JP3420808B2 - Manufacturing method of semiconductor pressure sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor pressure sensor having an SOI structure, in which a semiconductor strain detecting element is provided at a strain generating portion such as a diaphragm.

[0002]

2. Description of the Related Art Generally, semiconductor pressure sensors are widely used to measure the pressure of fluid. This is to detect the pressure by converting the displacement amount or strain amount of the diaphragm into an electric signal.

As such a semiconductor pressure sensor, there is a diffusion type pressure sensor as shown in FIG. 4, in which a diaphragm 7 to be a strain generating portion is formed by anisotropically etching an N type single crystal silicon substrate 1. Then, the diffusion resistance layer 8 is formed by doping the upper surface of the single crystal silicon to be the diaphragm 7 with boron as an impurity by diffusion.

Further, a silicon oxide film 2 is formed on the upper surface of the silicon substrate 1, and an aluminum electrode 4 is provided on the diffusion resistance layer 8 to form a P-type piezoresistive element, which is used as a strain detecting element. The diffusion type pressure sensor is used.

Generally, in the diffusion type pressure sensor, the silicon substrate 1 and the piezoresistive element are electrically insulated by PN separation. Therefore, to detect defective insulation (imperfections in the junction), a voltage is applied to the two pairs of electrically separated piezoresistors, the polarity is inverted, and the leakage current before and after that is detected to detect it. It is normal to do.

Further, in the case of the diffusion type pressure sensor, the anodic bonding is performed as illustrated in FIG. That is, the sensor chip having the diffusion resistance layer 8 formed on the upper surface of the diaphragm 7 of the silicon substrate 1 and further provided with the silicon oxide film 2 and the aluminum electrode 4 of the strain detecting element is placed on the glass pedestal 10.
The glass pedestal 10 is placed on a dummy wafer 11 placed on the electrode 9. Further, the dummy wafer 11 is placed on the aluminum electrode 4 of the sensor chip, and the electrode 9 is placed thereon. A DC voltage source 19 applies a voltage between the upper and lower electrodes 9, 9.

Then, a high voltage is applied between the sensor chip and the glass pedestal 10 in a heated state of 300 to 400 ° C.
The sensor chip and the glass pedestal 10 are bonded together. At the time of this anodic bonding, the high voltage applied to the sensor chip is directly applied to the silicon substrate 1 due to the breakdown phenomenon in which the current rapidly increases when the voltage applied to the PN junction of the piezoresistive element exceeds a certain value. Therefore, the operation is performed without destroying the sensor chip.

[0008]

On the other hand, a diaphragm is formed on one surface of a single crystal silicon substrate by etching, and a silicon oxide film to be an insulating layer is formed on the other surface.
In a pressure sensor having an SOI structure composed of a piezoresistive element of a single crystal silicon or a polycrystalline silicon thin film formed thereon, when a defect of the insulating layer is to be detected, the insulation defect determination of the conventional diffusion type pressure sensor described above is performed. In the case of using the above detection means, since the silicon substrate and the piezoresistive element are electrically separated by the insulating film, when the insulating layers of the two pairs of electrically separated piezoresistive element parts are both defective. However, there is a problem in that the defect cannot be detected, which is insufficient as a means for detecting a defect in the insulating layer.

Further, when the pressure sensor having the SOI structure is to be anodically bonded to the glass pedestal, because of the structure, the silicon substrate and the piezoresistive element are electrically separated by the insulating film. There is a problem in that a high voltage is applied to the insulating film, which in turn destroys the insulating layer and causes insulation failure of the sensor chip.

In view of the above points, the present invention is capable of sufficiently detecting a defect in the insulating layer, does not destroy the insulating layer even when a high voltage is applied when the pressure sensor is anodically bonded to the glass pedestal, and It is an object of the present invention to newly provide a method for manufacturing a pressure sensor having an SOI structure which is less likely to be affected by noise and static electricity.

[0011]

The present invention is a silicon substrate.
Form the insulating layer (2) on the diaphragm (7) of (1)
Then, the strain detecting element (3) is provided on the insulating layer (2) to detect the strain.
The electrode film (4) is provided on the output element (3), and the silicon substrate
A pressure sensor chip having an electrode film (6) provided on (1).
The pedestal (10) on the anti-strain detection element side of the
To contact the strain sensor element of the pressure sensor chip (18).
Electrode film (4) on child (3) and silicon substrate (1)
When one electrode (9) is brought into contact with the upper electrode film (6),
The other electrode (9) is brought into contact with the pedestal (10) so that both electrodes
A voltage is applied between (9, 9) and the silicon substrate (1) and the table.
Method of manufacturing semiconductor pressure sensor for anodic bonding with seat (10)
Adopt the law .

