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Mask Usage Optimization Model

IP.com Disclosure Number: IPCOM000078687D
Original Publication Date: 1973-Feb-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Olufsen, DE: AUTHOR [+2]

Abstract

Analysis of the effects of integrated circuit masks in terms of quality limitations and, therefore, the resulting product yield losses has not been done in the past, due to the lack of a systematic mathematical approach in modeling the process. This model fills this requirement and also shows the best possible usage of the masks, from an economic viewpoint on product costs.

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Mask Usage Optimization Model

Analysis of the effects of integrated circuit masks in terms of quality limitations and, therefore, the resulting product yield losses has not been done in the past, due to the lack of a systematic mathematical approach in modeling the process. This model fills this requirement and also shows the best possible usage of the masks, from an economic viewpoint on product costs.

The model is an APL computer program which is designed to calculate the total variable costs (not including overhead and burden rates), based on mask and device unit costs, unit hours and the product yields. The product yields are derived from the mask initial quality, permanent and cleanable defect degradation rates, photoprocess qualities, and the remaining yield losses such as diffusion-limited-yields.

Using this calculation routine in an iterative fashion and varying the mask pass-factors and cleaning intervals, an optimum solution, cheapest cost of mask usage to the product output, may be found.

The model is also useful as a tool to show economic justification for process changes, which vary the yield losses in the manufacturing mode. Evaluations may also be performed, to predict the resulting yield improvements to be expected from the implementation of future improvements in manufacturing methods.

Some of the basic model equations are listed below:
1) AMQ = [(AIMQ) . (1-PDEGRT)/Passlife/2/] (1-CDEGRT)/Clean/2/.
2) PHOTOLY = (PROCLY) (AMQ)
3) FTY = (REMLY) (P...