JP2002022584A - Capacitive pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the measuring accuracy to be higher than before by preventing the deflection of a diaphragm which occurs when a lead pin is soldered in place from spreading to the center of the diaphragm. SOLUTION: The width of a communicating part (slit) is made smaller than the diameter of a pad formation chamber 1b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a capacitive pressure sensor, and more particularly to a capacitive pressure sensor whose diaphragm and base are made of sapphire.

[0002]

2. Description of the Related Art Conventionally, a capacitive pressure sensor using sapphire for a diaphragm or a base is often used because of its excellent corrosion resistance and the like. This sensor is formed by forming a movable electrode on a sapphire wafer forming a diaphragm, forming a fixed electrode in a recess of another sapphire wafer, and laminating the two wafers. Further, a lead wire connected to each electrode is drawn out by opening a through hole in the sapphire wafer on the fixed electrode side.

FIG. 4A is a plan view showing a conventional capacitive pressure sensor, and FIG. 4B is a sectional view taken along line BB 'of FIG.
As shown in these figures, a pressure sensor 110 includes a base 101 having a fixed electrode 101a provided in a concave portion, a movable electrode 102a, a reference electrode 102b, and pads 102c, 1c.
It comprises a diaphragm 102 provided with 02d, 102e and 102f, and lead pins soldered to each pad. FIG. 4B shows the solder 103.
c, 103d, lead pins 103a,
Only 103b is described. These lead pins 1
Reference numerals 03a and 103b are electrically connected to the reference electrode 102b and the fixed electrode 101a, respectively, and are used for detecting capacitance between the electrodes. Here, a lead pin immediately below the pad 102e that is not connected to any electrode is a hollow pin, and is used to introduce a reference pressure into the capacity chamber.

[0004] The pressure sensor 110 thus configured
The diaphragm 102 bends according to the pressure difference between the outside of the sensor and the inside of the capacitance chamber 101c, and the movable electrode 102
The capacitance changes due to a change in the distance between a and the fixed electrode 101a, and the pressure is measured.

Here, the manufacturing process of the pressure sensor 110 will be described. Base 101 and diaphragm 102
Is manufactured by processing a sapphire wafer. That is, the sapphire wafer is machined, laser-processed or ultrasonic-processed so that the lead pin 1
After opening through holes for inserting 03a, 103b and the like, forming a recess by dry etching, the fixed electrode 101a is formed by vapor deposition or the like. A plurality of these through holes and the fixed electrode 101a in the recess are formed on the same sapphire wafer.

On the other hand, a movable electrode 102a, a reference electrode 102b, and pads 102c to 102f are formed on another sapphire wafer by vapor deposition or the like. As described above, a plurality of these movable electrodes 102a and pads 102c to 102f are formed on the same sapphire wafer. Thereafter, the two wafers processed as described above are transferred to the fixed electrode 101a.
And the movable electrode 102a are positioned so as to face each other, and are directly joined under a predetermined heating atmosphere. Next, chips are formed by dicing the sapphire wafer. Finally, after the chip on the base 101 side is turned to the upper surface, a lead pin is dropped into the through hole, and a granular or ring-shaped solid solder (Sn-Ag solder) is placed in a gap between the through hole and the lead pin. The lead pin and the pad are connected by the molten solder that has been heated and melted, and has flowed into the through hole, thereby completing the sensor chip.

[0007] Through the above steps, conventionally, a sapphire capacitive pressure sensor excellent in corrosion resistance can be easily mass-produced.

[0008]

However, when soldering after dropping the lead pins from the back side,
It is known that the diaphragm is distorted when the molten solder solidifies. Such a distortion is, for example, shown in FIG.
The pad forming chamber 101b is as shown in FIG.
After being generated in the vicinity, it expands to the center of the capacity chamber 101c, causing distortion of the entire diaphragm 102. As a result, there arises a problem that the offset of the pressure sensor varies and the measurable pressure range is narrowed. In addition,
Although the detailed cause of this phenomenon has not been elucidated at present, it is definitely reproduced by the above-described manufacturing process.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and prevents the distortion of the diaphragm generated at the time of soldering the lead pins from expanding to the center of the diaphragm, thereby improving the measurement accuracy as compared with the prior art. An object of the present invention is to provide a capacitive pressure sensor.

