JPH08292101A - Pyroelectric infrared sensor element and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide the pyroelectric infrared sensor element, which is very accurate, inexpensive and highly sensitive. CONSTITUTION: A Cu film 2 is formed on a sensor holding substrate 1 made of SUS. Then, an MgO film 3 of oxide having a rock-salt crystal structure oriented in 100 faces is formed by an MO plasma CVD method, and a Pt film 4 oriented in 100 faces is formed by a sputtering method, sequencially. Furthermore, a pyroelectric PLT film 5 is formed by an rf magnetron sputtering method. The PLT film is patterned into the specified size by photolithography. Then, after an etching hole 6 is formed, a polyimide resin film 7 is formed at a part, where the PLT film is removed by patterning. Etching liquid is injected through the etching hole 6, and a space part 8 is formed at a part directly below the PLT film. Finally, an Ni-Cr electrode film 9 is formed at the PLT element part, and a pyroelectric infrared sensor element 10 is manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared sensor using a pyroelectric dielectric thin film and its manufacturing method.

[0002]

2. Description of the Related Art A pyroelectric infrared sensor is a thermal infrared sensor, and is characterized by being capable of operating at room temperature and having a small wavelength dependence of sensitivity. It is a sensor. This sensor has been put to practical use by using lead lanthanum titanate (PLT), which has a large pyroelectric characteristic. In this case, it is manufactured using a PLT film crystallized in the c-axis which is the crystal axis direction showing the highest pyroelectric coefficient.

In the case of a pyroelectric infrared sensor used as a point sensor, for example, the pyroelectric infrared sensor element 30, which is the heart of the pyroelectric infrared sensor, has the structure shown in FIG. The PLT film having a thickness of about 3 μm, on which the lower extraction electrode 23 and the upper extraction electrode 24 are arranged on the surface, is held only by the polyimide resin films 22 and 32 in order to reduce both the heat capacity and the heat conduction, and the PLT film is provided in the central portion. The sensor holding substrate 27 is made of ceramic and has a space penetrating in a V shape, and the periphery of the polyimide resin films 22 and 32 is held.

In order to realize the sensor element 30 having the above structure, it has been conventionally manufactured as follows (for example, Ryoichi Takayama, "Pyroelectric infrared image sensor", National Technical Report, Vol. 39). (No. 4) (1
993), pp. 122-130). An MgO single crystal substrate 21 cleaved at the (100) plane and mirror-polished was prepared. First, the substrate 21 was heated to 600 ° C. by an rf sputtering method using a lead lanthanum titanate ceramic target. And PL with c-axis orientation
The T film 5 is formed. The first layer polyimide resin film 22 is formed by applying a polyimide resin except the upper surface of the PLT film 5. Then, the Ni-Cr lower extraction electrode 2 is formed on the surface at a predetermined position by a sputtering method.
3 is formed, and a second layer polyimide resin film 32 is formed by further applying a polyimide resin film thereon.
In this way, the MgO single crystal substrate 21 on which the multilayer film structure is formed is inverted, transferred onto a ceramic sensor holding substrate 27 having a space penetrating in a square shape in the central portion, and bonded with an adhesive 28. To do. After the bonding, the multilayer film structure formed on the MgO single crystal substrate 21 is left, and MgO on the substrate is completely removed by phosphoric acid etching. The Ni-Cr upper extraction electrode 24 is formed on the surface of the PLT film 5 newly appeared by removing MgO, and further, the connection electrodes 26 and 25 and the upper extraction electrode 24 formed on the sensor holding substrate 27 made of ceramic in advance. , The lower extraction electrode 23 is connected by using conductive pastes 29 and 31, respectively (see FIG. 6).

[0005]

However, the pyroelectric infrared sensor element described above holds the PLT film, which is a pyroelectric dielectric film, only with the polyimide resin film, and uses the square-shaped sensor holding substrate to hold the PLT film. Since the structure holds the periphery of the polyimide resin film, the lead electrode is likely to be cut due to contraction due to the difference in material properties between the polyimide resin and the PLT film or the sensor holding substrate, and the polyimide resin film that holds the PLT film. There was a problem that cracks were likely to occur in the. In addition, the manufacturing method uses an expensive MgO single crystal substrate that is cleaved at the (100) plane and mirror-polished, so that the infrared sensor element becomes expensive, and the pyroelectric dielectric film is formed in the manufacturing process. After that, for the purpose of increasing the thermal sensitivity of the film (removing thermal noise), the MgO single crystal substrate (0.
(3 to 0.5 mm thickness) needs to be carefully removed by etching, which requires a long manufacturing time. Further, in order to remove the MgO substrate, Mg on the sensor holding substrate is required.
There is a problem that the manufacturing process of inverting and adhering the O substrate together is complicated.

