an oxide of the second element; or co-sputtering the first element from a first sputtering target consisting essentially of an oxide of the first element and the second element from a second sputtering target different from the first sputtering target, wherein the second sputtering target consists essentially of the second element; or co-sputtering the first element from a first sputtering target consisting essentially of an oxide of the first element and the second element from a second sputtering target different from the first sputtering target, the second sputtering target consisting essentially of an oxide of the second element.

In Example 164, the subject matter of any of Examples 159 to 163 can optionally include sputtering the first element and the second element comprising: sputtering the first element from a first sputtering source and sputtering the second element from a second sputtering source that is different from the first sputtering source; or sputtering the first element from a first target of a common sputtering source and sputtering the second element from a second target of the common sputtering source; or sputtering the first element and the second element from a common target.

In Example 165, the subject matter of any of Examples 159 to 164 can optionally include the first control loop comprising: determining whether the temperature of the substrate is changing, and in the case of determining that the temperature of the substrate is changing, controlling sputtering based on a change in the temperature of the substrate.

In Example 166, the article of any of Examples 159 to 165 can optionally include continuously sensing the temperature of the substrate and the plasma properties during sputtering of the first element and the second element.

In Example 167, the subject matter of Example 166 can optionally include wherein the temperature of the substrate is continuously sensed after a first (e.g., regular) cycle, and wherein the plasma properties are continuously sensed after a second (e.g., regular) cycle, wherein a length of the first cycle is greater than a length of the second cycle.

In example 168, the subject matter of any of examples 159 to 167 can optionally include that a cycle of the second control loop is shorter than a cycle of the first control loop.

In Example 169, the article of any of Examples 159 to 168 can optionally include that sensing plasma properties associated with sputtering of the first element and/or the second element comprises: optically sensing plasma properties associated with sputtering of the first element and/or the second element (e.g., using optical emission spectroscopy (OES) (e.g., via OES imaging), interferometry, atomic absorption spectroscopy, and/or laser-induced fluorescence, etc.).

In Example 170, the article of any of Examples 159 to 97 can optionally comprise the first element being bismuth and the second element being iron.

In Example 171, the article of Example 160 in combination with Example 168 or 170 can optionally include that the set temperature has a temperature value below 630°C (e.g., below 600°C).

In Example 172, the article of Example 161 in combination with any of Examples 168 to 171 can optionally have the threshold value at a working pressure of about 0.2* 10 ^-2 mbar being about 630°C.

In Example 173, the article of any of Examples 159 to 172 can optionally include the material layer including a predefined phase comprising the first element and the second element; and wherein the method further comprises: during sputtering the first element and the second element, rotating the substrate at a rotational speed equal to or greater than a predefined rotational speed indicating that in one rotation (revolution) of the substrate, a sublayer of the material layer having a thickness of (approximately) a lattice constant of a crystal structure associated with the predefined phase is formed.

In Example 174, the article of Example 173 in combination with any of Examples 168 to 172 can optionally include that the predefined phase is bismuth ferrite (BiFeO ₃ ).

In example 175, the article of example 173 or 174 can optionally include that sputtering the first element and the second element comprises sputtering the first element and the second element off-center on the substrate.

In Example 176, the article of Example 175 can optionally include the substrate being a wafer; and wherein the first element and the second element are sputtered to impinge on the wafer at approximately an average radius of the wafer.

In Example 177, the article of Example 175 or 176 can optionally include that sputtering the first element and the second element comprises confocal co-sputtering the first element and the second element with a focus off-center on the substrate.

In example 178, the subject matter of example 175 or 176 can optionally include sputtering the first element and the second element comprising sputtering the first element to impinge off-center on the substrate having a first focus and sputtering the second element to impinge off-center on the substrate having a second focus different from the first focus.

In Example 179, the article of any of Examples 159 to 178 can optionally include that controlling sputtering based on the temperature of the substrate comprises controlling a supply of oxygen based on the temperature of the substrate.

In Example 180, the subject matter of any of Examples 159 to 179 can optionally include wherein sputtering the first element and the second element comprises sputtering the first element according to a first power and the second element according to a second power; and wherein controlling the sputtering based on the temperature of the substrate comprises: determining, based on the temperature of the substrate, a power ratio between the first power and the second power, and controlling the first power and the second power according to the power ratio.

