JP2011220686A - Semiconductor acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor acceleration sensor that, without imposing any structural restriction, reduces differences in detection sensitivity among the X, Y and Z axes, is small in drift and reduces fluctuations in signal output among the three axes.SOLUTION: According to the invention, there is provided a semiconductor acceleration sensor having over a semiconductor substrate a frame part, a weight part, a flexible part arranged between the frame part and the weight part, a plurality of piezoresistance elements arranged on the flexible part in a first direction, a plurality of piezoresistance elements arranged in a second direction orthogonal to the first direction, and a plurality of bridge circuits each containing the pluralities of piezoresistance elements, at least one of the bridge circuits having a first resistor between either a high potential end or a low potential end that applies voltages to the bridge circuits on one hand and the bridge circuits on the other.

Description

The present invention relates to an acceleration sensor. In particular, the present invention relates to a semiconductor acceleration sensor that senses acceleration in at least two orthogonal directions, and an electronic component and an electronic device using the same.

In recent years, various electronic devices including portable terminals and game machines have been downsized, and functions have been diversified. In connection with this, the sensor mounted in an electronic device is required to be small in size and high in sensitivity, and as one of the technologies that meet such demand, a MEMS (Micro Electro Mechanical Systems) technology applying a semiconductor manufacturing technology is used. ing. One such small sensor is a semiconductor acceleration sensor, and a three-axis acceleration sensor using a piezoresistive element has been developed and put into practical use.

In general, a triaxial acceleration sensor using a piezoresistive element is a flexible beam that is a beam provided in a perpendicular X axis direction and a Y axis direction integrally formed with a frame portion that is a support formed on a substrate. The portion has a structure with a weight at the intersection. In the triaxial acceleration sensor, in order to detect acceleration in the X axis direction, Y axis direction, and Z axis direction, a piezoresistive element for detecting acceleration in the X axis direction and Z axis direction is provided in the X axis direction. Four piezoresistive elements for detecting acceleration in the Y-axis direction are provided on the upper surface of the flexible part on the upper surface of the flexible part.

One piezoresistive element is arranged on each of the frame portion side and the intersecting portion side of the flexible portion to form a piezoresistor pair, and the piezoresistive pair is formed on the upper surface of the flexible portion with the intersecting portion as the center. One set is arranged symmetrically to form a uniaxial acceleration sensor. The triaxial acceleration sensor detects accelerations in the X axis direction, the Y axis direction, and the Z axis direction by forming three uniaxial acceleration sensors in the flexible portion.

When a triaxial acceleration sensor using a piezoresistive element detects acceleration, the bending of the flexible portion caused by the inclination of the weight gives stress to the four piezoresistive elements, and the piezoresistive element has a small electric resistance due to the stress. Change occurs. A triaxial acceleration sensor using a piezoresistive element detects acceleration using a minute change in electric resistance generated in each piezoresistive element as a voltage output from a Wheatstone bridge circuit.

Here, when the triaxial acceleration sensor using a piezoresistive element detects acceleration in the X axis direction and the Y axis direction, that is, in the horizontal direction with respect to the upper surface of the triaxial acceleration sensor, the flexure of the flexible portion is When the acceleration in the Z-axis direction, that is, in the direction perpendicular to the upper surface of the three-axis acceleration sensor is detected, the flexible portion is bent due to the translational motion of the weight. The sensor that detects the acceleration in the X-axis direction and the sensor that detects the acceleration in the Y-axis direction have the same detection sensitivity. However, the sensor that detects the acceleration in the X-axis direction and the Z-axis due to the difference in the bending method. The detection sensitivity is different from that of the sensor that detects the acceleration in the direction, although it is arranged in the flexible portion provided in the same X-axis direction.

Such a difference in detection sensitivity for each axis for detecting acceleration is corrected by calculation in an IC chip used for detection. However, in order to increase the detection sensitivity, it is necessary to improve the triaxial acceleration sensor itself.

Therefore, as a technique for reducing the difference in sensitivity between the sensor that detects the acceleration in the X-axis direction and the Y-axis direction and the sensor that detects the acceleration in the Z-axis direction, Patent Document 1 discloses a technique on the flexible part in the X-axis direction. So that the longitudinal direction of the X-axis piezoresistive element arranged in parallel with the longitudinal direction of the flexible part in the X-axis direction is angled with the longitudinal direction of the flexible part in the X-axis direction. Is disclosed. Patent Document 2 discloses that the ratio of the cross-sectional area of the flexible part provided with the piezoresistive element and the cross-sectional area of the flexible part not provided with the piezoresistive element is adjusted. In Patent Document 3, there are differences in internal stress due to electrode thin films applied to the four piezoelectric elements, thermal stress due to changes in ambient temperature, and the like, so that the offset voltage is large and the offset voltage fluctuates. The electrode thin film pattern layout in the flexible region forming the piezoresistive element is made uniform in both the detection axis direction and the direction perpendicular to the detection axis direction by newly providing an electrode thin film pattern of the same width in the manufacturing process of It is disclosed.

JP 2003-294781 A JP 2006-98323 A JP 2003-92413 A

However, these technologies adjust the structure of the triaxial acceleration sensor beam and the arrangement of the piezoresistive elements formed on the beam, which is an obstacle to further downsizing the triaxial acceleration sensor, The increase in manufacturing cost is caused by the increase. In other words, in order to miniaturize the triaxial acceleration sensor, it is desirable to reduce the width of the beam. However, the piezoresistive element is arranged so as to have an angle with the longitudinal direction of the flexible portion, or the same manufacturing process as the extraction electrode In the method of newly providing an electrode thin film pattern having the same width, the width of the beam is limited. Further, in order to refine the beam so as to have such a structure, a more advanced refinement technique is required, which increases the manufacturing cost. Therefore, in order to further reduce the size of the triaxial acceleration sensor, the structure of the flexible portion and the piezoresistive element formed on the flexible portion is simple, and the triaxial acceleration in which the detection sensitivity of the triaxial is comparable. A sensor is desired.

The present invention provides a semiconductor acceleration sensor that reduces the difference in detection sensitivity of the X, Y, and Z axes, reduces drift, and reduces fluctuations in signal output between the three axes without providing structural limitations. This is the issue.

According to an embodiment of the present invention, a semiconductor substrate includes a frame portion, a weight portion, a flexible portion disposed between the frame portion and the weight portion, and the flexible portion in a first direction. A plurality of piezoresistive elements disposed; a plurality of piezoresistive elements disposed in a second direction orthogonal to the first direction; and a plurality of bridge circuits each including the plurality of piezoresistive elements. And at least one bridge circuit having a first resistor between the bridge circuit and one of a high potential end and a low potential end for applying a voltage to the bridge circuit. A semiconductor acceleration sensor is provided.

The semiconductor acceleration sensor is applied to a piezoresistive element that forms a bridge by connecting a resistance element between a power input terminal that is a high potential end or a low potential end and a piezoresistive element that forms a bridge. The voltage can be adjusted, and the adjustment can be made to reduce the difference in detection sensitivity by adjusting the output voltage between the acceleration sensors that detect the acceleration in the three-axis directions. The semiconductor acceleration sensor can improve the S / N ratio by suppressing drift.

The semiconductor acceleration sensor may further include a second resistor between the other of the high potential end and the low potential end and the bridge circuit.

The semiconductor acceleration sensor can adjust the voltage applied to the bridge circuit by connecting a resistance element between the power input terminal at the high potential end and the low potential side terminal and the bridge circuit. By adjusting the output voltage between the acceleration sensors that detect the acceleration in the axial direction, the difference in detection sensitivity can be adjusted. The semiconductor acceleration sensor can improve the S / N ratio by suppressing drift.

The semiconductor acceleration sensor may further include a third resistor between the bridge circuit and any one of the first output terminal and the second output terminal of the bridge circuit.

The semiconductor acceleration sensor can adjust the voltage applied to the bridge circuit by connecting a resistance element between the power input terminal at the high potential end and the low potential side terminal and the bridge circuit. By adjusting the output voltage between the acceleration sensors that detect the acceleration in the axial direction, the difference in detection sensitivity can be adjusted. The semiconductor acceleration sensor can improve the S / N ratio by suppressing drift.

The semiconductor acceleration sensor may further include a fourth resistor between the other of the first output terminal and the second output terminal and the bridge circuit.

The semiconductor acceleration sensor can adjust the voltage applied to the bridge circuit by connecting a resistance element between the power input terminal at the high potential end and the low potential side terminal and the bridge circuit. By adjusting the output voltage between the acceleration sensors that detect the acceleration in the axial direction, the difference in detection sensitivity can be adjusted. The semiconductor acceleration sensor can improve the S / N ratio by suppressing drift.

The semiconductor acceleration sensor may include the first resistor, the second resistor, the third resistor, and the fourth resistor in the frame portion.

The semiconductor acceleration sensor is a semiconductor in which a drift element is small and fluctuations in signal output between three axes are reduced without forming a structural limitation for downsizing the semiconductor acceleration sensor by forming a resistive element in the frame portion. An acceleration sensor can be provided. In addition, the semiconductor acceleration sensor tends to have lower detection sensitivity due to downsizing, but the semiconductor acceleration sensor can improve the S / N ratio by suppressing drift.

In the semiconductor acceleration sensor, the plurality of bridge circuits detect a first bridge circuit that detects acceleration in the first direction, a second bridge circuit detects acceleration in the second direction, and the first bridge circuit. And a third bridge circuit for detecting an acceleration in a third direction orthogonal to the second direction, wherein the first bridge circuit or the second bridge circuit is arranged around a horizontal direction of the weight portion. The acceleration in the first direction or the acceleration in the second direction is detected based on the deflection of the flexible part due to the rotational movement of the third part, and the third bridge circuit is based on the translational movement of the weight part in the vertical direction. The acceleration in the third direction may be detected based on the bending of the flexible portion.

When detecting the acceleration in the horizontal direction with respect to the upper surface of the semiconductor acceleration sensor, the flexure of the flexible part is caused by the rotational movement of the weight, but when detecting the acceleration in the vertical direction with respect to the upper surface, The bending is caused by the translational movement of the weight, and the detection sensitivity differs depending on the bending method of the flexible part. However, the semiconductor acceleration sensor is connected between the power input terminal at the high potential end and the terminal on the low potential side and the bridge circuit. The voltage applied to the bridge circuit can be adjusted by connecting a resistance element to the sensor, and the difference in detection sensitivity can be reduced by adjusting the output voltage between acceleration sensors that detect acceleration in three axes. Can be adjusted.

