JP2005503648A - Plasma reactor, coil magnet system - Google Patents

Abstract

The present invention is a method for processing a workpiece performed using plasma generated from a process gas in a plasma chamber of a plasma processing apparatus during a plasma processing operation. The apparatus includes an array of electromagnets mounted to surround the plasma chamber. The method comprises the steps of: generating a plasma from a process gas in the chamber; causing plasma particles to collide with the workpiece; selecting an arrangement of current signals supplied to the electromagnet; Given each selected arrangement, thereby applying one or more magnetic field configurations to the plasma during a plasma processing operation.

Description

【Technical field】
[0001]
<Description of related applications>
This application is based on and claims the benefit of US Provisional Application No. 60 / 318,890, filed September 14, 2001. The contents of the above application are incorporated herein by reference in their entirety.
[0002]
<Field of the present invention>
The present invention relates to a plasma processing system, and more particularly to a method and apparatus for controlling a plasma property by applying a magnetic field to the plasma, thereby improving the plasma processing of a workpiece.
[Background]
[0003]
<Background of the present invention>
A plasma is a collection of charged particles that is used to remove material from or deposit material on the workpiece. Plasma is used during integrated circuit (IC) manufacturing processes, for example, when etching (ie, removing) material from or over a semiconductor substrate, or when sputtering (ie, depositing) material on a semiconductor substrate. Used for. The plasma is formed by applying a radio frequency (RE) electrical signal to the process gas contained in the plasma chamber and ionizing the particles of the process gas. The high frequency power supply is coupled to the plasma via a capacitance, via an inductance, or via both capacitance and inductance. When plasma processing a workpiece, a magnetic field can be applied to the plasma to improve the properties of the plasma, thereby improving the controllability of the workpiece for plasma processing.
[0004]
A magnetic field is sometimes used during plasma processing of the workpiece, thereby holding the plasma in the chamber or changing the nature of the plasma during plasma processing. The magnetic field can be used, for example, to hold the plasma in the chamber, thereby reducing the loss of plasma to the chamber walls and increasing the plasma density. Increased plasma density increases the number of plasma particles impinging on the workpiece, thereby improving workpiece processing. For example, the processing time required for workpiece etching is reduced. By using a magnetic field to hold the plasma, it also prevents the deposition of plasma particles on surfaces within the chamber, such as the chamber wall surfaces and electrode surfaces.
[0005]
The magnetic field is also used to improve the uniformity of the plasma distribution within the chamber. A non-uniform distribution of plasma within the plasma chamber is undesirable. The reason is that non-uniform distribution results in non-uniform processing of the workpiece. A non-uniformly distributed plasma can in some circumstances result in plasma-induced damage to the workpiece being processed in the chamber.
[0006]
Permanent magnet or electromagnet arrays are sometimes used to apply a magnetic field to the plasma. The array of permanent magnets can be arranged, for example, such that they exert a magnetic field on the plasma inside the chamber. Alternatively, it can be placed and moved (eg, by rotating with respect to the chamber) to exert a rotating magnetic field on the plasma, thereby improving plasma uniformity. The
BEST MODE FOR CARRYING OUT THE INVENTION
[0007]
<Summary of the present invention>
The present invention relates to a method and apparatus that uses a magnetic field to control the processing of a workpiece by a plasma.
[0008]
<Detailed Description of the Invention>
FIG. 1 shows a schematic diagram of an example of a plasma processing apparatus (or reactor) 10 of a plasma processing system. The plasma processing apparatus 10 includes a plasma chamber 14 that provides an internal region 16 for containing and holding the plasma. A plurality of electrodes can be mounted in the chamber 14 in a relationship that generates a plasma relative to each other and to the process gas in the chamber 14. These electrodes are energized and generate a plasma from the process gas in the chamber 14.
[0009]
For ease of explanation of the present invention, only two electrode assemblies are depicted in this device 10. In particular, the first electrode assembly 18 is attached to the first side of the chamber 14 (the top of the interior 16 of the chamber 14 in the example apparatus 10). The second electrode assembly is in the form of a chuck-type electrode assembly 20, the second side of the chamber 14, ie the opposite side of the first side of the chamber 14 (the lower part of the interior 16 of the chamber 14 in the example apparatus 10). ) With a space from the first electrode assembly 18.
[0010]
The first electrode assembly 18 may comprise a plurality of electrode segments, each of which is electrically isolated from the other segments and independently powered by a corresponding high frequency power source. A process gas for the selected and selected transmission is independently supplied to the inside of the plasma chamber at a predetermined flow rate. However, to simplify the description of the present invention, the first electrode assembly 18 is depicted as a single showerhead type electrode. The first electrode assembly 18 has an inner chamber 22 (represented schematically in FIG. 1 using dashed lines). The inner chamber 22 is connected to a gas supply system 24 through an air supply line or a fluid path via a gas supply line.
[0011]
A selected gas or gases can be supplied to the electrode assembly 18 so that, for example, a process gas for purging the chamber 14 or forming a plasma within the chamber interior 16 is provided. The gas is provided as (or source gas). Process gas is transferred from the chamber 22 to the interior 16 of the plasma chamber 14 via a plurality of gas ports (not shown). The gas flow through the port of the first electrode is indicated by an arrow G indicating the direction.
[0012]
The first and second electrodes 18, 20 are electrically connected to respective high frequency sources 34, 36 via corresponding matching networks 30, 32, respectively. These high-frequency supply sources 34 and 36 supply voltage signals VB1 and VB2 to the corresponding electrodes 18 and 20, respectively. Matching networks 30, 32 can be inserted between the respective high frequency power sources 34, 36 in order to maximize the power transferred to the plasma by the respective electrode assemblies 18, 20. Alternatively, the matching networks 30, 32 can be coupled to the control system.
