JPH10229203A - Semiconductor dynamic quantity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor dynamic quantity sensor which can improve the reliability of an electrical connection between electrode sections and bonding pad sections and, at the same time, can simplify the manufacturing process of the sensor. SOLUTION: A gage resistor (diffused-type strain gauge) 4 is formed by diffusion on the inside of the diaphragm section (2) (strain-sensitive section) of an n- or p-type silicon substrate (semiconductor substrate) 3. A lead section (diffused layer) 5 is formed in an extended state by diffusing a p- or n-type semiconductor material, so that the section 5 comes into contact with the resistor 4. A thermally oxidized film (first protective film) 7 and a nitride film (second protective layer) 8 are successively formed on the surface of the substrate 3 in a laminated state. Contact holes 14 are formed through the nitride film 8 and thermally oxidized film 7, so that the holes 14 reach the lead section 5 (junctions 9). Bonding pads 16 are formed in the holes 14 and electrically connected top the lead section 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor dynamic quantity sensor in which a plurality of diffusion type strain gauge resistors are assembled in a bridge circuit, for example, and can be used as various sensors for pressure detection, acceleration detection, and the like.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 59-25393 discloses a pressure sensor using a semiconductor dynamic quantity sensor. This type of pressure sensor uses a diffusion type strain gauge resistance (hereinafter referred to as a gauge) by introducing pressure. In this method, a change in resistance due to the piezoresistive effect of the gauge resistance is converted into an electric signal of a bridge circuit to detect a pressure value.

FIGS. 3 and 4 show the structure of a conventional pressure sensor. The pressure sensor comprises a fixed portion 1 having a thick peripheral portion and a thin wall integrally formed from the fixed portion. In the diaphragm portion 2 of the n-type silicon substrate (semiconductor substrate) 3 having the shape of the diaphragm portion 2 formed therein, four gauge resistors 4 (4a to 4a) having a piezoresistive effect formed of a p-type region are provided.
4d) is formed, and each of the gauge resistors 4a to 4d is connected by a lead portion 5 as shown in FIG. 4, and each of the gauge resistors 4 is formed in a bridge circuit 6.

In the pressure sensor, the surface of the silicon substrate 3 is covered with a thermal oxide film (first protective film) 7 and a silicon nitride film (second protective film) 8 made of silicon nitride or the like. In each of the protective films 7 and 8, a contact hole 10 is formed at a portion corresponding to a predetermined portion of each of the joining portions 9a to 9d of the lead portions 5, and a material such as aluminum is formed at the portion where the contact hole 10 is formed. The electrode portion 11 is formed by vapor deposition, sputtering, or the like, and the bonding portion 12 is formed by extending the electrode portion 11 outward.

In the pressure sensor having such a configuration, a power supply voltage Vcc is applied through a bonding wire 13 connected by wire bonding to a bonding pad 12 serving as a bonding portion 9a, 9b of the bridge circuit 6 as shown in FIG. The strain caused by the pressure difference between the front and back of the diaphragm portion 2 is changed according to the change of each gauge resistor 4 in the bridge circuit
The output voltage Vo is taken out from the bonding pad 12 serving as the joints 9c and 9d through the bonding wire 13.

In the above-described pressure sensor, the thermal oxide film 7 and the nitride film 8 are formed on the surface of the silicon substrate 3, but the thermal oxide film 7 formed on the entire surface is formed in order to form the gauge resistance 4. A diffusion window is formed by etching at a location where the gauge resistor 4 is to be provided, and after diffusion using a p-type semiconductor impurity material such as boron, oxidation and etching are repeated again to lead (diffusion layer) 5. And then
A thermal oxide film 7 and a nitride film 8 are formed on the diffusion layer. As a method for forming the contact hole 10, a region excluding the portion where the contact hole 10 is formed on the nitride film 8 is covered with a resist film, and the nitride film 8 is etched by a plasma etching method. The contact hole 10 is obtained by removing the thermal oxide film 7 by etching the above-mentioned portion.