The semiconductor acceleration sensor has at least one of the first, second, and third bridge circuits to adjust so as to reduce a difference in detection sensitivity between the first, second, and third bridge circuits having different detection sensitivities. One of the resistors may be included.

The semiconductor acceleration sensor adjusts the voltage applied to the bridge circuit by connecting a resistance element to at least one of the plurality of bridge circuits, and adjusts the output voltage of the bridge circuits having different detection sensitivities. Adjustment can be made to reduce the difference in detection sensitivity.

In the semiconductor acceleration sensor, the acceleration in the first direction and the acceleration in the second direction are caused by bending of the flexible portion caused by a horizontal rotational movement of the weight portion. The output from the first output end and the second output end is detected, and the acceleration in the third direction is caused by the deflection of the flexible portion caused by the translational movement of the weight portion in the vertical direction. It may be detected as an output from the first output terminal and the second output terminal of the bridge circuit.

When detecting the acceleration in the horizontal direction with respect to the upper surface of the semiconductor acceleration sensor, the flexure of the flexible part is caused by the rotational movement of the weight, but when detecting the acceleration in the vertical direction with respect to the upper surface, The bending is caused by the translational movement of the weight, and the detection sensitivity differs depending on the bending method of the flexible part. However, the semiconductor acceleration sensor is connected between the power input terminal at the high potential end and the terminal on the low potential side and the bridge circuit. The voltage applied to the bridge circuit can be adjusted by connecting the resistor element to the first output by adjusting the detection sensitivity difference between the acceleration sensors for detecting the acceleration in the three-axis directions. It can be detected as an output from the end and the second output end.

A sensor module having the semiconductor acceleration sensor is provided.

A sensor module using the semiconductor acceleration sensor can be mounted and used in an electronic device that is required to be small and highly accurate, and the sensor module has a small drift and fluctuations in signal output between three axes. Reduce. Further, the semiconductor acceleration sensor tends to have a lower detection sensitivity due to downsizing, but by using the semiconductor acceleration sensor, it is possible to provide a sensor module that suppresses drift and improves the S / N ratio.

An electronic device having the semiconductor acceleration sensor is provided.

In an electronic device, miniaturization and high accuracy of a semiconductor acceleration sensor are required. By mounting the semiconductor acceleration sensor, a drift is small and fluctuation in signal output between three axes is reduced. Although the semiconductor acceleration sensor tends to have lower detection sensitivity due to downsizing, it is possible to provide an electronic device that suppresses drift and improves the S / N ratio by using the semiconductor acceleration sensor.

According to one embodiment of the present invention, a plurality of piezoresistive elements are formed by diffusing impurities on one surface of a semiconductor substrate, a resistive element is formed on one surface of the semiconductor substrate, A piezoresistive element is connected to form a bridge circuit, and the resistor is arranged between one of a high potential end and a low potential end for applying a voltage to the bridge circuit, and the bridge circuit. Wiring is formed, and a frame portion, a weight portion, and a flexible portion arranged between the frame portion and the weight portion are formed on the semiconductor substrate, and are arranged in the first direction. A plurality of piezoresistive elements, and a plurality of piezoresistive elements arranged in a second direction orthogonal to the first direction are formed in the flexible portion. A method for manufacturing an acceleration sensor is provided.

According to the method for manufacturing a semiconductor acceleration sensor, there is provided a method for manufacturing a semiconductor acceleration sensor that can be adjusted so as to suppress drift accurately and reduce a difference in detection sensitivity between acceleration sensors that detect acceleration in three axes. .

In the method for manufacturing the semiconductor acceleration sensor, the resistance element may be formed on the frame portion.

In the manufacturing method of the semiconductor acceleration sensor, the resistance element is formed in the frame portion, so that there is no limitation due to the width and length of the flexible portion. Therefore, when the semiconductor acceleration sensor is miniaturized, there is no need for a more advanced miniaturization technique or an increase in manufacturing cost.

In the method for manufacturing the semiconductor acceleration sensor, the piezoresistive element and the resistor may be formed in the same process.

According to the method for manufacturing a semiconductor acceleration sensor, in order to manufacture a semiconductor acceleration sensor that can be adjusted so as to suppress drift accurately and reduce a detection sensitivity difference between acceleration sensors that detect acceleration in three axes, Manufacturing by simultaneously forming the resistive element connected between the power supply input terminal, which is the potential end, the terminal on the low potential side, and the bridge circuit, or between the bridge circuit and the output terminal, in the same process as the piezoresistive element. The desired effect can be obtained without increasing the number of steps.

According to the present invention, there is provided a semiconductor acceleration sensor that reduces the difference in detection sensitivity of the X, Y, and Z axes, reduces drift, and reduces fluctuations in signal output between the three axes without providing structural limitations. can do.

It is a circuit diagram of the sensor circuit which concerns on one Embodiment of this invention, (a) is a X-axis direction, (b) is a Y-axis direction, (c) shows the sensor circuit for detecting a Z-axis direction. It is a wiring pattern figure of the acceleration sensor 100 which concerns on one Embodiment of this invention. It is a circuit diagram of the sensor circuit which concerns on one Embodiment of invention, (a) is a X-axis direction, (b) is a Y-axis direction, (c) shows the sensor circuit for detecting a Z-axis direction. It is a wiring pattern figure of the acceleration sensor 200 which concerns on one Embodiment of this invention. It is a circuit diagram of the sensor circuit which concerns on one Embodiment of this invention, (a) is a X-axis direction, (b) is a Y-axis direction, (c) shows the sensor circuit for detecting a Z-axis direction. It is a wiring pattern figure of the acceleration sensor 300 which concerns on one Embodiment of this invention. It is a circuit diagram of the sensor circuit which concerns on one Embodiment of this invention, (a) is a X-axis direction, (b) is a Y-axis direction, (c) shows the sensor circuit for detecting a Z-axis direction. It is a wiring pattern figure of the acceleration sensor 400 which concerns on one Embodiment of this invention. FIG. 9 is a diagram showing a wiring pattern diagram of the semiconductor acceleration sensor 400 shown in FIG. 8 again. It is a disassembled perspective view of the semiconductor acceleration sensor 400 concerning one Embodiment of this invention. It is a figure explaining the manufacturing process of the semiconductor acceleration sensor 400 concerning one Embodiment of this invention. It is a figure explaining the manufacturing process of the semiconductor acceleration sensor 400 concerning one Embodiment of this invention. It is a figure which shows the circuit structure of the processing circuit 550 which concerns on one Embodiment of this invention. It is a figure showing sensor module 500 concerning one embodiment of the present invention. It is a figure which shows the portable information terminal 600 which concerns on one Embodiment of this invention. It is a table | surface of the resistance value of the semiconductor acceleration sensor of the Example of this invention, and a comparative example, a shape, and a sensitivity.

Hereinafter, a semiconductor acceleration sensor according to the present invention will be described with reference to the drawings. However, the semiconductor acceleration sensor of the present invention can be implemented in many different modes and should not be construed as being limited to the description of the embodiments and examples shown below. Note that in the drawings referred to in this embodiment mode and examples, the same portions or portions having similar functions are denoted by the same reference numerals, and repetitive description thereof is omitted.

As described above, intensive research was conducted on a method for realizing a triaxial acceleration sensor in which the structure of the piezoresistive element formed in the flexible portion is simple and the triaxial detection sensitivity is comparable. . In the conventional solution, it is necessary to adjust the arrangement of the piezoresistive elements formed in the flexible portion so that the sensitivity of the piezoresistive elements is approximately the same, and in this method, the triaxial acceleration sensor is miniaturized. It becomes an obstacle to doing.

On the other hand, the triaxial acceleration sensor has a drift as a factor that affects the detection sensitivity. Drift is the time variation of the output value of the resistance element used for detection. In order to maintain high-precision detection sensitivity, it is necessary to suppress drift in the triaxial acceleration sensor. In the triaxial acceleration sensor, the drift in the Z-axis direction is different from that in the X-axis direction and the Y-axis direction.

Therefore, in a triaxial acceleration sensor with different detection sensitivity between axes, it is not a conventional method for increasing the detection sensitivity of the triaxial acceleration sensor by adjusting the arrangement of the piezoresistive elements, but the structural limitation is suppressed while suppressing drift. We examined a method in which the detection sensitivity of the three axes becomes the same without providing them.

(Embodiment 1)
FIG. 1 is a circuit diagram of a sensor circuit according to an embodiment of the present invention. (A) shows the sensor circuit 101 which detects the acceleration of the X-axis direction which is a 1st direction, (b) shows the sensor circuit 102 which detects the acceleration of the Y-axis direction which is a 2nd direction, (c ) Shows a sensor circuit 103 for detecting the Z-axis direction which is the third direction.

In the sensor circuit 101, the piezoresistive element Rx1, the piezoresistive element Rx2, the piezoresistive element Rx3, and the piezoresistive element Rx4 are connected so as to form a bridge circuit 51 in the X-axis direction, and the piezoresistive element Rx1 and the piezoresistive element Rx2 Is connected to the power input terminal VDx on the high potential side via the resistance element Rx5. The connection end of the piezoresistive element Rx3 and the piezoresistive element Rx4 is connected to the terminal VGx on the low potential side. Here, the terminal VGx may be grounded. In order to output a minute change in electric resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Rx1 and the piezoresistive element Rx4 is connected to the output terminal Vxout1 on the high potential side (+), and the piezoresistor The connection end of the element Rx2 and the piezoresistive element Rx3 is connected to the output terminal Vxout2 on the low potential side (−).

The sensor circuit 102 is connected so that the piezoresistive element Ry1, the piezoresistive element Ry2, the piezoresistive element Ry3, and the piezoresistive element Ry4 form a bridge circuit 52 in the Y-axis direction, and the piezoresistive element Ry1 and the piezoresistive element A connection end to Ry2 is connected to a power input terminal VDy on the high potential side via a resistance element Ry5. The connection end of the piezoresistive element Ry3 and the piezoresistive element Ry4 is connected to the terminal VGy on the low potential side. Here, the terminal VGy may be grounded. In order to output a minute change in electric resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Ry1 and the piezoresistive element Ry4 is connected to the output terminal Vyout1 on the low potential side (−), and the piezoresistor The connection end of the element Ry2 and the piezoresistive element Ry3 is connected to the output terminal Vout2 on the high potential side (+).

