TWI767241B - Gas sensing device - Google Patents

Abstract

A gas sensing device includes a thermal insulation single crystal substrate, a sensor for sensing gas concentration and a heater for providing a temperature which is needed for sensing gas. The sensor and heater are in a first surface of the thermal insulation single crystal substrate. The sensor has a micro-structure to improve a sensing accuracy.

Description

Gas sensing device

The present invention relates to a gas sensing device, in particular to a gas sensing device in which a heater and a sensor are on the same plane.

FIG. 1 shows a conventional gas sensing device 10 , which includes a substrate composed of silicon 12 and silicon dioxide 14 , a sensor 16 and a heater 18 . At present, the gas sensing devices 10 of solid metal oxides are mostly fabricated in MEMS style. The manufacturing process of the gas sensing device 10 is to first form a metal oxide on the silicon dioxide 14 by physical coating to form the sensor 16 . The sensor 16 is used to sense the concentration of gas, such as oxygen or nitrogen. concentration. Next, in order to prevent the silicon 12 from dispersing the heat provided by the heater 18 to other places, resulting in poor heating effect of the heater 18 , the silicon 12 under the sensor 16 is removed, for example, by etching to remove the silicon 12 . Finally, a heater 18 is formed on the silicon dioxide 14 below the sensor 16 to provide the temperature required for gas sensing. However, the sensor 16 can only be formed by a low-temperature process in the conventional method, which limits the quality of the sensor 16 and cannot be applied to high-temperature environment monitoring. On the other hand, limited by the material of the substrate, the sensor 16 can only be formed by coating, resulting in poor quality of the sensor 16 . In addition, the conventional gas sensing device 10 needs to hollow out the substrate under the sensor 16 , resulting in a fragile mechanical structure of the gas sensing device 10 .

One of the objectives of the present invention is to provide a gas sensing device in which the heater and the sensor are on the same plane.

One of the objectives of the present invention is to provide a gas sensing device with a high-quality sensor.

One of the objectives of the present invention is to provide a gas sensing device with a stronger mechanical structure.

According to the present invention, a gas sensing device includes a thermally insulating single crystal substrate, a sensor and a heater. The sensor is formed on the first surface of the thermally insulating single crystal substrate by organometallic chemical vapor deposition, so it has a microstructure that can sense the concentration of gas more accurately, and the organometallic chemical vapor deposition is high temperature process, which helps to improve the quality of the sensor, and also enables the sensor to be applied to high temperature environment monitoring. The heater is on the first surface of the thermally insulating single crystal substrate to provide the temperature required for gas sensing. Since the thermally insulating single crystal substrate can block thermal conduction, it is not necessary to hollow out the thermally insulating single crystal substrate under the heater, so that the gas sensing device has a strong mechanical structure.

10: Gas sensing device

12: Silicon

14: Silica

16: Sensor

18: Heater

20: Gas sensing device

22: Thermally insulated single crystal substrate

222: First Surface

224: Second Surface

24: Sensor

242: Microstructure

244: Electrodes

246: Electrodes

26: Heater

262: Electrodes

28: circuit board

30: heat insulation solid crystal

Figure 1 shows a conventional gas sensing device.

FIG. 2 shows an embodiment of the gas sensing device of the present invention.

Figure 3 shows a cross-sectional view at the location of the section line AA' in Figure 2 .

FIG. 4 shows an example of the layout of the sensors and heaters in FIG. 2 .

FIG. 5 shows another embodiment of the gas sensing device of the present invention.

