Patent Publication Number: US-2007117414-A1

Title: Methods and apparatus for epitaxial film formation

Description:
The present application claims priority to U.S. Provisional Patent Application Ser. No. 60/723,675, filed Oct. 5, 2005 and entitled “METHODS AND APPARATUS FOR EPITAXIAL FILM FORMATION,” (Attorney Docket No. 9759/L) which is hereby incorporated herein by reference in its entirety for all purposes. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates generally to semiconductor device manufacturing, and more particularly to methods and apparatus for epitaxial film formation.  
     BACKGROUND  
      Some conventional methods of forming an epitaxial layer on a substrate may introduce contaminants to a surface of a substrate on which the epitaxial layer is formed. Further, temperatures associated with some conventional methods of forming an epitaxial layer on a substrate may be harmful to a semiconductor device formed thereon. Consequently, improved methods and apparatus for forming epitaxial layers are desired.  
     SUMMARY OF THE INVENTION  
      In a first aspect of the invention, a first system is provided for semiconductor device manufacturing. The first system includes (1) an epitaxial chamber adapted to form an epitaxial layer on a surface of a substrate; and (2) a plasma generator coupled to the epitaxial chamber and adapted to introduce plasma to the epitaxial chamber.  
      In a second aspect of the invention, a first method is provided for semiconductor device manufacturing. The first method includes the steps of (1) providing a semiconductor device manufacturing system having (a) an epitaxial chamber adapted to form an epitaxial material layer on a surface of a substrate; and (b) a plasma generator coupled to the epitaxial chamber and adapted to introduce plasma to the epitaxial chamber; and (2) employing the semiconductor device manufacturing system to clean the surface of the substrate prior to forming the epitaxial material layer on the substrate.  
      In a third aspect of the invention, a second method is provided for semiconductor device manufacturing The second method includes the steps of (1) providing a semiconductor device manufacturing system having (a) an epitaxial chamber adapted to form an epitaxial material layer on a surface of a substrate; and (b) a plasma generator coupled to the epitaxial chamber and adapted to introduce plasma to the epitaxial chamber; and (2) employing the semiconductor device manufacturing system to form the epitaxial material layer on the substrate. Numerous other aspects are provided in accordance with these and other aspects of the invention.  
      Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       FIG. 1  is a block diagram of a semiconductor device manufacturing system including a plasma generator coupled to an epitaxial chamber in accordance with an embodiment of the present invention.  
       FIG. 2  is a block diagram of the semiconductor device manufacturing system of  FIG. 1  including a high-temperature epitaxial chamber in accordance with an embodiment of the present invention.  
       FIG. 3  is a block diagram of the semiconductor device manufacturing system of  FIG. 2  in which the high-temperature epitaxial chamber includes at least one heating module above and at least one heating module below a substrate support in accordance with an embodiment of the present invention.  
       FIG. 4  is a block diagram of the semiconductor device manufacturing system of  FIG. 1  including a low-temperature epitaxial chamber in accordance with an embodiment of the present invention.  
       FIG. 5  is a block diagram of the semiconductor device manufacturing system of  FIG. 4  in which the low-temperature epitaxial chamber includes a heating module below a substrate support in accordance with an embodiment of the present invention.  
       FIG. 6  illustrates a method of preparing a substrate surface for epitaxial film formation in accordance with an embodiment of the present invention.  
       FIG. 7  illustrates a method of epitaxial film formation in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION  
      The present invention provides methods and apparatus for manufacturing semiconductor devices. More specifically, the present invention provides a semiconductor device manufacturing system including an epitaxial chamber coupled to a plasma generator adapted to introduce plasma to the epitaxial chamber. Further, the present invention provides methods and apparatus for cleaning a surface of a substrate prior to forming an epitaxial layer on the substrate. Additionally, the present invention provides methods and apparatus for forming an epitaxial layer on the substrate.  
       FIG. 1  is a block diagram of a semiconductor device manufacturing system  101  including a plasma generator  103  coupled to an epitaxial chamber  105  in accordance with an embodiment of the present invention. The plasma generator  103  may be adapted to introduce plasma to the epitaxial chamber  105 . For example, the plasma generator  103  may include and/or be coupled to a microwave cavity (not shown). Further, the plasma generator  103  may include and/or be coupled to a microwave generator (not shown) coupled to the microwave cavity. The plasma generator  103  may receive a gas such as hydrogen or the like from a gas supply  107  and generate a plasma  109  based on the gas. The plasma  109  may be output from the plasma generator  103  into the epitaxial chamber  105 .  
