(A) new uncooled IR detector using silicon diode : micromachined isolated silicon diode for IR detection(MISIR)

Abstract

In the dissertation, a new uncooled IR detector using silicon diode has been studied. The new IR detector uses a silicon diode for temperature sensing and electrochemical etching for thermal isolation. The detector has been names as micromachined isolated silicon diode for IR detection (MISIR), which represents its structure and operation mechanism. Infrared (IR) detector can extend human vision beyond the red into far IR by making the patterns of thermal radiation visible. Among IR detectors, thermal detectors can be operated at room temperature without an expensive cryogenic cooler, which makes them suitable for many applications. Two major issues of thermal IR detectors are thermal isolation and temperature sensing mechanism. To enhance responsivity, highly sensitive temperature mechanism and low thermal conductance of the detector structure are required. In the respect of temperature sensing mechanism, MISIR utilizes the thermal characteristics of a silicon diode. Forward current of a silicon diode shows a exponential dependence on temperature. Temperature coefficient of current (TCC) of a silicon diode amount to about 10%K, which is higher by a few tens times than temperature coefficient of resistance (TCR) in metal resistance of bolometers. A good thermal isolation between the detector structure and substrate us desirable to prevent the heat of the detector from dissipating away to the substrate. Many thermal IR detectors have been fabricated using micromachining techniques. In the surface micromachining structure, thermal isolation is limited by the thickness of a sacrificial layer. The other approach for the thermal isolation is bulk micromachining technique using anisotropic silicon etching. But the anisotropic etching needs a special equipment and specific substrate for accomplishing a fine dimensional control of the silicon etch. Electrochemical etching can overcome the limit of the surface micromachined structure because it can etch the whol...