JP3724151B2 - Capacitance type sensor for pressure and temperature measurement, sensor device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure- and temperature-measuring capacitive sensor and sensor device comprising a single-crystal silicon silicon member and an insulating ceramic fixed to both surfaces thereof, and a method of manufacturing the same.
[0002]
[Prior art]
FIG. 7 is a cross-sectional view of a conventional capacitive sensor for pressure measurement.
The main constituent members of a conventional capacitance measuring sensor Sa for pressure measurement are a silicon member 1 made of single crystal silicon and a ceramic member 2 fixed to both surfaces thereof. In the center of the silicon member 1, an electrode plate 1e thinner than the silicon member and a thinner ring diaphragm 1d for supporting the electrode plate 1e are formed. Insulating films 1i made of, for example, SiO ₂ are formed on both surfaces of the electrode plate 1e. A through hole H1 passes through the center of two ceramic members 2a having substantially the same circumferential shape as the silicon member 1a. A low melting point glass thin film 2g is formed on the surface of the ceramic member 2 facing the silicon member 1a. The surface of the low-melting glass thin film 2g facing the electrode plate 1e, the surface of the through hole H1, and the other surface of the ceramic member 2a are covered with a thin film electrode 2m made of metal. The silicon member 1a and the ceramic member 2a are anodically bonded to each other through a low melting point glass thin film 2g and are firmly fixed to each other.
[0003]
In this way, two chambers surrounded by the ceramic member 2a, the electrode plate 1e, and the ring diaphragm 1d are formed, and each chamber is connected to the external space by the through hole H1. The thin film electrode 2m of the ceramic member facing the surface of the electrode plate 1e forms first and second capacitances with a space between them, that is, gaps G1 and G2, respectively. Since the ring diaphragm 1d is extremely thin, if a pressure difference is generated between the two chambers through the through holes H1, the electrode plate 1e moves correspondingly, and the first and second electrostatic capacitances on both sides of the electrode plate 1e. Therefore, a capacitance type pressure sensor is obtained. When there is no pressure difference, the two capacitances are equal. Then, a difference in capacitance is detected by a circuit (not shown), and a pressure difference signal is output. Therefore, if one gap is fixed to a known pressure, the absolute pressure of the other gap can be measured.
[0004]
Normally, a sensor device is configured by housing the sensor in a package so that an external force is not directly applied to the capacitance type sensor (hereinafter sometimes abbreviated as “sensor”). FIG. 8 is a cross-sectional view of a conventional capacitive sensor device. The first package member P1 in which an opening to the outside is formed is connected to one ceramic member 2a via a thin film electrode 2m, and the through hole H1 and the opening are connected. The second package member P2 in which the opening to the outside is formed is connected to the peripheral edge of the first package member P1, and the through hole H1 of the other ceramic member 2a is opened in the second package member P2. Yes. The package member is made of metal or ceramic.
[0005]
[Problems to be solved by the invention]
The capacitance type sensor composed of single crystal silicon and ceramic that are anodically bonded as described above has the following problems.
The linear expansion coefficients of single crystal silicon and insulating ceramic are both about 2 × 10 ^-6 to 4 × 10 ^-6 / ° C, but it is difficult to make the values exactly the same, for example, the values are the same at around room temperature. Even if it can be manufactured, if the temperature of the sensor changes, an apparent pressure difference will occur.
