JP3767836B2 - Deformable mirror and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a deformable mirror capable of deforming a reflecting surface, and more particularly to a deformable mirror that enables an accurate recording / reproducing operation with respect to optical disks having different thicknesses.
[0002]
[Prior art]
In recent years, optical disks are capable of recording a large amount of information signals at high density, and thus are being used in many fields such as audio, video, and computers. FIG. 17 is a configuration diagram showing an example of an optical pickup used in these apparatuses.
[0003]
In the optical pickup 100 shown in FIG. 17, the light emitted from the semiconductor laser 101 becomes parallel light 103 by the collimator lens 102. The parallel light 103 enters the beam splitter 104 and travels straight, passes through the quarter-wave plate 105, is reflected by the reflection mirror 106, and enters the objective lens 107. The light incident on the objective lens 107 is collected and forms a light spot 109 on the information storage medium surface of the optical disk 108 supported by the drive shaft of the rotary motor 113.
[0004]
Next, the reflected light 110 reflected by the optical disc 108 is incident on the beam splitter 104 again through the objective lens 107, the reflection mirror 106, and the quarter-wave plate 105. The reflected light 110 is reflected by the polarization beam splitter 104 by the action of the quarter-wave plate 105, passes through the aperture lens 111, and is received by the photodetector 112. The photodetector 112 detects the reproduction signal by detecting the light intensity of the reflected light.
[0005]
The objective lens 107 used in the optical pickup having such a configuration is designed in consideration of the thickness of the optical disk 108. However, for an optical disc having a thickness different from this design value, spherical aberration occurs, image forming performance deteriorates, and recording or reproduction becomes impossible.
[0006]
Conventionally, the thickness of an optical disk used for a compact disk, a video disk, an ISO standard magneto-optical disk apparatus for data, and the like has been approximately the same (about 1.2 mm). Therefore, it is possible to record / reproduce different types of optical disks (compact disk, video disk, magneto-optical disk, etc.) with one optical pickup.
[0007]
In recent years, in order to increase the density of optical disks, (1) a method for increasing the numerical aperture (NA) of the objective lens to improve optical resolution, and (2) a method for providing recording layers in multiple layers. Is being considered.
[0008]
As described in (1) above, when the NA of the objective lens is increased, the diameter of the focused beam decreases in inverse proportion, but in order to keep the disc tilt tolerance to the same extent as that of an objective lens having a normal NA. It is necessary to reduce the thickness of the disk. For example, if the NA of the objective lens is changed from 0.5 to 0.6, the disc tilt tolerance cannot be kept to the same level unless the disc thickness is reduced from 1.2 mm to 0.6 mm.
[0009]
However, when the disc is thinned in this way, if an objective lens corresponding to the thin optical disc is used to record and reproduce a thick optical disc, the spherical aberration increases and the imaging point widens, which makes recording and reproduction difficult. Become. Therefore, compatibility with a thick optical disc cannot be maintained, and two optical pickups are used, and a thin optical disc and a thick optical disc must be recorded and reproduced with separate optical pickups.
In addition, as described in (2) above, when using a multi-layer disc in which a plurality of recording layers are provided via a transparent layer having a certain thickness, the recording capacity is greatly increased with one disc. However, since the position of each recording layer as seen from the objective lens is different, accurate information recording / reproduction cannot be performed with one optical pickup.
[0010]
As means for solving such a problem, a method of correcting the substrate thickness by a deformable mirror is known. (Japanese Patent Laid-Open No. 5-151591).
[0011]
FIG. 18 shows an optical system of an optical device using this deformable mirror. In FIG. 18, a beam 103 is emitted from the semiconductor laser 101, passes through the collimator lens 102, the beam splitter 101, and the quarter wavelength plate 105 and reaches the beam splitter 202. Further, the beam 103 passes through the beam splitter 202 and the quarter wave plate 201 and reaches the deformable mirror 200.
