WO2017016576A1

WO2017016576A1 - Deposition source, vacuum deposition apparatus, and methods of operating thereof

Info

Publication number: WO2017016576A1
Application number: PCT/EP2015/067049
Authority: WO
Inventors: Frank Schnappenberger; Thomas Deppisch
Original assignee: Applied Materials, Inc.
Priority date: 2015-07-24
Filing date: 2015-07-24
Publication date: 2017-02-02
Also published as: KR102025917B1; KR20180021155A; TW201706433A; CN208400806U

Abstract

A deposition source (100, 200, 201, 300) for sputter deposition is described. The deposition source includes: a cathode (130, 230) for providing a target material to be deposited; at least one anode assembly (110, 210) having at least a first anode segment (111, 211) which faces a first portion of the cathode and a second anode segment (112, 212) which faces a second portion of the cathode; and a connector assembly (120). The connector assembly includes: a first electric connection (121) for connecting the first anode segment (111, 211) to a first reference potential (PI); a second electric connection (122) for connecting the second anode segment (112, 212) to a second reference potential (P2); and an adjusting means (150) for adjusting at least one of a first electric resistance of the first electric connection (121) and a second electric resistance of the second electric connection (122).

Description

DEPOSITION SOURCE, VACUUM DEPOSITION APPARATUS, AND METHODS

OF OPERATING THEREOF

TECHNICAL FIELD

[0001] Embodiments of the present invention relate to a deposition source for sputter deposition, a vacuum deposition apparatus, and methods of operating thereof. Embodiments specifically relate to a deposition source for sputtering by applying a DC voltage between a cathode and an anode assembly, a vacuum deposition apparatus with a deposition source for DC sputtering in a vacuum chamber, and a method of operating a sputter deposition source for coating a substrate with one or more thin layers. BACKGROUND

[0002] PVD processes, particularly sputtering processes, gain increasing attention in some technical fields, e.g. display manufacturing. A good deposition rate can be obtained with sufficient layer characteristics by various sputtering techniques. Sputtering, particularly magnetron sputtering, is a technique for coating substrates such as glass or plastic substrates with metallic or non-metallic layers. Accordingly, a stream of coating material is generated by sputtering a target with the use of a plasma. Material is released from the target surface as a result of collisions with high-energy particles from the plasma, wherein plasma parameters such as pressure, power, gas, magnetic field etc. are controlled. The material released from the target travels from the target toward one or more substrates to be coated and adheres thereto. A wide variety of materials, including metals, semiconductors and dielectric materials can be sputtered to desired specifications. Magnetron sputtering has found acceptance in a variety of applications including semiconductor processing, optical coatings, food packaging, magnetic recording, and protective wear coatings.

[0003] Sputtering devices may include at least one cathode including a target for providing the coating material to be deposited on the substrate, and at least one anode assembly. An electric field may be applied between the cathode and the anode assembly so that a gas located between the cathode and the anode assembly is ionized and a plasma is generated. The motion of the plasma ions may be controlled by magnetic elements. The coating material is provided through sputtering of the target by the plasma ions. [0004] Sputtering is accomplished using a wide variety of devices having differing electrical, magnetic, and mechanical configurations. The known configurations include power arrangements providing direct current (DC) or alternating current (AC) for producing the plasma, wherein DC sputtering may provide particularly high deposition rates. In a radio frequency (RF) sputtering apparatus, the plasma is ignited and maintained by applying an RF electric field. Accordingly, also non-conductive materials may be sputtered. However, RF sputtering provides lower deposition rates.

[0005] Sputtering devices with both static targets such as flat plate targets and rotating targets such as rotating cylindrical targets may be used. The anode assembly may be arranged at a given distance spaced apart from the cathode, depending on the cathode geometry and on the substrate geometry. Sputtering devices may be adapted for coating large area substrates, e.g. large area movable substrates. However, it may be difficult to obtain an excellent layer uniformity on large area substrates. According to the embodiments described herein, layer uniformity of sputtered layers can be improved. SUMMARY

[0006] In light of the above, according to the independent claims, a deposition source for sputter deposition, a vacuum deposition apparatus for sputter deposition and a method of operating a deposition source are provided. Further aspects, advantages, and features of the present invention are apparent from the dependent claims, the description, and the accompanying drawings.

[0007] According to one embodiment, a deposition source for sputter deposition is provided. The deposition source includes a cathode for providing a target material to be deposited on a substrate; at least one anode assembly having at least a first anode segment which faces a first portion of the cathode and a second anode segment which faces a second portion of the cathode; and a connector assembly. The connector assembly includes a first electric connection for connecting the first anode segment to a first electric potential, e.g. a ground electric potential or a positive electric potential; a second electric connection for connecting the second anode segment to a second electric potential, e.g. a ground electric potential or a positive electric potential; and an adjusting means for adjusting at least one of a first electric resistance of the first electric connection and a second electric resistance of the second electric connection. [0008] In some embodiments, the adjusting means includes at least one variable resistor or potentiometer.

[0009] According to another aspect, a vacuum deposition apparatus for sputter deposition is provided. The vacuum deposition apparatus includes a vacuum chamber and a deposition source. The deposition source includes: a cathode for providing a target material to be deposited; at least one anode assembly having at least a first anode segment which faces a first portion of the cathode and a second anode segment which faces a second portion of the cathode; and a connector assembly. The connector assembly includes a first electric connection for connecting the first anode segment to a first electric potential; a second electric connection for connecting the second anode segment to a second electric potential; and an adjusting means for adjusting at least one of a first electric resistance of the first electric connection and a second electric resistance of the second electric connection. In embodiments, the cathode and the anode assembly are positioned inside the vacuum chamber, wherein at least a control element of the adjusting means is positioned outside the vacuum chamber.