[0013]
Each electrode assembly 18, 20 can be cooled independently using a fluid. This fluid flows from the cooling system 38 through the fluid chambers 39, 41 (shown in dashed lines), respectively, into each electrode assembly 18, 20, and then returns to the cooling system. The plasma processing apparatus 10 further includes a vacuum system 40. The vacuum system 40 is connected to the plasma chamber 16 and an air path or a fluid path via a vacuum line. The plasma processing apparatus 10 optionally includes voltage probes 44, 46 in the form of a pair of electrodes, each of which corresponds to a corresponding high frequency power supply 34, 36 and a corresponding electrode assembly 18, 20, respectively. And capacitively coupled to the transfer line.
[0014]
Examples of voltage probes are described in detail in U.S. Patent Application No. 60 / 259,862 (filed Jan. 8, 2001) and have common reference numerals, the entire application is hereby incorporated by reference. Incorporated into.
[0015]
The plasma processing apparatus 10 optionally includes an optical probe 48 that determines the nature and state of the plasma based on the spectroscopic and optical properties of the plasma.
[0016]
An electromagnet system or array 51 is mounted to surround the periphery of the plasma chamber 14. The electromagnet 51 can be operated to apply one or more magnetic fields to the plasma during the plasma processing operation of the workpiece. By applying a magnetic field, the state of the plasma is improved, thereby improving the processing of the workpiece.
[0017]
FIG. 2 shows an example of the arrangement of the plurality of electromagnets 51 with respect to the plasma chamber 14. This device example 12 includes twelve electromagnets indicated by 51A-L. Each electromagnet 51 shown is in the form of a coil magnet with a coil of conductive material. Each coil is electrically connected to a power source 53 (shown schematically in FIG. 1).
[0018]
Each coil magnet 51 of a particular array is comprised of a coil of conductive material wound around an air core (not shown), or alternatively, for example, around the core 55 of magnetically permeable material. 1 is composed of a coil of conductive material wound partially on (which is partially depicted in FIG. 1). Each core 55 can have a cylindrical cross-section (as shown in the figure), or alternatively any elongated cross-section (a device illustrating the direction of the major axis) 10 in the vertical direction).
[0019]
The direction of each axis of the coil magnet 51 is determined radially with respect to the plasma chamber 14. That is, each axis of the coil magnet 51 extends radially between the electrode assemblies 18 and 20 from a virtual axis (longitudinal direction in the reactor example 10) extending through the center of the plasma chamber 14. The outer magnetic flux transmission structure 57 can be attached to surround the array of coil magnets 51. This state is well illustrated in FIG. Each coil / magnet 51 and each core 55 is continuous with the magnetic flux transmission structure 57.
[0020]
One of the magnetic flux transmission structures 57 is an annular wall type structure. Both the outer wall structure 57 and the core 55 of each coil magnet 51 can be made of a magnetically permeable material such as iron. Each core 55 can be formed on the outer ring structure 57, or can be formed on the outer ring structure 57 after being formed separately from the wall structure 57. .
[0021]
It can be seen from FIG. 2 that each coil magnet 51 and its corresponding core 55 extend radially between the outer ring structure 57 and the wall structure 59 of the plasma chamber 14. In the apparatus example 10, the wall-type structure 59 is cylindrical and constitutes the side wall of the processing chamber. The wall-type structure 59 of the plasma chamber 14 can be made of a suitable dielectric material or a suitable metal material. If the wall-type structure 59 is made of a metal material, the magnetic field that the wall-type structure 59 acts on the plasma in the plasma chamber 14 by the coil magnet 51 by using a non-magnetic metal material for fabrication. To avoid interference.
[0022]
The array of magnets in the example apparatus 10 is aligned vertically with respect to the plasma in FIG. 1, but this longitudinal arrangement is only one example. The array of magnets can also be placed in vertical alignment with respect to the processing chamber, structure (eg, electrode), and material (eg, workpiece or plasma) contained therein. For example, the device 10 can be fabricated such that the array of magnets is aligned vertically, such as the top surface of the workpiece, the center of the workpiece, or slightly above the workpiece, for example. Alternatively, the array of magnets can be longitudinally aligned with respect to the center of the plasma or, for example, slightly above or below the plasma.
[0023]
The control system of the plasma processing apparatus 10 is electrically connected to various components of the apparatus 10 to monitor and / or control the plasma processing apparatus 10. The control system can be electrically connected to the gas supply system 24, vacuum system 40, cooling system 38, voltage probes 44, 46, optical probe 48, each high frequency supply 34, 36, and power supply 53. And can be programmed to control their driving.
[0024]
The control system sends control signals to and receives input signals (eg, feedback signals) from the probes 44, 46, 48 and the system components 24, 34, 36, 38, 40, 53. The control system can monitor and control the plasma treatment of the workpiece. By controlling the power supply 53, the control system controls the transmission of power to each coil magnet constituting the array of coil magnets 51, thereby controlling the nature of the magnetic field acting on the plasma. Can do.
[0025]
The control system 60 can be configured by a computer system. The computer system includes a processor, computer memory accessible by the processor, where the memory is suitable for storing instructions and data, eg, a primary memory such as a random access memory. A secondary memory such as a memory, disk drive, etc.) and data input and output capabilities to communicate with the processor.
