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Low Density Mask Technique for High Reduction Photography

IP.com Disclosure Number: IPCOM000094082D
Original Publication Date: 1966-May-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Hance, CR: AUTHOR

Abstract

Compensating arrangements are provided in high reduction photography for unequal distribution of light in an aerial image formed from an artwork master containing wide ad narrow windows.

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Low Density Mask Technique for High Reduction Photography

Compensating arrangements are provided in high reduction photography for unequal distribution of light in an aerial image formed from an artwork master containing wide ad narrow windows.

In high reduction photography of the type used in the microelectronics industry, a problem frequently encountered is holding size ad geometry.

This occurs when the pattern to be photographed contains fine detail as well as course detail.

Such is illustrated by an artwork master 1 containing wide and narrow openings, respectively 2 and 3. Because of the characteristics of the optics, wide openings 2 of the master 1 is imaged at a higher brightness level than narrow opening 3. Since the optimum exposure for one size image can be too weak or too intense to properly record another size, invariably, there is either a drop-out of fine detail or unwanted growth of course detail.

Compensation for the uneven illumination of the image is provided by coating master 1 with a layer of photoresist 4 and exposing resist 4 with selective shielding of the openings 2 and 3. Thus, after processing, resist 4 is completely removed from the small detail area, i.e., small opening 3, but remains on the rest of the pattern, i.e., as an in-situ mask 4' over large opening 2.

The degree of masking depends on the resist density which can range between 0.2 and 0.4 and can be obtained either by using a dye photoresist such as Shipley A2-15 resist or by...