Browse Prior Art Database

Spectral Filtration for Laser End-Point Detect Developing Systems

IP.com Disclosure Number: IPCOM000046400D
Original Publication Date: 1983-Jul-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Johnson, C: AUTHOR [+4]

Abstract

A typical end-point detect developing system is shown in the drawing. In operation, the end-point detect operation is simple. The laser emits coherent radiation which is transmitted by the light pipe to impinge on an exploded portion of the wafer. The light propagates through the photoresist onto the wafer surface and is reflected at the substrate surface. The reflected light is transmitted by another light pipe to a photodetector, and the generated voltage is displayed on a strip chart recorder as a function of time. The incident and reflected light, within the films on the surface of the wafer, interfere constructively and destructively. The developer, in which the wafer is immersed, removes photoresist from the surface of the photoresist film as time progresses.

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Spectral Filtration for Laser End-Point Detect Developing Systems

A typical end-point detect developing system is shown in the drawing. In operation, the end-point detect operation is simple.

The laser emits coherent radiation which is transmitted by the light pipe to impinge on an exploded portion of the wafer. The light propagates through the photoresist onto the wafer surface and is reflected at the substrate surface. The reflected light is transmitted by another light pipe to a photodetector, and the generated voltage is displayed on a strip chart recorder as a function of time. The incident and reflected light, within the films on the surface of the wafer, interfere constructively and destructively. The developer, in which the wafer is immersed, removes photoresist from the surface of the photoresist film as time progresses. The rate of removal is a function of the incident exposure radiation to which the film has been subjected (in addition to the developer strength). As the film is dissolved away, the light reflected to the light pipe varies in intensity due to the constructive and destructive interference. The frequency of the variation is a function of the refractive indexes of the materials the light propagates through and the wavelength of the light. A sine-wave signal, modified by the nonlinear response of the photodetector, is recorded on the strip chart recorder as a function of time which corresponds to the dynamic dissolution rate of the photoresist in the developer. At end point the curve goes flat as further thinning of the film ceases...