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A Study of IR Emitter and IR Detector for NDIR Gas Sensor

초록/요약

In this paper, CO2 gas sensors using microheaters and infrared sensing devices for MEMS-based infrared incident were manufactured and analyzed. Micro-heaters manufactured with MEMS technology use Pt/Pt black materials to increase temperature and infrared radiation. In addition, by analyzing the size of the pattern of the active layer, an optimal infrared emitter with high radiation rate and thermal stability was produced. A micro-bolometer manufactured by an infrared detector has a -2.18%/℃ TCR using a VOX thin film as a sensing layer. And when the pattern of the electrode was designed and manufactured in an IDT shape, the device resistance was lowered by more than eight times. Ti material with a high infrared absorption rate was used as the absorption layer, and an infrared detector with high sensitivity was produced by analyzing according to the size of the area. The NDIR CO2 gas sensor manufactured through the IR emitter and the IR detector can be manufactured with a single chip, has no interference from other gases, and has advantages such as low power consumption, miniaturization, and portable.

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초록/요약

본 논문에서는 MEMS 기반의 적외선 입사를 위한 마이크로 히터와 적외선 감지소자를 이용한 CO2 가스 센서를 제작하고 특성을 분석하였다. MEMS 기술로 제작된 마이크로 히터는 Pt/Pt black 물질을 사용하여 적외선 온도와 적외선 방사율을 높이고 활성층의 패턴의 크기를 분석하여 방사율이 높고 열적 안정성을 가지는 최적의 적외선 방출기를 제작하였다. 또한, 적외선 감지기로 제작된 마이크로 볼로미터는 VOx 박막을 감지층으로 사용하여 -2.18%/℃ TCR을 가지며 전극의 패턴을 IDT 구조로 설계하여 소자 저항을 8배 이상 낮추었다. 흡수층은 적외선 흡수율이 높은 Ti를 사용하고 면적의 크기에 따라 분석하여 감지도가 높은 적외선 검출기를 제작하였다. 적외선 방출기와 적외선 검출기를 통해 제작된 비분산식 CO2 가스 센서는 단일 칩으로 제작이 가능하고 다른 가스에 의한 간섭이 없으며 저전력 소비, 소형화, 휴대용 등의 장점을 가진다.

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목차

TABLE OF CONTENTS
ABSTRACT i
국문 초록 iii
TABLE OF CONTENTS ⅳ
LIST OF TABLES ⅶ
LIST OF FIGURES ⅸ
CHAPTER 1. INTRODUCTION 1
1.1 Research background 1
1.2 Research content 6
CHAPTER 2. Theoretical Background 8
2.1 Infrared 8
2.1.1 Infrared region 8
2.1.2 Infrared heat transfer 9
2.1.3 Planck's law, Stefan-Boltzmann's law of blackbody radiation
10
2.1.4 Emissivity 11
2.2 Infrared gas sensor 12
2.2.1 Infrared gas sensor principle 12
2.2.2 Beer-Lambert's law 14
2.3 Micro-heater principle 15
2.4 Micro-bolometer 15
2.4.1 Micro-bolometer principle 15
2.4.2 TCR(temperature coefficient of resistance) 16
2.4.3 Responsivity 17
2.4.4 Noise 18
2.4.5 Detectivity 20
CHAPTER 3. Micro-heater and micro-bolometer fabrication 21
3.1 Micro-heater of MEMS technology fabrication 21
3.2 Micro-bolometer of MEMS technology fabrication 27
CHAPTER 4. Results and Discussion 33
4.1 Micro-heater experiment setup and measurement 33
4.2 Micro-bolometer experiment setup and measurement 39
4.3 CO2 NDIR gas sensor experiment setup and measurement 42
CHAPTER 5. Conclusion 43
REFERENCES 44

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