JP2002365152A - Pressure sensor, and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance detection precision and reliability for pressure detection, and reduce a size. SOLUTION: A pressure receiving recessed groove 4 is provided in a lower silicon substrate 1 to form a thin-walled part 5. A frame-like protrusion 6 is formed in a surface side of the thin-walled part 5, and a surface thereof is coated with a polycrystal membrane 7. A piezo-resistance element 8 is formed in a diaphragm part 5A of the thin-walled part 5, and an electrode 9 connected to the piezo-resistance element 8 is arranged on the surface 1A side of the silicon substrate 1. An upper silicon substrate 10 is anode-joined to the polycrystal membrane 7 of the frame-like protrusion 6 via a glass film 11 to partition a pressure chamber A, and a chamfer-like upper tapered part 10A is formed in the vicinity of the electrode 9. A space between the glass film 11 and the polycrystal membrane 7 is thereby joined with no clearance, and pressure inside the pressure chamber A is held thereby at a constant value to enhance the detection precision and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor formed on a silicon substrate by means of, for example, etching, and preferably used for detecting pressure by utilizing the bending deformation of a diaphragm, and a method of manufacturing the same. .

[0002]

2. Description of the Related Art Generally, a pressure sensor includes a substrate made of a silicon material, a thin portion provided on a front surface side of the substrate by forming a pressure receiving groove on the back surface side of the substrate,
A frame-like projection that surrounds part of the thin-walled portion in a frame shape and is provided on the surface side of the thin-walled portion and has an enclosed inside as a diaphragm portion; A glass plate defining a pressure chamber which closes the diaphragm portion and applies a reference pressure, and the diaphragm is provided by a differential pressure between the pressure receiving groove provided in the thin portion and the pressure chamber located in the diaphragm portion. There is known a device comprising a deflection detecting element for detecting a deflection when a portion is deformed (for example, Japanese Patent Application Laid-Open No. H11-118642).

In such a conventional pressure sensor, when a fluid pressure or the like acts on the diaphragm, the diaphragm of the thin portion is bent and deformed in accordance with the pressure. At this time, since the deflection detecting element is provided in the diaphragm, the deflection detecting element outputs a signal corresponding to the distortion of the diaphragm. For this reason, the pressure sensor detects the pressure applied to the diaphragm by detecting a signal from the deflection detecting element.

Further, as another conventional pressure sensor, a front side groove and a back side groove are provided on the front side and the back side of a silicon substrate, respectively, so that a gap between the front side groove and the back side groove is provided. There is known a configuration in which a thin portion is formed, an electrode serving as a deflection detecting element is provided in the thin portion, and a surface-side groove is closed on the surface side of the silicon substrate to join another silicon substrate. (For example, Proceedings of TRA
NSDUCER'87, S.Shojiet.al., Pp.305-308).

[0005]

In the prior art described in Japanese Patent Application Laid-Open No. H11-118642, an electrode connected to a deflection detecting element is provided on a substrate, and the electrode is formed on a glass plate. It is configured to be arranged around. For this reason, when an external wiring is connected to the electrode by bonding, the end of the glass plate may interfere with the bonding tool, and it is necessary to ensure a sufficient distance between the glass plate and the electrode. There is a problem that it is difficult to miniaturize and downsize the sensor.

According to another conventional technique described in Proceedings of TRANSDUCER '87, pp. 305 to 308, another silicon substrate for closing the front side groove is bonded to the silicon substrate, and the other silicon substrate is bonded to the silicon substrate. Since a configuration in which a chamfered inclined portion is provided on the end surface of the substrate is disclosed, interference with a bonding tool can be prevented by the inclined portion. However, in another conventional technique, two silicon substrates are bonded via an oxide film. Therefore, in order to bond them without gaps, the bonding surface of each silicon substrate is flat at the atomic level. Need to be As a result, a gap may be generated between the two silicon substrates due to slight unevenness of the bonding surface, and the pressure of the pressure chamber defined inside the front-side groove may change with time. However, there is a problem that the accuracy of pressure detection is apt to be lowered and reliability is low.

In another conventional technique, the upper silicon substrate is anisotropically etched after the upper silicon substrate is joined in order to close the groove on the surface of the lower silicon substrate. However, since the upper silicon substrate is opaque, there is a problem that it is difficult to accurately position the upper silicon substrate having a trapezoidal cross section by etching with respect to the surface-side concave groove of the lower silicon substrate.

Further, in another conventional technique, an upper silicon substrate and a lower silicon substrate are joined by using a high-temperature treatment of 800 ° C. or higher, which is higher than the melting point of aluminum, so that a transistor is previously formed on a flat upper silicon substrate. , Resistors, circuit elements such as aluminum wiring and wiring, and then
It is necessary to perform anisotropic etching on the upper silicon substrate. For this reason, circuit elements and wirings can be formed only on the surface side portion (short side portion of the trapezoidal cross section) of the upper silicon substrate remaining by etching, and the mounting area of the circuit elements and wirings is secured. In addition, there is a problem that the area of the entire pressure sensor becomes large.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a pressure sensor having high pressure detection accuracy and high reliability and capable of being miniaturized.

[0010]

According to a first aspect of the present invention, there is provided a pressure sensor, comprising: a lower silicon substrate made of a silicon material; and a pressure receiving groove formed on a back surface of the lower silicon substrate. A thin portion provided on the front surface side of the substrate, and a frame-like projection that surrounds the thin portion in a frame shape and is provided on the surface side of the thin portion and is surrounded by a diaphragm portion. An upper silicon substrate made of a silicon material which is disposed on the frame-shaped protrusion and defines a pressure chamber for closing the diaphragm portion and applying a reference pressure, and provided between the upper silicon substrate and the frame-shaped protrusion. A glass film that joins the upper silicon substrate to the frame-shaped protrusion, and the diaphragm portion is deformed by a pressure difference between the pressure-receiving groove provided in the thin portion and the pressure chamber located in the diaphragm portion. Check for deflection Deflection lies in the structure by the detecting element to.