[0010]

In order to achieve such an object, a capacitive pressure sensor according to the present invention comprises a base,
A fixed electrode disposed on the base, a side wall formed on the base and surrounding the fixed electrode; and a base opposed to the base and joined to the side wall, the base and the side wall being A diaphragm that forms a capacitance chamber with the portion, a movable electrode disposed on the diaphragm and facing the fixed electrode,
First and second pad formation chambers formed in the side wall portion and extending between the base and the diaphragm, and communicate the first and second pad formation chambers with the capacity chamber, respectively. First and second slits, a first pad disposed on the base in the first pad formation chamber, connected to the fixed electrode through the first slit, and the second pad A second pad disposed on the diaphragm in the forming chamber and connected to the movable electrode through the second slit, and communicating with the first and second pad forming chambers formed on the base, respectively; First and second through-holes, and first and second through-holes inserted into the first and second pad formation chambers through the first and second through-holes and connected to the first and second pads, respectively. In capacitive pressure sensor having a lead portion of, than the diameter of said first and second pad forming chamber is obtained by reducing the width of the first and second slits.

Further, the present invention includes, as another aspect, the following configuration. That is, the diaphragm and the base are made of sapphire, silicon, glass, or diamond. Further, a reference electrode provided on the diaphragm side is further provided.

Therefore, with this configuration, according to the present invention, the width of the communicating portion between the pad forming chamber and the capacitance chamber becomes narrower than before, and the distortion of the diaphragm generated in the pad forming chamber during soldering is reduced. It does not spread to the room, and a diaphragm that is flatter than before can be obtained. For this reason, it is possible to prevent variations in the offset of the pressure sensor and to obtain an advantage that the measurable pressure range is not narrowed.

[0013]

Next, one embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a plan view showing one embodiment of the present invention, and FIG.
FIG. 3 is a sectional view taken along line A ′. As shown in these figures, the pressure sensor 10 is a base 1 provided with a fixed electrode 1a in a recess.
Movable electrode 2a, reference electrode 2b and pads 2c, 2
d, 2e, 2f and lead pins soldered to each pad (FIG. 1 (b) shows lead pins 3a, 3d connected by solders 3c, 3d).
b only).

The pressure sensor 10 configured as described above is
The diaphragm 2 bends according to the pressure difference between the outside of the sensor and the inside of the capacity chamber 1c, and the movable electrode 2a and the fixed electrode 1a accompanying the deflection.
The capacitance changes due to the change in the distance to the pressure, and the pressure is measured.

Here, the manufacturing process of the pressure sensor 10 will be described. The base 1 and the diaphragm 2 are manufactured by processing a sapphire wafer. That is, a sapphire wafer is machined, laser-processed or ultrasonically processed to open a through-hole for inserting the lead pins 3a, 3b and the like, and a recess is formed by dry etching using Ar atoms. The fixed electrode 1a is formed by vapor deposition or the like. A plurality of these configurations are formed on the same sapphire wafer.

On the other hand, the movable electrode 2a, the reference electrode 2b and the pads 2c to 2c are deposited on another sapphire wafer by vapor deposition or the like.
Form f. As described above, a plurality of these components are formed on the same sapphire wafer. Thereafter, the two wafers processed as described above are aligned so that the fixed electrode 1a and the movable electrode 2a face each other, and are directly bonded under a predetermined heating atmosphere (for example, 400 to 1300 ° C.). .
Next, chips are formed by dicing the sapphire wafer. Finally, after making the chip on the base 1 side the top surface, drop the lead pin into the through hole,
Granular or ring-shaped solid solder (Sn-Ag solder)
Is placed in the gap between the through hole and the lead pin, melted by heating (for example, 300 ° C.), and the lead pin and the pad are connected by the molten solder flowing into the through hole, thereby completing the sensor chip.

The fixed electrode 1a, the movable electrode 2a, and the reference electrode 2b are formed of, for example, a Pt / adhesion enhancing film. Ti, V, Cr, Nb, Z
r, Hf, Ta or the like is used. Also, pad 2c
To 2f are formed, for example, of Au / barrier film / adhesion enhancing film. Pt or the like is used as the barrier film, and Nb or the like is used as the adhesion enhancing film.

Here, features of the present embodiment will be described. In the present embodiment, by reducing the width of the communicating portion (slit) between the pad forming chamber 1b and the capacity chamber 1c, the distortion of the diaphragm 2 generated in the pad forming chamber 1b is prevented from expanding to the capacity chamber 1c. can do.