In Example 181, the subject matter of any of Examples 159-180 can optionally include wherein sputtering the first element comprises radio frequency (RF) sputtering the first element according to a first power and a first power frequency; wherein sputtering the second element comprises direct current (DC) sputtering the second element according to a second power; and wherein controlling the sputtering based on the temperature of the substrate comprises: determining, based on the temperature of the substrate, a power ratio between the first power and the second power, and controlling the first power and the second power according to the power ratio, and/or determining, based on the temperature of the substrate, a frequency value of the first power frequency and controlling the sputtering of the first element according to the frequency value.

In Example 182, the subject matter of any of Examples 159-181 can optionally include wherein sputtering the second element comprises radio frequency (RF) sputtering the second element according to a second power and a second power frequency; sputtering the first element comprises direct current (DC) sputtering the first element according to a first power; and wherein controlling the sputtering based on the temperature of the substrate comprises: determining, based on the temperature of the substrate, a power ratio between the first power and the second power, and controlling the first power and the second power according to the power ratio, and/or determining, based on the temperature of the substrate, a frequency value of the second power frequency and controlling the sputtering of the second element according to the frequency value.

In Example 183, the subject matter of any of Examples 159-180 can optionally include wherein sputtering the first element comprises radio frequency (RF) sputtering the first element according to a first power and a first power frequency; wherein sputtering the second element comprises radio frequency (RF) sputtering the second element according to a second power and a second power frequency; and wherein controlling the sputtering based on the temperature of the substrate comprises: determining, based on the temperature of the substrate, a power ratio between the first power and the second power, and controlling the first power and the second power according to the power ratio, and/or determining, based on the temperature of the substrate, a frequency ratio between the first power frequency and the second power frequency and controlling the sputtering of the first element and the second element according to the frequency ratio.

In Example 184, the subject matter of any of Examples 159 to 183 can optionally include wherein sputtering the first element and the second element comprises sputtering the first element and the second element in an atmosphere; and wherein controlling the sputtering based on the temperature of the substrate comprises: determining, based on the temperature of the substrate, a pressure value representing a pressure of the atmosphere, and controlling the pressure of the atmosphere according to the pressure value.

In Example 185, the article of any of Examples 159 to 184 can optionally include that controlling sputtering based on plasma properties comprises controlling an oxygen supply based on plasma properties.

In Example 186, the subject matter of any of Examples 159 to 185 can optionally include wherein sputtering the first element and the second element comprises sputtering the first element according to a first power and the second element according to a second power; and wherein controlling the sputtering based on the plasma characteristics comprises: determining, based on the plasma characteristics, a power ratio between the first power and the second power, and controlling the first power and the second power according to the power ratio.

In Example 187, the subject matter of any of Examples 159-186 can optionally include wherein sputtering the first element comprises radio frequency (RF) sputtering the first element according to a first power and a first power frequency; wherein sputtering the second element comprises direct current (DC) sputtering the second element according to a second power; and wherein controlling the sputtering based on the plasma characteristics comprises: determining, based on the plasma characteristics, a power ratio between the first power and the second power, and controlling the first power and the second power according to the power ratio, and/or determining, based on the plasma characteristics, a frequency value of the first power frequency and controlling sputtering the first element according to the frequency value.

In Example 188, the subject matter of any of Examples 159-187 can optionally include wherein sputtering the second element comprises radio frequency (RF) sputtering the second element according to a second power and a second power frequency; sputtering the first element comprises direct current (DC) sputtering the first element according to a first power; and wherein controlling the sputtering based on the plasma characteristics comprises: determining, based on the plasma characteristics, a power ratio between the first power and the second power, and controlling the first power and the second power according to the power ratio, and/or determining, based on the plasma characteristics, a frequency value of the second power frequency and controlling the sputtering of the second element according to the frequency value.

In Example 189, the subject matter of any of Examples 159 to 186 can optionally include wherein sputtering the first element comprises radio frequency (RF) sputtering the first element according to a first power and a first power frequency; wherein sputtering the second element comprises radio frequency (RF) sputtering the second element according to a second power and a second power frequency; and wherein controlling the sputtering based on the plasma characteristics comprises: determining, based on the plasma characteristics, a power ratio between the first power and the second power, and controlling the first power and the second power according to the power ratio, and/or determining, based on the plasma characteristics, a frequency ratio between the first power frequency and the second power frequency and controlling sputtering the first element and the second element according to the frequency ratio.

