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Proceedings Paper

Oxide chemical mechanical polishing closed-loop time control
Author(s): Joern Luetzen; Shapna Pal; Simon Gonzales; Yuval Bar
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Paper Abstract

Oxide chemical mechanical polishing process control has been limited in the past to off-line verification of layer thicknesses. This procedure causes a significant delay in feedback due to the off-line scrubbing process and wafer transfer. Recently, systems have been introduced to endpoint on the polish platen itself using interference-based methods. While these approaches allow a better control of the thickness remaining, they do not replace the off-line measurement because the correlation of the signal with the absolute thickness is difficult and no uniformity information is retrieved. An integrated measurement tool, that provides feedback immediately after the polish cycle, represents an intermediate solution. This methodology reduces the set-up time significantly and allows a 100% control of the outgoing product with increased throughput versus using an off-line measurement system. In respect to optimizing the wafer to wafer variation within lot, the polish time can be adjusted for the subsequent wafer based on the previously polished wafers. The utilized closed loop control algorithm (PID-type) can take the incoming distribution into account as well as first wafers effects and changes in layer type. Considering the results of the measurement of previously polished wafers, the polish time for the following wafer is adjusted to center the thickness distribution around the target. A system as described was implemented on an IPEC 472 polisher at Motorola MOS6. Lot charts showing thickness variations before and after the implementation of CLC have been recorded showing an improved distribution with CLC feedback leading to improvements in process capability by a factor of 1.5. In summary, integrated metrology with closed loop control provides improved process control as well as enhanced throughput for oxide CMP.

Paper Details

Date Published: 3 September 1999
PDF: 9 pages
Proc. SPIE 3882, Process, Equipment, and Materials Control in Integrated Circuit Manufacturing V, (3 September 1999); doi: 10.1117/12.361305
Show Author Affiliations
Joern Luetzen, Motorola, Inc. (United States)
Shapna Pal, Motorola, Inc. (United States)
Simon Gonzales, Motorola, Inc. (United States)
Yuval Bar, NOVA Measuring Instruments Inc. (United States)

Published in SPIE Proceedings Vol. 3882:
Process, Equipment, and Materials Control in Integrated Circuit Manufacturing V
Anthony J. Toprac; Kim Dang, Editor(s)

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