JPH09329499A - Infrared sensor and infrared detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an infrared sensor and an infrared detector having a high accuracy by providing a light receiving portion in which two heat sensitive resistive films for detecting infrared light are formed and one heat sensitive resistive film detecting temperature of a base board. SOLUTION: Incident infrared light is absorbed by a glass layer 13 to be converted to heat. Thereby temperature of the heat sensitive resistive films 5, 5' is increased, the light receiving portion 4 is thermally isolated from a base board 1 by a beam part 3, temperature in the light receiving portion 4 becomes uniform and the two heat sensitive resistive film 5, 5' become the same temperature. Since the heat sensitive film 10 formed on the base board 1 has a large heat capacity, detection of temperature of an object can be achieved without a special light screening means. Temperature distribution profile in the light receiving portion 4 is uniform and thereby an output voltage of a bridge circuit becomes twice as large as that in the case where one heat sensitive resistive film for detecting infrared light is used, so that temperature detection with a high accuracy can be achieved.

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 an infrared detector for non-contact temperature detection and temperature measurement. More specifically, the infrared light receiving section has a bridge structure (micro air bridge), The present invention relates to an infrared sensor having a temperature compensation function and high detection sensitivity, and relates to an infrared detector using the infrared sensor.

[0002]

2. Description of the Related Art Conventionally, a thermal infrared detector is known as an infrared detector for detecting the surface temperature of an object in a non-contact manner. The thermal infrared detector is a sensor that measures the surface temperature of a high-temperature object or a moving object in a non-contact manner, and the infrared energy radiated from a detected object such as an object or a moving object causes the thermal resistance of the infrared detection unit to change. The temperature rises, and the change in electrical resistance due to the temperature rise of the heat-sensitive resistor is detected as a temperature change to measure the surface temperature of the object to be detected.

Generally, a thin film made of a thermistor material or a metal resistance material whose resistance value changes with temperature, or a thin film thermoelectric body is used for the infrared detecting section. Since the amount of infrared rays radiated from the object to be detected is generally weak, the heat-sensitive part of the sensor receiving it has a small heat capacity, high infrared absorption characteristics, and is a highly accurate element manufacturing technique from the viewpoint of manufacturing. Is required. Therefore, the infrared sensor is generally formed by applying semiconductor fine processing technology.

An infrared sensor based on semiconductor fine processing technology is disclosed in, for example, Japanese Patent Publication No. 7-65937,
It is disclosed in Japanese Patent No. 136379. In these infrared sensors, the infrared detection section is provided on the insulating thin film formed on the substrate, and the portion corresponding to the back side of the substrate is removed by etching, or a sacrificial layer for bridge formation is formed to remove the substrate. It is an infrared sensor having a cross-linking structure (micro air bridge) that supports an insulating thin film on which an infrared detecting portion is formed on a peripheral substrate left by being removed by selective etching.

In the infrared sensor having such a structure, since the thermal resistance between the infrared detector and the substrate can be increased, the heat capacity of the infrared sensor can be extremely reduced. Therefore, it is possible to realize an infrared detector having a high response speed of temperature detection and high sensitivity.

For example, in the infrared sensor disclosed in Japanese Patent Application Laid-Open No. 6-160174, the temperature rise of the heat-sensitive portion is increased by optimizing the shape of the cross-linking portion of the infrared sensor. The device is designed to be highly sensitive by not scattered to the side. In this infrared sensor, the thermal resistance of the beam portion is reduced by adopting a structure including an infrared ray receiving portion (circular or square), four beam portions supporting the light receiving portion, and a substrate supporting these beam portions. As a result, it becomes difficult for the heat energy of the light receiving portion to dissipate to the substrate side through the beam portion. Therefore, the heat conversion efficiency of incident infrared rays in the light receiving section is improved, and an infrared detector with higher sensitivity can be obtained.

Further, an infrared detector previously proposed by the present applicant is disclosed in Japanese Patent Laid-Open No. 2012-201229. This infrared detector is intended for a high-sensitivity infrared sensor and is formed by using a thermistor material as a heat sensitive resistor. In this structure, four thermistors are formed in a Wheatstone bridge as shown in FIG. 9A, and infrared rays are received by the thermistors T2 and T3 on opposite sides of the bridge. When the temperature of the thermistors T2 and T3 rises due to the incidence of infrared rays, the resistance value changes by ΔR. Assuming that the voltage fluctuation due to the change in the resistance is ΔV, the resistance of the thermistor decreases as the temperature rises, and the thermistor on the opposite side is composed of the same characteristics. Therefore, the terminal voltage Va at the bridge a point is V1 + ΔV. Become. Similarly, terminal voltage V at point b
b becomes V2-ΔV. The output voltage V of the bridge is expressed by the following equation.

V = Va-Vb = V1 + ΔV- (V2-ΔV) = 2ΔV ... (1) (However, V1 and V2 are equal)

That is, as shown in the equation (1), the bridge output is doubled, and it is understood that the infrared detector is further improved as compared with the infrared detector having the conventional structure.

In the infrared detector disclosed in Japanese Unexamined Patent Publication No. 6-160174, as shown in FIGS. 12A to 12C, the beam portions 31 extending from the four corners of the cavity portion 30 provided in the substrate are provided. It has a bridge structure for supporting the light receiving section 32 of the infrared detecting section, or a beam structure 31 extending from each of the four sides of the hollow section 30 for supporting the light receiving section 32 of the infrared detecting section. Therefore, assuming that the area of the infrared light receiving portion is constant, the longest length of the beam portion 31 is the cavity portion 3.
It is a structure supported at four corners of 0. This structure is the light receiving portion 32.
In order to minimize the dissipation of heat from
Since the temperature of the infrared light receiving portion can be raised rapidly, it contributes to the improvement of sensor sensitivity.

