JPS60127719A - Method of producing pyroelectric infrared ray detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a pyroelectric infrared detection element capable of detecting infrared rays with high sensitivity.

[Technical background of the invention and its problems]

In general, pyroelectric infrared detection elements are put into practical use in intruder detectors, fire alarms, etc. as non-contact temperature sensors that can measure the temperature of an object while being separated from it. The pyroelectric material used in this pyroelectric infrared detection element is ceramic.

There are ferroelectrics made of single crystal and polymeric materials. For example, PbTiO3 and PZT are known as ceramics, LiTaO3 is known as a single crystal, and ferroelectric materials such as polyvinylidene fluoride (PVF2) are known as polymer materials.

Among these, ceramics have the advantage of being easy to process and mass-produced, but have the problem of poor performance and unreliable properties. Single crystals have the great advantages of perfection and uniformity unique to single crystals, and the reproducibility and reliability of pyroelectric properties, but they have the disadvantage of high manufacturing costs. Furthermore, in the case of polymeric materials, they have the advantage of low manufacturing costs, such as the ease with which large-area sheets can be mass-produced, but they have the problem of inferior performance.

On the other hand, in order to increase the response speed and sensitivity to infrared rays, the pyroelectric element used in a pyroelectric infrared detection element usually has a small heat capacity, t, and a film thickness of 100 μm or less, which is one strength higher. Due to this problem, a film thickness of 5 μm or more is required. In order to form this pyroelectric element, a block of ceramic or single crystal of pyroelectric material is usually cut and polished into a thin plate of 100 μm. However, if the thickness of the pyroelectric element is reduced to 100 μm or less in order to increase the sensitivity of the detection element, processing of the thin plate becomes difficult and the yield rate decreases significantly, causing problems in mass production. Furthermore, since the thin plate of a normal pyroelectric element is bonded to a substrate with a conductive adhesive to form an infrared detection element, the thinner the pyroelectric element becomes, the more brittle the pyroelectric material itself becomes. Therefore, there was a problem in that it was difficult to assemble the detection element.

[Purpose of the invention]

The present invention was developed in view of the above, and provides a method for manufacturing a pyroelectric infrared detection element that has pyroelectric performance equal to or better than that of a single crystal, has excellent response speed and sensitivity to infrared rays, and is excellent in mass production. The purpose is to provide.

[Summary of the invention]

The present invention forms an amorphous oxide thin film on a conductive substrate, recrystallizes the amorphous oxide thin film by heat treatment, and forms a polycrystalline ferroelectric oxide thin film with pyroelectricity. It is characterized by forming.

The amorphous ferroelectric thin film becomes a polycrystalline ferroelectric oxide thin film whose polarization axis is oriented perpendicular to the substrate by recrystallization. Therefore, the pyroelectric coefficient (dPS/dT) is the same as that of a single crystal, but since it is a polycrystal, the thermal conductivity K ("4") is higher than that of a single crystal.
c) and thermal diffusion coefficient (a/l/sec) are smaller, so that the pyroelectric performance of the detection element of the present invention is actually higher than that of a detection element using a single crystal.

Another feature of the present invention is that since a polycrystalline ferroelectric oxide thin film of, for example, 100 μm or less is formed directly on the substrate, it is very easy to fabricate a pyroelectric element by cutting regardless of the film thickness.

The present invention will be explained in detail below.

The pyroelectric material used in the present invention is Pb5Ge301
1 (lead germanate), PbTi0a (lead titanate), PZ'l' (titanic acid, lead zirconate), Li
A ferroelectric oxide having excellent pyroelectric properties such as TaO3 (lithium tantalate) is used. Methods for forming this amorphous oxide on a substrate include a vapor deposition method and a liquid quenching method. When using a sputtering method as the vapor deposition method, for example, as shown in FIG.
A target 5 of the crystalline oxide of the pyroelectric material connected to a high frequency power source 4 is provided in a vacuum container 3 in which a vacuum chamber 3 is provided with an exhaust pulp 2, and a conductive substrate 6 is placed opposite to the target 5 to generate high frequency power. An amorphous oxide thin film 7 is formed on the substrate by sputtering. Next, as shown in FIG. 2, the amorphous oxide thin film 7 on the surface of the substrate 6 was heated (using a heater 8) to recrystallize it, and the polarization axis was oriented perpendicular to the substrate. A polycrystalline pyroelectric ferroelectric oxide thin film 9 is formed.

This thin film-like pyroelectric material formed on the substrate is directly cut into a mosaic shape and used for a pyroelectric infrared detection element.

In order to form an amorphous oxide on a substrate, an amorphous oxide having a uniform composition can be easily produced by rotating the substrate, especially when using a sputtering method. Further, the substrate is preferably a metallic thin plate or thin film that is slightly larger than the ferroelectric oxide and has conductivity.

