Patent Publication Number: US-2004052969-A1

Title: Methods for operating a chemical vapor deposition chamber using a heated gas distribution plate

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     [0001] This application is related to U.S. Ser. No. ______ (AMAT/7346) by Tsuei et al. and entitled “HEATED GAS DISTRIBUTION PLATE FOR A PROCESSING CHAMBER”; and U.S. Ser. No. ______ (AMAT  6249 ) by Cui et al. and entitled “CHAMBER CLEANING METHOD USING REMOTE AND IN SITU PLASMA CLEANING SYSTEMS.” 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] Embodiments of the present invention generally relate to methods for operating a chemical vapor deposition chamber, and more specifically, methods for cleaning the chemical vapor deposition chamber.  
       [0004] 2. Description of the Related Art  
       [0005] In the fabrication of integrated circuits and semiconductor devices, materials, such as oxides, are typically deposited on a substrate in a process chamber, such as a chemical vapor deposition (CVD) chamber. The deposition processes typically result in deposition of some of the materials on the walls and components of the deposition chamber, such as the gas distribution plate or faceplate. Since the materials are distributed through the gas distribution plate during processing, a layer of deposition is often formed on the gas distribution plate, which may clog the holes of the plate or flake off in particles that rain down on the substrate, thereby affecting the uniformity of deposition on the substrate and contaminating the substrate. Consequently, it is necessary to clean the interior of the deposition chamber on a regular basis.  
       [0006] Several methods of cleaning the deposition chamber, including the gas distribution plate, have been developed. For example, a remote plasma cleaning procedure may be employed in which an etchant plasma is generated remote from the deposition chamber by a high density plasma source such as a microwave plasma system, toroidal plasma generator or similar device. Dissociated species from the etchant plasma are then transported to the deposition chamber where they can react with and etch away the undesired deposition build up. It is also common to remove the unwanted deposition material that builds up on the interior of chamber walls with an in situ chamber clean operation. Common chamber cleaning techniques include the use of an etchant gas, such as fluorine, to remove the deposited material from the chamber walls and other areas. The etchant gas is introduced into the chamber and plasma is formed so that the etchant gas reacts with and removes the deposited material from the chamber walls.  
       [0007] Conventional chamber cleaning methods, however, still require a considerable amount of time. The longer it takes to clean the chamber, the lower the number of substrates that can be processed in a given time (i.e., throughput) and the more gas that is consumed to clean the chamber.  
       [0008] Therefore, a need exists for an improved method for cleaning a deposition chamber.  
       SUMMARY OF THE INVENTION  
       [0009] Embodiments of the present invention are generally directed to a method for processing a substrate. In one embodiment, the method includes introducing one or more precursors into a chemical vapor deposition chamber through a gas distribution plate heated by a heating mechanism disposed at a bottom plate of the gas distribution plate, and reacting the precursors to deposit a material on a substrate surface.  
       [0010] In another embodiment, the present invention is directed to a method for cleaning a chemical vapor deposition chamber, which includes introducing a cleaning gas into the chamber through a gas distribution plate heated by a heating mechanism disposed at a bottom plate of the gas distribution plate, forming a plasma within the chamber, and reacting the cleaning gas with deposits within the chamber until substantially all the deposits are consumed.  
       [0011] In yet another embodiment, the invention is directed to a method for cleaning a chemical vapor deposition chamber, which includes introducing a cleaning gas into a remote plasma source connected to the chamber, striking a plasma in the remote plasma source to form a reactive species, importing the reactive species into the chamber through a gas distribution plate heated by a heating mechanism disposed at a bottom plate of the gas distribution plate, and using the reactive species to clean the chamber.  
