Method of controlling the uniformity of PECVD-deposited thin films

Abstract

We have discovered that controlling a combination of PECVD deposition process parameters during deposition of silicon-containing thin film provides improved control over surface standing wave effects. By minimizing surface standing wave effects, the uniformity of film properties (particularly film thickness) across a substrate surface onto which the films have been deposited is improved. The process parameters which have the greatest effect on surface standing wave effects include: the spacing between the upper and lower electrodes in the plasma reactor; the RF frequency of the plasma source; the amount RF power to the plasma source; the process chamber pressure; the relative concentrations of the various components in the precursor gas composition; and the precursor gas overall flow rate relative to the substrate processing volume.

1 . A method of increasing film deposition uniformity of a PECVD deposited film over a substrate surface having an equivalent radius of about 0.7 meter or greater, the method comprising adjustment of the following combination of variables: reducing the electrode spacing between parallel plate electrodes in a process chamber in which the PECVD film is deposited to be below about 1000 mils; reducing the electron density of the plasma used during deposition to be less than about 10 10 /cm 3 ; and selecting a plasma source gas in which reactive species are dissociated at an electron density used during deposition of the film.  
     
     
         2 . A method in accordance with  claim 1 , wherein said PECVD deposited film is a silicon-containing film.  
     
     
         3 . A method in accordance with  claim 2 , wherein said silicon-containing film is selected from the group consisting of silicon nitride, silicon oxide, and combinations thereof.  
     
     
         4 . A method in accordance with  claim 1  or  claim 2 , wherein a pressure at the surface of the substrate is less than about 1.5 Torr.  
     
     
         5 . A method in accordance with  claim 4 , wherein said pressure ranges from about 0.5 Torr to about 1.5 Torr.  
     
     
         6 . A method in accordance with  claim 5 , wherein said pressure ranges from about 0.7 Torr and about 1.0 Torr.  
     
     
         7 . A method in accordance with  claim 1  or  claim 2 , wherein a plasma sheath width, s, is more than about 20 mils.  
     
     
         8 . A method in accordance with  claim 1  or  claim 2 , wherein said plasma thickness, 2 d, is less than about 1000 mils.  
     
     
         9 . A method in accordance with  claim 1  or  claim 2 , wherein power applied to produce said plasma is RF power which is applied at a frequency ranging between about 13.56 MHz and about 3 MHz.  
     
     
         10 . A method in accordance with  claim 9 , wherein said frequency ranges between about 13.56 MHz and about 7 MHz.  
     
     
         11 . A method in accordance with  claim 1  or  claim 2 , wherein the total gas flow to said process chamber is such that the volumetric gas turnover is at least 0.015 process chamber volumes per minute.  
     
     
         12 . A method in accordance with  claim 11 , wherein said volumetric gas turnover ranges from about 0.015 to about 0.08 chamber volumes per minute.  
     
     
         13 . A method in accordance with  claim 12 , wherein said volumetric gas turnover ranges from about 0.02 to about 0.07 chamber volumes per minute.  
     
     
         14 . A method in accordance with  claim 2 , wherein an a-SiN x :H film is deposited and wherein the concentration of NH 3  in the plasma source gas mixture is such that the ratio of NH3:SiH 4  ranges from about 2:1 to about 15:1, and the ratio of NH 3 :N 2  ranges from about 0.3:1 to about 2:1.  
     
     
         15 . A method in accordance with  claim 1  or  claim 2 , wherein said spacing between electrodes ranges between about 400 mils and 1000 mils.  
     
     
         16 . A method in accordance with  claim 1  or  claim 2 , wherein the amount of RF power applied to the plasma source gas ranges from about 0.2 W/cm 2  of substrate to about 0.6 W/cm 2  of substrate.  
     
     
         17 . A method in accordance with  claim 1  or  claim 2 , wherein the temperature of said substrate ranges from about 200° C. to about 400° C. during deposition of said film.  
     
     
         18 . A method in accordance with  claim 1 , wherein said method is used to deposit a silicon-containing film selected from the group consisting of silicon nitride, silicon oxide, silicon oxynitride, a-Si, doped a-Si, and combinations thereof.  
     
     
         19 . A method in accordance with  claim 1  or  claim 2 , wherein said silicon-containing film is deposited at a rate of at least about 1,000 Å/min.