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Advanced Cleaning Process for 1x Mask (Pmma Resist) to Remove Chrome Opaque Defects and Contamination

IP.com Disclosure Number: IPCOM000034938D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Vo, CV: AUTHOR

Abstract

The continued presence of high chrome opaque defects (less than lum size) and contamination on mask product following the use of conventional cleaning methods results in excessive rejects. The rework process loop described in this article effectively cleans a large percentage of these rejects, thereby significantly improving mask product line yields. (Image Omitted) The process flow chart shown in the figure illustrates both a conventional mask cleaning procedure (solid line) and the disclosed rework process loop (dashed line). Masks normally proceed through conventional cleaning processes [1] and microscopic inspection (dimensional) [2] before reaching final product inspection (defects) [3], after they are either shipped out [4], transferred for specified repairs [5], or rejected [6] to automatic process restart.

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Advanced Cleaning Process for 1x Mask (Pmma Resist) to Remove Chrome Opaque Defects and Contamination

The continued presence of high chrome opaque defects (less than lum size) and contamination on mask product following the use of conventional cleaning methods results in excessive rejects. The rework process loop described in this article effectively cleans a large percentage of these rejects, thereby significantly improving mask product line yields.

(Image Omitted)

The process flow chart shown in the figure illustrates both a conventional mask cleaning procedure (solid line) and the disclosed rework process loop (dashed line). Masks normally proceed through conventional cleaning processes [1] and microscopic inspection (dimensional) [2] before reaching final product inspection (defects)


[3], after they are either shipped out [4], transferred for specified repairs [5], or rejected [6] to automatic process restart. Roughly 75% of the last group are identified as rejects due to chrome opacity or contamination. The disclosed rework process loop accepts these rejects for a three-step chemical treatment which is key to the effectiveness of the disclosed salvage operation. This treatment involves the use of a premixed etchant which is composed of the following ingredients (by volume):

Acetic acid 28%

Hydrochloric acid 1%

Ceric ammonium nitrate 1%

Deionized (DI) H2O 70% The chemical treatment
[7] of reject masks begin with an etchant spray, with the spray fixture set at...