JPH0735768A - Capacitance-type sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a capacitance-type sensor with airtightness and sensitivity improved. CONSTITUTION:A sensing substrate 2 with a diaphragm 4 formed is made of a silicon wafer. A groove-like recess 11 is formed on a joint face of the sensing substrate 2, and a thin film of polyimide resin 16 is formed entirely on the joint face. The thin film is subjected to etching to have a part of the thin film left in the recess 11, and then the polyimide resin 16 is fused to form an insulation part 12. An extraction line 10 is formed on a surface of the insulation part 12 integrally with a movable electrode 5. A fixed substrate 3 with a recess 8 formed is made of another silicon wafer. A recess 13 is formed on a joint face of the fixed substrate 3 oppositely to the insulation part 12 of the sensing substrate 2, and another insulation part 14 is formed similarly to the insulation part 12. Then after the sensing substrate 2 and the fixed substrate 3 are joined with each other, polyimide resin is again made to reflow, fabricating a pressure sensor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type sensor and its manufacturing method. Specifically, a capacitance-type sensor used to detect a change in capacitance that occurs in proportion to the displacement of the detection unit and measure a physical quantity such as a vehicle acceleration or a gauge pressure of air, and the like. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, in a capacitance type pressure sensor 51 in which a detection substrate 52 made of silicon and a fixed substrate 53 made of silicon or glass are joined, as shown in FIG. , An extremely thin metal wiring (thickness of 0.05 μm or less) 55 connected to the movable electrode 54 is provided on the upper surface of the detection substrate 52, and the metal wiring 55 is provided between the detection substrate 52 and the fixed substrate 53 on the detection substrate 52. It was connected to the external lead electrode 56.

However, in such a structure, since the metal wiring 55 is provided between the flat bonding surfaces of the detection substrate 52 and the fixed substrate 53, as shown in FIG. Since the metal wiring 55 is sandwiched between the portions 53, the peripheral portions of the metal wiring 55 are not in close contact with each other, and a non-bonded portion proportional to the thickness is formed. Therefore, a gap 57 is formed on the joint surface, and the airtightness of the pressure sensor 51 is significantly deteriorated, and the stability and reliability of the pressure sensor 51 are impaired.

The metal wiring 55 is a thin insulating film 5 made of SiO ₂ provided on the surfaces of the detection substrate 52 and the fixed substrate 53.
Since it is provided so as to sandwich 8, 58, the detection substrate 52
Capacitance is generated between the metal wiring 55 and the metal wiring 55 or between the fixed substrate 53 and the metal wiring 55. This electrostatic capacitance acts as a parasitic capacitance on the pressure sensor 51, and significantly deteriorates the characteristics of the pressure sensor 51.

Further, as shown in FIG. 6A, a thin insulating film 58 made of SiO ₂ formed on the joint surface of the detection substrate 52.
Phosphorus or the like is injected into the inside of the to form the n ⁺ diffusion layer 63,
Further, there is a pressure sensor 61 having another structure in which a p ⁺ diffusion layer 62 made of boron or the like is formed inside and connected to the external lead electrode 56.

However, in such a structure, the movable substrate 54 is formed by forming the diffusion layers 62 and 63 on the detection substrate 52.
Since the external lead-out electrode 56 is connected to the detection substrate 52, the detection substrate 52 cannot be insulated, and a large capacitance is generated by the pn junction. The large capacitance due to the pn junction acts as a parasitic capacitance with respect to the pressure sensor 61, which also causes the characteristics of the pressure sensor 61 to be significantly deteriorated.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the drawbacks of the above-mentioned conventional examples, and an object thereof is to face the lower side of the metal wiring provided on the detection substrate or to face the metal wiring. By embedding a meltable insulator such as quartz glass, low melting point glass or polyimide resin also in the area of the fixed substrate, the above problem is solved.

[0008]

SUMMARY OF THE INVENTION An electrostatic capacitance type sensor of the present invention is an electrostatic capacitance sensor which joins two substrates and detects a physical quantity as a change in electrostatic capacitance between electrodes provided on both substrates. In a type sensor, a lead line for drawing the electrode provided on the substrate to the outside is provided on the bonding surface of one of the substrates, and a region where the lead line of one substrate is wired or the remaining one substrate Is characterized in that an insulating portion in which a meltable insulating material is embedded is formed in at least one of the areas facing the lead lines.

