JP2000230857A - Thermal type infrared sensor and thermal type infrared array element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the numerical aperture of a thermal type infrared sensor and also the production yield of a thermal type infrared array element. SOLUTION: A semiconductor substrate 31 has a hollow 32 on which a diaphragm 33 having 8 beams 38 and a body 39 is formed. On the beams 38 of the diaphragm 33 a p-type poly-Si 34 and an n-type poly-Si 35 are formed and alternately connected through a wiring 36, a layer insulation layer is formed on the diaphragm 33, a passivation film is formed on the layer insulation layer, a thermal absorption metal layer 37 is formed on the passivation film through an amorphous Si, and four infrared detectors 41 are formed on the diaphragm 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal infrared sensor and a thermal infrared array element.

[0002]

2. Description of the Related Art FIG. 10 is a partially cut plan view showing a conventional thermal infrared sensor. As shown in FIG.
A cavity 3 is formed on the cavity 2 of the semiconductor substrate 1. The diaphragm 3 is formed of a silicon nitride film as a thermally insulating material. The diaphragm 3 has a beam 8 and a main body 9. Further, p-type poly Si4 and n-type poly Si5 are formed on the diaphragm 3, and p-type poly Si4 and n-type poly Si5 are formed.
Are connected alternately by a wiring 6 made of Al, and the p-type poly S
i4 and n-type poly Si5 form a pair of thermocouples, and these thermocouples are arranged and connected in series to form a thermopile. Further, a heat absorbing layer 7 is formed on the thermocouple via an interlayer insulating layer (not shown), and a thermopile type infrared detecting section 11 having the thermocouple and the heat absorbing layer 7 is formed on the diaphragm 3. I have. That is, the thermal infrared sensor 10 is an independent type in which one infrared detecting unit 11 is formed on one diaphragm 3. FIG. 10 shows 2 × 2 = 4 thermal infrared sensors 10.

In order to manufacture the thermal infrared sensor 10, after forming a silicon nitride film on the semiconductor substrate 1, an etching hole 12 is provided in a part of the silicon nitride film, and a Si etching solution is supplied through the etching hole 12. Infiltrate and form a cavity 2 by anisotropic etching. That is, a thermal isolation structure is formed by silicon micromachining technology. Thereafter, an infrared detector 11 having a thermocouple and a heat absorbing layer 7 is provided.

In this thermal infrared sensor, the sensitivity of the thermal infrared sensor 10 is determined by the temperature difference between the heat absorbing layer 7 and the semiconductor substrate 1. This temperature difference is the width W of the beam 8.
It is determined by the magnitude of the thermal resistance of the beam 8 determined by ₁ and the length L ₁ of the beam 8. In order to make the output signal of the thermal infrared sensor 10 a practical level, a method of increasing the thermal resistance of the beam portion 8 of the diaphragm 3 of the thermal infrared sensor 10 and increasing the area of the heat absorbing layer 7 A method of increasing heat absorption energy, a method of using a material having high heat absorption efficiency as the material of the heat absorption layer 7, and the like are employed.

FIG. 11 is a diagram showing a part of a conventional thermal infrared array device having the thermal infrared sensor shown in FIG. As shown in the figure, each thermal infrared sensor 10 is arranged in an array, and a circuit section 1 for x and y address switches is provided.
3, the x wiring 14 and the y wiring 15 are provided, and a signal of a desired thermal infrared sensor pixel can be taken out.
In FIG. 11, the decoder section and the preamplifier section are omitted.

[0006]

In the thermal infrared sensor 10 shown in FIG. 10, a method of increasing the thermal resistance of the beam 8 in order to improve the sensitivity, that is, the length L _{1 of the} beam 8
To increase the distance from the heat absorbing layer 7 to the semiconductor substrate 1 (heat sink) and to reduce the cross-sectional area of the beam portion 8. However, when the length L ₁ of the beam portion 8 is increased, high sensitivity is achieved, but the aperture ratio of the thermal infrared sensor 10 (the area of the heat absorbing layer 7 which is directly related to the infrared absorption amount with respect to the area of the cavity 2). ), The heat absorption energy is reduced, and the output signal is reduced depending on the condition, so that the object cannot be reliably detected. On the other hand, by increasing the area of the heat absorbing layer 7, moreover by increasing the length L ₁ of the beam portion 8, the area occupied by the thermal infrared sensor 10 is increased, the element area of the thermal infrared array element is increased I will.

