JPH0361830A - Pressure sensor - Google Patents

Abstract

PURPOSE: To enable pressure measurement by providing a detecting element equipped with a resistance element on the recess of a semiconductor substrate having a recess formed at a particular surface, and mounting a reference resistance means whose temperature is controlled according to semiconductor substrate temperature. CONSTITUTION: A recess 102 is formed, by anisotropic etching, in the first surface 104 substantially-parallel to (100) surface of a semiconductor substrate 100, where a detecting element 106 is fitted. The element 106 is bridged over the recess 102, for example. The element 106 involves a resistance element 108 and is fitted on the recess 102 at a prescribed distance, and has a predetermined shape. The element 108 is used so that the size related to the resistance and temperature of the element 108 may be given, and the magnitude of its signal changes with the pressure lower than the atmospheric pressure by means of changing thermal coupling. This pressure sensor involves a reference resistance means 122 consisting of resistance elements 124. The resistance of the element 124 changes with a change in pressure, and a signal having a value predetermined under a predetermined pressure condition is supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an integrated semiconductor device in the field of sensors and sources of radiation of electromagnetic energy, and in particular to an integrated semiconductor device in which signal processing circuits can also be integrated in applications involving sensing, and a method for manufacturing the same. The invention incorporates a thermoelectric transducer (ther+++al-to-ele) into a semiconductor circuit chip.
ctric transducer) or electrostatic element (
static electric elements) can be integrated to obtain significantly greater thermal and physical isolation compared to the arrangement of components in conventional devices. Further, the semiconductor device of the present invention can also be manufactured by a batch process.

The present invention can be applied in the fields of flow detection, combustible gas detection, humidity detection, pressure detection, etc., but is not limited to these fields.

In the semiconductor device of the present invention, a depression is formed on the first surface of the semiconductor substrate. Furthermore, a member constituting a thermoelectric transducer or an electrostatic element having a predetermined shape is included at a predetermined distance above the depression. The member is connected to the first surface in at least one location, and the recess opens around at least a portion of a thermoelectric transducer or electrostatic element of a predetermined shape, and the recess provides a physical connection between the member and the semiconductor substrate. and thermal insulation can be obtained.

The integrated semiconductor device of the present invention configured as described above can provide a space in which the transducer or element and the semiconductor are substantially physically and thermally insulated.

Further, the method for manufacturing a semiconductor device of the present invention includes the step of providing a semiconductor substrate having a first surface having a predetermined direction with respect to the crystal structure of the semiconductor substrate. Also,
The method also includes the step of providing a layer of material forming the member on the first surface. Additionally, exposing a predetermined region of at least the first surface, the exposed surface region comprising:
It is defined in part by transducers or elements of a predetermined shape placed at a predetermined distance.

Additionally, the predetermined shape of the transducer or element is oriented such that the anisotropic etch undercut is completed in a minimum amount of time. Finally, the method of the present invention applies anisotropic etching to the exposed surfaces to undercut the component and create depressions.

Various embodiments of flow detection, combustible gas detection, humidity detection, pressure detection, etc. to which the present invention can be applied will be described below.

First, an example in which the present invention is applied to a flow sensor will be described.

For many years, thermal wind gauging (thern+alane
(mometry) was an effective means to measure fluid flow. By definition, the principle of operation of a thermal flow meter is based on heat conduction. Usually, a resistive element with a temperature-sensitive resistance is placed in the flow of fluid.

The current flowing through the resistive element causes the temperature of the resistive element to rise due to power consumption. The fluid being monitored removes heat from the resistive element through its flow. The final temperature of the resistive element, indicated by the resistance measurement, is a function of fluid velocity and thermal conductivity.

Conventional resistance value change elements are generally of heat wire, heat film, thermistor type, etc. Such flow meters are inexpensive, yet very fast response resistance transducers, accurate and robust. These demands can be in conflict with each other, as demonstrated by conventional thermal flow meters. Inexpensive flow meters usually consist of bulk type sensing elements and have poor response time characteristics. Fast-response flow meters use expensive and fragile sensing elements. Accurate flow meters are typically expensive and require extensive assembly of sensing elements and support structures. Furthermore, conventional flow meters must be inserted completely into the region of fluid flow and are therefore susceptible to damage or deterioration from impact with dust, debris, and other debris.

The flow meter of the present invention satisfies all the characteristics required of an ideal meter in a form close to ideal.

The flow meter of the present invention is manufactured using a silicon-compatible process.
It is inexpensive because it can be manufactured by low-cost batch processes such as It is superior to traditional solid-state thermal flowmeters due to its increased sensitivity of larger changes in , and its improved signal-to-noise ratio. And its structure is
It is such that it does not need to be fully inserted into the fluid stream, so that dust, debris, and other debris will not impinge on the element, but will flow by it. Therefore, the flow meter of the present invention is less susceptible to performance degradation than conventional thermal flow meters.

1 and 2 are side sectional views of an embodiment of a flow sensor according to the invention. A single crystal semiconductor 10 has a first surface 14 covered by a dielectric layer 12, such as silicon nitride.
has. In this embodiment, the device 22 of FIG. 4 comprises a permalloy resistive element or grid 16 and leads 24 sputtered onto a dielectric layer 12, and the device 22 is covered with a dielectric layer 18, such as silicon nitride. There is.

Dielectric layer 12 provides electrical isolation between device 22 and semiconductor 10, and dielectric layers 12 and 18 provide passivation to device 22.

By creating a richness under the grid 16, sufficient thermal and physical isolation is provided between the grid 16 of the resistive element and the semiconductor 10. Recess 20 is typically formed using a suitable etching technique as described below. Without this depression 20, the grid 16 of the sensing element
For example, if the resistive element grid 16 was separated from the semiconductor 10 only by a solid dielectric layer, it would be difficult to obtain sufficient thermal and physical insulation between the solid dielectric Since the thermal conductivity of is typically greater than that of air, the grid 16 of resistive elements will substantially conduct heat to the semiconductor 10.

Sufficient thermal and physical insulation between the grid 16 of sensing elements and the semiconductor 10 has the advantage of being adaptable to a wide variety of devices such as sensors. For example, when the semiconductor device of the present invention is applied to a flow sensor, by configuring a very thin sensing element that is sufficiently thermally insulated from the semiconductor substrate, the sensing element can be made very thin in the air flow. Adapted to allow for sensitive measurements. This is because the temperature of thinly formed parts is easily influenced by air flow. This is in contrast to solid state thermal flow meters which have sensing elements that allow substantial heat to escape to the semiconductor body. The temperature sensitivity of a device having such a configuration is greatly influenced by the heat of the semiconductor itself.