[0007]

When the contact hole 10 is formed by the above-described method, the thermal oxide film 7 is etched with the above-mentioned hydrofluoric acid mixed solution, and as shown in FIG. Since the nitride film 8 is hardly etched by the hydrofluoric acid mixed solution, the nitride film 8 is etched outward from the etched portion of the nitride film 8 by the thickness of the thermal oxide film 7 to the outside. The nitride film 8 has an eave shape with respect to the thermal oxide film 7, and in this state, at each of the joints 9a to 9d, an electrode portion 11 and a bonding pad 12 for electrically connecting to each of the joints 9a to 9d are deposited. Otherwise, if formed by a sputtering method or the like, disconnection occurs between the electrode portion 11 and the bonding pad 12 due to the nitride film 8 having an eaves shape. There is a problem that detection is said that can not be the supply and the output voltage Vo of the pressure Vcc.

One of the methods for solving the above problems is as follows. After a thermal oxide film 7 and a nitride film 8 are sequentially formed on the silicon substrate 3, a resist film is formed at a portion (a contact hole forming portion) except a predetermined portion on the nitride film 8, and the nitride film is formed by plasma etching. 8 to form a contact hole,
After that, the resist film is removed. The inside of the contact hole of the nitride film 8 and the exposed portion of the thermal oxide film 7 are so formed that the outer shape of the contact hole formed in the thermal oxide film 7 is smaller than the outer shape of the contact hole formed in the nitride film 8. A resist film is formed on the nitride film 8 so that the resist film reaches a part thereof, and thereafter, the thermal oxide film 7 exposed to the outside is removed by etching using a hydrofluoric acid mixed solution or the like. A contact hole 10 extending from the nitride film 8 to each of the junctions 9a to 9d as shown by 3 is formed.

By adopting such a forming method, it is possible to prevent the nitride film 8 from becoming an eaves shape with respect to the thermal oxide film 7, so that the electrode portion 11 and the bonding pad 12 are formed by vapor deposition or sputtering. Even in this case, disconnection between the electrode portion 11 and the bonding pad 12 can be prevented. However, such a method of forming a contact hole includes a first resist film forming step for forming a contact hole in the nitride film 8 and a second resist film for forming a contact hole in the thermal oxide film 7. Since the formation of the resist film in two steps, ie, the formation step, is required, the manufacturing process becomes complicated and the manufacturing cost increases, so that it is not the best pressure sensor forming means. Therefore, the present invention focuses on the above problems, and provides a semiconductor dynamic quantity sensor capable of improving reliability of electrical connection between the electrode portion and the bonding pad portion and simplifying a manufacturing process. is there.

[0010]

According to the present invention, there is provided a p-type or n-type diffusion strain gauge formed by diffusion inside a strain-sensitive portion of an n-type or p-type semiconductor substrate. A p-type or n-type diffusion layer extended to be in contact with the strain gauge, a protection layer formed on the surface of the semiconductor substrate, and formed to reach the diffusion layer from the protection layer. And a bonding pad formed in the contact hole and electrically connected to the diffusion layer.

Also, a p-type or n-type diffusion strain gauge formed by diffusion inside a strain-sensitive portion of an n-type or p-type semiconductor substrate, and a p-type extension formed so as to be in contact with the strain gauge Or an n-type diffusion layer; first and second protective layers sequentially formed on the surface of the semiconductor substrate;
A contact hole formed from the second protective layer to reach the diffusion layer; and a bonding pad formed in the contact hole and electrically connected to the diffusion layer.