[0011]

However, in the infrared detector typified by Japanese Patent Laid-Open No. 6-160174, in order to further improve the sensor sensitivity, the area of the light receiving portion on which infrared rays are incident is increased. There is a need to. However, if the area of the light receiving portion is increased, the length of the beam portion must be relatively shortened. As a result, the thermal resistance of the beam portion connecting (bridging) the light receiving portion and the substrate becomes small, the heat dissipation of the light receiving portion becomes large, and the sensor sensitivity decreases.

If the width of the beam portion is narrowed to increase the thermal resistance in order to solve these problems, the mechanical strength of the beam portion becomes weak during the process of manufacturing the sensor element or in the actual use state. There was a drawback that breakage and breakage were likely to occur.

Further, in the case of an infrared detector composed of four thermistors, for example, disclosed in Japanese Patent Laid-Open No. 2012-201229, the thermistors T2 and T3 shown in FIG. Therefore, a minute difference in shape due to a pattern formation error in manufacturing appears as a difference in heat capacity. Further, the thermistors T2 and T3 are unlikely to be at the same temperature due to subtle fluctuations in the incidence of infrared rays due to the thermistors T2 and T3 being formed separately. Therefore, the output voltage of the bridge circuit composed of these thermistors is not always exactly doubled due to the offset voltage, and there is a drawback that the voltage becomes lower than that.

The present invention has been made in order to solve the above problems, and detects infrared rays emitted from an object to be detected to detect the temperature of the object to be detected in a non-contact type. Another object of the present invention is to provide an infrared sensor and an infrared detector that can increase the temperature detection sensitivity and have high detection accuracy.

[0015]

In order to solve the above-mentioned problems, the present invention provides a substrate, a cavity portion provided in the substrate, and a beam portion supporting the cavity portion in a bridged manner. In an infrared sensor consisting of a light-receiving part, the light-receiving part formed with two heat-sensitive resistive films for infrared detection and one heat-sensitive resistive film for detecting the temperature of the substrate on the substrate are arranged. It is an infrared sensor characterized in that.

A second aspect of the present invention is an infrared sensor comprising a substrate, a cavity provided in the substrate, and a light receiving portion supported in the cavity by a beam so as to form a bridge. It is an infrared sensor characterized in that the light receiving portion having one heat sensitive resistive film formed thereon and two heat sensitive resistive films for temperature compensation are disposed on the substrate.

A third invention is an infrared sensor comprising a substrate, a hollow portion provided in the substrate, and a light receiving portion supported in the hollow portion by a beam portion in a bridging manner, and extending from the substrate. Two infrared-sensitive heat-sensitive resistive films formed on the light-receiving portion supported by four hook-shaped beam portions, two temperature-compensating heat-sensitive resistive films formed on the substrate, and the temperature of the substrate It is an infrared sensor characterized by comprising one heat-sensitive resistance film formed on a substrate for measuring.

A fourth aspect of the present invention is an infrared sensor comprising a substrate, a cavity provided in the substrate, and a light receiving portion supported in the cavity by a beam so as to form a bridge. The infrared sensor is formed on the substrate. First and second cavity portions, first and second light receiving portions supported by four hook-shaped beam portions extending in the first and second cavity portions, respectively, and the first and second cavity portions. Two heat-sensitive resistive films formed on each of the two light receiving portions, a heat-sensitive resistive film formed on the substrate for measuring the temperature of the substrate, and an infrared transmission filter disposed on the substrate, An infrared reflection preventing film provided on the infrared transmitting filter on the light receiving unit side; and an infrared reflecting film provided on the infrared transmitting filter on the second light receiving unit side to block infrared rays, The light receiving part is for infrared detection, and the second light receiving part is temperature compensated. An infrared sensor, which comprises using as.

A fifth invention is the infrared sensor according to any one of the first to fourth inventions, characterized in that the beam portion is thinner than the light receiving portion. It is an infrared sensor.

A sixth invention is the infrared sensor according to the fourth invention, characterized in that the infrared transmission filter is formed of silicon.

A seventh invention is the infrared sensor according to any one of the first to sixth inventions, wherein the heat-sensitive resistance film is formed of Mn-Ni-Co type oxide. It is a sensor.

An eighth invention is the infrared sensor according to any one of the fourth to seventh inventions, wherein the infrared antireflection film is ZnS or SiO ₂ and the infrared reflection film is A.
It is an infrared sensor characterized by comprising a metal film of u, Al, or the like.

A ninth aspect of the invention is the infrared sensor according to any one of the first to eighth aspects of the invention, in which four heat-sensitive resistive films are arranged to form a bridge circuit, and the bridge circuit faces each other. The two heat-sensitive resistive films arranged on the sides are used as infrared-sensitive heat-sensitive parts, and the two heat-sensitive resistive films arranged on the remaining opposite sides of the bridge circuit are used as temperature-compensating heat-sensitive parts to form four bridge circuits. The output voltage of the infrared detector is temperature-corrected by detecting a change in the output voltage of the bridge circuit due to incidence of infrared rays on the heat-sensitive resistance film and providing a heat-sensitive resistance film for measuring the substrate temperature. It is an infrared sensor.

A tenth invention is the infrared sensor according to any one of the first to ninth inventions, wherein the pressure inside the package in which the infrared sensor is housed is sealed with negative pressure and / or low thermal conductivity gas. It is characterized by

An eleventh aspect of the present invention is an infrared sensor comprising a sensor chip in which four heat-sensitive resistive films are arranged, means for amplifying a differential output voltage of a bridge circuit by the four heat-sensitive resistive films, and the four heat-sensitive resistors. means for detecting the substrate temperature by the heat-sensitive resistive film provided in the vicinity of the membrane, and means for converting the amplified signal into a digital signal, means for converting the voltage corresponding <br/> on the substrate temperature to a digital signal A means for storing an approximate expression for calculating the temperature of the target object, and means for calculating the temperature of the target object by the output voltage of the bridge circuit and the signal voltage of the substrate temperature by the approximate expression (micro Processor: DSP, CPU)
And an means for displaying a result of the arithmetic processing, the infrared detector.

