JPH05231946A - Infrared detector - Google Patents

Abstract

PURPOSE:To obtain an infrared detector wherein a strain and a breakdown are not caused by an internal stress even when a heat insulation film is thinned, of which a manufacture yield is high and which shows high sensitivity and durability in use. CONSTITUTION:An infrared detector has a film-form body of a plurality of layers comprising a pair of electrode layers 30 and 50 and a thermistor layer 40 held between the two electrode layers 30 and 50, on a heat insulation film 20. The film-form body of at least one layer is formed in separation in a narrow width in a pattern wherein strip-shaped narrow-width parts separated by a break are juxtaposed in a folded and continuous manner.

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 an infrared detecting element for detecting infrared rays by using a thermistor whose resistance changes with temperature change.

[0002]

2. Description of the Related Art Conventionally, as a general structure of an infrared detecting element using a thermistor, a thermistor and a pair of electrodes sandwiching both sides of the thermistor are superposed on a heat insulating film formed on a substrate. Is being formed and is hit by infrared rays,
When the temperature of the thermistor rises, the resistance of the thermistor changes. Therefore, it is possible to detect infrared rays by detecting this resistance change with a pair of electrodes. In some cases, an infrared absorption film is provided on the surface of the thermistor in order to increase the detection sensitivity so that the temperature rise and resistance change of the thermistor can be performed quickly.

The infrared detecting element is often used for detecting the weak infrared rays emitted from an object or a human body, and particularly high sensitivity is required for such an application. Therefore, in the conventional infrared detection element, a part of the substrate is dug out, a heat insulating film is formed so as to pass through the hollowed out part, and an infrared detection part composed of an electrode and a thermistor is installed on the heat insulating film. There is a so-called diaphragm structure. In this structure, the heat generated in the infrared detecting section is unlikely to escape to the substrate side, so that the temperature rise and resistance change of the thermistor are sensitively performed, and the infrared detection sensitivity is increased.

Such an infrared detecting element is also capable of detecting infrared rays emitted from a stationary object or a stationary human body, and has the advantage that it does not malfunction due to vibration and is strong against shock. Further, since the semiconductor process is used for manufacturing, mass production is possible and cost reduction can be achieved. In the infrared detecting element as described above, if the thermal resistance of the heat insulating film is R, the energy of the infrared light incident on a unit area per unit time is I, and the area of the infrared absorbing film is S, the temperature rise of the infrared detecting portion will occur. ΔT is ΔT =
It is represented by RIS. In this equation, the thermal resistance R increases as the thermal conductivity of the thermal insulating film becomes smaller and as the film thickness becomes thinner. Therefore, in order to increase the temperature rise ΔT, that is, the detection sensitivity, the thermal conductivity of the thermal insulating film is The smaller and thinner the film, the more preferable.

[0005]

However, the conventional infrared detecting element as described above has a problem that the thermal insulating film is apt to be distorted or broken. In the infrared detecting element having the above-mentioned structure, the structure formed on the heat insulating film such as the electrode, thermistor or infrared absorbing film is a rectangular film or a plane having a certain area. Therefore, if there is expansion and contraction due to heat in the element manufacturing process or the operating environment, a large internal stress is generated due to the difference in the coefficient of thermal expansion of each layer, and this internal stress causes distortion and destruction of the thermal insulation film. It was. As described above, in order to increase the detection sensitivity of the infrared detection element, the deeper the substrate under the heat insulating film is digged or the thinner the heat insulating film is, the more internal stress due to heat absorption is generated. As a result, the thermal insulation film becomes larger and is likely to be distorted or broken. Therefore, the infrared detection element provided with a thin thermal insulation film to increase the detection sensitivity has a lower manufacturing yield and is inferior in durability during use.

Therefore, the object of the present invention is to solve the above problems of the prior art, and even if the thermal insulation film is thinned, distortion or breakage due to internal stress does not occur, the manufacturing yield is high, and it is high in use. An object of the present invention is to provide an infrared detection element capable of exhibiting sensitivity and durability.

