STUDY OF THERMAL EFFECTS IN GAAS MICROMACHINED POWER SENSOR MICROSYSTEMS BY AN OPTICAL INTERFEROMETER TECHNIQUE

A contactless and non-invasive optical interferometric method is used to study the temperature distribution and thermal time response in a G aAs micromachined power sensor. Temperature variations in the sensor a ctive area-a cantilever beam-are sensed by an infrared laser beam. The temperature increase due to pulsed power dissipation in the cantileve r induces an increase both in the GaAs refractive index and in the can tilever thickness. This results in a change in the phase and intensity of the reflected laser beam which is interferometrically detected. Th e spatial temperature distribution along the cantilever beam is studie d using measurements of the optical phase and intensity as a function of the dissipated power. The optical signal is analysed taking into ac count Fabry-Perot interference. The thermal time constant of the senso r of about 5 msec is obtained from transient optical signal measuremen ts. Results of the optical analysis are consistent with those of elect rical characterization of the sensor and with the simulation of the te mperature distribution. (C) 1998 Published by Elsevier Science Ltd. Al l rights reserved.