JPH08159866A - Infrared-ray sensor - Google Patents

Abstract

PURPOSE: To lower the external noise coming in a high impedance circuit part due to electric induction by installing a heat sensing part in an insulating thin film part formed on a void part formed in a part of a sensor substrate and keeping the surrounding of the heat sensing part vacuum. CONSTITUTION: In the infrared-ray sensor 1, infrared-rays are made selectively incident on one heat sensing part 7 through a front cover 10, an infrared-ray transmitting window 14, and a void part 3. Radiation of infrared-rays is shielded by an infrared-ray shielding film 11 in the other heat sensing part 8. The differential output of the heat sensing part 7 and the heat sensing part 8 is led to the outside through an oscillation circuit 9 and moreover a flexible substrate. Since the void part 3, which is the surrounding of the heat sensing part 7, is kept in vacuum condition, the energy of the radiated infrared-rays is not lost through the air and the heat sensing part 7 can be heated efficiently by a slight quantity of the infrared-rays and the sensitivity is improved. Furthermore, since the oscillation circuit 9 is installed near the heat sensing parts 7, 8, the part for the line 16 with high impedance can be shortened and external noise penetrating due to electric induction can be lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared sensor for contactlessly measuring the temperature of an object.

[0002]

2. Description of the Related Art In a thermal infrared sensor (thermistor type bolometer), an infrared sensitive portion having a large impedance of several MΩ is used in order to have high sensitivity so that weak infrared rays can be detected.

As conventional techniques relating to the thermal infrared sensor for detecting such weak infrared rays, there are, for example, the inventions disclosed in JP-A-3-140449 and JP-A-4-1535. However, in these infrared sensors, in general, although noise (electrical noise) is likely to be introduced into the signal line in a high-impedance circuit, no consideration is given to noise in these disclosed inventions. It was

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a novel noise capable of reducing external noise that has intruded into a high impedance circuit portion by electric induction. It is to provide an infrared sensor.

[0005]

That is, the object of the present invention is (1) a thermal infrared ray which heats a temperature-sensitive part by irradiation of infrared rays and measures the amount of infrared rays incident from the temperature change of the temperature-sensitive part. A sensor, wherein the temperature sensitive part is provided in an insulating thin film part formed on a cavity part provided in a part of the sensor substrate, and a vacuum sealing means for maintaining a vacuum around the temperature sensitive part. An electronic circuit whose oscillation frequency changes according to the temperature change of the temperature sensing part is provided on the same or different substrate as the sensor substrate, and information about the amount of infrared rays incident by the change of the oscillation frequency is externally provided. It is achieved by an infrared sensor characterized in that it is adapted to transmit to.

Another object of the present invention is (2) a thermal infrared sensor which heats a temperature-sensitive part by irradiation of infrared rays and measures the amount of incident infrared rays from the temperature change of the temperature-sensitive part, which is a cavity. A sensor substrate in which the temperature sensitive portion is provided in an insulating thin film portion formed in the hollow portion, and the hollow portion of the sensor substrate is covered to maintain a vacuum around the temperature sensitive portion. On the same or a different substrate as the vacuum sealing means and the sensor substrate, the oscillation frequency changes due to the temperature change of the temperature sensing unit, and information about the amount of infrared rays incident due to the change of the oscillation frequency is externally provided. It is achieved by an infrared sensor, characterized in that it comprises an electronic circuit adapted to transmit.

Further, the object of the present invention is (3) in the above (1) or (2), wherein the temperature sensing section uses a Schottky junction between a semiconductor material and a metal material. It is also achieved by the infrared sensor shown.

An object of the present invention is (4) the infrared ray as set forth in any one of (1) to (3) above, wherein the insulating thin film portion is insulating at least against heat. It is also achieved by sensors.

The object of the present invention is (5) the above-mentioned (1) to () in which the insulating thin film portion has any structure selected from a cross-linking type, a cantilever type and a diaphragm type. It is also achieved by the infrared sensor shown in 4).

The object of the present invention is also achieved by (6) the infrared sensor shown in the above (1) to (4), wherein the insulating thin film portion has a crosslinked structure.

Further, the object of the present invention is also achieved by (7) the infrared sensor shown in the above (1) or (6), wherein the semiconductor material is polycrystalline silicon.

Further, the object of the present invention is also achieved by (8) the infrared sensor shown in the above (1) or (6), wherein the semiconductor material is amorphous silicon.

The present invention can also be achieved by (9) the infrared sensor described in any of the above (1) to (8), wherein the metallic material is molybdenum.

