Method of measuring thickness of epitaxial layer

A method of measuring the thickness of an epitaxial layer, said method comprising:

• providing a substrate having a dielectric layer thereon, wherein said dielectric layer only covers a portion of said substrate;
• forming an epitaxial layer over said substrate and said dielectric layer, wherein the portion of said epitaxial layer on said dielectric layer grows into a polycrystal layer;
• measuring the thickness of said polycrystal layer and the thickness of said dielectric layer;
• and
• measuring the thickness difference between said polycrystal layer plus said dielectric layer and said epitaxial layer, thereby the thickness of said epitaxial layer equals to the result of the total thickness of said polycrystal layer plus said dielectric layer minus the thickness difference between said polycrystal layer plus said dielectric layer and said epitaxial layer.

A method of measuring the thickness of an epitaxial layer, said method comprising:

• providing a silicon substrate having a non-single crystal layer thereon, wherein said non-single crystal layer only covers a portion of said substrate;
• forming an epitaxial silicon layer over said silicon substrate and said non-single crystal layer, wherein the portion of said epitaxial silicon layer on said non-single crystal layer grows into a polysilicon layer;
• measuring the thickness of said polysilicon layer and the thickness of said non-single crystal layer;
• and
• measuring the thickness difference between said polysilicon layer plus said non-single crystal layer and said epitaxial silicon layer, thereby the thickness of said epitaxial silicon layer equals to the result of the total thickness of said polysilicon layer plus said non-single crystal layer minus the thickness difference between said polysilicon layer plus said non-single crystal layer and said epitaxial silicon layer.