Multi-Frequency Hollow Cathode System for Substrate Plasma Processing

Abstract

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.

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).