[0010] According to another aspect, a method of operating a deposition source for sputter deposition is provided. The method includes spatially controlling a charge flow between a cathode and first and second anode segments of an anode assembly by adjusting at least one of a first electric resistance of a first electric connection connected to the first anode segment and a second electric resistance of a second electric connection connected to the second anode segment. The first electric connection may be configured for connecting the first anode segment to a first electric potential, e.g. a positive electric potential, and the second electric connection may be configured for connecting the second anode segment to a second electric potential, e.g. a positive electric potential. [0011] Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing the individual method actions. The method may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments described herein are also directed at methods for operating the described apparatus. [0012] Further advantages, features, aspects and details that can be combined with embodiments described herein are evident from the dependent claims, the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments and are described in the following:

[0014] FIG. 1 is a schematic view of a deposition source for sputter deposition according to embodiments described herein;

[0015] FIG. 2 is a schematic view of a deposition source for sputter deposition according to embodiments described herein;

[0016] FIG. 3 is a schematic view of a deposition source for sputter deposition according to embodiment described herein;

[0017] FIG. 4 is a plan view of a vacuum deposition apparatus with a deposition source for sputter deposition according to embodiments described herein; [0018] FIG. 5 is a perspective view of the vacuum deposition apparatus shown in FIG. 4;

[0019] FIG. 6 is a schematic view of a vacuum deposition apparatus with several sputter deposition sources according to embodiments described herein; and

[0020] FIG. 7 shows a flowchart of a method for operating a deposition source for sputter deposition according to embodiments described herein.

DETAILED DESCRIPTION OF EMBODIMENTS

[0021] Reference will now be made in detail to the various embodiments described herein, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation and is not meant as a limitation. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[0022] In the present disclosure, a "deposition source" may be understood as a deposition source for sputter deposition including a cathode for providing a target material to be deposited on a substrate. The cathode may include a target made of the material to be deposited. For example, the target may be made of or include at least one material selected from the group consisting of: aluminum, silicon, tantalum, molybdenum, niobium, titanium, indium, gallium, zinc, tin, silver and copper. Particularly, the target material can be selected from the group consisting of indium, gallium and zinc. Typically, on the other hand, the anode assembly is not provided with a target material to be deposited.

[0023] Sputtering may be accomplished with a wide variety of devices having differing electrical, magnetic, and mechanical configurations. Some configurations include a power supply connected to the cathode and/or to the anode assembly for connecting the cathode and/or the anode assembly to different electric potentials, e.g. for connecting the anode assembly to a ground electric potential or a positive electric potential and for connecting the cathode to a negative electric potential. A potential difference and, thus, an electric field may be applied to a gas located between the cathode and the opposedly charged anode assembly so that the gas is ionized and a plasma is maintained in a region between the cathode and the anode. [0024] The power supply may be adapted for providing direct current (DC) for producing the plasma. For example, a first output terminal of the power supply having a ground electric potential or a positive electric potential may be connected to the anode assembly, and a second output terminal of the power supply having a negative electric potential may be connected to the cathode. As used herein, the term "connected to an electric potential" may stand for an electric connection to a conductor having an electric potential, e.g. a ground potential, a positive potential or a negative potential with reference to the ground potential.

[0025] FIG. 1 shows a deposition source 100 for sputter deposition, including a cathode 130 and an anode assembly 110. The anode assembly includes two or more anode segments, e.g. a first anode segment 111 and a second anode segment 112, wherein the first anode segment 111 faces a first portion of the cathode and the second anode segment 112 faces a second portion of the cathode. An electric field may be applied to a gas located between the cathode and the first anode segment and between the cathode and the second anode segment, in order to ionize the gas for sputtering the target.

[0026] Further, the deposition source 100 includes a connector assembly 120 with a first electric connection 121 for connecting the first anode segment 111 to a first electric potential PI, e.g. a positive electric potential, and a second electric connection 122 for connecting the second anode segment 112 to a second electric potential P2, e.g. a positive electric potential. The connector assembly 120 further includes an adjusting means 150 for adjusting at least one of a first electric resistance of the first electric connection 121 and a second electric resistance of the second electric connection 122. [0027] For example, the adjusting means 150 may be configured to increase or decrease the first electric resistance of the first electric connection 121 connecting the first anode segment 110 with the first electric potential PI. A decrease of the electric resistance of the first electric connection 121 may lead to an increase in an electric current flowing through the first anode segment. Thus, a charge flow from the cathode 130 to the first anode segment 111 may be increased, which in turn may lead to a higher sputtering rate in an upper part of the cathode and to a higher deposition rate in an upper part of the substrate. In other words, an electric field between the cathode and the first anode segment may be varied by varying the electric resistance of the first electric connection connecting the first anode segment to the first electric potential PI. [0028] In some embodiments, the adjusting means 150 may additionally or alternatively be configured to increase or decrease the second electric resistance of the second electric connection 122 connecting the second anode segment 112 with the second electric potential P2. An increase in the electric resistance of the second electric connection 122 may lead to a decrease in an electric current flowing through the second anode segment. Thus, a charge flow from the cathode 110 to the second anode segment 112 may be reduced, which in turn may lead to a lower sputtering rate in a lower part of the cathode and to a lower deposition rate in a lower part of the substrate. In other words, an electric field between the cathode and the second anode segment 112 may be varied by varying the electric resistance of the second electric connection 122 connecting the second anode segment to the second electric potential P2, which may be a constant positive potential.

[0029] By adjusting at least one of the first electric resistance of the first electric connection and the second electric resistance of the second electric connection, the deposition rate may be spatially controlled, so that a better uniformity of the layer to be deposited on the substrate can be achieved. In particular, for some applications, a desired layer uniformity of layers deposited on large area substrates may be +1-3% or better, which may be difficult to achieve over the full area of the substrate. However, according to embodiments disclosed herein, by adjusting the first electric resistance and/or the second electric resistance, a good layer uniformity may be achieved.