In the embodiment of FIG. 1, a member or sensing element 34 is provided in a bridging manner over the recess 20 and has first and second ends connected to the first surface 14 of the semiconductor. . In this way, the detection element 34 has a substantially rectangular shape when viewed from above, and includes the resistance element 16 and the dielectric layers 12 and 1.
It consists of part of the day.

In the embodiment of FIG. 2, the member or sensing element 32 comprises a resistive element 16 and a portion of the dielectric layers 12 and 18, and is connected to the first surface 14 of the semiconductor at one end of the sensing element 32. , cantilevered above the depression 20. Having only one end of the sensing element 32 connected to the semiconductor body 10 has the advantage that the sensing element 32 can be expanded and contracted in almost any direction without substantial restraint from the semiconductor body 10. There are various advantages including. In addition, since the heat loss transferred through the sensing element 32 takes place only at one end thereof, the sensing element 32 becomes significantly more thermally insulated. FIG. 3 is a front cross-sectional view of an embodiment consisting of two detection elements 32 or 34, and FIGS. 10 to 13 are plan views of various embodiments. Regarding the flow sensor of the present invention, a set of members is a preferred embodiment with various advantages. As explained below, for example, by using two substantially independent components and comparing the signal from one with the signal from the other, it is possible to automatically compensate for temperature changes in the environment. . Moreover, such a configuration reduces the background voltage within a single detection element.
tage) can be easily removed, greatly improving measurement accuracy. Additionally, the use of two measuring elements in a flow sensor, as explained below, allows the upstream sensing element to be cooler than the downstream sensing element, thereby indicating flow direction as well as velocity.

However, even one sensing element supported above the depression 20 can be a flow sensor. For example, an air turbulence signal generated by a flow sensor of one sensing element would be suitable for detecting the presence or absence of air flow. By amplifying only the alternating current component of the resistance change of the element due to air turbulence, the slow component or direct current component of the resistance element due to changes in ambient temperature, for example, is not detected.

In this embodiment, permalloy can be used to form a layer with a thickness of several hundred angstroms accurately by sputtering, and due to the characteristics of permalloy, the distance between the resistance value of the grid, that is, the resistance element 16, and the temperature of the resistance element 16 is determined in advance with a superfluous sensitivity. Permalloy is chosen to form the resistive element 16 because of its ability to obtain a well-defined correlation. For example, a very thin member or sensing element 32 or 34 may be formed from interdigitated element 16 and dielectric layers 12 and 18. When applied as a flow sensor, the flow of air across the detection element 32 or 34 cools the resistance element 16 in a predetermined relationship with the velocity of the air flow, causing a change in resistance value and controlling the air flow. It will be possible to measure it.

In this embodiment, the detection elements 32 and 34 are typically 1.
8 to 1. The thickness is about ξcm.

This thickness includes resistive element 16 and dielectric layers 12 and 18, each typically on the order of a few thousand angstroms thick. This very thin and highly sensitive configuration, along with the fact that resistive element 16 is well isolated from the substrate of semiconductor 10 by recess 20, which typically ranges from 0.001 to 0.010 inches in addition, The device is capable of highly sensitive flow velocity measurements.

As previously mentioned, an embodiment of the resistive element 16 is comprised of a permalloy grid, as shown in FIG.

The lead portion 24 is made of permalloy.

This is because additional processes can be eliminated.

That is, making the lead portion 24 from other materials requires additional processing. The lead part 24 of the permalloy becomes slightly hot, but the lead part 24 in FIG.
As shown in FIG. 0, FIG. 12, FIG. 12, and FIG.
heat is transferred to the substrate, and heating of the lead portion 24 is relatively small.

As mentioned above, the first and second
A flow transducer consisting of a resistive element has various advantages. Embodiments of such a configuration, when combined with a circuit such as that shown in FIG. 5, yield a more sensitive flow transducer that is independent of ambient temperature by eliminating background signals and providing a direct measurement signal. be able to.

For purposes of describing the operation of the sensor embodiment illustrated in FIG. 3 and the circuit illustrated in FIG. 5, the resistive elements in these figures are designated 16A and 16B. Each resistance element 1
6A and 16B are resistive elements 16. Resistance element 16
A and 16B are at least approximately identical and typically matched, but need not be matched.

A substantial advantage of the present invention is that a circuit such as that shown in FIG. A detection device can be obtained.

The circuit shown in FIG. 5 has three differential amplifiers each consisting of, for example, TLO87. As shown, each of the two amplifiers 50.52 has a resistive element 16A or 16B connected in parallel to the feedback loop. The resistance element 16A is connected to the amplifier 50 via its lead portion 24.
is connected between the output 54 and the negative input 59 of. Resistance element 1
6B also connects the amplifier 52 via its lead portion 24.
is connected between the output 56 and the sign input 58 of.

Negative input 5B to amplifier 52 is connected via resistor 64 to wiper 66 of potentiometer 62. A negative input 59 to the amplifier 50 is connected to the wiper 6 through a resistor 70.
Connected to 6. Positive cuff 2 of amplifiers 50 and 52
and 74 are connected to ground or reference potential 76, respectively.

Output 56 of amplifier 52 is connected to amplifier 80 via resistor 82.
The output 54 of the amplifier 50 is connected to the negative input of the resistor 8
6 to the positive input of an amplifier 80. A positive input 84 of amplifier 80 is connected to ground or reference potential 76 via a resistor 88 . The resistor 90 is the amplifier 80
is connected between the output 92 of the ingestion cuff 8 and the ingestion cuff 8.

The first terminal 94 of the potentiometer 62 has a voltage of +15VDC.
Also, the second terminal 96 of potentiometer 62 is provided for connection to a negative power supply, such as -15 VDC. Potentiometer 62 provides a means for selecting a predetermined potential anywhere between the positive and negative voltages of the power supply.

In operation, the illustrated circuit generates a voltage between output 92 and ground or reference potential 76 that has a predetermined relationship to the velocity of the fluid across sensing element 32 or 34 consisting of resistive elements 16A and 16B.

Resistance elements 16A and 16B are connected to amplifiers 50 and 5, respectively.
2 and a feedback loop.

Each operational amplifier 50 and 52 maintains a constant current in its feedback loop. Thus, the current through each resistive element 16A and 16B is independent of the resistance value of that resistive element. In that feedback loop,
In order to maintain a constant current, each operational amplifier effectively changes its output voltage in response to changes in the resistance of resistive element 16A or 16B. As mentioned above, the resistance value of each permalloy resistance element 16A or 16B changes in a predetermined relationship with the temperature of that resistance element. Thus, the voltage output of each operational amplifier 50,52 has a predetermined relationship to the temperature of its associated resistive element.

