Browse Prior Art Database

Wet Etch End Point Determination Using Optical Character Regognition

IP.com Disclosure Number: IPCOM000034281D
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Connolly, TJ: AUTHOR [+2]

Abstract

This article addresses the determination of optimum developing times for resist images on semiconductor wafers exposed in step-and-repeat lithograpy using an E-beam or optical lithography tool. The disclosed process views the developed condition of a dose "wedge" contained on the wafer in real time and compares it to development of the lines imaged on the wafer by means of an optical monitoring system. The dose "wedge" has been employed as a development indicator in prior art. Optimum developing time can be a function of many variables: developer temperature, concentration and age; exposure time, intensity; etc. Existing approaches to this determination employ a send-ahead wafer to characterize the developer and then use the time so determined to process the remaining wafers.

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Wet Etch End Point Determination Using Optical Character Regognition

This article addresses the determination of optimum developing times for resist images on semiconductor wafers exposed in step-and-repeat lithograpy using an E-beam or optical lithography tool. The disclosed process views the developed condition of a dose "wedge" contained on the wafer in real time and compares it to development of the lines imaged on the wafer by means of an optical monitoring system. The dose "wedge" has been employed as a development indicator in prior art. Optimum developing time can be a function of many variables: developer temperature, concentration and age; exposure time, intensity; etc. Existing approaches to this determination employ a send-ahead wafer to characterize the developer and then use the time so determined to process the remaining wafers. This process may require multiple dipping of the send-ahead wafer if initially underdeveloped. Endpoint may be determined by use of a laser interferometer and usually requires an algorithm.

(Image Omitted)

The disclosed procedure is real-time, eliminating the need for monitor and/or send-ahead wafers for lithography wet etch processes, monitoring occuring during wafer development. An optical viewing system is employed in combination with the referenced dose "wedge" to provide a real time method of determining correct pattern development on wafers exposed on various lithography tools. The dose "wedge" is viewed using a closed-circuit TV camera with an appropriate lens to provide a 40X magnification. As the dose "wedge" changes during the etch (or development) process, the real-time image can be monitored and, at the correct dose level, action taken to remove the wafer(s) from the etch (developer) so...