New Capping Technique for Zone-Melting Recrystallization of Silicon-on-Insulator Films

摘要

In the zone-melting recrystallization (ZMR) process for preparing silicon-on-insulator (SOI) films, a polycrystalline Si (poly-Si) film on a SiO2-coated Si substrate is recrystallized by the passage of a molten Si zone. To obtain a device-quality SOI film, the poly-Si film must be encapsulated to ensure that the molten Si zone will exhibit uniform wetting as it traverses the film. In this letter, we report a new capping technique that has made it possible to achieve a major improvement in the effectiveness and reproducibility of ZMR performed by the graphite strip heater technique. This new capping technique employs high-temperature NH3 annealing to ensure uniform wetting by the molten Si zone during zone-melting recrystallization of Si-on-insulator films. By using this technique, we have reproducibly prepared 0.5-micrometer-thick films with (100) crystalline texture that are improved in smoothness, void density, and thickness uniformity. In addition, recrystallized 1-micrometer-thick films have been obtained with large areas that are free of subboundaries, containing only threading dislocations at densities of less than 2,000,000/sq cm.