A first method of manufacturing a capacitance type sensor according to the present invention is a method of manufacturing a capacitance type sensor according to claim 1, wherein a concave portion is formed on a bonding surface of a substrate on which the insulating portion is formed. Forming a meltable insulating thin film on the entire bonding surface, removing the thin film other than the recess by etching, and further melting the thin film remaining in the recess to melt the insulator in the recess. And the insulating portion is formed.

A second method of manufacturing a capacitance type sensor according to the present invention is a method of manufacturing a capacitance type sensor according to claim 1, wherein the concave portion is formed on the bonding surface of the substrate on which the insulating portion is formed. Forming a thin film of a meltable insulator on the entire bonding surface, planarizing the thin film by a physical etching method such as plasma etching, and then removing the thin film other than the concave portion by etching. Thus, the insulating portion is formed by leaving the insulator in the recess.

A third method of manufacturing a capacitive sensor according to the present invention is the method of manufacturing a capacitive sensor according to claim 1, wherein the bonding surface of the substrate on which the insulating portion is formed is joined. To form a concave portion, to form a meltable thin film of an insulating material on the entire bonding surface, and polishing the thin film to remove the thin film other than the concave portion to leave the insulating material in the concave portion, It is characterized in that the insulating portion is formed.

[0012]

In the capacitance type sensor of the present invention, the insulator provided in the wiring region of the lead line or the region facing the lead line on the bonding surface of at least one of the substrates is once melted and then resolidified. By doing so, the lead wire can be embedded in the insulating portion, and the gap generated between the substrates at the lead wire portion can be filled with the insulator.
Therefore, for example, air or the like does not enter between the electrodes that are kept at a constant reference pressure such as a vacuum from the gap generated between the substrates, and the airtightness of the capacitance type sensor is enhanced, and the stability and reliability of the capacitance type sensor are improved. Can be improved.

Further, the lead line is insulated by the insulating portion from the wired substrate or the bonded substrate. Therefore, the parasitic capacitance generated between the leader line and both substrates can be made extremely small, so that the sensitivity of the capacitance type sensor can be prevented from lowering and the characteristics of the capacitance type sensor can be improved. .

According to the manufacturing method of the present invention, the capacitance type sensor having the above structure can be easily manufactured. Further, according to the first manufacturing method, the insulating portion can be obtained with a small number of manufacturing steps. According to the second manufacturing method, it is possible to obtain an insulating portion having a flat surface. Further, according to the third manufacturing method, it is possible to obtain an insulating portion having a flat surface with a small number of manufacturing steps.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a pressure sensor 1 according to an embodiment of the present invention.
Indicates. FIG. 1A is a sectional view of the pressure sensor 1, FIG.
FIG. 1B is a plan view showing a detection substrate 2 that constitutes the pressure sensor 1. The pressure sensor 1 is made of silicon in which a diaphragm portion 4 elastically supported on the entire surface of a rectangular frame is formed. A fixed substrate 3 made of silicon is overlaid on the detection substrate 2. An insulating film 7 made of SiO ₂ is formed on the peripheral portion of the fixed substrate 3 and is joined to the detection substrate 2 by a low temperature joining method or the like. In addition, the upper surface of the diaphragm portion 4 has A
The movable electrode 5 is formed by sputtering 1 or the like. An external extraction electrode 9 is provided on the upper surface of the detection substrate 2, and the movable electrode 5 is connected to the external extraction electrode 9 by an extraction line 10 provided integrally with the movable electrode 5.

A diaphragm portion 4 is provided inside the fixed substrate 3.
Has a recess 8 formed therein so that it can be freely displaced in its thickness direction. A fixed electrode 6 is formed in the recess 8 so as to face the movable electrode 5, and a fixed electrode 6 is formed between the movable electrode 5 and the fixed electrode 6. The capacitors are configured with a small gap in between.

FIG. 1C is a sectional view of the pressure sensor 1 which is partially broken at a portion corresponding to the line AA 'in FIG. 1B. A part of the bonding surface (broken line portion in FIG. 1B) of the detection substrate 2 is subjected to etching treatment as described later to form a groove-shaped recess 11, and the recess 11 can be melted by heating. For example, a polyimide resin 16 which is an insulator is embedded to form the insulating portion 12. Further, the polyimide resin 1 is formed in the groove-shaped recess 13 on the joint surface of the fixed substrate 3.
Another insulating portion 14 in which 6 is embedded is formed. The lead wire 10 is embedded in the polyimide resin 16 of the insulating portion 14, and is joined to the detection substrate 2 and the fixed substrate 3 without a gap.

