JPH06147969A - Infrared sensor - Google Patents

Abstract

PURPOSE:To improve the response sensitivity and measurement accuracy of an infrared sensor by preventing the influence of the Joule's heat of two temperature-sensitive sections on the output of the sensor which is the difference between the self-generating quantities of heat of the two sections. CONSTITUTION:A first infrared-ray detecting means 11 detects the quantity of infrared rays radiated from an object 13 to be measured for temperature and second infrared-ray detecting means 12 detects the infrared rays radiated from an infrared-ray radiating source 14. The output signals of the means 11 and 12 are sent to a difference detecting means 15 and the means 15 detects the difference between the two output signals. The output signal of the means 15 is fed back to an infrared-ray radiating source control means 16. The means 16 controls the output of the source 14 so that the output of the means 15 can become zero, namely, the outputs of the first and second infrared-ray detecting means 11 and 12 can become equal to each other. The current value of the source 14, namely, the value converted into the temperature of the object 13 when the output of the means 15 becomes zero is displayed by means of a displaying means 17.

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 measuring the temperature of an object to be temperature measured in a non-contact manner. The present invention relates to an infrared sensor in which infrared rays from an object are incident and the true amount of infrared rays is measured by the difference between the outputs of the two (differential output).

[0002]

2. Description of the Related Art Infrared sensors (thermobolometers) are
A temperature sensitive part is formed of a substance having a thermistor effect such as amorphous germanium, and infrared rays are incident on this temperature sensitive part.
The temperature rise due to the infrared rays is measured by the change of the current value or the voltage value, and the infrared ray amount, that is, the temperature of the non-temperature measurement object is detected.

Therefore, when the temperature sensing portion has a small heat capacity and a small amount of heat is transferred from the temperature sensing portion to the outside with respect to a small amount of infrared rays, the temperature rise becomes large and the response sensitivity of the sensor becomes good. For this reason, recently, a structure in which a fine cross-linking portion (bridge) is formed on a silicon substrate by using a semiconductor fine processing technique and a temperature sensitive portion is formed on the cross-linking portion is adopted. .

On the other hand, since the infrared rays emitted from the non-temperature measurement object are extremely small, they are easily affected by the environment in which the infrared sensor is used, and external disturbances such as heat conduction and radiation from the sensor package and body. Therefore, various measures have been conventionally performed in the measurement.

For example, temperature-sensitive parts having the same structure are provided on a pair of bridge parts, and infrared rays radiated from an object to be measured are made incident on only one of the temperature-sensitive parts and the other part is made sensitive. The temperature sensing part has a structure that is completely shielded from infrared rays. By calculating the output difference (differential output) between the two, the true incident infrared ray amount is detected, the influence of disturbance is removed, and the response sensitivity is improved.

[0006]

However, the conventional infrared sensor having such a structure has the following problems.

That is, as described above, the infrared sensor converts the temperature of the non-temperature measurement object into a change in the electric resistance value of the temperature sensing portion, and detects the resistance value. It is necessary to apply a voltage using a tester (measuring instrument) and to supply a current to the temperature sensing part. At this time, Joule heat is generated according to the electric resistance value, and each of the temperature sensitive parts self-heats and its temperature rises.

However, since the infrared rays are incident on one of the two temperature-sensitive portions and the infrared rays are completely shielded on the other, the temperatures of the two are different. Therefore, the temperature-sensitive portion on the side where the infrared rays are incident has a small electric resistance value, while the temperature-sensitive portion shielded from the infrared rays has a large electric resistance value, and the electric resistance values of the both are different. Therefore, the amount of self-heating due to the Joule heat also differs between the two temperature sensing parts. When the amount of self-heat generation between the temperature sensing parts is different as described above, an error occurs in the difference output between the two temperature sensing parts, so that the true amount of infrared rays emitted from the temperature measured object can be accurately detected. However, there was a problem that the response sensitivity was lowered.

The present invention has been made in view of the above problems, and an object thereof is to provide an infrared sensor having improved response sensitivity by preventing the influence of self-heating amount due to Joule heat of two temperature sensing parts. It is in.

