JPH11211482A - Electrode structure of surface micromachine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the S/N ratio of an oscillating body OC and prevent the short circuit by the contact of the OC with an electrode by arranging a drive detecting electrode for detecting the driving state of the OC and a servo electrodes for regulating the position of the OC on both sides of the OC. SOLUTION: A pair of drive detecting electrodes 30, 40 for detecting the oscillating state of an oscillating body OC are provided on both sides of the OC, and servo electrodes 31, 32, 41, 42 for regulating the position of the OC are arranged on both the sides thereof. A voltage of a prescribed period from a drive circuit is alternately applied to drive electrodes 33, 34, 43, 44 to drive and oscillate the OC. The change of the OC when an angle speed is generated is detected by angle speed detecting electrodes ODT1, ODT2, and the angle speed is determined by an angle speed detecting circuit. The capacity change of the OC is detected by the drive detecting electrodes 30, 40, and the voltage to be applied to the servo electrodes 31, 32, 41, 42 is regulated to a voltage corresponding to the capacity by a servo circuit to correct the position of the OC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface micromachine for detecting an angular velocity, and more particularly to an electrode structure of a surface micromachine capable of returning a vibrating body to a normal driving position in a driving state.

[0002]

2. Description of the Related Art Conventionally, in a surface micromachine,
Two driving electrodes are provided on the substrate, and a vibrating body is provided between the driving electrodes. The vibrating body is provided with a constant gap with respect to the substrate, and applies an electrostatic force 180 degrees out of phase to the two driving electrodes. When an angular velocity is generated by driving the vibrating body, Coriolis force is generated in the vibrating body, and the movement of the vibrating body subjected to the Coriolis force is detected by an angular velocity detecting electrode provided opposite to the vibrating body. It has been known.
For example, such a sensor is disclosed in JP-A-4-242444. The sensor disclosed in this publication,
The drive electrode provided on the substrate side and the drive electrode provided on the vibrating body side have a comb shape in the vibration detection direction, and the vibrating body is elongated in one direction.

[0003] A structure for drawing out wiring from a driving electrode is disclosed in US Pat. No. 5,620,931. In this structure, a drive electrode for driving a vibrator made of polysilicon is provided on a substrate in a bare state.

[0004]

However, when the vibrating body is driven with the driving electrode provided on the substrate side and the driving electrode provided on the vibrating body side in a comb shape, the vibrating body is driven stably. However, in order to prevent the contact between the vibrating body and the driving electrode on the substrate side, it is necessary to increase the gap between the comb teeth, so that the thickness of the vibrating body increases. Becomes large. For this reason, when the large vibrating body is elongated in one direction, the vibrating body is likely to be twisted due to the stress or the like. in this way,
If the vibrating body is twisted, noise is generated in the angular velocity detection signal, and the S / N ratio becomes poor.

When the potential of the driving electrode on the substrate side is largely different from that of the vibrating body, when the vibrating body makes a large displacement, when both come into contact, an electrical short circuit occurs,
It is not reliable.

Therefore, the present invention has been made in view of the above-mentioned problems, and it is intended to improve the S / N ratio of a vibrating body and prevent an electric short circuit even when the vibrating body comes into contact with an electrode. Is a technical task.

[0007]

The technical means taken to solve the above problem is to provide a pair of drive detecting electrodes for detecting the driving state of the vibrating body on both sides of the vibrating body, A servo electrode for adjusting the position of the vibrating body was provided.

As described above, a pair of drive detecting electrodes for detecting the driving state of the vibrating body are provided on both sides of the vibrating body, and servo electrodes for adjusting the position of the vibrating body are provided on both sides of the driving detecting electrodes. The electrodes make it possible to adjust the position of the vibrating body. Even if the vibrating body is twisted, the torsion adjustment can be performed to reduce noise, thereby improving the S / N ratio. In this case, it is possible to adjust the position of the vibrating body by applying a voltage to the servo electrode based on the signal from the drive detection electrode, and to adjust the torsion.

In this case, if a structure is adopted in which at least one of the drive detection electrode and the servo electrode is vertically separated, different voltages can be applied to the vertically separated drive detection electrode and the upper and lower electrodes of the servo electrode. Thus, accurate position adjustment of the vibrating body becomes possible.

Further, the vibrating body, the drive electrode, the drive detecting electrode and the servo electrode, on a plane perpendicular to the substrate plane, pass through the center of gravity of the vibrating body, and are parallel to a plane parallel to the driving direction and a plane perpendicular to the driving direction. If the plane is symmetrical, the balance becomes good, the control is easy, and the S / N ratio can be improved.