In order to solve the above-mentioned conventional problems, the present invention provides a pyroelectric infrared sensor element having a structure in which a polyimide resin film is not used for holding a pyroelectric dielectric film and is inexpensive, and a method for manufacturing the same. The purpose is to provide.

[0007]

In order to achieve the above object, the first pyroelectric infrared sensor element of the present invention has a metal film having a void portion disposed on a sensor holding substrate, and the void portion is provided. A (100) -oriented rock salt-type crystal structure oxide film is disposed so as to cover the Pt electrode film, and a (100) -oriented Pt electrode film is arranged on the rock-salt-type crystal structure oxide film. A pyroelectric dielectric film and an insulating dielectric film are arranged, and an electrode film is arranged on the pyroelectric dielectric film.

Next, in the second pyroelectric infrared sensor element of the present invention, a metal film having a void portion is arranged on the sensor holding substrate, and the metal film having the void portion is covered (10
0) A plane-oriented conductive NiO electrode film is arranged,
A pyroelectric dielectric film and an insulating dielectric film are arranged on the electrode film, and the electrode film is arranged on the pyroelectric dielectric film.

In the above-mentioned first and second element structures of the present invention, it is preferable that the metal film having the void portion is a Cu film.

In the first element structure of the present invention, the rock salt type crystal structure oxide film is preferably at least one film selected from MgO, NiO and CoO.

In the first and second element structures of the present invention, it is preferable that the pyroelectric dielectric film is a lead lanthanum titanate film.

In the first element structure of the present invention, ceramic or SUS is used as the sensor holding substrate.
It is preferably a substrate.

In the second element structure of the present invention, it is preferable that the sensor holding substrate is a ceramic substrate.

Next, according to the first manufacturing method of the present invention, a metal film is formed on the sensor holding substrate, and (1) is formed on the metal film.
A (00) plane-oriented rock salt type crystal structure oxide film is formed, a (100) plane oriented Pt electrode film is formed on the rock salt type crystal structure oxide film, and a pyroelectric dielectric film is formed on the Pt electrode film. After forming a body film, the pyroelectric dielectric film is patterned into a predetermined shape, an insulating dielectric film is formed in the patterning removed portion, and the insulating dielectric film is used as a masking pattern. Etching holes are sequentially formed in the film thickness direction with respect to the Pt electrode film and the rock salt type crystal structure oxide film, and an etching solution is injected through the etching holes to remove a required portion of the metal film by etching to form a void portion, Finally, a structure is provided in which an electrode film is formed on the pyroelectric dielectric film.

Next, in the second manufacturing method of the present invention, a metal film is formed on the sensor holding substrate, and (1) is formed on the metal film.
00) plane-oriented conductive NiO electrode film is formed,
After forming a pyroelectric dielectric thin film on the O electrode film, the pyroelectric dielectric film is patterned into a predetermined shape, and an insulating dielectric film is formed on the patterning removed portion. NiO as a masking pattern using a conductive dielectric film
An etching hole is formed in the film thickness direction of the electrode film, an etching solution is injected from the etching hole to remove a required portion of the metal film by etching to form a void portion, and finally, on the pyroelectric dielectric film. It has a structure of forming an electrode film.

In the above-described first and second manufacturing methods of the present invention, it is preferable that the metal in which the void portion is formed is a Cu film.

In the first manufacturing method of the present invention, MgO, NiO is used as the rock salt type crystal structure oxide film.
And at least one film selected from CoO.

In the first and second manufacturing methods of the present invention, the pyroelectric dielectric film is preferably lead lanthanum titanate.

In the first manufacturing method of the present invention, the sensor holding substrate is made of ceramic or SU.
It is preferably an S substrate.

Further, in the second manufacturing method of the present invention, the sensor holding substrate is preferably a ceramic substrate.

