Multi-Frequency Hollow Cathode System for Substrate Plasma Processing
A hollow cathode system is provided for plasma generation in substrate plasma processing. The system includes a plurality of electrically conductive plates stacked in a layered manner. Dielectric sheets are disposed between each adjacently positioned pair of the plurality of electrically conductive plates. A number of holes are each formed to extend through the plurality of electrically conductive plates and dielectric sheets. The system also includes at least two independently controllable radiofrequency (RF) power sources electrically connected to one or more of the plurality of electrically conductive plates. The RF power sources are independently controllable with regard to frequency and amplitude.
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This application is related to U.S. patent application Ser. No. ______ (Attorney Docket No.: LAM2P704A), filed on an even date herewith, and entitled “Multi-Frequency Hollow Cathode and Systems Implementing the Same,” which is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTIONConventional hollow cathodes are required to operate at high pressures on the order of hundreds of milliTorr (mTorr) to atmospheric. Some conventional hollow cathodes operate most effectively at pressures on the order of 1 to 10 Torr, and have interior dimensions sized on the order of millimeters (mm). To be operable, a conventional hollow cathode's interior cavity diameter should be within the range of a few plasma sheath thicknesses. It is this scaling that present a problem for use of conventional hollow cathodes in some semiconductor fabrication processes, such as plasma etch processes, where low pressures are required.
More specifically, conventional hollow cathodes require high radiofrequency (RF) power to generate a plasma at lower gas pressures and have relatively large sizes. Conventional hollow cathodes are not capable of generating high plasma densities with thin plasma sheath thicknesses under simultaneous conditions of low frequency RF power, low pressure, and small hollow cathode dimensions. Therefore, conventional hollow cathodes are not suitable for use in semiconductor fabrication operations where both low pressure and low frequency RF power are simultaneously required, such as in plasma etch operations. It is within this context that the present invention arises.
SUMMARY OF THE INVENTIONIn one embodiment, a hollow cathode system for plasma generation in substrate plasma processing is disclosed. The hollow cathode system includes a plurality of electrically conductive plates stacked in a layered manner. Dielectric sheets are disposed between each adjacently positioned pair of the plurality of electrically conductive plates. Also, each of a number of holes is formed to extend through the plurality of electrically conductive plates and dielectric sheets disposed there between. The hollow cathode system also includes at least two independently controllable RF power sources electrically connected to one or more of the plurality of electrically conductive plates.
In another embodiment, a system is disclosed for substrate plasma processing. The system includes a chamber formed by surrounding walls, a top plate, and a bottom plate. A substrate support is disposed within the chamber. The system also includes a hollow cathode assembly disposed within the chamber above and spaced apart from the substrate support. The system also includes a process gas source in fluid communication with the hollow cathode assembly to supply process gas to the hollow cathode assembly. The system further includes a plurality of RF power sources in electrical communication with the hollow cathode assembly. Each of the plurality of RF power sources is independently controllable with regard to RF power frequency and amplitude. During operation of the system, a plurality of RF powers respectively transmitted from the plurality of RF power sources to the hollow cathode assembly transform the process gas into a plasma within the hollow cathode assembly, such that reactive species with the plasma move from the hollow cathode assembly to a substrate processing region over the substrate support.
Other aspects and advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention.
A hollow cathode plasma source is operated by creating an electric field in a confined space within the hollow cathode. The electric field excites a process gas supplied to the confined space to transform the process gas into a plasma within the confined space. The plasma is separated by a sheath from the surfaces of the hollow cathode that surround the confined space. In one embodiment, the electric field created within the hollow cathode is referred to as a saddle electric field due to its shape. The electric field within the hollow cathode creates pendulum electrons. The pendulum electrons are born at a surface of the hollow cathode surrounding the confined space, or in the sheath surrounding the plasma. The electrons born at a surface of the hollow cathode or within the sheath are accelerated to an opposing portion of the sheath, whereby the electrons cause ionization of neutral constituents in the process gas, creation of radical species within the process gas, and/or generation of more “fast” electrons.
The electric field within the hollow cathode also confines the plasma within the confined space of the hollow cathode, thereby increasing the plasma density in the confined space. Hollow cathodes provide an attractive means for generating high plasma density, but can have a narrow range of operation with regard to pressure, dimensions, and/or driving voltage. The present invention provides hollow cathodes and associated methods of use that extend the range of operation of the hollow cathodes to be suitable for plasma etch processes in semiconductor fabrication, particularly at advanced technology nodes, i.e., at smaller critical dimension sizes within the integrated circuitry.