With this configuration, since the glass film is provided between the frame-shaped protrusion and the upper silicon substrate, they can be joined using anodic bonding. For this reason, since the glass film flows at the time of anodic bonding, even if there are slight irregularities (for example, about 10 to 20 nm) on the bonding surface,
The frame-shaped protrusion and the upper silicon substrate can be joined without any gap, and the pressure chamber can be securely sealed.

According to a second aspect of the present invention, an upper tapered portion is provided on the outer peripheral side of the upper silicon substrate, the upper tapered portion gradually expanding from the front surface to the rear surface, and the upper tapered portion is formed on the front surface of the lower silicon substrate. The present invention has a configuration in which an electrode is provided at the periphery and connected to the deflection detecting element.

Thus, even when the electrode is connected to an external wiring or the like by bonding, the upper taper portion of the upper silicon substrate can prevent the bonding tool from contacting and interfering with the upper silicon substrate. The electrodes can be arranged closer to the upper silicon substrate.

According to a third aspect of the present invention, a lower tapered portion is formed on the outer peripheral side of the upper silicon substrate, the lower tapered portion gradually expanding from the rear surface side to the front surface side, and a rear surface located on the front surface side of the lower tapered portion. An upper taper portion that gradually reduces from the side toward the front surface, and an electrode connected to the flexure detecting element located on the surface side of the lower silicon substrate around the lower taper portion and the upper taper portion. Is provided.

Thus, a lower tapered portion is provided on the outer peripheral side of the upper silicon substrate in addition to the upper tapered portion.
The upper tapered portion and the lower tapered portion intersect on the outer peripheral side of the upper silicon substrate, and the angle of the cross section at the end can be made obtuse. Therefore, as compared with the case where only the upper tapered portion is provided on the upper silicon substrate, the angle of the cross section at the end of the upper silicon substrate can be increased, and the strength of the end can be increased.

According to a fourth aspect of the present invention, there is provided a pressure sensor manufacturing method, wherein a lower silicon wafer made of a silicon material has a frame-shaped projection on the surface side surrounding the lower silicon wafer and an inner side of the frame-shaped projection. And a deflection detecting element for detecting a deflection positioned at an upper end of the lower silicon wafer. The upper silicon wafer made of a silicon material is provided with a through hole having an inclined end face by using an anisotropic etching process. The rear surface side of the upper silicon wafer is joined to the protrusion via a glass film, and a pressure receiving groove is provided on the rear surface side of the lower silicon wafer at a position corresponding to the frame-shaped protrusion. Form a diaphragm part surrounded by a frame-shaped protrusion on the front side,
In another embodiment, the lower silicon wafer and the upper silicon wafer are cut along the pressure receiving groove.

With this configuration, the frame-shaped protrusion of the lower silicon wafer and the upper silicon wafer can be anodic-bonded via the glass film. Then, after forming the pressure-receiving groove in the lower silicon wafer, the pressure-receiving groove surrounding the pressure-receiving groove is cut together with the lower silicon wafer and the upper silicon wafer to form a pressure sensor in which the upper silicon substrate is joined to the lower silicon substrate. can do.

Further, since the upper silicon wafer and the lower silicon wafer can be anodically bonded via the glass film, the bonding can be performed at a temperature lower than the melting point of aluminum forming the electrodes and the like. For this reason, after forming transistors, resistors, circuit elements such as aluminum wiring, and wiring on the lower silicon wafer, the upper silicon wafer that has been subjected to the anisotropic etching process can be joined, and the through-hole provided on the upper silicon wafer can be formed. The upper silicon wafer and the lower silicon wafer can be aligned with sufficient accuracy through the holes. Further, since circuit elements and wiring can be formed on the lower silicon wafer, the area of the entire pressure sensor can be reduced and the size can be reduced as compared with other conventional techniques.

According to a fifth aspect of the present invention, an electrode connected to a deflection detecting element is provided on the surface side of the lower silicon wafer, and the through hole is formed when the upper silicon wafer is joined to the frame-shaped projection of the lower silicon wafer. The structure is such that anisotropic etching is performed from the surface side of the upper silicon wafer at the position where the electrodes are exposed.

Thus, the inner wall surface of the through hole is formed to be inclined, and the through hole can be gradually opened from the back side to the front side of the upper silicon wafer to be opened. Therefore, after the pressure sensor is formed by cutting the lower silicon wafer or the like, the outer peripheral side of the upper silicon substrate can be inclined in a chamfered shape by the inclined through hole.
As a result, even when the electrode is connected to an external wiring or the like by bonding, it is possible to prevent the bonding tool from contacting and interfering with the upper silicon substrate.

According to a sixth aspect of the present invention, an electrode connected to a deflection detecting element is provided on the front side of the lower silicon wafer, and a through hole is formed when the upper silicon wafer is joined to a frame-shaped projection of the lower silicon wafer. The configuration is such that the upper silicon wafer is formed by performing anisotropic etching from the front side and the back side of the upper silicon wafer at positions where the electrodes are exposed.

