9703237 Muscat The objective of this CAREER project is to understand how water and other polar molecules initiate and sustain silicon dioxide etching in the gas phase using hydrogen fluoride. Oxide etching is an important process in the fabrication of microelectronic devices and is a paradigm for gas phase adaptation of the aqueous solutions that are currently used to prepare semiconductor surfaces between primary processing steps such as plasma etching and deposition. A mechanism is proposed for gas phase etching of silicon dioxide in HF/water mixtures to understand how water initiates and sustains etching and how the strong HF bond is broken. Experiments in both the fast etching regime where rates are industrially viable and the single layer regime where the surface and gas phase can be controlled precisely in an ultra high vacuum apparatus will be studied. Real time Fourier Transform Infrared (FTIR) spectroscopy and mass spectrometry done in situ will be complemented with ellipsometric and Auger measurements made after etching to examine the mechanistic details. Specifically, the rate of production and chemical bonding of surface silanol (Si-OH) groups will be examined in the fast etching regime as a function of pressure, surface temperature, and the fractional saturation vapor pressures of HF and a hydroxyl-bearing molecule, such as water, alcohols, glycols, and glycerol. Precise coverages of HF and a hydroxyl-bearing molecule will be deposited on an oxide surface in an ultra high vacuum chamber to examine chemical bonding, clearing of the final oxide layer, and a bifurcation in the reaction when the dosing order is reversed. %%% The project addresses fundamental research issues in a topical area of materials science having high technological relevance. The research will contribute basic materials science knowledge at a fundamental level to important aspects of microelectronics materials and devices, in general. An important feature of the program is the emphasis on education, and on the integration of research and education through the training of students in a fundamentally and technologically significant research area. ***