[0006]
This is due to the conventional manufacturing method, particularly the anodic bonding method. 9A and 9B are cross-sectional views of the capacitance type sensor in the conventional anodic bonding process, where FIG. 9A shows the first anodic bonding and FIG. 9B shows the second anodic bonding. In anodic bonding, a silicon member and a ceramic member are stacked, placed on a heater on a metal surface at a predetermined temperature (the surface of the heater T is coated with a metal film Ts to apply a voltage to the anodic bonding portion), and voltage is applied to the bonding portion. And do it. At the time of the first anodic bonding, the first silicon member 1a and the ceramic member 2a are bonded in a state where both materials are thermally expanded at a temperature of 200 to 700 ° C., and then the other ceramic member 2a is bonded to the previous two. The layers were stacked and anodic bonded in the same way. In either case, a temperature gradient was generated with the heater side at a high temperature, and tensile or compressive stress remained on the silicon member having a mechanical strength lower than that of the ceramic member. In order to prevent this, even if the temperature at the time of the first and second anodic bonding is the same, a temperature difference of several tens of degrees Celsius still occurs on both surfaces of the silicon member, and there is a difference in residual stress between both surfaces of the silicon member. It was happening. Therefore, even when there is no pressure difference between the two chambers, an apparent pressure difference occurs, which may not be suitable for highly accurate pressure measurement.
[0007]
Moreover, only the pressure (or pressure difference) could be measured with the sensor having the above structure.
In view of the above problems, an object of the present invention is to provide a sensor manufacturing method in which the distortion of a silicon member is small and there is no apparent pressure difference, and furthermore, a highly accurate multilayer capacitance capable of measuring not only pressure but also temperature. It is to provide a sensor and a manufacturing method thereof.
[0008]
[Means for Solving the Problems]
In order to achieve the above object , at least thin film electrodes opposed to the electrode portions are provided on both surfaces of a first silicon member made of single crystal silicon having an electrode portion thinner than the thickness of the silicon member and a ring diaphragm supporting the electrode portion. In a capacitive sensor for pressure and temperature measurement in which two ceramic members are anodically bonded via a low melting point glass film, and the electrode part and the thin film electrode form two capacitances, The second silicon member made of a crystal and formed with a flat concave electrode portion is a four-layer capacitive sensor in which the ceramic member is anodically bonded to the ceramic member through a low-melting glass film, The electrode portion of the second silicon member and the second electrode thin film of the ceramic member formed on the portion facing the second silicon member form a third capacitance with a gap in between. It is assumed that.
[0010]
The ceramic member has a through hole opened at a portion facing the electrode portion of the second silicon member, and the second electrode thin film has an inner surface of the through hole and the first silicon member. It is preferable that the first silicon member is a common electrode having three capacitances.
[0011]
It is preferable that a through hole leading to the gap is opened in the second silicon member.
A method of manufacturing a capacitive sensor for measuring pressure and temperature of the above four-layer structure , wherein the two ceramic members are anodically bonded to both surfaces of the first silicon member via a low-melting glass film. The anodic bonding is performed in a state where the first silicon member and the two ceramic members are laminated in three layers, and the whole is heated to a uniform temperature, so that the first bonding is performed . after forming the said two ceramic members with silicon member in a three-layer structure, to be anodically bonded via a low-melting glass said second silicon member to a predetermined surface of the ceramic member.
[0012]
The low melting point glass may be a film formed in advance on the insulating ceramic member.
The anodic bonding is performed by two heaters that are independently temperature controlled with the three-layer structure and the second silicon member interposed therebetween, and the anodic bonding temperature may be arbitrarily changed.
[0013]
The capacitance sensor for pressure and temperature measurement of the four-layer structure described above is directed to the opening of the through hole of the second silicon member and the through hole of the ceramic member on which the second silicon member is disposed and to the outside. The first package forming the first pressure chamber having the opening opened in the same space, and the opening of the through hole of the other ceramic member and the opening opened to the outside in the same space. A second package forming two pressure chambers is added, and the first pressure chamber is filled with a fluid having a large dielectric constant temperature coefficient, and the first pressure chamber and the second pressure chamber are filled with each other. The pressure difference is measured, and the temperature can be measured from the temperature change of the third capacitance.
[0014]
According to the manufacturing method of the present invention, the three-layer structure of the silicon member and the ceramic member bonded to both surfaces thereof is anodically bonded at a uniform temperature at the same time. It is smaller than the situation where both sides are different, and is symmetrical in the plane direction inside the silicon member. Therefore, the electrode portion does not move and the gap does not change due to the temperature change of the sensor, that is, each capacitance does not change. Therefore, it can be expected that an apparent pressure difference does not always occur even if the sensor temperature changes.
