Mem mirror device, method of controlling mem mirror device, and method of manufacturing mem mirror device

Abstract

To provide a MEMS mirror device in which characteristics such as a resonance frequency do not fluctuate while a micromirror is irradiated with light.SOLUTION: The MEMS mirror device includes a substrate, a cavity provided in the substrate, a mirror unit provided in the cavity and held hollow, and a drive unit for driving the mirror unit, the drive unit including a piezoelectric element in which a first electrode layer, a piezoelectric layer, and a second electrode layer are sequentially laminated upward from the surface of the substrate, and the mirror unit is rotated by applying a voltage between the first electrode layer and the second electrode layer to expand or contract the piezoelectric layer, thereby controlling the reflection direction of incident light incident on the mirror unit, wherein the mirror unit is provided with a heater.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a MEMS mirror device, and more particularly to a piezoelectric MEMS mirror device that drives a mirror using a piezoelectric body. [Background technology]

[0002] In a piezoelectric MEMS mirror device, a gimbal or the like connected to a micromirror has a driving section equipped with a piezoelectric body, and the micromirror is driven by utilizing the inverse piezoelectric properties of the piezoelectric body.

[0003] For example, in MEMS mirror devices used in head-up displays and LiDAR, light such as visible light and infrared light is irradiated onto a micromirror, which is driven by applying a voltage to a piezoelectric material and reflected by the micromirror, and is used for sensing and image drawing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-220531

[0005] [overview] When light is irradiated onto a micromirror, the reflectivity of the light from the micromirror is about 90%, and the remaining 10% of the light is mainly converted into heat, heating the micromirror and the surrounding drive units, causing a rise in temperature. As a result, the temperature characteristics of the silicon material that makes up the MEMS mirror device change, causing problems such as changes in resonance frequency, distortion, and phase shift, which vary depending on the temperature.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a MEMS mirror device in which characteristics such as resonant frequency do not fluctuate while the micromirror is irradiated with light.

[0007] One aspect of the present disclosure is A MEMS mirror device, A substrate; a cavity provided in the substrate; a mirror portion provided in the cavity portion and held in midair; a driving unit for driving the mirror unit, the driving unit including a piezoelectric element in which a first electrode layer, a piezoelectric layer, and a second electrode layer are laminated in this order from the surface of the substrate upward; Including, A MEMS mirror device that applies a voltage between a first electrode layer and a second electrode layer to expand and contract a piezoelectric layer, thereby rotating a mirror portion and controlling the reflection direction of incident light that is incident on the mirror portion, The mirror part is a MEMS mirror device equipped with a heater.

[0008] Another aspect of the present invention is A method for controlling the above-mentioned MEMS mirror device, a step of heating the mirror portion to a constant temperature T1 using a heater; a step of supplying incident light to the mirror portion after the temperature of the mirror portion reaches a constant temperature T1; a step of driving the mirror unit with a driving unit; The present invention relates to a method for controlling a MEMS mirror device.

[0009] Another aspect of the present invention is A method for manufacturing a MEMS mirror device in which a mirror section and a drive section are held in air on a substrate, comprising the steps of: providing a substrate having a front surface and a back surface; forming an insulating layer on a surface of a substrate; forming a driving section including a piezoelectric element by stacking a first electrode layer, a piezoelectric layer, and a second electrode layer on an insulating layer; a temperature sensor forming process in which an AlCu film is formed on a substrate and then etched to leave the AlCu film on the driving portion to form a temperature sensor; a microheater formation process in which a Pt film is formed on the surface of the substrate and then etched to leave the Pt film on the mirror portion to form a microheater; forming a reflective film to cover the microheater of the mirror portion; and etching the substrate from the backside to form a cavity, and holding the mirror part and the drive part in the air. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view of a MEMS mirror device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the MEMS mirror device of FIG. 1 as viewed in the II-II direction. [Figure 3] FIG. 3 shows an example of the shape of the microheater. [Figure 4A] FIG. 4A is a cross-sectional view of a manufacturing process of the MEMS mirror device according to the first embodiment of the present invention. [Figure 4B] FIG. 4B is a cross-sectional view of a manufacturing process of the MEMS mirror device according to the first embodiment of the present invention. [Figure 4C] FIG. 4C is a cross-sectional view of a manufacturing process of the MEMS mirror device according to the first embodiment of the present invention. [Figure 4D] FIG. 4D is a cross-sectional view of a manufacturing process of the MEMS mirror device according to the first embodiment of the present invention. [Figure 4E] FIG. 4E is a cross-sectional view of a manufacturing process of the MEMS mirror device according to the first embodiment of the present invention. [Figure 4F] FIG. 4F is a cross-sectional view of a manufacturing process of the MEMS mirror device according to the first embodiment of the present invention. [Figure 4G] FIG. 4G is a cross-sectional view of a manufacturing process of the MEMS mirror device according to the first embodiment of the present invention. [Figure 4H] FIG. 4H is a cross-sectional view of a manufacturing process of the MEMS mirror device according to the first embodiment of the present invention. [Figure 4I] FIG. 4I is a cross-sectional view of a manufacturing process of the MEMS mirror device according to the first embodiment of the present invention. [Figure 5] FIG. 5 is a plan view of a MEMS mirror device according to the second embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view of the MEMS mirror device of FIG. 5 as viewed in the direction VI-VI. [Figure 7] 7A to 7C are cross-sectional views of a manufacturing process of the MEMS mirror device according to the second embodiment of the present invention. [Figure 8] FIG. 8 is a cross-sectional view of a MEMS mirror device according to the third embodiment of the present invention. [Figure 9] 9A to 9C are cross-sectional views of a manufacturing process for a MEMS mirror device according to the third embodiment of the present invention. [Figure 10] FIG. 10 is a plan view of a MEMS mirror device according to the fourth embodiment of the present invention. [Figure 11] FIG. 11 is a plan view of a MEMS mirror device according to the fifth embodiment of the present invention.

