Formation of Silicon-Nitride Structures by Direct Electron-Beam Writing
Localized deposits of silicon nitride, which are stable to at least 500(DEGREES)C, have been formed by a new technique: electron bombardment of nitrogen molecules weakly bound on a clean Si(100)-(2 X 1) surface chilled to T (TURN) 30(DEGREES)K. This process is fairly efficient; for an initial coverage of one monolayer of molecular nitrogen, we estimate the effective dissociation cross section (primary electron energy = 2000 eV) to be (0.54 - 1.2) X 10('-15) cm('2). Using Auger electron spectroscopy and LEED, we have studied the growth of a silicon nitride/silicon interface rigorously free from contamination and from damage due to sputtering or ion implantation. In the Si(LVV) Auger spectrum of silicon nitride, a strong peak at 83 eV predominates; the 91-eV peak characteristic of clean Si vanishes entirely for sufficiently thick nitride films ((TURN) 25 - 30 (ANGSTROM)). LEED measurements, with the substrate at T (TURN) 30(DEGREES)K, reveal no ordered overlayers--the pattern stays (2 X 1), but the background increases with nitridation until a fully disordered structure results. Our Auger and LEED data further indicates that the initial stage of electron-induced nitridation is the formation of a monolayer of chemisorbed nitrogen via the nucleation and lateral growth of islands.
University of Illinois - Urbana-Champaign
Networked Digital Library of Theses and Dissertations
University of Illinois at Urbana-Champaign