Manufacturing method of semiconductor substrate

Abstract

Closure at the opening of a trench with an epitaxial film is restrained, and thereby, filling morphology in the trenches is improved. A method for manufacturing a semiconductor substrate includes a step for growing an epitaxial layeron the surface of a silicon substrate, a step of forming a trenchin this epitaxial layer, and a step of filling the inside of the trenchwith the epitaxial film, wherein mixed gas made by mixing halogenoid gas into silicon source gas is circulated as material gas in filling the inside of the trench with the epitaxial film, and when the standard flow rate of the halogenoid gas is defined as Xslm and the film formation speed of the epitaxial film formed by the circulation of the silicon source gas is defined as Yμm/min, in the case when the aspect ratio of the trench is less than 10, an expression Y<0.2X+0.10 is satisfied, and in the case that the aspect ratio of the trench is between 10 and less than 20, an expression Y<0.2X+0.05 is satisfied, and in the case that the aspect ratio of the trench is 20 or more, an expression Y<0.2X is satisfied.