A semiconductor pressure sensor according to claim 1.
Manufacturing method of the electrode film on the strain sensing element (3)
(4) and the electrode film (6) on the silicon substrate (1)
-Contact one electrode (9) through the wafer (11)
And another dummy wafer (11) on the pedestal (10).
Then, the other electrode (9) is brought into contact, and between the two electrodes (9, 9)
Voltage is applied to the silicon substrate (1) and the pedestal (10)
A method of manufacturing a semiconductor pressure sensor that uses anodic bonding is used.
It

[0013]

According to the above-described first aspect of the invention, the quality of the insulating layer of the strain sensing element can be detected by measuring the insulation resistance between the electrode connected to the silicon substrate and the electrode of each strain sensing element. . Further, when the pedestal is anodically bonded to the pressure sensor, most of the current flows from the electrode connected to the silicon substrate, and no potential difference occurs between the strain sensing element and the silicon substrate via the insulating layer. It has the effect of preventing the dielectric breakdown of.

According to the second aspect of the invention, the dummy window is used.
Since a voltage is applied between both electrodes using the
The plate and the pedestal can be more appropriately anodically bonded.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a semiconductor pressure sensor of the present invention will be described below with reference to FIGS. In addition,
1 to 3, parts corresponding to those of the conventional example shown in FIGS. 4 and 5 are given the same reference numerals,
Detailed description thereof will be omitted.

FIG. 1 is a vertical sectional view showing a pressure sensor chip 18 of this embodiment, FIG. 2 is a schematic vertical sectional view showing its anodic bonding method, and FIG. 3 is a vertical sectional view showing its mounting state. The pressure sensor chip of is manufactured by the following method.

The silicon oxide film 2 is formed by thermally oxidizing a silicon wafer . The diaphragm 7 is obtained by etching a silicon oxide film formed in the same manner as the silicon oxide film 2 into a predetermined shape and then processing it into a concave shape by anisotropic etching.

The strain detecting element 3 can be obtained by forming a polycrystalline silicon film and then etching away a predetermined portion of the polycrystalline silicon film. The silicon nitride film 5, which is a protective layer, can be obtained by forming the entire surface of the silicon nitride film on the substrate after forming the strain sensing element 3 and removing a predetermined portion by etching.

The aluminum electrode film 4 and the aluminum electrode film 6 are obtained by etching away a predetermined portion of the aluminum film formed on the silicon nitride film 5. As shown in FIG. 1, the aluminum electrode film 4 detects strain. The aluminum electrode film 6 is connected to the element 3 and the silicon substrate 1, respectively.

Further, in order to obtain an electrical ohmic contact between the aluminum electrode film 4, the strain detecting element 3 and the aluminum electrode film 6 and the silicon substrate 1, heat treatment is performed at 350 to 450 ° C. for 30 to 120 minutes.

The pressure sensor chip 18 having a so-called SOI structure having the electrodes connected to the silicon substrate 1 is constructed as described above. Further, the anodic bonding of the pressure sensor chip 18 configured as described above is performed as shown in FIG.

The pressure sensor chip 18 is placed on the glass pedestal 10. The glass pedestal 10 is placed on the dummy wafer 11 placed on the electrode 9. The dummy wafer 11 is formed on the aluminum electrode film 4 and the electrode film 6 of the pressure sensor chip 18.
And place the electrode 9 on it.

Then, the pressure sensor chip 18 and the glass pedestal 10 are heated to 350 to 450 ° C., and a high voltage is applied between the upper and lower electrodes 9 and 9 by a DC voltage source 19 so that the silicon of the pressure sensor chip 18 is made. Substrate 1 and glass pedestal 1
Join 0.

When anodic bonding is carried out by such a method, most of the current flows through the low resistance aluminum electrode film 6 connected to the silicon substrate, so that the silicon substrate via the strain sensing element 3 and the insulating layer (silicon oxide film 2) is used. Since there is no potential difference in No. 1, it is possible to prevent dielectric breakdown.

When the pressure sensor of this example is actually used, it is mounted in a sensor case as shown in FIG. The sensor case is formed by integrally combining the stem 12 and the can 13 while keeping airtightness. The stem 12 has an opening 12a open to the atmosphere at the center thereof. As shown in the figure, the pressure sensor is installed on the stem 12 so that the central opening 10a of the glass pedestal 10 matches the opening 12a, and the space of the diaphragm 7 of the pressure sensor is opened to the atmosphere.

