BACKGROUND

1. Technical Field

The present invention relates to a physical quantity sensor, a method for manufacturing a physical quantity sensor, an inertial measurement unit, a portable electronic apparatus, an electronic apparatus, and a vehicle.

2. Related Art

Recently, as an example of a physical quantity sensor, a gyro sensor which uses a gyro sensor element utilizing the silicon MEMS (micro-electromechanical system) technology has been developed. Among physical quantity sensors, the gyro sensor, which detects an angular velocity, is quickly coming into widespread use, for example, for the motion sensing function of a game machine or the like.

As such a gyro sensor, for example, JP-A-2009-175079 discloses a sensor element that forms an angular velocity sensor. The sensor element has a support substrate, a fixed part fixed to the support substrate, a vibrator supported to the fixed part via an elastic beam (support beam), a movable comb-like electrode provided on the vibrator, and a fixed comb-like electrode meshing with the movable electrode with a space between them. In the angular velocity sensor of such a configuration, a voltage applied to the fixed comb-like electrode generates an electrostatic force between the movable electrode and the fixed comb-like electrode and this electrostatic force causes the vibrator to vibrate in direction of an X-axis (drive detection). An angular velocity about a Z-axis (or Y-axis) acting on the vibrator in such a vibrating state generates a Coriolis force and this Coriolis force causes the vibrator to vibrate in the direction of the Y-axis (or Z-axis) (detection vibration). Detecting an electrical signal corresponding to the magnitude of the vibration amplitude in the Y-axis (or Z-axis) direction of the vibrator due to the Coriolis force enables detection of the angular velocity of rotation.

Such a sensor element can be manufactured by dry etching. For example, JP-T-7-503815 discloses a so-called Bosch process, which is a Si deep reactive ion etching technique in which an etching step and a sidewall protection film deposition step are repeated, alternately switching between the two types of reactive plasma gases of SF6 (etching gas) and C4F8 (deposition gas).

However, if the sensor element described in JP-A-2009-175079 is to be manufactured by the dry etching technique described in JP-T-7-503815, the etching gas may not become incident perpendicularly on the silicon wafer because of the density distribution of the etching gas, and the processed wall may be processed at an angle that is different from ideal perpendicularity because of the angle of incidence of the etching gas. In this way, while the cross-sectional shape of the sensor element and particularly the cross-sectional shape of the elastic beam (support beam) should ideally be, for example, rectangular, the resulting cross-sectional shape is a parallelogram, trapezoid or the like due to the processing error. Therefore, the drive vibration of the vibrator includes not only a vibration component in the X-axis direction, which is the desired direction of drive vibration, but also a vibration component in the Y-axis direction or Z-axis direction. Thus, a quadrature signal, which is a type of unwanted signal, increases, affecting the detection signal. This poses a problem in that the detection accuracy drops.

SUMMARY

An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following configurations or application examples.

Application Example 1

A physical quantity sensor according to this application example includes a plurality of beams connected via a turnaround part. A groove is provided on a main surface of at least one beam of the plurality of beams. Wall thicknesses on the main surface of two sidewalls facing each other of the groove in a direction orthogonal to a longitudinal direction of the beam satisfy 0.9≤T1/T2≤1.1, where T1 is the wall thickness of one sidewall and T2 is the wall thickness of the other sidewall.

In the physical quantity sensor according to this application example, even if the plurality of beams connected via the turnaround part has an asymmetrical cross-sectional shape (for example, a parallelogram or trapezoid as a non-rectangular shape), a groove that satisfies 0.9≤T1/T2≤1.1, where the wall thickness T1 of one sidewall and the wall thickness T2 of the other sidewall are stable, is formed on the main surface of at least one beam of the plurality of beams. With this configuration, an increase of a quadrature signal, which is a type of unwanted signal, can be stably reduced. Thus, a drop in detection accuracy can be reduced.

Application Example 2

In the physical quantity sensor described in the above application example, it is preferable that the groove is provided at a center part in the longitudinal direction of the beam.

In this application example, the groove is provided at a center part in the longitudinal direction of the beam. This improves balance in the longitudinal direction of the beam and thus can reduce the quadrature signal more significantly.

Application Example 3

In the physical quantity sensor described in the above application example, it is preferable that the sidewalls have a surface in a recessed shape on the main surface side, when viewed in a plan view from a direction orthogonal to the longitudinal direction.

