The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 24, 2012
Filed:
Feb. 08, 2007
Ashwin M. Purohit, Gloucester, MA (US);
Ashwin M. Purohit, Gloucester, MA (US);
Axcelis Technologies, Inc., Beverly, MA (US);
Abstract
A method for clamping a workpiece involves placing the workpiece on a clamping surface of an electrostatic clamp. A clamping voltage is applied to the electrostatic clamp at a first frequency, therein providing a first clamping force between the workpiece and the electrostatic clamp. The application of clamping voltage at the first frequency is halted and another clamping voltage at a second frequency is applied to the electrostatic clamp, therein providing a second clamping force between the workpiece and the electrostatic clamp. The second frequency is greater than the first frequency, wherein the second clamping force is less than the first clamping force. The application of the clamping voltage at the second frequency is then halted, and the workpiece is removed from the electrostatic clamp. The clamping voltage can be controlled based on a set of performance criteria, such as a desired minimum clamping force and a maximum de-clamp time.