JPH06213725A - Window material for infrared sensor - Google Patents

Abstract

PURPOSE:To enhance sensitivity of sensor by introducing infrared rays efficiently to an infrared temperature-sensitive film. CONSTITUTION:A window member 17 is bonded to the surface of a silicon substrate 11. A window member 17 has basic material of a silicon substrate 18 applied with infrared anti-reflection films 19a, 19b to the opposite sides thereof. The infrared anti-reflection films 19a, 19b are composed of zinc sulfide(ZnS). The infrared anti-reflection films 19a, 19b increase the ratio of infrared rays transmitting through the window member 17 and impinging on an infrared temperature-sensitive film 16 thus enhancing the sensitivity of sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a window material for an infrared sensor which measures the temperature of an object to be measured in a non-contact manner.

[0002]

2. Description of the Related Art Recently, various techniques have been developed for producing an infrared sensor suitable for a non-contact thermometer or the like by utilizing a semiconductor fine processing technique. There are various types of infrared sensors such as a thermobolometer type and a thermopile type. Among them, the thermobolometer-type infrared sensor forms an infrared temperature-sensitive film with a substance having a thermistor effect, measures the temperature rise due to the received infrared light by changing the electrical resistance value, and knows the amount of infrared light. It is superior to other types in that it can be easily miniaturized.

In this thermobolometer type infrared sensor, if the heat capacity of the infrared thermosensitive film is small and the amount of heat transferred from the infrared thermosensitive film to the outside is small, the temperature rises accordingly and the response sensitivity to a small amount of infrared rays is high. Become.
Therefore, conventionally, a very small bridge portion is formed on a supporting substrate made of a semiconductor material by using a microfabrication technique, and an infrared thermosensitive film is further formed on the bridge portion. . That is, the response sensitivity is improved by forming a cross-linked structure in which the heat-sensitive part of the element is floated from the support substrate.

On the other hand, in measuring, since a small amount of infrared rays emitted from the object to be measured is targeted, various measures are required. For example, two identical infrared temperature sensitive films are provided on one sensor, one infrared temperature sensitive film is irradiated with infrared rays, and the other infrared temperature sensitive film is shielded so that infrared rays do not enter. By constantly comparing the difference between the output of the infrared thermosensitive film on which the infrared rays are incident and the output of the infrared thermosensitive film on which the infrared rays are not incident, electrical noise and thermal disturbance are removed, and the net infrared rays are removed. The amount can be detected.

In such an infrared sensor, various measures are taken so that infrared rays can be efficiently incident on one of the infrared temperature-sensitive films, but from a practical point of view, a fine crosslinked structure is mechanically Must be physically protected. for that reason,
Conventionally, in order to protect the crosslinked structure, the infrared sensor element is housed in a container such as a can. As described above, in the conventional infrared sensor, the sensor element is housed in the container. However, when the sensor is housed in the container, when the sensor element is used in a non-contact thermometer or the like, the problem of heat conduction, size restriction, and cost increase. There was a problem with the points. Therefore, a mounting method capable of protecting the sensor element at a low cost by a simple method has been desired.

By the way, in this type of infrared sensor, it is necessary to provide a window member as an infrared selective entrance means on the front side of the sensor element in order to selectively enter infrared light into one of the pair of infrared thermosensitive films. . As the window material, various materials such as a semiconductor material such as silicon and a metal can be used, but it is preferable to use silicon from the viewpoint of economy and stability.

[0007]

However, when the infrared sensor having the window member made of silicon is used for a thermometer, there are the following problems. That is, since the transmittance of the silicon wafer for infrared rays having a wavelength of about 10 μm emitted from the human body is about 50%, the remaining about 5%.
0% of the infrared rays are reflected by the window material, so that they are not incident on the infrared temperature-sensitive film and the sensor sensitivity deteriorates.

The present invention has been made in view of the above problems, and an object thereof is to provide an infrared sensor window material capable of efficiently guiding infrared rays to an infrared temperature sensitive film and improving sensor sensitivity. To do.

[0009]

The window material for an infrared sensor according to the present invention is a window material used in an infrared sensor for detecting infrared rays by an infrared thermosensitive film, and is provided on at least one surface of a base material having infrared transparency. Zinc sulfide (ZnS) or selenium zinc (ZnS) is provided at a position corresponding to the infrared thermosensitive film.
An infrared ray antireflection film formed of Se) is provided.

In this infrared sensor window material, since the infrared antireflection film is formed of zinc sulfide, the infrared transmission efficiency is remarkably improved, so that the amount of infrared light incident on the infrared temperature sensitive film is increased and the sensor The sensitivity is improved. Moreover, since the infrared ray antireflection film formed of zinc sulfide can be formed by sputtering in vacuum, it is suitable for manufacturing using the semiconductor technology together with the sensor body.

As the base material of this window material, various materials such as a semiconductor material such as silicon or metal can be used.
Similar to the support substrate of the sensor body, it is preferable to use silicon that can be easily and inexpensively obtained and has a stable material. As described above, when a window material is manufactured using a silicon substrate and is used for a thermometer, the transmittance of infrared rays emitted from a human body near a wavelength of 10 μm is about 50%. Therefore, in the case where the same pair of infrared thermosensitive films are provided on one sensor, the infrared rays are incident on one infrared thermosensitive film, and the infrared thermosensitive films on the other are shielded so that the infrared rays do not enter. On the other hand, it is necessary to form the infrared ray antireflection film of zinc sulfide on the side of the window material on which the infrared rays are incident, while forming the infrared ray shielding film of aluminum (Al) or the like on the side to be shielded.

