Method for TMAH etching of CMOS integrated circuits
AssigneeOptical ETC Inc.
InventorJon Geist
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Abstract
A method for preparing and using a tetramethylammonium hydroxide etchant (180). The etchant is prepared by combining precisely known quantities of the etchant components obtained from liquid sources of tetramethylammonium hydroxide (110) and dissolved silicate (115). A precise quantity of an acidic (relative to tetramethylammonium hydroxide) oxidizer is added at intervals during a long etch as well as just before immersing a sample holder (135) and sample in the etchant (180). A precise quantity of tetramethylammonium hydroxide such as can obtained from a pipette (175) is also added during long etches to compensate for the reduction in etchant pH caused by the addition of the oxidizer.
Claims7
A method for preparing an etchant comprising:
- providing a solution of tetramethylammonium hydroxide in water;
- mixing a liquid source of silicate ions is mixed with said solution;
- adding an oxidizer to said solution at a time later than 10 minutes following immersion of a sample comprised of silicon in solution in order to produce an etchant.
Dependencies are inferred from the claim text.