[0011] [Detailed explanation] <First Embodiment> 1. Structure Fig. 1 is a plan view of a MEMS mirror device according to a first embodiment of the present invention, generally designated 100, and Fig. 2 is a cross-sectional view of the MEMS mirror device 100 of Fig. 1 as viewed in the II-II direction. The MEMS mirror device 100 of Fig. 1 is a single-axis MEMS mirror device for horizontal scanning in which a mirror section 50 rotates around a beam (axis in the Y-axis direction) 30, and reflected light is scanned in the X-axis direction.

[0012] The MEMS mirror device 100 includes a substrate 10, such as an SOI substrate. A cavity 60 is provided in the substrate 10, and an annular support portion 20 is provided above the cavity 60. Two beams (torsion bars) 30 extending in a first direction (Y-axis direction) are provided inside the support portion 20, and a mirror portion 50 is connected between them.

[0013] A reflective film 51 made of, for example, Al / Cu is provided on the upper surface of the mirror section 50. A pair of drive sections 40 are provided on both sides of the mirror section 50, facing each other with the mirror section 50 in between. Both ends of each drive section 40 are connected to beams 30 on both sides of the mirror section 50. The support section 20, beams 30, mirror section 50, and drive section 40 are each formed from a part of the substrate 10, and have a hollow structure arranged above a cavity section 60.

[0014] The driving unit 40 includes a piezoelectric element 35 in which a first electrode layer 31, a piezoelectric layer 32, and a second electrode layer 33 are stacked in this order from the surface of the substrate 10 upward. The first electrode layer 31 is made of, for example, Pt / TiO2, the piezoelectric layer 32 is made of, for example, PZT (lead zirconate titanate), and the second electrode layer 33 is made of, for example, IrO / IrO2.

[0015] By applying a voltage between the first electrode layer 31 and the second electrode layer 33 of the piezoelectric element 35 and creating a potential difference on both sides of the piezoelectric layer 32, the piezoelectric layer 32 deforms due to its inverse piezoelectric properties. By alternately deforming the piezoelectric layers 32 of the drive units 40 arranged on both sides of the mirror unit 50, the mirror unit 50 can be rotated in the X-axis direction around the beam 30 in the Y-axis direction as a central axis.

[0016] The mirror section 50 includes a microheater 52 provided, for example, along the periphery of the mirror section. The microheater 52 is made of, for example, Pt wiring. FIG. 3 shows an example of the shape of the microheater 52, and it may be Pt wiring provided so as to go back and forth around the periphery of the mirror section as shown in (a), or Pt wiring provided in an accordion shape as shown in (b). The shape of the microheater 52 is not limited to that shown in FIG. 2, and other shapes may be used as long as they can heat the mirror section 50.

[0017] On the other hand, the driving unit 40 has a microheater 42 and a temperature sensor 44 arranged to extend from one end to the other end of the driving unit 40. The microheater 42, like the microheater 52 of the mirror unit 50, is made of, for example, Pt wiring and may have a shape as shown in FIG. 3. The temperature sensor 44 is a resistance temperature detector made of, for example, AlCu wiring and may have the same shape as the microheaters 42, 52 shown in FIG. 3.