In example 190, the article of any of examples 159 to 189 can optionally include wherein sputtering the first element and the second element comprises sputtering the first element and the second element in an atmosphere; and wherein controlling the sputtering based on the plasma characteristics comprises: determining, based on the plasma characteristics, a pressure value representing a pressure of the atmosphere, and controlling the pressure of the atmosphere according to the pressure value.

Example 191 is a sputter controller comprising: a power supply configured to operate one or more sputter sources, wherein the one or more sputter sources are configured to sputter at least a first element and a second element; and a controller configured to: (eg, continuously (eg, at predefined (eg, regular) time intervals)) receive plasma data representing plasma properties associated with sputtering of the first element and/or the second element; determine, based on the plasma data, one or more operating parameters of the one or more sputter sources; control the power supply based on the one or more operating parameters; (eg, continuously (eg, at predefined (eg, regular) time intervals)) receiving temperature data representing a temperature of the material layer; determining whether the temperature of the substrate is changing; in the event that the temperature of the substrate is changing, adjusting the one or more operating parameters based on a temperature change of the substrate; and controlling the power supply based on the adjusted one or more operating parameters.

In Example 192, the subject matter of Example 191 can optionally include wherein the temperature data comprises the temperature of the substrate; and/or wherein the temperature data comprises the temperature of a heating element (e.g., a resistive heating element and/or a lamp array) configured to heat the substrate to the set temperature.

Example 193 is a sputtering system comprising: the sputter controller of example 191 or 192; and the one or more sputtering sources.

In Example 194, the sputtering system of Example 193 can optionally further comprise: a temperature sensor configured to sense a temperature representing the temperature of the substrate and to provide temperature data according to the sensed temperature to the sputtering controller.

In Example 195, the subject matter of Example 194 can optionally include wherein the temperature sensor is configured to sense the temperature of the substrate; and/or wherein the sputtering system further comprises a heater configured to heat the substrate to a set temperature, and wherein the temperature sensor is configured to sense a temperature representative of a temperature of the substrate.

In example 196, the sputtering system of any of examples 193 to 195 can optionally further comprise: a substrate carrier on which a substrate can be placed; and a motor configured to drive the substrate holder to rotate according to a set rotation speed; wherein the controller of the sputter controller is configured to adjust the rotation speed based on the one or more operating parameters.

In example 197, the sputtering system according to any one of examples 193 to 196 can optionally further comprise: a vacuum chamber; and a device (e.g., a mass flow controller and/or a gate valve) configured to define an oxygen flow into the vacuum chamber; the control device of the sputter controller configured to control the device to define the oxygen flow depending on the one or more operating parameters.

In Example 198, the sputtering system of any of Examples 193 to 197 can optionally further comprise: an optical sensor configured to sense plasma properties.

Example 199 is a method comprising: radio frequency (RF) sputtering a first element (e.g., Bi) according to a first power frequency value; and radio frequency (RF) sputtering a second element (e.g., Fe) according to a second power frequency value that is different from the first power frequency value.

Example 200 is a method comprising: radio frequency (RF) sputtering a first element (e.g., Bi or Fe) according to a first power frequency value; and direct current (DC) sputtering a second element (e.g., Fe or Bi).

In example 201, the article of example 199 or 200 can optionally include wherein the first element is sputtered with a first sputtering source and wherein the second element is sputtered with a second sputtering source; or wherein the first element and the second element are sputtered with a common sputtering source.

Example 202 is a magnetron sputtering source comprising: a first target having a circular shape or an annular shape, the first target containing a first material; a second target having an annular shape, the second target containing a second material different from the first material and arranged concentrically to the first target and not electrically conductively connected to the first target; a magnet system configured to generate a first magnetic field through the first target and a second magnetic field through the second target, wherein a first field strength distribution of the first magnetic field differs from a second field strength distribution of the second magnetic field.

In example 203, the subject matter of example 202 can optionally include that the first field strength distribution and the second field strength distribution are preconfigured.

