JP2009294127A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device having few noises and improved detection reproducibility of angular velocity. <P>SOLUTION: This semiconductor device having a vibrator 100 movable in the X-axis direction, in the Y-axis direction, and in the Z-axis direction in an XYZ three-dimensional coordinate system, includes casings 201-203 for storing the vibrator 100 so as to be out of contact with the vibrator 100, driving means 401-402 for moving the vibrator 100 reciprocally in the Z-axis direction, control means 501-506 for controlling movement of the vibrator 100 so that the vibrator 100 is out of physical contact with the casings 201-203, and detection means 601-610 for detecting a variation of each relative position between the vibrator 100 and the casings 201-203. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a semiconductor device used for an acceleration or angular velocity sensor, and more particularly, to an acceleration or angular velocity sensor that can detect accelerations in a plurality of axial directions and angular velocities around a plurality of axes in an XYZ three-dimensional coordinate system. The present invention relates to a semiconductor device.

  In recent years, high-performance, small, and low-priced acceleration sensors and angular velocity sensors have been increasingly installed in in-vehicle devices and portable terminals.

  Among them, there is a high demand for multi-axis acceleration sensors and multi-axis angular velocity sensors that can detect accelerations in a plurality of axial directions or angular velocities around a plurality of axes with one sensor.

  Examples of practical applications include a triaxial acceleration sensor for detecting a hard disk drive drop in a mobile device, a biaxial angular velocity sensor for correcting camera shake in a camera / video, and the like.

  Furthermore, there is an increasing demand for mounting both a multi-axis acceleration sensor and a multi-axis angular velocity sensor for the purpose of accurately operating and controlling more advanced and complex movements such as a humanoid robot.

For this reason, there has been proposed an acceleration / angular velocity sensor that can detect accelerations in a plurality of axial directions and angular velocities around a plurality of axes with a single chip / one sensor as shown in Patent Document 1-3.
Japanese Patent No. 3534251 Japanese Patent No. 3008074 JP 2004-333327 A

  However, in the angular velocity sensor described in Patent Document 1, since the vibrator is connected to the fixed portion through the flexible portion, an impact applied to the fixed portion is transmitted to the vibrator and noise may increase.

  In the angular velocity sensor described in Patent Document 1, the angular velocity is obtained from the Coriolis force acting on the vibrator. However, since the Coriolis force is minute compared to an external force such as gravity, an increase in noise causes a decrease in detection accuracy of the angular velocity. It becomes.

  Further, in the angular velocity sensor described in Patent Document 1, the vibration surface may pulsate due to the rotational motion about the connecting portion between the vibrator and the flexible part being applied to the vibrator during operation. Therefore, the magnitude of the Coriolis force acting on the vibrator varies, and it is difficult to obtain the angular velocity with good reproducibility.

  On the other hand, since the gyro device described in Patent Documents 2 and 3 has a structure in which the gyro rotor is lifted by electrostatic force and does not physically contact the gyro case, noise due to impact from the outside is relatively small.

  However, since the angular velocity is detected from the torque acting on the gyro rotor, it is necessary to rotate the gyro rotor at a high speed in order to detect the angular velocity with high accuracy. Therefore, it may take a long time from turning on the power to reaching the desired number of revolutions.

  Furthermore, the acceleration / angular velocity sensor described in Patent Documents 1-3 may sometimes be described below.

  In the angular velocity sensor described in Patent Document 1, since the vibrator is connected to the flexible portion, the vibrator may be inclined with respect to the fixed portion due to the pulsation of the vibration surface described above.

  In addition, the acceleration / angular velocity sensor described in Patent Document 2 or 3 detects the angular velocity from the torque of the rotational motion, so that the gyro rotor may be inclined in the gyro case.

  Therefore, in any of the acceleration / angular velocity sensors, there is a possibility that the vibrator (or gyro rotor) inclined during operation may come into contact with the fixed portion (or gyro case).