Further, if an insulating film is provided in a portion where the vibrating body is adjacent when the driving body and the angular velocity are generated, even if a large force acts on the vibrating body and comes into contact with a driving electrode or the like, the insulating film is formed. The provision prevents an electrical short and improves reliability.

[0012]

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

FIG. 1 shows a surface micromachine 10 according to the present invention.
0 shows the entire structure. Surface micromachine 10
0 functions as a sensor for detecting the angular velocity, and is hereinafter referred to as a sensor. In this sensor, a vibrating body OC is disposed at the center, and the vibrating body OC is fixed to the substrate 1 side, and is floatingly supported on the substrate 1 at four locations from both sides in the Y direction by beams extending in the Y direction. The vibrating body OC has a rectangular ring shape in outer shape, and has a plurality of slits inside. Angular velocity detection electrodes ODT1 and ODT2 for detecting respective velocities are provided between the slits, and the signals are transmitted to an angular velocity detection electrode pad outside the vibrator.

On the substrate side, two sets of drive electrodes 33 and 3 are provided.
4/43 and 44 are provided, and a voltage is applied from two drive electrode pads provided on the substrate. In this case, two sets of driving electrodes 33 and 34 are provided between the driving electrodes 33, 34/43, and 44, with the vibrating body OC floatingly supported with a fixed gap with respect to the substrate 1 between the driving electrodes 33, 34/43, and 44. / 43 and 44 are alternately applied with an electrostatic force 180 ° out of phase, so that the vibrating body OC becomes Y
Vibrates in the X direction while being supported by the beam in the direction. In this case, the drive voltage can be reduced by applying an electrostatic force that matches the resonance frequency of the vibrating body OC.

When the vibrating body OC is vibrated in the X direction, if an angular velocity about the Z axis is generated, a Coriolis force is generated in the vibrating body OC in the Y axis direction, and the Coriolis force is generated. The angular velocity is detected by detecting the movement of the vibrating body OC with the angular velocity as a change in capacitance between the vibrating body OC and the angular velocity detecting electrodes ODT1 and ODT2 and the angular velocity detecting circuit. still,
A known driving method is used for the periodic driving of the vibrating body OC, and the description thereof is omitted here.

The sensor according to the present invention has a drive detecting electrode 30/40 for detecting a drive state of the vibrating body OC in addition to the above-described structure.
Electrodes 31 and 32 for adjusting the position of the oscillator OC
41 and 42 are added, each of which is characterized by having separate upper and lower electrodes. The vibrating body OC, the drive electrodes 33, 34, 43 and 44, the drive detection electrodes 30 and 40, and the servo electrodes 31 and Reference numerals 32, 41, and 42 are plane-symmetric with respect to a plane passing through the center of gravity G of the vibrating body on a plane perpendicular to the substrate plane. That is, it passes through the center of gravity G of the vibrating body OC,
A plane perpendicular to the substrate and parallel to the driving direction (X direction) (ZX
Plane) and a plane (YZ plane) perpendicular to the drive direction, the balance is good,
It becomes easier to control the vibrating body OC. In this case, by giving accurate vibration to the vibrating body OC, it is possible to prevent noise from being detected in the angular velocity detection signal and to improve the S / N ratio.

The drive detection electrodes 30/40 are connected to the servo electrodes 3 based on a change in potential between the drive detection electrodes and the vibrating body OC.
A servo voltage is applied to 1, 32/41, 42 to vibrate the body O
The position C is adjusted. In this case, according to the circuit configuration shown in FIG. 1, a voltage of a predetermined cycle from the drive circuit is alternately applied to the drive electrodes 33, 34/43, and 44, and the vibrating body O
C is driven in the X direction to generate vibration, and a change in the vibrating body OC when an angular velocity is generated is detected by an angular velocity detection electrode ODT1,
Detected from ODT2. Based on the angular velocity signal, it is operated and amplified by an angular velocity detection circuit to obtain the value. At this time, the vibrating body O
The capacitance change with respect to the drive position of C is detected by the drive detection electrode 30/4.
0, and the voltage corresponding to the capacitance is applied to the servo electrode 3
The voltage applied to 1, 32/41, 42 is adjusted by a servo circuit to correct the position of the vibrating body OC.