Further, the sensor circuit 103 is connected so that the piezoresistive element Rz1, the piezoresistive element Rz2, the piezoresistive element Rz3, and the piezoresistive element Rz4 form a bridge circuit in the Z-axis direction, and the piezoresistive element Rz1 and the piezoresistive element Rz2 are connected. Is connected to the power input terminal VDz on the high potential side via the resistance element Rz5. The connection end of the piezoresistive element Rz3 and the piezoresistive element Rz4 is connected to the terminal VGz on the low potential side. Here, the terminal VGz may be grounded. In order to output a minute change in electric resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Rz1 and the piezoresistive element Rz3 is connected to the output terminal Vzout1 on the high potential side (+), and the piezoresistor The connection end of the element Rz2 and the piezoresistive element Rz4 is connected to the output terminal Vzout2 on the low potential side (−).

The sensor circuit 101 according to the embodiment of the present invention can adjust the voltage applied from the power input terminal VDx to the connection end of the piezoresistive element Rx1 and the piezoresistive element Rx2 by connecting the resistor element Rx5. . That is, the voltage Vx applied between the power input terminal VDx and the low potential side terminal VGx of the sensor circuit 101 is divided into the combined resistance of the four piezoresistive elements forming the bridge circuit 51 and the resistive element Rx5. Therefore, the voltage Vx1 is applied to the bridge circuit 51. Although the output voltage of the sensor circuit 101 is also reduced by adjusting the voltage, the effect of suppressing drift is proportional to the square of the voltage applied to the bridge resistance. For example, even if the output voltage is reduced to 1/2 by adjusting the voltage, the drift can be suppressed to 1/2 ² , that is, 1/4.

Further, the sensor circuit 102 includes the resistance element Ry5, so that the voltage applied to the connection terminal between the piezoresistance element Ry1 and the piezoresistance element Ry2 from the power input terminal VDy can be adjusted. Similarly, since the sensor circuit 103 includes the resistance element Rz5, it is possible to adjust the voltage applied from the power input terminal VDz to the connection end of the piezoresistance element Rz1 and the piezoresistance element Rz2. In the sensor circuit 102 and the sensor circuit 103, the output voltage is also reduced by adjusting the voltage as described above, but the effect of suppressing the drift is proportional to the square of the voltage applied to the bridge resistance. For example, even if the output voltage is reduced to 1/2 by adjusting the voltage, the drift can be suppressed to 1/2 ² , that is, 1/4.

The sensor circuit 101 that detects the acceleration in the X-axis direction, the sensor circuit 102 that detects the acceleration in the Y-axis direction, and the sensor circuit 103 that detects the Z-axis direction include the resistance element Rx5, the resistance element Ry5, and the resistance element Rz5, respectively. By having it, the output voltage can be adjusted, and the detection sensitivity that is different in each axial direction can be adjusted while suppressing drift. Unlike an acceleration sensor that detects acceleration in the X-axis direction and the Y-axis direction, the acceleration sensor that detects acceleration in the Z-axis direction generally has high detection sensitivity. In addition, the drift in the Z-axis direction tends to increase with respect to the X-axis direction and the Y-axis direction. For this reason, an acceleration sensor that detects the acceleration in the X-axis direction and the Y-axis direction while adjusting the output voltage by connecting the resistor element Rz5 to the sensor circuit 103 for detecting the Z-axis direction and suppressing drift, and The detection sensitivity can be adjusted to the same extent. Therefore, it is not necessary to connect a resistance element to the sensor circuit that detects acceleration of all three axes, and the resistance element may be connected only to a sensor circuit that detects acceleration in the axial direction for which drift is to be adjusted.

In the present embodiment, the method of connecting the resistance element Rx5, the resistance element Ry5, and the resistance element Rz5 to the power input terminal side has been described. However, the resistance element Rx5, the resistance element Ry5, and the resistance element Rz5 are connected to the low potential side. You may make it connect to the terminal side.

Next, a semiconductor acceleration sensor 100 according to an embodiment of the present invention in which the sensor circuit 101, the sensor circuit 102, and the sensor circuit 103 are applied to a three-axis acceleration sensor will be described with reference to FIG. The semiconductor acceleration sensor 100 includes a flexible portion 111 in the X-axis direction, a flexible portion 112 in the Y-axis direction, and an intersection 115 (weight support portion) between the flexible portion 111 in the X-axis direction and the flexible portion 112 in the Y-axis direction. ), A frame portion 121 and a weight portion 131.

A piezoresistive element Rx1, a piezoresistive element Rx2, a piezoresistive element Rx3, and a piezoresistive element Rx4 are formed on the flexible portion 111 in the X axis direction to detect acceleration in the X axis direction. 101 is formed. Further, in order to detect the acceleration in the Z-axis direction, the piezoresistive element Rz1, the piezoresistive element Rz2, the piezoresistive element Rz3, and the piezoresistive element Rz4 are formed in the flexible portion 111 in the X-axis direction. A sensor circuit 103 is formed.

A piezoresistive element Ry1, a piezoresistive element Ry2, a piezoresistive element Ry3, and a piezoresistive element Ry4 are formed on the flexible portion 112 in the Y-axis direction to detect acceleration in the Y-axis direction. 102 is formed. Note that a dummy resistance element 191 and a dummy resistance element 192 may be disposed in the flexible portion 112 in the Y-axis direction to balance the flexible portion 111 in the X-axis direction. A weight part 131 is formed on the lower side of the intersecting part 115, and the weight part 131 is shaken according to the acceleration, whereby the flexible part 111 in the X-axis direction and the flexible part 112 in the Y-axis direction are bent.

The flexible portion 111 in the X-axis direction and the flexible portion 112 in the Y-axis direction are supported by a frame portion 121. The frame portion 121 includes power input terminals VDx, VDy, and VDz and low-potential side terminals VDx, VGy, and VGz. And output terminals Vxout1, Vxout2, Vyout1, Vyout2, Vzout1, and Vzout2. Although the power input terminals VDx, VDy, and VDz are shown as three terminals, they can be branched from one common input terminal.

The resistance element Rx5, the resistance element Ry5, and the resistance element Rz5 according to the first embodiment of the present invention are preferably formed in the frame portion 121. Since the resistance element is formed in the frame portion 121, there is no influence on the bending generated in the flexible portion 111 in the X-axis direction and the flexible portion 112 in the Y-axis direction detected by the piezoresistive element. Further, the resistance element Rx5, the resistance element Ry5, and the resistance element Rz5 may be formed of any resistance element. However, by forming the resistance element Rx5, the resistance element Ry5, and the resistance element Rz5, a desired effect can be obtained without increasing the number of manufacturing steps.

In the present embodiment, the semiconductor acceleration sensor 100 includes the flexible portion 111 in the X-axis direction and the flexible portion 112 in the Y-axis direction. However, the semiconductor acceleration sensor 100 according to the present invention has a beam shape. A diaphragm-like flexible part may be used instead of the flexible part. That is, the piezoresistive element that supports the weight portion with the diaphragm and detects the acceleration in the X-axis direction and the Y-axis direction may be arranged in the axial direction orthogonal to each other on the upper surface of the diaphragm.

As described above, the semiconductor acceleration sensor according to the present embodiment of the present invention is a piezoresistive element that forms a bridge by connecting a resistive element between a power input terminal and a piezoresistive element that forms a bridge. The applied voltage can be adjusted, and adjustment can be made to reduce the difference in detection sensitivity by adjusting the output voltage between the acceleration sensors that detect acceleration in the three-axis directions. Further, by forming the resistance element in the frame portion of the semiconductor acceleration sensor, the semiconductor has a small drift and reduces fluctuations in signal output between the three axes without providing a structural limitation for downsizing the semiconductor acceleration sensor. There is an excellent effect that an acceleration sensor can be provided. Although the semiconductor acceleration sensor has a tendency to decrease the detection sensitivity due to downsizing, the semiconductor acceleration sensor according to the present invention of the present embodiment can improve the S / N ratio by suppressing drift.

(Embodiment 2)
In the first embodiment, a resistance element is connected between the bridge circuit and the power supply input terminal or the low-potential side terminal so as to reduce the difference in detection sensitivity between the acceleration sensors that detect the acceleration in the triaxial direction. In the second embodiment, an example in which a resistance element is connected between the bridge circuit and both the power supply input terminal and the low potential side terminal will be described.

FIG. 3 is a circuit diagram of a sensor circuit according to an embodiment of the present invention. (A) shows the sensor circuit 201 which detects the acceleration of a X-axis direction, (b) shows the sensor circuit 202 which detects the acceleration of a Y-axis direction, (c) shows the sensor circuit for detecting a Z-axis direction. 203 is shown.

The sensor circuit 201 has a bridge circuit 51 in the X-axis direction including four piezoresistive elements, and the connection end of the piezoresistive element Rx1 and the piezoresistive element Rx2 is a power source on the high potential side via the resistive element Rx6a. Connected to the input terminal VDx. The connection end of the piezoresistive element Rx3 and the piezoresistive element Rx4 is connected to the low potential side terminal VGx via the resistive element Rx6b. Here, the terminal VGx may be grounded. In order to output a minute change in electric resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Rx1 and the piezoresistive element Rx4 is connected to the output terminal Vxout1 on the high potential side (+), and the piezoresistor The connection end of the element Rx2 and the piezoresistive element Rx3 is connected to the output terminal Vxout2 on the low potential side (−).

The sensor circuit 202 has a bridge circuit 52 in the Y-axis direction including four piezoresistive elements, and the connection end of the piezoresistive element Ry1 and the piezoresistive element Ry2 is connected to the high potential side via the resistive element Ry6a. It is connected to a certain power input terminal VDy. The connection end of the piezoresistive element Ry3 and the piezoresistive element Ry4 is connected to the low potential side terminal VGy via the resistive element Ry6b. Here, the terminal VGy may be grounded. In order to output a minute change in electric resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Ry1 and the piezoresistive element Ry4 is connected to the output terminal Vyout1 on the low potential side (−), and the piezoresistor The other ends of the element Ry2 and the piezoresistive element Ry3 are connected to the output terminal Vyout2 on the high potential side (+).

Further, the sensor circuit 203 has a bridge circuit in the Z-axis direction including four piezoresistive elements, and the connection end of the piezoresistive element Rz1 and the piezoresistive element Rz2 is on the high potential side via the resistive element Rz6a. Connected to the power input terminal VDz. The connection end of the piezoresistive element Rz3 and the piezoresistive element Rz4 is connected to the low potential side terminal VGz via the resistive element Rz6b. Here, the terminal VGz may be grounded. In order to output a minute change in electric resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Rz1 and the piezoresistive element Rz3 is connected to the output terminal Vzout1 on the high potential side (+), and the piezoresistor The connection end of the element Rz2 and the piezoresistive element Rz4 is connected to the output terminal Vzout2 on the low potential side (−).

