JP3129504B2 - Infrared detector - Google Patents

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 that detects infrared rays by using a thermistor whose resistance changes with a change in temperature.

[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 surfaces of the thermistor are stacked on a heat insulating film formed on a substrate. Has been formed,
When the temperature of the thermistor rises, the resistance of the thermistor changes. This change in resistance is detected by a pair of electrodes so that infrared light can be detected. In some cases, the surface of the thermistor is provided with an infrared absorbing film in order to increase the detection sensitivity, so that the temperature of the thermistor and the resistance change quickly.

[0003] Infrared detecting elements are often used to detect faint infrared rays emitted from an object or a human body. In such an application, particularly high sensitivity is required. Therefore, in the conventional infrared detecting element, a part of the substrate was dug, a heat insulating film was formed so as to pass through the hollow part, and an infrared detecting unit including an electrode and a thermistor was installed thereon. There is a so-called diaphragm structure. With this structure, it is difficult for the heat generated in the infrared detection section to escape to the substrate side, so that the temperature of the thermistor and the resistance change occur sensitively, and the detection sensitivity of infrared rays increases.

[0004] Such an infrared detecting element can also detect infrared rays radiated from a stationary object or a stationary human body, and has the advantages that it does not malfunction due to vibration and is strong against impact. In addition, since the semiconductor device is manufactured using a semiconductor process, mass production is possible and cost reduction can be achieved. In the infrared detecting element as described above, if the thermal resistance of the thermal insulating film is R, the energy of the infrared ray incident on a unit area per unit time is I, and the area of the infrared absorbing film is S, the temperature of the infrared detecting section rises. ΔT is ΔT =
Represented by RIS. In this equation, the thermal resistance R increases as the thermal conductivity of the thermal insulating film decreases and as the film thickness decreases, so that in order to increase the temperature rise ΔT, that is, to increase the detection sensitivity, the thermal conductivity of the thermal insulating film must be increased. The smaller and the thinner the film, the better.

[0005]

However, the conventional infrared detecting element as described above has a problem that the thermal insulating film is easily distorted or broken. This is because, in the infrared detecting element having the above-described structure, the structure formed on a heat insulating film such as an electrode, a thermistor or an infrared absorbing film has a rectangular film shape or a planar shape each having a certain area. Therefore, if there is expansion and contraction due to heat in the element manufacturing process or usage environment, a large internal stress is generated due to a difference in the coefficient of thermal expansion of each layer, and this internal stress causes distortion or destruction of the thermal insulating film. It was. As described above, in order to increase the detection sensitivity of the infrared detecting element, the larger the substrate below the heat insulating film is dug or the thinner the heat insulating film, the more the internal stress due to heat absorption becomes. As a result, the possibility of distortion or destruction of the heat insulating film increases. Therefore, an infrared detecting element provided with a thin heat insulating film in order to enhance the detection sensitivity has a lower production yield and lower durability in use.

Accordingly, an object of the present invention is to solve the problems of the prior art. Even if the thermal insulating film is thinned, distortion or destruction due to internal stress does not occur, the production yield is high, and the production yield is high. An object of the present invention is to provide an infrared detecting element capable of exhibiting sensitivity and durability.

[0007]

According to the present invention, there is provided an infrared detecting element comprising a plurality of layers including a pair of electrode layers and a thermistor layer sandwiched between both electrode layers on a heat insulating film. In an infrared detection element having a film-like body of
At least one layer of the film-like body is formed separately in a narrow width.

The basic structure of the infrared detecting element is similar to that of a conventional infrared detecting element using a thermistor. In the infrared detecting section of the infrared detecting element, at least one thermistor layer and a pair of electrode layers sandwiching the thermistor layer are provided on a heat insulating film formed on the substrate. The substrate is dug below the thermal insulation film,
The thermal insulation film that supports the infrared detector on the substrate is made narrower, for example, so that the heat of the infrared detector does not easily escape to the outside. It is configured by combining various structures employed in ordinary infrared detecting elements, such as forming a layer or a filter layer that selectively absorbs only a specific wavelength.