[0010]

The infrared sensor according to the present invention has a temperature measured object 13 as shown in FIG.
First infrared detecting means 11 for converting infrared rays radiated from the device into an electric signal, an infrared radiation source 14 for emitting infrared rays separately from the temperature-measuring object 13, and the infrared radiation source 1
Second infrared detecting means 12 for converting infrared rays radiated from 4 into an electric signal, and difference detecting means 15 for detecting a difference between output signals of the first infrared detecting means 11 and the second infrared detecting means 12. An infrared radiation source control means 16 for controlling the amount of infrared radiation emitted from the infrared radiation source 14 so that the output of the difference detection means 15 becomes zero upon receiving the output signal of the difference detection means 15. .

Further, in the infrared sensor of the present invention, the temperature of the infrared radiation source 14 when the output of the difference detecting means 15 becomes zero, that is, the temperature of the temperature measured object 13 is displayed on the display means 17. .

In the infrared sensor of the present invention, the first infrared detecting means 11 detects the amount of infrared rays emitted from the temperature-measuring object 13, while the second infrared detecting means 12 emits the infrared rays from the infrared radiation source 14. Infrared rays are detected and converted into electrical signals and output. The output signals of the first infrared detecting means 11 and the second infrared detecting means 12 are sent to the difference detecting means 15 to detect the difference. The output signal of the difference detection means 15 is fed back to the infrared radiation source control means 16. The infrared radiation source control means 16 controls the output of the infrared radiation source 14 so that the output of the difference detection means 15 is zero, that is, the outputs of the first infrared detection means 11 and the second infrared detection means 12 are the same. . When the output of the difference detecting means 15 becomes zero, that is, when the outputs of the first infrared detecting means 11 and the second infrared detecting means 12 become the same, the temperature conversion value of the infrared radiation source 14, that is, The temperature of the temperature measurement object 13 is displayed on the display means 17.

As described above, in the infrared sensor of the present invention, when measuring the amount of infrared rays, the "zero-point method" that enables highly sensitive and highly accurate measurement is applied. And the reference amount is adjusted so that the difference becomes zero. In the infrared sensor of the present invention, the amount of infrared rays (temperature) incident on each of the first infrared detecting means 11 and the second infrared detecting means 12 is adjusted to be the same.

Therefore, when the first infrared detecting means 11 and the second infrared detecting means 12 are constituted by the temperature sensitive parts having the thermistor effect, the electric resistance values of the two temperature sensitive parts become the same, and the joules are the same. The self-heating value due to heat is also the same. Therefore, the output of the difference detecting means 15 is not affected, and therefore high-sensitivity and high-accuracy measurement can be performed.

Specifically, the infrared sensor of the present invention is formed of a semiconductor material and is provided on a sensor substrate having a pair of cross-linking portions and the one cross-linking portion, and radiated from an object to be temperature-measured. A first temperature-sensing part for converting infrared rays into an electric signal, and the same structure as the first temperature-sensing part,
A second temperature sensitive portion provided on the other bridge portion, a micro heater provided on the sensor substrate corresponding to the second temperature sensitive portion, the first temperature sensitive portion and the second temperature sensitive portion. And a micro-heater control unit that receives the output signal of the comparator and controls the temperature of the micro-heater so that the output of the comparator becomes zero. It will be equipped.

As the sensor substrate, a semiconductor substrate made of silicon, germanium or the like is used, but it is preferable to use a silicon substrate which can be easily and inexpensively obtained. The temperature sensitive portion is formed of a film of amorphous germanium (a-Ge), amorphous silicon (a-Si), polycrystalline silicon, or the like. Sputtering, ion beam sputtering, CVD (Chemical Vapor Deposition) or the like is used for forming the film in the temperature sensitive portion.

The bridging portion is formed of a silicon oxide film (SiOx),
Silicon nitride film (SiNy), silicon oxynitride
Although it can be formed of a (SiOxNy) film or the like, it is particularly preferably formed of a silicon oxynitride 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 stable crosslinked structure. The optimum conditions for forming this silicon oxynitride film differ depending on the type of sensor substrate used because the coefficient of thermal expansion differs depending on the crystal plane orientation of the substrate material.