2 (a), (b), (c), and (d) are partially cutaway sectional views showing a method for producing the insulating portion 14 of the pressure sensor 1. The method for producing the pressure sensor 1 will be described below with reference to FIG. I will describe. First, the fixed substrate 3 in which the depression 8 is formed by etching the silicon wafer is created. A recess 13 for forming the insulating portion 14 is formed on the bonding surface of the fixed substrate 3 by dry etching to a depth of about 1.5 mm (FIG. 2A). Next, the thin film 15 of the polyimide resin 16 is formed on the entire bonding surface of the fixed substrate 3 (FIG. 2).
(B)). After covering the thin film 15 with a photoresist, the thin film 15 other than the recess 13 is subjected to photoetching.
Is removed to leave a part of the thin film 15 in the recess 13 (see FIG. 2).
(C)). Next, the fixed substrate 3 is heat-treated at about 200 ° C. to melt a part of the remaining thin film 15 and cool it with its surface being substantially flat, and the polyimide resin 16 is embedded in the recess 13. The insulated portion 14 is formed (FIG. 2D).

On the other hand, another silicon wafer is subjected to an etching process to form the diaphragm portion 4 with high precision. Similarly to the insulating portion 14, the insulating portion 12 in which the polyimide resin 16 is embedded is formed on the detection substrate 2, and aluminum or the like is sputtered on the surface of the insulating portion 12 to form the lead wire 10 together with the movable electrode 5. Next, the insulating parts 12 and 14 are made to face each other, and the two substrates 2 and 3 are connected to each other by
A low temperature bonding of 200 ° C. is performed, and a heat treatment of about 200 ° C. or more is performed again to reflow the insulating parts 12 and 14, and FIG.
The pressure sensor 1 having the structure as shown in (c) is prepared.

When the pressure of the fluid such as air is introduced into the pressure sensor 1 thus produced, the diaphragm 4 is displaced by the introduced pressure. This displacement changes the magnitude of the electrostatic capacitance C of the capacitor included in the pressure sensor 1, and this change causes another external extraction electrode 9 connected to the external extraction electrode 9 and the fixed electrode 6 on the detection substrate 2 ( The magnitude of the introduced pressure can be known by detecting with a detection circuit or the like connected to (not shown).

In this pressure sensor 1, since the polyimide resin 16 forming a thick insulating layer is sandwiched between the lead wire 10 and the detection substrate 2, it is possible to surely insulate the both. No electrostatic capacitance is parasitic between the lead wire 10 and the detection substrate 2. Also, leader line 1
Since the polyimide resin 16 is also sandwiched between 0 and the fixed substrate 3, no electrostatic capacitance is parasitic between the lead wire 10 and the fixed substrate 3. Therefore, it is possible to prevent the sensitivity of the pressure sensor 1 from deteriorating and improve the sensor characteristics such as linearity.

Furthermore, after the two substrates 2 and 3 are joined together, heat treatment is performed to re-melt the polyimide resin 16, so that the lead wire 10 wired on the detection substrate 2 is surrounded by the polyimide resin 16. The further melted polyimide resin 16 will enter the gap between the substrates 2 and 3. When cooled in this state, the lead wire 10 does not create a gap between the two substrates 2 and 3, and moreover, the two substrates 2 and 3 can be closely joined, so that the reliability of the pressure sensor 1 is improved. You can also let it.

The insulating portion 14 can also be formed as shown in FIG. A recess 13 is formed in the fixed substrate 3 having the recess 8 by dry etching (FIG. 3).
(A)). Next, a silicon layer having a slower etching rate than the polyimide resin 16 is formed on the entire bonding surface of the fixed substrate 3, for example,
The SiN _x layer 21 is formed thicker than the depth of the recess 13,
From the top of the SiN _x layer 21, a thin film 15 of polyimide resin 16
Are formed (FIG. 3B). Next, the thin film 15 is covered with a photoresist film 22 so that the surface is flat (FIG. 3C), and the thin film 15 of the polyimide resin 16 is flattened by plasma etching (FIG. 3C).
(D)). Then, the thin film 15 of the polyimide resin 16 is dry-etched, the etching is stopped when the SiN _x layer 21 on the bonding surface is removed, and the thin film 15 of the polyimide resin 16 is left in the recess 13 to form the insulating portion 14. This can be done (FIG. 3 (e)). The insulating portion 12 can also be created in the same manner.

Further, another method of forming the insulating portion 14 is shown in FIG. A recess 13 is formed by dry etching on the fixed substrate 3 in which the recess 8 is formed (FIG. 4A), and a thin film 15 of polyimide resin 16 is formed on the entire bonding surface of the fixed substrate 3 in the recess 13.
Is formed to be thicker than the depth (FIG. 4B). After that, the thin film 15 may be polished to expose the bonding surface and leave the thin film 15 in the recess 13 to form the insulating portion 14. The insulating portion 12 can also be created in the same manner.

