Systems to improve front-side process uniformity by back-side metallization

Abstract

Systems to improve front-side process uniformity by back-side metallization are disclosed. In some implementations, a back-side process system deposits a metal layer on the back-side of a wafer prior to performing a plasma-based process on the front side of the wafer. Presence of the back-side metal layer reduces variations in, for example, thickness of a deposited and/or etched layer resulting from the plasma-based process.

What is claimed is: 
     
         1 . A system to process a semiconductor wafer, the system comprising:
 a back-side process system configured to deposit a tungsten titanium (W—Ti) layer on a back side of a gallium arsenide (GaAs) wafer to form a W—Ti metal layer on the back side of the GaAs wafer; and   a front-side process system comprising an electrode and a platen and configured to perform a plasma-based process on a front side of the GaAs wafer that is positioned on the platen, the W—Ti metal layer affecting at least one of an etch rate and a deposition rate during the plasma-based process to facilitate improved uniformity in thickness of a layer resulting from the plasma-based process.   
     
     
         2 . The system of  claim 1  wherein the W—Ti metal layer covers substantially the entire area of the back side of the GaAs wafer. 
     
     
         3 . The system of  claim 1  wherein the W—Ti metal layer is deposited using a sputtering process. 
     
     
         4 . The system of  claim 1  wherein the W-TI metal layer has a thickness in a range of approximately 500 angstroms to 2,000 angstroms. 
     
     
         5 . The system of  claim 1  wherein the plasma-based process includes a deposition process. 
     
     
         6 . The system of  claim 5  wherein the deposition process includes a plasma-enhanced chemical vapor deposition (PECVD) process. 
     
     
         7 . The system of  claim 1  wherein the plasma-based process includes an etching process. 
     
     
         8 . The system of  claim 7  wherein the etching process includes a reactive ion etching process. 
     
     
         9 . The system of  claim 1  wherein the layer resulting from the plasma-based process includes a nitride layer. 
     
     
         10 . The system of  claim 1  wherein the improved uniformity includes a reduction in relative standard deviation of measured thickness values by a factor of at least two when compared to similar thickness values corresponding to a GaAs wafer without a W—Ti metal layer on its back side. 
     
     
         11 . A system to process a semiconductor wafer, the system comprising:
 a sputtering system configured to deposit a metal layer on a back side of a wafer to form a metal layer on the back side of the wafer; and   a plasma-process apparatus comprising an electrode and a platen and configured to perform a plasma-based process on the front side of the wafer that is positioned on the platen, the metal layer reducing variation in radio frequency (RF) coupling during the plasma-based process on the front side of the wafer, the reduced RF coupling facilitating improved uniformity in at least one of an etch rate and a deposition rate during the plasma-based process.   
     
     
         12 . The system of  claim 11  wherein the variation in RF coupling includes a contribution from one or more features defined by or associated with a wafer handling device. 
     
     
         13 . The system of  claim 12  wherein the wafer handling device includes a wafer platen. 
     
     
         14 . The system of  claim 12  wherein the wafer handling device includes a wafer chuck. 
     
     
         15 . The system of  claim 11  wherein the metal layer is removed after the plasma-based process. 
     
     
         16 . A system to process a semiconductor wafer, the system comprising:
 a back-side process system configured to deposit a metal layer on a first side of a wafer to form a metal layer on the first side of the wafer; and   a front-side process system comprising an electrode and a platen and configured to perform a plasma-based process according to a design on a second side of the wafer that is positioned on the platen, the metal layer including varying thickness profiles to accommodate the design, the varying thickness profiles affecting at least one of an etch rate and a deposition rate during the plasma-based process.   
     
     
         17 . The system of  claim 15  wherein the metal layer is formed on a back side of the wafer and the plasma-based process is performed on a front side of the wafer. 
     
     
         18 . The system of  claim 17  wherein the metal layer covers substantially the entire area of the back side of the wafer. 
     
     
         19 . The system of  claim 17  wherein the metal layer covers one or more selected portions of the back side of the wafer. 
     
     
         20 . The system of  claim 15  wherein the metal layer is removed after the plasma-based process.