Control of Microtopography at Silicon Surfaces and Interfaces

Cornell University, Ithaca NY

Investigators

Abstract

This project addresses properties of defects at silicon and other semiconductor surfaces and explores methods to control the topography of surfaces and interfaces at the atomic level. The research involves the study of surface atomic diffusion, the energetics and dynamics of surface atomic steps, oxidation-induced strain and detailed control of surface and interface morphology. Scanning tunneling microscopy and low energy electron microscopy are used to observe the connection between atomic step motion and the evolution of overall surface shape. Results are expected to be of interest to fundamental surface science and in the fabrication of advanced semiconductor devices and circuits. The research may contribute to the design and control of interfaces in heterogeneous magnetic systems such as are used in magneto-resistive applications as well. Surfaces with predetermined arrays of atomic scale features may also be of value in making patterned substrates for biological sensors. The primary project goal is to more fully understand the fundamental processes involved in Si morphology control and to explore the extension and application of these processes to other materials. Specific objectives of the project include: 1)Study of the temperature and growth rate conditions to create atomically flat mesa structures on Si(001) and Si(111) by vapor deposition plus related work on the use of chemical etching as an alternative to sublimation. 2)Study of the types of point defects existing at high temperatures through AFM and STM observations on quenched Si surfaces with extremely large terraces. 3)Develop ways to make potentially useful patterns of steps on Si and other substrates as templates for adsorbed or deposited structures. Applications will be sought with bio-molecules and with magnetic layers. 4)Study of the kinetics of oxide growth on atomically flat Si using an X-ray technique to monitor the intensity of forbidden reflections-analogous to RHEED oscillations. %%% The project addresses basic research issues in a topical area of materials science with high technological relevance. 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. The project assists development of technical, communication, and organizational/management skills in students through unique educational experiences made possible by a forefront highly collaborative research environment. Key collaborators in this project include Cornell-based researchers Dr. C.C. Umbach (Materials Science & Eng.), Prof. J. Engstrom (Chem. Eng.), Dr R. Headrick (CHESS), Prof M. Hines (Chemistry), Dr R. Tromp (IBM), and Dr N. Bartelt (Sandia). ***