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Proceedings Paper

Automated Product Test Wafer Procedure
Author(s): Andrew Brown; Anna Minvielle; Anita Salugsugan
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Paper Abstract

An automated test wafer procedure has been developed using the KLA 2020 wafer inspector to measure registration and critical dimensions on production wafers. The procedure reduces operator interactions to loading the wafer and entering information for wafer identification. The analysis of the registration data is performed on a PC using the methods established by Perloff to determine both intrafield and grid errors. These results are then used to correct the stepper. CD data is also analyzed by the program and corrections to the exposure time are calculated. It was found that the KLA 2020 is as much as 10 times faster and 4 times more precise in obtaining registration data then an operator reading optical verniers on a microscope. Due to the high precision of the reading, the analysis does not need a large number of readings to obtain precise and accurate stepper corrections. Further, significant improvements can be obtained by adding registration targets to measure the intrafield errors. Using the KLA 2020 and computer analysis we have demonstrated an ability to reduce the errors for a manually aligned run to a one sigma distribution of 0.09 um for x and y translation, 0.4 PPM for scaling and orthogonality, and 2.3 PPM for rotation from the first test wafer for a GCA 6100. Nearly all of this variation is due to operator misalignment or the inability of the stepper to correct the errors. The corrections with this technique measuring the same wafer are precise to + 0.01 um in translation and + 0.5 PPM for rotation, scaling, and orthogonality. It has also been shown that a simple linear equation can be used to correct exposure time, even when a process is not tightly controlled.

Paper Details

Date Published: 17 April 1987
PDF: 7 pages
Proc. SPIE 0775, Integrated Circuit Metrology, Inspection, & Process Control, (17 April 1987); doi: 10.1117/12.940432
Show Author Affiliations
Andrew Brown, Advanced Micro Devices (United States)
Anna Minvielle, Advanced Micro Devices (United States)
Anita Salugsugan, Advanced Micro Devices (United States)

Published in SPIE Proceedings Vol. 0775:
Integrated Circuit Metrology, Inspection, & Process Control
Kevin M. Monahan, Editor(s)

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