In various embodiments described herein, different arrays of hollow cathodes are disclosed for use in plasma processing of a substrate, e.g., semiconductor wafer. During operation, a process gas is supplied to an array of hollow cathodes to generate plasma within each hollow cathode in the array. Then, the reactive constituents of the plasma are passed from the array of hollow cathodes to a low pressure environment within which the substrate is disposed, thereby allowing the reactive constituents to contact and do work on the substrate. Additionally, in some embodiments, the array of hollow cathodes are operated in a manner whereby ion processing and radical processing of the substrate are decoupled and independently controlled.
Multiple radiofrequency (RF) power sources 109A, 109B are connected to supply RF power to the hollow cylinder 101. More specifically, each of the multiple RF power sources 109A, 109B is connected to supply RF power through respective matching circuitry 111, to the hollow cylinder 101. The matching circuitry 111 is defined to prevent/mitigate reflection of the RF power from the hollow cylinder 101, such that the RF power will be transmitted through the hollow cylinder 101 to the reference ground potential 107. It should be understood that although the example embodiment of
During operation, a process gas is flowed through an interior cavity of the hollow cathode assembly 100, as depicted by arrows 113. Also, during operation, RF power supplied to the hollow cylinder 101 from the multiple RF power sources 109A, 109B transforms the process gas into a plasma 115 within the hollow cylinder 101. In the plasma 115, the process gas is transformed to include both ionized constituents and radical species which may be capable of doing work on a substrate when exposed to the substrate. It should be appreciated that more than one RF power source 109A, 109B is used to supply RF power to the hollow cathode assembly 100. Each of the RF power sources 109A, 109B is independently controllable with regard to RF power frequency and amplitude.
The plasma 115 is confined within the hollow cylinder 101 by the electric field generated by the RF power supplied from the multiple RF power sources 109A, 109B. Also, a sheath 117 is defined within the hollow cylinder 101 about the plasma 115.
In contrast to the hollow cathode assembly 100 of
Therefore, it should be understood that use of multiple independent RF power sources at appropriate frequencies to power a hollow cathode can extend the operational range of the hollow cathode well beyond what is achievable with use of either a single RF frequency power source or DC power source. In following, use of multiple independent RF power sources at appropriate frequencies with an appropriately configured hollow cathode assembly can extend the effective process gas operational pressure range of the hollow cathode assembly, and thereby enable use of the hollow cathode assembly as a plasma source in semiconductor fabrication processes. Moreover, for a given hollow cathode assembly configuration, use of more than two RF power sources at different frequencies can substantially increase the effective process gas operational pressure range of the given hollow cathode assembly.
In one embodiment, two RF power frequencies are supplied to the hollow cathode assembly 100. In one instance of this embodiment, the two RF power frequencies are about 2 megaHertz (MHz) and about 60 MHz. In another embodiment, three RF power frequencies are supplied to the hollow cathode assembly 100. In one instance of this embodiment, one of the three RF power frequencies is within a range extending from about 100 kiloHertz (kHz) to about 2 MHz, and the other two RF power frequencies are about 27 MHz and about 60 MHz. In this embodiment, the lowest frequency is used to set up the hollow cathode effect. Also in this embodiment, the highest frequency is used to establish the initial plasma with the required sheath size. Also in this embodiment, the intermediate frequency is used to bridge process regimes and aid in making the plasma strike efficiently. This three RF power frequency embodiment provides for hollow cathode plasma generation at process gas pressures within a range extending from about one milliTorr (mTorr) to hundreds of mTorr. The upper end of the process gas pressure range (hundreds of mTorr) can be used for chamber cleaning operations. The lower end of the process gas pressure range (about one mTorr) can be used for plasma etching processes in advanced gate and contact fabrication operations.
In various embodiments, the multiple RF power frequencies supplied to the hollow cathode can be binned into five ranges. A first of the five ranges is DC. A second of the five ranges is referred to as a low range, and extends from hundreds of kHz to about 5 kHz. A third of the five ranges is referred to as a medium range, and extends from about 5 kHz to about 13 MHz. A fourth of the five ranges is referred to as a high range, and extends from about 13 MHz to about 40 MHz. A fifth of the five ranges is referred to as a very high range, and extends from about 40 MHz to more than 100 MHz. It should be understood that operation of the hollow cathode with different RF power frequency combinations may require different matching circuitry designs, various RF return current path considerations, and use of different inter-electrode dielectric material thicknesses.
