JP3258484B2 - Gas rate sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas rate sensor for detecting an angular velocity acting on a substrate.

[0002]

2. Description of the Related Art A gas rate sensor of this type is known from Japanese Patent Publication No. 3-29858. The basic operation principle of such a gas rate sensor will be described with reference to FIG. 4. When the angular velocity acts on the substrate a, the gas flow flowing through the gas flow path b bends and the heat wire pair c,
d is cooled, the resistance value changes according to the temperature difference of the heat wire at this time, and the change changes the potential of the middle point e of the pair of heat wires c and d. An output signal proportional to the angular velocity is obtained based on the difference between the pair c and d and the potential of the middle point h of the pair of reference resistors f and g forming the resistance bridge circuit.

In such a gas rate sensor, a pair of reference resistors f and g are fixed resistors and are disposed outside the gas passage b. Therefore, when detecting the angular velocity, only the change in the resistance value due to the temperature change of the heat wire is involved. However, if only the change in the resistance value of the heat wire is involved, when the angular velocity acting on the base a is small and the resistance value of the heat wire changes only slightly, the angular velocity signal cannot be detected properly. , The sensitivity was inferior.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and provides a highly sensitive gas rate sensor capable of accurately detecting an angular velocity signal even when the angular velocity acting on a substrate is small. The purpose is to do.

[0005] Further, the present invention relates to an I-type semiconductor device using a semiconductor substrate.
A highly sensitive gas rate sensor that can accurately detect an angular velocity signal even when the angular velocity acting on the substrate is small, even if it has a very small and extremely precise substrate formed by micromachining processing using C manufacturing technology. The purpose is to provide.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a gas flow path provided with a pair of heat wires, and a method for injecting gas into the gas flow path toward the heat wire pair. A base having a nozzle hole, and a pair of reference resistors forming a pair of heat wires and a resistance bridge circuit. Each of the heat wires is formed based on a deflection of a gas flow generated when an angular velocity acts on the base. In the gas rate sensor, a signal corresponding to the difference in the change in the resistance temperature characteristic is detected using the resistance bridge circuit, and an output signal proportional to the angular velocity is obtained based on the detection signal. Provided in a gas flow path on the downstream side of the heat wire pair, so that heated gas comes into contact with the reference resistor when passing through the heat wire. And it is characterized in and.

In this case, it is preferable to make the resistance value of the reference resistor larger than that of the heat wire so that a large current flows through the heat wire to heat the heat wire more.

Further, in the present invention, the reference resistor pair is provided close to the heat wire pair.

Further, the present invention relates to an I-type semiconductor device using a semiconductor substrate.
The substrate is formed by micromachining using a C manufacturing technique.

Further, the present invention is characterized in that each heat wire and each reference resistor are formed of platinum.

[0011]

According to the present invention, a pair of reference resistors
Since the gas that has passed through the heat wire is provided in the gas flow path on the downstream side of the heat wire pair so that the gas is in contact with the reference resistor, the heat wire is cooled by the passage of the gas to reduce the resistance value. The resistance is warmed by the gas heated by the heat wire, and the resistance increases. Therefore, it is possible to obtain an output larger by the change in the reference resistance value than in the conventional case where the reference resistance is a fixed resistance.

Further, when a pair of reference resistors are provided close to the pair of heat wires, the reference resistor can be efficiently heated by the gas heated by the heat wire, so that the amount of change in the reference resistance value can be reduced. It is possible to increase it.

Further, when each of the heat wires and each of the reference resistors are formed of platinum, their temperature sensing characteristics are improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an exploded perspective view of a base of a gas rate sensor according to one embodiment of the present invention, and FIG. 2 is a II-I of FIG.
FIG. 3 is an explanatory schematic view for explaining the operation of the gas rate sensor.

The overall structure will be described with reference to FIG. 1. The gas rate sensor comprises an ultra-small base 1 formed by micromachining using a semiconductor substrate, and the base 1
And a resistance bridge circuit 3 that detects an angular velocity signal based on the deflection of the gas flow when the angular velocity acts on the substrate 1.

