JPH11160348A - Semiconductor accelerometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor accelerometer whose sensitivity is high and whose temperature characteristic is excellent without making the width of a beam part large. SOLUTION: A semiconductor accelerometer is provided with a plumb hob 1 which is subjected to an acceleration so as to be displaced, with a flexure which comprises a central part 2a and a beam 2b which is extended to all directions from the outer edge of the central part 2a and in which the plumb hob 1 is coupled to the rear surface of the central part 2a, with a support member 3 which supports the flexure 2 and with piezoresistances RX1 to RX4, RY1 to RY4 by which a strain generated in the flexure 2 due to the displacement of the plumb hob 1 is detected in at least two directions, i.e. the X-axis direction and the Y-axis direction. The piezoresistances RX1 to RX4, RY1 to RY4 are arranged near the coupling part of the central parts 2a to the beam 2b. The piezoresistances RX1 to RX4, RY1 to RY4 in the respective axial directions are constituted of a bridge circuit. Then, interconnections 4 which connect the piezoresistances RX1 to RX4, RY1 o RY4 which are installed so as to sandwich the central part 2a in the respective axial directions are formed on the central part 2a. The interconnections 4 in the respective axial directions are crossed orthogonally. Middle points of the interconnections 4 in the respective axial directions are derived electrically onto the support member 3 via a part on the beam 2b in the different axial directions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor acceleration sensor.

[0002]

2. Description of the Related Art FIGS. 7 and 8 are schematic structural views showing a conventional semiconductor acceleration sensor. FIG. 7 (a) is a schematic plan view showing a state viewed from above, and FIG. It is sectional drawing. In the semiconductor acceleration sensor shown in FIG. 7, by processing a desired portion of a semiconductor substrate made of silicon using a semiconductor etching technique, a weight portion 1, a thin flexible portion 2, and a frame-shaped support member 3 are formed. Become composed. Here, the weight portion 1 is connected to the lower surface of the central portion 2a of the cross-shaped bending portion 2, and four beam-shaped beam portions 2 are formed from the outer edge of the central portion 2a.
b (a terminal portion of the bending portion 2) extends and is connected to the inner side surface (shown by a wavy line) of the support member 3.

The beam 2b has piezoresistors RX1 to RX4, RY1 to RY4, and RZ1 to detect accelerations in the X, Y, and Z directions from the distortion of the beam 2b caused by the displacement of the weight 1. R
Z4 is formed.

On the lower surface of the support member 3, a weight 1
A lower stopper (not shown) made of silicon or glass and having a concave portion at a position corresponding to the above is bonded by anodic bonding or the like.

The semiconductor acceleration sensor shown in FIG. 8 is different from the semiconductor acceleration sensor shown in FIG. 7 in that the center of the weight portion 1 is connected to the center portion 2a of the bending portion 2 via the neck portion 1a. 2b is provided with a notch groove 5. By providing the cutout grooves 5, a beam portion 2b longer than the semiconductor acceleration sensor shown in FIG. 7 can be obtained for the same chip size, and a small and highly sensitive semiconductor acceleration sensor can be realized.

In the above-described semiconductor acceleration sensor, the arrangement of piezoresistors for obtaining high-sensitivity output is disclosed in
There is one described in JP-A-331646. According to the present invention, of the piezoresistors formed in the beam portion, a piezoresistor for detecting distortion in the X and Y axes directions is disposed in the beam portion near the central portion of the bending portion, and a distortion in the Z axis direction other than the disposition portion is provided. A piezoresistor that detects the current is arranged. Accordingly, when acceleration in the X and Y axis directions is applied, distortion near the center of the bent portion where a large stress occurs can be detected by the piezo resistance.
Acceleration detection with high sensitivity in the X and Y axis directions becomes possible.

Hereinafter, piezo resistors RX1 to RX4, RY1 to RY4, RZ
The specific arrangement of 1 to RZ4 will be described. As shown in FIGS. 7 and 8, piezoresistors RZ1 and RZ3 for acceleration detection in the Z-axis direction and piezoresistors RZ1 and RZ3 are respectively provided at connection portions of the beam portion 2b with the support member 3 on the center line in the Y-axis direction. Are arranged so that their longitudinal directions are parallel to the Y-axis direction, and Z
Piezoresistors RZ2 and RZ4 for detecting acceleration in the axial direction are arranged such that the longitudinal directions of the piezoresistors RZ2 and RZ4 are parallel to the Y-axis direction.