[0009] The multi-layered film is a thin-layered structure which is formed in such a manner as to be sequentially stacked on the heat insulating film, such as the thermistor layer, the electrode layer and the infrared absorbing layer, and requires a certain area. Means The material and the thickness of the layers can be arbitrarily set according to the purpose and required performance of each layer. The outer shape of the film is a rectangle, a polygon, a circle, or any other figure shape, and the film having a plurality of layers may have the same outer shape, or may have different outer shapes. May be combined. The details of the structure may be different depending on the individual film-shaped members, such as a connection structure to an external circuit added to the electrode layer of the film-shaped members.

At least one layer of such a plurality of layers is formed to be narrowly separated. The term “narrowly separated formation” means that the entire film-like body is constituted by an aggregate of narrow band-like or string-like portions separated from each other. Specifically, by forming a plurality of slits and cuts in the film-like body, the film-like body can be separated and formed into a narrow width. More specifically, the film-like body is formed by a single continuous narrow portion having a folded band shape or a spiral shape, or a band-like shape formed by forming a number of parallel slits inside the film-like body. An example in which a large number of narrow portions are arranged and both ends thereof are integrally provided can be exemplified. The width of the narrow portion to be separated and formed, and the width of the gap formed between the narrow portions are within a range that does not impair the original function of each film-like body, in addition to the effect of reducing internal stress. if there is,
Can be set to any width.

As a 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 a pattern forming means by masking by photolithography or selective etching is applied. By combining such ordinary pattern forming techniques, the film can be separated and formed into an arbitrary pattern with a narrow width.

[0012] The number of layers of the film-like body separated and formed in a narrow width may be at least one layer, or a plurality of layers of the film-shaped body may be separated and formed in a narrow width. Normally, if one of the film-like bodies stacked vertically is separated and formed to have a narrow width, the other is a uniform film-like body, but the internal stress generated between each other,
It can be absorbed and relaxed by the thinner film formed separately. Specifically, a pair of electrode layers are formed separately in a narrow width, and a thermistor layer between them is not formed separately, or conversely, a thermistor layer is formed in a narrow width, and the electrode layer is formed separately. You can keep it. In addition, if an infrared absorption layer, which tends to increase heat absorption, that is, expansion due to temperature rise, is formed to be narrow and narrow, it is effective in alleviating internal stress.

[0013] The film-like body separated and formed into a narrow width is easily deformed in the width direction of the narrow portion, that is, in a direction in which a gap is provided between the narrow portions, and has a high ability to relieve internal stress. It is preferable that the narrow portions are arranged in a direction in which the internal stress is easily generated. In the case where a narrow portion is formed in a plurality of layers of the film, if the separation pattern of the narrow portion is changed depending on the layer, the internal stress can be uniformly reduced in any direction.

[0014]

The infrared detecting section of the infrared detecting element is made of various materials such as a thermistor layer, an electrode layer, and an infrared absorbing layer.
The structure is stacked on the heat insulating film. When manufacturing such an infrared detecting element, various thin film forming techniques and pattern forming techniques are applied, so that the infrared detecting element is heated during the manufacturing process and causes thermal expansion. In addition, at the time of use, we absorb infrared rays and raise temperature,
Naturally, thermal expansion occurs.

If the upper and lower membranes are joined and integrated over the entire surface, the difference in deformation due to thermal expansion becomes the internal stress as it is, and the difference between the membranes or between the membrane and the heat insulating film is obtained. I will join in between. On the other hand, if the film is separated and formed to be narrow, the film can relatively freely move and deform in the width direction of the narrow portion. The narrow portion moves and deforms in accordance with the thermal deformation of the other film-like body, and the internal stress generated therebetween can be absorbed or reduced.

[0016] Therefore, if one of the plurality of layers of the film constituting the infrared detecting section has a layer separated and formed in a narrow width, the internal stress is reduced by that much. As a result, distortion and destruction of the heat insulating film due to internal stress can be prevented. Even if each film is separated and formed in a narrow width, if it has a certain area as a whole, each function can be fully exhibited, so that the function and characteristics as an infrared detecting element are affected. It is rare to give.

