Patent Publication Number: US-2009226614-A1

Title: Porous gas heating device for a vapor deposition system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to pending U.S. patent application Ser. No. 11/693,067, entitled “VAPOR DEPOSITION SYSTEM AND METHOD OF OPERATING”, Docket No. TTCA-195, filed on Mar. 29, 2007; and pending U.S. patent application Ser. No. 12/xxx,xxx, entitled “GAS HEATING DEVICE FOR A VAPOR DEPOSITION SYSTEM”, Docket No. TTCA-216, filed on Feb. dd, 2008. The entire content of these applications is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to a method and system for substrate processing, and more particularly to a method and system for distributing a gas during substrate processing. 
     2. Description of Related Art 
     During material processing, such as semiconductor device manufacturing for production of integrated circuits (ICs), vapor deposition is a common technique to form thin films, as well as to form conformal thin films over and within complex topography, on a substrate. Vapor deposition processes can include chemical vapor deposition (CVD) and plasma enhanced CVD (PECVD). For example, in semiconductor manufacturing, such vapor deposition processes may be used for gate dielectric film formation in front-end-of-line (FEOL) operations, and low dielectric constant (low-k) or ultra-low-k, porous or non-porous, dielectric film formation and barrier/seed layer formation for metallization in back-end-of-line (BEOL) operations, as well as capacitor dielectric film formation in DRAM production. 
     In a CVD process, a continuous stream of film precursor vapor is introduced to a process chamber containing a substrate, wherein the composition of the film precursor has the principal atomic or molecular species found in the film to be formed on the substrate. During this continuous process, the precursor vapor is chemisorbed on the surface of the substrate while it thermally decomposes and reacts with or without the presence of an additional gaseous component that assists the reduction of the chemisorbed material, thus, leaving behind the desired film. 
     In a PECVD process, the CVD process further includes plasma that is utilized to alter or enhance the film deposition mechanism. For instance, plasma excitation can allow film-forming reactions to proceed at temperatures that are significantly lower than those typically required to produce a similar film by thermally excited CVD. In addition, plasma excitation may activate film-forming chemical reactions that are not energetically or kinetically favored in thermal CVD. 
     Other CVD techniques include hot-filament CVD (otherwise known as hot-wire CVD or pyrolytic CVD). In hot-filament CVD, a film precursor is thermally decomposed by a resistively heated filament, and the resulting fragmented molecules adsorb and react on the surface of the substrate to leave the desired film. Unlike PECVD, hot-filament CVD does not require formation of plasma. However, hot-filament CVD generally suffers from low deposition rate and poor deposition uniformity due to inefficient thermal decomposition and inadequate filament design and flow conditions. 
     SUMMARY OF THE INVENTION 
     The invention relates to a method and system for substrate processing, and more particularly to a method and system for distributing a gas during substrate processing. 
     The invention further relates to a system for depositing a thin film using chemical vapor deposition (CVD). 
     The invention further relates to a method and system for depositing a thin film using pyrolytic CVD, wherein a gas distribution device comprising one or more porous gas distribution elements is utilized to pyrolize a film forming composition. 
     According to one embodiment, a gas distribution device configured to be coupled to a processing system is described. The gas distribution device is configured to heat a process gas, such as one or more constituents of a film forming composition. For example, the system may be used to deposit a thin film on a substrate using a vapor deposition process. The gas distribution device comprises one or more porous gas distribution elements configured to be heated and pyrolize a process gas flowing through the one or more porous gas distribution elements. For example, the one or more porous gas distribution elements may comprise an open-celled foam. 
     According to another embodiment, a gas distribution device configured to be coupled to a processing system is described. The gas distribution device comprises a temperature control element; and one or more porous gas distribution elements coupled to a temperature control element and configured to be temperature-controlled and distribute a process gas flowing through the one or more porous gas distribution elements, wherein the one or more porous gas distribution elements comprises an open-celled foam. 
     According to yet another embodiment, a method of depositing a thin film on a substrate is described, the method comprising: coupling a gas heating device to a process chamber, the gas heating device comprising one or more porous gas distribution elements configured to receive an electrical current from one or more power sources; elevating a temperature of the gas heating device by coupling the electrical current from the one or more power sources to the gas heating device; providing a substrate on a substrate holder in the process chamber of a deposition system; providing a film forming composition to a gas distribution system located above the substrate and opposing an upper surface of the substrate; pyrolizing one or more constituents of the film forming composition using the gas heating device; and exposing the substrate to the film forming composition in the process chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  depicts a schematic view of a deposition system according to an embodiment; 
         FIG. 2  depicts a schematic view of a gas distribution system according to an embodiment; 
         FIG. 3A  provides a top view of a gas distribution device according to an embodiment; 
         FIG. 3B  provides a cross-sectional view of the gas distribution device depicted in  FIG. 3A ; 
         FIG. 4A  provides a top view of a gas distribution device according to another embodiment; 
         FIG. 4B  provides a cross-sectional view of the gas distribution device depicted in  FIG. 4A ; 
         FIG. 5A  provides a top view of a gas distribution device according to another embodiment; 
         FIG. 5B  provides a cross-sectional view of the gas distribution device depicted in  FIG. 5A ; 
         FIG. 6  depicts a schematic view of a gas distribution system according to another embodiment; 
         FIG. 7  depicts a schematic view of a gas distribution system according to another embodiment; 
         FIG. 8  depicts a schematic view of a gas distribution system according to another embodiment; 
         FIG. 9  depicts a schematic view of a gas distribution system according to another embodiment; and 
         FIG. 10  illustrates a method of depositing a film on a substrate according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS 
     In the following description, in order to facilitate a thorough understanding and for purposes of explanation and not limitation, specific details are set forth, such as a particular geometry of the deposition system and descriptions of various components. 