Operational amplifier 80 amplifies the difference between the voltage outputs of operational amplifier 50 and operational amplifier 52, and the voltage at output 92 of operational amplifier 80 is proportional to the voltage difference between the voltage outputs of operational amplifier 50 and operational amplifier 52. Therefore, the voltage at output 92 is
It has a predetermined relationship with the temperature difference between the resistance element 16A and the resistance element 16B. The temperature of resistive element 16A and resistive element 16B has a predetermined relationship with the velocity of the fluid across the sensing element. Therefore, the amplifier 80
The voltage at output 92 of will have a predetermined relationship to the fluid velocity across resistive elements 16A and 16B.

The flow of fluid first across the sensing element comprising the first member, resistive element 16A, and then over the sensing element comprising the second member, resistive element 16B, causes resistive element 16A to be cooler than resistive element 16B. It turns out. because,
The fluid flow across the resistance element 16A is
This is because the heat is taken away from the resistive element 16B and the heat is carried to the vicinity of the resistive element 16B. Assuming that the circuit supply voltage at wiper 66 is positive, the output voltage of amplifier 52 will be greater than the output voltage of amplifier 50. This difference is multiplied by amplifier 80 and the output voltage at output 92 has a predetermined relationship to the velocity of the fluid. As previously mentioned, the output voltage at output 92 can also provide a directional indication. For example, if the resistive elements 16A or 16B are arranged along the flow within the duct, the second embodiment of the present invention
A two sensing element sensor can be used to detect the direction of fluid flow as well as the flow rate. This is because, as mentioned above, the upstream sensing element is cooler than the downstream sensing element.

As described above, the circuit shown in FIG. 5 operates resistance elements 16A and 16B in constant current mode.

Further, any other circuit may be used as long as it has a circuit that operates the resistance elements 16A and 16B or other sensors of the present invention in a constant voltage mode, a constant temperature or constant resistance mode, or a constant power mode.

Next, an example in which the present invention is applied as a humidity sensor will be described. In this application, the sensor of the present invention can measure atmospheric water vapor density or relative humidity without surface adsorption effects and optical influences, and realizes a one-chip semiconductor circuit equivalent to a signal processing circuit at a low cost. It is possible.

The humidity sensor of the present invention is based on the principle that the thermal conductivity of air changes as the water vapor concentration changes. Here, the water vapor concentration is defined as the ratio of the number of water vapor molecules per unit volume to the number of dry air molecules per unit volume. This concentration is often determined by the specific humidity, which is a constant ratio of the molecular weight of water to the average molecular weight of dry air.
molar humidity (hun+1dity)
It is called “humidity”.

The humidity sensor of the present invention therefore provides molar humidity directly which is converted to specific humidity via circuitry, not shown, which provides a suitable multiplier for the molar humidity measurement.

It is also of interest to convert molar humidity measurements to relative humidity measurements. Such conversion requires measurement of ambient temperature and standard humidity chart data (sta
ndard psychometric chart
A corresponding automatic adjustment has to be made according to the data>. Some altitude effects due to air mixing density changes also become an issue in the conversion to relative humidity. This is because, for a given mole fraction of water vapor, as measured by thermal conductivity, the partial pressure of water vapor will change with altitude. Therefore, for the most accurate relative humidity measurements, the conversion is based on an altitude-dependent factor.
nt factor). Such conversion would be performed by circuitry not shown.

Environmental control applications require a device that reads out the enthalpy of mixed air with respect to the enthalpy at some low reference temperature and zero humidity. Enthalpy varies linearly with temperature at constant molar humidity, and to the extent excluding freezing and condensation, it varies linearly with molar humidity at constant temperature. Determination of enthalpy can be obtained by circuit from molar humidity measurements and mixed air temperature. The circuit, not shown, produces a readout offset for the dry air that is proportional to the difference between the mixed air and the reference temperature and converts the molar humidity output to an enthalpy scale.

Hereinafter, an example of application of the present invention to a humidity sensor will be explained in detail by way of an example using the drawings.

In its simple form, the humidity sensor of the invention comprises a substrate 100
a semiconductor having a recess 102 etched or otherwise formed in a first surface 104 of the semiconductor;
Furthermore, it has a detection element 106 as indicated by the reference numeral 106. The sensing element 106 may be bridge-shaped over the depression 102, similar to the sensing element 34 of FIG. 1, or cantilevered, as shown in FIGS. 2 and 6. In other words, it is probably shaped like a cantilever beam. The member or sensing element 106 is typically designated by the reference numeral 108.
It has a resistive element shown in , and has a predetermined shape provided above the depression 102 at a predetermined distance. Sensing element 106 has at least one
The first surface 104 is connected to the first surface 104 at two locations. Hollow 1
02 forms an opening in the first surface around at least a portion of the predetermined interception of the member or sensing element 106.

When resistive element 10B is heated by supplying current, there is a predetermined relationship between the resistance value of resistive element 108 and the temperature.

The humidity sensor of the present invention further includes a flow prevention means 116 as shown in FIG. 8, thereby substantially preventing air flow over the detection element 106 and preventing cooling of the resistance element 108 due to the air flow. The flow stop means 116 has an opening 118 to equalize the humidity level of the sensing element 106 and the semiconductor body 100 with the humidity level of the surrounding environment. Additionally, a filter 120 is provided to prevent the sensor from being contaminated by airborne particulates.

The resistive element 108 is used to provide a signal having a magnitude related to the resistance value of the resistive element 108, that is, the temperature, and the magnitude of the signal is determined between the element 108 and the semiconductor substrate 100 via the recess 102. Varies with humidity due to varying thermal coupling. This change in thermal coupling occurs through changes in air conductivity as well as changes in molar humidity.
As a result, humidity can be measured.

In a typical application of this humidity sensor, the chip or semiconductor body 100 has a header.
It is bonded to a glass member 114 provided at 112 with an epoxy adhesive. This glass member 114 thermally insulates the base body 100 from the protruding portion 112 of the hollow. This protruding portion 112 typically has a through hole (not shown) for connecting a wire bonding arrangement to make an electrical connection.

Furthermore, this humidity sensor has a reference resistance means 122 consisting of a resistance element 124. As discussed further below, a sensor according to the present invention includes a series resistive element 126 with a near-zero thermal coefficient of resistance over the required predetermined temperature range. As shown in FIG. 7 and below, series resistive element 126 may be connected in series with resistive element 124. Alternatively, series resistive element 126 may be connected in series with resistive element 108. For example, the series resistive element 126 may be chromium silicide (chr).
ome5ilicide) or a nichrome element.

