JP3287104B2 - Pyroelectric material, method of manufacturing pyroelectric light-receiving element using the same, and infrared sensor using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric material, a method for producing a pyroelectric light-receiving element using the same, and an infrared sensor using the same.

[0002]

2. Description of the Related Art In recent years, pyroelectric infrared sensors have been used as human detection sensors for automatic doors, automatic flushing equipment for toilets, lighting equipment, air conditioning equipment, security equipment, and the like. A pyroelectric material having pyroelectric properties is used for the light receiving element for use. The performance of the photodetector for pyroelectricity is required to be as thin as possible in order to obtain high sensitivity, in addition to the inherent characteristics of the pyroelectric material, such as the pyroelectric coefficient, heat capacity, and tan δ. There is a need for a pyroelectric material that does not crack or chip during the thinning of the pyroelectric light-receiving element and has stable mechanical strength in a thin plate state. Furthermore, from the viewpoint of mass productivity, a pyroelectric material having a low polarization voltage and a low sintering temperature is required.

As a material satisfying these required characteristics, Pb
TiO_Three Pyroelectric materials have been developed. However
This pyroelectric material has poor sinterability, and a large sintered body is obtained.
And it requires high temperature and high voltage for polarization,
Furthermore, there was a problem that the product yield was low. There
In order to solve these problems, PbTiO
_Three Pyroelectric material with sintering properties and relaxation of polarization conditions
And PbTiO_Three -Pb (Co_1/2 W_1/2 ) O_Three Special
It is disclosed in Japanese Patent Publication No. 58-41790.

Further, a method of manufacturing a thin plate for a pyroelectric light receiving element is as follows.
The pyroelectric material is fired at 1200 ° C. to 1250 ° C. for 6 hours to obtain a block having a thickness of 10 mm and a length and width of 50 mm.
The pyroelectric material in the form of a block was cut into a thickness of 500 μm, coated with an Ag paste on both sides, baked at 700 ° C., and subjected to a polarization treatment in silicon oil at 4 KV / mm for 10 minutes. Thereafter, it is cut into a predetermined pyroelectric size. Thereafter, this element is polished on both sides with a plane polisher to obtain a thin plate for a pyroelectric light-receiving element of 60 μm. Next, light-receiving electrodes are formed on both surfaces of the thin plate for the pyroelectric light-receiving element to form a pyroelectric light-receiving element.

Further, recent infrared sensors are manufactured using these pyroelectric materials or using a pyroelectric light-receiving element obtained by the above-described method for manufacturing a pyroelectric light-receiving element.

[0006]

However, in the above-mentioned conventional structure, the pyroelectric material is easy to sinter and easily polarized, but on the other hand, it is liable to be cracked or chipped at the time of processing a thin plate, and is stable in a thin plate state. It has been found that there is a problem that the obtained mechanical strength cannot be realized. For this reason, it is extremely difficult to reduce the thickness of the pyroelectric light-receiving element, requiring a large number of work steps,
There was a problem that the productivity was low, the workability was poor, and the product yield was low. In addition, there is a problem that it is difficult to obtain a high-sensitivity pyroelectric light-receiving element because the thickness cannot be reduced.

[0007] The method of manufacturing the photodetector for pyroelectricity requires many working steps, requires much time for polishing work, and lacks workability and productivity. However, since the electrical characteristics and sensitivity of the infrared sensor are unstable, it is difficult to obtain a high-quality infrared sensor. Cracking and chipping during thin plate processing,
In addition, there is a problem that the reliability of the pyroelectric light receiving element is reduced due to the occurrence of microcracks on the element surface and the product yield is poor.

Further, since the pyroelectric material block is fired, the evaporation and diffusion of the Pb component, which is the main raw material, in the block are different, so that a stable and dense fired block cannot be obtained. .

Further, since the infrared sensor uses the above-described pyroelectric material or uses the pyroelectric light-receiving element obtained by the above-described manufacturing method, the sensitivity is low, the reliability is low, and the durability is low. There was a problem of lacking.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a high-quality pyroelectric light-receiving element which is less likely to be cracked or chipped at the time of processing a thin plate while maintaining easy polarization conditions. It is possible to provide a pyroelectric material capable of cracking or chipping when processing the pyroelectric material into a thin plate, and to prevent deterioration in the reliability of the element due to microcracks on the surface of the light-receiving element for pyroelectricity with high quality. To provide a method for manufacturing a pyroelectric light-receiving element capable of manufacturing a high-sensitivity pyroelectric light-receiving element with high productivity and a high yield, and have excellent electrical characteristics stability and excellent durability and reliability. An object of the present invention is to provide an infrared sensor having high sensitivity and excellent productivity.