     However, one skilled in the relevant art will recognize that the various embodiments may be practiced without one or more of the specific details, or with other replacement and/or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of various embodiments of the invention. Similarly, for purposes of explanation, specific numbers, materials, and configurations are set forth in order to provide a thorough understanding of the invention. Nevertheless, the invention may be practiced without specific details. Furthermore, it is understood that the various embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale. 
     In the description and claims, the terms “coupled” and “connected,” along with their derivatives, are used. It should be understood that these terms are not intended as synonyms for each other. Rather, in particular embodiments, “connected” may be used to indicate that two or more elements are in direct physical or electrical contact with each other while “coupled” may further mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention, but do not denote that they are present in every embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. Various additional layers and/or structures may be included and/or described features may be omitted in other embodiments. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,  FIG. 1  schematically illustrates a deposition system  1  for depositing a thin film, such as a conductive film, a non-conductive film, or a semi-conductive film. For example, the thin film can include a dielectric film, such as a low dielectric constant (low-k) or ultra-low-k dielectric film, or the thin film may include a sacrificial layer for use in air gap dielectrics. Deposition system  1  can include a chemical vapor deposition (CVD) system, whereby a film forming composition is thermally activated or decomposed in order to form a film on a substrate. For example, the deposition system  1  comprises a pyrolytic CVD system. 
     The deposition system  1  comprises a process chamber  10  having a substrate holder  20  configured to support a substrate  25 , upon which the thin film is formed. Furthermore, the substrate holder is configured to control the temperature of the substrate at a temperature suitable for the film forming reactions. 
     The process chamber  10  is coupled to a film forming composition delivery system  30  configured to introduce a film forming composition to the process chamber  10  through a gas distribution system  40 . Furthermore, a gas distribution device  45  is coupled to the gas distribution system  40  and configured to chemically modify the film forming composition. The gas distribution device  45  comprises one or more porous gas distribution elements  55  disposed on an interior surface of the gas distribution system  40  or embedded within the gas distribution system  40  or both, and a power source  50  that is coupled to the one or more porous gas distribution elements  55  and that is configured to deliver electrical power to the one or more porous gas distribution elements  55 . For example, the one or more porous gas distribution elements  55  can comprise one or more resistively heated porous elements. When electrical current flows through and effects heating of the one or more resistively heated porous elements, the interaction of these heated elements with the film forming composition causes pyrolysis of one or more constituents of the film forming composition. 
     The process chamber  10  is further coupled to a vacuum pumping system  60  through a duct  62 , wherein the vacuum pumping system  60  is configured to evacuate the process chamber  10  and the gas distribution system  40  to a pressure suitable for forming the thin film on the substrate  25  and suitable for pyrolysis of the film forming composition. 
     The film forming composition delivery system  30  can include one or more material sources configured to introduce a film forming composition to the gas distribution system  40 . For example, the film forming composition may include one or more gases, or one or more vapors formed in one or more gases, or a mixture of two or more thereof. The film forming composition delivery system  30  can include one or more gas sources, or one or more vaporization sources, or a combination thereof. Herein vaporization refers to the transformation of a material (normally stored in a state other than a gaseous state) from a non-gaseous state to a gaseous state. Therefore, the terms “vaporization,” “sublimation” and “evaporation” are used interchangeably herein to refer to the general formation of a vapor (gas) from a solid or liquid precursor, regardless of whether the transformation is, for example, from solid to liquid to gas, solid to gas, or liquid to gas. 
     When the film forming composition is introduced to the gas distribution system  40 , one or more constituents of the film forming composition are subjected to pyrolysis by the gas distribution device  45  described above. The film forming composition can include film precursors that may or may not be fragmented by pyrolysis in the gas distribution system  40 . The film precursor or precursors may include the principal atomic or molecular species of the film desired to be produced on the substrate. Additionally, the film forming composition can include a reducing agent that may or may not be fragmented by pyrolysis in the gas distribution system  40 . The reducing agent or agents may assist with the reduction of a film precursor on substrate  25 . For instance, the reducing agent or agents may react with a part of or all of the film precursor on substrate  25 . Additionally yet, the film forming composition can include a polymerizing agent (or cross-linker) that may or may not be fragmented by pyrolysis in the gas distribution system  40 . The polymerizing agent may assist with the polymerization of a film precursor or fragmented film precursor on substrate  25 . 
     According to one embodiment, when forming a copolymer thin film on substrate  25 , a film forming composition comprising two or more monomer gases is introduced to the gas distribution system  40  and is exposed to the gas distribution device  45 , i.e., the one or more porous gas distribution elements  55 , having a temperature sufficient to pyrolyze one or more of the monomers and produce a source of reactive species. These reactive species are introduced to and distributed within process space  33  in the vicinity of the upper surface of substrate  25 . Substrate  25  is maintained at a temperature lower than that of the gas distribution device  45  in order to condensate and induce polymerization of the chemically altered film forming composition at the upper surface of substrate  25 . 
     For example, when forming an organosilicon polymer, monomer gas(es) of an organosilicon precursor is used. Additionally, for example, when forming a fluorocarbon-organosilicon copolymer, monomer gases of a fluorocarbon precursor and organosilicon precursor are used. 
     Further yet, the film forming composition can include an initiator that may or may not be fragmented by pyrolysis in the gas distribution system  40 . An initiator or fragmented initiator may assist with the fragmentation of a film precursor, or the polymerization of a film precursor. The use of an initiator can permit higher deposition rates at lower heat source temperatures. For instance, the one or more heating elements can be used to fragment the initiator to produce radical species of the initiator (i.e., a fragmented initiator) that are reactive with one or more of the remaining constituents in the film forming composition. Furthermore, for instance, the fragmented intiator or initiator radicals can catalyze the formation of radicals of the film forming composition. 
