Abstract:
Embodiments of the invention provide a method and an apparatus for generating a gaseous chemical precursor for a processing system. In one embodiment, an apparatus for generating the gaseous chemical precursor used in a vapor deposition processing system is provided and includes a canister having a sidewall, a top, and a bottom encompassing an interior volume therein, an inlet port and an outlet port in fluid communication with the interior volume, and an inlet tube extending from the inlet port into the canister, wherein the inlet tube contains an outlet positioned to direct a gas flow away from the outlet port and towards the sidewall of the canister.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. Ser. No. 11/613,153 (APPM/006798.C3), filed Dec. 19, 2006, and issued as U.S. Pat. No. 7,429,361, which is a continuation of U.S. Ser. No. 10/198,727 (APPM/006798), filed Jul. 17, 2002, and issued as U.S. Pat. No. 7,186,385, which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the invention generally relate to a method and apparatus for providing gas to a processing chamber. 
         [0004]    2. Description of the Related Art 
         [0005]    Integrated circuits have evolved into complex devices that can include millions of transistors, capacitors and resistors on a single chip. The evolution of chip design continually requires faster circuitry and greater circuit density demanding increasingly precise fabrication processes. The precision processing of substrates requires precise control of temperature, rate and pressure in the delivery of fluids used during processing. The control of these fluids is typically facilitated using a gas panel that contains various valves, regulators, flow controllers and the like. 
         [0006]    Fluids used during processing are provided to the gas panel and liquid or gas is formed from a central gas source or a supply vessel positioned proximate the panel. Some process gases may be generated at or near the gas panel from a solid material through a sublimation process. Sublimation is generally a process through which a gas is produced directly from a solid at a certain pressure and temperature without passing through a liquid state. Some gases that may be produced through a sublimation process include xenon difluoride, nickel carbonyl, tungsten hexacarbonyl, and pentakis(dimethylamino) tantalum (PDMAT) among others. As these materials tend to be very active and expensive, careful control of the sublimation process is required in order to manage the generation of the sublimed solid without undue waste. 
         [0007]    A conventional sublimation process is typically performed in a heated vessel loaded or filled with a solid precursor material to be sublimed. As gas is needed, the vessel walls and/or tray supporting the solid precursor material are heated and the gas is produced. 
         [0008]    An alternative gas generation process includes mixing a solid or liquid precursor material with a liquid. A carrier gas is then bubbled through the mixture to carry the generated process gas. 
         [0009]    However, as the carrier gas is bubbled through or impacted against either a solid precursor or liquid/solid mixture, particulates from the solid precursor and or liquid may become entrained in the carrier gas and transferred into the process chamber. Liquid or solid particulates may become a source of chamber or substrate contamination. Thus, reduction of particulates passing from precursor gas generator into a processing chamber would serve at least two purposes. First, such a reduction in particulates would reduce substrate defects. Second, a reduction in particulates would reduce the downtime required for cleaning the contaminated chamber surfaces. 
         [0010]    Therefore, there is a need for an improved method and apparatus for providing a precursor gas to a processing chamber. 
       SUMMARY OF THE INVENTION 
       [0011]    One aspect of the present invention generally provides an apparatus for generating gas for a processing system. In one embodiment, the apparatus for generating gas for a processing system includes a canister containing a precursor material. The canister includes a top, a bottom, and a sidewall defining an interior volume. The interior volume has an upper region and a lower region, wherein the lower region is at least partially filled by the precursor material. An inlet port and an outlet port are formed through the canister and are in communication with the upper region. At least one baffle is disposed within the upper region of the canister between the inlet and outlet port. 
         [0012]    In another aspect of the invention, a method for generating gas for a processing system is provided. In one embodiment, the method for generating gas includes the steps of providing a precursor material contained in the lower region of the canister, flowing a carrier gas from the inlet port through the upper region of the canister along an extended mean path to the outlet port, and heating the precursor material to generate a process gas. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    A more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof that are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0014]      FIG. 1  is a simplified schematic view of a processing system having one embodiment of a gas generation system; 
           [0015]      FIG. 2A  is a sectional side view of one embodiment of a gas generation canister; 
           [0016]      FIG. 2B  is a sectional top view of one embodiment of a gas generation canister; 
           [0017]      FIG. 3  is a sectional view of another embodiment of a gas generation canister; and 
           [0018]      FIG. 4  is a sectional side view of another embodiment of a gas generation canister. 
       
    
    
       [0019]    To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the figures. 