The present invention can also be achieved by (10) the infrared sensor according to any one of the above (1) to (8), wherein the metal material is molybdenum silicide.

In the infrared sensor according to the present invention, since the hollow portion around the temperature sensing portion is kept in a vacuum state, the thermal energy lost from the temperature sensing portion due to heat conduction to the peripheral members and further to the space is minimized. As a result, the temperature rise of the temperature sensing part is increased, the sensor sensitivity is remarkably improved, and the oscillation circuit is provided in the vicinity of the temperature sensing part in the infrared sensor chip. The impedance wiring portion is shortened, and the noise that has intruded into the high impedance portion from the outside by electrical induction is reduced.

In the present specification, "vacuum" means a state in which the pressure is 1.0 Torr or less. However, if the pressure is 10 ^-3 Torr or less, 10 ^-3 Tor
The effect is substantially the same as in the case of r.

More specifically, in the infrared sensor of the present invention, a cavity is formed in the sensor substrate, two temperature-sensing parts of the same shape are provided on the cavity, and one of the temperature-sensing parts receives infrared rays. It is desirable to have a configuration in which the infrared rays are selectively made incident and the infrared rays are blocked from entering the other temperature sensitive portion. By detecting the difference between the output of the temperature sensing part where these infrared rays are incident and the output of the temperature sensing part on the side where the infrared rays are blocked, electrical noise and thermal disturbance are removed to obtain a net amount of infrared rays. be able to.
Further, in the case of handling a weak signal such as a thermal infrared sensor (thermistor type bolometer, hereinafter also simply referred to as bolometer) according to the present invention, the output of the bolometer in the vicinity of the temperature sensing unit is of a type resistant to noise. It is desirable to convert it to a signal. Therefore, an electronic circuit whose oscillation frequency changes due to a change in the electric resistance of the temperature sensing part is formed on the sensor substrate on which the temperature sensing part is formed or on another substrate located in the immediate vicinity of the temperature sensing part. By providing the output as the change of the oscillation frequency, the output of the bolometer alone could be taken out only by the weak analog signal, but it is possible to take out the necessary information as the change of the frequency. External noise (analog)
Can be made less susceptible to.

As the sensor substrate which can be used in the present invention, for example, a semiconductor substrate made of silicon, germanium or the like can be cited, but it is preferable to use a silicon substrate which can be easily and inexpensively obtained.

The shape (structure) of the insulating thin film portion for supporting the temperature sensitive portion according to the present invention may be a bridge (bridge) structure with both ends supported, a cantilever type, a diaphragm type structure or the like. However, a crosslinked structure with four-point support is desirable in order to reduce the heat capacity and to provide a stable structure.

The insulating thin film portion for supporting the temperature sensitive portion can be formed by using a thin film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film. It is preferable to use a thin film of the ride film. 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 a structure that stably supports the temperature sensitive portion.
As a structure for supporting the temperature sensitive portion by the insulating thin film portion, for example, an insulating thin film such as a silicon oxynitride film is formed on both surfaces of a silicon substrate, and one surface is cross-linked (bridge) shaped in advance. Or a cantilever shape, a diaphragm shape, etc., and the other surface is patterned into a window of an arbitrary size by etching (one surface is left with a film of a bridge (bridge) shape, the other surface is Remove the window-shaped part of any size)
In addition, aqueous hydrazine and potassium hydroxide (KO
H) or the like for anisotropic etching.

Next, a Schottky junction between a polycrystalline silicon film and molybdenum or molybdenum silicide is formed in the temperature sensitive portion formed on the insulating thin film portion formed on the cavity portion provided on the sensor substrate. Is preferably provided. Sputtering, ion beam sputtering, LP-CVD (Low Pressure Chemical Vapor Deposition), etc. are used for forming the polycrystalline silicon film forming the Schottky junction, but the grain size of the silicon crystal is large and stable. The LP-CVD method that can obtain the film is desirable.

The temperature sensitive portion may be a Schottky junction between an amorphous silicon film and molybdenum or molybdenum silicide. In this case, a sputtering method or a PCVD (plasma CVD) method is used for forming the amorphous silicon film, and the PCVD method is preferable because it has good controllability of the impurity concentration in silicon.

Further, the molybdenum or molybdenum silicide film is formed by an electron beam vapor deposition method, a sputtering method or the like, and a sputtering method having good adhesion to the base is desirable.