     For example, when forming a fluorocarbon-organosilicon copolymer, the initiator can be perfluorooctane sulfonyl fluoride (PFOSF) used in the polymerization of a cyclic vinylmethylsiloxane, such as 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (V 3 D 3 ). 
     Additionally, for example, when forming a porous SiCOH-containing film, the film forming composition may comprise a structure-forming material and a pore-generating material. The structure-forming material may comprise diethoxymethylsilane (DEMS) and the pore-generating material may comprise alpha-terpinene (ATRP). The porous SiCOH-containing film may be used as a low dielectric constant (low-k) material. 
     Further, for example, when forming a cross-linked neopentyl methacrylate organic glass, the film forming composition may comprise a monomer, a cross-linker, and an initiator. The monomer may comprise trimethylsilylmethyl methacrylate (TMMA), propargyl methacrylate (PMA), cyclopentyl methacrylate (CPMA), neopentyl methacrylate (npMA), and poly (neopentyl methacrylate) (P(npMA)), and the cross-linker may comprise ethylene glycol diacrylate (EGDA), ethylene glycol dimethacrylate (EGDMA),  1 , 3 -propanediol diacrylate (PDDA), or 1,3-propanediol dimethacrylate (PDDMA), or any combination of two or more thereof. Additionally, the initiator may comprise a peroxide, a hydroperoxide, or a diazine. Additionally yet, the initiator may comprise a tert-butyl peroxide (TBPO). 
     Further yet, for example, the polymer film may comprise P(npMA-co-EGDA) (poly(neopentyl methacrylate-co-ethylene glycol diacrylate)), and the monomer comprises npMA (neopentyl methacrylate) and the cross-linker comprises EGDA (ethylene glycol diacrylate). The polymer film may be used as a sacrificial air gap material. 
     According to one embodiment, the film forming composition delivery system  30  can include a first material source  32  configured to introduce one or more film precursors to the gas distribution system  40 , and a second material source  34  configured to introduce a (chemical) initiator to the gas distribution system  40 . Furthermore, the film forming gas delivery system  30  can include additional gas sources configured to introduce an inert gas, a carrier gas or a dilution gas. For example, the inert gas, carrier gas or dilution gas can include a noble gas, i.e., He, Ne, Ar, Kr, Xe, or Rn. 
     Referring now to  FIG. 2 , a gas distribution system  100  is illustrated according to an embodiment. The gas distribution system  100  comprises a housing  140  configured to be coupled to or within a process chamber of a processing system (such as process chamber  10  of deposition system  1  in  FIG. 1 ), and a gas distribution device  141  configured to be coupled to the housing  140 , wherein the combination form a plenum  142 . The gas distribution system  100  may be thermally insulated from the process chamber, or it may not be thermally insulated from the process chamber. 
     The gas distribution system  100  is configured to receive a process gas or mixture of process gases, such as a film forming composition, into the plenum  142  from a process gas delivery system, such as a film forming composition delivery system (not shown), and distribute the process gas to a process space  133  in the process chamber through an outlet  146  of the gas distribution device  141 . For example, the gas distribution system  100  can be configured to receive one or more constituents of a film forming composition  132  and an optional initiator  134  into plenum  142  from the film forming composition delivery system. The one or more constituents of the film forming composition  132  and the optional initiator  134  may be introduced to plenum  142  separately as shown, or they may be introduced through the same opening. 
     The gas distribution device  141  comprises one or more porous gas distribution elements configured to receive an electrical current from one or more power sources  150  and heat the process gas flowing through the one or more porous gas distribution elements. For example, the one or more porous gas distribution elements may comprise a porous gas distribution plate as illustrated in  FIG. 2 . However, the one or more porous gas distribution elements may be distributed in order to tailor the spatial distribution of the temperature and/or chemical composition of the process gas flowing through the porous gas distribution device. 
     According to an embodiment, the gas distribution device  141  can include an open-celled foam. For example, the open-celled foam may comprise a metal-containing foam, a metal foam, or a metal alloy foam. Additionally, for example, the open-celled foam may comprise a non-metal foam. Additionally yet, for example, the open-celled foam may comprise a ceramic foam. Further, the open-celled foam may or may not further include a protective surface coating. Further yet, the open-celled foam may comprise a non-metal foam coated with metal-containing material. When a coating is applied, open-celled foams may be coated using a vapor deposition process, such as physical vapor deposition (PVD) or sputter deposition, or chemical vapor deposition (CVD), or PVD-like or CVD-like deposition processes, or plating, or a combination thereof. 
     As an example, the open-celled foam may include Duocel® Foam that is commercially available from ERG Materials and Aerospace Corporation (900 Stanford Avenue, Oakland, Calif. 94608). A wide range of materials are commercially offered by ERG Materials and Aerospace Corporation including, but not limited to, aluminum, copper, tin, zinc, nickel, Inconel, silicon, silver, gold, silicon carbide, silicon nitride, silicon nitride carbide, boron carbide, boron nitride, hafnium carbide, tantalum carbide, and zirconium carbide. Various materials may be vapor deposited onto an existing open-celled foam including, for example, sputter-deposited tungsten. 
     Additionally, the open-celled foam may be fabricated to have a specific foam density, pore size, or ligament structure. For example, the foam density can range from approximately 3% to approximately 60% of the density of the solid base material. In a non-limiting embodiment, a foam density of approximately 15% to approximately 50% and, desirably, approximately 20% to approximately 40%, is used. Additionally, for example, the pore size can range from approximately 5 pores to approximately 60 pores per linear inch. In a non-limiting embodiment, a pore size of approximately 25 pores to approximately 55 pores per linear inch and, desirably, approximately 30 pores to approximately 50 pores per linear inch, is used. 
