JPH08122163A - Heat dependence detection device - Google Patents

Abstract

PURPOSE: To read a heat dependence detector signal at an accurate atmosphere temperature. CONSTITUTION: A first temperature sensing sensor 6, a second temperature sensing sensor 7, and a heat dependency detector (moisture sensor) 8 are provided at a sealing side with a slow thermal response, a free edge side with a fast thermal response, and a second temperature sensing sensor 7 of the free edge side, respectively, on the SiO2 film surface of a sheet-shaped Si substrate 2 which is supported in a cantilever shape where one edge side is fixed onto a base plate 1. The temperature when the temperature detected by the first temperature sensing sensor 6 and that detected by the second temperature sensing sensor 7 become equal to each other is an ambient temperature. The temperature of the heat dependence detector is read at this point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat dependence detecting device, and more specifically, to temperature (humidity), measured values such as temperature, humidity, gas, infrared ray, pressure, vacuum degree, acceleration, flow rate and flow velocity. The present invention relates to an apparatus for measuring a dependent physical quantity to be measured.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram for explaining an example of a conventional detection device. FIG. 5 (a) is a plan view and FIG. 5 (b) is a sectional view taken along line BB of FIG. 5 (a). In the drawing, 31 is, for example, a Si substrate, 32 is a cavity provided in the Si substrate 31, and as is well known, the upper portion of the cavity 2 is, for example, Si substrate.
A bridge 33 made of an insulating film such as O ₂ or Ta ₂ O ₅ is laid, and a resistor pattern 34 made of, for example, Pt or NiCr is arranged on the bridge 33. on top of the resistor pattern 34, a protective film 35 made of SiO _1, Ta ₂ O ₅ or the like is provided, current is applied to the resistor pattern 34 through Bonn dengue wire 36, the resistive element antibodies pattern 34, the The heat generating portion or the temperature sensitive (heat) portion A is heated.

Taking the case of measuring the humidity using the detector as described above as an example, the resistance value of the resistor 34 depends on the ambient temperature and humidity. A resistance value related to ambient temperature is measured by passing such a minute current, and then a resistance value related to ambient temperature and humidity is measured by flowing a current having humidity sensitivity. The ambient humidity is measured by subtracting the measured value for.

The detection device as described above uses the microfabrication technology of semiconductors and integrated circuits to generate heat or space from the substrate 31 (a cavity 32 is provided in the substrate 31 to avoid heat conduction with the substrate 31). Although the temperature-sensitive portion A is formed, the chip has a thickness of 0.1 to 2 mm and a width of 0.5 × 0.5 mm to 10 × 10 mm in view of the usual semiconductor manufacturing technology. . When the above-mentioned cavity 32 is provided within this size, the distance between the heat generating portion or temperature sensing portion A and the cavity wall 32b, especially the cavity bottom portion 32, is increased.
Since it is close to 50 to 300 μm with respect to a, a large interval cannot be secured. If this distance is short, the heat generating portion is affected by the temperature state of the substrate 31 having a much larger heat capacity than the heat generating portion A, and the effect of thermal insulation due to the hollow portion is lost. That is, since the heat radiation from the substrate 31 and the heat conduction of the atmosphere in the cavity 32 are close to each other, the effect of such heat insulation is lost.

In addition, when the temperature of the substrate 31 is low and water in the atmosphere is condensed and water droplets are attached to the periphery of the substrate 31, for example, when measuring the humidity, the temperature sensing ( (Heat) Part A is heated to heat (heat)
Since the water droplets in the vicinity of the portion A are evaporated and the heat of vaporization is taken away, the temperature detected by the temperature-sensitive (heat) portion A is detected as a temperature lower than the actual ambient temperature. As a result, the detected humidity becomes higher than the actual humidity, which causes a drawback that the temperature and humidity are not correctly detected.

FIG. 6 is a main part configuration diagram for explaining another example of the conventional detection apparatus. In the figure, 31 is a substrate, 32 is a cavity, 33 is a bridge made of an insulating film, and 34 is a heat or sense. A heating material, 34a is a lead pattern for the heat-generating or temperature-sensitive material 34, 36 is a bonding wire, 37 is a lead wire, 38 is a package base, 39 is a package cap, and the detection portion composed of the substrate 31 to the bonding wire 36 is As in the case of FIG. 5, the ambient temperature, humidity, and other physical quantities are measured.