[0012]

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

FIG. 1 shows a vertical sectional structure of an infrared sensor 10 according to an embodiment of the present invention. The infrared sensor 10 according to this embodiment includes a silicon substrate 11 as a sensor substrate.
The window material (front lid) 17 is joined to the front surface of the above, while the back lid 26 is joined to the back surface.

The silicon substrate 11 has a pair of cavities 12,
13 are provided. An insulating film 14 is formed on the upper surface of the silicon substrate 11. The insulating film 14 is provided with bridging portions 14a and 14b of the same structure facing the cavities 12 and 13, respectively. As the insulating film 14, a silicon oxide film (SiOx), a silicon nitride film (SiNy),
A silicon oxynitride (SiOxNy) film or the like can be used, but a silicon oxynitride film is particularly preferable. The silicon oxynitride film has the properties of both a silicon oxide film and a silicon nitride film, and therefore has a good stress balance and can form stable crosslinked portions 14a and 14b.

Infrared thermosensitive films 15 and 16 are provided on the central portions of the bridge portions 14a and 14b, respectively.
The infrared temperature sensitive films 15 and 16 are made of amorphous germanium (a-Ge) and amorphous silicon (a-S), respectively.
i) or a film of polycrystalline silicon or the like. Sputtering, ion beam sputtering, CVD (chemical vapor deposition) or the like is used for forming the infrared temperature sensitive films 15 and 16.

Electrode pads 21 and 22 are provided around the bridging portions 14a and 14b on the insulating film 14. These electrode pads 21 and 22 are electrically connected to the infrared thermosensitive films 15 and 16 via electrode wiring layers (not shown). A flexible printed circuit board (FPC) 23 is connected to the electrode pads 21 and 22 by soldering.

The window material 17 has a film thickness of 1.
The infrared ray antireflection films 19a and 19b having a thickness of 3 μm are formed. The infrared antireflection films 19a and 19b are each formed of zinc sulfide (ZnS). These infrared ray antireflection films 19a and 19b are formed, for example, at a pressure of 5 × 10 ^-2 To
A film can be formed by performing sputtering for 27 minutes under the conditions of rr and a radio frequency (RF) voltage of 1.3 KV. The infrared reflection preventing films 19a and 19b may be formed on any one surface of the silicon substrate 18.

On the surfaces of the infrared ray antireflection films 19a and 19b, the infrared ray shielding films 20a and 20b made of, for example, an aluminum film are provided on the halves on the side facing the infrared temperature sensitive film 15 on the right side in the figure. Therefore, infrared rays are prevented from entering the infrared temperature sensitive film 15 side. The window member 17 has a flexible printed circuit board (F
PC) 23. A soldering method or an anodic bonding method is used to bond the window member 17.

On the other hand, an insulating film 24 made of the same material as the insulating film 14 is provided on the back surface of the silicon substrate 11, and a back lid 25 is bonded to the insulating film 24. The back cover 25 is also formed of a silicon substrate 26 like the window member 17, and an infrared reflection film 27 formed of an aluminum film is formed on the upper surface thereof. This case back 2
The soldering method or the anodic bonding method is also used for the bonding of No. 5.

In the infrared sensor 10, infrared rays pass through the window material 17 from the front surface side and are selectively incident on only one infrared temperature sensitive film 16 side. The infrared thermosensitive film 16 on which the infrared rays are incident and the infrared thermosensitive film 1 on which the infrared rays are not incident
The true infrared ray amount can be detected by obtaining the differential output with respect to 5 through the electrode pads 21 and 22 and the flexible printed board 23. It should be noted that the back cover 25 shields infrared rays that are incident from the back surface side.

Here, in the infrared sensor 10 of the present embodiment, since the infrared ray antireflection films 19a and 19b made of zinc sulfide are provided on the surface of the window member 17, the infrared ray transmitted through the window member 17 is not detected. The percentage is high. Therefore, the amount of infrared rays incident on the infrared thermosensitive film 16 increases, and the sensor sensitivity improves.

2 and 3 are characteristic diagrams showing the relationship between the film thickness of each of the infrared ray antireflection films 19a and 19b and the wavelength dependence of the transmittance. FIG. 2 shows the infrared antireflection film 19
When the film thicknesses of a and 19b are 1.4 μm, FIG. 3 shows the results when the film thickness of the infrared reflection preventing films 19a and 19b is 0.7 μm, and both of them show improved transmittance in the vicinity of the wavelength of 10 μm. .

In the above embodiment, the infrared antireflection film 1 is used.
Although an example using zinc sulfide as 9a and 19b has been described, similar results were obtained when selenium zinc was used.

[0024]

As described above, according to the window material for an infrared sensor of the present invention, the infrared antireflection film formed of zinc sulfide is provided at the position corresponding to the infrared temperature sensitive film. Has the effect of significantly improving the transmittance and improving the sensor sensitivity.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram showing a relationship between a film thickness of an infrared antireflection film and wavelength dependency of transmittance.

FIG. 3 is a characteristic diagram showing a relationship between a film thickness of an infrared antireflection film and wavelength dependency of transmittance.

[Explanation of symbols]

 10 Infrared Sensor 11 Silicon Substrate 14a, 14b Cross-Linking Part 15, 16 Infrared Temperature Sensitive Film 17 Window Material 18 Silicon Substrate (Base Material for Window) 19a, 19b Infrared Reflection Preventing Film 20a, 20b Infrared Shielding Film

Claims (1)

[Claims] 1. A window material used in an infrared sensor for detecting infrared rays by means of an infrared thermosensitive film, wherein zinc sulfide or a zinc sulfide is provided at a position corresponding to the infrared thermosensitive film on at least one surface of a substrate having infrared transparency. An infrared sensor window material comprising an infrared antireflection film formed of any one of selenium zinc.