Methods and apparatus for stable substrate processing with multiple rf power supplies

Abstract

Methods and apparatus for processing substrates are provided herein. In some embodiments, a physical vapor deposition chamber includes a first RF power supply having a first base frequency and coupled to one of a target or a substrate support; and a second RF power supply having a second base frequency and coupled to one of the target or the substrate support, wherein the first and second base frequencies are integral multiples of each other, wherein the second base frequency is modified to an offset second base frequency that is not an integral multiple of the first base frequency.

1 . A method of processing a substrate disposed on a substrate support in a physical vapor deposition (PVD) chamber having a target comprising a source material to be deposited on the substrate, the method comprising:
 providing RF energy to one of the target or the substrate support from a first RF power supply having a first base frequency;   simultaneously providing RF energy to one of the target or the substrate support from second RF power supply having a second base frequency, wherein the first and second base frequencies are integral multiples of each other, wherein the second base frequency is modified to an offset second base frequency that is not an integral multiple of the first base frequency; and   processing a substrate using a plasma formed from the RF energy provided to the PVD chamber.   
     
     
         2 . The method of  claim 1 , wherein the substrate comprises a feature having a sidewall and a bottom, and wherein the method provides a sidewall to bottom coverage ratio of greater than about 38%. 
     
     
         3 . The method of  claim 1 , wherein the second base frequency is offset from the integral multiple of the first base frequency by at least  10  kHz. 
     
     
         4 . The method of  claim 1 , wherein the second base frequency is offset to a frequency defined by X*(f1)+/−Y*(f1), wherein (f1) is the first base frequency, X is an integer between 1 and 5, and Y is a real number between 0.0005 and 0.05. 
     
     
         5 . The method of  claim 1 , wherein the first base frequency is 13.56 MHz and the offset second base frequency is equal to or greater than 40.73 MHz or is equal to or lesser than 40.66 MHz. 
     
     
         6 . The method of  claim 1 , wherein the first base frequency is 40.68 MHZ and the offset second base frequency is equal to or greater than 13.57 MHz or is equal to or lesser than 13.55 MHz. 
     
     
         7 . The method of  claim 1 , wherein the first RF power supply is coupled to the substrate support and wherein the second RF power supply is coupled to the target. 
     
     
         8 . The method of  claim 1 , further comprising modifying the second RF power supply such that the second RF power supply itself provides the offset second base frequency. 
     
     
         9 . The method of  claim 1 , further comprising coupling a frequency control module to the second RF power supply to modify the second base frequency to the offset second base frequency. 
     
     
         10 . The method of  claim 1 , further comprising modifying firmware for operating the second RF power supply to include software with instructions to modify the second base frequency to the offset second base frequency. 
     
     
         11 . The method of  claim 1 , further comprising operating the second RF power supply in a fixed frequency mode at the offset second base frequency. 
     
     
         12 . The method of  claim 1 , further comprising operating the second RF power supply in a frequency tuning mode centered about the offset second base frequency. 
     
     
         13 . The method of  claim 1 , wherein the RF energy provided to the target is from an RF power supply having a base frequency of 13.56 MHz, 27.12 MHz, 60 MHz, or 162 MHz. 
     
     
         14 . The method of  claim 1 , wherein the RF energy provided to the substrate support is from an RF power supply having a base frequency of 2 MHz, 13.56 MHz, or 60 MHz. 
     
     
         15 . The method of  claim 1 , wherein the first base frequency is greater than the second base frequency. 
     
     
         16 . The method of  claim 1 , wherein the first RF power supply is coupled to the substrate support and the second RF power supply is coupled to the target. 
     
     
         17 . The method of  claim 1 , wherein the second RF power supply is coupled to the substrate support and the first RF power supply is coupled to the target.