[0007]

In order to solve the above-mentioned problems, an infrared detecting element according to the present invention has a plurality of layers including a pair of electrode layers and a thermistor layer sandwiched between the electrode layers on a heat insulating film. In the infrared detection element provided with the film body of
At least one layer of film-like body is formed in a narrow width.

As the basic structure of the infrared detecting element, the same structure as the infrared detecting element using a conventional thermistor is adopted. In the infrared detecting portion of the infrared detecting element, at least one thermistor layer and a pair of electrode layers sandwiching the thermistor layer are provided on the heat insulating film formed on the substrate. The substrate is dug under the thermal insulation film,
The width of the thermal insulation film that supports the infrared detection part on the substrate is made narrower so that the heat of the infrared detection part does not easily escape to the outside, or the infrared absorption with high infrared absorption rate on the thermistor layer A layer or a filter layer that selectively absorbs only a specific wavelength is formed in advance, and various structures adopted in a usual infrared detection element are combined.

The multi-layered film-like body is a thin layer structure portion which is formed so as to be sequentially stacked on the thermal insulation film such as the thermistor layer, the electrode layer and the infrared absorption layer, and which requires a certain area. Means The material, layer thickness, etc. can be arbitrarily set according to the purpose and required performance of each layer. The outer shape of the membranous body may be a rectangle, a polygon, a circle, or any other figure shape, and the multi-layered membranous body may have the same outer shape or may have different outer shapes. May be combined. Among the film-like bodies, the electrode layer may have a detailed structure, such as a structure for connecting to an external circuit added thereto.

At least one layer of the multi-layered film is separated and formed in a narrow width. The term “separately formed into a narrow width” means that the entire film-shaped body is composed of an assembly of strip-shaped or string-shaped portions having a narrow width and separated from each other. Specifically, by forming a plurality of slits or cuts in the film-like body, it is possible to separately form the film-like body in a narrow width. More specifically, the film-shaped body is composed of one continuous narrow portion in the shape of a folded belt or a spiral, or a large number of parallel slits are formed inside the film-shaped body to form a strip-shaped body. An example is one in which a large number of narrow width portions are arranged and both ends thereof are integrally connected. The width of the narrow portion to be formed separately and the width of the gap formed between the narrow portions are such that the internal stress relaxation effect can be mentioned and the original function of each film body is not hindered. if there is,
Can be set to any width.

As means for separating and forming the film-like body into a narrow width, a thin layer forming technique in ordinary semiconductor processing or the like, a fine processing technique, or pattern forming means by masking by photolithography or selective etching is applied. By combining such ordinary pattern forming techniques, it is possible to separate and form the film-like body into a narrow width in an arbitrary pattern.

The number of layers of the film-like body separated and formed in the narrow width may be at least one layer, or a plurality of layers of the film-like body may be separately formed in the narrow width. Usually, if one of the film bodies stacked vertically is separated and formed into a narrow width, even if the other is a uniform film body, the internal stress generated between them is
It can be absorbed and relaxed by the film-shaped body which is separated and formed into a narrow width. Specifically, the pair of electrode layers may be separated and formed in a narrow width, and the thermistor layer between them may not be formed separately, or conversely, the thermistor layer may be formed in a narrow width and the electrode layer may be formed separately. You can leave it. Further, if the infrared absorption layer, which is likely to expand heat absorption, that is, expansion due to temperature rise, is separately formed in a narrow width, it is effective in relaxing internal stress.

Since the film-like body separated and formed into a narrow width is easily deformed in the width direction of the narrow width portion, that is, in the direction in which a gap is formed between the narrow width portions, the ability to relieve internal stress is high. It is preferable that the narrow portions are arranged in a direction in which internal stress is likely to occur. When forming a narrow portion in a film body having a plurality of layers, by changing the separation pattern of the narrow portion depending on the layer, it is possible to uniformly exert the internal stress relaxing ability in any direction.