Further, when a thermal infrared array element is formed from a large number of thermal infrared sensors 10, the number of diaphragms 3 is increased. Therefore, the thermal infrared array element is manufactured by the yield of the diaphragm 3 depending on the number of diaphragms 3. The yield is affected, and the production yield of the thermal infrared array element is low.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been made to provide a thermal infrared sensor having a small occupied area and capable of reliably detecting an object to be detected, and a thermal infrared array element having a high production yield. The purpose is to provide.

[0009]

In order to achieve this object, the present invention provides a thermal infrared sensor in which a cavity is provided in a substrate, a diaphragm is formed on the cavity, and an infrared detector is formed on the diaphragm. In the method, a plurality of the infrared detecting sections are formed on the diaphragm.

In this case, a heat absorbing layer is provided in the infrared detecting section, and the heat resistance from each of the heat absorbing layers to the substrate is made equal.

In these cases, the infrared detector is of a thermopile type, bolometer type or pyroelectric type.

In these cases, a heat absorbing layer is provided on the infrared detecting section, and a heat conductive layer is provided below the heat absorbing layer.

In these cases, a region having high thermal insulation is provided at the boundary of the infrared detecting section.

In this case, a heat separating hole or a heat separating slit is provided at the boundary of the infrared detecting section to provide the region having high thermal insulation.

In the thermal infrared array device, the thermal infrared sensor is provided.

In this case, the infrared detectors are not arranged in one of the vertical and horizontal directions.

[0017]

In the thermal infrared sensor according to the present invention, since a plurality of infrared detecting portions are formed on the diaphragm, the aperture ratio of the infrared detecting portion can be increased, so that the occupied area is reduced. And the output signal can be increased, so that the object to be detected can be reliably detected.

Further, when a heat absorbing layer is provided in the infrared detecting section and the heat resistance from each heat absorbing layer to the substrate is made equal,
The sensitivity of each infrared detection unit can be made equal.

When the infrared detector is of a thermopile type, bolometer type or pyroelectric type, the sensitivity of the infrared detector can be improved.

Further, when a heat absorbing layer is provided in the infrared detecting section and a heat conductive layer is provided below the heat absorbing layer, thermal separation of each heat absorbing layer is performed. Can be reduced.

Further, when a region having high thermal insulation is provided at the boundary between the infrared detecting units, crosstalk between adjacent infrared detecting units can be reduced.

Further, when a heat separation hole or a heat separation slit is provided at the boundary of the infrared detecting section to provide a region having high thermal insulation, crosstalk between adjacent infrared detecting sections can be reliably reduced. Further, in the anisotropic etching for forming the cavity, the anisotropic etching can be easily performed because the etching liquid enters through the heat separation holes and the heat separation slits.

In the thermal type infrared array element according to the present invention, the number of diaphragms can be reduced, so that the production yield can be increased, and the area used for wiring can be reduced, so that the element can be reduced. Since the area can be reduced, the manufacturing cost can be reduced.

When the infrared detectors are arranged not to be aligned in one of the vertical and horizontal directions, if the objects to be detected exist in the vertical and horizontal directions, they are aligned in the vertical and horizontal directions. Since the probability of detection by any one of the thermal infrared sensors increases, the detection target can be reliably detected.

[0025]