The stem 12 is provided with a terminal 16 integrally formed with the stem 12 and a terminal 14 electrically insulated from the stem 12 by an insulating seal glass 15. The aluminum electrode film 6 of the pressure sensor chip 18 is connected to one terminal 16 by a gold wire 20, and the terminal 16 is grounded.

The aluminum electrode film 4 of the pressure sensor chip 18 is connected to the other terminal 14 by a gold wire 17,
Is connected to a predetermined position of the measuring circuit. The pressure sensor chip 18 arranged on the stem 12 is housed so as to be covered by the can 13.

With the above structure, the stem 12 and the can 1
Since 3 is grounded together, the pressure sensor chip 18 placed inside is placed in a stable state against noise and static electricity,
Accurate pressure measurement is possible.

[0029]

As described above in detail , according to the method of manufacturing a semiconductor pressure sensor of the present invention , in the pressure sensor chip,
The electrode film on the strain sensing element and the electrode film on the silicon substrate are
Contact the electrode to one side and use this electrode for anodic bonding
Since the voltage is applied to the strain sensing element and the insulating layer
The potential difference no longer occurs in the silicon substrate through the
Anodic bonding without causing dielectric breakdown of the insulating layer.
The effect is that you can Furthermore, on the silicon substrate
Measure the insulation resistance between the electrode film of the
The insulation provided on the silicon substrate.
The effect that it is possible to easily detect whether the layer is good or bad
There is.

In the present invention, a dummy wafer is used.
If a voltage is applied between both electrodes, the silicon substrate and the pedestal
And the effect of being able to more appropriately perform anodic bonding
is there.

[Brief description of drawings]

FIG. 1 is used in a method for manufacturing a semiconductor pressure sensor of the present invention .
FIG. 3 is a vertical sectional view showing an example of a sensor chip to be used .

FIG. 2 is a vertical cross-sectional explanatory view showing an anodic bonding means of the above embodiment.

FIG. 3 is a vertical cross-sectional view illustrating a state when the pressure sensor of the above embodiment is used.

FIG. 4 is a vertical cross-sectional view illustrating a conventional diffusion type pressure sensor chip .

FIG. 5 is an explanatory longitudinal sectional view showing an anodic bonding means of the conventional example.

[Explanation of symbols]

1 ... Silicon substrate 2 ... Silicon oxide film 3 ... Strain detection element 4 ... Aluminum electrode film of strain sensing element 5 ... Silicon nitride film 6 ... Aluminum electrode film on silicon substrate 7 ... diaphragm 8 ... Diffusion resistance layer 9 ... Electrode 10 ... Glass pedestal 11 ... Dummy wafer 12: Stem (sensor case) 13 ... Can (sensor case) 14 ... Terminal (for sensor input / output signal) 15 ... Glass seal (for insulation) 16 ... Terminal (for grounding) 17 ... Gold wire 18 ... Pressure sensor chip 19 ... DC voltage source 20 ... Gold wire

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Makoto Oizumi 1-30-4 Higashimagome, Ota-ku, Tokyo Inside President Nokeki Seisakusho (56) References JP-A-4-162779 (JP, A) 58-92746 (JP, U) Actual development 61-66958 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 29/84 G01L 1/22 G01L 9/04

Claims (2)

(57) [Claims] 1. A diaphragm of a silicon substrate (1)
Form the insulating layer (2) on (7), and then on the insulating layer (2)
A strain detecting element (3) is installed on the
An electrode film is provided on the silicon substrate (1) by providing a polar film (4).
For the pressure sensor chip (18) provided with (6),
The pedestal (10) is brought into contact with the anti-strain detection element side, and the pressure sensor
Electrode film on the strain detecting element (3) of the sensor chip (18)
(4) and the electrode film (6) on the silicon substrate (1)
One of the electrodes (9) is brought into contact with the pedestal (10)
One electrode (9) is contacted, and voltage is applied between both electrodes (9, 9).
By applying a positive voltage to the silicon substrate (1) and the pedestal (10).
Manufacturing method of semiconductor pressure sensor characterized by joining
Law. 2. The manufacture of the semiconductor pressure sensor according to claim 1.
In the manufacturing method, the electrode film (4) and the strain detecting element (3)
And a dummy wafer on the electrode film (6) on the silicon substrate (1)
One electrode (9) is contacted via (11) and
The other through the dummy wafer (11) on the pedestal (10)
The electrodes (9) of the above are contacted, and a voltage is applied between both electrodes (9, 9).
Applying an anodic contact between the silicon substrate (1) and the pedestal (10)
A method of manufacturing a semiconductor pressure sensor, characterized by: