JPH05332828A - Infrared ray sensor - Google Patents

Abstract

PURPOSE:To achieve a reliable infrared ray sensor which can be manufactured in a mass, inexpensively with a simple process without damaging an infrared ray detection element and with less thermal loss to a substrate and can perform high-sensitivity infrared ray detection. CONSTITUTION:A lower crystal glass substrate 11 in that the upper surface is mirror-surface finished and a groove 12 is formed at the center and an upper crystal glass substrate 13 where the rear surface is mirror-surface finished are adhered and joined while the mirror surfaces oppose each other via a gap G of the groove 12 and then an infrared ray detection element 14 consisting of a sandwich structure of a lower electrode 15, a pyroelectric film 16, and an upper electrode 17 is formed and laid out on the surface of the upper crystal glass substrate 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared sensor, and more particularly to a substrate structure on which an infrared detecting element is mounted.

[0002]

2. Description of the Related Art FIG. 5 is a cross-sectional view of an essential part showing the structure of a conventional infrared sensor. In the figure, 1 is a MgO substrate,
Reference numeral 2 is a Pt electrode formed on the MgO substrate 1, 3 is a photoelectric conversion film formed on the Pt electrode 2 and formed of a pyroelectric thin film for detecting infrared rays, and 4 is formed on the photoelectric conversion film 3. NiCr electrodes 5 are polyimide films as protective films. A silicon substrate may be used instead of the MgO substrate 1 described above.

In the thermal type infrared sensor thus constructed, it is ideal that the absorbed infrared rays contribute to the temperature change of the photoelectric conversion film 3 efficiently. However, if the heat loss from the photoelectric conversion film 3 to the MgO substrate 1 is large, the sensitivity of the sensor will be significantly reduced. Therefore, as mentioned above, M
etching the gO substrate 1 to remove the lower side of the sensor,
The cavity 1a was provided to suppress heat loss to the MgO substrate 1.

[0004]

However, in the infrared sensor thus constructed, the process of removing the lower part of the MgO substrate 1 to form the cavity 1a is performed by a photolithography process or etching with a strong acid or strong alkaline solution. Since extremely high technology such as steps and complicated process are required, there is a problem that the manufacturing cost becomes high. Further, as described above, since a chemical having a strong chemical action is used as the etching liquid, there is a problem that the sensor material is damaged and the reliability is lowered.

Therefore, the present invention has been made in order to solve the above-mentioned conventional problems. The purpose of the present invention is to produce the infrared detecting element by a simple process without damaging it, and to excel in mass productivity. An object of the present invention is to provide an infrared sensor that enables low cost, low heat loss to a substrate, high sensitivity infrared detection, and highly reliable infrared detection.

[0006]

In order to achieve such an object, an infrared sensor according to the present invention comprises a first insulating substrate having at least one surface mirror-finished and a first insulating substrate.
A second insulating substrate made of the same material as that of the first insulating substrate and having at least one surface mirror-finished, and laminated on the other surface of the first insulating substrate or the second insulating substrate. An infrared detecting element having a sandwich structure of a first electrode, a pyroelectric film, and a second electrode;
Groove is provided on at least one mirror-finished surface of the insulative substrate and the second insulative substrate, and the first insulative substrate and the second insulative substrate are mirror-finished via the gap of the groove. Are arranged so as to face each other, and the first insulating substrate and the second insulating substrate are in close contact with each other.

[0007]

In the present invention, the first insulating substrate and the second insulating substrate are directly adhered to each other through the gap of the groove without using a sealing material to form a substrate structure.

[0008]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing the configuration of an embodiment of an infrared sensor according to the present invention. In the figure, the lower quartz glass substrate 11 constituting the first insulating substrate is provided with a shallow groove 12 having a substantially square shape and a concave cross section in the central portion on the surface side. The surface roughness Ra of the quartz glass substrate 11 on which the groove 12 is formed is Ra =
A flat mirror finish of 100 Å or less is applied.

The upper quartz glass substrate 13 constituting the second insulating substrate is formed to have a plate thickness thinner than that of the above-mentioned quartz glass substrate 11 by about 1/3, and the quartz glass substrate 13 is also formed. Roughness is Ra = 100Å
A flat mirror-like finish of less than or equal to is applied.

The quartz glass substrate 11 and the quartz glass substrate 13 thus constructed are mirror-finished on the surface and formed with the grooves 12, and the front side of the lower quartz glass substrate 11 and the upper side which is mirror-finished on the back side. Quartz glass substrate 13
The back surface of the lower quartz glass substrate 11 and the rear surface of the lower quartz glass substrate 11 are laminated at room temperature so that their mirror surfaces face each other, and are heated to about 200 to 1100 ° C. The substrate structure is constituted by the gap G of the groove 12 between the quartz glass substrate 11 and the quartz glass substrate 13, which are tightly adhered to each other and firmly fixed by direct bonding.

