Process for dynamic control of the concentration of one or more reactants in a plasma-enhanced process for formation of integrated circuit structures

In a plasma etch process for etching various aluminum patterns on integrated circuit structures on semiconductor wafers in a plasma etching chamber, wherein the amount of aluminum to be removed will vary from wafer to wafer, depending upon the particular aluminum pattern to be etched, resulting in the need for a change in flow rate of etchant gas into said etching chamber from wafer to wafer, to thereby control the concentration of said etchant gas in said etching chamber, the improvement which comprises:

• a) loading into a plasma etch chamber a semiconductor wafer having an integrated circuit structure formed thereon including an aluminum layer having a mask thereon to define a desired pattern of aluminum on said structure;
• b) flowing into said plasma etch chamber a mixture of a chlorine etchant gas capable of plasma etching aluminum, and a non-reactive gas selected from the group consisting of argon and helium in an initial flow ratio of about 5:1;
• c) igniting a plasma in said chamber to plasma etch said masked aluminum layer;
• d) monitoring the respective optical emissions of said argon or helium non-reactive gas and said chlorine etching gas during said etch and comparing the ratio of emission intensities to an initial ratio of emission intensities to determine the amount of said aluminum etchant gas being consumed by said aluminum;
• and
• e) changing the flow of said chlorine etching gas into said plasma etch chamber to match the amount of etchant gas being consumed by the portions of said aluminum exposed by said mask;
• whereby the concentration of aluminum etchant gas in said chamber will remain constant during said etch regardless of the amount of aluminum being etched to provide the particular aluminum pattern desired for a particular integrated circuit structure.