JPH0346522A - Infrared sensor - Google Patents

Abstract

PURPOSE:To improve responsiveness and sensitivity by forming a heat sensitive thin-film body and an IR absorptive layer on the front surface of a substrate, forming the rear side thereof as a space and installing an IR transmission filter in the route for IR rays. CONSTITUTION:The heat sensitive thin-film body 2 and the IR absorptive layer 5 are formed on the front surface of the substrate 1 laminated with an insulating layer 1a on a semiconductor layer 1b and the space S is formed on the rear side thereof. The IR transmission filter 7 is installed in the route for the incident IR rays to the absorptive layer 5. The sensor is microminiaturized by the use of the thin-film body 2 and the heat sensitive part consists of the small thickness part A of the substrate 1 and the thin-film body 2 and is small in thickness as a whole so that this part has an extremely small heat capacity and extremely good responsiveness. The space S communicates with the front surface in the relation with the part A to form the non hermetically closed state and the part where the volume of the air in the space S is increased and decreased by a temp. change is replenished and discharged. The accuracy of the measurement is thus maintained without allowing the part formed with the thin-film body to be deformed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an infrared sensor.

[Conventional technology]

Conventionally, a pyroelectric infrared sensor is well known as an infrared sensor. This pyroelectric infrared sensor is a sensor that senses infrared rays by utilizing a charge transfer phenomenon induced by infrared rays from an infrared generating body such as a human body or a heating element. Irradiation with infrared rays causes a temperature rise within the sensor, and this temperature rise induces charge transfer due to the pyroelectric effect. However, this pyroelectric infrared sensor
It can only be detected when there is a change in the intensity of infrared rays. Even if an infrared ray generator is within the sensing area, if it is stationary or the intensity of its infrared rays does not change, infrared rays cannot be detected.

On the other hand, as a sensor that eliminates the above-mentioned drawbacks, there is an infrared sensor that uses a resistance-type or thermocouple-type temperature sensor. This sensor detects infrared rays by absorbing infrared rays, converting them into thermal energy, and detecting the resulting temperature rise. By compensating for atmospheric temperature fluctuations, the infrared emitting body remains stationary, or the infrared emission intensity changes. Even if there is no change, detection is possible as long as it exists within the sensing area.

[Problem to be solved by the invention]

However, conventional infrared sensors using temperature sensitive bodies
There is a problem that responsiveness and sensitivity are not sufficient. Specifically, the temperature sensing part of a conventional infrared sensor uses a bulk temperature sensing element (for example, a semiconductor powder sintered thermistor), or a metal resistance wire or metal thermocouple wire arranged inside a sheath. There is also one in which a temperature-sensitive thin film is placed on a heavy-colored edged substrate made of ceramic or the like. The reason why the responsiveness and sensitivity of these conventional sensors are not sufficient is that the heat sensing portion of the sensor has a large heat capacity, and the degree of temperature rise due to infrared absorption is small and the rate of temperature rise is slow.

Further, in order to remove disturbance light such as sunlight, an infrared transmission filter is usually provided, but in conventional infrared sensors, the problem is that installing the filter significantly increases the cost. In an infrared sensor, the temperature sensing part and the infrared filter are separate, which results in high assembly and manufacturing costs.

In view of the above circumstances, the first object of the present invention is to provide an infrared sensor with sufficient responsiveness and sensitivity. A second object is to provide an infrared sensor [Means for solving the problem] In order to solve the above problem, the infrared sensor according to claims 1 to 7 is provided with a temperature-sensitive thin film formed on the surface of the substrate. , there is a space on the back side of the same temperature-sensitive thin film forming part of the substrate, and
An infrared absorbing layer is also formed in the temperature-sensitive thin film forming portion, and an infrared transmitting filter is installed in the path of the infrared rays incident on the infrared absorbing layer.

In addition, the infrared sensor according to claim 2 is a substrate in which the space communicates with the surface of the substrate and is in a non-sealed state.
For example, as in the infrared sensor according to the third aspect of the present invention, a substrate is used that has a structure in which an insulating layer is laminated on a semiconductor layer, and the temperature-sensitive thin model-shaped portion is made of only the insulating layer.

In particular, a substrate is used in which an insulating layer made of silicon nitride or silicon oxide is laminated on a silicon single crystal layer.