In example 204, the article according to example 203 can optionally comprise that the magnet system comprises one or more first magnets which are used to generate the first magnetic field by the first target, and one or more second magnets configured to generate the second magnetic field through the second target; and in that: the one or more first magnets have a first magnetic field strength, and wherein the one or more second magnets have a second magnetic field strength that is different from the first magnetic field strength; and/or the one or more first magnets have a geometry that is different from the one or more second magnets; and/or a number of magnets of the one or more first magnets differs from a number of magnets of the one or more second magnets.

In example 205, the subject matter of example 202 can optionally include the magnet system comprising: one or more first magnets configured to generate the first magnetic field through the first target and one or more second magnets configured to generate the second magnetic field through the second target; and a magnet control device configured to: control a distance between the one or more first magnets and the first target, and/or control a distance between the one or more second magnets and the second target; and/or control an orientation of the one or more first magnets relative to the first target, and/or control an orientation of the one or more second magnets relative to the second target.

In example 206, the article of any of examples 202 to 205 can optionally include that the first material includes iron and the second material includes bismuth.

In example 207, the article of example 206 can optionally include wherein the first magnetic field has a first magnetic field strength and wherein the second magnetic field has a second magnetic field strength that is greater than the first magnetic field strength.

In example 208, the magnetron sputtering source according to any one of examples 202 to 207 can optionally further comprise: a third target having an annular shape, wherein the third target contains a third material that is different from the first material and the second material, and wherein the third target is arranged concentrically to the second target and is not electrically conductively connected to the first target and the second target.

In example 209, the article of example 208 can optionally include that the magnet system is configured to generate a third magnetic field through the third target, wherein a third field strength distribution of the third magnetic field is different from the second field strength distribution of the second magnetic field and the first field strength distribution of the first magnetic field.

In example 210, the article of example 208 or 209 can optionally include the first target consisting essentially of bismuth, the second target consisting essentially of iron, and the third target consisting essentially of bismuth ferrite; or the first target consisting essentially of bismuth, the second target consisting essentially of bismuth ferrite, and the third target consisting essentially of titanium.

Example 211 is a method comprising depositing a layer of material on a substrate rotating at a rotational speed equal to or greater than a predefined rotational speed, the layer of material comprising at least a first element (e.g., Bi) and a second element (e.g., Fe) in a predefined phase; wherein the predefined rotational speed indicates that upon rotation (revolution) of the substrate, a sublayer of the layer of material having a thickness of (approximately) a lattice constant of a crystal structure associated with the predefined phase is formed.

In Example 212, the method of Example 211 can optionally further comprise: wherein depositing the material layer comprises: generating a deposition material stream for depositing onto the substrate, the deposition material stream comprising the first element and the second element.

In Example 213, the method of Example 212 can optionally further comprise: wherein the deposition material stream is generated in an atmosphere containing oxygen (e.g., by reactive co-sputtering the first element and the second element) (wherein the atmosphere optionally further contains an inert gas) or wherein the deposition material stream contains oxygen (e.g., in case of two sputtering targets: the first sputtering target can contain an oxide of the first element and/or the second sputtering target can contain an oxide of the second element; or in case of a single sputtering target: the common sputtering target can contain an oxide of the first element and the second element).

In example 214, the article of example 212 or 213 can optionally include generating the deposition material stream to impinge off-center on the substrate.

In Example 215, the article of Example 214 can optionally comprise that the substrate is a wafer; and that the deposition material stream to impact the wafer at approximately an average radius of the wafer.

In Example 216, the article of any of Examples 212 to 215 can optionally include that generating the deposition material stream comprises confocal co-sputtering the first element and the second element with the focus being off-center on the substrate.

In example 217, the article of any of examples 212 to 216 can optionally include generating the deposition material stream comprising generating a first deposition material stream by sputtering the first element and generating a second deposition material stream by sputtering the second element.

In example 218, the subject matter of examples 214 and 217 can optionally include the first deposition material stream being generated to off-center impact the substrate at a first focus and the second deposition material stream being generated to off-center impact the substrate at a second focus different from the first focus.

In Example 219, the method of any of Examples 212 to 218 can optionally further comprise: heating the substrate to a predetermined temperature prior to depositing the material layer on the substrate.

