Study on crystallization mechanism of GeSn interlayer for low temperature Ge/Si bonding

Ziwei Wang,Donglin Huang,Wei Huang,Songyan Chen,Shaoying Ke,Jianyuan Wang,Cheng Li,Zongpei Li,Ziqi Zhang

doi:10.1007/s10854-021-05741-9

Abstract

Low temperature bonding technologies is necessary in next-generation photonic integrated circuits, such as flexible optoelectronic devices, low dark current Ge/Si devices and so on. Since Germanium-Tin (GeSn) alloy has lower crystallization temperature, in this work, amorphous GeSn with 5% Sn alloy by magnetron sputtering is introduced as an intermediate layer for wafer bonding innovatively. And high strength Ge/Si heterojunction with a crystal GeSn layer is realized without any surface activation process. Two mechanisms in the interlayer crystallization are put forward and substantiated experimentally and theoretically: (1) the a-GeSn turns to be poly-GeSn due to the induction of the c-Ge substrate. (2) Stress between Si wafer and interlayer due to thermal mismatch contributes to the crystallization. It is concluded that GeSn semiconductor interlayer bonding would be one of the potential technologies for bonding process.

Highlights

Wafer bonding plays an important role in Micro-Electronic-Mechanical-System (MEMS) integrated packaging[1, 2], and in homojunctions[3] and heterojunctions[4]
Note that the Sn components are uniformly distributed in the GeSn layer and no segregation is observed on the surface
As shown in Figure 2p, the full width at half maximum (FWHM) of Ge-Sn peak from GeSn films decrease with the increase of annealing temperature, close to the substrate peak of Ge

Summary

Introduction

Wafer bonding plays an important role in Micro-Electronic-Mechanical-System (MEMS) integrated packaging[1, 2], and in homojunctions[3] and heterojunctions[4]. By contrast, when annealed at 400 °C slices separated and large areas of air bubbles are introduced, which is proved to be caused by the segregation of Sn from GeSn in high temperature. The Ge/GeSn/Si wafers annealed at 300 °C has a good bonding strength.

Results

Conclusion