[0030] According to embodiments described herein, it may not be necessary to connect the anode segments 111, 112 to respective individually adjustable power supplies, wherein a voltage level supplied to each of the anode segments is adjustable by control units of the respective power supplies. In contrast thereto, according to the embodiment shown in FIG. 1, no adjustable power supply may be necessary, because a charge flow through the anode segments may be individually adjusted by varying an electric resistance of at least one of the first electric connection 111 and the second electric connection 112. However, in some embodiments, an adjustable power supply may be provided. [0031] In some embodiments described herein, both the first potential PI and the second potential P2 may be a ground or zero potential. In other words, both the first anode segment 111 and the second anode segment 112 may be connected to an earthed conductor, e.g. to a grounded vacuum chamber or to an output terminal of a power supply provided on a ground potential with respect to a negative cathode potential. At the same time, an electric resistance of at least one electric connection connecting an anode segment and the earthed conductor may be adjustable, so that the charge flow through said anode segment may be controlled by adjusting the electric resistance.

[0032] For example, in some implementations, the first potential PI may correspond to the second potential P2, wherein the first and second potentials PI, P2 are positive with respect to a ground or zero potential. An example would be to connect both the first anode segment and the second anode segment to the same positive output terminal of a power supply, whereas a negative output terminal of the power supply may be connected to the cathode.

[0033] In some embodiments, the first anode segment may be connected to a first output terminal of a power supply having a first potential PI (e.g. providing a first positive voltage), and the second anode segment may be connected to a second output terminal of a power supply having a second potential P2 (e.g. providing a second positive voltage) different from the first potential PI . [0034] In some implementations, the first and/or the second potentials PI, P2 may be adjustable, e.g. by connecting the first anode segment and the second anode segment to a power supply with an adjustable output voltage. In other implementations, the first and/or the second potentials PI, P2 may be constant, e.g. ground potentials or constant positive potentials.

[0035] The first electric connection 121 and the second electric connection 122 may include electric conductors, e.g. wires, cables, leads etc., wherein a first end of the electric conductor may be connected to the respective anode segment and a second end of the electric conductor may be connected to a respective further conductor providing the first or second electric potential PI, P2, e.g. an output terminal of a power supply. One or more electric resistors may be inserted between the first end of the electric conductor and the second end of the electric conductor. For example, the first electric resistance of the first electric connection 121 may be measured between the first end of a conductor connected to the first anode segment and the second end of the conductor connected to the output terminal of a power supply, wherein one or more electric resistors may be inserted into the conductor between the first and the second end.

[0036] According to embodiments described herein, at least one of the first electric resistance of the first electric connection 121 and the second electric resistance of the second electric connection 122 is adjustable via the adjusting means 150. The adjusting means may include at least one first variable resistor for adjusting the first electric resistance of the first electric connection 121 and/or at least one second variable resistor for adjusting the electric resistance of the second electric connection 122. For example, potentiometers may be used as variable resistors. The first variable resistor may be inserted into the first electric connection 121 between the first anode segment 111 and the first electric potential PI, so that the first variable resistor is part of the first electric connection. Analogously, the second variable resistor may be inserted into the second electric connection 122 between the second anode segment 112 and the second electric potential P2, so that the second variable resistor is part of the second electric connection.

[0037] As the anode segments may not be directly connected to a ground potential, e.g. with a grounded vacuum chamber, the anode segments may also be referred to as being installed on "floating ground".

[0038] In the embodiment shown in FIG. 1, the first anode segment 111 faces an upper portion of the cathode, and the second anode segment 112 faces a lower portion of the cathode. In some embodiments, the first anode segment may face a first side portion of the cathode, and the second anode segment may face a second side portion of the cathode, wherein the anode segments may be located on different cathode sides. In particular, the anode segments may be arranged in such a way with respect to the cathode and/or with respect to the substrate that the density of the plasma to be generated between the cathode and the individual anode segments may be controlled for ensuring a more uniform layer characteristic on the substrate. In some embodiments, more than two anode segments may be provided, e.g. three, four, five, six, seven, eight or more anode segments, wherein each anode segment may face a different portion of the cathode. Further, in some embodiments, the connector assembly may include an electric connection with an adjustable electric resistance for at least one of the anode segments, particularly for two or more of the anode segments. More particularly, the connector assembly may include an electric connection with an adjustable electric resistance for each of the anode segments.

[0039] The cathode 130 as well as the anode segments of the anode assembly 110 may have an arbitrary shape suitable for sputter deposition. For example, the deposition source may be provided with static cathodes such as flat plate cathodes, e.g. planar cathodes, with movable cathodes and/or with rotatable cathodes, e.g. with rotating cylindrical cathodes. In some embodiments, the cathode may be a rotatable cathode with a rotatable cylindrical target.

Similarly, the anode segments may be provided as static plates or rods, e.g. planar or cylindrical anode segments. In some embodiments, the anode segments are movable, e.g. movable in accordance with the cathode or in accordance with a magnet assembly provided in the cathode.

[0040] FIG. 2 shows a deposition source 200 for coating a substrate according to embodiments described herein. [0041] The deposition source 200 may include a cathode 230 which is rotatable around a rotation axis Al. In the present disclosure, a "rotatable cathode" may be understood as an at least partially cylindrical cathode having a rotation axis. In particular, a "rotatable cathode" may be understood as a cathode which rotates around the rotation axis during sputtering. For example, a "rotatable cathode" may be driven by a drive during sputter deposition of target material on the substrate. In the present disclosure, a cylindrical rotatable cathode may extend along a longitudinal axis from a first end of the rotatable cathode to a second end of the rotatable cathode, e.g. along a longitudinal rotation axis around which the rotatable cathode may be rotatable. The portion of the rotatable cathode including the target material to be deposited may extend from the first end of the rotatable cathode to the second end of the rotatable cathode.

