Browse Prior Art Database

Missing Peak Algorithm Modification for Etch End Point Detection

IP.com Disclosure Number: IPCOM000049344D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Coombs, EG: AUTHOR

Abstract

The end point of the quartz etch process for wafer personalization is determined by monitoring an infrared reflectivity signal. Thin film interference takes place in the quartz layer on the wafer's test site. As the quartz etches away, its thickness can be determined by counting the maxima and minima in the reflectivity signal and by knowing the initial thickness of the film. See Fig. 1.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Missing Peak Algorithm Modification for Etch End Point Detection

The end point of the quartz etch process for wafer personalization is determined by monitoring an infrared reflectivity signal. Thin film interference takes place in the quartz layer on the wafer's test site. As the quartz etches away, its thickness can be determined by counting the maxima and minima in the reflectivity signal and by knowing the initial thickness of the film. See Fig. 1.

When the reflectivity signal exhibits anomalous behavior, the peak finding portion of the end-point detect algorithm cannot find all the peaks. See Fig. 2. This happens when a shift in reflectivity occurs which is not due to thin film interference effects.

The missing peak due to the anomalous reflectivity can be detected by using a statistical criterion. The algorithm establishes an average peak to peak time and compares each subsequent time to it. If the peak to peak time is greater than the average by 20 (two times the standard deviation of the average), the missing peek condition is detected and two peaks are inserted. The algorithm then updates the etch rate and etch time calculations, and continues monitoring the reflectivity signal as before.

1

Page 2 of 2

2

[This page contains 3 pictures or other non-text objects]