FIG. 1 is a partially cutaway plan view showing a thermal infrared sensor according to the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. As shown in the figure, a semiconductor substrate 31 made of Si
A cavity 33 is formed on the cavity 32 of the semiconductor substrate 31, and a diaphragm 33 made of silicon nitride, which is a thermally insulating material, is formed on the cavity 32. The diaphragm 33 has eight beam portions 38.
And a main body 39. Further, a p-type poly Si 34 and an n-type poly Si 35 are formed on the beam portion 38 of the diaphragm 33, and the p-type poly Si 34 and the n-type poly Si 35 are alternately connected by a wiring 36 made of Al.
And n-type poly-Si 35 form a pair of thermocouples, and the thermocouples are arranged and connected in series to form a thermopile. Further, an interlayer insulating layer 46 is formed on the diaphragm 33,
A passivation film 47 is formed on the interlayer insulating layer 46, an amorphous Si 48 is formed on the passivation film 47 in a region above the main body 39, and an amorphous Si 4
8, a heat absorbing layer 37 made of gold and black is formed, a thermocouple and a thermopile type infrared detecting section 41 having the heat absorbing layer 37 are formed on the diaphragm 33, and the thermal type infrared sensor 40 is 2 × 2 = 4. It has an infrared detecting section 41. That is, the thermal infrared sensor 40 is of a shared type in which a plurality of infrared detectors 41 are formed on one diaphragm 33. Since the length L ₂ and the width W _{2 of} each beam portion 38 are equal, the thermal resistance from each heat absorbing layer 37 to the semiconductor substrate 31 is equal.

Next, a method of manufacturing the thermal infrared sensor shown in FIGS. 1 and 2 will be described. First, after a silicon nitride film is formed on the semiconductor substrate 31, an etching hole 42 is provided in a part of the silicon nitride film, and S
An i-etchant is infiltrated, a cavity 32 is formed by anisotropic etching, and a diaphragm 33 is formed. Next,
Poly-Si is formed on the diaphragm 33, p-type and n-type impurities are doped in a region to be a thermocouple of poly-Si, and each poly-Si is patterned to form a p-type poly-Si and an n-type poly-Si. And p-type poly Si34 and n-type poly Si
35 are alternately connected by a wiring 36 via an interlayer insulating layer 46. Next, a passivation film 47 is formed on the interlayer insulating layer 46, an amorphous Si 48 is formed on the passivation film 47, and a heat absorption layer 37 is formed on the amorphous Si 48.

Next, the thermal resistance of the beam portion 8 of the thermal infrared sensor 10 shown in FIG.
Consider the thermal resistance of the beam portion 38 of the thermal infrared sensor 40 shown in FIG. Four of the four infrared sensors shown in FIG.
One of the cavity 2 of the area and the area of the cavity 32 are the same, the length L ₂ of the length L ₁ and the beam portion 38 of the beam part 8 are the same, the thermoelectric logarithm is assumed to be the same. Suppose now that the width W _{2 of the} beam 38 is
Is twice the width W ₁ of the beam portion 8 and the infrared detecting portions 41 adjacent to each other of the thermal infrared sensor 40 are thermally separated, the thermal resistance of the beam portion 8 and the thermal resistance of the beam portion 38 are reduced. Is the same. That is, it can be said that the sensitivity of infrared rays is equivalent. And
The aperture ratio when the specific detection capability (D *) of the thermal infrared sensor 10 is close to the maximum value is about 4/9 (0.44). The aperture ratio is approximately 0.69, and the aperture ratio of the thermal infrared sensor 40 is approximately 1.55 times the aperture ratio of the thermal infrared sensor 10. Also, another point of view, when the aperture ratio of the thermal infrared sensor 40 is equal to the aperture ratio of the conventional thermal infrared sensor 10, than the length L ₁ of the length L ₂ of the beam portion 38 the beam portion 8 The sensitivity can be improved because the thermal resistance of the beam portion 38 can be made higher than the thermal resistance of the beam portion 8. From a different point of view, when the output signal of the thermal infrared sensor 40 and the output signal of the thermal infrared sensor 10 are made equal, the occupied area of the thermal infrared sensor 40 is smaller than the occupied area of the thermal infrared sensor 10. Become.

As described above, in the thermal infrared sensor shown in FIGS. 1 and 2, since the four infrared detecting sections 41 are formed on the diaphragm 33, the thermal infrared sensor 40 (one per infrared sensor) is provided. Since the aperture ratio of the infrared detector 41) can be increased, the occupied area can be reduced, and the output signal can be increased, so that the object to be detected can be reliably detected. In addition, the heat absorbing layer 3
7, the adhesion of the heat absorbing layer 37 made of gold black can be improved. Further, since the thermal resistance from each heat absorbing layer 37 to the semiconductor substrate 31 is equal, the sensitivity of each infrared detecting unit 41 can be equalized.

