TWI411064B - Microelectromechanical system - Google Patents

Abstract

Provided is an MEMS device wherein a conductive member is prevented from breaking due to a contact with an external object, while suppressing unnecessary stress applied onto a chip main body (1) of an MEMS chip. First and second pads (13) formed on fixed sections on the upper surface of the chip main body are electrically connected, respectively, to first and second power feed bodies (502) formed on the base, by means of conductive members (6). A pair of through holes (202), which expose each of the first and second pads on the upper surface of the chip main body, are formed in a first cover (2) bonded on the upper surface of the chip main body. The conductive members extend from the first and second power feed bodies to the first and second pads through the through holes. The first cover is provided with grooves (203), each of which extends from each of the through holes to the side surface of the first cover and is opened on the side surface and the upper surface of the first cover so as to house each of the conductive members extending from each of the through holes to each of the first and the second power feed bodies.

Description

MEMS device

The present invention relates to a micro electromechanical systems (MEMS) device.

In the past, as a MEMS device formed by a micro machining technique or the like, for example, an optical scanner (hereinafter, referred to as a MEMS optical scanner), an acceleration sensor, and a gyro sensor are known. Wait.

Such a MEMS device is usually packaged once on a package substrate, and is packaged twice on a wiring board such as a printed circuit board (see, for example, Japanese Laid-Open Patent Publication No. 2005-257944).

As a MEMS device, a MEMS optical scanner having a MEMS wafer and a substrate 5' on which a MEMS wafer is packaged is provided as shown in FIG. 11C. The MEMS wafer includes a substrate 1' on which a mirror has been formed, and a first cover 2' composed of a transparent substrate and bonded to the upper surface (top surface) of the substrate 1'. The substrate 1 'by the Department of SOI (Silicon on Insulator upper, silicon-on-insulator) substrate 100' is formed, the SOI substrate 100 'of the first silicon substrate by lines 101a' and the second insulating layer (SiO ₂ layer) 101c ', The two substrates 101b' are stacked in this order. A mirror surface 21' is provided on the upper surface of the substrate 1'. In the MEMS device, the first cover 2' is bonded to the upper surface of the crucible 1' for the purpose of vacuum sealing or contamination prevention. By joining the second cover to the lower surface (bottom surface) of the crucible 1', the airtight space surrounded by the first cover 2', the second cover, and the frame 10' of the substrate 1' can be made vacuum.

As shown in FIGS. 11A and 11B, the substrate 1' includes a rectangular frame-shaped frame 10', a rectangular plate-shaped movable portion 20', and one of the torsionally deformable hinges 30' and 30'. The movable portion 20' is disposed inside the frame 10' and is provided with a mirror surface 21'. The hinge 30 is disposed inside the frame 10' so as to sandwich the movable portion 20', and connects the frame 10' and the movable portion 20'. The substrate 1' is provided with an electrostatic driving type driving means. This driving means is composed of two movable electrodes 22' and two fixed electrodes 12' opposed to the movable electrode 22', and the movable portion 20' is driven by an electrostatic force. The movable electrodes 22' and 22' are formed on both sides of the movable portion 20' in a direction orthogonal to the direction in which the pair of hinges 30', 30' are coupled. The fixed electrode 12' is formed to face the movable electrode 22' with respect to the frame 10'. The movable electrode 22' and the fixed electrode 12' are electrically connected to the pad 13', respectively.

In the MEMS device of FIG. 11B, the pad 13' formed on the upper surface of the substrate 1' and the lead terminal 506' provided on the package substrate 5' are electrically connected via the bonding wire 6'. In the MEMS device of FIG. 11C, the through electrode 206' embedded in the through hole 202' formed in the first cover 2' and the lead terminal in the thickness direction are inserted into the base 5' via the bonding wire 6'. Electrical connection.

In the MEMS optical scanner of FIG. 11C, a concave portion 510' for securing a displacement space of the movable portion 20' is formed on a surface of the base 5' opposite to the substrate 1'. In the MEMS optical scanner, since the airtight space surrounded by the first cover 2', the frame 10', and the base 5' is vacuumed, the device characteristics can be improved (deflection angle can be increased) ).

In the MEMS device of FIG. 11C, as described above, the through electrode 206' embedded in the through hole 202' formed in the first cover 2' and the lead terminal in the thickness direction are inserted into the substrate 5' via the bonding. Line 6' is electrically connected. In the MEMS device, since the bonding wire 6' protrudes more than the surface of the first cover 2', the bonding wire 6' is in contact with an external object during processing, and the bonding wire is broken. Further, in the method of covering the bonding wire 6' with a resin to protect it, a large amount of resin is required. Due to the large amount of resin, the stress applied to the substrate 1' is increased to cause a change in substrate characteristics. Further, in the production of a large amount of resin, the resin may flow to the upper portion of the light incident on the first cover 2' or the upper portion of the exit portion, and unevenness may be formed in the first cover 2'. The optical properties have changed.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a MEMS device capable of suppressing unnecessary stress applied to a device body and preventing breakage of a bonding wire due to contact with an external object.

The present invention is a MEMS device including a MEMS wafer and a substrate for accommodating the MEMS wafer, and has the following configuration. The MEMS wafer includes a wafer body formed of a semiconductor substrate and a first cover bonded to an upper surface of the wafer body. A first power supply body and at least one second power supply body that are connected to an external voltage source are formed on the substrate. The wafer main body includes a fixing portion, a movable portion that is movably supported by the fixing portion, a first electrode that is electrically connected to the fixing portion, and at least one second electrode that is electrically connected to the movable portion. The movable portion is displaced relative to the fixed portion by the driving force applied to the voltage between the first electrode and the second electrode. A first pad electrically connected to the first electrode and the second electrode, and at least one second pad are formed on the fixing portion of the upper surface of the wafer body. The first pad and the second pad are electrically connected to the first power supply body and the second power supply body, respectively, by a conductive member. The first cover is formed with a pair of through holes formed by exposing each of the first pads and the second pads on the upper surface of the wafer main body. The conductive member extends from the first power supply body and the second power supply body to the first pad and the second pad via the respective through holes. The first cover is provided with a groove that extends from each of the through holes to the side surface of the first cover in order to accommodate the conductive members that extend from the respective through holes to the first power supply body and the second power supply body, and is first The side of the cover is open to the upper surface.

According to this configuration, the bonding wire can be prevented from protruding more than the surface of the first cover, so that unnecessary stress can be suppressed from being applied to the wafer main body, and the conductive member can be prevented from being damaged due to contact with the external object.

Further, it is preferable that the first cover is formed of an insulating substrate, and the conductive member is formed of tantalum.

Further, it is preferable that the conductive member is a bonding wire.

Further, it is preferred that the external voltage source be formed on a different surface of the substrate. According to this configuration, it is possible to prevent interference of an electrical signal input and output via an external voltage source.

Furthermore, it is preferable to have the following structures. The movable portion is a movable plate having a mirror on the upper surface, and the fixed portion is a frame surrounding the shape of the mirror. The movable plate is pivotally supported on the frame via a hinge.

Furthermore, it is preferable to have the following structures. The peripheral portion of the upper surface of the upper surface of the wafer body is hermetically bonded to the peripheral edge portion of the first cover, and the second cover is hermetically bonded to the peripheral portion of the lower surface of the wafer main body, thereby providing the first cover and the second cover. There is an airtight space between them. A movable portion is housed in the airtight space. Further, each of the through holes is sealed by a sealing resin.

Further, it is preferable that each of the grooves is filled with the sealing resin. Thereby, a small amount of resin can be used to protect the bonding wires. Further, according to this configuration, the through hole has the function of the resin storage portion, and the resin can be prevented from expanding on the surface of the first cover.

Furthermore, it is preferable to have the following structures. The first pad and the second pad are films formed on the upper surface of the wafer body, and the opening area of each of the through holes is larger than the area of the corresponding first pad and the second pad, and is in the lower end opening of each through hole. The first pad and the second pad are completely housed. According to this configuration, the first cover and the pads do not overlap each other, and the first cover and the wafer main body can be joined. Therefore, it is possible to prevent the joint property and the airtightness from being impaired due to the thickness of each of the pads. According to this configuration, it is possible to reduce the size of the wafer body and to suppress a decrease in operational stability and a decrease in stability over time.

Further, it is preferable that a deaerator is provided in one of the first cover and the second cover, and the deaerator is exposed to an airtight space for capturing impurities generated in the airtight space. According to this configuration, the high degree of vacuum in the airtight space can be maintained, and thus the change in the characteristics of the device due to the change in the degree of vacuum can be prevented.

Furthermore, it is preferable to have the following structures. A recess for accommodating the MEMS wafer is formed on the substrate. The power supply body is exposed on an upper surface of a peripheral portion surrounding the base of the recess. The height position of the power supply body is lower than the upper end of each through hole. According to this configuration, the height difference between the pad in the thickness direction of the wafer main body and the first power supply body can be reduced. Further, the bonding wires can be bonded to the pads without protruding from the grooves. Therefore, it is possible to further prevent the bonding wire from being damaged due to contact with an external object. Further, it is possible to further prevent unnecessary stress from being applied to the wafer body.

Further, it is preferable that the mirror provided on the upper surface of the movable plate of the wafer main body is a convex surface or a concave surface. According to this configuration, it is possible to generate an optical effect without newly providing an optical component such as a lens. Thereby, the configuration of the optical system in which the wafer body is mounted is simplified, and the cost can be reduced.

Further, it is preferable that the movable plate has a structure in which a mirror layer is laminated on the substrate layer via the intermediate layer, the intermediate layer is vapor-deposited on the substrate layer, and the mirror layer is vapor-deposited on the intermediate layer.

Further, it is preferable that the intermediate layer is formed of a material having a thermal expansion coefficient different from that of the substrate layer and the mirror layer. Thereby, the shrinkage ratio of the inner surface side and the outer surface side of the movable plate after the vapor deposition intermediate layer and the mirror layer are cooled can be made different. Therefore, the thickness of the intermediate layer can be appropriately set in accordance with the thermal expansion coefficient of the material constituting the substrate layer, the intermediate layer, and the mirror layer. By appropriately setting the thickness of the intermediate layer, the shape of the cooled movable plate can be deformed into a convex shape or a concave shape, whereby the desired wafer body can be easily obtained.

Further, it is preferred that the intermediate layer and the mirror layer are formed of a material which can be vapor-deposited at different temperatures. Thereby, the shrinkage ratio of the inner surface side and the outer surface side of the movable plate after the vapor deposition intermediate layer and the mirror layer are cooled can be made different. Therefore, by appropriately setting the vapor deposition temperature of the intermediate layer and the mirror layer, the shape of the cooled movable plate can be deformed into a convex shape or a concave shape, whereby the desired wafer body can be easily obtained.

Further, it is preferable that the intermediate layer is mainly formed of cerium oxide, and the mirror layer is mainly formed of aluminum. According to this configuration, the characteristics of the mirror surface formed on the movable plate can be made to correspond to a wide-wavelength laser beam.

Further, it is preferred that the intermediate layer is mainly formed of chromium or titanium, and the mirror layer is mainly formed of gold. According to this configuration, the characteristics of the mirror surface formed on the movable plate can be made to correspond to the laser beam of a specific wavelength.

(Embodiment 1)

In the present embodiment, as an example of a MEMS (Micro Electro Mechanical Systems) device, a MEMS optical scanner is used in series.

Hereinafter, the MEMS scanner of the present embodiment will be described with reference to Figs. 1 to 3 . In addition, the z-axis direction shown in FIG. 1 is set to the up-down direction (the direction of the arrow of the arrow symbol is set to the upward direction).