Also, a center portion 2a of the beam portion 2b in the Y-axis direction
Piezoresistors RY1 to RY4 for detecting the acceleration in the Y-axis direction are arranged at the connection portions with the X-axis direction beam portions 2b, respectively.
The piezoresistors RX1 to RX4 for detecting the acceleration in the X-axis direction are arranged at the connection portions with the central portion 2a.

As the piezoresistors RX1 to RX4 and RY1 to RY4 for detecting accelerations in the X and Y axes, the longitudinal direction of the piezoresistors is parallel to the longitudinal direction of the beam 2b (for example, the piezoresistors RY1 to RY4). A piezoresistor (hereinafter, referred to as a “vertical piezoresistor”) is disposed so that its longitudinal direction is parallel to the Y-axis direction, and the longitudinal direction of the piezoresistor is perpendicular to the longitudinal direction of the beam 2b (for example, piezoresistor). There is a piezo resistor (hereinafter referred to as “lateral piezo resistor”) arranged so that the longitudinal direction of the resistors RY1 to RY4 is perpendicular to the Y-axis direction.

Here, when a vertical piezoresistor is used,
There is an advantage that the width of the beam portion 2b can be reduced as compared with the case where the lateral piezoresistance is used. The sensitivity S of the acceleration sensor is
Since there is a relationship of S∝1 / b with the width b of the beam portion 2b, further improvement in sensitivity can be expected by using a vertical piezoresistor.

[0011]

However, in order to extract the output from the piezoresistors arranged as described above,
A bridge circuit as shown in FIG. 8 must be formed. The problem here is that adjacent piezoresistors (eg, RX1 and RX3) must be connected facing each other on the bridge circuit. Japanese Patent Application Laid-Open No. Hei 6-331646 discloses the arrangement of piezoresistors and a method of connecting a bridge circuit, but specifically describes how to connect and wire individual piezoresistors on a pattern. Is not disclosed.

The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor acceleration sensor having high sensitivity and excellent temperature characteristics without increasing the width of a beam portion. Is to do.

[0013]

According to the first aspect of the present invention,
A flexure portion having a weight portion displaced by acceleration, a central portion and a beam portion extending in four directions from an outer edge of the central portion, the flexure portion having the weight portion connected to a lower surface of the central portion, And a piezoresistor for detecting a strain generated in the bending portion by displacement of the weight portion in at least two directions of X and Y axes, wherein the piezoresistance is provided between the center portion and the beam portion. In the semiconductor acceleration sensor in which the piezoresistors in each axial direction are arranged in the form of a bridge circuit, the wiring connecting the piezoresistors provided across the central portion in each axial direction is disposed near the connection portion with Provided on the central portion, the wires in each axial direction are orthogonally crossed, and the midpoint of the wires in each axial direction is electrically drawn out onto the support member via a beam portion in a different axial direction. It is characterized by comprising.

According to a second aspect of the present invention, in the semiconductor acceleration sensor according to the first aspect of the present invention, one of the orthogonally crossing wirings is replaced with an impurity diffusion layer formed in the central portion at least at the orthogonally crossing portion. The wires intersect at right angles so that the wires intersecting at right angles do not conduct.

According to a third aspect of the present invention, in the semiconductor acceleration sensor according to the first or second aspect, the weight portion is connected to the center portion via a neck portion, and the weight portion and the beam portion are connected to each other. Characterized in that a notch groove is provided between them.

[0016]

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

Embodiment 1 FIG. 1 is a schematic configuration diagram showing a semiconductor acceleration line sensor according to an embodiment of the present invention, (a) is a schematic plan view, and (b) is a schematic cross-sectional view. is there. The semiconductor acceleration sensor has a bent portion 2 composed of four beam portions 2b orthogonal to each other and a lower surface of a rectangular central portion 2a of the bent portion 2 in order to detect at least accelerations in the X-axis and the Y-axis. And a frame-shaped support member 3 that supports the bending portion 2. Here, a piezo-resistor RX is provided on one side of the beam portion 2b in the X-axis direction near the connection portion with the central portion 2a.
1 and RX3 are arranged, and piezo resistors RX2 and RX4 are arranged on the other side. Also, the central portion 2 of the beam portion 2b in the Y-axis direction
Piezoresistors RY1 and RY3 are arranged on one side in the vicinity of the connection portion with a, and piezoresistors RY2 and RY4 are arranged on the other side.