[0011]

To achieve this object, the present invention comprises the following arrangement.

[0012] pyroelectric material according to claim 1, in the general formula _{Pb x [Ti y (Co z} W 1-z) 1-y] 1-x O n ( where, n is an arbitrary number) Where x, y, and z are 0.502 ≦ x ≦
0.510, 0.80 ≦ y ≦ 0.97, 0.46 ≦ z ≦
0.49, and a part of Pb atoms is Ca
The main component is 20 to 30 mol% substituted by atoms, and MnO ₂ is added as an auxiliary component in an amount of 3% by weight or less.
And has an average particle size of 5 μm or less .

[0013]

According to a second aspect of the present invention, there is provided a method for manufacturing a pyroelectric light-receiving element, wherein the pyroelectric material according to the first aspect has a thickness of 5 μm to 100 μm by a slip casting method or an extrusion molding method.
m at a firing temperature of 1050 ° C. to 1200 ° C.
And a firing step of firing for 10 to 120 minutes.

According to a third aspect of the present invention, there is provided a method for manufacturing a pyroelectric light-receiving element according to the second aspect , wherein the firing step of the thin plate is performed on a platinum plate or a ceramic plate having a platinum layer laminated on the surface. are doing.

According to a fourth aspect of the present invention, in the method for manufacturing a pyroelectric light-receiving element according to any one of the second to third aspects, light-receiving electrodes are formed on both surfaces of the thin plate fired in the firing step. A configuration having a polarization step of performing polarization via an electrode is provided.

[0017] The infrared sensor according to claim 5 or 6 ,
When the pyroelectric material according to claim 1 is processed into a thin plate,
A pyroelectric light-receiving element manufactured by processing and firing the thin plate , or a pyroelectric light-emitting element manufactured by the method for manufacturing a pyroelectric light-receiving element according to any one of claims 2 to 4. It has a configuration provided with a light receiving element.

Here, x <0.501, y <0.79,
When the composition is z> 0.50, the sinterability is deteriorated, the mechanical properties are inferior, and the thinning process is difficult. Therefore, high sensitivity cannot be obtained as an infrared sensor, which is not preferable. With a composition of z <0.45, y> 0.98, thinning processing is possible, but it is not preferable because high sensitivity as an infrared sensor cannot be obtained due to lack of pyroelectric characteristics. x
A composition of> 0.511 is not preferable because it promotes crystal grain growth and deteriorates sinterability and requires a high sintering temperature. The optimum value of the polarization voltage and the Curie temperature can be given within the range of 20 to 30 mol% for the substitution amount of Ca atoms, and the sensitivity can be improved by adding MnO ₂ at 3 wt% or less.

If the substitution amount of Ca atoms is less than 20 mol%, it tends to be difficult to suppress the crystal grain growth.
As the content exceeds 0 mol%, crystal grain growth is promoted, and sinterability tends to deteriorate. M
If nO ₂ is added in an amount exceeding 3% by weight, crystal grain growth is promoted and sinterability tends to deteriorate, which is not preferable.

Pyroelectric materials can generally be easily manufactured by powder metallurgical methods. For example, PbTiO ₃ , PbO, TiO ₂ , CoO, W
O ₃ , CaCO ₃ , CaO, MnO _2, etc. are accurately weighed at a predetermined ratio, and these are well pulverized and mixed by a ball mill or the like. If it exceeds 5 μm, the sinterability tends to decrease, and the firing density decreases, which is not preferable. still,
At this time, the raw material used may be a compound that is converted into an oxide by heating, such as a hydroxide, a carbonate, or an oxalate.

Next, the mixture is mixed with, for example, 600 to 90
It is obtained by calcining at a temperature of about 0 ° C. and further pulverizing by a ball mill or the like to obtain a prepared powder. In this firing, since there is a possibility that a part of PbO as one composition may evaporate and evaporate, the firing is preferably performed in a closed furnace. Further, the holding at the maximum temperature of 1050 to 1200 ° C is 10 to 12
About 0 minutes is enough. Further, it is preferable that the average particle diameter of the prepared powder of the pyroelectric material is pulverized to 5 μm or less.