With reference back to
The RF power source 109A represents a first RF power source 109A in electrical communication with the electrically conductive member 101, so as to enable transmission of a first RF power to the electrically conductive member 101. The RF power source 109B represents a second RF power source 109A in electrical communication with the electrically conductive member 101, so as to enable transmission of a second RF power to the electrically conductive member 101. The first and second RF power sources 109A, 109B are independently controllable, such that the first and second RF powers are independently controllable with regard to frequency and amplitude.
Further with regard to
The matching circuitry 111 includes a first matching circuit connected between the first RF power source 109A and the electrically conductive member 101. The first matching circuit is defined to prevent reflection of the first RF power from the electrically conductive member 101. Also, the matching circuitry 111 includes a second matching circuit connected between the second RF power source 109B and the electrically conductive member 101. The second matching circuit is defined to prevent reflection of the second RF power from the electrically conductive member 101. In various embodiments, the hollow cathode system of
While the hollow cylinder 101 represents the electrically conductive member in the example embodiment of
As shown in
In one embodiment, the first RF power source 109A is in electrical communication with the central solid cylinder 301, through appropriate matching circuitry 111. Also, in this embodiment, the second RF power source 109B is in electrical communication with the outer hollow cylinder 303, through appropriate matching circuitry 111. In another embodiment, both the first and second RF power sources 109A, 109B are in electrical communication with each of the central solid cylinder 301 and the outer hollow cylinder 303, through respective and appropriate matching circuitry 111.
As shown in
In one embodiment, the first RF power source 109A is in electrical communication with the central hollow cylinder 401, through appropriate matching circuitry 111. Also, in this embodiment, the second RF power source 109B is in electrical communication with the outer hollow cylinder 403, through appropriate matching circuitry 111. In another embodiment, both the first and second RF power sources 109A, 109B are in electrical communication with the central hollow cylinder 401, through appropriate matching circuitry 111. Also, in this embodiment, the second RF power source 109B is in electrical communication with the outer hollow cylinder 403, through appropriate matching circuitry 111. In yet another embodiment, both the first and second RF power sources 109A, 109B are in electrical communication with each of the central hollow cylinder 401 and the outer hollow cylinder 403.
In one embodiment, the first process gas inlet 407A of the first interior cavity 405A is in fluid communication with a first process gas source, and the second process gas inlet 407B of the second interior cavity 405B is in fluid communication with a second process gas source. In one version of this embodiment, the process gas inlets 407A, 407B of both the first and second interior cavities 405A, 405B are in fluid communication with a common process gas source. In another version of this embodiment, the first and second process gas sources are independently controllable with regard to process gas type, process gas pressure, process gas flow rate, process gas temperature, or any combination thereof
In the embodiment of
Because higher process gas pressures require lower frequency RF power to generate an optimum plasma density, vice-versa, the first electrically conductive member 501 having the smaller sized portion of the interior cavity 505 may be connected to a lower frequency one of the RF power sources 109A, 109B. In a complementary manner, the second electrically conductive member 503 having the diffuser-shaped portion of the interior cavity 505 may be connected to a higher frequency one of the RF power sources 109A, 109B.
In the example embodiments of
It should be understood that not all embodiments are required to include upper and lower ground plates 650A, 605B. For instance, other structures within a plasma processing chamber around the hollow cathodes may provide a suitable RF power return path. For example,
Additionally, in some embodiments, multiple RF power frequencies can be applied to a single cathode plate 601. For example, in a hollow cathode that includes multiple cathode plates 601, one or more of the multiple cathode plates 601 may be individually connected to receive multiple RF power frequencies.