     As shown in  FIG. 2 , the one or more power sources  150  may be configured to couple electrical current directly to the gas distribution device  141 . For example, electrical power from the one or more power source  150  may be directly coupled to the one or more porous gas distribution elements. Additionally, for example, electrical power from the one or more power source  150  may be directly to the open-celled foam via direct physical connection of electrical leads to the open-celled foam. Electrical contact may, for instance, be facilitated by various techniques, including soldering, welding, brazing, etc. 
     The one or more power sources  150  may include a direct current (DC) power source, or they may include an alternating current (AC) power source, or combination thereof. For instance, when the one or more power sources  150  couple electrical power to the gas distribution device  141 , the porous gas distribution device may be elevated to a temperature sufficient to pyrolize one or more constituents of the film forming composition. 
     According to another embodiment, the gas distribution device  141  can include an open-celled foam, and one or more electrodes coupled to the open-celled foam, wherein at least one of the one or more electrodes is coupled to the power source, and wherein at least one of the one or more electrodes is coupled to electrical ground for the power source. 
     For example, as shown in  FIGS. 3A and 3B , a top view and a cross-sectional view of a gas distribution device  170  is presented, respectively. The gas distribution device  170  may be configured to be coupled to the housing  140  shown in  FIG. 1 . The gas distribution device  170  comprises an open-celled foam  172  disposed between a first electrode  174  located at a top surface of the open-celled foam  172  and a second electrode  176  located at a bottom surface of the open-celled foam  172 . A voltage difference can be applied by a power source  179  across the first electrode  174  and the second electrode  176  to cause a flow of electrical current through the open-celled foam  172 . The flow of electrical current through the open-celled foam  172  may, in turn, cause heating via Joule (ohmic) heating. 
     Joule heating refers to the increase in temperature of a conductor as a result of the resistance to a flow of electrical current. The resistance of the conductor is related to the resistivity of the conductor and various geometric parameters, such as the length of the conductor and a cross-sectional dimension of the conductor. At the atomic level, Joule heating is the result of moving electrons colliding with atoms of the conductor, where upon momentum is transferred to the atom thereby increasing its kinetic energy and thus producing heat. Joule&#39;s Law is expressed as Q=I 2 Rt, where Q represents the heat generated by a constant current I flowing through a conductor of resistance R for a time period t. 
     As illustrated in  FIGS. 3A and 3B , the first electrode  174  and the second electrode  176  may span substantially the entire area of the top and bottom surfaces, respectively, of the open-celled foam  172  in order to subject each region of the open-celled foam  172  to about the same voltage difference and, thus, distribute the current flow through the open-celled foam  172 . Openings  178  on the first electrode  174  and the second electrode  176  permit the flow of process gas through the gas distribution device  170 . 
     The openings  178  can be distributed in various density patterns on the first electrode  176  and the second electrode  178 . For example, openings  178  in the first electrode  174  and the second electrode  176  may or may not be aligned. Additionally, for example, more openings can be formed near the center of the first electrode  174  and the second electrode  176  and less openings can be formed near the periphery of the first electrode  174  and the second electrode  176 . Alternatively, for example, more openings can be formed near the periphery of the first electrode  174  and the second electrode  176  and less openings can be formed near the center of the first electrode  174  and the second electrode  176 . Additionally yet, the size of the openings can vary on the first electrode  174  and the second electrode  176 . For example, larger openings can be formed near the center of the first electrode  174  and the second electrode  176  and smaller openings can be formed near the periphery of the first electrode  174  and the second electrode  176 . Alternatively, for example, smaller openings can be formed near the periphery of the first electrode  174  and the second electrode  176  and larger openings can be formed near the center of the first electrode  174  and the second electrode  176 . Further yet, the shape of the openings  178  may vary. 
     According to another embodiment, the gas distribution device  141  can include an open-celled foam, and a resistive heating element coupled to the open-celled foam and configured to heat the open-celled foam when electrical current from the one or more power sources flows through the resistive heating element. 
     For example, as shown in  FIGS. 4A and 4B , a top view and a cross-sectional view of a gas distribution device  190  is presented, respectively. The gas distribution device  190  may be configured to be coupled to the housing  140  shown in  FIG. 1 . The gas distribution device  190  comprises an open-celled foam  192 , and a resistive heating element  194  coupled to a top surface of the open-celled foam  192 . Alternatively, the resistive heating element  194  may be coupled to a bottom surface of the open-celled foam  192 , or it may be embedded with the open-celled foam  192 . 
     A voltage difference can be applied by a power source  196  between a first end of the resistive heating element  194  and a second of the resistive heating element  194  to cause a flow of electrical current through the resistive heating element  194 . The flow of electrical current through the resistive heating element  194  may, in turn, cause heating via Joule (ohmic) heating. This heating may elevate the temperature of the open-celled foam  192 . The resistive heating element  194  may be formed in a serpentine-like path as shown in  FIG. 4A , or a spiral-like path, or any arbitrary shape. Further, the resistive heating element  194  may or may not be electrically insulated from the open-celled foam  192  depending, for example, on the material/electrical properties of the open-celled foam  192 . 
     Although one resistive heating element  194  is shown in  FIGS. 4A and 4B , a plurality of heating elements may be utilized. The heating elements may be distributed in order to tailor the spatial distribution of the temperature and/or chemical composition of the process gas flowing through the porous gas distribution device. 
     According to yet another embodiment, the gas distribution device  141  can include an open-celled foam, and one or more temperature control elements coupled to the open-celled foam. 