As the microheater, one having an electric resistance such as a polycrystalline silicon film is used. CVD (Chemical Vapor Deposition), sputtering, ion beam sputtering, or the like is used for producing this polycrystalline silicon film.

[0019]

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

FIG. 2 shows an overall configuration including a measurement system of a thermal infrared sensor according to an embodiment of the present invention. The temperature-sensitive parts 21 and 22 having the same structure are formed on the sensor substrate 23, respectively. A partition section 24 is provided between the temperature sensitive sections 21 and 22.
Is provided, and the space between them is shielded so that infrared rays cannot pass through. An infrared incident window 25 is provided in a portion facing one of the temperature sensing parts 21, and the temperature measured object 2
The infrared ray A radiated from 6 is incident. A heater (micro heater) 27 is provided on the sensor substrate 23 so as to face the other temperature sensitive portion 22. The temperature sensing portion 22 is completely shielded from infrared rays from the outside, and only the infrared rays B from the heater 27 are incident. The temperature of the heater 27 is controlled by the heater controller 28, and the temperature at this time is displayed by the display 32.
Is displayed.

Each of the temperature sensing parts 21 and 22 has a thermistor effect, and its electric resistance value changes according to a temperature change, and converts the received infrared ray amount into an electric signal (current value or voltage value). be able to. These temperature sensing parts 21,
The output signal of 22 is amplified to a predetermined level by amplifiers 29 and 30, respectively, and then input to a comparator 31. The comparator 31 detects the difference between the two input signals and feeds it back to the heater controller 28. The heater control unit 28 receives this feedback signal, controls the current value flowing through the heater 27 so that the difference becomes zero, and adjusts the amount of infrared rays emitted. By repeating such a feedback operation, the output of the comparator 31 becomes zero, that is, the infrared ray amounts incident on the temperature sensing portions 21 and 22 become the same. The current value of the heater 27 at this time is converted into a temperature value which is converted in advance, and this temperature is displayed.
Is displayed in.

Next, an example in which the present invention is applied to an infrared sensor using a semiconductor manufacturing technique using a silicon substrate as a sensor substrate will be described.

In the infrared sensor of this embodiment, a silicon substrate (thickness 300 to 400 μm) 41 as a sensor substrate is used.
Two cavities 42 and 43 are formed in the. A bridge portion (bridge) 44, on the surface side of these hollow portions 42, 43,
45 are provided. Circular infrared ray receiving portions 46 and 47 are formed in the central portions of the bridge portions 44 and 45, respectively, so that infrared rays can be received efficiently.
Temperature sensitive portions 48 and 49 are formed on the upper surfaces of the infrared ray receiving portions 46 and 47, respectively. The temperature sensitive portions 48 and 49 are each formed of a substance having a thermistor effect, for example, amorphous germanium (a-Ge).

An infrared incident window 50 is formed on the back surface side of the silicon substrate 41 so as to correspond to one of the temperature sensing parts 48, and the infrared radiation emitted from the object to be measured through the infrared incident window 50 is transmitted to the temperature sensing part 48. It is designed to guide you. A bridge portion 51 is formed on the back surface side of the silicon substrate 41 corresponding to the other temperature sensitive portion 49, and the micro heater 5 is formed in the bridge portion 51.
3 is provided. The microheater 53 is formed of, for example, a polycrystalline silicon film that exhibits electric resistance. The micro heater 53 is the heater control unit 28 of FIG.
The heat generation temperature, that is, the amount of infrared rays to be radiated is controlled by the control. Although not shown, the temperature sensing parts 48 and 49 are respectively connected to the amplifier 2 of FIG.
9 and 30 are connected.

