WO2022259912A1 - 光走査装置、電子機器 - Google Patents
光走査装置、電子機器 Download PDFInfo
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- WO2022259912A1 WO2022259912A1 PCT/JP2022/022091 JP2022022091W WO2022259912A1 WO 2022259912 A1 WO2022259912 A1 WO 2022259912A1 JP 2022022091 W JP2022022091 W JP 2022022091W WO 2022259912 A1 WO2022259912 A1 WO 2022259912A1
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- 230000003287 optical effect Effects 0.000 title claims abstract description 58
- 238000001514 detection method Methods 0.000 claims abstract description 61
- 230000003071 parasitic effect Effects 0.000 claims abstract description 25
- 239000004065 semiconductor Substances 0.000 claims description 4
- 229910004298 SiO 2 Inorganic materials 0.000 description 18
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 18
- 238000010586 diagram Methods 0.000 description 17
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 17
- 238000000034 method Methods 0.000 description 10
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 description 9
- 229910052451 lead zirconate titanate Inorganic materials 0.000 description 9
- 235000012239 silicon dioxide Nutrition 0.000 description 9
- 239000000377 silicon dioxide Substances 0.000 description 9
- 229910052681 coesite Inorganic materials 0.000 description 8
- 229910052906 cristobalite Inorganic materials 0.000 description 8
- 229910052682 stishovite Inorganic materials 0.000 description 8
- 229910052905 tridymite Inorganic materials 0.000 description 8
- 238000005530 etching Methods 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 244000126211 Hericium coralloides Species 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000010030 laminating Methods 0.000 description 2
- 230000010355 oscillation Effects 0.000 description 2
- 238000000059 patterning Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B3/00—Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes
- B81B3/0064—Constitution or structural means for improving or controlling the physical properties of a device
- B81B3/0086—Electrical characteristics, e.g. reducing driving voltage, improving resistance to peak voltage
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
- G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
- G02B26/0841—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD the reflecting element being moved or deformed by electrostatic means
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2201/00—Specific applications of microelectromechanical systems
- B81B2201/04—Optical MEMS
- B81B2201/042—Micromirrors, not used as optical switches
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2203/00—Basic microelectromechanical structures
- B81B2203/01—Suspended structures, i.e. structures allowing a movement
- B81B2203/0136—Comb structures
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2203/00—Basic microelectromechanical structures
- B81B2203/03—Static structures
- B81B2203/0353—Holes
Definitions
- the present disclosure relates to optical scanning devices and electronic devices.
- An optical scanning device that scans incident laser light in two-dimensional directions is known. Conventional examples of optical scanning devices are described, for example, in Patent Document 1 and Non-Patent Document 1 listed below. In such an optical scanning device, it is necessary to detect the deflection angle of the movable mirror that scans the laser light, and noise is likely to be mixed in the signal used for that purpose.
- One of the purposes of the specific aspects of the present disclosure is to reduce the noise of the signal used to detect the deflection angle of the movable mirror.
- An optical scanning device includes: (a) a mirror having a reflecting surface; (b) a driving unit that oscillates the mirror; and (d) a dummy capacitance unit that generates a dummy capacitance substantially equivalent to the capacitance in the initial state of the detection unit, and (e) the detection unit, It has a movable electrode whose position changes in relation to the movement of the driving section and a fixed electrode which does not relate to the movement of the driving section, and is configured to generate the electrostatic capacitance between the movable electrode and the fixed electrode.
- the dummy capacitance section has a first electrode and a second electrode, and is configured to generate the dummy capacitance between the first electrode and the second electrode;
- the movable electrode, the fixed electrode, the first electrode, and the second electrode are provided on the same active layer, which is a semiconductor layer, and are separated from each other, and the active layers sandwich an insulating layer. and
- a second parasitic capacitance generated between the provided active layer and the support layer is substantially equivalent;
- a signal path is configured, and the dummy capacitance and the second parasitic capacitance are connected in series to configure a second signal path.
- FIG. 1 is a plan view showing the configuration of the optical scanning device (optical deflector) according to the first embodiment.
- FIG. 2A is an enlarged view of the deflection angle detector.
- FIG. 2B is an enlarged view of the dummy comb structure.
- FIG. 3A is an enlarged view of the detection pad.
- FIG. 3B is an enlarged view of a dummy detection pad.
- FIG. 4 is an enlarged view of the vicinity of read signal input pads.
- FIG. 5 is a schematic cross-sectional view corresponding to the aa line direction shown in FIG.
- FIG. 6 is a diagram for explaining the sites where parasitic capacitance is generated.