FIG. 3 is a sectional view showing another thermal infrared sensor according to the present invention. As shown in the figure, a thermal conductor layer 49 made of metal is formed between the passivation film 47 and the amorphous Si.

In this thermal infrared sensor, since the thermal absorption of each heat absorbing layer 37 is easy, the influence from the adjacent infrared detecting section 41 can be eliminated, and the infrared detecting section 4 can be removed.
1 can reduce crosstalk.

FIG. 4 is a partially cutaway plan view showing another thermal infrared sensor according to the present invention, and FIG. 5 is a front sectional view showing the thermal infrared sensor shown in FIG. As shown in the figure, a plurality of heat separation holes 51 are formed at the boundaries between the infrared detection units 41, that is, between the heat absorbing layers 37, and regions with high thermal insulation are provided at the boundaries between the infrared detection units 41.

In this thermal infrared sensor, the thermal resistance between the adjacent infrared detectors 41 is increased, so that crosstalk between the infrared detectors 41 can be reduced. In addition, since the conduction of heat is limited to the beam portion 38 on which the thermocouple is formed, the sensitivity of the infrared detection unit 41 can be improved. Further, since the heat separation hole 51 is provided near the center of the diaphragm 33, the anisotropic etching for forming the cavity 32 allows the Si etchant to enter from the heat separation hole 51. Can be easily performed, and the strength of the diaphragm 33 is not significantly reduced.

FIG. 6 is a partially cut plan view showing another thermal infrared sensor according to the present invention. As shown in the figure, a plurality of heat separating slits 52 are formed between the heat absorbing layers 37 of each infrared detecting section 41.

In this thermal type infrared sensor, since the thermal resistance between the adjacent infrared detectors 41 increases, crosstalk between the infrared detectors 41 can be reduced. In addition, since the conduction of heat is limited to the beam portion 38 on which the thermocouple is formed, the sensitivity of the infrared detection unit 41 can be improved. Further, since the thermal separation slit 52 is provided in the vicinity of the center of the diaphragm 33, in the anisotropic etching for forming the cavity 32, since the Si etching liquid also enters from the thermal separation slit 52, the anisotropic etching is performed. Can be easily performed.

FIG. 7 is a diagram showing a part of a thermal infrared array element according to the present invention. As shown in the figure, a plurality of thermal infrared sensors 40 are arranged vertically and horizontally, and a circuit section 43 for an x, y address switch, an x wiring 44, and a y wiring 45
Is provided, and a signal of a desired thermal infrared sensor pixel can be extracted to the outside. In FIG. 7, the decoder section and the preamplifier section are omitted.

In this thermal type infrared array device, the number of diaphragms 33 can be reduced, so that the production yield can be increased, and the area used for the x wirings 44 and y wirings 45 can be reduced. Since the element area can be reduced, the manufacturing cost can be reduced.

FIG. 8 is a diagram showing a part of another thermal type infrared array element according to the present invention. As shown in the figure, three thermal infrared sensors 40 arranged vertically in the plane of FIG. 8 are shifted from each other in the lateral direction of FIG. 8, and three thermal infrared sensors 40 arranged in the lateral direction of FIG. The infrared sensor 40 is shifted vertically in FIG. 8.

In this thermal infrared array element, when the object to be detected exists in the vertical direction or the horizontal direction in FIG. 8, one of the three thermal infrared sensors 40 arranged in the vertical direction in FIG. Since the probability of detection by one or any one of the three thermal infrared sensors 40 arranged in the horizontal direction of FIG. 8 increases, the detection target can be reliably detected.

FIG. 9 is a view showing a part of another thermal type infrared array element according to the present invention. As shown in the figure, the positions of the thermal infrared sensors 40 adjacent to each other in the horizontal direction of FIG. 9 are shifted by half of the vertical dimension of the thermal infrared sensor 40 in the vertical direction of FIG. 9, and are arranged in the horizontal direction of FIG. Three thermal infrared sensors 40 belonging to every other row of the thermal infrared sensor 40 and arranged vertically in FIG. 9 are shifted in the horizontal direction in FIG. Wired in a staggered fashion.

