Method and apparatus for forming a borophosphosilicate film

Abstract

A method and apparatus for improving film stability and moisture resistance of a borophosphosilicate film. The BPSG film according to the present invention is formed under plasma conditions in which high and low frequency RF power is employed to generate the plasma. The high frequency power supply provides most of the energy to break the molecules in the process gas thereby forming the plasma and promoting the necessary reactions. The low frequency power supply regulates and controls ion bombardment of the BPSG film as it is formed. In a preferred embodiment, nitrogen is included in the process gas and the low frequency RF power supply is used to precisely control ion bombardment during deposition processing thereby allowing incorporation of an unexpectedly elevated amount of nitrogen into the film further improving film stability.

What is claimed is:  
     
         1 . A method of depositing a borophosphosilicate glass (BPSG) layer over a substrate disposed in a substrate processing chamber, said method comprising: 
 introducing a process gas consisting of separate sources of silicon, boron, phosphorus and oxygen, and if said oxygen sources does not include nitrogen a separate nitrogen source, into said processing chamber;    forming a plasma from said process gas in a reaction zone proximate said substrate using both high and low frequency RF signals to deposit said BPSG layer over said substrate.    
     
     
         2 . The method of  claim 1  wherein said silicon source is silane (SiH 4 ).  
     
     
         3 . The method of  claim 1  wherein said oxygen source is nitrous oxide (N 2 O).  
     
     
         4 . The method of  claim 1  wherein said oxygen source does not include nitrogen and wherein said nitrogen source is either molecular nitrogen (N 2 ) or ammonia (NH 3 ).  
     
     
         5 . The method of  claim 1  wherein said boron and phosphorus sources are diborane (B 2 H 6 ) and phosphine (PH 3 ), respectively.  
     
     
         6 . The method of  claim 1  wherein said BPSG layer has a refractive index between 1.49 and 1.51 when initially deposited.  
     
     
         7 . The method of  claim 1  wherein on the order of 1×10 21  atoms/cm 3  of nitrogen are incorporated into said BPSG layer when initially deposited.  
     
     
         8 . The method of  claim 1  wherein said high frequency component is between about 13-14 MHz.  
     
     
         9 . The method of  claim 8  wherein said high frequency component is 13.56 MHz.  
     
     
         10 . The method of  claim 8  wherein said low frequency component is less than 500 KHz.  
     
     
         11 . The method of  claim 10  wherein said low frequency component is between about 350-440 KHz.  
     
     
         12 . The method of  claim 1  further comprising setting and maintaining pressure within said chamber at a level between about 1 and 20 Torr during deposition of said BPSG layer.  
     
     
         13 . The method of  claim 1  further comprising heating said substrate to a temperature between 150-650° C. during deposition of said BPSG layer.  
     
     
         14 . A method of depositing a borophosphosilicate glass (BPSG) layer over a substrate disposed in a substrate processing chamber, said method comprising: 
 introducing a process gas consisting of a silicon source, nitrous oxide, a boron source and a phosphorus source into said processing chamber;    forming a plasma from said process gas in a reaction zone proximate said substrate using both high and low frequency RF signals to deposit said BPSG layer over said substrate.    
     
     
         15 . The method of  claim 14  wherein said BPSG layer has a refractive index between 1.49 and 1.51 when initially deposited.  
     
     
         16 . The method of  claim 15  wherein on the order of 1×10 21  atoms/cm 3  of nitrogen are incorporated into said BPSG layer when initially deposited.  
     
     
         17 . The method of  claim 16  wherein said silicon source is silane.  
     
     
         18 . A method of depositing a borophosphosilicate glass (BPSG) layer over a substrate disposed in a substrate processing chamber, said method comprising: 
 introducing a process gas consisting of a silicon source, an oxygen source, a boron source, a phosphorus source and a nitrogen source into said processing chamber;    forming a plasma from said process gas in a reaction zone proximate said substrate using both high and low frequency RF signals to deposit said BPSG layer over said substrate.    
     
     
         19 . The method of  claim 18  wherein said BPSG layer has a refractive index between 1.49 and 1.51 when initially deposited.  
     
     
         20 . The method of  claim 19  wherein on the order of 1×10 21  atoms/cm 3  of nitrogen are incorporated into said BPSG layer when initially deposited.  
     
     
         21 . The method of  claim 20  wherein said silicon source is silane.  
     
     
         22 . The method of  claim 21  wherein said oxygen source is selected from the group consisting of molecular oxygen, ozone and nitrous oxide.  
     
     
         23 . The method of  claim 21  wherein said nitrogen source is selected from the group consisting of molecular nitrogen, ammonia and nitrous oxide.  
     
     
         24 . The method of  claim 1  wherein said BPSG layer consists essentially of silicon, oxygen, boron, phosphorus and nitrogen.  
     
     
         25 . The method of  claim 14  wherein said BPSG layer consists essentially of silicon, oxygen, boron, phosphorus and nitrogen.  
     
     
         26 . The method of  claim 18  wherein said BPSG layer consists essentially of silicon, oxygen, boron, phosphorus and nitrogen.