[0018] Electrode pads P1 to P10 made of, for example, AlCu are provided on the substrate 10 and are connected to the microheaters 42 and 52 by, for example, a wiring layer made of AlCu.

[0019] The microheater 52 of the mirror section 50 has both ends connected to electrode pads P5 and P10, respectively, and the mirror section 50 can be heated by applying a voltage between the electrode pads P5 and P10.

[0020] The microheater 42 provided on the left drive unit 40 has both ends connected to electrode pads P1 and P4, respectively, and the drive unit 40 can be heated by applying a voltage between the electrode pads P1 and P4.

[0021] In addition, the microheater 42 provided on the right-hand drive unit 40 has both ends connected to electrode pads P6 and P9, respectively, and the drive unit 40 can be heated by applying a voltage between the electrode pads P6 and P9.

[0022] On the other hand, the temperature sensor 44 provided on the right-hand drive unit 40 has both ends connected to electrode pads P7 and P8, respectively, and the temperature of the drive unit 40 can be measured by measuring the voltage change between the electrode pads P7 and P8.

[0023] The temperature sensor 44 in the left driver 40 is a dummy and does not actually function as a temperature sensor. That is, the temperature sensor 44 may be provided in only one of the driver 40 on the right or left side of the mirror unit 50. Even in this case, in order to maintain the left-right symmetry of the driver 40, the temperature sensor 44 itself is formed in both driver 40, and only one temperature sensor 44 is used.

[0024] 2. Control method Next, a method for controlling the MEMS mirror device 100 will be described with reference to Fig. 1. First, before irradiating light onto the mirror portion 50 of the MEMS mirror device 100, voltages are applied between the electrode pads P5 and P10, between the electrode pads P1 and P4, and between the electrode pads P6 and P9 to heat the microheaters 52 and 42. The heated temperature is measured by detecting the voltage between the electrode pads P7 and P8.

[0025] Here, we have described the case where the microheaters 42 of both drive units 40 are used, but it is also possible to use only the microheater 42 of one of the drive units 40, or only the microheater 52 of the mirror unit 50.

[0026] When the temperature T1 detected by the temperature sensor 44 reaches a predetermined temperature, the mirror section 50 is irradiated with light and the mirror section 50 is driven by the driving section 40. The temperature T1 is equal to or higher than the temperature T2 to which the mirror section 50 is heated when irradiated with light alone, or is approximately the same as T2. For example, T1 is approximately 120°C to approximately 150°C, and T2 is approximately 120°C.

[0027] The microheaters 52 and 42 may be turned off after the mirror section 50 is irradiated with light. For example, the microheaters 52 and 42 may be turned off simultaneously with the irradiation of light, or after a certain period of time has elapsed.

[0028] In this way, before irradiating light onto the mirror section 50 of the MEMS mirror device 100, the microheaters 52, 42 are used to heat the vicinity of the mirror section 50 to a constant temperature T1 (T1≧T2) that is equal to or higher than the temperature T2 to which the mirror section 50 is heated when only light is irradiated. This prevents the temperature of the vicinity of the mirror section 50 from changing even when light is irradiated onto the mirror section 50. In other words, the temperature of the vicinity of the mirror section 50 can be kept constant while the MEMS mirror device 100 is operating. This prevents changes in characteristics such as changes in resonant frequency, distortion, and phase shifts that are caused by changes in the temperature near the mirror section 50, enabling stable operation of the MEMS mirror device 100.

[0029] 3. Manufacturing method Next, a method for manufacturing the MEMS mirror device 100 according to the first embodiment of the present invention will be described with reference to Figures 4A to 4I. Figures 4A to 4I are cross-sectional views as seen in the II-II direction in Figure 1. The method for manufacturing the MEMS mirror device 100 includes the following steps 1 to 10.

[0030] Step 1: As shown in FIG. 4A, a substrate 10 is prepared. The substrate 10 is, for example, an SOI substrate consisting of a silicon layer 11, a silicon oxide layer 12, and a silicon layer 13. A silicon oxide insulating layer 15 and an aluminum oxide barrier layer 16 are formed on the substrate 10 by, for example, thermal CVD. Furthermore, a first electrode layer 31 made of Pt / TiO2, a piezoelectric layer 32 made of PZT, and a second electrode layer 33 made of Ir / IrO2 are sequentially formed on the barrier layer 16 by, for example, sputtering. The second electrode layer 33 may be made of Ir / IrO2, Pt / TiO2, Pt / SRO, or the like.