[0026]
The method of the present invention will be described with reference to an example of a plasma processing system. The operation of this plasma processing system can be understood by referring to FIG. A workpiece (or substrate) 62 to be processed is placed on a support surface provided by the chucked electrode assembly 20. The control system activates the vacuum system 40, which initially sets the pressure in the interior 16 of the plasma chamber 14 to the base pressure (typically 10 ^-7 Torr-10 ^-4 Torr), and confirm the vacuum holding capacity and cleanliness of the chamber 14.
[0027]
The control system then raises the chamber pressure to a level appropriate for plasma formation and processing of the workpiece 62 with the plasma (a suitable internal pressure is in the range of, for example, about 1 mTorr to about 1000 mTorr). . In order to bring the chamber interior 16 to an appropriate pressure, the control system activates the gas supply system 24 to supply process gas at a predetermined process flow rate to the chamber interior 16 via a gas introduction line. If necessary, the vacuum system 40 is throttled using a gate valve (not shown). Process gas may flow through the port and into the first electrode assembly, as indicated by arrow G in FIG.
[0028]
The particular gas (es) contained in the gas supply system 24 depends on the particular plasma processing application. For example, for plasma etching applications, gas supply system 24 can supply chlorine, hydrogen bromide, octafluorocyclobutane, or various other fluorocarbon compound gases. For CVD applications, the gas supply system 24 can supply silane, ammonia, tungsten tetrachloride, titanium tetrachloride, or similar gases.
[0029]
During CVD, plasma can be used to form a metal thin film, semiconductor thin film or insulator thin film (ie, conductive, semiconductive or insulating material) on the semiconductor wafer. In plasma-enhanced CVD, plasma is used to supply the reaction energy required to deposit the desired material.
[0030]
The control system then activates the high frequency sources 34, 36 corresponding to the first and second electrode assemblies 18, 20. The high frequency power supplies 34 and 36 can supply voltages to the corresponding electrodes 18 and 20 at a selected frequency. During the plasma processing operation, the control system independently controls the frequency sources 34, 36 to drive, for example, the frequency and / or power supply 34, 36 to the corresponding electrode assembly 18, 20 respectively. The magnitude of the voltage can be adjusted.
[0031]
The high frequency power supplies 34, 36 can be operated to convert low pressure process gas to plasma. The power sources 34, 36 can be operated, for example, to generate an alternating electric field between the first electrode 18 and the second electrode 20, whereby between the electrodes 18, 20. This causes an electron flow to occur. For example, an electron is accelerated in this electric field, and the flow of electrons heated therein transfers the kinetic energy to it by multiple collisions between the electrons and gas atoms and molecules, thereby allowing the process gas to flow. Each atom and molecule of is ionized. This process creates a plasma 54 that is confined and held in the chamber 14.
[0032]
Since each high-frequency source 34, 36 can be controlled independently of each other by the control system, the power supply has a relatively low frequency (ie, a frequency below 550 kHz), an intermediate frequency (ie, a frequency on the order of 13.56 MHz). ) Or a relatively high frequency (about 60 to 150 MHz). In the example of the etching reactor, the high frequency source 34 for the first electrode assembly 18 can be operated at a frequency of 60 MHz and the high frequency source 36 for the second electrode assembly 20 is It is possible to operate at 2 MHz.
[0033]
More generally, in order to improve the performance of the reactor described above (or a plasma processing apparatus having one or more electrodes operated at one or more frequencies, the control system is programmed and operated. , Thereby causing one or more magnetic fields to act on the plasma during workpiece processing, so that the nature of the magnetic field (eg, magnetic field shape and direction, magnetic field strength, magnetic field duration, etc. ).
[0034]
According to the present invention, it is possible to create a large number of possible magnetic field configurations using a single magnet array 51 having no moving parts. 2 and 3 show two magnetic field configurations that can be applied to the plasma 54 using a magnet system (the plasma 54 is shown schematically only in FIG. 1). FIG. 2 shows a cross-type magnetic field configuration, and FIG. 3 shows a bucket-shaped magnetic field configuration.
[0035]
The illustrated crossed magnetic field configuration has non-linear (ie, arched) magnetic field lines. This crossed magnetic field configuration can be used to improve plasma uniformity. Increasing the plasma uniformity increases the process uniformity for a single substrate 62 and also increases the process uniformity among multiple substrates that are sequentially processed by the apparatus 10. The electromagnet array 51 can be operated to rotate the intersecting magnetic field configuration in the following manner. By applying a bucket-shaped magnetic field configuration (FIG. 3) to the plasma, the loss due to the plasma wall is reduced and the plasma density is increased.
[0036]
An example of a circuit 68 for implementing a power supply 53 that supplies power to the coil magnets 51A-L to create the desired magnetic field configuration is shown schematically in FIG. In particular, each of the series of arbitrary waveform generators 70A-L is shown in FIG. 4 as coil magnets 51A-L of the electromagnet system via corresponding amplifiers 71A-L. Is not electrically connected).
[0037]
Each arbitrary waveform generator 70A-L can be electrically connected to a control system (via electrical connections not shown in FIG. 4). The control system 60 can be programmed to control each of the arbitrary waveform generators 70A-L independently of each other so that the respective coil magnets 51A-L can be controlled from the respective generators. A current waveform having an arbitrary shape, intensity, and phase is transmitted to the coil, and as a result, a polarity is given to the corresponding coil magnets 51A to 51L to create a magnetic field that acts on the plasma.
[0038]
All of the arbitrary waveform generator 70 can be phase locked to a single low power reference signal source 72. Each generator 70 can shift the phase of its output with respect to the reference signal from the reference signal source 72.