- FIG. 7 is a plan view for explaining capacitive components formed in each part of the optical scanning device.
- FIG. 1 is a plan view showing the configuration of the optical scanning device (optical deflector) according to the first embodiment.
- FIG. 2A is an enlarged view of the deflection angle detector.
- FIG. 2B
- FIG. 8A is a cross-sectional view showing a connection relationship of portions forming capacitive components in the optical scanning device.
- FIG. 8B is an equivalent circuit diagram showing the connection relationship of each capacitive component.
- 9A is a waveform diagram showing an example of the read signal
- FIG. 9B is a waveform diagram showing an example of the voltage signal Vout1
- FIG. 9C is a waveform diagram showing an example of the voltage signal Vout2
- FIG. 9D is a waveform diagram showing an example
- FIG. 9D is an enlarged waveform diagram showing an example of a differential signal between voltage signals V out1 and V out2
- 10A to 10G are process diagrams showing an example of a method for manufacturing an optical scanning device.
- FIG. 12 is a plan view showing the configuration of the optical scanning device of the second embodiment.
- 13 is a partially enlarged view of the optical scanning device shown in FIG. 12.
- FIG. 14 is a partially enlarged view of the optical scanning device shown in FIG. 12.
- FIG. 15A and 15B are partial cross-sectional views of the optical scanning device of the second embodiment.
- FIG. 1 is a plan view showing the configuration of an optical scanning device (optical deflector) 1 according to the first embodiment.
- the surface on which the laser beam to be scanned is incident is the front surface, and the opposite surface is the back surface.
- FIG. 1 shows a plan view seen from the surface side.
- the optical scanning device 1 of this embodiment has a generally bilaterally symmetrical structure in a plan view.
- the optical scanning device 1 mainly includes a reflecting portion (mirror) 2, a torsion bar 3, an inner piezoelectric actuator 4, an inner frame portion 5, an outer piezoelectric actuator (driving portion) 6, and an outer frame portion (frame) 7.
- the left-right direction in the drawing is defined as the X-axis, the vertical direction as the Y-axis, and the thickness direction of the optical scanning device 1 (the direction orthogonal to the paper surface) as the Z-axis. These axes are assumed to be orthogonal at the center o of the optical scanning device 1 .
- the reflecting section 2 is a movable mirror having a substantially circular reflecting surface in plan view, and is configured to be swingable about the Y-axis and the X-axis by an inner piezoelectric actuator 4 and an outer piezoelectric actuator 6 .
- an inner piezoelectric actuator 4 and an outer piezoelectric actuator 6 By reflecting the laser light by such a reflecting section 2, the laser light made incident on the reflecting section 2 can be scanned in two-dimensional directions.
- the torsion bars 3 are provided above and below the reflecting section 2 one by one in plan view.
- the torsion bar 3 extends from the reflecting portion 2 along the Y-axis direction and is coupled to the inner circumference of the inner frame portion 5 . Also, the torsion bar 3 is connected to the upper and lower ends of the left and right inner piezoelectric actuators 4 .
- the inner piezoelectric actuator 4 and the outer piezoelectric actuator 6 are provided on the left and right sides of the reflector 2 in plan view, respectively.
- the inner piezoelectric actuators 4 are connected to each other and have a nearly elliptical shape extending along the Y-axis in plan view.
- the outer piezoelectric actuator 6 is interposed between the inner frame portion 5 and the outer frame portion 7 .
- the outer piezoelectric actuators 6 each include a plurality of piezoelectric cantilevers 13 .
- the piezoelectric cantilevers 13 the one closest to the reflecting section 2 and the one furthest away are shorter in the Y-axis direction than the other piezoelectric cantilevers 13 .
- the inner frame portion 5 surrounds the reflecting portion 2 and the torsion bar 3.
- the inner frame portion 5 has an almost elliptical shape extending along the Y-axis as a whole in plan view.
- the driving pads 15 and the driving GND pads 16 are provided on the left and right upper sides of the outer frame portion 7 in plan view.
- the driving pad 15 has a plurality of circular portions in plan view.
- the driving pads 15 and the driving GND pads 16 are electrically/physically connected to the outside through bonding wires (not shown) when the optical scanning device 1 is packaged.
- the drive pad 15 and drive GND pad 16 on the right side of the figure are used to supply a drive voltage to the inner piezoelectric actuator 4 on the right side of the figure.
- the drive pad 15 and drive GND pad 16 on the left side of the figure are used to supply drive voltage to the inner piezoelectric actuator 4 on the left side of the figure.
- Each inner piezoelectric actuator 4 is interposed between the torsion bar 3 and the inner frame portion 5, and by twisting the torsion bar 3, causes the reflecting portion 2 to oscillate around the Y-axis at the first frequency. Resonance is used for this oscillation.
- the first frequency is, for example, 15 kHz to 25 kHz.
- Each outer piezoelectric actuator 6 is supplied with a drive voltage of the second frequency via a drive pad 15 and a drive GND pad 16 . Thereby, the reflector 2 oscillates around the X-axis at the second frequency. Resonance is not used for oscillation about the X axis.
- the second frequency is lower than the first frequency described above, and is set to 60 Hz, for example.
- a laser beam incident on the reflecting section 2 from a light source (not shown) is reflected in directions corresponding to the swing angles (deflection angles) of the reflecting section 2 around the X-axis and the Y-axis.
- the direction of reflection changes from moment to moment according to the change in the deflection angle of the reflector 2 .
- the laser light reflected by the reflector 2 is scanned around the Y-axis at the first frequency and around the X-axis at the second frequency.
- a deflection angle detection unit (detection unit) 20 is for detecting the deflection angle of the reflection unit 2 by detecting the movement associated with the non-resonant vibration of the outer piezoelectric actuator 6 as a change in capacitance.
- 20a and a movable electrode 20b are configured integrally with the outer frame portion 7 .
- the fixed electrode 20a has a comb-teeth electrode 20c as shown in FIG. 2(A).
- the movable electrode 20b has a comb-teeth electrode 20d as shown in FIG.
- the comb-teeth electrode 20c and the comb-teeth electrode 20d are arranged such that their electrode branches are alternately arranged one by one along the X-axis direction.
- the position of the comb-teeth electrode 20c of the fixed electrode 20a does not change regardless of the movement of the outer piezoelectric actuator 6, and the position of the comb-teeth electrode 20d of the movable electrode 20b changes with the movement of the outer piezoelectric actuator 6.
- a capacitive component electrostatic capacitance
- the dummy comb-tooth structure portion 21 is a portion provided in a pair with the deflection angle detection portion 20, and includes a fixed electrode 21a and a movable electrode 21b.
- the fixed electrode 21 a is configured integrally with the outer frame portion 7 .
- the movable electrode 21b has a comb-teeth electrode 21d as shown in an enlarged view in FIG. 2(B).
- no comb-teeth electrode is provided on the fixed electrode 21a. Therefore, no capacitive component is formed in the dummy comb-teeth structure portion 21 .
- the dummy comb structure 21 is provided to balance the weight between the left and right outer piezoelectric actuators 6 .
- the dummy comb structure 21 and the deflection angle detector 20 are electrically connected to each other by a Si layer 53 (see FIG. 5, which will be described later), which is an active layer, through a groove 17 provided between the respective fixed electrodes 20a and 21a. physically and physically separate.
- the trenches 17 extend to the SiO 2 layer 52 and are electrically and physically separated.
- the detection pad 22 is connected to the fixed electrode 20a and arranged at the lower right end in the drawing.
- the detection GND pad 24 is arranged above the detection pad 22 in the figure.
- the detection pad 22 has a comb-teeth electrode 22a.
- Island-like dummy electrode branches 24a are provided between the electrode branches of the comb-teeth electrode 22a.
- the dummy electrode branches 24a are not connected to the detection GND pads 24 and the like, and are separated like islands.
- a comb-teeth structure 26 is formed by the comb-teeth electrode 22a and each dummy electrode branch 24a.
- the comb-tooth structure 26 is a part for balancing with the dummy detection part 27 and equalizing the etching area.
- the GND pad 24 for detection, the comb-teeth electrode 22a, and the dummy electrode branch 24a are electrically and physically separated from each other by the Si layer 53 by the groove 17.
- the dummy detection pad 23 is connected to the fixed electrode 21a and arranged at the lower left end in the drawing.
- the detection GND pad 25 is arranged above the dummy detection pad 23 in the figure.
- the dummy detection pad 23 is connected with a comb-teeth electrode (first electrode) 23a
- the detection GND pad 25 is connected with a comb-teeth electrode (second electrode).
- 25a are connected, and a dummy detection section (dummy capacitance section) 27 is configured by these comb-teeth electrodes 23a and 25a.
- the comb-teeth electrodes 23 a and 25 a are electrically and physically separated from each other by the Si layer 53 by the grooves 17 .
- the magnitude of the capacitance component (dummy capacitance) formed by the dummy detection section 27 is substantially equivalent to the capacitance component formed by the comb electrodes 20c and 20d of the deflection angle detection section 20 in the initial state. is designed to Note that the initial state refers to a state in which the outer piezoelectric actuator 6 does not change.
