AVS 50th International Symposium
    Surface Science Thursday Sessions
       Session SS1-ThM

Paper SS1-ThM9
Oxygen Etching of Low- and High-Index Si Surfaces

Thursday, November 6, 2003, 11:00 am, Room 310

Session: Patterned Growth and Etching of Semiconductors
Presenter: A.A. Baski, Virginia Commonwealth University
Authors: J.L. Skrobiszewski, Virginia Commonwealth University
A.A. Baski, Virginia Commonwealth University
Correspondent: Click to Email
When Si surfaces are exposed to O@sub 2@ at elevated temperatures, both oxide nucleation and etching can occur, with etching dominating at higher temperatures. We have used scanning tunneling microscopy (STM) to study the transition regime where both processes occur on the low-index (001) and (111) surfaces, as well as on the high-index (5 5 12) and (113) surfaces. All of these surfaces were exposed to O@sub 2@ at sample temperatures of 675 to 750°C, pressures on the low 10@super -7@ Torr scale, and exposures of 5 to 400 Langmuirs. On the low-index surfaces, the surface morphology can be significantly disrupted in this transition regime by etch pits, as well as monoatomic height islands caused by etching around oxide-induced pinning sites. The original terrace-plus-step morphology is only maintained for temperatures above 750°C, where only step-flow etching occurs. For the transition regime on the high-index Si(5 5 12) surface, no etch pits are found on the terraces, but three-dimensional pyramidal or linear islands are observed on terraces and along step edges. These islands presumably form at oxide nucleation sites and grow in size as the surrounding surface is etched away. Interestingly, both the pyramidal and linear islands incorporate (113) facet planes, indicating an enhanced stability of this orientation against etching. When the Si(113) surface is exposed to O@sub 2@ under similar conditions, the resulting morphology also shows no etch pits and incorporates 3D islands, but without any well-defined facet planes. The etching behavior of the high-index surfaces in the transition regime is therefore qualitatively different from that observed for the low-index planes.