Furthermore, the humidity sensor of the present invention has a heater consisting of an element 128, and is adapted to control the temperature of the semiconductor substrate 100 to a predetermined temperature.

Element 128 comprises a resistive element, such as a permalloy element, that substantially transfers heat to the semiconductor substrate.

Like resistive element 108, resistive element 124 is comprised of a permalloy grid as shown in FIG. In this way, the resistive element 124 not only serves as a reference resistance for the resistive element 108, but also serves as a temperature measuring means for the resistive element 124 or the automatically temperature-controlled semiconductor substrate 100. Permalloy has a predetermined relationship between temperature and resistance. In this way, the semiconductor substrate 100 can be maintained at a predetermined high temperature by adjusting the current flowing through the resistive element 12B and controlling the temperature of the substrate 100 with the resistive element 124.

As described above, resistive elements 108, 124, 126 and 1
26 is silicon nitride (silicon n1tride)
) is sandwiched between two dielectric layers such as
layer 127 covers at least a portion of first surface 104 .

By having a permalloy resistive element 124 that substantially conducts heat to the semiconductor body 100, the temperature of the resistive element 124 is substantially regulated by the temperature of the semiconductor body. Furthermore, because resistive element 124 is substantially thermally coupled to semiconductor body 100, the resistance value of resistive element 124 does not substantially change with changes in humidity. Thus, the signal from resistive element 124 is canceled by the signal from resistive element 108, effectively providing a resulting signal that will have a predetermined value under conditions of predetermined specific humidity. I will do it. A circuit such as that shown in FIG.
and 16B are replaced with the resistive elements 108 and 124 of the humidity sensor, and resistive element 126 is placed in series with either resistive element 108 or 124, as appropriate.

The temperature versus resistance curve of a permalloy element is non-linear.

The temperature versus resistance curve of resistive element 108 has a first predetermined slope when operating at a first predetermined operating temperature. That is, at a second predetermined temperature, such as an autotemperature temperature of the substrate 100, the resistance value 1
The resistance value of 24 is established such that the temperature versus resistance curve of resistive element 124 has a slope that approximately matches the predetermined slope of resistive element 108 at its operating temperature.

The overall effective resistance value of resistive element 10B or 124 is:
Suitably, resistive element 12 is connected in series to either resistive element 10B or 124, in this example, resistive element 124.
Adjusted by adding 6. Furthermore, the thermal coefficient of the series resistance element is approximately zero. As a result, the total effective resistance of the reference resistive element is made equal to the total effective resistance at the second predetermined temperature. In this way, the effective resistances of the reference resistance element and the humidity sensing element are approximately equal, and the signals passing through the two elements are canceled such that the sum of the signals is approximately zero at a predetermined humidity. . Again, this can be achieved by a circuit such as that shown in FIG.

Next, an example in which the present invention is applied as a combustible gas sensor will be described. As mentioned above, the present invention can be applied as a sensor for detecting combustible gas. An embodiment of the combustible gas sensor of the present invention as shown in FIG. 9 is similar to the flow sensor shown in FIG. 3, except that the reaction member 130 is thermally coupled to one of the resistive elements. Very similar. When warmed in the presence of flammable gas and oxygen, reaction member 130 will indicate the presence of flammable gas.

In addition, flow stop means, such as flow stop means 116 used in the humidity sensor, may also be used to substantially prevent air flow across the first and second sensing elements shown in the embodiment.

In FIG. 9, a reactive member 130 is thermally coupled to a resistive element 142 within a sensing element 140. In FIG. In one embodiment of the flammable gas sensor of the present invention, the reaction member 130 includes:
It is warmed by resistive element 142, typically with a catalytic reactivity of, for example, iron oxide, platinum or palladium.
lyHcally active) consists of a thin film. In such embodiments, when the catalytically reactive thin film is heated in the presence of flammable gas and oxygen, an exothermic reaction occurs resulting in a change in temperature and therefore a change in the resistance of its corresponding resistive element 142. . In this way, the temperature change in the resistance element 142 due to the exothermic reaction indicates the presence of combustible gas and causes the resistance value of the resistance element to change.

In other embodiments of the invention, the reaction member 130 is made of a metal oxide resistive element, such as iron oxide or tin oxide, and is warmed by a resistive element 142 . The metal oxide resistive element may be shaped similar to element 16 shown in FIG. In such embodiments, when heated by resistive element 142 in the presence of flammable gas and oxygen, the resistance of the metal oxide resistive element changes to detect the presence of flammable gas.

The combustible gas sensor of the present invention then has a chip or semiconductor body having a recess 134 etched or otherwise formed in a first surface 136 of the semiconductor body 132.

This combustible gas sensor has a detection element 34 shown in FIG.
The sensor element 140 has a sensing element 140 which is either bridged over the recess 134 or cantilevered like the sensing element 32 shown in FIG. The sensing element typically includes a resistive element, generally designated 142, consisting of a permalloy grid as shown in FIG.

The detection element 140 has a predetermined shape, is provided on the depression 134 at a predetermined distance, and has at least a -
The first surface 136 is connected to the first surface 136 at a point. Hollow 134
forms an opening in first surface 136 around at least a portion of the predetermined shape of sensing element 140 .

The member or sensing element 140 provides sufficient physical and thermal insulation between the resistive element 142 and the semiconductor body 132. As mentioned above, this member, that is, the detection element 140
is a reactive member 130 thermally coupled to a resistive element 142;
have.

Resistive element 142 has a predetermined relationship between the resistance value of resistive element 142 and temperature as it warms up with a current applied thereto.

Furthermore, the charging and discharging gas sensor of the present invention has a flow stopper, such as the flow stopper 116 shown in FIG. , substantially preventing resistive element 142 from being cooled by the air flow. This flow stop means, such as the opening 118 shown in FIG. 8, allows combustible gas to enter and exit the cut half 130.

As previously mentioned, in the first embodiment of the combustible gas sensor of the present invention, the reaction member 130 typically comprises a catalytically reactive thin film. In such embodiments, when the reactive member 130 is warmed by the resistive element 142 in the presence of flammable gas and oxygen, an exothermic reaction occurs and the temperature changes, thus causing the resistive element 142 . resistance value changes. This change in resistance value of resistance element 142 does not indicate the presence of combustible gas. In a second embodiment, the reaction member 130 typically consists of a metal oxide resistive element. In such embodiments,
When this resistance element is heated by the resistance element 142 in the presence of flammable gas and oxygen, its resistance value changes, thereby detecting the presence of combustible gas.

