Patent ID: 8017029
Filing Date: 2011-09-13
Classification: G03F,H01J

Abstract:
1. A method of controlling etch rate distribution on a workpiece in a chamber of a plasma reactor having a workpiece support pedestal inside said chamber, comprising: providing a two-dimensional array of optical ports in said pedestal; placing the backside of the workpiece on said support pedestal and performing an etch process on said workpiece by coupling RF power into an interior of said chamber; during said etch process, illuminating the backside of said workpiece through said optical ports with light; viewing through each of said ports light reflected from a top surface of said workpiece; determining plural etch depths from the light received through said plural optical ports, and deducing from said plural etch depths a spatial distribution of etch rate across the top surface of said workpiece; changing the spatial distribution of etch rate by adjusting a tunable element of said reactor, said tunable element comprising an array of gas injection orifices, each of said orifices opening into said chamber, said adjusting said tunable element comprising changing an individual gas flow rate through each individual one of said orifices independently of gas flow rates through the other orifices; and monitoring changes in said spatial distribution of etch rate and modifying the adjustment of said tunable element in response to said changes in said spatial distribution of etch rate in accordance with a desired etch rate distribution.