The sensor circuit 201 according to the embodiment of the present invention can adjust the voltage applied to both ends of the bridge circuit 51 by connecting the resistance element Rx6a and the resistance element Rx6b to the bridge circuit 51. That is, the voltage Vx applied between the power supply input terminal VDx and the low potential side terminal VGx of the sensor circuit 201 is the combined resistance of the four piezoresistive elements forming the bridge circuit 51, the resistance element Rx6a, and the resistance Since the voltage is divided to the element Rx6b, the voltage Vx1 is applied to the bridge circuit 51. Although the output voltage of the sensor circuit 201 is also reduced by adjusting the voltage, the effect of suppressing drift is proportional to the square of the voltage applied to the bridge resistance. For example, even if the output voltage is reduced to 1/2 by adjusting the voltage, the drift can be suppressed to 1/2 ² , that is, 1/4.

For example, when the voltage applied between the power supply input terminal VDx and the low potential side terminal VGx is 3 V, the resistances of the four piezoresistive elements, the resistive elements Rx6a, and the resistive elements Rx6b are equal. In this case, the voltage Vx1 applied to the bridge circuit 51, the voltage Vx2 applied to the resistance element Rx6a, and the voltage Vx3 applied to the resistance element Rx6b are each divided to 1 V, and the output voltage of the sensor circuit 201 is However, the drift can be reduced to 1/9.

Similarly, the sensor circuit 202 can adjust the voltage applied to one end of the bridge circuit 52 by connecting the resistance elements Ry6a and Ry6b to the bridge circuit 52. Similarly, the sensor circuit 203 can adjust the voltage applied to one end of the bridge circuit 53 by connecting the resistance elements Rz6a and Rz6b to the bridge circuit 53. In the sensor circuit 202 and the sensor circuit 203, the output voltage is also reduced by adjusting the voltage as described above, but the effect of suppressing the drift is proportional to the square of the voltage applied to the bridge resistance. For example, even if the output voltage is reduced to 1/2 by adjusting the voltage, the drift can be suppressed to 1/2 ² , that is, 1/4.

The sensor circuit 201 that detects the acceleration in the X-axis direction, the sensor circuit 202 that detects the acceleration in the Y-axis direction, and the sensor circuit 203 that detects the Z-axis direction include a resistance element Rx6a, a resistance element Rx6b, a resistance element Ry6a, and a resistance The output voltage can be adjusted by including the element Ry6b, the resistance element Rz6a, and the resistance element Rz6b, and the detection sensitivity that is different in each axial direction can be adjusted while suppressing drift. The acceleration sensor 203 that detects acceleration in the Z-axis direction generally has high detection sensitivity, unlike the acceleration sensor that detects the acceleration in the X-axis direction and the Y-axis direction in terms of how the flexible portion bends. In addition, the drift in the Z-axis direction tends to increase with respect to the X-axis direction and the Y-axis direction. For this reason, in particular, by connecting the resistance element Rz6a and the resistance element Rz6b to the sensor circuit 203 for detecting the Z-axis direction, the acceleration in the X-axis direction and the Y-axis direction is adjusted while adjusting the drift output voltage and suppressing the torsion. The acceleration sensor and the detection sensitivity can be adjusted to the same extent. Therefore, it is not necessary to connect a resistance element to the sensor circuit that detects acceleration of all three axes, and the resistance element may be connected only to a sensor circuit that detects acceleration in the axial direction for which drift is to be adjusted.

Next, a semiconductor acceleration sensor 200 according to an embodiment of the present invention in which the sensor circuit 201, the sensor circuit 202, and the sensor circuit 203 are applied to a three-axis acceleration sensor will be described with reference to FIG. The semiconductor acceleration sensor 200 includes a flexible portion 111 in the X-axis direction, a flexible portion 112 in the Y-axis direction, and an intersection 115 (weight support portion) between the flexible portion 111 in the X-axis direction and the flexible portion 112 in the Y-axis direction. ), A frame portion 121 and a weight portion 131.

The arrangement and configuration of each piezoresistive element for detecting acceleration in the X-axis direction, the Y-axis direction, and the Z-axis direction are the same as those of the first embodiment in the flexible portion 111 in the X-axis direction. The mechanism for detecting by the acceleration sensor is the same as that of the first embodiment.

The resistance element Rx6a, the resistance element Rx6b, the resistance element Ry6a, the resistance element Ry6b, the resistance element Rz6a, and the resistance element Rz6b according to the second embodiment of the present invention are preferably formed in the frame 121. Since the resistance element is formed in the frame portion 121, there is no influence on the bending generated in the flexible portion 111 in the X-axis direction and the flexible portion 112 in the Y-axis direction detected by the piezoresistive element. The resistance element Rx6a, the resistance element Rx6b, the resistance element Ry6a, the resistance element Ry6b, the resistance element Rz6a, and the resistance element Rz6b may be formed of any resistance element, but the manufacturing process is increased by forming the resistance element Rx6a, resistance element Rx6b, resistance element Rz6a, and resistance element Rz6b. The intended effect can be obtained without any problem.

In the present embodiment, the voltage applied to both ends of the bridge circuit can be balanced by connecting the resistance elements to both ends of the bridge circuit. Further, the resistance element Rx6a and the resistance element Rx6b, the resistance element Ry6a and the resistance element Ry6b, and the resistance element Rz6a and the resistance element Rz6b may be formed by a combination of resistance elements having the same resistance value, but resistances having different resistance values. You may form with the group of an element. When there is a restriction on the position where the resistance element is formed, it is possible to meet the restriction on the position where the resistance element is formed by changing the resistance value between the resistance element on the power input terminal side and the resistance element on the low potential side. it can.

In the present embodiment, the semiconductor acceleration sensor 200 includes the flexible portion 111 in the X-axis direction and the flexible portion 112 in the Y-axis direction. However, the semiconductor acceleration sensor 200 according to the present invention has a beam shape. A diaphragm may be used as a film-like flexible part instead of the flexible part. That is, the piezoresistive element that supports the weight portion with the diaphragm and detects the acceleration in the X-axis direction and the Y-axis direction may be arranged in the axial direction orthogonal to each other on the upper surface of the diaphragm.

As described above, the semiconductor acceleration sensor according to the present embodiment of the present invention has a voltage applied to the bridge circuit by connecting a resistance element between the power input terminal and the low potential side terminal and the bridge circuit. And adjusting the output voltage between the acceleration sensors that detect the acceleration in the three-axis directions can be adjusted to reduce the difference in detection sensitivity. Further, by forming the resistance element in the frame portion of the semiconductor acceleration sensor, the semiconductor has a small drift and reduces fluctuations in signal output between the three axes without providing a structural limitation for downsizing the semiconductor acceleration sensor. There is an excellent effect that an acceleration sensor can be provided. Although the semiconductor acceleration sensor has a tendency to decrease the detection sensitivity due to downsizing, the semiconductor acceleration sensor according to the present invention of the present embodiment can improve the S / N ratio by suppressing drift.

(Embodiment 3)
In the first and second embodiments, a resistance element is connected between the bridge circuit, the power supply input terminal, and the low potential side terminal so as to reduce the difference in detection sensitivity between the acceleration sensors that detect the acceleration in the three-axis direction. In the third embodiment, an example in which a resistance element is connected between the bridge circuit and the output terminal will be described.

FIG. 5 is a circuit diagram of a sensor circuit according to an embodiment of the present invention. (A) shows a sensor circuit 301 for detecting acceleration in the X-axis direction, (b) shows a sensor circuit 302 for detecting acceleration in the Y-axis direction, and (c) shows a sensor circuit for detecting the Z-axis direction. 303 is shown.

The sensor circuit 301 has a bridge circuit 51 in the X-axis direction including four piezoresistive elements, and the connection end of the piezoresistive element Rx1 and the piezoresistive element Rx2 is a power source on the high potential side via the resistor element Rx6a. Connected to the input terminal VDx. The connection end of the piezoresistive element Rx3 and the piezoresistive element Rx4 is connected to the low potential side terminal VGx via the resistive element Rx6b. Here, the terminal VGx may be grounded. In order to output a minute change in electric resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Rx1 and the piezoresistive element Rx4 is connected to the output terminal on the high potential side (+) via the resistor element Rx7. The connection end of the piezoresistive element Rx2 and the piezoresistive element Rx3 is connected to the low potential side (−) output terminal Vxout2.

The sensor circuit 302 has a bridge circuit 52 in the Y-axis direction including four piezoresistive elements, and the connection end of the piezoresistive element Ry1 and the piezoresistive element Ry2 is connected to the high potential side via the resistive element Ry6a. It is connected to a certain power input terminal VDy. The connection end of the piezoresistive element Ry3 and the piezoresistive element Ry4 is connected to the low potential side terminal VGy via the resistive element Ry6b. Here, the terminal VGy may be grounded. In order to output a minute change in electric resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Ry1 and the piezoresistive element Ry4 is connected to the output terminal Vyout1 on the low potential side (−), and the piezoresistor The connection end of the element Ry2 and the piezoresistive element Ry3 is connected to the high potential side (+) output terminal Vyout2 via the resistance element Ry7.

Further, the sensor circuit 303 has a bridge circuit in the Z-axis direction including four piezoresistive elements, and the contact end of the piezoresistive element Rz1 and the piezoresistive element Rz2 is on the high potential side via the resistive element Rz6a. Connected to the power input terminal VDz. The connection end of the piezoresistive element Rz3 and the piezoresistive element Rz4 is connected to the low potential side terminal VGz via the resistive element Rz6b. Here, the terminal VGz may be grounded. In order to output a minute change in electric resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Rz1 and the piezoresistive element Rz3 is connected to the output terminal Vzout1 on the high potential side (+) via the resistor element Rz7. The connection end of the piezoresistive element Rz2 and the piezoresistive element Rz4 is connected to the output terminal Vzout2 on the low potential side (−).