Resistive element 142 is also protected within two dielectric layers, such as silicon nitride, overlying at least a portion of first layer 144 or first surface 136 . As shown, the reaction member 130 is provided on the dielectric layer 146 of the sensing element 140.

When the first embodiment of the combustible gas sensor of the present invention is used, it is desirable to use a second resistive element 150, as shown by the second sensing element 148. As shown, the second sensing element 148 has a predetermined shape disposed a predetermined distance above the depression 134, and the second sensing element 148 has at least - The recess 134 defines an opening in the first surface 136 around at least a portion of the predetermined shape of the sensing element 148 . Recess 132 provides sufficient physical and thermal isolation between second resistive element 148 and semiconductor body 132.

The detection element 140 and the detection element 14 are different from each other, except that the detection element 148 does not have a reaction member like the reaction member 130.
8 may be substantially the same. The detection element 14B has a resistance element 150, and the detection element 1
It will be used as a reference sensing element with the same response as 40 to provide automatic temperature compensation. In addition, the signal from the reference resistive element 150 acts to cancel the signal from the sensing element 142, eliminating the level of background signals caused by temperature changes induced by the responsive member 130. can be measured directly. Substantially the same circuit as shown in FIG. 5 is used to accomplish this purpose, with resistive elements 16A and 1 of FIG.
6B and the resistance elements 142 and 150 are replaced.

Next, an example in which the present invention is applied as a pressure sensor will be described. As mentioned above, the invention has application as a pressure sensor - for example, as a sensor for measuring pressures below atmospheric pressure. A pressure sensor that covers a relatively wide dynamic range is desired. For example, common industrial processes using various gases such as oxygen, argon, nitrogen and hydrogen at varying temperatures and pressures often require pressure measurements as part of process control.

Conventional thermal conductivity pressure sensors that heat tungsten in sub-atmospheric ranges have not been satisfactory. This is because the relatively low dynamic range, high power and voltage requirements, fragility, relatively low sensitivity due to low thermal resistance coefficient, and the cooling time constant of heated tungsten due to oxygen partial pressure
This is because tungsten has the disadvantage of being easily oxidized, resulting in a short lifespan, if it increases faster than the tungsten (stant). The pressure sensor of the present invention significantly reduces or eliminates these disadvantages.

The pressure sensor of the invention is based on the change in thermal conductivity of a unit gas volume. In particular, the mean free path length (mean f
Since the ree path lengths) are limited by the distance between the sensing element 106 and the underlying semiconductor substrate 100 in FIG. 7, for example, the amount of heat transfer from the sensing element (heat rea+oval rate) and thermal conductivity are decreases with decreasing gas pressure. This causes a temperature increase in the resistance element 108, assuming that the resistance element 108 is operated with a constant current.

The pressure sensor of the present invention may have substantially the same configuration as the humidity sensor of the present invention, and will be explained using the same diagram used to explain the humidity sensor.

In its simple form, the pressure sensor of the invention comprises a substrate 100
a semiconductor body having a recess 102 etched or otherwise formed in a first surface 104 of the semiconductor body, further comprising a sensing element 106 such as 106;
has. The detection element 106 is the detection element 3 in FIG.
4, it may be bridge-shaped over the recess 102, or it may be cantilevered as shown in FIGS. 2 and 6. Dew. The member or sensing element 106 typically includes a resistive element, generally indicated at 108, and is of a predetermined shape positioned a predetermined distance above the depression 102. Sensing element 106 is connected to first surface 104 at at least one location, such as shown at location 110 .

The depression 102 defines an opening in the first surface around at least a portion of the predetermined configuration of the member or sensing element 106 .

Resistive element 108 has a predetermined relationship between the resistance value of resistive element 108 and the temperature when the resistive element 108 is heated by supplying current.

The pressure sensor of the present invention further includes a flow stopper 116 as shown in FIG. 8, thereby substantially preventing the flow of air over the detection element 106 and preventing the resistance element 10B from being cooled by the flow of air. The flow stop means 116 has an opening 118 to equalize the humidity level of the sensing element 106 and the semiconductor body 100 with the humidity level of the surrounding environment. Additionally, a filter 120 is provided to prevent the sensor from being contaminated by airborne particulates.

Resistive element 108 is used to provide a signal having a magnitude that is related to the resistance value and temperature of resistive element 108 , the magnitude of which is applied to the resistive element 108 via dimple 102 .
The thermal coupling between the semiconductor body 100 and the semiconductor body 100 varies with pressure below atmospheric pressure. This change in thermal coupling occurs through a change in the conductivity of the air as well as a change in pressure, resulting in a pressure measurement.

In a typical application of this pressure sensor, the chip or semiconductor body 100 has a header.
It is bonded to a glass member 114 provided at 112 with an epoxy adhesive. This glass member 114 thermally insulates the base body 100 from the protruding portion 112 of the hollow. This protruding portion 112 typically has a through hole (not shown) for connecting a wire bonding arrangement to make an electrical connection.

Furthermore, this pressure sensor has a reference resistance means 122 consisting of a resistive element 124. As mentioned above with respect to the humidity sensor of the invention, the sensor according to the invention has a It has a series resistive element 126 with a thermal coefficient of resistance of almost zero.

As shown in FIG. 7 and below, series resistive element 126 may be connected in series with resistive element 124; alternatively, series resistive element 126 may be connected in series with resistive element 10. Good too. For example, the series resistive element 126 may be a chromium silicide or nichrome element.

Furthermore, the pressure sensor of the present invention has a heater consisting of an element 128, and is adapted to control the temperature of the semiconductor substrate 100 to a predetermined temperature.

Element 128 comprises a resistive element, such as a permalloy element, that substantially transfers heat to the semiconductor substrate.

Like resistive element 108, resistive element 124 is comprised of a permalloy grid as shown in FIG. In this way, resistor element 124 not only serves as a reference resistance for resistor element 10B, but also resistor element 124 or automatic temperature control. ! It also serves as a temperature measuring means for the jointed semiconductor substrate 100. Permalloy has a predetermined relationship between temperature and resistance. in this way,
The semiconductor body 100 can be maintained at a predetermined high temperature by moderating the current flowing through the resistive element 128 and monitoring the temperature of the base body 100 with the resistive element 124.

As described above, resistive elements 108, 124, 126 and 1
26 is silicon nitride (silicon n1tride)
) is sandwiched between two dielectric layers such as
layer 127 covers at least a portion of first surface 104 .