[0031] 4B, a photoresist layer is formed on the second electrode layer 33, the piezoelectric layer 32, the first electrode layer 31, and the barrier layer 16, and then exposed to light to pattern it. The patterned photoresist layer is then used as a mask for etching (patterning / etching step). This forms a piezoelectric element 35 consisting of the second electrode layer 33, the piezoelectric layer 32, and the first electrode layer 31.

[0032] 4C, an aluminum oxide barrier layer 36 and a silicon oxide insulating layer 37 are formed over the entire surface by the ALD method and the CVD method, respectively, and then a patterning / etching process is performed to form contacts. In this process, the silicon oxide insulating layer 15 on the mirror section 50 formation region is also etched, exposing the surface of the substrate 10.

[0033] Step 4: As shown in FIG. 4D, an AlCu / TiO layer is formed by sputtering, and then patterned and etched to form a temperature sensor 44. Furthermore, a silicon nitride layer is formed by plasma CVD, and then patterned and etched to form a passivation film 45. Openings are made in the passivation film 45 at predetermined positions, and a wiring layer made of, for example, AlCu is formed.

[0034] Step 5: As shown in Fig. 4E, after removing the native oxide film on the surface of the substrate 10, a Pt / TiO2 film is formed over the entire surface by sputtering, and then patterned and etched to form microheaters 42, 52 on the mirror section 50 formation region and on the piezoelectric element 35. Next, an insulating film 53 made of silicon oxide is formed by CVD so as to cover the microheaters 42, 52.

[0035] Step 6: As shown in Fig. 4F, after removing the surface oxide film of the substrate 10, an AlCu layer is formed by sputtering on the region where the mirror section 50 is to be formed, and then patterned and etched. As a result, a reflective film 51 is formed so as to cover the microheater 52.

[0036] Step 7: As shown in FIG. 4G, the silicon layer 13 is etched using the reflective film 51 and the insulating film 53 as an etching mask. For example, the RIE method using CF4 gas as an etching gas is used for the etching. In this case, the silicon oxide layer 12 below the silicon layer 13 serves as an etching stopper.

[0037] Step 8: As shown in FIG. 4H, a support substrate 70 such as a silicon wafer is attached to the front surface side (plus side of the Y axis) of the substrate 10 with adhesive 71.

[0038] Step 9: As shown in FIG. 4I, the silicon layer 11 is etched from the back side (the negative side of the Y axis) using the silicon oxide layer 12 as an etching stopper. Next, the silicon oxide layer 12 is etched. As a result, a cavity 60 is formed, and a hollow structure is obtained in which the support section 20, the beam 30, the mirror section 50, and the drive section 40 are held in the air above the cavity 60. Next, the adhesive 71 is dissolved to remove the support substrate 70, and then a dicing tape 72 is attached to the back side and the substrate 10 is diced to obtain individual MEMS mirror devices 100 as shown in FIG. 2.

[0039] Through the above steps, the MEMS mirror device 100 can be fabricated in which the mirror section 50 and both drive sections 40 are equipped with microheaters 42, 52, respectively, and one (right) drive section 40 is equipped with a temperature sensor 44.

[0040] In this manufacturing method, the insulating layer 15 on the mirror portion 50 formation area is also etched in step 3, so the height of the microheater 52 can be lowered, the unevenness around the mirror portion 50 can be reduced, and a flat reflective surface can be obtained.

[0041] <Embodiment 2> Fig. 5 is a plan view of a MEMS mirror device according to a second embodiment of the present invention, generally designated 200, and Fig. 6 is a cross-sectional view of the MEMS mirror device 200 of Fig. 5 as viewed in the direction VI-VI. In Figs. 5 and 6, the same reference numerals as in Figs. 1 and 2 indicate the same or corresponding parts.

[0042] Compared to the above-described MEMS mirror device 100, the MEMS mirror device 200 has a configuration in which the driving section 40 does not have a microheater 42. This simplifies the device structure and manufacturing process.

[0043] In the control method for the MEMS mirror device 200, the microheater 52 in the mirror section 50 heats the vicinity of the mirror section 50, and the temperature is measured by the temperature sensor 44 in the right-side drive section 40. Specifically, when the temperature T1 detected by the temperature sensor 44 reaches a predetermined temperature, the mirror section 50 is irradiated with light, and the drive section 40 is used to drive the mirror section 50.

