MEMS 마이크로핫플레이트 기반 고속 응답 정전용량형 폴리이미드 습도센서 = High speed capacitive polyimide humidity sensors based on MEMS microhotplates

다국어 초록 (Multilingual Abstract)

The measurement of relative humidity has always been a difficult and challenging one because of its interactions with the environmental variables such as temperature and pressure. This thesis presents a humidity sensor utilizing the polyimide film which relative dielectric constant is changed by moist of atmosphere.
The polyimide thin film humidity sensor is fabricated on a silicon substrate using procedures which are compatible with standard IC process. This will facilitate the integration of this sensor and other units with their associated interface electronics, leading to micro sensor systems.
The structure of the humidity sensor is parallel capacitor with consists of three layers of Chromium / Polyimide / Chromium on microhotplates. Final curing temperature of polyimide is 350℃ and hold time for 1hour. Top electrode was formed to porous for fast absorption and adsorption of moisture into crack. After device was completed, it was produced by dry etching from top electrode to silicon. These ways have two advantages. One thing is that moisture is to penetrate into polyimide directly. The other thing is to utilize microhotplates on suspended bridge structure. Role of microhotplates is to dehumidify moisture in polyimide for high response.
The characteristics of fabricated devices were measured under various chamber conditions, and obtained linear characteristics in the range of 10~97%RH was independent of temperature change and hysteresis of ±1.2 % relative humidity.