Method for the preparation of an epitaxial silicon wafer with intrinsic gettering

Abstract

This invention is directed to a novel process for the preparation of a silicon wafer comprising a surface having an epitaxial layer deposited thereon. In one embodiment, an epitaxial layer is deposited onto a surface of a silicon wafer. The wafer is also heated to a temperature of at least about 1175° C. This heat treatment begins either during or after the epitaxial deposition. Following the heat treatment, the heated wafer is cooled for a period of time at a rate of at least about 10° C./sec while (a) the temperature of the wafer is greater than about 1000° C., and (b) the wafer is not in contact with a susceptor. In this process, the epitaxial deposition, heating, and cooling are conducted in the same reactor chamber.

We claim:  
     
         1 . A process for the preparation of a silicon wafer comprising a surface having an epitaxial layer deposited thereon, the process comprising: 
 depositing an epitaxial layer onto a surface of a silicon wafer;    heating the wafer to a temperature of at least about 1175° C. during and/or after the epitaxial deposition; and    cooling the heated wafer for a period of time at a rate of at least about 10° C./sec while (a) the temperature of the wafer is greater than about 1000° C., and (b) the wafer is not in contact with a susceptor,    wherein the epitaxial deposition, heating, and cooling are conducted in the same reactor chamber.    
     
     
         2 . The process of  claim 1  wherein the wafer is supported by pins during said cooling.  
     
     
         3 . The process of  claim 1  wherein the susceptor is removed from contact with the wafer before about 2 seconds after said heating is terminated.  
     
     
         4 . The process of  claim 1  wherein the susceptor is removed from contact with the wafer before about 1 second after said heating is terminated.  
     
     
         5 . The process of  claim 1  wherein (a) said reactor chamber comprises a reactor mechanism which requires the susceptor to be in a rotational home position before the susceptor may be removed from contact with the wafer, and (b) the susceptor is in the rotational home position before about 2 seconds after said heating is terminated.  
     
     
         6 . The process of  claim 1  wherein (a) said reactor chamber comprises a reactor mechanism which requires the susceptor to be in a rotational home position before the susceptor may be removed from contact with the wafer, and (b) the susceptor is in the rotational home position when said heating is terminated.  
     
     
         7 . The process of  claim 1  wherein said cooling rate is at least about 20° C./sec.  
     
     
         8 . The process of  claim 1  wherein said cooling rate is at least about 30° C./sec.  
     
     
         9 . A process for the preparation of a silicon wafer comprising a surface having an epitaxial layer deposited thereon, the process comprising: 
 depositing an epitaxial layer onto a surface of a silicon wafer,    heating the wafer to a temperature of at least about 1175° C. during and/or after the epitaxial deposition, and    cooling the heated wafer at a rate of at least about 10° C./sec for a period of time while the temperature of the wafer is greater than about 1000° C.,    wherein the epitaxial deposition, heating, and cooling are conducted in the same reactor chamber; and the surface of the wafer at the beginning of the epitaxial deposition has an average light scattering event concentration of at least about 0.5/cm 2 , as measured by a laser-based auto inspection tool configured to detect light scattering events corresponding to polystyrene spheres having diameters of no less than about 0.12 μm.    
     
     
         10 . The process of  claim 9  wherein the wafer has an oxygen concentration of no greater than about 18 ppma.  
     
     
         11 . The process of  claim 9  wherein the wafer is in contact with a susceptor during at least a portion of said heating, but not during at least a portion of said cooling.  
     
     
         12 . The process of  claim 9  wherein the wafer is supported by pins during at least a portion of said cooling.  
     
     
         13 . The process of  claim 9  further comprising heating the surface of the wafer in an atmosphere consisting essentially of no oxidants to remove a silicon oxide layer from the surface before the epitaxial deposition.  
     
     
         14 . The process of  claim 13  wherein the epitaxial deposition begins no greater than about 30 seconds after the silicon oxide layer is removed.  
     
     
         15 . The process of  claim 13  wherein the epitaxial deposition begins from about 5 to about 15 seconds after the silicon oxide layer is removed.  
     