The thickness of the insulating layer in the temperature-sensitive thin film forming portion is, for example,
As in the infrared sensor according to claim 6, about 0.5 to 1.
It should be selected within the range of 5μ. If it is too thin, the strength will be insufficient, and if it is too thick, the heat capacity will increase.

For example, as in the infrared sensor according to a fourth aspect of the present invention, the space is formed by digging from the surface side of the substrate.

Examples of the temperature-sensitive thin film body include a thin film resistor, a thin film thermocouple, and a thin film thermocouple, as in the infrared sensor according to claim 7.
Examples include thermopile.

In order to also solve the second problem, claim 5
In the described infrared sensor, in addition, at least a portion of the infrared transmission filter is made up of a substrate.

Next, the configuration of the infrared sensor of the present invention will be specifically explained with reference to the drawings.

In the infrared sensor, as shown in FIG. 1ia), a temperature-sensitive thin film 2 is formed on the surface of a substrate 1. The temperature-sensitive thin film forming portion of the substrate 1 has a space S on the back side and is a thin portion A. The substrate 1 itself has a structure in which an insulating layer (for example, a layer made of a silicon nitride film or a silicon oxide film) la is laminated on a semiconductor layer (for example, a silicon single crystal layer) 1b, and a part of the insulating layer 1a The area is part A, which is thin. In other words, the temperature-sensitive thin film body type 2 part consists only of the thread-colored edge layer 1a.

An infrared absorbing layer 5 is provided on the temperature-sensitive thin body 2, and the infrared absorbing layer 5, which is installed on the back side of the substrate 1 where the infrared transmission filter 7 passes the infrared rays, is completely black (gold). (It is an aggregate of fine particles that are so fine that even though the incident light is reflected, they are trapped inside and appear pitch black to the human eye), platinum black, bismuth black, soot, etc. It is formed by When the infrared absorbing layer 5 has conductivity, an even thinner insulating layer is interposed between the IA sensitive thin film body 2 and the infrared absorbing layer 5.

On the other hand, the infrared transmission filter 7 may be an infrared bandpass filter (one that transmits only visible light but all the infrared light, or an infrared bandpass filter that transmits only a specific wavelength of infrared light), etc. It has infrared transmission ability.

Depending on the material of the substrate 1 (for example, silicon single crystal), the resistor plate 1 itself can be made into at least a part of the structure of the filter. When using a filter that is filtered only from the ld portion of the semiconductor layer (for example, a silicon single crystal layer) of the substrate 1, a filter in which the following optical film 6 is laminated on the ld portion of the semiconductor layer (for example, a silicon single crystal layer) is used as a filter. There are cases.

The structure of the optical film 6 may be an amorphous silicon film, an interference filter type in which a plurality of optical thin films made of silicon or other suitable materials are laminated, or an optical film made of other suitable materials on the amorphous silicon film. An example is an interference filter type in which a plurality of thin films are laminated. 1st
The infrared transmission filter 7 shown in FIG.
This configuration is a combination of the optical film 6 and the optical film 6.

There is a temperature rise in the filter 7 due to the light it absorbs and cuts, but there is a space S between it and the temperature sensing part, so it is thermally insulated, although not completely, and the temperature rise in the filter 7 will impede infrared sensing. This is effectively prevented.

When viewed from a plane, the shape of the thinner part A is as shown in Figure 1 (bl
As shown in , it has a rectangular shape, and is continuous with other insulating layer parts on the 9 m side, but is not continuous on the long side as it is interrupted by a gap 8. A space S looks through this gap 8. In other words, the thin portion A serves as a double-supported beam bridging over the space S, while the space S passes through the surface side of the substrate 1 and is in a non-sealed state. In addition, the thinner part A
Instead of being a double-sided beam, it may be a cantilever beam in which one of the short sides is also interrupted by a gap.

In order to create such a thin partial hole in the form of a double-sided beam or cantilever beam, it is necessary to form a space S. It is best to use a substrate material that has the property that etching progresses well in the direction of the surface, but that etching does not progress easily in the direction horizontal to the surface. Specifically, a crystalline material such as a silicon single crystal plate is exemplified.

The anisotropic etching characteristics of this silicon single crystal plate will be briefly explained.

In silicon single crystal plates, (100) plane and (11O)
Does etching proceed easily in the direction perpendicular to the surface (11
1) Etching is difficult to proceed in the direction perpendicular to the surface. Therefore, it is possible to form a recess that matches the shape of the hollow mask window.

