Method and system for ion-assisted processing

Abstract

A system for processing a substrate includes a plasma chamber to produce a plasma including reactive gas ions at a first pressure, a bias supply to supply a bias between the plasma chamber and the substrate, a plasma sheath modifier disposed between the plasma chamber and substrate, the plasma sheath modifier having an aperture configured to direct the reactive ions toward the substrate in a beam having an ion beam profile, and a process chamber enclosing the substrate, the process chamber at a second pressure different than the first pressure to define a pressure differential.

What is claimed is: 
     
         1 . A system for processing a substrate, comprising:
 a plasma chamber operable to produce a plasma including reactive gas ions at a first pressure;   a bias power supply to supply a bias voltage between the plasma chamber and the substrate;   a plasma sheath modifier disposed between the plasma chamber and the substrate, the plasma sheath modifier having an aperture configured to direct the reactive ions toward the substrate in a beam having an ion beam profile; and   a process chamber enclosing the substrate, the process chamber at a second pressure different than the first pressure to define a pressure differential.   
     
     
         2 . The system of  claim 1 , further comprising a power supply to control a plasma power of the plasma and a substrate holder to hold the substrate, the system operable to vary the ion beam profile by varying one or more of: the plasma power and the substrate holder to control a separation distance between the plasma sheath modifier and the substrate. 
     
     
         3 . The system of  claim 1 , the system operable to vary the ion beam profile in a region proximate the substrate, between a converging beam, a parallel beam, and a diverging beam. 
     
     
         4 . The system of  claim 1 , the plasma sheath modifier operable to form a converging beam of reactive gas ions incident on a first region of the substrate when the bias voltage is applied between the plasma chamber and the substrate, the aperture having a first width that is greater than a second width characteristic of the first region of the substrate. 
     
     
         5 . The system of  claim 1 , wherein the process chamber is operable to receive a flow of inert gas such that the second pressure is higher than the first pressure. 
     
     
         6 . The system of  claim 1 , further comprising a heater to configured to establish a temperature gradient on the substrate and to generate a gradient in a condensation rate of the reactive gas ions along a plane of the substrate. 
     
     
         7 . The system of  claim 6 , wherein the heater is further configured to establish a first temperature in a central region of the substrate and a second temperature in a region of the substrate outside of the central region, and wherein the condensation rate of the reactive gas ions is less at the second temperature than at the first temperature. 
     
     
         8 . The system of  claim 1 , wherein the process chamber is operable to receive a flow of inert gas from an inert gas source across a front surface of the substrate to prevent a portion of reactive gas neutrals from the plasma from striking the substrate as the beam having the ion beam profile strikes the substrate. 
     
     
         9 . The system of  claim 8 , wherein the bias power supply is configured to provide the bias voltage at a level dependent on the flow of inert gas so the beam having the ion beam profile is less influenced by the flow of inert gas than the reactive gas neutrals. 
     
     
         10 . The system of  claim 8 , further comprising a substrate holder to hold the substrate and scan the substrate with respect to the plasma chamber to move the substrate from a current position to a next position, and wherein the bias power supply provides the bias voltage in response to a position of the substrate relative to the plasma chamber. 
     
     
         11 . The system of  claim 10 , wherein the bias power supply is configured to remove the bias voltage between the plasma chamber and the substrate after a first exposure at the current position and re-establish the bias voltage between the plasma chamber and the substrate once the substrate holder has moved the substrate to the next position.