JP2020165768A - Infrared sensor - Google Patents

Abstract

To provide an infrared sensor which employs a MEMS structure and yet offers quick convergence of thermal balance and superior thermal response.SOLUTION: An infrared sensor is provided, comprising a frame-shaped frame unit 2 having a cavity 2a therein, an insulative support film 3 formed on the frame unit to cover the cavity, a first heat sensitive element 4A and a second heat sensitive element 4B disposed spaced apart on the insulative support film directly above the cavity, a first insulative protection film 5A formed over the first heat sensitive element, a second insulative protection film 5B formed over the second heat sensitive element, and an infrared shield 6 provided directly above the second heat sensitive element, where the first insulative protection film and the second insulative protection film are at least partially in contact with each other.SELECTED DRAWING: Figure 1

Description

The present invention relates to an infrared sensor that detects infrared rays from a measurement object and measures the temperature of the measurement object.

Conventionally, an infrared sensor has been used as a temperature sensor that non-contactly detects infrared rays radiated from an object to be measured and measures the temperature of the object to be measured.
For example, in Patent Document 1, an insulating film, a first heat-sensitive element and a second heat-sensitive element provided on one surface of the insulating film at a distance from each other, and one surface of the insulating film are provided. The conductive first wiring film formed and connected to the first heat-sensitive element, the conductive second wiring film connected to the second heat-sensitive element, and the insulating property facing the second heat-sensitive element. An infrared sensor having an infrared reflective film provided on the other surface of the film has been proposed.

Further, in order to reduce the heat capacity of the infrared sensor and improve the responsiveness, for example, Patent Documents 2 and 3 describe an infrared sensor adopting a so-called MEMS structure. The infrared sensor adopting this MEMS structure has a configuration in which a plurality of sensor portions are provided on a thin film formed inside the frame-shaped frame portion.

Japanese Unexamined Patent Publication No. 2011-102791 Japanese Unexamined Patent Publication No. 2014-219334 JP-A-11-14449

The following problems remain in the above-mentioned conventional technique.
That is, in the infrared sensor adopting the above-mentioned MEMS structure, since the sensor portion on the light receiving side (detection side) and the sensor portion on the compensation side are separated and connected only by the thin film portion which is the base, it is difficult to thermally bond with each other. Since the convergence of the thermal balance between the light receiving side and the compensating side is delayed, it takes time to stabilize the temperature, and there is a problem that the thermal response is poor.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an infrared sensor having a quick convergence of thermal balance and excellent thermal responsiveness even if a MEMS structure is adopted.

The present invention has adopted the following configuration in order to solve the above problems. That is, the infrared sensor according to the first invention has a frame-shaped frame portion having a cavity inside, an insulating support film formed from the frame portion to the cavity portion, and directly above the cavity portion. A first heat-sensitive element and a second heat-sensitive element provided on the insulating support film and separated from each other, a first insulating protective film formed on the first heat-sensitive element, and the second heat-sensitive element. A second insulating protective film formed on the heat-sensitive element and an infrared shielding portion provided directly above the second heat-sensitive element are provided, and the first insulating protective film and the second insulation are provided. It is characterized in that the sex protective film is connected at least in part.

In this infrared sensor, since the first insulating protective film and the second insulating protective film are connected at least in part, the first insulating protective film and the second insulating property which are connected and connected are connected. Heat conduction is quickly performed by thermally coupling the first heat-sensitive element and the second heat-sensitive element via the protective film. Therefore, the change in the environmental temperature can be efficiently transmitted between the light receiving side and the compensating side, the heat balance between the light receiving side and the compensating side converges quickly, and the thermal responsiveness is improved.

