Modeling and laboratory scale proof of concept of the horizontal ribbon growth process: Application to silicon wafer manufacturing

摘要

In this work we focus on the development of the Horizontal Ribbon Growth technique to produce highly pure silicon wafers for use in solar cells. We divide this preliminary work in two parts: a small scale experiment and the development of mathematical models to describe the crystallization phenomena. We begin by constructing a laboratory scale experiment to demonstrate the HRG concept using water as the working fluid. We made use of the fact that ice floats on water just like silicon would float on top of its melt. Therefore it is possible to conveniently test and analyze the operability of this technique. We find that the initial seeding process needs to be carefully controlled in order to extract a uniform wafer. Appropriate surface cooling and wall heating are necessary to guarantee the continuous formation of an ice film. We then develop simple mathematical models to predict the crystallization rate and thermal profiles of the system. We state that the driving force for crystallization is convective cooling and the film grows in one direction (downwards). Finally we propose how to validate the model using experimental data and how to extend the work to grow silicon ribbons.