Further, an infrared detecting element 14 having a substantially square shape as a whole is formed and arranged in the central portion on the front surface side of the quartz glass substrate 13 bonded and fixed to the quartz glass substrate 11. 14 is a pyroelectric film 16 on the lower electrode 15 formed on the surface of the quartz glass substrate 13.
Is formed, and the upper electrode 17 is formed on the pyroelectric film 16.
Are formed in a laminated structure.

In this case, the infrared detecting element 14 is arranged so as to be substantially aligned with the position of the gap G formed by the groove 12 of the lower quartz glass substrate 11 and corresponding to the upper quartz glass substrate 13. Is becoming Although not shown, a heat absorption film made of, for example, platinum black may be formed and arranged on the upper electrode 17 as needed.

According to this structure, since the infrared detecting element 14 is mounted on the upper quartz glass substrate 13 through the gap formed by the groove 12 formed in the lower quartz glass substrate 11, the infrared detecting element 14 is mounted. The heat from the element 14 is less likely to be absorbed by the lower quartz glass substrate 11, that is, the heat loss of the infrared detection element 14 is reduced, and high-sensitivity infrared detection is possible.

Further, according to this structure, since the lower quartz glass substrate 11 and the upper quartz glass substrate 13 are made of the same material, the temperature characteristic of the infrared detecting element 14 is adversely affected even if the ambient temperature used changes. Therefore, infrared rays can be detected with high accuracy.

Next, a method of manufacturing the infrared sensor described with reference to FIG. 1 will be described. 2A to 2D are cross-sectional views of steps for explaining an embodiment of a method for manufacturing an infrared sensor. In the figure, first, as shown in FIG. 2A, at least a quartz glass substrate 11 having mirror-polished surfaces of peripheral portions which are opposed to each other and are bonded is prepared.

Next, as shown in FIG. 2B, a groove 12 is formed in the central portion of the surface of the quartz glass substrate 11 by a wet etching method or a dry etching method using an HF etching solution or the like.

Next, as shown in FIG. 2 (c), a quartz glass substrate 13 having mirror-polished surfaces which are opposed to each other and are bonded is prepared.

Next, as shown in FIG. 2D, a quartz glass substrate 11 having a mirror-polished surface and a groove 12 formed therein and a quartz glass substrate 13 having a mirror-polished surface 13 are clean without using a bonding agent. In the atmosphere, the mirror-finished sides are overlapped and bonded at around room temperature, and heat treatment is performed in a high temperature atmosphere of about 200 to 1100 ° C. to strengthen the bond. As a result, a substrate structure is formed in which the gap G formed by the groove 12 is interposed between the quartz glass substrate 11 and the quartz glass substrate 13.

Next, as shown in FIG. 2 (e), the unbonded surface side of the quartz glass substrate 13 is polished, and the quartz glass substrate 13 is processed into a predetermined plate thickness according to the infrared detection level. The polishing may be performed by dry etching or wet etching in addition to mechanical polishing. Further, the back side of the quartz glass substrate 11 joined to the quartz glass substrate 13 may be simultaneously polished to be processed into a predetermined plate thickness.

Next, as shown in FIG. 2 (f), a lower electrode 15, a pyroelectric film 16 and an upper electrode 17 are sequentially laminated on the surface of the quartz glass substrate 13 to form an infrared detecting element 14 for completion. ..

FIG. 3 shows the result of an experimental determination of the relationship between the bonding strength and the heat treatment temperature for bonding the quartz glass substrates to each other. In the figure, the curve shows the bonding strength of the quartz glass substrates 11 and 13, and the bonding strength of the quartz glass substrates is an average value at each temperature. As is clear from the figure, the bonding strength of the bonding portion between the quartz glass substrates 11 and 13 of this embodiment is
It was found to be good enough to fabricate an infrared sensor.

Next, a mechanism of directly bonding the quartz glass substrate 11 and the quartz glass substrate 13 will be described.
FIG. 4 is a diagram illustrating changes in the process of joining the quartz glass substrate 11 and the quartz glass substrate 13. In the figure, first, as shown in FIG.
It is considered that in the state in which the quartz glass substrate 13 and the quartz glass substrate 13 are laminated and laminated at room temperature, the gap d is closely adhered to each other by the physical bonding force mainly due to the Van der Waals force.

Further, when the quartz glass substrate 11 and the quartz glass substrate 13 are laminated and bonded at room temperature and then heat-treated, the molecular structure of the quartz glass is Si--O--Si bond as shown in FIG. 4 (b). It is considered that a chemical bond such as "a" is formed, and the chemical bond is further strengthened, resulting in close contact.