The infrared sensor according to the second invention is the lower metal in the first invention, between the first heat-sensitive element and the insulating support film and between the second heat-sensitive element and the insulating support film. The lower metal film is provided with a film, and is characterized in that the lower metal film extends continuously from directly below the first heat-sensitive element to directly below the second heat-sensitive element.
That is, in this infrared sensor, since the lower metal film extends continuously from directly below the first heat-sensitive element to directly below the second heat-sensitive element, it is connected to the first heat-sensitive element via the lower metal film. Further thermal coupling with the second thermal element makes the thermal balance converge faster. Further, when the lower metal film is a film that reflects infrared rays (lower infrared ray reflecting film), the lower infrared ray reflecting film reflects infrared rays from above that have passed through the first heat sensitive element and reflects upward again to the first heat sensitive element. High light receiving efficiency can be obtained by returning to. Further, the lower metal film can block infrared rays entering the first heat-sensitive element or the second heat-sensitive element from below, suppress noise components, and enable more accurate measurement.

In either the first or second invention, the infrared sensor according to the third invention is used between the first heat-sensitive element and the insulating support film and between the second heat-sensitive element and the insulating support film. A lower insulating layer is provided between the two, and the lower insulating layer extends continuously from directly below the first heat-sensitive element to directly below the second heat-sensitive element.
That is, in this infrared sensor, since the lower insulating layer extends continuously from directly below the first heat-sensitive element to directly below the second heat-sensitive element, it is connected to the first heat-sensitive element via the lower insulating layer. Further thermal coupling with the second thermal element accelerates the convergence of the thermal balance.

The infrared sensor according to the fourth invention has a slit portion between the first insulating protective film and the second insulating protective film in any one of the first to third inventions. It is characterized by that.
That is, in this infrared sensor, since a slit portion is provided between the first insulating protective film and the second insulating protective film, there is a gap between the first heat sensitive element and the second heat sensitive element. By providing an air layer with a slit portion in a part thereof, it becomes easy to make a temperature difference between the first heat sensitive element and the second heat sensitive element. That is, in addition to improving the thermal balance between the connected first insulating protective film and the second insulating protective film, the balance between sensitivity and responsiveness is adjusted according to the position and length of the slit portion. be able to.

According to the present invention, the following effects are obtained.
That is, according to the infrared sensor according to the present invention, since the first insulating protective film and the second insulating protective film are connected at least partially, they are mutually connected between the light receiving side and the compensating side. The change in the environmental temperature can be efficiently transmitted to the infrared ray, the heat balance between the light receiving side and the compensating side converges quickly, and the thermal responsiveness is improved.

It is sectional drawing which shows 1st Embodiment of the infrared sensor which concerns on this invention (the sectional view taken along line AA of FIG. 3). It is schematic cross-sectional view which shows the state which the infrared sensor was mounted on the stem member in 1st Embodiment. It is a top view which shows the infrared sensor in 1st Embodiment. It is sectional drawing which shows the 2nd Embodiment of the infrared sensor which concerns on this invention (the sectional view taken along line BB of FIG. 5). It is a top view which shows the infrared sensor in 2nd Embodiment. It is sectional drawing which shows the 3rd Embodiment of the infrared sensor which concerns on this invention. It is sectional drawing which shows the 4th Embodiment of the infrared sensor which concerns on this invention. It is sectional drawing which shows the 5th Embodiment of the infrared sensor which concerns on this invention. It is a top view which shows the 6th Embodiment of the infrared sensor which concerns on this invention. It is a top view which shows the 7th Embodiment of the infrared sensor which concerns on this invention.

Hereinafter, the first embodiment of the infrared sensor according to the present invention will be described with reference to FIGS. 1 to 3. In some of the drawings used in the following description, the scale is appropriately changed as necessary in order to make each part recognizable or easily recognizable.

As shown in FIGS. 1 to 3, the infrared sensor 1 of the present embodiment has a frame-shaped frame portion 2 having a cavity portion 2a inside, and an insulating property formed from above the frame portion 2 to above the cavity portion 2a. A first heat-sensitive element 4A and a second heat-sensitive element 4B formed on the support film 3 and an insulating support film 3 directly above the cavity 2a and separated from each other, and a first heat-sensitive element 4A formed on the first heat-sensitive element 4A. The insulating protective film 5A of No. 1, the second insulating protective film 5B formed on the second heat-sensitive element 4B, and the infrared shielding portion 6 provided directly above the second heat-sensitive element 4B are provided. ing.