In the detection device as described above, as the influence of the heat received by the temperature sensitive material 34 on the substrate, the heat radiation from the peripheral substrate 31 (a ₁ ), the heat radiation from the external package 39 (a ₂ ), the bridge Heat conduction from the suspension 33 (b ₁ ), heat conduction from the package base 38 (b ₂ ),
There is heat conduction in the surrounding convection (b ₃ ). This temperature sensitive material 3
The response time of the ambient temperature of 4 is 8
When the temperature of 0 ° C. is changed to 20 ° C., the temperature-sensitive material 34 becomes 2
It takes about 20 minutes to reach 0 ° C. Temperature sensitive material 34
Is not in contact with the packages 38, 39 and the substrate 31 because it is through the cavity 32 of the substrate 31, and may have a small heat capacity, so that it may adapt to the temperature of the ambient atmosphere more rapidly. However, in reality, it takes a lot of time as described above. The package-based response time is also about 20 min. Therefore, the temperature sensitive material does not have a short response time with or without a cavity.

In the detection device as described above, by arranging the material of the heat-generating or temperature-sensitive part and its arrangement, for example, temperature, humidity, gas, infrared rays, pressure, vacuum degree, acceleration, flow rate, flow velocity, etc. are detected. As the physical phenomenon to be measured, the following principles 1 to 7, namely, 1. As the resistance value change of the electric resistor, 2. It has a sensitive film for desorbing an atmosphere and the electric resistance value of the sensitive film changes. 3. It has a sensitive film that desorbs an atmosphere, and the capacitance of the sensitive film changes. 4. A sensitive film for desorbing an atmosphere is provided, and a change in weight of the sensitive film is used as a change in resonance frequency. 5. Having a sensitive film for desorbing the atmosphere, the reaction heat is generated by the chemical reaction of the sensitive film, and this heat is used as the resistance value change of another resistor. 6. The temperature change is taken as the output voltage change of the thermocouple membrane, Deflection is the output voltage change of the piezoresistive effect,
It is measured by using.

[0009]

When the physical quantity of the object to be measured is measured by using the above-mentioned measurement principles 1 to 7, the measured value is influenced by the temperature. If you don't know it accurately, you will get meaningless measurement results. For example, when the pressure of a gas is detected by piezo resistance, if the temperature of the gas is not known, the accurate pressure cannot be known. It suffices that the temperature of the gas and the temperature of the piezoresistive (the piezoresistive have temperature dependence) have a certain known relationship, but if not, a solution of temperature compensation is used. However, if the piezoresistor is left in gas until temperature equilibrium is reached,
In reality, the temperature variation of the gas and the temperature variation of the piezoresistance cannot follow because of the large heat capacity of the piezoresistance. As a result, temperature compensation becomes incomplete.

The present invention has been made in view of the above circumstances, and in particular, in a detection device in which a heat-dependent detector such as a heat-generating or temperature-sensitive material is provided on a substrate, the heat-dependent detector is Detecting that the temperature of the entire substrate provided has reached the ambient temperature, read the signal of the thermal dependency detector by the command of the detection signal, and obtain the signal of the thermal dependency detector at the correct ambient temperature. It was made for the purpose of doing.

[0011]

In order to solve the above-mentioned problems, the present invention has (1) a plate-shaped substrate having one end fixed to a base plate and supported in a cantilever shape. A first temperature sensor on the fixed side of the base plate above,
A second temperature sensor and a heat-dependent detector that detects a physical quantity of a measurement target are provided on the free end side that is separated from the fixed side, and the temperature detected by the first temperature sensor and the second temperature sensor. When the temperature reaches substantially the same temperature, to detect the physical quantity of the measurement object of the heat dependence at the temperature by the heat dependence detector, further,
(2) The heat-dependent detector is a detector in which a physical quantity of a heat-dependent measured object is detected as a resistance value, and the heat-dependent detector also serves as the second temperature sensor. It is what

[0012]