The position for forming the temperature sensing portion is not particularly limited as long as it is on the insulating thin film portion formed on the hollow portion provided on the sensor substrate, and for example, the same position. It is possible to provide two hollow portions, and to arrange the same temperature sensitive portion in the center of the thin film portion on both hollow portions.

As the vacuum sealing means for holding the temperature sensing portion in a vacuum, for example, a lid body (front lid and back lid) joined to both sides of the sensor substrate is used. After bonding to one surface of the sensor substrate, the other lid body is bonded to the other surface of the sensor substrate in a vacuum, so that it is provided around the temperature sensing part, for example, in the cavity provided in the sensor substrate and a part of the lid body. A vacuum that keeps the digging part (hereinafter, the cavity of the sensor substrate and the entire space of the digging part of the lid body collectively referred to as simply the cavity) in a vacuum state. A sealing means etc. can be mentioned.

Next, the electronic circuit whose oscillation frequency changes according to the temperature change of the temperature sensing part may be any circuit capable of transmitting information regarding the amount of incident infrared rays to the outside due to the change of the oscillation frequency in the electronic circuit. , For example, as described above, by using a temperature-sensitive part whose resistance value changes by selectively receiving infrared light and receiving infrared light, and another temperature-sensing part that blocks the incidence of infrared light and whose resistance value does not change, It is possible to use an oscillating circuit or the like configured such that the temperature change can be known by a value obtained from the ratio of the number of oscillations of the oscillator when these temperature sensing parts are alternately connected during temperature measurement.

A silicon substrate or a glass substrate can be used as the lid. In the case of using the lid, in order to selectively guide infrared rays to only one of the pair of temperature sensitive parts, a silicon substrate is used as the lid,
An infrared reflective film such as an aluminum film or a copper film is provided on the substrate, and a window (opening) is partially provided in the infrared reflective film in a portion corresponding to a temperature sensitive portion to which infrared rays are to be guided. Is desirable.

As the means for joining the lid and the sensor substrate,
For example, there is a bonding method by a solder bump method in which a lid and a sensor substrate are formed on a barrier metal, or anodic bonding. Particularly, in the case where the temperature sensor surroundings of the infrared sensor are kept in a vacuum state, one of the joining of the front lid or the back lid and the sensor substrate is performed in vacuum according to the procedure shown in the above-mentioned sealing means. For example, Pyrex glass (trade name)
Then, the anodic bonding can be directly performed with the sensor substrate made of silicon.

[0029]

EXAMPLES The present invention will be specifically described below with reference to examples. The following examples are for explaining the present invention, and the present invention is not limited to these examples.

First, as the structure of the infrared sensor 1 of this embodiment, as shown in FIGS. 1 and 2, a silicon substrate 2 as a sensor substrate is provided, and a cavity 3 is formed in this silicon substrate 2. ing. The cavity 3 is opened on the upper and lower surfaces of the silicon substrate 2, and on the upper surface of the silicon substrate 2, two bridges are formed on the cavity 3 as an insulating thin film portion by a four-point supporting bridge structure. A silicon oxynitride film 6 having parts 4 and 5 is formed.

A minute thermistor is provided as a temperature sensing portion 7 and 8 in the central portion of each bridge portion 4 and 5. Each of these temperature sensitive portions 7 and 8 is made of polycrystalline silicon. In the temperature-sensitive parts 7 and 8,
Although not shown, a Schottky junction is formed between molybdenum or molybdenum silicide and polycrystalline silicon, and an end portion of an electrode wiring layer formed of an aluminum film is electrically connected to the other end of the electrode wiring layer. The temperature sensitive parts 7 and 8 formed by extending the chrome film on the periphery of the upper surface of the silicon substrate 2 change the oscillation frequency on the silicon substrate 2 due to the temperature change of the temperature sensitive part. It is connected to an electronic circuit (hereinafter, also simply referred to as “oscillation circuit”) 9 that transmits information regarding the amount of incident infrared rays to the outside due to changes in the oscillation frequency.

By the way, in order to make the infrared sensor highly sensitive, it is very effective to make a vacuum atmosphere around the temperature sensing portion. Therefore, in the infrared sensor 1 of this embodiment,
For the purpose of maintaining a vacuum in the cavity 3 around the temperature sensitive portions 7 and 8 which are minute thermistors, the cavity 3 was maintained in a vacuum state by performing vacuum sealing when the upper lid 10 was joined. It is a thing.

That is, the back cover 15 is bonded to the lower surface of the silicon substrate 2 in order to keep the cavity 3 in a vacuum state. The back cover 15 is made of, for example, silicon or Pyrex glass (trade name).