Thus, on the inner wall surface of the through hole, a lower inclined surface whose opening area is reduced from the rear surface side to the front surface side of the upper silicon wafer, and a rear inclined surface continuous with the lower inclined surface. And an upper inclined surface whose opening area gradually expands from the top toward the front side. Therefore, the lower inclined surface and the lower inclined surface can intersect at the end of the inner wall. As a result, the angle of the cross section at the end of the inner wall surface can be made obtuse, and the through hole is formed only from the surface side using anisotropic etching.
The angle of the cross section at the end of the inner wall surface of the through hole can be increased, and the strength of the end can be increased. Further, since the etching can be performed from both the front side and the rear side of the upper silicon wafer, the etching time can be reduced to about half as compared with the case where the etching is performed from one side.

According to a seventh aspect of the present invention, a plurality of unit sensors are formed in a row on the lower silicon wafer, and the through holes are formed in a long groove shape along the rows of the unit sensors.

Thus, a common through hole can be used for a plurality of unit sensors (pressure sensors) arranged in a line.

According to an eighth aspect of the present invention, a plurality of unit sensors are formed in a lattice pattern on the lower silicon wafer, and the through holes are formed in a mesh pattern corresponding to each unit sensor. .

Thus, since the through holes are arranged in a mesh shape corresponding to each unit sensor, each through hole can be reduced, and the strength of the upper silicon wafer at the time of processing, bonding, etc. can be increased.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pressure sensor according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, FIGS. 1 to 11 show a first embodiment. In the figures, reference numeral 1 denotes a rectangular lower silicon substrate formed of, for example, silicon single crystal or the like, and a surface 1A of the lower silicon substrate 1 Oxide films 2 and 3 are formed on and back surface 1B, respectively.

Reference numeral 4 denotes a pressure receiving groove for receiving a pressure applied to the pressure sensor.
And is formed in a substantially square shape on the back surface 1B side. The pressure receiving groove 4 is gradually reduced from the back surface 1B of the lower silicon substrate 1 to the front surface 1A by performing anisotropic etching on the back surface 1B side of the lower silicon substrate 1 via the oxide film 3. It forms a tapered bottomed hole.

Reference numeral 5 denotes a thin portion provided on the surface 1A side of the lower silicon substrate 1 by the pressure receiving groove 4. The thin portion 5 has a substantially square shape corresponding to the pressure receiving groove 4.

Reference numeral 6 denotes a frame-shaped protrusion provided on the surface side of the thin portion 5. The frame-shaped protrusion 6 is formed in a substantially rectangular frame shape by, for example, silicon oxide or the like. A polycrystalline film 7 made of silicon is formed. Further, the frame-shaped protrusion 6 surrounds a part of the thin portion 5 in a frame shape. As a result, the inner portion of the thin portion 5 that is surrounded by the frame-shaped protrusions 6 has a diaphragm that bends and deforms in accordance with the pressure difference between the pressure in the pressure-receiving groove 4 and the pressure in the pressure chamber A described later. 5A.

, 8,... Are, for example, four piezoresistive elements provided in the diaphragm portion 5A. 1 is formed by injecting and diffusing into the surface 1A side to make piezoresistance. Further, a wide diffusion layer wiring (not shown) is connected to each piezoresistive element 8, and the piezoresistance element 8 is connected to an electrode 9 described later through these diffusion layer wirings. The resistance value of the piezoresistive element 8 changes according to the bending deformation of the diaphragm 5A.

9, 9, ... are the surface 1 of the lower silicon substrate 1.
The electrode 9 is formed on the oxide film 2 on the side A, and the electrode 9 is formed of a thin film using a metal conductive material such as aluminum. The electrode 9 is connected to the diffusion layer wiring through a through hole (not shown) provided in the oxide film 2 and is connected to the piezoresistive element 8 through the diffusion layer wiring. The electrode 9 is connected to an external wiring or the like by bonding a metal wire or the like.

Reference numeral 10 denotes an upper silicon substrate made of silicon single crystal provided on the surface side of the frame-shaped protrusion 6. The upper silicon substrate 10 is provided on the surface of the frame-shaped protrusion 6 via a glass film 11 described later. Anodically bonded to the polycrystalline film 7. The upper silicon substrate 10 defines a pressure chamber A for closing the diaphragm 5A and applying a reference pressure. On the left and right ends of the outer periphery of the upper silicon substrate 10, an upper tapered portion 10A that is inclined in a chamfered shape is formed. As a result, the cross section of the upper silicon substrate 10 has a substantially trapezoidal shape that expands from the front side to the rear side, and its end is inclined at an inclination angle θ1 of, for example, about 54.74 degrees.

Reference numeral 11 denotes a glass film formed between the back surface of the upper silicon substrate 10 and the polycrystalline film 7 on the surface of the frame-shaped protrusion 6. The glass film 11 is formed on the back surface of the upper silicon substrate 10. For example, it is formed into a thin film by sputtering borosilicate glass containing sodium, and is joined to the polycrystalline film 7 on the lower silicon substrate 1 side by anodic bonding.

The pressure sensor according to the present embodiment has the above-described configuration.
This will be described with reference to FIG.

First, as shown in FIGS. 4 and 5, an upper silicon wafer 12 made of single-crystal silicon having a {100} face on the front and back sides is formed. Then, as shown in FIGS. Oxide films 13 and 14 are formed on front surface 12A and back surface 12B of wafer 12, respectively. Next, an etching process is performed with a photoresist (not shown) applied on the oxide film 13 on the surface 12A side, and a substantially rectangular long groove-shaped opening 13A is formed at a position corresponding to a through hole 15 described later. Are formed.

Next, using the oxide film 13 as a mask, an anisotropic etching process is performed from the surface 12A side of the upper silicon wafer 12 to form a through hole 15 having an inner wall surface along the {111} plane as shown in FIG. Form. Thereby, the through hole 15
Are gradually expanded from the back surface 12B toward the front surface 12A, are formed in a long groove shape along a row of unit sensors 18 described later, and extend forward and backward of the upper silicon wafer 12. An upper silicon substrate portion 16 having a trapezoidal cross section is formed in the upper silicon wafer 12 between two adjacent through holes 15, and the upper silicon substrate portion 16 has a substantially parallel rod shape. It extends forward and backward along the through hole 15.

