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Polish profile control using magnetic control head

Published online by Cambridge University Press:  15 March 2011

Manabu Tsujimura ,
Yu Ishii ,
Norio Kimura  and
Masahiro Ota
Manabu Tsujimura
Affiliation:
Precision Machinery Group, Ebara Corporation 4-2-1 Honfujisawa Fujisawa, Japan
Yu Ishii
Affiliation:
Precision Machinery Group, Ebara Corporation 4-2-1 Honfujisawa Fujisawa, Japan
Norio Kimura
Affiliation:
Precision Machinery Group, Ebara Corporation 4-2-1 Honfujisawa Fujisawa, Japan
Masahiro Ota
Affiliation:
Department of mechanical engineering, graduate school of eng. Tokyo Metropolitan University 1-1, Minami-Oosawa, Hachi-oji, Tokyo, Japan
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Abstract

Magnetic bearing technology is widely used in various technical fields, and is particularly appreciated in the semiconductor industry, where it is applied to the turbo molecular pump and wafer transfer system due to the excellent controllability it provides, even at speeds as high as 50,000 rpm. This report discusses the adoption of magnetic bearing technology to control the wafer carrier tilt angle during polishing. When the wafer is polished on a viscoelastic pad, the wafer carrier is inclined and pressed into the pad. Therefore, the reaction force on the wafer from the pad is concentrated at the wafer edge, increasing the polish rate at the edge relative to the rest of the wafer. Modification of the tilt angle is thought to offer a possible means of normalizing the distribution of the reaction force from the pad and correcting the nonuniformity of the polish rate. The wafer carrier was confirmed to press slightly into the pad and to be tilted 18 × 10-5 rad by the viscoelasticity of the pad (without tilt angle control). Constant current control led to better control of the polish rate profile relative to feedback control. The polish rate in the outer area of the wafer was increased by tilting the carrier to the positive side, and the polish rate of the wafer center area could be reduced by tilting it to the negative side. The best profile was obtained with control current of Im = -0.4 A. When the wafer carrier was tilted in the reverse direction, the polish rate became almost zero. It was concluded that hydro-planing occurred between the wafer and the pad. Accordingly, this report demonstrates the possibility of improving the polish rate profile by maintaining the wafer carrier in a horizontal position using magnetic control.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 816: Symposium K – Advances in Chemical-Mechanical Polishing , 2004 , K3.1
Copyright
Copyright © Materials Research Society 2004

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