Method for manufacturing a semiconductor substrate and method for suppressing occurrence of cracks in a growth layer

A method for manufacturing a semiconductor substrate, comprising:

• an embrittlement processing step of reducing strength of an underlying substrate;
• and
• a crystal growth step of forming a growth layer on the underlying substrate,
• wherein the embrittlement processing step includes a through hole formation step of forming through holes in the underlying substrate;
• wherein the underlying substrate is freestanding and the through holes allow airflow to pass through the underlying substrate;
• wherein a ratio of an area occupied by the through holes to a surface of the underlying substrate on which the growth layer is formed is 50% or more;
• and
• wherein the crystal growth step is a step of forming the growth layer having a shrinkage rate different from that of the underlying substrate.