FIGS. 2 and 3 show the electrode structure of the drive detection electrode 30, the servo electrodes 31, 32, and the drive electrodes 33, 34 on one side of the vibrating body OC. Since the drive detection electrode 30 and the servo electrodes 31 and 32 have the same structure,
First, one electrode structure of the drive detection electrode 30 and the servo electrodes 31 and 32 will be described with reference to FIG.
In this case, since the electrode structures of the drive detection electrode 40, the servo electrodes 41 and 42, and the drive electrodes 43 and 44 on the other side are symmetrical, the description is omitted.

In FIG. 2, an insulating layer NL is provided on a substrate BS.
Are formed. The lower electrode DE made of a conductive material is formed on the insulating layer NL, and the vibrating body OC and the upper electrode UE are made of a conductive material. Lower electrode DE
The upper electrode UE and the upper electrode UE have a structure that sandwiches the vibrating body OC with a certain gap. Upper electrode UE and lower electrode DE
And an insulating layer IS interposed between the upper electrode UE
And the lower electrode DE are electrically insulated by the insulating layer IS. Further, the upper electrode UE has a support portion SP extending in the thickness direction.
The wiring part WI for supplying a voltage to the upper electrode UE is formed on the supporting part SP with the same film as the vibrating body OC. With such a configuration, the upper electrode U
Different potentials can be detected between E and the lower electrode DE, and different voltages can be applied to the upper electrode UE and the lower electrode DE.

Next, referring to FIG. 3, the drive electrodes 33, 3
4. The structure of the drive detection electrode 30, and the servo electrodes 31, 32 will be described. A drive detection electrode 30 having the electrode configuration shown in FIG. 2 is provided on the substrate. Drive detection electrode 30
The upper electrode DU and the lower electrode DD are insulated by the insulating layer IS, and the displacement of the position of the vibrating body OC can be detected from the upper electrode DU and the lower electrode DD by a change in potential as a change in capacitance.

The drive detection electrode 30 has servo electrodes 3 having the same electrode structure as the detection drive electrode 30 on both sides and in parallel.
1, 32 are provided. The lower electrodes SD1 and SD2 of the servo electrodes 31 and 32 are the lower electrodes D of the drive detection electrodes 30.
D, and the upper electrodes SU1 and SU2 of the servo electrodes 31 and 32 are parallel to the upper electrode DU of the drive detection electrode 30, and are substantially on both sides of the drive detection electrode 30. Are provided in parallel with the Y direction in FIG. Further, the drive electrodes 33 and 34 on one side are disposed so as to sandwich the servo electrodes 31 and 32 from both sides in the Y direction.

In the case of driving the vibrating body OC for a sensor having such an electrode structure, two sets of driving electrodes 3 are used.
Voltages are alternately applied to 3, 34/43, and 44 so that electrostatic forces having phases different by 180 degrees are applied. Then, the vibrating body OC includes the drive electrodes 33 and 34 and the drive electrodes 43 and
A suction force is generated between the first and second members 44 and 44 to vibrate in the X direction. Therefore, when an angular velocity about the Z axis as a rotation axis occurs during the vibration, Coriolis force is applied to the vibrating body OC, and vibration in the Y direction is applied. The angular velocity is detected by detecting the vibration in the Y direction by the plurality of angular velocity detection electrodes ODT1 and ODT2.

However, when the vibrating body OC is vibrating without torsion when driving the vibrating body OC, the angular velocity detection signal does not include noise and the angular velocity can be accurately detected. If twist occurs in S /
In order to improve the N ratio, it is necessary to correct the twist.

When the torsion of the vibrating body OC is corrected, the potential from the drive detection electrode 30 for detecting different potentials on the upper side and the lower side of the vibrating body OC is detected as described above.
It is possible to know how much the vibrating body OC is displaced in the Z direction, and based on the displacement, apply a voltage corresponding to the displacement to the servo voltages 31, 32/41, 42 provided on both sides of the drive detection electrodes 30/40. By doing so, it is possible to perform fine position adjustment by sucking the vibrating body OC in a direction in which the torsion is eliminated.

Next, with reference to FIGS. 4 to 20, the steps of manufacturing the electrode structure will be described below. The following steps are applied to the drive detection electrode 30 and the servo electrodes 31, 32 in which the lower electrode DE and the upper electrode UE are separated by an insulating layer.

In step 1 (see FIG. 4), first, a nitride film 2 serving as an etching stopper which is not etched is formed on a silicon wafer (substrate) 1, and polysilicon (poly-Si) 3 serving as a lower electrode is formed on the silicon film (poly-Si) 3. 2 is formed. At this time, in the case of non-doping, doping such as ion implantation and diffusion is performed, and an oxide film 4 serving as a separation electrode is formed on the poly-Si3.