The pyroelectric light-receiving element is manufactured by forming the above-mentioned pyroelectric material into a thin plate having a thickness of 5 μm to 100 μm by a known slip casting method or extrusion molding method, and forming the thin plate with platinum or a platinum layer. On the ceramic plate on which the surface is formed, baking is performed at 1050 ° C. to 1200 ° C. for 10 minutes to 120 minutes. Next, a light-receiving electrode is formed on both surfaces of the obtained thin plate by a known method such as a sputtering method, and this electrode is polarized to obtain a pyroelectric light-receiving element. The thickness of the thin plate of the pyroelectric material is desirably 5 μm to 100 μm. 5 μm thick
If it is less than 3, the mechanical strength of the pyroelectric light-receiving element tends to be low, which is not preferable. Also, if the thickness is 1
If it exceeds 00 μm, the sensitivity as a pyroelectric light-receiving element as an infrared sensor tends to be deteriorated, which is not preferable.

The thin plate of the pyroelectric material is formed at a temperature of 1050 ° C. on a platinum plate or a ceramic plate having a surface layer formed of platinum.
Firing at 1200 ° C. for 10 minutes to 120 minutes is desirable. In the case of other metal plates, at a high temperature of 1000 ° C. or more, the metal plate is easily melted and the surface layer is degraded, and Pb tends to react with the ceramic layer in a single ceramic plate, which is not preferable. The firing temperature is desirably 1050 ° C to 1200 ° C. At temperatures below 1050 ° C., no sintering occurs and 12
When the temperature exceeds 00 ° C., the crystal grain growth is promoted and the sinterability tends to be deteriorated. When the thickness of the platinum layer of the ceramic plate on which the platinum layer is laminated is less than 5 μm, it is easily affected by the surface roughness of the ceramic plate.
When the thickness exceeds μm, it is difficult to form a smooth and less undulating surface layer, and any of them is not preferable.

[0024]

With this configuration, 0.502 ≦ x ≦ 0.51
0, 0.80 ≦ y ≦ 0.97, 0.46 ≦ z ≦ 0.49
Pb that satisfies the condition_x [Ti_y (Co_z W_1-z )_1-y ]
_1-x O_n (Where n is an arbitrary number) is the pyroelectric material.
Thus, high pyroelectric characteristics can be obtained. Also, P
20 to 30 mol% of b atoms were partially replaced by Ca atoms
So that a suitable Curie temperature can be obtained.
The polarization voltage can be significantly reduced. Also, MnO
_Two Was added to the system, improving sinterability and improving sensitivity.
Thickness and improve mechanical properties
Easy thinning of 5-100 μm
You. 3000V /
It is possible to obtain a pyroelectric light-receiving element having a high sensitivity of W or more.

In the thinning of the pyroelectric material, a slip casting method or an extrusion molding method is used, so that the thinning with excellent thickness accuracy can be performed with a small number of work steps. Since the thickness of the thin plate is thin, the firing temperature can be lowered and the firing time can be shortened, so that productivity can be increased and energy saving can be achieved. The infrared sensor uses an extremely thin and high-sensitivity pyroelectric light-receiving element, so that the reliability can be improved with high sensitivity.

By using an adjustment powder having an average particle diameter of 5 μm or less, the sintering reaction proceeds, the firing temperature can be reduced, the firing time can be shortened, and the mechanical strength of the pyroelectric material can be reduced. Large thin plates can be manufactured.

Since the pyroelectric thin plate is fired on a platinum plate or a ceramic plate having a surface layer formed of platinum, it does not react and fuse with the thin plate and can be fired in a flat state.
Product yield is higher.

By forming light receiving electrodes on both surfaces of the thin plate and performing polarization through these electrodes, it is possible to perform polarization processing at a low voltage and reduce the number of working steps.

[0029]

An embodiment of the present invention will be described below with reference to the drawings.

(Example 1) As raw materials, chemically pure PbTiO ₃ , TiO ₂ , CoO, WO ₃ , CaCO _3
3 , MnO ₂ is prepared and the general formula Pb _x [Ti _y (CO _z
W _1-z) in _{1-y] 1- x O n} , x, y, z are x =
Each material was prepared such that 0.505, y = 0.80, z = 0.46, the substitution amount of Ca atoms for Pb atoms was 24 mol%, and the addition amount of Mno ₂ was 1 wt%. Using a ball mill, wet mixing was performed to obtain a mixture.

The mixture was dried and calcined at 800 ° C. for 2 hours. Next, various binders, desensitizing agents, and solvents are added to the calcined product and kneaded to obtain a viscosity of 10 ps to 30 p.
s slurry was prepared. The average particle size of the raw material powder of this slurry was 3.5 μm. Next, the slurry was subjected to a conventional slip casting method to a thickness of 50 μm ± 1.
A green sheet of μm was obtained. The green sheet was cut into a predetermined size, deinterposed at 450 ° C. for 120 minutes, and then fired on a platinum plate at a firing temperature of 1100 ° C. for 60 minutes to produce a pyroelectric element having a thickness of 40 μm ± 1 μm.