In this thermal infrared array element, when the object to be detected exists in the vertical direction or the horizontal direction in FIG. 9, one of the three thermal infrared sensors 40 arranged in the vertical direction in FIG. Since the probability of detection by one or any one of the two thermal infrared sensors 40 arranged in the horizontal direction of FIG. 9 increases, the detection target can be reliably detected.

In the above-described embodiment, the thermopile type infrared detecting section 41 is provided, but a bolometer type or pyroelectric type infrared detecting section may be provided. Can be improved.
Further, in the above embodiment, the semiconductor substrate 31 is used as the substrate, but another substrate may be used. Further, in the above-described embodiment, four infrared detection units 41 are formed on one diaphragm 33, but a plurality of infrared detection units may be formed on one diaphragm. Also,
In the above-described embodiment, the diaphragm 33 having the eight beam portions 38 is provided, but a diaphragm having four beam portions may be provided. Further, in the above-described embodiment, the heat isolation hole 51 or the heat isolation slit 52 is provided at the boundary of the infrared detection unit 41 to provide a region having high thermal insulation, but oxygen is injected at the boundary of the infrared detection unit. A region having high thermal insulation may be provided by forming an oxide film having high thermal resistance. In the above-described embodiment, the amorphous Si layer 48 is provided below the heat absorbing layer 37. However, when a heat absorbing film made of a material other than gold and black is used, the amorphous Si layer may not be provided. . Further, in the above-described embodiment, four infrared detectors 41 are formed on one diaphragm 33, but one diaphragm 33 is formed.
When n infrared detectors are formed above, a diaphragm of 1 / n of the total number of pixels is sufficient.

[Brief description of the drawings]

FIG. 1 is a partially cutaway plan view showing a thermal infrared sensor according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a cross-sectional view illustrating another thermal infrared sensor according to the present invention.

FIG. 4 is a partially cutaway plan view showing another thermal infrared sensor according to the present invention.

FIG. 5 is a front sectional view showing the thermal infrared sensor shown in FIG. 4;

FIG. 6 is a partially cutaway plan view showing another thermal infrared sensor according to the present invention.

FIG. 7 is a diagram showing a part of a thermal infrared array element according to the present invention.

FIG. 8 is a diagram showing a part of another thermal infrared array element according to the present invention.

FIG. 9 is a diagram showing a part of another thermal infrared array element according to the present invention.

FIG. 10 is a partially cut plan view showing a conventional thermal infrared sensor.

FIG. 11 is a diagram showing a part of a conventional thermal infrared array element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 31 ... Semiconductor substrate 32 ... Cavity 33 ... Diaphragm 34 ... p-type poly Si 35 ... n-type poly Si 36 ... Wiring 37 ... Heat absorption layer 38 ... Beam part 39 ... Body part 40 ... Thermal infrared sensor 41 ... Infrared detecting part 49 … Thermal conductor layer 51… thermal separation hole 52… thermal separation slit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 37/02 H01L 37/02

Claims (8)

[Claims] 1. A thermal infrared sensor in which a cavity is provided in a substrate, a diaphragm is formed on the cavity, and an infrared detector is formed on the diaphragm, wherein a plurality of infrared detectors are formed on the diaphragm. Characterized thermal infrared sensor. 2. The thermal infrared sensor according to claim 1, wherein a heat absorbing layer is provided in the infrared detecting section, and the thermal resistance from each of the heat absorbing layers to the substrate is made equal. 3. The infrared detector according to claim 1, wherein said infrared detector is of a thermopile type, a bolometer type or a pyroelectric type.
Or a thermal infrared sensor according to 2. 4. The thermal infrared sensor according to claim 1, wherein a heat absorbing layer is provided in the infrared detecting section, and a heat conductive layer is provided below the heat absorbing layer. 5. The thermal infrared sensor according to claim 1, wherein a region having high thermal insulation is provided at a boundary of said infrared detecting section. 6. A thermal infrared sensor according to claim 5, wherein a heat separation hole or a heat separation slit is provided at a boundary of said infrared detecting section to provide said region having high thermal insulation. 7. A thermal infrared array device comprising the thermal infrared sensor according to claim 1. 8. The thermal infrared array element according to claim 7, wherein said infrared detecting sections are not arranged in one of a vertical direction and a horizontal direction.