Wafer pin chuck fabrication and repair
View Patent ↗In a wafer chuck design featuring pins or “mesas” making up the support surface, engineering the pins to have an annular shape, or to contain holes or pits, minimizes sticking of the wafer, and improves wafer settling. In another aspect of the invention is a tool and method for imparting or restoring flatness and roughness to a surface, such as the support surface of a wafer chuck. The tool is shaped such that the contact to the surface being treated is a circle or annulus. The treatment method may take place in a dedicated apparatus, or in-situ in semiconductor fabrication apparatus. The tool is smaller than the diameter of the wafer pin chuck, and may be approximate to the spatial frequency of the high spots to be lapped. The movement of the tool relative to the support surface is such that all areas of the support surface may be processed by the tool, or only those areas needing correction.
1. A method for lapping a wafer chuck having a wafer support surface that is populated with pins, each of the pins having a pitted terminal surface having a roughness, the terminal surfaces collectively configured to contact and support a semiconductor wafer, said method comprising:
(a) providing a lapping tool having a toroidal surface having a recessed central region (i) having a diameter that is less than that of said wafer chuck;
(b) bringing said lapping tool into contact with said terminal surfaces of said pins of said wafer chuck;
(c) passing said lapping tool over all of said support surface of said wafer chuck, and thereby abrading high spots on said collection of terminal surfaces of said pins, and thereby bringing said collection of terminal surfaces of pins to a flat condition while maintaining a roughness; wherein the toroidal surface and the recessed central region of the tool allows gradual transition as the tool passes over the high spots by maintaining contact with adjacent lower spots of the pins during lapping.
2. The method of claim 1 , wherein the tool is ceramic.
3. The method of claim 1 , wherein the tool is the same material as the pin chuck.
4. The method of claim 1 , wherein said terminal surface has a SPQ plateau roughness of at least 23.9 nm.