Deposition of multiple layer thin films using a broadband spectral

Abstract

A method is provided for monitoring and controlling the deposition of multiple layer thin films using a broadband spectral monitor and a generalized model of the film. A design specification, including the number of layers and the material, refractive index, and thickness of each layer, is provided for the desired thin film. A target optical thickness is computed for the end point of each layer using correction factors based on the generalized model, preferably a single layer model, of the multilayer thin film. A monitor chip, such as a silicon substrate, is used for monitoring the multiple layers of film deposition. During deposition of the film, a broadband spectral monitor (BBSM) comprising a source of broadband light is directed onto the monitoring chip. Light reflected by the monitoring chip is received by a photosensor that provides a broadband reflectance spectrum to a computer. The BBSM reflectance spectrum is fit to the generalized model to produce an output corresponding to the optical thickness of the deposited film. When the broadband spectral monitor optical thickness measurement equals the target optical thickness at the end point of the layer, deposition of that layer is terminated and deposition of the next layer may commence. This process is repeated during the deposition of each successive layer until the entire multiple layer thin film is complete.