In Example 220, the subject matter of Examples 212 and 219 can optionally include that the material layer contains the first element and the second element in a predefined atomic ratio; wherein the first element has a greater temperature dependent evaporation rate from the substrate and/or the material layer than the second element; that the deposition material stream has an atomic ratio of the first element to the second element that is greater than the predefined atomic ratio; and that the temperature value is adjusted to evaporate atoms of the first element from the substrate and/or the material layer such that the material layer has the predefined atomic ratio of the first element and the second element.

In example 221, the article of example 220 can optionally include the temperature being set to a temperature value equal to or greater than a threshold value representing a vapor pressure of the first element at a working pressure of an atmosphere in which the material layer is to be deposited.

In example 222, the method of examples 212 and 219 can optionally further include setting the temperature to a temperature value less than a threshold value representing a vapor pressure of the first element at a working pressure of an atmosphere in which the material layer is to be deposited.

In Example 223, the subject matter of any of Examples 211-222 can optionally include that depositing the material layer comprises sputtering the first element according to a first power and the second element according to a second power to deposit the material layer on the substrate; and that the method further comprises: (e.g., continuously (e.g., at predefined (e.g., regular) time intervals)) sensing a temperature of the substrate, and controlling the first power and the second power to adjust a power ratio between the first power and the second power based on the temperature of the substrate.

In Example 224, the subject matter of any of Examples 211-223 can optionally include that depositing the material layer comprises sputtering the first element according to a first power and the second element according to a second power to deposit the material layer on the substrate; and that the method further comprises: (e.g., continuously (e.g., at predefined (e.g., regular) time intervals)) sensing plasma characteristics associated with sputtering the first element and/or the second element, and controlling the first power and the second power to adjust the power ratio between the first power and the second power based on the plasma characteristics.

In example 225, the method of example 223 or 224 can optionally further comprise controlling the rotation speed based on the first power and the second power.

In Example 226, the article of any of Examples 211 to 225 can optionally include the first element being bismuth and the second element being iron.

In Example 227, the subject matter of Examples 213 and 226 can optionally include that the predefined phase is bismuth ferrite (BiFeO ₃ ).

In Example 228, the article of Example 219 in combination with Example 226 or 227 can optionally have the threshold value at a working pressure of about 0.2* 10 ^-2 mbar being about 630°C.

In Example 229, the method of any of Examples 211 to 228 can optionally further comprise: during the application of the material layer, irradiating the substrate and/or the sublayer with a linear lamp arrangement.

Example 230 is a method comprising: depositing a material layer on a substrate, the material layer comprising at least a first element (e.g., Bi) and a second element (e.g., Fe) in a predefined phase; and during depositing the material layer: irradiating the substrate and/or the deposited material using a linear lamp arrangement, and rotating the substrate while irradiating the substrate and/or the deposited material using the linear lamp arrangement.

Example 231 is a method comprising: depositing a material layer on a substrate, the material layer comprising at least a first element (e.g., Bi) and a second element (e.g., Fe) in a predefined phase; and after depositing the material layer: irradiating the material layer using a linear lamp arrangement, and rotating the substrate while irradiating the material layer using the linear lamp arrangement.

Example 232 is a method comprising: forming a complementary metal oxide semiconductor (CMOS) structure in or over a substrate; forming a metallization structure over the CMOS structure; forming one or more memristive devices over the metallization structure, wherein forming the one or more memristive devices comprises: reactively co-sputtering bismuth, iron, and titanium in an atmosphere comprising oxygen (the atmosphere optionally further comprising an inert gas) to create a layer of material comprising (e.g., consisting essentially of) titanium-doped bismuth ferrite (Ti: _BiFeO3 ); or co-sputtering bismuth, iron, oxygen, and titanium to create a layer of material comprising (e.g., consisting essentially of) titanium-doped bismuth ferrite (Ti:BiFeO5).

In Example 233, the method of Example 232 can optionally further comprise forming a metal layer over the metallization structure prior to forming the one or more memristive devices.

In Example 234, the method of Example 233 can optionally further comprise: during or after forming the one or more memristive devices, irradiating the material layer using a linear lamp array, wherein the metal layer is configured to reflect at least 70% (e.g., at least 90%) of incident radiation from the linear lamp array.