[0042] As compared to a planar cathode, a rotatable cathode may provide the advantage that the target material is reliably utilized around the whole circumference of the target during sputtering, and there are no edge portions of the target in a lateral direction of the target, where less sputtering may occur on the target surface. Thus, by utilizing rotatable cathodes, material costs can be reduced and the target can be used for a longer time period, before a target exchange becomes necessary.

[0043] In some implementations, the rotatable cathode 230 could be configured to rotate with a rotation speed in the range of 1 to 50 rounds per minute, 5 to 30 rounds per minute or 15 to 25 rounds per minute around the rotation axis Al. The rotation can include at least one or more full 360° rotations. Typically, the rotatable cathode 230 could be configured to rotate with a speed of about 20 rounds per minute.

[0044] The rotatable cathode 230 may be provided at least partially as a hollow cylinder in order to provide for an inner space for receiving a magnet assembly or "magnetron". As used herein, "magnetron sputtering" refers to sputtering using a magnet assembly, that is, a unit capable of generating a magnetic field. Typically, a magnet assembly consists of one or more permanent magnets. Applying a magnetic field to the gas may lead to an increased ionization rate due to the electrons moving along a helical path and may further help in confining the motion of the plasma ions.

[0045] As is shown in FIG. 2, the deposition source may include an anode assembly 210 including a first anode segment 211 and a second anode segment 212. The first anode segment 211 may face an upper portion of the rotatable cathode 230 and the second anode segment 212 may face a lower portion of the rotatable cathode 230. Further, a connector assembly may be provided, including a first electric connection 121 connecting the first anode segment 211 to a first electric potential PI, a second electric connection 122 connecting the second anode segment 212 to a second electric potential P2, and an adjusting means including a first variable resistor or potentiometer 251 for adjusting a first electric resistance of the first electric connection 121 and a second variable resistor or potentiometer 252 for adjusting a second electric resistance of the second electric connection 122. [0046] An anode assembly 210 may be provided by mechanically connecting the first anode segment 211 and the second anode segment 212, whereas the first anode segment 211 and the second anode segment 212 may be electrically separated from each other. A mechanical connection of the first anode segment and the second anode segment may improve the mechanical stability of the anode assembly. For example, the first anode segment 211 and the second anode segment 212 may be held together by an isolating part, which ensures an electric separation of the anode segments.

[0047] In some embodiments, the first anode segment and the second anode segment are provided spaced apart from each other. For example, the first anode segment may be provided on a first side of the cathode, and the second anode segment may be provided as a separate component on a second side of the cathode. However, in the embodiment shown in FIG. 2, the first anode segment 211 and the second anode segment 212 are arranged next to each other on the same side of the cathode.

[0048] In order to provide for a homogenous plasma density between the cathode and the anode assembly, the anode assembly 210 may extend in an axial direction, wherein the first anode segment 211 is arranged next to the second anode segment 212 in the axial direction. The axial direction may be parallel to the rotation axis Al of the cathode 230. Further, the axial direction may correspond to an extension direction of the substrate to be coated, e.g. a height or a width direction of the substrate. When the first anode segment 211 and the second anode segment 212 extend adjacent to each other in the axial direction, a deposition rate and, thus, a layer uniformity along said axial direction may be controlled. Further, particularly if a distance between the first anode segment 211 and the second anode segment 212 in the axial direction is small, e.g. smaller than 10 cm and particularly smaller than 1 cm, a more homogenous electric field can be applied to the target along the axial direction, which may be the extension direction of both the cathode and the anode assembly.

[0049] According to some embodiments, which may be combined with other embodiments disclosed herein, the anode assembly 210 is provided as an anode rod, the first anode segment 211 being provided as a first rod segment and the second anode segment 212 being provided as a second rod segment adjacent to the first rod segment. The first rod segment may be electrically separated from the second rod segment, for example via an isolator that is arranged between the rod segments. The anode rod and the cathode 230 may be positioned essentially parallel and next to one another. The shape of the anode rod can be cylindrical. However, other shapes are possible. It is advantageous to avoid sharp edges in order to prevent electric field concentrations or arcing. Typically, the minimum bending radius of the anode rod should be 2 mm or above, e.g. 10 mm or above, particularly about 50 mm.

[0050] An outer dimension of the anode rod, e.g. an outer dimension perpendicular to the longitudinal axis of the anode rod, may be smaller than an outer diameter of the cylindrical cathode 230. For example, an outer diameter of the anode rod may be less than 50% or less than 25% of an outer diameter of the cathode. A distance between an outer surface of the anode rod and an outer surface of the cathode wall may be smaller than the outer dimension of the anode rod. The anode rod may be provided with a heat sink for cooling purposes.

[0051] In order to provide for a spatially homogenous deposition rate, the anode rod may extend parallel to the cathode 230 along the axial direction over more than 80%, particularly 100% or more of a total axial length of the cathode 230. The anode rod may include more than two rod segments, e.g. three, four or more rod segments which may extend one after another in the axial direction. A precise spatial control of the deposition rate is possible, if each of said rod segments is connected to a respective electric potential via an electric connection whose electric resistance is adjustable.

[0052] The first electric potential PI may correspond to the second electric potential P2. In particular, both the first anode segment 211 and the second anode segment 212 may be connected to the same output terminal of a D.C. power supply 10, wherein the output terminal may be configured for providing a constant positive voltage with respect to a negative cathode voltage. A variable resistor or potentiometer may be inserted between the anode segments and the output terminal of the D.C. power supply, respectively. The first electric resistance of the first (second) electric connection may be measured between a first end of the first (second) electric connection connected to the first (second) anode segment and a second end of the first (second) electric connection connected to the first (second) electric potential, e.g. connected to the output terminal of the D.C. power supply 10.

