Low-expansion unit, method of manufacturing the same and semiconductor provided with the same

Abstract

A low-expansion unit includes a plate member and an iron-nickel layer. Upper and lower surface layers of the plate member each have the iron-nickel layer thereon and/or therein. While the plate member has a relatively large thermal expansion coefficient, the iron-nickel layers, which are formed on and/or in the upper and lower surface layers of the plate member, have a relatively small thermal expansion coefficient. Therefore, thermal expansion coefficient of the low-expansion unit is as a whole restrained to a relatively small value. Also, the plate member includes pure iron whose thermal conductivity is relatively high. Meanwhile, the iron-nickel layers, which are formed on the plate member, are relatively thin. Therefore, the low-expansion unit has a relatively large thermal conductivity in a direction of thickness thereof.