In Example 235, the article of any of Examples 232 to 234 can optionally include that co-sputtering of bismuth, iron, oxygen, and titanium comprises sputtering at least one of bismuth, iron, and/or titanium from an oxide target (e.g., bismuth oxide (e.g., Bi2O3), and/or iron oxide (e.g., Fe2O3), and/or titanium oxide (e.g., TiO2).

In Example 236, the article of any of Examples 232 to 235 can optionally include that co-sputtering of bismuth, iron, oxygen, and titanium comprises sputtering bismuth, iron, and titanium from a common target.

In Example 237, the article of any of Examples 232 to 236 can optionally comprise reactive co-sputtering of bismuth, iron, and titanium comprising: co-sputtering bismuth from a bismuth target, iron from an iron target, and titanium from a titanium target; or co-sputtering bismuth, iron, and titanium from a common target; or co-sputtering bismuth, iron, and titanium from a common target, bismuth from a bismuth target, and iron from an iron target; or co-sputtering bismuth, iron, and titanium from a first target, and bismuth and iron from a second target different from the first target; or co-sputtering bismuth and titanium from a common target and iron from an iron target; or co-sputtering iron and titanium from a common target and bismuth from a bismuth target; or co-sputtering bismuth and titanium from a first target and iron and titanium from a second target.

In Example 238, the article of any of Examples 232 to 237 can optionally include the one or more memristive devices being formed at a temperature of the substrate equal to or greater than 630°C.

In Example 239, the article of any of Examples 232 to 238 can optionally include that the one or more memristive devices are formed at a temperature of the substrate below 630°C; that bismuth is sputtered according to a first power and that iron is sputtered according to a second power; and wherein the method further comprises, during sputtering: (eg, continuously (eg, at predefined (eg, regular) time intervals)) sensing a temperature of the substrate, and controlling sputtering based on the temperature of the substrate; and/or (eg, continuously (eg, at predefined (eg, regular) time intervals)) sensing plasma properties associated with the sputtering. and controlling sputtering based on plasma properties.

In Example 240, the article of Example 239 can optionally include the material layer having a predefined titanium concentration; wherein bismuth is sputtered from a first sputtering target according to the first power, and wherein iron is sputtered from a second sputtering target according to the second power, wherein the second sputtering target is different from the first sputtering target; further wherein bismuth and iron are sputtered from a third sputtering target according to a third power, wherein the third sputtering target is different from the first sputtering target and the second sputtering target, and the third sputtering target contains bismuth, iron, and titanium; and wherein the method further comprises, during sputtering, controlling the third power such that the material layer has the predefined titanium concentration.

Example 241 is a non-transitory computer-readable medium containing instructions that, when executed by one or more processors, cause the one or more processors to perform the method of any of Examples 1-49, 56-73, 86-107, 115-142, 159-190, 199-201, and/or 211-240.

Example 242 is a sputtering source (e.g., magnetron sputtering source) comprising: a plurality of sputtering targets; and a target controller configured to: control a position and/or orientation of at least one sputtering target of the plurality of sputtering targets relative to the others; and/or rotate at least one sputtering target of the plurality of sputtering targets in the plane.

In example 243, the article of example 242 can further optionally include each sputtering target of the plurality of sputtering targets being stripe-shaped.

In example 244, the article of example 242 or 243 can further optionally include the plurality of sputtering targets being arranged in an alternating sequence of targets having at least the first element and targets having at least the second element.

In Example 245, the sputtering source of any of Examples 242 to 244 may optionally include the features of any of Examples 202 to 210.

In Example 246, the method of any of Examples 1 to 49, 56 to 73, 86 to 107, 115 to 142, 159 to 190, 199 to 201, and/or 211 to 240 can optionally further comprise: controlling a position and/or orientation of at least one sputtering target of a plurality of sputtering targets relative to the others; and/or rotating at least one sputtering target of the plurality of sputtering targets in the plane.

Example 247 is a wafer chuck comprising: a base plate for supporting a wafer, the base plate having an inner region and an outer region, the inner region being closer to a center of the base plate than the outer region; and one or more resistive heaters for heating the base plate, the one or more resistive heaters configured to generate more heat in the outer region than in the inner region of the base plate.