     
         16 . The process of  claim 13  wherein the surface of the wafer is heated to at least about 1100° C. to remove the silicon oxide layer, and the epitaxial deposition begins no greater than about 30 seconds after the surface of the wafer reaches about 1100° C.  
     
     
         17 . The process of  claim 13  wherein the surface of the wafer is heated to at least about 1100° C. to remove the silicon oxide layer, and the epitaxial deposition begins from about 5 to about 15 seconds after the surface of the wafer reaches about 1100° C.  
     
     
         18 . The process of  claim 13  wherein the surface of the wafer is heated to at least about 1150° C. to remove the silicon oxide layer, and the epitaxial deposition begins no greater than about 30 seconds after the surface of the wafer reaches about 1150° C.  
     
     
         19 . The process of  claim 13  wherein the surface of the wafer is heated to at least about 1150° C. to remove the silicon oxide layer, and the epitaxial deposition begins from about 5 to about 15 seconds after the surface of the wafer reaches about 1150° C.  
     
     
         20 . The process of  claim 9  wherein said heating begins after the epitaxial deposition ends.  
     
     
         21 . The process of  claim 9  wherein said heating begins within about 2 seconds after the epitaxial deposition ends.  
     
     
         22 . The process of  claim 9  wherein the wafer has a temperature which is at least about 1175° C. during at least a portion of the epitaxial deposition.  
     
     
         23 . The process of  claim 9  wherein the wafer has a temperature which is greater than about 1200° C. during at least a portion of the epitaxial deposition.  
     
     
         24 . The process of  claim 9  wherein said cooling rate is at least about 20° C./sec.  
     
     
         25 . The process of  claim 9  wherein said cooling rate is at least about 30° C./sec.  
     
     
         26 . The process of  claim 9  wherein the wafer is cooled from about 1175 to about 1000° C. at an average rate of at least about 20° C./sec during said cooling.  
     
     
         27 . The process of  claim 9  wherein the wafer is cooled from about 1175 to about 1000° C. at an average rate of at least about 30° C./sec during said cooling.  
     
     
         28 . A process for the preparation of a silicon wafer comprising a surface having an epitaxial layer deposited thereon, the process comprising: 
 depositing an epitaxial layer having a thickness of at least about 0.1 and less than 3 μm onto a surface of a silicon wafer,    heating the wafer to a temperature of at least about 1175° C. during and/or after the epitaxial deposition, and    cooling the heated wafer at a rate of at least about 10°C./sec for a period of time while the temperature of the wafer is greater than about 1000° C.,    wherein the epitaxial deposition, heating, and cooling are conducted in the same reactor chamber.    
     
     
         29 . The process of  claim 28  wherein the epitaxial layer has a thickness of from about 0.25 to about 2 μm.  
     
     
         30 . The process of  claim 28  wherein the epitaxial layer has a thickness of from about 0.65 to about 1 μm.  
     
     
         31 . The process of  claim 28  wherein the wafer is in contact with a susceptor during at least a portion of said heating, but not during at least a portion of said cooling.  
     
     
         32 . The process of  claim 28  wherein the wafer is supported by pins during at least a portion of said cooling.  
     
     
         33 . The process of  claim 28  wherein the wafer has an oxygen concentration of no greater than about 18 ppma.  
     
     
         34 . The process of  claim 28  wherein the surface of the wafer at the beginning of the epitaxial deposition has an average light scattering event concentration of at least about 0.5/cm 2 , as measured by a laser-based auto inspection tool configured to detect light scattering events corresponding to polystyrene spheres having diameters of no less than about 0.12 μm.  
     
     
         35 . The process of  claim 28  wherein said cooling rate is at least about 20° C./sec.  
     
     
         36 . The process of  claim 28  wherein said cooling rate is at least about 30° C./sec.  
     
     
         37 . The process of  claim 28  wherein the wafer is cooled from about 1175 to about 1000° C. at an average rate of at least about 20° C./sec during said cooling.  
     
     
         38 . The process of  claim 28  wherein the wafer is cooled from 1175 about to about 1000° C. at an average rate of at least about 30° C./sec during said cooling.