By having a permalloy resistive element 124 that substantially conducts heat to the semiconductor body lOO, the temperature of the resistive element 124 is substantially regulated by the temperature of the semiconductor body. Furthermore, because resistive element 124 is substantially thermally coupled to semiconductor body 100, the resistance value of resistive element 124 does not substantially change with changes in pressure. Thus, the signal from resistive element 124 is canceled by the signal from resistive element 108, effectively providing a resulting signal that will have a predetermined value under the condition of predetermined pressure. It turns out. A circuit such as that shown in FIG. 5 is used to achieve this purpose, and resistive element 16A of FIG.
and 16B are replaced with the resistance elements 108 and 124 of the pressure sensor, and the low resistance resistance element 126 is replaced with resistance element 1 as appropriate.
It will be provided in series with either 08 or 124.

The temperature versus resistance curve of a permalloy element is non-linear.

The temperature versus resistance curve of resistive element 10B has a first predetermined slope when operating at a first predetermined operating temperature. For example, at a second predetermined temperature, such as the thermostatted temperature of the chip or substrate 100, typically measured by the resistive element 124, the resistance value 1
The resistance value of 24 is established such that the temperature versus resistance curve of resistive element 124 has a slope that approximately matches the predetermined slope of resistive element 108 at its operating temperature.

The overall effective resistance value of resistive element 108 or 124 is:
Suitably, either resistive element 108 or 124, in this example resistive element 124, has resistive element 12 in series.
Adjusted by adding 6. Furthermore, the thermal coefficient of the series resistance element is approximately zero. As a result, the total effective resistance of the reference resistive element is made equal to the total effective resistance at the second predetermined temperature. In this way, the effective resistances of the reference resistance element and the pressure sensing element are approximately equal, and the signals passing through the two elements are canceled such that the sum of the signals is approximately zero at a predetermined humidity. . Again, this can be achieved by a circuit such as that shown in FIG.

Although the pressure sensor of the present invention has been described as being sensitive to changes in humidity levels, this is not a problem in normal applications. This is because, over the range of use of the pressure sensor of the present invention, the response to pressure changes is large compared to the response to humidity changes.

Now, firstly, when considering the phenomenon related to the sensor of the present invention, as the pressure of the gas becomes lower, that is, the density of the gas becomes lower, there are fewer molecules that have to take away heat from the heated member having the resistive element. It is thought that this will happen. Then, when a constant current is passed through the resistive element, if there are fewer molecules, the member will heat up as the pressure decreases.

However, in such a case, the mean free path length of the molecule is an appreciable fraction of the distance between the member, that is, the detection element and the semiconductor.
action of the din+exion)
Only when .

For pressures when the mean free path length is short compared to the distance between the member, that is, the sensing element, and the semiconductor substrate, the amount of heat escaping from the sensing element does not change to a detectable level as the pressure changes. For example, A pressure change of 10% reduces the gas density by a commensurate amount, but increases by the exact same amount, e.g. 10%, to compensate for the mean free path length and the actual total path length. .

Thus, for pressures when the mean free path length is short compared to the distance between the sensing element and the semiconductor substrate, molecules stop when they collide, and fewer molecules are present; Since the molecules will advance by 10% without being stopped, it can be approximated that the amount of heat transferred from the detection element will be the same. This is a very accurate positioning or correction factor only when the mean free path length of the molecules of the gas is short compared to the distance between the sensing element and the semiconductor body.

As described above, the pressure sensor of the present invention will not normally sense pressure near normal atmospheric pressure, for example, in the range of 1 atm to 0.1 atm.

Particularly, in view of this example, the permalloy resistive element, combined with the microstructure, acts as a heater and temperature sensor, and can be used to detect many It can be seen as a comprehensive invention that provides the basis for detecting things that undergo physical changes. In fact, any physical extenuant that changes in a material composition in such a way as to cause a temperature change can in principle be detected by a sensor based on the structure described above.

Further, the member or detection element may be, for example, a static electric element as described above.
), and can serve as a thermoelectric conversion element for detection purposes, to provide electromagnetic radiation, or to otherwise serve as a source of thermal energy. Of course, such a generic element is not limited to having a resistive element of permalloy, since any suitable thermoelectric or electrostatic element would suffice.Other examples of sensing elements are zinc oxide, single crystal film,
These include thin film thermocouple bonds, pyroelectric materials such as thermistor films of semiconductor materials, or metal films other than permalloy with suitable thermal resistance coefficients.

1 and 4 will now be described in greater detail than in the specific examples described above. The present invention includes a semiconductor body 10 having a recess 20 etched or otherwise formed in a first surface of the body. Furthermore, the present invention provides a member having a thermoelectric conversion element or an electrostatic conversion element as indicated by the reference numeral 16, that is, a detection element 32.
or 34, and the detection element is a structure provided above the depression 20 at a predetermined distance and connected to the first surface 14 at at least one point. The recess defines an opening on the first surface around at least a portion of the predetermined configuration of the member or sensing element.

The depression provides sufficient physical and thermal insulation between the thermoelectric or electrostatic elements.

Such an integrated semiconductor device can be manufactured through a batch process as described below, and sufficient physical and thermal insulation can be obtained between the thermoelectric conversion element or electrostatic element and the semiconductor substrate.

The manufacture of such a device according to the invention comprises the steps of providing a semiconductor body with a first surface having a predetermined orientation with respect to the crystal structure of the body;
providing a layer of material for structuring on the surface of the device.

The manufacturing method of the invention further comprises the step of exposing at least a predetermined area of the first surface, the exposed area of the surface being partially recessed when the indentation is later provided. The predetermined configuration has a predetermined configuration such that it is placed at a predetermined distance above the etching, and the predetermined configuration has directionality, so that the predetermined configuration is formed by anisotropic etching. Undercuts can be made in a minimum amount of time.

An embodiment of the method of the invention is to first provide a (100) silicon wafer surface. The surface 14 has a layer of silicon nitride 12, typically about 3000 angstroms thick, applied by conventional sputtering techniques in a low pressure gas discharge.
A permalloy-like layer of approximately 800 angstroms, consisting of 20% nickel and 20% iron, is sputtered onto the silicon nitride.

Using a suitable photomask, photoresist and etching material, a permalloy element 22 consisting of grid 16 and leads 24 is formed.

A second layer 18 of silicon nitride, typically sooo angstroms thick, is deposited by sputtering over the entire Permalloy element to protect the resistive element and its leads from oxidation.