[0053] In some embodiments, the cathode 230 is connected to a first output terminal 11 of the power supply 10, which may be configured for providing a negative voltage, and at least one of the first electric connection 121 and the second electric connection 122 is connected to a second output terminal 12 of the power supply, which may be configured for providing a zero voltage or a positive voltage. In particular, in some cases, the second output terminal 12 of the power supply may be provided on a ground potential. At the same time, the walls of a process chamber housing the deposition source may be on a ground potential. Therefore, in some implementations, both the potential of the second output terminal 12 and the potential of the process chamber walls may be the ground potential.

[0054] In some embodiments, both the first electric connection 121 and the second electric connection 122 may be connected to a ground potential. [0055] By adjusting the first electric resistance and/or the second electric resistance, the sputter and deposition rates can be spatially controlled. For example, if the uniformity of a layer coated on a substrate is not satisfactory, the first and/the second resistances may be adjusted as necessary for obtaining a more uniform coating layer on the following substrates. The layer uniformity may be checked manually or automatically, and the adjustment of the respective first and/or second resistances via the adjusting means may be performed manually or automatically subsequent to a coating process or during a coating process.

[0056] In some embodiments, the first electric resistance and/or the second electric resistance may be adjusted in-situ, for example during coating processing or without a need to flood a vacuum chamber, in which the anode segments may be arranged. In particular, in-situ spatial adjustment of the deposition rate may be possible in a display coating apparatus, e.g. in an apparatus for coating glass substrates. In such systems, movable substrates such as thin glass substrates may be coated while being moved past processing equipment.

[0057] In some embodiments, in-situ spatial adjustment of the deposition rate may be possible in so-called web coating systems. In such systems, substrates such as flexible substrates may be coated while being moved past processing equipment. Particularly, coating of metal, semiconductor or plastic films or foils is in high demand in the packaging industry, semiconductor industry and other industries. Systems performing this task generally include a movable substrate support for moving the substrate past the deposition source, e.g. a processing drum, coupled to a processing system for moving the substrate. So-called web coating systems allowing substrates to be coated while being moved on a guiding surface of a substrate support, e.g. a processing drum, can provide for a high throughput.

[0058] The substrate to be coated may enter a source housing of the deposition source on a first side, and the coated substrate may exit the source housing on a second side. A characteristic of the coating layer of the moving substrate, e.g. a spatial uniformity of a layer coated on the substrate, may be checked, e.g. via an optical instrument such as a camera, and a potential lack of layer uniformity may be signalled to a control unit configured for controlling the adjusting means. The adjusting means may then be controlled to adjust at least one of the first electric resistance and the second electric resistance so that the detected lack of layer uniformity may be corrected.

[0059] In some embodiments described herein, the deposition source may include a detector for detecting a characteristic of a coated substrate, and a control unit 30 for controlling the adjusting means in dependence of a detector signal. For example, the characteristics of the coated substrate may be a measure characterizing a spatial layer uniformity, in particular a coating layer thickness in a first substrate region and a coating layer thickness in a second substrate region. Each substrate region may be associated with one of the anode segments. For example, an upper anode segment may be associated with an upper substrate region, and a lower anode segment may be associated with a lower substrate region. The detector may be an optical detector such as a camera. The detector may be arranged inside a vacuum chamber for performing sputter processing. The detector may be arranged outside a vacuum chamber, e.g. at a substrate exit of a web coating system.

[0060] FIG. 3 shows a deposition source 201 for coating a substrate according to embodiments described herein. The configuration of the deposition source 201 may essentially correspond to the configuration of deposition source 200 shown in FIG. 2, so that reference can be made to the above explanations, which are not repeated here.

[0061] The sputter deposition source 201 comprises a cylindrical cathode 230 for providing a target material to be deposited on a substrate, and an anode assembly 210 with a total of three anode segments (first anode segment 211, second anode segment 212, and third anode segment 213), wherein each anode segment faces a different portion of the cylindrical cathode 230. The three anode segments are arranged next to each other in a linear arrangement along an axial direction of the anode assembly 210.

[0062] The first anode segment 211 is connected to an output terminal 12 of a power supply 10 via a first electric connection 121, e.g. a wire, wherein a first variable resistor or potentiometer 251 is inserted into the first electric connection 121. The second anode segment 212 is connected to the output terminal 12 of the power supply 10 via a second electric connection 122, wherein a second variable resistor or potentiometer 252 is inserted into the second electric connection 122. The third anode segment 213 is connected to the output terminal 12 of the power supply 10 via a third electric connection 123, wherein a third variable resistor or potentiometer 253 is inserted into the third electric connection 123. By providing such an arrangement, the density of a plasma 60 between the cathode 230 and the anode assembly 210 can be spatially controlled in three distinct regions along a height of the substrate, by individually adjusting the resistances of the first electric connection, 121, the second electric connection 122, and the third electric connection 123.

[0063] In some embodiments disclosed herein, the variable resistors may be low-ohmic resistors. For example, the resistance of the variable resistors may be adjustable between 0 and 10 Ohm, respectively.

[0064] According to some embodiments, which may be combined with other embodiments described herein, the power supply 10 may be an adjustable power supply, which may be configured for providing an adjustable D.C. voltage. The adjustable D.C. voltage provided by the power supply may be an adjustable potential difference between the first output terminal 11 connected to the cathode 230 and the second output terminal 12 connected to one or more anode segments. Further, a power control unit may be provided for controlling an output power of the power supply 10. By adjusting an output power of the power supply 10, a desired overall charge flow, particularly a constant overall charge flow, between the cathode and the anode assembly may be maintained. [0065] In other words, whereas the adjusting means may be configured for individually adjusting the charge flow in a localized region between the cathode and a respective anode segment, the adjustable power supply may be configured for adjusting a total charge flow between the cathode and all anode segments of the anode assembly.