On the upper surface of the silicon oxynitride film 6 of the silicon substrate 2, the front cover 1 is joined after the back cover 15 is bonded.
0 is bonded in vacuum. The front lid 10 is made of silicon, and the infrared lid 11 is formed on the front lid 10. Infrared antireflection film 1
On the surface of 1, an infrared shielding film 12 is formed by a multilayer film in which a titanium layer is laminated on an aluminum film or a copper layer, for example, and the infrared shielding film 12 is located at a position facing the infrared light receiving portion 13. An infrared transmission window (aperture) 14 is provided to guide infrared rays to the inside.

Further, the electronic circuit (oscillation circuit) 9 whose oscillation frequency changes according to the temperature change of the temperature sensing part is
Although it is desirable to provide it monolithically on the silicon substrate 2 on which the 8 is formed, it can be formed on the substrate of the back cover 15. In the latter case, it is necessary to configure the temperature sensing parts 7 and 8 and the oscillation circuit 9 to be electrically connected when the back cover 15 is joined.

In the infrared sensor 1, infrared rays are emitted from the front cover 1.
It selectively enters one of the temperature sensitive parts 7 through the infrared transmission window (aperture) 14 of 0 and the cavity 3. In the other temperature-sensitive section 8, the infrared ray shielding film 11 blocks the incidence of infrared rays. The differential output between the temperature sensing unit 7 on which the infrared rays are incident and the temperature sensing unit 8 on which the infrared rays are shielded is guided to the outside via the oscillation circuit 9 and further via a flexible substrate (not shown).
Here, since the inside of the cavity 3 (including the dug portion of the front cover 10) around the temperature sensing unit 7 is kept in a vacuum state, the energy of the incident infrared rays is not lost through the atmosphere, It is possible to efficiently heat the temperature sensitive part 7 with a small amount of infrared rays,
The sensitivity is improved. On the other hand, the cavity portion 3 around the other temperature sensing portion 8 is also kept in the same vacuum state. Therefore, the true amount of infrared rays can be detected by the differential output between the two temperature sensing parts 7 and 8.

Besides the present embodiment, the shape (structure) of the insulating thin film portion formed on the cavity portion 3 of the silicon substrate 2 which is the sensor substrate is other than the above-mentioned four-point support bridge structure. Also, for example, a diaphragm type structure and a cantilever type structure may be used.

Further, in the chip of the infrared sensor 1, since the oscillation circuit 9 is provided in the vicinity of the temperature sensing portions 7 and 8, the portion of the high impedance wiring 16 is shortened and the wiring 16 of high impedance is externally connected. It is possible to reduce the noise that has penetrated into the portion by electrical induction.

The oscillator circuit 9 may be of any circuit type as long as it meets the object of the present invention. In this embodiment, the oscillator circuit as shown in FIG. 3 was used. As shown in FIG. 3, the oscillation circuit 9 includes a temperature sensing portion 7 as a detection thermistor R ₃ whose electric resistance (impedance) changes by receiving infrared rays, and a reference resistance thermistor which blocks infrared irradiation and prevents impedance from changing. R ₂
The temperature sensing unit 8 is used as HI of control signal B
Switching the -LO, for oscillating at a frequency corresponding to the resistance value of the thermistor R ₂ or R _3, in which it is possible to know the temperature variation by comparing the frequency of both. The control signal A turns the oscillation on and off.
It is a signal to do.

As shown in FIGS. 1 and 2, by providing the oscillator circuit 9 in the chip of the infrared sensor 1 in the vicinity of the temperature sensing parts 7 and 8, the high impedance wiring part 16 is shortened, The noise that had invaded the high impedance wiring portion 16 by electrical induction was reduced. In addition, the thermal infrared sensor (thermistor type bolometer) alone could output the output only with a weak analog signal, but since it was possible to extract the necessary information as a change in frequency, external noise (analog ) Became less susceptible to.

Next, a manufacturing process block diagram of the infrared sensor used in this embodiment as one embodiment of the present invention is shown in FIGS.

FIG. 4 is a block diagram of a manufacturing process of an oscillation circuit as an electronic circuit in which the oscillation frequency changes according to the temperature change of the temperature sensing part of the infrared sensor, and is a cross section at the stage where the oscillation circuit is formed on the sensor substrate. It is a schematic diagram showing a structure.

From FIG. 4, the thickness of the sensor substrate 31 is 3
Using an n-type single crystal silicon substrate of 00 μm and plane orientation (100), fabrication was performed according to the following steps.