In this infrared sensor, the amount of infrared rays (temperature) incident from the object to be measured through the infrared incident window 50.
The electric resistance value of one of the temperature sensing parts 48 changes in accordance with. Further, the infrared rays radiated from the micro-heater 53 are incident on the other temperature sensing section 49, and the electric resistance value of the temperature sensing section 48 also changes according to the amount of the infrared rays. These two temperature sensing parts 48,
The temperature of the micro-heater 53 is adjusted so that the outputs of the temperature sensing parts 48 and 49 become equal so that the outputs of the temperature measurement parts and the infrared rays emitted from the micro-heater 53 become equal. . Therefore, the temperatures of the two temperature sensing parts 48 and 49 are the same, and the electric resistance values thereof are also the same. Therefore, the amount of self-heating due to Joule heat becomes the same, and the differential output of the comparator 31 is not affected, and therefore high-sensitivity and high-accuracy measurement becomes possible.

FIGS. 4A to 4D to 6A to
(C) shows the manufacturing process of this infrared sensor. First, as shown in FIG.
A silicon substrate 41 of 0) was prepared. Next, a silicon oxynitride film (SiOxNy) 61 having a film thickness of 2 μm as shown in FIG. 7B was formed on both surfaces of the silicon substrate 41 by the plasma CVD method. That is, the silicon substrate 41 is heated to 450 ° C.
The pressure is 0.45Toor, the high frequency output is 400W, and the reaction gas is monosilane (Si H ₄ ) 15SCCM, nitrogen (N ₂ ) 203SCCM, laughing gas (N ₂ O) 32SCCM.
Then, silicon oxynitride was vapor-phase grown on the silicon substrate 12.

Next, sputtering is performed using germanium (Ge) as a target, and as shown in FIG. 4C, the amorphous germanium (a-Ge) film 6 is formed on the silicon oxynitride film 61 on the surface of the silicon substrate 41.
Formed 2. In this sputtering, the gas flow rate was argon (Ar) = ₂ SCCM, hydrogen (H ₂ ) = 1 SCCM, the film forming pressure was 3 × 10 ⁻³ Torr, and the high frequency pressure was 200 W.
I went for a minute. Next, annealing treatment was performed at 500 ° C. to promote polycrystallization of amorphous germanium. Then, as shown in FIG. 4D, for example, C is formed on the silicon oxynitride film 61 on the back surface of the silicon substrate 41.
A polycrystalline silicon film 63 was formed by the VD method. This C
For VD, the silicon substrate 41 was heated to 750 ° C., the pressure was 0.7 Toor, the time was 20 minutes, and the reaction gas was monosilane (Si H ₄ ) = 30 SCCM as film forming conditions.

Then, reactive ion etching (RI
By performing step E), the polycrystallized amorphous germanium film 62 was patterned to form temperature-sensitive films 48 and 49 as shown in FIG. This reactive ion etching uses carbon tetrafluoride (CF ₄ ) as an etching gas.
And oxygen (O ₂ ) are used, and the flow rate is CF ₄ = 38 SCCM,
O ₂ = ₂ SCCM, etching pressure 0.2 Torr,
The high frequency output was 150 W and the etching time was 10 minutes.

Further, the polycrystalline silicon film 63 was patterned by the reactive ion etching under the same conditions as described above except that the etching time was 15 minutes to form the micro heater 53. It should be noted that the position of the micro-heater 53 is set so as to face the temperature sensing section 49.

Next, as shown in FIG. 5B, a metal film, for example, a titanium film 64 was formed on each surface of the silicon substrate 41 by a vapor deposition method.

Subsequently, as shown in FIG. 5C, the titanium film 64 was patterned by reactive ion etching to form wiring of the titanium film 64 on each of the temperature sensitive parts 48, 49 and the micro heater 53.

Next, a silicon oxynitride film (SiOxNy) having a film thickness of 2 μm as shown in FIG. 6A is formed on both surfaces of the silicon substrate 41 by the plasma CVD method under the same conditions as in the step of FIG. 4B. ) 65 was formed. next,
This silicon oxynitride film 65 and the underlying silicon oxynitride film 61 are selectively etched, and as shown in FIG.
The window portions 66 for forming 45 and 51 and the cavity portions 42 and 43 were formed.

Finally, wet etching is selectively performed on both surfaces of the silicon substrate 12 through the window portion 66, as shown in FIG.
As shown in (C), bridge portions 44, 45, 51 and cavity portions 42, 43 were formed. This wet etching was performed by anisotropic etching using a hydrazine aqueous solution.