  For this reason, the dimension of the fixed part (gyro case) surrounding the vibrator (gyro rotor) must be increased.

  In addition, by increasing the distance between the vibrator (gyro rotor) and the fixed portion (gyro case), it is difficult to detect minute changes in the distance, and the accuracy of acceleration / angular velocity detection may be reduced.

  Therefore, an object of the present invention is to solve the above-described problems in a semiconductor device.

  As a means for solving the above-described problems, the present invention provides a semiconductor device having a vibrator that can move in the X-axis direction, the Y-axis direction, and the Z-axis direction in an XYZ three-dimensional coordinate system, and does not contact the vibrator The housing in which the vibrator is stored, the driving means for reciprocating the vibrator in the Z-axis direction, and the movement of the vibrator so that the vibrator and the housing are not in physical contact with each other. Control means for controlling, and detection means for detecting a change amount of a relative position between the vibrator and the casing.

  According to the present invention, since the vibrator is not connected to the casing, the influence from the outside such as an impact on the casing is reduced, resulting in low noise.

  According to the present invention, since the vibration surface does not pulsate and stable single vibration is obtained, the angular velocity detection reproducibility is improved.

  According to the present invention, it is not necessary to form the flexible portion, and the manufacturing process can be shortened.

  According to the present invention, since the motion of the vibrator is a single vibration, the momentum is small, and a stable motion can be obtained in a short time, so the startup time is shortened.

  According to the present invention, since the motion of the vibrator is not a rotational motion but a single vibration, the electrode structure / driving circuit can be simplified, so that the cost is reduced.

  According to the present invention, since the vibrator is not inclined in the housing, a housing having a size with a minimum necessary distance from the vibrator can be used, and thus the size is reduced.

  According to the present invention, since the interval between the vibrator and the housing is small, it is easy to detect a minute change in the interval, so that the accuracy is improved.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The scope of the present invention is not limited to these forms unless specifically described in the following description to limit the present invention.

[Embodiment 1]
FIG. 1 is a diagram showing a semiconductor device as a first embodiment of the present invention.

  1A is a plan view of the semiconductor device of the present embodiment as viewed from above, and FIG. 1B is a cross-sectional view taken along line BB in FIG. 1A. FIG.1 (c) is sectional drawing at the time of cut | disconnecting by CC line in Fig.1 (a).

  In FIG. 1, 100 is a vibrator, 201-203 is a housing, 300 is a cavity, 401-402 is a drive electrode as a drive means, 501-506 is a control electrode as a control means, and 601-610 is a detection means. The detection electrodes are shown. Also, the X, Y, and Z axes are taken in the respective directions in FIG.

  In FIG. 1, the vibrator 100 is housed in a casing 201-203 and is disposed in the cavity 300 so as not to contact the casing 201-203. Drive electrodes 401-402, control electrodes 501-506, and detection electrodes 601-610 are arranged around the vibrator 100. The vibrator 100 can move in the X-axis direction, the Y-axis direction, and the Z-axis direction in the XYZ three-dimensional coordinate system.

  Here, control electrodes 501 and 502 and detection electrodes 601-604 are provided in the X-axis direction so as to face the vibrator 100. Control electrodes 503 and 504 and detection electrodes 605-608 are provided in the Y-axis direction. Drive electrodes 401 and 402, control electrodes 505 and 506, and detection electrodes 609 and 610 are provided in the Z-axis direction.

  At this time, the vibrator 100 is in physical contact with any of the housing 201-203, the drive electrodes 401-402, the control electrodes 501-506, and the detection electrodes 601-610 as shown in FIGS. Not done. The reason will be described below.

  The vibrator 100 before power-on is in contact with a grounded stopper electrode (not shown). The vibrator 100 can be regarded as a conductor as will be described later.

  Now, when a voltage is applied to the drive electrodes 401-402 after turning on the power, a potential difference is generated between the drive electrodes 401-402 and the vibrator 100, so that charges are induced in the vibrator 100 and an electrostatic force is generated. .