[0012]
The deformable mirror 200 is configured so that its mirror surface can be deformed. When the disk is thick, the deformable mirror driving circuit 203 deforms the mirror surface so that the disk becomes thicker than the beam 103. A spherical aberration that cancels the generated spherical aberration is given. The beam 103 returns through the quarter wave plate 201, is reflected by the beam splitter 202, and reaches the objective lens 107. The light incident on the objective lens 107 is condensed and forms a light spot 109 on the information recording medium surface of the optical disk 108.
[0013]
Next, the reflected light reflected by the optical disk 108 passes through the objective lens 107 and the beam splitter 202, the quarter-wave plate 201, the deformable mirror 200, and the quarter-wave plate 105 again to the beam splitter 104. Incident. The reflected light 110 is reflected by the beam splitter 104, passes through the aperture lens 111, and is received by the photodetector 112. The photodetector 112 detects the reproduction signal by detecting the light intensity of the reflected light.
[0014]
FIG. 19 is a diagram showing a specific configuration of the deformable mirror 200 described in Japanese Patent Laid-Open No. 5-151591, which is ““ Adaptive optics for optimization of image resolution ”(“ Applide Optics ”, vol. 26). , pp.3772-3777, (1987), JPGaffarel, etc.) ”.
[0015]
The deformable mirror 200 includes a deformation plate 301 having a mirror surface 300 formed on the surface thereof, each piezoelectric actuator 302 that pressurizes several places on the back side of the deformation plate 301, the deformation plate 301, each piezoelectric actuator 302, and the deformation plate 301. It is composed of a fixed base substrate and the like, and the voltage applied to each piezoelectric actuator 302 is changed to displace the deformation plate 301 by a desired amount and deform the mirror surface 300 into a desired shape.
[0016]
[Problems to be solved by the invention]
However, in the deformable mirror using each piezoelectric actuator 302 shown in FIG. 19, if an error occurs in the drive voltage of the piezoelectric actuator 302, an error also occurs in the displacement. In particular, when there is an error in the driving voltage of each piezoelectric actuator 302, the deformable mirror 300 is greatly deviated from the desired surface.
[0017]
Further, when the environmental temperature changes, there is a problem that the displacement of each piezoelectric actuator 302 is affected by thermal expansion, and the mirror surface 300 is displaced from a desired mirror surface.
[0018]
Further, the diameter of the light beam for aberration correction is about 4 mm, and in order to realize accurate deformation of the deformable mirror, a large number of piezoelectric actuators 302 must be provided in the range of 4 mm in diameter, and the configuration becomes complicated. In addition, the assembly becomes complicated, the deformable mirror main body becomes large, and the optical pickup becomes large.
[0019]
Therefore, the present invention has been made to solve the above-described problems, is easy to control, is hardly affected by the environmental temperature, and can deform and hold the mirror surface with high accuracy. Another object of the present invention is to provide a deformable mirror that can be manufactured at low cost with a small and simple structure and a method for manufacturing the deformable mirror.
[0020]
Another object of the present invention is to provide a deformable mirror which can improve the deformability, and as a result, does not generate large stress locally, and can improve its life, and a method for manufacturing the same. To do.
[0021]
[Means for Solving the Problems]
The deformable mirror of the present invention is Reflective surface that reflects incident light on the surface Having membranous A flexible member; Formed by a single crystal Si substrate, The outer circumference of the flexible member edge Part An opening was formed on the inside to support A support frame; The Support frame Are arranged opposite to each other via the flexible member, The opening Inside Opposite to Said Form a space that allows elastic deformation of the flexible member In a circular area Curved surface Substrate provided with And Said Support frame Of the above Aperture Is an octagon Formed into Is , Said The flexible member is The reflective frame is supported by the support frame so as to cover the opening and the space in a flat state, and the curved portion of the substrate is deformed into the curved portion by elastic deformation of the flexible member. It is formed so as to give a predetermined aberration to light incident on the reflecting surface through the opening by being in close contact with the light. .
[0022]
According to such a configuration, the reflecting surface of the flexible member is deformed following the cross-sectional shape of the curved surface portion. For this reason, if the shape accuracy of the curved surface portion is kept high, the deformed shape of the reflecting surface can be determined with high accuracy, and aberration correction can be performed with high accuracy.