The first insulating protective film 5A and the second insulating protective film 5B are connected at least in part. In the present embodiment, the first insulating protective film 5A and the second insulating protective film 5B are continuous one-layer protective films, and intermediate portions of the insulating support films 3 (with the first heat-sensitive element 4A). The film is formed in a state of being connected to the second heat-sensitive element 4B).
Further, the infrared sensor 1 of the present embodiment includes an infrared absorbing film 7 formed on the first insulating protective film 5A and provided directly above the first heat sensitive element 4A.

The frame portion 2 is formed of, for example, single crystal silicon, and after forming an insulating support film 3 on the single crystal silicon substrate, the insulating support film 3 is left by etching or the like and is hollow in the single crystal silicon substrate. Part 2a is formed.
The insulating support film 3 is a diaphragm portion composed of a plurality of insulating layers such as Si—O / Si—N / Si—O.

That is, the infrared sensor 1 of the present embodiment has a so-called MEMS structure in which the first heat sensitive element 4A and the second heat sensitive element 4B are provided on the frame portion 2 and the insulating support film 3.
As shown in FIG. 2, the infrared sensor 1 of the present embodiment is used, for example, by being adhered with a solder material or the like onto a stem member 8 in which a plurality of pin members P project from above.

The first heat-sensitive element 4A is a sensor unit on the light receiving side (detection side), and the second heat-sensitive element 4B is a sensor unit for compensation.
The first heat-sensitive element 4A and the second heat-sensitive element 4B are formed on the insulating support film 3 with a heat-sensitive film 11 formed of a thermistor material, and at least one of the top and bottom of the heat-sensitive film 11 facing each other. It is provided with a pair of counter electrodes 12.
The pair of counter electrodes 12 of the present embodiment are comb-shaped electrodes having a comb-shaped pattern formed on the heat-sensitive film 11 so as to face each other, and have a plurality of comb portions 12a.

Further, a plurality of pattern wirings 13 connected to the pair of counter electrodes 12 are formed on the insulating support film 3. At the end of the pattern wiring 13, a pad portion 13a connected to the wiring on the stem member 8 or the pin member P by wire bonding or the like is formed.
In each pattern wiring 13, the distance from the heat-sensitive film 11 to the pad portion 13a is set to be equivalent.
Further, one of the pair of counter electrodes 12 of the first heat sensitive element 4A and one of the pair of counter electrodes 12 of the second heat sensitive element 4B are connected by a pattern wiring 13.

The thermal film 11 is a thin film thermistor portion formed of a thermistor material such as a spinel composition or a nitride composition. For example, the heat-sensitive film 11 is formed of a Ti—Al—N thermistor material in a rectangular shape. That is, the heat-sensitive film 11 of the present embodiment has a general formula: T _x Al _y N _z (0.70 ≦ y / (x + y) ≦ 0.95, 0.4 ≦ z ≦ 0.5, x + y + z = 1). It consists of the metal nitride shown, and its crystal structure is a hexagonal wurtzite-type single phase.

The counter electrode 12 and the pattern wiring 13 are patterned with a plurality of metal layers such as Au / Cr, Au / Ti, and Pt / Ti.
The first insulating protective film 5A and the second insulating protective film 5B are formed of an insulating layer such as Si—O (SiO _2, etc.).

The infrared shielding portion 6 is an infrared reflecting film formed on the second insulating protective film 5B and directly above the second heat sensitive element 4B in a substantially quadrangular shape. The infrared shielding portion 6 is formed of a material having an infrared reflectance higher than that of the second insulating protective film 5B, and is formed of, for example, a gold thin film. In addition to the gold thin film, it may be formed of, for example, a mirror-surfaced aluminum vapor-deposited film or an aluminum foil. The infrared shielding portion 6 has a size larger than that of the second heat sensitive element 4B and is formed so as to cover the infrared shielding portion 6.