Next, after the oxide films 13 and 14 are removed from the upper silicon wafer 12, borosilicate glass containing sodium is formed in a thin film on the back surface 12B of the upper silicon wafer 12 by means such as sputtering. , Glass film 1
Form one.

The glass film 11 may be formed on a frame-shaped protrusion 6 of a lower silicon wafer 17 to be described later, instead of the back surface 12B of the upper silicon wafer 12. In this case, the polarity of the high voltage applied to the upper silicon wafer 12 and the lower silicon wafer 17 at the time of anodic bonding is reversed with respect to the case where the glass film 11 is formed on the upper silicon wafer 12.

On the other hand, the lower silicon wafer 17 has an oxide film 2 and a unit sensor 18 (pressure sensor) to be described later.
3. The frame-shaped protrusion 6, the polycrystalline film 7, the piezoresistive element 8, and the electrode 9 are formed in advance. At this time, the frame-shaped protrusions 6 and the like are arranged in a row along the upper silicon substrate 16 toward the front and the rear. Also, circuit elements such as transistors, resistors, and wirings and wirings may be formed on the lower silicon wafer 17 in advance.

Then, as shown in FIG. 9, the upper silicon substrate 16 of the upper silicon wafer 12 is placed on the frame-like projection 6 of the lower silicon wafer 17 with the glass film 11 interposed therebetween. In this state, the upper silicon wafer 12 is anodically bonded to the lower silicon wafer 17 so that the polycrystalline film 7 on the frame-shaped protrusion 6 has the glass film 11 formed on the back surface 12B of the upper silicon wafer 12. Join.

Thereafter, as shown in FIG. 11, on the back surface of the lower silicon wafer 17, a position corresponding to the frame-shaped projection 6 is subjected to anisotropic etching to form the pressure receiving groove 4. As a result, a diaphragm portion 5A surrounded by the frame-shaped protrusion 6 is formed on the front surface side of the lower silicon wafer 17.

Finally, as shown in FIGS. 10 and 11, the lower silicon wafer 17 is cut together with the upper silicon wafer 12 so as to surround each pressure receiving groove 4, and the unit sensor 18 (pressure sensor) indicated by a two-dot chain line is cut. ) Disconnect each time. At this time,
The lower silicon substrate 1 having a substantially quadrangular shape can be taken out from the lower silicon wafer 17 and the upper silicon substrate 10 can be taken out from the upper silicon wafer 12, and the upper silicon substrate 10 has an upper tapered portion 10A due to the inclined surface of the through hole 15. Can be formed. Thereby, the pressure sensor shown in FIGS. 1 to 3 can be processed.

Here, the unit sensor 18 is surrounded by the pressure-receiving groove 4 provided on the back surface of the lower silicon wafer 17, the frame-shaped protrusion 6 provided on the front surface, and the frame-shaped protrusion 6. This shows one (one unit) pressure sensor constituted by a piezoresistive element 8 provided on a diaphragm 5A and an upper silicon wafer 12 joined to a frame-shaped protrusion 6.

The pressure sensor according to the present embodiment is formed by the above-described manufacturing method. When fluid pressure or the like acts on the pressure receiving groove 4 of the pressure sensor, the pressure receiving groove 4 and the pressure chamber A , A pressure difference is generated. At this time, the diaphragm portion 5A of the thin portion 5 is bent and deformed by the pressure difference between the pressure receiving groove 4 and the pressure chamber A.
Changes according to the bending (strain) generated in the diaphragm portion 5A. Therefore, the pressure acting on the pressure receiving groove 4 is detected by detecting the resistance value of the piezoresistive element 8 through the electrode 9.

Thus, in this embodiment, since the glass film 11 is provided between the frame-shaped protrusion 6 of the lower silicon substrate 1 and the upper silicon substrate 10, they can be joined by using anodic bonding. For this reason, since the glass film 11 flows at the time of anodic bonding, even if the bonding surface has slight irregularities (for example, about 10 to 20 nm) by forming the polycrystalline film 7 on the surface of the frame-shaped protrusion 6. The frame-shaped protrusion 6 and the upper silicon substrate 10 can be joined without any gap,
The pressure chamber A can be securely sealed. As a result, the pressure in the pressure chamber A can be maintained at a constant value, and fluctuation in the detected value of the pressure can be suppressed to improve reliability.

Further, since the upper silicon substrate 10 (upper silicon wafer 12) can be easily cut as compared with a glass plate, workability at the time of cutting can be improved, and
The cutting margin removed by cutting can be reduced. For this reason, many pressure sensors (unit sensors 18) can be manufactured from one lower silicon wafer 17, and productivity can be improved.

Further, on the outer peripheral side of the upper silicon substrate 10, there is provided an upper tapered portion 10A gradually expanding from the front side to the rear side, and on the front surface 1A side of the lower silicon substrate 1, the upper tapered portion 10A is formed. Since the electrode 9 connected to the piezoresistive element 8 is provided on the periphery, the upper tapered portion 10A of the upper silicon substrate 10 can be used even when the electrode is connected to an external wiring or the like using bonding or the like. This can prevent the bonding tool from contacting and interfering with the upper silicon substrate 10. For this reason,
The electrode 9 can be arranged close to the upper silicon substrate 10, and the size of the pressure sensor can be reduced.