The infrared sensor of the above means comprises an infrared light receiving portion having two heat-sensitive resistance films formed therein, and the light receiving portion has a bridge structure in which the hollow portion formed on the substrate is supported in the air by four beam portions. The structure is characterized in that the light receiving portion is supported by four hook-shaped beam portions in a gap formed between the hollow portion and the infrared light receiving portion. Further, the structure is characterized in that two heat-sensitive resistance films for temperature compensation and one heat-sensitive resistance film for measuring the substrate temperature are formed on the substrate in which the cavity is formed.

Further, another structure of the infrared sensor of the above means is that two light receiving portions supported by four hook-shaped beam portions from the substrate and two heat sensitive resistors formed on the two light receiving portions, respectively. The substrate is composed of a film and one thermosensitive resistance film for measuring the temperature of the substrate formed on the substrate, and one of the light receiving portions is used for infrared detection and the other light receiving portion is used for temperature compensation. An infrared transmitting filter is arranged on the upper part, and an infrared reflection preventing film is provided on the light receiving portion side of the filter for infrared detection, and an infrared reflecting film is provided on the other light receiving portion side to shield light.

Further, since the infrared sensor of the above means has a structure in which the beam portion supporting the infrared light receiving portion is formed in a hook shape along the cavity of the substrate and the gap between the light receiving portion, the light receiving portion area is large. Since it can be formed, the amount of heat received by infrared rays also increases. Further, since the effective length of the beam portion can be increased, the thermal resistance of the beam portion is increased, and the heat conduction from the light receiving portion to the substrate is suppressed.

As a result, the temperature distribution in the light receiving portion becomes uniform, and the temperatures of the two heat-sensitive resistive films formed in the light receiving portion become the same temperature. Therefore, when the infrared detector comprises a bridge circuit with two heat-sensitive resistive films for infrared detection and temperature compensation of such an infrared sensor, respectively,
The incidence of infrared rays can efficiently increase the output due to the temperature rise of the infrared detecting thermal resistance film.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an infrared sensor and an infrared detector according to the present invention will be described below. FIG.
2A is a plan view showing an embodiment of an infrared sensor according to the present invention, and FIGS. 2A and 2B are sectional views taken along line XX ′ in FIG. 1.

The infrared sensor of this embodiment is composed of a sensor chip made of a silicon substrate, and the infrared sensor shown in FIGS.
Describing with reference to (a), the substrate 1 is a single crystal silicon substrate, and the cavity 1 is formed in the substrate 1. The cavity 2 is formed by selectively etching a part of the substrate 1 by applying a semiconductor fine processing technique. The beam 3 extending from the corner of the cavity 2 extends in a hook shape along the edge of the cavity 2 to support the infrared light receiving portion 4 in a bridge shape, and the portion directly below the infrared light receiving portion 4 is the cavity 2. There is. Four L-shaped opening portions 2a are formed around the four beam portions 3.
2d is formed, and the cavity 2 is formed immediately below the L-shaped openings 2a to 2d.

Two heat-sensitive resistance films 5 and 5'are formed in the center of the infrared ray receiving portion 4. The heat-sensitive resistance films 5 and 5'of the light-receiving part 4 are formed on the substrate 1 by thermal oxidation to form an insulating film 6a.
Further, the insulating film 6a is formed on the electrode film 9 formed so as to face the insulating films 7 and 8 formed by sputtering, CVD (chemical vapor deposition) or the like. Further, at the same time as the heat sensitive resistance films 5 and 5 ', the heat sensitive resistance films 10, 10' and 1 '
0 ″ is formed in the same manufacturing process. Heat-sensitive resistance film 5,
A protective insulating film 11 is formed on 5 ', 10, 10', 10 ", and a buffer film 12 and a glass layer 1 are formed on the protective insulating film 11.
3 and the insulating film 14 are sequentially formed by the CVD method or the like.

The infrared sensor chip shown in FIG.
The buffer film 12, the glass layer 13, the insulating film 14, and the insulating films 7 and 8 on the substrate 1 formed on the heat-sensitive resistance films 5, 5 ', 10, 10', and 10 "of (a) are omitted, and the whole is omitted. FIG. 3 is a cross-sectional view showing an embodiment in which the film thickness of is reduced to reduce the heat capacity.

Next, a method of manufacturing the infrared sensor chip used in the infrared detector of the present invention will be described in detail with reference to FIG. As the substrate 1, a silicon substrate having a plane orientation (110) or (100) and a thickness of about 250 μm is used. This silicon substrate is 900-110
By performing thermal oxidation treatment at a temperature of 0 ° C., the substrate 1
Of silicon oxide (Si
O ₂ ) insulating films 6a and 6b are formed. Insulating film 6b
Becomes a mask for etching when the cavity 2 is formed by removing a part of the substrate in the final step.

After that, aluminum oxide (A) having a film thickness of 0.1 to 3 μm is formed by a method such as a sputtering method or a CVD method.
An insulating film 7 of l ₂ O ₃ ) or tantalum oxide (Ta ₂ O ₅ ) is formed. Since the insulating film 7 made of aluminum oxide or tantalum oxide has a larger coefficient of thermal expansion than the insulating film 6b made of silicon oxide, it has a function of relaxing thermal stress applied to the substrate.

Then, an insulating film 8 is further formed on the insulating film 7. The insulating film 8 is formed by forming a material such as silicon oxide (SiO ₂ ) or oxynitride silicon (SiNO) having a film thickness of 0.1 to 1 μm by a sputtering method or a plasma CVD method. When a thermistor material having a metal oxide composition is used as the heat-sensitive resistance films 5, 5 ', 10, 10', and 10 ", the insulating film 8 has the above-mentioned heat-sensitive component as a constituent of the insulating film 7 in a heat treatment step. Functions as a diffusion prevention layer that prevents diffusion into the resistance film,
It has a role of preventing a change in electric resistance due to a reaction between the insulating film 7 and the heat sensitive resistance film and maintaining stability of electric performance of the heat sensitive resistance film.