[0021]

According to the above-described structure of the pyroelectric infrared sensor element of the present invention, the metal film having the void portion on the sensor holding substrate and the (100) -oriented rock salt type crystal structure oxidation covering the void portion. A physical film, a Pt electrode film having a (100) plane orientation, a pyroelectric dielectric film and an insulating dielectric film on the Pt electrode film, and an electrode film on the pyroelectric dielectric film. By adopting the configuration, it is possible to realize a pyroelectric infrared sensor element which has high accuracy, is less likely to be damaged, is inexpensive, and has a simplified manufacturing process. That is, since the oxide film or the Pt film that holds the pyroelectric dielectric film is hard and the expansion coefficient is not significantly different from that of the pyroelectric dielectric film, electrode breakage and cracks in the holding film are less likely to occur. Also,
Since it is not necessary to use an expensive MgO single crystal substrate, the cost is low. Further, in the manufacturing process, the steps of reversing, transferring and removing the substrate material are eliminated and the steps are simplified.

In the above, a metal film having a void portion on the sensor holding substrate and the void portion are covered (100).
By adopting a configuration including at least a plane-oriented conductive NiO film, a pyroelectric dielectric film and an insulating dielectric film on the NiO electrode film, and an electrode film on the pyroelectric dielectric film, Further, it is possible to realize a pyroelectric infrared sensor element which has high accuracy, is less likely to be damaged, is inexpensive, and has a simplified manufacturing process.

Next, according to the constitution of the manufacturing method of the present invention,
The pyroelectric infrared sensor element can be manufactured efficiently and rationally. For example, the heat capacity and the heat conduction can be reduced by only the manufacturing process of removing a predetermined portion of the metal film of the sacrificial layer from the etching hole with an etching solution without requiring the inversion, transfer, and removal processes of the prior art substrate material. Therefore, a pyroelectric infrared sensor element that is inexpensive, has low thermal noise, and is highly sensitive can be easily realized.

[0024]

EXAMPLES The present invention will be described in more detail below with reference to examples.

(Embodiment 1) The pyroelectric infrared sensor element 10 of this embodiment has a size of 1.5 as shown in FIG.
A Cu film 2 having a void portion 8 (size of about 400 μm square, thickness of 20 μm) is arranged on a sensor holding substrate 1 having a square of 1 mm and a thickness of 1 mm, and a MgO film 3 having a thickness of 2 μm and Pt are sequentially arranged thereon. The lower electrode film 4 is arranged and 200 μm on it
PLT film 5 and polyimide resin film 7 having a corner and a thickness of 3 μm
And the electrode film 9 on the PLT film is arranged.

A method of manufacturing the pyroelectric infrared sensor element 10 configured as described above will be described. The manufacturing process is shown in FIG.

First, a Cu film 2 having a thickness of 20 μm is formed on the SUS sensor holding substrate 1 by an acidic electrolytic plating method. On the surface of the Cu film 2, a MgO film 3 (thickness 2 μm) of a rock salt type crystal structure oxide having a crystal orientation perpendicular to the surface in the <100> direction is formed by a plasma MOCVD method. This film formation is performed by using a mixed gas of magnesium acetylacetonate vapor and oxygen as a CVD source gas and heating the surface of the Cu film 2 to 400 ° C. Further, a Pt film is epitaxially grown by 0.2 μm on the surface of the MgO film 3 by a sputtering method to form a lower extraction electrode film 4 of the Pt film crystallized in the <100> direction with respect to the film surface. Further, a PLT film 5 having a c-axis crystal orientation of 3 μm in thickness is formed on the surface of the lower extraction electrode film 4 by the rf magnetron sputtering method. A resist is applied, and the PLT film is patterned to have a size of 200 μm square. Pt for lower extraction electrode after patterning removal
Etching holes 6 having a diameter of 20 μmφ are formed in the film thickness direction in the film and the MgO film. A polyimide resin film (photonice) 7 is formed on the part where the PLT film is removed by patterning except the etching hole 6 part. Ammonia etchant is injected through the etching hole to remove a part of the Cu layer 2 by etching to form the void 8 directly below the patterned PLT film. Finally, the pyroelectric infrared sensor element 10 is formed by forming the Ni-Cr film light-receiving electrode film 9 on the patterned PLT film by the sputtering method.

