JPH08101070A - Infrared detection element - Google Patents

Abstract

PURPOSE: To increase the degree of freedom in the setting of detection area for an infrared detection element. CONSTITUTION: A thin film body 6 is formed on a substrate 1 provided with an opening having substantially square plan view. Four infrared detecting parts A1, A2, B1, B2 are formed on the thin film 6 above the opening and four compensation resistors C1-C4 are formed on the thin film 6 while infrared absorption layers 20a-20d are formed in a rectangular region 19. Since the distances between four infrared detecting parts can be shortened infinitely, specifications for wider detection area can be dealt with while keeping high sensitivity detecting conditions without causing any significant variation of sensitivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detecting element, and more particularly to a thermal type infrared detecting element for detecting infrared rays by detecting a temperature change due to absorption of infrared rays.

[0002]

2. Description of the Related Art There are two types of infrared detecting elements, a quantum type and a thermal type. Quantum type infrared detectors have very high sensitivity, but they need to be cooled to a low temperature before use.
It is also expensive.

On the other hand, the thermal type infrared detecting element is generally used widely because it does not require cooling and its cost is low, though it is less sensitive than the quantum type. In this thermal infrared detection element, infrared rays are detected by detecting a rise in temperature of the infrared detection section associated with the incidence of infrared rays.

There are mainly three types of this type, one using a pyroelectric element, one using a thermocouple or a thermopile, and one using a resistor.

The one using a pyroelectric element is intended to detect the temperature change on the surface of the pyroelectric element due to the incidence of infrared rays by the pyroelectric effect. The pyroelectric effect is accompanied by a change in the polarization state when the temperature changes. Detect the electric current.

The one using a thermocouple or a thermopile is for detecting a thermoelectromotive force generated in a PN junction between different kinds of metals or a semiconductor. In particular, a thermopile is connected with several thermocouples in series to increase the output. It is intended.

The one using a resistor is intended to detect a temperature change by a resistance value change of the resistor.

Among these thermal infrared detecting elements, those using a resistor are different from those using a pyroelectric element.
Since the infrared rays can be detected even if the incident infrared rays are constant, and the infrared rays are more advantageous than the thermopile, their use is increasing recently. When actually using an infrared detecting element using such a resistor, depending on the purpose of use, a plurality of infrared detecting units may be provided, or a compensating resistor for temperature compensation may be provided. It is used with various circuit-wise ideas.

One of such devices is a non-directional infrared detecting element devised so that there is no difference in sensitivity regardless of the moving direction of the detected object. One example thereof will be described with reference to FIGS. 8 is a sectional view of the infrared detecting element, FIG. 9 is a plan view, FIG. 10 is a dimensional drawing of the planar shape of the infrared detecting element, and FIG. 11 is a circuit diagram.

As shown in the figure, a resistor 2 whose resistance value changes by absorbing infrared rays is formed on the surface of a substrate 1, and a pair of electrodes for detecting the resistance value of the resistor 2 and a lower electrode. 3 and the upper electrode 4 are formed so as to be sandwiched above and below the resistor 2. An infrared absorption layer 5 that absorbs incident infrared rays is formed on the resistor 2, the lower electrode 3, and the upper electrode 4. The infrared detectors A1 and B1 are configured by the configuration described above.

The infrared detecting portions A1 and B1 are formed on the thin film body 6 formed on the substrate 1.
Since the substrate portion below B1 is removed, the infrared detecting portions A1 and B1 are formed on the so-called thin film bridge structure 7. In other words, the infrared detectors A1 and B1
Is on the thin film body 6 stretched so as to cover the opening 1a formed on the substrate 1 and the peripheral portion thereof is supported by the substrate 1,
It is formed in a region above the opening 1a. With such a configuration, it is possible to increase the temperature change of the infrared detection unit 6 even when an infrared ray with a small energy is incident, and to reduce the time constant to improve the detection speed.

FIG. 8 shows the sectional structure at the position where the infrared detecting portions A1 and B1 are formed. The plane structure of the entire infrared detecting element will be described with reference to FIG. As shown in the figure, the thin film body 6 is provided at four corners on the substrate 1 having a substantially square shape in plan view.
Through, the compensating resistors C1 to C4 having a substantially L-shape in plan view are formed such that the L-shaped corner portions of the compensating resistors C1 to C4 are close to the corners of the substrate 1. At the same time, at the four corners of the substantially square area in plan view surrounded by these four compensating resistors C1 to C4, the infrared detecting portions A1, A2, B1, B2 having a substantially square shape in plan view are formed.
Are formed. Openings 1a are formed below the infrared detecting portions A1, A2, B1 and B2, respectively. The infrared detecting section A1 and the infrared detecting section A2 are formed at one diagonal position of a substantially square area in a plan view, and the infrared detecting section B1 and the infrared detecting section B2 are paired with each other in a substantially square area in a plan view. It is formed in a corner position.

The compensating resistors C1 to C4 are composed of infrared detectors A1, A2,
Infrared detectors A1, A2, B have the same sectional structure as B1, B2.
It has the same resistance value and temperature coefficient of resistance as the resistor of 1, B2. However, in the plan view, the circuit pattern formed on the thin film body 6, the lower electrode and the upper electrode, the compensation resistor C1
The electrodes and the like connected to C4 are omitted as appropriate.

