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. 2011;11(3):2580-91.
doi: 10.3390/s110302580. Epub 2011 Mar 1.

Development of micro-heaters with optimized temperature compensation design for gas sensors

Woo-Jin Hwang  1 , Kyu-Sik Shin, Ji-Hyoung Roh, Dae-Sung Lee, Sung-Hoon Choa
Affiliations

Development of micro-heaters with optimized temperature compensation design for gas sensors

Woo-Jin Hwang et al. Sensors (Basel). 2011.

Abstract

One of the key components of a chemical gas sensor is a MEMS micro-heater. Micro-heaters are used in both semiconductor gas sensors and NDIR gas sensors; however they each require different heat dissipation characteristics. For the semiconductor gas sensors, a uniform temperature is required over a wide area of the heater. On the other hand, for the NDIR gas sensor, the micro-heater needs high levels of infrared radiation in order to increase sensitivity. In this study, a novel design of a poly-Si micro-heater is proposed to improve the uniformity of heat dissipation on the heating plate. Temperature uniformity of the micro-heater is achieved by compensating for the variation in power consumption around the perimeter of the heater. With the power compensated design, the uniform heating area is increased by 2.5 times and the average temperature goes up by 40 °C. Therefore, this power compensated micro-heater design is suitable for a semiconductor gas sensor. Meanwhile, the poly-Si micro-heater without compensation shows a higher level of infrared radiation under equal power consumption conditions. This indicates that the micro-heater without compensation is more suitable for a NDIR gas sensor. Furthermore, the micro-heater shows a short response time of less than 20 ms, indicating a very high efficiency of pulse driving.

Keywords: NDIR gas sensor; infrared radiation; micro-heater; micro-hotplate; semiconductor gas sensor; uniform heating characteristics.

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Figures

Figure 1.
Figure 1.
Numerical mesh model for the MEMS micro-heater.
Figure 2.
Figure 2.
The power compensation structure of poly-Si film to enhance the temperature distribution. (a) current flow map in the micro-heater. (b) schematic drawing of compensation design of poly-Si film. (c) picture of compensation design in poly-Si micro-heater.
Figure 3.
Figure 3.
Analyzed heating characteristics of micro-heaters by FEM simulation. (a) standard poly-Si micro-heater. (b) power compensated poly-Si micro-heater.
Figure 4.
Figure 4.
The fabrication process of the MEMS micro-heater.
Figure 5.
Figure 5.
Fabricated micro-heater. (a) packaged micro-heater using TO39 package. (b) SEM image of the micro-heater.
Figure 6.
Figure 6.
Measured average temperature of micro-heaters at 350 °C as maximum temperature. (a) standard poly-Si micro-heater. (b) power compensated poly-Si micro-heater.
Figure 7.
Figure 7.
Measured within 10% of high temperature distribution of micro-heaters at 350 °C as maximum temperature. (a) standard poly-Si micro-heater. (b) power compensated poly-Si micro-heater.
Figure 8.
Figure 8.
The measured maximum and average temperature at different power consumption of micro-heaters with standard micro-heater and power compensated micro-heater.
Figure 9.
Figure 9.
The measured maximum and average radiance at different power consumption of micro-heaters with standard micro-heater and power compensated micro-heater.
Figure 10.
Figure 10.
The modulation depth of the micro-heater ranging from frequency of 0∼100 Hz.
See this image and copyright information in PMC

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