Further, the outer shape of the contact hole formed in the first protective layer is formed larger than the outer shape of the contact hole formed in the second protective layer.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pressure sensor (semiconductor dynamic quantity sensor) according to the present invention is a p-type silicon substrate (semiconductor substrate) 3 formed by diffusion inside a diaphragm portion 2 (strain-sensitive portion) of an n-type or p-type silicon substrate. A type or n-type gauge resistor (diffusion type strain gauge) 4, a lead portion (diffusion layer) 5 extended to be in contact with the gauge resistance 4 and formed by diffusion of a p-type or n-type semiconductor material, A thermal oxide film (first protective film) 7 and a nitride film (second protective layer) 8 sequentially formed on the surface of the silicon substrate 3 and a lead portion 5 from the nitride film 8 via the thermal oxide film 7. The contact hole 14 is formed so as to reach the (joining portion 9), and the bonding pad 16 is formed in the contact hole 14 and electrically connected to the lead portion 5. Therefore, as compared with the conventional pressure sensor in which the bonding pad portion is drawn out from the electrode portion, the lead portion 5 is directly connected to the pressure sensor.
Since the bonding pad portion is formed, the reliability of electrical connection between the bonding pad portion and an external circuit can be improved.

The outer shape of the contact hole formed in the thermal oxide film 7 is formed to be larger than the outer shape of the contact hole formed in the nitride film 8. Conventionally, when forming the contact holes in the ride film 8, two resist film forming steps were necessary in order to prevent disconnection between the electrode portion and the bonding pad portion. As a result, the manufacturing process can be simplified.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor dynamic quantity sensor according to the present invention will be described with reference to the pressure sensors shown in FIGS. 1, 2 and 4 as in the conventional example. The same reference numerals are given and the detailed description is omitted.

FIG. 1 is a sectional view of a principal part showing a pressure sensor of the present invention, FIG. 2 is an enlarged sectional view of a principal part of the pressure sensor, and FIG. 4 is a circuit diagram showing a bridge circuit of the pressure sensor.

In the drawing, reference numeral 3 denotes an n-type semiconductor substrate which forms a fixed portion 1 having a thick peripheral portion and a thin diaphragm portion (strain-sensitive portion) 2 integrally formed from the fixed portion. The silicon substrate 4 is formed in the diaphragm portion 2 and the gauge resistors (strain gauges) 4 (4a to 4d) having a piezoresistive effect are formed in the diaphragm portion 2 and the gauge resistors 4a to 4d are formed in the diaphragm portion 2.
A lead portion (diffusion layer) made of a low-resistance body for connecting between 4d, 6 is a bridge circuit composed of gauge resistors 4a to 4d, and 7 is a silicon substrate 3 formed by a thermal oxidation furnace.
A thermal oxide film (first protective film) 8 formed on the surface protects the thermal oxide film 5 from external contamination such as moisture and sodium, and a silicon nitride film (second protective film) made of silicon nitride or the like. And 9 (9a to 9d) are bonding portions (bonding portions of the diffusion layer), which are portions where the respective lead portions 5 are connected to each other and form contact holes described later in detail, and 14 are
A contact hole 15 is formed in a portion of each of the protective films 7 and 8 corresponding to a formation portion of each of the joints 9a to 9d. A conductive material such as aluminum is formed in a formation portion of the contact hole 14 by vapor deposition or sputtering. Electrode part, 16
Are the respective joints 9a to 9b to be the bottom of the contact hole 14.
The bonding pad 13 formed on the electrode 9d together with the electrode 15 is a bonding wire connected to each bonding pad 16 by wire bonding, and thus constitutes a pressure sensor.

In the pressure sensor having such a configuration, the power supply voltage Vcc is applied to the bonding pads 16 serving as the bonding portions 9a and 9b of the bridge circuit 6 through the bonding wires 13 connected by wire bonding, so that the front and rear surfaces of the diaphragm portion 2 are formed. The output voltage Vo is taken out from the bonding pad 16 serving as the joints 9c and 9d of the bridge circuit 6 to the outside via the bonding wire 13 in accordance with the change in each of the gauge resistors 4a to 4d.

Next, a method for manufacturing such a pressure sensor will be described.