       [0012] In still another embodiment, the invention is directed to a method for processing a substrate. The method includes introducing one or more precursors into a chemical vapor deposition chamber through a gas distribution plate heated by a heating mechanism disposed at a bottom plate of the gas distribution plate, reacting the precursors to deposit a material on a substrate surface, removing the substrate from the chamber, introducing a cleaning gas into the chamber through the gas distribution plate, and reacting the cleaning gas with deposits within the chamber until substantially all the deposits are consumed. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013] So that the manner in which the above recited features of the present invention, and other features contemplated and claimed herein, are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which 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 cross-sectional view of a CVD chamber in accordance with various embodiments of the invention shown in FIGS.  3 A- 5 C;  
     [0015]FIG. 2 is an exploded view of the gas distribution assembly in accordance with various embodiments of the invention shown in FIGS.  3 A- 5 C;  
     [0016]FIG. 3A illustrates a partial schematic cross-sectional view of a gas distribution plate in accordance with an embodiment of the invention;  
     [0017]FIG. 3B illustrates a schematic perspective view of a high temperature heat exchanger fluid channel in accordance with an embodiment of the invention;  
     [0018]FIG. 4A illustrates a partial schematic cross-sectional view of a gas distribution plate in accordance with an embodiment of the invention;  
     [0019]FIG. 4B illustrates a cross-sectional view of a heating element in accordance with an embodiment of the invention;  
     [0020] FIGS.  5 A-C illustrate partial cross-sectional views of the gas distribution assembly in accordance with various embodiments of the invention;  
     [0021]FIG. 6 is a graph illustrating the effect on the clean rate and the deposition rate as the temperature of the gas distribution plate increases in accordance with an embodiment of the invention;  
     [0022]FIG. 7 illustrates a flow chart of a process for processing a substrate in accordance with an embodiment of the invention;  
     [0023]FIG. 8 illustrates a flow chart of a process for cleaning a CVD chamber in accordance with an embodiment of the invention; and  
     [0024]FIG. 9 illustrates a flow chart of a process for cleaning a CVD chamber in accordance with another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0025]FIG. 1 illustrates a cross-sectional view of a CVD chamber  100  in accordance with various embodiments of the invention shown in FIGS.  3 A- 5 C. The chamber  100  includes a gas distribution assembly  20 , which includes a gas box  50  connected to a gas distribution plate or faceplate  11 . The gas box  50  is typically water-cooled to a temperature of approximately below 100 degrees Celsius. A substrate support pedestal  12  is disposed below the gas distribution plate  11  so as to define a processing region therebetween for processing a substrate  16 . The substrate support pedestal  12  is generally heated by a heater (not shown) at approximately 100 degrees Celsius to 600 degrees Celsius. As a result, the bottom surface of the gas distribution plate  11  is heated by radiation from the heater and/or the plasma, while the top surface of the gas distribution plate  11  is cooled from being in contact with the gas box  50 . The gas box  50  supplies processing gases into the chamber  100  through inlets or holes (not shown) in the gas distribution plate  11  so that the gases may be uniformly distributed across the processing region. The processing gases are exhausted through a port  24  by a vacuum pump system  32 .  
     [0026] The substrate support pedestal  12  is mounted on a support stem  13  so that the substrate support pedestal  12  can be controllably moved by a lift motor  14  between a lower (loading/off-loading) position and an upper (processing) position. Motors and optical sensors can be used to move and determine the position of movable mechanical assemblies, such as, the throttle valve of the vacuum pump  32  and the motor for positioning the substrate support pedestal  12 .  
     [0027] A thermal or plasma enhanced process may be performed in the chamber  100 . In a plasma process, a controlled plasma can be formed adjacent to the substrate  16  by applying RF energy to the gas distribution plate  11  from RF power supply  25  with the substrate support pedestal  12  grounded. An RF power supply  25  can supply either a single or mixed frequency RF power to the gas distribution plate  11  to enhance the decomposition of any reactive species introduced into the chamber  100 . A mixed frequency RF power supply typically supplies power at a high RF frequency of about 13.56 MHz and at a low RF frequency of about 350 kHz.  
     [0028] A system controller  34  controls the motor  14 , the gas mixing system  19 , and the RF power supply  25  over control lines  36 . The system controller  34  may also control analog assemblies, such as mass flow controllers and RF generators. The system controller  34  controls the activities of the CVD processing chamber  100  and executes system control software stored in a memory  38 , which may be a hard disk drive, a floppy disk drive, and a card rack. The controller  34  may be one of any form of general purpose computer processor (CPU) that can be used in an industrial setting for controlling various chambers and sub-processors. Various support circuits may be coupled to the CPU for supporting the processor in a conventional manner.  
     [0029] Software routines may be stored in the memory  38  or executed by a second CPU that is remotely located. The software routines are generally executed to perform process recipes or sequences and to dictate the timing, mixture of gases, RF power levels, substrate support pedestal position, and other parameters of a particular process. The software routines, when executed, transform the general purpose computer into a specific process computer that controls the chamber operation so that a chamber process is performed. Alternatively, the software routines may be performed in a piece of hardware as an application specific integrated circuit or a combination of software or hardware. Other details of the CVD processing chamber  100  may be described in U.S. Pat. No. 5,000,113, entitled “A Thermal CVD/PECVD Processing chamber and Use for Thermal Chemical Vapor Deposition of Silicon Dioxide and In-situ Multi-step Planarized Process”, issued to Wang et al., and assigned to Applied Materials, Inc., the assignee of the invention, and is incorporated by reference herein to the extent not inconsistent with the invention.  