       DETAILED DESCRIPTION 
       [0020]      FIG. 1  generally depicts a simplified schematic of a semiconductor wafer processing system  120 . The processing system  120  generally includes a processing chamber  106  coupled to a gas delivery system  104 . The processing chamber  106  may be any suitable processing chamber, for example, those available from Applied Materials, Inc. located in Santa Clara, Calif. Exemplary processing chambers include DPS CENTURA® etch chambers, PRODUCER® chemical vapor deposition chambers, and ENDURA® physical vapor deposition chambers, among others. 
         [0021]    The gas delivery system  104  generally controls the rate and pressure at which various process and inert gases are delivered to the processing chamber  106 . The number and types of process and other gases delivered to the processing chamber  106  are generally selected based on the process to be performed in the processing chamber  106  coupled thereto. Although for simplicity a single gas delivery circuit is depicted in the gas delivery system  104  shown in  FIG. 1 , it is contemplated that additional gas delivery circuits may be utilized. 
         [0022]    The gas delivery system  104  is generally coupled between a carrier gas source  102  and the processing chamber  106 . The carrier gas source  102  may be a local or remote vessel or a centralized facility source that supplies the carrier gas throughout the facility. The carrier gas source  102  typically supplies a carrier gas such as argon, nitrogen, helium or other inert or non-reactive gas. 
         [0023]    The gas delivery system  104  typically includes a flow controller  110  coupled between the carrier gas source  102  and a process gas source canister  100 . The flow controller  110  may be a proportional valve, modulating valve, needle valve, regulator, mass flow controller or the like. One flow controller  110  that may be utilized is available from Sierra Instruments, Inc., located in Monterey, Calif. 
         [0024]    The source canister  100  is typically coupled to and located between a first and a second valve  112 ,  114 . In one embodiment, the first and second valves  112 ,  114  are coupled to the canister  100  and fitted with disconnect fittings (not shown) to facilitate removal of the valves  112 ,  114  with the canister  100  from the gas delivery system  104 . A third valve  116  is disposed between the second valve  114  and the processing chamber  106  to prevent introduction of contaminates into the processing chamber  106  after removal of the canister  100  from the gas delivery system  104 . 
         [0025]      FIGS. 2A and 2B  depict sectional views of one embodiment of the canister  100 . The canister  100  generally comprises an ampoule or other sealed container having a housing  220  that is adapted to hold precursor materials  214  from which a process (or other) gas may be generated through a sublimation or vaporization process. Some solid precursor materials  214  that may generate a process gas in the canister  100  through a sublimation process include xenon difluoride, nickel carbonyl, tungsten hexacarbonyl, and pentakis(dimethylamino) tantalum (PDMAT), among others. Some liquid precursor materials  214  that may generate a process gas in the canister  100  through a vaporization process include tetrakis(dimethylamino) titanium (TDMAT), tertbutyliminotris(diethylamino) tantalum (TBTDET), and pentakis(ethylmethylamino) tantalum (PEMAT), among others. The housing  220  is generally fabricated from a material substantially inert to the precursor materials  214  and gas produced therefrom, and thus, the material of construction may vary based on gas being produced. In one embodiment, tungsten hexacarbonyl is generated within the canister  100  and the housing  220  is fabricated from a material substantially inert to tungsten hexacarbonyl, for example, stainless steel, aluminum, PFA, or other suitable non-organic material. 
         [0026]    The housing  220  may have any number of geometric forms. In the embodiment depicted in  FIGS. 2A and 2B , the housing  220  comprises a cylindrical sidewall  202  and a bottom  232  sealed by a lid  204 . The lid  204  may be coupled to the sidewall  202  by welding, bonding, adhesives, or other leak-tight method. Alternately, the joint between the sidewall  202  and the lid  204  may have a seal, o-ring, gasket, or the like, disposed therebetween to prevent leakage from the canister example, a hollow square tube. 
         [0027]    An inlet port  206  and an outlet port  208  are formed through the canister to allow gas flow into and out of the canister  100 . The ports  206 ,  208  may be formed through the lid  204  and/or sidewall  202  of the canister  100 . The ports  206 ,  208  are generally sealable to allow the interior of the canister  100  to be isolated from the surrounding environment during removal of the canister  100  from the gas delivery system  104 . In one embodiment, valves  112 ,  114  are sealingly coupled to ports  206 ,  208  to prevent leakage from the canister  100  when removed from the gas delivery system  104  (shown in  FIG. 1 ) for recharging of the precursor material  214  or replacement of the canister  100 . Mating disconnect fittings  236 A,  236 B may be coupled to valves  112 ,  114  to facilitate removal and replacement of the canister  100  to and from the gas delivery system  104 . Valves  112 ,  114  are typically ball valves or other positive sealing valves that allows the canister  100  to be removed from the system efficiently loaded and recycled while minimizing potential leakage from the canister  100  during filling, transport, or coupling to the gas delivery system  104 . Alternatively, the canister  100  can be refilled through a refill port (not shown) such as a small tube with a VCR fitting disposed on the lid  204  of the canister  100 . 
