TWI452272B - Thermopile sensing element - Google Patents

Description

Thermopile sensing component

The present invention is a thermopile sensing element, and more particularly to a thermopile sensing element having a three-layer structure infrared absorber.

The thermopile sensing element is mainly composed of a plurality of thermocouples in series, and the thermocouple has opposite ends. As long as there is a temperature difference between the two ends, the thermocouple can output a voltage signal, and the larger the temperature difference, the thermocouple output The larger the voltage signal is, the temperature of the body to be measured can be estimated by measuring the output voltage of the thermocouple, so the thermopile sensing element can be used as the measuring temperature.

Referring to FIG. 8, a thermopile sensing component of U.S. Patent No. 6,949,286 is disclosed, which comprises a substrate 50 having an opening 51 facing upwardly, and a diaphragm disposed on the substrate 50. 52, the film 52 covers the cavity 51, a thermocouple layer 53 is formed on the film 52, and a heat absorbing layer 54 is partially formed on the thermocouple layer 53; wherein the thermocouple layer 53 is heated by the heat absorbing layer 54. The area covered is referred to as a hot junction, and the area not covered by the heat absorbing layer 54 is referred to as a cold junction.

When the heat absorbing layer 54 absorbs infrared heat energy and the temperature rises, the temperature can be directly transmitted to the hot junction of the thermocouple layer 53, since the cold junction is not covered by the heat absorbing layer 54, at this time, the thermocouple layer 53 The temperature difference between the hot junction and the cold junction creates a temperature difference, so the thermocouple layer 53 can output a voltage signal.

However, the heat absorbing layer 54 disclosed in the U.S. Patent is a block composed of a mixture of cerium oxide and gold (Au) particles, which is not a general transistor process. The materials used cannot be manufactured in a low-cost standard process in a semiconductor foundry, but a special material process is required, resulting in increased costs.

In addition, since the heat absorbing layer 54 is additionally fabricated, the bulk thereof is increased to cause an increase in heat capacity, so that the thermal reaction time proportional to the heat capacity is also increased, thereby reducing the thermal reaction speed of the element.

It is therefore a primary object of the present invention to provide a thermopile sensing element such that the heat absorbing layer thereon is compatible with a typical semiconductor process and the volume of the heat absorbing layer can be thinned to reduce heat capacity.

For the purpose of the prior art, the technical means adopted by the present invention is such that the thermopile sensing element comprises: a substrate having a cavity; a substrate layer formed on the substrate and covering the cavity; a thermoelectric The dipole layer is formed on the base layer and comprises a plurality of thermocouple pairs connected in series, each thermocouple pair having opposite ends, one end forming a hot junction portion and being located above the hole, and forming the other end a cold junction portion corresponding to the substrate; and an infrared absorber disposed on the thermocouple layer and in thermal contact with the thermal contact portion of the plurality of thermocouple pairs, the infrared absorber comprising There is: a first metal layer; a dielectric layer formed on the first metal layer; and a second metal layer formed on the dielectric layer.

With the above configuration, the thermopile sensing element of the present invention can achieve the following effects:

1. The infrared absorbing system has a layered structure, which can be completed by a metal deposition, a dielectric deposition and an etching process in a general transistor process, and can be manufactured at a low cost.

2. The thermopile sensing element of the present invention can adjust the sheet resistance value of the first and second metal layers and the thickness and refractive index of the dielectric layer according to the requirement of absorbing the infrared band, so that the infrared absorber is The specific infrared ray band has an optimum absorption rate, and by controlling the thickness of the dielectric value layer, the volume of the infrared absorbing body is controlled within a certain range, so that the heat capacity of the infrared absorbing body is lowered to shorten the infrared absorbing body. Thermal reaction time.

Referring to FIG. 1 and FIG. 2, a preferred embodiment of the present invention is disclosed. The thermopile sensing element comprises a substrate 10, a substrate layer 20, a thermocouple layer 30 and an infrared absorber 40.

The substrate 10 has a cavity 100.

The base layer 20 is formed on the substrate 10 and over the cavity 100, wherein the base layer 20 can completely cover the cavity 100; or the base layer 20 can form an etched window and partially cover the Above the cavity 100.

The thermocouple layer 30 is formed on the base layer 20, and includes a plurality of series of thermocouple pairs 300. Each of the thermocouple pairs 300 has opposite ends, and one end forms a hot junction portion 321 and is located corresponding to the space. Above the hole 100, a cold junction portion 322 is formed at the other end and is located above the substrate 10, and the plurality of thermocouple pairs 300 are arranged radially. Each thermocouple pair 300 includes a first thermocouple 31 and a a second thermocouple 32, wherein the first and second thermocouples 31, 32 are made of different thermocouple materials, the first thermocouple 31 is formed on the base layer 20, and the second thermocouple 32 is formed on The first thermocouple 31 is connected to the first thermocouple of another adjacent thermocouple pair 300, thus forming the plurality of thermocouple pairs 300 into a series structure; wherein the second thermocouple 32 of the thermocouple pair 300 The first thermocouple 31 of another adjacent thermocouple pair 300 is not connected, thus separating two adjacent thermocouple pairs 300 from each other. The two thermocouple pairs can be defined as a pair of thermocouples 301 and a pair of thermocouples. 302.

