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Proceedings Paper

Rationalizing the mechanism of HMDS degradation in air and effective control of the reaction byproducts
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Paper Abstract

The concern over molecular contamination on the surfaces of optics continues to grow. Most recently, this concern has focused on siloxane contamination resulting from hexamethyldisilazane (HMDS) which is commonly used as a wafer treatment to improve photoresist adhesion onto wafers. From this process, HMDS vapor can be found within FABs and process tools where it has been linked to issues related to lens hazing. This type of surface contamination is significantly detrimental to the imaging process and is generally corrected by extensive surface cleaning or even lens replacement. Additionally, this type of repair also requires adjustment of the optical axis, thereby contributing to an extended downtime. HMDS is known to be very sensitive to the presence of water and is therefore believed to degrade in humid airstreams. This research focuses on rationalizing the reaction mechanisms of HMDS in dry and humid airstreams and in the presence of several adsorbent surfaces. It is shown that HMDS hydrolyzes in humid air to trimethylsilanol (TMS) and ammonia (NH3). Furthermore, it is shown that TMS can dimerize in air, or on specific types of adsorption media, to form hexamethyldisiloxane (HMDSO). Additionally, we report on the relative impact of these reaction mechanisms on the removal of both HMDS and its hydrolysis products (TMS, HMDSO and NH3).

Paper Details

Date Published: 24 March 2008
PDF: 12 pages
Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 692230 (24 March 2008); doi: 10.1117/12.772998
Show Author Affiliations
Kevin Seguin, Donaldson Co., Inc. (United States)
Andrew J. Dallas, Donaldson Co., Inc. (United States)
Gerald Weineck, Donaldson Co., Inc. (United States)

Published in SPIE Proceedings Vol. 6922:
Metrology, Inspection, and Process Control for Microlithography XXII
John A. Allgair; Christopher J. Raymond, Editor(s)

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