In this structure, even if the thickness of each film or the heat insulating film is small, the occurrence of distortion or destruction due to internal stress can be reliably prevented. It can also be improved.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. However, FIGS.
Examples and Example 1 shown in the following paragraphs show the technical scope of the present invention.
This is a reference technology that deviates. FIG. 2 shows the entire structure of the infrared detecting element. On a surface of a substrate 10 made of silicon or the like, a thermal insulating film 20 made of silicon oxynitride or the like is formed. In the central portion of the heat insulating film 20, the substrate 10
Is dug out from below by etching etc.
It is 2. An electrode layer 30 made of a conductive metal such as chromium, a thermistor layer 40, an electrode layer 50, and an infrared absorbing layer 60 are sequentially stacked and formed on the heat insulating film 20 at the center of the lacking space 12. The electrode layer 30 is extended outward, and an end of the extension 31 is provided on the substrate 10.
A connection pad 32 is provided on the upper part of FIG. Electrode layer 5
0 has an extension 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,
3 shows a planar structure of the electrode layer 50. Each of them is basically a square film having the same dimensions. 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 left and right in the drawing. It is folded back from below and is continuous. Adjacent narrow part 5
5 are cuts 54 cut from the outer edge of the electrode layer 50.
Are separated from each other. The extension 51 is connected to a part of the narrow portion 55. As shown in FIG. 1 (b),
The thermistor layer 40 has a uniform surface as a whole. As shown in FIG. 1C, the electrode layer 30 has a narrow portion 35 and a cut 54 having the same pattern as the electrode layer 50. However, the extension 31 extends in a direction opposite to the electrode layer 50. Although not shown, the infrared absorbing layer 60
Like the thermistor layer 40, the whole is a uniform surface.

In the infrared detecting element having such a structure, when a temperature change occurs due to a heat treatment in a manufacturing process or an infrared ray irradiating an infrared detecting portion during use, the infrared absorbing layer 60 and the thermistor layer 40 are used. 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 portion 55, that is, in the vertical direction in FIG. 1, the electrode layers 30 and 50 can freely move and deform to some extent. for that reason,
The electrode layers 30 and 50 are provided on the infrared absorbing layer 6 adjacent thereto.
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 having a structure partially different from that of the above embodiment. This embodiment is different from the above embodiment in that the upper and lower electrode layers 30 and 50 have different patterns formed to be separated into narrow widths. That is, the upper electrode layer 50 is formed such that the narrow portion 55 and the cut 54 extend from the top to the bottom in the figure. Lower electrode layer 3
0 is formed so that the narrow portion 55 and the cut 54 extend to the left and right in the figure.

Therefore, in this embodiment, the electrode layer 30
In the figure, the ability to relieve internal stress in the vertical direction of the figure is high,
In the electrode layer 50, the ability to relieve internal stress in the left-right direction in the drawing is enhanced, and if both functions are combined, the function of alleviating internal stress in any of up, down, left, and right directions can be exhibited. Next, in the embodiment of FIG. 4, FIG.
As shown in (c), the electrode layers 30 and 50 are entirely uniform. Then, as shown in FIG. 4 (b), a large number of slits 4 extending vertically in the figure are formed in the thermistor layer 40.
4 are formed, and a strip-shaped narrow portion 45 formed between the slits 44 is integrally connected at upper and lower sides. In this embodiment, the narrow portion 45 of the thermistor layer 40 is deformed 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 of FIG. 5, as shown in FIG. 5A, the thermistor layer 40 has a uniform surface as a whole, but as shown in FIG. Numeral 60 is formed separately by a number of slits 64 in the vertical direction, and has a structure in which narrow portions 65 forming a strip in the vertical direction are connected at the upper and lower sides. In this case, the thermal expansion of the thermistor layer 40 and the two electrode layers 30 and 50 causes the infrared absorption layer 60
By moving and deforming the narrow portion 65, the internal stress is absorbed and alleviated.