Since the upper silicon wafer 12 and the lower silicon wafer 17 can be anodically bonded via the glass film 11, the bonding can be performed at a temperature lower than the melting point of aluminum forming the electrodes 9 and the like. Therefore, after forming transistors, resistors, circuit elements such as aluminum wiring, and wiring on the lower silicon wafer 17, the upper silicon wafer 12 having been subjected to the anisotropic etching process can be joined, and The upper silicon wafer 12 and the lower silicon wafer 17 can be positioned with sufficient accuracy through the through holes 15 provided. Further, circuit elements are provided on the lower silicon wafer 17,
Since the wiring can be formed, the area of the entire pressure sensor can be reduced and the size can be reduced as compared with other conventional technologies.

A plurality of unit sensors 18 are formed in a row on the lower silicon wafer 17, and a long groove-shaped through hole 15 is formed on the upper silicon wafer 12 along the row of the unit sensors 18. A common through hole 15 can be used for a large number of pressure sensors arranged in a line.

Next, FIGS. 12 to 16 show a second embodiment. The feature of this embodiment is that a lower taper portion is formed on the outer peripheral side of the upper silicon substrate in addition to the upper taper portion. It is in. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

Reference numeral 21 denotes an upper silicon substrate made of a silicon single crystal provided on the surface side of the frame-shaped protrusion 6, and the upper silicon substrate 21 is provided on the surface of the frame-shaped protrusion 6 via a glass film 22 described later. Anodically bonded to the polycrystalline film 7. The upper silicon substrate 21 defines a pressure chamber A that closes the diaphragm 5A and applies a reference pressure. On the left and right ends of the outer periphery of the upper silicon substrate 21, a lower tapered portion 21A gradually expanding from the back surface to the front surface, and a lower tapered portion 21A positioned on the front surface side of the lower tapered portion 21A. Upper tapered portion 2 gradually reduced from the back side to the front side
1B, and the outer peripheral side of the upper silicon substrate 21 is
Both the front surface side and the back surface side are inclined in a chamfered shape by the lower taper portion 21A and the upper taper portion 21B.

As a result, the cross section of the upper silicon substrate 21 has a substantially hexagonal shape that expands from the front side to the back side, and its ends are formed by the lower tapered portion 21A and the upper tapered portion 2A.
1B, it is inclined at an inclination angle θ2 of, for example, about 109.48 degrees.

Reference numeral 22 denotes a glass film formed between the back side of the upper silicon substrate 21 and the polycrystalline film 7 on the surface of the frame-shaped protrusion 6. The glass film 22 is made of the glass according to the first embodiment. Like the film 11, it is formed on the back surface of the upper silicon substrate 21 by means such as sputtering, and is joined to the polycrystalline film 7 on the lower silicon substrate 1 by anodic bonding.

The pressure sensor according to the present embodiment has the above-described configuration.
This will be described with reference to FIGS.

First, an upper silicon wafer 23 made of single crystal silicon having a {100} plane on the front and back surfaces is formed, and an oxide film 24 is formed on the front surface 23A and the back surface 23B of the upper silicon wafer 23 as shown in FIG. , 25 are formed. Next, the oxide films 24 on the front surface 23A and the back surface 23B,
An etching process is performed in a state where a photoresist (not shown) is applied on the surface 25 to form openings 24A and 25A having a substantially rectangular long groove shape at positions corresponding to through holes 26 described later.

Next, as shown in FIG.
5 as a mask, surface 23A of upper silicon wafer 23
Anisotropic etching is performed from the side and the back surface 23B side to form a through hole 26 whose inner wall surface is along the {111} plane. As a result, through holes 26 are formed in the upper silicon wafer 23 from the middle position in the thickness direction toward the front surface 23A and the back surface 23B, respectively, and the inner wall surface of the through hole 26 has the front surface 23A from the back surface 23B side. A lower inclined surface 26A whose opening area is gradually reduced toward the side, and an upper inclined surface 26B whose opening area is gradually expanded from the back surface side to the front surface side continuously from the lower inclined surface 26A. Can be provided.

As a result, an upper silicon substrate portion 27 having a hexagonal cross section is formed between two adjacent through holes 26, and an end surface end portion (left and right end portions) of the upper silicon substrate portion 27 is formed. ), The lower inclined surface 26A and the upper inclined surface 26B intersect with each other, and the angle of the end section is set to, for example, an inclination angle θ2 of about 109.48 degrees.

Next, after removing the oxide films 24 and 25 from the upper silicon wafer 23, a borosilicate glass containing sodium is formed in a thin film on the back surface 23B of the upper silicon wafer 23 by means such as sputtering. , Glass film 2
Form 2

As shown in FIG. 16, the upper silicon substrate portion 27 of the upper silicon wafer 23 is sandwiched between the frame-shaped projections 6 of the lower silicon wafer 17 with the glass film 22 interposed therebetween.
Is placed. In this state, the upper silicon wafer 23 is anodically bonded to the lower silicon wafer 17, so that the polycrystalline film 7 on the frame-shaped protrusion 6 has the glass film 22 formed on the back surface 23B of the upper silicon wafer 23. Joined.

Thereafter, on the back surface of the lower silicon wafer 17, anisotropic etching is performed at a position corresponding to the frame-shaped protrusion 6, thereby forming the pressure receiving groove 4. As a result, a diaphragm portion 5A surrounded by the frame-shaped protrusion 6 is formed on the front surface side of the lower silicon wafer 17.

Finally, similarly to the first embodiment, the lower silicon wafer 17 is cut together with the upper silicon wafer 12, and cut into each pressure receiving groove 4. As a result, FIG.
And the pressure sensor shown in FIG. 13 can be processed.

