Atomically Controlled Processing for Group IV Semiconductors by Chemical Vapor Deposition

Abstract

One of the main requirements for Si-based ultrasmall devices is atomic-order control of process technology. Here we show the concept of atomically controlled processing for group IV semiconductors based on atomic-order surface reaction control. By ultraclean low-pressure chemical vapor deposition using SiH4 and GeH4 gases, high-quality low-temperature epitaxial growth of Si, Ge, and Si1-xGex with atomically flat surfaces and interfaces on Si(100) is achieved, and atomic-order surface reaction processes on group IV semiconductor surface are formulated based on a Langmuir-type surface adsorption and reaction scheme. In in-situ doped Si1-xGex epitaxial growth on the (100) surface in a SiH4–GeH4–dopant (PH3, or B2H6 or SiH3CH3)–H2 gas mixture, the deposition rate, the Ge fraction and the dopant concentration are explained quantitatively assuming that the reactant gas adsorption/reaction depends on the surface site material and that the dopant incorporation in the grown film is determined by Henry's law. Self-limiting formation of 1–3 atomic layers of group IV or related atoms in the thermal adsorption and reaction of hydride gases on Si(100) and Ge(100) is generalized based on the Langmuir-type model. Si or SiGe epitaxial growth over N, P or B layer already-formed on Si(100) or SiGe(100) surface is achieved. Furthermore, the capability of atomically controlled processing for advanced devices is demonstrated. These results open the way to atomically controlled technology for ultralarge-scale integrations.