Next, in order to detect the applied acceleration, a Wheatstone bridge circuit must be formed using four piezoresistors for each axis. In this case, in order to obtain a high detection output, piezoresistors (for example, RX1 and RX3) arranged adjacently on one beam 2b must be wired so as to face each other on the circuit.

FIG. 2 is a schematic wiring diagram of the piezoresistor of the semiconductor acceleration sensor according to the present embodiment. FIG. 2A is a schematic wiring diagram of the piezoresistors RX1 to RX4 for detecting the acceleration in the X-axis direction. (B) is a schematic wiring diagram of piezo resistors RY1 to RY4 for detecting acceleration in the Y-axis direction. First, the piezoresistors RX1 and RX2 are connected by a wire 4 formed on the central portion 2a, and the other ends of the piezoresistors RX1 and RX2 are supported by wires 4 formed on the beam portion 2b.
The terminals X3,
Each is connected to X4. The piezoresistors RX3 and RX4 are connected by a wire 4 formed on the central portion 2a, and the other ends of the piezoresistors RX3 and RX4 are supported by wires 4 formed on the beam portion 2b. It is drawn up and connected to terminals X5 and X6 provided on the support member 3, respectively.

Next, the wiring to the terminal at the intermediate point of the wiring 4 between the piezoresistors for extracting the detection output of the acceleration is performed as follows. Piezo resistor RX1 and piezo resistor RX2
Is branched on the central portion 2a, and the wiring 4
Is formed on the beam portion 2b so as to pass between the piezoresistors RY1 and RY3 formed for detecting the acceleration in the Y-axis direction, is pulled out onto the support member 3, and is provided on the support member 3. Connected to terminal X1. Similarly, a wiring 4 connecting the piezoresistors RX3 and RX4 is branched on the central portion 2a, and the wiring 4 connects between the piezoresistors RY2 and RY4 formed for detecting the acceleration in the Y-axis direction. It is formed on the beam portion 2 b so as to pass through, is pulled out onto the support member 3, and is connected to a terminal X <b> 2 provided on the support member 3.

Similar wiring is performed for the piezo resistors RY1 to RY4 in the Y-axis direction. First, the piezoresistors RY1 and RY2 are connected by a wire 4 formed on the central portion 2a, and the other ends of the piezoresistors RY1 and RY2 are supported by the wires 4 formed on the beam portion 2b. Pulled out to the top,
The terminals are connected to terminals Y3 and Y4 provided on the support member 3, respectively. Further, the piezoresistors RY3 and RY4 are connected by a wire 4 formed on the central portion 2a, and the other ends of the piezoresistors RY3 and RY4 are supported by the wires 4 formed on the beam portion 2b. It is pulled up and connected to terminals Y5 and Y6 provided on the support member 3, respectively.

Next, a wiring 4 connecting the piezoresistors RY1 and RY2 is branched on the central portion 2a.
Piezoresistance formed to detect axial acceleration
It is formed on the beam portion 2b so as to pass between RX1 and RX3, is drawn out onto the support member 3, and is connected to a terminal Y1 provided on the support member 3. Similarly, the piezo resistance RY
A wire 4 connecting the piezoresistor 3 and the piezoresistor RY4 is branched on the central portion 2a, and the wire 4 passes between the piezoresistors RX2 and RX4 formed for detecting the acceleration in the X-axis direction. 2b, is pulled out onto the support member 3 and is connected to a terminal Y2 provided on the support member 3.

Here, at the intersection of the wirings 4, a multilayer wiring via an insulating film such as a silicon oxide film or a silicon nitride film or the central portion 2 a is formed at the intersection so that the wirings 4 are not electrically connected. A multi-layer wiring using an impurity diffusion layer formed on the substrate is used.

Embodiment 2 = FIG. 3 is a schematic configuration diagram showing a semiconductor acceleration sensor according to another embodiment of the present invention, and FIG. 3 (a) is a schematic plan view showing a state viewed from above. (b) is a schematic cross-sectional view showing a part of the intersection of the wiring 4. The semiconductor acceleration sensor according to the present embodiment has a configuration in which a crossing portion of each wiring 4 is formed as a multilayer wiring using an impurity diffusion layer 5 in the semiconductor acceleration sensor shown in FIG.