In the hollow cathode system 700, at least two independently controllable RF power sources 109A, 109B are electrically connected to the electrically conductive plate 701. Each of the at least two independently controllable RF power sources 109A, 109B is independently controllable with regard to RF power frequency and amplitude. In the example embodiment of
When deployed in a plasma processing system, a first end of each of the number of holes 707 is in fluid communication with a process gas source. And, a second end of each of the number of holes 707 is in fluid communication with a substrate processing region. In this manner the process gas flows through holes 707, as indicated by arrows 709. As the process gas flows through the holes 707, RF powers emitted from the central cathode plate 701 transforms the process gas into plasma 710 within each hole 707. It should be understood that a pressure of the process gas within the hole 707 may suitable for plasma production within an RF power frequency range corresponding to less than all of the at least two independently controllable RF power sources 109A, 109B. However, as long as at least one of the RF power sources 109A, 109B is operated at a frequency suitable for plasma production with the supplied process gas pressure, the other RF power frequencies can be utilized to influence the plasma characteristics, i.e., the ion and/or radical generation within the plasma.
The system 800 also includes a substrate support 803 disposed within the chamber 801. The substrate support 803 is defined to hold a substrate 802 thereon during performance of a plasma processing operation on the substrate. In the embodiment of
In one embodiment, the substrate support 803 includes a bias electrode 807 for generating an electric field to attract ions toward the substrate support 803, and thereby toward the substrate 802 held on the substrate support 803. Also, in one embodiment, the substrate support 803 includes a number of cooling channels 809 through which a cooling fluid can be flowed during plasma processing operations to maintain temperature control of the substrate 802. Also, in one embodiment, the substrate support 803 can include a number of lifting pins 811 defined to lift and lower the substrate 802 relative to the substrate support 803. In one embodiment, a door assembly 813 is disposed within the chamber wall 801A to enable insertion and removal of the substrate 802 into/from the chamber 801. Additionally, in one embodiment, the substrate support 803 is defined as an electrostatic chuck equipped to generate an electrostatic field for holding the substrate 802 securely on the substrate support 803 during plasma processing operations.
The system 800 further includes a hollow cathode assembly 815 disposed within the chamber 801 above and spaced apart from the substrate support 803, so as to be positioned above and spaced apart from the substrate 802 when positioned on the substrate support 803. A substrate processing region 817 exists between the hollow cathode assembly 815 and the substrate support 803, so as to exist over the substrate 802 when positioned on the substrate support 803. In one embodiment, a vertical distance as measured perpendicularly between the hollow cathode assembly 815 and the substrate support 803, i.e., process gap, is within a range extending from about 1 centimeter (cm) to about 10 cm. In one embodiment, the vertical distance as measured perpendicularly between the hollow cathode assembly 815 and the substrate support 803 is about 5 cm. Also, in one embodiment, a vertical position of the substrate support 803 relative to the hollow cathode assembly 815, vice-versa, is adjustable either during performance of the plasma processing operation or between plasma processing operations.
The system 800 further includes a process gas source 819 in fluid communication with the hollow cathode assembly 815, to supply process gas to the hollow cathode assembly 815. In the example embodiment of
The system 800 also includes a plurality of RF power sources 109A, 109B in electrical communication with the hollow cathode assembly 815. Each of the plurality of RF power sources 109A, 109B is independently controllable with regard to RF power frequency and amplitude. Also, RF power is transmitted from each of the RF power sources 109A, 109B through respective matching circuitry 111 to ensure efficient RF power transmission through the hollow cathode assembly 815. During operation of the system 800, a plurality of RF powers are respectively transmitted from the plurality of RF power sources 109A, 109B to the hollow cathode assembly 815. The process gas is transformed into a plasma within each of the multiple hollow cathodes 823 of the hollow cathode assembly 815. Reactive species 825 within the plasma move from the hollow cathode assembly 815 to the substrate processing region 817 over the substrate support 803, i.e., onto the substrate 802 when disposed on the substrate support 803.
In one embodiment, upon entering the substrate processing region 817 from the hollow cathode assembly 815, the used process gas flows through peripheral vents 827, and is pumped out through exhaust ports 829 by an exhaust pump 831. In one embodiment, a flow throttling device 833 is provided to control a flow rate of the used process gas from the substrate processing region 817. In one embodiment, the flow throttling device 833 is defined as a ring structure that is movable toward and away from the peripheral vents 827, as indicated by arrows 835.