      In some embodiments, the plasma generator  103  may be a remote plasma generator or inductively coupled to the epitaxial chamber  105  although other configurations may be used. The plasma generator  103  may be adapted to create a plasma comprising ionized H 2  (e.g., H 2   + ) species, although a plasma comprising different species, ions and/or radicals may be employed. For example, deposition gases for use during epitaxial layer formation such as source gases, etchant gases, dopant gases, etc., also may be supplied from the plasma generator  103  (as described below) or otherwise supplied to the epitaxial chamber  105 . In one or more embodiments, the plasma generator  103  may be adapted to produce a large area of plasma  109  having a uniform density, which may enable a substantially uniform epitaxial layer to be formed during subsequent processing.  
      The plasma generator  103  may be similar to the reaction chamber of U.S. Pat. No. 6,450,116, issued Sep. 17, 2002, entitled “Apparatus For Exposing a Substrate to Plasma Radicals”, which is hereby incorporated by reference herein in its entirety. However, a plasma generator  103  of a different configuration may be employed.  
      The epitaxial chamber  105  may be adapted to clean a surface of a substrate (not shown) included therein before forming an epitaxial layer on the substrate. For example, the epitaxial chamber  105  may expose the substrate (and plasma  109  introduced to the chamber  105 ) to a variety of process parameters (e.g., temperature, pressure, etc.) as described, for example, further below with reference to  FIG. 6  such that a surface of the substrate may be cleaned. Further, the epitaxial chamber  105  may be adapted to form an epitaxial layer on the substrate (as described, for example, with reference to  FIG. 7 ). The epitaxial chamber  105  may output unwanted gasses and/or byproducts via an exhaust or pump  111 .  
      The epitaxial chamber  105  may include a plasma-exciting apparatus  113 , such as one or more coils, positioned outside a vacuum portion  115  of the chamber  105  (e.g., in addition to or in place of the plasma generator  103 ). The plasma-exciting apparatus  113  may be formed from metal or another suitable material and the vacuum portion  115  of the chamber  105  may comprise quartz or another suitable material. Placing components of the plasma-exciting apparatus  113  (e.g., metal components) outside the vacuum portion  115  of the chamber  105  may prevent the components from contaminating the chamber  105  and/or any substrates processed with the chamber  105 .  
      Details of a first exemplary epitaxial chamber  105  that may be included in the semiconductor device manufacturing system  101  are described below with reference to  FIGS. 2-3  and details of a second exemplary epitaxial chamber  105  that may be included in the semiconductor device manufacturing system  101  are described below with reference to  FIGS. 4-5 .  
       FIG. 2  is a block diagram of the semiconductor device manufacturing system  101  of  FIG. 1  including a high-temperature epitaxial chamber  201  in accordance with an embodiment of the present invention. With reference to  FIG. 2 , the high-temperature epitaxial chamber  201  may include a substrate holder  203  (e.g., susceptor) adapted to support a substrate  205 . The high-temperature epitaxial chamber  201  may be adapted to receive plasma output from the plasma generator  103  and expose the plasma and the substrate  205  to a desired temperature such that a surface of the substrate  205  is cleaned.  
       FIG. 3  is a block diagram of the semiconductor device manufacturing system  101  of  FIG. 2  in which the high-temperature epitaxial chamber  201  includes at least one lower heating module  301  (such as an infrared lamp or lamp array or another radiant heat source, only one shown) below the substrate holder  203  and at least one upper heating module  303  (such as an infrared lamp or lamp array or another radiant heat source, only one shown) above the substrate holder  203 . The high-temperature epitaxial chamber  201  may employ the lower heating module  301  and upper heating module  303  to heat the substrate  205  to a desired temperature while exposing the substrate to a cleaning species such as a hydrogen plasma. In some embodiments, a substrate temperature of less than about 700° C., and more preferably between about 400° C. and 600° C. may be employed to clean the surface of the substrate  205  (although a larger or smaller and/or different temperature range may be employed). Use of ionized hydrogen species may reduce the temperature required to remove oxygen, organics, halogens and/or other contaminants from the substrate  205 . Thereafter, an epitaxial layer may be formed on the clean surface of the substrate (as described below).  