In example 248, the article of example 247 can further optionally include the one or more resistive heaters comprising one or more electrically conductive lines configured such that a resistance of the one or more electrically conductive lines is greater in the outer region than in the inner region.

In example 249, the article of example 247 or 248 can optionally further comprise the one or more resistive heaters comprising one or more electrically conductive leads (e.g., the), wherein the turns of the one or more electrically conductive leads in the outer region are closer together than the turns of the one or more electrically conductive leads in the inner region.

In Example 250, any of the sputtering systems described with reference to any of the preceding examples may include the wafer chuck of any of Examples 247 to 249.

In Example 251, the method of any of Examples 1 to 49, 56 to 73, 86 to 107, 115 to 142, 159 to 190, 199 to 201, and/or 211 to 240 can optionally further comprise heating the substrate during application of the material layer using one or more resistive heaters configured to generate more heat in an outer region than in an inner region.

Although the invention has been particularly shown and described with reference to certain aspects, it should be apparent to those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is therefore to be determined in the appended claims. claims, and all changes which come within the meaning and range of equivalence of the claims are therefore intended to be incorporated.

Claims (20)

A magnetron sputtering source (104(n)), comprising: • a first target (106(n, 1)) with an annular shape or a circular shape, the first target (106(n, 1)) comprising a first material; • a second target (106(n, 2)) with an annular shape, wherein the second target (106(n, 2)) comprises a second material different from the first material and is arranged concentrically to the first target (106(n, 1)); • a magnet system (206(n)) configured to generate a first magnetic field through the first target (106(n, 1)) and a second magnetic field through the second target (106(n, 2)), wherein a first field strength distribution of the first magnetic field differs from a second field strength distribution of the second magnetic field. The magnetron sputtering source (104(n)) according to Claim 1 , wherein the magnet system (206(n)) comprises one or more first magnets (208(n, 1)) configured to generate the first magnetic field through the first target (106(n, 1)), and one or more second magnets (208(n, 2)) configured to generate the second magnetic field through the second target (106(n, 1)); and wherein: • the one or more first magnets (208(n, 1)) have a first magnetic field strength and wherein the one or more second magnets (208(n, 2)) have a second magnetic field strength different from the first magnetic field strength; and/or • the one or more first magnets (208(n, 1)) have a geometry different from the one or more second magnets (208(n, 2)); and/or • a number of magnets of the one or more first magnets (208(n, 1)) is different from a number of magnets of the one or more second magnets (208(n, 2)). The magnetron sputtering source (104(n)) according to Claim 1 or 2 , wherein the magnet system (206(n)) comprises: • one or more first magnets (208(n, 1)) configured to generate the first magnetic field through the first target (106(n, 1)), and one or more second magnets (208(n, 2)) configured to generate the second magnetic field through the second target (106(n, 2)); and • a magnet control device configured to: o control a distance between the one or more first magnets (208(n, 1)) and the first target (106(n, 1)) and/or control a distance between the one or more second magnets (208(n, 2)) and the second target (106(n, 2)); and/or o controlling an orientation of the one or more first magnets (208(n, 1)) relative to the first target (106(n, 1)) and/or controlling an orientation of the one or more second magnets (208(n, 2)) relative to the second target (106(n, 2)). The magnetron sputtering source (104(n)) according to any of the Claims 1 until 3 , wherein the first material comprises iron and the second material comprises bismuth. The magnetron sputtering source (104(n)) according to Claim 4 , wherein the first magnetic field has a first magnetic field strength and wherein the second magnetic field has a second magnetic field strength that is less than the first magnetic field strength. The magnetron sputtering source (104(n)) according to any of the Claims 1 until 5 , further comprising: • a third target (106(n, 3)) having an annular shape, wherein the third target (106(n, 3)) comprises a third material that is different from the first material and the second material, and wherein the third target (106(n, 3)) is arranged concentrically to the second target (106(n, 2)). The magnetron sputtering source (104(n)) according to Claim 6 , wherein the first target (106(n, 1)) consists essentially of bismuth, wherein the second target (106(n, 2)) consists essentially of iron, and wherein the third target (106(n, 3)) consists essentially of bismuth ferrite; or wherein the first target (106(n, 1)) consists essentially of bismuth, wherein the second target (106(n, 2)) consists essentially of bismuth ferrite, and wherein the third target (106(n, 3)) consists essentially of titanium. A sputter controller (108), comprising: • a power supply configured to operate one or more sputter sources (104(n)), wherein the one or more sputter sources (104(n)) are configured