[0023]
In addition, since the opening inside the support frame that borders the outer peripheral edge of the flexible member is formed in an octagonal shape, stress applied to the flexible member is substantially applied to the entire flexible member during deformation. It can be evenly distributed, the deformability of the flexible member is improved, and the life is improved. Moreover, it is easy to hold | maintain the reflective surface of this flexible member to a plane at the time of no deformation | transformation, and this state can be maintained stably. The shape of the opening inside the support frame is most preferably a regular octagon.
[0024]
On the other hand, the shape of the curved surface portion may be any shape as long as it can correct the aberration specified in advance. In an optical device equipped with this deformable mirror, the reflecting surface of the flexible member is held flat, and no aberration is given to incident light on the reflecting surface of the flexible member, and the flexible member is It is possible to selectively set a state in which a predetermined aberration is given to light incident on the reflecting surface of the flexible member by sucking the curved surface of the reference surface substrate and elastically deforming the flexible member. Thereby, a plurality of optically different lights can be generated.
[0025]
Said Support frame is {100} plane and [110] orientation flat Preferably have sides parallel to .
[0026]
Further, the present invention provides the above Deformable mirror of Production method Because Single crystal Si substrate , With octagonal opening Covered by etching mask, The Single crystal Si substrate Wet The opening of the support frame is formed by etching. Including the etching process , In the etching step, Etching mask The four sides of the octagon of the opening in FIG. 2 are two sides parallel to each other and two sides perpendicular to the two sides. Along the {110} plane perpendicular to the surface of the single crystal Si substrate And the positive of the opening The other four sides of the octagon The above On the {100} plane perpendicular to the surface of the single crystal Si substrate The etching mask is arranged so as to be in line .
[0027]
When the single crystal Si substrate is etched under such conditions, an octagonal one can be obtained as the opening of the support frame.
[0028]
Of the etching process before, Said Laminating flexible member on single crystal SI substrate In the etching step, Without etching the flexible member, Said Etching single crystal SI substrate By You may form the opening part of a support frame.
[0029]
As a result, the support frame and the flexible member can be formed simultaneously. Also, if the surface of the single crystal Si substrate is flattened, the flexible member to be laminated can be formed in a flat shape. The reflective surface of the sex member can be held flat.
[0030]
Said Etching mask Of the opening at Octagonal Said Four sides along the {110} plane Length of Are equal to each other and the octagonal Said The other four sides along the {100} plane Length of Should be equal to each other.
[0031]
As a result, the four sides on the octagonal {110} plane forming the opening of the support frame are equal to each other, and the other four sides on the octagonal {100} plane are equal to each other. The octagon is shaped.
[0032]
Said Etching mask Of the opening at Octagonal Said Of four sides along the {110} plane each The length is A, and the octagon Said Of the other four sides along the {100} plane each If the length is B, it is preferable that A <B.
[0033]
Thereby, the octagon that forms the opening of the support frame can be reproduced well.
[0034]
More preferably, Said The thickness of the support frame is T, The Support frame In the above Aperture of When the average value of the lengths of the sides of the octagon is L and L> 2 * T * (1 / tan (54.7 °) + √ (2)), Said Etching mask Of the opening at The lengths A and B of each side of the octagon are given by the following equations (1) and (2) expressed .
A = L-2 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (1)
B = L + 2 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (2)
In this case, the octagon that forms the opening of the support frame is a regular octagon.
[0035]
Further, the present invention provides the above In a method of manufacturing a deformable mirror, a single crystal Si substrate is used. Has a square opening Covered by etching mask, The Single crystal Si substrate Wet The opening of the support frame is formed by etching. Including an etching step, In the etching step, the etching mask Square of the opening at 4 sides But said On the {100} plane perpendicular to the surface of the single crystal Si substrate The etching mask is arranged so as to be in line .
[0036]
Here, it is assumed that the opening of the support frame is slightly small, and the length A of four sides along the octagonal {110} plane forming the etching mask is 0 (A = 0). When the single crystal Si substrate is etched under the condition described in Item 8, an octagonal opening can be obtained as the opening of the support frame.