The electrode film 9 has a film thickness of 0.1 to 0.1 on the surface of the insulating film 8.
It is formed so as to face each other at 0.5 μm. Electrode film 9
The most preferable material is platinum (Pt), but nickel (Ni) or chromium (Cr) may be used.

Next, heat sensitive resistance films 5, 5 ', 10, 10', 10 "having a thickness of 0.1 to 0.5 .mu.m are formed on the electrode film 9 by a sputtering method or the like. This heat-sensitive resistance film is formed by sputtering using a thermistor sintered body made of a transition metal oxide of Mn—Ni—Co system as a target.As an example of the sputtering conditions, the sputtering pressure is 0.2 to 0.7 Pa. , Substrate 1
At a heating temperature of 200 to 500 ° C. in an Ar gas atmosphere. By patterning, the heat-sensitive resistance film 5,
After forming 5 ', 10, 10' and 10 ", heat treatment is performed in air at a temperature of 400 to 900 ° C for 1 to 5 hours.

The thermal resistance film is not limited to the above composition system, and may be a thin film made of another composition used as a thermistor material, a silicon carbide thin film or an amorphous material formed by the plasma CVD method. Needless to say, it may be a Si thin film.

The above-mentioned heat-sensitive resistance film can obtain various electric characteristics by changing the composition, film thickness, electrode shape of the target material or by forming the film as a multi-layer structure by changing the composition of each layer. .

Subsequently, the heat-sensitive resistance films 5, 5 ', 10, 1
After forming 0 ′ and 10 ″, a passivation film for protecting these heat-sensitive resistive films is formed. The protective insulating film 11 such as a silicon oxide film, a silicon nitride thin film, or an oxynitride silicon thin film forms a heat-sensitive resistor. Membrane 5,
5 ', 10, 10', on the formed at a thickness of 1 to 3 [mu] m. Over the protective insulating film 11 10 ', the buffer film 12 made further thin film of tantalum oxide or titanium oxide, (TiO ₂₎
Is formed. This buffer film 12 has a film thickness of 0.01 to 1 μm.
m is sufficient, and by forming this film, a part of the composition constituting the glass layer at the time of heat stress or heat treatment generated when the glass layer 13 of the borosilicate glass-based oxide in the subsequent step is formed. Heat-sensitive resistance film 5, 5 ', 10, 10', 1
It is possible to prevent the electric characteristics from fluctuating by diffusing to 0 ″.

After the buffer film 12 is formed by patterning and heat treatment is performed, the glass layer 13 is formed by the sputtering method. The glass layer 13 of the present embodiment is made of lead borosilicate glass (P
sputtering an oxide target of _{bO-B 2 O 3 -SiO 2} ) based is formed. The glass layer 13 is formed 30
A heat treatment is performed at a temperature of about 0 to 800 ° C. to melt once and improve the step coverage on the step of the underlying film. At the same time, it becomes possible to reduce pinholes in the glass layer 13. This film also serves as a good infrared absorbing film. Infrared absorption spectra of a silicon oxide film formed by sputtering and a lead borosilicate glass layer are shown in FIGS. 5A and 5B, respectively.

As is clear from FIGS. 5A and 5B, the lead borosilicate glass-based glass layer has a thickness of about 6 to 11 μm.
Has an absorption band at the wavelength of (about 110 to 21 in terms of temperature)
However, the silicon oxide film has an absorption band at a wavelength of about 8 to 9.5 μm (converted to a temperature of about 30 to 90 ° C.). As described above, it has been confirmed that the lead borosilicate glass-based glass layer is more effective for detection in a wider temperature range than the conventionally used silicon oxide film.

The glass layer 13 is not limited to the lead borosilicate glass of this embodiment. For example, by using a borosilicate glass-based material (including an undoped borosilicate glass) in which another element is added instead of lead, it is possible to change the heat treatment temperature after film formation in the present embodiment. It is possible to obtain electrical and mechanical performances equivalent to those of lead borosilicate glass.

Next, on the glass layer 13, a film thickness of 0.
The insulating film 14 made of silicon oxide, silicon nitride, or silicon oxynitride having a thickness of 05 to 2 μm is formed. The insulating film 14 is formed to protect the glass layer 13 when the cavity 2 is formed by performing anisotropic etching. Then, for the L-shaped openings 2a to 2d forming the light receiving portion 4 and the beam portion 3 supporting the light receiving portion 4, the protective insulating film 11, the glass layer 13, and the insulating film 14 are made of buffered hydrogen fluoride (BHF). Patterning by etching away.

The L-shaped opening 2a is formed by etching.
2D, if the insulating films 11, 13, and 14 laminated on the beam portion 3 shown in FIG. 2A are removed at the same time, as shown in FIG. The film thickness of 3 can be made smaller than that of the light receiving portion 4. By reducing the film thickness of the beam portion 3, the thermal resistance of the beam portion 3 is increased, the heat absorbed by the light receiving portion 4 is less likely to be dissipated, and the detection sensitivity of the infrared sensor can be increased. Similarly, FIG.
3B, if the insulating film 11 is removed in FIG.
As shown in, it is possible to reduce the thickness of the beam portion 3,
The thermal resistance of the beam portion 3 increases, and the heat absorbed by the light receiving portion 4 is less likely to be dissipated, and the detection sensitivity of the infrared sensor can be increased.

The final manufacturing process of the infrared sensor chip is as follows:
This is a step of performing anisotropic etching to form the cavity 2 in the silicon substrate. The insulating film 6b is patterned by using a photolithography technique to form an etching mask. As the etchant, for example, hydrazine hydrate is used. With this etchant, the cavity 2 is formed in the silicon substrate by selectively etching and removing the back side of the substrate at about 110 ° C. for about 2 hours.
The light receiving part 4 has a cross-linked structure, and an infrared sensor chip is formed.

