Patent ID: 7495460

Claim:
A heater unit used for a wafer prober for testing a semiconductor wafer, comprising: a wafer holding body comprising a chuck top including an electrically conductive layer on a surface thereof and a support body supporting said chuck top, said support body having a base portion opposing said chuck top and a side portion extending from a perimeter of said base portion to said chuck top to support said chuck top, wherein a cavity portion is formed between said chuck top and said base portion of said support body and a reflection plate is provided in said cavity portion, an emissivity of the surface of the reflection plate opposing the chuck top is at most 0.5, a distance between the surface of the reflection plate opposing the chuck top and the surface of the chuck top opposing the reflection plate is at least 1 mm, Young's modulus of the support body is 200 GPa or more, and a thermal conductivity of the support body is 40 W/mK or less.