Thus, in the present embodiment, the same operation and effect as in the first embodiment can be obtained. However, in the present embodiment, on the outer peripheral side of the upper silicon substrate 21, a lower tapered portion 21A gradually expanding from the back surface side to the front surface side, and the lower tapered portion 21A is located on the surface side of the lower tapered portion 21A. Since the upper tapered portion 21B that gradually reduces from the back surface side to the front surface side is provided, the lower tapered portion 21A and the upper tapered portion 21B intersect on the outer peripheral side of the upper silicon substrate 21, and the angle of the end section ( The inclination angle θ2) can be made obtuse. Therefore, as compared with the case where only the upper tapered portion 10A is provided as in the upper silicon substrate 10 according to the first embodiment, the angle of the cross section at the end of the upper silicon substrate 21 can be increased, and Strength can be increased.

The upper silicon wafer 23 has the surface 2
Since the anisotropic etching process is performed from both sides of 3A and the back surface 23B, the inner wall surface of the through hole 26 has a lower tapered portion 2
The lower inclined surface 26A serving as 1A and the upper inclined surface 26B serving as the upper tapered portion 21B can be easily formed.

Further, the surface 2 of the upper silicon wafer 23
Since etching can be performed from both sides of the 3A side and the back surface 23B side, the etching time can be reduced to about half compared with the case where etching is performed from one side, and productivity can be improved.

FIGS. 17 to 19 show a third embodiment. The feature of this embodiment is that a plurality of unit sensors are formed in a lower silicon wafer in a grid pattern, and a through hole is formed. That is, they are arranged in a mesh shape corresponding to each unit sensor. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

Reference numeral 31 denotes an upper silicon substrate made of a silicon single crystal provided on the surface side of the frame-shaped protrusion 6. The upper silicon substrate 31 has front ends extending leftward and rightward at both ends extending forward and backward. It has portions 32, 32, and has a substantially "D" shape as a whole. Also, the upper silicon substrate 3
1 is anodically bonded to a polycrystalline film 7 on the surface of the frame-shaped protrusion 6 via a glass film 33 described later, and a diaphragm 5A
To define a pressure chamber A for providing a reference pressure.

The lower and right taper portions 31A which gradually expand from the back side to the front side are formed on the left and right ends of the outer periphery of the upper silicon substrate 31, each of which has a substantially "U" shape. An upper taper portion 31B is provided on the front surface side of the side taper portion 31A and gradually reduced from the back surface side to the front surface side.
Both the front surface side and the back surface side are inclined in a chamfered shape by 1A and the upper tapered portion 31B. Thereby, the cross section of the upper silicon substrate 31 has a substantially hexagonal shape that expands from the front surface side to the rear surface side.

Reference numeral 33 denotes a glass film formed between the back side of the upper silicon substrate 31 and the polycrystalline film 7 on the surface of the frame-shaped protrusion 6, and the glass film 33 is made of the glass according to the first embodiment. Like the film 11, it is formed on the back surface of the upper silicon substrate 31 by means such as sputtering, and is joined to the polycrystalline film 7 on the lower silicon substrate 1 by anodic bonding.

The pressure sensor according to the present embodiment has the above-described configuration.
This will be described with reference to FIG.

The upper silicon wafer 34 made of single-crystal silicon is anisotropically etched from the front and back surfaces of the upper silicon wafer 34 in the same manner as the through holes 26 according to the second embodiment, to thereby increase the thickness. A through-hole 35 is formed which is expanded from the middle position in the vertical direction toward the front surface and the back surface. At this time, the unit sensors 36 indicated by two-dot chain lines are arranged in a lattice pattern on the lower silicon wafer 17, and the through holes 35 correspond to the electrode 9 of the unit sensor 36 (pressure sensor) corresponding to each unit sensor 36. Provided only on the periphery and arranged in a substantially mesh shape. Then, after forming the glass film 33 on the back surface side of the upper silicon wafer 34, the upper silicon wafer 34 is anodically bonded to the frame-shaped protrusion 6 of the lower silicon wafer 17.

After forming the pressure receiving grooves 4 in the lower silicon wafer 17 in the same manner as in the first embodiment, the lower silicon wafer 17 is cut together with the upper silicon wafer 34 by surrounding each pressure receiving groove 4. Then, each unit sensor 36 shown by a two-dot chain line in FIG. 19 is separated. Thereby, the pressure sensor shown in FIGS. 17 and 18 can be processed.

Thus, in the present embodiment, the same operation and effect as those of the first embodiment can be obtained. However, in the present embodiment, since the through holes 35 are arranged in a mesh shape in the upper silicon wafer 34, when forming the long groove-like through holes 15 and 26 as in the first and second embodiments, In comparison, the strength of the upper silicon wafer 34 can be increased, and the upper silicon wafer 34 can be prevented from being damaged at the time of processing such as anisotropic etching at the time of bonding, cutting, and the like. And increase the production yield.

In each of the above embodiments, the lower silicon substrate is formed of single crystal silicon. However, the lower silicon substrate may be formed of, for example, an SOI (Silicon on Insulator) substrate.

[0076]

As described above in detail, according to the first aspect of the present invention, a glass film is provided between the frame-shaped protrusion of the lower silicon substrate and the upper silicon substrate, and these are joined by anodic bonding. can do. For this reason, since the glass film flows at the time of anodic bonding, even if there is slight unevenness on the bonding surface, the frame-shaped protrusion and the upper silicon substrate can be bonded without a gap, and the pressure chamber is securely sealed. Can be. As a result, the pressure in the pressure chamber can be maintained at a constant value, and fluctuations in the detected value of the pressure can be suppressed to improve reliability.