[0039]
The power supply arrangement of FIG. 4 allows the control system (operated by the series of arbitrary waveform generators 70A-L) to supply independent current waveforms to each of the coil magnets 51. Waveform, intensity, phase and period are independent of the current waveform generated by all other arbitrary waveform generators in series. Thus, the reference signal from the reference signal source 72 is used to synchronize the current waveform transmitted to the coil magnet 51 from the system of the arbitrary waveform generator.
[0040]
The control system can be independently programmed for each arbitrary waveform generator 70, thereby generating a different waveform with respect to the start phase locked to the reference signal from the reference signal source 72. Such an arrangement provides great flexibility, for example, when applying more than one magnetic field configuration to the plasma. This arrangement allows the control system to apply, for example, two consecutive magnetic field configurations to a particular substrate during the plasma processing operation. Such two magnetic field configurations can be the same or different from each other. The form of the magnetic field can be stationary or rotating.
[0041]
For example, such an arrangement (ie, using a separate arbitrary waveform generator for each coil magnet) allows the operator to program the control system so that it remains stationary during processing operations. A magnetic field configuration (eg, with respect to azimuth) and a rotating magnetic field configuration can be applied to the plasma. Each applied magnetic field configuration can be selected to produce a specific change in the plasma. For example, a rotating, crossed magnetic field configuration is used to improve plasma uniformity.
[0042]
As another example, such an arrangement may also have a local magnetic field (eg, a low or high magnetic field region) acting at a specific location within the processing chamber, even if the acting magnetic field is rotating. To allow the waveform to be formed. Such a local magnetic field can be used to correct variations in plasma characteristics due to azimuth. Such variations are caused, for example, by asymmetric gas injection and plasma pumping.
[0043]
Another circuit 76 that can be used as the power supply 53 is shown schematically in FIG. A single arbitrary waveform generator 77 drives a series of amplifiers 7lA-L, each supplying current to a corresponding coil magnet (not shown in FIG. 5). A phase delay circuit 78 is coupled between the arbitrary waveform generator and all but one of the amplifiers. Basically, the same signal is sent to each of the coil magnets 51A to 51L, but the only difference is that the phases of the signals are different from each other due to the presence of the phase delay circuit. Therefore, the circuit 76 can be used so that, for example, the current waveform applied to the coil magnet 51 has the same waveform and period, and only the phases are different from each other.
[0044]
The power supply circuit 76 can supply a rotating magnetic field form or a magnetic field form whose direction changes. The form of the magnetic field formed and rotated by the power supply circuit 76 includes the shape of the current waveform transmitted to the coil magnet, the number of relative positions of the coil magnet in the coil magnet system, and the relative position of each coil magnet 51. It depends on several factors such as the intensity and the phase difference between the current signals. By creating a control system to control the generator 70 of the arbitrary waveform of the circuit 76, for example, creating a rotating, crossed magnetic field configuration with non-linear (eg, arched) magnetic field lines Is possible.
[0045]
<Driving>
The control system can pass a steady current through any (or all) coil magnets 51. The control system can also cause any (or all) coil magnets 51 to pass a time-varying current (eg, using the power supply circuit 68). The distribution of the steady and / or time-varying current through the coil magnet 51 determines the magnetic field form acting on the plasma and determines the change in the magnetic field form over time. An appropriate current waveform is sent to the coil magnet 51 to rotate the magnetic field acting on the plasma, for example.
[0046]
The current waveform supplied to each coil magnet 51A-L polarizes each coil radially. During radial polarization, the ends on either side of each coil magnet are assumed to take north and south magnetic polarization. In general, the lines of magnetic force extend between the two poles of the coil magnet 51. The direction of current flow in each coil determines the polarization direction of each coil magnet. The magnitude of the current flowing through the coil magnet determines the strength of the magnetic field formed by each coil magnet and the strength of the magnetic field acting on the plasma.
[0047]
Other arrangements of magnet arrays are possible. For example, the axis of each coil magnet 51 extends radially from a virtual axis extending between the electrode assemblies 18 and 20 in the example reactor 10, but other arrangements are possible. For example, each coil magnet 51 can be arranged so that its axis is perpendicular to the reactor 10. Each coil oriented in the vertical direction may be an air coil or a coil wound around the core material. When each coil is wound around a core material, each core may be a separate structure or may form part of a continuous structure such as a ring or yoke.
[0048]
Such a vertical arrangement has several disadvantages (compared to the radial arrangement in example reactor 10). For example, if an array of radially extending electromagnets is used to generate a magnetic field, most of the magnetic field lines enter the chamber. However, when a vertical arrangement is used, the majority of the magnetic field lines flow along the outside of the plasma chamber 14, such a tendency when the coil is wrapped around a yoke surrounding the plasma chamber. A relatively small amount of “leak” or “outer edge” from the side of each vertically arranged coil enters the plasma chamber 14.
[0049]
Thus, the vertical arrangement will rely on the magnetic field at the outer edge of the side of each vertical coil to exert a magnetic field on the plasma in the chamber. Magnet systems that use a vertical arrangement of coils rely on the magnetic field at the outer edge to exert a magnetic field on the plasma, so the same magnetic field strength is created when creating a specific form with a specific magnetic field strength. More power is required compared to using a radial arrangement to create the same form with A radially arranged magnet system uses less current compared to a vertically arranged magnet system.
[0050]
Since the vertical arrangement relies on the magnetic field lines emanating from the sides of each coil, each coil fires a magnetic field line into the chamber, which e.g. exits from the opposite side and leaves the chamber. The structure surrounding the outside is also required to shield the area surrounding the plasma processing apparatus from the magnetic field. If a vertically oriented electromagnet is wound, for example, around the yoke, a second permeable shield is required if the area surrounding the device needs to be shielded from the magnetic field.