  Therefore, the vibrator 100 can be floated by determining an appropriate potential difference.

  Further, when a voltage is applied to the control electrodes 501-506 provided in the X axis, Y axis, and Z axis directions, an electrostatic force is similarly generated between the control electrodes 501-506 and the vibrator 100. By doing so, the vibrator 100 can be electrostatically levitated in the cavity 300 in a non-contact state.

  At this time, it is desirable that the cavity 300 be in a vacuum state so that the vibrator 100 can vibrate at high speed (about several tens of kHz).

  For this reason, a getter material (not shown) that adsorbs impurity gas is provided in a region that is not physically in contact with the vibrator 100, the drive electrodes 401-402, the control electrodes 501-506, and the detection electrodes 601-610 in the cavity 300. It is installed.

  This non-contact electrostatic levitation is based on the same principle as the gyro device described in Patent Documents 2 and 3.

  Further, the control electrodes 501 to 504 and the detection electrodes 601 to 608 provided in the X axis and Y axis directions are physically separated from each other in the XY direction as shown in FIGS. Is electrically insulated. The detection electrodes 601-610 detect the amount of change in the relative position between the vibrator 100 and the housing 201-203. In addition to the above-described stopper electrode, wiring connected to each electrode is not shown.

  The operation of the semiconductor device in this embodiment will be described.

  Now, the vibrator 100 is electrostatically levitated at a position equidistant from each of the detection electrodes 601 to 610 provided in the X-axis, Y-axis, and Z-axis directions. This position is the origin. Here, when an AC voltage is applied to the drive electrodes 401 and 402, the vibrator 100 reciprocates in the Z-axis direction by electrostatic force. At this time, since the vibrator 100 moves from the origin position, the distance between the vibrator 100 and each of the detection electrodes 601-610 changes.

  Even when an external force such as gravity is applied to the vibrator 100, the distance between the vibrator 100 and each of the detection electrodes 601-610 changes. The detection electrodes 601-610 detect this change in distance as a change in capacitance.

  Subsequently, position adjustment is performed so that the vibrator 100 returns to the origin position, but the content differs between the XY direction and the Z-axis direction.

  In the XY direction, a voltage is applied to the control electrodes 501 to 504 to generate an electrostatic force so that the distances between the detection electrodes 601 to 608 provided in the X axis direction and the Y axis direction and the vibrator 100 are equal. Then, the position of the vibrator 100 is adjusted.

  In the Z-axis direction, the vibrator 100 periodically reciprocates. Therefore, an electrostatic force is generated by applying a voltage to the control electrodes 505 and 506 so that the distance from the detection electrodes 609 and 610 takes a desired value according to the reciprocation period, thereby adjusting the motion of the vibrator 100.

  These electrostatic forces are calculated from the amount of change in capacitance detected by each of the detection electrodes 601-610 and applied to the control electrodes 501-506.

  Next, a method for detecting acceleration / angular velocity in the semiconductor device according to the present embodiment will be described.

  When the vibrator 100 is moved from the origin by an external force, a voltage is applied to the control electrodes 501 to 506 to apply an electrostatic force to the vibrator 100 and return the position to the origin. The magnitude of the electrostatic force at this time is equal to the magnitude of the external force that has moved the position of the vibrator 100. Therefore, between the applied electrostatic force F, the mass m of the vibrator, and the acceleration a due to the external force,

の関係が成り立つ。

The relationship holds.

  Since this relationship holds for each direction of the X-axis, Y-axis, and Z-axis, the magnitude of acceleration in each direction of the X-axis, Y-axis, and Z-axis due to external force can be obtained from Equation 1.

  On the other hand, when a rotational force is applied to the vibrator 100 reciprocating in the Z-axis direction around the X axis or the Y axis that is perpendicular to the movement direction, the vibrator 100 is moved in a direction perpendicular to the movement direction and the rotation axis. Will shift.

