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Proceedings Paper

Temperature measurements of semiconductor wafers via laser thermometer with fiber optic communication line
Author(s): O. V. Lukin; Alexander N. Magunov
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Paper Abstract

Productive and reliable techniques and probes are required for thermometiy of semiconductor crystals in plasma processes of microtechnology. A technique may be considered as productive when the time one takes to perform a preliminaiy to the temperature measurement is negligible as compared with the duration of the etching or deposition itself. The reliability of measurement may be achieved when it is directly measured the temperature of semiconductor wafer and not of holder or test satellite. Interferometric technique for temperature measurements of glasses' and semiconductor crystals57 is used in many laboratories. This technique holds much promise for noncontact thermometry of semiconductors since the temperature coefficient of refraction n1dn/dJ' is almost two orders of magnitude greater than the thermal expansion coefficient h'dh/dt (here n is refractive index, h is thickness, T is temperature of wafer). Semiconductor wafer, on being heated to several tens of degrees, changes its optical thickness nh many times as compared to wavelength ? of sounding light: A(nh)>>A. In consequence of this, it possible to register numerous interference maxima and minima which are used for calculation of tempera! changes in temperature. The phase shift of 2t (one interferogram fringe) for 500 pm thick silicon wafer irradiated by HeNe laser (1. 15 pm) is caused by the temperature change of AT=5.2 K when T=300 K and AT=3.4 K at 650 K.8 The time it takes for the optical setup to be adjust completely after loading of a wafer into reactor is approximately equals to 20+30 S.9 In this paper fluther advancements of the interferometric laser thermometry towards total elimination of any adjustment procedure are presented. In addition, we observe a distinct increase in the temperature when a wafer is placed onto cooled holder and is heated by RF plasma. Furthermore, it has been found and explained an anomalous fringe shift in SF6 plasma.

Paper Details

Date Published: 5 August 1994
PDF: 4 pages
Proc. SPIE 2321, Second International Conference on Optoelectronic Science and Engineering '94, (5 August 1994); doi: 10.1117/12.182032
Show Author Affiliations
O. V. Lukin, Institute of Microelectronics (Russia)
Alexander N. Magunov, Institute of Microelectronics (Russia)

Published in SPIE Proceedings Vol. 2321:
Second International Conference on Optoelectronic Science and Engineering '94
Wang Da-Heng; Anna Consortini; James B. Breckinridge, Editor(s)

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