Next, the dimensions of the infrared detecting element will be described with reference to FIG. As shown in the drawing, the substrate 1 is formed in a 4.4 mm square, and the opening 1a is formed in a 1.3 mm square at a position 0.6 mm apart from the outer peripheral edge of the substrate 1 in the horizontal and vertical directions. The distance between the adjacent openings 1a is 0.6 mm. The infrared detectors A1, A2, B1 and B2 are each 0.8 mm square at a position 0.8 mm apart from the outer peripheral edge of the substrate 1 in the horizontal and vertical directions. The distance between adjacent infrared detectors is 1.2 mm.

Next, an example of the circuit of the infrared detecting element is shown in FIG.
It will be described based on 1. Infrared detector as shown
A1 and the infrared detecting section A2 are connected in series to form one arm (first arm 9) of the Wheatstone bridge 8, and the infrared detecting section A3 and the infrared detecting section A4 are connected in series to form the first arm. A second arm 10 that faces 9 is configured. Further, the compensating resistor C1 and the compensating resistor C2 are connected in series to form one arm (third arm 11) of the Wheatstone bridge 8, and the compensating resistor C3 and the compensating resistor C4 are connected in series. The 4th which is done and is facing the 3rd arm
The arm 12 is configured. The connection point between the first arm 9 and the fourth arm 12 is the power supply terminal on the high potential side of the Wheatstone bridge 8, and the third arm 11 and the second arm 1
The connection point of 0 is the power supply terminal on the low potential side. Also,
The connection points between the first arm 9 and the third arm 11 and the connection points between the second arm 10 and the fourth arm 12 are the output terminals 13 and 14 of the Wheatstone bridge 8. Here, the potentials of the output terminals 13 and 14 are set to V2 and V1, respectively.

With the above structure, the non-directionality of the sensitivity of the infrared detecting element is achieved. The principle will be described below. When this infrared detection element is actually used for detecting a human body or an object, an optical system composed of a lens or a mirror is installed on the front surface of the infrared detection element, and an image of the real space is placed on the upper surface of the infrared detection element. Do by tying. On the contrary,
It means that the planar shape (sensing surface shape) of the infrared detecting portion formed on the upper surface of the infrared detecting element is projected in the real space. Now, a case where the infrared detection element is installed on the ceiling with the detection surface (the upper surface of the infrared detection section) facing downward and the human body is detected will be described based on the overhead view of FIG.

As shown in FIG. 12, the lens 15 detects the detection surface of the infrared detecting element 16 (infrared detecting portions A1, A2, B1, B).
The upper surface of 2) is projected in real space. In other words, the detection surfaces of the infrared detection units A1, A2, B1, and B2 are the area a
It is projected on 1, a2, b1, and b2. First, the human body is in the regions a1 and b1.
Consider the case of moving parallel to. At that time, the human body first crosses the regions a1 and b2. Therefore, the infrared rays emitted from the human body are incident on the infrared detecting sections A1 and B2. As a result, the resistance value of the resistors of the infrared detection units A1 and B2 becomes small, and as a result, the potential V1 drops and the potential V2 rises. The output of the Wheatstone bridge (the output of the infrared detection element) is the potential difference ΔV (ΔV = |
V1-V2 |).

Next, when the human body moves and crosses the regions a2 and b1, similarly, the potential V1 decreases and the potential V2 increases similarly. The output of the infrared detection element is the potential difference ΔV (ΔV = | V1-V2 |) between the potential V1 and the potential V2.

Next, consider the case where the human body moves vertically to the areas a1 and b1. At that time, first, the human body crosses the regions a1 and b1. Therefore, the infrared rays from the human body are detected by the infrared ray detectors A1, B1.
Will be incident on. As a result, the resistance values of the resistors A1 and B1 of the infrared detecting section are reduced, and as a result, the potential V1 decreases and the potential V2 increases. The output of the infrared detection element in this case has the same magnitude as the output of the infrared detection element when the human body moves in parallel to the regions a1 and b1.

Next, when the human body moves and crosses the areas a2 and b2, the same output is obtained in the same way.

Now, consider the case where the human body moves diagonally from the area b1 to the area b2. At that time, the human body first crosses the region b1. Therefore, infrared rays from the human body enter the infrared detecting section B1. As a result, the resistance value of the resistor of the infrared detection unit B1 becomes smaller, and as a result, the potential
V1 will go down. The element output at this time is half the size when the human body moves in parallel to the regions a1 and b1.

Next, when the human body moves and crosses the areas a1 and a2, the infrared rays from the human body enter the infrared detecting sections A1 and A2. As a result, the resistance value of the resistors of the infrared detection parts A1 and A2 becomes small, and as a result, the potential V2 rises. The element output at this time is approximately the same as when moving in parallel to the regions a1 and b1 when an infrared ray with a small energy is incident such as infrared rays from the human body, that is, when the change in the resistance value is very small. It will be

Next, when the human body moves and crosses the area b2,
In the same way, the potential V1 drops, and an element output that is half the size when moving in parallel to the regions a1 and b1 is obtained.