The infrared absorber 40 is disposed on the thermocouple layer 30 and is in thermal contact with the hot junction portion 321 of the plurality of thermocouple pairs 300.

When the infrared absorbing body 40 absorbs heat to cause a temperature change, the heat is conducted to the hot junction portion 321 of the thermocouple layer 30, and the temperature of the hot junction portion 321 rises relative to the temperature of the cold junction portion 322 to generate a temperature. The difference is further, and the voltage signal is output from the first thermocouple pair 301 and the last thermocouple pair 302. By measuring the magnitude of the voltage signal, the temperature change can be estimated.

Referring to FIG. 3, the structure of the infrared absorber 40 is disclosed. The infrared absorber 40 includes a first metal layer 41, a dielectric layer 42 and a second metal layer 43. The dielectric layer 42 Formed on the first metal layer 41, and the second metal layer 43 is formed on the dielectric layer 42 such that the first metal layer 41, the dielectric layer 42 and the second metal layer 43 are formed below. The upper stacked structure, wherein the first metal layer 41 serves as a reflective layer, and the second metal layer 43 has a semi-transmissive property.

The thermopile sensing element of the present invention is characterized in that a high absorptivity infrared absorber 40 can be designed for an infrared band of a specific wavelength. Referring to FIG. 4 to FIG. 7, the heat absorption rate waveforms of the infrared absorbing body 40 with respect to different infrared wavelengths are disclosed, wherein the horizontal axis represents the infrared wavelength (μm), and the vertical axis represents the absorption rate of the infrared absorbing body 40 corresponding to the infrared wavelength. . For example, since the thermopile sensing element is usually operated in the infrared band of 8 to 14 (μm), it is assumed that the infrared absorption body 40 is about 8 to 14 (μm) in the infrared band, and the average heat absorption rate is up to 90. %, the following four simulation tests were done.

As shown in FIG. 4, the sheet resistance values Rr and Rs of the first and second metal layers 41 and 43 and the thickness d of the dielectric layer 42 are preset to a certain value. In this embodiment, the first The sheet resistance value Rr of the metal layer 41 is set to 1.2 (ohm/sq.), the sheet resistance value Rs of the second metal layer 43 is set to 377 (ohm/sq.), and the thickness d of the dielectric layer 42 is set. When the refractive index n of the dielectric layer 42 is adjusted and the refractive index n of the dielectric layer 42 is adjusted, the infrared absorber 40 can be in the infrared band at 8 to 14 by adjusting the refractive index n of the dielectric layer 42. (μm) for the best absorption rate. As can be seen from FIG. 4, when the refractive index of the dielectric layer 42 is set to 2, the average heat absorption rate of the infrared absorber 40 in the infrared band of about 8 to 14 (μm) can reach 90%, and the general method is The refractive index of the dielectric layer 42 is set to 1.4 or more.

As shown in FIG. 5, the sheet resistance values Rr and Rs of the first and second metal layers 41 and 43 and the refractive index n of the dielectric layer 42 are preset to a certain value. In this embodiment, The sheet resistance value Rr of a metal layer 41 is set to 1.2 (ohm/sq.), and the sheet resistance value Rs of the second metal layer 43 is set to 377 (ohm/sq.), and the dielectric layer 42 is refracted. The rate n is set to 2, so the dielectric can be known by adjusting several different thicknesses d of the dielectric layer 42. The thickness of the layer 42 is such that the infrared absorber 40 achieves an optimum absorption rate in the infrared band of 8 to 14 (μm). As can be seen from FIG. 5, when the thickness d of the dielectric layer 42 is set to 1250 (nm), the infrared absorber 40 has an average heat absorption rate of 90% in the infrared band of about 8 to 14 (μm). The general method is to set the thickness d of the dielectric layer 42 to 500 nm or more.

Similarly, as shown in FIG. 6, in the present simulation test, the sheet resistance value Rr of the first metal layer 41 is set to 1.2 (ohm/sq.), and the refractive index n of the dielectric layer 42 is set to 2. The thickness d of the dielectric layer 42 is set to 1250 (nm). As can be seen from FIG. 6, when the sheet resistance value Rs of the second metal layer 43 is set to 300 or 400 (ohm/sq.), The infrared absorber 40 has an average heat absorption rate of about 90% in the infrared band of about 8 to 14 (μm). It is common practice to set the sheet resistance value Rs of the second metal layer 43 to be greater than 100 (ohm/sq.). .