Instead of the MgO film 3 of rock salt type crystal structure oxide crystallized in the <100> direction,
Plasma MOC using nickel acetylacetonate or cobalt acetylacetonate as source gas
N produced by the VD method and crystallographically oriented in the <100> direction
It has been found that the same sensor element can be manufactured by using the iO film or the CoO film.

It has also been found that the same sensor element can be manufactured when a ceramic substrate such as alumina is used as the sensor holding substrate.

(Embodiment 2) The pyroelectric infrared sensor element 20 of this embodiment has a size of 1.5 as shown in FIG.
A Cu film 2 having a void portion 8 (having a size of about 400 μm square and a thickness of 20 μm) is arranged on a sensor holding substrate 1 having a square shape of 1 mm and a thickness of 1 mm, and a conductive NiO film having a thickness of 2 μm is formed thereon.
A film 13 (with Li added) is arranged, and a 200 μm square is placed on the film 13.
A PLT film 5 and a polyimide resin film 7 having a thickness of 3 μm;
The structure is such that the electrode film 9 is arranged on the PLT film.

A method of manufacturing the pyroelectric infrared sensor element 20 configured as above will be described. The manufacturing process is shown in FIG.

First, the alumina ceramic substrate is used as the sensor holding substrate 1, and the Cu film 2 having a thickness of 20 μm is formed in the same manner as in the first embodiment. In this case, since the Cu film is formed on both surfaces of the sensor holding substrate, the Cu film is removed by etching or polishing on one surface. On the surface of the Cu film 2 on the opposite surface, the direction perpendicular to the surface is <100 by the plasma MOCVD method.
Conductivity N of rock-salt type crystal structure oxide crystallized in the> direction
An iO film 13 (with Li added) (thickness 2 μm) is formed. For this film formation, a mixed gas of vapor of nickel acetylacetonate, vapor of Li dipivaloyl methane chelate and oxygen was used as the CVD source gas, and the surface of the Cu film 2 was 400
Perform by heating to ℃. Further, a PLT film 5 having a thickness of 3 μm and having a c-axis crystal orientation is formed on the surface of the conductive NiO film 13 by rf magnetron sputtering to epitaxially grow the PLT film. As in Example 1, a resist is applied and the PLT film is patterned to have a size of 200 μm square. Etching holes 6 having a diameter of 20 μmφ are formed in the film thickness direction in the Pt film for the lower extraction electrode and the MgO film that have been patterned and removed. A polyimide resin film (photonice) 7 is formed on the part where the PLT film is removed by patterning except the etching hole 6 part. Ammonia etchant is injected through the etching hole to remove a part of the Cu layer 2 by etching, and a void portion 8 is formed immediately below the patterned PLT film. Finally, N is formed on the patterned PLT film by sputtering.
The pyroelectric infrared sensor element 20 is formed by forming the light-receiving electrode film 9 of the i-Cr film.

[0033]

According to the pyroelectric infrared sensor element of the present invention, an accurate, durable, inexpensive, and highly sensitive sensor element can be easily realized. Therefore, an infrared sensor system using the same has been conventionally used. It can be manufactured at a lower price than Therefore, there is an effect that it can be used in a wider range in the field of using an infrared sensor, which is extremely effective in practical use.

According to the manufacturing method of the present invention, the pyroelectric infrared sensor element can be manufactured efficiently, rationally, and inexpensively, so that it can be used in a wider range in the field of infrared sensor utilization. It is effective and extremely effective in practical use.

[Brief description of drawings]

FIG. 1 is a partially cut external view of a pyroelectric infrared sensor element according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the pyroelectric infrared sensor element of Example 1 of the present invention.

FIG. 3 is a partially cut external view of a pyroelectric infrared sensor element according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a manufacturing process of a pyroelectric infrared sensor element according to a second embodiment of the present invention.

FIG. 5 is an external view of a part of a conventional pyroelectric infrared sensor element torn apart.

FIG. 6 is a view showing a manufacturing process of a conventional pyroelectric infrared sensor element.

