JPH07325105A - Semiconductor sensor - Google Patents

Abstract

PURPOSE:To contrive improvement of detection accuracy of beam breakage. CONSTITUTION:A silicon substrate is processed by etching or the like, and a weight part 13 supported in the form of a cantilever through a beam part 11 is provided on a frame-shaped support part 12. A piezoresistance 15 for detecting acceleration is formed by displacement of the weight part 13 on the beam part 11. A first and a second conductor routes for damage detection 18, 21 extending up to the support part 13 are provided on the silicon substrate via the beam part 11 and part of the weight part 13 on the lower face side thereof. The second conductor route 21 leads to the upper face of the silicon substrate through a conductor part 23 and a contact hole 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor sensor for detecting acceleration and pressure of a vehicle such as an automobile.

[0002]

2. Description of the Related Art As a conventional technique using such a semiconductor sensor as an acceleration sensor, for example, TRANS. Vol. ED-2
6 DEC. 1979. "A Batch-Fabricated Silicon Accelerom
as disclosed in FIG. 5 and shown in FIG.
Is processed by etching or the like to form a support portion 2 and a thick weight portion 4 continuous from the support portion 2 via a thin beam portion 3.
And a plurality of piezoresistors 5 are formed on the upper surface of the beam portion 3 so as to form a bridge circuit, and when the weight portion 4 is displaced by acceleration and the beam portion 3 is bent, the stress of the piezoresistor 5 is generated. The resistance value changes, and the acceleration value is detected by the change in the resistance value. For example, as disclosed in Japanese Utility Model Laid-Open No. 5-52763, as shown in FIG. 6, the silicon substrate 1 is processed by etching or the like so that the supporting portion 2 is formed. And this support 2
Is provided with a thick weight portion 4 which is continuous through a thin beam portion 3, a movable electrode 6 is formed on the lower surface of the weight portion 4, and a stationary electrode 7 facing the movable electrode 6 is made of glass or the like. When the weight portion 4 is displaced by acceleration by joining the substrate 8 to the silicon substrate 1 with a gap between the electrodes 6 and 7, the gap amount between the electrodes 6 and 7 is changed according to the displacement amount of the weight portion 4. It is known that the acceleration is detected by the change of the electrostatic capacitance.

In the acceleration sensor shown in FIGS. 5 and 6, since a large stress is concentrated on the thin beam portion 3 of the silicon substrate 1, cracks may occur in the beam portion 3 or its peripheral portion. Since the beam portion 3 is easily broken, and the mechanical damage to the beam portion 3 makes it impossible to accurately detect the acceleration, the beam portion 3 is formed on the surface of the silicon substrate 1 as shown in FIG. A conductive path 9 made of a conductive metal layer of aluminum or the like continuous to the support portion 2 via 3 is drawn around, and the conductive path 9 is configured to be broken when the beam portion 3 is damaged. There is known a semiconductor sensor configured to detect the damage of the beam portion 3 when it becomes non-conductive (for example, Japanese Patent Publication No. 5-58140).
(See Japanese Patent Publication No. Hei 1-163637).

[0004]

However, in the above-mentioned conventional example, since the damage cannot be detected unless the conductive path 9 is broken, the damage received by the beam portion 3 is limited to only one side. For example, when a crack is generated from the back surface side of the beam portion 3 where the conductive path 9 is not formed and the crack does not reach the conductive path 9 on the front surface side of the beam portion 3 (half crack), the conductive path 9 is broken. Therefore, there is a problem that damage to the beam portion 3 cannot be detected.

The present invention has been made by paying attention to this point, and its main purpose is to detect the damage even if only one side of the beam portion occurs, and to improve the damage detection accuracy. It is intended to provide a possible semiconductor sensor.

[0006]

The present invention provides a semiconductor sensor comprising a silicon substrate having a weight portion continuously formed from a support portion through a beam portion, wherein the semiconductor sensor detects an external force by displacement of the weight portion. Conductor paths for detecting damage to the beam portion are formed on the upper and lower surfaces of the portion.

Further, according to the present invention, in the above structure, the beam portion is provided with a piezoresistor for detecting an external force by the displacement of the weight portion, and the conductor path on the upper surface side is formed outside the piezoresistor.

[0008]

According to the present invention, the conductor paths for damage detection are formed on both the upper and lower surfaces of the beam portion, so that even if the damage is on only one side such as a half crack, the damage is caused by the damage to the beam portion. Since the conductor path on either the upper or lower surface is broken, damage to the beam is detected.

Further, according to the present invention, since the conductor path on the upper surface side is formed around the piezoresistor, the conductor path on the upper surface side is broken before the piezoresistor is damaged, so that the beam portion is damaged. Is detected early.

