Pecvd deposition of smooth silicon films

Abstract

Smooth silicon films having low compressive stress and smooth tensile silicon films are deposited by plasma enhanced chemical vapor deposition (PECVD) using a process gas comprising a silicon-containing precursor (e.g., silane), argon, and a second gas, such as helium, hydrogen, or a combination of helium and hydrogen. Doped smooth silicon films and smooth silicon germanium films can be obtained by adding a source of dopant or a germanium-containing precursor to the process gas. In some embodiments dual frequency plasma comprising high frequency (HF) and low frequency (LF) components is used during deposition, resulting in improved film roughness. The films are characterized by roughness (Ra) of less than about 7 Å, such as less than about 5 Å as measured by atomic force microscopy (AFM), and a compressive stress of less than about 500 MPa in absolute value. In some embodiments smooth tensile silicon films are obtained.

1 . (canceled) 
     
     
         2 . A method for forming a smooth silicon germanium film on a semiconductor substrate in a plasma-enhanced chemical vapor deposition apparatus, the method comprising:
 supplying a process gas comprising a silicon-containing reactant, a germanium-containing reactant, argon, and a second gas, to the plasma enhanced chemical vapor deposition apparatus; and   forming a plasma in said apparatus to deposit a smooth silicon germanium film on the semiconductor substrate, under conditions configured for depositing a silicon germanium film characterized by roughness (Ra) of less than about 7 Å and a compressive stress of less than about 500 MPa in absolute value, or under conditions configured for depositing a smooth tensile silicon germanium film, characterized by Ra of less than about 7 Å.   
     
     
         2 . The method of  claim 1 , wherein the deposition is performed under conditions configured for depositing a smooth silicon germanium film characterized by Ra of less than about 5 Å, and a compressive stress of less than about 300 MPa in absolute value, or under conditions configured for depositing a smooth tensile silicon film, characterized by Ra of less than about 5 Å. 
     
     
         3 . The method of  claim 1 , wherein the second gas is selected from the group consisting of helium, hydrogen and combinations thereof. 
     
     
         4 . The method of  claim 1 , wherein the silicon-containing reactant is silane, and wherein the process gas comprises less than about 12% by volume of silane. 
     
     
         5 . The method of  claim 4 , wherein the process gas comprises less than about 5% by volume of silane. 
     
     
         6 . The method of  claim 1 , wherein the process gas comprises between about 15-85% by volume of argon. 
     
     
         7 . The method of  claim 1 , comprising forming plasma using both high frequency (HF) and low frequency (LF) plasma generation, wherein the LF power is between about 17-80% of total power. 
     
     
         8 . The method of  claim 1 , wherein the germanium-containing reactant is germane. 
     
     
         9 . The method of  claim 8 , wherein the deposited film is a hardmask. 
     
     
         10 . The method of  claim 9 , wherein the smooth silicon germanium hardmask film is deposited to a thickness of between about 500-10,000 Å. 
     
     
         11 . The method of  claim 1 , wherein the smooth silicon germanium film is deposited in a memory device stack. 
     
     
         12 . The method of  claim 11 , wherein the thickness of the deposited film in a memory device stack is between about 200-800 Å. 
     
     
         13 . The method of  claim 1 , wherein the film is deposited at a temperature of between about 300-650° C. 
     
     
         14 . The method of  claim 1 , wherein the film is deposited at a pressure of between about 1-9 Torr. 
     
     
         15 . The method of  claim 1 , wherein the second gas is selected from the group consisting of helium, hydrogen and combinations thereof, the silicon-containing reactant is silane, and wherein the process gas comprises less than about 12% by volume of silane, the germanium-containing reactant is germane, and wherein the silicon germanium film is deposited at a temperature of between about 300-650° C. and at a pressure of between about 1-9 Torr. 
     
     
         16 . The method of  claim 15 , wherein the silicon germanium film is deposited at a pressure of between about 2-6 Torr. 
     
     
         17 . The method of  claim 15 , wherein depositing the silicon germanium film comprises forming plasma using both high frequency (HF) and low frequency (LF) plasma generation, wherein the LF power is between about 17-80% of total power. 
     
     
         18 . A method for forming a smooth silicon film on a semiconductor substrate in a plasma-enhanced chemical vapor deposition (PECVD) apparatus comprising a PECVD process chamber, the method comprising:
 supplying a process gas to the PECVD apparatus, wherein the process gas comprises a silicon-containing reactant, argon, and helium, wherein the silicon-containing reactant is disilane; and   depositing a smooth silicon film on the semiconductor substrate, the depositing comprising:
 (a) flowing the process gas to the PECVD process chamber wherein the flow rate of disilane is 0.05-12% of the total process gas flow rate, the flow rate of argon is 16-84% of the total process gas flow rate, and the flow rate of helium is 25-83% of the total process gas flow rate; 
 (b) forming a plasma using both high frequency (HF) and low frequency (LF) plasma generation, wherein the LF power is 17-80% of the total (HF and LF) power; and 
 (c) maintaining a deposition temperature of 350-550° C. and maintaining a pressure of 2-6 Torr in the PECVD process chamber; 
   wherein the deposited smooth silicon film is characterized by roughness (Ra) of less than about 7 Å, and a compressive stress of less than about 500 MPa in absolute value, or wherein the deposited smooth silicon film is tensile and is characterized by Ra of less than about 7 Å.   
     
     
         19 . The method of  claim 18 , wherein the deposited smooth silicon film is characterized by Ra of less than about 5 Å, and a compressive stress of less than about 300 MPa in absolute value, or wherein the deposited smooth silicon film is a tensile film and is characterized by Ra of less than about 5 Å. 
     
     
         20 . The method of  claim 18 , wherein the process gas comprises less than about 5% by volume of disilane.