Comparison of different bonding techniques for efficient strain transfer using piezoelectric actuators

TL;DR

This study compares bonding techniques for strain transfer from piezoelectric substrates to semiconductor membranes, revealing that polymer-based SU8 bonding achieves higher efficiency than gold-thermo-compression, explained by interface structures.

Contribution

It provides a comparative analysis of bonding methods for strain transfer efficiency using XRD and FEM, highlighting the superior performance of SU8 bonding.

Findings

SU8 bonding shows higher strain transfer efficiency than gold-thermo-compression.

Interface structures significantly influence strain transfer performance.

XRD and FEM results are consistent in explaining the observed differences.

Abstract

In this paper strain transfer efficiencies from single crystalline piezoelectric lead magnesium niobate-lead titanate (PMN-PT) substrate to a GaAs semiconductor membrane bonded on top are investigated using state-of-the-art x-ray diffraction (XRD) techniques and finite-element-method (FEM) simulations. Two different bonding techniques are studied, namely gold-thermo-compression and polymer-based SU8 bonding. Our results show a much higher strain-transfer for the "soft" SU8 bonding in comparison to the "hard" bonding via gold-thermo-compression. A comparison between the XRD results and FEM simulations allows to explain this unexpected result with the presence of complex interface structures between the different layers.