     [0030]FIG. 2 illustrates an exploded view of the gas distribution assembly  20  in accordance with various embodiments of the invention shown in FIGS.  3 A- 5 C. The gas distribution assembly  20  includes a gas manifold  30 , the gas box  50  (or gas injection cover plate), a showerhead assembly  34 , and an isolator  36 , all of which are mounted on an electrically grounded chamber lid  38 . The isolator  36  is generally composed of a non-conductor material to isolate RF power from the grounded chamber lid  38 . The showerhead assembly  34  includes a perforated blocker plate  40  and the gas distribution plate  11 . The blocker plate  40  is generally a flat circular member having a plurality of holes. The gas distribution plate  11  is a dish-shaped device having a circular, centrally disposed cavity defined by a side wall  51  and a bottom plate  60  through which are formed a plurality of holes  44 . The blocker plate  40  and the gas distribution plate  11  are configured to provide a uniform distribution of gases over the substrate surface through their respective holes. An annular flange portion  22  of the gas distribution plate  11  projects outwardly in a horizontal plane from the upper portion of the gas distribution plate  11 . The flange portion  22  serves to provide engagement of the gas distribution plate  11  with the gas box  50 . A cavity between the blocker plate  40  and the gas box  50  also serves as an additional agitation stage to continue mixing the process gases. O-rings  46  are disposed between the various components to help ensure hermetic seals to prevent leakage of the gases.  
     [0031]FIG. 3A illustrates a partial schematic cross-sectional view of a gas distribution plate  311  in accordance with one embodiment of the invention. The gas distribution plate  311  includes a flange portion  322 , a side wall  351  and a bottom plate  360 . A channel  310  is disposed inside the bottom plate  360  for containing fluid, such as, a high temperature heat exchanger fluid  350 . Other types of fluid that may heat the gas distribution plate  311  are also contemplated by the invention. The channel  310  may be disposed circumferentially around the perimeter of the bottom plate  360 . In one embodiment, the channel  310  is disposed on the same level as the plurality of holes (not shown) disposed through the bottom plate  360 . In this manner, the high temperature heat exchanger fluid  350  is configured to provide heating throughout the gas distribution plate  311 . The heat exchanger fluid  350  may be provided by a heat exchanger system (not shown) at high temperatures sufficient to heat the gas distribution plate  311  to a temperature of greater than approximately 100 degrees Celsius. The channel  310  may also include an inlet  320  and an outlet  330  for the fluid, which are disposed inside the flange portion  322  and the side wall  351  on one side of the gas distribution plate  311 , as shown in FIG. 3B. The inlet  320  and the outlet  330  may be made from a polyamide composition material, such as Vespel® by Dupont of Newark, Del. In this manner, the inlet  320  and the outlet  330  may serve as RF insulators, insulating the high temperature heat exchanger fluid  350  from the outside environment.  
     [0032] Another embodiment in which the gas distribution plate may be heated is illustrated in FIG. 4A. In this embodiment, the gas distribution plate  411  includes a channel  410  disposed inside a bottom plate  460  for containing a heating element  430 . In another embodiment, the heating element  430  may be cast in place in a molded or otherwise fabricated gas distribution plate  411 . The heating element  430  may be disposed circumferentially around the perimeter of the bottom plate  460 . The heating element  430  may be disposed on the same level as the plurality of holes (not shown) disposed through the bottom plate  460 . In this manner, the heating element is configured to electrically provide heating around the gas distribution plate  411 . In one example, the heating element  430  is configured to heat the gas distribution plate  411  to a temperature of greater than approximately 100 degrees Celsius. FIG. 4B illustrates that the heating element  430  may be insulated with RF insulating material  450 , such as, magnesium oxide, fiber glass or nylon, which may be available from Watlow Electric Manufacturing Company of St. Louis, Mo. An adapter  440  may be connected to the heating element  430  to reduce the potential danger from the RF hot material extruding out of the gas distribution plate  411 . The adapter  440  may also protect the o-ring (not shown) disposed between the gas distribution plate  411  and the gas box (not shown) since the temperature of the adapter  440  is significantly lower than the temperature of the heating element  430 .  
     [0033] The heated gas distribution plate in accordance with various embodiments of the invention may be enhanced by the gas distribution assembly  20  illustrated in FIGS.  5 A-C. FIG. 5A illustrates a partial cross-sectional view of the gas distribution assembly  20  in accordance with one embodiment of the invention. The flange portion  22  of the gas distribution plate  11  is in contact with the gas box  50 . Typically, a soft RF gasket is disposed between the flange portion  22  and the gas box  50 . In accordance with this embodiment of the invention, a hard RF gasket  510  is disposed between the flange portion  22  and the gas box  50  to reduce the contact area between the gas distribution plate  11  and the gas box  50 . The hard RF gasket  510 , in effect, increases the distance or space between the flange portion  22  and the gas box  50 . In this manner, heat transfer/loss from the gas distribution plate  11  may be minimized.  