[0044] The temperature T1 is equal to or higher than the temperature T2 to which the mirror section 50 is heated when irradiated with light, or is substantially the same as T2. After irradiating the mirror section 50 with light, the microheater 42 may be turned off.

[0045] In this way, by using the microheater 52 to heat the area near the mirror portion 50 to a constant temperature T1 before irradiating light onto the mirror portion 50 of the MEMS mirror device 200, changes in characteristics such as changes in resonant frequency, distortion, and phase shift due to changes in temperature near the mirror portion 50 can be prevented, enabling stable operation of the MEMS mirror device 200.

[0046] The manufacturing process of the MEMS mirror device 200 is the same as the manufacturing process of the MEMS mirror device 100 according to the first embodiment, except for the following steps.

[0047] After steps 1 to 4 (FIGS. 4A to 4D) are performed, in step 5, as shown in FIG. 7, the surface oxide film of the substrate 10 is removed, and then a Pt / TiO2 film is formed by sputtering, and patterned / etched to form a microheater 52 only in the region where the mirror section 50 is formed. The microheater 42 is not formed in the drive section 40. Next, an insulating film 53 made of silicon oxide is formed by CVD so as to cover the microheater 52.

[0048] Subsequently, steps 6 to 9 (FIGS. 4F to 4I) are performed to complete the MEMS mirror device 200 as shown in FIG.

[0049] <Third Embodiment> Fig. 8 is a cross-sectional view of a MEMS mirror device according to a third embodiment of the present invention, generally designated 300, as viewed in the same direction as the VI-VI direction in Fig. 5. In Fig. 8, the same reference numerals as those in Figs. 1 and 2 indicate the same or corresponding parts.

[0050] Compared to the above-described MEMS mirror device 200, the MEMS mirror device 300 has a structure in which the silicon oxide insulating layer 15 and aluminum oxide barrier layer 16 remain below the microheater 52 of the mirror section 50. This allows the manufacturing process to be shortened.

[0051] The control method for the MEMS mirror device 300 is the same as that for the MEMS mirror device 200, with the microheater 52 in the mirror section 50 heating the area near the mirror section 50, and the temperature being measured by the temperature sensor 44 in the driver section 40 on the right side. When the temperature T1 detected by the temperature sensor 44 reaches a predetermined temperature, the mirror section 50 is irradiated with light, and the driver section 40 is used to drive the mirror section 50.

[0052] The manufacturing process of the MEMS mirror device 300 is the same as the manufacturing method of the MEMS mirror device 200 according to the second embodiment, except for the following steps.

[0053] After steps 1 and 2 (FIGS. 4A and 4B) are performed, a Pt / TiO2 film is formed by sputtering and then patterned and etched to form a microheater 52 in the mirror section 50 formation region, without performing an etching process on the insulating layer 15 and barrier layer 16 in the mirror section 50 formation region, as shown in FIG. 9. This simplifies the manufacturing process.

[0054] Subsequently, steps 5 to 9 (FIGS. 4E to 4I) are performed to complete the MEMS mirror device 300 as shown in FIG.

[0055] <Fourth Embodiment> Fig. 10 is a plan view of a MEMS mirror device according to a fourth embodiment of the present invention, the entire device being designated by 400. In Fig. 10, the same reference numerals as in Figs. 1 and 2 indicate the same or corresponding parts.

[0056] In the MEMS mirror device 400, similarly to the above-described MEMS mirror device 100, a support section 20 is provided on a cavity section 60 provided in a substrate 10, and two beams (torsion bars) 30 extending in a first direction (Y-axis direction) are provided inside the support section 20. A mirror section 50 is connected between the beams 30, and a pair of drive sections 40 are provided on both sides of the mirror section 50, facing each other with the mirror section 50 in between.

[0057] The MEMS mirror device 400 further includes spring sections 80 on both sides of the support section 20, and the support section 20 is held in the air by the two spring sections 80. The spring section 80 has a shape in which linear drive sections 85 extending in the Y-axis direction are connected in series, and each drive section 85 is provided with a microheater 82 and a temperature sensor 84.

[0058] In the MEMS mirror device 400, the reflected light from the mirror section 50 can be scanned in the X-axis direction by the driver 40, and the reflected light from the mirror section 50 can be scanned in the Y-axis direction by the driver 85, making it possible to scan in two axial directions.