This means that an oblique movement (for example, area a1
Movement from the area a2)), three outputs are obtained with the movement of the human body, of which the first output and the first output are half of the output in the case of parallel or vertical movement, Two
It means that the output of is about the same as the output of parallel or vertical movement. Therefore, in the case of diagonal movement, if the second output is used as the detection signal, the same output as in the case of movement in the parallel or vertical direction is obtained. As a result, detection signals having substantially the same magnitude can be obtained by moving in either direction. That is, the infrared detection element described above has no directivity in sensitivity.

[0025]

However, upon actual evaluation, it was found that such a conventional non-directional infrared detecting element has the following problems.

When detecting a detection target in the detection area, it is desirable that the sensitivity be constant regardless of the distance from the infrared detecting element to the detection target, but in reality, as the distance to the detection target increases, the sensitivity increases. Sensitivity tends to decrease. However, if there is a sensitivity equal to or higher than a certain threshold in the detection area, no particular problem will occur. However, in the conventional infrared detecting element, the sensitivity is suddenly lowered when the distance is longer than a certain distance, and the predetermined sensitivity cannot be obtained when the distance is further longer. That is, it has been found that there is a problem that the sensitivity greatly varies depending on the distance to the detection target.

The cause can be explained as follows. The detection target in the real space is projected as an image of a certain size on the detection surface of the infrared detection element, and the size of the image is related to the distance to the detection target if the optical systems are the same. , The smaller the distance, the larger the size.

Therefore, when the object to be detected is at a short distance, the image of the object to be detected is largely projected on the detection surface, and in some cases, it may happen that the four infrared detecting sections are entirely covered. In such a case, infrared rays may be incident on all infrared ray detecting portions and all resistance values may decrease. That is, in such a case, the infrared detector A1,
A state occurs in which the resistance values of all the resistors A2, B1, and B2 become small, and the signal output at this time is as shown in FIG. 12 when the human body moves in parallel to the regions a1 and b1 (when the human body is The output is approximately twice as large as the output when crossing approximately two detection areas).

On the other hand, when the object to be detected is distant, the image of the object to be detected is projected on the detection surface in a small size, and the image only covers one or two infrared detecting portions. In such a case, infrared rays will be incident on only one or two infrared ray detecting portions.

When infrared rays are incident on the two infrared detecting sections, the output is obtained when the human body moves in parallel to the areas a1 and b1 as shown in FIG. 12 (when the human body crosses approximately two detection areas). Becomes When the infrared ray is incident only on one infrared ray detecting section, only half of the output is obtained.

As described above, the problem that the sensitivity greatly differs depending on the detection distance occurs because the size of the image to be detected differs depending on the detection distance, and the number of infrared ray detecting sections on which infrared rays enter differs. It was.

Therefore, the four infrared detecting sections are arranged as close to each other as possible so that the image formed by the detection target in the detection area on the detection surface can cover all the four infrared detecting sections. Irrespective of the distance to the object, the infrared rays from the object to be detected are made incident on all four infrared ray detecting parts, and a study was conducted to prevent the phenomenon that the sensitivity suddenly decreases depending on the distance. However, when actually trying to bring the infrared detectors close to each other, the following problems occur.

As shown in FIG. 8, the infrared detectors A1, A
When the thin film bridge structure 7 in which 2, B1 and B2 are formed is formed, it is generally performed by etching the substrate 1 from the back surface side of the substrate 1. At this time, it is common practice to use a silicon single crystal for the substrate 1 and use an anisotropic etching technique for etching, which utilizes the fact that the etching rate greatly varies depending on the plane orientation of the crystal.

In particular, when the thin film bridge structure 7 is formed, the substrate 1 whose surface is the (100) plane of silicon is used. In this case, the wall surface of the hole (cavity 1b) dug by etching is surrounded by the (111) plane, but the (111) plane is 54.7 ° from the surface of the substrate 1.
Form a fixed angle. Therefore, the thickness of the substrate 1
Assuming d, the edge position of the opening 1c on the back surface side of the cavity 1b is ^20.5 d / 2 outside the opening 1c in the horizontal direction from the edge position of the opening 1a on the front surface side of the cavity portion 1b. You will come to the position moved in the direction. Therefore, the distance between the adjacent openings 1a cannot be smaller than 2 ^0.5 d. That is, conventionally, there has been a problem that even if the infrared detecting portions are made to come close to each other, they cannot be brought closer to each other.

The present invention has been made in view of the above problems, and an object thereof is to provide a structure of an infrared detecting element having a higher degree of freedom in setting a detection area.