The MEMS scanner of the present embodiment includes a MEMS wafer 600 and a substrate 5 on which the MEMS wafer 600 is packaged. Power supply bodies 502a and 502b are formed on the substrate 5 with a voltage source to be connected to the outside.

The MEMS wafer 600 is formed using an SOI substrate 100 as a semiconductor substrate. The MEMS wafer 600 is composed of a wafer body (micromirror device) 1, a first cover 2, and a second cover 3. The wafer main body 1 has a frame (fixed portion) 10 having a rectangular frame shape, a movable portion, a pair of hinges 30, a first electrode 12, and a second electrode 22. The movable portion of this embodiment is constituted by a movable plate 20 of a rectangular shape. The hinge 30 is configured to be torsionally deformable and is disposed on the frame 10 to join the frame 10 and the movable plate 20. The hinge 30 supports the movable panel 20 in such a manner that the movable panel 20 can rotate freely within a certain fixed angle range with respect to the frame 10. The movable plate 20 is disposed inside the frame 10, and a rectangular mirror 21 is provided on the upper surface. The hinges 30 and 30 are disposed inside the frame 10 so as to sandwich the movable plate 20. The first cover 2 is formed of an insulating substrate. As an example of the insulating substrate, in the present embodiment, a glass substrate is used. The peripheral edge portion of the upper surface of the first cover 2 is hermetically bonded to the peripheral edge portion of the upper surface of the frame 10 of the wafer main body 1. The second cover 3 is formed of a glass substrate. The second cover 3 is hermetically bonded to the peripheral portion of the lower surface of the frame 10 of the wafer body 1. The first electrode 12 is electrically connected to the frame 10. The second electrode 22 is electrically connected to the movable plate 20. Further, the movable plate 20 is displaced relative to the frame 10 by the driving force applied to the voltage between the first electrode 12 and the second electrode 22. Further, as shown in Fig. 1, the direction in which the pair of hinges 30 are coupled is set to the y-axis direction.

Here, the outer shape of the wafer main body 1, the first cover 2, and the second cover 3 is rectangular, and the first cover 2 and the second cover 3 are formed to have the same outer dimensions as the wafer main body 1.

The wafer body 1 is formed by processing the SOI substrate 100 by a bulk micromachining technique or the like. In the SOI substrate 100, an insulating layer (SiO ₂ layer) 100c is interposed between the first conductive layer (active layer) 100a and the second germanium layer (germanium substrate) 100b having conductivity. Two sheets of glass sheets, such as Pyrex (registered trademark) glass, are superposed in the thickness direction and joined to form the first lid 2 . The second cover 3 is formed by processing a glass substrate made of Pyrex (registered trademark) glass or the like. Further, in the SOI substrate 100, the thickness of the first buffer layer 100a is set to 30 μm, and the thickness of the second buffer layer 100b is set to 400 μm. The thickness of the first cover 2 and the second cover 3 is set to be in the range of about 0.5 mm to 1.5 mm. These thicknesses are an example and are not particularly limited. Moreover, the surface of the first layer 10c of the SOI substrate 100 is a (100) plane. Further, the outer shape of the wafer main body 1 is about several mm square, but is not particularly limited.

The frame 10 of the wafer main body 1 is formed by using the first tantalum layer 100a of the SOI substrate 100, the insulating layer 100c, and the second tantalum layer 100b, respectively. In the frame 10, the portion formed by the first layer 100a is joined to the outer periphery of the first cover 2 over the entire circumference. The portion of the frame 10 formed by the second layer 100c is joined to the outer periphery of the second cover 3 over the entire circumference. On the upper surface of the frame 10, a pair of pads 13 (first pad 13a and second pad 13b) electrically connected to a driving mechanism for driving the movable plate 20 are formed. The first pad 13a is electrically connected to the first electrode 12. The second pad 13b is electrically connected to the second electrode 22. Each of the pads 13 has a circular shape in plan view and is formed of a first metal film (for example, an Al film). Further, in the present embodiment, the frame 10 constitutes a peripheral portion of the wafer main body 1. Further, in the present embodiment, the thickness of each of the pads 13 is set to 500 nm, but the thickness is not particularly limited as long as it is an example.

Further, the movable plate 20 and the hinges 30 of the wafer main body 1 are formed using the first meandering layer 100a of the SOI substrate 100, and are designed to be extremely thinner than the frame 10. Further, the mirror 21 provided on the movable plate 20 is formed by the surface of the reflective film 21a formed on the portion of the movable plate 20 formed by the first meandering layer 100a, and The second metal film (for example, an Al film) is formed. In the present embodiment, the thickness of the reflective film 21a is set to 500 nm, but the thickness is not particularly limited as long as it is an example.

Hereinafter, as shown in FIGS. 3A to 3C, the direction in which the pair of hinges 30 are coupled is set to the y-axis direction, the thickness direction of the frame 10 is set to the z-axis direction, and the direction orthogonal to the z-axis direction and the y-axis direction is set. This is explained for the x-axis direction.

In the wafer main body 1, a pair of hinges 30 are arranged side by side in the y-axis direction, and the movable plate 20 is displaceable around the pair of hinges 30 with respect to the frame 10 (rotatable in the y-axis direction). That is, the pair of hinges 30 connect the frame 10 and the movable panel 20 so that the movable panel 20 can swing freely with respect to the frame 10. In other words, the movable plate 20 to be disposed inside the frame 10 is oscillatably supported with respect to the frame 10 via the two hinges 30 integrally formed integrally from the movable plate 20. Here, the movable plate 20 is configured such that its center of gravity is coupled to the shaft of the pair of hinges 30. In addition, the thickness dimension (the dimension in the z-axis direction) of each hinge 30 is set to 30 μm, and the width dimension (the dimension in the x-axis direction) is set to 5 μm, and these dimensions are not particularly limited as an example. Further, the shape of the movable plate 20 and the mirror 21 in plan view is not limited to a rectangular shape, and may be, for example, a circular shape. Further, the inner peripheral shape of the frame 10 is not limited to a rectangular shape, and may be, for example, a circular shape.

The wafer main body 1 has a pair of comb-shaped first electrodes (fixed electrodes) 12 and 12 and a pair of comb-shaped second electrodes (movable electrodes) 22 and 22, and is configured to be movable by electrostatic force. Board 20. The first electrodes 12 are respectively formed on the two inner side surfaces of the frame 10 that are perpendicular to the x-axis (the surfaces facing the movable plate 20). The second electrodes 22 are respectively formed on the two outer side surfaces (the surfaces facing the frame 10) perpendicular to the x-axis in the movable plate 20. Further, although the drive mechanism of the present embodiment is configured to drive the movable plate 20 by electrostatic force, the movable plate 20 may be driven by electromagnetic force or a piezoelectric element.

Each of the first electrodes 12 is formed of the first tantalum layer 100a. The plurality of teeth of each of the first electrodes 12 are arranged side by side in the y-axis direction, and each of the teeth extends in the x-axis direction. Each of the second electrodes 22 is formed by the first meandering layer 100a. The plurality of teeth of each of the second electrodes 22 are arranged side by side in the y-axis direction, and each of the teeth extends in the x-axis direction. Each of the first electrodes 12 and each of the second electrodes 22 is disposed such that the teeth 12a and the teeth 22a are alternately arranged in the y-axis direction. By applying a voltage between the first electrode 12 and the second electrode 22, an electrostatic force acting in a direction in which the first electrode 12 and the second electrode 22 are attracted to each other is generated. In addition, the distance between the teeth a of the adjacent first electrode 12 and the teeth of the second electrode 22 in the y-axis direction is appropriately set (for example, about 5 μm to 20 μm).

The first pad 13a formed on the first buffer layer 100a of the frame 10 is electrically connected to the first electrode 12. The second pad 13b is electrically connected to the second electrode 22. The plurality of slits 10a, 10a, and 10a are formed to reach the depth of the insulating layer 100c to electrically insulate the first electrode 12 from the second electrode 22. In the present embodiment, each of the slits 10a is a groove, and the shape of the slit 10a in plan view is a shape that is not open to the outer side surface side of the frame 10. Thereby, the adhesion between the frame 10 and the first cover 2 is prevented from being lowered, and the airtightness of the space surrounded by the frame 10, the first cover 2, and the second cover 3 is secured. Furthermore, each of the pads 13 is provided for external power supply. Each of the pads 13 is made of a material (for example, Au or Al, Al-Si) which can be ohmically contacted to the first layer 100a and can be wire bonded.

The slits 10a, 10a, and 10a are formed on the first layer 100a of the frame 10. Thereby, the two anchor portions 31 and 32, the rectangular island portion 36 in which the anchor portion 31 and the pad 13a are formed, and the conductive portion 37 in which the anchor portion 32 and the island portion 36 are L-shaped in plan view are formed. The first conductive structure 38 is the same as the second electrode 22 of the movable plate 20, and the second conductive structure 39 is formed of the remaining portion and the other electrode 13b is formed, and the first electrode 12 is formed. The same potential, wherein one end of each of the hinges 30, 30 is continuously and integrally coupled to the outer side surface of the movable panel 20, and the other end of each of the hinges 30, 30 is continuously and integrally coupled to the two anchor portions 31. , the inner side of 32.

The first cover 2 is formed of a glass substrate. The first cover 2 is formed with two through holes 202 (202a, 202b) penetrating in the thickness direction thereof. The two through holes 202a and 202b expose each of the pads 13a and 13b, respectively. The opening areas of the through holes 202a and 202b of the first cover 2 are formed larger than the areas of the first pad 13a and the second pad 13b, respectively. The first pad 13a and the second pad 13b are completely housed in the respective through holes 202a and 202b. Each of the through holes 202 is formed in a tapered shape in which the opening area gradually increases as it leaves the wafer main body 1. Here, each of the through holes 202 of the first cover 2 is formed by a sand blast method, but a drilling method, an etching method, or the like may be suitably employed instead of the method.

In the MEMS optical scanner of the present embodiment, the shape of each of the pads 13 is formed into a circular shape having a diameter of 0.5 mm. Each of the through holes 202 is formed such that the opening diameter on the wafer body 1 side is larger than 0.5 mm. The diameter of each of the pads 13 is not particularly limited. The shape of each of the pads 13 may be formed in, for example, a square instead of a circle. Here, in order to reduce the opening diameter of the through hole 202, the shape of each of the pads 13 is more preferably circular than the square.

When the first cover 2 and the wafer main body 1 are joined, if a part of each of the pads 13 is interposed between the first cover and the wafer main body, the bonding property or airtightness of the MEMS wafer 600 is broken due to the thickness of the bonding pad 13. . Once the bondability or airtightness is broken, it is possible to lower the yield or the operational stability and the stability over time of the MEMS wafer 600 at the time of manufacture. If the width dimension of the frame 10 is increased in order to prevent the decrease in the bonding property or the airtightness, the miniaturization of the MEMS wafer 600 cannot be achieved.

According to the configuration of the present embodiment, the first cover 2 and the wafer main body 1 can be joined without sandwiching a part of each of the pads 13, and the bondability or airtightness of the MEMS wafer 600 can be prevented from being lowered. According to this configuration, it is possible to reduce the size of the wafer main body 1 and to achieve a reduction in operational stability and stability over time. According to this configuration, the width of the frame 10 is not increased, and the yield of the MEMS wafer 600 can be improved to reduce the cost.

Further, in the MEMS optical scanner of the present embodiment, the airtight space surrounded by the frame 10 of the wafer main body 1, the first cover 2, and the second cover 3 is a vacuum. By making the airtight space a vacuum, power consumption can be suppressed and the mechanical deflection angle of the movable panel 20 can be increased. In the MEMS optical scanner of the present embodiment, the concave portion 301 is formed on the surface of the second cover 3 facing the wafer main body 1 so as to face the airtight space. A deaerator 4 is disposed on the bottom surface of the recess 301. The getter 4 traps impurities generated in the airtight space. The deaerator 4 is preferably a non-evaporable degassing agent (for example, an alloy containing Zr as a main component and an alloy containing Ti as a main component).