[0059] In this control method for the MEMS mirror device 400, heating is performed by the microheater 52 of the mirror section 50 and the microheaters 42, 82 of the driving sections 40, 85, and the temperature is measured by the temperature sensors 44, 84 of the driving sections 40, 85. Specifically, when the temperature T1 detected by the temperature sensors 44, 84 reaches a predetermined temperature T2 (T1≧T2), the mirror section 50 is irradiated with light, and the mirror section 50 is driven using the driving sections 40, 85. After the mirror section 50 is irradiated with light, the microheaters 52, 42, 82 may be turned off.

[0060] <Fifth Embodiment> Fig. 11 is a plan view of a MEMS mirror device according to a fifth embodiment of the present invention, the whole of which is designated by 500. In Fig. 11, the same reference numerals as in Figs. 1 and 2 indicate the same or corresponding parts.

[0061] In the MEMS mirror device 500, the mirror section 50 is supported in midair above a cavity 60 provided in the substrate 10, with both sides held by spring sections 80 equipped with driver sections 85. The driver sections 85 are a pair of driver sections 85 arranged parallel to each other and connected between the mirror section 50 and the substrate 10. The spring section 80 has a shape in which linear driver sections 85 extending in the Y-axis direction are connected in series, and each driver section 85 is provided with a microheater 82 and a temperature sensor 84. In FIG. 11 , three driver sections 85 are provided on each side of the mirror section 50, and are connected in series to form the spring section 80.

[0062] In the MEMS mirror device 500, by providing the spring portion 80 on which the drive portion 85 is formed, the mirror portion 50 can be driven around the X axis, and the reflected light of the mirror portion 50 can be scanned in the Y axis direction.

[0063] In this control method for the MEMS mirror device 500, heating is performed by the microheater 52 of the mirror section 50 and the microheater 82 of the driving section 85, and the temperature is measured by the temperature sensor 84 of the driving section 85. Specifically, when the temperature T1 detected by the temperature sensor 84 reaches a predetermined temperature T2 (T1≧T2), light is irradiated onto the mirror section 50, and the mirror section 50 is driven using the driving section 85. After the mirror section 50 is irradiated with light, the microheaters 52 and 82 may be turned off.

[0064] In the first to fifth embodiments, the MEMS mirror device is described as having a microheater for heating and a temperature sensor for measuring temperature, but it is also possible to measure the temperature with an external temperature sensor without providing a temperature sensor for measuring temperature. Alternatively, the voltage value to be applied to the microheater to reach temperature T1 (T1≧T2) may be determined in advance, and the voltage may be set to that value.

[0065] Furthermore, the temperature sensor 44 for measuring the temperature may be formed on only one of the pair of drive parts 40, 85. However, in order to maintain the left-right symmetry of the shape, it is preferable to provide a dummy temperature sensor.

[0066] <Additional Notes> The present disclosure provides: A MEMS mirror device, A substrate; a cavity provided in the substrate; a mirror portion provided in the cavity portion and held in midair; a driving unit for driving the mirror unit, the driving unit including a piezoelectric element in which a first electrode layer, a piezoelectric layer, and a second electrode layer are laminated in this order from the surface of the substrate upward; Including, A MEMS mirror device that applies a voltage between a first electrode layer and a second electrode layer to expand and contract a piezoelectric layer, thereby rotating a mirror portion and controlling the reflection direction of incident light that is incident on the mirror portion, The mirror part is a MEMS mirror device equipped with a heater. In this way, by providing a heater in the mirror part of the MEMS device, the temperature of the mirror part can be preheated using the heater before irradiating it with light. This prevents the temperature of the mirror part from changing even when light is irradiated onto it, preventing changes in characteristics such as changes in resonance frequency, distortion, and phase shift due to changes in the temperature of the mirror part, and enabling stable operation of the MEMS mirror device.

[0067] In the present disclosure, the driving unit further includes a temperature sensor. By including the sensor in the driving unit, it is possible to measure the temperature near the mirror unit and know when the temperature near the mirror unit has reached a predetermined temperature.

[0068] In the present disclosure, a heater is also provided in the driving unit, which can preheat the driving unit, into which some light may be incident, to a predetermined temperature.

[0069] In the present disclosure, the mirror section is held in the air by beams extending in one axis direction connected to both sides, and the driving sections are a pair of driving sections arranged on either side of the mirror section, with both ends of each driving section connected to the beams connected to both sides of the mirror section and supported in the air. In such a MEMS device, the mirror section can be rotated around one axis direction (the Y-axis direction in Figure 1) and the reflected light can be scanned in the X-axis direction.

