Browse Prior Art Database

In-situ Exposure Tool Monitor

IP.com Disclosure Number: IPCOM000014231D
Original Publication Date: 1999-Oct-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 3 page(s) / 105K

Publishing Venue

IBM

Related People

Joseph Fatula: AUTHOR [+3]

Abstract

Post Disclosure Text Drawings This idea addresses the problem of knowing when enough energy has been used to expose photoresist. Current techniques are to monitor (the) tool with a meter to establish stability, then optimize process settings and run product adjusting to achieve the required critical dimension or resist clearnance; a procedure which incurs many misprocessed wafers.

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In-situ Exposure Tool Monitor

Post Disclosure Text & Drawings This idea addresses the problem of knowing when enough energy has been used to expose photoresist. Current techniques are to monitor (the) tool with a meter to establish stability, then optimize process settings and run product - adjusting to achieve the required critical dimension or resist clearnance; a procedure which incurs many misprocessed wafers.

What we suggest is to monitor the reflection of the expose light from the surface of the wafer/resist as it is being exposed and monitor the change in the amplitude of the peaks which represent the spectral composition of said light. By comparing with a reference spectrum (e.g. that of the wafer/resist at the start of the exposure, or taken at another time), and monitoring the rate of change in the amplitude, one can determine the point at which the resist has been exposed to the correct amount of light required to make the image in the photoresist. The change in the amplitude of the peaks which represent the spectrum of the reflected light is known to be related to the resist absorption, and the reaction of the photo-active-compound (PAC) reacting with the photons in the incident light.

The attached drawing shows the relative positioning of the fiber optic bundles in the optical path of an Ultratech Stepper for example. One bundle samples the light after it passes through the mask but before it exposes the resist - this fiber optic leads to the referen...