Further, the first cover 2 is formed by two glass plates. Among the two glass plates, one glass plate is formed with an opening penetrating in the thickness direction. The other glass plate is formed into a flat shape. The two glass plates are joined to each other to form a first cover 200 having a concave portion 201 formed on one surface thereof. The first cover 200 is disposed such that the concave portion 201 faces the wafer main body 1 . By providing the recess 201, a space for the movable plate 20 to rotate in the y-axis direction with respect to the frame 10 is secured. The concave portion 201 of the present embodiment has a smooth inner bottom surface as compared with the concave portion 201 formed by sandblasting or the like, so that diffusion reflection, light diffusion, scattering loss, and the like of the inner bottom surface can be reduced. The first cover 2 in the present embodiment is formed using a transparent substrate. When the light from the visible light to the near-infrared light is incident on the first cover, it is preferable that the first cover 2 is formed of a glass substrate. When the infrared light is incident on the first cover, it is preferable that the first cover 2 is formed of a ruthenium substrate.

The second cover 3 is formed of a glass substrate. A concave portion 301 is formed on the surface of the second cover 3 opposite to the wafer main body 1. By providing the recess 301, a space for the movable plate 20 to rotate in the y-axis direction is secured. Further, a film-shaped degassing agent 4 is disposed on the inner bottom surface of the concave portion 301. The both sides in the thickness direction may be formed in a planar shape in accordance with the thickness dimension of the second ruthenium layer 100b of the SOI substrate 100 or the like. The concave portion 301 of the second cover 3 is formed by a sand blast method or the like. Further, similarly to the first cover 2, the glass plate having the opening penetrating in the thickness direction may be joined to the flat glass plate to form the second cover 3 having the concave portion 301 on one side. Further, the second cover 3 does not have to be formed of a light-transmitting substrate. The second cover 3 may be formed of a substrate (for example, a ruthenium substrate) which is formed of a material which is easily bonded to the wafer main body 1 and has a small difference in linear expansion coefficient from 矽 (Si). The recess 301 at this time is formed by photolithography and etching techniques.

Further, it is preferable that each of the covers 2, 3 is a borosilicate glass which is easily joined to the wafer main body 1 and has a small difference in linear expansion coefficient with respect to ruthenium (for example, Pyrex (registered trademark) of Corning Corporation or Tempax of SCHOTT Corporation). (registered trademark)) formed. Each of the covers 2 and 3 may be formed of soda lime glass, alkali-free glass, quartz glass or the like. Further, in the present embodiment, the thickness of each of the covers 2 and 3 is set to about 0.5 mm to 1.5 mm, and the depth of each of the recesses 201 and 301 is set to be 300 μm to 800 μm. The thickness or depth is an example and can be appropriately set according to the amount of displacement of the movable plate 20 in the z-axis direction. The thickness or depth is not particularly limited as long as it does not interfere with the depth of the rotational movement of the movable plate 20.

Next, the operation of the MEMS optical scanner of this embodiment will be briefly described.

In the MEMS optical scanner of the present embodiment, the pulse voltage is supplied between the opposing second electrode 22 and the first electrode 12 by the pair of pads 13a and 13b, whereby the second electrode 22 and the first electrode are provided. The 12 pieces generate an electrostatic force to rotate the movable plate 20 about the y-axis. In the MEMS optical scanner of the present embodiment, by applying a pulse voltage of a predetermined driving frequency between the second electrode 22 and the first electrode 12, an electrostatic force can be periodically generated, and the movable plate 20 can be swung.

In the stationary state, the upper surface of the movable plate 20 is not inclined parallel to the xy plane due to the internal stress, but is slightly inclined from the xy plane. At this time, when a pulse voltage is applied between the second electrode 22 and the first electrode 12, the movable plate 20 is rotated about the y-axis while the pair of hinges 30 and 30 are twisted by the driving force in the z-axis direction. When the voltage application is stopped in a state where the teeth of the second electrode 22 and the teeth of the first electrode 12 are completely overlapped with each other, the movable plate 20 continues to rotate while twisting the pair of hinges 30 and 30 by the inertial force. Further, when the inertial force of the movable plate 20 in the rotational direction is equal to the restoring force of the pair of hinges 30, 30, the rotation of the movable plate 20 is stopped. At this time, when a pulse voltage is applied between the second electrode 22 and the first electrode 12 to generate an electrostatic force, the movable plate 20 has a restoring force of the pair of hinges 30 and 30 and a driving force of each of the electrodes 22 and 12. And began to turn in the opposite direction. The movable plate 20 is swung around the y-axis direction by repeating the rotation caused by the driving force of the respective electrodes 22, 12 and the rotation caused by the restoring forces of the pair of hinges 30, 30.

In the MEMS optical scanner of the present embodiment, the movable plate 20 is driven by the resonance phenomenon by applying a pulse voltage of about twice the resonance frequency of the vibration system constituted by the movable plate 20 and the pair of hinges 30 and 30. . At this time, the rotation angle from the plane perpendicular to the z-axis increases. Further, the form or frequency of application of the voltage between the electrodes 22 and 12 is not particularly limited. The applied voltage between the electrodes 22 and 12 may be, for example, a sinusoidal voltage.

Hereinafter, a method of manufacturing the MEMS wafer 600 of the MEMS optical scanner of the present embodiment will be described with reference to FIGS. 4A to 4D. 4A to 4D are schematic cross-sectional views showing portions corresponding to the A-B' cross section of Fig. 3A.

First, a metal film (for example, an Al film) having a predetermined film thickness (for example, 500 nm) is formed on one surface of the SOI substrate 100 as a semiconductor substrate by a sputtering method, a vapor deposition method, or the like. Then, the metal film is patterned by the photolithography technique and the etching technique to form the pads 13a and 13b and the reflection film 21a, thereby obtaining the structure shown in FIG. 4A. Further, in the present embodiment, since the material and thickness of each of the pads 13a and 13b and the reflection film 21a are set to be the same, the pads 13a and 13b and the reflection film 21a can be simultaneously formed. When the materials or thicknesses of the pads 13a and 13b and the reflective film 21a are different, the pads 13a and 13b and the reflective film are respectively provided in different steps. At this time, the step of forming each of the pads 13a and 13b and the reflective film may be performed first.

Then, the first photoresist layer is patterned so as to cover the portion corresponding to the movable plate 20, the pair of hinges 30 and 30, the frame 10, the first electrodes 12 and 12, and the second electrodes 22 and 22. 130 is formed on the first buffer layer 100a of the SOI substrate 100. The first photoresist layer 130 is used as a mask, and the first germanium layer 100a is etched to a depth (first predetermined depth) of the insulating layer 100c, whereby the structure shown in FIG. 4B is obtained. In this step, the SOI substrate 100 as a semiconductor substrate is etched from the upper surface to the first predetermined depth. The etching of the first layer 100a can be performed by a dry etching apparatus capable of performing etching with high anisotropy, for example, an inductively coupled plasma (ICP) type etching apparatus. Further, in this step, the insulating layer 100c is used as an etch stop layer.

Then, after the first photoresist layer 130 on the SOI substrate 100 is removed, the second photoresist layer 131 is formed on the entire upper surface of the SOI substrate 100. Then, the portion corresponding to the frame 10 is exposed. The patterned third photoresist layer 132 is formed on the second buffer layer 100b of the SOI substrate 100. The third photoresist layer 132 is used as a mask, and the second germanium layer 100b is etched to a depth (second predetermined depth) of the insulating layer 100c, whereby the structure shown in FIG. 4C is obtained. In this step, the SOI substrate 100 as a semiconductor substrate is etched from the lower surface to a second predetermined depth. Further, the etching of the second buffer layer 100b can be performed by a dry etching apparatus which can perform high anisotropy and can be vertically drilled, for example, an inductively coupled plasma (ICP) type etching apparatus. Further, in this step, the insulating layer 100c is used as an etch stop layer.

Next, in the insulating layer 100c of the SOI substrate 100, the portion between the frame 10 and the movable plate 20 (the portion between the second electrode 22 and the first electrode 12) is etched from the lower surface of the SOI substrate 100. The wafer body 1 is formed. Then, the second photoresist layer 131 and the third photoresist layer 132 are removed. Then, the wafer main body 1, the first cover 2, and the second cover 3 are joined by anodic bonding or the like to obtain the MEMS wafer 600 having the structure shown in FIG. 3D.

In the bonding step, from the viewpoint of protecting the mirror surface 21 of the wafer main body 1, it is preferable to bond the wafer main body 1 and the second lid 3 after bonding the first lid 2 to the wafer main body 1. In this step, the first cover 2 in which the first concave portion 201, the through holes 202, and the grooves 203 are formed is superposed on the wafer main body 1 to form a laminated body. When the laminated body is heated to a predetermined temperature (for example, 300 ° C to 400 ° C) under a vacuum of a predetermined degree of vacuum (for example, 10 Pa or less), the first cover layer 100a is placed on the lower side of the first cover 2 side. A predetermined voltage (for example, about 400 V to 800 V) is applied between the first cover 2 and held in this state for a predetermined period of time (for example, about 20 minutes to 60 minutes), whereby the wafer main body 1 and the first cover can be used. 2 joints. The anode bonding of the second layer 100b and the second lid 3 is performed by the same method as described above. Further, instead of the anodic bonding, the wafer main body 1 and the first lid 2 and the wafer main body 1 and the second lid 3 may be joined by a normal temperature bonding method or the like. Further, after the patterning of the first layer, the SOI substrate 100 is bonded to the first lid 2, and thereafter, the patterning of the second layer and patterning of the insulating layer may be performed, thereby forming the wafer body 1. Then, the wafer body 1 and the second cover 3 are bonded.

In the method of manufacturing the MEMS wafer 600 described above, all of the steps of the wafer body 1, the first cover 2, and the second cover 3 are performed at the wafer level until the bonding is completed, thereby forming a plurality of MEMS wafers 600. Wafer level package structure. Further, the step of dividing the wafer level package structure into individual MEMS wafers 600 is performed. In short, in the method of manufacturing the MEMS wafer 600 of the present embodiment, the first wafer in which the plurality of wafer bodies 1 are formed, the second wafer in which the plurality of first covers 2 are formed, and the plurality of second wafers are formed The third wafer of the cover 3 is bonded to form a wafer level package structure. Thereafter, the wafer level package structure is divided into the outer dimensions of the wafer body 1. Thereby, the planar dimensions of the first cover 2 and the second cover 3 can be made to conform to the outer dimensions of the wafer main body 1, so that the mass productivity of the small MEMS wafer 600 can be improved.

Further, on the substrate 5, a plurality of power supply members 502 (502a, 502b) for electrically connecting the pads 13a and 13b of the MEMS wafer 600 via the respective conductive members 6 are formed on the upper surface. In the present embodiment, the conductive member 6 is formed by a bonding wire which is made of a thin metal wire. The conductive member 6 may be formed of Si instead of the bonding wire. In the present embodiment, the pad 13a and the power supply body 502a are connected by a bonding wire 6. The pad 13b and the power supply body 502b are connected by a bonding wire 6. Here, as the metal thin wires constituting the bonding wires 6, for example, an Au thin wire such as an Au thin wire or a 1% Si-Al wire or a 1% Mg-Al wire may be used, but an Au thin wire excellent in conductivity is preferable. In addition, the material of the power supply body 502 is not particularly limited as long as it is a metal having high oxidation resistance, and is preferably Au from the viewpoint of adhesion to the bonding wire 6.