- the dummy detection portion 27 is formed on the outer frame portion 7 so that the capacitance component does not change depending on the deflection angle.
- the read signal input pad 28 is arranged above the detection GND pad 25 on the left end side in the figure.
- the read signal input pad 29 is arranged on the right side of the drawing above the detection GND pad 24 .
- These reading signal input pads 28 and 29 are used to input signals (reading signals) used for reading deflection angles.
- FIG. 4 shows an enlarged plan view of the vicinity of the read signal input pad 28. As shown in FIG. Although an enlarged view is omitted, the signal input pad 29 has the same structure.
- FIG. 5 is a schematic cross-sectional view corresponding to the aa line direction shown in FIG.
- the optical scanning device 1 of the present embodiment has a SiO 2 (silicon dioxide) layer as an etching stop layer on one surface side (upper side in the figure) of a Si (silicon) layer 51 as a support layer for holding the reflecting section 2 and the like. 52 is provided, and a Si layer 53 is provided thereon as an active layer for element formation.
- SiO 2 silicon dioxide
- the optical scanning device 1 includes, in order from the bottom in the drawing, a SiO2 layer 50 as an insulating layer, a Si layer 51 as a supporting layer that holds the element, and an SiO2 layer as an etching stop layer.
- (BOX layer) 52 Si layer 53 as an active layer for forming an element
- SiO 2 layer 54 as an insulating layer from the piezoelectric drive section on the upper layer side
- Pt (platinum) layer 55 as a lower electrode layer
- piezoelectric It includes a PZT (lead zirconate titanate) layer 56 as a body layer and a Pt layer 57 as an upper electrode layer.
- PZT lead zirconate titanate
- the reflecting portion 2 is formed by forming a reinforcing rib layer 60 formed by partially etching the Si layer 51 as a base, a SiO 2 layer 52 , a Si layer 53 , an SiO 2 layer 54 and a Pt layer 55 . It is constructed by stacking.
- the left and right inner piezoelectric actuators 4 as resonance drive units are formed by laminating a Si layer 53, a SiO2 layer 54, a Pt layer 55, a PZT layer 56, and a Pt layer 57.
- each of the piezoelectric cantilevers 13 of the left and right outer piezoelectric actuators 6 as non-resonant drive portions is formed by laminating a Si layer 53, a SiO2 layer 54, a Pt layer 55, a PZT layer 56, and a Pt layer 57. .
- the fixed electrode 20a and its comb-teeth electrode 20c, and the movable electrode 20b and its comb-teeth electrode 20d, which constitute the deflection angle detection section 20, are each composed of the Si layer 53.
- the Si layer 51 as a support layer can be used as the base of the device.
- the comb-teeth electrode 20d of the movable electrode 20b is connected to the detection GND pad 24 by the Si layer 53 surrounded by grooves.
- the comb-teeth electrode 20 c of the fixed electrode 20 a is integrated with the outer frame portion 7 .
- the comb-teeth electrode 21 d that constitutes the dummy comb-teeth structure portion 21 is composed of the Si layer 53 .
- the left and right detection GND pads 24 , 25 are provided on the Si layer 53 laminated on the SiO 2 layer 50 , the Si layer 51 , and the SiO 2 layer 52 . Further, the left and right signal reading signal input pads 28 and 29 are exposed to the same side as the reflecting surface of the reflecting section 2 by etching up to the SiO 2 layer 52 on the Si layer 51 as a support layer. It is configured to allow Thereby, it is possible to electrically connect to the Si layer 51 from the upper surface side of the optical scanning device 1 (the side on which the laser beam is incident).
- FIG. 6 is a diagram for explaining the sites where parasitic capacitance is generated.
- FIG. 6 shows a plan view of the optical scanning device 1 as viewed from the rear side, and four portions 71, 72, 73, and 74 where parasitic capacitance is generated are shown in dark gray. Since the optical scanning device 1 of this embodiment uses an SOI (Silicon on Insulator) structure as shown in FIG. , a parasitic capacitance is formed because the SiO 2 layer 52 is sandwiched between the layers.
- the portions 71 and 72 correspond to areas where the driving pad 15 and the driving GND pad 16 are formed, respectively.
- the parts 73 and 74 respectively correspond to areas where the fixed electrodes 20a and 21a are formed.
- the portions 73 and 74 are separated by the groove 17 described above.
- FIG. 7 is a plan view for explaining capacitive components formed in each part of the optical scanning device.
- FIG. 7 is a reduced plan view of FIG. 1 to show the locations where capacitive components are formed.
