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Browse Prior Art Database

In Situ Etch Rate Detecting Technique

IP.com Disclosure Number: IPCOM000059959D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 3 page(s) / 64K

Publishing Venue

IBM

Related People

Beardsley, GJ: AUTHOR [+3]

Abstract

To insure proper isolation in deep dielectric isolation technology in a silicon substrate 10, trench 12 is generally etched through an epitaxial layer 14, including a subcollector 16, to the silicon substrate, as indicated in Fig. 1. This detecting technique provides a quick and accurate measurement of trench depth during the etching process. When etching a trench with FREON* 12 and oxygen, as is known, a mask 18 made of silicon dioxide is generally used which is also etchable by the FREON 12 and oxygen. This technique is provided to ensure that the silicon dioxide mask 18 is not etched away before the trench 12 is completely formed in the substrate 10 by monitoring the etch rate ratio between that of silicon and silicon dioxide, i.e.

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In Situ Etch Rate Detecting Technique

To insure proper isolation in deep dielectric isolation technology in a silicon substrate 10, trench 12 is generally etched through an epitaxial layer 14, including a subcollector 16, to the silicon substrate, as indicated in Fig. 1. This detecting technique provides a quick and accurate measurement of trench depth during the etching process. When etching a trench with FREON* 12 and oxygen, as is known, a mask 18 made of silicon dioxide is generally used which is also etchable by the FREON 12 and oxygen. This technique is provided to ensure that the silicon dioxide mask 18 is not etched away before the trench 12 is completely formed in the substrate 10 by monitoring the etch rate ratio between that of silicon and silicon dioxide, i.e.,

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The detection of silicon and silicon dioxide etch rates while etching trenches is accomplished with the use of a laser beam, preferably a red beam having a wavelength of 6328 Angstroms, and an array 20 of silicon mesas 22, each of which is 10 micrometers by 15 micrometers completely surrounded by silicon trenches which are 2.5 micrometers wide and 5 micrometers deep. The mesas 22 are covered with islands of the silicon dioxide 18. The laser beam indicated at 24 in Fig. 2, having a diameter of about one millimeter, is directed onto array 20, and the reflected signal is detected by a laser beam detector and recorded on a strip chart recorder, as indicated in Fig. 3. An interference pattern is formed as a result of reflections from surfaces 26, 28 and 30. When reactive ion etching begins, i.e., when the plasm...