Further, when the substrate 5 is packaged twice with respect to a wiring board (circuit board) such as a printed circuit board, the surface is packaged so as to be formed over the side surface (the inner surface of the cutout portion formed on the side surface) and the back surface. The external electrode 504 formed by the continuous conductor pattern (terminal pattern) can form a solder fillet when the package is applied twice on the wiring board, thereby improving the package strength. Further, each of the power supply bodies 502a and 502b and the external electrodes 504a and 504b are formed continuously. The material of the external electrode 504 is preferably Au in the same material as the power supply body 502. The external electrodes 504 may also be disposed on different faces of the substrate 5. In this configuration, it is possible to prevent interference of an electrical signal input and output via the external electrode 504. Furthermore, even when the external electrodes 504 are disposed on different faces, the power supply body 502 is formed on the upper surface.

As described above, the first cover 2 of the MEMS wafer 600 has a plurality of (here, two) through holes 202a and 202b which are formed to expose the respective pads 13a and 13b of the wafer main body 1 over the entire periphery. Further, a plurality of (here, two) trenches 203a and 203b are formed, which are respectively connected to the respective through holes 202 and open on the opposite side to the through hole 202 side, and pass through the electrically connected wafer. A bonding wire 6 of the pads 13a and 13b of the body 1 and the power supply body 502 of the package substrate 5. Each of the power supply bodies 502a and 502b of the substrate 5 is disposed so as to have a short distance from the corresponding pads 13a and 13b of the wafer main body 1 (the pads 13 electrically connected via the bonding wires 6), and the trenches 203a, 203a, 203b is formed to extend in the direction in which the one-to-one corresponding pads 13a and 13b and the power supply bodies 502a and 502b are arranged. The grooves 203a, 203b are designed to be able to accommodate the depth of the bonding wires 6 so that the bonding wires 6 passing through the grooves 203a, 203b do not protrude from the surface of the first cover 2. Further, the groove 203 may be formed to penetrate the thickness direction of the first cover 2 by the structure of the wafer main body 1. Among them, from the viewpoint of the joint area of the wafer main body 1 and the first lid 2 or the airtightness of the inside of the MEMS wafer 600, it is preferable that the thickness direction is not penetrated. The depth of the grooves 203a and 203b is preferably smaller than the length of the through holes 203a and 203b by about 200 μm to 400 μm. In particular, in the present embodiment, since a part of the slit 10a is formed around the pad 13a, at least the groove 203a needs to be formed so as not to penetrate the thickness direction of the first cover 2 in order to ensure airtightness. Furthermore, the trench 203 has a width dimension that can pass through the bonding wire 6. In the present embodiment, the width dimension of the grooves 203a and 203b is set to be smaller than the opening diameter of the through holes 202a and 202b in the surface of the first cover 2, but is not particularly limited. Further, the shape of the openings of the grooves 203a and 203b is not particularly limited, and the inner side faces of the grooves 203a and 203b may be tapered. Further, the method of forming the grooves 203a and 203b of the first cover 2 is not limited to the drilling method, and may be a sand blast method or an etching method. The method of forming the grooves 203a and 203b can be suitably employed depending on the material of the first cover 2 or the desired opening shape of the grooves 203a and 203b. Further, the conductive member may be formed of bismuth (Si) instead of the bonding wire 6. In this case, the crucible is filled in the through hole 202 or the groove 203.

Further, the base 5 is formed with a concave portion 501 at the center portion, and the MEMS wafer 600 is mounted on the inner bottom surface of the concave portion 501. In the present embodiment, the depth of the concave portion 501 is set such that the upper surface of each of the power supply bodies 502 is lower than the upper surface of the first cover 2. According to this configuration, the bonding wire 6 does not protrude from the upper surface of the cover 2 and is housed in the groove 203 and is connected to the power supply body 502. Further, the height difference between the pads 13a and 13b in the thickness direction of the wafer main body 1 and the power supply bodies 502a and 502b is reduced, and the bonding wires 6 are not overlapped with the first cover 2 at both ends of the grooves 203a and 203b. contact. When determining the depth dimension of the recess 501, the height from the back surface of the MEMS wafer 600 to the upper surfaces of the pads 13a, 13b is also considered. The depth dimension of the concave portion 501 is set, for example, to a range of about several hundred μm to 1 mm. In other words, the height difference between the pads 13a and 13b in the thickness direction of the wafer main body 1 and the power supply bodies 502a and 502b can be adjusted by appropriately setting the depth dimension of the concave portion 501 of the substrate 5. Furthermore, the MEMS wafer 600 is followed by a wafer bonding material for the substrate 5 (wafer bonding). As the wafer bonding material, for example, a resin-based wafer bonding material (for example, a silicone resin or an epoxy resin) is used. In order to improve the accuracy of the height dimension from the inner bottom surface of the concave portion 501 of the base 5 to the upper surfaces of the solder pads 13a and 13b, for example, a resin in which a plurality of spherical spacers are mixed may be used as the wafer bonding material. Further, the substrate 5 is formed of a ceramic substrate, but is not particularly limited to a ceramic substrate.

In the present embodiment, as shown in FIG. 2B, it is preferable that the upper surfaces of the pads 13a and 13b are lower than the surfaces of the power supply bodies 502a and 502b of the substrate 5 (the height difference is, for example, about 200 μm to 500 μm). The depth dimension of the recess 501 of the substrate 5 is set. According to the above configuration, it is possible to prevent the bonding wires 6 from coming into contact with the first cover 2 at both ends of the grooves 203a and 203b, and it is possible to achieve good wire bonding. Further, in order to achieve good wire bonding, it is preferable that the opening diameters of the through holes 202a and 202b on the surface of the first cover 2 are larger than the depths of the grooves 203a and 203b.

In the manufacture of the MEMS device of the present embodiment, the MEMS wafer 600 manufactured by the above-described manufacturing method is mounted on the substrate 5 on the substrate 5. Thereafter, the pads 13a and 13b of the wafer body 1 in the MEMS wafer 600 and the power supply bodies 502a and 502b of the substrate 5 are electrically connected via a bonding wire 6. At the time of this connection, the bonding wire 6 is passed through the groove 203 of the first cover 2.

According to the MEMS device (MEMS scanner) of the present embodiment described above, the first cover 2 is formed with a plurality of through holes 202 that expose the respective pads 13a and 13b of the wafer main body 1 over the entire circumference. Further, a pair of grooves 203a and 203b are formed which are respectively in communication with the respective through holes 202a and 202b and open on the opposite side to the through holes 202a and 202b, and are passed through the electrode which is electrically connected to the wafer body 1. The bonding wires of the pads 13a, 13b and the power supply bodies 502a, 502b of the substrate 5. The bonding wire 6 can be prevented from protruding from the surface of the first cover 2, and it is possible to suppress unnecessary stress from being applied to the wafer main body 1 and prevent damage of the bonding wire 6 due to contact with an external object.

Further, in the MEMS device of the present embodiment, the space surrounded by the frame 10, the first cover 2, and the second cover 3 constituting the peripheral portion of the wafer main body 1 in the MEMS wafer 600 is an airtight space, and Since the cover 2 does not overlap with the pads 13a and 13b, a part of each of the pads 13a and 13b is not interposed between the first cover 2 and the wafer body 1, so that it is possible to prevent the pads 13 from being obstructed by the pads 13. Since the cover 2 is bonded to the wafer main body 1, it is possible to prevent the bonding property or the airtightness from being broken by the influence of the thickness of each of the pads 13, thereby reducing the size of the wafer main body 1, and suppressing the decrease in the operational stability and the elapsed time. Reduced stability.

Further, in the MEMS device of the present embodiment, the airtight space of the MEMS wafer 600 is a vacuum environment, and the deaerator 4 is disposed on a portion of the second cover 3 facing the airtight space, so that the gas can be improved. The degree of vacuum in the dense space can also suppress the change in the degree of vacuum of the airtight space described above, thereby preventing the change in the characteristics of the device (the mechanical deflection angle of the movable plate 20 in the present embodiment) caused by the change in the degree of vacuum. Further, according to the structure of the MEMS wafer 600, the deaerator 4 may be disposed on the first cover 2 facing the airtight space, or may be disposed on both the first cover 2 and the second cover 3. Degassing agent 4.

However, in the MEMS device described above, as shown in FIG. 5, a plurality of protective portions 7 including resins respectively filled in the respective trenches 203 to protect the bonding wires 6 may be provided. Further, the resin used as the material of the protective portion 7 is a thermosetting resin. However, it is not limited to the thermosetting type, and an ultraviolet curable resin or a combination of ultraviolet rays and heat may be used.

In the MEMS device of the configuration of Fig. 5, the bonding wires 6 can be protected by a small amount of resin. Further, the through hole 202 has a function as a resin storage portion, and it is possible to suppress the resin from spreading on the upper surface of the first cover 2. Further, the protective portion 7 is formed by filling the grooves 203a and 203b with a resin by a droplet separator or the like.

Further, in the MEMS device of the present embodiment, each of the hinges 30 and 30 is formed by the first meandering layer 100a of the SOI substrate 100. According to this configuration, the accuracy of the thickness dimension of each of the hinges 30 and 30 can be improved as compared with the case where the tantalum substrate is used as the semiconductor substrate. Further, the accuracy of the resonance frequency of the vibration system composed of the movable portion 20 and the pair of hinges 30, 30 can be improved.

(Embodiment 2)

In the present embodiment, as in the first embodiment, a MEMS optical scanner is exemplified as an example of a MEMS device.

Hereinafter, the MEMS optical scanner of the present embodiment will be described with reference to Figs. 6 to 8 .

The basic configuration of the MEMS optical scanner of the present embodiment is substantially the same as that of the first embodiment, and the structures of the movable portion and the second cover 3 are different. The same components as those in the first embodiment are denoted by the same reference numerals, and their description will be appropriately omitted.

In the present embodiment, the movable portion is constituted by the movable plate 20 and the movable frame 24. A movable plate 20 having a rectangular shape in which the mirror 21 is provided on the upper surface, and a frame shape (rectangularly rotatably supported) by inserting a pair of hinges 30 and 30 (the first hinges 30a and 30a) with the frame 10 are formed. The frame-like movable frame 24. A movable plate 20 is disposed inside the movable frame 24. The movable plate 20 is coupled to the movable frame 24 via one of the twistable deformations of the hinges 30 and 30 (the second hinges 30b and 30b).

The second hinges 30b and 30b are arranged side by side in a direction (x-axis direction) orthogonal to the y-axis direction connecting the first hinges 30a and 30a. In short, the pair of second hinges 30b and 30b are arranged side by side in the x-axis direction. The movable plate 20 is displaceable around the second hinges 30b and 30b with respect to the movable frame 24 (rotatable around the x-axis). In other words, the second hinges 30b and 30b connect the movable frame 24 and the movable plate 20 so that the movable plate 20 can swing freely with respect to the movable frame 24. Here, the center of gravity of the movable plate 20 is formed so as to be coupled to the axes of the pair of second hinges 30b and 30b. In addition, each of the second hinges 30b and 30b has a thickness dimension (dimension in the z-axis direction) of 30 μm and a width dimension (dimension in the y-axis direction) of 30 μm. However, these numerical values are not examples and are not Specially limited. Further, the shape of the movable plate 20 and the mirror 21 in plan view is not limited to a rectangular shape, and may be, for example, a circular shape. Further, the inner peripheral shape of the movable frame 24 is not limited to a rectangular shape, and may be, for example, a circular shape.