With this application example, the quadrature signal can also be reduced by the recessed shape provided on the surface on the main surface side, of the sidewalls. Thus, the length in the longitudinal direction of the groove can be shortened and a drop in the strength of the beam can be reduced.

Application Example 4

In the physical quantity sensor described in the above application example, it is preferable that the recessed shape is curved.

In this application example, the recessed shape provided on the surface on the main surface side, of the sidewalls, is curved. This can increase the strength (rigidity) of the beam against a bending force in the longitudinal direction.

Application Example 5

In the physical quantity sensor described in the above application example, it is preferable that the wall thicknesses T1 and T2 satisfy 0.05 μm≤T1≤0.5 μm and 0.05 μm≤T2≤0.5 μm.

With this application example, the beam can be formed without reducing the strength (rigidity) of the part where the groove is formed.

Application Example 6

In the physical quantity sensor described in the above application example, it is preferable that the plurality of beams is provided in a sensor element and that the sensor element is an angular velocity sensor element that can detect an angular velocity.

This application example can provide an angular velocity sensor in which an increase of a quadrature signal is reduced.

Application Example 7

An inertial measurement unit according to this application example includes: the physical quantity sensor described in the above Application Example 6; an acceleration sensor; and a control unit which controls the physical quantity sensor and the acceleration sensor.

In the inertial measurement unit according to this application example, the control unit controls the physical quantity sensor (angular velocity sensor), in which an increase of a quadrature signal is reduced, and the acceleration sensor. Thus, an inertial measurement unit that can output highly reliable physical quantity data can be provided.

Application Example 8

A portable electronic apparatus according to this application example includes: the physical quantity sensor described in one of the above application examples; a case which accommodates the physical quantity sensor; a processing unit which is accommodated in the case and processes output data from the physical quantity sensor; a display unit accommodated in the case; and a light-transmissive cover which closes an opening of the case.

In the portable electronic apparatus according to this application example, the processing unit performs control based on output data outputted from the physical quantity sensor. Thus, a highly reliable portable electronic apparatus that can achieve the effects of the physical quantity sensor can be provided.

Application Example 9

It is preferable that the portable electronic apparatus described in the above application example includes a satellite positioning system and thus measures a moving distance or a trajectory of movement of a user.

This application example can provide a highly reliable portable electronic apparatus that can measure the moving distance or the trajectory of movement of the user via the satellite positioning system.

Application Example 10

An electronic apparatus according to this application example includes: the physical quantity sensor described in one of the above application examples; and a control unit which performs control based on a detection signal outputted from the physical quantity sensor.

In the electronic apparatus according to this application example, the control unit performs control based on a detection signal outputted from the physical quantity sensor. Thus, a highly reliable electronic apparatus that can achieve the effects of the physical quantity sensor can be provided.

Application Example 11

A vehicle according to this application example includes: the physical quantity sensor described in one of the above application examples; and an attitude control unit which controls an attitude, based on a detection signal outputted from the physical quantity sensor.

In the vehicle according to this application example, the attitude control unit controls the attitude, based on a detection signal outputted from the physical quantity sensor. Thus, a highly reliable vehicle that can achieve the effects of the physical quantity sensor can be provided.

Application Example 12

It is preferable that the vehicle described in the above application example includes at least one system from among an engine system, a braking system, and a keyless entry system, and that the attitude control unit controls the system, based on the detection signal.

In this application example, the attitude control unit controls at least one system from among an engine system, a braking system, and a keyless entry system, based on a detection signal outputted from the physical quantity sensor. Thus, a highly reliable vehicle that can achieve the effects of the physical quantity sensor can be provided.

Application Example 13

A method for manufacturing a physical quantity sensor according to this application example is a method for manufacturing a physical quantity sensor in which a plurality of sensor elements is arranged on a wafer, each sensor element including a plurality of beams connected via a turnaround part, with a groove provided on a main surface of at least one beam of the plurality of beams. The method includes: deciding at least one of a number of the beams where the groove is to be formed and a length in a longitudinal direction of the groove, according to distribution of the sensor elements arranged within a surface of the wafer; and forming the groove in the beam, based on the decision.

In the method for manufacturing the physical quantity sensor according to this application example, at least one of the number of beams where the groove is to be formed and the length in the longitudinal direction of the groove is decided according to the distribution of the sensor elements arranged within the plane of the wafer, and the groove is formed in the beam, based on the decision. Thus, a physical quantity sensor in which irregular occurrence of a quadrature signal within the surface of the wafer is reduced can be manufactured.

