Initial surface reactions of atomic layer deposition

Abstract

Atomic layer deposition (ALD) is a promising thin film deposition technique for sub-45 nm CMOS technology with unique capabilities, such as ultraprecise thickness control and conformal deposition on high aspect ratio three-dimensional nanostructures, and so on. The operating principle of ALD is a self-limited surface reaction between species formed by the discretely pulsed precursor vapors and the reaction surface. It is possible to theoretically calculate the ideal deposition thickness from the growth rate and the number of cycles performed, but the initial growth rate is often non-linear. Understanding the initial growth mechanics is crucial for the use of ALD on thin gate dielectric processes as well as nanotechnology. The film growth during the first few cycles of deposition may be linear, enhanced, or inhibited. This paper gives a brief overview on the basics of ALD operation, and attempts to explain what factors into the initial growth by discussing interface formation, etching, and passivation behaviors. Also addressed is the application of novel ALD techniques in nanotechnology for patterning and nanomaterials.