Browse Prior Art Database

Photoresist Shelflife Monitor

IP.com Disclosure Number: IPCOM000035781D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Powers, JE: AUTHOR

Abstract

This article concerns a real-time Photoresist Shelflife Monitor (PSM) for tracking photoresist shelflife as it is affected by storage time and temperature.

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Photoresist Shelflife Monitor

This article concerns a real-time Photoresist Shelflife Monitor (PSM) for tracking photoresist shelflife as it is affected by storage time and temperature.

Positive photoresists used in semiconductor manufacturing processes generally suffer a loss of photoactivity, if not kept under refrigeration, due to storage at too high a temperature for too long a time. Existing functional tests to establish photoresist adequacy are time consuming and may result in costly rework when done on a product basis. The real-time monitor described in this article makes use of a thermocouple, microprocessor and clock/counter system to record and present the amount of time a photoresist container has spent above a known critical temperature while in storage.

The drawing is a schematic diagram of a PSM. The thermocouple 1 provides an input signal (a voltage corresponding to actual container storage temperature) to the analog-to-digital converter 2 whose digital output is fed, for comparison, to a predetermined temperature set-point value in the comparator 3. Thermocouple 1 is calibrated by means of the potentiometer control 4. The temperature set- point value, which is dependent upon the photoresist type, is adjusted by means of potentiometer control 5. Both components 2 and 3 are incorporated into the battery-powered microprocessor chip 6, as is the clock/counter 7. The clock/counter 7 may be activated above (and deactivated below), an established tempera...