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.
Claims13
A method for preparing an etchant comprising tetramethylammonium hydroxide, dissolved silicate ions, and water, wherein a liquid source of dissolved silicate ions is mixed with tetramethylammonium hydroxide and water.
A method for etching silicon with a TMAH etchant comprising TMAH and water wherein an oxidizer obtained from a liquid source of oxidizer is added to said TMAH etchant at a time later than ten minutes following the beginning of the process of etching a sample comprised of silicon.
Dependencies are inferred from the claim text.