Apparatus and methods related to copper plating of wafers

Abstract

Apparatus and methods related to copper plating of wafers. In some implementations, a method for copper plating a wafer can include estimating a change in surface area exposed on a side of the wafer. The estimated change, such as an increase in surface area, can be based at least in part on a number of vias formed on the side of the wafer. The method can further include adjusting a plating parameter, such as a plating time interval, based on the estimated change. Additionally, a number of processing techniques can be implemented to reduce oxidation of the plated copper.

What is claimed is: 
     
         1 . A method for copper plating a wafer, the method comprising:
 estimating a change in surface area exposed on a side of the wafer, the estimated change based at least in part on a number of vias formed on the side of the wafer; and   adjusting a plating parameter based on the estimated change.   
     
     
         2 . The method of  claim 1  wherein the vias include through-wafer vias (TWVs). 
     
     
         3 . The method of  claim 2  wherein each of the TWVs is modeled as a trapezoidal prism to calculate an exposed surface area of the TWV. 
     
     
         4 . The method of  claim 3  wherein the exposed surface area of the TWV is corrected with an oval approximation for a rectangular sectional shape of the trapezoidal prism. 
     
     
         5 . The method of  claim 4  wherein the exposed surface area of the TWV is further corrected based on different likely plating thicknesses corresponding to different portions of the TWV. 
     
     
         6 . The method of  claim 5  wherein the exposed surface area of the TWV is further corrected based on an estimated roughness inside the TWV. 
     
     
         7 . The method of  claim 1  wherein the plating parameter includes a plating time interval. 
     
     
         8 . The method of  claim 7  further comprising selecting the plating time interval to yield a desired plating thickness on the side of the wafer. 
     
     
         9 . The method of  claim 8  wherein the side of the wafer is a backside of the wafer. 
     
     
         10 . The method of  claim 9  wherein the wafer includes gallium arsenide (GaAs). 
     
     
         11 . The method of  claim 7  further comprising mounting the wafer on a fixture to yield a wafer-fixture assembly. 
     
     
         12 . The method of  claim 11  further comprising loading the wafer-fixture assembly into a plating tool such that the fixture facilitates immersion of the wafer at a desired depth in a plating solution. 
     
     
         13 . The method of  claim 12  further comprising performing a plating operation for the plating time interval to yield a plated copper layer. 
     
     
         14 . The method of  claim 13  further comprising rinsing and drying the wafer. 
     
     
         15 . The method of  claim 14  further comprising providing a holding environment for the rinsed and dried wafer, the holding environment substantially free of an airflow to reduce oxidation of the plated copper layer. 
     
     
         16 . A copper plating system comprising:
 a plating tool configured to receive a wafer and form a plated copper layer on a side of the wafer; and   a processor configured to provide control functionality for the plating tool, the processor further configured to estimate a change in surface area exposed on the side of the wafer, the estimated change based at least in part on a number of vias formed on the side of the wafer, the processor further configured to facilitate adjustment of a plating parameter based on the estimated change.   
     
     
         17 . The copper plating system of  claim 16  further comprising a computer-readable medium (CRM) in communication with the processor, the CRM including data utilized by the processor for calculating the estimated change. 
     
     
         18 . The copper plating system of  claim 17  wherein the CRM further includes at least some algorithm utilized by the processor for the calculation. 
     
     
         19 . A copper plating apparatus comprising:
 a plating tool configured to receive a wafer and form a plated copper layer on a side of the wafer;   a rinse and dry system configured to clean the wafer after the formation of the plated copper layer;   a holding device configured to hold the cleaned wafer; and   a cabinet surrounding at least the holding device, the cabinet configured to provide an environment that is substantially free of air flow to reduce oxidation of the plated copper layer.   
     
     
         20 . The copper plating apparatus of  claim 19  further comprising a robotic system configured to provide automated movements of the wafer.