The infrared absorbing film 7 is formed of a material directly above the first heat-sensitive element 4A and having a higher infrared absorbing property than the first insulating protective film 5A. The infrared absorbing film 7 includes, for example, a film containing an infrared absorbing material such as carbon black, an infrared absorbing glass film (such as a borosilicate glass film containing 71% silicon dioxide), an antimonated tin oxide (ATO) film, and gold black. Those formed of a membrane, a porous metal membrane, etc. can be adopted.

The heat-sensitive film 11 is set to, for example, a thickness of 200 nm, and the insulating support film 3 is set to, for example, a thickness of 1000 nm. Further, the infrared shielding portion 6 and the infrared absorbing film 7 are set to, for example, a thickness of 100 nm, and the first insulating protective film 5A and the second insulating protective film 5B are set to, for example, a thickness of 500 nm.

In the method for manufacturing the infrared sensor 1 of the present embodiment, for example, an insulating support film 3 is first formed on a silicon substrate having a crystal plane orientation (100) by a plasma CVD method or the like, and then a heat-sensitive film is further formed on the insulating support film 3. The 11 and the counter electrode 12 are formed into a film by sputtering, PVD, or the like, and a pattern is formed by etching or the like to form a first heat-sensitive element 4A and a second heat-sensitive element 4B.

Next, a first insulating protective film 5A and a second insulating protective film 5B are applied onto the insulating support film 3 so as to cover the first heat-sensitive element 4A and the second heat-sensitive element 4B. A film is formed by CVD or the like, and an infrared shielding portion 6 and an infrared absorbing film 7 are patterned on the first insulating protective film 5A and the second insulating protective film 5B by sputtering or the like.
Next, the back surface side of the silicon substrate is etched by etching the window opening with RIE or the like using a mask to form the frame portion 2 having the cavity portion 2a while leaving the insulating support film 3, and the infrared sensor 1 having a MEMS structure is formed. Is produced.

As described above, in the infrared sensor 1 of the present embodiment, since the first insulating protective film 5A and the second insulating protective film 5B are connected at least partially, the first insulation connected and connected. Heat conduction is quickly performed by thermally coupling the first heat-sensitive element 4A and the second heat-sensitive element 4B via the sex protective film 5A and the second insulating protective film 5B. Therefore, the change in the environmental temperature can be efficiently transmitted between the light receiving side and the compensating side, the heat balance between the light receiving side and the compensating side converges quickly, and the thermal responsiveness is improved.

Next, the second to seventh embodiments of the temperature sensor according to the present invention will be described below with reference to FIGS. 4 to 10. In the following description of each embodiment, the same components described in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The difference between the second embodiment and the first embodiment is that in the first embodiment, the first heat sensitive element 4A and the second heat sensitive element 4B are heat sensitive formed of a thermistor material such as Ti-Al-N. In contrast to the film 11 and the pair of comb-shaped counter electrodes 12, in the infrared sensor 21 of the second embodiment, as shown in FIGS. 4 and 5, the first thermal element 24A and the second heat sensitive element 24A and the second The point is that the heat sensitive element 24B of No. 24 is composed of a heat sensitive film 25 formed of a dielectric material and a pair of counter electrodes 22 formed above and below the heat sensitive film 25.

That is, in the second embodiment, the heat-sensitive film 25 is formed in a rectangular shape with a dielectric material such as BT, BST, SBT, PZT, PLZT, which has a temperature dependence of the dielectric constant.
Further, the pair of counter electrodes 22 are formed in a rectangular shape above and below the heat-sensitive film 25 made of a dielectric material in order to increase the capacitance, and are provided so as to sandwich the heat-sensitive film 25.

Next, the difference between the third embodiment and the first embodiment is that in the first embodiment, the first heat-sensitive element 4A and the second heat-sensitive element 4B are directly formed on the insulating support film 3. On the other hand, in the infrared sensor 31 of the third embodiment, as shown in FIG. 6, the first heat sensitive element 4A and the second heat sensitive element 4B are formed via the lower metal film 33 on the insulating support film 3. It is a point that has been done.
That is, the infrared sensor 31 of the third embodiment includes a lower metal film 33 between the first heat-sensitive element 4A and the insulating support film 3 and between the second heat-sensitive element 4B and the insulating support film 3. ing.