[0010]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view showing the outline of an acceleration sensor (semiconductor sensor) according to an embodiment of the present invention. In the acceleration sensor shown in FIG. 1, a groove 10 and a thin beam portion 11 are formed by selective etching, and a thick weight portion 13 continuous to the frame-shaped support portion 12 via the beam portion 11 is cantilevered. A supporting N-type silicon substrate 14 and a beam portion 11 of the silicon substrate 14 are provided with a piezoresistor 15 formed so as to form a bridge circuit, and when the beam portion 11 is bent by the acceleration applied to the weight portion 13, The stress causes the resistance value of the piezoresistor 15 to change. Also on the silicon substrate 14,
A pair of upper and lower stoppers 16 and 17 made of an insulating material such as glass are fixed to the lower side.
In order to prevent the stress destruction of the beam portion 11 against an excessive acceleration, the displacement of the weight portion 13 in the vertical direction is regulated. The lead wire 15a is connected to the bridge circuit.
Is connected, and the resistance value change of the piezoresistor 15 is output to the outside.

2A and 2B are plan views showing the substrate surface of the silicon substrate 14 shown in FIG. 1. FIG. 2A shows the upper surface of the silicon substrate 14, and FIG. 2B shows the lower surface of the silicon substrate 14. Shows. In FIG. 2 (a), on the upper surface of the silicon substrate 14, a single piece extending to the support portion 12 so as to surround the outside of the piezoresistor 15 via both side ends of the beam portion 11 in the plane direction and a part of the weight portion 13. A first conductor path 18 consisting of a continuous conductor path of is formed of a conductive material such as aluminum, and its extended end is located on the support portion 12 and has two first terminal portions 19,
20 are integrally formed. In FIG. 2B, a second diffusion layer is formed inside the lower surface of the silicon substrate 14 and extends to both sides of the beam portion 11 in the plane direction and a part of the weight portion 13 to reach the support portion 12. 3 is formed, and the second conductor path 21 is formed by diffusing and forming a relay connection conductor portion 23 and a contact hole in the silicon substrate 14 from the upper surface side through the trench portion 22 as shown in FIG. Is connected to a wiring portion 25 made of a conductive material such as aluminum formed on the upper surface of the silicon substrate 14 via 24, and the end portion of the wiring portion 25 is located on the supporting portion 12 and has two second terminals. Parts 26, 27 (Fig. 2
(See (a)) is integrally formed. 2 and 3, the wiring structure around the piezoresistor 15 is omitted.

Then, the first conductor path 18 and the second conductor path 21 are provided through the first terminal portions 19 and 20 and the second terminal portions 26 and 27.
Is supplied with a predetermined amount of current so that the conductor paths 18 and 21 are normally energized, and when the beam portion 11 or the weight portion 13 is broken or cracked, the first path is caused by the damage. Either the conductor path 18 or the second conductor path 21, or both of the first conductor path 18 and the second conductor path 21 are broken so as to be in a non-conductive state. Damage to the vicinity of the beam portion 11 is detected by the breakage of the path 18 or the second conductor path 21.

FIG. 4 is an explanatory view showing an example of a method of manufacturing the acceleration sensor shown in FIGS. 1 to 3. First, an oxide film 28 made of SiO ₂ is formed on the upper surface of the N-type silicon substrate 14 except for a predetermined region. The second conductor path 21 is formed in the region excluding the oxide film 28 by diffusion of boron or the like (FIG. 4).
(A)).

Next, an N type epitaxial layer (hereinafter referred to as an epi layer) 14a is grown and formed on the upper surface of the silicon substrate 14 (FIG. 4B).

Next, a resist (not shown) is patterned on the upper surface of the epi layer 14a located above the end of the second conductor path 21, and the area excluding this resist is etched with an etching solution of, for example, hydrofluoric nitric acid. The trench portion 22 is formed by partially removing it (FIG. 4C).

Next, after removing the resist, the conductor portion 23 and the lead 29 are provided at predetermined portions of the trench portion 22 and the epi layer 14a by diffusion of boron or the like, and the piezoresistive 15 is formed by ion implantation of boron or the like. An oxide film 28 is formed again on the upper surface of the layer 14a (FIG. 4 (d)).

Next, contact holes 24 and 30 are formed in the oxide film 28 corresponding to predetermined portions of the conductor portion 23 and the lead 29,
The wiring portion 25 and the second terminal portion are formed on the upper surface of the oxide film 28 by vapor deposition or the like.
26, 27 (see FIG. 2A), the wiring electrode 31, the first conductor path 18, and the first terminal portions 19, 20 (see FIG. 2A) are formed (FIG. 4E). This allows the piezoresistor 15 to lead 29
It is connected to the wiring electrode 31 via.

Next, Si ₃ N _{4 is formed} on the lower surface of the silicon substrate 14.
An etching resistant film 32 made of is formed into a pattern, and the silicon substrate 14 is anisotropically etched with an alkali etching solution such as KOH. As a result, the N-type silicon substrate 14 is etched to the vicinity of the second conductor path 21 so as to leave the beam portion 11, and at the same time, the groove portion 10 is removed by etching. When the etching resistant film 31 is removed, the groove portion 10 and the beam portion 11 are removed. , Support 12,
A wafer structure having a weight 13 is obtained (FIG. 4).
(F)).

