JP2002198574A - Thermopile infrared rays detecting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem wherein affinity of adhesion between an insulating film and thermopile materials are inferior generally, peeling is apt to be generated in work of lift-off or the like in a thermopile forming process, the peeling becomes the cause of deterioration of yield, in the case that the insulating film is formed on a semiconductor substrate and two different kinds of the thermopile materials are formed on the insulating film, usually, when a thermopile infrared rays detecting element on the semiconductor substrate is formed. SOLUTION: In this thermopile infrared rays detecting element, thermopile is formed by interposing the substrate and an insulating adhesive layer formed on the substrate. The insulating adhesive layer is constituted of laminate of an insulating thin film and a substrate metal thin film formed on the insulating thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric infrared detector for detecting infrared rays.

[0002]

2. Description of the Related Art Conventionally, as one method of forming a thermoelectric deposit on a semiconductor substrate such as silicon, there is a method shown in FIG. The semiconductor substrate 41 is shown in FIG. After forming an insulating thin film 42 on the semiconductor substrate 41 (FIG. 4)
(B)) Two kinds of different material thin films to be a thermopile are patterned and formed on the insulating thin film.
As shown in (C), the first thermoelectric material 43 is formed into a thin film by a vacuum film forming technique such as evaporation and sputtering. On this occasion,
A pattern to be formed is formed in advance with a negative resist so that the pattern can be formed by the lift-off method. Next, a pattern is formed with a negative resist according to the pattern of the second thermoelectric deposit, and a second thermoelectric deposit material is formed by the vacuum film forming technique. After that, the second thermoelectric material thin film 44 is also patterned by the lift-off method as shown in FIG. Finally, a part of the semiconductor substrate is etched with an alkaline solution, thinned or completely removed to remove the insulating thin film into a thin diaphragm (to be a hot junction).
When the rim 46 left without being etched with an alkaline solution is used as a cold junction, the junction of the two types of material thin films serving as thermocouples is disposed at both ends on the hot junction and the cold junction, respectively. The thermoelectric bank type infrared detecting element configured as described above is obtained. This is shown in FIG.

In this case, as the insulating thin film formed on the silicon semiconductor substrate, silicon nitride, silicon oxide, or a two-layer thin film of silicon nitride and silicon oxide is usually used, and is formed by a chemical vapor deposition method (CVD). In many cases, the film is formed by a physical vapor deposition method (PVD) such as sputtering. When the two types of material thin films constituting the thermoelectric deposit are formed on the insulating thin film, the thermoelectric deposit is formed by PVD such as vapor deposition or sputtering, and the pattern of the thermoelectric deposit is formed by a lift-off method in a photolithography process. However, these insulating thin films and the two types of material thin films constituting the thermoelectric deposit generally have poor adhesion, and in order to enhance the adhesion, the thin films are formed while heating the substrate in a vacuum chamber. ing.

As another method for improving the adhesion, as shown in Japanese Utility Model Application Laid-Open No. 4-96870, the tips of the first thermocouple material thin film pattern and the second thermocouple material thin film pattern constituting the thermopile are connected to each other. Connected in series on the intermediate metal thin film pattern previously arranged on the insulating thin film, further arrange the intermediate metal thin film pattern on the tip of each thermocouple material thin film pattern again, only the hot junction and cold junction There is also a method of maintaining the adhesion with the method.

[0005]

SUMMARY OF THE INVENTION
A material of a type is formed in a vacuum chamber on the insulating thin film on which the resist is patterned. At this time, although the semiconductor substrate itself is heated by a heater or the like to improve adhesion, Since the heat resistance of the resist is limited, the heating temperature is also limited. Therefore, sufficient adhesion may not be obtained depending on changes in various factors such as the surface cleanliness of the insulating thin film, the types of the two metals constituting the thermoelectric deposit, the film formation rate, the degree of vacuum, and the heating temperature. Yes, which constitutes a thermopile to be adhered and remain on the insulating thin film during lift-off.
Either one or both of the types of material may peel off.

[0006] In the method in which the tip of each thermocouple material of Japanese Utility Model Application Laid-Open No. 4-96870 is sandwiched from above and below and is brought into close contact with the insulating thin film, there is a possibility that the adhesion at the connection portion can be obtained.
In the middle part of the pattern of each thermocouple material, the adhesion is weak, and the pattern may float and peel off.

Unless these peeling phenomena are solved, production of a thermoelectric pile type infrared detecting element having a high yield cannot be expected.

An object of the present invention is to prevent separation of the two types of materials constituting a thermocouple during pattern formation, which is a conventional disadvantage.

[0009]

Means for Solving the Problems In order to solve the above problems, the present invention employs a thermoelectric type infrared detecting element having the following structure.