Specifically, as shown in Figure 6+8) and (1)), (
100) A mask 21 with a window 22 is provided on the surface of a silicon single crystal plate 20 having a plane 20 as the surface, and anisotropic i-etching is performed. The mask 21 is made of an insulating film such as a silicon nitride film or a silicon oxide film. In this case, if the side 22a of the window 22 is oriented parallel to the intersection line of the (111) plane and the (100) plane, the area below the mask 21 will not be etched, as shown in FIG. A recess 23 having the same shape as the window 22 is formed.

Also, as shown in Figure 8 fa) and (b), (110)
Anisotropic etching may be performed by providing a mask 26 with a window 27 on the surface of the silicon single crystal plate 25 having a flat surface. The mask 26 also consists of a rim of a silicon nitride film or a silicon oxide film. In this case, side 2 of window 27
If 7a is oriented parallel to the intersection line of the (111) plane and the 0 (110) plane, then Fig. 9 (81
(As shown in C1, the area below the mask 26 is not etched, and a recess 28 that matches the shape of the window 27 is formed.

In this case, if the (111) plane is perpendicular to the (110) plane, it will be dug perpendicularly from the surface as shown in Figure 9 Tbl, and the (111) plane will become the (110) plane. If it is a (111) plane with an incident angle of 35.3° to and (100
) If the direction is not parallel to the intersection line of the (111) planes, side etching proceeds under the mask and a recess surrounded by the final (111) planes is formed. Therefore, by utilizing this, a double-sided beam or cantilever pattern (pattern portion P indicated by the dotted chain line in FIG. ), and make the direction of the window at an angle to the direction parallel to the intersection line (
By making the direction of the window side not parallel to the above-mentioned intersection line, the space S can be formed by digging the back surface of the double-sided beam or cantilever beam pattern from the front side of the substrate.

In this case, the insulating inseam around the thin part of the wall will also be shaved off a little, creating a space slightly larger than the window. The double-sided beam or cantilever pattern portion of the mask becomes a thin portion made of an insulating layer as it is.

Of course, the direction of the window side of a mask having a double-sided beam pattern or a cantilever beam pattern may be parallel to the intersection line. for example,
When using a silicon single crystal plate with the (100) plane as the surface, it is possible to create a structure in which a cantilever-like thin part a extends into the space S, as shown in Figures 4(a) and (bl). Anisotropic etching is performed by providing a cantilever pattern portion a on a mask 21' (made of silicon oxide or silicon nitride film) on the surface of the silicon single crystal layer 20'. The cantilever pattern portion a of 21' can be used as the thin portion A as it is.

In addition, when a silicon single crystal plate with the (110) plane as the surface is used, a structure in which a thin beam-shaped part a' is extended across the space S as shown in Figure 5+81 (bl) is obtained. I will explain the latter case a little more.

As shown in Fig. 5(a), when the double-supported beam pattern part a' protrudes from the side parallel to the intersection line of the (111) plane and the (110) plane and reaches the opposite side, the back side of the double-supported beam pattern part a' is dug from the substrate surface to form a space S. Anisotropic etching is performed by providing a double-supported beam-like pattern portion a on a mask 26' (made of a silicon oxide film or a silicon nitride film) on the surface of the silicon single crystal layer 25'. The double-supported beam pattern portion a' can be used as the thin portion A as it is. In this case, depending on whether the (1.11) plane corresponding to the protruding side is a (111) plane perpendicular to the <110> plane or a (111) plane with an incident angle of 35.3°, the The included side wall shapes are different. In the former case, it is dug vertically as shown by the solid line in Figures 5(a) and (b), and in the latter case, it is dug diagonally at an angle of 35.3° to the surface, as shown by the -dotted chain line. It is dug into. In addition, due to the crystal plane, in the case of the former 3, the width W/length J<0.354, and in the latter case, the width W
/Length A<0.71.

As the esotynda solution, a mixture of ethylenediamine, pyrocatechol and water, a mixture of potassium hydroxide and water, etc. are usually used. Since these solutions hardly etch silicon oxide films or silicon nitride films, there is an advantage that a mask of a silicon oxide film or a silicon nitride film can be used, and that the mask can be used as an insulating film after anisotropic etching. Furthermore, these solutions have a low etching rate for a silicon single crystal portion doped with a high concentration of boron. Therefore, if strict control of the digging depth is required, the boron high concentration 1i (
10"/cJ or more). If it is not necessary to be so precise, depth control by adjusting the cutting time and the cutting time will suffice.