In the above embodiment, the structure of one infrared sensor chip has been described. In reality, however, a large number of infrared sensor chips having the above structure are formed on one silicon substrate to form a cavity. After being formed, it is completed by dividing it into individual infrared sensor chips. Further, it goes without saying that the shape of the electrode film is not limited to the shape shown in the embodiment and may be a comb-like shape.

As shown in FIG. 1, the light receiving portion 4 formed in the central portion of the sensor chip is held in the air in a bridge form by the beam portion 3 extending from the edge of the cavity 2. Light receiving part 4
The lead portions 15a and 15b drawn out from the electrode films 9 below the two heat-sensitive resistance films 5 and 5'formed on the substrate are connected to the electrode pad portions 16a and 16b formed on the substrate through the beam portion 3, respectively. There is. The electrode pad portions 16a and 16b are respectively connected to the electrode films directly below the heat sensitive resistance films 10 'and 10 ". The lead portions at the other ends of the electrode films immediately below the heat sensitive resistance films 10' and 10" are the electrode pad portions 23a, 23b, respectively. The lead portions 17a and 17b at the other end extending from the electrode film 9 immediately below the heat-sensitive resistance films 5 and 5'are
Similarly, it is connected to the electrode pad portions 18a and 8b formed on the substrate through the beam portion 3, respectively. On the sensor chip, the heat-sensitive resistance film 10, the lead portions 19a,
19b and electrode pad portions 20a and 20b are formed as independent heat sensitive elements.

FIG. 4 shows an embodiment in which the infrared sensor chip of the above embodiment is assembled on the stem of the package. In the figure, a chip 22 is adhered and fixed on a base (stem) 21 made of an insulator or metal, and each electrode pad portion 16a formed on the chip 22.
16b, 18a, 18b, 20a, 20b, 23a, 2
3b and the terminal provided on the base 21 are bonding wires 2
Wiring is connected at 4. Base 21 with chip 22
Is sealed with a cap provided with an infrared transmitting filter made of glass, plastic, or single crystal silicon material having high infrared transmittance according to a known technique. When the package is sealed with the cap, the air inside the package is evacuated to a negative pressure state. Since the assembly structure of the cap provided with the infrared transmitting filter is a known technique, its illustration is omitted.

The infrared detector assembled as shown in FIG. 4 and provided with an infrared transmitting filter is wired so as to form a Wheatstone bridge circuit as shown in FIG. In FIG. 9, the resistance elements T ₂ and T ₃ correspond to the heat-sensitive resistance films 5 and 5 ′, which are heat-sensitive parts for infrared detection, and the resistance elements T ₁ and T ₄ are heat-sensitive resistance formed on the substrate. Membrane 1
Corresponding to 0 ', 10 ", it functions as a heat-sensing portion for temperature compensation. The heat-sensitive resistance films 5, 5'and 10', 10" are arranged so as to be located on opposite sides of the bridge circuit.

Next, the operation of the infrared sensor of the above embodiment will be described. Infrared rays that have entered through the infrared ray transmitting filter provided on the cap that seals the base 21 are absorbed by the glass layer 13 and converted into heat. Then, the temperature of the heat sensitive resistance films 5 and 5'is raised, the light receiving portion 4 is thermally insulated from the substrate 1 by the beam portion 3 having a large heat resistance, and the heat absorbed by the light receiving portion 4 is dissipated to the substrate. Since it is difficult, the temperature distribution in the light receiving portion becomes uniform, and the two heat sensitive resistance films 5 and 5'become at the same temperature. On the other hand, since the heat-sensitive resistance films 10 'and 10 "formed on the substrate have a larger heat capacity than the light-receiving portion, the temperature rise due to the incident infrared rays is almost negligible, so that special light-shielding means is used. It is possible to detect the temperature of the target object without using T. Since the temperature distribution of the light receiving portion becomes uniform as described above, T ₂ and T ₃ of the bridge circuit shown in FIG. It changes to the resistance value.
The output voltage of the bridge circuit is twice as high as that in the case where there is only one heat-sensitive resistance film for infrared detection, and temperature detection can be performed with higher accuracy than conventional infrared detectors.

On the other hand, in such a thermistor bolometer type infrared detector, when the input voltage is increased, the value of ΔV described above is increased and the output voltage of the bridge circuit, that is, the infrared detector is increased, which causes the influence of noise. There is an advantage that it is hard to receive and highly accurate temperature detection is possible.

However, in the infrared sensor of FIG.
When the voltage applied to the bridge circuit is increased, the heat-sensitive part (heat-sensitive resistance film) self-heats and its temperature rises. However, since the heat capacity of the light-receiving part and the substrate is different, the heat-sensitive part on the light-receiving part and the substrate (thermistor ) The degree of change in resistance is different. Therefore, there is a drawback that the potentials at the connection points a and b of the bridge circuit in FIG. 9 change, and the output voltage (error voltage) of the bridge circuit occurs even if infrared rays are not incident. That is, there is a drawback that an offset voltage is generated and the input voltage of the infrared detector cannot be increased. In addition, when used in an environment where the ambient temperature fluctuates rapidly, there is a drawback that an error voltage occurs.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, a sensor chip which is an infrared sensor capable of obtaining a large output signal by improving the above drawbacks will be described. FIG. 6A is a perspective view showing an embodiment of the infrared sensor.
(B) is the XX 'sectional view. FIG. 6 (a),
(B) shows a structure of an infrared sensor in the case of forming two light receiving parts of one chip, which is supported on one substrate 1 by a bridge structure of beam parts 3 having the same structure as in FIG. Two light receiving portions 4 and 4'are formed in the hollow portions 2 and 2 '. Two light-sensitive resistance films 5 and 5'are respectively provided on the light receiving portions 4 and 4 '.
And 27, 27 'are formed. Further, a heat-sensitive resistance film 10 is provided on the substrate to detect the temperature of the substrate 1. In FIG. 6, the heat-sensitive resistance film 10 is formed in the approximate center of the substrate 1.
Is arranged. Then, a lid 29 made of silicon through which infrared rays are transmitted is provided on these substrates 1. One of the lids 29 on the side of the light receiving portion 4'has a structure having a partition portion for shielding the light receiving portion for temperature compensation from infrared rays. The lid 29 made of silicon has a function as an infrared transmission filter. Further, an infrared ray antireflection film 25 made of ZnS, SiO ₂ or the like is formed on the surface of the lid 29 on the side of the light receiving portion 4 for infrared detection, and the infrared ray is shielded on the side of the light receiving portion 4'for temperature compensation. An infrared reflection film 26 made of aluminum (Al), gold (Au), or the like, which has a high infrared reflectance, is formed on. As shown in FIG. 4, the infrared sensor thus configured has a base (stem) made of an insulator or a metal.
The electrode pads on the chip and terminals on the base are connected by bonding wires. Alternatively, it is mounted in a surface mounting package.