First, an n-type silicon substrate 3, which is a semiconductor substrate, is formed into a thin diaphragm 2 by an appropriate method such as wet etching using an alkaline etching solution such as KOH while leaving the fixing portion 1, and thereafter, the silicon substrate 3 is formed. 3
Into a thermal oxidation furnace to form a thermal oxide film 7 on the front and back surfaces.

Next, in the diaphragm portion 2, the thermal oxide film 7 on the surface corresponding to the location where each of the gauge resistors 4a to 4d is formed is removed, and a p-type semiconductor material such as boron is used to diffuse the silicon oxide in the silicon substrate 3. Each gauge resistance 4a
To 4d, and a thermal oxide film 7 is formed again in the formation portions of the gauge resistors 4a to 4d. And each gauge resistance 4
In order to form the bridge circuits 6a to 4d as shown in FIG. 4, for example, the thermal oxide film 7 is removed from both ends of each of the gauge resistors 4a to 4d in a predetermined pattern, and boron having a higher concentration than the gauge resistors 4a to 4d. The respective lead portions 5 are formed by diffusion using a p-type semiconductor material such as, and the bridge circuit 6 is formed. In this case, each of the joints 9a to 9d formed by each of the lead portions 5 is formed in a joint shape such that a contact hole 14, an electrode 15, and a bonding pad 16, which will be described in detail later, can be formed. After forming the bridge circuit 6, a nitride film 8 made of silicon nitride is formed on the thermal oxide film 7 on the surface of the silicon substrate 3.

Next, in the diaphragm portion 2, the nitride film 8 corresponding to the formation portion of each of the joining portions 9a to 9d is removed by a plasma etching method or the like, and the thermal oxide film 7 in the portion where the nitride film 8 is removed is provided. Is removed using a hydrofluoric acid mixed solution or the like (the thermal oxide film 7 formed on the back surface side of the silicon substrate 3 is removed by removing the thermal oxide film 7), whereby the nitride film 8 is removed from the thermal oxide film 7 Each contact hole 14 that reaches each of the junctions 9a to 9d via is formed.

Next, at a position where the contact hole 14 is formed, an electrode portion 15 and a bonding pad 16 are formed using a conductive member made of aluminum or the like by vapor deposition or sputtering.

Next, the pressure sensor is completed by wire bonding the bonding pad 16 and an external circuit (not shown) using the bonding wire 13.

In such a pressure sensor, when the contact hole 14 is formed, the resist film is formed only when the contact hole is formed in the nitride film 8. However, the nitride film 8 is formed by such a forming method. Contact hole 1 reaching each of junctions 9a to 9d from above
2, the outer shape of the contact hole 14 formed in the nitride film 8 is smaller than the outer shape of the contact hole 14 formed in the thermal oxide film 7, as shown in FIG. Since the thermal oxide film 7 has an eaves shape, such a contact hole 14
When the electrode portion 15 and the bonding pad 16 are formed in each of the bonding portions 9a to 9b by a vapor deposition method, a sputtering method, or the like using a conductive material such as aluminum, a disconnection easily occurs between the electrode portion 15 and the bonding pad 16. This is as described above.

However, even in such a case, a bonding pad 16 electrically connected to each of the joints 9a to 9d is formed directly at the position where the contact hole 14 is formed. 13 can be wire-bonded, so that power supply to the bridge circuit 6 and output from the bridge circuit 6 are not interrupted.

Therefore, the pressure sensor of the present invention can improve the reliability of the electrical connection between the input and output of the bridge circuit 6 as compared with the conventional pressure sensor, and can also be used when the contact hole 14 is formed in the manufacturing process. Since the resist film forming step is only one step when forming a contact hole in the nitride film 8, the manufacturing process can be simplified,
Therefore, the manufacturing cost can be kept low.

In this embodiment, the silicon substrate 3 is n
Although the type, the gauge resistor 4 and the lead 5 have been described as p-type,
They may be reversed.