[0036]

In order to achieve the above-mentioned object, the infrared detecting element according to claim 1 is a thin film body which covers an opening formed on a substrate so that a peripheral portion thereof is supported by the substrate. The first infrared detecting section, the second infrared detecting section, the third infrared detecting section, and the fourth infrared detecting section, which are provided with at least a resistor whose resistance value changes by absorbing infrared rays. Formed on the thin film body, four compensating resistors having the same resistance value and temperature coefficient of resistance as the resistor body are formed on the thin film body, and a predetermined on the thin film body is formed above the opening. At the four corners of the rectangular area, the first infrared detecting section and the second infrared detecting section are arranged so as to come to one diagonal position of the rectangular area, and the third infrared detecting section and the fourth infrared The detection unit is placed at the other diagonal position of the rectangular area. And a series circuit composed of the first infrared detecting section and the second infrared detecting section is used as the first arm of the Wheatstone bridge, and the third infrared detecting section and the fourth infrared detecting section are configured. And a circuit in which four compensating resistors are connected in series, two each being a third arm and a fourth arm of the Wheatstone bridge, respectively. It is characterized by that.

An infrared detecting element according to a second aspect of the present invention includes a first infrared detecting section and a second infrared detecting section, each of which has a thin film body formed on a substrate and provided with a resistor whose resistance value changes by absorbing infrared rays. Forming a third infrared detecting section and a fourth infrared detecting section on the thin film body, and forming four compensating resistors having the same resistance value and temperature coefficient of resistance as the resistor body on the thin film body;
The first infrared detecting section and the second infrared detecting section are arranged at four corners of a predetermined rectangular area on the substrate so as to come to one diagonal position of the rectangular area, and the third infrared detecting section is arranged. Section and the fourth infrared detecting section are arranged so as to come to the other diagonal position of the rectangular area, and a series circuit composed of the first infrared detecting section and the second infrared detecting section is connected to a Wheatstone bridge. The first arm is used as the second arm facing the first arm, and the series circuit including the third infrared detection unit and the fourth infrared detection unit is used as the second arm. With the circuits connected in series as the third arm and the fourth arm of the Wheatstone bridge and connected on the rectangular area to be detected, the entire image is projected inside the rectangular area. First red The first infrared detecting unit, the second infrared detecting unit, and the line infrared detecting unit so that the line detecting unit, the second infrared detecting unit, the third infrared detecting unit, and the fourth infrared detecting unit are projected over the regions. The third infrared detector and the fourth infrared detector are arranged close to each other.

An infrared detecting element according to claim 3 is the infrared detecting element according to claim 1 or 2, wherein at least the first infrared detecting section, the second infrared detecting section and the third infrared detecting section are provided. An infrared absorption layer is formed so as to cover the rectangular area in which the fourth infrared detection section is formed.

[0039]

In the infrared detecting element according to the first aspect, since all four infrared detecting portions are formed on the same thin film bridge structure, it is generally used when forming a thin film bridge structure. Also by anisotropic etching using the silicon (100) plane, it is possible to arrange the infrared detecting portions in close proximity to each other as long as the pattern accuracy permits.

In other words, the infrared detecting sections can be freely arranged in close proximity to each other at a position determined by the specifications of the infrared detecting element set by the size of the detection area and the size of the detection target and the specifications of the optical system. become.

With such a configuration, the change in the resistance value of the resistors of the infrared detecting portions caused by the movement of the detection object is such that the resistance values of the resistors of the four infrared detecting portions are all reduced. You can operate in the mode.
That is, it is possible to operate with higher sensitivity than before,
Within the specifications of the element, the sensitivity does not suddenly decrease due to the detection distance.

Further, since four infrared ray detecting parts are mounted on the same thin film bridge structure, the influence of heat between the infrared ray detecting parts is different from that of the conventional one, and the infrared ray detecting parts are provided on separate thin film bridge structures. It is much larger than when it is formed. That is, if a temperature rise occurs in one infrared detector,
This means that the other three infrared detectors are also affected by the temperature rise. That is, when infrared rays emitted from a moving object enter the infrared detection element, the temperature of all four infrared detection sections rises, and the resistance value of the resistors provided therein decreases. In the case of, it is very likely to occur. This has the effect of enabling operation at a higher sensitivity than in the past and making it less likely that the sensitivity will change significantly depending on the detection distance.

Further, in the infrared detecting element according to the second aspect of the invention, the whole image of the detection object in the detection area, which is connected to the detection surface, is within a rectangular area surrounding the four infrared detecting portions. Are arranged in close proximity to each other so as to project over the area of the four infrared detection units. With this configuration, the infrared light emitted from the detection target is incident on all four infrared detection units regardless of the distance to the detection target, so that the sensitivity sharply decreases depending on the distance to the detection target. Nothing will happen. Also, in this case,
The sensitivity can be increased to about twice that of the conventional infrared detection element.