The sensor of the present invention is not limited to the configuration illustrated above. For example, in addition to sensing infrared rays, another temperature-sensitive thin film body for sensing ambient temperature may be provided at a position where no temperature rise occurs due to infrared irradiation, and on the outside of a thinner part.

A semiconductor element (for example, a transistor) for a signal processing circuit, a control circuit, etc. may be formed on the substrate of the infrared sensor.

It goes without saying that the materials of the filter, substrate, etc. of the infrared sensor of the present invention are not limited to those exemplified above.

[For production]

The temperature sensor according to the present invention has very good responsiveness.

Since this uses a temperature-sensitive thin film, it can be miniaturized, and as shown in FIG. This is because the overall thickness of the temperature-sensing part is extremely thin, and the heat capacity of the temperature-sensing part is extremely small.The temperature-sensing part quickly reaches a sufficiently high temperature due to the heat energy from the infrared absorption layer. It becomes like this.

If the space S passes through the surface and is in a non-sealed state,
Since the increase or decrease in the volume of the air in the space caused by temperature changes is immediately replenished and exhausted, the temperature-sensitive thin film forming part is not deformed and the measurement accuracy is high. When the space S is in a sealed state, the air volume in the sealed space increases or decreases depending on the ambient temperature, and the temperature-sensitive thin film forming part is pushed up or down, deforming and distorting the temperature-sensitive thin film body. Sufficient measurement accuracy may not be obtained.

If the temperature-sensitive thin film forming part is a double-sided beam or cantilever beam, the heat from the temperature-sensing part does not immediately transfer to the thick part of the substrate, and the thermal energy of the incident infrared rays increases the temperature of the temperature-sensing part. will increase more effectively.

In addition, when digging to create a space from the surface side of the substrate, the mask for forming the groove is formed on the same side as the mask for the temperature-sensitive thin film, so mutual alignment of the masks is accurate and easy. This makes manufacturing easier.

If the excavation to create the space is performed from the back side of the substrate, the mask for forming the excavation is made on the opposite side from the mask for the temperature-sensitive thin film, so the position of the excavation and the position of the temperature-sensitive thin film do not match. <It is not easy to manufacture, as special manufacturing equipment such as a double-sided mask aligner is required.

〔Example〕

Next, one embodiment of the temperature-sensitive sensor of the present invention will be described, including the manufacturing process.

FIGS. 2(a) and (bl) show the main structure of an embodiment of the temperature sensor of the present invention, and FIGS. 3(a) to (jl are
I will show you step by step how this temperature sensor is manufactured.

As shown in Figure 3+a), the surface is (1
10) After forming a silicon nitride film 11.11' with a thickness of 1000 nm on both sides of the N-type silicon single crystal wafer 10 using the LPCVD method, as shown in FIG. PCV only on the silicon nitride film 11 on the formation side
A silicon nitride film 12 having a thickness of 6,000 wafers is laminated using the D method. Next, as shown in FIG. 3(C), the surface of the silicon nitride film 12 is coated with a thickness of 20 mm using a sputtering method.
000 platinum films 13 are laminated.

7 Next, as shown in FIG. 3Fdl, a resist mask 14 with a predetermined pattern is applied on the platinum film 13 using photolithography technology, and then, as shown in FIG. Using a milling method, unnecessary parts of the platinum film 13 are selectively removed and patterned. ! A JL thin film body (platinum thin film resistor) 2 is formed.

After forming the temperature-sensitive thin film body 2, as shown in FIG. 3 (fl), the resist mask 14 is removed and an insulating film 15 made of a silicon nitride film with a thickness of 5,000 wafers is laminated using the PCVD method. As shown in FIG. 3 (Ir), the resist mask 16 is laminated again, and the silicon nitride films 11, 12, and 15 are opened using the plasma etching method, and then the resist mask is removed. Remove 16.

The window opened in the silicon nitride film is silicon single crystal wafer 1
0 from the surface side to create a space on the back side of the temperature-sensitive thin film body 2 forming part. The 8 patterns of the resist mask 16 are aligned so that the sides of the windows are parallel or perpendicular to the intersection line of the (111) plane and the (100) plane.
) plane is selected as the (111) plane that intersects perpendicularly with the (110) plane.