For example, noble metals such as platinum, gold, palladium, and nickel, or alloys thereof, are suitable for the present invention because they are not oxidized by heat treatment. Also, the substrate is BaPbO3, V2O3
, ReO3, or the like, or a thin film formed by vapor-depositing noble metals such as platinum, gold, palladium, nickel, or the above-mentioned conductive ceramics on an insulating substrate.

Further, it is preferable that the thermal expansion coefficient of the conductive substrate is equal to or larger than that of the ferroelectric oxide.

This is to prevent cracks from forming during heat treatment. When heating an amorphous oxide to obtain a ferroelectric oxide thin film, the heating means may be uniform heating or sequential heating from one end to the other using a laser, an infrared image furnace, or the like.

Liquid quenching methods include the dipping method, in which a substrate is immersed in a molten oxide and pulled up to form an amorphous oxide thin film on the surface of the substrate, and the molten oxide is sprayed onto the surface of the substrate to form a thin film. Examples include a spray method and a method of forming an amorphous oxide thin film by bringing an oxide melt into contact with a rotating metallic single roll or twin rolls.

[Embodiments of the invention]

The present invention will be specifically explained below with reference to Examples.

Using the high frequency sputtering equipment shown in Figure 1, Pb5Qe3O was
A sintered body having the composition shown by A is used as a target 5, and argon and oxygen (mixing ratio 6
A thin oxide film 7 with a thickness of 30 μm is applied to a ceramic substrate 6 on which gold (1 μm) with a thickness of 1 μm is deposited at a fighting angle of 100 and placed opposite the target 5 by discharging in the atmosphere described in 4).
was sputter deposited. In this case, the base body 6 is water-cooled. When the obtained thin film 7 was examined by X-ray diffraction, only one broad diffraction line was observed, confirming that it was amorphous.

Further, this amorphous oxide thin film 7 was subjected to heat treatment at 9700° C. using a heater 8 as shown in FIG. When this was examined using X-ray diffraction and an optical microscope, it was found that the film was a ferroelectric P b 5 Ge 3011 with a crystal grain size of 300 μm and a 0-plane surface.
It was confirmed that the film was a polycrystalline thin film 9.

Next, C-plane oriented Pb5Ge3O was formed on this substrate.
11 Polycrystalline thin film 9 was cut to 3.5 m using a diamond cutter.
I cut it into corners and made an infrared detection element.

Voltage sensitivity (R
v) was measured and found Rv -450 at a frequency of 10Hz.
¥W and Toku9. This is Pb5Ge3O with the same shape and dimensions.
It was found that the Rv of an infrared detection element using a No. 11 single crystal was large (Rv = 300 $).

〔Effect of the invention〕

As described above, according to the present invention, a pyroelectric infrared detection device is provided with a ferroelectric oxide polycrystalline thin film having pyroelectric properties and oriented such that the polarization axis is perpendicular to the film surface on a conductive substrate. The device exhibits greater response sensitivity than when using a single crystal.

In addition, in the present invention, since a polycrystalline thin film is formed on a substrate,
Even if the thickness of the thin film is small, processing of the thin film is easy and the infrared detecting element can be manufactured easily, so it can be said that it is a detecting element with excellent mass production. Therefore, the detection element of the present invention can be used not only for intruder detectors and fire alarms, but also for spectrophotometers, gas analyzers, laser detectors, and millimeter wave detectors that require high sensitivity. It is also expected to be applied to pyroelectric devices such as tape measure (imager), pyroelectric vidicon, and pyroelectric two-dimensional array.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a sputter deposition apparatus according to an embodiment of the present invention, and Fig. 2 is a schematic diagram of a sputter deposition apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view showing the infrared detecting element of the present invention; FIG. 1... Gas introduction pulp, 2... Exhaust valve 3...
・Vacuum container, 4...High frequency power supply 5° target
, 6... Substrate 7... Amorphous oxide thin film, 8... Heater 9...
Ferroelectric oxide thin film.

Claims (5)

[Claims] (1) After forming an amorphous ferroelectric oxide thin film on a conductive substrate, the amorphous ferroelectric oxide thin film is heated and recrystallized to produce a pyroelectric oxide. A method for manufacturing a pyroelectric infrared detection element, characterized by forming a dielectric oxide thin film. (2) The method for manufacturing a pyroelectric infrared detecting element according to claim 1, wherein the thermal expansion coefficient of the base is much larger than that of the ferroelectric oxide. (3) The thickness of the amorphous oxide thin film formed on the substrate is 5 μm
The method for manufacturing a pyroelectric infrared detection element according to claim 1, wherein the diameter is 100 μm or more and 100 μm or less. (4) A method for manufacturing a pyroelectric infrared detecting element according to claim 1, characterized in that an amorphous oxide thin film is deposited on a substrate by a vapor deposition method. (5) A method for manufacturing a pyroelectric infrared detecting element according to claim 1, characterized in that an amorphous oxide thin film is formed on a substrate by a liquid quenching method.