MECHANICS OF RELAXING SiGe ISLANDS ON A VISCOUS GLASS

• 来源期刊: 力学学报（英文版）
• 学科: 物理学
• 年，卷（期）: 2002,（5）
• 页码范围: 441-456
• 页数: 16页
• 分类号: O3
• 语种: 英文

摘要

A process has been developed recently to fabricate a structure com-prising, from top to bottom, a SiGe thin film, a glass layer, and a Si wafer. TheSiGe film is a perfect crystal, and is under biaxial compression. The SiGe film ispatterned into islands. On annealing, the glass flows and the islands relax. Theresulting strain-free islands are used as substrates, to grow epitaxial optoelectronicdevices. This article describes a series of studies on the annealing process, combiningexperiment and theory. A small island relaxes by expansion, starting at the edgesand diffusing to the center. A large island wrinkles before the expansion reaches thecenter. After some time, the wrinkles either disappear, or cause the island to fracture.We model the island as an elastic plate, and the glass layer as a viscous liquid. Thestrains in the islands are measured by X-ray diffraction and Raman spectroscopy, andthe wrinkle amplitudes by atomic force microscope. The data are compared with thetheoretical predictions. We determine the conditions under which the islands relax byexpansion without significant wrinkling, and demonstrate that a cap layer suppresseswrinkles, relaxing a large island crack-free.