FIG. 2 is an enlarged plan view of the pad forming chamber shown in FIG. As shown in the figure, in the present embodiment, the width X in the communicating portion (slit) between the pad forming chamber 1b and the capacity chamber 1c is smaller than the diameter of the pad forming chamber 1b (ie, X < Y). Therefore, the joint area between the diaphragm 2 and the base 1 in the communicating portion becomes larger than before, and it is possible to prevent the distortion of the diaphragm 2 generated at the time of soldering from expanding to the capacity chamber 1c. In the case where the shape of the pad forming chamber 1b is a polygon or the like, the diameter of the inscribed circle may be set to the above-described Y and compared with the width X of the communicating portion (slit). The above relationship between X and Y is established between each pad formation chamber and the capacity chamber. As specific values of X and Y, (0.3,
1.0) and the like. The unit of each numerical value is mm
(Millimeters).

Here, experimental results according to the present embodiment will be described. FIG. 3 is a graph comparing the flatness of the diaphragm in the present embodiment and the conventional example. The vertical axis indicates the amount of deflection in a direction perpendicular to the wafer surface, and the horizontal axis indicates the position on the dashed line from the pad edge to the diaphragm edge. As shown in FIG. 3A, in the conventional example, the bending at the pad edge is almost 0 μm, whereas the bending at the diaphragm edge is about 1.2 μm. On the other hand, as shown in FIG. 3B, in the present embodiment, the bending at the pad edge is almost 0 μm, and the bending at the diaphragm edge is a very small value of less than 0.1 μm. Therefore, it is understood that the use of this embodiment can prevent the bending generated in the pad formation chamber from expanding to the capacity chamber.

In the above, the case where sapphire is used as the material of the diaphragm and the base has been described, but the present invention is not limited to this. For example, a single crystal material such as silicon, glass, or diamond may be used. Further, the reference electrode is not an essential component, and may be added as needed. Therefore, the present invention includes a configuration using only the movable electrode and the fixed electrode.

[0022]

As described above, in the present invention,
Since the width of the communicating portion (slit) between the pad forming chamber and the capacity chamber is smaller than the diameter of the pad forming chamber, the joint area between the diaphragm and the base is increased as compared with the conventional structure, and both are strongly fixed. You. Therefore, the distortion of the diaphragm generated in the pad forming chamber during soldering does not spread to the capacity chamber, and a diaphragm that is flatter than before can be obtained. Further, it is possible to prevent variations in offset of the pressure sensor and to obtain an advantage that the measurable pressure range is not narrowed. Further, by making the diaphragm flat, it is possible to reduce temperature hysteresis, which is an error during pressure measurement.

[Brief description of the drawings]

FIG. 1A is a plan view showing one embodiment of the present invention, and FIG. 1B is a sectional view taken along line AA ′.

FIG. 2 is a plan view showing a pad forming chamber according to FIG. 1;

FIG. 3 is a graph comparing the flatness of a diaphragm in the present embodiment and a conventional example.

FIG. 4A is a plan view showing a conventional example, and FIG.
It is a line sectional view.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base, 1a ... Fixed electrode, 1b ... Pad formation room, 1c
... Capacity chamber, 2 ... Diaphragm, 2a ... Movable electrode, 2b ...
Reference electrode, 2c, 2d, 2e, 2f ... pad, 3a, 3
b: Lead pin, 3c, 3d: Solder, 10: Pressure sensor, X: Width of communicating portion, Y: Diameter of pad formation chamber.

Claims (3)

[Claims] 1. A base, a fixed electrode provided on the base, a side wall formed on the base and surrounding the fixed electrode, and a side wall facing the base. A diaphragm joined to form a capacity chamber together with the base and the side wall, a movable electrode disposed on the diaphragm and facing the fixed electrode, and a base formed in the side wall and the base and the diaphragm; First and second pad forming chambers extending between the first and second pad forming chambers, first and second slits respectively connecting the first and second pad forming chambers to the capacity chamber, and the first pad A first pad disposed on the base in the formation chamber and connected to the fixed electrode through the first slit; and a second pad disposed on the diaphragm in the second pad formation chamber. Through the slit of the A second pad connected to the moving electrode; first and second through holes formed on the base and communicating with the first and second pad formation chambers; respectively, the first and second through holes A capacitive pressure sensor having first and second leads inserted into the first and second pad forming chambers through holes and connected to the first and second pads, respectively, The first pad is larger than the diameter of the second pad formation chamber.
And a width of the second slit is reduced. 2. The capacitive pressure sensor according to claim 1, wherein the diaphragm and the base are made of sapphire, silicon, glass, or diamond. 3. The capacitive pressure sensor according to claim 1, further comprising a reference electrode provided on the diaphragm side.