Piezoeletric wet etch process with reduced resist lifting and controlled undercut

US9755139B2 · kind B2 · utility

Assignee

• TEXAS INSTRUMENTS INCORPORATED · US

Inventors

• Neng Jiang · Plano, US
• Xin Li · Beijing, CN
• Joel Soman · Dallas, US
• Thomas Warren Lassiter · Garland, US
• Mary Alyssa Drummond Roby · Plano, US
• YungShan Chang · Plano, US

Key dates

• Filing date: Jun 13, 2015
• Grant date: Sep 5, 2017
• Expiry date: Mar 10, 2036

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10N30/8554

Abstract

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.