A thermoelectric deposit type infrared detecting element in which a thermoelectric deposit is formed via a substrate and an insulating adhesive layer formed on the substrate, wherein the insulating adhesive layer comprises an insulating thin film and the insulating thin film. A thermoelectric bank type infrared detecting element, which is formed by laminating a base metal thin film formed thereon.

According to the present invention, two different types of material thin films constituting the thermoelectric deposit adhere to the base metal thin film constituting the insulating adhesion layer, and the base metal thin film is provided on the substrate. Because it is in close contact with the
The material thin films of the types do not peel at all even during lift-off of pattern formation. Materials such as antimony, bismuth, and tellurium, which are thermoelectric material, have low adhesion to silicon nitride and silicon oxide, which are generally used as insulating thin films, and have poor compatibility. This is because adhesion to metal materials such as gold and gold becomes very strong.

Next, the underlying metal thin film which the insulating adhesive layer comprises is not continuous but is intermittently patterned.
The thermoelectric deposit type infrared detecting element is characterized in that a rim serving as a cold junction and the underlying metal thin film on a diaphragm serving as a hot junction are discontinuous.

According to the present invention, the underlying metal thin film constituting the insulating adhesion layer is patterned discontinuously.
The amount of heat at the hot junction, whose temperature has been increased by receiving infrared rays, does not escape to the cold junction through the base metal thin film. Therefore, the temperature difference between the hot junction and the cold junction is maintained, and a decrease in sensitivity cannot occur. That is, the material thin film constituting the thermoelectric bank does not peel off, and the heat of the hot junction does not escape to the cold junction.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A thermoelectric deposit type infrared detecting element in which a thermoelectric deposit is formed via a substrate and an insulating adhesive layer formed on the substrate, wherein the insulating adhesive layer comprises an insulating thin film and the insulating thin film A thermoelectric deposit type infrared detecting element characterized in that the thermoelectric deposit type infrared detecting element is constituted by a laminated structure of a base metal thin film formed on an insulating thin film. In particular, according to the present invention, since the insulating adhesive layer has a laminated structure of an insulating thin film and a base metal thin film,
In manufacturing, even in severe processes such as lift-off in the process of formation, it is possible to configure a thermoelectric bank without peeling from the insulating adhesive layer which is the base, and the yield is greatly improved. The effect can be achieved.

[0015]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to FIG. As shown in FIG. 1A, first, there is a silicon semiconductor substrate 11 having a thickness of 200 μm. If the plane orientation to the orientation flat is (100),
Since the anisotropic etching can be performed in the last step of etching the silicon substrate shown in FIG. 1F, a cross section is formed at an inclination of about 54 ° along the <111> plane of the close-packed surface. can do. The plane orientation is (110)
In this case, since isotropic etching is performed, a cross section perpendicular to the plane of the substrate can be obtained. Here, an example in which a (110) plane silicon substrate is employed will be described.

Next, in order to form an insulating adhesive layer, silicon nitride is formed as a thin insulating film 12 on the silicon substrate to a thickness of 2 μm by plasma CVD (FIG. 1).
(B)). Here, since silicon nitride has higher selectivity to an alkaline etching solution than silicon oxide, silicon nitride is used in the last step of silicon substrate etching shown in FIG. Even when the silicon nitride thin film and the alkaline etchant are in direct contact with each other, the etching rate of silicon nitride is 100 times slower than the etching rate of silicon, and the silicon nitride remains sufficiently even if the etching time is slightly longer. Therefore, the film thickness of silicon nitride is hardly affected by the etching time, and the original thickness remains.

On the silicon nitride thin film, FIG.
As shown in (C), a base metal thin film 17 serving as an adhesion layer is formed. Before that, a resist pattern for patterning the base metal and the first thermoelectric material 13 to be applied first is formed. Must. A reverse heat taper pattern suitable for lift-off of the underlying metal thin film 17 and the first thermoelectric material 13 to be applied first is formed using a high heat-resistant negative resist for lift-off.

Then, chromium or titanium is deposited as the underlying metal thin film 17 by 100 to 500 ° by resistance heating evaporation or electron beam gun evaporation. If the next thermoelectric material cannot be formed in-line with the same vacuum apparatus as in-line, it is better to deposit gold on chromium or titanium in a thickness of 100 to 500 ° to prevent oxidation of chromium or titanium.

After the formation of chromium or titanium, the first
Of antimony as a thermoelectric material 13 is formed by resistance heating evaporation. The film thickness is 1-5 μm, and the substrate heating temperature is 100-
Set to 150 ° C. Thereafter, the negative resist is stripped with a resist stripper, and when lift-off is completed, the chromium or titanium thin film as a patterned base metal and the antimony thin film as a first thermoelectric material are the silicon nitride films as insulating thin films. (FIG. 1D). Usually, when chromium or titanium does not exist as a base metal at the time of this lift-off, the pattern of antimony often peels off from silicon nitride, and the yield is extremely deteriorated.

