Low-cost optical instrumentation for thermal characterization of MEMS

Abstract

A low-cost, non-destructive and flexible technique based on thermoreflectometry is presented in this paper to map the temperature of running devices integrated on a silicon chip. The analysed device is a micromachined gas sensor using silicon-on-insulator technology (SOI). The interests and limitations of the proposed optical technique are described and compared with commonly used methods in microelectronics. Moreover, experimental results of thermal mapping for micromachined gas sensors are also compared with numerical simulations. From the measured temperature distribution over the entire active area of micromachined gas sensors, optimized designs can be proposed for avoiding hot spots that degrade the performance of the integrated gas sensors.

Bulk and surface micromachined MEMS in thin film SOI technology

“…The active area of our membranes can be heated to working temperatures equal to 400 • C with 25 mW only, which is a much better result in comparison with other recently published microheaters [12,13]. Thermal uniformity was confirmed by thermo-reflectometry measurements [14]. Thermal ageing and reliability tests (deformation, high frequency switching and high temperature) were performed in order to validate the high reliability of the membrane.…”

High Spatial Resolution Optical Fiber Two Color Pyrometer With Fast Response

“…Infrared cameras for temperature measurement collect the infrared rays from the heated body. IR cameras with a standard objective allow spatial resolutions around 1 mm and must be equipped with an additional close-up lens to increase its spatial resolution up to 5 − 10 m [1], [2], with the consequent increasing cost. Even more, it is difficult to know the emissivity of the material which is needed to extract the absolute temperature and have highest frame rates when using special digitalization process of around 30 kHz [3].…”

“…It has a higher spatial resolution, it being of 0.5 m, this spatial resolution depends on the wavelength and on the spot of the laser [4], however the acquisition time is long; depending on the material under study it can take from seconds to several minutes to obtain the temperature of a single point [5]. Another temperature measurement with high spatial resolution (0.3 − 0.5 m) is the transient thermoreflectance imaging which uses an ultrashort laser pulse to excite the material and a weaker probe beam to detect the transient reflectance [2], [6]. However, the thermoreflectance coefficients depend on the wavelength, material and texture of the surface, so it is important to do an in-situ calibration [7].…”

Thermo-mechanical characterization of surface-micromachined microheaters using in-line digital holography

“…These techniques possess limitations such as poor resolution, issues concerning repeatability or coating the device with different layers. Thermo-reflectometry, a non-destructive optical technique for thermal characterization, has been proposed [5]. Though the technique provides a spatial resolution of 0.5 μm to 1 μm, the main difficulty arises with the requirement of knowledge on a thermoreflectivity coefficient of the material used.…”