Further, a nichrome electrode having a thickness of 0.2 μm and a diameter of 2 mm was formed on both surfaces of the pyroelectric element by using a sputtering device.
To form an electrode. Then, through this electrode, in silicon oil under the conditions of 4 KV / mm, 10
A polarization treatment was performed for a minute to produce a pyroelectric light-receiving element.

Next, an infrared sensor as shown in FIGS. 1 and 2 was manufactured using the obtained pyroelectric light-receiving element.

FIG. 1 is a circuit diagram of an infrared sensor according to a first embodiment of the present invention, and FIG. 2 is a sectional view of a main part of the infrared sensor according to the first embodiment of the present invention. In the figure,
1 is a pyroelectric light receiving element, 2 is a resistor, 3 is a field effect transistor (FET), 4 is a printed circuit board, 5 is a hermetic seal, 6 is a silicon plate mounted on a window provided in a metal cap 7, 8 is an infrared sensor.

The infrared sensor 8 is manufactured by forming a circuit composed of a combination of a pyroelectric light receiving element 1, a resistor 2, and an FET 3 on a printed circuit board 4, and electrically and mechanically forming the pyroelectric light receiving element 1 with a conductive paste. To the terminals of the printed circuit board 4. Next, this was soldered to a pin of the hermetic seal 5, and a metal cap 7 having a silicon plate 6 attached to the window was welded to the hermetic seal 5 to produce an infrared sensor 8.

Next, the minimum thickness due to surface grinding which does not cause cracking or chipping, the measurement frequency of the infrared sensor constituted by the obtained light receiving element is 1 Hz, and the heat source temperature is 50
The sensitivity at 0K was measured. The results are shown in (Table 1).

[0037]

[Table 1]

As is clear from Table 1, a pyroelectric light-receiving element having an average thickness of 40 μm and a uniform thickness was obtained, and an infrared sensor using this was 4500 V /
It was found to have a sensitivity greater than W.

Example 2 As raw materials, chemically high-purity PbTiO ₃ , TiO ₂ , CoO, WO ₃ , CaCO _3
3 , MnO ₂ is used.

The experiment was conducted by changing the substitution amount of Ca atoms, x, y, and z and changing the addition amount of MnO ₂ . as a result,
When the composition contains less than 20 mol% of Ca atoms, the Curie temperature is too high, and polarization tends to be difficult.
It has been found that the Curie temperature is too low for a composition larger than 1%, and lacks practicality. Also, x <0.50
With a composition of 1, y <0.79, z> 0.50, processing of 30 μm or less is impossible, so that high sensitivity cannot be obtained as a sensor. With a composition of z <0.45, y> 0.98, processing of a thin plate is possible, but high sensitivity cannot be obtained. In addition, it was found that the sinterability deteriorated when the composition was x> 0.511.

Further, it was found that when 5% by weight of MnO ₂ was added, crystal grain growth was promoted and sinterability deteriorated.

Next, the average particle size of the pyroelectric material was confirmed. When the average particle size exceeded 5 μm, it was found that the firing density was low. Further, firing conditions were confirmed. As a result, the thin plate of the pyroelectric material is made of platinum or a ceramic plate having a surface layer formed of platinum at 1050 ° C. to 1200 ° C.
It was found that firing for 10 minutes to 120 minutes was suitable. In the case of other metal plates, at a high temperature of 1000 ° C. or higher, it was confirmed that the metal plate was easily melted and the surface layer was deteriorated, and that in the case of the ceramic plate, Pb reacted with the ceramic layer. If the firing temperature is 1050 ° C. or less,
At 200 ° C. or higher, it was found that the sinterability was poor. This is presumably because the crystal grain growth was promoted.

Next, the optimum conditions for the thickness of the thin plate of the pyroelectric material were confirmed. As a result, when the thickness is 5 μm or less, the impact resistance of the pyroelectric light-receiving element is low, and the mechanical strength is poor.
From the above, it was found that the sensitivity of the pyroelectric light receiving element was poor.