Next, KOH40wt%, H2O60wt%, temperature 8
Anisotropic etching treatment is performed using Esotynda solution at 0°C. The etching time was 1 hour and 40 minutes, as shown in Figure 3 (h
), a space S with a depth of 200 IIm and a thin part A of the supporting beam are formed.

After forming the space S, as shown in FIG. 3 (11), the silicon nitride film 11' on the back surface is removed using a plasma etching method, and then the silicon nitride film 15 is removed as shown in FIG. If an infrared absorbing layer 18 is formed by laminating a full black layer thereon by a vacuum deposition method, the infrared sensor shown in FIGS. 2(a) and 2(b) is completed.

In the completed temperature sensor, the substrate 1' is a stack of a wafer 10 and a silicon nitride film (insulating layer) 11, 12,
Further, it goes without saying that the space S communicates with the surface of the substrate through the gap 8 which was a window during the formation of the trench.

Further, the infrared filter 7' is composed only of a silicon single crystal layer 10d having a thickness of approximately 100 μm. In addition, 2a
is the pull-out terminal section.

As seen above, this infrared sensor is easily manufactured by applying the technology used in the semiconductor manufacturing process. ), the element can be easily formed using semiconductor process manufacturing technology in the same way. In this case, the semiconductor element portion is usually formed before the infrared sensor portion.

〔Effect of the invention〕

As described above, the infrared sensors according to claims 1 to 7 have excellent responsiveness and sensitivity because the heat capacity of the temperature sensing portion is very small.

In addition, the infrared sensor according to the second aspect of the present invention has excellent measurement accuracy because the space behind the temperature-sensitive thin film forming portion is in a non-sealed state.

In addition, the infrared sensor according to the fourth aspect of the present invention is easy to construct because the digging for creating the space is done from the surface side of the substrate.

In addition, in the infrared sensor according to the fifth aspect, the infrared transmission filter can be easily installed, and the infrared sensor can be manufactured more easily.

[Brief explanation of drawings]

FIG. 1 (al, Tbl is a diagram showing the main part of an embodiment of the infrared sensor of the present invention, and FIG. 1 (al) is a schematic cross-sectional view, and FIG. 1 (b) is a partial plan view. Figure (al, (
BL is a diagram showing the main parts of another example of the infrared sensor of the present invention, where FIG. FIG.
l, (bl and FIG. 5 (al, (b) are respectively,
FIG. 4 is a diagram illustrating the state when providing a thin portion in the form of a cantilever beam or both beams on the substrate, and FIG. 4 (al and FIG. 5(a) are plan views, and FIG. 4 fb) and FIG. 5(b) are cross-sectional views. Figure 6 (al, (bl), Figure 7 (a), Tbl
4, is a diagram for explaining the anisotropic etching characteristics of a silicon single crystal plate, and FIGS. 6(a) and 7+81
are plan views 1, 6 (bl) and 7 (bl is a cross-sectional view. FIG. 8+a) and FIG. 9 are plan views, and FIG.
b) and FIG. 9fbl, (C) are cross-sectional views. 1.1'...Substrate 1b...Semiconductor layer...Infrared absorption layer S...Space 1a, 1'a...Haruiro edge! -2...Temperature-sensitive thin body 5.18 7.7'...Infrared transmission film

Claims (1)

[Scope of Claims] 1. A temperature-sensitive thin film is formed on the surface of the substrate, and a space is formed on the back side of the temperature-sensitive thin film forming portion of the substrate, and an infrared absorbing layer is also formed in the temperature-sensitive thin film forming portion. and an infrared transmission filter is provided on the path of infrared rays incident on the infrared absorbing layer. 2. The infrared sensor according to claim 1, wherein the space communicates with the surface of the substrate. 3. The infrared sensor according to claim 1 or 2, wherein the substrate has a structure in which an insulating layer is laminated on a semiconductor layer, and the temperature-sensitive thin film forming portion consists only of the insulating layer. 4. The infrared sensor according to any one of claims 1 to 3, wherein the space is formed by digging from the surface side of the substrate. 5. The infrared sensor according to any one of claims 1 to 4, wherein at least a part of the infrared transmission filter is constituted by a substrate. 6 The thickness of the insulating layer in the temperature-sensitive thin film body forming portion is approximately 0.
The infrared sensor according to any one of claims 3 to 5, which has a diameter of 5 to 1.5 μm. 7. The infrared sensor according to any one of claims 1 to 6, wherein the temperature-sensitive thin film body is one of a thin film resistor, a thin film thermocouple, and a thin film thermopile.