FIGS. 7 and 8 show an embodiment in which the infrared sensor chip shown in FIG. 6 is mounted in a surface mounting package, which will be described with reference to the drawings. In FIG. 7, the sensor chip 22 'is mounted and fixed inside the ceramic package 30, the terminal portion 28b of the electrode 28a of the package 30 projects into the package 30, and the electrode pad of the chip 22' and the terminal portion 28b of the package 30 are separated. It is wired by the bonding wire 23 and the lead frame. The ceramic package 30 whose wiring is completed is an infrared transmitting filter, for example, a metal plate (cover, infrared reflecting film) 26 such as Kovar, iron / nickel alloy, etc. A silicon substrate (antireflection film) 25 is adhesively fixed with a low melting point glass or the like so as to close the portion to form a metal plate (lid) 29, and further, the metal plate 29 and the ceramic package 30 are sealed with an adhesive or the like. .

FIG. 8 shows a package structure in which a ceramic package 30 on which a sensor chip is mounted is sealed with a cap (lid) 29. The cap 29 is a silicon substrate 29.
An infrared reflection film 26 having an opening 26a is laminated on a. As the sealing material of the cap 29, nickel or gold is plated, and the cap 29 is sealed by brazing with a low melting point brazing material such as Au—Sn or soldering with a solder material (PbSn). The silicon substrate 29a, which is an infrared reflection preventing film, is exposed in the opening 26a of the infrared reflection film 26 of the cap 29. Since the concave portion 30a is formed on the bottom surface of the ceramic package 30 and the light receiving portion 4 is formed at a position apart from the bottom surface of the ceramic package 30, it is possible to prevent heat from being diffused from the light receiving portion through the ambient atmosphere and improve the sensitivity. Is effective in.

The infrared sensor shown in FIGS. 7 and 8 has a structure in which the sensor chip 22 'is mounted on the ceramic package 30. The infrared ray incident on the light receiving section 4 through the infrared ray antireflection film causes a heat sensitive section (heat sensitive resistance film). 5, 5 ') is converted into heat and the temperature of the light receiving section 4 rises. The light receiving section 4'is
Infrared rays are shielded by the infrared reflecting film 26, so that the fluctuation of the ambient temperature of the light receiving section 4'is detected. This infrared sensor is constituted by the bridge circuit shown in FIG. 9. The heat-sensitive resistance films 5 and 5'on the light-receiving section 4 are used as the resistance elements T2 and T3 in FIG. 9, and the heat-sensitive resistance films 27 and 27 'on the light-receiving section 4'are provided. The resistance element T of FIG.
By wiring so as to be 1, T4, it is possible to form an infrared detector capable of detecting accurate temperature measurement in a non-contact manner.

Further, when the B constants and resistance values of the four heat-sensitive resistive films formed on the sensor chip have large variations, or the difference in heat capacity due to variations in the shape of the light receiving portion causes temperature drift and sensitivity variations. It appears as a fluctuation error of the bridge output voltage. In such a case, the fluctuation error of the output voltage can be reduced by mounting the trimming thermistor and the resistor in the amplifier circuit and correcting the variation.

That is, since the infrared sensor according to the embodiment of the present invention shown in FIG. 6 has a structure in which two light receiving portions 4 and 4'having the same shape and the same structure are formed on one chip, the heat-sensitive resistance is reduced. When the films 5, 5 ', 27, 27' are constructed in a bridge circuit, even if the ambient temperature changes suddenly or the applied voltage of the bridge circuit is increased and each thermosensitive resistive film self-heats Since the heat dissipation constants of the parts are the same, and the two heat-sensitive resistive films arranged in the respective light-receiving parts also have the same temperature for the above reason, the bridge output (corresponding to the dark current) when infrared rays are not incident ) Can be zero. Therefore, since the output of the infrared detector can be increased, as a result, the S / N ratio is increased, and the infrared detector capable of accurately detecting the temperature of the detection target can be provided.

Further explaining the present invention, the thermosensitive resistive film 10 on the sensor chip shown in FIG. 1 or 6 is used to measure the substrate temperature of the sensor chip. That is, when performing non-contact temperature measurement, the amount W of infrared energy incident on the infrared sensor is determined by Stefan Boltzmann (Stefa
It is known from (n-Boltzmann) 's law to obey the following equation.

W = σ (ε _B T _B ⁴ −ε _S T _S ⁴ ) ... (2)

Where W is the infrared energy incident on the infrared detector, σ is the Stefan-Boltzmann constant, ε _{B is} the emissivity of the target object, ε _{S is} the emissivity of the sensor light receiving part, and T _{B is} the emissivity.
Target object temperature, T _S : substrate temperature of the sensor chip.

