Wafer–to–wafer transfer process of barium strontium titanate for frequency tuning applications using laser pre-irradiation

Abstract

This paper describes laser-assisted film transfer technology for barium strontium titanate (BST) deposited on a sapphire substrate. BST is a promising ferroelectric material for varactors, which are required for frequency-tunable RF applications. However, the deposition temperature of BST (600 ~ 700 °C) is too high for surface acoustic wave (SAW) substrates. In this study, BST grown on a sapphire substrate at 650 °C was transferred at low temperature (140 °C) to a borosilicate glass substrate as well as a LiTaO3 substrate. The transferred BST films were characterized as tunable capacitors. A key process in the BST film transfer technology is the laser pre-irradiation of a buffer Pt layer beneath BST from the backside of the sapphire substrate to weaken the BST-to-Pt adhesion. The mechanism of delamination at the BST/Pt interface is discussed using a simple 1D heat transfer model.

Highly transparent piezoelectric PZT membranes for transducer applications

“…An alternative way for getting optimal PZT on transparent electrode is to use film transfer processing [15]. In that case, the optimal PZT stack grown on suitable substrate is transferred to a host substrate following various possible techniques (grinding of the donor substrate [16], etching of sacrificial layer between PZT and the grown substrate [17][18][19][20], laser lift-off [21]). More details about transfer processing can be found in the review paper of Song et al [22].…”