JPH10242481A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress leakage current by forming an insulation layer on the concave surface of a semiconductor pressure sensor in which a thin part is formed by making a concave surface in a semiconductor substrate. SOLUTION: A concave surface 12 is made in a silicon substrate 10 on the bonding face 11 side and a diaphragm (thin part) 14 thinner than a supporting part 13 is formed. A semiconductor pressure sensor 9 is anode bonded to a glass base through a bonding face 11 such that the diaphragm 14 receives pressure from a pressure medium. A gauge resistor 15 is connected through a lead part 17 to form the diaphragm 14 constituting a bridge circuit. A thermal oxide film 18 is deposited, at a predetermined thickness, on the bonding face 11 and the concave surface 12 of the silicon substrate 10. The pressure medium being introduced into the concave surface 12 can be isolated from the bridge circuit by the thermal oxide 18 deposited on the concave surface 12 and leakage current can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor, and more particularly to a semiconductor pressure sensor suitable for detecting the pressure of a conductive substance.

[0002]

2. Description of the Related Art Conventionally, various semiconductor pressure sensors have been proposed, for example, as disclosed in Japanese Patent Publication No. 59-25393. As shown in FIG. 3, the semiconductor pressure sensor 1
In the figure, a diaphragm 3 is formed by providing a concave surface 2 in the center of a semiconductor substrate. A strain is generated in a gauge resistor 4 formed in the diaphragm 3 by introducing a pressure medium, and a resistance value change due to a piezoresistance effect of the gauge resistor 4 is caused. Is converted into an electric signal of a bridge circuit to detect a pressure value. The semiconductor pressure sensor 1 is joined to a glass pedestal 6 having a hole 5 for introducing a pressure medium, and the glass pedestal 6 is bonded to a metal stem 8 having a hole 7 communicating with the hole 5.

[0003]

The thermal expansion coefficients of the semiconductor pressure sensor 1 and the glass pedestal are substantially equal, and the distortion of the diaphragm caused by the difference in the thermal expansion coefficients is reduced. The glass pedestal 6 is an insulator, and the semiconductor pressure sensor 1 and the metal stem 8 are insulated by the glass pedestal 6. However, there is a possibility that a leak current A flowing from the gauge resistor 4 to the metal stem 8 via the pressure medium may be generated. There is a possibility that a slight error may occur in the measured pressure value. The present invention provides a semiconductor pressure sensor that can suppress the possibility of occurrence of a leak current.

[0004]

According to the present invention, there is provided a semiconductor pressure sensor in which a concave portion is formed on a semiconductor substrate to form a thin portion, and an insulating layer formed on the concave surface is provided.

Further, the present invention provides a semiconductor pressure sensor in which a concave portion is formed on a semiconductor substrate to form a thin portion, wherein a bridge circuit having a gauge resistor formed on the diaphragm and to which a predetermined voltage is applied is provided. An insulating layer capable of withstanding the predetermined voltage.

In the present invention, the insulating layer is a thermal oxide film.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor pressure sensor 9 is a semiconductor substrate.
10 is provided with a concave surface 12 and a diaphragm 14 (thin portion) is formed. By forming an insulating layer 18 on the concave surface 12,
Leak current can be suppressed.

It is desirable that the insulating layer 18 can withstand a predetermined voltage applied to a bridge circuit 16 having a gauge resistor 15 formed on the diaphragm 14.

Further, the insulating layer 18 may be a thermal oxide layer, and there is no fear that the manufacturing process becomes complicated.

[0010]

An embodiment of the present invention will be described below. FIG. 1 is a sectional view of a semiconductor pressure sensor, and FIG. 2 is an explanatory diagram of a bridge circuit.

The semiconductor pressure sensor 9 has a concave surface 12 on the side of the bonding surface 11 of the silicon substrate 10 (semiconductor substrate).
A diaphragm 14 (thin portion) which is thinner than the support portion 13 is formed. The semiconductor pressure sensor 9 is anodically bonded to a glass pedestal (not shown) by a bonding surface 11 and a diaphragm 14 is provided.
Are configured to receive the pressure of the pressure medium. Reference numeral 15 denotes a gauge resistor. The gauge resistor 15 is formed on the diaphragm 14 and connected by a lead 17 so as to form a bridge circuit 16.

Reference numeral 18 denotes a thermal oxide film (insulating layer) made of silicon oxide.
A predetermined thickness (for example, 0.05 μm) is formed on the concave surface 11 and the concave surface 12. Reference numeral 19 denotes a thermal oxide film made of silicon oxide. The thermal oxide film 19 is formed on the surface 20 of the silicon substrate 10. Reference numeral 21 denotes a nitride film made of silicon nitride. The nitride film 21 is formed on the thermal oxide film 19 by lamination. Reference numeral 22 denotes a contact hole, which is provided to penetrate the thermal oxide film 19 and the nitride film 21. Reference numeral 23 denotes an electrode portion made of aluminum. The electrode portion 23 is formed so as to fill the contact hole 22 and is connected to the lead portion 17. Further, a bonding wire (not shown) is connected to the electrode portion 23.

The diaphragm 14 of the semiconductor pressure sensor 9 is distorted by the pressure of the pressure medium, and the resistance of each gauge resistor 15 of the bridge circuit 16 changes according to the pressure. Further, as shown in FIG. 2, the power supply voltage V
cc (voltage) is applied, and the bridge circuit 16 outputs an output voltage Vo corresponding to the pressure of the pressure medium.