     [0034] Another embodiment in which heat transfer may be minimized from the gas distribution plate is illustrated in FIG. 5B. In this embodiment, the gas assembly  520  includes a gas distribution plate  511 , which has a flange portion  522  in contact with a gas box  50 . The flange portion  522  defines recesses or grooves  540 , which provides a distance between the flange portion  522  and the gas box  50  or the isolator  36 . In this manner, the recesses  540  are designed to reduce the contact area between the gas box  50  and the flange portion  522 , thereby minimizing heat transfer from the gas distribution plate  511 .  
     [0035] Yet another embodiment in which heat transfer may be minimized from the gas distribution plate is illustrated in FIG. 5C. In this embodiment, a thermal isolator  575  is disposed between a gas distribution plate  571  and the gas box  50 . The thermal isolator  575  may be made from any material, such as ceramic, that provides thermal insulation between the gas distribution plate  571  and the gas box  50 . By disposing the thermal isolator  575  between the gas distribution plate  571  and the gas box  50 , the gas distribution plate  571  is in contact with the gas box  50  only through the thermal isolator  575 . The thermal isolator  575 , therefore, works to minimize heat transfer from the gas distribution plate  571 .  
     [0036] Other means for minimizing heat transfer from the gas distribution plate to the gas box  50  are also contemplated by the invention. For instance, the o-rings  46  between the gas distribution plate and the gas box  50  may be positioned closer toward the periphery of the gas distribution plate and the gas box  50  so as to increase the space between the two components.  
     [0037] Recently, it has been observed (as shown in FIG. 6) that at low temperatures, the deposition rate on a gas distribution plate during processing is much higher than at high temperatures and the etch rate on the gas distribution plate during cleaning is much lower than at high temperatures. Accordingly, it is desirable to operate the gas distribution plate at high temperatures, particularly during processing and cleaning. By operating the gas distribution plate at high temperatures, the deposition rate on the gas distribution plate during processing is minimized, while the clean rate is maximized, thereby reducing the chamber cleaning period. By reducing the chamber cleaning period, the mean number of substrates between maintenance is increased. Furthermore, since less film is being deposited on the gas distribution plate during processing, more precursors are available to be deposited on the substrate, thereby resulting in an increased deposition rate on the substrate. Additional benefits to using a heated gas distribution plate during processing also include a reduction of dielectric constant in the deposited film on the substrate and a reduction of particle contamination on the substrate.  
     [0038]FIG. 7 illustrates a process  700  for processing a substrate in the CVD chamber  100  in accordance with an embodiment of the invention. At step  710 , one or more precursors are introduced into the CVD chamber  100 . The precursors are introduced through a gas distribution plate heated by a heating mechanism, such as the high temperature heat exchanger fluid  350 , which was described with reference to FIGS. 3A and B, or the heating element  430 , which was described with reference to FIGS. 4A and B. In one embodiment, the gas distribution plate is heated at all times, such as, during processing, cleaning and even during status or idle state. Other heating mechanisms capable of heating the gas distribution plate to a temperature of greater than approximately 100 Celsius are also contemplated by the invention. At step  720 , the precursors are reacted to deposit a material on the substrate surface. At step  730 , the substrate is removed from the chamber  100 . At step  740 , the chamber  100  is cleaned. FIGS. 8 and 9 describe various methods of cleaning the chamber  100 .  
     [0039]FIG. 8 illustrates a process  800  of cleaning a CVD chamber in accordance with one embodiment of the invention. At step  810 , a cleaning gas, such as fluorine, is introduced into the CVD chamber  100  through the heated gas distribution plate. At step  820 , a plasma is formed within the chamber  100 . The plasma may be formed by applying an electric field to the cleaning gas. Typically, the electric field is generated by connecting the substrate support pedestal  12  to a source of radio frequency (RF) power. Alternatively, the RF power source may be coupled to the gas distribution plate  11 , or to both the gas distribution plate  11  and the substrate support pedestal  12 . At step  830 , the cleaning gas reacts with deposits within the chamber  100  until the deposits are consumed.  
     [0040]FIG. 9 illustrates a process  900  of cleaning a CVD chamber in accordance with another embodiment of the invention. At step  910 , a cleaning gas is introduced into a remote plasma source (not shown), which is connected to the chamber  100 . The remote plasma source is generally configured to provide a remotely generated plasma to the chamber  100 . At step  920 , a remote plasma is generated by applying an electrical field to the cleaning gas in the remote plasma source (not shown), forming a plasma of reactive species. At step  930 , the reactive species generated in the remote plasma source are imported into the chamber  100  through the heated gas distribution plate. At step  940 , the reactive species are used to clean the chamber  100 .  
     [0041] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.