Optically Probing the Chemistry of Thin Film Processes

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9411504 Herman This research is concemed with the development of optical diagnostic techniques for obtaining a detailed view of the chemistry that occurs on and near the surface during thin film processing. These in situ techniques are used to identify the chemical steps in representative materials processes, specifically plasma-assisted chemical etching. The proposed work consist of two related phases. The first is the development and use of laser-induced thermal desorption (LITD) to study the steady-state surface layer that is formed during etching in a high charge density plasma, specifically an ECR (electron cyclotron resonance) plasma. The chemistry of the formation and desorption of this layer, which is often only a monolayer thick, is key to understanding the etching process. Plasma-induced optical emission and laser induced fluorescence (LIF) will be used to examine the desorbed products. Laser-induced thermal desorption and other optical probes will be used to investigate the ECR etching of important prototype alloy materials in real time. The second phase of the proposed investigation is the development of high-spatial resolution optical probes of pattemed thin film processing, such as the etching of films with a pattemed mask on the surface. Understanding the details of the chemistry that occurs on and immediately above the surface of the exposed film and mask, and near the sidewalls of the mask, is complex. The proposed approach is to probe the gas near the surface with LIF and the surface itself wih Raman microprobe spectroscopy, at times simultaneously, both with 1 micron lateral resolution. This will be done in situ and usually in real-time. %%% The processing of materials often depends critically on the chemistry that occurs on and near the surface. This is true for applications in microelectronics and optoelectronics, which includes patterned etching and the atomic layer-controlled growth of heterostructures, monolayers and films, in nanoma nufacturing, and in the manufacture of optical films and protective coatings. However, a fundamental understanding of the chemical steps that occur is often lacking in such materials processing. This occurs, in part, because of the complex nature of the processes which may include the interplay between events on the surface and in the overlying gas phase, and, in part, because of a lack of diagnostics to identify species and to measure their concentrations with sufficient spatial resolution. The linked goals of this proposal are to develop in situ, real time optical diagnostics that are necessary to obtain a detailed view of these chemical processes, and to use them to identify the chemical steps involved in the processes of several key, yet representative, materials processes.