Such a silicon wafer is made of Pyrex glass, and after fixing the upper and lower stoppers 16 and 17 by anodic bonding or the like, it is diced into individual chips, and lead wires are connected to electrode terminals (not shown) of the wiring electrodes 32. 1 to 3 by connecting 15a by wire bonding or the like and connecting the first terminal portions 19, 20 and the second terminals 26, 27 to the outside by appropriate connecting means (for example, wire bonding) not shown. The acceleration sensor shown in is completed.

As described above in detail, in the present embodiment, the first and second conductors extending to the support portion 12 on the upper surface and the lower surface side of the silicon substrate 14 via the beam portion 11 and a part of the weight portion 13 are provided. Road 1
8 and 21 are formed, and at least one of the conductor paths 18 and 21 is configured to be broken when the beam portion 11 is damaged. Even if damaged, either the upper or lower conductor path
Since the parts 18 and 21 are broken and become non-conductive, damage to the beam can be detected.

Further, according to this embodiment, since the first conductor path 18 is formed outside the piezoresistor 15, for example, when the side end of the beam portion 11 is damaged, the first conductor path 18 located outside the first portion is positioned. Since the conductor path 18 is broken prior to the damage of the piezoresistor 15, the damage of the beam portion 11 can be detected before the damage of the piezoresistor 15.

In this embodiment, the first and second conductor paths 1
8 and 21 are passed through the beam 11 and a part of the weight 13 to support 12
Although the conductor paths 18 and 21 are formed so as to extend up to, the first conductor path 18 is provided, for example, by extending the first conductor path 18 so as to surround the entire circumference of the weight portion 13 along the groove portion 10 to detect damage to the weight portion 13. It is also possible to provide the second conductor path 21 or to extend the second conductor path 21 toward the weight portion 13 side.
If at least a part of 21 is formed so as to pass through the beam portion 11, the design can be changed appropriately.

Further, in the present embodiment, the first conductor path 18 is formed as an independent conductor path by printing, vapor deposition or the like of aluminum, but conductors made of diffusion or the like are partially provided to form one conductor path. It is also possible to use a part of the wiring electrode 31 of the piezoresistor 16.

Further, in this embodiment, the second conductor path 21 is connected to the beam portion.
Although it is formed so as not to be exposed to the outside of the lower surface side of 11, the surface of the second conductor path 21 may be exposed to the outside with, for example, SiO ₂
It may be covered with an oxide film made of.

In this embodiment, the first and second conductor paths 1
The damage detection means consisting of 8 and 21 was applied to the acceleration sensor that detects the acceleration by changing the resistance value of the piezoresistor 15.
Such damage detecting means can also be applied to a capacitance type acceleration sensor as shown in FIG. 6 of a conventional example.

The semiconductor sensor of the present invention can be used as a sensor for detecting a pressure such as a tactile pressure or atmospheric pressure, a physical external force of mechanical vibration, etc., in addition to the acceleration sensor described in the embodiments.

[0028]

As described above in detail, the present invention is a semiconductor sensor which comprises a silicon substrate having a weight portion continuously formed from a support portion through a beam portion, and which detects an external force by displacement of the weight portion. By forming a conductor path for detecting damage to the beam section at least on the upper and lower sides of the beam section, even if the damage is on only one side such as a half crack, the conductor path on either the upper or lower side is Because it breaks
It is possible to provide a semiconductor sensor capable of detecting damage to a beam portion and improving damage detection accuracy.

According to the present invention, in the above structure, the beam portion is provided with a piezoresistor for detecting an external force by the displacement of the weight portion, and the conductor path on the upper surface side is formed outside the piezoresistor. It is possible to provide a semiconductor sensor that can detect damage to the beam portion before the resistance is damaged, thereby enabling early detection of damage.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an outline of an acceleration sensor according to an embodiment of the present invention.

2 is a plan view showing the upper and lower surfaces of the silicon substrate of FIG. 1. FIG.

FIG. 3 is a cross-sectional view near the beam portion of FIG.

FIG. 4 is an explanatory diagram showing a manufacturing process of the acceleration sensor according to the embodiment.

FIG. 5 is a cross-sectional view showing a conventional example.

FIG. 6 is a cross-sectional view showing another conventional example.

FIG. 7 is a plan view showing another conventional example.

[Explanation of symbols]

 11 Beam part 12 Support part 13 Weight part 14 Silicon substrate 15 Piezoresistor 18 First conductor path 21 Second conductor path

Claims (2)

[Claims] 1. A semiconductor sensor comprising a silicon substrate having a weight portion continuously formed from a support portion via a beam portion, wherein the semiconductor sensor detects an external force by displacement of the weight portion, wherein the upper and lower surfaces of the beam portion are provided with A semiconductor sensor characterized in that a conductor path for detecting damage to a beam portion is formed. 2. The piezoresistor for detecting an external force by the displacement of the weight portion is provided on the beam portion, and the conductor path on the upper surface side is formed around the piezoresistor outside the piezoresistor. Semiconductor sensor.