      In some embodiments, the high-temperature epitaxial chamber  201  may be similar to the thermal reactor of U.S. Pat. No. 5,108,792, issued Apr. 28, 1992, entitled “Double-Dome Reactor For Semiconductor Processing”, which is hereby incorporated by reference herein in its entirety. However, a high-temperature epitaxial chamber  201  of a different configuration may be employed.  
      In contrast,  FIG. 4  is a block diagram of the semiconductor device manufacturing system  101  of  FIG. 1  including a low-temperature epitaxial chamber  401  in accordance with an embodiment of the present invention. With reference to  FIG. 4 , similar to the high-temperature epitaxial chamber  201 , the low-temperature epitaxial chamber  401  may include the substrate holder  203  (e.g., susceptor) adapted to support substrate  205 . The low-temperature epitaxial chamber  401  may be adapted to receive plasma output from the plasma generator  103  and expose the plasma and the substrate to a low temperature to clean a surface of the substrate  205 . For example,  FIG. 5  is a block diagram of the semiconductor device manufacturing system  101  of  FIG. 4  in which the low-temperature epitaxial chamber  401  includes at least one heating module  501  positioned below the substrate support  203  in accordance with an embodiment of the present invention. The low-temperature epitaxial chamber  401  may employ the lower heating module  501  to heat the substrate  205  to a desired temperature while exposing the substrate  205  to a cleaning species such as a hydrogen plasma. In some embodiments, a substrate temperature of less than about 700° C., and more preferably between about 400° C. and 600° C. may be employed to clean the surface of the substrate  205  (although a larger or smaller and/or different temperature range may be employed). Use of ionized hydrogen species may reduce the temperature required to remove oxygen, organics, halogens and/or other contaminants from the substrate  205 . Thereafter, an epitaxial layer may be formed on the clean surface of the substrate (as described below).  
      In some embodiments, the low-temperature epitaxial chamber  401  may be similar to the chamber of U.S. Pat. No. 6,455,814, issued Sep. 24, 2002, entitled “Backside Heating Chamber For Emissivity Independent Thermal Processes”, which is hereby incorporated by reference herein in its entirety. However, a low-temperature epitaxial chamber  401  of a different configuration may be employed.  
      The plasma generator  103  may be coupled (e.g., inductively) to any suitable chamber, such as a preclean chamber. For example, the plasma generator  103  may be coupled to an EpiClean chamber, which is manufactured by the assignee of the present application, Applied Materials, Inc. of Santa Clara, Calif. The EpiClean chamber may be adapted to heat a substrate from a lower side of the substrate. Further, the EpiClean chamber may be adapted to operate at pressures of less than about 5 Torr (e.g., by using a pump, such as a turbo pump). Alternatively, a semiconductor device manufacturing system including a remote plasma generator coupled to an epitaxial chamber may be employed. For example, a remote plasma generator may be coupled to the high-temperature epitaxial chamber  201 , low-temperature epitaxial chamber  401 , or the like.  
      An exemplary cleaning operation that may be performed within the semiconductor device manufacturing system  101  is now described with reference to  FIG. 6  which illustrates a method  600  of preparing a substrate surface for epitaxial layer formation in accordance with an embodiment of the present invention. With reference to  FIG. 6 , in step  601 , the method  600  begins. In step  602 , a substrate is loaded into the epitaxial chamber  105  of the semiconductor device manufacturing system  101 . In step  603 , the substrate is heated to a desired temperature. For example, the substrate may be heated to a temperature of less than about 700° C., preferably about 400° C. to about 600° C. (although a larger or smaller and/or different temperature range may be employed). In step  604 , the plasma generator  103  is employed to generate and supply a plasma to the epitaxial chamber  105 . For example, a hydrogen plasma may be generated and supplied to the epitaxial chamber  105 . Other reactive species may be similarly employed. Thereafter in step  605 , the substrate is cleaned using the plasma. In this manner, a surface of the substrate may be cleaned (e.g., pre-cleaned) before additional processing, such as forming an epitaxial layer on the substrate, which may require a clean substrate surface. Use of ionized hydrogen species may reduce the temperature required to remove oxygen, organics, halogens and/or other contaminants from the substrate.  
