JP2582418Y2 - Chip type infrared sensor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared sensor using a thermopile element, and more particularly to a structure for sealing a thermopile element.

[0002]

2. Description of the Related Art A conventional infrared sensor using a thermopile element 3 will be described with reference to FIG. First, the thermopile element 3 is provided with the pits 30 on the substrate 10 to be the heat sink 34 covered with the insulating film to form the diaphragm 33. Are arranged in large numbers. The substrate 10 is made of a material having good thermal conductivity such as a silicon wafer.

The thermopile element 3 generally has a header 9 for a hermetic seal in order to extract an output to the outside.
0 and wire-bonded.
The thermopile element 3 has a structure in which a cap 62 is covered and sealed in consideration of stability over time or physical protection. An inert gas is used as an internal gas at the time of sealing, and usually nitrogen is used. In the cap 62,
An infrared transmission window 6 is provided to introduce infrared light, and a silicon wafer is used as a material.

The operation of the infrared sensor in which the thermopile element 3 is sealed is as follows. First, infrared rays emitted from a detection target existing outside the sensor pass through the infrared transmission window 6 and reach the thermopile element 3. Since the heat capacity of the diaphragm 33 is small, the temperature rises instantaneously due to the absorbed infrared rays. However, the heat sink 34 has a large heat capacity and is not easily heated because it is in contact with the header 90. There is a difference. Accordingly, the hot junction 3 of the thermocouple 35
Since a temperature difference also occurs between 8 and the cold junction 39, a DC voltage output is obtained. Here, it is known that the amount of infrared rays emitted from the detection target correlates with the temperature of the detection target. Since the thermopile element 3 also emits infrared rays correlated with its own temperature, the diaphragm 3
The temperature rise of 3 is determined by the temperature difference between the object to be detected and the thermopile element 3. That is, the temperature of the detection target can be known using the infrared sensor, and the infrared sensor functions as a radiation thermometer.

[0005] The infrared rays that reach the thermopile element 3 are not only from outside the infrared sensor. Naturally, since the infrared transmitting window 6 or the cap 62 constituting the infrared sensor also has a certain temperature, the infrared rays radiated therefrom also reach the thermopile element 3. However, the thermopile element 3, the header 90, the cap 62, and the infrared transmission window 6, which normally constitute an infrared sensor, are in close contact with each other. Therefore, there is no possibility that the temperature of the diaphragm 33 rises due to the infrared rays emitted from the infrared ray transmitting window 6 and the cap 62 and no output is generated. However, when a sudden temperature change is applied to the infrared sensor from the outside, for example, when the cap 62 is touched with a finger, this is not always the case. If the cap 62 is touched, the temperature in the very near portion first rises, and the heat is transmitted to warm the header 90 and the thermopile element 3. However, no matter how close the components are, the infrared sensor having the current outer shape of 4 to 5 mm cannot transfer heat instantaneously, and a temperature difference occurs between the cap portion and the thermopile element 3. Once a temperature difference is created, the radiated infrared rays from the cap 62 cannot be neglected, that is, the diaphragm 3 is illuminated by the infrared rays emitted from the cap 62.
The temperature of 3 changes. This change appears in the form of noise in the output, and the infrared sensor can no longer correctly measure the temperature of the detection target.

[0006]

As described above, in the infrared sensor using the conventional thermopile element 3, as described above,
If a sudden temperature change is given, an error occurs in the output due to radiation from the cap 62 or the infrared transmitting window 6, and there is a problem that the device cannot be used as a radiation thermometer. Therefore, conventionally, when this infrared sensor is used as a radiation thermometer, the entire sensor is protected by a metal block or the like having a large heat capacity so that a rapid temperature change does not occur. However, very large blocks are required to completely eliminate the effects of external temperature changes. Therefore, at present, when this infrared sensor is used as an accurate radiation thermometer, a block of an appropriate size is used, but it is necessary to restrict the use environment after all. In order to further correct the error, a complicated configuration that monitors the temperatures of the infrared transmission window 6 and the cap 62 with another temperature sensor is required.

Therefore, an object of the present invention is to solve the above-mentioned problem, eliminate the temperature difference between the thermopile element 3 and the other parts of the package, and eliminate the output error due to radiation from the package components such as the infrared transmission window 6. Accordingly, an object of the present invention is to provide an infrared sensor capable of obtaining a stable output even in an environment where temperature changes sharply without requiring a block or the like.

