Piezoelectric MEMS fabrication flow

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In recent years, MEMS device technology has evolved further and has become indispensable for various sensors and actuators. In particular, the use of piezoelectric materials, which are expected to contribute to miniaturization and higher performance of MEMS, is expected. This section introduces the manufacturing process of piezoelectric MEMS and the required technology, using PZT, which has excellent piezoelectric properties among piezoelectric materials.

Piezoelectric MEMS fabrication flow

1. Formation of piezoelectric element

A piezoelectric element is formed by sandwiching a few μm of ferroelectric between noble metal electrodes.

The sputtering equipment provided by ULVAC can stably form the world’s highest level PZT sputtered film. (Compatible with film deposition on CMOS: PZT film deposition temperature <500 ° C)  PZT full stack (upper and lower electrodes + PZT) can be consistently deposited with a multi-chamber.

Introduction of low temperature PZT sputtering process

Introduction of Sputtering system

2. Upper electrode Pt / PZT etching

Apply resist mask.

The upper electrode and PZT are etched by dry etching to separate elements.

We provide Pt / PZT etching process with high selectivity to Pt which is the lower electrode. (Selection ratio: PZT / Pt> 5 @ 8inch,> 10 @ 6inch)

Introduction of PZT etching process

Introduction of Etching system

3. Pt etching of bottom electrode

Apply resist mask.

The lower electrode is separated by dry etching. It realizes high uniformity and precise end point detection so that the material under the lower electrode is not cut too much. (Distribution <3% @ 8inch)

Introduction of PZT etching process

Introduction of Etching system

4. Formation of passivation film

A passivation layer of SiO2 is formed by CVD.

5. Pulling out the electrode part

Etching SiO2 to extract the electrode part.

6. Formation of hollow structure

Dry etching of the silicon on the back side forms movable parts.

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