     For example, as shown in  FIGS. 5A and 5B , a top view and a cross-sectional view of a gas distribution device  180  is presented, respectively. The gas distribution device  180  may be configured to be coupled to the housing  140  shown in  FIG. 1 . The gas distribution device  180  comprises an open-celled foam  182  coupled to a temperature control element  184  located at a top surface of the open-celled foam  182 , as shown in  FIG. 5A , or a bottom surface of the open-celled foam  182 , or both. As shown in  FIG. 5B , a temperature of the temperature control element  184  can be controlled by a temperature control system  189 . 
     The temperature control element  184  may be heated or cooled in order to increase or decrease, respectively, a temperature of the open-celled foam  182 . The open-celled foam  182  can be in thermal contact with the temperature control element  184 . For example, the open-celled foam  182  may be coupled to the temperature control element  184  via a weld joint, or one or more fasteners, etc. 
     The temperature control element  184  may include one or more resistive heating elements, or one or more thermoelectric devices, or any combination thereof. The temperature control element  184  may include one or more fluid channels configured to flow a heated or cooled heat transfer fluid through the temperature control element  184 . 
     As illustrated in  FIGS. 5A and 5B , the temperature control element  184  may span substantially the entire area of the top and/or bottom surfaces of the open-celled foam  182  in order to subject each region of the open-celled foam  182  to about the same temperature. Openings  188  on the temperature control element  184  permit the flow of process gas through the gas distribution device  180 . 
     The openings  188  can be distributed in various density patterns on the temperature control element  184 . For example, openings can be formed near the center of the temperature control element  184  and less openings can be formed near the periphery of the temperature control element  184 . Alternatively, for example, more openings can be formed near the periphery of the temperature control element  184  and less openings can be formed near the center of the temperature control element  184 . Additionally yet, the size of the openings can vary on the temperature control element  184 . For example, larger openings can be formed near the center of the temperature control element  184  and smaller openings can be formed near the periphery of the temperature control element  184 . Alternatively, for example, smaller openings can be formed near the periphery of the temperature control element  184  and larger openings can be formed near the center of the temperature control element  184 . Further yet, the shape of the openings  188  may vary. 
     Referring now to  FIG. 6 , a gas distribution system  200  is illustrated according to another embodiment. The gas distribution system  200  comprises a housing  240  configured to be coupled to or within a process chamber of a processing system (such as process chamber  10  of deposition system  1  in  FIG. 1 ), and a gas distribution device  241  configured to be coupled to the housing  240 . The gas distribution system  200  may be thermally insulated from the process chamber, or it may not be thermally insulated from the process chamber. 
     Additionally, gas distribution system  200  comprises an intermediate gas distribution plate  260  coupled to housing  240  such that the combination of housing  240 , intermediate gas distribution plate  260  and gas distribution device  241  form a plenum  242  above intermediate gas distribution plate  260  and an intermediate plenum  243  between the intermediate gas distribution plate  260  and the gas distribution device  241 , as shown in  FIG. 6 . The intermediate gas distribution plate  260  comprises a plurality of openings  262  arranged to distribute and introduce the film forming composition to the intermediate plenum  243 . 
     The gas distribution system  200  is configured to receive a process gas or mixture of process gases, such as a film forming composition, into the plenum  242  from a process gas delivery system, such as a film forming composition delivery system (not shown), and distribute the process gas to a process space  233  in the process chamber through an outlet  246  of the gas distribution device  241 . For example, the gas distribution system  200  can be configured to receive one or more constituents of a film forming composition  232  and an optional initiator  234  into plenum  242  from the film forming composition delivery system. The one or more constituents of the film forming composition  232  and the optional initiator  234  may be introduced to plenum  242  separately as shown, or they may be introduced through the same opening. 
     The gas distribution device  241  comprises one or more porous gas distribution elements configured to receive an electrical current from one or more power sources  250  and heat the process gas flowing through the one or more porous gas distribution elements. For example, the one or more porous gas distribution elements may comprise a porous gas distribution plate as illustrated in  FIG. 6 . However, the one or more porous gas distribution elements may be distributed in order to tailor the spatial distribution of the temperature and/or chemical composition of the process gas flowing through the porous gas distribution device. 
     According to an embodiment, the gas distribution device  241  can include an open-celled foam. Further, the open-celled foam may be heated using any one of the techniques described above. 
     Referring now to  FIG. 7 , a gas distribution system  300  is illustrated according to another embodiment. The gas distribution system  300  comprises a housing  340  configured to be coupled to or within a process chamber of a processing system (such as process chamber  10  of deposition system  1  in  FIG. 1 ), and a gas distribution plate  341  configured to be coupled to the housing  340 . The gas distribution system  300  may be thermally insulated from the process chamber, or it may not be thermally insulated from the process chamber. 
     Additionally, gas distribution system  300  comprises a gas distribution device  360  coupled to housing  340  such that the combination of housing  340 , gas distribution device  360  and gas distribution plate  341  form a plenum  342  above gas distribution device  360  and an intermediate plenum  343  between the gas distribution device  360  and the gas distribution plate  341 , as shown in  FIG. 7 . 
     The gas distribution system  300  is configured to receive a process gas or mixture of process gases, such as a film forming composition, into the plenum  342  from a process gas delivery system, such as a film forming composition delivery system (not shown), and distribute the process gas to a process space  333  in the process chamber through an outlet  346  of the gas distribution plate  341 . For example, the gas distribution system  300  can be configured to receive a first flow  332  of one or more constituents of a film forming composition or an initiator into plenum  342  from the film forming composition delivery system. Additionally, for example, the gas distribution system  300  can be configured to receive a second flow  334  of one or more constituents of a film forming composition or an initiator into intermediate plenum  343  from the film forming composition delivery system. Any constituent of the film forming composition or the initiator or both may be introduced directly to the intermediate plenum  343  in order to avoid or reduce interaction with the gas distribution device  360 . For example, the initiator may be introduced to plenum  342  in order to interact with the gas distribution device  360  and undergo pyrolysis, while the remaining constituents of the film forming composition may be introduced to the intermediate plenum  343 . 