Next, a manufacturing process of the semiconductor pressure sensor 9 will be described.

First, an alkaline etching solution (such as KOH)
A concave surface 12 is formed on the silicon substrate 10 by an appropriate method such as wet etching by a method, and a diaphragm 14 is formed. Thereafter, the silicon substrate 10 is put into a thermal oxidation furnace, and each of the thermal oxide films 18 and
Form 19. Next, the thermal oxide film 19 on the surface 20 corresponding to the formation location of the gauge resistor 15 is removed, and a gauge resistor 15 is formed at a predetermined position on the silicon substrate 10 by diffusion using a semiconductor material such as boron, and the gauge is again formed. A thermal oxide film 19 is formed where the resistor 15 is formed. Then, the thermal oxide film 19 is removed from both ends of the gauge resistor 15 in a predetermined pattern, a lead portion 17 is formed by diffusion using a semiconductor material such as boron having a higher concentration than the gauge resistor 15, and a bridge circuit 16 is formed. . After the bridge circuit 16 is formed, a nitride film 21 made of silicon nitride is formed on the thermal oxide film 19 on the surface 20 of the silicon substrate 10.

Next, an adhesive tape is stuck on the joining surface 11 side,
The nitride film 21 corresponding to the formation part of the lead portion 17 is removed by a plasma etching method or the like, and the thermal oxide film 19 where the nitride film 21 has been removed is removed using a hydrofluoric acid mixed solution to obtain a nitride film. Lead part 17 from film 21
Is formed. At this time,
Since adhesive tape is stuck on the bonding surface 11 side, the bonding surface
The hydrofluoric acid mixture does not touch the 11 and the concave surface 12, and the thermal oxide film 18 formed on the bonding surface 11 and the concave surface 12 is not removed. next,
The electrode portion 23 is formed at the position where the contact hole 22 is formed by using aluminum by vapor deposition or sputtering. Finally, the adhesive tape is peeled off, and the semiconductor pressure sensor 9 is completed.

The semiconductor pressure sensor 9 of this embodiment described above.
According to the thermal oxide film 18 formed on the concave surface 12, the concave surface 12
And the bridge circuit 16 can be insulated, and the leak current A described in the conventional example can be prevented.

The insulating layer formed on the concave surface 12 may be a nitride film made of, for example, silicon nitride, but if the thermal oxide film 18 is used as in this embodiment, the surface 20 of the silicon substrate 10 Since it can be formed simultaneously with the thermal oxide film 19, there is no possibility that the manufacturing process becomes complicated. Although the thermal oxide film 18 (insulating layer) of this embodiment is formed on the bonding surface 11 and the concave surface 12, for example, the semiconductor pressure sensor 9 is formed on the bonding surface.
In the case of bonding to the glass pedestal by 11, there is no possibility that a leak current A passing through the bonding surface 11 occurs, and the insulating layer may be formed on the concave surface 12.

The thickness of the thermal oxide film 18 can be appropriately changed depending on the temperature of the thermal oxidation furnace and the like. For example, if the potential of the metal stem 8 is stabilized at a potential close to the power supply voltage Vcc, the thermal Although the oxide film 18 may be thinner than in this embodiment, it is desirable that the thermal oxide film 18 be able to withstand the power supply voltage Vcc applied to the bridge circuit 16, for example, a special structure for stabilizing the potential of the metal stem 8. Becomes unnecessary.

In this embodiment, the lead 17 is formed after the gauge resistor 15 is formed. For example, the gauge resistor 15 may be formed after the lead 17 is formed. It is not limited to this embodiment.

[0021]

According to the present invention, there is provided a semiconductor pressure sensor in which a concave portion is formed on a semiconductor substrate to form a thin portion, the insulating layer having an insulating layer formed on the concave portion. Can be.

Further, the present invention provides a semiconductor pressure sensor in which a concave portion is formed on a semiconductor substrate to form a thin portion, a bridge circuit having a gauge resistor formed in the thin portion and to which a predetermined voltage is applied, and a bridge circuit formed on the concave portion. And an insulating layer capable of withstanding the predetermined voltage, so that the possibility of occurrence of a leak current can be suppressed.

Further, in the present invention, the insulating layer is a thermal oxide film, and there is no fear that the manufacturing process becomes complicated.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor pressure sensor showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a bridge circuit according to the embodiment.

FIG. 3 is a sectional view showing a conventional semiconductor pressure sensor.

[Explanation of symbols]

 9 Semiconductor pressure sensor 10 Silicon substrate (semiconductor substrate) 12 Concave surface 14 Diaphragm (thin part) 15 Gauge resistance 16 Bridge circuit 18 Thermal oxide film (insulating layer)

Claims (3)

[Claims] 1. A semiconductor pressure sensor in which a concave surface is provided on a semiconductor substrate to form a thin portion, the semiconductor pressure sensor having an insulating layer formed on the concave surface. 2. A semiconductor pressure sensor in which a concave portion is formed on a semiconductor substrate and a thin portion is formed, a bridge circuit having a gauge resistor formed in the thin portion and to which a predetermined voltage is applied, and a bridge circuit formed on the concave surface. A semiconductor pressure sensor comprising: an insulating layer capable of withstanding a voltage. 3. The semiconductor pressure sensor according to claim 1, wherein the insulating layer is a thermal oxide film.