| 摘要 |
<p>PROBLEM TO BE SOLVED: To radially slide off a foreign substance deposited near the center through a recess by providing the recess at a part of a protrusion on concentric circle to the wafer holder center and reducing the pressure in the recess below an atmosphere pressure. SOLUTION: Delivery openings 2, chucking holes 1a, annular protrusions 1b and annular recesses Z are provided for a wafer holder 1. The annular recess Z has staggered notches so that neighboring places are not recessed. In the outermost recess, the atmosphere pressure must be lowered for the holding purpose, it is concentric and no annular recess Z is provided. Thus, a foreign substance deposited near the center can be slid off radially through the recess whereas the contact surface to a wafer is decreasing. When it is assembled in a stepper, a foreign substance on the wafer back side is collapsed by the vacuum chucking and it is expectable to lessen the yield reduction.</p> |