     The gas distribution device  360  comprises one or more porous gas distribution elements configured to receive an electrical current from one or more power sources  350  and heat the process gas flowing through the one or more porous gas distribution elements. For example, the one or more porous gas distribution elements may comprise a porous gas distribution plate as illustrated in  FIG. 7 . However, the one or more porous gas distribution elements may be distributed in order to tailor the spatial distribution of the temperature and/or chemical composition of the process gas flowing through the porous gas distribution device. 
     According to an embodiment, the gas distribution device  360  can include an open-celled foam. Further, the open-celled foam may be heated using any one of the techniques described above. 
     Referring now to  FIG. 8 , a gas distribution system  400  is illustrated according to another embodiment. The gas distribution system  400  comprises a housing  440  configured to be coupled to or within a process chamber of a processing system (such as process chamber  10  of deposition system  1  in  FIG. 1 ), and a multi-component gas distribution plate  441  configured to be coupled to the housing  440 . The gas distribution system  400  is configured to receive a process gas and distribute the process gas to a process space  433  in the process chamber through an outlet  446 . The gas distribution system  400  may be thermally insulated from the process chamber, or it may not be thermally insulated from the process chamber. 
     The multi-component gas distribution plate  441  is configured to independently couple a first composition  432  from a first plenum  442  through a first array of openings  448  to the process space  433  and a second composition  434  from a second plenum  443  through a gas distribution device  444  comprising a second array of porous gas distribution elements  452  to the process space  433  without mixing the first composition  432  and the second composition  434  prior to the process space  433 . The first array of openings  448  and the second array of porous gas distribution elements  452  can be arranged, distributed or sized as described above. 
     The gas distribution device  444  comprises porous gas distribution elements configured to receive an electrical current from one or more power sources  450  and heat the process gas flowing through the one or more porous gas distribution elements. For example, the one or more porous gas distribution elements may comprise a porous gas distribution cylinder or annular ring as illustrated in  FIG. 8 . However, the one or more porous gas distribution elements may be distributed in order to tailor the spatial distribution of the temperature and/or chemical composition of the process gas flowing through the porous gas distribution device. 
     According to an embodiment, the gas distribution device  444  can include an open-celled foam. Further, the open-celled foam may be heated using any one of the techniques described above. 
     The first composition  432  can include one or more constituents of the film forming composition wherein interaction with the gas distribution device  444  is not desired. Additionally, the second composition  434  can include one or more constituents of the film forming composition wherein interaction with the gas distribution device  444  is desired. For example, the first composition  432  can include one or more film forming gases and the second composition  434  can include an initiator. While the one or more film forming gases are introduced to process space  433 , the initiator undergoes pyrolysis prior to introduction to process space  433 . Once the one or more film forming gases and the initiator radicals interact in process space  433 , the initiator radicals can catalyze the dissociation of at least one constituent of the one or more film forming gases. 
     Referring now to  FIG. 9 , a gas distribution system  500  is illustrated according to yet another embodiment. The gas distribution system  500  comprises a housing  540  configured to be coupled to or within a process chamber of a processing system (such as process chamber  10  of deposition system  1  in  FIG. 1 ), and a multi-component gas distribution plate  541  configured to be coupled to the housing  540 . The gas distribution system  500  is configured to receive a process gas and distribute the process gas to a process space  533  in the process chamber through an outlet  546 . The gas distribution system  500  may be thermally insulated from the process chamber, or it may not be thermally insulated from the process chamber. 
     The multi-component gas distribution plate  541  is configured to independently couple a first composition  532  from a first plenum  542  through a gas distribution device  548  comprising a first array of porous gas distribution elements  552  to the process space  533  and a second composition  534  from a second plenum  543  through a second array of openings  544  to the process space  533  without mixing the first composition  532  and the second composition  534  prior to the process space  533 . The first array of porous gas distribution elements  552  and the second array of openings  544  and can be arranged, distributed or sized as described above. 
     The gas distribution device  548  comprises porous gas distribution elements configured to receive an electrical current from one or more power sources  550  and heat the process gas flowing through the one or more porous gas distribution elements. For example, the one or more porous gas distribution elements may comprise a porous gas distribution cylinder or annular ring as illustrated in  FIG. 9 . However, the one or more porous gas distribution elements may be distributed in order to tailor the spatial distribution of the temperature and/or chemical composition of the process gas flowing through the porous gas distribution device. 
     According to an embodiment, the gas distribution device  548  can include an open-celled foam. Further, the open-celled foam may be heated using any one of the techniques described above. 
     The first composition  532  can include one or more constituents of the film forming composition wherein interaction with the gas distribution device  548  is desired. Additionally, the second composition  534  can include one or more constituents of the film forming composition wherein interaction with the gas distribution device  548  is not desired. For example, the first composition  532  can include an initiator and the second composition  534  can include one or more film forming gases. While the one or more film forming gases are introduced to process space  533 , the initiator undergoes pyrolysis prior to introduction to process space  533 . Once the one or more film forming gases and the initiator radicals interact in process space  533 , the initiator radicals can catalyze the dissociation of at least one constituent of the one or more film forming gases. 