As described above, the insulating portion can be formed by various methods. Further, not only polyimide resin but also other meltable insulators such as quartz glass and low melting point glass can be used. Further, an insulator that can be melted at a temperature as low as possible is preferable, and if an insulator that can be melted at a temperature lower than the temperature at the time of low-temperature bonding is used, a pressure sensor without a gap can be obtained by performing heat treatment once. .

Needless to say, such a structure can be applied not only to a pressure sensor but also to a capacitance type acceleration sensor.

[0027]

According to the capacitance type sensor of the present invention,
By once melting and then re-solidifying the insulator provided in the wiring region of the lead line of the bonding surface of at least one of the substrates or in the region facing the lead line,
The lead wire can be embedded in the insulating portion, and a gap generated between the substrates at the lead wire portion can be filled with an insulator. Therefore, for example, air or the like does not enter between the electrodes that are kept at a constant reference pressure such as a vacuum from the gap generated between the substrates, and the airtightness of the capacitance type sensor is enhanced, and the stability and reliability of the capacitance type sensor are improved. Can be improved.

Further, the lead line is insulated by the insulating portion from the wired substrate or the bonded substrate. Therefore, the parasitic capacitance generated between the leader line and both substrates can be made extremely small, so that the sensitivity of the capacitance type sensor can be prevented from lowering and the characteristics of the capacitance type sensor can be improved. .

Further, according to the manufacturing method of the present invention, the capacitance type sensor having the above structure can be easily manufactured.

[Brief description of drawings]

1A is a cross-sectional view of a pressure sensor according to an embodiment of the present invention, FIG. 1B is a plan view showing a detection substrate of the same pressure sensor, and FIG. 1C is a sectional view of FIG. FIG. 6 is a cross-sectional view in which the pressure sensor of the above is partially broken at a position corresponding to the line A ′.

2 (a), (b), (c), and (d) are partially cutaway cross-sectional views showing a method of manufacturing a pressure sensor according to an embodiment of the present invention.

3 (a), (b), (c), (d), and (e) are partially cutaway sectional views showing a method of manufacturing a pressure sensor which is another embodiment of the present invention.

4 (a), (b) and (c) are partially cutaway sectional views showing a method of manufacturing a pressure sensor which is still another embodiment of the present invention.

5A is a plan view showing a detection substrate of a conventional pressure sensor, and FIG. 5B is a partially cutaway sectional view of the above pressure sensor.

FIG. 6A is a plan view showing a detection substrate of another conventional pressure sensor, and FIG. 6B is a partially cutaway sectional view of the above pressure sensor.

[Explanation of symbols]

 2 Detection Substrate 5 Movable Electrode 7 Insulating Film 10 Leading Wire 12 Insulating Part 15 Thin Film

Claims (4)

[Claims] 1. A capacitance type sensor which joins two substrates and detects a physical quantity as a change in capacitance between electrodes provided on the both substrates, wherein one of the substrates has a joining surface. A lead line for drawing out the electrode provided on the substrate to the outside is wired, and in at least one region of the region where the lead line of one substrate is wired or the region opposite to the lead line of the remaining one substrate. A capacitive sensor having an insulating portion in which a meltable insulating material is embedded. 2. The method for manufacturing the capacitance type sensor according to claim 1, wherein a recess is formed in a joint surface of a substrate on which the insulating portion is formed, and the whole insulator is meltable. Is formed, the thin film other than the recess is removed by etching, and the thin film remaining in the recess is melted to embed the insulator in the recess to form the insulating portion. Manufacturing method of capacitance type sensor. 3. The method for manufacturing the capacitance type sensor according to claim 1, wherein a recess is formed in a joint surface of a substrate forming the insulating portion, and the meltable insulator is formed on the entire joint surface. Thin film is formed, the thin film is planarized by a physical etching method such as plasma etching, and then the thin film other than the recess is removed by etching to leave the insulator in the recess, A method for manufacturing a capacitance type sensor, comprising forming a portion. 4. The method for manufacturing the capacitance type sensor according to claim 1, wherein a concave portion is formed on a joint surface of a substrate on which the insulating portion is formed, and the meltable insulator is formed on the entire joint surface. Forming a thin film, and polishing the thin film to remove the thin film other than the concave portion to leave the insulator in the concave portion to form the insulating portion. Manufacturing method.