The hollow cathode assembly 815 is defined over an area of the substrate support 803 upon which the substrate 802 is to be received for plasma processing. The multiple hollow cathodes 823 of the hollow cathode assembly 815 are defined in exposure to the substrate processing region 817. The multiple hollow cathodes 823 are distributed in a substantially uniform manner relative to the area of the substrate support 803 upon which the substrate 802 is to be received for plasma processing. In one embodiment, about 100 hollow cathodes 823 are distributed in a substantially uniform manner relative to the area of the substrate support 803 upon which the substrate 802 is to be received for plasma processing. However, it should be understood that other embodiments may utilize more or less hollow cathodes 823. In the example embodiment of
The system 900A further includes an exhaust plenum 907 formed within the chamber 801 above the hollow cathode assembly 901. The exhaust plenum 907 is fluidly connected to an exhaust pump 909. The hollow cathode assembly 901 includes multiple exhaust holes 911 formed to extend completely through the hollow cathode assembly 901 from the substrate processing region 817 to the exhaust plenum 907. The multiple exhaust holes 911 are distributed in a substantially uniform manner relative to the area of the substrate support 803 upon which the substrate 802 is to be received for plasma processing. Also, each of the multiple exhaust holes 911 is isolated from the multiple hollow cathodes 905 and the process gas distribution channels within the hollow cathode assembly 901. It should be appreciated that the vertical pump out capability afforded by the multiple exhaust holes 911 within the hollow cathode assembly 901 provides for improved control over reactive species residence time on the substrate 802, as a function of radial position on the substrate.
In an operation 1207, a plurality of RF powers are transmitted to the multiple hollow cathodes. The plurality of RF powers are independently controlled with regard to frequency and amplitude, and include at least two different frequencies. Also, at least one of the plurality of RF powers transforms the process gas into a plasma as the process gas flows through the multiple hollow cathodes. Reactive species within the plasma enter the substrate processing region to do work on the substrate.
In one embodiment, the plurality of RF powers include two or more frequencies from the group consisting of 2 megaHertz (MHz), 27 MHz, 60 MHz, and 200 kiloHertz (kHz). In other embodiments, the plurality of RF powers include at least two different RF power frequencies corresponding to one or more of a low range, medium range, high range, and very high range. The low frequency range extends from hundreds (100's) of kHz to about 5 kHz. The medium range extends from about 5 kHz to about 13 MHz. The high range extends from about 13 MHz to about 40 MHz. The very high range extends from about 40 MHz to more than 100 MHz.
The method can further include an operation for controlling a pressure of the process gas. In one embodiment, the pressure of the process gas enables formation of the plasma by some of the plurality of RF powers and does not enable formation of the plasma by others of the plurality of RF powers. In one embodiment, the pressure of the process gas is controlled within a range extending from about 1 milliTorr (mTorr) to about 500 mTorr. The method can also include an operation for setting a process gap distance, as measured perpendicularly between the substrate and the multiple hollow cathodes, within a range extending from about 1 cm to about 10 cm.
It should be appreciated that simultaneous use of multiple RF power frequencies/amplitudes, in combination with the hollow cathode embodiments described herein, can advantageously provide an ability to preferentially control generation of different types of reactive species within the plasma. For example, application of an RF power within the above-mentioned low frequency range can be used to promote generation of ions in the plasma. And, application of an RF power within the above-mentioned high frequency range can be used to promote generation of radicals in the plasma. In following, application of multiple RF powers including a combination of low and high frequencies at appropriate amplitudes can be used to generate a particular mixture of ions and radicals in the plasma that is suitable for a specific plasma processing operation.
Considering the foregoing, the method of
Numerous multi-frequency RF powered hollow cathode embodiments are disclosed herein that enable use of hollow cathode systems at lower process gas pressures suitable for use in semiconductor fabrication processes, such as plasma etching processes. The hollow cathode structures disclosed herein can be driven at high frequency, e.g., 60 MHz, and low frequency, e.g., 2 MHz or less, to provide for a sustained plasma within the hollow cathodes at low pressure, while also generating high enough plasma density. In this situation, the high frequency RF power component can strike and drive the plasma, while the low frequency RF component can provide for decreased plasma sheath size relative to the hollow cathode interior cavity size. In this situation, the saddle field of the hollow cathode may be parallel to the plane of the hollow cathode electrode.
As discussed herein, in one embodiment, two or more RF power frequencies can be used to drive a common electrode within the hollow cathode assembly. In another embodiment, a high frequency RF powered electrode can be sandwiched between low frequency RF powered electrodes, such that a saddle field exists along an axis of the hollow cathode interior cavity, when the low frequency RF powered electrodes are operated in phase.