Further, the infrared detecting element according to claim 3 is characterized in that an infrared absorbing layer is formed so as to cover at least four rectangular regions surrounding the entire infrared detecting portions. That is, the infrared absorbing layer is formed not only on the four infrared detecting portions but also on the thin film body between the infrared detecting portions. Further, the infrared absorption layer may be formed on the thin film body near the periphery of the rectangular region. With this configuration, the incident infrared rays can be absorbed by the entire rectangular area. That is, the infrared detecting element according to the third aspect can form a state in which there is substantially no gap between the adjacent infrared detecting portions. This is the same as setting the distance between adjacent infrared detectors to zero,
Therefore, as described above, it is possible to operate with higher sensitivity than before, and the sensitivity does not change significantly depending on the detection distance.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the infrared detecting element of the present invention will be described with reference to FIGS. 1 is a plan view, FIG.
Is a cross-sectional view, and FIG. 3 is a cross-sectional view showing a state in which an infrared detection element is mounted on a package. However, the same components as those shown in FIG. 8 or 9 are designated by the same reference numerals. In the figure, on the surface of a substrate 1 having a (100) plane of a silicon single crystal and having a thickness of 300 μm and a substantially square shape in plan view,
A thin film body 6 is formed which is a composite film of a total thickness of 0.5 μm, which is composed of a thin film of silicon nitride of 0.05 μm, a thin film of silicon oxide of 0.4 μm and a thin film of silicon nitride of 0.05 μm. A portion of the substrate 1 composed of silicon is removed from the back side of the substrate 1 to give a thin film body 6
A cavity 17 is formed that reaches Therefore, the thin film body 6 in the portion of the cavity 17 that covers the opening 17a on the substrate surface side is formed to have a so-called thin film bridge structure 18 in which only the peripheral portion is supported by the substrate 1.

Infrared detectors A1, A2, B1 and B2 each having a substantially square shape in a plan view are provided on the thin film bridge structure 18 in a predetermined rectangular area 19 (a virtual square shape in a plan view surrounding four infrared detectors). Regions) are formed at four corners. The infrared detecting section A1 (first infrared detecting section) and the infrared detecting section A2 (second infrared detecting section) are formed at one diagonal position of the rectangular area 19, and the infrared detecting section B1 (third infrared detecting section). ) And the infrared detector B2 (fourth infrared detector) are formed at the other diagonal position of the rectangular area 19.

The infrared detectors A1, A2, B1 and B2 are made of amorphous silicon and have a thickness of 1.0 μm and a resistor 2.
The lower electrode 3 and the upper electrode 4, and the resistor 2 or the upper electrode 4 for detecting the resistance value of the resistor 2 and extracting it to an external circuit, which is formed by sandwiching the resistor 2 with chromium having a thickness of 0.2 μm. Infrared absorption layers 20a-2 formed above the
0d and. However, in this embodiment, the infrared absorption layer 20e is also formed on the thin film body 7 between the infrared detection parts. In the plan view of FIG. 1, the infrared absorption layer 20e is not shown.

The lower electrode 3 and the upper electrode 4 are respectively
The thin film bridge structure 18 is drawn out toward the outer periphery of the substrate 1, and a part of them is connected to an electrode terminal 21 for connecting to an external circuit. Also, infrared detector
It has the same cross-sectional structure as A1, A2, B1, B2, and infrared detector A
Compensation resistors C1 to C4, which are substantially L-shaped in plan view and have the same resistance value and temperature coefficient of resistance as those of the resistors 2 of 1, A2, B1 and B2, are provided at the four corners of the substrate 1 with the compensation resistors C1 to C4 The L-shaped corners are arranged so as to be close to the corners of the substrate 1. In the present embodiment, the compensation resistors C1 to C4 are formed on the thin film body 6 on the substrate 1, not on the thin film bridge structure 18. Further, electrodes are respectively connected to the compensation resistors C1 to C4, but the illustration is omitted.

Next, the dimensions of each part of the infrared detection element will be described with reference to FIG. As shown in the figure, the substrate 1 is
It is formed in a 4.4 mm square, and the opening 17a is at the center of the substrate 1.
It is formed in 2mm square. Also, the infrared detectors A1, A2, B1,
B2 is arranged so as to be close to the center of the opening 17a with a distance of 0.2 mm.

Next, an embodiment of the circuit of the infrared detecting element will be described with reference to FIG. As shown in the figure, the infrared detection unit A1 and the infrared detection unit A2 are connected in series to form one arm (first arm 9) of the Wheatstone bridge, and the infrared detection unit A3 and the infrared detection unit A4 are A second arm 10 that is connected in series and faces the first arm 9 is configured. Further, the compensating resistor C1 and the compensating resistor C2 are connected in series to form one arm (third arm 11) of the Wheatstone bridge, and the compensating resistor C3 and the compensating resistor C4 are connected in series. 4th facing the 3rd arm
The arm 12 is configured. The connection point between the first arm 9 and the fourth arm 12 is the power supply terminal on the high potential side of the Wheatstone bridge, and the third arm 11 and the second arm 10 are connected.
Is a power supply terminal on the low potential side. Further, the connection point between the first arm 9 and the third arm 11 and the connection point between the second arm 10 and the fourth arm 12 are the output terminals 13 and 14 of the Wheatstone bridge. With such a configuration, the non-directionality of the sensitivity of the infrared detection element is achieved.

Next, an embodiment in which an infrared detecting element is mounted on a package will be described with reference to FIG. In the figure,
Reference numeral 22 is an infrared detecting element, 23 is a flat plate-shaped stem for mounting the infrared detecting element 22, 24 is a through hole formed in the stem 23, and the stem 2 is inserted through an adhesive 25.
3, an external terminal fixed to 3, a bonding wire 26 for connecting the electrode terminal of the infrared detection element 22 and the external terminal,
Reference numeral 27 denotes a hollow cap that covers the mounting surface of the infrared detecting element 22 of the stem 23, and 28 denotes an infrared filter fixed to the cap 27 so as to close the infrared incident window 27a for allowing infrared rays formed on the cap 27 to enter. .

