Patent ID: 8017526
Filing Date: 2011-09-13
Classification: H01J,H01L

Abstract:
1. A method of processing a wafer in a plasma reactor, comprising: placing the wafer on a wafer support surface in a chamber of the reactor; introducing a process gas into the chamber; establishing a predetermined set of process conditions including chamber pressure and flow rates of constituents of the process gas; simultaneously coupling HF power and VHF power to the wafer; setting the level of said HF power and the level of said VHF power to respective optimum levels at which a first process parameter is at a first target value and a second process parameter is at a second target value, said first and second process parameters comprising either: (a) plasma ion density in the chamber and plasma ion energy at the wafer surface, respectively, or (b) etch rate and critical dimension, respectively; wherein placing the wafer on the wafer support is preceded by finding said optimum levels of said HF power and VHF power, and wherein finding said optimum levels comprises: processing a set of test wafers under said predetermined process conditions in a plasma reactor, and, during the processing of each different one of said test wafers, simultaneously coupling VHF and HF power to the one test wafer and setting said VHF and HF power to respective levels during processing of respective ones of said test wafers; determining respective levels of the first process parameter during processing of respective ones of said test wafers, and correlating said respective levels of the first process parameter with corresponding levels of HF and VHF power to produce a first array of data correlating each VHF, HF power level pair to a first process parameter value; searching said first array of data for a constant first parameter set of VHF and HF power level pairs at which the first process parameter is at or at least nearly at the first target value, corresponding to a first curve in VHF-HF power space having a constant first parameter value; and finding an optimum VHF and HF power level pair in said constant density set at which the second process parameter is at or at least nearly at the second target value.