1. Oxidation: The sensor substrate 31 is heated to a high temperature (110
The silicon oxide film 32 is exposed to an oxidizing atmosphere at 0 ° C.
(Film thickness: about 6000 angstrom) is grown.

2. P-well patterning: A P-well region pattern is formed in the oxide film by using a photo-etching method (using a photoresist), and then the oxide film in the P-well region is removed by etching using this photoresist as a mask ( Open) and rinse away the photoresist.

3. P-well diffusion: For example, boron is thermally diffused (about 1200 ° C.) in the patterned portion to form a P-well layer (or P by an ion implantation method).
A well layer may be formed in some cases. ), An oxide film is again grown on that portion. The portion other than the patterning is blocked by the oxide film, so that boron does not enter.

4. P ⁺ patterning: The oxide film in the region to be the P ⁺ layer is removed (opened) by the same method as the P well patterning.

5. P ⁺ diffusion: Boron is thermally diffused (about 1000 ° C.) in the patterned portion to form a P ⁺ layer (source and drain regions of the P channel transistor), and an oxide film is again grown in that portion. The portion other than the patterning is blocked by the oxide film, so that boron does not enter.

6. N ⁺ patterning: The oxide film in the region to be the N ⁺ layer is removed (opened) by the same method as the P well patterning.

7. N ⁺ diffusion: Phosphorus is thermally diffused (about 1000 ° C.) in the patterned portion to form an N ⁺ layer (source and drain regions of N-channel transistor), and an oxide film is again grown in that portion. Since the portion other than patterning is blocked by the oxide film, phosphorus does not enter.

8. Gate oxidation and contact hole
Patterning: Gate oxide and oxide film in the contact hole region are removed (opened) in the same manner as in P well patterning.

9. Gate oxidation: expose to a high temperature (1000 ° C) oxidizing atmosphere to thin the silicon oxide film (about 150
0 angstrom) Re-grow.

10. Contact patterning: The oxide film in the contact region is removed (opened) by the same method as the P well patterning.

11. Wiring patterning: Evaporating aluminum in a vacuum to deposit (evaporate) an aluminum film on the entire surface of the substrate, and then use photo-etching with a photoresist to form a pattern, using the photoresist as a mask, Unnecessary parts are removed by etching and the photoresist is washed away. Next, raise the temperature (about 400
(° C.), the electrical connection between aluminum and silicon is improved (sintering), and the fabrication of the oscillation circuit 33 is completed.

However, the contact patterning in step 10 and the wiring patterning in step 11 are carried out in the subsequent metallization (wiring) manufacturing step.

FIG. 5 is a block diagram of the manufacturing process of the temperature sensing portion (Schottky diode) of the infrared sensor, and is a schematic view showing a cross-sectional structure at the stage where the temperature sensing portion is formed on the sensor substrate.

From FIG. 5, a silicon oxynitride film 34 is formed on the sensor substrate 31 on which the oscillation circuit 33 has been manufactured (up to the gate oxidation step).

Next, a temperature sensitive film 35 of polycrystalline silicon having a thickness of about 1 μm is formed at a position corresponding to the center of the cross-linked portion formed in the subsequent step, and on the temperature sensitive film 35 of polycrystalline silicon. Growing an oxide film, removing a part of the oxide film (opening),
A low concentration of phosphorus (dose:
1 × 10 ¹² cm ⁻² ) of ion-implanted portion 36 is formed, and then sputter-deposited metal molybdenum (or molybdenum silicide) 37 is formed on the phosphorus-low-concentration ion-implanted portion 36 to form a low phosphorus concentration. A Schottky junction was formed at the interface between the ion-implanted portion 36 and the metal molybdenum film 37. In this embodiment, the temperature dependence of the reverse current of the temperature sensitive portion (Schottky diode) due to the Schottky junction is used as a temperature sensitive element. Further, in approximately half of the temperature-sensitive film 35 of polycrystalline silicon, a part of the formed oxide film is removed (opened), and a high concentration of phosphorus (dose amount: 1 × 1) is formed in the patterned portion.
0 ¹⁶ cm ^-2 or more) to form n ⁺ silicon 38 by ion implantation, and the n ⁺ silicon 38 and n ⁺ silicon 3 are formed in a later step.
The ohmic contact is obtained at the interface between the aluminum layer formed on the electrode 8 and the electrode. This completes the production of the temperature sensitive portion 39.