As can be understood from the above description, the movable plate 20 can rotate about the axis of the pair of first hinges 30a and 30a and the rotation of the pair of second hinges 30b and 30b about the axis. In short, the mirror 21 of the movable panel 20 is configured to be two-dimensionally rotatable. Here, the movable panel 20 includes a frame-shaped support body 29 integrally provided on the lower side of the movable frame 24 and supporting the movable frame 24, and the support body 29 is rotatable integrally with the movable frame 24.

A second recess 301 for ensuring a displacement space of the movable panel 20 is formed on the upper surface of the second cover 3 opposite to the wafer main body 1.

Further, in the present embodiment, one of the first pads 13a and the two second pads 13b and 13c are arranged side by side at substantially equal intervals on the frame 10 so as to be arranged on the straight line in a plan view, on the first cover 2 Three tapered through holes 202 (202a, 202b, 202c) for respectively exposing the respective pads 13 are formed, and grooves 203 (203a, 203b, 203c) communicating with the through holes 202 are formed in the respective through holes 202. ).

Further, similarly to the first embodiment, the frame 10 includes the comb-shaped first electrodes 12 and 12 (12a, 12a). The movable plate 20 includes comb-shaped second electrodes 22 and 22 (22b, 22b). The first electrodes 12a and 12a are respectively formed on the two inner side faces of the frame 10 which are perpendicular to the x-axis. The second electrodes 22b and 22b are respectively formed on the two outer side surfaces of the movable plate 20 which are perpendicular to the y-axis. Further, the movable frame 24 includes comb-shaped second electrodes 22, 22 (22a, 22a) and comb-shaped first electrodes 12, 12 (12b, 12b). The second electrodes 22a and 22a are respectively formed on the two outer side surfaces of the movable frame 24 which are perpendicular to the x-axis. The first electrodes 12b and 12b are respectively formed on two inner side surfaces perpendicular to the y-axis of the movable frame 24. Between the first electrodes 12a and 12a and the second electrodes 22a and 22a, between the first electrodes 12b and 12b and the second electrodes 22b and 22b, electrostatic forces due to voltages are applied between them.

Each of the first electrodes 12b has a comb shape in plan view and is formed by a part of the movable frame 24. A plurality of teeth constituting each of the first electrodes 12b are arranged side by side in the y-axis direction. Each of the second electrodes 22b is constituted by a part of the movable plate 20. The plurality of teeth constituting each of the second electrodes 22b are arranged side by side in the y-axis direction. The teeth of the first electrode 12b and the teeth of the second electrodes 22b and 22b are alternately arranged in the x-axis direction so as to be spaced apart by a predetermined distance (for example, about 2 μm to 5 μm), whereby the electrodes 12b and 22b are disposed. . By applying a voltage between the first electrode 12b and the second electrode 22b, an electrostatic force acting in the direction of attraction between the first electrode 12b and the second electrode 22b is generated.

A plurality of slits 10a, 10a, and 10a are formed in the frame 10 by the portion formed by the first layer 100a. A plurality of slits 20a, 20a, 20a, and 20a are formed in the movable frame 24 at a portion formed by the first layer 100a. Thereby, the pad 13 (13b) in the center of the sixth of the three pads 13, 13, and 13 is electrically connected to the first fixed electrodes 12 and 12 to have the same potential. The pad 13 (13a) on the right side is electrically connected to the first movable electrodes 22 and 22 and the second movable electrodes 26 and 26 to have the same potential. The pad 13 (13c) on the left side is electrically connected to the second movable electrodes 27 and 27 of the mirror portion 24 to have the same potential.

Here, the plurality of slits 10a, 10a, 10a of the frame 10 are formed to a depth reaching the insulating layer 100c. In the same manner as in the first embodiment, the slits 10a, 10a, and 10a are formed as grooves, and the shapes of the slits 10a, 10a, and 10a in plan view are not opened on the outer side surface side of the frame 10. . Thereby, the adhesion between the frame 10 and the first cover 2 is prevented from being lowered, and the airtightness of the space surrounded by the frame 10, the first cover 2, and the second cover 3 is secured.

Further, each of the slits 20a, 20a, 20a, and 20a of the movable frame 24 is formed as a groove, and is formed to reach the support body composed of a part of the insulating layer 100c of the SOI substrate 100 and a part of the second meandering layer 100b. The depth of the insulating layer 100c in 29. In short, in the present embodiment, since the movable frame portion 24 is supported by the support body 29, the movable frame 24 and the support body 29 can be integrally rotated around the pair of first hinges 30a and 30a. In addition, the support body 29 is formed in a frame shape (rectangular frame shape) covering a portion other than the teeth of the first electrodes 12a and 12a and the second electrodes 22a and 22a of the movable frame 24 (see FIG. 8). Further, the plurality of grooves 20a, 20a, 20a, and 20a of the movable frame 24 are designed to include a shape in which the center of gravity of the movable portion 20 of the support body 29 is located on an axis parallel to the y-axis. However, the movable plate 20 smoothly swings around the pair of first hinges 30a and 30a, and scans the reflected light as appropriate. Further, in the present embodiment, the thickness of the portion of the support 29 composed of the second ruthenium layer 100b is set to be the same as the thickness of the portion of the frame 10 formed by the second ruthenium layer 100b, but is not limited to the same. Can be thinner or thicker.

In the MEMS optical scanner of the present embodiment, for example, the potential of each of the first electrode 12a and the second electrode 22b is set to a potential of the pad 13a electrically connected to the second electrode 22a and the first electrode 12b as a reference potential. Sexual change. Thereby, the movable frame 24 can be rotated around the pair of first hinges 30a and 30a. At the same time, the movable portion 20 can be rotated about the pair of second hinges 30b, 30b. In short, by supplying a pulse voltage through the pair of pads 13b and 13a, an electrostatic force is generated between the first electrode 12a and the second electrode 22a, and the movable frame 24 is rotatable in the y-axis direction. Further, the pulse voltage is supplied through the pair of pads 13a and 13c, whereby an electrostatic force is generated between the first electrode 12b and the second electrode 22b, and the movable plate 20 is rotated in the x-axis direction. However, in the MEMS optical scanner of the present embodiment, by applying a predetermined pulse voltage of the first driving frequency between the first electrode 12a and the second electrode 22a, an electrostatic force is periodically generated, and the movable portion 20 can be swung. . Further, by applying a pulse voltage of a predetermined second driving frequency between the first electrode 12b and the second electrode 22b, an electrostatic force is periodically generated, and the movable portion 20 can be swung. Further, the apparatus main body 1 of the present embodiment is formed on the space side surrounded by the frame 10 and the first cover 2, and a ruthenium oxide film 111a is formed on the surface of the portion of the first ruthenium layer 100a where the reflection film 21a is not formed ( Refer to Figure 9F).

In the MEMS optical scanner of the present embodiment, about twice the frequency of the resonance frequency of the vibration system formed by the movable frame 24 and the pair of first hinges 30a and 30a is applied between the first electrode 12a and the second electrode 22a. Pulse voltage. Thereby, the movable plate 20 is driven with the resonance phenomenon, and the rotation angle when the surface perpendicular to the z-axis is used as a reference increases. Further, the movable plate 20 is applied by applying a pulse voltage of about twice the resonance frequency of the vibration system composed of the movable plate 20 and the pair of second hinges 30b and 30b between the first electrode 12b and the second electrode 22b. Driven with resonance. Thereby, the rotation angle when the surface parallel to the upper surface of the movable frame 24 is used as a reference increases.

Hereinafter, a method of manufacturing the MEMS optical scanner of the present embodiment will be described with reference to Fig. 9. 9A to D are schematic cross-sectional views showing portions corresponding to the A-B section of Fig. 6.

First, the yttrium oxide films 111a and 111b are formed on the upper and lower surfaces of the SOI substrate 100 as a semiconductor substrate by a thermal oxidation method or the like, and the structure shown in FIG. 9A is obtained.

Then, the portion of the movable portion 20 of the yttrium oxide film 111a on the upper surface of the SOI substrate 100 that retains the portion other than the predetermined region of the reflective film 21a, the portion corresponding to the first hinges 30a and 30a, and the like is used. In the shadow technique and the etching technique, the first layer 100a is patterned, whereby the structure shown in FIG. 9B is obtained.

Thereafter, a metal film (for example, an Al film) having a predetermined film thickness (for example, 500 nm) is formed on the upper surface of the SOI substrate 100 by a sputtering method, a vapor deposition method, or the like. Further, the metal film is patterned by the photolithography technique and the etching technique to form the pads 13 and 13 and the reflection film 21a, thereby obtaining the structure shown in FIG. 9C. In the present embodiment, since the material and film thickness of each of the pads 13 and 13 and the reflection film 21a are set to be the same, the pads 13 and the reflection film 21a are simultaneously formed. When the material or film thickness of each of the pads 13 and the reflective film 21a is different, each of the pads 13 and the reflective film 21 are formed in different steps.

Next, the upper surface of the SOI substrate 100 is formed to cover the movable frame 24, the movable plate 20, the pair of first hinges 30a, the pair of second hinges 30b, the frame 10, the first electrodes 12a and 12b, and the second electrode 22a. The first photoresist layer 130 patterned in a manner corresponding to the portion corresponding to 22b. By using the first photoresist layer 130 as a mask and etching the first buffer layer 100a to the depth (first predetermined depth) of the insulating layer 100c, the first buffer layer 100a is patterned to obtain the 9D pattern. The configuration shown. The etching of the first layer 100a in this step is performed by a dry etching apparatus capable of performing etching with high anisotropy, for example, an inductively coupled plasma (ICP) type etching apparatus. Further, in this step, the insulating layer 100c is used as an etch stop layer.

Next, after the first photoresist layer 130 on the upper surface of the SOI substrate 100 is removed, the second photoresist layer 131 is formed on the entire upper surface of the SOI substrate 100. Then, on the lower surface of the SOI substrate 100, a third photoresist layer 132 patterned to expose the portions corresponding to the frame 10 and the support 29 is formed. By using the third photoresist layer 132 as a mask, the second germanium layer 100b is patterned to a depth (second predetermined depth) of the insulating layer 100c, whereby the second germanium layer 100b is patterned to obtain the 9E. The structure shown in the figure. The etching of the second germanium layer 100b in this step can also be performed by a dry etching apparatus capable of performing anisotropic (heterogeneity) and vertical deep excavation, for example, an inductively coupled plasma (ICP) type. Etching device, etc. Further, in this step, the insulating layer 100c is used as an etch stop layer.

Next, the wafer body 1 is formed by etching unnecessary portions of the insulating layer 100c of the SOI substrate 100 from the lower side of the SOI substrate 100. Then, the second photoresist layer 131 and the third photoresist layer 132 are removed. Thereafter, the wafer body 1, the first cover 2, and the second cover 3 are joined by anodic bonding or the like, whereby the MEMS wafer 600 having the structure shown in Fig. 9F is obtained. In the bonding step, from the viewpoint of protecting the mirror surface 21 of the wafer main body 1, it is preferable to bond the wafer main body 1 and the second lid 3 after bonding the first lid 2 and the wafer main body 1. Further, after patterning the first layer, the SOI substrate 100 and the first lid 2 may be bonded, and the second layer is patterned and the insulating layer is patterned to form the wafer body 1 and then bonded. The wafer body 1 and the second cover 3.

