Method of tungsten etching

Abstract

A method for etching a tungsten containing layer in an etch chamber is provided. A substrate is placed with a tungsten containing layer in the etch chamber. A plurality of cycles is provided. Each cycle comprises a passivation phase for forming a passivation layer on sidewalls and bottoms of features in the tungsten containing layer. Additionally, each cycle comprises an etch phase for etching features in the tungsten containing layer.

What is claimed is: 
     
       1. A method for etching a tungsten containing in an etch chamber, comprising:
 placing a substrate with a tungsten containing layer in the etch chamber; 
 provide a plurality of cycles, wherein each cycle comprises:
 a passivation phase for forming a passivation layer of silicon oxide on sidewalls and bottoms of features in the tungsten containing layer; and 
 an etch phase for etching features in the tungsten containing layer. 
 
 
     
     
       2. The method, as recited in  claim 1 , wherein the passivation phase comprises:
 adsorbing a silicon precursor into the sidewalls of the features in the tungsten containing layer; and 
 exposing the tungsten containing layer to a plasma that scavenges Cl from the sidewalls. 
 
     
     
       3. The method, as recited in  claim 2 , wherein the silicon precursor is SiCl x , where x is an integer between 1 and 4. 
     
     
       4. The method, as recited in  claim 2 , wherein the adsorbing the silicon precursor into the sidewalls comprises:
 providing an adsorption gas comprising SiCl 4 ; 
 forming the adsorption gas into a plasma. 
 
     
     
       5. The method, as recited in  claim 2 , wherein the silicon precursor is mixed with at least one inert gas. 
     
     
       6. The method, as recited in  claim 2 , wherein the exposing the tungsten containing layer to a plasma that scavenges Cl from the sidewalls, comprises:
 providing a scavenger gas comprising SO 2 ; and 
 forming the scavenger gas into a plasma. 
 
     
     
       7. The method, as recited in  claim 1 , wherein the passivation layer is etched more slowly than the tungsten containing layer. 
     
     
       8. The method, as recited in  claim 1 , wherein the plurality of cycles further comprises an opening phase for opening the tungsten containing layer. 
     
     
       9. The method, as recited in  claim 8 , wherein the opening phase comprises exposing the tungsten containing layer to at least one of perfluorocarbons, O 2 , SF 6 , NF, and Cl 2 . 
     
     
       10. A method for forming a passivation layer on sidewalls of etched tungsten features, the method comprising:
 forming etched features in a tungsten layer of a wafer, the etched features having sidewalls; 
 adsorbing a silicon precursor to the sidewalls; and 
 subsequent to the step of absorbing, oxygenating the silicon precursor adsorbed to the sidewalls; 
 wherein the silicon recursor is oxygenated using a plasma that contains SO 2  and O 2 . 
 
     
     
       11. The method, as recited in  claim 10 , wherein the silicon precursor is halogenated. 
     
     
       12. The method, as recited in  claim 10 , wherein the plasma scavenges halogen radicals. 
     
     
       13. The method, as recited in  claim 12 , wherein the halogen radicals are generated during the oxygenating of the silicon precursor. 
     
     
       14. The method, as recited in  claim 1 , wherein the etch phase is subsequent to the passivation phase in each cycle. 
     
     
       15. A method for etching a tungsten containing layer in an etch chamber, comprising:
 placing a substrate with a tungsten containing layer in the etch chamber; and   provide a plurality of cycles, wherein each cycle comprises:
 a passivation phase for forming a silicon containing passivation layer on sidewalls or bottoms of features in the tungsten containing layer; and 
 an etch phase for etching features in the tungsten containing layer. 
   
     
     
       16. The method, as recited in claim 15, wherein the passivation phase comprises:
 adsorbing a silicon precursor into the sidewalls of the features in the tungsten containing layer; and   exposing the tungsten containing layer to a plasma that scavenges Cl from the sidewalls.   
     
     
       17. The method, as recited in claim 16, wherein the silicon precursor is SiCl x , where x is an integer between 1 and 4. 
     
     
       18. The method, as recited in claim 16, wherein the adsorbing the silicon precursor into the sidewalls comprises:
 providing an adsorption gas comprising SiCl 4 ;   forming the adsorption gas into a plasma.   
     
     
       19. The method, as recited in claim 16, wherein the silicon precursor is mixed with at least one inert gas. 
     
     
       20. The method, as recited in claim 16, wherein the exposing the tungsten containing layer to a plasma that scavenges Cl from the sidewalls, comprises:
 providing a scavenger gas comprising SO 2 ; and   forming the scavenger gas into a plasma.   
     
     
       21. The method, as recited in claim 15, wherein the passivation layer is etched more slowly than the tungsten containing layer. 
     
     
       22. The method, as recited in claim 15, wherein the plurality of cycles further comprises an opening phase for opening the tungsten containing layer. 
     
     
       23. The method, as recited in claim 22, wherein the opening phase comprises exposing the tungsten containing layer to at least one of perfluorocarbons, O 2 , SF 6 , NF, and Cl 2 . 
     
     
       24. The method, as recited in claim 15, wherein the etch phase is subsequent to the passivation phase in each cycle.