[0015]
Also, in 4-layer structure according to the present invention, in the case of the closed space newly added gap, a sensor-specific constant capacitance, it can be regarded as this reference pressure, compared with this Thus, absolute pressure can be measured. Further, it can be used for correcting a slight difference between the two capacitances for measurement, and pressure measurement with high accuracy is possible.
[0016]
In the case of an open space, the same fluid is put in the newly added gap and the conventional gap, and the capacitance is not subject to pressure fluctuations. Only a change in capacitance occurs and temperature can be measured.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
Example 1
FIG. 1 is a cross-sectional view of a capacitive sensor having a fixed gap according to the present invention. A second silicon member is newly added to the ceramic member of the conventional three-layer structure sensor. Only the parts different from the conventional sensor (FIG. 7) will be described. A low melting point glass thin film 2g is formed on both surfaces of one ceramic member 2b, and a through hole H2 is further opened. Metal thin films 2m and 2n are formed on the surface of the through hole H2, the bottom (first silicon member) and the surface of the low melting point glass thin film 2g.
[0018]
A recess is formed in the second silicon member 1b that is anodically bonded to the ceramic member 2b, and its bottom portion (which is an electrode portion) is a flat surface, and an insulating film 1i is formed. The metal thin film 2n of the ceramic member 2b facing the electrode portion forms a third capacitance with a space between them, that is, a fixed gap G3 interposed therebetween. Since the third capacitance does not depend on the pressure, it can be regarded as an absolute pressure or can be used to correct a slight difference between the two capacitances.
[0019]
Next, a method for manufacturing the sensor will be described.
FIG. 2 is a cross-sectional view in the manufacturing process of each ceramic member of the capacitance type sensor having the third capacitance according to the present invention, wherein (a1) and (a2) are (b1 ) And (b2) are after through-hole formation, and (c1) and (c2) are after thin-film electrode formation.
[0020]
First, a low melting glass film 2g having a thickness of several μm made of borosilicate glass such as Pyrex glass is formed on one surface of plate-like ceramic members 2a and 2b having a thickness of several mm by sputtering (FIG. 2 (a1)). (A2)), through holes H1 and H2 (only the ceramic member 2b) were formed by ultrasonic machining or the like (FIGS. 2 (b1) and (b2)). Next, a thin film electrode 2m made of gold and chrome was deposited from both sides by sputtering or the like on the inner surface of the through hole H1 and a predetermined region on both sides connected to the inner surface (FIG. 2 (c1), (c2)).
[0021]
FIG. 3 is a sectional view showing a state at the time of three-layer simultaneous anodic bonding according to the present invention.
In the silicon member 1a, a recess corresponding to a gap for forming a capacitance is processed from both surfaces by plasma etching, and then a ring-shaped groove is processed to provide a ring diaphragm 1d and an electrode whose peripheral portion is supported by the ring diaphragm 1d. Part 1e is formed. Dielectric films 1i such as SiO ₂ are formed on both surfaces of the electrode portion 1e in order to increase the capacitance.
[0022]
The low melting point glass films 2g of the ceramic members 2a and 2b are adhered to both surfaces of the silicon member 1a to form a total of three layers, and these three layers are sandwiched between two heaters T and pressurized and heated, and the silicon member 1a The ceramic members 2a and 2b were subjected to anodic bonding by applying a voltage (power source E).
At the time of anodic bonding, the pressing pressure was about 100 N / cm ² or less, and the temperature was maintained in the range of 200 to 700 ° C. The applied voltage was 300 to 700V. In particular, the temperatures of the two heaters were controlled so that there was no temperature difference between the silicon member 1a and the ceramic members 2a and 2b. Therefore, when the temperature was lowered to room temperature, the heat of the silicon member 1a and the ceramic members 2a and 2b The thermal strain caused by a small difference in expansion coefficient is symmetric with respect to the ring diaphragm surface, and the ring diaphragm does not shift in either direction, and this three-layer structure (if there is no through hole H2) No difference was found between the two capacitances and the temperature did not change.