         [0028]    The canister  100  has an interior volume  238  having an upper region  218  and a lower region  234 . The lower region  234  of canister  100  is at least partially filled with the precursor materials  214 . Alternately, a liquid  216  may be added to a solid precursor material  214  to form a slurry  212 . The precursor materials  214 , the liquid  216 , or the premixed slurry  212  may be introduced into canister  100  by removing the lid  204  or through one of the ports  206 ,  208 . The liquid  216  is selected such that it is non-reactive with the precursor materials  214 , that the precursor materials  214  are insoluble therein, and that the liquid  216  has a negligible vapor pressure compared to the precursor materials  214 . For example, a liquid  216  added to a solid precursor material  214  such as tungsten hexacarbonyl should have a higher vapor pressure than the tungsten hexacarbonyl by greater than about 1×10 3  Torr to ensure that the sublimating vapor comprises mainly tungsten hexacarbonyl and only a negligible quantity of liquid. 
         [0029]    Precursor materials  214  mixed with the liquid  216  may be sporadically agitated to keep the precursor materials  214  suspended in the liquid  216  in the slurry  212 . In one embodiment, precursor materials  214  and the liquid  216  are agitated by a magnetic stirrer  240 . The magnetic stirrer  240  includes a magnetic motor  242  disposed beneath the bottom  232  of the canister  100  and a magnetic pill  244  disposed in the lower region  234  of the canister  100 . The magnetic motor  242  operates to rotate the magnetic pill  244  within the canister  100 , thereby mixing the slurry  212 . The magnetic pill  244  should have an outer coating of material that is a non-reactive with the precursor materials  214 , the liquid  216 , or the canister  100 . Suitable magnetic mixers are commercially available. One example of a suitable magnetic mixer is IKAMAG® REO available from IKA® Works in Wilmington, N.C. Alternatively, the slurry  212  may be agitated other means, such as by a mixer, a bubbler, or the like. 
         [0030]    The agitation of the liquid  216  may induce droplets of the liquid  216  to become entrained in the carrier gas and carried toward the processing chamber  106 . To prevent such droplets of liquid  216  from reaching the processing chamber  106 , an oil trap  250  may optionally be coupled to the exit port  208  of the canister  100 . The oil trap  250  includes a body  252  containing a plurality of interleaved baffles  254  which extend past a centerline  256  of the oil trap body  252  and are angled at least slightly downward towards the canister  100 . The baffles  254  force the gas flowing towards the processing chamber  106  to flow a tortuous path around the baffles  254 . The surface area of the baffles  254  provides a large surface area exposed to the flowing gas to which oil droplets that may be entrained in the gas adhere to. The downward angle of the baffles  254  allows any oil accumulated in the oil trap to flow downward and back into the canister  100 . 
         [0031]    The canister  100  includes at least one baffle  210  disposed within the upper region  218  of the canister  100 . The baffle  210  is disposed between inlet port  206  and outlet port  208 , creating an extended mean flow path, thereby preventing direct (i.e., straight line) flow of the carrier gas from the inlet port  206  to the outlet port  208 . This has the effect of increasing the mean dwell time of the carrier gas in the canister  100  and increasing the quantity of sublimated or vaporized precursor gas carried by the carrier gas. Additionally, the baffles  210  direct the carrier gas over the entire exposed surface of the precursor material  214  disposed in the canister  100 , ensuring repeatable gas generation characteristics and efficient consumption of the precursor materials  214 . 
         [0032]    The number, spacing and shape of the baffles  210  may be selected to tune the canister  100  for optimum generation of precursor gas. For example, a greater number of baffles  210  may be selected to impart higher carrier gas velocities at the precursor material  214  or the shape of the baffles  210  may be configured to control the consumption of the precursor material  214  for more efficient usage of the precursor material. 