[0066] As an example, the output power delivered by the power supply 10 (P_out) and the power dissipated in the variable resistors or potentiometers 251, 252, 253 (P_RI, P _R2, P_R3) may be measured, e.g. by calculating a product of the current flowing through the variable resistors and the voltage drops across the variable resistors. In FIG. 3, respective voltmeters (V) and current measurement devices (A) are indicated. Then, the dissipated power is subtracted from the output power, resulting in the power deposited in the plasma: P_PLAS_MA= Pout - P_RI - P_R2 - P_R^ The power control unit may be configured for controlling the output power P_out of the power supply 10 such that P_PLAMSA remains essentially constant during sputtering. The deposition rate may be estimated as proportional to the power deposited in the plasma P_PLASMA- In order not to the change the deposition rate during an adjustment of the variable resistors, the power deposited in the plasma may be kept constant by the power control unit as described above. Thus, the uniformity of the deposited layer may be adjusted independently of the overall deposition rate. [0067] In particular, during sputtering, to some extent also outer surfaces of the anode assembly may be coated with a target material, the effect of which may result in an overall drop of the electric field between the cathode and the coated anode surfaces over time. This drop may be compensated for by increasing the potential difference between the first output terminal 1 1 and the second output terminal 12 of the power supply 10. The power supply may include the power control unit for controlling an output power of the power supply for maintaining a constant overall charge flow or electric current between the cathode and the anode assembly.

[0068] As is indicated in FIG. 3, also the chamber walls of a vacuum chamber 510 which typically houses the cathode and the anode assembly of the sputter deposition source may to some extent have the effect of an anodic surface. This is because the chamber is typically grounded, so that an electric potential of the chamber walls may be higher than an electric potential of the typically negatively charged cathode.

[0069] In order to be in a position to adjust a spatial extension of the plasma 60 towards the chamber walls of the vacuum chamber 510, according to some embodiments described herein, the vacuum chamber 510 may be connected to an additional electric potential P4 via an additional electric connection 124. An additional variable resistor or potentiometer 254 may be inserted in the additional electric connection 124 so that the electric resistance of the additional electric connection 124 may also be adjusted. [0070] In some embodiments, the additional electric potential P4 may be a ground potential. In some embodiments, the additional electric potential P4 may correspond to one or more of the first electric potential PI and the second electric potential P2. In some embodiments, the additional electric potential P4 may be the electric potential of the second output terminal 12 of the power supply 10, which may be a ground potential or a positive potential. In particular, the vacuum chamber 510 may be electrically connected to the second output terminal 12, wherein the additional variable resistor or potentiometer 254 is inserted in the additional electric connection 254. The additional variable resistor or potentiometer 254 may be a high- ohmic electric resistor, which may be variable up to several tenths of kQ, e.g. 45 kQ. High resistance values of the additional variable resistor or potentiometer 254 will have the effect that almost the entire current will flow via the anode segments 21 1 , 212, 213, and the vacuum chamber will act as an anode to an only limited or insignificant extent.

[0071] As also the additional variable resistor or potentiometer 254 may dissipate some of the output power provided by the power supply, said dissipated power (P_R4) may be measured by a respective voltmeter (V) and current measurement device (I) which are indicated in FIG. 3. In this case, the power (P_PLASMA) deposited in the plasma may be calculated by using the following formula: P_PLAS_MA= Pout - P_RI - P_R2 - P_R3 - P_R4- The power control unit may be configured for controlling the output power P_out of the power supply 10 such that P_PLAMSA remains essentially constant during sputtering.

[0072] FIG. 4 shows a plan view of a vacuum deposition apparatus 500 with a deposition source 300 for sputter deposition according to embodiments described herein. FIG. 5 shows a perspective view of the vacuum deposition apparatus shown in FIG. 4. The vacuum deposition apparatus 500 includes a vacuum chamber 510 and a deposition source 300 for sputter deposition, which may have some or all of the features of any of the embodiments described above, so that reference can be made to the above explanations.

[0073] The sputter deposition source includes a rotatable cathode 230 for providing a target material to be deposited, a first anode assembly 310 with two or more anode segments and a second anode assembly 315 with two or more anode segments. In some embodiments, the cathode 230 and the anode assemblies 310, 315 are positioned inside the vacuum chamber 510, and at least a control element of an adjusting means 350 is positioned outside the vacuum chamber 510. The adjusting means 350 is configured for adjusting the electric resistances of electric connections connecting anode segments with respective electric potentials. The electric resistances of the electric connections can be adjusted from outside the vacuum chamber, for example during sputtering or while keeping the vacuum chamber evacuated, because the control element of the adjusting means 350 is positioned outside the vacuum chamber 510.

[0074] The first anode assembly 310 may have the form of a first anode rod extending parallel to the cathode 230 on a first cathode side, and the second assembly 315 may have the form of a second anode rod 315 extending parallel to the cathode on a second cathode side opposite the first cathode side. The substrate 20 to be coated may be moved past the cathode on a third cathode side. The cathode may include a magnetron for steering a plasma toward the third cathode side, where the substrate is located.

[0075] The substrate 20 to be coated may enter a source housing of the deposition source on a first side, and the coated substrate may exit the source housing on a second side. A characteristic of the coating layer of the substrate, e.g. a spatial uniformity of a layer coated on the substrate, may be checked, e.g. via an optical instrument such as a camera, and a potential lack of layer uniformity may be signalled to a control unit configured for controlling the adjusting means. The adjusting means may then be controlled to adjust at least one of the first electric resistance and the second electric resistance so that the detected lack of layer uniformity may be corrected.

[0076] In the embodiment shown in FIG. 5, the first anode assembly 310 includes a total of four rod segments 311, 312, 313, 314 in a linear arrangement, wherein each rod segment may be connected to a respective electric potential via a respective electric connection 321, 322, 323, 324, wherein the adjusting means 350 may be adapted for individually adjusting an electric resistance of each of said electric connections 321, 322, 323, 324. Thus, the plasma density in four distinct regions in a height direction of the substrate may be individually controlled. The first anode assembly may extend parallel to the cathode 230 over more than 50%, particularly more than 80%, more particularly 100% or more of a total axial length of the cathode 230, in order to allow for a deposition rate adjustment over the full height of the cathode which may correspond to a height of the substrate 20.

[0077] Similarly, the second anode assembly 315 which is arranged on the opposite side of the cathode 230 may include a total of four rod segments 316, 317, 318, 319 in a linear arrangement, wherein each rod segment may be connected to a respective electric potential via a respective electric connection 326, 327, 328, 329, wherein the adjusting means 350 may be adapted for individually adjusting an electric resistance of each of said electric connections 326, 327, 328, 329. Thus, the plasma density of a second plasma cloud in four distinct regions in a height direction of the substrate may be individually controlled. The second anode assembly 315 may extend parallel to the cathode 230 over more than 50%, particularly more than 80%, more particularly 100% or more of a total axial length of the cathode 230, in order to allow for a deposition rate adjustment over the full height of the cathode.

[0078] At least one variable resistor or potentiometer may be inserted into each of the electric connections 321, 322, 323, 324, 326, 327, 328, 329. In some embodiments, all rod segments 311, 312, 313, 314, 316, 317, 318, 319 may be connected to the same output terminal of a power supply via a respective electric connection. The output terminal may have a constant or variable electric potential, e.g. a positive potential. In some embodiments, the rod segments 311, 312, 313, 314 of the first anode assembly 310 may be connected to an output terminal of a first power supply, and the rod segments 316, 317, 318, 319 of the second anode assembly may be connected to a further output terminal of the first power supply or to an output terminal of a second power supply. In some embodiments, each of the electric connections may be connected to a ground potential. [0079] In some embodiments, the vacuum deposition apparatus may include an additional electric connection 124 for connecting the vacuum chamber 510 to an additional electric potential, and wherein the adjusting means 350 is configured for adjusting an electric resistance of the additional electric connection 124. For example, an additional variable resistor or potentiometer 254 may be included in the additional electric connection 124.

[0080] FIG. 6 shows a schematic view of a sputtering apparatus 400 according to embodiments described herein.

[0081] The sputtering apparatus 400 includes a vacuum chamber 410 and a deposition source in accordance with any of the embodiments described herein. In the shown embodiment, the deposition source includes four rotatable cathodes 230 and five corresponding anode assemblies 210, each facing at least one of the cathodes 230. The cathodes 230 and the anode assemblies 210 are arranged inside the vacuum chamber 410. More than four rotatable cathodes may be provided. Further, more than five anode assemblies may be provided. For example, two anode assemblies may be provided for each cathode, similar to the arrangement shown in FIG. 5.

[0082] Several D.C. power supplies 10 may be arranged outside the vacuum chamber 410 and electrically connected to the cathodes 230 and anode assemblies 210 via respective electric connections. Each anode assembly 210 may include a first anode segment and a second anode segment. As is indicated in FIG. 6, each power supply 10 may include a first output terminal connected to at least one of the cathodes. Further, each of the power supplies 10 may include a second output terminal connected to two anode segments of at least one of the anode assemblies via a first electric connection 421 and a second electric connection 422. The electric resistance of the first electric connection 421 may be adjusted via a first potentiometer, and the electric resistance of the second electric connection 422 may be adjusted via a second potentiometer.

[0083] However, in some embodiments, only a single D.C. power supply may be provided including two or more output terminals for providing a potential difference to be applied between the cathodes and anode assemblies.

[0084] As is indicated in FIG. 6, further chambers 411 can be provided adjacent to the vacuum chamber 410. The vacuum chamber 410 can be separated from the adjacent chambers by valves having a valve housing 404 and a valve unit 405, respectively. After a carrier 406 with a substrate 20 to be coated is, as indicated by arrow 401, inserted in the vacuum chamber 410, the valve units 405 can be closed. Accordingly, the atmosphere in the vacuum chambers 410 can be individually controlled by generating a technical vacuum, for example, with vacuum pumps connected to the vacuum chambers 410, and/or by inserting process gases in the deposition region of the vacuum chamber 410.

[0085] According to typical embodiments, process gases can include inert gases such as argon and/or reactive gases such as oxygen, nitrogen, hydrogen and ammonia, ozone, activated gases or the like.

[0086] Within the vacuum chamber 410, rollers 408 are provided in order to transport the carrier 406 with the substrate 20 into and out of the vacuum chamber 410. The term "substrate" as used herein shall embrace both inflexible substrates, e.g., a glass substrate, a wafer, slices of transparent crystal such as sapphire or the like, and flexible substrates, such as a web or a foil.

[0087] FIG. 6 shows the rotatable cathodes 230 with magnet assemblies or magnetrons 431 provided in the rotatable cathodes 230, wherein the magnetrons 431 may be provided within backing tubes that are equipped with the target material on an outer surface, respectively.

[0088] FIG. 7 shows a flowchart of a method of operating a deposition source according to embodiments described herein. In a first box 602, the method comprises spatially controlling a charge flow between a cathode and first and second anode segments of an anode assembly by adjusting at least one of a first electric resistance of a first electric connection connected to the first anode segment and a second electric resistance of a second electric connection connected to the second anode segment. The first electric connection may be configured for connecting the first anode segment to a first electric potential, e.g. an output terminal of a power supply for providing a positive voltage, and the second electric connection may be configured for connecting the second anode segment to a second electric potential, e.g. an output terminal of a power supply for providing a positive voltage. The first electric potential may correspond to the second electric potential. In particular, both the first anode segment and the second anode segment may be connected to a ground potential or to the same output terminal of a power supply via respective electric connections with adjustable resistances.