3000 angstrom thick silicon nitride first
, and a second layer of silicon nitride 5000 angstroms thick would result in an asymmetrical layer member of the dielectric, i.e., a sensing element, but this lack of symmetry This can be corrected by providing layers of equal thickness. Figures 10, 11, 12 and 13
As shown, openings 152 are etched through the nitride to the surface of the (100) silicon to form the respective parts. Although the members are shown here as having straight edges, such shapes may be modified to have curved edges, for example.

Finally, an anisotropic etch that does not attack the silicon nitride is used to etch away the silicon beneath the part in a controlled manner. Potassium hydroxide (KOH) and isopropyl alcohol (isopr.

A suitable etching agent is a mixture of pyl alcohol). The slope of the etched depression is (111)
plane, other crystal planes that resist etching, and the bottom of the surface enrichment of the (100) plane, which resists etching more weakly. The bottom of the recess is separated from the member by, for example, 0.
Located at a predetermined distance of 0.004 inches. This is usually done by adjusting the etching duration. For example, a doped silicon etch stop, such as a boron-implanted layer, may be used to control the thickness of the recess, but such a stop is typically not necessary with the present invention.

In order to undercut the part in a minimum amount of time, the predetermined shape of the straight edge or axis of the part, for example, is usually set at a non-zero angle 15 with respect to the (110) axis of the silicon.
It is oriented by 4. The invention includes providing a straight mineral mouth or shaft at an angle to minimize the time of undercutting or, in the case of bridged members, to undercut. I'm reading.

However, it is conceivable that the member is shaped without straight edges, or that the axis is not easily defined, but that the shape itself is oriented, for example, to achieve a minimum undercut time. By angling the dowel at approximately 45 degrees, the member or sensing element is undercut in a minimum amount of time. For example, using a 45 degree angle, a cantilever of normal dimensions as shown above can be undercut in approximately 90 minutes, compared to several hours of etching time using a 0 degree orientation. can.

In addition to minimizing the time the member is undercut, using a non-zero orientation results in the production of a two-ended bridge as shown in FIG. Such a member is (110) oriented at the edge of the member:
It is practically impossible to make. Assuming that the edge of the part is (110) oriented, anisotropic etching can be evaluated at (111) crystal planes exposed along the edge of the part, or at inside corners such as 160. This is because it is not undercut. As is known from the prior art, cantilever-shaped members oriented along the (110) axis are etched primarily along the length of the beam from the free end of the cantilever. Here, there is a slight undercut from the end of the cantilever beam, but there is not much.

This results in undercutting from a direction including the ends of the member compared to a member made according to the invention as described above.

Even when oriented at 45 degrees, it is possible to quickly round and smooth the support interface at the edge of the component and the semiconductor. In this way, the insulation 1 shown in FIGS.
It is possible to avoid the occurrence of a stress concentration area where the two (111) planes under i12 collide. It may be desirable in certain devices to connect the first and second members by means of a connecting means, ie, in a sense, to provide the first and second elements in one member. Examples of such connection means include the connection means shown at 156 in FIG. 10 for connecting two cantilever-shaped members as shown in FIG. There is a connecting means, designated 158 in FIG. 12, for connecting the bridging members. Such connection means may help maintain uniformity of the space and thermal conductivity between the respective members and the bottom of the recess, contributing to uniformity of performance in each type of device. Become. For similar reasons, it may be advantageous to provide two elements in one member in the exemplary manner shown in FIG.

Furthermore, there may be applications in which it is desired to connect components to the semiconductor body at auxiliary locations, such as location 159 shown in FIG. 10, for processing or device configuration.

A small rectangular etched hole 152 is shown at the connecting end of one of the cantilever shaped members in FIGS. 1O and 11 and at both ends of the bridge shape in FIGS. The holes assist in undercutting or shaping the semiconductor substrate to which the component is attached. However, such a hole 152 at the end of the member is not necessary for full performance of the device.

Etched holes 15 along the edge of the member as shown
2 is 0 for normal flow sensors and combustible gas sensors.
．． In the case of humidity sensors and pressure sensors, the opening width is about 0.001 inch, and if the width of the humidity sensor and pressure sensor is narrow, the influence of gas flow can be reduced. Helps reduce.

The semiconductor bodies of FIGS. 10, 11, 12, and 13 are shown in the form of flow sensors or combustible gas sensors and are numbered 10 or 132. For example, a humidity sensor and a pressure sensor, such as that shown in FIG. 6, are similar in construction, but typically include one member and element placed a predetermined distance above the depression.

FIGS. 1O-13 show an area 60 for the integration of a circuit such as that shown in FIG.

As previously mentioned, the practical effectiveness of the present invention for sensing by thermal means is achieved by providing an air gap or depression 20 below member 32 or 34. Thereby, the sensing member is sufficiently thermally and physically insulated from the substrate by an air gap and typically as shown by a rectangular area of dielectric material attached at one or both ends to the silicon substrate. You will be supported. As previously mentioned, although rectangular members are used, in fact any other shape could be used.

In accordance with the embodiments described above, typical dimensions of member 32 or 34 are on the order of 0.005 to 0.00 inches wide, on the order of 0.010 to 0.020 inches long, and on the order of 0.02 inches thick.
．． It is about 8 to 1.2 microns. A typical permalloy element, such as element 16 shown in FIG.
00 angstroms thick, but typically 800 angstroms
In the range of 1600 angstroms, the preferred composition is 80% nickel and 20% iron, and the resistance is about 1000 ohms at room temperature.

Resistance values for various applications are typically eg 25"C
It ranges from approximately 500 to 2000 ohms at room temperature.

When the temperature of the permalloy element is increased to approximately 400''C, the resistance value increases approximately three times.

The width of the lines of the permalloy grid 16 is approximately 6 microns with a spacing of approximately 4ξ. The recess 20 typically has a gap of about 0.004 inches between the member and the semiconductor body 10, but this gap can vary from about 0.001 to 0.01 inches. The typical thickness of the semiconductor body 10 or substrate is 0,000 inches. These dimensions are given by way of example only and are not meant to be limiting.

A member of the typical dimensions described above has a very small thermal capacity and thermal impedance, resulting in a thermal time constant of approximately 0.005 votes. Therefore, a small change in thermal input results in a new thermal parallel with a slightly different sensing element temperature. This difference allows a sufficient electrical output signal to be produced.

The strength-to-weight ratio of such a configuration is
to-weight) is very good, and a two-end bridge type of the typical dimensions mentioned above has a 10,000 gr.
avities) and can withstand mechanical stress well. Even single-ended structures when used as cantilevered structures can withstand 10,000 gravity shocks.

For example, it is advantageous in many applications to warm a member or sensing element, such as member 32 or 34 of FIGS. 1 and 2, above room or ambient temperature in order to optimize its sensing performance. There is.