The sensor circuit 301 according to the embodiment of the present invention can adjust the voltage applied to both ends of the bridge circuit 51 by connecting the resistance element Rx6a and the resistance element Rx6b to the bridge circuit 51. That is, the voltage Vx applied between the power supply input terminal VDx and the low potential side terminal VGx of the sensor circuit 301 is the combined resistance of the four piezoresistive elements forming the bridge circuit 51, the resistive element Rx6a, and the resistance Since the voltage is divided to the element Rx6b, the voltage Vx1 is applied to the bridge circuit 51. In the sensor circuit 301, the output voltage is also reduced by adjusting the voltage as described above, but the effect of suppressing the drift is proportional to the square of the voltage applied to the bridge resistance. For example, even if the output voltage is reduced to 1/2 by adjusting the voltage, the drift can be suppressed to 1/2 ² , that is, 1/4.

Similarly, the sensor circuit 302 can adjust the voltage applied to both ends of the bridge circuit 52 by connecting the resistance elements Ry6a and Ry6b to the bridge circuit 52. Similarly, the sensor circuit 303 can adjust the voltage applied to both ends of the bridge circuit 53 by connecting the resistance elements Rz6a and Rz6b to the bridge circuit 53. Although the output voltage of the sensor circuit 302 and the sensor circuit 303 is also reduced by adjusting the voltage as described above, the effect of suppressing the drift is proportional to the square of the voltage applied to the bridge resistance. For example, even if the output voltage is reduced to 1/2 by adjusting the voltage, the drift can be suppressed to 1/2 ² , that is, 1/4.

A sensor circuit 301 that detects acceleration in the X-axis direction, a sensor circuit 302 that detects acceleration in the Y-axis direction, and a sensor circuit 303 that detects the Z-axis direction include a resistance element Rx6a, a resistance element Rx6b, a resistance element Ry6a, and a resistance The output voltage can be adjusted by including the element Ry6b, the resistance element Rz6a, and the resistance element Rz6b, and the detection sensitivity that is different in each axial direction can be adjusted while suppressing drift. The acceleration sensor 303 that detects the acceleration in the Z-axis direction is generally high in detection sensitivity, unlike the acceleration sensor that detects the acceleration in the X-axis direction and the Y-axis direction in terms of how the flexible portion bends. In addition, the drift in the Z-axis direction tends to increase with respect to the X-axis direction and the Y-axis direction. For this reason, in particular, the output voltage is adjusted by connecting the resistance element Rz6a and the resistance element Rz6b to the sensor circuit 303 for detecting the Z-axis direction, and acceleration in the X-axis direction and the Y-axis direction is suppressed while suppressing drift. The acceleration sensor to detect and the detection sensitivity can be adjusted to the same extent. Therefore, it is not necessary to connect a resistance element to the sensor circuit that detects acceleration of all three axes, and the resistance element may be connected only to a sensor circuit that detects acceleration in the axial direction for which drift is to be adjusted.

In the present embodiment, the description has been made based on the sensor circuit of the second embodiment in which the resistance elements Rx6a and Rx6b, the resistance elements Ry6a and Ry6b, and the resistance elements Rz6a and Rz6b are connected. Alternatively, the sensor circuit of the first embodiment in which a resistance element is connected to any one of the terminals on the low potential side may be used. In addition, although the method of connecting the resistor element Rx7, the resistor element Ry7, and the resistor element Rz7 to the output terminal on the high potential side has been described, the resistor element Rx7, the resistor element Ry7, and the resistor element Rz7 are connected to the output terminal on the low potential side. You may make it do.

Next, a semiconductor acceleration sensor 300 according to an embodiment of the present invention in which the sensor circuit 301, the sensor circuit 302, and the sensor circuit 303 are applied to a three-axis acceleration sensor will be described with reference to FIG. The semiconductor acceleration sensor 300 includes a flexible portion 111 in the X-axis direction, a flexible portion 112 in the Y-axis direction, and an intersection 115 (weight support portion) between the flexible portion 111 in the X-axis direction and the flexible portion 112 in the Y-axis direction. ), A frame portion 121 and a weight portion 131.

The arrangement and configuration of each piezoresistive element for detecting acceleration in the X-axis direction, the Y-axis direction, and the Z-axis direction are the same as those of the first embodiment in the flexible portion 111 in the X-axis direction. The mechanism for detecting by the acceleration sensor is the same as that of the first embodiment.

The resistor element Rx6a, the resistor element Rx6b, the resistor element Ry6a, the resistor element Ry6b, the resistor element Rz6a, the resistor element Rz6b, the resistor element Rx7, the resistor element Ry7, and the resistor element Rz7 according to the present invention of Embodiment 3 are formed in the frame 121. It is preferable to do. In addition, since the resistance element is formed in the frame portion 121, it does not affect the bending that occurs in the flexible portion 111 in the X-axis direction and the flexible portion 112 in the Y-axis direction detected by the piezoresistive element. Further, the resistance element Rx6a, the resistance element Rx6b, the resistance element Ry6a, the resistance element Ry6b, the resistance element Rz6a, the resistance element Rz6b, the resistance element Rx7, the resistance element Ry7, and the resistance element Rz7 may be formed of any resistance element. By forming with a piezoresistive element, the intended effect can be obtained without increasing the number of manufacturing steps.

In the present embodiment, the voltage applied to both ends of the bridge circuit can be balanced by connecting the resistance elements to both ends of the bridge circuit. Further, the resistance element Rx6a and the resistance element Rx6b, the resistance element Ry6a and the resistance element Ry6b, and the resistance element Rz6a and the resistance element Rz6b may be formed by a combination of resistance elements having the same resistance value, but resistances having different resistance values. You may form with the group of an element. When there is a restriction on the position where the resistance element is formed, it is possible to meet the restriction on the position where the resistance element is formed by changing the resistance value between the resistance element on the power input terminal side and the resistance element on the low potential side. it can.

In this embodiment, the semiconductor acceleration sensor 300 includes the X-axis direction flexible portion 111 and the Y-axis direction flexible portion 112. However, the semiconductor acceleration sensor 300 according to the present invention has a beam shape. A diaphragm may be used as a film-like flexible part instead of the flexible part. That is, the piezoresistive element that supports the weight portion with the diaphragm and detects the acceleration in the X-axis direction and the Y-axis direction may be arranged in the axial direction orthogonal to each other on the upper surface of the diaphragm.

As described above, the semiconductor acceleration sensor according to the present embodiment of the present invention has a voltage applied to the bridge circuit by connecting a resistance element between the power input terminal and the low potential side terminal and the bridge circuit. And adjusting the output voltage between the acceleration sensors that detect the acceleration in the three-axis directions can be adjusted to reduce the difference in detection sensitivity. Further, by forming the resistance element in the frame portion of the semiconductor acceleration sensor, the semiconductor has a small drift and reduces fluctuations in signal output between the three axes without providing a structural limitation for downsizing the semiconductor acceleration sensor. There is an excellent effect that an acceleration sensor can be provided. Although the semiconductor acceleration sensor has a tendency to decrease the detection sensitivity due to downsizing, the semiconductor acceleration sensor according to the present invention of the present embodiment can improve the S / N ratio by suppressing drift.

(Embodiment 4)
In the third embodiment, the example in which the resistance element is connected between the bridge circuit and one output terminal has been described. In the fourth embodiment, the resistance element is connected between the bridge circuit and both output terminals. An example will be described.

FIG. 7 is a circuit diagram of a sensor circuit according to an embodiment of the present invention. (A) shows a sensor circuit 401 that detects acceleration in the X-axis direction, (b) shows a sensor circuit 402 that detects acceleration in the Y-axis direction, and (c) shows a sensor circuit for detecting the Z-axis direction. 403 is shown.

The sensor circuit 401 has a bridge circuit 51 in the X-axis direction including four piezoresistive elements, and the connection end of the piezoresistive element Rx1 and the piezoresistive element Rx2 is a power supply that is on the high potential side via the resistive element Rx6a. Connected to the input terminal VDx. The connection end of the piezoresistive element Rx3 and the piezoresistive element Rx4 is connected to the low potential side terminal VGx via the resistive element Rx6b. Here, the terminal VGx may be grounded. In order to output a minute change in electric resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Rx1 and the piezoresistive element Rx4 is connected to the output terminal on the high potential side (+) via the resistor element Rx8a. The connection end of the piezoresistive element Rx2 and the piezoresistive element Rx3 is connected to the low potential side (−) output terminal Vxout2 via the resistive element Rx8b.

The sensor circuit 402 has a bridge circuit 52 in the Y-axis direction including four piezoresistive elements, and the connection end of the piezoresistive element Ry1 and the piezoresistive element Ry2 is connected to the high potential side via the resistive element Ry6a. It is connected to a certain power input terminal VDy. The connection end of the piezoresistive element Ry3 and the piezoresistive element Ry4 is connected to the low potential side terminal VGy via the resistive element Ry6b. Here, the terminal VGy may be grounded. In order to output a minute change in electric resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Ry1 and the piezoresistive element Ry4 is connected to the output terminal on the low potential side (−) via the resistive element Ry8b. The connection end of the piezoresistive element Ry2 and the piezoresistive element Ry3 is connected to the output terminal Vyout2 on the high potential side (+) via the resistive element Ry8a.

Further, the sensor circuit 403 has a bridge circuit in the Z-axis direction including four piezoresistive elements, and the connection end of the piezoresistive element Rz1 and the piezoresistive element Rz2 is on the high potential side via the resistive element Rz6a. Connected to the power input terminal VDz. The connection end of the piezoresistive element Rz3 and the piezoresistive element Rz4 is connected to the low potential side terminal VGz via the resistive element Rz6b. Here, the terminal VGz may be grounded. In order to output a minute change in electrical resistance generated in each piezoresistive element as a voltage, the connection end of the piezoresistive element Rz1 and the piezoresistive element Rz3 is connected to the output terminal on the high potential side (+) via the resistor element Rz8a. The connection end of the piezoresistive element Rz2 and the piezoresistive element Rz4 is connected to the output terminal Vzout2 on the low potential side (−) via the resistive element Rz8b.

The sensor circuit 401 according to the embodiment of the present invention can adjust the voltage applied to both ends of the bridge circuit 51 by connecting the resistance element Rx6a and the resistance element Rx6b to the bridge circuit 51. That is, the voltage Vx applied between the power supply input terminal VDx and the low-potential side terminal VGx of the sensor circuit 401 is the combined resistance of the four piezoresistive elements forming the bridge circuit 51, the resistive element Rx6a, and the resistance Since the voltage is divided to the element Rx6b, the voltage Vx1 is applied to the bridge circuit 51. In the sensor circuit 401, the output voltage is also reduced by adjusting the voltage as described above, but the effect of suppressing the drift is proportional to the square of the voltage applied to the bridge resistance. For example, even if the output voltage is reduced to 1/2 by adjusting the voltage, the drift can be suppressed to 1/2 ² , that is, 1/4.

