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Measuring the Thickness of the Bottom Layer of a Two Layer Composite Dielectric Coating on a Silicon Substrate

IP.com Disclosure Number: IPCOM000077431D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Bratter, RL: AUTHOR

Abstract

The present method involves a nondestructive approach of measuring the thickness of the lower layer of a two-layer insulative coating composite on a semiconductor substrate. The layers must, of course, be transparent to the light used.

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Measuring the Thickness of the Bottom Layer of a Two Layer Composite Dielectric Coating on a Silicon Substrate

The present method involves a nondestructive approach of measuring the thickness of the lower layer of a two-layer insulative coating composite on a semiconductor substrate. The layers must, of course, be transparent to the light used.

With reference to the figure, silicon layer 10 is covered with a composite comprising Si(3)N(4) layer 11 and SiO(2) layer 12. Plane polarized (p polarized) light 13 is projected onto the surface of the coating at Brewster's angle. With light incident at Brewster's angle, no light is reflected and all is transmitted. Since, due to the refraction within SiO(2) layer 12, the light incident at the SiO(2) - Si(3)N(4) interface 14 is no longer at Brewster's angle, both reflection 15 and transmission 16 take place at this interface. Similarly, incident light upon the Si(3)N(4) - silicon interface at point 17 is also transmitted and reflected at 18. Eventually, two reflected beams, that from the SiO(2) - Si(3)N(4) interface 19 and that from Si(3)N(4) - silicon interface 20, emerge from the coating.

Utilizing the optical interference between these two emerging beams, the thickness of the Si(3)N(4) layer may be determined. The measurements necessary for determining this optical interference may be taken, with either a modified ellipsometer or a modified spectrophotometer. This modified apparatus may be produced by outfitting a UV vi...