Near equilibrium growth of silicon by CVD I. The Si-Cl-H system

Abstract

Epitaxial growth of silicon is normally performed at high temperatures in cold wall reactors where the growth rate is limited by the supply of reactant via gas phase diffusion. The packing density of wafers in such reactors is low and there is an urgent need to improve this situation. Growth in a hot wall reactor is already used for the deposition of polycrystalline silicon at low temperatures (600ȁ700°C). At temperatures above 1000°C, favoured for monocrystalline growth, strong depletion effects occur; enhanced by the deposition of silicon on the quartz walls of the reactor. These drawbacks prevent the use of a hot wall system for high temperature growth of silicon. Kinetic and thermodynamic reasoning points to possibilities and advantages of near equilibrium growth. The thickness homogeneity of the deposit increases when growth and etching occur simultaneously, i.e., when apart from solid silicon also gaseous silicon containing reaction products are formed. The small supersaturation used provides for epitaxial growth of silicon on silicon, whereas nucleation and growth on the hot quartz walls and boats is prevented. Some results of calculations and experiments in the Si-Cl-H system are reported and the feasibility of the method is discussed.