Operation: One end of the flat Si substrate surface is fixed on the base plate and supported in a cantilever shape. As a result, the thermal response on the free end side of the substrate is accelerated, and a thermal dependency detector and a second temperature sensor for detecting the temperature on the free end side are provided on the free end side of the substrate, and A first temperature sensor for detecting the temperature of the fixation side is provided on the fixation side, and the temperature at the time when the temperatures detected by the first and second temperature sensors on the substrate become equal is the ambient temperature. The thermal dependency detector detects the physical quantity of the object to be measured at the ambient temperature according to the command of the temperature comparison signal in which the detected temperatures are equal.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a heat dependence detecting device according to the present invention will be referred to as a humidity detecting device, and the humidity detecting device will be described with reference to the drawings. [Embodiment 1] (corresponding to claim 1) Fig. 1 is a view for explaining the structure of a first embodiment of a humidity detector according to the present invention, in which 1 is a base plate and 2 is a base plate.
Is a Si substrate (hereinafter referred to as a substrate), 3 and 4 are cavities, 5
Is a bridge, 6 is a first temperature sensor, 7 is a second temperature sensor, 8 is a humidity sensor, 9 is a lead terminal, and 10 is a bonding wire.

In FIG. 1, a substrate 2 is, for example, a Si crystal plate cut into a rectangular plate, and an insulating film such as SiO ₂ is formed on the surface thereof. The substrate 2 is anisotropically etched. A cavity 3 is formed substantially in the center of the substrate 2, and a cavity 4 is formed near one end of the substrate 2, and a bridge 5 made of an insulating film such as SiO ₂ is provided above the cavity 4. Further, on the symmetry axis OO line of the substrate 2, a first temperature sensor 6 and a second temperature sensor 7 having an axially symmetric resistance pattern made of Pt, NiCr or the like with the cavities 3 and 4 sandwiched therebetween are provided. Has been. Further, on the upper surface of the bridge 5, a lead 8a is provided with a moisture-sensitive conductive material or the like which changes resistance due to moisture absorption, for example, a porous sintered material such as TiO ₂ or V ₂ O ₅ or a synthetic resin such as a copolymer of styrene. , 8b is provided between the first temperature sensor 6, the second temperature sensor 7,
On the substrate 2 on which the humidity sensor 8 is formed, for example, Si
An insulating film such as O ₂ or Ta ₂ O ₅ is coated and protected.

In the substrate 2 on which the first temperature sensor 6, the second temperature sensor 7 and the humidity sensor 8 are formed, the humidity sensor 8 and the second temperature sensor 7 are arranged on the free end side of the substrate 2. Thus, the first temperature sensor 6 side is fixed to the base plate 1 and supported in a cantilever shape. A plurality of lead terminals 9 are provided on the base plate 1 to which the substrate 2 is fixed, and the lead terminals 9 are the leads 6 of the first temperature sensor 6 on the substrate 2.
Bonding wires 10 are connected to the pads a, 6b, the leads 7a, 7b of the second temperature sensor 7 and the leads 8a, 8b of the humidity sensor 8, respectively. When the substrate 2 is fixed to the base plate 1, the center of the first temperature sensitive sensor 6 is preferably aligned with the symmetry axis OO line which is the center line with respect to the base plate 1 and the substrate 2.

As described above, in the humidity detector shown in FIG. 1, the tip of the substrate 2 (humidity sensor 8 supported in the shape of a cantilever).
The second temperature sensor 7, near the free end side where
The first temperature sensor 6 is arranged near the base (on the side where the base plate 1 is fixed). For this reason, the heat capacity of the humidity sensor 8 portion of the substrate 2 is small and responds quickly to the ambient temperature, but at the base portion where the first temperature sensor 6 is arranged, the heat capacity is large because it is fixed to the base plate 1, and
Since the convection of the ambient atmosphere is also hindered and heat exchange is difficult, the thermal response is slow and the response to changes in the ambient temperature becomes slow. Therefore, the first temperature sensor 6 and the second temperature sensor 6
By comparing the temperatures detected by the temperature sensor 7, the substrate 2
It is confirmed whether the temperature of is equal to the ambient temperature. Furthermore, since the cavity 3 is provided between the first temperature sensor 6, the second temperature sensor 7 and the humidity sensor 8, the second temperature sensor 7 and the humidity sensor 8 are arranged from the base plate 1 side.
The heat conduction to the side is small, and the humidity sensor 8 is
Since it is provided on the bridge 5 that is bridged over, the heat effect from the side of the base plate 1 to the second temperature sensor 7 and the humidity sensor 8 is reduced, and the above-mentioned action is further enhanced and the ambient temperature detection accuracy is improved. be able to.

FIG. 2 is a block diagram of a humidity measuring circuit using the humidity detector shown in FIG. 1, in which 11 is a drive unit.
Reference numeral 12 is a comparison circuit, 13 is a determination circuit, 14 is a switching circuit, 15 is a humidity sensor drive circuit, 16 is a humidity measurement circuit, and 17 is a humidity data output. The same reference numerals as in the above are attached.