FIG. 4 shows the detection area of the infrared detecting element shown in FIG. In this embodiment, by using a mirror,
The image is projected on the detection surface so that the detection area is not obliquely below the element but in an oblique direction with a certain angle. As a result, the substantially quadrangular pyramid-shaped detection area 30 of the infrared detection element 29 has a side of a substantially square shape in plan view at a position 5 m away from the infrared detection element 29 arranged at the apex of the substantially quadrangular pyramid-shaped detection area 30. The length was 0.58 m, and the length of one side of the substantially square shape in plan at a position 9 m away from the infrared detection element 29 was 1.05 m. When the element of this embodiment is used, the human body can be reliably detected even at a position 10 m away from the infrared detecting element 29.

As described above, according to the embodiment of the present invention, it is possible to comply with the element specifications of a wider detection area without causing a large change in sensitivity as compared with the conventional one. In addition, since the distance between the infrared detectors can be freely shortened, there is an advantage that the degree of freedom in designing the optical system is increased.

If the rectangular area 19 surrounding the entire four infrared detecting portions, that is, the portion where the infrared absorbing layers 20a to 20e are present is taken as the light receiving area, the infrared detecting element of the present invention has the light receiving area occupied in the thin film bridge structure. The ratio of That is, this indicates that the infrared detection element of the present invention has a larger aperture ratio, and therefore has the advantage of higher sensitivity.

On the other hand, the detection area of the conventional infrared detecting element shown in FIG. 9 is the area shown in FIG. FIG.
As shown in 3, the detection area of the infrared detection element 31 is
It is a collection of four detection areas (areas a1, a2, b1, b2 shown in FIG. 12) by the four infrared detection units. In this case, the detection areas represented by the areas a1, a2, b1, and b2 each have a substantially quadrangular pyramid shape, but a detection target area exists between these detection areas. The distance between the adjacent detection areas 32 and 33 at a position 5 m away from the infrared detection element 31 is 0.21 m, and the distance between the detection areas 32 and 33 at a position 9 m away from the infrared detection element 31 is 0.36. It became m. Also, the area shown in FIG.
Regarding the maximum range of the detection area of a substantially quadrangular pyramid shape including a1, a2, b1, b2, the length of one side of the substantially square shape in plan view at a position 5 m away from the infrared detection element 31 is 0.58 m, The length of one side of the substantially square-shaped plan view at a position 9 m away from the infrared detection element 31 was 1.05 m 2. In this case, when the distance from the infrared detection element 31 exceeds 7 m, the detection sensitivity of the human body suddenly decreases, and a phenomenon occurs that a predetermined sensitivity cannot be obtained.

Next, different embodiments of the infrared detecting element of the present invention will be described with reference to FIGS. Figure 5
Is a plan view, FIG. 6 is a dimensional diagram, and FIG. 7 is an explanatory diagram showing a detection area. However, the difference between the configuration of the present embodiment and the conventional configuration shown in FIG. 9 is the size of the infrared detection parts A1, A2, B1, B2 and the position and size of the opening 1a. Are denoted by the same symbols.

The formation positions of the infrared detecting portions A1, A2, B1 and B2 will be described with reference to FIG. As shown in FIG. 6, the distance between the adjacent infrared detecting portions A2 and B2 is set to 0.7 mm, and the distance between the adjacent infrared detecting portions A1 and B2 is set to 0.5 mm. The length of one side of the infrared detection parts A1, A2, B1, and B2, which are substantially square in plan view, is 1.05 mm. Infrared detector A1, A2,
B1 and B2 are respectively formed at positions 0.8 mm apart from the outer peripheral edge of the substrate 1 in the horizontal and vertical directions. As shown in FIG. 6, in the infrared detecting element of the present embodiment, the infrared detecting section A1, A2, B1, B2 is increased in size without changing the distance from the outer peripheral edge of the substrate 1 to the infrared detecting section. A1, A2, B1, B
The distance between the two is reduced.

In this embodiment, the mirror is used so that the image is projected onto the detection surface so that the oblique direction with a certain angle becomes the detection area, not directly under the element. As a result, as shown in FIG. 5, the detection area of the element has a gap of 0.12 m at 5 m and 0.21 m at 9 m. As a result, as shown in FIG. 7, the detection area is 5 m away from the infrared detection element 34, and the distance between the adjacent detection areas 35 and 36 is 0.12 m, which is 9 m away from the infrared detection element 34. Detection area at position 3
The distance between 5 and 36 was 0.21m. In addition, the regions a1 and a
Regarding the maximum range of the detection area in the shape of a quadrangular pyramid that includes 2, b1 and b2, the length of one side of the maximum area in the shape of a square in plan view that is 5 m away from the infrared detection element 34 is 0.58 m. The length of one side of the maximum range of the square shape in plan view at a position 9 m away from the infrared detection element 30 was 1.05 m.