     Referring again to  FIG. 1 , the power source  50  is configured to provide electrical power to the one or more porous gas distribution elements  55  in the gas distribution system  40 . For example, the power source  50  can be configured to deliver either DC power or AC power. Additionally, for example, the power source  50  can be configured to modulate the amplitude of the power, or pulse the power. Furthermore, for example, the power source  50  can be configured to perform at least one of setting, monitoring, adjusting or controlling a power, a voltage, or a current. 
     Referring still to  FIG. 1 , a temperature control system  22  can be coupled to the gas distribution system  40 , the gas distribution device  45 , the process chamber  10  and/or the substrate holder  20 , and configured to control the temperature of one or more of these components. The temperature control system  22  can include a temperature measurement system configured to measure the temperature of the gas distribution system  40  at one or more locations, the temperature of the gas distribution device  45  at one or more locations, the temperature of the process chamber  10  at one or more locations and/or the temperature of the substrate holder  20  at one or more locations. The measurements of temperature can be used to adjust or control the temperature at one or more locations in deposition system  1 . 
     The temperature measuring device, utilized by the temperature measurement system, can include an optical fiber thermometer, an optical pyrometer, a band-edge temperature measurement system as described in pending U.S. patent application Ser. No. 10/168544, filed on Jul. 2, 2002, the contents of which are incorporated herein by reference in their entirety, or a thermocouple such as a K-type thermocouple. Examples of optical thermometers include: an optical fiber thermometer commercially available from Advanced Energies, Inc., Model No. OR2000F; an optical fiber thermometer commercially available from Luxtron Corporation, Model No. M600; or an optical fiber thermometer commercially available from Takaoka Electric Mfg., Model No. FT-1420. 
     Alternatively, when measuring the temperature of one or more resistive heating elements, the electrical characteristics of each resistive heating element can be measured. For example, two or more of the voltage, current or power coupled to the one or more resistive heating elements can be monitored in order to measure the resistance of each resistive heating element. The variations of the element resistance can arise due to variations in temperature of the element which affects the element resistivity. 
     According to program instructions from the temperature control system  22  or the controller  80  or both, the power source  50  can be configured to operate the gas distribution device  45 , e.g., the one or more porous gas distribution elements, at a temperature ranging from approximately 100 degrees C to approximately 600 degrees C. For example, the temperature can range from approximately 200 degrees C to approximately 550 degrees C. The temperature can be selected based upon the film forming composition and, more particularly, the temperature can be selected based upon a constituent of the film forming composition. 
     Additionally, according to program instructions from the temperature control system  22  or the controller  80  or both, the temperature of the gas distribution system  40  can be set to a value approximately equal to or less than the temperature of the gas distribution device  45 , i.e., the one or more heating elements. For example, the temperature can be a value less than or equal to approximately 600 degrees C. Additionally, for example, the temperature can be a value less than approximately 550 degrees C. Further yet, for example, the temperature can range from approximately 80 degrees C to approximately 550 degrees C. The temperature can be selected to be approximately equal to or less than the temperature of the one or more heating elements, and to be sufficiently high to prevent condensation which may or may not cause film formation on surfaces of the gas distribution system and reduce the accumulation of residue. 
     Additionally yet, according to program instructions from the temperature control system  22  or the controller  80  or both, the temperature of the process chamber  10  can be set to a value less than the temperature of the gas distribution device  45 , i.e., the one or more heating elements. For example, the temperature can be a value less than approximately 200 degrees C. Additionally, for example, the temperature can be a value less than approximately 150 degrees C. Further yet, for example, the temperature can range from approximately 80 degrees C to approximately 150 degrees C. However, the temperature may be the same or less than the temperature of the gas distribution system  40 . The temperature can be selected to be less than the temperature of the one or more resistive film heating elements, and to be sufficiently high to prevent condensation which may or may not cause film formation on surfaces of the process chamber and reduce the accumulation of residue. 
     Once film forming composition enters the process space  33 , the film forming composition adsorbs on the substrate surface, and film forming reactions proceed to produce a thin film on the substrate  25 . According to program instructions from the temperature control system  22  or the controller  80  or both, the substrate holder  20  is configured to set the temperature of substrate  25  to a value less than the temperature of the gas distribution device  45 , the temperature of the gas distribution system  40 , and the process chamber  10 . For example, the substrate temperature can range up to approximately 80 degrees C. Additionally, the substrate temperature can be approximately room temperature. For example, the substrate temperature can range up to approximately 25 degrees C. However, the temperature may be less than or greater than room temperature. 
     The substrate holder  20  comprises one or more temperature control elements coupled to the temperature control system  22 . The temperature control system  22  can include a substrate heating system, or a substrate cooling system, or both. For example, substrate holder  20  can include a substrate heating element or substrate cooling element (not shown) beneath the surface of the substrate holder  20 . For instance, the heating system or cooling system can include a re-circulating fluid flow that receives heat from substrate holder  20  and transfers heat to a heat exchanger system (not shown) when cooling, or transfers heat from the heat exchanger system to the substrate holder  20  when heating. The cooling system or heating system may include heating/cooling elements, such as resistive heating elements, or thermoelectric heaters/coolers located within substrate holder  20 . Additionally, the heating elements or cooling elements or both can be arranged in more than one separately controlled temperature zone. The substrate holder  20  may have two thermal zones, including an inner zone and an outer zone. The temperatures of the zones may be controlled by heating or cooling the substrate holder thermal zones separately. 
     Additionally, the substrate holder  20  comprises a substrate clamping system (e.g., electrical or mechanical clamping system) to clamp the substrate  25  to the upper surface of substrate holder  20 . For example, substrate holder  20  may include an electrostatic chuck (ESC). 