However, in the method of manufacturing the MEMS wafer 600 of the present embodiment, in the same manner as in the first embodiment, the mirror forming substrate and the respective covers 2 and 3 are respectively formed at the wafer level, thereby forming a plurality of MEMS lights. Wafer level package structure for the scanner. Further, the step of dividing the wafer-level package structure into individual MEMS optical scanners is performed. In short, in the manufacturing method, the first wafer on which the plurality of mirror formation substrates are formed, the second wafer on which the plurality of first covers 2 are formed, and the third wafer on which the plurality of second covers 3 are formed are bonded And a wafer level package structure is formed. Further, in each of the first covers of the wafer-level package structure, a light-transmissive resin or a low-melting-point glass is formed on the outer surface side opposite to each of the mirror-formed substrates, and each fine-period structure is formed. Thereafter, the wafer-level package structure is divided into the outer dimensions of the mirror-forming substrate. Thereby, the planar dimensions of the respective covers 2, 3 can be made to conform to the outer dimensions of the mirror-forming substrate, so that a small MEMS optical scanner including a fine periodic structure can be manufactured by a simple process, and mass productivity can be improved.

In the MEMS optical scanner of the present embodiment described above, in the same manner as in the first embodiment, the plurality of MEMS wafers 600 are formed by performing the main body 1, the first cover 2, and the second cover 3 at the wafer level. Wafer level package structure. Further, the wafer-level package structure is divided into individual MEMS wafers 600.

According to the MEMS device (MEMS scanner) of the present embodiment described above, in the same manner as in the first embodiment, the first cover 2 is formed with a plurality of through holes in which the pads 13 of the wafer main body 1 are exposed throughout the entire periphery. 202, and a plurality of trenches 203 are formed, which are respectively connected to the respective through holes 202 and open on the opposite side of the through hole 202 side, and pass through the bonding pads 13 and the substrate electrically connected to the wafer body 1. The bonding wire of the power supply body 502 of 5 can prevent the bonding wire 6 from protruding from the surface of the first cover 2, and can suppress unnecessary stress applied to the wafer body 1 while preventing the bonding wire 6 from being brought into contact with an external object. Broken.

Further, in the MEMS device, as shown in FIG. 10, a plurality of (here, three) protective portions 7 including resin which are respectively filled in the respective trenches 203 and protected the bonding wires 6 may be provided. The bonding wire 6 can be protected by a small amount of resin, and the through hole 202 has a function as a resin storage portion, so that expansion of the resin on the surface of the first cover 2 can be suppressed.

However, in each of the above embodiments, the MEMS optical scanner is exemplified as the MEMS device, but the MEMS device is not limited to the MEMS optical scanner, and may be, for example, an acceleration sensor or a gyro sensor, a micro relay, or A vibrating power generation device that converts vibration energy into electric energy, a BAW (Bulk Acoustic Wave) resonance device that includes a resonance element in a longitudinal vibration mode in a thickness direction of a piezoelectric layer, an infrared sensor, and the like.

(Embodiment 3)

In the present embodiment, a wafer body (micromirror device) 1 using a movable body will be described with reference to the drawings. The basic configuration of the MEMS device using the micromirror device 1 is substantially the same as that of the second embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted as appropriate. Fig. 12 shows the configuration of the wafer body 1. The wafer body 1 has a movable plate 20, a hinge 30, a frame 10, and a pair of comb-shaped electrodes 12, 22. The wafer body 1 is formed by, for example, etching a portion of a three-layer SOI (Silicon on Insulator) substrate from the front and back surfaces.

The movable panel 20 is formed in a rectangular shape in a plan view, and is swingably supported by the hinge 30 with respect to the frame 10. The hinge 30 is formed by penetrating the center of the upper and lower edges of the movable plate 20 through the center of the movable plate 20, and supports the movable plate 20 to function as a twisting spring when the movable plate 20 is swung. The comb-shaped electrode 22 and the comb-teeth electrode 22 are formed on the left and right end edges of the movable plate 20 and the frame 10, respectively. The comb-shaped electrode 22 is formed to protrude outward of the movable plate 10, and the comb-shaped electrode 12 is formed to protrude toward the inner side of the frame 10. The comb-teeth electrode 22 and the comb-teeth electrode 12 are disposed to face each other, are attracted to each other by electrostatic force, and are driven to move the movable panel 20 with respect to the frame 10.

A mirror 21 for reflecting aluminum or gold or the like of the laser beam is formed on the surface of the movable plate 20. The incident light is reflected by forming a mirror 21 corresponding to the wavelength of the laser beam used on the surface of the movable panel 20. The posture of the movable panel 20 with respect to the frame 10 at this time is controlled, whereby the incident light is reflected at a desired angle, and the laser beam is scanned.

Figures 13 and 14 show the cross section of the movable panel 20. Fig. 13 is a view showing a movable plate 20 in which the mirror 21 is formed in a convex shape, and Fig. 14 is a view showing a movable plate 20 in which the mirror 21 is formed in a concave shape. Here, the convex or concave shape means a convex or concave shape in which an optical effect is actively generated. For example, with respect to the movable plate 20 having a side of 1 mm, the difference in height between the edge portion and the center portion is a curved surface having irregularities of about several μm.

The movable plate 20 has a substrate layer 15 as a base, a mirror layer (metal film) 17 constituting the mirror 21, and an intermediate layer 16 formed between the substrate layer 15 and the mirror layer 17. The substrate layer 15 is formed of silicon or the like. The intermediate layer 16 contains cerium oxide as a main component and is formed on the outer surface side of the substrate layer 15 by vapor deposition. The mirror layer 17 contains aluminum as a main component and is formed on the outer surface side of the intermediate layer 16 by vapor deposition.

The substrate layer 15, the intermediate layer 16, and the mirror layer 17 contain materials having different thermal expansion coefficients (the thermal expansion coefficients of tantalum, cerium oxide, and aluminum are different), so the shrinkage ratio of the inner and outer surfaces of the movable plate due to cooling after vapor deposition Differently, the movable plate 20 is deformed into a convex shape or a concave shape. At this time, the curvature of the movable plate 20 can be adjusted by changing the thickness of the intermediate layer 16 and the mirror layer 17. Further, the curvature of the movable plate 20 can be adjusted by changing the vapor deposition temperature of the intermediate layer 16 and the mirror layer 17.

Figs. 15A to 15E show the method of forming the convex mirror 21 shown in Fig. 13 on the movable plate 20. The convex mirror 21 is realized, for example, by forming the intermediate layer 16 thicker on the substrate layer 15. First, with respect to the outer surface (upper surface in the drawing) of the substrate layer 15 shown in Fig. 15A, the intermediate layer 16 is formed thick as shown in Fig. 15B. The intermediate layer 16 is formed thick by setting the evaporation time to be long. The vapor deposition temperature at this time depends on the material of the intermediate layer 16. The movable plate 20 on which the intermediate layer 16 is formed on the outer surface of the substrate layer 15 is temporarily cooled. At this time, since the substrate layer 15 and the intermediate layer 16 contain materials having different thermal expansion coefficients, the shrinkage ratio is different, and thus the movable plate 20 is deformed into a convex shape or a concave shape. In the present embodiment, the material forming the substrate layer 15 has a larger coefficient of thermal expansion than the material forming the intermediate layer 16, and the shrinkage ratio at the time of cooling is also larger. Therefore, as shown in Fig. 15C, the movable plate 20 is deformed into a convex shape.

Thereafter, as shown in Fig. 15D, the mirror layer 17 is formed by vapor deposition on the outer surface (upper surface in the drawing) of the intermediate layer 16. Further, the movable plate 20 of the mirror layer 17 is formed on the outer surface of the intermediate layer 16, and is cooled again. At this time, the movable plate 20 is deformed into a concave shape by the contraction of the mirror layer 17, but the degree of deformation of the 15Cth image is not restored. As a result, as shown in Fig. 15E, the movable plate 20 is deformed to be deformed. In the convex state, a convex mirror 21 is formed on the outer surface thereof.

The movable plate 20 having the convex mirror 21 of Figs. 13 and 15A to E can be obtained by different vapor deposition temperatures when the intermediate layer 16 and the mirror layer 17 are formed. For example, the material forming the intermediate layer 16 and the mirror layer 17 is appropriately selected, and the vapor deposition temperature of the intermediate layer 16 is set to be higher than the vapor deposition temperature of the mirror layer 17, whereby the same movable plate 20 can be obtained.

Figs. 16A to 6E show the principle of forming the concave mirror 21 shown in Fig. 14 on the movable plate 20. The concave mirror 21 is realized, for example, by forming the intermediate layer 16 thinly on the substrate layer 15. First, with respect to the outer surface (upper surface in the drawing) of the substrate layer 15 shown in Fig. 16A, the intermediate layer 16 is formed thin as shown in Fig. 16B. The intermediate layer 16 is formed thin by setting the evaporation time to be short. The vapor deposition temperature at this time depends on the material of the intermediate layer 16. The movable plate 20 having the intermediate layer 16 formed on the outer surface of the substrate layer 15 is temporarily cooled as in the case shown in Figs. 15A to 15E. In the present embodiment, the movable plate 20 is deformed into a convex shape as in the case shown in Fig. 15C. However, since the thickness of the intermediate layer 16 is thin, the deformation of the movable plate 20 is not optically effective. The extent of it.

Thereafter, as shown in Fig. 16D, the mirror layer 17 is formed by vapor deposition on the outer side surface (upper surface in the drawing) of the intermediate layer 16. Further, the movable plate 20 of the mirror layer 17 is formed on the outer side surface of the intermediate layer 16, and is cooled again. At this time, the movable plate 20 is deformed into a concave shape by the contraction of the mirror layer 17, and as shown in Fig. 16E, the movable plate 20 is deformed into a concave shape, and a concave mirror 21 is formed on the outer surface thereof.

The movable plate 20 including the concave mirror 21 shown in Figs. 14 and 16A to E can be obtained by different vapor deposition temperatures when the intermediate layer 16 and the mirror layer 17 are formed. For example, the material for forming the intermediate layer 16 and the mirror layer 17 is appropriately selected, and the vapor deposition temperature of the intermediate layer 16 is set lower than the vapor deposition temperature of the mirror layer 17, whereby the same movable plate 20 can be obtained.

As described above, according to the wafer main body 1 of the present embodiment, since the mirror 21 of the movable panel 20 is formed in a convex shape or a concave shape, it is not necessary to provide an optical component such as a lens in the subsequent stage of the wafer main body 1, or to be convex or The concave mirror 21 produces an optical effect. The configuration of the optical system in which the machine having the wafer body 1 is incorporated is simplified, and the cost is reduced.

Further, by forming an intermediate layer 16 containing a material having a thermal expansion coefficient different from that of the substrate layer 15 and the mirror layer 17 by vapor deposition, the vapor deposition intermediate layer 16 and the mirror layer 17 can be cooled inside the movable plate 20 The shrinkage rates of the surface side and the outer surface side are different. Therefore, the thickness of the intermediate layer 16 is appropriately set in accordance with the thermal expansion coefficient of the material constituting the substrate layer 15, the intermediate layer 16, and the mirror layer 17, whereby the shape of the cooled movable plate 20 is deformed into a convex shape or a concave shape. Thereby, the wafer body 1 can be easily obtained.

Further, by forming the intermediate layer 16 at a vapor deposition temperature different from that of the mirror layer 17, the inner surface side and the outer surface side of the movable plate 20 after the vapor deposition intermediate layer 16 and the mirror layer 17 are cooled can be formed. The shrinkage rate is different. Therefore, by appropriately setting the vapor deposition temperature of the intermediate layer 16 and the mirror layer 17, the shape of the cooled movable plate 20 can be deformed into a convex shape or a concave shape, whereby the wafer main body 1 can be easily obtained.