[0008]

According to the present invention, in order to achieve the above object, a first substrate made of a silicon wafer having a thermopile element for infrared detection formed on a front surface, and a sealing substrate formed on a back surface. A second substrate made of a silicon wafer having a groove for use, a glass film formed on the back surface, and a mask formed of a metal film on the front surface, and a portion other than the mask serving as an infrared transmission window. In the above, the front surface of the first substrate and the back surface of the second substrate are bonded and adhered to each other by using the anodic bonding technology, so that the thermopile elements on the front surface of the first substrate have two sheets. A chip-type infrared sensor having a structure sealed between substrates was manufactured.

[0009]

According to the present invention, since the substrate on which the cold junction of the thermopile element is formed is in direct contact with the substrate serving as the infrared transmission window, heat transfer between the two is very fast, and a temperature difference hardly occurs. . Here, the infrared rays emitted from the infrared transmitting window do not change the temperature of the diaphragm of the thermopile element, and the output obtained from the thermopile element is influenced only by the infrared rays emitted from an external detection target. Therefore, if this infrared sensor is used for a radiation thermometer, stable and reliable temperature measurement can be performed even in an environment where the temperature changes greatly.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of a main part of the chip type infrared sensor of the present invention, and FIG. 2 is a plan view of a front surface of a first substrate constituting the chip type infrared sensor.

The chip-type infrared sensor according to the present invention comprises a first substrate 1 and a second substrate 2 each composed of two silicon wafers processed into a specific shape. First, a thermopile element 3 is provided on the front surface of the first substrate 1.
Are formed, and the configuration of the thermopile element 3 is as follows. An insulating coating 31 is formed on the front surface of the first substrate 1, and the insulating coating 31 floats up near the center of the first substrate 1, and is spatially separated from the first substrate 1 to form a cavity. 32 are being made. In forming the structure having the hollow portion 32, a readily soluble metal such as an aluminum film is first formed on the first substrate 1 and then patterned into a target shape of the hollow portion 32. And SiO ₂ film or Si
₃ N ₄ was formed by patterning the insulating film 31 made of a film can be produced by dissolving the aluminum film from the through hole 37. From this, the insulating coating 31 at a location corresponding to the cavity 32 becomes a diaphragm 33 and the first
The portion in contact with the substrate 1 serves as a heat sink 34.

On the insulating film 31, a diaphragm 33 is provided.
A large number of thermocouples 35 are formed so as to be hot junctions 38 on the upper side and cold junctions 39 on the heat sink 34. Thermocouple 3
As for 5, bismuth and antimony were mainly used. At the end of the thermocouple 35, a lead electrode 36 is formed of aluminum or the like. Further, although not shown in the figure, a black body using gold or the like may be formed on the diaphragm in order to increase the infrared absorption efficiency.

Next, the second substrate 2 will be described. Second
On the back surface of the substrate 2, silicon itself as a substrate material is processed by etching to form a sealing groove 4. Since the sealing groove 4 needs to be large enough to accommodate the thermopile element 3 when the first substrate 1 and the second substrate 2 are bonded together later, the planar shape is larger than the insulating film 31 and the depth thereof. Needs to be larger than the thickness of the thermopile element 3.
The silicon of the substrate material is also etched from the front surface of the second substrate 2 to provide an electrode extraction hole 5 penetrating the front surface. An infrared transmitting window 6 is provided on the front surface of the second substrate 2.
Is provided. This is manufactured by forming a mask 61 with a metal film such as chromium on the entire front surface of the second substrate 2 and removing the chromium film by a required size by etching. Therefore, the thickness of the mask 61 may be opaque to infrared light. Further, a glass film 7 is formed on a back surface of the second substrate 2 at a position not corresponding to the sealing groove 4 or the electrode extraction hole 5 by a method such as sputtering. Here, low melting glass was used for the glass film 7.