The lower metal 33 extends continuously from directly below the first heat-sensitive element 4A to directly below the second heat-sensitive element 4B.
The lower metal film 33 is formed of, for example, a gold thin film, a mirror-surfaced aluminum vapor-deposited film, an aluminum foil, or the like. Further, by interposing an insulating film between the lower metal film 33 and the first heat-sensitive element 4A and the second heat-sensitive element 4B, even if the conductive lower metal film 33 is adopted, the lower metal film 33 and the lower metal film 33 It is possible to prevent conduction with the first heat sensitive element 4A or the second heat sensitive element 4B. When the counter electrode 12 of the first heat sensitive element 4A and the second heat sensitive element 4B is a comb-shaped electrode formed directly above the heat sensitive film 11, the heat sensitive film 11 is compared with the distance between the plurality of comb portions 12a. If the film thickness is sufficiently large (for example, 10 times or more), even if the lower metal film 33 is arranged directly under the thermal film 11, it has almost no effect on the measurement of infrared rays.

As described above, in the infrared sensor 31 of the third embodiment, since the lower metal film 33 extends continuously from directly below the first heat sensitive element 4A to directly below the second heat sensitive element 4B, the lower metal film 33 is formed. The first heat sensitive element 4A and the second heat sensitive element 4B are further thermally coupled via 33, and the convergence of the heat balance is accelerated.
Further, when the lower metal film 33 is a film that reflects infrared rays (lower infrared ray reflecting film), the lower infrared ray reflecting film reflects infrared rays from above that have passed through the first heat sensitive element 4A and is reflected upward again. High light receiving efficiency can be obtained by returning to the heat sensitive element 4A.
Further, the lower metal film 33 can block infrared rays entering the first heat sensitive element 4A or the second heat sensitive element 4B from below, and suppress noise components to enable more accurate measurement. ..

Next, the difference between the fourth embodiment and the third embodiment is that in the third embodiment, the first heat sensitive element 4A and the second heat sensitive element 4B are formed on the lower metal film 33. On the other hand, in the infrared sensor 41 of the fourth embodiment, as shown in FIG. 7, the first heat sensitive element 4A and the second heat sensitive element 4B are formed on the lower insulating layer 43 on the insulating support film 3. It is a point.
That is, the infrared sensor 41 of the fourth embodiment includes a lower insulating layer 43 between the first heat sensitive element 4A and the insulating support film 3 and between the second heat sensitive element 4B and the insulating support film 3. ing.

The lower insulating layer 43 extends continuously from directly below the first heat-sensitive element 4A to directly below the second heat-sensitive element 4B.
The lower insulating layer 43 is formed of an insulating material such as a Si—O material.
As described above, in the infrared sensor 41 of the fourth embodiment, the lower insulating layer 43 extends continuously from directly below the first heat-sensitive element 4A to directly below the second heat-sensitive element 4B, so that the lower insulating layer extends. The first heat-sensitive element 4A and the second heat-sensitive element 4B are further thermally coupled via 43, and the convergence of the heat balance is accelerated.

Next, the difference between the fifth embodiment and the third embodiment is that in the third embodiment, the first heat sensitive element 4A and the second heat sensitive element 4B are directly formed on the lower metal film 33. On the other hand, in the infrared sensor 51 of the fifth embodiment, as shown in FIG. 8, a lower metal film 33 and a lower insulating layer 43 are formed on the insulating support film 3, and the first heat sensitive element 4A is formed on the lower metal film 33. And the point where the second heat sensitive element 4B is formed.
That is, the infrared sensor 51 of the fifth embodiment can obtain a synergistic effect by both the lower metal film 33 and the lower insulating layer 43, and the thermal balance between the first heat sensitive element 4A and the second heat sensitive element 4B can be obtained. Converges faster.