[0089] The method may further comprise detecting a characteristic of a coated substrate, e.g. a property of a coating layer such as a layer thickness, a layer uniformity, etc., and adjusting the first electric resistance and/or the second electric resistance depending on the detected characteristic. For example, a difference in coating layer thickness between a first region of the substrate and a second region of the substrate may be detected. Then, the first electric resistance of the first electric connection may be, e.g., decreased, in order to increase a charge flow through the first anode segment which may lead to an increased deposition rate toward the first region of the substrate.

[0090] The adjusting action may be performed in-situ, e.g. during sputtering or from outside the vacuum chamber, without flooding the vacuum chamber.

[0091] Further, the method may comprise adjusting an output power of a power supply, in order to maintain a constant overall charge flow between the cathode and the anode assembly.

[0092] While the foregoing is directed to embodiments of the invention, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A deposition source (100, 200, 201, 300) for sputter deposition, comprising: a cathode (130, 230) for providing a target material to be deposited on a substrate (20); at least one anode assembly (110, 210) having at least a first anode segment (111, 211) which faces a first portion of the cathode and a second anode segment (112, 212) which faces a second portion of the cathode; and a connector assembly (120), comprising: a first electric connection (121) for connecting the first anode segment (111, 211) to a first electric potential (PI); a second electric connection (122) for connecting the second anode segment (112, 212) to a second electric potential (P2); and an adjusting means (150, 350) for adjusting at least one of a first electric resistance of the first electric connection (121) and a second electric resistance of the second electric connection (122).

2. The deposition source of claim 1, wherein the adjusting means (150) comprises at least one first variable resistor or potentiometer (251) for adjusting the first electric resistance of the first electric connection (121) and at least one second variable resistor or potentiometer (252) for adjusting the second electric resistance of the second electric connection (122).

3. The deposition source of claim 1 or 2, wherein the first electric potential (PI) corresponds to the second electric potential (P2), particularly wherein both the first and the second anode segments are configured to be connectable to a ground potential or to an output terminal of a power supply for providing a positive, a negative or a ground electric potential.

4. The deposition source of any of claims 1 to 3, further comprising a detector for detecting a characteristic of a coated substrate and a control unit (30) for controlling the adjusting means in dependence of a signal of the detector.

5. The deposition source of any of claims 1 to 4, further comprising a D.C. power supply (10), wherein the cathode (230) is connected to a first output terminal (11) of the power supply and at least one of the first anode segment and the second anode segment is connected to a second output terminal (12) of the power supply.

6. The deposition source of claim 5, comprising a power control unit configured for controlling an output power of the power supply (10) for maintaining a constant overall charge flow between the cathode and the anode assembly.

7. The deposition source of any of claims 1 to 6, wherein the cathode (130, 230) has a cylindrical form and is rotatable around a rotation axis (Al).

8. The deposition source of any of claims 1 to 7, wherein the anode assembly (210) extends in an axial direction, particularly parallel to the rotation axis (Al) of the cathode (230), the first anode segment (211) being arranged next to the second anode segment (212) in the axial direction.

9. The deposition source of claim 8, wherein the anode assembly (210) is provided as an anode rod, the first anode segment (211) being provided as a first rod segment and the second anode segment (212) being provided as a second rod segment adjacent to the first rod segment.

10. The deposition source of claim 9, wherein the anode rod comprises three, four or more rod segments (311, 312, 313, 314) provided in a linear arrangement, each rod segment being connectable to a respective electric potential via a respective electric connection (321, 322, 323, 324), wherein the adjusting means (350) is adapted for adjusting an electric resistance of each of said electric connections (321, 322, 323, 324).

11. The deposition source of any of claims 8 to 10, wherein the anode segments of the anode assembly (210) extend parallel to the cathode (230) over more than 50%, particularly more than 80%, more particularly 100% or more of a total axial length of the cathode (230).

12. The deposition source of any of claims 1 to 11, further comprising: a second anode assembly (315) with two or more further anode segments, wherein the connector assembly comprises two or more further electric connections for connecting the further anode segments to an electric potential, respectively, and wherein the adjusting means (350) is adapted to adjust the electric resistances of the further electric connections.

13. The deposition source of claim 12, wherein the first anode assembly (310) is provided as a first anode rod extending parallel to the cathode (230) on a first cathode side, and the second assembly is provided as a second anode rod (315) extending parallel to the cathode on a second cathode side opposing the first cathode side.

14. A vacuum deposition apparatus (500), comprising: a vacuum chamber (510); and a deposition source (100, 200, 201, 300) according to any of claims 1 to 13, wherein the cathode (230) and the anode assembly (210, 310) are positioned inside the vacuum chamber (510), and wherein at least a control element of the adjusting means (150, 350) is positioned outside the vacuum chamber (510).

15. The vacuum deposition apparatus of claim 14, wherein the connector assembly comprises an additional electric connection (124) for connecting the vacuum chamber (510) to an additional electric potential (P4), and wherein the adjusting means is configured for adjusting an electric resistance of the additional electric connection (124).

16. A method of operating a deposition source, particularly a deposition source (100, 200, 201, 300) of any of claims 1 to 13, comprising: spatially controlling a charge flow between a cathode (130, 230) and first and second anode segments of an anode assembly (110) by adjusting at least one of a first electric resistance of a first electric connection (121) connected to the first anode segment and a second electric resistance of a second electric connection (122) connected to the second anode segment.