The patterning of the second thermoelectric material 14 is performed in a similar process. Pattern formation of a negative resist for lift-off, vapor deposition of chromium or titanium, and bismuth as a second thermoelectric material 14 formed by resistance heating vapor deposition (film thickness: 1 to 5 μm, substrate heating temperature: 100 to 150 ° C.) After peeling, a bismuth pattern is formed (FIG. 1).
(E)). Bismuth is easy to peel off from silicon nitride like antimony. However, if there is a chromium or titanium base, it does not peel off during lift-off.

Finally, the silicon is etched from the back surface of the silicon semiconductor substrate 11 on which the thermoelectric material is not attached by potassium hydroxide (3.
0 wt%). The surface with thermopile material is covered with a Teflon-based jig to prevent the thermopile material from being attacked by potassium hydroxide. Etching is completed when silicon is sufficiently etched and silicon nitride is exposed from the back surface. At this time, a portion where silicon is etched to form a thin diaphragm of the silicon nitride film becomes a hot junction 15 that is easily heated, and a portion of the rim left by etching becomes a cold junction 16 that is hardly heated. Figure 1
It is shown in (F).

As described above, the improvement of the adhesion between antimony and bismuth due to the presence of chromium or titanium, which is the material of the base metal thin film constituting the insulating adhesion layer, requires a lift-off in manufacturing. Not only does it not peel off even after a series of steps including peeling, but also peels off even if it is peeled off using a cellophane adhesive tape specified in Japanese Industrial Standards for adhesion test method JIS H8504. Since it was not possible, the effect of the adhesion could be easily confirmed.

Embodiment 2 Hereinafter, a second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 2A, first, there is a silicon semiconductor substrate 21 having a thickness of 200 μm. Here, as in the first embodiment, an example in which a silicon substrate having a (110) plane orientation with respect to the orientation flat will be described.

Next, in order to form an insulating adhesive layer, silicon nitride is formed as an insulating thin film 22 on the silicon substrate to a thickness of 2 μm by plasma CVD (FIG. 2).
(B)). The reason for selecting silicon nitride is according to the first embodiment.

On the silicon nitride thin film, FIG.
As shown in (C), a base metal thin film 27 to be an adhesion layer is formed. Chromium or titanium as base metal
After vapor deposition or sputtering with a thickness of 00 to 500 °, gold is deposited by vapor deposition or sputtering with a thickness of 100 to 500 °. After the underlayer metal is formed, it must be once exposed to the atmosphere. Therefore, it is better to form gold on the chromium or titanium thin film so as not to oxidize the thin film.

Next, the chromium or titanium thin film as the base metal is patterned. Example 1 of pattern outline
However, the pattern is divided so as not to be continuous from the hot junction to the cold junction, and is arranged intermittently. This is shown in FIG. First, the positive resist is patterned so that the surface of the chromium or titanium thin film to be etched is exposed. Then, gold is sufficiently etched and removed with aqua regia. Further, chromium is sufficiently etched and removed with a mixed solution of cerium ammonium nitrate and perchloric acid. After that, it is sufficiently washed with a rinse solution and pure water.

While the underlying metal of chromium or titanium is still on the silicon nitride, a negative resist is patterned with a first thermoelectric deposition mask pattern, and antimony, which is a first thermoelectric deposition material, is subjected to resistance heating evaporation to a thickness of 1 to 5 μm. Is formed with a thickness of Thereafter, when the resist is removed by a lift-off method, an antimony pattern as shown in FIG. 2E is formed.

In this state, the negative resist is patterned with a mask pattern of a second thermoelectric deposit base metal which is substantially the same as the second thermoelectric deposit pattern but does not overlap with the antimony pattern of the first thermoelectric deposit at the joint. Then, chromium or titanium as a base metal is formed in a thickness of 100 to 500 ° by vapor deposition or sputtering. In the same intermittent pattern as the base metal of the first thermoelectric bank, the center part of the diaphragm serving as the hot junction and the rim serving as the cold junction are separated. Further, as in the case of the first embodiment, 100 to 500
When a film is formed by vapor deposition or sputtering with a thickness of 、 and lift-off is performed, a base metal pattern for the second thermoelectric deposit is formed, and a negative resist is patterned thereon with the second thermoelectric deposit mask pattern. Finally, as a second thermoelectric bank, bismuth 24 is deposited to a thickness of 1 to 5 μm by resistance heating evaporation, and lift-off completes a thermoelectric bank that is in close contact with the intermittent base metal. This cross section is shown in FIG.

