AVS 50th International Symposium
    Manufacturing Science and Technology Tuesday Sessions
       Session MS-TuP

Paper MS-TuP11
Temperature Sensor for Multi-layered Substrate using Optical Fiber type Low-coherence Interferometry

Tuesday, November 4, 2003, 5:30 pm, Room Hall A-C

Session: Poster Session
Presenter: K. Takeda, Wakayama University, Japan
Authors: K. Takeda, Wakayama University, Japan
T. Shiina, Wakayama University, Japan
M. Ito, Wakayama University, Japan
Y. Okamura, Wakayama University, Japan
N. Ishii, Tokyo Electron Ltd., Japan
Correspondent: Click to Email
Multi-layered substrates, such as silicon on insulator (SOI) are very useful for MEMS and so on. In the fabrication processes of multi-layered substrates, plasma etching is frequently employed. In such process, the temperature control of each layer, especially top layer, will be required to realize much finer pattern because the interlayer of SOI etc. is dielectric with low thermal conductivity. We have developed novel temperature sensor for measuring each layer of multi-layered substrates using low-coherence interferometry. The sensor is based on Michelson interferometer, which consists of a super luminescent diode (SLD: wavelength = 1550 nm), a laser diode (LD: wavelength = 850 nm), a scanning reference mirror, optical fibers and so on. In this sensor, the optical pass length of each layer is derived from the length between peaks of SLD interference signals. The shift of each optical pass length is precisely measured by Michelson interferometer using LD, which uses the same optical path as that using SLD. The sensor is, therefore, robust to mechanical and temperature disturbances. We have evaluated the shift of each layer of the three-layered substrate. The top and bottom layers of the substrate are silicon, 360 µm in thickness. The interlayer is made of quartz, 1 mm in thickness. As a result, it has been verified that the shift of optical length of each layer is proportional to each temperature measured by thermo-couple sensors, which corresponds to theoretical values. From these results, we have confirmed that the developed sensor can measure the temperature of each layer without continuous monitoring the shift of optical pass length if the initial temperature is known.