     Furthermore, the substrate holder  20  can facilitate the delivery of heat transfer gas to the back-side of substrate  25  via a backside gas supply system to improve the gas-gap thermal conductance between substrate  25  and substrate holder  20 . Such a system can be utilized when temperature control of the substrate is required at elevated or reduced temperatures. For example, the backside gas system can comprise a two-zone gas distribution system, wherein the backside gas (e.g., helium) pressure can be independently varied between the center and the edge of substrate  25 . 
     Vacuum pumping system  60  can include a turbo-molecular vacuum pump (TMP) capable of a pumping speed up to approximately 5000 liters per second (and greater) and a gate valve for throttling the chamber pressure. For example, a 1000 to 3000 liter per second TMP can be employed. TMPs can be used for low pressure processing, typically less than approximately 1 Torr. For high pressure processing (i.e., greater than approximately 1 Torr), a mechanical booster pump and dry roughing pump can be used. Furthermore, a device for monitoring chamber pressure (not shown) can be coupled to the process chamber  10 . The pressure measuring device can be, for example, a Type 628B Baratron absolute capacitance manometer commercially available from MKS Instruments, Inc. (Andover, Mass.). 
     Referring still to  FIG. 1 , the deposition system  1  can further comprise a controller  80  that comprises a microprocessor, memory, and a digital I/O port capable of generating control voltages sufficient to communicate and activate inputs to deposition system  1  as well as monitor outputs from deposition system  1 . Moreover, controller  80  can be coupled to and can exchange information with the process chamber  10 , the substrate holder  20 , the temperature control system  22 , the film forming composition supply system  30 , the gas distribution system  40 , the gas distribution device  45 , and the vacuum pumping system  60 , as well as the backside gas delivery system (not shown), and/or the electrostatic clamping system (not shown). A program stored in the memory can be utilized to activate the inputs to the aforementioned components of deposition system  1  according to a process recipe in order to perform the method of depositing a thin film. 
     Controller  80  may be locally located relative to the deposition system  1 , or it may be remotely located relative to the deposition system  1  via an internet or intranet. Thus, controller  80  can exchange data with the deposition system  1  using at least one of a direct connection, an intranet, or the internet. Controller  80  may be coupled to an intranet at a customer site (i.e., a device maker, etc.), or coupled to an intranet at a vendor site (i.e., an equipment manufacturer). Furthermore, another computer (i.e., controller, server, etc.) can access controller  80  to exchange data via at least one of a direct connection, an intranet, or the internet. 
     The deposition system  1  can be periodically cleaned using an in-situ cleaning system (not shown) coupled to, for example, the process chamber  10  or the gas distribution system  40 . Per a frequency determined by the operator, the in-situ cleaning system can perform routine cleanings of the deposition system  1  in order to remove accumulated residue on internal surfaces of deposition system  1 . The in-situ cleaning system can, for example, comprise a radical generator configured to introduce chemical radical capable of chemically reacting and removing such residue. Additionally, for example, the in-situ cleaning system can, for example, include an ozone generator configured to introduce a partial pressure of ozone. For instance, the radical generator can include an upstream plasma source configured to generate oxygen or fluorine radical from oxygen (O 2 ), nitrogen trifluoride (NF 3 ), O 3 , XeF 2 , ClF 3 , or C 3 F 8  (or, more generally, C x F y ), respectively. The radical generator can include an ASTRON® reactive gas generator, commercially available from MKS Instruments, Inc., ASTeX® Products (90 Industrial Way, Wilmington, Mass. 01887). 
     Although the porous gas distribution device has been described for use in a deposition system, the porous gas distribution device may be used in any system requiring gas heating. Other systems in semiconductor manufacturing and integrated circuit (IC) manufacturing may include etching systems, thermal processing systems, etc. 
       FIG. 9  illustrates a method of depositing a thin film on a substrate according to another embodiment. The method  800  includes, at  810 , coupling a gas heating device to a process chamber for a deposition system, wherein the gas heating device comprises one or more porous gas distribution elements configured to receive an electrical current from one or more power sources. For example, the one or more porous gas distribution elements may comprise an open-celled foam. 
     In  820 , a temperature of the gas heating device is elevated. For example, the temperature may be elevated by flowing electrical current to or through the porous gas distribution element as described above. 
     In  830 , a substrate is provided in the process chamber of the deposition system. For example, the deposition system can include the deposition system described above in  FIG. 1 . The substrate can, for example, be a Si substrate. A Si substrate can be of n- or p-type, depending on the type of device being formed. The substrate can be of any size, for example a 200 mm substrate, a 300 mm substrate, or an even larger substrate. According to an embodiment of the invention, the substrate can be a patterned substrate containing one or more vias or trenches, or combinations thereof. 
     In  840 , a film forming composition is provided to a gas distribution system that is configured to introduce the film forming composition to the process chamber above the substrate. For example, the gas distribution system can be located above the substrate and opposing an upper surface of the substrate. 
     In  850 , one or more constituents of the film forming composition are subjected to pyrolysis using the gas heating device. The gas heating device can be any one of the systems described in  FIGS. 2 through 8  above, or any combination thereof. 
     In  860 , the substrate is exposed to the film forming composition to facilitate the formation of the thin film. The temperature of the substrate can be set to a value less than the temperature of the one or more heating elements, e.g. one or more resistive film heating elements. For example, the temperature of the substrate can be approximately room temperature. 
     The method may further comprise adjusting a first flow of the film forming composition through one of the one or more porous gas distribution elements relative to a second flow of the film forming composition through another of the one or more porous gas distribution elements. Additionally, the method may further comprise adjusting a first temperature of one of the one or more porous gas distribution elements relative to a second temperature of another of the one or more porous gas distribution elements. 
     Although only certain embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.