[0037]
Of the etching process before, Said Laminating flexible member on single crystal Si substrate In the etching step, Without etching the flexible member, Said Etching single crystal Si substrate By You may form the opening part of a support frame.
[0038]
As a result, the support frame and the flexible member can be formed simultaneously. In addition, the flexible member laminated on the single crystal Si substrate can be formed in a flat shape, and after the etching is finished, the reflective surface of the flexible member is held flat by the opening of the support frame. be able to.
[0039]
Said Etching mask Of the opening at The quadrangle is preferably a square.
[0040]
More preferably, Said The thickness of the support frame is T, Said support frame Aperture of If the average value of the length of each side of the octagon is L, and L = 2 * T * (1 / tan (54.7 °) + √ (2)), Said Etching mask Of the opening at The length C of one side of the square is given by the following equation (3) expressed .
C = 4 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (3)
In this case, the octagon that forms the opening of the support frame is a regular octagon.
[0041]
Further, the present invention provides the above Deformable mirror of In the manufacturing method, a single crystal Si substrate is Has an opening Covered by etching mask, The Single crystal Si substrate Wet The opening of the support frame is formed by etching. Including an etching step, Of the etching mask The opening is From the square area and each corner of the square area Along each diagonal direction Radially Extend In the etching step, each diagonal line connecting the vertices of the wedge-shaped regions facing each other in the etching mask is perpendicular to the surface of the single crystal Si substrate {110 } In a state along the plane, so that each side of the rectangular region of the opening in the etching mask is in a state along the {100} plane perpendicular to the surface of the single crystal Si substrate. The etching mask is disposed. .
[0042]
Here, it is assumed that the opening of the support frame is very small, and when the single crystal Si substrate is etched under the conditions described in claim 10, an octagonal shape is formed as the opening of the support frame. Can be obtained.
[0043]
Of the etching process before, Said Laminating flexible member on single crystal Si substrate In the etching step, Without etching the flexible member, Said Etching single crystal Si substrate By You may form the opening part of a support frame.
[0044]
As a result, the support frame and the flexible member can be formed simultaneously. Moreover, the flexible member laminated | stacked on a single crystal Si substrate can be formed in planar shape, and the reflective surface of a flexible member can be hold | maintained at a plane by the opening part of a support frame.
[0045]
Preferably, Said The thickness of the support frame is T, and the support frame In the above Aperture of If the average value of the length of each side of the octagon is L, and L <2 * T * (1 / tan (54.7 °) + √ (2)),
Said Etching mask Of the opening at Connect the vertices of each wedge-shaped area facing each other For each diagonal Length D, In the opening Of rectangular area Face each other The separation distance E of each side, and The Rectangular area Located between each wedge-shaped region in Each side Length of F is the following formula (4), (5) and (6) expressed .
D = L * (1 + √ (2)) + 2 * T / tan (54.7 °) ± 6% (4)
E = L * (1 + √ (2)) − 2 * T ± 6% (5)
F = L (6)
In this case, the octagon that forms the opening of the support frame is a regular octagon.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
1 to 4 show a first embodiment of the deformable mirror of the present invention. FIG. 1 is a plan view showing a deformable mirror according to the first embodiment, FIG. 2 is a sectional view showing the deformable mirror broken along line XX in FIG. 1, and FIG. 3 is a modification of FIG. FIG. 4 is an exploded perspective view showing the deformable mirror of FIG. 1 in an exploded manner.
[0047]
The deformable mirror 1 includes a silicon substrate 50, a flexible member 2 attached to the back side of the silicon substrate 50, and a reference surface substrate 6 disposed below the flexible member 2. The silicon substrate 50 has an opening 53 whose inside is opened in an octagon, and the center of the opening 53 is slightly shifted to the left from the shape center of the silicon substrate 50 in FIG. .
[0048]
As shown in FIG. 4, the flexible member 2 has a square shape slightly larger than the opening 53, and an outer peripheral edge thereof is fixed to a flat support surface of the silicon substrate 50. More specifically, the outer peripheral edge of the flexible member 2 is fixed to the support surface of the silicon substrate 50 via the silicon thermal oxide film 51a. Further, the flexible member 2 is fixed to the silicon substrate 50 in a state in which it is flattened by applying a tensile stress.