Some hollow cathodes may require higher process gas pressures during operation. In this case, in one embodiment, a hollow cathode array can be immersed between low frequency RF powered electrodes driven either in phase or out of phase. In this embodiment, the low frequency RF powered electrode provides a high pressure environment above the lower pressure substrate processing region. When driven in phase and close to the hollow cathode array, the low frequency RF powered electrodes generate a saddle field therebetween and along the axes of the hollow cathodes within the hollow cathode array. When drive out of phase, i.e., in a push-pull relationship, the low frequency RF powered electrodes generate a saddle field on a side of the hollow cathode array facing the instantaneous anode. This out of phase configuration can be exploited to insert ions and electrons into the low pressure substrate processing region.
In one embodiment, the hollow cathodes are configured to include a pinch off point having low enough conductance to sustain a pressure drop on the order of hundreds of mTorr at flow rates of hundreds of sccm (standard cubic centimeter). The hollow cathodes of this embodiment enable high pressure hollow cathode array operation in conjunction with a low pressure substrate processing region. In this embodiment, a high pressure side of the hollow cathode, i.e., above the pinch point, is used to create a high pressure hollow cathode. Also, the low pressure side of the hollow cathode, i.e., below the pinch point, can be combined with an electrostatic lens for ion or electron extraction from the hollow cathode plasma.
It should be understood that many different configurations of RF powered electrodes can be implemented within the multi-frequency RF powered hollow cathodes disclosed herein. For example, as disclosed herein with regard to
Additionally, the hollow cathodes can include other shapes not explicitly shown herein, or direct the flow of process gas off-normal from the electrode surface of the hollow cathode. In some embodiments, hollow cathodes can be placed in arrays of unit cells, where electrodes having different frequency combinations are disposed in close proximity to each other. Also, in some embodiments, such as described with regard to
While this invention has been described in terms of several embodiments, it will be appreciated that those skilled in the art upon reading the preceding specification and studying the drawings will realize various alterations, additions, permutations and equivalents thereof. The present invention includes all such alterations, additions, permutations, and equivalents as fall within the true spirit and scope of the invention.
Claims
1. A hollow cathode system for plasma generation in substrate plasma processing, comprising:
- a plurality of electrically conductive plates stacked in a layered manner;
- dielectric sheets disposed between each adjacently positioned pair of the plurality of electrically conductive plates;
- a number of holes each formed to extend through the plurality of electrically conductive plates and dielectric sheets; and
- at least two independently controllable radiofrequency (RF) power sources electrically connected to one or more of the plurality of electrically conductive plates.
2. A hollow cathode system for plasma generation in substrate plasma processing as recited in claim 1, wherein a first end of each of the number of holes is in fluid communication with a process gas source, and wherein a second end of each of the number of holes is in fluid communication with a substrate processing region.
3. A hollow cathode system for plasma generation in substrate plasma processing as recited in claim 1, wherein each of the at least two independently controllable RF power sources is independently controllable with regard to RF power frequency and amplitude.
4. A hollow cathode system for plasma generation in substrate plasma processing as recited in claim 3, wherein each of the at least two independently controllable RF power sources is defined to generate RF power having a frequency of either 2 megaHertz (MHz), 27 MHz, 60 MHz, or 400 kiloHertz (kHz).
5. A hollow cathode system for plasma generation in substrate plasma processing as recited in claim 1, wherein the plurality of electrically conductive plates includes a top ground plate, a central cathode plate connected to receive RF power from each of the at least two independently controllable RF power sources, and a bottom ground plate.
6. A hollow cathode system for plasma generation in substrate plasma processing as recited in claim 1, wherein the plurality of electrically conductive plates includes multiple cathode plates separated from each other by dielectric sheets, wherein each of the multiple cathode plates is connected to receive RF power from one or more of the at least two independently controllable RF power sources.
7. A hollow cathode system for plasma generation in substrate plasma processing as recited in claim 6, wherein the plurality of electrically conductive plates includes a top ground plate.
8. A hollow cathode system for plasma generation in substrate plasma processing as recited in claim 7, wherein the plurality of electrically conductive plates includes a bottom ground plate.
9. A hollow cathode system for plasma generation in substrate plasma processing as recited in claim 6, wherein at least one of the multiple cathode plates that is to be exposed to a higher pressure process gas within the number of holes is connected to a lower frequency one of the at least two independently controllable RF power sources.
10. A hollow cathode system for plasma generation in substrate plasma processing as recited in claim 6, wherein at least one of the multiple cathode plates that is to be exposed to a lower pressure process gas within the number of holes is connected to a higher frequency one of the at least two independently controllable RF power sources.