[0014]

The infrared detecting portion of the infrared detecting element is made of various materials such as a thermistor layer, an electrode layer, and an infrared absorbing layer, and each has a plurality of layers of film-shaped bodies having different thermal expansion characteristics.
It has a structure of being stacked on the heat insulating film. Since various thin film forming techniques and pattern forming techniques are applied when manufacturing such an infrared detecting element, they are heated during the manufacturing process to cause thermal expansion. Also, when used, it absorbs infrared rays and raises the temperature,
Naturally, thermal expansion occurs.

When the upper and lower film-like bodies are integrally bonded to each other over the entire surface, the difference in deformation due to thermal expansion becomes an internal stress as it is, and the film-like bodies or the film-like body and the heat insulating film are combined. I will join you in the meantime. On the other hand, if the film-like body is formed separately in a narrow width, the film-like body can be relatively freely moved and deformed in the width direction of the narrow width portion, so that the film-like body is laminated vertically. In addition, the narrow portion is moved and deformed in accordance with the thermal deformation of the other film-shaped body, and the internal stress generated between the two can be absorbed or relieved.

Therefore, if even one of the plural layers of the film-like body forming the infrared detecting section has a thinly separated layer, the internal stress is alleviated by that much. As a result, distortion or breakage of the thermal insulation film due to internal stress can be prevented. Even if each film-like body is separated and formed into a narrow width, if it has a certain area as a whole, each function can be sufficiently exerted, so that the function and characteristics as an infrared detection element are not affected. Is rarely given.

With this structure, even if the thickness of each film or the heat insulating film is thin, it is possible to surely prevent the occurrence of distortion or destruction due to internal stress, so that the sensitivity of the infrared detecting element is improved, or the size and manufacturing efficiency are improved. It can also be improved.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows the entire structure of the infrared detection element. Substrate 1 made of silicon, etc.
The thermal insulation film 2 made of silicon oxynitride, etc.
0 is formed. In the central portion of the thermal insulation film 20, the substrate 10 is dug from the lower side by etching or the like to form a cutout space 12. An electrode layer 3 made of a conductive metal such as chromium is formed on the heat insulating film 20 in the center of the void space 12.
0, the thermistor layer 40, the electrode layer 50, and the infrared absorption layer 60 are sequentially stacked and formed. Electrode layer 30
Is extended to the outside, and at the end of this extension 31,
A connection pad 32 is provided on the substrate 10.
The electrode layer 50 also includes an extension portion 51 extending in a direction different from that of the electrode layer 30, and a similar connection pad 52 is provided.

FIG. 1 shows an electrode layer 30, a thermistor layer 40,
The planar structure of the electrode layer 50 is shown. Each of them is basically a film-like body having a square shape with the same size. And
As shown in FIG. 1A, the upper electrode layer 50 has a strip-shaped extension 51 on one side, and the entire electrode layer 50 has a strip-shaped narrow portion 55 extending in the left-right direction in the drawing. It folds downward from and continues. Adjacent narrow part 5
5 are notches 54 cut from the outer edge of the electrode layer 50.
Are separated from each other. The extension portion 51 is connected to a part of the narrow width portion 55. As shown in Figure 1 (b),
The thermistor layer 40 has a uniform surface as a whole. As shown in FIG. 1 (c), the electrode layer 30 is formed with a narrow portion 35 and a cut 54 having the same pattern as the electrode layer 50. However, the extension portion 31 extends in the opposite direction to the electrode layer 50. Although not shown, the infrared absorption layer 60 is
Similar to the thermistor layer 40, the entire surface has a uniform surface.

In the infrared detecting element having such a structure, if a temperature change occurs due to heat treatment in the manufacturing process, or when the infrared detecting portion is irradiated with infrared rays during use, the infrared absorbing layer 60 and the thermistor layer 40 are formed. Causes thermal expansion as in the case of the conventional infrared detecting element. However, since the electrode layers 30 and 50 are separated from each other in the width direction of the narrow width portion 55, that is, in the vertical direction in FIG. 1, they can be freely moved and deformed to some extent. for that reason,
Infrared absorbing layer 6 adjacent to the electrode layers 30, 50
0, it can be deformed according to the thermal expansion of the thermistor layer 40, and internal stress is absorbed or relaxed.

