| Summary: | 碩士 === 國立成功大學 === 微機電系統工程研究所 === 93 === Infrared Sensors are mainly sorted in Quantum type and Thermal type. The principle of quantum type infrared sensor is “photovoltaic effect”, a process which the energy of the photon is transferred to an electron. Quantum type infrared sensors have much higher sensitivity than thermal type’s but need other cooling system to keep normal operation. Life time and price are other two major faults and made them developed most for military purpose.
Thermal type infrared sensors, which make use of TCR (Temperature Coefficient of Resistance), have grown up in recent years by the maturation of CMOS process and MEMS (Micro-Electro-Mechanical System) technology. They have two advantages over quantum type sensors, CMOS compatible and room temperature operation environment, the former make them cheap and the later make them commercial-attracted, though their sensitivity is much lower than their opponents.
However, the thermal type infrared sensors are highly process-sensitive. There are two main streams in this region; one is focus on sensing material which has simple readout circuits instead, the other is focus on readout circuits and using a simple BJT/Diode to simulate resistance/current variation. They both do not have a circumspect consideration in manufacturing process, which often conflict with each other.
Our application was reviewed by National Chip Implementation Center and manufactured thorough TSMC 0.35μm 2P4M CMOS/MEMS process. The post TMAH etching process was implemented in National Cheng Kung University’s Center of Micro/NANO Technology Research.
In system design, we adopt a Closed-Loop scheme which construct from electro-thermal balance, forming a negative feedback system, and keep the temperature of unit cell stable. We integrated the sensing unit with a front part of readout circuits in a unit cell, and probe their performance before and after TMAH etching.
Several experimental procedures which suit for a 3mm x 3mm size chip are also showed. We make possible that a cut chip could run through whole TMAH electrochemical etching process and still be able to get probed. These experiences may be helpful to students who would apply CMOS/MEMS process.
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