40. Measuring the Foundation of a Transistor

Abstract

The process of creating a homemade transistor (using a recipe by Jeri Ellsworth) involves the forming of an oxide layer onto the surface of a p-doped silicon wafer with a crystal orientation of. Deposition channels for the p-n junctions are etched into the oxide layer using hydrofluoric acid, followed by the spinning of the liquid n-type dopant into the channels. The n-type dopant is then driven into the silicon by steam heat treatment.

The process by which the oxide layer is formed and measured has yet to be rigorously analyzed for this technique. The focus of this project is to standardize the methodology in order to obtain reproducible quantitative data. To form an oxide layer, a silicon wafer is placed inside a quartz tube heated to 1000 C^o within a furnace. A measured amount of steam from a steam generator is piped into the quartz tube thereby forming the oxide layer on the surface of the silicon wafer for a period of time. The thickness of the oxide layer is measured either by analyzing the constructive interference of the reflected light or by an atomic force microscope. This preliminary work serves as the foundation for future projects on producing quality p-n junctions and working transistors.