Similarly, the sensor circuit 402 can adjust the voltage applied to both ends of the bridge circuit 52 by connecting the resistance elements Ry6a and Ry6b to the bridge circuit 52. Similarly, the sensor circuit 403 can adjust the voltage applied to both ends of the bridge circuit 53 by connecting the resistance elements Rz6a and Rz6b to the bridge circuit 53. Although the output voltage of the sensor circuit 402 and the sensor circuit 403 is also reduced by adjusting the voltage as described above, the effect of suppressing drift is proportional to the square of the voltage applied to the bridge resistance. For example, even if the output voltage is reduced to 1/2 by adjusting the voltage, the drift can be suppressed to 1/2 ² , that is, 1/4.

A sensor circuit 401 for detecting acceleration in the X-axis direction, a sensor circuit 402 for detecting acceleration in the Y-axis direction, and a sensor circuit 403 for detecting the Z-axis direction are a resistance element Rx6a, a resistance element Rx6b, a resistance element Ry6a, and a resistance The output voltage can be adjusted by including the element Ry6b, the resistance element Rz6a, and the resistance element Rz6b, and the detection sensitivity that is different in each axial direction can be adjusted while suppressing drift. The acceleration sensor 403 that detects the acceleration in the Z-axis direction generally has high detection sensitivity, unlike the acceleration that detects the acceleration in the X-axis direction and the Y-axis direction in terms of how the flexible portion bends. In addition, the drift in the Z-axis direction tends to increase with respect to the X-axis direction and the Y-axis direction. For this reason, in particular, the output voltage is adjusted by connecting the resistance element Rz6a and the resistance element Rz6b to the sensor circuit 403 for detecting the Z-axis direction, and the acceleration in the X-axis direction and the Y-axis direction is controlled while suppressing drift. The acceleration sensor to detect and the detection sensitivity can be adjusted to the same extent. Therefore, it is not necessary to connect a resistance element to the sensor circuit that detects acceleration of all three axes, and the resistance element may be connected only to a sensor circuit that detects acceleration in the axial direction for which drift is to be adjusted.

In the present embodiment, the description has been made based on the sensor circuit of the second embodiment in which the resistance elements Rx6a and Rx6b, the resistance elements Ry6a and Ry6b, and the resistance elements Rz6a and Rz6b are connected. Alternatively, the sensor circuit of the first embodiment in which a resistance element is connected to any one of the terminals on the low potential side may be used.

Next, a semiconductor acceleration sensor 400 according to an embodiment of the present invention in which the sensor circuit 401, the sensor circuit 402, and the sensor circuit 403 are applied to a triaxial acceleration sensor will be described with reference to FIG. The semiconductor acceleration sensor 400 includes a flexible portion 111 in the X-axis direction, a flexible portion 112 in the Y-axis direction, and an intersection 115 (weight support portion) between the flexible portion 111 in the X-axis direction and the flexible portion 112 in the Y-axis direction. ), A frame portion 121 and a weight portion 131.

The arrangement and configuration of each piezoresistive element for detecting acceleration in the X-axis direction, the Y-axis direction, and the Z-axis direction are the same as those of the first embodiment in the flexible portion 111 in the X-axis direction. The mechanism for detecting by the sensor is the same as that of the first embodiment.

Resistor Rx6a, Resistor Rx6b, Resistor Ry6a, Resistor Ry6b, Resistor Rz6a, Resistor Rz6b, Resistor Rx8a, Resistor Rx8b, Resistor Ry8a, Resistor Ry8b, Resistor Rz8a and resistance element Rz8b are preferably formed in the frame portion 121. In addition, since the resistance element is formed in the frame portion 121, it does not affect the bending that occurs in the flexible portion 111 in the X-axis direction and the flexible portion 112 in the Y-axis direction detected by the piezoresistive element. Further, the resistance element Rx6a, the resistance element Rx6b, the resistance element Ry6a, the resistance element Ry6b, the resistance element Rz6a, the resistance element Rz6b, the resistance element Rx8a, the resistance element Rx8b, the resistance element Ry8a, the resistance element Ry8b, the resistance element Rz8a, and the resistance element Rz8b Any resistance element may be used, but by using a piezoresistive element, the intended effect can be obtained without increasing the number of manufacturing steps.

In the present embodiment, the voltage applied to both ends of the bridge circuit can be balanced by connecting the resistance elements to both ends of the bridge circuit. Further, the resistance element Rx6a and the resistance element Rx6b, the resistance element Ry6a and the resistance element Ry6b, and the resistance element Rz6a and the resistance element Rz6b may be formed by a combination of resistance elements having the same resistance value, but resistances having different resistance values. You may form with the group of an element. In addition, the resistance element Rx8a, the resistance element Rx8b, the resistance element Ry8a, the resistance element Ry8b, the resistance element Rz8a, and the resistance element Rz8b may each be formed of a combination of resistance elements having the same resistance value, but resistance elements having different resistance values. You may form with the group of. When there is a restriction on the position where the resistance element is formed, it is possible to meet the restriction on the position where the resistance element is formed by changing the resistance value between the resistance element on the power input terminal side and the resistance element on the low potential side. it can.

In the present embodiment, the semiconductor acceleration sensor 400 includes the X-axis direction flexible portion 111 and the Y-axis direction flexible portion 112. However, the semiconductor acceleration sensor 400 according to the present invention has a beam shape. A diaphragm may be used as a film-like flexible part instead of the flexible part. That is, the piezoresistive element that supports the weight portion with the diaphragm and detects the acceleration in the X-axis direction and the Y-axis direction may be arranged in the axial direction orthogonal to each other on the upper surface of the diaphragm.

As described above, the semiconductor acceleration sensor according to the present embodiment of the present invention has a voltage applied to the bridge circuit by connecting a resistance element between the power input terminal and the low potential side terminal and the bridge circuit. And adjusting the output voltage between the acceleration sensors that detect the acceleration in the three-axis directions can be adjusted to reduce the difference in detection sensitivity. Further, by forming the resistance element in the frame portion of the semiconductor acceleration sensor, the semiconductor has a small drift and reduces fluctuations in signal output between the three axes without providing a structural limitation for downsizing the semiconductor acceleration sensor. There is an excellent effect that an acceleration sensor can be provided. Although the semiconductor acceleration sensor has a tendency to decrease the detection sensitivity due to downsizing, the semiconductor acceleration sensor according to the present invention of the present embodiment can improve the S / N ratio by suppressing drift.

(Embodiment 5) (Method for Manufacturing Semiconductor Acceleration Sensor)
A method for manufacturing the semiconductor acceleration sensor according to the present invention of the above-described embodiment will be described below. In the present embodiment, description will be made using the semiconductor acceleration sensor 400 described in the fourth embodiment as an example of the manufacturing method. The semiconductor acceleration sensor described in the first to third embodiments is also manufactured by the same manufacturing method. FIG. 9 is a diagram showing the wiring pattern diagram of the semiconductor acceleration sensor 400 shown in FIG. 8 again, and FIG. 10 is an exploded perspective view of the semiconductor acceleration sensor 400. 11 and 12 are diagrams for explaining the manufacturing process of the semiconductor acceleration sensor 400 with cross-sectional views taken along the line AA ′ of FIGS. 9 and 10.

Referring to FIG. 10, in the semiconductor acceleration sensor 400, an acceleration sensor main body 450 is formed by using an SOI substrate in which a silicon oxide film 3 formed on a silicon substrate 1 and a silicon film 5 are stacked thereon, and a support substrate 141 is formed. To join. The silicon film 5 and the silicon oxide film 3 are provided with a frame portion 121, an X-axis direction flexible portion 111 disposed inside the frame portion 121, a Y-axis direction flexible portion 112, and an X-axis direction flexible portion. An intersection 115 between the flexible portion 111 and the flexible portion 112 in the Y-axis direction is formed. In addition, the silicon film 5 and the silicon oxide film 3 are formed with an opening 117 surrounded by a frame part 121, a flexible part 111 in the X-axis direction, a flexible part 112 in the Y-axis direction, and an intersecting part 115.

A frame portion 123 and a weight portion 131 are formed on the silicon substrate 1, and the weight portion 131 is disposed apart from the inner wall of the frame portion 123. The intersecting portion 115 and the weight portion 131 are joined via the silicon oxide film 3. In the present embodiment, the weight portion 131 has a substantially clover shape, but the shape of the weight portion 131 is not limited to this.

An example of the support substrate 141 is glass. When the support substrate 141 is glass, it can be bonded to the sensor body by anodic bonding. The support substrate 141 is not limited to glass, and a metal (stainless steel, invar made of Fe-36% Ni alloy, etc.), an insulating resin, or a semiconductor such as Si can be used. The bonding method can be appropriately selected from direct bonding, eutectic bonding, bonding with an adhesive, and the like. Further, the sensor main body can be directly mounted on a mounting substrate or a package substrate without providing the support substrate 141.

Next, the manufacturing process of the semiconductor acceleration sensor 400 will be described. The SOI substrate shown in FIG. 11A is manufactured by SIMOX, a bonding method, or the like. The silicon oxide film 3 also functions as an etching stopper layer in a process described later.

In the present embodiment, the piezoresistive elements Rx1 to Rx4 and the piezoresistive elements Rz1 to Rz4 are used as the flexible part 111 in the X-axis direction, the piezoresistive elements Ry1 to Ry4 are used as the flexible part 112 in the Y-axis direction, and the resistive element Rx6a. , Resistance element Rx6b, resistance element Ry6a, resistance element Ry6b, resistance element Rz6a, resistance element Rz6b, resistance element Rx8a, resistance element Rx8b, resistance element Ry8a, resistance element Ry8b, resistance element Rz8a, and resistance element Rz8b, Form each one.

A mask 7 for impurity diffusion is formed on the silicon substrate 5 side of the SOI substrate (FIG. 11B). As a material of the mask 7, for example, a silicon nitride film (Si ₃ N ₄ ), a silicon oxide film (SiO ₂ ), or the like Can be used. After a silicon oxide film is formed on the entire surface of the silicon film 5 by thermal oxidation or plasma CVD, a silicon nitride film is formed, and a resist pattern (not shown) is formed on the silicon nitride film. A piezoresistive element and an opening corresponding to the resistive element are formed in the oxide film by wet etching such as RIE (Reactive Ion Etching) and hot phosphoric acid. The mask 7 may have a single-layer structure, or may have a two-layer structure of a silicon oxide film and a silicon nitride film from the silicon film 5 side. In the case where the mask 7 has a two-layer structure, the silicon nitride film can be used for preventing diffusion of impurities, which will be described later.

Each piezoresistive element and each resistive element are formed by a thermal diffusion method or an ion implantation method (FIG. 11C). For example, when boron is diffused into the silicon film 5 using a thermal diffusion method, BBr ₃ or the like is exposed to at least the surface on which the mask 7 is formed, and impurities are deposited to form an impurity diffusion layer. The piezoresistive element and the resistive element can adjust the impurity concentration on the surface of the diffusion region by appropriately adjusting the formation conditions. In addition, the resistance value of the piezoresistive element and the resistive element can be adjusted by the width, length and cross-sectional area to be formed. The resistance value can be easily changed by adjusting the length. In the above-described embodiment, the resistance element is shown as one resistance element that gives one resistance value. However, a plurality of resistance elements may be connected in series to give one resistance value. That is, the resistance element R may be formed by connecting the resistance element R ′ and the resistance element R ″ in series.

Next, an insulating layer 9 is formed on the silicon film 5 (FIG. 11D). For example, an insulating layer of SiO ₂ is formed on the surface of the silicon film 5 using thermal oxidation or plasma CVD. A contact hole 13 is formed on the insulating layer 9 by RIE using a resist as a mask. The SiO ₂ film can be formed using a gas such as TEOS (Si (OC ₂ H ₅ ) ₄ ) / O ₂ or SiH ₄ / N ₂ O. When the thickness of the SiO ₂ film is 30 nm to 1 μm, the stress range is −200 MPa to +200 MPa, and the influence on the sensitivity and offset voltage of the acceleration sensor can be reduced. A contact hole 13 is formed on the insulating layer 9 by RIE using a resist as a mask.

Subsequently, the wiring 10 is formed so as to be connected to the piezoresistive element and the resistive element through the contact hole 13 (FIG. 11E). The wiring 10 is obtained by depositing a metal material such as Al, Al—Si, or Al—Nd by a sputtering method or the like and patterning it. In order to form an ohmic contact between the wiring 10 and the piezoresistive element and the resistive element, it is preferable to perform heat treatment (380 ° C. to 420 ° C.). A film such as a silicon nitride film (Si ₃ N ₄ ) may be formed on the wiring 10 as a protective film. The power input terminals VDx, VDy, and VDz, the ground terminals VGx, VGy, and VGz, and the output terminals Vxout1, Vxout2, Vyout1, Vyout2, Vzout1, and Vzout2 can be formed in the same process using the same material as the wiring 10. .

Thereafter, the silicon film 5 is etched by RIE or the like until the upper surface of the silicon oxide film 3 is exposed, and an opening 117 is provided to provide a frame portion 121, a flexible portion 111 in the X-axis direction, and a flexible portion in the Y-axis direction. 112 and the intersection 115 are formed (FIG. 12F). In addition, an opening along the inner frame of the frame portion 123 is formed using a mask in order to form a gap having an interval necessary for the weight portion 131 to move downward (support substrate 141). The gap can be appropriately set according to the dynamic range of the acceleration sensor, and is, for example, about 5 to 10 μm.

Further, a mask is formed on the lower surface of the silicon substrate 1 in order to form the frame portion 123 and the weight portion 131. Using this mask, the silicon substrate 1 is etched until the lower surface of the silicon oxide film 3 is exposed. For the etching, for example, DRIE (Deep Reactive Ion Etching) is used. In DRIE, an etching step of digging while eroding a material layer in the thickness direction and a deposition step of forming a polymer wall on a side wall formed as the erosion progresses by etching are alternately repeated. Since the side wall of the hole that has been dug is protected by forming a polymer wall in sequence, it is possible to advance erosion almost only in the thickness direction. An ion / radical supply gas such as SF ₆ can be used as an etching gas, and C ₄ F ₈ or the like can be used as a deposition gas.

Thereafter, the unnecessary silicon oxide film 3 used as an etching stopper is removed by RIE or wet etching. As a result, the silicon oxide film 3 exists only between the frame portion 121 and the frame portion 123, and between the intersecting portion 115 and the weight portion 131 (FIG. 12 (f)). The sensor body 450 is manufactured through the above steps.

Finally, the sensor main body 450 and the support substrate 141 are joined (FIG. 12G). When glass is used as the material of the support substrate 141, it is so-called Pyrex (registered trademark) glass containing movable ions such as Na ions, and anodic bonding is used for bonding to the SOI substrate 110. In order to prevent the weight 131 from sticking to the upper surface of the support substrate 141 due to electrostatic attraction during anodic bonding, a sticking prevention film (not shown) such as Cr is formed on the upper surface of the support substrate 141 by sputtering. May be. As a result, the sensor main body 400 and the support substrate 141 are joined, and the semiconductor acceleration sensor 400 is configured. The above is an example of a method for manufacturing an acceleration sensor, and the order can be changed as appropriate, and is not limited to the above order.

As described above, according to the semiconductor acceleration sensor manufacturing method of the present embodiment of the present invention, detection is performed by adjusting the output voltage between the acceleration sensors that accurately suppress drift and detect acceleration in three axes. In order to manufacture a semiconductor acceleration sensor that can be adjusted so as to reduce the sensitivity difference, a resistance element connected between the power input terminal and the low potential side terminal and the bridge circuit, or between the bridge circuit and the output terminal is provided. There is an excellent effect that can be formed simultaneously in the same process as the piezoresistive element.

In the present embodiment, the piezoresistive element and the resistive element are described by the method of simultaneously forming them on the SOI substrate in the same process. However, the piezoresistive element and the resistive element according to the present invention are formed using PZT, for example. It may be manufactured and pasted separately. When PZT is used as the piezoresistive element or the resistive element according to the present invention, high piezoelectric characteristics can be obtained.

(Embodiment 6)
In the present embodiment, an example in which the semiconductor acceleration sensor according to the present invention shown in the above-described embodiment is mounted as a sensor module on an electronic device will be described. Note that in this specification, an electronic device refers to all devices that can function using semiconductor technology, and a substrate on which an electronic component is mounted is also included in the scope of the electronic device.

The semiconductor acceleration sensor 100, 200, 300 or 400 is mounted on a circuit board on which an active element such as an IC is mounted, for example, and is supplied with a power input terminal VDx, a ground terminal VGx, an output by a known method and material such as wire bonding connection. The terminal Vxout1, the output terminal Vxout2, the power input terminal VDy, the ground terminal VGy, the output terminal Vyout1, the output terminal Vyout2, the power input terminal VDz, the ground terminal VGz, the output terminal Vzout1, and the output terminal Vzout2, and an active circuit board or IC By connecting the elements, the semiconductor acceleration sensor and the electronic circuit can be provided as one sensor module. This sensor module can be used by being mounted on a portable terminal such as a game machine or a mobile phone.

FIG. 13 is a diagram illustrating an example of a circuit configuration of a processing circuit 550 that processes an acceleration detection signal detected by the semiconductor acceleration sensor 100. The processing circuit 550 includes an amplifier circuit (Amp) 551 and a filter circuit 553. It can be similarly applied to the semiconductor acceleration sensor 200, 300, or 400.

  The amplifier circuit 551 amplifies each acceleration detection signal (resistance value change) in the X, Y, and Z axis directions output from the semiconductor acceleration sensor 100 according to the received acceleration with a predetermined amplification factor and outputs the amplified detection signal to the filter circuit 553. To do. The filter circuit 553 is a circuit including a resistor, a capacitor, and the like, and has a filter function of allowing a noise component included in the signal to pass therethrough. The filter circuit 553 outputs low-frequency signal components as acceleration detection signals in the X-axis direction, the Y-axis direction, and the Z-axis direction.

FIG. 14 is a diagram illustrating an example of a sensor module 500 for mounting the semiconductor acceleration sensor 100 and the processing circuit 550 described above on an electronic device. In the sensor module 500, a signal processing chip 501 including the processing circuit 550 described above, a memory chip 503, and a sensor chip 505 including the semiconductor acceleration sensor 100 are mounted on a substrate 507. The signal processing chip 501, the memory chip 503, and the sensor chip 505 are connected by a bonding wire 509. The memory chip 503 stores a correction value before shipment of the semiconductor acceleration sensor 100, a program for controlling the signal processing chip 501, parameters, and the like.

An example in which the sensor module 500 is mounted on a portable terminal as an electronic device will be described. FIG. 15 is a diagram illustrating an example of a portable information terminal 600 as an electronic device in which the sensor module 500 is mounted. The portable information terminal 600 includes a display unit 601 and an input unit 603, and the sensor module 500 is mounted inside the portable information terminal 600 on the input unit 603 side. The portable information terminal 600 has a function of storing various programs therein and executing communication processing, information processing, and the like by the various programs. In this portable information terminal 600, by using the acceleration detected by the sensor module 500 in the application program, for example, it is possible to add a function such as detecting the acceleration at the time of dropping and turning off the power. .

By mounting the sensor module 500 according to the present invention of the present embodiment on a portable terminal, new functions can be realized, and the convenience and reliability of the portable terminal can be improved. .

In addition, in a game machine controller or a portable game machine, a semiconductor acceleration sensor is required to be downsized and highly accurate, and by mounting the sensor module 500 according to the present invention of this embodiment, drift is reduced. Reduces fluctuations in signal output between the three axes. Although the semiconductor acceleration sensor has a tendency to decrease the detection sensitivity due to downsizing, the semiconductor acceleration sensor according to the present invention of this embodiment is suitable because the S / N ratio is improved by suppressing drift.

The effects of the semiconductor acceleration sensor according to the present invention described in the above embodiment will be described below with reference to examples. FIG. 16 is a list of resistance values, shapes, and sensitivities of the semiconductor acceleration sensors of Examples and Comparative Examples.

In the semiconductor acceleration sensors of Examples 1-1, 1-2, and 1-3, the resistance element according to the present invention is connected to the semiconductor acceleration sensor of Comparative Example 1. In the semiconductor acceleration sensor of Comparative Example 1, the detection sensitivity of the sensor circuit for detecting the Z-axis direction is higher than that of the sensor that detects acceleration in the X-axis direction and the Y-axis direction. Examples 1-1 and 1-2 correspond to the semiconductor acceleration sensor of the first embodiment, and Example 1-1 is between the power input terminal VDz of the sensor circuit 103 and the bridge circuit 53 for detecting the Z-axis direction. In Example 1-2, the resistor element Rz5 is connected between the low-potential-side terminal VGz and the bridge circuit 53 for detecting the Z-axis direction. It is. The semiconductor acceleration sensor of Example 1-3 corresponds to the semiconductor acceleration sensor of Embodiment 2, and is the same between the power input terminal VDz and the bridge circuit 53 and between the low potential side terminal VGz and the bridge circuit 53. A resistance element Rz6a and a resistance element Rz6b having resistance values (half the resistance value of the resistance element Rz5) are connected to each other. Here, in the semiconductor acceleration sensors of Examples 1-1, 1-2, and 1-3, since the resistance element is connected to the bridge circuit 53, the combined resistance of the bridge circuit 53 is decreased by the resistance value of the connected resistance element. To do.

As can be seen from FIG. 16, in the semiconductor acceleration sensors of Examples 1-1, 1-2, and 1-3, a resistance element is connected to the bridge circuit 53 of the sensor circuit 103 for detecting acceleration in the Z-axis direction. Thus, it is possible to adjust the output voltage to adjust the detection sensitivity to the same level as the acceleration sensor that detects acceleration in the X-axis direction and the Y-axis direction.

The semiconductor acceleration sensor of Comparative Example 2 has the same combined resistance as the bridge acceleration circuit and the semiconductor acceleration sensor of Comparative Example 1, but the flexible portion and the weight portion are different. Specifically, in the semiconductor acceleration sensor of Comparative Example 2, the width of the flexible portion is the same as that of the semiconductor acceleration sensor of Comparative Example 1, but the length is different, and the weight of the weight portion is different. Further, the width of the flexible portion of the semiconductor acceleration sensor of Comparative Example 3 is different from that of the semiconductor acceleration sensor of Comparative Example 2. Further, the semiconductor acceleration sensors of Comparative Example 1, Comparative Example 2 and Comparative Example 3 have different film forming conditions for the insulating layer 9, and the semiconductor acceleration sensors of Comparative Example 2 and Comparative Example 3 also have the X-axis direction and the Y-axis direction. The detection sensitivity of the sensor circuit for detecting the acceleration in the Z-axis direction is higher than that of the acceleration sensor for detecting the acceleration.

The semiconductor acceleration sensor of Example 2 is obtained by connecting the resistance element according to the present invention of Embodiment 1 to the semiconductor acceleration sensor of Comparative Example 2. Specifically, a resistance element Rz5 is connected between the power input terminal VDz of the sensor circuit 103 for detecting the Z-axis direction and the bridge circuit 53. The semiconductor acceleration sensor of Example 3 is obtained by connecting the resistance element according to the present invention of Embodiment 1 to the semiconductor acceleration sensor of Comparative Example 3, and the power input terminal of the sensor circuit 103 for detecting the Z-axis direction. A resistance element Rz5 is connected between VDz and the bridge circuit 53.

As can be seen from FIG. 16, the semiconductor acceleration sensors of the second and third embodiments adjust the output voltage by connecting a resistance element to the bridge circuit 53 of the sensor circuit 103 for detecting acceleration in the Z-axis direction. The detection sensitivity can be adjusted to the same level as the acceleration sensor that detects the acceleration in the X-axis direction and the Y-axis direction.

As described above, the semiconductor acceleration sensor according to the present invention has the sensor circuit 103 for detecting the acceleration in the Z-axis direction regardless of the width, length, weight, etc. of the flexible portion. By connecting a resistance element to the bridge circuit 53, the output voltage can be adjusted, and the detection sensitivity can be adjusted to the same level as the acceleration sensor that detects the acceleration in the X-axis direction and the Y-axis direction. In this embodiment, the case where the detection sensitivity of the acceleration sensor for detecting the acceleration in the Z-axis direction is high is illustrated, but the acceleration sensor that detects the acceleration in the X-axis direction or the Y-axis direction also has the same effect. It is clear.

In the semiconductor acceleration sensor according to the present invention, since a voltage applied to the bridge circuit is reduced by connecting a resistance element to the bridge circuit, drift is suppressed. In the semiconductor acceleration sensor according to the present invention, the combined resistance of the bridge circuit is reduced by connecting a resistance element, but the influence on the detection sensitivity is negligible.

DESCRIPTION OF SYMBOLS 1 Silicon substrate 3 Silicon oxide film 5 Silicon film 7 Mask 9 Insulating layer 10 Wiring 13 Contact hole 51 Bridge circuit in X-axis direction 52 Bridge circuit in Y-axis direction 53 Bridge circuit in Z-axis direction 100 Semiconductor acceleration sensor according to one embodiment 101 X-axis direction sensor circuit 102 Y-axis direction sensor circuit 103 Z-axis direction sensor circuit 111 X-axis direction flexible portion 112 Y-axis direction flexible portion 115 Intersection 117 Opening portion 121 Frame portion 123 Frame portion 131 Weight part 141 Support substrate 191 Dummy resistance element 192 Dummy resistance element 200 Semiconductor acceleration sensor 201 according to one embodiment X-axis direction sensor circuit 202 Y-axis direction sensor circuit 203 Z-axis direction sensor circuit 300 Semiconductor according to one embodiment Acceleration sensor 301 X-axis direction sensor circuit 302 Y-axis direction sensor Circuit 303 Z-axis Direction Sensor Circuit 400 Semiconductor Acceleration Sensor 401 According to One Embodiment X-axis Direction Sensor Circuit 402 Y-axis Direction Sensor Circuit 403 Z-axis Direction Sensor Circuit 450 Sensor Body 500 Sensor Module 501 Signal Processing Chip 503 Memory Chip 505 Sensor chip 507 Substrate 509 Bonding wire 550 Processing circuit 551 Amplifier circuit 553 Filter circuit 600 Portable information terminal 601 Display unit 603 Input unit Rx1 Piezoresistive element Rx2 Piezoresistive element Rx3 Piezoresistive element Rx4 Piezoresistive element Rx5 Resistive element Rx6a Resistance Element Rx6b Resistance element Rx7 Resistance element Rx8a Resistance element Rx8b Resistance element Ry1 Piezoresistance element Ry2 Piezoresistance element Ry3 Piezoresistance element Ry4 Piezoresistance element Ry5 Resistance element Ry6a Resistance Resistance element Ry6b Resistance element Ry8 Resistance element Ry8a Resistance element Ry8b Resistance element Rz1 Piezoresistance element Rz2 Piezoresistance element Rz3 Piezoresistance element Rz4 Piezoresistance element Rz5 Resistance element Rz6a Resistance element Rz6b Resistance element Rz8 Resistance element Rz8a Resistance element Rz8a Resistance element Rz8 Input terminal VGx Ground terminal Vxout1 Output terminal Vxout2 Output terminal VDy Power supply input terminal VGy Ground terminal Vyout1 Output terminal Vyout2 Output terminal VDz Power supply input terminal VGz Ground terminal Vzout1 Output terminal Vzout2 Output terminal

Claims (13)

A semiconductor substrate, a frame portion, a weight portion, a flexible portion disposed between the frame portion and the weight portion, and a plurality of piezoresistive elements disposed on the flexible portion in a first direction; A plurality of piezoresistive elements arranged in a second direction orthogonal to the first direction, and a plurality of bridge circuits each including the plurality of piezoresistive elements,
At least one bridge circuit having a first resistor is provided between any one of a high potential end and a low potential end for applying a voltage to the bridge circuit and the bridge circuit. Semiconductor acceleration sensor. The semiconductor acceleration sensor according to claim 1, further comprising a second resistor between the other of the high potential end and the low potential end and the bridge circuit. The third resistor is further provided between any one of the first output terminal and the second output terminal of the bridge circuit and the bridge circuit. Semiconductor acceleration sensor. The semiconductor acceleration sensor according to claim 3, further comprising a fourth resistor between the other of the first output terminal and the second output terminal and the bridge circuit. The semiconductor acceleration sensor according to claim 4, wherein the frame portion includes the first resistor, the second resistor, the third resistor, and the fourth resistor. The plurality of bridge circuits include a first bridge circuit that detects acceleration in the first direction, a second bridge circuit that detects acceleration in the second direction, the first direction, and the second direction. A third bridge circuit that detects acceleration in a third direction orthogonal to the direction of
The first bridge circuit or the second bridge circuit generates an acceleration in the first direction or an acceleration in the second direction based on a deflection of the flexible portion due to a rotational movement of the weight portion around a horizontal direction. Detect
The said 3rd bridge circuit detects the acceleration of a said 3rd direction based on the bending of the said flexible part by the translational motion to the perpendicular direction of the said weight part, The one of Claims 1 thru | or 5 characterized by the above-mentioned. A semiconductor acceleration sensor according to claim 1. In order to adjust the detection sensitivity difference between the first, second, and third bridge circuits having different detection sensitivities, at least one of the first, second, and third bridge circuits includes the resistor. The semiconductor acceleration sensor according to claim 6, further comprising: The acceleration in the first direction and the acceleration in the second direction are the first output end of the first bridge circuit due to the bending of the flexible part caused by the horizontal rotational movement of the weight part, and the Detected as an output from the second output end,
The acceleration in the third direction is generated from the first output end and the second output end of the third bridge circuit due to the bending of the flexible portion caused by the translational motion of the weight portion in the vertical direction. The semiconductor acceleration sensor according to claim 6, wherein the semiconductor acceleration sensor is detected as an output. A sensor module comprising the semiconductor acceleration sensor according to claim 1. An electronic apparatus comprising the semiconductor acceleration sensor according to claim 1. A plurality of piezoresistive elements are formed by diffusing impurities on one surface of a semiconductor substrate,
Forming a resistance element on one surface of the semiconductor substrate;
A bridge circuit is formed by connecting a predetermined number of the piezoresistive elements,
Forming a wiring so that the resistor is disposed between one of a high potential end and a low potential end for applying a voltage to the bridge circuit, and the bridge circuit;
Forming a frame portion, a weight portion, and a flexible portion disposed between the frame portion and the weight portion on the semiconductor substrate,
A plurality of piezoresistive elements arranged in a first direction and a plurality of piezoresistive elements arranged in a second direction orthogonal to the first direction are formed in the flexible portion; The manufacturing method of the semiconductor acceleration sensor characterized by the above-mentioned. The method of manufacturing a semiconductor acceleration sensor according to claim 11, wherein the resistance element is formed in the frame portion. 13. The method of manufacturing a semiconductor acceleration sensor according to claim 11, wherein the piezoresistive element and the resistor are formed in the same process.