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Interferometric Etch Depth and Temperature Determination

IP.com Disclosure Number: IPCOM000042237D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Bayer, T: AUTHOR [+3]

Abstract

A transparent sample in a dry etch reactor is illuminated by two coherent light beams which are brought to interference after having passed the sample through an etched and a non-etched surface, respectively. A reactive ion etch (RIE) reactor 2 is shown in the figure with sample 1 placed on cathode 3 and etching plasma 4. The beam of a laser 5 enters the reactor through suitable windows and is split by semitransparent mirror 8a into two partial beams 6 and 7. Beam 6 impinges vertically on the etched surface of sample 1, whereas beam 7 is directed by mirrors 8c and 8d to an unetched lateral surface of sample 1. Both beams are reflected at the outer and the inner surface of the sample (1a, 1c and 1b, 1d, respectively), so that each reflected beam has a phase difference corresponding to the optical path length in the sample.

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Interferometric Etch Depth and Temperature Determination

A transparent sample in a dry etch reactor is illuminated by two coherent light beams which are brought to interference after having passed the sample through an etched and a non-etched surface, respectively. A reactive ion etch (RIE) reactor 2 is shown in the figure with sample 1 placed on cathode 3 and etching plasma 4. The beam of a laser 5 enters the reactor through suitable windows and is split by semitransparent mirror 8a into two partial beams 6 and 7. Beam 6 impinges vertically on the etched surface of sample 1, whereas beam 7 is directed by mirrors 8c and 8d to an unetched lateral surface of sample 1. Both beams are reflected at the outer and the inner surface of the sample (1a, 1c and 1b, 1d, respectively), so that each reflected beam has a phase difference corresponding to the optical path length in the sample. The phase difference in the reflected beam 6 is determined by the thickness d of the sample (i.e., the etch depth), by the temperature-dependent index of refraction, and by the thermal expansion. The phase difference in beam 7, on the other hand, depends only on the temperature-dependent index of refraction and the thermal expansion of the length 1, as the lateral faces 1c, 1d of the sample are not attacked by RIE. The reflected beams 6 and 7 are directed to conventional detection means 1O and 11 outside the reactor where the temperature of sample 1 is determined from beam 7 and used to co...