Next, a method for manufacturing the infrared detecting element shown in FIG. 2 will be described. Formed on the surface of the substrate 1 in FIG.
The thin film body 6 made of silicon nitride and silicon oxide is formed by the plasma CVD method, using monosilane and ammonia, monosilane and dinitrogen monoxide as the introduction gas, and the substrate temperature is 400 ° C. and 250 ° C. and the frequency is 13.56 MHz. Was used. First, the thin film body 6 made of silicon nitride and silicon oxide was formed on one surface of the silicon substrate 1. A thin film of silicon nitride (not shown) was similarly formed on the opposite surface.

Next, on the surface of the silicon substrate 1 on which the thin film body 6 is formed, chromium is deposited as the lower electrode 3 of the resistor 2 by vacuum vapor deposition at a substrate temperature of 150 ° C. to a thickness of 0.2 μm. It was Then, using a general photolithography technique, the resist is patterned so that the desired pattern of the lower electrode 3 can be obtained.

Using this resist pattern as a mask,
In an etching solution containing cerium ammonium nitrate,
The lower electrode 3 made of chromium is pattern-etched. next,
Amorphous silicon resistor 2 was deposited by plasma CVD using monosilane and hydrogen gas at a substrate temperature of 270 ° C., a vacuum degree of 0.9 Torr, and a discharge power of 150 W. After that, the resist is patterned by using a general photolithography technique so that a desired pattern of the resistor 2 is obtained. Using this resist pattern as a mask, the amorphous silicon resistor 2 is pattern-etched in an etching solution containing nitric acid, acetic acid, and hydrofluoric acid. The resist is removed after etching to obtain the resistor 2 having a desired pattern.

Next, the upper electrode 4 made of chromium is patterned on the resistor 2 by the same process as the lower electrode. Next, on the upper electrode 4, the infrared absorption layers 20a ...
As 20e, a thin film of silicon oxide is deposited by the plasma CVD method as in the case of the thin film body 6. After that, a desired infrared absorption layer 20a is formed by using a photolithography method.
The resist is patterned so as to obtain a pattern of ~ 20e. Using this resist pattern as a mask, the infrared absorbing layers 20a to 20e of silicon oxide are pattern-etched in an etching solution composed of hydrofluoric acid and ammonium fluoride. After the etching, the resist is removed to form the infrared absorption layers 20a to 20e having a desired pattern.
Get.

Next, aluminum was deposited by vacuum evaporation at a substrate temperature of 150 ° C. and a thickness of 1.5 μm. After that, the electrode terminals 21 having a desired pattern are obtained by using a general photolithography technique.

Next, the infrared detector A of the silicon substrate 1
In order to pattern a silicon nitride thin film (not shown) on the surface opposite to the surface on which 1, A2, B1, and B2 are formed, a resist is patterned on the surface by the photolithography technique as in the previous case. Using this resist as a mask, the silicon nitride thin film on the back surface of the substrate 1 is patterned by the plasma etching method. The plasma etching conditions at this time are as follows: power 200W, gas pressure 400mTo
rr and introduced gas were carbon tetrafluoride. After removing the resist, the silicon substrate 1 is formed on the silicon substrate 1 using a so-called anisotropic etching method in which the etching rate is greatly different due to the difference in the crystal orientation of silicon using the patterned thin film of silicon nitride as a mask. The cavity 17 is formed. As anisotropic etching conditions, potassium hydroxide was used as the etchant, the etchant concentration was 40 wt%, and the liquid temperature was
It was set to 80 ° C. The infrared detection element formed as described above is bonded to the metal stem 23 using an adhesive (not shown) as shown in FIG. After that, the external terminal 24 fixed to the stem 23 and the electrode terminal 21 of the infrared detection element are connected by a gold bonding wire 26, a voltage is applied to the element, and the potentials of the output terminals 13 and 14 are detected from the outside. It can be so. Finally, a metal cap 27, in which an infrared filter 28 that selectively transmits infrared rays having a specific wavelength is fixed to an infrared entrance window 27a, is welded and sealed to the stem 23.

In this embodiment, as the infrared filter 28, a silicon substrate provided with an antireflection film on one surface and a selective transmission film on the other surface is used.
The cap 27 and the cap 27 were adhered to each other using low melting point glass.

The infrared detecting element according to the present invention is not limited to the one shown in the embodiment. The constituent materials, the manufacturing method, the manufacturing conditions, the manufacturing order, the dimensions, the number of constituent elements, etc. are not limited to these, and the optimum one may be selected according to the use and purpose.

[0067]

As described above, according to the infrared detecting element of claim 1, all the four infrared detecting parts are
Since they are formed on the same thin film bridge structure,
It is possible to make the distance between the infrared detecting sections as small as possible. Therefore, there is an effect that it is possible to comply with the specification of a wider detection area without causing a large change in sensitivity while maintaining the detection condition of high sensitivity. Further, since the distance between the infrared detecting portions can be reduced, the degree of freedom in designing the optical system is large, and the element can be close to the optimum design. Furthermore, since the aperture ratio is increased, the device sensitivity can be improved.

According to the infrared detecting element of claim 2,
The distance between the four infrared detecting units is made small so that the image of the detection target in the detection area covers all the infrared detecting units. Therefore, while maintaining the detection conditions of high sensitivity,
There is an effect that the specification of the detection distance can be met without causing a large sensitivity change.