The first substrate 1 and the second substrate 2 configured as described above are aligned with each other and bonded by an anodic bonding method. First, the first substrate 1
The front surface 11 and the rear surface 22 of the second substrate 2 are joined so that they contact each other. At this time, the thermopile element 3 except for a part of the extraction electrode 36 comes to a position to be accommodated in the sealing groove 4. Further, an electrode extraction hole 5 of the second substrate 2
Must be of a size or position that fits within the plane of the extraction electrode 36. The contacting portion between the two substrates is the contact surface 8 shown in FIG. 2, which corresponds to the portion where the glass film 7 is formed on the second substrate. After the combination, both substrates are heated to about 150 ° C., and a DC voltage of about 100 V is applied so that the first substrate 1 is negative and the second substrate 2 is positive. As a result, the metal ions in the glass film 7 move to the vicinity of the surface, and a large electrostatic attraction is generated between the two substrates, which leads to bonding. Since the anodic bonding can be performed between glass and a metal such as silicon or glass and aluminum, which is likely to form an oxide on the surface, the two substrates are bonded on the contact surface and the thermopile element 3 contained in the sealing groove 4 is formed. Is completely sealed.

Since this anodic bonding is usually performed in a nitrogen atmosphere, the inside of the sealing groove 4 is filled with nitrogen, so that the thermopile element 3 is always kept stable without the influence of oxidation or the like. Furthermore, by performing the bonding in a vacuum atmosphere, the thermopile element 3 can be vacuum-sealed, whereby the output can be greatly improved.

In the present embodiment, a silicon wafer is used as the first substrate 1. However, this can be replaced with another metal substrate as long as it has good thermal conductivity and its surface is polished and smooth. Further, a low-melting glass is formed on the second substrate 2, but it may be formed of another material as long as the glass contains ions.
VD method or spin coating may be used. . However, in this case, the temperature and voltage, which are the conditions for anodic bonding, change according to the glass material. For example, when Pyrex glass is used, the temperature is about 400 ° C. and the voltage is about 50V. Further, although aluminum is used for the lead electrode 36 involved in the bonding, other materials such as titanium, nickel, chromium, and iron can be used as long as the material easily oxidizes the surface.

[0017]

As is apparent from the embodiment, according to the present invention, the first substrate on which the thermopile element is formed and which serves as a heat sink and the second substrate which forms the infrared ray transmitting window are in close contact with each other. Therefore, heat transfer between the two substrates is performed quickly, and the two substrates are always kept at the same temperature. As a result, since there is almost no temperature difference between the cold junction temperature and the infrared transmission window, radiation from other parts of the package such as the infrared transmission window does not affect the diaphragm temperature of the thermopile element. That is, the thermopile element responds to only infrared rays coming from the outside and generates an output. If the infrared sensor of the present invention is used for a radiation thermometer, stable and reliable non-contact temperature measurement is always possible, and it can withstand use in a place where the environmental temperature changes greatly. Furthermore, since it is not necessary to protect with a metal block having a large heat capacity as in the prior art, it is very advantageous for downsizing the radiation thermometer.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a chip type infrared sensor of the present invention.

FIG. 2 is a plan view of a front surface of a first substrate of the chip-type infrared sensor of the present invention.

FIG. 3 is a sectional view of a main part of a conventional infrared sensor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first substrate 11 first substrate front surface 2 second substrate 21 second substrate front surface 3 thermopile element 30 pit 31 insulating film 32 hollow portion 33 diaphragm 34 heat sink 35 thermocouple 36 extraction electrode 37 through hole 38 Hot junction 39 Cold junction 4 Sealing groove 5 Electrode take-out hole 6 Infrared transmission window 61 Mask 62 Cap 7 Glass film 8 Contact surface 90 Header

Claims (1)

(57) [Scope of request for utility model registration] (1) A flat front surface is connected to the front surface.
A diaphragm that forms a hollow part, and the diaphragm
From the above cavity to the heat sink provided on the ram
Reaching the thermopile element having a plurality of thermocouples are formed, a first substrate made of silicon wafer, and a sealing groove to pay the thermopile element is applied to the back surface, and the glass film is formed on the back surface , and more front side is formed a mask of a metal film, its mass
Non-formation portion of the click has become a infrared transmission window, and a second substrate made of silicon wafer, and the back surface of the front surface and the second substrate of the first substrate by using the anodic bonding technique by a state in close contact are joined, the chip-type infrared sensor, wherein said first substrate front surface of the thermopile element is sealed structure between the first substrate and the second substrate.