[0051]
A second magnetically permeable shield or other magnetic flux shield structure is not required, for example, in the arrangement shown in FIGS. The reason is that the structure 57 realizes both a function of transmitting magnetic flux and a function of shielding magnetic flux.
[0052]
FIGS. 2, 3 and 6 show examples of magnetic field forms that can be applied to the plasma using coil magnets 51A-L. The direction of the current flowing through each of the coil magnets 51A-L is indicated by an arrow indicating the direction in FIGS. The relative magnitude of the current in each coil magnet is roughly indicated by the relative size of the arrows indicating the direction in FIGS. The absence of a direction arrow indicates that the instantaneous current magnitude in the corresponding coil magnet 51 is zero. The iron ring structure 57 closes the lines of magnetic force in each configuration.
[0053]
A rotating, crossed magnetic field configuration can be applied to the plasma, for example, by using either power supply circuit 68 or 76. For example, a composite current waveform whose phase is shifted with respect to the coil on the front side with respect to the rotation direction, that is, the coil on the opposite side with respect to the rotation direction of the magnetic field form can be supplied to each coil magnet 51. Such a method makes it possible to rotate the cross-type magnetic field configuration without mechanically rotating any of the coils and magnets.
[0054]
FIG. 2 shows a rotating and intersecting magnetic field configuration at a specific moment in time. At this moment, a relatively large amount of current flows through the coil magnets 51A and 51B in opposite directions. A small amount of current flows through the coil magnets 51L and 51G in opposite directions compared to the current in the coil magnets 51A and 51B. The coil magnet pairs 51K and 51D, 51J and 51E, and 51I and 51F have smaller amounts of current flowing in opposite directions in order (the state is relative to the arrow indicating the direction). Is represented in a size). Non-linear magnetic field lines typically extend between the coils of each pair of coil magnets, as indicated by arcuate arrows in the processing chamber 14. The current flowing through the coil magnets 51H and 51G can be instantaneously zero in magnitude (which depends, for example, on the exact magnetic field that is to be applied).
[0055]
Moreover, the following is understood from FIG. The field lines generally extend from coil magnets 51A, 51L, 51K, 51J and 51I on one side of the chamber to corresponding coil magnets 51B, 52C, 51D, 51B and 51E on the opposite side of the chamber, respectively. . The reduction in magnitude of the current (on the opposite side of the chamber) effectively creates a strong magnetic field gradient that increases from an azimuth position of about 11 o'clock to an azimuth position of about 5 o'clock. This slope helps to compensate for ExB drift.
[0056]
ExB drift can occur if a uniform magnetic field traverses the plasma chamber 14 parallel to the workpiece, whereas an electric field perpendicular to the workpiece is present in the chamber. The vector product of the magnetic fields by these electromagnets is parallel to the workpiece and perpendicular to both sets of magnetic field lines. This results in the direction of the vector product (i.e., the preferred direction), which increases the density of the plasma in one area (or corner) of the plasma chamber. This results in non-uniform workpiece processing, which is undesirable. To correct such ExB drift, the magnetic field morphology is rotated.
[0057]
However, if the magnetic field form is uniform, the rotating magnetic field simply causes “hot spots” (regions with relatively high electron density) around the plasma. In order to correct this effect, the magnetic field lines of the magnetic field form are curved, thereby sufficiently fanning out electrons ("fan out") to reduce the hot spot effect. become.
[0058]
FIG. 3 shows a bucket-type magnetic field configuration (or a bucket-shaped magnetic field configuration). This forms a magnetic bucket around the wall of the chamber 14. This configuration creates an arcuate annulus of magnetic field lines extending toward the center of the chamber. These annulus tend to concentrate the plasma in the center of the chamber. This brings a number of advantages. Among them, for example, the tendency to reduce the number of plasma particles impinging on the chamber sidewalls and other surfaces in the chamber 14 and increase the plasma density (by confining the plasma in a narrow space). Is included. As the plasma density increases, for example, the rate of etching or deposition increases. As workpieces are processed faster, for example, commercial productivity in semiconductor manufacturing increases.
[0059]
As shown in FIG. 3, the bucket-shaped magnetic field configuration has the same magnitude and opposite polarity current (i.e., reverse direction) in each pair of adjacent coil magnets 51 in the array. This can be realized by flowing a current. The reactor 12 can also be constructed by creating magnetic field lines having a bucket shape that rotates or vibrates.
[0060]
FIG. 6 shows a schematic view of an apparatus 80 for applying a rotating bucket-shaped magnetic field form to plasma. This device 80 is substantially the same as the device 12, the only difference being the number of coil magnets attached around the chamber 14. The same reference numerals are given to the same structures between these two embodiments 12 and 80, and description thereof will be omitted.
[0061]
The number of coil magnets mounted around the chamber 14 determines the resolution of the magnetic field produced by the magnet system. That is, as the number of coil magnets arranged around increases, the bucket-shaped magnetic field form covering the inside of the chamber wall becomes finer. In order to better control the “ambient” magnetic field (ie, the magnetic field in the part adjacent to the wall), a fairly large number of fairly small coils are mounted around the chamber 14 of the device 80.