As shown in FIGS. 1 and 2, the base 1 is formed by bonding a lower semiconductor substrate 4 and an upper semiconductor substrate 5, and has a gas passage 2 therein and a gas passage 2 provided therein. Has a nozzle hole 6 for jetting out. The gas flow path 2 is formed by abutting a concave portion 7 formed on the lower semiconductor substrate 4 and a concave portion 8 (see FIG. 2) formed on the upper semiconductor substrate 5 with each other. On the other hand, the nozzle hole 6
Is formed by aligning the bonding surface of the upper semiconductor substrate 5 with the groove 9 formed to communicate with the concave portion 7 of the lower semiconductor substrate 4. A micropump (not shown) is connected to the nozzle hole 6, and gas is ejected from the nozzle hole 6 to the gas flow channel 2 by driving the micropump.

The resistance bridge circuit 3 detects the angular velocity signal based on the deflection of the gas flow when the angular velocity acts on the base 1, and comprises a pair of heat wires 10, 11 and a pair of reference resistors 12, 13. Composed of a Wheatstone bridge circuit.

The pair of heat wires 10 and 11 are connected to the gas flow path 2.
Are arranged symmetrically with respect to each other with the center line therebetween, and a heat-sensitive resistance material is deposited on the upper surface of the bridge portion 14 formed so as to straddle the recessed portion 7 of the lower semiconductor substrate 4, and thereafter, the pattern is formed by etching. Molded. Here, in this embodiment, platinum having excellent heat-sensitive characteristics is used as the heat-sensitive resistance material, and the combined resistance of the heat wire pairs 10 and 11 is reduced to 15%.
It is set to 0Ω. On both sides of the heat wire pairs 10 and 11, electrode portions 15 connected to the heat wire pairs 10 and 11 are provided.
Are pattern-formed in the same manner as the heat wire pairs 10 and 11.

The reference resistor pairs 12 and 13 are symmetrically arranged on the upper surface of the bridge portion 14 on the downstream side of the heat wire pairs 10 and 11 in close proximity to the heat wires 10 and 11, respectively. And then etching to form a heat wire pair 10,
11 is formed into a pattern having substantially the same shape. Here, as the heat-sensitive resistance material, similarly to the heat wire pairs 10 and 11, platinum excellent in heat sensitivity is used, and the combined resistance of the reference resistance pairs 12 and 13 is set to 750Ω and that of the heat wire pairs 10 and 11 is used. Is larger. On both sides of the pair of reference resistors 12 and 13, electrode portions 16 connected to the pair of reference resistors 12 and 13 are formed by patterning.

Next, the operation of the gas rate sensor will be described with reference to FIG. FIG. 3 shows a pair of heat wires 10 and 11 and a pair of reference resistors 12 and 13 by an external power source (constant current power source) 17 connected to the electrode portions 15 and 16.
FIG. 3 is a schematic diagram showing a state in which a bias voltage is applied to.

When the lateral angular velocity does not act on the substrate 1 at all, the gas ejected from the nozzle hole 6 into the gas flow path 2 by the driving of the micropump flows along the center line of the gas flow path 2 and the heat wire The pairs 10 and 11 are cooled uniformly, and the base 1 is cooled.
When the lateral angular velocity acts on the gas flow path 2
Is deviated from one of the heat wire pairs 10 and 11 (to the heat wire 11 side in this embodiment).

At this time, the heat wire 11 is cooled by the gas flow and its resistance value decreases, and the potential at the midpoint A of the heat wire pair 10, 11 changes in accordance with the decrease in the resistance value.
When the gas passes through the heat wire 11, as described above, the combined resistance of the heat wire pair 10, 11 (150
Ω), the combined resistance of the reference resistance pairs 12 and 13 (7
50 Ω), a large current flows through the heat wire 11 and the heat wire 11 is heated to a high temperature. Therefore, the gas flow passing through the heat wire 11 is
The heat wire 11 is heated to a high temperature by heat exchange during cooling. The gas flow heated to a high temperature flows downstream and contacts the reference resistor 13.