to sputter at least a first element and a second element; and • a control device configured to: o receive plasma data representing plasma properties associated with the sputtering of the first element and/or the second element; o determine, based on the plasma data, one or more operating parameters of the one or more sputter sources; o control the power supply based on the one or more operating parameters; o receiving temperature data representing a temperature of the material layer; o determining whether the temperature of the substrate is changing; o in the event that the temperature of the substrate is changing, adjusting the one or more operating parameters based on a temperature change of the substrate; and o controlling the power supply based on the adjusted one or more operating parameters. The sputter control (108) according to Claim 8 , wherein the temperature data comprises the temperature of the substrate; and/or wherein the temperature data comprises a temperature of a heater configured to heat the substrate. The sputter control (108) according to Claim 8 or 9 , • wherein the power supply is configured to operate the one or more sputter sources (104(n)) for radio frequency sputtering the first element according to a first power frequency and for radio frequency sputtering the second element according to a second power frequency; • wherein the one or more operating parameters comprise a frequency ratio between the first power frequency and the second power frequency; and • wherein the control device is configured to control the operation of the one or more sputter sources by controlling the first power frequency and the second power frequency according to the frequency ratio. The sputter control (108) according to Claim 8 or 9 , wherein the power supply is configured to operate the one or more sputter sources (104(n)) for radio frequency sputtering the first element according to a first power and a first power frequency and for DC sputtering the second element according to a second power; and wherein the one or more operating parameters comprise: • a power ratio between the first power and the second power, and wherein the control device is configured to control the operation of the one or more sputter sources (104(n)) by controlling the first power and the second power according to the power ratio; and/or • a frequency value of the first power frequency, and wherein the control device is configured to control the operation of the one or more sputter sources (104(n)) by controlling the first power frequency according to the frequency value. The sputter control (108) according to any of the Claims 8 until 11 , wherein the control device is configured to control the power supply based on the plasma properties and the temperature of the substrate by means of a first control loop and a second control loop, wherein the first control loop comprises determining the one or more operating parameters based on the temperature of the substrate and controlling the sputtering according to the one or more operating parameters, and wherein the second control loop comprises determining the one or more operating parameters based on the plasma properties and controlling the sputtering according to the one or more operating parameters, wherein a cycle of the second control loop is shorter than a cycle of the first control loop. The sputter control (108) according to any of the Claims 8 until 12 , where the first element is bismuth and the second element is iron. A sputtering system (100), comprising: • the sputter control (108) according to any of the Claims 8 until 13 ; and • the one or more sputter sources. The sputtering system (100) according to Claim 14 , wherein at least one sputter source of the one or more sputter sources is a magnetron sputter source (104(n)) according to any of the Claims 1 until 7 . The sputtering system (100) according to Claim 14 or 15 , further comprising: a temperature sensor (126) configured to detect a temperature representing the temperature of the substrate (116) and to provide temperature data according to the detected temperature to the sputter controller (108). The sputtering system (100) according to any one of the Claims 14 until 16 , further comprising: a substrate holder (114) on which a substrate (116) can be placed; and a motor (132) configured to drive the substrate holder (114) to rotate according to a set rotation speed; wherein the control device of the sputter controller (108) is configured to set the rotation speed based on the one or more operating parameters. The sputtering system (100) according to any one of the Claims 14 until 17 , further comprising: an optical sensor (128) configured to detect plasma properties. A sputter source (104(n)) comprising: a plurality of sputter targets; and a target control device configured to: • control a position and/or orientation of at least one sputter target (106(n)) of the plurality of sputter targets relative to the others; and/or • rotate at least one sputter target (106(n)) of the plurality of sputter targets in the plane. A wafer chuck comprising: a base plate for supporting a wafer, the base plate having an inner region and an outer region, the inner region being closer to a center of the base plate than the outer region; and one or more resistive heaters (124) for heating the base plate, the one or more resistive heaters (124) being configured to generate more heat in the outer region than in the inner region of the base plate.

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