The present invention can be applied not only to a semiconductor physical quantity sensor having a bridge resistance composed of a plurality of gauge resistances but also to a semiconductor physical quantity sensor using a single gauge resistance. Further, the semiconductor dynamic quantity sensor of the present invention can be similarly used as other sensors such as an acceleration sensor in addition to the pressure sensor.

In the present embodiment, the method of forming the gauge resistor 4 and then forming the lead 5 made of a diffusion layer has been described. However, after forming the lead 5, the gauge resistor 4 is formed. The manufacturing process is not limited to the embodiment.

In this embodiment, the semiconductor dynamic quantity sensor in the case of forming two protective layers has been described as an example.
For example, even if the present invention is applied to a semiconductor physical quantity sensor in which a protective film of only a nitride film is formed on a silicon substrate,
This improves the reliability of the electrical connection between the electrode portion and the bonding pad portion.

[0032]

According to the present invention, there is provided a p-type or n-type diffusion type strain gauge formed by diffusion inside a strain-sensitive portion of an n-type or p-type semiconductor substrate, and an extension formed so as to be in contact with the strain gauge. A p-type or n-type diffusion layer to be formed, a protection layer formed on the surface of the semiconductor substrate, a contact hole formed to reach the diffusion layer from the protection layer, and formed in the contact hole, And a bonding pad electrically connected to the diffusion layer, and a p-type or n-type diffusion type formed by diffusion inside the strain-sensitive portion of the n-type or p-type semiconductor substrate. A strain gauge, and p extended to be in contact with the strain gauge.
And n-type diffusion layers, first and second protection layers sequentially formed on the surface of the semiconductor substrate, and formed so as to reach the diffusion layers from the first and second protection layers. Since it is composed of a contact hole and a bonding pad formed in the contact hole and electrically connected to the diffusion layer, the bonding pad portion and the external circuit are compared with a conventional pressure sensor. The reliability of the electrical connection can be improved.

Further, the outer shape of the contact hole formed in the first protective layer is formed to be larger than the outer shape of the contact hole formed in the second protective layer. In this case, since the resist film forming step for forming the contact hole is only one step, the manufacturing steps can be simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a semiconductor dynamic quantity sensor according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the embodiment.

FIG. 3 is a sectional view of a main part showing a conventional semiconductor dynamic quantity sensor.

FIG. 4 is a circuit diagram showing a circuit configuration of a semiconductor dynamic quantity sensor.

FIG. 5 is an enlarged sectional view of a main part showing a conventional semiconductor dynamic quantity sensor.

[Explanation of symbols]

 2 Diaphragm part (strain sensitive part) 3 Silicon substrate (semiconductor substrate) 4 Gauge resistance (strain gauge) 5 Lead part (diffusion layer) 7 Thermal oxide film (first protective film) 8 Nitride film (second protective film) ) 14 contact hole 15 electrode part 16 bonding pad

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Shimodori 1-1190-1 Fujibashi, Nagaoka City, Niigata Prefecture Japan R & D Center

Claims (3)

[Claims] 1. A p-type or n-type diffusion type strain gauge formed by diffusion inside a strain-sensitive portion of an n-type or p-type semiconductor substrate, and a p-type extended to be in contact with the strain gauge. Or an n-type diffusion layer, a protective layer formed on the surface of the semiconductor substrate, a contact hole formed to reach the diffusion layer from the protective layer, and the diffusion layer formed in the contact hole. And a bonding pad electrically connected to the semiconductor dynamic quantity sensor. 2. A p-type or n-type diffusion type strain gauge formed by diffusion inside a strain-sensitive portion of an n-type or p-type semiconductor substrate, and a p-type extended to be in contact with the strain gauge. Or an n-type diffusion layer; first and second protective layers sequentially formed on the surface of the semiconductor substrate;
A contact hole formed from the protective layer to the diffusion layer, and a bonding pad formed in the contact hole and electrically connected to the diffusion layer. Sensor. 3. The contact hole formed in the first protective layer is formed to be larger than the contact hole formed in the second protective layer. Item 3. A semiconductor dynamic quantity sensor according to item 2.