More specifically, as shown in FIG. 3B, the semiconductor substrate 6 is formed at a portion where the weight 4, the bending portion 2 and the wiring 4 of the semiconductor substrate 6 constituting the support member 3 intersect and in the vicinity thereof. An impurity diffusion layer 5 of the opposite conductivity type is formed, and an insulating film 7 such as a silicon oxide film or a silicon nitride film is formed on the surface of the semiconductor substrate 6 where the impurity diffusion layer 5 is formed.
Then, a part of the insulating film 7 on the impurity diffusion layer 5 on both sides of the intersecting wiring 4 is removed to form a contact hole, and the contact hole is buried to form the impurity diffusion layer 5.
A wiring 4 made of aluminum (Al) or the like is formed so as to be electrically connected to the semiconductor device, thereby forming a multilayer wiring.

The impurity concentration of the impurity diffusion layer 5 is desirably 1 × 10 ²⁰ cm ⁻³ or more so that the resistance between the wirings can be reduced and a change in temperature is small.

Embodiment 3 = FIG. 4 is a schematic configuration diagram showing a semiconductor acceleration sensor according to another embodiment of the present invention, and FIG. 4 (a) is a schematic plan view showing a state viewed from above. (b) is a schematic cross-sectional view showing a part of the intersection of the wiring 4. The semiconductor acceleration sensor according to the present embodiment has a configuration in which the wiring 4 with the middle point of the wiring 4 between the piezoresistors is connected via the impurity diffusion layer 5 in the semiconductor acceleration sensor shown in FIG.

More specifically, as shown in FIG. 4B, the semiconductor substrate 6 constituting the weight portion 1, the bending portion 2 and the supporting member 3 intersects with the wiring 4 of the semiconductor substrate 6 and the vicinity thereof. An impurity diffusion layer 5 of the opposite conductivity type is formed, and an insulating film 7 such as a silicon oxide film or a silicon nitride film is formed on the surface of the semiconductor substrate 6 where the impurity diffusion layer 5 is formed.
Then, a predetermined portion of the insulating film 7 on the impurity diffusion layer 5 is removed by etching to form a contact hole, and the contact hole is buried and formed so as to be electrically connected to the impurity diffusion layer 5. A wiring 4 such as Al) is formed. As a result, in the portion where the wirings 4 intersect, the wirings are electrically connected via the impurity diffusion layers 5 formed in the semiconductor substrate 6 to perform multilayer wiring. At this time,
The wiring 4 for connection with the middle point of the wiring between the piezoresistors is also electrically connected to the impurity diffusion layer 5.

The impurity concentration of the impurity diffusion layer 5 is desirably 1 × 10 ²⁰ cm ⁻³ or more so that the resistance between the wirings can be reduced and the temperature change is small.

Therefore, in the first to third embodiments, a multilayer structure in which an insulating film such as a silicon oxide film or a silicon nitride film is interposed at the intersection so that the wirings 4 are not electrically connected at the intersections of the wirings 4. Since the wiring and the multilayer wiring using the impurity diffusion layer 5 formed in the central portion 2a are used, a semiconductor acceleration sensor having high sensitivity and excellent temperature characteristics is formed without increasing the width of the beam. be able to.

In all of the above-described embodiments, as shown in FIG. 5, the weight portion 1 is connected to the lower surface of the central portion 2a via the neck portion 1a to surround the neck portion 1a as a semiconductor acceleration sensor. The cut groove 8 may be formed between the weight part 1 and the bending part 2 at the location. Accordingly, when the chip size is the same as in all the above embodiments, the sensitivity of the semiconductor acceleration sensor can be improved, and when the sensitivity is the same as in all the above embodiments, the chip size is reduced. be able to. However, the cut groove 8 does not necessarily need to be formed at a position surrounding the neck 1a, and may be formed at least in the lower part of the beam part 2b and in the vicinity thereof.

[0032]

According to the first aspect of the present invention, there is provided a weight portion which is displaced by receiving acceleration, a center portion and a beam portion which extends in four directions from the outer edge of the center portion, and the weight portion is provided on the lower surface of the center portion. Are connected to each other, a supporting member that supports the bending portion, and a strain generated in the bending portion due to displacement of the weight portion is at least two of X and Y axes.
A piezoresistor that detects in each direction, the piezoresistor is disposed in the vicinity of a connection portion between the center portion and the beam portion, and the piezoresistors in each axial direction are formed in a bridge circuit. Wiring connecting the piezoresistors provided across the central portion is provided on the central portion, wires in each axial direction are orthogonally crossed, and the midpoint of each axial wire is on a beam portion in a different axial direction. Therefore, a semiconductor acceleration sensor having high sensitivity and excellent temperature characteristics can be provided without increasing the width of the beam portion.

