The goal of this project is to identify the chemical steps in plasma-assisted chemical etching of electronic materials by obtaining a detailed view of the chemistry that occurs on the surface during this thin film process. The approach is to use optical probes of the surface, those that have been developed, and by developing and employing new surface-sensitive optical probes as needed, and by utilizing existing diagnostic techniques to probe the plasma. The etching of several key materials, including Si, GaN, and SiC, will be studied in several environments, including C12 and C12/Ar high charge density plasmas, to understand the molecular and surface processes that contribute to these materials processes. Laser-induced thermal desorption (LITD), a surface sensitive optical probe, will be used to study the steady-state surface layer that is formed during etching in an inductively coupled plasma (ICP), a prominent type of high charge density plasma. The chemistry of the formation and desorption of this layer, which is sometimes only a monolayer thick is considered key to understanding the etching process. Laser-desorption based methods will be used to probe in situ and in real time the plasma etching. When possible, laser induced fluorescence (LIF) will be used to examine the desorbed products. When LIF detection is not possible or feasible, the transient increase in plasma-induced emission (PIE) after laser desorption will be monitored to detect desorbed products. This LD-PIE method will be developed as part of the proposed work. Preliminary studies have shown that LD-PIE analysis can have submonolayer sensitivity. Other diagnostics will be used to characterize the plasma and the etching process, such as optical emission actinometry, Langmuir probing, and microwave interferometry. %%% The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The research will contribute basic materials science knowledge at a fundamental level to important fabrication aspects of electronic/photonic devices. New experimental optical tools are now available to allow more detailed observation of elementary surface processes which when better understood allow advances in fundamental science and technology. The basic knowledge and understanding gained from the research is expected to contribute to improving the perform-ance and stability of advanced devices and circuits. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. ***