According to the second aspect of the present invention, the upper silicon substrate is provided with an upper tapered portion which gradually expands from the front surface to the rear surface on the outer peripheral side, and the upper tapered portion is formed on the front surface of the lower silicon substrate. Since the electrode connected to the deflection detecting element is provided around the portion, the bonding tool is formed by the upper tapered portion of the upper silicon substrate even when the electrode is connected to an external wiring or the like by bonding. Contact and interference with the upper silicon substrate can be prevented, the electrodes can be arranged closer to the upper silicon substrate, and the size of the pressure sensor can be reduced.

According to the third aspect of the present invention, on the outer peripheral side of the upper silicon substrate, a lower tapered portion gradually expanding from the back surface side to the front surface side, and a lower tapered portion located on the front surface side. Since the upper tapered portion that gradually reduces from the back surface side to the front surface side is provided, the upper tapered portion and the lower tapered portion are crossed on the outer peripheral side of the upper silicon substrate, and the angle of the end section is made obtuse. Can be. Therefore, as compared with the case where only the upper tapered portion is provided on the upper silicon substrate, the angle of the cross section at the end of the upper silicon substrate can be increased, and the strength of the end can be increased.

According to the method of manufacturing a pressure sensor according to the fourth aspect of the present invention, the lower silicon wafer is provided with the frame-shaped protrusion and the deflection detecting element, and the upper silicon wafer is provided with the
A through-hole having an inclined end surface is provided by using anisotropic etching, and the lower silicon wafer is joined to the lower silicon wafer via a glass film at the frame-shaped protrusion, and a pressure receiving recess is formed in the lower silicon wafer. After the grooves are formed, the pressure receiving groove is surrounded and cut together with the lower silicon wafer and the upper silicon wafer. Therefore, the frame-shaped protrusion of the lower silicon wafer and the upper silicon wafer are interposed via a glass film. Anodic bonding. Then, after forming the pressure-receiving groove in the lower silicon wafer, the pressure-receiving groove surrounding the pressure-receiving groove is cut together with the lower silicon wafer and the upper silicon wafer to form a pressure sensor in which the upper silicon substrate is joined to the lower silicon substrate. can do.

Further, since the upper silicon wafer and the lower silicon wafer can be anodically bonded via the glass film, the bonding can be performed at a temperature lower than the melting point of aluminum forming the electrodes and the like. For this reason, after forming transistors, resistors, circuit elements such as aluminum wiring, and wiring on the lower silicon wafer, the upper silicon wafer that has been subjected to the anisotropic etching process can be joined, and the through-hole provided on the upper silicon wafer can be formed. The upper silicon wafer and the lower silicon wafer can be aligned with sufficient accuracy through the holes. Further, since circuit elements and wiring can be formed on the lower silicon wafer, the area of the entire pressure sensor can be reduced and the size can be reduced as compared with other conventional techniques.

According to the fifth aspect of the present invention, an electrode connected to the deflection detecting element is provided on the surface side of the lower silicon wafer,
Since the through hole was formed by performing anisotropic etching from the surface side of the upper silicon wafer at a position where the electrode was exposed when the upper silicon wafer was joined to the frame-shaped protrusion of the lower silicon wafer, The inner wall surface of the through-hole is formed to be inclined, and the through-hole can be gradually expanded and opened from the rear surface side to the front surface side of the upper silicon wafer. Therefore, after the pressure sensor is formed by cutting the lower silicon wafer or the like, the outer peripheral side of the upper silicon substrate can be inclined in a chamfered shape by the inclined through hole. As a result, even when the electrode is connected to an external wiring or the like by bonding, it is possible to prevent the bonding tool from contacting and interfering with the upper silicon substrate.

According to the invention of claim 6, an electrode connected to the deflection detecting element is provided on the surface side of the lower silicon wafer,
A structure in which through holes are formed by performing anisotropic etching from the front side and the back side of the upper silicon wafer at positions where electrodes are exposed when the upper silicon wafer is joined to the frame-shaped projection of the lower silicon wafer. Therefore, on the inner wall surface of the through-hole, the lower inclined surface gradually reduced from the back surface side to the front surface side, and gradually expanded from the back surface side to the front surface side continuously with the lower inclined surface. An open upper inclined surface is formed, and these two inclined surfaces can intersect on the inner wall surface of the through hole. For this reason, the angle of the cross section of the end of the inner wall surface can be made obtuse, and the end of the inner wall surface of the through hole can be compared with the case where the through hole is formed only from the surface side using anisotropic etching. The angle of the cross section can be increased,
The strength of the end can be increased.

Further, since the etching can be performed from both the front side and the rear side of the upper silicon wafer, the etching time can be reduced to about half as compared with the case where the etching is performed from one side, and the productivity is improved. can do.

According to the seventh aspect of the present invention, a plurality of unit sensors are formed in a row on the lower silicon wafer.
Since the through holes are formed in a long groove shape along the row of the unit sensors, a common through hole can be used for a plurality of unit sensors (pressure sensors) arranged in a row.

According to the eighth aspect of the present invention, a plurality of unit sensors are formed in a lattice pattern on the lower silicon wafer, and the through holes are formed in a mesh pattern corresponding to each unit sensor. Since the through-holes are arranged in a mesh shape corresponding to each unit sensor, each through-hole can be made small, and the strength of the upper silicon wafer at the time of processing, bonding and the like can be increased.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a pressure sensor in FIG.

FIG. 3 is a cross-sectional view of the pressure sensor as viewed from a direction indicated by arrows III-III in FIG.

FIG. 4 is a plan view showing an upper silicon wafer according to the first embodiment.

FIG. 5 is a cross-sectional view of the upper silicon wafer as viewed from a direction indicated by arrows VV in FIG. 4;

FIG. 6 is a plan view showing a state where an oxide film is formed on an upper silicon wafer.