According to a second aspect of the present invention, in the semiconductor acceleration sensor according to the first aspect, one of the orthogonally intersecting wires is orthogonally interposed via an impurity diffusion layer formed in a central portion at least at a portion where the intersecting orthogonally intersects. Since the wires cross each other so that each of the wires crossing each other does not conduct, the impurity diffusion layer can be formed when forming the piezoresistor.
Each wiring can be prevented from conducting without increasing the number of steps.

According to a third aspect of the present invention, in the semiconductor acceleration sensor according to the first or second aspect, the central portion is connected via a neck portion, and a cut groove is provided between the weight portion and the beam portion. Therefore, further miniaturization and higher sensitivity can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a semiconductor acceleration line sensor according to an embodiment of the present invention, where (a) is a schematic plan view and (b) is a schematic sectional view.

FIGS. 2A and 2B are schematic wiring diagrams of piezoresistors of the semiconductor acceleration sensor according to the embodiment; FIG. 2A is a schematic wiring diagram of piezoresistors for detecting acceleration in an X-axis direction;
FIG. 5 is a schematic wiring diagram of a piezo resistor for detecting acceleration in the Y-axis direction.

3A and 3B are schematic configuration diagrams illustrating a semiconductor acceleration sensor according to another embodiment of the present invention, in which FIG. 3A is a schematic plan view illustrating a state viewed from above, and FIG. It is a schematic sectional drawing which shows a part.

4A and 4B are schematic configuration diagrams illustrating a semiconductor acceleration sensor according to another embodiment of the present invention, in which FIG. 4A is a schematic plan view illustrating a state viewed from above, and FIG. It is a schematic sectional drawing which shows a part.

FIG. 5 is a schematic sectional view showing a semiconductor acceleration sensor according to another embodiment of the present invention.

6A and 6B are schematic configuration diagrams showing a semiconductor acceleration sensor according to a conventional example, in which FIG. 6A is a schematic plan view showing a state viewed from above, and FIG. 6B is a schematic sectional view.

7A and 7B are schematic configuration diagrams showing a semiconductor acceleration sensor according to a conventional example, where FIG. 7A is a schematic plan view showing a state viewed from above, and FIG. 7B is a schematic sectional view.

FIG. 8 is a circuit diagram showing connection of piezoresistors in X-axis, Y-axis, and Z-axis directions.

[Explanation of symbols]

 RX1 to RX4, RY1 to RY4, RZ1 to RZ4 Piezoresistors X1 to X6, Y1 to Y6 Terminal 1 Weight 1a Neck 2 Flexure 2a Central 2b Beam 3 Support member 4 Wiring 5 Impurity diffusion layer 6 Semiconductor substrate 7 Insulation Membrane 8 Notch 9 Power supply

Continued on the front page (72) Inventor Hitoshi Yoshida 1048 Odomo Kadoma, Kadoma City, Osaka Inside Matsushita Electric Works, Ltd.

Claims (3)

[Claims] A weight portion that is displaced by receiving acceleration, a central portion, and a beam portion extending from an outer edge of the central portion in all directions;
A bending portion in which the weight portion is connected to a lower surface of the central portion,
A support member for supporting the bending portion, and a strain generated in the bending portion due to displacement of the weight portion being at least two of X and Y axes.
A piezoresistor that detects in a direction, the piezoresistor is disposed near a connection portion between the central portion and the beam portion, and the piezoresistors in each axial direction are configured as a bridge circuit in a semiconductor acceleration sensor. A wire connecting the piezoresistors provided across the central portion in each axial direction is provided on the central portion, and the wires in each axial direction are orthogonally crossed,
A semiconductor acceleration sensor, wherein a midpoint of the wiring in each axial direction is electrically drawn out onto the support member via a beam portion in a different axial direction. 2. The method according to claim 1, wherein one of the orthogonally crossing wires is
2. The semiconductor acceleration according to claim 1, wherein at least the orthogonally intersecting portions intersect at right angles via an impurity diffusion layer formed in the central portion so that each of the intersecting wires does not conduct. Sensor. 3. The weight portion is connected to the center portion via a neck portion, and a cut groove is provided between the weight portion and the beam portion. Item 3. A semiconductor acceleration sensor according to item 2.