The present invention is not limited to the configuration of the above embodiment, and an intermediate layer 16 containing materials having different thermal expansion coefficients or different vapor deposition temperatures may be formed at least between the substrate layer 15 and the mirror layer 17. Further, the present embodiment can be variously modified. For example, the material for forming the intermediate layer 16 and the mirror layer 17 is not limited to the above. For example, as a material for forming the intermediate layer 16, it may be a material containing chromium or titanium as a main component. As a material for forming the mirror layer 17, it may be a material containing gold as a main component. At this time, the characteristics of the mirror 21 can be changed corresponding to the wavelength of the reflected laser beam or the like. Thus, the degree of freedom in design can be improved by forming the movable panel 20 into a plurality of layers.

(Embodiment 4)

A wafer body (micromirror device) 1 using a movable body according to a fourth embodiment of the present invention will be described with reference to the drawings. Fig. 17 shows the constitution of the wafer body. The wafer main body 1 includes a frame 10, a movable frame 24, a movable plate 20, a first hinge 30a, a second hinge 30b, comb-shaped first electrodes 12a and 12b, and comb-shaped second electrodes 22a and 22b. The movable frame 24 is formed at the same time as the movable plate 20 by, for example, etching a portion of a three-layer SOI (Silicon on Insulator) substrate from the front and back surfaces. Further, the first hinge 30a is formed at the same time as the second hinge 30b by, for example, etching one of the three layers of the SOI substrate from the back surface.

The movable plate 20 is formed in a rectangular shape in a plan view, and is supported by the second hinge 30b so as to be swingable with respect to the movable frame 24. The second hinge 30b is formed so as to penetrate the center of the movable plate 20 in the upper and lower end edges of the movable plate 20, and functions as a twisted spring when the movable plate 20 is supported while supporting the movable plate 20. The second electrode 22b and the first electrode 12b are formed on the left and right end edges of the movable plate 20 and the movable frame 24, respectively. The second electrode 22b is formed to protrude outward of the movable plate 20, and the first electrode 12b is formed to protrude toward the inside of the movable frame 24. The second electrode 22b and the first electrode 12b are disposed to face each other, and are attracted to each other by electrostatic force, and the movable plate 20 is swing-driven with respect to the movable frame 24.

The movable frame 24 is formed in a rectangular frame shape so as to surround the periphery of the movable plate 20, and is supported by the first hinge 30a so as to be swingable with respect to the frame 10. The first hinge 30a is formed so as to penetrate the center of the movable frame 24 in the upper and lower end edges of the movable frame 24, and supports the movable frame 24 as a twisted spring when the movable frame 24 swings. The second electrode 22a and the first electrode 12a are formed on the left and right end edges of the movable frame 24 and the frame 10, respectively. The second electrode 22a is formed to protrude outward of the movable frame 24, and the first electrode 12a is formed to protrude inside the frame 10. The second electrode 22a and the first electrode 12a are disposed to face each other, and are attracted to each other by electrostatic force, and the movable frame 24 is swing-driven with respect to the frame 10.

The second hinge 30b and the first hinge 30a are disposed coaxially. Thereby, the movable plate 20 and the movable frame 24 are rotated about the same rotation axis. At this time, the rotation of the movable panel 20 with respect to the frame 10 is combined with the rotation of the movable frame 24 with respect to the frame 10 and the rotation of the movable panel 20 with respect to the movable frame 24. Further, a metal film 12 such as aluminum or gold for reflecting a laser beam is formed on the surface of the movable plate 20. A metal film 12 corresponding to the wavelength of the laser beam used is formed on the surface of the movable plate 20, thereby reflecting the incident light. By controlling the posture of the movable panel 20 with respect to the frame 10 at this time, the incident light is reflected at a desired angle, and the laser beam is scanned.

Fig. 18 is a view showing the operation of the wafer main body 1 of the present embodiment. The one-point chain line in the figure indicates the transition of the deflection angle (posture) with respect to the movable frame 24 of the frame 10, and the two-point chain line indicates the transition of the deflection angle with respect to the movable panel 20 of the movable frame 24. The deflection angle of the movable panel 20 relative to the frame 10 (i.e., the absolute deflection angle of the movable panel 20) is shown by the deflection angle of the movable frame 24 with respect to the frame 10 as indicated by the one-dot chain line and the two-dot chain line. The yaw angles of the movable plates 20 with respect to the movable frame 24 are added together, and are indicated by solid lines in Fig. 18. According to the wafer main body 1 of the present embodiment, a region in which the deflection angle of the movable plate 20 linearly changes (in the waveform shown by the solid line, an approximate straight line region) is enlarged, and is offset with respect to the movable plate 20 of the frame 10. The corner transition is close to the ideal triangular waveform shown by the dashed line in Figure 18.

As a transition of the deflection angle of the movable panel 20 with respect to the frame 10, an ideal triangular wave is represented by the following formula and developed in a Fourier series.

In Equation 1, it is considered that the first item and the second item correspond to the movable plate 20 or the movable frame 24, respectively, and the movable plate 20 and the movable frame 24 satisfy the resonance frequency of 1:3 and the maximum deflection angle (amplitude) of 9:1. When the relationship, or the resonance frequency is 3:1 and the maximum deflection angle is 1:9, the transition of the deflection angle with respect to the movable plate 20 of the frame 10 can be approximated to an ideal triangular wave. The resonance frequency and the maximum deflection angle of the movable plate 20 and the movable frame 24 can be made by the mass of the movable plate 20 and the movable frame 24, the torsional rigidity of the second hinge 30b and the first hinge 30a (spring constant), and the second The potential difference between the electrode 22b and the first electrode 12b and the second electrode 22a and the first electrode 12a is appropriately set. In the present embodiment, the movable frame 24 is larger than the movable plate 20, and therefore the movable plate 20 and the movable frame 24 are preferably set to have a relationship of a resonance angle of 3:1 and a maximum deflection angle of 1:9.

As described above, according to the wafer main body 1 of the present embodiment, the movable plate 20 is independently driven by the respective electrodes 12b and 22b, and the movable frame 24 is independently driven by the respective electrodes 12a and 22a. At this time, the swing of the movable frame 24 by the respective electrodes 12a and 22a is transmitted to the movable panel 20 via the second hinge 30b, and the swing of the movable panel 20 by the respective electrodes 12b and 22b (i.e., relative) The relative swinging of the movable plate 20 of the movable frame 24 is combined. Thereby, the degree of freedom in designing the absolute vibration waveform with respect to the movable panel 20 of the frame 10 can be improved, so that the movable panel 20 can be swung in a desired waveform.

Further, since the second hinge 30b is disposed coaxially with the first hinge 30a, the absolute vibration waveform of the movable plate 20 can be easily brought close to a desired waveform. Further, by setting the resonance frequency and the maximum deflection angle of the movable plate 20 and the movable frame 24 to the above relationship, the vibration waveform of the movable plate 20 with respect to the frame 10 can be approximated to the waveform of the triangular wave. Thereby, it is possible to enlarge the region in which the deflection angle of the movable plate 20 linearly changes, and it is possible to improve the scanning accuracy of the laser beam. Further, when the movable body of the embodiment is applied to the acceleration sensor, the potential difference generated in each of the electrodes 12a, 12b, 22a, and 22b is detected, whereby the acceleration can be detected with high precision. Further, the electrostatic force of each of the electrodes 12a, 12b, 22a, and 22b can swing and drive the movable plate 20 and the movable frame 24, so that the wafer body 1 can be obtained in a simple and inexpensive configuration. Moreover, since the mirror 21 is formed on the surface of the movable plate 20, the wafer main body 1 as a micromirror element can be obtained simply and inexpensively.

The present embodiment can be variously changed. For example, by appropriately changing the relationship between the resonance frequency and the maximum deflection angle of the movable panel 20 and the movable frame 24, the vibration waveform of the movable panel 20 with respect to the frame 10 can be changed.

For example, a fine wave as an example of a vibration waveform of the movable plate 20 with respect to the frame 10 is represented by the following equation and developed in a Fourier series.

Therefore, by setting the movable plate 20 and the movable frame 24 to satisfy the relationship of the resonance frequency of 1:2 and the maximum deflection angle of 2:1, or satisfying the relationship of the resonance frequency of 2:1 and the maximum deflection angle of 1:2, The movable plate 20 is swung by approximating the vibration waveform of the relatively fine wave.

Further, as another example of the vibration waveform of the movable plate 20 with respect to the frame 10, the rectangular wave is represented by the following equation and developed in a Fourier series.

Therefore, the movable plate 20 and the movable frame 24 can be set to satisfy the relationship of the resonance frequency of 1:3 and the maximum deflection angle of 3:1, or satisfy the relationship of the resonance frequency of 3:1 and the maximum deflection angle of 1:3, thereby enabling The movable plate 20 is swung by approximating a vibration waveform of a relatively rectangular wave.

Further, the present invention is not limited to the configuration in which the second hinge 30b and the first hinge 30a are disposed coaxially, and may be arranged in parallel or at a predetermined angle. At this time, the degree of freedom in designing the vibration waveform with respect to the movable panel 20 of the frame 10 is improved. Further, the shape of the movable plate 20 and the movable frame 24 is not limited to that shown in Fig. 17, and may be any shape.

(Embodiment 5)

Hereinafter, a wafer body (micromirror device) 1 using the movable body 20 according to the fifth embodiment of the present invention will be described. Fig. 19 is a view showing the configuration of a wafer body (micromirror device) 1 of the fifth embodiment. The wafer main body 1 of the present embodiment differs from the wafer main body 1 of the fourth embodiment in that a plurality of movable frames 24 disposed between the frame 10 and the first movable plate 10 are provided in Fig. 17. That is, in the present embodiment, a plurality of movable frames 24 (24a, 24b, 24c, and 24d) are disposed outside the movable panel 20, and the frame 10 is disposed outside the movable frame 20. The movable frame 24 and the movable plate 20 are connected in series by a hinge 30 (30a, 30b, 30c, 30d, 30e), and the outermost movable frame 24a of Fig. 19 is connected to the frame 10 by the first hinge 30a. The number of the plurality of movable frames disposed on the outer side of the movable panel 20 is not limited to the example shown in FIG. In the wafer main body 1 of the present embodiment, the movable plate 20 can be oscillated with high precision even by a plurality of movable frames 24 connected in series, even with a vibration waveform other than the triangular wave.

20 is a view showing a movable panel 20 when four movable frames 24 are disposed outside the movable panel 20, and the relationship between the resonant frequency and the maximum deflection angle of the movable panel 20 and each movable frame 24 is appropriately set according to Equation 2. The deflection angle with each movable frame 24 is changed. The relative deflection angles of the movable plate 20 and each movable frame 24 are respectively represented by a point chain, a two-dot chain line, a three-dot chain line, a dotted line, and a broken line, and the deflection angles of the movable plate 20 with respect to the frame 10 are respectively The waveforms of the one-point chain line, the two-point chain line, the three-point chain line, the dotted line, and the dotted line are combined by a solid line. According to the present embodiment, as compared with the fourth embodiment, the movable plate 20 can be tilted by a vibration waveform that approximates a more preferable fine wave.

21 and 20, four movable frames 24a, 20b, 20c, and 20d are disposed outside the movable plate 20, and the resonance frequency of the movable plate 20 and each movable frame 24 is appropriately set according to Equation 3. The transition of the deflection angle of the movable panel 20 and each movable frame 24 in the case of the relationship of the maximum deflection angle. As described above, according to the present embodiment, compared with the fourth embodiment, the movable plate 20 can be tilted by a vibration waveform similar to a more ideal rectangular wave.