[0070] In the present disclosure, the mirror section has beams extending in one axis direction connected to both sides and held in the air, and the driving sections are a pair of driving sections arranged on either side of the mirror section, with both ends of each driving section connected to the beams connected to both sides of the mirror section and supported in the air, and a driving section arranged parallel to the one axis direction and connected between the beams on both sides of the mirror section and the substrate. In such a MEMS device, the mirror section can be rotated in one axis direction (the Y-axis direction in FIG. 1) and in a direction perpendicular to the one axis direction (the X-axis direction in FIG. 1), and reflected light can be scanned in two axes directions, the X-axis direction and the Y-axis direction.

[0071] In the present disclosure, the mirror section is connected to the substrate on both sides and held in midair, and the driving section is a pair of driving sections arranged parallel to each other and connected between the mirror section and the substrate. In such a MEMS device, the mirror section can be rotated around the direction in which the driving sections are arranged (the X-axis direction in FIG. 10), and the reflected light can be scanned in the Y-axis direction.

[0072] In this disclosure, the heater is a Pt microheater, allowing for the use of materials common in MEMS fabrication processes.

[0073] In this disclosure, the temperature sensor is a resistance temperature detector made of AlCu, which allows the same material as the wiring to be used, simplifying the process.

[0074] The present disclosure provides: A method for controlling the above-mentioned MEMS mirror device, a step of heating the mirror portion to a constant temperature T1 using a heater; a step of supplying incident light to the mirror portion after the temperature of the mirror portion reaches a constant temperature T1; a step of driving the mirror unit with a driving unit; The present invention relates to a method for controlling a MEMS mirror device. In this way, by using a heater to heat the mirror portion to a constant temperature T1 before irradiating it with light, the temperature of the mirror portion does not change even when light is irradiated on it, preventing changes in characteristics such as changes in resonant frequency, distortion, and phase shift due to changes in the temperature of the mirror portion, and enabling stable operation of the MEMS mirror device.

[0075] The present disclosure further includes a step of stopping heating of the mirror portion after supplying the incident light, because the temperature of the mirror portion can be maintained constant by the incident light after supplying the incident light.

[0076] In the present disclosure, the constant temperature T1 is equal to or higher than the temperature T2 at which the mirror section is heated by the supply of incident light. By setting T1≧T2, the temperature of the mirror section does not fluctuate even when incident light is supplied to the mirror section.

[0077] In the present disclosure, the constant temperature T1 is the same as the temperature T2 to which the mirror section is heated by the supply of incident light. In particular, by setting T1=T2, the mirror section can be heated efficiently.

[0078] The present disclosure provides: A method for manufacturing a MEMS mirror device in which a mirror section and a drive section are held in air on a substrate, comprising the steps of: providing a substrate having a front surface and a back surface; forming an insulating layer on a surface of a substrate; forming a driving section including a piezoelectric element by stacking a first electrode layer, a piezoelectric layer, and a second electrode layer on an insulating layer; a temperature sensor forming process in which an AlCu film is formed on a substrate and then etched to leave the AlCu film on the driving portion to form a temperature sensor; a microheater formation process in which a Pt film is formed on the surface of the substrate and then etched to leave the Pt film on the mirror portion to form a microheater; forming a reflective film to cover the microheater of the mirror portion; and etching the substrate from the backside to form a cavity, and holding the mirror part and the drive part in the air. This manufacturing method makes it possible to fabricate the microheater in the mirror section and the temperature sensor in the driving section.

[0079] In the present disclosure, the temperature sensor forming step includes a step of removing the insulating film from the mirror portion to expose the surface of the substrate, and the microheater forming step is a step of forming a Pt film on the surface of the substrate to form the microheater. By using such a step, it is possible to reduce the irregularities around the mirror portion, thereby obtaining a flatter mirror portion.

[0080] In the present disclosure, the microheater formation process is a process of forming a Pt film on an insulating layer on a substrate to form a microheater. By using this process, the process of removing the insulating layer on the substrate can be omitted, thereby simplifying the manufacturing process.

