Method of depositing silicon with high step coverage

Abstract

A method is disclosed for depositing silicon with high deposition rates and good step coverage. The process is performed at high pressures, including close to atmospheric pressures, at temperatures of greater than about 650° C. Silane and hydrogen are flowed over a substrate in a single-wafer chamber. Advantageously, the process maintains good step coverage and high deposition rates (e.g., greater that 50 nn/min) even when dopant gases are added to the process, resulting in commercially practicable rates of deposition for conductive silicon. Despite the high deposition rates, step coverage is sufficient to deposit polysilicon into extremely deep trenches and vias with aspect ratios as high as 40:1, filling such structures without forming voids or keyholes.

1 . A method of depositing a non-epitaxial silicon layer on a substrate within a reaction chamber at a pressure of greater than about 500 Torr, comprising introducing process gases into the reaction chamber and flowing the process gases over the substrate at a desired reaction temperature, with a process gas residence time in the reaction chamber of less than about 100 seconds and a flow rate of 14 slm or more.  
   
   
       2 . The method of  claim 1 , wherein the residence time is less than about 60 seconds.  
   
   
       3 . The method of  claim 2 , wherein the residence time is less than about 20 seconds.  
   
   
       4 . The method of  claim 1 , wherein the pressure is greater than about 700 Torr.  
   
   
       5 . The method of  claim 1 , wherein the reaction chamber comprises a single-wafer horizontal reaction chamber having a constant height above the wafer in a cross-section taken along a gas flow axis.  
   
   
       6 . The method of  claim 5 , wherein the reaction chamber is vertically divided by a horizontal divider plate upstream and downstream of the substrate, the divider plate approximately in the plane of the substrate.  
   
   
       7 . The method of  claim 1 , wherein the process gases comprise monosilane and hydrogen.  
   
   
       8 . The method of  claim 1 , wherein introducing process gases into the reaction chamber fills a hole in the substrate.  
   
   
       9 . The method of  claim 1 , wherein the hole has a width of about 0.25 μm or less.  
   
   
       10 . The method of  claim 9 , wherein the hole has an aspect ratio of greater than about 5:1.  
   
   
       11 . The method of  claim 9 , wherein silicon fills the hole with a step coverage of greater than about 80%.  
   
   
       12 . The method of  claim 1 , wherein the flow rate is about 28 slm or more.  
   
   
       13 . The method of  claim 1 , further comprising flowing a dopant source into the reaction chamber while introducing process gases, thereby in situ doping the silicon layer.  
   
   
       14 . The method of  claim 13 , wherein in situ doping comprises flowing arsine into the reaction chamber.  
   
   
       15 . The method of  claim 1 , wherein the reaction chamber is maintained at about 700° C. or more during introducing process gases into the reaction chamber.  
   
   
       16 . A method of forming a non-epitaxial silicon layer on a substrate, comprising: 
 providing the substrate in a single substrate, laminar flow reaction chamber;    horizontally flowing process gases through the reaction chamber at 14 slm or more thereby depositing the non-epitaxial silicon layer on the substrate, wherein depositing the silicon layer fills a hole in the substrate at a rate of about 50 nm/min or more with a step coverage of about 80% or more, the hole having an aspect ratio of about 5:1 or greater and a width of about 0.25 μm or less; and    maintaining a pressure of about 500 Torr or more in the reaction chamber during depositing the silicon layer.    
   
   
       17 . The method of  claim 16 , wherein horizontally flowing process gases comprises flowing monosilane into the process chamber.  
   
   
       18 . The method of  claim 17 , wherein horizontally flowing comprises inhibiting formation of higher silanes than monosilane.  
   
   
       19 . The method of  claim 18 , wherein inhibiting formation comprises flowing hydrogen into the reaction chamber.  
   
   
       20 . The method of  claim 16 , wherein depositing the silicon layer is performed at about 700° C. or more.  
   
   
       21 . The method of  claim 16 , wherein the pressure is about 700 Torr or more.  
   
   
       22 . The method of  claim 16 , wherein the aspect ratio is about 10:1 or greater.  
   
   
       23 . The method of  claim 22 , wherein the width is about 0.15 μm or less.  
   
   
       24 . The method of  claim 16 , wherein the flow rate is in the range of about 20 slm to 60 slm.  
   
   
       25 . The method of  claim 16 , wherein a residence time of the process gases in the reaction chamber is about 60 seconds or less.