According to the infrared detecting element of the third aspect, since the infrared absorbing layer is formed so as to cover the entire predetermined rectangular area surrounding the four infrared detecting portions, the distance between the infrared detecting portions is further increased. You can expect the same effect as making it smaller. Therefore, there is an effect that it is possible to comply with the specification of a wider detection area without causing a large change in sensitivity while maintaining the detection condition of high sensitivity. Also,
Since the distance between the infrared detectors can be reduced, the degree of freedom in designing the optical system is large, and the element can be close to the optimum design. Further, as a result, an element having a large aperture ratio and high element sensitivity can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of an infrared detection element of the present invention.

FIG. 2 is a cross-sectional view showing an embodiment of an infrared detection element of the present invention.

FIG. 3 is a cross-sectional view showing an embodiment in which the infrared detection element of the present invention is mounted on a package.

FIG. 4 is an explanatory diagram showing an example of a detection area of the infrared detection element of the present invention.

FIG. 5 is a plan view showing another embodiment of the infrared detecting element of the present invention.

FIG. 6 is a dimensional view showing another embodiment of the infrared detecting element of the present invention.

FIG. 7 is an explanatory view showing an embodiment in which the detection area of the infrared detecting element of the present invention is different.

FIG. 8 is a sectional view showing an example of a conventional infrared detecting element.

FIG. 9 is a plan view showing an example of a conventional infrared detecting element.

FIG. 10 is a dimensional diagram showing an example of a conventional infrared detection element.

FIG. 11 is a circuit diagram showing an example of a circuit of an infrared detection element.

FIG. 12 is an overhead view for explaining a detection area of an infrared detection element.

FIG. 13 is an explanatory diagram showing an example of a detection area of a conventional infrared detection element.

[Explanation of symbols]

A1 infrared detector (first infrared detector) A2 infrared detector (second infrared detector) B1 infrared detector (third infrared detector) B2 infrared detector (fourth infrared detector) C1 to C4 compensation resistors DESCRIPTION OF SYMBOLS 1 Substrate 1a, 17 Opening 2 Resistor 5, 20a-20e Infrared absorption layer 6 Thin film body 8 Wheatstone bridge 9 Arm (1st arm) 10 Arm (2nd arm) 11 Arm (3rd arm) 12 Arm (4th arm) ) 19 rectangular area

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 31/09 35/32 A // G01V 8/12

Claims (3)

[Claims] 1. A thin film body is provided so as to cover an opening formed on a substrate so that a peripheral portion thereof is supported by the substrate, and at least a resistor is provided which absorbs infrared rays to change a resistance value. The first infrared detecting unit, the second infrared detecting unit, the third infrared detecting unit, and the fourth infrared detecting unit are formed on the thin film body above the opening, and have the same resistance value and resistance temperature coefficient as the resistor body. Four compensating resistors are formed on the thin film body, and the first infrared detecting section and the second infrared detecting section are provided at four corners of a predetermined rectangular area on the thin film body formed above the opening. Is arranged so as to be located at one diagonal position of the rectangular area, and the third infrared detection section and the fourth infrared detection section are arranged so as to be located at the other diagonal position of the rectangular area, Comprised of a first infrared detecting section and the second infrared detecting section The series circuit is a first arm of a Wheatstone bridge, and the series circuit including the third infrared detection section and the fourth infrared detection section is a second arm facing the first arm, and the four compensation circuits are provided. An infrared detecting element, wherein a circuit in which two resistors are connected in series is used as a third arm and a fourth arm of the Wheatstone bridge, respectively. 2. A first infrared detecting section, a second infrared detecting section, a third infrared detecting section, and a fourth infrared detecting section, each of which has a thin film body formed on a substrate and which has a resistance that changes by absorbing infrared rays. An infrared detector and an infrared detector are formed on the thin film body, and four compensating resistors having the same resistance value and temperature coefficient of resistance as the resistor body are formed on the thin film body. At the four corners, the first infrared detecting section and the second infrared detecting section are arranged so as to come to one diagonal position of the rectangular area, and the third infrared detecting section and the fourth infrared detecting section are arranged. Is arranged so as to be on the other diagonal position of the rectangular area, and the series circuit composed of the first infrared detecting section and the second infrared detecting section is used as a first arm of a Wheatstone bridge, and the third infrared A direct component composed of a detector and the fourth infrared detector. A circuit in which the circuit is a second arm facing the first arm and the four compensation resistors are connected in series, two circuits each being a third arm and a fourth arm of the Wheatstone bridge, are the detection targets. In a state where the entire image formed on the rectangular area is projected inside the rectangular area, the image is the first infrared detecting section, the second infrared detecting section, the third infrared detecting section, and the fourth infrared. The first infrared detecting section, the second infrared detecting section, the third infrared detecting section and the fourth infrared detecting section are arranged close to each other so as to project over the area of the detecting section. Infrared detection element. 3. At least the first infrared detector, the second infrared detector, the third infrared detector, and the fourth infrared detector.
The infrared detection element according to claim 1 or 2, wherein an infrared absorption layer is formed so as to cover the rectangular area in which the infrared detection section is formed.