As is clear from the above, the energy received by the infrared detector is determined by the emissivity and temperature of the target object and the sensor light receiving section. Therefore, the temperature of the substrate of the sensor chip is measured by the heat-sensitive resistive film 10 on the sensor chip, and the infrared incident energy is obtained from the bridge output by the infrared light incident on the infrared light receiving portion forming the bridge circuit. You can know the temperature. 10 and 11 are block diagrams showing an example of a temperature measuring circuit using the infrared detector of the present invention.

The infrared detector of the present invention is provided in the vicinity of the target object.
Installed in the infrared sensor,
On the sensor chip that makes up the Wheatstone bridge
The four thermistors output signals according to the amount of incident infrared rays.
Output. Its specific sensor circuit is shown in FIG.
You. As shown in Figure 9, the output voltage from the bridge circuit
(Infrared output signal) V_AIs output and is the heat-sensitive resistance film 10
Output voltage (sensor temperature output signal) V_BIs entered
You. As shown in FIG. 10, the output signal V of the bridge circuit
_AIs the differential amplifier A₁Is input to and amplified. Differential amplification
Bowl A₁Output signal is low to remove the noise component.
Anti-aliasing filter F consisting of a bass filter₁
Through the sample and hold circuit H₁, A / D conversion circuit
CV₁Is input to Output signal V_AIs the A / D conversion circuit C
V₁Is converted into a digital signal. Meanwhile, the sensor
Output voltage (sensor temperature output)
Force signal) V_BIs the differential amplifier A₂Amplified with the same as above
, Anti-aliasing filter F₂, Sample & ho
Field circuit H₂, A / D conversion circuit Cv₂Through digital
Converted to a signal. A / D conversion circuit CV₁, CV₂Contact
Continued DSP (Digital Signal Processor) or CP
In U (central control unit), the ROM (not shown) is red
Output signal voltage V of external line detector_AAnd the sensor chip temperature
Sensor temperature output signal V_BThe relational expression of is stored,
According to this relational expression, the A / D conversion circuit CV ₁, CV₂of
Capture the output signal and measure the temperature T of the target object_BAnd calculate
The result of the relational expression is output to the display unit D.

The relational expression stored in the ROM is as follows. If the temperature of the target object is T _B , the infrared output voltage is Vc, and the output voltage of the substrate temperature is V _B , the temperature T _B (° C.) of the target object is calculated from the experimental results. It can be approximated by the following equation.

T _B = f (V _B ) · Vc ³ + g (V _B ) · Vc ² + h (V _B ) · Vc + i (V _B ) ... (3)

Therefore, the temperature of the target object can be detected with high accuracy by programming the above approximate expression in the DSP or CPU and calculating the temperature T _{B of the} target object by this approximate expression (3). It can be displayed on the display unit.

Further, in these infrared detectors, the heat loss of the light receiving portion whose temperature is raised by the incidence of infrared rays occurs not only in the heat dissipation from the beam portion but also in the air. Therefore, when sealing with a stem or ceramic etc. and packaging,
In order to reduce the heat dissipation around the light receiving part,
For example, if the structure is surrounded by a gas having a small thermal conductivity such as Xe gas or Kr gas, the output can be further increased. The same effect can be obtained by making the internal pressure of the package a negative pressure instead of the gas having a small thermal conductivity as described above.

[0070]

As described above, in the infrared detector of the present invention, the beam portion supporting the infrared light receiving portion extends like a hook along the cavity of the substrate and the gap (L-shaped opening) of the light receiving portion. With this structure, the area of the light receiving portion can be made larger than that of the conventional structure. Also, by increasing the effective length of the beam part, the thermal resistance of the beam part can be increased, so that heat conduction from the light receiving part to the substrate is suppressed, and the heat receiving light is increased because the light receiving part area becomes large. Energy becomes large. Since the thermal resistance of the beam portion is large, heat dissipation is small and the temperature distribution of the light receiving portion is uniform. Therefore, when infrared rays enter, the heat-sensitive resistance film formed on the light receiving portion for infrared detection has the same temperature. In addition, since the two thermosensitive resistance films for temperature compensation are also formed on the same substrate, when a bridge circuit is constructed by these thermosensitive resistive film for infrared detection and thermosensitive resistive film for temperature compensation, the infrared incident Since the temperature rise of the two infrared-sensitive heat-sensitive resistive films and the sensor temperature compensation by the temperature-sensitive thermal resistive film for measuring the ambient environment temperature can be accurately performed, there is an advantage that the sensitivity can be improved over the conventional structure. is there.

Further, one of the two light receiving portions having the same shape and size as shown in FIG. 6 is used as an infrared light receiving portion,
By shielding the other from infrared rays and using it as a temperature compensator, the two light-receiving parts have the same heat dissipation constant, and the two heat-sensitive resistive films arranged in each light-receiving part have the same reasons as described above. Since the temperature is the same, the fluctuation of the ambient temperature can be more accurately detected, and the applied voltage of the bridge circuit can be increased, so that the output of the infrared detector is further increased as compared with the first embodiment. Larger size enables highly sensitive temperature detection.

Further, according to the infrared sensor and the infrared detector of the present invention, the temperature control device utilizing the temperature data of the infrared detection circuit based on the equation (3) is used as the heating roller of the fixing device such as the conventional copying machine. By using it for temperature control, the roller temperature can be controlled in a non-contact manner, so the problem of scratches on the roller surface, which was a problem with conventional temperature sensors, can be solved, and high-quality images can be obtained. Benefits arise.

Further, since there is no moving part such as a chopper required for the conventional non- contact type infrared detector, that is, the pyroelectric type infrared detector, there is an advantage that mechanical failure is eliminated. Further, there is an advantage that the temperature range (Curie temperature) of the pyroelectric element does not prevent the pyroelectric element from being used in a high temperature portion such as the fixing device, and the use temperature range is widened and the use is greatly expanded. Furthermore, because of its structure, compared to the thermopile type infrared detector, the thermal resistance between the light receiving part and the substrate can be made large, so that a large output voltage is generated.
Highly sensitive temperature detection is possible.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of an infrared sensor of the present invention.