[0062]
When a magnetic field with high resolution is required, the inner ends of the cores of the coil magnets 51 adjacent to each other are just before contacting each other. This is illustrated in FIG. Since this device 80 has, for example, twice the number of coil magnets 51 as compared with the device 12 mounted around the chamber, the device 80 has a bucket shape realized using the device 12. It is possible to operate so as to realize a high resolution compared to the magnetic field form. The number of coils used depends on the required magnetic field resolution. Generally, the resolution of the magnetic field increases as the number of magnets increases.
[0063]
The length of the annular portion can be increased by combining a magnet and increasing the number such as two or three. That is, when the two electromagnets 51 are operated in combination to create a bucket-shaped magnetic field form, the magnitude and direction of the current flowing in the coils 51A and 51B are made the same at each moment. Similarly, the magnitudes and directions of the currents flowing through the coils 51C and D are also the same. In this way, the coils 51A and 51B (and the coils 51C and 51D, hereinafter the same) substantially function as a single coil. As the annulus in the form of a bucket-shaped magnetic field extending into the chamber becomes longer, the plasma is more tightly squeezed toward the center of the plasma chamber 14, thereby increasing the plasma density and reaction rate.
[0064]
The device 80 can also be operated (eg, using the circuit 76 of FIG. 5) to create a rotating or oscillating bucket-shaped magnetic field configuration, which is illustrated in FIG. It has the same resolution as the non-rotating bucket-shaped magnetic field configuration shown. However, this device creates an overlapping annular pattern, and such a pattern tends to squeeze the plasma more uniformly (compared to the magnetic field configuration of FIG. 3).
[0065]
Bucket-shaped magnetic field configurations made according to the example method described below also have advantageous effects. This is because at any point in time, at least some locations have non-zero instantaneous magnetic field strengths. That is, at each point in time, at several locations within the processing chamber, the acting magnetic field is always non-zero.
[0066]
An oscillating or rotating bucket magnetic field has an advantageous effect. The reason is that such a magnetic field prevents the field lines from constantly striking the processing chamber wall (s) at the same location (s). If the bucket-type magnetic field lines are not rotated, so, for example, if the wall is always struck at the same location, it will cause plasma particles to enter those locations along the magnetic field lines that enter the wall. Can result in degradation of the wall material at those locations.
[0067]
Such local degradation of the wall material caused by a static magnetic field can occur, for example, at locations such as between adjacent annular portions. At such points, the magnetic field lines from adjacent annular portions enter the chamber wall 14 together. The bucket-type magnetic field that acts in this way can be static, vibrated, or rotated, but for long periods of time it is a static bucket-type (or other type of plasma) It can be seen that it is not preferable to apply a magnetic field of the type). The reason is that it causes local degradation to the walls of the processing chamber.
[0068]
FIG. 6 shows the instantaneous state of the current and magnetic field in the device 80 when the device 80 is operated to create a rotating bucket-shaped magnetic field configuration. FIG. 7 shows a graph representing the magnitude of current flowing through the four coil magnets 51 while the rotating bucket-shaped magnetic field configuration of the above example is created. The rotating bucket-shaped magnetic field configuration in the device 80 has essentially the same magnetic field resolution as that applied using the device 12.
[0069]
The coil magnets 51A-X are basically operated as two separate magnet systems, each creating a bucket-shaped magnetic field configuration independently of the other magnet systems. The first magnet system includes 51A, 51C, 51E, 51G, 51I, 51K, 51M, 51O, 51Q, 51S, 51U and 51W, and the second magnet system includes the other coil magnets 51. Prepare.
[0070]
The graph of FIG. 7 shows the current flowing through the coil magnets 51A-D. It can be seen that the current waveforms in the adjacent coil magnets (eg, 51A and 51B) are 90 degrees out of phase with each other. The currents in all other coils and magnets (such as the coil magnets 51A and 51C) are 180 degrees out of phase with each other.
[0071]
FIG. 6 shows magnetic field lines at time tx. This time tx is also shown in the graph of FIG. At time tx, the maximum current flows through one set of coil magnets (a set including 51B and 51D), and the magnitude of current flows in the other set of coil magnets (a set including 51A and 51B). Is zero. The adjacent coils in each set (e.g. 51B and 51D) are in the opposite direction, as indicated by the arrows indicating the current direction in the opposite direction represented in the graph of FIG. 6 and FIG. Current flows.
[0072]
FIG. 7 shows that each current waveform is a sine curve. In addition, it can be seen from the graph of FIG. 7 that the magnetic field created in the above-described rotary bucket-shaped magnetic field configuration does not disappear at any point during the plasma processing operation. The reason is that the current does not become zero in all the coil magnets 51A to X at any instant.
[0073]
The structure and operation of the device 80 described above is only one example. It can be envisaged to build a device with three or more independent magnet systems, thereby creating, for example, three or more rotating magnetic field configurations.
[0074]
One or more magnetic field configurations can be applied to the plasma during the processing of a particular workpiece (such as a semiconductor) to improve processing quality and yield. It is possible. For example, a selected magnetic field configuration can be applied to the plasma during an etching operation (or alternatively a deposition operation) in which a pattern is etched on the surface of a semiconductor material wafer. Because the arbitrary waveform generator and the coil magnet 51 system can be used to create a magnetic field, and the arbitrary waveform generator can be controlled by a control system, the manufacturer can select a specific semiconductor. Appropriate magnetic field configurations can be selected for materials and for specific semiconductor etching (or deposition) applications
The determination of the optimal magnetic field configuration combination for a particular application can be made empirically. That is, during the processing of a specific type of wafer, a specific current waveform is introduced into selected coil magnets of one or more magnet systems and the results are examined. The quality of the etching / deposition results can be correlated or examined in light of the magnetic field configuration used in the etching / deposition process.