In step 2 (see FIG. 5), a portion to be insulated is masked with resist 5 and dry-etched with CHF ₃ gas or wet-etched with buffered hydrofluoric acid. Is removed by ashing.

In step 3 (see FIG. 6), the lower electrode DE made of poly-Si is formed by etching using the resist 6 as a mask for the lower electrode, and after the etching, the resist 6 is removed.

In step 4 (see FIG. 7), a nitride film is formed and an insulating layer 7 is formed. In step 5 (see FIG. 8), phosphor glass is formed on the insulating layer with a constant thickness. After forming the sacrificial layer 8, SOG (spin on glass),
Alternatively, the surface of the sacrificial layer 8 is flattened by chemical polishing (CMP), and a nitride film is formed thereon to form the insulating layer 9.

In step 6 (see FIG. 9), the portion of the anchor portion 12 that is insulated from the lower electrode DE by the resist 10 is masked, dry-etched, and the resist 10 is peeled off. Then, the portion excluding the anchor portion 12 is masked with the resist 11 and dry-etched,
After forming the groove 12a of the anchor portion 12, the resist 11
Is peeled off.

In step 8 (see FIG. 11), the anchor section 12
On the surface of the sacrifice layer 8 including the groove 12a, a structure (also referred to as a vibrator) OC which is to be moved later and poly-Si 13 to be a wiring portion WI are formed. Also at this time, in the case of non-doping, doping is performed by ion implantation.

In step 9 (see FIG. 12), the portions other than the portions to be separated as vibrators are masked with resist 14 and dry-etched to remove resist 14.
The vibrating body OC and the wiring part WI are separated. Then, Step 10
In (see FIG. 13), an insulating layer 15 is formed by forming a nitride film 15 on the poly-Si 13.

In step 11 (see FIG. 14), in order to protect the side wall of the wiring portion WI on the vibrating body side, the vicinity of the side wall is masked with a resist 16 in order to prevent contact with the vibrating body OC which moves later. Then, dry etching is performed to form a stopper portion ST for preventing contact with the vibrating body 51 using an insulating film, and then the resist 16 is stripped.

In step 12 (see FIG. 15), after forming a sacrificial layer 17 by forming a phosphor glass 17 on the surface, the surface of the sacrificial layer 17 is planarized by SOG or CMP, and a nitride film is formed thereon. Then, an insulating layer 18 is formed.

In step 13 (see FIG. 16), the resist 1
At 9, the portion that will later become the upper electrode UE is masked and dry-etched to form the shape of the upper electrode UE, and the resist 19 is stripped.

In step 14 (see FIG. 17), the upper electrode U
The surface other than the support part SP connected from E to the wiring part WI is
By masking with the resist 20 and performing dry etching, a groove of the support portion SP connecting the upper electrode UE and the wiring WI is formed.

In step 15 (see FIG. 18), poly-Si2
2 is formed on the surface of the support portion SP including the groove. At this time, similarly, in the case of non-doping, doping such as ion implantation / diffusion is performed, and thereafter, a portion serving as the upper electrode UE is masked with the resist 23.

In step 16 (see FIG. 19), poly-Si2
2 to form an upper electrode UE,
5 is peeled off. After that, an insulating layer 24 is formed by forming a nitride film for insulation from the outside of the upper electrode, a resist 25 is masked on the upper electrode UE, and dry etching is performed.

In step 17 (see FIG. 20), the resist 2
After peeling off the sacrifice layer 5, the sacrifice layer 8,
17, the portion into which the etching solution enters is removed, the vibrating body OC floats, and the tip of the vibrating body OC is the upper electrode UE.
And the lower electrode DE.

The surface micromachine manufactured as described above detects the position of the vibrating body OC by the drive detection electrodes 30/40, and the servo electrodes 31, 32/41 arranged on both sides of the drive detection electrodes 30/40. , 42, the position correction can be performed even when the vibrating body OC is twisted. Also, the vibrating body OC
Is greatly displaced, even if the vibrating body OC comes into contact with an electrode having a different potential difference, such as a drive electrode, an electrical short circuit does not occur because it is protected by the insulating film.

[0041]

According to the present invention, a pair of drive detecting electrodes for detecting the driving state of the vibrating body are provided on both sides of the vibrating body, and servo electrodes for adjusting the position of the vibrating body are provided on both sides of the drive detecting electrodes. Accordingly, the position of the vibrating body can be adjusted by the servo electrode. In this case, even when the vibrating body is twisted, a voltage can be applied to the servo voltage based on a signal from the drive detection electrode to adjust the conforming position of the vibrating body and noise can be reduced. , S / N ratio is improved.

