JPS6351493B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an infrared detection element and aims to improve the sensitivity of a pyroelectric infrared detector by effectively increasing the incident infrared energy.

Conventional Structure and Problems Since a pyroelectric infrared detector is a thermal sensor, its sensitivity strongly depends on the shape, dimensions, and support structure of the element. Therefore, in order to achieve higher sensitivity, it is necessary to minimize heat escape. For this purpose, it is better to suspend the material in mid-air, using a hollow support platform to support the material only at the edges. By adopting such a structure, high sensitivity can be achieved. However, in order to further increase the sensitivity, blackening is performed to bring the infrared absorption rate of the light-receiving electrode closer to 1, but the effect of this is not so great. Therefore, if high sensitivity was desired, an optical system was combined with a pyroelectric infrared detector. Conventionally, as shown in FIG. 1, a reflecting mirror 12 is used as an optical system, and incident infrared light 13 is collected by the reflecting mirror 12 and irradiated onto an infrared detector 11. However, in this case, the structure becomes large because the reflecting mirror 12 is used in combination with the infrared detector 11.
Even if a micromirror is used as a reflecting mirror, there is a limit to how small it can be made. Furthermore, the infrared detector 11 used only one light receiving surface, resulting in poor efficiency.

OBJECTS OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to provide a small and highly sensitive infrared detection element.

Structure of the Invention The present invention supports only the ends of a pyroelectric material and hollows out the center to suspend it in the air, and forms a reflector in the hollow to utilize infrared energy incident on both sides of the detection element. This is what I did.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 2 shows an embodiment of the present invention. A pyroelectric material 21 having infrared absorbing electrodes on both sides is adhered to a support 22 at its end portions as shown in the figure. This support is made of a Si substrate. Anisotropic etching is used to make holes in this Si substrate. This manufacturing process is shown in FIG. As shown in FIG. 3a, an oxide film 42 is formed to a thickness of about 1 μm on the Si plate 41 with the (100) plane 44 exposed. A photoresist is applied to this substrate and a mask 43 having a predetermined pattern is formed as shown in FIG. 3b. Thereafter, as shown in FIG. 3c, the oxide film 42 is removed by etching only on one side. Then, using this oxide film 42 as a mask,
Perform Si etching. For example, ethylene diamine, procatechol, caustic potash, etc. are used as the etching solution. According to this, since the etching speed is different between the (100) plane 44 and the (111) plane 45 of Si, it is possible to make a square pyramidal hole, and if you stop midway, you can make a trapezoidal hole as shown in Figure 3d. . The angle between the (100) and (111) planes is constant at 54.74°. However, to make a beautiful square pyramid, this side must be aligned in the (110) direction. This method involves drilling a number of holes in a large Si wafer.
Since the desired size can be cut later by dicing or the like, mass production is possible.

An infrared reflective electrode made of Au, Al, etc. is deposited on the Si plate with the trapezoidal hole thus created, and the inside of the trapezoidal hole becomes an infrared reflective plate. In this case, the Si surfaces 23 and 24 shown in FIG. 2 may or may not be masked, but it is more preferable that no metal be deposited on one side. Thereafter, the pyroelectric material 21 is placed on the support 22 prepared by dicing, and fixed on one side with a conductive adhesive and on the other side with an insulating adhesive. In this way, the side fixed with the insulating adhesive can be connected to the connection electrode on the surface side of the pyroelectric material 21.

In the infrared element constructed in this way, as shown in the cross-sectional view of FIG.
The light is directly incident on the front surface electrode 32 side, and is reflected by the support reflection surface 45 and enters the back surface absorption electrode 33 of the element 21 . Therefore, since the infrared light entering from the back surface is added to the infrared light entering from the front absorbing electrode 32, the effective incident infrared energy increases. This is much more advantageous in terms of heat capacity and electric capacity than a pyroelectric element with an equivalent area, and the output is larger. Although Si was selected for the support 22 because of its ease of processing, it is not limited to Si as long as it can be processed to produce the same effect.

Note that if the reflecting surface 45 is formed into a spherical, elliptical, parabolic, etc. shape, the light collection efficiency will further increase and the sensitivity will become even higher.

Effects of the Invention As described above, the present invention makes the support of the pyroelectric material hollow, suspends the pyroelectric material, forms light receiving electrodes on both sides of the pyroelectric material, and places a reflector in the hollow part of the support. In the formed infrared detector, the effective infrared input of the pyroelectric material is increased, and an external optical system is not required, making it possible to obtain a compact and highly sensitive infrared detector.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an infrared detector using a conventional reflecting mirror, Figure 2 is a perspective view of an infrared detector according to the present invention, and Figures 3 a to d are fabrication of the Si support used in the present invention. Cross-sectional views showing the steps in order, Figure 4 is the second
It is a sectional view taken along the line AA' in the figure. 21...Pyroelectric body, 22...Support, 23, 24
... Support surface, 32 ... Surface infrared absorption electrode, 3
3... Back infrared absorbing electrode, 34... Incident infrared light,
41...Si, 42...Si insulating film, 43...photoresist, 44...Si (100) plane, 45...Si
(111) face.

Claims (1)

[Claims] 1. An infrared detection element, characterized in that a pyroelectric material is attached to a support having a recess in the center, the center of the pyroelectric material is floated, and the support has a reflective surface at the bottom of the recess.