[0023]
Then, a thin film electrode 2n was formed by sputtering on a predetermined region of the ceramic member 2b, the inner surface and the bottom surface (first silicon member 1a) of the through hole H2.
Next, the second silicon member 1b in which the recess corresponding to the gap was formed by plasma etching was attached to the ceramic member 2b having the above three-layer structure. FIG. 4 is a cross-sectional view illustrating the anodic bonding of the second silicon member and the three-layer structure of the sensor having the four-layer structure according to the present invention. In this case, the temperature of the two heaters was set lower than that in the anodic bonding of the three-layer structure so that the thermal strain did not increase.
[0024]
It is obvious that the manufacturing method up to the above three-layer structure can also be applied to the manufacture of a conventional sensor for pressure measurement having a three-layer structure.
Example 2
FIG. 5 is a cross-sectional view of a capacitive sensor capable of measuring temperature according to the present invention. In this capacitive sensor Sc, instead of the second silicon member 1b in the first embodiment, a third silicon member 1c in which a through hole H3 that communicates the gap G3 and the outside of the sensor is opened in the electrode portion 1e. Is attached. Since other parts of the sensor having the four-layer structure and the manufacturing method thereof are the same as those in the first embodiment, the description thereof is omitted.
[0025]
FIG. 6 is a sectional view of a capacitive sensor device capable of measuring temperature according to the present invention. Similarly to the conventional sensor device, the ceramic member 2a is attached to the package member P1, and the package member P2 is joined to the package member P1 with the openings of the through holes H1 and H3 inside.
A fluid having a large dielectric constant temperature change, such as silicon oil, is put in a package and connected to a pressure source. Thus, by measuring the pressure difference from the change in capacitance of the silicon member 1a, the capacitance of a fixed gap of silicon member 1 c side does not change the pressure change, it is possible to measure the temperature from the capacitance change .
[0026]
【The invention's effect】
According to the present invention, two ceramic members having at least a thin film electrode opposed to the electrode portion on both surfaces of a first silicon member made of single crystal silicon having an electrode portion and a ring diaphragm supporting the electrode portion have a low melting point. Method for manufacturing a capacitive sensor for pressure and temperature measurement, having an at least three-layer structure in which an electrode portion and a thin film electrode form two capacitances with a gap interposed therebetween, which are anodically bonded through a glass film In the above, the anodic bonding is performed in a state where the first silicon member and the two ceramic members are laminated in three layers, and the whole is heated to a uniform temperature. It is small and symmetrical in the plane direction inside the silicon member. Therefore, the electrode portion does not move and the gap does not change due to the temperature change of the sensor, that is, each capacitance does not change, and an apparent pressure difference does not always occur even if the sensor temperature changes.