FIG. 2 shows an embodiment of the gas sensing device 20 of the present invention. Figure 3 shows a cross-sectional view at the location of the section line AA' in Figure 2 . In FIGS. 2 and 3 , the gas sensing device 20 includes a thermally insulating single crystal substrate 22 , a sensor 24 and a heater 26 . The thermally insulating single crystal substrate 22 may be, but is not limited to, a ceramic substrate, such as a sapphire substrate. The thermally insulating single crystal substrate 22 has a first surface 222 and a second surface 224 opposite to each other. Both the sensor 24 and the heater 26 are located on the first surface 222 of the thermally insulating single crystal substrate 22, that is, the sensor The detector 24 and the heater 26 are located on the same plane. The sensor 24 is formed on the thermally insulating single crystal substrate 22 by means of metal-organic chemical vapor deposition (MOCVD). Since MOCVD is epitaxial growth, the sensor 24 is formed. Then there is a micro-structure 242 , and no additional micro-structure process is required to form the micro-structure 242 for the sensor 24 . The microstructures 242 include, but are not limited to, columnar structures. The microstructures 242 can make the sensor 24 have better quality to more accurately sense the concentration of the gas. In addition, MOCVD is a high temperature process, which not only helps to improve the quality of the sensor 24, but also enables the sensor 24 to be applied to high temperature environment monitoring. The heater 26 surrounds the sensor 24 to quickly provide the temperature required for gas sensing by means of lateral heat conduction, and the thermally insulating single crystal substrate 22 can block thermal conduction, so there is no need to hollow out the substrate under the heater 26 to isolate heat conduction path, so that the gas sensing device 20 of the present invention has a strong mechanical structure.

FIG. 4 shows an example of the layout of the sensors 24 and heaters 26 in FIG. 2 . In FIG. 4 , the sensor 24 includes two electrodes 244 and 246 respectively connected to the positive terminal (+) and the negative terminal (-) of the voltage source, and the sensing distance between the electrodes 244 and 246 can be changed. The heater 26 includes an electrode 262 surrounding the sensor 24, and two terminals of the electrode 262 are respectively connected to the positive terminal (+) and the negative terminal (-) of the voltage source.

FIG. 5 shows another embodiment of the gas sensing device 20 of the present invention. In FIG. 5 , the gas sensing device 20 also includes the thermally insulating single crystal substrate 22 , the sensor 24 and the heater 26 as shown in FIG. 3 . In addition, the gas sensing device 20 further includes a circuit board 28 and a spacer Thermal die bond 30 . A number of circuits (not shown) may be provided on the circuit board 28 to perform various functions. The thermal insulation die bonding 30 is between the second surface 224 of the thermal insulation single crystal substrate 22 and the circuit board 28, and is used to fix the thermal insulation single crystal substrate 22 on the circuit board 28. The thermal insulation die bonding 30 can further prevent the heater from being heated. The heat generated at 26 is transferred to the circuit board 28 via the thermally insulating single crystal substrate 22 .

The above description of the preferred embodiments of the present invention is for illustrative purposes, and is not intended to limit the present invention to the exact form disclosed. Modifications or changes are possible based on the above teachings or learning from the embodiments of the present invention. Rather, the embodiments are intended to illustrate the principles of the present invention and to facilitate those familiar with the technology. The practitioner selects and describes the practical application of the present invention with various embodiments, and the technical idea of the present invention is intended to be determined by the scope of the following claims and its equivalents.

20: Gas sensing device

22: Thermally insulated single crystal substrate

222: the first surface of the thermally insulating single crystal substrate

224: the second surface of the thermally insulating single crystal substrate

24: Sensor

242: Microstructure

26: Heater

Claims (7)

A gas sensing device, comprising: a thermally insulating single crystal substrate having a first surface and a second surface, wherein the second surface is on the back of the first surface; a sensor on the first surface , for sensing the concentration of the gas; and a heater, on the first surface, for providing the temperature required for gas sensing. The gas sensing device of claim 1, wherein the thermally insulating single crystal substrate is a ceramic substrate. The gas sensing device of claim 1, wherein the thermally insulating single crystal substrate is a sapphire substrate. The gas sensing device of claim 1, wherein the sensor is formed on the thermally insulating single crystal substrate by metal organic chemical vapor deposition. The gas sensing device of claim 1, wherein the sensor has a microstructure. The gas sensing device of claim 1, wherein the heater surrounds the sensor. The gas sensing device of claim 1, further comprising: a circuit board; and a heat-insulating die bonding between the second surface and the circuit board for fixing the heat-insulating single crystal substrate on the circuit board and prevent the heat generated by the heater from being transferred to the circuit board.

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