Next, the difference between the sixth and seventh embodiments and the second embodiment is that in the second embodiment, the first insulating protective film 5A and the second insulating protective film 5B are first to each other. The infrared sensors 61 and 71 of the sixth and seventh embodiments are continuously connected along the heat sensitive element 24A and the second heat sensitive element 24B, as shown in FIGS. 9 and 10. In addition, slit portions S1 and S2 are formed between the first insulating protective film 5A and the second insulating protective film 5B.

That is, in the infrared sensor 61 of the sixth embodiment, as shown in FIG. 9, one slit portion S1 is formed between the first insulating protective film 5A and the second insulating protective film 5B, and the first slit portion S1 is formed. In the infrared sensor 71 of the seventh embodiment, as shown in FIG. 10, two slit portions S2 are formed between the first insulating protective film 5A and the second insulating protective film 5B.
The slit portions S1 and S2 are provided between the first heat-sensitive element 24A and the second heat-sensitive element 24B, and in the sixth embodiment, the first insulating protective film is provided on both ends of the slit portion S1. The 5A and the second insulating protective film 5B are connected. Further, in the seventh embodiment, the first insulating protective film 5A and the second insulating protective film 5B are connected between both ends of the two slit portions S2 and between the two slit portions S2. ..

As described above, the infrared sensors 61 and 71 of the sixth and seventh embodiments have slit portions S1 and S2 between the first insulating protective film 5A and the second insulating protective film 5B. By providing an air layer by slit portions S1 and S2 in a part between the first heat sensitive element 24A and the second heat sensitive element 24B, the temperature of the first heat sensitive element 24A and the second heat sensitive element 24B It becomes easier to make a difference. That is, in addition to the improvement of the thermal balance by the connected first insulating protective film 5A and the second insulating protective film 5B, the sensitivity and responsiveness are increased according to the positions and lengths of the slit portions S1 and S2. You can adjust the balance of.

By embedding a substance having a higher thermal conductivity than the first insulating protective film 5A and the second insulating protective film 5B in the slit portions S1 and S2, the responsiveness becomes higher. Further, the sensitivity can be improved by embedding a substance having a thermal conductivity lower than that of the first insulating protective film 5A and the second insulating protective film 5B in the slit portions S1 and S2.

The technical scope of the present invention is not limited to each of the above embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in each of the above embodiments, the first heat-sensitive element and the second heat-sensitive element having a heat-sensitive film are adopted, but even if a thermistor such as a chip thermistor or a pyroelectric element is adopted as the heat-sensitive element. I do not care.

1, 21, 31, 41, 51, 61, 71 ... Infrared sensor, 2 ... Frame part, 2a ... Cavity part, 3 ... Insulating support film, 4A, 24A ... First heat sensitive element, 4B, 24B ... Second Heat-sensitive element, 5A ... 1st insulating protective film, 5B ... 2nd insulating protective film, 6 ... infrared shielding part, 33 ... lower metal film, 43 ... lower insulating layer, S1, S2 ... slit part

Claims (4)

A frame-shaped frame part with a hollow part inside,
An insulating support film formed from above the frame portion to above the cavity portion,
A first heat-sensitive element and a second heat-sensitive element provided on the insulating support film directly above the cavity and separated from each other.
A first insulating protective film formed on the first heat sensitive element and
A second insulating protective film formed on the second heat-sensitive element,
It is provided with an infrared shielding portion provided directly above the second heat sensitive element.
An infrared sensor characterized in that the first insulating protective film and the second insulating protective film are connected at least in part. In the infrared sensor according to claim 1,
A lower metal film is provided between the first heat-sensitive element and the insulating support film and between the second heat-sensitive element and the insulating support film.
An infrared sensor characterized in that the lower metal film extends continuously from directly below the first heat-sensitive element to directly below the second heat-sensitive element. In the infrared sensor according to claim 1 or 2.
A lower insulating layer is provided between the first heat-sensitive element and the insulating support film and between the second heat-sensitive element and the insulating support film.
An infrared sensor characterized in that the lower insulating layer continuously extends from directly below the first heat-sensitive element to directly below the second heat-sensitive element. In the infrared sensor according to any one of claims 1 to 3.
An infrared sensor characterized by having a slit portion between the first insulating protective film and the second insulating protective film.

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