      In step  606 , the method  600  of  FIG. 6  ends. Through use of the present methods and apparatus a surface of a substrate in an epitaxial chamber may be cleaned, preferably at a low temperature through use of a plasma. Consequently, contaminants may be removed from a surface of the substrate. In this manner, the present methods and apparatus may clean a substrate surface while avoiding high temperatures, which may adversely affect processing of semiconductor devices on the substrate. A method similar to the method  600  of  FIG. 6  may be employed with a preclean chamber, such as an EpiClean chamber, which is manufactured by the assignee of the present application, Applied Materials, Inc. of Santa Clara, Calif.  
       FIG. 7  illustrates a method  700  of epitaxial film formation in accordance with an embodiment of the present invention. With reference to  FIG. 7 , in step  701 , the method  700  begins. In step  702 , a substrate is loaded into the epitaxial chamber  105  of the semiconductor device manufacturing system  101 . In step  703 , the substrate is cleaned. For example, the substrate may be cleaned using the method  600  of  FIG. 6 , or via any other known method. In step  704 , the substrate is heated to a desired temperature. For example, the substrate may be heated to a temperature of between about 200° C. and 700° C., although other temperatures may be used. In step  705 , a plasma is generated using the plasma generator  103 . For example, a plasma that includes one or more of a carrier gas, etchant gas, silicon source, dopant source, and/or the like may be generated and supplied to the epitaxial chamber.  
      Exemplary source materials useful in the deposition gas to deposit silicon-containing compounds include silanes, halogenated silanes and organosilanes. Silanes include silane (SiH 4 ) and higher silanes with the empirical formula Si x H (2x+2) , such as disilane (Si 2 H 6 ), trisilane (Si 3 H 8 ), and tetrasilane (Si 4 H 10 ), as well as others. Halogenated silanes include compounds with the empirical formula X′ y Si x H (2x+2−y) , where X′=F, Cl, Br or I, such as hexachlorodisilane (Si 2 Cl 6 ), tetrachlorosilane (SiCl 4 ), dichlorosilane (Cl 2 SiH 2 ) and trichlorosilane (Cl 3 SiH). Organosilanes include compounds with the empirical formula R y Si x H (2x+2−y) , where R=methyl, ethyl, propyl or butyl, such as methylsilane ((CH 3 )SiH 3 ), dimethylsilane ((CH 3 ) 2 SiH 2 ), ethylsilane ((CH 3 CH 2 )SiH 3 ), methyldisilane ((CH 3 )Si 2 H 5 ), dimethyldisilane ((CH 3 ) 2 Si 2 H 4 ) and hexamethyldisilane ((CH 3 ) 6 Si 2 ). Organosilane compounds have been found to be advantageous silicon sources as well as carbon sources in embodiments which incorporate carbon in the deposited silicon-containing compound. The preferred silicon sources include silane, dichlorosilane and disilane.  
      The deposition gas may contain at least a silicon source and a carrier gas, and may contain at least one secondary elemental source, such as a germanium source and/or a carbon source. Also, the deposition gas may further include a dopant compound to provide a source of a dopant, such as boron, arsenic, phosphorous, gallium and/or aluminum. In an alternative embodiment, the deposition gas may include at least one etchant, such as hydrogen chloride or chlorine.  
      Germanium sources useful to deposit silicon-containing compounds include germane (GeH 4 ), higher germanes and organogermanes. Higher germanes include compounds with the empirical formula Ge x H (2x+2) , such as digermane (Ge 2 H 6 ), trigermane (Ge 3 H 8 ) and tetragermane (Ge 4 H 10 ), as well as others. organogermanes include compounds such as methylgermane ((CH 3 )GeH 3 ), dimethylgermane ((CH 3 ) 2 GeH 2 ), ethylgermane ((CH 3 CH 2 )GeH 3 ), methyldigermane ((CH 3 )Ge 2 H 5 ), dimethyldigermane ((CH 3 ) 2 Ge 2 H 4 ) and hexamethyldigermane ((CH 3 ) 6 Ge 2 ).  
      Carbon sources useful to deposit silicon-containing compounds include organosilanes, alkyls, alkenes and alkynes of ethyl, propyl and butyl. Such carbon sources include methylsilane (CH 3 SiH 3 ), dimethylsilane ((CH 3 ) 2 SiH 2 ), ethylsilane (CH 3 CH 2 SiH 3 ), methane (CH 4 ), ethylene (C 2 H 4 ), ethyne (C 2 H 2 ) propane (C 3 H 8 ), propene (C 3 H 6 ), butyne (C 4 H 6 ), as well as others.  
      Boron-containing dopants useful as a dopant source include boranes and organoboranes. Boranes include borane, diborane (B 2 H 6 ), triborane, tetraborane and pentaborane, while alkylboranes include compounds with the empirical formula R x BH (3−x) , where R=methyl, ethyl, propyl or butyl and x=1, 2 or 3. Alkylboranes include trimethylborane ((CH 3 ) 3 B), dimethylborane ((CH 3 ) 2 BH), triethylborane ((CH 3 CH 2 ) 3 B) and diethylborane ((CH 3 CH 2 ) 2 BH). Dopants may also include arsine (AsH 3 ), phosphine (PH 3 ) and alkylphosphines, such as with the empirical formula R x PH( 3−x) , where R=methyl, ethyl, propyl or butyl and x=1, 2 or 3. Alkylphosphines include trimethylphosphine ((CH 3 ) 3 P), dimethylphosphine ((CH 3 ) 2 PH), triethylphosphine ((CH 3 CH 2 ) 3 P) and diethylphosphine ((CH 3 CH 2 ) 2 PH). Aluminum and gallium dopant sources may include alkylated and/or halogenated derivates, such as described with the empirical formula R x MX (3−x) , where M=Al or Ga, R=methyl, ethyl, propyl or butyl, X=Cl or F and x=0, 1, 2 or 3. Examples of aluminum and gallium dopant sources include trimethylaluminum (Me 3 Al), triethylaluminum (Et 3 Al), dimethylaluminumchloride (Me 2 AlCl), aluminum chloride (AlCl 3 ), trimethylgallium (Me 3 Ga), triethylgallium (Et 3 Ga), dimethylgalliumchloride (Me 2 GaCl) and gallium chloride (GaCl 3 )  
      In step  706 , an epitaxial layer is formed on the substrate. Different process and/or operational parameters may be employed based on chemistries employed to form the epitaxial layer. For example, the semiconductor device manufacturing system  101  may form an epitaxial layer of silicon, silicon germanium and/or another suitable semiconductor material on a surface of a substrate by using an RF-excited low-energy plasma at temperatures from about 200° C. to about 700° C. The semiconductor device manufacturing system  101  may excite the plasma inductively or by another suitable method using a source having a frequency of about 10 MHz to about 10 GHz (although a larger or smaller and/or different frequency range may be employed). In some embodiments, the semiconductor device manufacturing system  101  may be adapted such that an electron kinetic energy of the plasma is less than about 15 V (although a larger or smaller and/or different kinetic energy range may be employed).  
      In step  707 , the method  700  of  FIG. 7  ends. Through use of the present methods and apparatus an epitaxial layer may be formed on a surface of a substrate using a low-energy plasma. When an RF plasma is employed in accordance with the present invention, use of the RF plasma may avoid substrate contamination by metal components associated with convention DC plasma systems. The present methods and apparatus may be employed to create silicon-on-insulator substrates and/or substrates employed for optical applications. Further, because the present methods and apparatus employ plasma to form (e.g., dissociate and deposit) an epitaxial layer of one or more materials on a substrate rather than a thermal source, the epitaxial layer may be formed using a lower temperature.  
      Through use of the present invention, a wide pressure range may be employed for epitaxial layer formation. Different plasma frequencies may be used for different chemistries, and a large area uniform density plasma may be formed (e.g., for uniform deposition).  
      The foregoing description discloses only exemplary embodiments of the invention. Modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, in the embodiments above, each high-temperature epitaxial chamber includes at least one lower heating module  301  below the substrate holder  203  and/or at least one upper heating module  303  above the substrate holder  203 . Any number of such heating modules may be employed.  
      Accordingly, while the present invention has been disclosed in connection with exemplary embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.