MEMS-based infrared detector for body thermometer

摘要

Infrared detectors have many application fields. One of those, MEMS-based thermopile is attractive for many low-cost commercial and industrial applications, mainly because it does not require cooling for operation and the process technologies are relatively simple. The MEMS thermopile fabricated on a silicon nitride microbridge structure was proposed. Using microbridge rather conventional membrane makes it possible to fabricate much smaller micro thermopile and to reduce heat loss because of small contact area at silicon rim. The bridge material is only composed of Si_3N_4. The thermocouple was used a poly-Si and an aluminum. The characteristic of electromotive force (EMF) generation was evaluated for various patterns at hot junction. Aluminum thermocouple shape on bridge structure was designed two patterns. One was a square shape and the other shape was a hollow square. The output voltage of hollow square-type electrode was increased in compared with square-type electrode from 3.03uV/℃ to 4.609uV/℃ at body temperature (37℃). With the same membrane dimensions and the same overall thickness of the chip a thermopile on microbridge is almost 53% smaller a conventional thermopile chip.