As described above, the quartz glass substrate 11 is used.
The quartz glass substrate 13 and the quartz glass substrate 13 are adhered and firmly bonded to each other by a state of being laminated and laminated and by a comprehensive bonding form by a physicochemical bonding force in the heat treatment process. It will be.

According to such a method, since the quartz glass substrate 11 and the quartz glass substrate 13 are directly bonded to each other via the gap G of the groove 12, a substrate structure for mounting the infrared detecting element 14 can be formed. Detection element 14
A substrate structure with less heat loss can be formed by a simple process.

Further, according to such a method, since the infrared detecting element 14 is formed after the etching process of the quartz glass substrates 11 and 13, damage due to etching and heat treatment of the sensor material is completely eliminated, and infrared detecting is performed. The reliability of the element 14 can be significantly improved.

Further, according to such a method, after the quartz glass substrate 11 and the quartz glass substrate 13 are laminated and bonded to each other, heat treatment is further performed in a temperature range of 200 to 1100.degree. Therefore, for example, when a large number of infrared sensors are formed on a wafer and divided into individual chips by dicing or the like, mechanical strength that can withstand the impact is obtained, and mass production is facilitated.

In the above-mentioned embodiment, the case where the groove 12 is provided in the lower quartz glass substrate 11 to form the gap G has been described, but the present invention is not limited to this, and the groove 12 is formed. It may be provided on the upper quartz glass substrate 13 or further on both quartz glass substrates 11 and 13 side, and the same effect as in the above-mentioned embodiment can be obtained.

Further, in the above-mentioned embodiment, the groove 12
The case where the infrared detecting element 14 has a square shape has been described, but the present invention is not limited to this, and needless to say, it may have a rectangular shape, a polygonal shape, a circular shape, or an elliptical shape.

Further, in the above-mentioned embodiment, the groove 1 provided between the quartz glass substrate 11 and the quartz glass substrate 13 is used.
The inside of 2 may be a vacuum or other enclosure.

Further, in the above-mentioned embodiment, the case where the quartz glass substrate 11 and the quartz glass substrate 13 are used as the first insulating substrate and the second insulating substrate, respectively, has been described, but the present invention is not limited to this. The glass substrate is a transparent insulator that is not limited to visible light,
Even if a sapphire substrate or a silicon substrate is used, direct bonding can be performed by a physicochemical action, and the same effect as that of the above-described embodiment can be obtained.

[0032]

As described above, according to the present invention,
Since the first insulating substrate and the second insulating substrate do not need a sealing material and are directly adhered to each other through the gap of the groove to form a substrate structure, heat loss of the infrared detecting element is reduced. , It becomes possible to detect infrared rays with high sensitivity. In addition, since this substrate structure can be formed by simplifying processes such as a photolithography process and an etching process which are highly sophisticated and complicated as in the conventional case, the process is simplified, mass productivity is excellent, and manufacturing cost is low. Further, since the infrared detecting element can be formed after the production of this substrate, the infrared detecting element is not damaged by the etching liquid having a strong chemical action, and extremely excellent effects such as highly reliable infrared detection can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of an infrared sensor according to the present invention.

FIG. 2 is a sectional view of a step illustrating a method for manufacturing an infrared sensor according to the present invention.

FIG. 3 is a diagram showing the relationship between the bonding strength and the heat treatment temperature in the bonding mode of quartz glass substrates.

FIG. 4 is a diagram for explaining a bonding mode between quartz glass substrates.

FIG. 5 is a sectional view showing a configuration of a conventional infrared sensor.

[Explanation of symbols]

 11 Quartz Glass Substrate 12 Groove 13 Quartz Glass Substrate 14 Infrared Detector 15 Lower Electrode 16 Pyroelectric Film 17 Upper Electrode G Gap

Claims (3)

[Claims] 1. A first insulating substrate having at least one surface mirror-finished, and a second insulating substrate made of the same material as the first insulating substrate and having at least one surface mirror-finished. And an infrared detection element having a sandwich structure of a first electrode, a pyroelectric film, and a second electrode laminated on the other surface of the first insulating substrate or the second insulating substrate, A groove portion is provided on at least one mirror-finished surface of the first insulating substrate and the second insulating substrate, and the first insulating substrate and the second insulating substrate have a groove portion. An infrared sensor, characterized in that the mirror surfaces are arranged so as to face each other through the gap (1), and the first insulating substrate and the second insulating substrate are closely bonded to each other. 2. The infrared sensor according to claim 1, wherein the first insulating substrate and the second insulating substrate are made of quartz glass. 3. The infrared sensor according to claim 1, wherein at least one of the first insulating substrate and the second insulating substrate is made of silicon.