[0044]

As described above, the present invention provides a compound of the general formula Pb_x 
[Ti_y (Co_z W_1-z )_1-y ]_1-x O _n (N
Is an arbitrary number) 0.502 ≦ x ≦ 0.510
0.80 ≦ y ≦ 0.97, 0.46 ≦ z ≦
0.49, that is, of the composite perovskite structure
The ratio of A site ion to B site ion is subtle from 1: 1
And some of the Pb atoms are replaced with Ca atoms by 20 to 3
0 mol%, and MnO_Two 3
Weight% or less, maintaining easy polarization conditions
High-sensitivity, high-quality focus that is unlikely to crack or chip during thin plate processing
A pyroelectric material that can provide dielectric ceramics with high yield has been developed.
It can be manifested. The average particle size of the pyroelectric material is 5 μm
By using the following adjustment powder, the sintering reaction proceeds,
The firing temperature can be lowered and the firing time can be shortened.
Quality pyroelectric material that can produce thin plates with high mechanical strength
Can be realized.

The method of manufacturing the photodetector for pyroelectricity is as follows. A pyroelectric material is formed into a thin plate having a thickness of 5 μm to 100 μm by an existing slip casting method and extrusion molding method.
Alternatively, on a ceramic plate having a surface layer formed of platinum,
Bake at 050 ° C to 1200 ° C for 10 minutes to 120 minutes.
Furthermore, since a light-receiving electrode is formed on both surfaces of the thin plate by a sputtering method and polarization is performed through this electrode, cracks and chipping when processing the pyroelectric material into a thin plate are extremely small, and the light-receiving element for pyroelectricity is used. Of pyroelectric light-receiving elements that can produce high-reliability, high-quality, high-sensitivity pyroelectric light-receiving elements with high productivity and high yield, with significantly reduced occurrence of microcracks and the like on the surface of the surface The method can be realized. Since the pyroelectric thin plate is fired on a platinum plate or a ceramic plate with a surface layer formed of platinum, it can be fired in a flat state without reaction and fusion with the thin plate, and high productivity. And a method for manufacturing a pyroelectric light-receiving element that can be produced at a high yield. Since these excellent pyroelectric materials or light receiving element materials obtained therefrom are used, an infrared sensor with excellent productivity, high sensitivity and high product yield can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an infrared sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part of the infrared sensor according to the first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pyroelectric light receiving element 2 Resistance 3 Field effect transistor (FET) 4 Printed circuit board 5 Hermetic seal 6 Silicon plate 7 Metal cap 8 Infrared sensor

──────────────────────────────────────────────────続 き Continuing on the front page (51) Int.Cl. ⁷ Identification code FI H01L 37/02 C04B 35/00 J (72) Inventor Koichi Watanabe 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 56) references Patent flat 6-267330 (JP, a) patent 3196461 (JP, B2) US Patent 4983839 (US, a) United States Patent 4764492 (US, a) (58 ) investigated the field (Int.Cl. ⁷ G01J 1/00-1/60 G01J 5/00-5/62 C04B 35/00-35/22 C04B 35/42-35/51 H01L 37/02

Claims (6)

(57) [Claims] (1) The general formula is Pb _x [Ti _y (Co
_{z W 1-z) 1-} y] 1-x O n ( where, n is represented by an arbitrary number), x, y, z is 0.502 ≦ x ≦ 0.510,0.8
The condition of 0 ≦ y ≦ 0.97, 0.46 ≦ z ≦ 0.49 is satisfied, and a part of Pb atoms is 20-30 mol of Ca atoms.
The main component is l% -substituted one, and
3% by weight or less of MnO ₂ is contained and the average particle size is 5 μm
A pyroelectric material characterized by the following . 2. The pyroelectric material according to claim 1, having a thickness of 5 μm to 1 μm by a slip casting method or an extrusion molding method.
A thinning process for forming a thin plate having a thickness of 00 μm, and a firing process for firing the thin plate obtained in the above process at a firing temperature of 1050 ° C. to 1200 ° C. for 10 to 120 minutes. Of manufacturing a pyroelectric light receiving element. 3. The method for producing a pyroelectric light receiving element according to claim 2, wherein the firing step of the thin plate characterized in that the platinum layer to platinum plate or surface is performed on the ceramic plates are stacked. 4. A receiving electrode on both sides of the sheet that has been fired at the firing step, of claim 2 or 3, characterized in that it has a polarization step of performing polarization through the electrode A method for manufacturing the pyroelectric light-receiving element according to any one of the above. 5. A thin plate comprising the pyroelectric material according to claim 1.
An infrared sensor , comprising: a pyroelectric light-receiving element formed by processing and firing the thin plate . 6. An infrared sensor comprising a pyroelectric light-receiving element manufactured by the method for manufacturing a pyroelectric light-receiving element according to any one of claims 2 to 4 .