In FIG. 2, the first temperature sensor 6 and the second temperature sensor 7 are connected in series, and are driven by the drive unit 11 at a constant current, for example. At this time, the first temperature sensor 6
When the resistance values of the second temperature sensor 7 and the resistance value of the second temperature sensor 7 are selected to be equal at the same temperature, the voltages across the first temperature sensor 6 and the second temperature sensor 7 are equal at the same temperature, so the comparison circuit 12 Thus, it is determined by voltage comparison whether or not the temperature detected by the first temperature sensor 6 and the temperature detected by the second temperature sensor 7 are equal.

This determination is made by the determination circuit 13,
When the temperatures of the first temperature sensor 6 and the second temperature sensor 7 are completely equal to each other or equal to each other within an allowable error range, the switching circuit 14 is turned on (closed), and the humidity sensor drive circuit 15
Is driven. The humidity sensor drive circuit 15 is a circuit for applying a current of a predetermined level to the humidity sensor 8, and the humidity sensor 8 can obtain a resistance value according to ambient temperature and humidity. This resistance value is corrected by the atmosphere temperature detected by the second temperature sensor having a resistance value equal to that of the first temperature sensor 6 by the measuring circuit 16, the relative humidity is obtained under the constant atmosphere temperature condition, and the data output To be done.

In the humidity measuring circuit described above, it was explained that the humidity sensor 8 measures the humidity at the correct ambient temperature when the temperatures of the base plate 1 side and the free end side of the substrate 2 are constant. If the ambient temperature according to the temperatures detected by the first temperature sensor 6 and the second temperature sensor 7 is known, until the first temperature sensor 6 and the second temperature sensor 7 reach the ambient temperature. The humidity at a temperature substantially equal to the ambient temperature is detected without waiting time. Also,
The driving of the switching circuit 14 is, as shown by the dotted line,
Turns on and off the output signal of the humidity sensor 8 that is constantly driven.
You may make it FF.

[Second Embodiment] (Corresponding to Claim 2) FIG. 3 is a diagram for explaining an example of the configuration of a second embodiment of the humidity detector according to the present invention, in which 18 is a temperature sensing element. A sensor 19 is a humidity sensor, and the same reference numerals as those in FIG. 1 are attached to the portions having the same functions as those in FIG.

The humidity detector shown in FIG. 3 differs from the humidity detector shown in FIG. 1 in that the temperature detecting function of the second temperature sensor 7 arranged on the free end side of the substrate 2 and the humidity of the humidity sensor 8 are provided. One humidity sensor 19 is also provided with the function of detection, and the humidity detecting unit 19 is a bridge that is bridged in the cavity 4 on the free end side of the substrate 2 like the humidity detector shown in FIG. 5, the temperature sensor 18 corresponding to the first temperature sensor 6 is provided on the base plate side of the substrate 2 as in the case shown in FIG.

The temperature sensor 18 is the first temperature sensor 6 described above.
Similarly to, Pt and Ni provided on the SiO ₂ film of the substrate 2
Like the humidity sensor 8, the humidity sensor 19 is also made of a resistance pattern of Cr or the like, and leads 19a and 19 are arranged on the bridge 5 made of an insulating film such as SiO _{2 so} as to face _each other at a predetermined interval.
A film made of the same material as that of the humidity sensor 8 whose resistance changes due to moisture absorption is connected between b and leads 19a, 19
When a weak current is applied between b, it acts as a resistor that does not depend on humidity, and when a current of a predetermined value or more is applied, it has a resistance value that depends on humidity.

FIG. 4 is a block diagram of a humidity measuring circuit using the humidity detector shown in FIG.
5 is a drive circuit, 22 is a comparison circuit, 23 is a judgment circuit, 24
Is a switching circuit, 27 is a measuring circuit, and 28 is a data output section. The parts having the same operations as in FIG. 3 are denoted by the same reference numerals as in FIG.

As described above, since the humidity sensor 19 has the functions of a temperature sensor and a humidity sensor, when it is used as a temperature sensor, it is used as a temperature sensor 19R and when it is used as a humidity sensor. , Humidity sensor 19H. Therefore, the applied current value is different between the case where it functions as the temperature sensor 19R and the case where it functions as the humidity sensor 19H, and the drive circuits that output such two-stage currents may be the same. However, in order to facilitate understanding, in the block diagram of FIG.
9 is separately described as a drive circuit 21 when it is used as the temperature sensor 19R and as a drive circuit 25 when it is used as the humidity sensor 19H.