11. A system for substrate plasma processing, comprising:
- a chamber formed by surrounding walls, a top plate, and a bottom plate;
- a substrate support disposed within the chamber;
- a hollow cathode assembly disposed within the chamber above and spaced apart from the substrate support;
- a process gas source in fluid communication with the hollow cathode assembly to supply process gas to the hollow cathode assembly; and
- a plurality of radiofrequency (RF) power sources in electrical communication with the hollow cathode assembly, wherein each of the plurality of RF power sources is independently controllable with regard to RF power frequency and amplitude,
- wherein during operation of the system, a plurality of RF powers respectively transmitted from the plurality of RF power sources to the hollow cathode assembly transform the process gas into a plasma within the hollow cathode assembly, such that reactive species with the plasma move from the hollow cathode assembly to a substrate processing region over the substrate support.
12. A system for substrate plasma processing as recited in claim 11, wherein the hollow cathode assembly is defined over an area of the substrate support upon which a substrate is to be received for plasma processing, and wherein the hollow cathode assembly includes multiple hollow cathodes each defined in exposure to a processing region within the chamber between the hollow cathode assembly and the substrate support, and wherein the multiple hollow cathodes are distributed in a substantially uniform manner relative to the area of the substrate support upon which the substrate is to be received for plasma processing.
13. A system for substrate plasma processing as recited in claim 12, further comprising:
- a process gas plenum formed within the chamber above the hollow cathode assembly, wherein the process gas plenum is in fluid communication with both the process gas source and each of the multiple hollow cathodes within the hollow cathode assembly, and wherein the process gas plenum is formed to distribute the process gas to each of the multiple hollow cathodes within the hollow cathode assembly in a substantially uniform manner.
14. A system for substrate plasma processing as recited in claim 13, further comprising:
- an anode plate disposed within the process gas plenum and over the hollow cathode assembly, wherein the anode plate is electrically connected to a negative bias to drive ions from the multiple hollow cathodes into the processing region.
15. A system for substrate plasma processing as recited in claim 12, further comprising:
- a process gas supply line connected in fluid communication between the process gas source and the hollow cathode assembly, wherein the hollow cathode assembly is formed to include process gas distribution channels in fluid communication with the process gas supply line, wherein the process gas distribution channels are formed to direct the process gas from the process gas supply line to each of the multiple hollow cathodes within the hollow cathode assembly in a substantially uniform manner.
16. A system for substrate plasma processing as recited in claim 15, further comprising:
- an exhaust plenum formed within the chamber above the hollow cathode assembly, wherein the hollow cathode assembly includes multiple exhaust holes formed to extend completely through the hollow cathode from the processing region to the exhaust plenum, wherein the multiple exhaust holes are distributed in a substantially uniform manner relative to the area of the substrate support upon which the substrate is to be received for plasma processing, and wherein each of the multiple exhaust holes is isolated from the multiple hollow cathodes and the process gas distribution channels within the hollow cathode assembly.
17. A system for substrate plasma processing as recited in claim 12, further comprising:
- a cathode plate disposed between the hollow cathode assembly and the processing region, wherein the cathode plate is electrically connected to a positive bias to pull ions from the multiple hollow cathodes into the processing region.
18. A system for substrate plasma processing as recited in claim 12, further comprising:
- a source plasma region formed within the chamber above the hollow cathode assembly, wherein the source plasma region is in fluid communication with both the process gas source and each of the multiple hollow cathodes within the hollow cathode assembly; and
- a coil assembly disposed to transform process gas within the source plasma region into a source plasma, whereby the source plasma drives secondary plasma generation in each of the multiple hollow cathodes within the hollow cathode assembly in a substantially uniform manner.
19. A system for substrate plasma processing as recited in claim 11, wherein each of the plurality of RF power sources is defined to generate RF power having a frequency of either 2 megaHertz (MHz), 27 MHz, 60 MHz, or 400 kiloHertz (kHz).
Type: Application
Filed: Apr 11, 2011
Publication Date: Oct 11, 2012
Applicant: Lam Research Corporation (Fremont, CA)
Inventors: John Patrick Holland (San Jose, CA), Peter L. G. Ventzek (San Francisco, CA)
Application Number: 13/084,343
International Classification: C23F 1/08 (20060101);