Chemistry and Biochemistry Department

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Chemistry and Biochemistry Department

Thesis Defense

The Production of Atomically Smooth Si(100) Surfaces at Low Temperature Using Low Energy Electron Enhanced Etching (LE4)

Julian Chavez

ABSTRACT

Modern transistors, the fundamental components used in electronic devices, are reaching dimensions bordering on several atoms. At these sizes, the surface roughness of the Si(100) substrate (silicon with the (100) plane orientation) becomes more critical on the performance of the device than larger sized transistors. Future technologies, such as proposed designs for quantum computers, may also suffer from these roughness effects. Current etching methods used in the industry do not uniformly remove silicon from the surface and often impart unwanted damage at the atomic level. Therefore, there is a necessity in developing and investigating techniques to produce atomically smooth surfaces. We used a newer plasma-based method called low energy electron enhanced etching (LE4) at a relatively low temperature of 60 °C with hydrogen gas as the only etching species. Several experimental parameters (e.g. plasma power and hydrogen composition) were varied and their effects on the etching of the Si(100) surface were investigated utilizing a combination of atomic force microscopy (AFM) and profilometry. The influence each parameter had on surface smoothness is discussed. Newly developed mechanisms that explain etching characteristics are also proposed. From the results, we developed a recipe that yielded the most atomically smooth surface achievable by LE4. Root mean square (RMS) roughness values smaller than the length of a silicon unit cell (~5 Å) were obtained for surface areas between 0.0625 to 25 µm2. Si(100) surfaces of this caliber were previously only achievable at temperatures around 1200 °C, meaning LE4 presents a “new world record” in low temperature, low damage etching.

Committee Members Friday, June 3, 2016

Dr. Samir J. Anz (chair) 11:00 – 1:00 PM

Dr. Timothy C. Corcoran Bldg. 4/1-314

Dr. Francis X. Flores