[0075]
For example, if the workpiece is damaged or the processing result is not uniform, the distribution of the current waveform introduced into the coil magnet 51 is corrected (the program of the control system is By redoing, for example, the morphology, intensity, gradient, period, etc. of the magnetic field morphology acting on the plasma can be modified.
[0076]
When processing a semiconductor in a plasma chamber, the semiconductor is susceptible to damage caused by non-uniform concentrations of electrons in the plasma (either high or low concentration areas). Most of the damage caused by plasma concentration non-uniformity occurs near the final stage of the processing operation. Two or more magnetic field configurations can be used to reduce damage resulting from plasma non-identity during processing of a workpiece (such as a semiconductor).
[0077]
During the first part of the processing operation (ie) when the workpiece is relatively less susceptible to damage due to plasma density inhomogeneities, the plasma density is increased by applying one or more bucket-type magnetic field configurations to the plasma. Thereby increasing the processing speed. In the early stages of processing operations, by increasing the plasma density, for example, material can be rapidly etched from the workpiece. Then, near the end of the process, when it becomes dangerous to process at such a high speed, another magnetic field is applied to the processing chamber, thereby during the final critical phase of the processing operation. Plasma uniformity can be improved.
[0078]
As another example, a bucket-shaped magnetic field configuration having a relatively large annular field can be applied to the plasma during the initial stages of processing. A bucket-shaped magnetic field configuration having an intermediate sized annular field can then be applied to the plasma, and then a bucket-shaped magnetic field configuration having a relatively small annular field can be applied to the plasma. By gradually reducing the size of the annular field in the form of a bucket-shaped magnetic field during the processing action (stepwise or continuously over the processing time), the plasma density is gradually reduced as the processing progresses. Can be reduced. During the final critical phase of the plasma treatment, a rotating, crossed magnetic field configuration with curvilinear magnetic field lines is applied to the plasma, thereby ensuring that the plasma is uniform during the final critical phase of the plasma treatment. Can be increased.
[0079]
A number of known causes can cause local inhomogeneities in the plasma. These causes include gas injection non-uniformity, high-frequency excitation field non-uniformity acting on the plasma, pumping non-uniformity in the plasma chamber, and the like. Each coil magnet can be operated with an arbitrary waveform generator independent of each other, so the controller for controlling the placement of the current sent to the array of magnets can be programmed to create local non-uniformities in the plasma Can be compensated. In this way, the controller can be programmed to create a rotating magnetic field, thereby providing local inhomogeneities in the applied magnetic field and compensating for density inhomogeneities occurring in the plasma. it can.
[0080]
In the above example, the electrodes of the plasma chamber are described as being driven by corresponding voltage sources, but this does not necessarily require that each electrode be driven by a corresponding voltage source. It will be understood that it does not mean something. Thus, for example, during processing, for example, one or the other of the pair of electrodes 18, 20 of the system 10 is constantly at ground level, or other static It is possible to have a voltage level that is not (ie, does not change).
[0081]
The many features and advantages of the present invention are apparent from the detailed description. It is therefore anticipated that the appended claims will cover all such features and advantages of the method of following within the true spirit and scope of the invention. Further, since many variations and modifications will be apparent to those skilled in the art, it is not intended that the invention be limited only to the structures and operating aspects shown and described. Furthermore, the methods and apparatus of the present invention often determine empirically the appropriate values of operating parameters, as well as related apparatus and methods (which are inherently complex) used in semiconductor technology. Or by performing computer simulations to arrive at the best design for a given application. Accordingly, all suitable modifications and equivalents should be considered within the spirit and scope of the invention.
[Brief description of the drawings]
[0082]
FIG. 1 is a schematic diagram of an example of a plasma processing system for illustrating the present invention, the plasma processing system showing a workpiece and plasma in a plasma chamber of a plasma processing apparatus and an outer magnetic flux transfer Fig. 2 shows the structure and an array of electromagnets surrounding the periphery of the processing chamber.
FIG. 2 is a schematic top view of a portion of the apparatus of FIG. 1, showing the processing chamber, the bottom electrode, the outer magnetic flux transmission structure, and an array of electromagnets surrounding the processing chamber and within the processing chamber; The acting cross-type magnetic field form is shown.
FIG. 3 is a view similar to FIG. 2, but differs from FIG. 2 in that it shows a bucket-shaped magnetic field configuration acting inside the processing chamber.
FIG. 4 is a schematic diagram of an example of a power supply circuit for supplying power to an array of magnets.
FIG. 5 is a schematic diagram of a second example of a power supply circuit for supplying power to an array of magnets.
6 is a schematic diagram similar to FIG. 3, but differs from FIG. 3 in that it shows a bucket-shaped magnetic field configuration applied to the processing chamber using two electromagnet systems.
7 is a graph showing the current flow in four adjacent electromagnets of the apparatus of FIG.
[Explanation of symbols]
[0083]
DESCRIPTION OF SYMBOLS 10, 12, 80 ... Plasma processing apparatus, 14 ... Plasma chamber, 16 ... Internal region, 18 ... 1st electrode assembly, 20 ... 2nd electrode assembly (chuck type electrode) Assembly), 22 ... inner chamber, 24 ... gas supply system, 30, 32 ... matching network, 34, 36 ... high frequency source, 38 ... cooling system, 39, 41 ... Fluid chamber, 40 ... Vacuum system, 44, 46 ... Voltage probe, 48 ... Optical probe, 51, 51A-L ... Electromagnet (coil magnet), 53 ... Power supply, 54 ..Plasma, 55 ... core, 57 ... magnetic flux transmission structure, 59 ... wall type structure, 60 ... control system, 62 ... workpiece (substrate), 68 ... circuit, power Supply Road, 70A～L ... arbitrary waveform generator, 71A～L ... amplifier, 72 ... reference signal source, 76 ... power supply circuit, 78 ... phase delay circuit.

