Single Crystal Silicon‐on‐Oxide by a Scanning CW Laser Induced Lateral Seeding Process

Abstract

A 1 μm thick layer of silicon dioxide is grown on selected areas of a {100} silicon wafer such that the resulting silicon dioxide surface is coplanar with the surface of the silicon wafer. A 0.5 μm thick layer of polycrystalline silicon is deposited onto the silicon wafer using a low pressure CVD process. By scanning a focused CW argon laser beam onto the area where the polycrystalline silicon is deposited directly on the exposed silicon substrate, the polycrystalline silicon is converted into an epitaxial layer by a liquid phase process. By scanning the laser beam from the epitaxial region to the region where the polycrystalline silicon is deposited on the silicon dioxide layer, the polycrystalline silicon is converted into a single crystal through a zone melting process, where the previously formed epitaxial layer is used as the seed. This process is named “lateral seeding.” It is found that the resulting area of the single crystal on the silicon dioxide layer is dependent on the temperature of the substrate and the crystallographic direction of the edges of the oxide layer. The best results are obtained with a high substrate temperature and with the edges of the oxide layers aligned along a direction. Single crystal regions that extended as much as 80 μm from the epitaxial seed region onto the silicon dioxide region have been obtained. It is inferred from the experimental results that a line‐shaped beam with a flat intensity profile is preferred for improved lateral seeding results.