1. . . Chip body

1'. . . Substrate

2. . . First cover

2'. . . First cover

3. . . Second cover

4. . . Degassing agent

5. . . Base

5'. . . Base

6. . . Conductive member

6'. . . Welding line

7. . . Protection department

10. . . frame

10'. . . frame

10a. . . Slit

12. . . First electrode

12'. . . Fixed electrode

12a. . . tooth

12b. . . First electrode

13. . . Solder pad

13'. . . Solder pad

13a. . . First pad

13b. . . 2nd pad

13c. . . 2nd pad

15. . . Substrate layer

16. . . middle layer

17. . . Mirror layer

20. . . Movable part

20'. . . Movable part

20a. . . Slit

twenty one. . . Reflective film, mirror surface

twenty one'. . . Mirror surface

21a. . . Reflective film

twenty two. . . Second electrode

twenty two'. . . Movable electrode

22a. . . Second electrode

22b. . . Second electrode

twenty four. . . Movable frame

24a. . . Movable frame

24b. . . Movable frame

24c. . . Movable frame

24d. . . Movable frame

27. . . Second movable electrode

29. . . Support

30. . . Hinge

30'. . . Hinge

30a. . . Hinge

30b. . . Hinge

30d. . . Hinge

30e. . . Hinge

31. . . Anchor

32. . . Anchor

36. . . Island

37. . . Conductive part

38. . . First conductive structure

39. . . Second conductive structure

100. . . SOI substrate

100'. . . SOI substrate

100a. . . First layer

100b. . . Second layer

100c. . . Insulation

101a'. . . First substrate

101b'. . . Second substrate

101c'. . . Insulation

10a. . . Slit

111a. . . Cerium oxide film

111b. . . Cerium oxide film

132. . . Third photoresist layer

201. . . First recess

202'. . . Through hole through hole

202'. . . Through hole

202a. . . Through hole

202b. . . Through hole

202c. . . Through hole

203a. . . Trench

203b. . . Trench

203c. . . Trench

206'. . . Through electrode

301. . . Second recess

501. . . Concave

502a. . . Power supply

502b. . . Power supply

504a. . . External electrode

504b. . . External electrode

506'. . . Lead terminal

510'. . . Concave

600. . . MEMS chip

A. . . line

A'. . . line

B. . . line

B'. . . line

Fig. 1 is a schematic exploded perspective view of a MEMS device (MEMS optical scanner) according to the first embodiment.

Fig. 2A is a schematic perspective view of the MEMS device of the first embodiment.

2B is a schematic cross-sectional view of a principal part of the MEMS device of the first embodiment.

Fig. 3A is a schematic plan view showing a MEMS wafer in the MEMS device of the first embodiment.

Fig. 3B is a schematic cross-sectional view taken along line AA of Fig. 3A of the MEMS wafer in the MEMS device of the first embodiment.

Fig. 3C is a schematic cross-sectional view taken along line A-B' of Fig. 3A of the MEMS wafer in the MEMS device of the first embodiment.

Fig. 4A is a cross-sectional view showing a state in which a pad and a reflective film are formed in the manufacture of a MEMS wafer in the MEMS device of the first embodiment.

Fig. 4B is a cross-sectional view showing a state in which the first layer is etched in the manufacture of the MEMS wafer in the MEMS device of the first embodiment.

Fig. 4C is a cross-sectional view showing a state in which the second layer is etched in the manufacture of the MEMS wafer in the MEMS device of the first embodiment.

4D is a cross-sectional view showing a state in which the first cover and the first cover are bonded to the wafer body in the manufacture of the MEMS wafer in the MEMS device according to the first embodiment.

Fig. 5 is a schematic perspective view showing another configuration example of the MEMS device of the first embodiment.

Fig. 6 is a schematic exploded perspective view of the MEMS device (MEMS optical scanner) of the second embodiment.

Fig. 7 is a schematic perspective view of the MEMS device of the second embodiment.

Fig. 8 is a schematic perspective view showing a MEMS wafer in the MEMS device of the second embodiment.

Fig. 9A is a cross-sectional view showing a case where a tantalum oxide film is formed in the manufacture of a MEMS wafer in the MEMS device of the second embodiment.

Fig. 9B is a cross-sectional view showing a state in which a first layer is patterned in the manufacture of a MEMS wafer in the MEMS device of the second embodiment.

Fig. 9C is a cross-sectional view showing a state in which a pad and a reflective film are formed in the manufacture of a MEMS wafer in the MEMS device of the second embodiment.

Fig. 9D is a cross-sectional view showing a state in which the first layer is etched in the manufacture of the MEMS wafer in the MEMS device of the second embodiment.

Fig. 9E is a cross-sectional view showing a state in which the second layer is etched in the manufacture of the MEMS wafer in the MEMS device of the second embodiment.

Fig. 9F is a cross-sectional view showing the state in which the first cover and the first cover are bonded to the wafer main body in the manufacture of the MEMS wafer in the MEMS device of the second embodiment.

Fig. 10 is a schematic perspective view showing another configuration example of the MEMS device of the second embodiment.

Fig. 11A is a schematic plan view showing a mirror forming substrate of the prior art.

Fig. 11B is a schematic cross-sectional view showing a mirror-formed substrate packaged on a substrate in the prior art.

Fig. 11C is a schematic cross-sectional view showing a MEMS device (MEMS optical scanner) in the prior art.

Fig. 12 is a perspective view showing the wafer body of the third embodiment.

Figure 13 is a cross-sectional view showing a movable plate having a convex mirror of the third embodiment.

Fig. 14 is a cross-sectional view showing a movable plate having a concave mirror of the third embodiment.

Fig. 15A is a cross-sectional view showing the substrate layer in the process of forming a convex mirror on the movable plate.

Fig. 15B is a cross-sectional view showing the intermediate layer in the process of forming a convex mirror on the movable plate.

Fig. 15C is a cross-sectional view showing the movable plate after cooling in the process of forming a convex mirror on the movable plate.

Fig. 15D is a cross-sectional view showing a mirror layer formed in a process of forming a convex mirror on a movable plate.

Fig. 15E is a cross-sectional view showing a mirror layer which is deformed into a convex shape in the process of forming a convex mirror on the movable plate.

Fig. 16A is a cross-sectional view showing the substrate layer in the process of forming a concave mirror on the movable plate.

Fig. 16B is a cross-sectional view showing the intermediate layer in the process of forming a concave mirror on the movable plate.

Fig. 16C is a cross-sectional view showing the movable plate after cooling in the process of forming a concave mirror on the movable plate.

Fig. 16D is a cross-sectional view showing a mirror layer formed in a process of forming a concave mirror on a movable plate.

Fig. 16E is a cross-sectional view showing a mirror layer which is deformed into a concave shape in the process of forming a concave mirror on the movable plate.

Figure 17 is a perspective view of the wafer body of the fourth embodiment.

Fig. 18 is a view showing the operation of the wafer main body of the fourth embodiment, wherein the one-dot chain line indicates the deflection angle with respect to the movable frame of the fixed portion, and the two-dot chain line indicates the deflection angle with respect to the movable plate of the movable frame. The line system represents the transition of the deflection angle with respect to the movable plate of the frame.

Figure 19 is a plan view showing the configuration of a wafer body according to Embodiment 5 of the present invention.

Fig. 20 is a view showing the operation of the wafer main body according to the fifth embodiment of the present invention.

Figure 21 is a view showing the operation of another wafer body according to Embodiment 5 of the present invention.

1. . . Chip body

2. . . First cover

3. . . Second cover

4. . . Degassing agent

5. . . Base

10. . . frame

10a. . . Slit

12. . . First electrode

13a. . . First pad

13b. . . 2nd pad

20. . . Movable part

twenty one. . . Reflective film, mirror surface

twenty two. . . Second electrode

30. . . Hinge

31. . . Anchor

36. . . Island

37. . . Conductive part

38. . . First conductive structure

39. . . Second conductive structure

100. . . SOI substrate

100a. . . First layer

100b. . . Second layer

100c. . . Insulation

201. . . First recess

202a. . . Through hole

202b. . . Through hole

203a. . . Trench

203b. . . Trench

301. . . Second recess

501. . . Concave

502a. . . Power supply

502b. . . Power supply

504a. . . External electrode

504b. . . External electrode

600. . . MEMS chip

Claims (16)

A MEMS device includes a MEMS wafer and a substrate for accommodating the MEMS wafer. The MEMS device is characterized in that the MEMS wafer includes a wafer body formed of a semiconductor substrate, and a first cover to be bonded to the upper surface of the wafer body, and a first power supply body and at least one second power supply body to be connected to an external voltage source, wherein the wafer body includes a fixing portion, a movable portion supported by the fixing portion, at least one first electrode electrically connected to the fixing portion, and at least one second electrode electrically connected to the movable portion, and configured to be applied to the above a driving force caused by a voltage between the first electrode and the second electrode, wherein the movable portion is displaced relative to the fixing portion, and the fixing portion on the upper surface of the wafer main body is provided with the first electrode and a first pad electrically connected to the second electrode and at least one second pad, wherein the first pad and the second pad are respectively electrically connected to the first power supply by the conductive member The first and second power supply bodies are electrically connected to each other, and one of the first pads and the second pads on the upper surface of the wafer main body is exposed to the through hole, and the conductive member is formed from the first The first power supply body and the second power supply body extend through the through holes to the first and second pads, and the first cover includes a groove for receiving the through holes. Extending to the above-described first power supply body and the second power supply body The conductive member extends from each of the through holes to the side surface of the first cover, and is open to the side surface and the upper surface of the first cover. The MEMS device according to claim 1, wherein the first cover is made of an insulating substrate, and the conductive member is formed of ruthenium. The MEMS device of claim 1, wherein the conductive member is a bonding wire. The MEMS device of claim 1, wherein the external voltage source is formed on a different surface of the substrate. The MEMS device of claim 1, wherein the movable portion has a movable plate having a mirror on an upper surface thereof, the fixed portion is a frame surrounding the shape of the mirror, and the movable plate is hinged via a hinge Supported in the above framework. The MEMS device according to claim 1, wherein a peripheral portion of the first cover is hermetically bonded to a peripheral portion of the upper surface of the wafer body, and a peripheral portion of the lower surface of the wafer body is The second cover is hermetically joined, and an airtight space is formed between the first cover and the second cover. The movable portion is accommodated in the airtight space, and the through holes are sealed by a sealing resin. The MEMS device according to claim 3, wherein each of the grooves is filled with the sealing resin. The MEMS device according to claim 6, wherein the first pad and the second pad are formed on a film on an upper surface of the wafer body. The opening area of each of the through holes is larger than the area of the corresponding first pad and the second pad, and the first pad and the second pad are completely accommodated in the lower end opening of each through hole. The microelectromechanical system device according to claim 6, wherein a deaerator is provided on one of the first cover and the second cover, and the deaerator is exposed to the airtight space for capturing Impurities generated in the airtight space. The microelectromechanical system device according to any one of claims 1 to 9, wherein a recess for accommodating the MEMS wafer is formed on the substrate, and the power supply body is exposed on a base surrounding the recess. The upper surface of the peripheral portion and the height position of the power supply body are lower than the upper ends of the respective through holes. The MEMS device of claim 5, wherein the mirror of the movable plate is convex or concave. The MEMS device according to claim 5, wherein the movable plate is formed by laminating a mirror layer on the substrate layer via an intermediate layer, and the intermediate layer is vapor-deposited on the substrate layer, and the reflection is performed. The mirror layer is vapor deposited on the intermediate layer. The MEMS device of claim 12, wherein the intermediate layer is formed of a material having a thermal expansion coefficient different from that of the substrate layer and the mirror layer. A MEMS device as claimed in claim 12 or 13, wherein The intermediate layer and the mirror layer are formed of a material that can be vapor-deposited at different temperatures. The MEMS device of claim 12, wherein the intermediate layer is formed mainly of cerium oxide, and the mirror layer is mainly formed of aluminum. The MEMS device of claim 12, wherein the intermediate layer is formed mainly of chromium or titanium, and the mirror layer is mainly formed of gold.