As shown in FIG. 7, in the simulation test, the sheet resistance value Rs of the second metal layer 43 is set to 377 (ohm/sq.), and the refractive index n of the dielectric layer 42 is set to 2, The thickness d of the dielectric layer 42 is set to 1250 (nm), as can be seen from FIG. 7, when the sheet resistance value Rr of the first metal layer 41 is set to 1 or 10 (ohm/sq.), the infrared absorption The average heat absorption rate of the body 40 in the infrared band of about 8 to 14 (μm) can reach 90%. Generally, the sheet resistance value Rr of the first metal layer 43 is set to be less than 200 (ohm/sq.), for example. Between 1 and 10 (ohm/sq.).

In summary, the infrared absorber 40 is a three-layer stacked structure which can be completed by metal deposition, dielectric deposition and etching in a known semiconductor process, and metal deposition, dielectric deposition and etching. The process is currently easily completed by a semiconductor foundry, and thus can be produced at a low cost; on the other hand, from the structure of the thermal sensing element, the infrared absorber 40 can be adjusted correspondingly according to the demand of the infrared band to be absorbed. The parameters of the respective constituent members, for example, the sheet resistance values of the first and second metal layers and the thickness and refractive index of the dielectric layer, etc., allow the infrared absorbing body 40 to have an optimum absorption rate in a desired infrared ray band.

10. . . Substrate

100. . . Hole

20. . . Base layer

30. . . Thermocouple layer

300. . . Thermocouple pair

301. . . Initial thermocouple pair

302. . . Terminal thermocouple pair

31. . . First thermocouple

32. . . Second thermocouple

321. . . Hot junction

322. . . Cold junction

40. . . Infrared absorber

41. . . First metal layer

42. . . Dielectric layer

43. . . Second metal layer

50. . . Substrate

51. . . Hole

52. . . Diaphragm

53. . . Thermocouple layer

54. . . Heat absorbing layer

Figure 1 is a schematic plan view of a thermopile sensing element of the present invention.

2 is a schematic cross-sectional view of a thermopile sensing element of the present invention.

Fig. 3 is a cross-sectional view of the infrared absorber.

4 to 7 are graphs showing the relative absorption rates of infrared wavelengths of several preferred embodiments of the thermopile sensing elements of the present invention.

Figure 8: Schematic diagram of the sensing element of the thermopile.

10. . . Substrate

100. . . Hole

20. . . Base layer

30. . . Thermocouple layer

31. . . First thermocouple

32. . . Second thermocouple

40. . . Infrared absorber

41. . . First metal layer

42. . . Dielectric layer

43. . . Second metal layer

Claims (7)

A thermopile sensing component comprising: a substrate having a cavity; a substrate layer formed on the substrate and overlying the cavity; a thermocouple layer formed on the substrate layer, the inclusion a pair of thermocouples connected in series, each pair of thermocouples having opposite ends, one end forming a hot junction portion and being located above the hole, and the other end forming a cold junction portion corresponding to the substrate Above; wherein each thermocouple pair comprises a first thermocouple and a second thermocouple, and the first and second thermocouples are made of different thermocouple materials, and the first thermocouple is formed on the base layer The second thermocouple is formed on the first thermocouple and connected to the first thermocouple of another adjacent thermocouple pair such that the plurality of thermocouple pairs form a tandem structure; wherein the second pair of thermocouples The thermocouple is not connected to the first thermocouple of another adjacent thermocouple pair and is separated from each other; and an infrared absorber is disposed on the thermocouple layer and connected to the hot junction of the plurality of thermocouple pairs to form a thermal contact The infrared absorber includes a first metal layer having a sheet resistance of less than 10 (ohm/sq.); a dielectric layer formed on the first metal layer; and a second metal layer formed on the dielectric layer And having a semi-transmissive property, the sheet resistance of the second metal layer is between 300 and 400 (ohm/sq.). The thermoelectric stack sensing element according to claim 1, wherein the first metal layer has a sheet resistance value of 1.2 (ohm/sq.), and the second metal layer has a sheet resistance value of 377 (ohm/sq. ), the thickness of the dielectric layer is At 1250 (nm), the dielectric layer has a refractive index of 2. The thermoelectric stack sensing element according to claim 1, wherein the first metal layer has a sheet resistance value of 1.2 (ohm/sq.), and the dielectric layer has a thickness of 1250 (nm), the dielectric The refractive index of the layer is 2. The thermoelectric stack sensing element according to claim 1, wherein the first metal layer has a sheet resistance value of 1 to 10 (ohm/sq.), and the second metal layer has a sheet resistance value of 377 ( Ohm/sq.), the dielectric layer has a thickness of 1250 (nm), and the dielectric layer has a refractive index of 2. The thermoelectric stack sensing element of claim 1, wherein the dielectric layer has a refractive index greater than 1.4. The thermoelectric stack sensing element of claim 5, wherein the dielectric layer has a thickness greater than 500 nm. The thermopile sensing element of claim 1, wherein the substrate layer covers the entire cavity.