The present invention has been described with reference to the examples.
The present invention is not limited to the above embodiments, but can be variously modified without changing the gist thereof. For example, the cavities 42 and 43 below the bridges 44, 45 and 51 are formed by using a hollowing method by anisotropic etching.
You may use what is called a sacrificial layer method formed in the lower part of 5,51.

Further, in the above embodiment, the temperature sensing unit 4
Infrared rays are incident on each of 8 and 49 from the same direction.
The infrared rays from 3 may enter the temperature-sensitive parts 48 and 49 from different directions. Further, in the above-described embodiment, the micro heater 53 is formed in the same process as the sensor main body, but the micro heater may be formed in a separate process and externally attached to the sensor main body.

[0036]

As described above, according to the infrared sensor of the first and second aspects, the infrared rays radiated from the temperature measured object are detected by the first infrared detecting means, and the temperature measured object is Separately, an infrared radiation source for radiating infrared rays is provided, and the infrared radiation emitted from the infrared radiation source is guided to the second infrared detection means, and the difference between the output signals of the first infrared detection means and the second infrared detection means is calculated. Since the amount of infrared radiation emitted from the infrared radiation source is controlled so that the output of the differential detection means is zero, the response sensitivity is improved and a highly accurate measurement value is obtained. be able to.

Particularly, according to the infrared sensor of the third aspect, since the pair of bridge portions are provided on the semiconductor substrate and the temperature sensitive portions are formed on the bridge portions, respectively, the response sensitivity is improved. Since the amount of infrared rays incident on the two temperature-sensing parts is the same, the self-heating amount due to Joule heat is also the same, and there is no error in the differential output of the comparator due to this self-heating. There is an effect that it is possible to provide an infrared sensor capable of measuring sensitivity and high accuracy.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a main part of an infrared sensor according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the overall configuration of the infrared sensor of FIG.

FIG. 3 is a block diagram for explaining the basic principle of the present invention.

FIG. 4 is a cross-sectional view showing a manufacturing process of the infrared sensor of FIG.

FIG. 5 is a cross-sectional view showing a manufacturing process of the infrared sensor of FIG.

FIG. 6 is a cross-sectional view showing a manufacturing process of the infrared sensor of FIG.

[Explanation of symbols]

 11 First Infrared Detection Means 12 Second Infrared Detection Means 13, 26 Temperature Measured Object 14 Infrared Radiation Source 15 Difference Detection Means 16 Infrared Radiation Source Control Means 17 Display Means 21, 22, 48, 49 Temperature Sensing Section 23, 41 Sensor Substrate 42, 43 Cavity 44, 45, 51 Bridge 46, 47 Infrared Receiver 53 Micro Heater

Claims (3)

[Claims] 1. A first infrared detecting means for converting infrared rays radiated from an object to be measured into an electric signal, an infrared radiation source which emits infrared rays separately from the object to be measured, and the infrared radiation source A second infrared detecting means for converting the emitted infrared rays into an electric signal; a difference detecting means for detecting a difference between output signals of the first infrared detecting means and the second infrared detecting means; An infrared sensor comprising: an infrared radiation source control means for controlling the amount of infrared radiation emitted from the infrared radiation source so that the output of the difference detection means becomes zero upon receiving an output signal. 2. The infrared sensor according to claim 1, further comprising display means for displaying the temperature of the infrared radiation source when the output of the difference detection means becomes zero. 3. Formed from a semiconductor material,
A sensor substrate having a pair of cross-linking portions, a first temperature-sensing portion which is provided on the one cross-linking portion and converts infrared rays radiated from an object to be measured into an electric signal, and the first temperature-sensing portion. A second temperature sensitive part having the same structure as that of the first temperature sensitive part provided on the other bridge part, and a micro heater provided on the sensor substrate corresponding to the second temperature sensitive part; And a comparator for detecting the difference between the output signals of the temperature sensing unit and the second temperature sensing unit, and for controlling the temperature of the micro heater so that the output of the comparator becomes zero upon receiving the output signal of the comparator. An infrared sensor, comprising: a micro-heater control unit for performing.