Next, FIG. 6 is a block diagram of the manufacturing process of the metallization (wiring) on the sensor substrate of the infrared sensor. The metallization (wiring) is formed on the sensor substrate.
FIG. 3 is a schematic view showing a cross-sectional structure at a stage where the is formed.

As shown in FIG. 6, after the contact patterning of the above-described oscillation circuit manufacturing process 10 is performed on the sensor substrate 31 on which the temperature sensing section 39 is manufactured, the temperature sensing section 39 formed of a Schottky diode is used. The electrical wiring was formed by the chromium layer 40 at a position corresponding to a bridge portion having a width of 20 μm formed in a later step.

Next, the connection between the temperature sensitive portion 39 and the wiring by the chromium layer 40 and the above-mentioned oscillation circuit manufacturing process 11
The wiring pattern of the aluminum layer 41 (thickness of about 1.5 μm
m) is formed by sputtering with good step coverage. This completes the fabrication of metallization (wiring) on the sensor substrate.

Next, FIG. 7 is a block diagram of a process for producing an oscillating circuit on a sensor substrate of an infrared sensor and a silicon oxynitride film for protecting a temperature sensing part, and a metal pad for soldering, which is on the sensor substrate. FIG. 3 is a schematic view showing a cross-sectional structure at a stage where an oscillation circuit, a silicon oxynitride film for protecting the temperature sensing portion, and a metal pad for soldering are formed.

From FIG. 7, the temperature sensitive portion 3 already formed from the hydrazine solution used when forming a cavity in the silicon substrate as the sensor substrate 31 by anisotropic etching described later.
9 and the chromium layer 40 and the aluminum layer 41, in order to protect the electric wiring, after the film formation of the aluminum layer 41 and the wiring patterning in the manufacturing process 11 of the oscillation circuit, the silicon oxynitride film 42 having a thickness of 3 μm is entirely covered. Then, a film is formed.

Next, a solder-bonding metal pad 43 used for solder-bonding with a front cover, which will be described later, is formed by depositing a copper layer 44 and a titanium layer 45 on the silicon oxynitride film 42 (in order from the top). Formed. As a result, the production of the oscillation circuit on the sensor substrate, the silicon oxynitride film for protecting the temperature sensing portion, and the production of the solder bonding metal pad are completed.

Although a silicon oxynitride film (not shown) is initially formed on the lower side of the sensor substrate 31, the sensor substrate 31 and the glass substrate of the back cover described later are anodically bonded. Silicon is exposed during the manufacturing process, for example, during the manufacturing process for forming contact holes.

Next, FIG. 8 is a block diagram of a manufacturing process of a bridge portion (micro bridge) by Si anisotropic etching of a sensor substrate of an infrared sensor, in which a bridge portion and a cavity are formed on the sensor substrate. It is a schematic diagram showing the cross-sectional structure of.

From FIG. 8, the temperature sensing portion 3 of the sensor substrate 31 having the silicon oxynitride film 42 for protection of the oscillation circuit and the temperature sensing portion and the metal pad 43 for solder bonding manufactured.
9 is subjected to Si anisotropic etching using a hydrazine solution to form a cavity 46a on the sensor substrate, so that the bridge portion 47 (micro bridge) formed by the silicon oxynitride film 42 that is not subjected to the etching is formed. It is obtained in the form of being bridged to the hollow portion 46a (actually, a bridge structure with four-point support). By these, Si on the sensor substrate
The fabrication of the bridge portion (micro bridge) by anisotropic etching is completed.

In this embodiment, the temperature sensing portion 39 is provided on the bridge portion 47 in order to reduce the amount of heat dissipated from the temperature sensing portion 39 as much as possible, but the infrared ray receiving area is wide. In order to achieve this, the bridge portion 47 formed by the silicon oxynitride films 34 and 42 is also formed in the same way as the widened infrared light receiving portion 13 is provided in the central portion of the bridge portions 4 and 5 shown in FIG. Ride film 4
When patterning 2, it is desirable to widen the portion corresponding to the central portion of the bridge portion. Also, FIG.
As shown in Fig. 5, the portions 4a, 5 supporting the central portion of the bridge portion.
In order to minimize the amount of heat dissipated through a,
Similarly to the case where the central portion has a shape in which the supporting members 4a and 5a are thin (width 10 μm or 20 μm) and supported by four points, a part of the silicon oxynitride film 42 described above may be formed in a thin shape. More desirable.

Next, FIG. 9 is a block diagram of a vacuum sealing packaging manufacturing process of the sensor substrate and the lid of the infrared sensor, showing a sectional structure at a stage where the sensor substrate and the lid are vacuum sealed and packaged. It is a schematic diagram.