Claims (26)

A method for processing a workpiece performed using plasma generated from a process gas in a plasma chamber of a plasma processing apparatus during a plasma processing operation, comprising:
The apparatus comprises an array of electromagnets mounted so as to surround the plasma chamber,
The method comprises the following steps:
Generating a plasma from a process gas in the chamber;
Causing plasma particles to collide with the workpiece;
Selecting an arrangement of current signals supplied to the electromagnet;
Each electromagnet is provided with each selected arrangement, thereby causing one or more magnetic field configurations to act on the plasma during a plasma processing operation. The method of claim 1 comprising the following features:
At least one of the magnetic field forms is a non-rotating magnetic field form. The method of claim 1 comprising the following features:
At least one of the magnetic field forms is a rotating magnetic field form. The method of claim 3 comprising the following features:
The at least one rotating magnetic field configuration corrects the plasma density non-uniformity of the plasma, whereas
The at least one rotating magnetic field configuration acts on the plasma. The method of claim 4 comprising the following features:
The at least one rotating magnetic field form is a cross-type magnetic field form. The method of claim 5, comprising the following features:
The crossed magnetic field lines have a non-linear shape. The method of claim 2, comprising the following features:
The at least one non-rotating magnetic field form is a bucket-shaped magnetic field form. The method of claim 1 comprising the following features:
The one or more magnetic field configurations include a cross-type magnetic field configuration and a bucket-shaped magnetic field configuration. The method of claim 1 comprising the following features:
Giving the arrangement
Providing the current signal to exert a bucket-shaped magnetic field configuration on the plasma during the first part of the plasma processing operation; and
Applying a cross-type magnetic field configuration to the plasma during the second part of the plasma processing operation. The method of claim 9, comprising the following features:
During the first portion of the plasma processing operation, a plurality of bucket-shaped magnetic field configurations are applied to the plasma, thereby reducing the plasma density to a predetermined rate. The method of claim 10 comprising the following features:
The line of magnetic force in the form of the intersecting magnetic field has a non-linear shape. 12. The method of claim 11, comprising the following features:
The intersecting magnetic field morphology corrects the plasma inhomogeneity. The method of claim 1 comprising the following features:
At least one of the magnetic field forms changes its direction during processing. 14. The method of claim 13, comprising the following features:
At least one of the magnetic field configurations that change its direction during processing changes its direction by rotation. A method for processing a workpiece performed using plasma generated from a process gas in a plasma chamber of a plasma processing apparatus during a plasma processing operation, comprising:
The apparatus comprises an array of electromagnets mounted so as to surround the plasma chamber,
The method comprises the following steps:
Generating a plasma from a process gas in the chamber;
Causing plasma particles to collide with the workpiece;
Supplying a current signal arrangement to the electromagnet;
Accordingly, during the plasma processing operation, the electromagnet causes a rotating bucket-shaped magnetic field form to act on the plasma. The method of claim 15 comprising the following features:
The electromagnet array is:
Comprising a first system of electromagnets and a second system of electromagnets;
Each electromagnet of each system is placed between the pair of electromagnets of the other system. The method of claim 16, comprising the following features:
The current signal in the at least one electromagnet system is non-zero intensity at any point during the magnetic field rotation. Plasma processing equipment for processing workpieces with the following configuration:
A plasma chamber having an internal region for holding the plasma;
Plasma source;
A vacuum system in fluid communication with the internal region of the plasma chamber;
A gas supply system in fluid communication with the internal region of the plasma chamber;
A plurality of coil magnets attached to surround the periphery of the plasma chamber, each coil magnet having an axis extending radially from the axis of the plasma chamber;
A plurality of arbitrary waveform generators, each generator being electrically connected to a corresponding one of the plurality of coils and magnets; and
A control system electrically coupled to the gas supply system, the vacuum system, the cooling system, and the plurality of arbitrary waveform generators;
The control system is configured to operate the arbitrary waveform generator so that the coil magnet exerts a magnetic field configuration on the plasma during the plasma processing operation. The plasma processing apparatus according to claim 18, comprising the following features:
The plasma generation source includes one or more electrode assemblies mounted in the chamber and one or more radio frequency power sources, and each radio frequency power source is electrically coupled to a corresponding electrode assembly. Yes. The plasma processing apparatus according to claim 19, comprising the following features:
Each coil magnet is an air coil. The plasma processing apparatus according to claim 19, comprising the following features:
Each coil magnet has a core made of a magnetically permeable material. The plasma processing apparatus according to claim 21, comprising the following features:
In addition, an outer magnetic flux transmission structure attached to surround the coil magnet array,
Each coil / magnet and each core has a continuous magnetic flux between the magnetic flux transmission structure. The plasma processing apparatus according to claim 22, comprising the following features:
The magnetic flux transmission structure is an annular wall type structure. The plasma processing apparatus according to claim 23, comprising the following features:
The annular wall structure is made of a magnetically permeable material. The plasma processing apparatus according to claim 24, comprising the following features:
Each core is attached to the annular wall structure. The plasma processing apparatus according to claim 18, comprising the following features:
Each of the arbitrary waveform generators constituting the plurality of arbitrary waveform generators,
A corresponding one of the plurality of coils and magnets is electrically coupled via a corresponding one of the plurality of amplifiers.

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