- the capacitive component corresponding to the formation regions of the driving pad 15 and the driving GND pad 16 on the upper left side in the drawing is assumed to be Cr-L .
- the capacitive component corresponding to the formation regions of the drive pad 15 and the drive GND pad 16 on the upper right side in the drawing is assumed to be Cr-R .
- the capacitive components (first parasitic capacitance and second parasitic capacitance) corresponding to the forming regions of the fixed electrodes 20a and 21a are assumed to be C s ⁇ L and C s ⁇ R , respectively.
- Cv be a capacitive component formed in the deflection angle detection unit 20 (capacitance of the detection unit).
- Cd be a capacitance component (dummy capacitance) formed in the dummy detection unit 27 .
- FIG. 8A is a cross-sectional view showing a connection relationship of portions forming capacitive components in the optical scanning device.
- the portion related to the capacitive component is deformed for easy understanding.
- the capacitive component CsL is formed on the signal path leading from the Si layer 51, which is the support layer, to the dummy detection pad 23.
- the capacitive component CsR is formed on the signal path leading from the Si layer 51 as the support layer to the detection pad 22 .
- the capacitive component C r ⁇ L and the capacitive component C r ⁇ R are respectively formed on the signal paths leading from the Si layer 51 as the supporting layer to the GND pad 24 for detection.
- a capacitive component (dummy capacitance) Cd is formed in the dummy detection section 27 and connected to the detection GND pad 24 (that is, GND potential).
- a capacitive component (detection capacitance) Cv is formed in the deflection angle detection section 20 and connected to a detection GND pad 24 (that is, GND potential).
- FIG. 8B is an equivalent circuit diagram showing the connection relationship of each capacitive component. As shown, the capacitive component CsL and the capacitive component Cd are connected in series, the capacitive component CsR and the capacitive component Cv are connected in series, and these are connected in parallel. Capacitance components C r ⁇ R and C r ⁇ L are connected in parallel to these signal paths (first signal path, second signal path).
- the circuit connection lines indicated by solid lines represent connections through the Si layer 53 which is the active layer, and the circuit connection lines shown by dotted lines represent connections through the Si layer 51 which is the support layer. .
- a read signal input from the read signal input pad 28 is input in parallel to each of the capacitance components C s ⁇ L , C s ⁇ R , C r ⁇ R , and C r ⁇ L through the Si layer 51 of the support layer. be.
- the read signal passing through the capacitive components C r ⁇ R and C r ⁇ L reaches the GND potential as it is, but the read signal passing through the capacitive components C s ⁇ L and C s ⁇ R changes the capacitive components C d and C v . It reaches the GND potential through the
- a voltage signal Vout1 obtained by dividing the voltage by the capacitance component Cs -L and the capacitance component Cd is obtained from the dummy detection pad 23.
- FIG. A voltage signal V out2 obtained by dividing the voltage by the capacitive component C s ⁇ R and the capacitive component C v is obtained from the detection pad 22 . Therefore, by taking the difference between these voltage signals V out1 and V out2 , it is possible to obtain a signal in which the common in-phase noise components are canceled. This improves the detection accuracy of the deflection angle. Moreover, since it is not necessary to add a new layer as a support layer (base), an increase in cost can be suppressed.
- FIG. 9A is a waveform diagram showing an example of the read signal
- FIG. 9B is a waveform diagram showing an example of the voltage signal Vout1
- FIG. 9C is a waveform diagram showing an example of the voltage signal Vout2
- FIG. 9D is a waveform diagram showing an example
- FIG. 9D is an enlarged waveform diagram showing an example of a differential signal between voltage signals V out1 and V out2 ;
- V in (t) be the read signal that is the input voltage at time t
- N(t) be the noise
- v(t) be the differential signal between the voltage signals V out1 (t) and V out2 (t).
- Vout1 (t) Vin (t)+N(t)
- Vout2 (t) Vin (t)+v(t)+N(t)
- Vout2(t)-Vout1 ( t) v(t)
- the capacitive component Cv and the capacitive component Cd are substantially equal, and the equivalent circuit is made symmetrical. out2 are equal.
- the deflection angle detector 20 operates and the capacitive component Cv decreases, that is, when the impedance increases, the voltage signal Vout2 increases relative to the voltage signal Vout1 according to the voltage division rule.
- the opposite phenomenon occurs when the capacitive component Cv increases. Therefore, by obtaining the difference between the voltage signal V out1 and the voltage signal V out2 , the common noise component is cancelled, and the change in voltage can be detected by the deflection angle detector 20 . Specifically, as shown in FIG.
- the capacitive component Cv changes according to the frequency of the outer piezoelectric actuator 6, which is a non-resonant driving section, so the impedance also changes periodically.
- the voltage signal V out2 also changes periodically. Since there are two points at which the capacitance is maximized per period, the variation period 90 of the difference signal is twice the drive frequency. Also, the change 91 of the difference signal corresponds to the change of the deflection angle.
- 10(A) to 10(G) and 11(A) to 11(F) are process diagrams showing an example of a method of manufacturing an optical scanning device.
- An example of a method for manufacturing the optical scanning device 1 will be briefly described below with reference to the drawings.
- a substrate on which a SiO2 layer 50, a Si layer 51, a SiO2 layer 52, a Si layer 53, and a SiO2 layer 54 are laminated is prepared ( FIG . 10(A)).
- a Pt layer 55 is formed on the side not in contact with 53 (FIG. 10(B)).
- a PZT layer 56 is formed on one side of the Pt layer 55 (the side not in contact with the SiO 2 layer 54) (FIG. 10C), and further one side of the PZT layer 56 (the side not in contact with the Pt layer 55).
- a Pt layer 57 is formed on the surface (FIG. 10(D)). Any known method may be used as the film forming method.
- the Pt layer 57 and the PZT layer 56 are patterned into a predetermined shape (Fig. 10(E)).
- Any known method may be used for the patterning here.
- this embodiment uses a method of forming a mask pattern using a resist film (photosensitive film), performing etching, and then peeling off the resist film (the same applies to patterning in subsequent steps).
- the Pt layer 55 is patterned into a predetermined shape (FIG. 10(F)), and then the SiO 2 layer 54 is patterned into a predetermined shape (FIG. 10(G)). Furthermore, the Si layer 53 is patterned into a predetermined shape (FIG. 11(A)), and then the SiO 2 layer 52 is patterned into a predetermined shape (FIG. 11(B)).
- the SiO 2 layer 50 on the back side is patterned into a predetermined shape (FIG. 11(C)), the Si layer 51 is patterned into a predetermined shape (FIG. 11(D)), and the rib portion 60 is formed (FIG. 11(D)). FIG. 11(E)).
- the SiO 2 layer 52 is patterned into a predetermined shape (FIG. 11(F)).
- the optical scanning device 1 is completed.
- the optical scanning device 1 can be applied to any electronic device that requires laser beam scanning.
- it can be applied to pico projectors used in head-up displays and wearable devices.
- the present invention can also be applied to a device that changes the light distribution pattern according to the presence of an oncoming vehicle, a preceding vehicle, a pedestrian, or various other objects when irradiating light forward of the vehicle.
- it can be applied to an object detection device such as LiDAR (Light Detection And Ranging).
- object detection device such as LiDAR (Light Detection And Ranging).
- MEMS sensors such as acceleration sensors, angular velocity sensors, pressure sensors, and myoelectric sensors.
- FIG. 12 is a plan view from the back side of the optical scanning device according to the second embodiment.
- 13 and 14 are partially enlarged views of the optical scanning device shown in FIG. 12, respectively.
- the overall configuration of the optical scanning device 1a according to the second embodiment is the same as that of the optical scanning device 1 according to the above-described first embodiment, and only the structure of the Si layer 51, which is the supporting layer, is different.
- the structure of the Si layer 51 of the optical scanning device 1a according to the second embodiment, which is different from the optical scanning device 1 of the first embodiment will be omitted, and the structure of the Si layer 51 will be described in detail.
- the Si layer 51 of the optical scanning device 1a is an active layer that constitutes a capacitive component C s ⁇ L and a capacitive component C s ⁇ R , which are capacitive components corresponding to the formation regions of the fixed electrodes 20a and 21a.
- a plurality of through-holes 80 are provided in a region overlapping with a certain Si layer 53 (that is, a portion related to generation of parasitic capacitance).
- the through holes 80 are arranged in rows in the horizontal direction and the vertical direction in the drawing, but the arrangement of the through holes 80 is not limited to this.
- the area where each through-hole 80 is arranged corresponds to the above-described portions 73 and 74 (see FIG. 6).
- a plurality of through-holes 81 are similarly provided in the regions 71 and 72 described above, that is, the regions where the driving pads 15 and the driving GND pads 16 are formed.
- the size of each of the through holes 80 and 81 for example, if each of the through holes 80 and 81 has a substantially square shape as shown in the drawing, one side thereof can be about 50 ⁇ m to 150 ⁇ m.
- 15A and 15B are partial cross-sectional views of the optical scanning device of the second embodiment.
- 15A is a sectional view corresponding to line aa shown in FIG. 13, and
- FIG. 15B is a sectional view corresponding to line bb shown in FIG.
- the through hole 80 is formed by partially removing the Si layer 51 as the support layer to reach the SiO 2 layer (BOX layer) 52 .
- the Si layer 51, which is the support layer is not removed and the SiO 2 layer (BOX layer) 52 is not exposed in the portion where the through hole 80 does not exist.
- each through hole 81 has the same structure.
- These through holes 80 and 81 are formed in the step of etching the Si layer 51 during the manufacturing process of the optical scanning device 1 described in the first embodiment (see FIG. 11E). It is possible to Since the Si layer 51, which is a support layer, also has a role of ensuring the mechanical strength of the optical scanning device 1a, only partial removal by the through holes 80 and 81 can prevent a decrease in mechanical strength. .
- each through- hole 80 By providing each through- hole 80, the overlapping area between the Si layer 51 as the support layer and the Si layer 53 as the active layer can be reduced.
- the value of sR can be reduced.
- the difference between the capacitive component Cv and the capacitive component Cs -R which are the capacitive components to be detected, becomes smaller, so that the amount of change in the voltage by the deflection angle detecting section 20 can be increased.
- the capacitive component Cv which is the capacitive component to be detected
- the electrodes are formed in a direction orthogonal to the support layer.
- the parasitic capacitance generated by the overlapping portion of the Si layer 53 and the Si layer 51, which is the support layer, tends to increase in value because it is formed in a direction parallel to the support layer and the like.
- the capacitance component Cv may be about 1 pF, while the capacitance component Cs -R may be about several tens of pF.
- the resonance drive section in each of the above-described embodiments may be used for non-resonance drive, or the non-resonance drive section may be used for resonance drive.
- the case of using a piezoelectric drive type actuator was exemplified, but an antistatic drive type or electromagnetic drive type actuator may be used.
- the capacitance component of the dummy detection section is formed by comb-teeth electrodes, it may be formed by parallel plate electrodes.
- the through-holes 80 and 81 are illustrated as substantially square in plan view as an example, they are not limited to this, and can be made in various plan view shapes such as circles, triangles, and hexagons. Further, the through holes 80 and 81 may not all have the same shape when viewed from above, and may have different shapes when viewed from above.
- Optical scanning device 2: Reflector (movable mirror), 3: Torsion bar, 4: Inner piezoelectric actuator, 5: Inner frame, 6: Outer piezoelectric actuator, 7: Outer frame (frame), 13: Piezoelectric Cantilever 15: Drive pad 16: Drive GND pad 17: Groove 20: Deflection angle detector 20a: Fixed electrode 20b: Movable electrode 20c, 20d: Comb electrode 21: Dummy comb structure Part 21a: Fixed electrode 21b: Movable electrode 22: Detection pad 22a: Comb electrode 23: Dummy detection pad 23a: Comb electrode 24: GND pad for detection 24a: Dummy electrode branch 25: GND pad for detection, 25a: comb-teeth electrode, 26, 27: comb-teeth structure, 28, 29: read signal input pad, 50: SiO 2 layer, 51: Si layer, 52: SiO 2 layer (BOX layer), 53: Si layer, 54: SiO2 layer, 55: Pt layer, 56: PZT (lea