  For example, the direction of movement shifts in the Y-axis direction when a rotational motion acts around the X axis, and the direction of motion shifts in the X-axis direction when a rotational motion acts around the Y axis. The force that generates this deviation is the Coriolis force, and when the mass m of the vibrator, the displacement dz / dt of the vibrator in the Z-axis direction per unit time of the vibrator, and the angular velocity ω in the rotation direction, the Coriolis force Fc. The size of

で表される。このときｄｚ／ｄｔは往復運動の振幅と周期（又は振動数）から求めることができる。したがって、数２からコリオリ力によるＸ軸まわり・Ｙ軸まわりに生じた角速度の大きさを求めることができる。

It is represented by At this time, dz / dt can be obtained from the amplitude and period (or frequency) of the reciprocating motion. Therefore, the magnitude of the angular velocity generated around the X axis and the Y axis due to the Coriolis force can be obtained from Equation 2.

  As described above, since the acceleration or angular velocity is detected from the external force or Coriolis force, it is necessary to determine which is the change in position of the vibrator.

  The Coriolis force depends on the displacement dz / dt of the vibrator in the Z-axis direction as shown in Equation 2. That is, it depends on the vibration period or frequency of the vibrator. On the other hand, the external force is irrelevant to the displacement dz / dt of the vibrator in the Z-axis direction as shown in Equation 1.

  Therefore, by comparing the drive signal of the vibrator and the output signal of the displacement amount using a known comparison operation circuit, etc., when the drive signal and the output signal are synchronized, the Coriolis force is not synchronized. Can be determined as external force.

  By adopting the configuration shown in the first embodiment, a highly accurate and reliable acceleration / angular velocity sensor can be provided.

  An example in which the semiconductor device shown in FIG. 1 is specifically manufactured will be described below. Resist patterning is performed on two Pyrex (registered trademark) glass substrates having a diameter of 150 mm and a thickness of 500 μm, and etching is performed to form a recess in a portion where the vibrator is located. Here, etching with a depth of 5 μm was performed with dilute hydrofluoric acid.

  Subsequently, drive electrodes, control electrodes, and detection electrodes are formed in the recesses on the glass substrate. Here, a lift-off of a gold / chromium laminated film was adopted.

  Thereafter, the surface of one glass substrate (hereinafter referred to as the first glass substrate) on which the recesses, the drive electrodes, the control electrodes, and the detection electrodes are formed is bonded to the p-type silicon substrate by anodic bonding. Create a bonded substrate. Here, the specific size of the p-type silicon substrate is a diameter of 150 mm, a thickness of 50 μm, and a specific resistance of about 0.01 to 0.03 Ωcm.

  Subsequently, resist patterning is performed on the silicon substrate surface of the first bonded substrate, and etching is performed to form the X-axis / Y-axis direction casing, control electrode, detection electrode, and vibrator.

  Here, the Bosch process, which is a typical anisotropic dry etching of silicon, was employed.

  In the first bonded substrate, the X-axis / Y-axis direction housing and the control electrode / detection electrode are bonded to the first glass substrate, but the vibrator is formed on the concave portion of the first glass substrate. Therefore, it is separated from the first glass substrate after the etching.

  For this reason, from this process to the process of bonding another glass substrate (hereinafter referred to as a second glass substrate) and the first bonding substrate, the silicon substrate surface of the first bonding substrate is used. Handle in an upward state. By doing in this way, it was made not to fall with the vibrator still on the 1st bonded substrate.

  The casing, the control electrode / detection electrode, and the vibrator along the XY plane are formed of the same member of p-type silicon having a specific resistance of 0.01 to 0.03 Ωcm, and can be regarded as a conductor. A gap was provided between each electrode to insulate each other.

  The vibrator has a solid shape of 1.5 mm × 1.5 mm × 0.05 mm, and the distance between the vibrator and the control electrode / detection electrode is 5 μm in each of the X-axis and Y-axis directions.

  Subsequently, a non-evaporable getter material is installed in a region that is not in physical contact with the vibrator and each electrode in a space surrounded by the first glass substrate and the X-axis / Y-axis direction casing.

  Then, the 2nd bonding board | substrate is created by bonding the surface in which the recessed part, the drive electrode, the control electrode, and the detection electrode of the 2nd glass substrate were formed with the silicon substrate surface of a 1st bonding board | substrate. The bonding process was performed by anodic bonding under reduced pressure conditions of a temperature of 300 ° C. and a pressure of 0.133 Pa. As a result, a cavity covered with the first and second glass substrates and the silicon substrate is formed in the second bonded substrate.

  Thereafter, a heat treatment at a temperature of 450 ° C. is performed to activate the getter material, and the oxygen generated during anodic bonding is adsorbed to secure the inside of the cavity in the above-described reduced pressure state.

  Note that a conductor such as a metal material, a magnetic body, or the like can be used for the vibrator 100.

  In this semiconductor device, when the vibrator is vibrated at a frequency of 20 kHz and amplitude of 3 μm, the acceleration sensitivity is 2.0 V / G, the angular velocity sensitivity is 6.5 mV / deg / sec, the acceleration resolution is 0.003 μG, and the angular velocity resolution is It was 0.024 mdeg / sec.

  As a result, acceleration / angular velocity detection with higher resolution can be realized as compared with a conventional acceleration / angular velocity sensor of the same size.

  In the present embodiment, various methods and numerical values are given as specific examples, but any of them is not limited to the methods and numerical values listed here, and can be freely selected according to the purpose. For example, in FIG. 1, the drive electrode has a rectangular shape. However, the drive electrode can be applied without limitation of a shape such as a circular shape or a cross shape.

[Embodiment 2]
FIG. 2 is a diagram showing a semiconductor device as a second embodiment of the present invention.

  2A is a plan view of the semiconductor device according to the present embodiment as viewed from above, and FIG. 2B is a cross-sectional view taken along line BB in FIG. 2A. 2C is a cross-sectional view taken along line CC in FIG. 2A. The numbers and symbols in the figure are the same as those in FIG.

  The difference between the present embodiment and the first embodiment is that the drive electrode and the control electrode in the Z-axis direction are shared. That is, the control electrodes 505 and 506 in the Z-axis direction in FIG. 1 are omitted, and the function is added to the drive electrodes 401 and 402.

  Since both the drive electrode and the control electrode have a function of defining the movement of the vibrator in the Z-axis direction, they can be shared.

  Thus, there is an effect that simplification such as reduction in the number of wirings can be achieved. In addition, each electrode area can be widened in a limited space. This also has the effect that a large electrostatic force can be applied to the drive electrode, and the detection sensitivity can be improved on the detection electrode.

[Embodiment 3]
FIG. 3 is a diagram showing a semiconductor device as a third embodiment of the present invention.

  3A is a plan view of the semiconductor device according to the present embodiment as viewed from above, and FIG. 3B is a cross-sectional view taken along the line BB in FIG. 3A. FIG. 3C is a cross-sectional view taken along the line CC in FIG. The numbers and symbols in the figure are the same as those in FIG.

  The difference between this embodiment and the other embodiments is that the detection electrode is provided only in the Z-axis direction, only the control electrode is arranged in the X-axis / Y-axis direction, and the control electrode and the drive electrode in the Z-axis direction are provided. This is a common point.

  That is, the control electrodes 501 and 502 are provided in the X-axis direction, the control electrodes 503 and 504 are provided in the Y-axis direction, and the detection electrodes 601-608 and the drive electrodes 401 and 402 having the control electrode functions are provided in the Z-axis direction. By arranging the detection electrodes as shown in FIG. 3, it is possible to determine the displacement amount of the vibrator in each of the XYZ directions even if the detection electrodes are provided only in the Z-axis direction.

  Thus, there is an effect that simplification such as reduction in the number of wirings can be achieved. In addition, each electrode area can be widened in a limited space. Thus, the drive electrode can obtain a large electrostatic force even at a low voltage, and the detection electrode has an effect of improving the detection sensitivity.

[Embodiment 4]
FIG. 4 is a diagram showing a semiconductor device as a fourth embodiment of the present invention.

  4A is a plan view of the semiconductor device according to the present embodiment as viewed from above, and FIG. 4B is a cross-sectional view taken along line BB in FIG. 4A. 4C is a cross-sectional view taken along line CC in FIG. 4A. The numbers and symbols in the figure are the same as those in FIG.

  The difference between this embodiment and other embodiments is that the drive electrode, the control electrode, and the detection electrode are shared in each of the XYZ directions. In other words, the detection electrodes 601 to 606 provided in each direction have a control electrode function, and the detection electrodes 605 and 606 in the Z-axis direction have a driving function of the vibrator 100.

  In this case, measurement and drive / control can be performed from a set of electrodes by applying a measurement signal of capacitance between the electrodes and a signal for applying a voltage to apply an electrostatic force to the vibrator at a designated timing. Can be done.

  For this reason, there is an effect that simplification such as reduction in the number of wires on the sensor can be achieved. In addition, since the electrode area can be increased in each direction of XYZ, there is an effect that it can be driven and controlled with a large electrostatic force even at a low voltage and the detection sensitivity can be improved.

  The present invention relates to an acceleration / angular velocity sensor capable of detecting accelerations in a plurality of axial directions and angular velocities around a plurality of axes in an XYZ three-dimensional coordinate system, and is used in the fields of transportation equipment, industrial equipment, information appliances, and the like. Available. Specifically, it is suitable for attitude control / navigation of automobiles / ships / aircrafts, operation / attitude control of industrial / amusement robots, camera / video camera shake correction, game controller / navigation of portable terminals, etc. .

1 is a diagram showing a semiconductor device as a first embodiment of the present invention. It is a figure which shows the semiconductor device as the 2nd Embodiment of this invention. It is a figure which shows the semiconductor device as the 3rd Embodiment of this invention. It is a figure which shows the semiconductor device as the 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Vibrator 201-203 Case 300 Cavity 401-402 Drive electrode 501-506 Control electrode 601-610 Detection electrode

Claims (10)

In a semiconductor device having a vibrator that can move in the X-axis direction, the Y-axis direction, and the Z-axis direction in an XYZ three-dimensional coordinate system,
A housing in which the vibrator is stored so as not to contact the vibrator;
Drive means for reciprocating the vibrator in the Z-axis direction;
Control means for controlling movement of the vibrator so that the vibrator and the housing do not come into physical contact with each other;
And a detecting unit configured to detect a change amount of a relative position between the vibrator and the housing. Calculate the X-axis direction, Y-axis direction, Z-axis direction acceleration and angular velocity around the X-axis and around the Y-axis given to the vibrator from the amount of change in the relative position between the vibrator and the housing. The semiconductor device according to claim 1. 3. The semiconductor device according to claim 1, wherein the driving unit is the same as a control unit that controls movement of the vibrator in the Z-axis direction. The semiconductor device according to claim 1, wherein the detection unit is provided only in the Z-axis direction. 5. The semiconductor according to claim 1, wherein the control unit and the detection unit are the same in at least one of an X-axis direction, a Y-axis direction, and a Z-axis direction. apparatus. The semiconductor device according to claim 1, wherein the angular velocity is calculated from a Coriolis force applied to the vibrator. The semiconductor device according to claim 1, wherein at least one of the driving unit and the control unit controls the vibrator with electrostatic force. The semiconductor device according to claim 1, wherein the detection unit detects a change amount of a relative position between the vibrator and the housing by detecting a capacitance. 9. The semiconductor device according to claim 1, further comprising an electrode disposed around the vibrator along an XY plane, wherein the electrode is made of the same member as the vibrator. The semiconductor device according to claim 1, wherein the vibrator is made of silicon.

Images