         [0033]    The baffle  210  may be attached to the sidewall  202  or the lid  204 , or the baffle  210  may be a prefabricated insert designed to fit within the canister  100 . In one embodiment, the baffles  210  disposed in the canister  100  comprise five rectangular plates fabricated of the same material as the sidewall  202 . Referring to  FIG. 2B , the baffles  210  are welded or otherwise fastened to the sidewall  202  parallel to each other. The baffles  210  are interleaved, fastened to opposing sides of the canister in an alternating fashion, such that a serpentine extended mean flow path is created. Furthermore, the baffles  210  are situated between the inlet port  206  and the outlet port  208  on the lid  204  when placed on the sidewall  202  and are disposed such that there is no air space between the baffles  210  and the lid  204 . The baffles  210  additionally extend at least partially into the lower region  234  of the canister  100 , thus defining an extended mean flow path for the carrier gas flowing through the upper region  218 . 
         [0034]    Optionally, an inlet tube  222  may be disposed in the interior volume  238  of the canister  100 . The tube  222  is coupled by a first end  224  to the inlet port  206  of the canister  100  and terminates at a second end  226  in the upper region  218  of the canister  100 . The tube  222  injects the carrier gas into the upper region  218  of the canister  100  at a location closer to the precursor materials  214  or the slurry  212 . 
         [0035]    The precursor materials  214  generate a precursor gas at a predefined temperature and pressure. Sublimating or vaporized gas from the precursor materials  214  accumulate in the upper region  218  of the canister  100  and are swept out by an inert carrier gas entering through inlet port  206  and exiting outlet port  208  to be carried to the processing chamber  106 . In one embodiment, the precursor materials  214  are heated to a predefined temperature by a resistive heater  230  disposed proximate to the sidewall  202 . Alternately, the precursor materials  214  may be heated by other means, such as by a cartridge heater (not shown) disposed in the upper region  218  or the lower region  234  of the canister  100  or by preheating the carrier gas with a heater (not shown) placed upstream of the carrier gas inlet port  206 . To maximize uniform heat distribution throughout the slurry  212 , the liquid  216  and the baffles  210  should be good conductors of heat. 
         [0036]    In one exemplary mode of operation, the lower region  234  of the canister  100  is at least partially filled with a mixture of tungsten hexacarbonyl and diffusion pump oil to form the slurry  212 . The slurry  212  is held at a pressure of about 5 Torr and is heated to a temperature in the range of about 40° C. to about 50° C. by a resistive heater  230  located proximate to the canister  100 . Carrier gas in the form of argon is flowed through inlet port  206  into the upper region  218  at a rate of about 200 standard cc/min. The argon flows in an extended mean flow path defined by the tortuous path through the baffles  210  before exiting the canister  100  through outlet port  208 , advantageously increasing the mean dwell time of the argon in the upper region  218  of the canister  100 . The increased dwell time in the canister  100  advantageously increases the saturation level of sublimated tungsten hexacarbonyl vapors within the carrier gas. Moreover, the tortuous path through the baffles  210  advantageously exposes the substantially all of the exposed surface area of the precursor material  214  to the carrier gas flow for uniform consumption of the precursor material  214  and generation of the precursor gas. 
         [0037]      FIG. 3  depicts a sectional view of another embodiment of a canister  300  for generating a process gas. The canister includes a sidewall  202 , a lid  204  and a bottom  232  enclosing an interior volume  238 . At least one of the lid  204  or sidewall  202  contains an inlet port  206  and an outlet port  208  for gas entry and egress. The interior volume  238  of the canister  300  is split into an upper region  218  and a lower region  234 . Precursor materials  214  at least partially fill the lower region  234 . The precursor materials  214  may be in the form of a solid, liquid or slurry, and are adapted to generate a process gas by sublimation and/or vaporization. 
         [0038]    A tube  302  is disposed in the interior volume  238  of the canister  300  and is adapted to direct a flow of gas within the canister  300  away from the precursor materials  214 , advantageously preventing gas flowing out of the tube  302  from directly impinging the precursor materials  214  and causing particulates to become airborne and carried through the outlet port  208  and into the processing chamber  106 . The tube  302  is coupled at a first end  304  to the inlet port  206 . The tube  302  extends from the first end  304  to a second end  326 A that is positioned in the upper region  218  above the precursor materials  214 . The second end  326 A may be adapted to direct the flow of gas toward the sidewall  202 , thus preventing direct (linear or line of sight) flow of the gas through the canister  300  between the ports  206 ,  208 , creating an extended mean flow path. 
         [0039]    In one embodiment, an outlet  306  of the second end  326 A of the tube  302  is oriented an angle of about 15° to about 90° relative to a center axis  308  of the canister  300 . In another embodiment, the tube  302  has a ‘J’-shaped second end  326 B that directs the flow of gas exiting the outlet  306  towards the lid  204  of the canister  300 . In another embodiment, the tube  302  has a second end  326 C having a plug or cap  310  closing the end of the tube  302 . The second end  326 C has at least one opening  328  formed in the side of the tube  302  proximate the cap  310 . Gas, exiting the openings  328 , is typically directed perpendicular to the center axis  308  and away from the precursor materials  214  disposed in the lower region  234  of the canister  300 . Optionally, an at least one baffle  210  (shown in phantom) as described above may be disposed within the chamber  300  and utilized in tandem with any of the embodiments of the tube  302  described above. 
         [0040]    In one exemplary mode of operation, the lower region  234  of the canister  300  is at least partially filled with a mixture of tungsten hexacarbonyl and diffusion pump oil to form the slurry  212 . The slurry  212  is held at a pressure of about 5 Torr and is heated to a temperature in the range of about 40° C. to about 50° C. by a resistive heater  230  located proximate to the canister  300 . A carrier gas in the form of argon is flowed through the inlet port  206  and the tube  302  into the upper region  218  at a rate of about 200 standard cc/min. The second end  326 A of the tube  302  directs the flow of the carrier gas in an extended mean flow path away from the outlet port  208 , advantageously increasing the mean dwell time of the argon in the upper region  218  of the canister  300  and preventing direct flow of carrier gas upon the precursor materials  214  to minimize particulate generation. The increased dwell time in the canister  300  advantageously increases the saturation level of sublimated tungsten hexacarbonyl gas within the carrier gas while the decrease in particulate generation improves product yields, conserves source solids, and reduces downstream contamination. 
         [0041]      FIG. 4  depicts a sectional view of another embodiment of a canister  400  for generating a precursor gas. The canister  400  includes a sidewall  202 , a lid  204  and a bottom  232  enclosing an interior volume  238 . At least one of the lid  204  or sidewall  202  contains an inlet port  206  and an outlet port  208  for gas entry and egress. Inlet and outlet ports  206 ,  208  are coupled to valves  112 ,  114  fitted with mating disconnect fittings  236 A,  236 B to facilitate removal of the canister  400  from the gas delivery system  104 . Optionally, an oil trap  250  is coupled between the outlet port  208  and the valve  114  to capture any oil particulate that may be present in the gas flowing to the process chamber  106 . 
         [0042]    The interior volume  238  of the canister  300  is split into an upper region  218  and a lower region  234 . Precursor materials  214  and a liquid  216  at least partially fill the lower region  234 . A tube  402  is disposed in the interior volume  238  of the canister  400  and is adapted to direct a first gas flow F 1  within the canister  400  away from the precursor material and liquid mixture and to direct a second gas flow F 2  through the mixture. The flow F 1  is much greater than the flow F 2 . The flow F 2  is configured to act as a bubbler, being great enough to agitate the precursor material and liquid mixture but not enough to cause particles or droplets of the precursor materials  214  or liquid  216  from becoming airborne. Thus, this embodiment advantageously agitates the precursor material and liquid mixture while minimizing particulates produced due to direct impingement of the gas flowing out of the tube  402  on the precursor materials  214  from becoming airborne and carried through the outlet port  208  and into the processing chamber  106 . 
         [0043]    The tube  402  is coupled at a first end  404  to the inlet port  206 . The tube  402  extends from the first end  404  to a second end  406  that is positioned in the lower region  234  of the canister  400 , within the precursor material and liquid mixture. The tube  402  has an opening  408  disposed in the upper region  218  of the canister  400  that directs the first gas flow F 1  towards a sidewall  202  of the canister  400 . The tube  400  has a restriction  410  disposed in the upper region  238  of the canister  400  located below the opening  408 . The restriction  410  serves to decrease the second gas flow F 2  flowing toward the second end  406  of the tube  402  and into the slurry  212 . By adjusting the amount of the restriction, the relative rates of the first and second gas flows F 1  and F 2  can be regulated. This regulation serves at least two purposes. First, the second gas flow F 2  can be minimized to provide just enough agitation to maintain suspension or mixing of the precursor materials  214  in the liquid  216  while minimizing particulate generation and potential contamination of the processing chamber  106 . Second, the first gas flow F 1  can be regulated to maintain the overall flow volume necessary to provide the required quantity of sublimated and/or vapors from the precursor materials  214  to the processing chamber  106 . 
         [0044]    Optionally, an at least one baffle  210  (shown in phantom) as described above may be disposed within the chamber  400  and utilized in tandem with any of the embodiments of the tube  402  described above. 
         [0045]    While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow.