Process and apparatus for cleaning a silicon surface

Abstract

A low pressure-high hydrogen flow rate process of cleaning a silicon wafer surface is described. The combination of process pressures below about 1 Torr with hydrogen flow rates up to about 3 SLM has been found to remove substantially all oxygen contamination from the silicon wafer surface at process temperatures less than about 800° C. without the use of a reactive gas. After processing at such process pressures and flow rates, even lower levels of oxygen contamination may be achieved by then increasing the process pressure, the hydrogen flow rate, and the process temperature, though the process temperature still remains less than 800° C. The combination of low pressure and high hydrogen flow rate can be achieved using a vacuum pumping speed of at least 30 cubic meters per hour. The present invention also describes an apparatus for cleaning a silicon wafer surface in which the processes of the present invention and other processes can be practiced.

What is claimed is:  
     
         1 . A process for cleaning a surface of a silicon wafer in a chamber, the process comprising: 
 first transferring the silicon wafer into the chamber;    evacuating the chamber to a process pressure of less than about 1 Torr;    while maintaining the process pressure, flowing hydrogen gas across the surface of the silicon wafer;    heating the silicon wafer to a process temperature of not higher than about 800° C.; and    maintaining the silicon wafer at the process pressure and at the process temperature while flowing hydrogen gas across the surface.    
     
     
         2 . The process according to  claim 1 , wherein the silicon wafer is transferred into the chamber at a temperature less than the process temperature.  
     
     
         3 . The process according to  claim 1 , wherein the silicon wafer is transferred into the chamber at a temperature between about 450° C. and about 600° C.  
     
     
         4 . The process according to  claim 1 , wherein the silicon wafer is transferred into the chamber at a temperature of about 550° C.  
     
     
         5 . The process according to  claim 1 , wherein the process pressure is between about 0.1 Torr and about 1 Torr.  
     
     
         6 . The process according to  claim 1 , wherein the process pressure is between about 0.2 Torr and about 0.5 Torr.  
     
     
         7 . The process according to  claim 1 , wherein hydrogen gas is flowed at a rate of between about 0.03 SLM and about 3 SLM.  
     
     
         8 . The process according to  claim 1 , wherein hydrogen gas is flowed at a rate of about 0.3 SLM.  
     
     
         9 . The process according to  claim 1 , further comprising maximizing the flow of hydrogen gas across the surface while maintaining the process pressure at less than about 1 Torr.  
     
     
         10 . The process according to  claim 1 , wherein the process pressure is maintained while flowing hydrogen gas using a pumping speed of at least about 30 cubic meters per hour.  
     
     
         11 . The process according to  claim 1 , wherein the process pressure is maintained while flowing hydrogen gas using a pumping speed between about 30 and about 200 cubic meters per hour.  
     
     
         12 . The process according to  claim 1 , wherein the process pressure is maintained while flowing hydrogen gas using a pumping speed of about 100 cubic meters per hour.  
     
     
         13 . The process according to  claim 1 , wherein the process temperature is between about 700° C. and about 800° C.  
     
     
         14 . The process according to  claim 1 , wherein the process temperature is between about 750° C. and about 775° C.  
     
     
         15 . The process according to  claim 1 , wherein the silicon wafer is maintained at the process pressure and at the process temperature while flowing hydrogen gas across the surface for less than about 5 minutes.  
     
     
         16 . The process according to  claim 1 , wherein the silicon wafer is maintained at the process pressure and at the process temperature while flowing the hydrogen gas across the surface until substantially all interfacial oxygen contamination is removed from the surface.  
     
     
         17 . The process according to  claim 1 , wherein evacuating the chamber occurs prior to heating the silicon wafer.  
     
     
         18 . The process according to  claim 1 , wherein flowing hydrogen gas occurs prior to heating the silicon wafer.  
     
     
         19 . The process according to  claim 1 , wherein the process pressure comprises a partial pressure of water and oxygen of less than about 10 μTorr.  
     
     
         20 . The process according to  claim 1 , wherein the process pressure comprises a partial pressure of water and oxygen of between about 1 μTorr to about 5 μTorr.  
     
     
         21 . A process for cleaning a surface of a silicon wafer in a chamber, the process comprising: 
 first transferring the silicon wafer into the chamber;    evacuating the chamber to a first process pressure of less than about 1 Torr;    while maintaining the first process pressure, flowing hydrogen gas across the surface of the silicon wafer at a first flow rate;    heating the silicon wafer to a first process temperature of not higher than about 800° C.;    maintaining the silicon wafer at the first process pressure and at the first process temperature while flowing hydrogen gas at the first flow rate across the surface; then    increasing the first process pressure to a second process pressure of greater than about 1 Torr;    increasing the flow of hydrogen gas across the surface of the silicon wafer from the first flow rate to a second flow rate while maintaining the second process pressure;    increasing the first process temperature to a second process temperature, the second process temperature still being not higher than about 800° C.; and    maintaining the silicon wafer at the second process pressure and the second process temperature while flowing hydrogen gas at the second flow rate across the surface.    
     
     
         22 . The process according to  claim 21 , wherein the second process pressure is between about 10 Torr and about 100 Torr.  
     
     
         23 . The process according to  claim 21 , wherein the second flow rate is greater than about 3 SLM.  
     
     
         24 . The process according to  claim 21 , wherein the second flow rate is between about 10 SLM and about 50 SLM.  
     
     
         25 . The process according to  claim 21 , wherein the first process temperature is not higher than about 770° C.  
     
     
         26 . The process according to  claim 21 , wherein the second process temperature is between about 775° C. and about 800° C.  
     
     
         27 . The process according to  claim 21 , wherein the silicon wafer is maintained at the first process pressure and at the first process temperature while flowing hydrogen gas at the first flow rate across the surface for less than about 3 minutes, and 
 wherein the silicon wafer is maintained at the second process pressure and at the second process temperature while flowing hydrogen gas at the second flow rate across the surface for less than about 3 minutes.    
     
     
         28 . A process for cleaning a surface of a silicon wafer in a chamber, the process comprising: 
 first transferring the silicon wafer into the chamber at a transfer temperature of less than about 600° C.;    evacuating the chamber to a first process pressure of less than about 1 Torr;    flowing hydrogen gas across the surface of the silicon wafer at a first flow rate of up to about 3 SLM while maintaining the first process pressure;    heating the silicon wafer to a first process temperature of not higher than about 770° C.;    maintaining the silicon wafer at the first process pressure and at the first process temperature while flowing hydrogen gas across the surface at the first flow rate for less than about 3 minutes; then    increasing the first process pressure to a second process pressure of between about 10 Torr and about 100 Torr;    increasing the flow of hydrogen gas across the surface of the silicon wafer from the first flow rate to a second flow rate of between about 10 SLM and about 50 SLM;    increasing the first process temperature to a second process temperature, the second process temperature being not higher than about 800° C.; and    maintaining the silicon wafer at the second process pressure and the second process temperature while flowing hydrogen gas at the second flow rate across the surface for not more than about 3 minutes.    
     
     
         29 . The process according to  claim 28 , wherein the first process pressure is between about 0.1 Torr and about 1 Torr.  
     
     
         30 . The process according to  claim 28 , wherein the first process pressure is between about 0.2 Torr and about 0.5 Torr.  
     
     
         31 . The process according to  claim 28 , wherein the first flow rate is between about 0.03 SLM and about 3 SLM.  
     
     
         32 . The process according to  claim 28 , wherein the first flow rate is about 0.3 SLM.  
     
     
         33 . The process according to  claim 28 , wherein the first process temperature is between about 700° C. and about 770° C.  
     
     
         34 . The process according to  claim 28 , wherein evacuating the chamber occurs prior to heating the silicon wafer.  
     
     
         35 . The process according to  claim 28 , wherein flowing hydrogen gas occurs prior to heating the silicon wafer.  
     
     
         36 . The process according to  claim 28 , wherein the second process pressure is about 25 Torr.  
     
     
         37 . The process according to  claim 28 , wherein the second flow rate is about 20 SLM.  
     
     
         38 . The process according to  claim 28 , wherein the first process temperature is about 750° C. and the second process temperature is about 780° C.  
     
     
         39 . The process according to  claim 28 , wherein the second process temperature is between about 775° C. and about 800° C.  
     
     
         40 . The process according to  claim 28 , wherein the silicon wafer is maintained at the first process pressure and at the first process temperature while flowing hydrogen gas at the first flow rate across the surface for about 1 minute.  
     
     
         41 . The process according to  claim 28 , wherein the silicon wafer is maintained at the second process pressure and at the second process temperature while flowing hydrogen gas at the second flow rate across the surface for about 1 minute.  
     
     
         42 . An apparatus for cleaning a surface of a silicon wafer, the silicon wafer having a first surface corresponding to the surface to be cleaned and a second surface, the apparatus comprising: 
 a housing having: 
 a chamber defined by surfaces comprised of quartz;  
 a reflector positioned outside the chamber;  
 a susceptor positioned within the chamber and configured to accommodate the silicon wafer such that the first surface faces the reflector;  
 an inlet port; and  
 a vacuum port positioned opposite the inlet port such that a gas introduced from the inlet port flows across the first surface towards the vacuum port; and  
   a heater configured to radiate heat towards only the second surface of the silicon wafer.    
     
     
         43 . The apparatus according to  claim 42 , wherein the surfaces defining the chamber comprise a low outgassing quartz.  
     
     
         44 . The apparatus according to  claim 42 , wherein the surfaces defining the chamber comprise an infrared-transparent quartz.  
     
     
         45 . The apparatus according to  claim 42 , wherein the surfaces defining the chamber comprise an upper quartz dome, a lower quartz dome, and a quartz lining.  
     
     
         46 . The apparatus according to  claim 42 , wherein the second surface of the silicon wafer is in contact with the susceptor, and the susceptor transfers heat from the heater to the silicon wafer.  
     
     
         47 . The apparatus according to  claim 42 , wherein the heater comprises one lamp module positioned outside the chamber.  
     
     
         48 . The apparatus according to  claim 42 , wherein the heater comprises a plurality of lamps positioned outside the chamber.  
     
     
         49 . The apparatus according to  claim 42 , further comprising a vacuum system connected with the vacuum port.  
     
     
         50 . The apparatus according to  claim 49 , wherein the vacuum system comprises a high-speed vacuum pump.  
     
     
         51 . The apparatus according to  claim 49 , wherein the vacuum system comprises a point-of-use pump connected with the vacuum port via a 2-inch diameter vacuum line.  
     
     
         52 . The apparatus according to  claim 42 , wherein the reflector comprises a gold plating.  
     
     
         53 . The apparatus according to  claim 42 , wherein the susceptor is configured to be able to rotate the silicon wafer.  
     
     
         54 . The apparatus according to  claim 42 , wherein the inlet port defines a slit such that gas introduced through the inlet port flows across the first surface in a plane.  
     
     
         55 . A computer-readable medium having stored thereon instructions to direct operation of a cleaning apparatus, the instructions comprising: 
 first transferring a silicon wafer into a chamber;    evacuating the chamber to a process pressure of less than about 1 Torr;    while maintaining the process pressure, flowing hydrogen gas across a surface of the silicon wafer;    heating the silicon wafer to a process temperature of not higher than about 800° C.; and    maintaining the silicon wafer at the process pressure and at the process temperature while flowing hydrogen gas across the surface.    
     
     
         56 . A computer-readable medium having stored thereon instructions to direct operation of a cleaning apparatus, the instructions comprising: 
 first transferring a silicon wafer into a chamber;    evacuating the chamber to a first process pressure of less than about 1 Torr;    while maintaining the first process pressure, flowing hydrogen gas across a surface of the silicon wafer at a first flow rate;    heating the silicon wafer to a first process temperature of not higher than about 800° C.;    maintaining the silicon wafer at the first process pressure and at the first process temperature while flowing hydrogen gas at the first flow rate across the surface; then    increasing the first process pressure to a second process pressure of greater than about 1 Torr;    increasing the flow of hydrogen gas across the surface of the silicon wafer from the first flow rate to a second flow rate while maintaining the second process pressure;    increasing the first process temperature to a second process temperature, the second process temperature still being not higher than about 800° C.; and    maintaining the silicon wafer at the second process pressure and the second process temperature while flowing hydrogen gas at the second flow rate across the surface.    
     
     
         57 . A computer-readable medium having stored thereon instructions to direct operation of a cleaning apparatus, the instructions comprising: 
 first transferring the silicon wafer into the chamber at a transfer temperature of less than about 600° C.;    evacuating the chamber to a first process pressure of less than about 1 Torr;    flowing hydrogen gas across the surface of the silicon wafer at a first flow rate of up to about 3 SLM while maintaining the first process pressure;    heating the silicon wafer to a first process temperature of not higher than about 770° C.;    maintaining the silicon wafer at the first process pressure and at the first process temperature while flowing hydrogen gas across the surface at the flow rate for less than about 3 minutes; then    increasing the first process pressure to a second process pressure of between about 10 Torr and about 100 Torr;    increasing the flow of hydrogen gas across the surface of the silicon wafer from the first flow rate to a second flow rate of between about 10 SLM and about 50 SLM;    increasing the first process temperature to a second process temperature, the second process temperature being not higher than about 800° C.; and    maintaining the silicon wafer at the second process pressure and the second process temperature while flowing hydrogen gas at the second flow rate across the surface for not more than about 3 minutes.