Thermal gradient enhanced CVD deposition at low pressure

Abstract

A method wherein a thermal gradient over a substrate enhances Chemical Vapor Deposition (CVD) at low pressures. An upper heat source is positioned above the substrate and a lower heat source is positioned below the substrate. The upper and lower heat sources are operated to raise the substrate temperature to 400-700° and cause a heat gradient of 100-200° C. between the upper and lower heat sources. This heat gradient causes an increase in the deposition rate for a given reactant gas flow rate and chamber pressure. The preferred parameters for implementation of the present invention for poly crystalline silicon deposition include the temperature of the upper heat source 100-200° C. above the lower heat source, a substrate temperature in the range of 400-700° C., a reactant gas pressure between 250 and 1000 mTorr, and a gas flow rate of 200-800 sccm. The substrate is rotated, with 5 RPM being a typical rate. A deposition rate of 2000 angstroms per minute deposition of poly crystalline silicon is achieved with a 200° C. temperature differential, substrate temperature of 650° C., pressure of 250 mTorr and silane flow of 500 sccm.

1 - 12 . (Cancelled)  
     
     
         13 : An apparatus for depositing materials onto a wafer, comprising: a wafer carrier disposed between first and second thermal plates, and heaters for first and second thermal plates that are controlled to provide a temperature gradient between the first and second thermal plates, wherein the temperature between the first and second thermal plates increases with increasing distance away from the second thermal plate toward the first thermal plate.  
     
     
         14 : The apparatus according to  claim 13  further comprising gas injectors that provide a flow of process gas between the first and second thermal plates.  
     
     
         15 : The apparatus according to  claim 13  wherein the heaters comprise resistance heaters.  
     
     
         16 : The apparatus according to  claim 13  wherein the heaters comprise a first lamp for providing heat to the first thermal plate and a second lamp for providing heat to the second thermal plate.  
     
     
         17 : The apparatus according to  claim 16 , wherein the first lamp supplies a different amount of heat energy than the second lamp.  
     
     
         18 : The apparatus according to  claim 17 , wherein the temperature gradient includes a temperature difference in the range of 100° C. to 200° C. between the first and second thermal plates.  
     
     
         19 : The apparatus according to  claim 13  further comprising gas injectors that provide a flow of process gas between the first and second thermal plates at a flow rate in the range of 200 sccm to 800 sccm.  
     
     
         20 : The apparatus according to  claim 13 , further comprising a deposition chamber in which the wafer carrier and the first and second thermal plates are disposed.  
     
     
         21 : The apparatus according to  claim 20 , wherein the deposition chamber comprises a single wafer deposition chamber.  
     
     
         22 : An apparatus for depositing materials onto a wafer, comprising a wafer carrier disposed between first and second thermal plates, heaters for first and second thermal plates that are controlled to provide a temperature gradient between the first and second thermal plates, and gas injectors that provide a flow of process gas between the first and second thermal plates at a flow rate in the range of 200 sccm to 800 sccm.  
     
     
         23 : The apparatus according to  claim 22 , wherein the gas injectors are temperature controlled.  
     
     
         24 : The apparatus according to  claim 22 , wherein the gas injectors supply process gas over the wafer carrier at a gas velocity in excess of 100 cm/sec.  
     
     
         25 : The apparatus according to  claim 22 , wherein the temperature between the first and second thermal plates increases with increasing distance away from the second thermal plate toward the first thermal plate.  
     
     
         26 : The apparatus according to  claim 25 , wherein the temperature gradient has a magnitude in the range of 50-100° C. per inch.  
     
     
         27 : The apparatus according to  claim 22  wherein the heaters comprise a first lamp for providing heat to the first thermal plate and a second lamp for providing heat to the second thermal plate.  
     
     
         28 : The apparatus according to  claim 27 , wherein the first lamp supplies a different amount of heat energy than the second lamp.  
     
     
         29 : The apparatus according to  claim 28 , wherein the temperature gradient includes a temperature difference in the range of 100° C.-200° C. between the first and second thermal plates.  
     
     
         30 : The apparatus according to  claim 22 , further comprising a deposition chamber in which the wafer carrier and the first and second thermal plates are disposed.  
     
     
         31 : The apparatus according to  claim 30 , wherein the deposition chamber comprises a single wafer deposition chamber.  
     
     
         32 : The apparatus according to  claim 22  wherein the heaters comprise resistance heaters.