FIG. 2 is a sectional view of a sensor chip showing an embodiment of an infrared sensor of the present invention.

FIG. 3 is a sectional view of a sensor chip showing another embodiment of the infrared sensor of the present invention.

FIG. 4 is a perspective view in which a sensor chip of the infrared sensor of the present invention is mounted on a base.

FIG. 5 is a diagram showing infrared absorption characteristics.

FIG. 6A is a perspective view showing another embodiment of the infrared sensor of the present invention, and FIG. 6B is a sectional view taken along line XX ′ of FIG.

FIG. 7 is a perspective view showing an embodiment in which an infrared sensor of the present invention is mounted.

FIG. 8 is a perspective view showing another embodiment in which the infrared sensor of the present invention is mounted.

FIG. 9 is a circuit diagram showing an embodiment of a detection circuit of the infrared detector of the present invention.

FIG. 10 is a block diagram showing an embodiment of an infrared detector of the present invention.

FIG. 11 is a block diagram showing another embodiment of the infrared detector of the present invention.

FIG. 12 is a plan view showing a main part of a conventional infrared sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 substrate 2 cavity part 2a-2d L-shaped opening part 3 beam part 4,4 'light receiving part 5,5' heat-sensitive resistance film (10,10 ', 10 ", 27,
27 ') 6a, 6b Insulating film 7,8 Insulating film 9 Electrode film 11 Protective insulating film 12 Buffer film 13 Glass layer 14 Insulating film 15a, 15b Lead part (17a, 17b, 19a,
19b,) 16a, 16b Electrode pad portions (18a, 18b, 20)
a, 20b, 23a, 23b) 21 base 22, 22 'chip 23, 24 bonding wire 25 antireflection film (silicon substrate) 26 infrared reflection film 26a opening 27 ceramic package 28a electrode 28b terminal 29 metal plate, lid, Cap 29a Infrared reflective film (light-shielding substrate)

Claims (11)

[Claims] 1. An infrared sensor comprising a substrate, a hollow portion provided in the substrate, and a light receiving portion supported in the hollow portion by a beam portion in a bridging manner. An infrared sensor, comprising: the light receiving portion having the above-mentioned structure and one heat-sensitive resistance film for detecting the temperature of the substrate, which are arranged on the substrate. 2. An infrared sensor comprising a substrate, a hollow portion provided in the substrate, and a light receiving portion supported in the hollow portion in a bridge shape by a beam portion. An infrared sensor, comprising: the light receiving portion having the structure described above; and two heat-sensitive resistance films for temperature compensation disposed on the substrate. 3. An infrared sensor comprising a substrate, a hollow portion provided on the substrate, and a light receiving portion supported in the hollow portion by a beam portion in a bridging manner, wherein four hooks extending from the substrate are provided. Two infrared-sensitive heat-sensitive resistive films formed on the light-receiving portion supported by beam-shaped beams, two temperature-compensating heat-sensitive resistive films formed on the substrate, and for measuring the temperature of the substrate An infrared sensor, comprising: a heat-sensitive resistance film formed on a substrate. 4. An infrared sensor comprising a substrate, a hollow portion provided in the substrate, and a light receiving portion supported in the hollow portion by a beam portion in a bridging manner. Two cavities, first and second light receiving sections supported by four hook-shaped beam sections extending in the first and second cavity sections, respectively, and the first and second light receiving sections The two heat-sensitive resistance films formed on the substrate, the heat-sensitive resistance film formed on the substrate for measuring the temperature of the substrate, and the infrared transmission filter on the substrate, and An infrared reflection preventing film provided on the infrared transmission filter and an infrared reflection film provided on the infrared transmission filter on the side of the second light receiving unit to block infrared rays are provided, and the first light receiving unit is provided with infrared rays. It is used for detection and the second light receiving portion is used for temperature compensation. Infrared sensor and said and. 5. The infrared sensor according to claim 1, wherein the beam portion is thinner than the light receiving portion. 6. The infrared sensor according to claim 4, wherein the infrared transmission filter is made of silicon. 7. The infrared sensor according to claim 1, wherein the heat-sensitive resistance film is formed of Mn—Ni—Co-based oxide. 8. The infrared sensor according to claim 4, wherein the infrared reflection preventing film is made of ZnS or SiO ₂ , and the infrared reflection film is made of a metal film of Au, Al or the like. A featured infrared sensor. 9. The infrared sensor according to claim 1, wherein four thermosensitive resistive films are arranged to form a bridge circuit, and two thermosensitive resistive films are arranged on opposite sides of the bridge circuit. The heat-sensitive resistive film is used as an infrared-sensing heat-sensitive part, and the two heat-sensitive resistive films arranged on the remaining opposite sides of the bridge circuit are used as temperature-compensating heat-sensitive parts, and the four heat-sensitive resistive films forming the bridge circuit have infrared rays. An infrared sensor, which detects a change in the output voltage of the bridge circuit due to incidence and provides a temperature sensitive resistance film for measuring the substrate temperature to correct the output of the infrared detector. 10. The infrared sensor according to claim 1, wherein the pressure inside the package accommodating the infrared sensor is sealed with a negative pressure and / or a gas having a low thermal conductivity. 11. An infrared sensor comprises a sensor chip having four heat-sensitive resistive films arranged thereon, means for amplifying a differential output voltage of a bridge circuit by the four heat-sensitive resistive films, and a means for amplifying the differential output voltage in the vicinity of the four heat-sensitive resistive films. A means for detecting the substrate temperature by the provided heat-sensitive resistive film, a means for converting the amplified signal into a digital signal, a means for converting a voltage corresponding to the substrate temperature into a digital signal, and calculating the temperature of the target object For storing an approximate expression for calculating the temperature of the target object by the output voltage of the bridge circuit and the signal voltage of the substrate temperature by the approximate expression (microprocessor: DSP, CP
U) and a means for displaying a result of the arithmetic processing, an infrared detector.