As shown in FIG. 9, the front cover 48 corresponding to the sensor substrate 31 is made of the material of the front cover 48 having a thickness of 2 in this embodiment.
A single crystal silicon substrate 49 having a plane orientation (100) of 00 μm
Is used to form a silicon oxide film 50 having a thickness of about 0.1 μm on both surfaces of the silicon substrate 49 as a mask for anisotropic etching with an infrared antireflection film and hydrazine.

Further, on the side where infrared rays are incident (upper side in FIG. 9), a metal (copper / titanium laminated) film 51 is formed in order to block the incidence of infrared rays from other than the target object.
The metal film 51 is removed by etching at a portion directly above the infrared receiving portion of the sensor substrate 31 to provide an infrared transmission window (aperture) 52. If a Fresnel lens is provided in this aperture 52, infrared rays can be focused on the infrared light receiving section, and the temperature of the temperature sensing section 31 can be further raised.

Next, on the surface of the front cover 48 facing the sensor substrate 31, a solder bonding metal pad (not shown) used for solder bonding with the solder bonding metal pad 43 of the sensor substrate 31 is formed. The solder-bonding metal pad was a laminated film of copper and titanium, similarly to that on the sensor substrate 31 side.

Further, in order to avoid contact with the respective constituent members provided in the bridge portion 47 having the oscillation circuit and the temperature sensing portion, the parts facing the bridge portion 47 having the oscillation circuit 33 and the temperature sensing portion 39 are different from each other. The cavity 46b is formed by digging down by about 100 μm by means of isotropic etching. Simultaneously with the formation of this cavity 46b, the silicon substrate 48 can be simultaneously dug from the front and back by anisotropic etching to separate it from the adjacent chip. It should be noted that each chip is not completely separated before being bonded to the sensor substrate 31, but is connected by a thin silicon beam (digit),
After bonding with the sensor substrate 31, dicing is performed to separate the individual chips. This is desirable because a large number of chips can be aligned (aligned) at one time in a wafer (batch) process during solder bonding.

Next, the back cover 53 corresponding to the sensor substrate 31.
In this embodiment, the material of the back cover 53 has a thickness of 300 μm.
A glass substrate 54 manufactured by Pyrex (trade name) was used. The surface of the glass substrate 54 on the side to be bonded to the sensor substrate 31 has the glass surface of the substrate exposed, but the opposite surface shields visible light and infrared light, and is therefore a metal (lamination of copper and chromium).
The film 55 was formed by vapor deposition.

Next, the procedure of the above-mentioned sensor substrate, the joining means for the front lid and the back lid, and the vacuum sealing means performed at the joining will be described.

First, the lower surface of the sensor substrate 31 and the glass substrate surface of the back cover 53 are bonded by anodic bonding. This bonding is performed in a vacuum or in the atmosphere. Particularly when it is performed in the atmosphere, it is necessary to avoid mixing of dust and the like and to have a sufficiently clean atmosphere.

Next, before installing in the vacuum container, solder is applied to the solder bonding metal pads of the sensor substrate 31 and the front cover 48. Then, the sensor substrate 31 to which the back cover 53 is joined is installed in a vacuum container having a heating mechanism and an alignment function, and the front cover 48 is also installed in the same container.
The container is evacuated and evacuated (vacuum pressure <× 10 ^-6 Torr)
After that, the solder bonding metal pad on the sensor substrate 31 side is aligned with the solder bonding metal pad of the front cover 48, and the solder bonding is performed by heating, thereby vacuuming the sensor substrate and the lid of the infrared sensor. The fabrication of the sealed packaging can be completed.

[0078]

In the infrared sensor of the present invention, since the oscillating circuit is provided in the vicinity of the temperature sensing portion, the high impedance wiring portion is shortened, and the high impedance wiring portion intrudes from the outside by electrical induction. It is possible to reduce the noise that has been present, and it can be detected more accurately by converting it into a noise-resistant signal in the immediate vicinity of the temperature sensing part. More specifically, it is necessary to receive weak infrared rays. The sensor can extract the necessary information only as a weak analog output signal and can extract it as a frequency change by the oscillation circuit, so that it is affected by external noise (analog) entering the output signal line. It is possible to realize a highly sensitive sensor that can be made difficult and can detect more accurate information.

Further, since the infrared sensor of the present invention can utilize the temperature characteristic of the reverse saturation current of the Schottky diode, it can be applied to a thermometer for measuring the temperature of a target object in a non-contact manner. And high precision can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cross-sectional structure of an infrared sensor used in this example as one embodiment of the present invention.