The embodiment shown in FIG. 6 shows another example of a pattern when a film is separated and formed into a narrow width. That is, the film-shaped body S is composed of a narrow portion 5 continuously connected in a spiral form from the center to the outer periphery, and a gap portion 4 separating the portions. As the film S, the electrode layer 3 described above is used.
It can be applied to any layer such as 0, 50, thermistor layer 40, and infrared absorption layer 60.

In this embodiment, since the direction of separation of the narrow portion 5 exists in any of the upper, lower, left and right directions, there is a capability of absorbing and relaxing internal stress in any of the upper, lower, left and right directions. Next, more specific examples will be described. Example 1 An infrared detecting element having the structure shown in FIGS. 1 and 2 was manufactured.

A thermal insulating film 20 was formed on the silicon substrate 10 by laminating 5000-nm-thick silicon oxynitride by glow discharge decomposition. The film formation conditions were as follows: a mixed gas of monosilane, ammonia, nitrogen and carbon monoxide was used, the ratio of dinitrogen monoxide to the total amount of ammonia, nitrogen and carbon monoxide was 30%, the substrate temperature was 20 ° C., the pressure was 1 Torr, and the frequency was 1
The discharge power was 3.56 MHz and the discharge power was 30 W.

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

It should be noted that chromium, which is the material of the electrode layers 30 and 50, has a lower thermal conductivity and an improved detection sensitivity when an impurity is added. 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 was patterned into a 2 × 2 mm square by a photolithography process to form an infrared absorbing layer 60. The film formation conditions were as follows.
The temperature was 50 ° C., the pressure was 1 Torr, the frequency was 13.56 KHz, and the discharge power was 30 W. Subsequently, aluminum was deposited and patterned by electron beam evaporation to form connection pads 52.

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

When the infrared detecting element was used, no distortion or destruction of the thermal insulating film 20 occurred, and it was confirmed that the detection sensitivity was good and the quality 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 formed in a narrow width, the film formed in the narrow width is formed. The internal stress generated between the plurality of film-like bodies can be absorbed or reduced.

As a result, distortion and destruction of the heat insulating film can be prevented, the production yield can be improved, and the durability during use can be increased. In addition, the manufacturing process requires only changing the formation pattern of the film-like body as compared with the conventional method,
It can be manufactured relatively easily technically, without increasing the total number of steps or increasing the working time, and is excellent in productivity and inexpensive. Furthermore, if the heat insulating film is unlikely to be distorted or broken, it becomes possible to manufacture an element which is more sensitive to temperature change and has higher infrared detection sensitivity than the conventional case.

[Brief description of the drawings]

FIG. 1 shows an upper side electrode layer (a), a thermistor layer (b), and a lower side electrode layer (c) of an infrared detecting element showing an embodiment of the present invention.
Top view of each

FIG. 2 is a cross-sectional view of the infrared detecting element according to the first embodiment;

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 each of a thermistor layer (a) and an infrared absorbing layer (b) showing another embodiment.

FIG. 6 is a plan view showing a pattern of a film in another embodiment.

[Explanation of symbols]

 DESCRIPTION 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

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takuro Ishida 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. References JP-A-3-292147 (JP, A) JP-A 62-40818 (JP, U) JP-A-5-507144 (JP, A) International publication 91/16607 (WO, A1) (58) Survey Field (Int.Cl. ⁷ , DB name) G01J 1/00-1/60 G01J 5/00-5/62

Claims (3)

(57) [Claims] 1. An infrared detecting element comprising a plurality of film bodies including a pair of electrode layers and a thermistor layer sandwiched between both electrode layers on a heat insulating film, wherein at least two film bodies are provided. There, it is separated formed in the narrow
Thus, the film-like body having a plurality of layers separated and formed in a narrow width has a width corresponding to that of the narrow width portion.
An infrared detection element comprising a combination of films having different release patterns . 2. The method according to claim 1, wherein the plurality of layers include the electrode layer.
Infrared absorption that is arranged on the surface side of
The infrared detecting element according to claim 1, further comprising a layer. 3. A film-like body having a plurality of layers separated and formed in a narrow width.
Is a film-like body in which the separation pattern of the narrow part is spiral
The infrared detecting element according to claim 1, comprising: