Browse Prior Art Database

HC Photoresist Develop End Point Detection Algorithm

IP.com Disclosure Number: IPCOM000049160D
Original Publication Date: 1982-May-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Manning, SA: AUTHOR [+2]

Abstract

The end point of a photoresist develop process is detected by analyzing a reflected infrared light source signal from the wafer. Light interference occurs as the resist film is developed off the wafer test site. When all of the resist layer is developed, the interference ceases and a signal flattening will result at the end point (Fig. 1).

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HC Photoresist Develop End Point Detection Algorithm

The end point of a photoresist develop process is detected by analyzing a reflected infrared light source signal from the wafer. Light interference occurs as the resist film is developed off the wafer test site. When all of the resist layer is developed, the interference ceases and a signal flattening will result at the end point (Fig. 1).

However, in the case of high contrast (HC) photoresist developing, the uneven intensity distribution of the E-beam exposure system causes a diffraction grating pattern on the test site. The reflected infrared signal from the wafer test site then contains premature and false flat signal regions resulting in the incorrect detection of the end point (Fig. 2).

Previous end-point detection algorithms detected the flat signal region by computing the slope with a predetermined threshold. When the slope value was less than the threshold, the end point was detected. A process delay time (Delta
T) is added to the end-point call time to ensure adequate product site developing. These previous algorithms become unreliable when used with signals similar to Fig. 2 because of their false end-point detection triggered by premature flat regions.

False end-point detection is resolved by the HC end-point detect algorithm. When the actual end point is detected, the slope of the reflected signal will remain less than the algorithm threshold for the duration of the process delay time. If the slope...