The temperature sensor 18 and the temperature sensor 19R are connected in series, and the temperature sensor 18 is further connected to the drive circuit 2
0, the temperature sensor 19R is connected to the drive circuit 21, and the temperatures of the base plate 1 side and the free end side on the substrate 2 are detected. The voltages across the respective terminals are compared by the comparison circuit 22, and the determination circuit 23 determines whether or not the respective detected temperatures are above a predetermined range. When the temperature determination result is within the range, the switching circuit The drive circuit of the temperature sensor 19R is switched to the drive circuit 25 of the humidity sensor 19H via 24. The measuring circuit 27 subtracts and corrects the resistance values of the temperature sensors 18 and 19R, calculates the humidity based on the voltage value obtained as a function of the humidity, and outputs the data 28. Further, as shown by the dotted line, the measuring circuit 27 by the switching circuit 24 may be opened and closed.

According to the humidity detecting device according to the embodiment shown in FIGS. 3 and 4, the single humidity sensor 19 provided at the free end of the substrate 2 functions as a temperature sensor and a humidity sensor. As in the case of Example 1, it is possible to measure the humidity at an accurate ambient temperature, and at the same time,
It can be a small-sized humidity measuring device. 1 to
Although the humidity measuring device is described in FIG. 4, it is applied to all the heat dependency detecting devices affected by the ambient temperature.

[0028]

As is apparent from the above description, the present invention has the following effects. (1) Effect corresponding to claim 1: Since the temperature sensors are respectively provided on the side having a large heat capacity fixed to the substrate and the side having a small heat capacity on the free end side, the temperature detected by each temperature sensor can be adjusted. By comparing, an accurate ambient temperature can be obtained,
The reliability of the measurement result of the heat dependency detecting device affected by the ambient temperature is improved. (2) Effect corresponding to claim 2: In addition to the above effect, since one of the two temperature-sensitive sensors using the resistor as a temperature detecting element uses the resistor of the heat-dependent detector itself, A simple and small heat-dependent detection device can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the structure of a first embodiment of a humidity detector according to the present invention.

FIG. 2 is a block diagram of a humidity measuring circuit using the humidity detector shown in FIG.

FIG. 3 is a diagram for explaining an example of a configuration of a second embodiment of the humidity detector according to the present invention.

FIG. 4 is a block diagram of a humidity measuring circuit using the humidity detector shown in FIG.

FIG. 5 is a configuration diagram for explaining an example of a conventional detection device.

FIG. 6 is a main part configuration diagram for explaining another example of the conventional detection device.

[Explanation of symbols]

1 ... Base plate, 2 ... Si substrate (hereinafter referred to as substrate), 3, 4 ... Hollow part, 5 ... Bridge, 6 ... First temperature sensor,
7 ... 2nd temperature sensor, 8 ... Humidity sensor, 9 ... Lead terminal, 10 ... Bonding wire, 11 drive part, 12 comparison circuit, 13 determination circuit, 14 switching circuit, 1
5 is a humidity sensor drive circuit, 16 is a humidity measurement circuit, 17 is a humidity data output, 18 is a temperature sensor, 19 is a humidity sensor, 20, 21, 25 are drive circuits, 22 is a comparison circuit, 2
3 is a determination circuit, 24 is a switching circuit, 27 is a measurement circuit, and 28 is a data output section.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G01N 25/64 Z 27/18

Claims (2)

[Claims] 1. One end side is fixed on a base plate,
It has a plate-shaped substrate supported in a cantilever shape, a first temperature-sensitive sensor on the fixed side of the base plate on the substrate, and a second temperature-sensitive sensor and a cover on the free end side separated from the fixed side. A heat-dependent detector that detects a physical quantity of a measurement target is provided, and when the temperatures detected by the first temperature sensor and the second temperature sensor reach substantially equal temperatures,
A thermal dependence detection device, wherein a physical quantity of a thermal dependence measurement target at the temperature is detected by the thermal dependence detector. 2. The heat-dependent detector according to claim 1, wherein the heat-dependent physical quantity of an object to be measured is detected as a resistance value, and the heat-dependent detector uses the second temperature-sensitive sensor. A thermal dependence detection device, which is also used as a heat detector.