FIG. 7 is an enlarged cross-sectional view of the upper silicon wafer viewed from the direction of arrows VII-VII in FIG.

FIG. 8 is an enlarged sectional view showing a state in which a through hole is formed in the upper silicon wafer.

FIG. 9 is an enlarged sectional view showing a state in which an upper silicon wafer is joined to a lower silicon wafer.

FIG. 10 is a plan view showing a state where an upper silicon wafer is joined to a lower silicon wafer.

11 is an enlarged cross-sectional view of a part of the lower silicon wafer and a part of the upper silicon wafer, which is enlarged from a direction indicated by an arrow XI-XI in FIG.

FIG. 12 is a sectional view showing a pressure sensor according to a second embodiment.

FIG. 13 is a plan view showing the pressure sensor in FIG.

FIG. 14 is an enlarged sectional view showing a state in which an oxide film is formed on an upper silicon wafer according to the second embodiment.

FIG. 15 is an enlarged sectional view showing a state in which a through hole is formed in an upper silicon wafer.

FIG. 16 is an enlarged sectional view showing a state in which an upper silicon wafer is joined to a lower silicon wafer.

FIG. 17 is a sectional view showing a pressure sensor according to a third embodiment.

18 is a plan view showing the pressure sensor in FIG.

FIG. 19 is a plan view showing a state in which an upper silicon wafer is joined to a lower silicon wafer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lower silicon substrate 4 Pressure receiving groove 5 Thin part 5A Diaphragm 6 Frame-shaped protrusion 7 Polycrystalline film 8 Piezoresistive element (bending detection element) 9 Electrode 10, 21, 31 Upper silicon substrate 11, 22, 33 Glass film 10A , 21B, 31B Upper taper portion 12, 23, 34 Upper silicon wafer 15, 26, 35 Through hole 17 Lower silicon wafer 18, 36 Unit sensor 21A, 31A Lower taper portion

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F055 AA40 BB05 CC02 DD05 EE14 FF43 GG01 4M112 AA01 BA01 CA01 CA03 CA04 CA05 CA08 CA11 CA12 CA13 EA03 EA04 EA06 EA11 EA13 FA01

Claims (8)

[Claims] 1. A lower silicon substrate made of a silicon material, a thin portion provided on a front surface side of the lower silicon substrate by forming a pressure receiving groove on a back surface side of the lower silicon substrate, and the thin portion formed into a frame shape. A frame-shaped projection provided on the surface side of the thin-walled portion and having the inside surrounded by a diaphragm, and a pressure chamber disposed on the frame-shaped projection and closing the diaphragm to apply a reference pressure. An upper silicon substrate made of a silicon material that defines the glass substrate, a glass film provided between the upper silicon substrate and the frame-shaped protrusion to join the upper silicon substrate to the frame-shaped protrusion, and a glass film positioned on the diaphragm. A pressure sensor comprising a deflection detecting element provided in the thin portion and configured to detect a deflection when the diaphragm portion is deformed by a pressure difference between the pressure receiving groove and the pressure chamber. 2. An upper tapered portion which gradually expands from a front surface side to a rear surface side is provided on an outer peripheral side of the upper silicon substrate, and is located around the upper tapered portion on a front side of the lower silicon substrate. The pressure sensor according to claim 1, wherein an electrode connected to the deflection detecting element is provided. 3. A lower tapered portion that gradually expands from a back surface to a front surface on an outer peripheral side of the upper silicon substrate;
An upper taper portion which is located on the front surface side of the lower taper portion and gradually reduces from the back surface side to the front surface side, and the lower taper portion and the upper taper portion are provided on the front surface side of the lower silicon substrate. 2. The pressure sensor according to claim 1, wherein the pressure sensor is configured to be provided at a periphery and connected to the deflection detecting element. 4. A lower silicon wafer made of a silicon material includes a frame-shaped projection on the surface side of the lower silicon wafer and a deflection detection element positioned inside the frame-shaped projection to detect deflection. The upper silicon wafer made of a silicon material is provided with a through hole having an inclined end surface by using an anisotropic etching process. The frame-shaped projection of the lower silicon wafer is provided with a glass film through the upper silicon wafer. A back face side is joined, a pressure receiving groove is provided on a back side of the lower silicon wafer at a position corresponding to the frame-shaped projection, and a diaphragm surrounded by the frame-shaped projection on the front side of the lower silicon wafer. A method for manufacturing a pressure sensor, comprising forming a portion and cutting the pressure receiving groove along with the lower silicon wafer and the upper silicon wafer. 5. An electrode connected to the deflection detecting element is provided on a surface side of the lower silicon wafer, and the through hole is
5. A structure in which anisotropic etching is performed from a surface side of the upper silicon wafer at a position where the electrodes are exposed when the upper silicon wafer is joined to the frame-shaped projection of the lower silicon wafer. 3. The method for manufacturing a pressure sensor according to claim 1. 6. An electrode connected to the deflection detecting element is provided on a surface side of the lower silicon wafer, and the through hole is
When the upper silicon wafer is joined to the frame-shaped projection of the lower silicon wafer, the electrode is exposed by performing anisotropic etching from the front side and the back side of the upper silicon wafer. The method for manufacturing a pressure sensor according to claim 4. 7. The lower silicon wafer is formed with a plurality of unit sensors arranged in a row, and the through-holes are formed in a long groove shape along the rows of the unit sensors. 7. The method for manufacturing a pressure sensor according to 6. 8. The lower silicon wafer is formed by arranging a plurality of unit sensors in a grid pattern, and the through holes are formed in a mesh pattern corresponding to each unit sensor. 7. The method for manufacturing a pressure sensor according to 5 or 6.