As in the first embodiment, the silicon is etched with potassium hydroxide (30 wt%) as an alkaline etching solution from the back surface of the silicon semiconductor substrate 21 on which the thermoelectric material is not attached. The surface with thermopile material is covered with a Teflon-based jig to prevent the thermopile material from being attacked by potassium hydroxide. Etching is completed when silicon is sufficiently etched and silicon nitride is exposed from the back surface. At this time, a portion where silicon is etched to form a thin diaphragm of the silicon nitride film becomes a hot junction 25 that is easily heated, and a portion of the rim left by etching becomes a cold junction 26 that is hardly heated.
This is shown in FIG.

FIG. 3 is an enlarged view of the element in which the thermoelectric pile in the right half of FIG. 2 (G) has been removed so that the pattern of the underlying metal thin film can be seen. Reference numeral 31 denotes a pattern of a chromium or titanium thin film serving as a base metal of antimony of the first thermoelectric material.
Reference numeral 32 denotes a pattern of a chromium or titanium thin film serving as a base metal of bismuth of the second thermoelectric material. The outer frame 33 is a rim portion to be a cold junction. An aa ′ cross-sectional view is also shown below.

The chromium or titanium thin film, which is the base metal of the present invention, is designed discontinuously from the hot junction to the cold junction, so that the infrared heat absorbed and heated by the hot junction is released to the cold junction. There is no. Also, even if the underlying metal thin film is intermittent, the thermoelectric thin film does not peel off even after a series of steps including lift-off, and also has a Japanese Industrial Standard plating adhesion test method JIS H8504.
Even when a peeling test using a cellophane pressure-sensitive adhesive tape specified in (1) was carried out, there was no peeling, so that it could be easily confirmed.

[0032]

Conventionally, thermomonitor materials such as antimony and bismuth, which have poor adhesion with the silicon nitride or silicon oxide film as the insulating thin film constituting the insulating adhesion layer, form a pattern in manufacturing. It was very common to peel off during several lift-off steps. However, according to the present invention, antimony and bismuth of the thermoelectric deposit material, with the interposition of the chromium or titanium thin film of the underlying metal, the adhesion is greatly improved, without peeling even after several lift-offs. Even if a peeling test using a cellophane adhesive tape specified in Japanese Industrial Standards plating adhesion test method JIS H 8504 is carried out, there is no peeling. Therefore, according to the present invention, it is possible to construct a thermopile with good adhesion, and it is possible to secure a very high yield, so that a special effect can be obtained.

Further, according to the present invention, the thermoelectric material such as antimony and bismuth having poor adhesion with the silicon nitride or silicon oxide film as the insulating thin film constituting the insulating adhesion layer is used as the base metal thin film. By obtaining the interposition of a chromium or titanium thin film, the adhesion is greatly improved, and it does not peel off during several lift-offs in the process of forming a pattern.
Even if a peeling test using a cellophane adhesive tape specified in H8504 is not performed, the product does not peel off, so that it is possible to supply a stable quality product.

Further, as described above, in addition to the extremely high production yield, the chromium or titanium thin film as the base metal thin film has a discontinuous pattern that does not directly connect the hot junction and the cold junction. When detecting infrared light, it absorbs infrared light and does not allow the heat of the heated hot junction to escape to the cold junction, so it is possible to provide an infrared detecting element with highly efficient and stable electrical performance Becomes

[Brief description of the drawings]

FIG. 1 is an embodiment of a step of disposing a base metal thin film between an insulating thin film and a thermoelectric thin film of the present invention.

FIG. 2 is an embodiment of the process of the present invention in which a discontinuous underlying metal thin film is arranged between an insulating thin film and a thermoelectric thin film.

FIG. 3 is an example of the discontinuous underlying metal thin film of the present invention viewed from the thermopile side without the thermopile material.

FIG. 4 shows an example of a process for forming a thermoelectric bank directly on an insulating thin film using a conventional thermoelectric bank type infrared detecting element.

[Explanation of symbols]

 Reference Signs List 11 semiconductor substrate 12 insulating thin film 13 base metal thin film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshiro Nakamoto 840 Takeno, Shimotomi, Tokorozawa-shi, Saitama F-Term in Technical Research Institute, Citizen Watch Co., Ltd. 2G065 BA11 DA20 2G066 BA08 BA55 4M118 AA10 AB10 BA06 CA14 CA35 EA01 GA10

Claims (3)

[Claims] 1. A thermoelectric bank type infrared detecting element in which a thermoelectric bank is formed via a substrate and an insulating adhesive layer formed on the substrate, wherein the insulating adhesive layer comprises an insulating thin film and a base metal. A thermoelectric bank type infrared detecting element comprising thin films laminated. 2. The method according to claim 1, wherein the base metal thin film is intermittently patterned, and the rim serving as a cold junction and the base metal thin film on a diaphragm serving as a hot junction are formed discontinuously. The thermoelectric bank type infrared detecting element according to claim 1. 3. The thermoelectric infrared detector according to claim 1, wherein the substrate is a semiconductor substrate.