In this case, if a structure is adopted in which at least one of the drive detection electrode and the servo electrode is vertically separated, different voltages can be applied to the vertically separated drive detection electrode and the upper and lower electrodes of the servo electrode. Thus, accurate position adjustment of the vibrating body becomes possible.

Further, the vibrating body, the drive electrode, the drive detecting electrode and the servo electrode are arranged on a plane perpendicular to the substrate plane, passing through the center of gravity of the vibrating body, parallel to the driving direction, and to a plane perpendicular to the driving direction. If the plane is symmetrical, the balance becomes good, the control is easy, and the S / N ratio can be improved.

Further, if an insulating film is provided at a portion where the vibrating body is adjacent when the driving body and the angular velocity are generated, even if a large force acts on the vibrating body and comes into contact with a driving electrode or the like, the insulating film is formed. The provision prevents an electrical short and improves reliability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a surface micromachine according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of an electrode structure of a surface micromachine according to an embodiment of the present invention.

FIG. 3 is an electrode layout diagram of a key portion of the surface micromachine according to the embodiment of the present invention.

FIG. 4 is a manufacturing step (step 1) of the surface micromachine in one embodiment of the present invention.

FIG. 5 is a manufacturing step (step 2) of the surface micromachine according to the embodiment of the present invention.

FIG. 6 is a manufacturing step (step 3) of the surface micromachine in one embodiment of the present invention.

FIG. 7 is a manufacturing step (step 4) of the surface micromachine in one embodiment of the present invention.

FIG. 8 is a manufacturing step (step 5) of the surface micromachine in one embodiment of the present invention.

FIG. 9 is a manufacturing step (step 6) of the surface micromachine in one embodiment of the present invention.

FIG. 10 is a manufacturing step (step 7) of the surface micromachine in one embodiment of the present invention.

FIG. 11 is a manufacturing step (step 8) of the surface micromachine in one embodiment of the present invention.

FIG. 12 is a manufacturing step (step 9) of the surface micromachine in one embodiment of the present invention.

FIG. 13 is a manufacturing step (step 10) of the surface micromachine in one embodiment of the present invention.

FIG. 14 is a manufacturing step (step 11) of the surface micromachine in one embodiment of the present invention.

FIG. 15 is a manufacturing step (step 12) of the surface micromachine in one embodiment of the present invention.

FIG. 16 is a manufacturing step (step 13) of the surface micromachine in one embodiment of the present invention.

FIG. 17 is a manufacturing step (step 14) of the surface micromachine in one embodiment of the present invention.

FIG. 18 is a manufacturing step (step 15) of the surface micromachine in one embodiment of the present invention.

FIG. 19 is a manufacturing step (step 16) of the surface micromachine in one embodiment of the present invention.

FIG. 20 is a manufacturing step (step 17) of the surface micromachine in one embodiment of the present invention.

[Explanation of symbols]

 7, 9, 15, 18, 24 Insulating layer (insulating film) 30, 40 Driving detection electrode 32, 41, 42 Servo electrode 33, 34, 43, 44 Driving electrode 100 Surface micromachine BS substrate OC oscillator ODT1, ODT2 Angular velocity detection Electrode SP stopper (insulating film)

Claims (4)

[Claims] A driving electrode provided on a substrate, a vibrating body provided with a constant gap on the substrate, and an angular velocity detecting electrode provided facing the vibrating body; A surface micromachine that applies a voltage to the vibrating body to drive the vibrating body and detects a change in angular velocity by the angular velocity detection electrode, wherein a vibration state in the driving direction of the vibrating body and a driving direction and angular velocity are detected on both sides of the vibrating body. A pair of drive detection electrodes for detecting a vibration state in a direction perpendicular to the angular velocity detection direction to be provided,
An electrode structure of a surface micromachine having servo electrodes for adjusting the position of the vibrating body disposed on both sides of the drive detection electrodes. 2. The surface micromachine electrode structure according to claim 1, wherein at least one of said drive detection electrode and said servo electrode is vertically separated. 3. The vibration body, the drive electrode, the drive detection electrode, and the servo electrode, on a plane perpendicular to a substrate plane, pass through a center of gravity of the vibration body and are parallel to a driving direction;
2. The electrode structure of a surface micromachine according to claim 1, wherein the electrode structure is plane-symmetric with respect to a plane perpendicular to the driving direction. 4. The electrode structure of a surface micromachine according to claim 1, wherein an insulating film is provided at a portion where said vibrating body is adjacent when driving and generating angular velocity.