Rayleigh Light Scattering Measurements of Transient Gas Temperature in a Rapid Chemical Vapor Deposition Reactor

A laser-induced Rayleigh light scattering (RLS) system was used to measure transient gas temperatures in a simulated rapid chemical vapor deposition (RCVD) Introduction Manufacture of integrated circuits on silicon substrate wafers is an area of substantial research and development. The integrated circuit is made by a series of chemical reaction, photolithography, and etching processes to create and modify thin film layers. These layers form resistors, wires, capacitors, and insulators required to create the desired circuitry. The silicon substrate wafer is about eight inches in diameter, and hundreds of IC chips are manufactured in parallel on this surface. Thin films of silicon are deposited by a temperature-dependent reaction called chemical vapor deposition ͑CVD͒. Traditionally, many wafers are processed simultaneously in quasi-steady state CVD reactors. However, increasing complexity of semiconductor design and higher quality results of single wafer processing has shifted the focus of microchip fabrication from conventional furnace processing to rapid thermal processing, including rapid chemical vapor deposition ͑RCVD͒ ͓͑1͔͒. A typical RCVD process consists of starting a flow of silicon laden carrier gas which transports reactants to substrate wafer surface. Then radiative heating is initiated, ramping the wafer to high temperature to initiate the reaction that causes silicon to atomistically deposit on the wafer surface. The temperature is maintained for a limited period before cooling. Film quality depends on the steady and laminar supply of silicon-laden carrier gas to the wafer surface. Because the reaction is strongly temperature dependent, the carrier gas temperature is a critical parameter. While a large body of numerical work examines carrier gas in the CVD process, the accuracy of the numerical results detailing isotherms and flow lines is largely unknown and untested, and very little numerical work examines RCVD. A good summary of rapid thermal processing technology is found in Fair ͓2͔. The present work presents transient gas temperature measurements in a simulated RCVD chamber. The reactor geometry is that of an axisymmetric jet impinging on a wafer surface, and is illustrated i