Float zone silicon sheet growth. Final report, September 23, 1993--December 31, 1996

Energy Materials Research was organized in 1984. The specific objective of the company is to generate new concepts and to move targeted applications of newly developing technologies into commercial production. The initial technology described here is the outgrowth of a research program to develop concepts and techniques for low-cost energy production from renewable energy resources. The first major project implements an innovative process for the direct production of crystalline silicon sheet from a polycrystalline silicon source. The apparatus is designed to achieve this objective. Its primary goal is the efficient, low cost production of crystal silicon sheet of the highest quality silicon for the electronics industry. The objective of this phase of the project is to develop a laboratory processor that will produce single crystal ribbons or sheets of semiconductor quality silicon. A summary description of the overall process to be implemented is as follows: a single crystal seed in the form of a sheet is placed on a substrate in a non-reactive ambient and a carefully controlled thermal environment. The seed is heated to a stabilized temperature near the melting point in the zone designated for the crystal growth. A melt zone is developed. Melting is accomplished in the growth zone with a unique heating source which provides a very low thermal gradient in the pull direction but permits a high thermal gradient normal thereto. The sheet is pulled from the melt allowing crystallization to occur nearly normal to the pulling direction. The melt is replenished from a polycrystalline source heated by an ancillary RF power supply. Development of this process, unique to silicon sheet technology, provides several important benefits