Typical operating temperatures range from approximately 100"C to 400@C. With preferred permalloy elements, this can be achieved with input power of only a few milliwatts. Such power levels are As mentioned above, it can be identical to an integrated circuit provided on the same semiconductor with the sensor if desired.

A typical temperature sensor in industry has an electrical impedance of 100 ohms. However, for the purposes of the present invention, such impedances have a number of disadvantages. For processing purposes, 0.1% of the normal impedance at 100 ohms rather than the normal 1000 ohm impedance suitable for the preferred resistive elements of the present invention.
It is more difficult to obtain impedance accuracy of . The impedance of usually 1000 ohms was selected for the permalloy element used in the present invention because of the electrical transfer phenomenon (e
This is because element failure due to electromigration was considered. Electrical migration is a physical failure mechanism that, in permalloy, occurs within a conductor due to the flow of material that occurs when the current exceeds a dangerous limit, typically on the order of lo-6 amperes per square centimeter. Therefore, in order to achieve the desired operating temperature within the permalloy element 16, a relatively large impedance, for example on the order of 1000 ohms at a room temperature of 25°C, is desirable; the higher impedance allows the desired operating temperature to be achieved without exceeding dangerous current densities. can be obtained.

As a result, members 32 or 34, for example as described above,
Typical dimensions of 0,00 as reported by the prior art
It must be significantly larger than the 1 inch wide and 0.004 inch long microstructures. The area of the material required for the permalloy resistive element used in the present invention must have sufficient surface area to provide the permalloy grid shown at 16. The preferred 45-degree orientation of the member as described above is from the viewpoint of processing time, as this direction requires the minimum processing time when creating a wider microstructure and when creating a bridge shape as shown in Figure 1. becomes very important.

As mentioned above, for many possible applications, the preferred thermoelectric or electrostatic elements are the permalloy resistive elements described above. When sandwiched within a silicon nitride member or sensing element, the permalloy element is protected from oxidation by air and can be used as a heating element to temperatures in excess of 400°C. Such permalloy elements have resistance versus temperature characteristics similar to bulk platinum, with both permalloy and platinum having thermal resistance coefficients of approximately 4000 ppm at 0''C.
Permalloy is superior to platinum in structure according to the invention. Although platinum is commonly used as a material for temperature sensing elements, permalloy has the advantage of having twice the resistivity of platinum. Furthermore, in thin films, platinum must be at least 3500 angstroms thick, whereas permalloy can achieve its maximum coefficient of thermal resistance at a thickness range of about 800 to 1600 angstroms. Permalloy is about 160
The maximum thermal resistance coefficient can be achieved at a thickness of 0 angstroms, but the resistivity is twice as high and the thermal resistance coefficient is only slightly lower at 1600 angstroms, so 8
00 angstroms is chosen as the preferred thickness. Therefore, using a permalloy element with a thickness of about 800 angstroms, platinum requires only 1/8th the surface area required for the same resistance value, increasing the thermal efficiency of the sensing element, reducing the required area, and reducing unit cost. Can be lowered.

In this way, the permalloy element is an efficient heater element and detection element for temperature changes in the microstructure.
Combining both heater and detection functions in the same element on a well thermally insulated structure allows for low cost, small heat capacity, favorable sensitivity and fast response.

Additionally, the Permalloy heater and sensing elements, which are typically sandwiched within a supporting insulating film of silicon nitride on the order of 1 micron, provide passivation against oxidation of the Permalloy film, especially at high temperatures. It is also
The high resistance of silicon nitride to etching processes also allows for precise dimensional control of components 32 or 34, for example. In addition, for the control of important heat transfer factors, the recess 20 may be
It can be etched to a depth on the order of 0 inches.

Thus, using embodiments of the invention, permalloy will be combined with microstructures as described above to form both a temperature sensor and a heater or radiation source. The use of silicon nitride as a support and passivation material allows the etch time needed to obtain the desired structure. Furthermore, the directionality according to the invention allows for undercutting in minimal time and for creating the desired structure without artificial etch stops. And, the use of deep anisotropic etching to control the depth of the recess in the range of 0.001 to 0.010 inches makes it possible to create thermoelectric or electrostatic devices on integrated semiconductor devices using traditional methods. Also, greater thermal insulation can be achieved.

Although the present invention has been described above based on Examples, it will be obvious to those skilled in the art that various modifications can be made within the scope of the present invention. It is therefore intended that the invention be limited only by the scope of the claims that follow. For example, although the recess designated by the reference numeral 20 was formed using the purposeful etching technique described above, embodiments according to the present invention are limited to those having the recess formed by the technique described above. Not done.

[Brief explanation of drawings]

1, 2, and 3 are cross-sectional views of an embodiment of the present invention, FIG. 4 is a diagram showing an embodiment of a grid of electrical resistance elements adapted to the present invention, and FIG. 5 is a sectional view of an embodiment of the present invention. , a circuit diagram of an embodiment of the sensor of the present invention, FIGS. 6, 7, and 8 are diagrams showing an embodiment of the sensor of the present invention, and FIG. 9 is a circuit diagram of an embodiment of the flammable gas sensor of the present invention. 10, 11, 12 and 13 are diagrams showing embodiments and orientations of microstructures of the present invention. 10, , Single crystal semiconductor 12, tS, , Silicon nitride 14, , First surface 16, , Grid 20, , Recess 24, , Lead portion 32.34. ,, detection element 50.52.80. , amplifier 62 , potentiometer 114 , glass member 116 , flow stopper 11B , opening 120 , filter 122 , reference resistance means 128 , element 130 , reaction member 156 .158. ,, connection means

Claims (3)

[Claims] (1) It has a (100) plane and a <110> direction, and the (1
00) a semiconductor substrate having a recess formed by anisotropic etching on a first surface substantially parallel to the <110>plane; a single thin film dielectric member including a resistor element having a predetermined shape and connected to the first surface at at least one location; a reference resistor whose temperature is adjusted according to the temperature of the semiconductor substrate; comprising: a heating element for controlling the temperature of the base body to a predetermined temperature; and a flow prevention means for preventing a gas flow applied to the thin film dielectric member and substantially preventing cooling of the resistance element means by the air flow, A pressure sensor characterized in that pressure is measured by a change in thermal coupling between the resistive element means and a semiconductor substrate caused by a change in gas conductivity due to a change in pressure. (2) The pressure sensor according to claim 1, wherein the non-zero angle is 45 degrees. (3) The pressure sensor according to claim 1, wherein the predetermined shape of the resistance element is a lattice shape.