[0027]
In addition, a second silicon member made of a silicon single crystal and having an electrode portion which is a flat concave portion is anodically bonded to the ceramic member of the three-layer structure sensor according to the above manufacturing method via a low melting point glass film. Since the third capacitance is added, absolute pressure and temperature can be measured using the third capacitance. As a result, no other thermometer is required and the instrumentation can be simplified.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a capacitive sensor having a fixed capacitance according to the present invention. FIG. 2 is a cross-sectional view in the manufacturing process of each ceramic member of the capacitive sensor having a fixed capacitance according to the present invention. (A1) and (a2) are after low-melting glass film formation, (b1) and (b2) are after through-hole formation, and (c1) and (c2) are after thin-film electrode formation. FIG. 4 is a cross-sectional view showing a state at the time of three-layer simultaneous anodic bonding according to the present invention. FIG. 4 is a cross-sectional view showing at the time of anodic bonding between a second silicon member and a three-layer structure of a four-layer sensor according to the present invention. FIG. 5 is a cross-sectional view of a capacitive sensor capable of measuring temperature according to the present invention. FIG. 6 is a cross-sectional view of a capacitive sensor device capable of measuring temperature according to the present invention. Sectional view of sensor [FIG. 8] Sectional view of conventional capacitive sensor device [FIG. 9] Conventional It is a cross-sectional view of the capacitive sensor in anodic bonding step, (a) shows the time of the first anodic bonding, (b) shows a time second anodic bonding [description of symbols]
DESCRIPTION OF SYMBOLS 1a 1st silicon member 1b 2nd silicon member 1d Ring diaphragm 1e Electrode part 1i Insulating film 2a Ceramic member 2b Ceramic member 2g Low melting glass film 2m Thin film electrode 2n Thin film electrode H1 Through hole H2 Through hole H3 Through hole G1 Gap G2 Gap G3 Fixed gap Sa Conventional capacitance type sensor Sb Capacitance type sensor Sc according to the present invention Capacitance type sensor T according to the present invention T Heater Ts Metal surface portion P1 of the heater P1 Package member P2 Package member E Power source

Claims (7)

Two ceramic members having at least a thin film electrode facing the electrode portion on both surfaces of a first silicon member made of single crystal silicon having an electrode portion thinner than the thickness of the silicon member and a ring diaphragm supporting the electrode portion have a low melting point. An electrode that is a flat recess made of a single crystal of silicon in a capacitive sensor for pressure and temperature measurement, which is anodically bonded through a glass film, and in which the electrode part and the thin film electrode form two capacitances A second silicon member having a portion formed thereon is a four-layer capacitive sensor formed by anodically bonding the ceramic member through a low melting point glass film; and an electrode portion of the second silicon member; A pressure which is characterized in that a third electrostatic capacity is formed with a gap between the second electrode thin film of the ceramic member formed in a portion facing this and a gap; Capacitive sensor for degree measurement. The ceramic member has a through hole opened at a portion facing the electrode portion of the second silicon member, and the second electrode thin film has an inner surface of the through hole and the first silicon member. 2. The pressure and temperature according to claim 1, wherein the first silicon member is formed as a common electrode having three capacitances. Capacitive sensor for measurement. 3. The capacitive sensor for pressure and temperature measurement according to claim 1, wherein the second silicon member is provided with a through hole leading to the gap. 4. A method of manufacturing a capacitive sensor for pressure and temperature measurement according to claim 1, wherein the two ceramic members are anodic bonded to both surfaces of the first silicon member via a low melting point glass film. In addition, the anodic bonding is performed in a state where the first silicon member and the two ceramic members are laminated in three layers, and the whole is heated to a uniform temperature, so that the first bonding is performed. After forming one silicon member and the two ceramic members into a three-layer structure, the second silicon member is anodically bonded to a predetermined surface of the ceramic member through a low-melting glass. And a method for manufacturing a temperature sensor. 5. The method of manufacturing a capacitive sensor for pressure and temperature measurement according to claim 4, wherein the low-melting glass is a film formed on the insulating ceramic member in advance. 6. The anodic bonding according to claim 4 or 5, wherein the anodic bonding is performed by two heaters that are independently temperature controlled with the three-layer structure and the second silicon member interposed therebetween, and the anodic bonding temperature is arbitrarily changed. The manufacturing method of the capacitive sensor for pressure and temperature measurement of description. 3. The through-hole of the second silicon member and the through-hole of the ceramic member on which the second silicon member is disposed in the pressure and temperature measuring capacitive sensor of the four-layer structure according to claim 2 The first package forming the first pressure chamber having the opening opened to the outside in the same space, and the opening of the through hole of the other ceramic member and the opening opened to the outside are the same A second package forming a second pressure chamber in the space is added, and the first pressure chamber is filled with a fluid having a large dielectric constant temperature coefficient, and the first pressure chamber and the second pressure chamber are filled. A capacitance type sensor device for pressure and temperature measurement, characterized in that the pressure difference between the pressure chambers of the first and second pressure chambers can be measured, and the temperature can be measured from the temperature change of the third capacitance.

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