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Abstract
Description
[2]本開示に係る一態様の電子機器は、前記[1]の光走査装置を備える電子機器である。
図1は、第1実施形態の光走査装置(光偏向器)1の構成を示す平面図である。本実施形態では、走査対象となるレーザ光が入射される側の面を表面とし、これと反対側の面を裏面とする。図1では表面側から見た平面図が示されている。図示のように本実施形態の光走査装置1は、平面視において概ね左右対称な構造を有している。
Vout1(t)=Vin(t)+N(t)
Vout2(t)=Vin(t)+v(t)+N(t)
Vout2(t)-Vout1(t)=v(t)
図12は、第2実施形態に係る光走査装置の裏面側からの平面図である。また、図13、図14は、それぞれ図12に示す光走査装置の部分拡大図である。なお、第2実施形態に係る光走査装置1aの全体構成は上記した第1実施形態に係る光走査装置1と共通であり、支持層であるSi層51の構造のみが異なっている。以下、第2実施形態に係る光走査装置1aについて、第1実施形態の光走査装置1との共通点については説明を省略し、相違点に係るSi層51の構造を詳細に説明する。
なお、本開示は上記した各実施形態の内容に限定されるものではなく、本開示の要旨の範囲内において種々に変形して実施をすることが可能である。例えば、上記した各実施形態における共振駆動部を非共振駆動で利用してもよいし、非共振駆動部を共振駆動で利用してもよい。また、上記した各実施形態では圧電駆動方式のアクチュエータを用いる場合を例示していたが、制電駆動方式や電磁駆動方式のアクチュエータでもよい。また、ダミー検出部の容量成分を櫛歯電極で形成していたが平行平板電極で形成してもよい。また、上記した各実施形態では読み取り信号入力用パッドを2つ設けていたが、1つでもよいし3つ以上設けてもよい。また、読み取り信号を逆側(可動電極側)から印加してもよい。また、各貫通孔80、81の平面視形状については一例として略正方形を図示していたがこれに限定されず、円形、三角形、六角形など種々の平面視形状にすることができる。また、各貫通孔80、81の平面視形状が全て同じでなくてもよく、異なる平面視形状のものが混在していてもよい。
Claims (9)
- 反射面を有するミラーと、
前記ミラーを揺動させる駆動部と、
前記駆動部の動きを静電容量の変化により検出する検出部と、
前記検出部の初期状態の前記静電容量と略等価なダミー静電容量を生じさせるダミー容量部と、
を含み、
前記検出部は、前記駆動部の動きに関わって位置が変動する可動電極と、前記駆動部の動きに関わらない固定電極とを有し、当該可動電極と固定電極との間に前記静電容量を生じるように構成されており、
前記ダミー容量部は、第1電極と第2電極を有し、当該第1電極と第2電極との間に前記ダミー静電容量を生じるように構成されており、
前記可動電極、前記固定電極、前記第1電極及び前記第2電極は、同一の半導体層である活性層に設けられて各々が分離しており、
前記活性層は、絶縁層を挟んで、共通の半導体層である支持層と対向配置されており、
前記固定電極が設けられた前記活性層と前記支持層との間に生じる第1寄生容量と、前記第1電極が設けられた前記活性層と前記支持層との間に生じる第2寄生容量とが略等価であり、
前記検出部の静電容量と前記第1寄生容量とが直列接続されて第1信号経路を構成し、前記ダミー静電容量と前記第2寄生容量と直列接続されて第2信号経路を構成する、
光走査装置。 - 前記第1信号経路と前記第2信号経路とが並列接続されており、
前記活性層は、前記検出部の静電容量と前記第1寄生容量との分圧が得られる検出用パッドと、前記ダミー静電容量と前記第2寄生容量との分圧が得られるダミー検出力パッドとを有する、
請求項1に記載の光走査装置。 - 前記支持層は、前記ミラーの前記反射面と同じ側に露出するように構成された信号入力用パッドを有する、
請求項1又は2に記載の光走査装置。 - 前記固定電極の平面視面積と前記第1電極の平面視面積が略等しい、
請求項1~3の何れか1項に記載の光走査装置。 - 前記可動電極と前記固定電極は、各々が櫛歯電極を有しており、当該櫛歯電極の相互間で前記静電容量が生じる、
請求項1~4の何れか1項に記載の光走査装置。 - 前記第1電極と前記第2電極は、各々が櫛歯電極を有しており、当該櫛歯電極の相互間で前記ダミー静電容量が生じる、
請求項1~5の何れか1項に記載の光走査装置。 - 前記支持層に読み取り信号が入力され、前記検出部の静電容量と前記第1寄生容量との分圧と、前記ダミー静電容量と前記第2寄生容量との分圧との差分に基づいて前記ミラーの偏向角が求められる、
請求項1~6の何れか1項に記載の光走査装置。 - 前記支持層は、前記第1寄生容量及び前記第2寄生容量の各々の発生に関連する部位において、各々が前記絶縁層まで達する複数の貫通孔を有する、
請求項1~7の何れか1項に記載の光走査装置。 - 請求項1~8の何れか1項に記載の光走査装置を備える電子機器。
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JP2004245890A (ja) | 2003-02-10 | 2004-09-02 | Denso Corp | 光走査装置 |
JP2017058418A (ja) * | 2015-09-14 | 2017-03-23 | 富士電機株式会社 | 光走査装置および内視鏡 |
US20220066197A1 (en) * | 2020-09-01 | 2022-03-03 | Beijing Voyager Technology Co., Ltd. | Capacitance sensing in a mems mirror structure |
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JP2004245890A (ja) | 2003-02-10 | 2004-09-02 | Denso Corp | 光走査装置 |
JP2017058418A (ja) * | 2015-09-14 | 2017-03-23 | 富士電機株式会社 | 光走査装置および内視鏡 |
US20220066197A1 (en) * | 2020-09-01 | 2022-03-03 | Beijing Voyager Technology Co., Ltd. | Capacitance sensing in a mems mirror structure |
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