[0081] In the present disclosure, the microheater formation process includes a process of leaving the Pt film on the driving section to form the microheater, and by using this process, the microheater can be formed on both the mirror section and the driving section at the same time. [Industrial Applicability]

[0082] The MEMS mirror device of the present invention can be applied to head-up displays, LiDAR, and the like. [Explanation of symbols]

[0083] 10 Substrate 11 Silicon layer 12 Silicon oxide layer 13 Silicon layer 15 Insulating layer 16 Barrier Layer 20 Support part 30 Beam 31 1st electrode layer 32 Piezoelectric layer 33 Second electrode layer 35 Piezoelectric element 40 Drive unit 42 Microheater 44 Temperature Sensor 48 wiring layer 50 Mirror section 51 Reflective film 52 Microheater 60 Cavity 100 MEMS mirror device

Claims

1. A MEMS mirror device, A substrate; a cavity provided in the substrate; a mirror portion provided in the cavity portion and held in the air; a driving unit for driving the mirror unit, the driving unit including a piezoelectric element in which a first electrode layer, a piezoelectric layer, and a second electrode layer are laminated in this order from the surface of the substrate upward; Including, a MEMS mirror device that applies a voltage between the first electrode layer and the second electrode layer to expand and contract the piezoelectric layer, thereby rotating the mirror portion and controlling a reflection direction of incident light that is incident on the mirror portion, The mirror portion is a MEMS mirror device having a heater.

2. The MEMS mirror device according to claim 1 , wherein the driving section further comprises a temperature sensor.

3. The MEMS mirror device according to claim 1 , further comprising a heater in the driving section.

4. The mirror portion has beams extending in one axial direction connected to both sides and held in a hollow space, 2. The MEMS mirror device according to claim 1, wherein the driving units are arranged on either side of the mirror unit, and each driving unit is a pair of driving units supported in midair with both ends connected to beams connected to either side of the mirror unit.

5. The mirror portion has beams extending in one axial direction connected to both sides and held in a hollow space, The drive unit is a pair of actuators arranged on either side of the mirror unit, each actuator having both ends connected to a beam connected to either side of the mirror unit and supported in midair; and The MEMS mirror device according to claim 1 , wherein the driving units are connected between the beams on both sides of the mirror unit and the substrate, and are arranged parallel to the uniaxial direction.

6. the mirror portion is connected to the substrate at both sides and held in the air; The MEMS mirror device according to claim 1 , wherein the driving section is a pair of driving sections that are connected between the mirror section and the substrate and arranged parallel to each other.

7. The MEMS mirror device according to claim 1 , wherein the heater is a microheater made of Pt.

8. 3. The MEMS mirror device according to claim 2, wherein the temperature sensor is a resistance temperature detector made of AlCu.

9. A method for controlling the MEMS mirror device according to any one of claims 1 to 8, comprising: a step of heating the mirror portion to a constant temperature T1 using the heater; supplying the incident light to the mirror portion after the temperature of the mirror portion reaches a constant temperature T1; driving the mirror unit with the drive unit; A method for controlling a MEMS mirror device, comprising:

10. The control method according to claim 9 , further comprising the step of stopping heating of the mirror portion after supplying the incident light.

11. The control method according to claim 9 , wherein the constant temperature T1 is equal to or higher than a temperature T2 at which the mirror portion is heated by the supply of the incident light.

12. The control method according to claim 9 , wherein the constant temperature T1 is the same as a temperature T2 to which the mirror portion is heated by the supply of the incident light.

13. A method for manufacturing a MEMS mirror device in which a mirror section and a driving section are held in air on a substrate, comprising the steps of: providing a substrate having a front surface and a back surface; forming an insulating layer on a surface of a substrate; forming a driving section including a piezoelectric element by stacking a first electrode layer, a piezoelectric layer, and a second electrode layer on an insulating layer; a temperature sensor forming step of forming an AlCu film on a substrate and then etching the AlCu film to leave the AlCu film on the driving portion to form a temperature sensor; a microheater formation process in which a Pt film is formed on the surface of the substrate and then etched to leave the Pt film on the mirror portion to form a microheater; forming a reflective film to cover the microheater of the mirror portion; and etching the substrate from the rear surface to form a cavity, and holding the mirror section and the drive section in the air.

14. a step of removing the insulating layer from the mirror portion to expose a surface of the substrate after the temperature sensor forming step; The method according to claim 13 , wherein the microheater forming step is a step of forming the Pt film on the surface of the substrate to form the microheater.

15. The method according to claim 13 , wherein the microheater forming step is a step of forming the Pt film on the insulating layer on the substrate to form the microheater.

16. The method according to claim 13 , wherein the microheater forming step includes a step of leaving the Pt film on the driving portion to form a microheater.

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