Piezoeletric wet etch process with reduced resist lifting and controlled undercut
A microelectronic device containing a piezoelectric thin film element is formed by oxidizing a top surface of a piezoelectric layer with an oxygen plasma, and subsequently forming an etch mask containing photoresist on the oxidized top surface. The etch mask is conditioned with an oven bake followed by a UV bake. The piezoelectric layer is etched using a three step process: a first step includes a wet etch of an aqueous solution of about 5% NH4F, about 1.2% HF, and about 18% HCl, maintaining a ratio of the HCl to the HF of about 15.0, which removes a majority of the piezoelectric layer. A second step includes an agitated rinse. A third step includes a short etch in the aqueous solution of NH4F, HF, and HCl.
TEXAS INSTRUMENTS INCORPORATED
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H01L H01L H01L H01L H01L
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Mary Alyssa Drummond Neng Joel Xin Thomas Warren YungShan
Roby Jiang Soman Li Lassiter Chang