FIG. 3 shows an embodiment which is partially different in structure from the above embodiment. This embodiment is different from the above-mentioned embodiment in that the upper and lower electrode layers 30 and 50 have different patterns to be formed separately in a narrow width. That is, the upper electrode layer 50 is formed so that the narrow portion 55 and the cut 54 extend from the top to the bottom of the drawing. Lower electrode layer 3
0 is formed so that the narrow width portion 55 and the break 54 extend in the left and right directions in the drawing.

Therefore, in this embodiment, the electrode layer 30
So, the ability to relieve the vertical stress in the figure is high,
In the electrode layer 50, the ability to relieve the internal stress in the left-right direction in the figure is enhanced, and if the functions of both are combined, the function of relieving the internal stress can be exerted in any of the up, down, left, and right directions. Next, in the embodiment of FIG. 4, FIG.
As shown in (c), the electrode layers 30 and 50 have a uniform surface as a whole. Then, as shown in FIG. 4B, the thermistor layer 40 has a large number of slits 4 extending vertically in the drawing.
4 is formed, and the strip-shaped narrow width portion 45 formed between the slits 44 is integrally connected at the upper and lower sides. In this embodiment, the narrow portion 45 of the thermistor layer 40 moves and deforms in accordance with the thermal expansion of the upper and lower electrode layers 30 and 50, thereby absorbing or relaxing the internal stress.

In the embodiment shown in FIG. 5, the thermistor layer 40 has a uniform surface as a whole as shown in FIG. 5 (a), but as shown in FIG. 60 is separated and formed by a large number of vertical slits 64, and a vertically narrow strip-shaped portion 65 is connected at the upper and lower sides. In this case, the infrared absorption layer 60 is protected against thermal expansion of the thermistor layer 40 and both electrode layers 30 and 50.
By moving and deforming the narrow width portion 65, the internal stress is absorbed and relaxed.

The embodiment of FIG. 6 shows another example of the pattern when the film-like body is formed in a narrow width. That is, the film body S is composed of a narrow width portion 5 which is continuously connected in a spiral shape from the center to the outer circumference, and a gap portion 4 which separates the narrow width portion 5. The film-shaped body S includes the electrode layer 3 described above.
It can be applied to any layer such as 0, 50, the thermistor layer 40, and the infrared absorption layer 60.

In this embodiment, since the separating direction of the narrow portion 5 exists in any of the upper, lower, left and right directions, there is an ability to absorb and relax internal stress in any of the upper, lower, left and right directions. Next, more specific examples will be described. -Example 1- An infrared detection element having the structure shown in FIGS. 1 and 2 was manufactured.

A thermal insulation film 20 was formed by stacking 5000 Å-thick silicon oxynitride on the silicon substrate 10 by the glow discharge decomposition method. The film forming conditions are a mixed gas of monosilane, ammonia, nitrogen and carbon monoxide, the ratio of dinitrogen monoxide to the total amount of ammonia, nitrogen and carbon monoxide is 30%, the substrate temperature is 20 ° C., the pressure is 1 Torr, and the frequency. 1
The discharge power was 30 W at 3.56 MHz.

On the heat insulating film 20, a chromium film having a thickness of 500 Å was formed at a substrate temperature of 200 ° C. by an electron beam evaporation method. Then, in a photolithography process, the electrode layer 30 on the lower side was formed by patterning into the shape shown in FIG. Next, by a glow discharge decomposition method, a p-type a-Si layer having a thickness of 1 μm was used.
A film of C was formed, and a thermistor layer 40 was formed by patterning into a square of 2 × 2 mm as shown in FIG. 1 (b) in a photolithography process. The film forming conditions are 900 mol% methane,
Using hydrogen-diluted monosilane to which 0.25 mol% of diborane was added, the substrate temperature was 180 ° C., the pressure was 0.9 Torr, the frequency was 13.56 KHz, and the discharge power was 20 W. Then, by electron beam evaporation method, the substrate temperature is 200 ° C and the thickness is 500Å
Then, a chromium film is formed, and patterning is performed by a photolithography process so that the narrow portions 55 are arranged in parallel with the narrow portions 35 of the lower electrode layer 30 as shown in FIG. 1 (a).
The electrode layer 50 on the upper side was formed. The dimensions of the upper electrode layer 50 and the lower electrode layer 30 are both 1.9.
It was × 1.9 mm.