FIG. 2 is a schematic diagram showing an external structure of a sensor substrate of an infrared sensor used in this example as one embodiment of the present invention.

FIG. 3 is a circuit diagram using an oscillation circuit that oscillates at a frequency according to a resistance value due to a temperature change of a pair of temperature sensing parts, as an electronic circuit of an infrared sensor used in this example as one embodiment of the present invention. Is.

FIG. 4 is a block diagram of a manufacturing process of an oscillation circuit of a temperature sensing part of an infrared sensor, which is a schematic diagram showing a cross-sectional structure at a stage where the oscillation circuit is formed on a sensor substrate.

FIG. 5 is a block diagram of a manufacturing process of a temperature sensitive portion (Schottky diode) of the infrared sensor, and is a schematic view showing a cross-sectional structure at a stage where the temperature sensitive portion is formed on the sensor substrate.

FIG. 6 is a block diagram of a manufacturing process of metallization (wiring) on the sensor substrate of the infrared sensor, which is a schematic view showing a cross-sectional structure at a stage where the metallization (wiring) is formed on the sensor substrate.

FIG. 7 is a block diagram of a process for producing an oscillation circuit and a temperature-sensitive portion protecting silicon oxynitride film on a sensor substrate of an infrared sensor, and a metal pad for soldering. FIG. FIG. 3 is a schematic view showing a cross-sectional structure at a stage where a silicon oxynitride film for protecting a portion and a metal pad for solder bonding are formed.

FIG. 8 is a block diagram of a manufacturing process of a bridge portion (microbridge) by Si anisotropic etching of a sensor substrate of an infrared sensor, which schematically shows a cross-sectional structure at a stage where a bridge portion and a cavity are formed on the sensor substrate. It is a figure.

FIG. 9 is a block diagram of a vacuum sealing packaging manufacturing process of the sensor substrate and the lid of the infrared sensor, which is a schematic diagram showing a cross-sectional structure at a stage where the sensor substrate and the lid are vacuum sealed and packaged.

[Explanation of symbols]

1 ... Infrared sensor, 2 ... Silicon substrate, 3 ... Cavity part, 4, 5 ... Cross-linking part, 6 ... Silicon oxynitride film, 7, 8 ...
Temperature sensor, 9 ... Electronic circuit, 10 ...
Front lid, 11 ... Infrared reflection preventing film, 12 ... Infrared shielding film, 13 ... Infrared receiving section, 1
4 ... Infrared transmitting window (aperture), 15 ... Back cover,
16 ... Wiring, 31 ... Sensor substrate,
32 ... Silicon oxide film, 33 ... Oscillation circuit, 34 ... Silicon oxynitride film, 35 ... Temperature sensitive film, 36
... Ion-implanted portion at a low concentration, 37 ... Metal molybdenum (or molybdenum silicide), 38 ... n ⁺ silicon, 39 ... Temperature sensitive portion, 40 ... Chromium layer,
41 ... Aluminum layer, 42 ... Silicon oxynitride film, 43 ... Solder bonding metal pad, 44 ... Copper layer, 45 ... Titanium layer,
46a, 46b ... Cavity part, 47 ... Bridge part,
48 ... Front cover, 49 ... Single crystal silicon substrate, 50 ... Silicon oxide film, 51 ... Metal film, 52 ... Infrared transmitting window (aperture), 53 ... Back cover, 54
... Glass substrate, 55 ... Metal film, A ... Oscillation ON-OFF
Control signals, B ... control signal for switching the HI-LO for, R ₂ ... reference resistor thermistor,
R ₃ ... Detection thermistor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoshi Komatsu 1500 Inoguchi, Nakai-cho, Ashigarakami-gun, Kanagawa Terumo Corporation

Claims (1)

[Claims] 1. A thermal infrared sensor that heats a temperature-sensitive part by irradiation of infrared rays, and measures the amount of infrared rays incident from the temperature change of the temperature-sensitive part, the cavity being provided in a part of a sensor substrate. The temperature-sensitive section is provided on the insulating thin film section formed on the section, and has a vacuum sealing means for holding a vacuum around the temperature-sensitive section, on the same substrate as the sensor substrate or on another substrate. An infrared sensor characterized in that an electronic circuit whose oscillation frequency changes according to the temperature change of the temperature sensing portion is provided, and information relating to the amount of incident infrared rays due to the change in the oscillation frequency is transmitted to the outside.