Title: In-process force monitoring for precision grinding semiconductor silicon wafers

Authors: Jeremiah A. Couey, Eric R. Marsh, Byron R. Knapp, R. Ryan Vallance

Addresses: Machine Dynamics Research Laboratory, The Pennsylvania State University, 21 Reber Building, University Park, 16802 PA, USA. ' Machine Dynamics Research Laboratory, The Pennsylvania State University, 21 Reber Building, University Park, 16802 PA, USA. ' Olympic Laser, Inc., 410 Ida Street West, Bremerton, WA 98312, USA. ' Precision Systems Laboratory, The George Washington University, 738 Phillips Hall, 801 22nd St. NW, Washington DC, 20052, USA

Abstract: Forces generated during precision wafer grinding are small and present challenges for accurate and reliable process monitoring. In this work, these challenges are met by incorporating noncontact displacement sensors into an aerostatic spindle that is calibrated to measure grinding forces from the relative motion between the spindle rotor and stator. This arrangement allows the calculation of grinding forces without introducing compliance into the structural loop of the grinding machine. Aerostatic spindles are used in precision wafer grinding requiring high stiffness and very low error motions (5–25 nm). Several experiments evaluate this force sensing approach in detecting workpiece contact, process monitoring with small depths of cut, and detecting workpiece defects. The results indicate that force measurements offer good performance for monitoring precision wafer grinding since this approach provides excellent contact sensitivity, high signal resolution, and has sufficient bandwidth to detect events occurring within a single revolution of the grinding wheel.

Keywords: silicon wafer grinding; grinding process monitoring; grinding sensors; semiconductor manufacturing; in-process force monitoring; precision grinding; noncontact displacement sensors; aerostatic spindles; force sensing; force measurements; workpiece contact; depth of cut; workpiece defects.

DOI: 10.1504/IJMTM.2005.007695

International Journal of Manufacturing Technology and Management, 2005 Vol.7 No.5/6, pp.430 - 440

Published online: 02 Sep 2005 *

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