It should be noted that chromium, which is the material of the electrode layers 30 and 50, has a smaller thermal conductivity and a higher detection sensitivity when impurities are added, so that the thermal conductivity is small instead of the above-mentioned materials. Nickel chrome can also be used. Next, a silicon oxide film having a thickness of 1 μm was formed by a glow discharge decomposition method and patterned into a square of 2 × 2 mm by a photolithography process to form an infrared absorption layer 60. The film forming conditions are 700 mol% of nitric oxide, and the substrate temperature is 2
The temperature was 50 ° C., the pressure was 1 Torr, the frequency was 13.56 KHz, and the discharge power was 30 W. Subsequently, an aluminum film was formed and patterned by the electron beam evaporation method to form the connection pad 52.

Finally, anisotropic etching is performed with potassium hydroxide so that the thermal insulating film 20 made of silicon oxynitride is left from the side of the silicon substrate 10 opposite to the thermal insulating film 20, and the thermal insulating film 20 is removed. The removal space 12 was formed, and an infrared detection element having a so-called diaphragm structure was manufactured. The size of the manufactured infrared detection element was a square of 2.5 × 2.5 mm.

When the infrared detecting element was used, it was confirmed that the thermal insulating film 20 was not distorted or broken at all, the detection sensitivity was good, and the quality performance was excellent.

[0031]

As described above, in the infrared detecting element according to the present invention, since the film-like bodies such as the electrode layer and the thermistor layer are separately formed in a narrow width, the film formed in the narrow width is formed. The sheet-like body can absorb or relax internal stress generated between a plurality of film-like bodies.

As a result, distortion and breakage of the heat insulating film can be prevented, the manufacturing yield can be improved, and the durability during use can be increased. Moreover, in the manufacturing process, as compared with the conventional method, it is only necessary to change the formation pattern of the film-shaped body,
It is relatively technically easy to manufacture without increasing the total number of steps or working time, is excellent in productivity, and is low in cost. Further, if the heat insulating film is less likely to be distorted or broken, the thickness of the heat insulating film can be made thinner than in the prior art to manufacture an element sensitive to temperature changes and having high infrared detection sensitivity.

[Brief description of drawings]

FIG. 1 is an upper side electrode layer (a), a thermistor layer (b), a lower side electrode layer (c) of an infrared detection element showing an embodiment of the present invention.
Each plan view of

FIG. 2 is a sectional view of the infrared detection element of the above.

FIG. 3 is a plan view of an upper electrode layer (a), a thermistor layer (b), and a lower electrode layer (c) showing another embodiment.

FIG. 4 is a plan view of an upper electrode layer (a), a thermistor layer (b), and a lower electrode layer (c) showing another embodiment.

FIG. 5 is a plan view of a thermistor layer (a) and an infrared absorption layer (b) showing another embodiment.

FIG. 6 is a plan view showing a pattern of a film-like body according to another embodiment.

[Explanation of symbols]

 10 Substrate 20 Thermal Insulation Film 30, 50 Electrode Layer 40 Thermistor Layer 60 Infrared Absorption Layer 35, 45, 55, 65, 5 Narrow Part 34, 54, 4 Cut 64 Slit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takuro Ishida 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Keiji Kakite, 1048, Kadoma, Kadoma City, Osaka Matsushita Electric Works Co., Ltd.

Claims (1)

[Claims] 1. An infrared detection element comprising a plurality of film-like bodies including a pair of electrode layers and a thermistor layer sandwiched between the electrode layers on a heat insulating film, and at least one film-like body. The infrared detecting element is characterized in that it is formed separately in a narrow width.