Method and Apparatus for Deposition of Mental Nitrides

Abstract

A structure including a metal nitride layer is formed on a workpiece by pre-conditioning a chamber that includes a metal target by flowing nitrogen gas and an inert gas at a first flow rate ratio into the chamber and igniting a plasma in the chamber before placing the workpiece in the chamber, evacuating the chamber after the preconditioning, placing the workpiece on a workpiece support in the chamber after the preconditioning, and performing physical vapor deposition of a metal nitride layer on the workpiece in the chamber by flowing nitrogen gas and the inert gas at a second flow rate ratio into the chamber and igniting a plasma in the chamber. The second flow rate ratio is less than the first flow rate ratio.

What is claimed is: 
     
         1 . A method of forming a structure including a metal nitride layer on a workpiece, comprising:
 before placing the workpiece in a chamber that includes a niobium target, pre-conditioning the chamber by flowing nitrogen gas and an inert gas at a first flow rate ratio into the chamber and igniting a plasma in the chamber while the nitrogen gas and the inert gas are flowing at the first flow rate ratio;   after the preconditioning, evacuating the chamber;   after the preconditioning, placing the workpiece on a workpiece support in the chamber; and   performing physical vapor deposition of a niobium nitride or niobium alloy nitride layer on the workpiece in the chamber by flowing nitrogen gas and the inert gas at a second flow rate ratio of nitrogen gas to inert gas into the chamber and igniting a second plasma in the chamber while the nitrogen gas and the inert gas are flowing at the second flow rate ratio, wherein the second flow rate ratio is less than the first flow rate ratio.   
     
     
         2 . The method of  claim 1 , wherein the metal target comprises substantially pure niobium and the metal nitride layer comprises substantially pure niobium nitride. 
     
     
         3 . The method of  claim 1 , wherein the second flow rate ratio is 2-30% less than the first flow rate ratio. 
     
     
         4 . The method of  claim 1 , wherein the first flow rate ratio is 4:100 to 1:1, and the second flow rate ratio is 3:100 to 48:52. 
     
     
         5 . The method of  claim 1 , wherein pre-conditioning the chamber comprises placing a shutter disk on the substrate support. 
     
     
         6 . The method of  claim 5 , wherein pre-conditioning comprises heating the shutter disk to a temperature and performing a physical vapor deposition comprises heating the workpiece to the same temperature. 
     
     
         7 . The method of  claim 6 , wherein the temperature is 200-500° C. 
     
     
         8 . The method of  claim 6 , wherein igniting plasma in preconditioning and igniting plasma in deposition use a same power level. 
     
     
         9 . A physical vapor deposition system, comprising:
 chamber walls forming a chamber;   a support to hold a workpiece in the chamber;   a vacuum pump to evacuate the chamber;   a gas supply to deliver nitrogen gas and an inert gas to the chamber;   an electrode to support a metal target;   a power source to apply power to the electrode; and   a controller configured to
 before a workpiece on which a metal nitride layer is to be deposited is placed in the chamber, cause the gas source to flow nitrogen gas and the inert gas at a first flow rate ratio of nitrogen gas to inert gas into the chamber and cause the power source to apply power sufficient to ignite a first plasma in the chamber to pre-condition the chamber while the nitrogen gas and the inert gas are flowing at the first flow rate ratio, 
 after the workpiece is placed in the chamber, cause the gas source to flow nitrogen gas and the inert gas at a second flow rate ratio of nitrogen gas to inert gas into the chamber, wherein the second flow rate ratio is less than the first flow rate ratio and comprises less nitrogen gas than the first flow rate ratio, and 
 cause the power source to apply power sufficient to ignite a second plasma in the chamber while the nitrogen gas and the inert gas are flowing into the chamber at the second flow rate ratio to deposit the metal nitride layer. 
   
     
     
         10 . The system of  claim 9 , comprising the metal target, and wherein the metal target comprises niobium. 
     
     
         11 . The system of  claim 10 , wherein the metal target is substantially pure niobium. 
     
     
         12 . The system of  claim 9 , wherein the second flow rate ratio is 2 to 30% less than the first flow rate ratio. 
     
     
         13 . The system of  claim 12 , wherein the first flow rate ratio is 4:100 to 1:1, and the second flow rate ratio is 3:100 to 48:52. 
     
     
         14 . The system of  claim 9 , comprising a robot configured to position a shutter disk into the chamber for the pre-condition of the chamber.