When the gas flow comes into contact with the reference resistor 13, the reference resistor 13 is heated by the gas flow to increase the resistance value. In response to the increase in the resistance value, the potential of the middle point B of the pair of reference resistors 12, 13 is increased. Change. At this time, since the reference resistor 13 is arranged close to the heat wire 11, the gas heated to a high temperature by the heat wire 11 efficiently heats the reference resistor 13 and increases the resistance value of the reference resistor 13. As a result, the potential change at the midpoint B can be increased. Therefore, when obtaining an output signal proportional to the angular velocity based on the potential difference between the middle points A and B,
Since the potentials at the midpoints A and B change in opposite directions, an output signal that is larger than that of the conventional case where the reference resistance is a fixed resistance is obtained by an amount corresponding to a large change in the resistance value of the reference resistance 13. Can be. As a result, even in a gas rate sensor having an ultra-small and extremely precise substrate formed by subjecting a semiconductor substrate to micromachining as in the present embodiment, a large output can be obtained for a minute angular velocity acting on the substrate. A signal can be obtained, high-precision detection can be performed with good sensitivity, and high reliability can be obtained.

The present invention is not limited to the above embodiment, but can be appropriately modified without departing from the gist of the present invention. For example, in the above embodiment, a gas rate sensor provided with an ultra-small base 1 formed by micromachining using a semiconductor substrate is taken as an example.
The present invention is not necessarily limited to this, and the present invention can of course be applied to a general gas rate sensor having a base formed by cutting a metal such as aluminum.

[0025]

As is apparent from the above description, according to the present invention, it is possible to obtain an output larger by the change in the reference resistance value than in the conventional case where the reference resistance is a fixed resistance. Therefore, it is possible to provide a highly sensitive gas rate sensor that can accurately detect an angular velocity signal even when the angular velocity acting on the base is small.

When a pair of reference resistors are provided close to the pair of heat wires, the amount of change in the reference resistance value is further increased, so that a gas rate sensor with higher sensitivity can be obtained.

Further, when the base is formed by micromachining by an IC manufacturing technique using a semiconductor substrate, even in a gas rate sensor having a very small and very precise base, the angular velocity acting on the base is small. In such cases, the angular velocity signal can be detected with high sensitivity and high accuracy.

Further, when each heat wire and each reference resistor are formed of platinum, their temperature-sensitive characteristics can be made excellent, so that the angular velocity can be detected with high accuracy, and more reliable. Can be enhanced.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a base of a gas rate sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an explanatory schematic diagram for explaining the operation of a gas rate sensor.

FIG. 4 is an explanatory schematic diagram for explaining a basic operation principle of a conventional gas rate sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Gas flow path, 3 ... Resistance bridge circuit, 6 ...
Nozzle holes, 10, 11, ... heat wire pairs, 12, 13, ...
Reference resistor pair,

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-240573 (JP, A) JP-A-3-48164 (JP, A) JP-A-5-2026 (JP, A) 101865 (JP, U) JP 5-4023 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 9/00 G01C 19/00

Claims (4)

(57) [Claims] A substrate having a gas flow path provided with a pair of heat wires and a nozzle hole for ejecting gas into the gas flow path toward the heat wire pair; a heat wire pair and a resistance bridge; A pair of reference resistors forming a circuit, and based on a deflection of a gas flow generated when an angular velocity acts on the base, a signal corresponding to a difference in a change in resistance temperature characteristic generated in each heat wire is transmitted to the resistance bridge. In the gas rate sensor, which is detected using a circuit and obtains an output signal proportional to the angular velocity based on the detection signal, the reference resistance pair is provided in a gas flow path downstream of the heat wire pair. A gas rate sensor characterized in that heated gas passes through the heat wire and comes into contact with the reference resistor. 2. The gas rate sensor according to claim 1, wherein said reference resistor pair is provided close to said heat wire pair. 3. The gas rate sensor according to claim 1, wherein the base is formed by micromachining using an IC manufacturing technique using a semiconductor substrate. 4. The gas rate sensor according to claim 1, wherein each heat wire and each reference resistor are made of platinum.