[Explanation of symbols]

 1 Sensor Holding Substrate 2 Cu Film 3 MgO Film 4 Pt Lower Extraction Electrode Film 5 PLT Film 6 Etching Hole 7 Polyimide Resin Film (Photo Nice) 8 Void Area 9 Electrode Film 10 Pyroelectric Infrared Sensor Element 13 Conductive NiO Film 20 Focus Electric infrared sensor element 21 MgO single crystal substrate 22 First layer polyimide resin film 23 Ni-Cr lower extraction electrode 24 Ni-Cr upper extraction electrode 25 Connection electrode 26 Connection electrode 27 Ceramic sensor holding substrate 28 Adhesive 29 Conductive paste 30 Pyroelectric infrared sensor element 31 Conductive paste 32 Second layer polyimide resin film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryoichi Takayama 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (14)

[Claims] 1. A metal film having a void portion is arranged on a sensor holding substrate so as to cover the void portion (100).
A plane-oriented rock salt type crystal structure oxide film is arranged, a (100) plane oriented Pt electrode film is arranged on the rock salt type crystal structure oxide film, and a pyroelectric dielectric film and a Pt electrode film are arranged on the Pt electrode film. A pyroelectric infrared sensor element in which an insulating dielectric film is arranged and an electrode film is arranged on the pyroelectric dielectric film. 2. A metal film having a void portion is arranged on a sensor holding substrate, and the void portion is covered (100).
A plane-oriented conductive NiO electrode film is arranged, and a pyroelectric dielectric film and an insulating dielectric film are arranged on the NiO electrode film,
A pyroelectric infrared sensor element having an electrode film disposed on the pyroelectric dielectric film. 3. The pyroelectric infrared sensor element according to claim 1, wherein the metal film having voids is a Cu film. 4. A rock salt type crystal structure oxide film comprising MgO, Ni
The pyroelectric infrared sensor element according to claim 1, which is at least one film selected from O and CoO. 5. A pyroelectric dielectric film comprising lead lanthanum titanate (P
The pyroelectric infrared sensor element according to claim 1, which is an LT) film. 6. The pyroelectric infrared sensor element according to claim 1, wherein the sensor holding substrate is a ceramic or SUS substrate. 7. The pyroelectric infrared sensor element according to claim 2, wherein the sensor holding substrate is a ceramic substrate. 8. A metal film is formed on the sensor holding substrate,
A (100) -oriented rock salt-type crystal structure oxide film is formed on the metal film, and (10) is formed on the rock-salt crystal structure oxide film.
0) A Pt electrode film having a plane orientation is formed, and a pyroelectric dielectric film is formed on the Pt electrode film, and then the pyroelectric dielectric film is patterned into a predetermined shape, and the Pt electrode film is patterned. Etching holes are sequentially formed in the film thickness direction in the Pt electrode film and the rock salt type crystal structure oxide film in the vicinity of the pyroelectric dielectric film element shape, and an insulating dielectric film is formed on the surface removed by the patterning. Pyroelectric consisting of forming an electrode film on the pyroelectric dielectric film by forming an air gap by injecting an etching solution from the etching hole and etching away a predetermined region of the metal film. Method for manufacturing infrared sensor element. 9. A metal film is formed on the sensor holding substrate,
A (100) plane-oriented conductive NiO electrode film is formed on the metal film, a pyroelectric dielectric film is formed on the NiO electrode film, and then the pyroelectric dielectric film is patterned into a predetermined shape. Forming an etching hole in the film thickness direction of the NiO electrode film in the vicinity of the patterned pyroelectric dielectric film element shape, and forming an insulating dielectric film on the patterning-removed partial surface. A pyroelectric infrared comprising: injecting an etching solution from the etching hole to etch and remove a predetermined region of the metal film to form a void portion, and finally to form an electrode film on the pyroelectric dielectric film. Manufacturing method of sensor element. 10. The method for manufacturing a pyroelectric infrared sensor element according to claim 8, wherein the metal film in which the void portion is formed is a Cu film. 11. A rock salt type crystal structure oxide film comprising MgO, Ni
The method for manufacturing a pyroelectric infrared sensor element according to claim 8, which is at least one film selected from O and CoO. 12. The method for manufacturing a pyroelectric infrared sensor element according to claim 8, wherein the pyroelectric dielectric film is a lead lanthanum titanate (PLT) film. 13. The method for manufacturing a pyroelectric infrared sensor element according to claim 8, wherein a ceramic or SUS substrate is used as the sensor holding substrate. 14. The method for manufacturing a pyroelectric infrared sensor element according to claim 9, wherein a ceramic substrate is used as the sensor holding substrate.