[0049]
Since the flexible member 2 can be deformed inside the opening 53, the deformable region of the flexible member 2 is octagonal like the opening 53.
[0050]
Here, as shown in FIG. 2, the flexible member 2 includes an upper electrode layer 8 and a reflective film 10 laminated thereon. The upper electrode layer 8 is made of a Ni film having a thickness of about 8 μm, for example. The reflective film 10 is made of a thin film such as Au or Al having a thickness of about 1 μm, for example.
[0051]
It is also possible to eliminate the reflective film 10 and use the surface of the upper electrode layer 8 as it is as a reflective surface. In this case, there is an advantage that the number of parts can be reduced and the manufacturing cost can be reduced.
[0052]
The reference surface substrate 6 has a cylindrical shape as shown in FIG. 4 and is produced by, for example, a glass mold method. In the reference surface substrate 6, the lower electrode layer 12, the wiring part 55, the wiring pad 56, and the spacer layer 54 are formed on the side facing the flexible member 2, and the insulating layer 9 is formed thereon (see FIG. (See FIG. 2). The lower electrode layer 12, the wiring part 55, and the wiring pad 56 are continuous.
[0053]
As shown in FIG. 2, the support surface on the outer periphery on the front side of the reference surface substrate 6 is flat, and an uneven surface (curved surface) 3 is formed on the inside thereof, and a lower electrode layer 12 is formed thereon. Further, a chamfered portion 59 is provided on the outer peripheral edge of the flat support surface, a wiring portion 55 is formed on the support surface, and a wiring pad 56 is formed on the chamfered portion 59. The chamfered portion 59 is not provided with the insulating layer 9. Therefore, the insulating layer 9 is not attached to the wiring pad 56 on the chamfered portion 59 (see FIG. 2).
[0054]
The lower electrode layer 12 and the spacer layer 54 are made of Al having a thickness of about 0.1 μm, for example, and the insulating layer 9 is made of silicon oxide having a thickness of about 0.5 μm, for example.
[0055]
Here, the wiring pad 56 is provided to electrically connect a wiring portion 55 for applying a voltage to the lower electrode layer 12 and a lower electrode pad 58 described later. The wiring portion 55 and the wiring pad 56 are formed with the same thickness and material as the lower electrode layer 12.
[0056]
The silicon substrate 50 and the reference surface substrate 6 are bonded with an adhesive so that the upper electrode layer 8 on the silicon substrate 50 side and the lower electrode layer 12 on the reference surface substrate 6 side face each other (see FIG. 2). More specifically, the flat support surfaces are closely adhered to each other. The flexible member 2 is in contact with the upper surface of the insulating layer 9 on the spacer 54 and the upper surface of the insulating layer 9 on the wiring portion 55 at the same height, and maintains flatness.
[0057]
For example, a conductive epoxy adhesive is used as the adhesive, and the silicon substrate 50 and the reference surface substrate 6 are fixed to each other by the adhesive 57a and the adhesive 57b as shown in FIG. Further, as shown in FIG. 2, the adhesive 57a includes a wiring pad 56 on the chamfered portion 59 of the reference surface substrate 6 and a lower electrode pad provided on the back surface of the silicon substrate 50 via a thermal oxide film 51a. 58 also serves as an electrical connection.
[0058]
The chamfered portion 59 of the reference surface substrate 6 exposes the wiring pad 56 to the outside when the silicon substrate 50 and the reference surface substrate 6 are bonded, and the adhesives 57a and 57b enter the chamfered portion 59, thereby allowing adhesion. The function of improving the reliability and ensuring the electrical connection between the wiring pad 56 and the lower electrode pad 58 is provided.
[0059]
The exposed portion 2b (see FIG. 3) of the flexible member 2 and the lower electrode pad 58 are connected to the drive circuit 7 by, for example, solder. The drive circuit 7 applies a voltage between the exposed portion 2b of the flexible member 2 and the lower electrode layer 12, or stops the application.
[0060]
Specifically, when the light beam incident on the reflective film 10 of the flexible member 2 is reflected without giving aberration, the drive circuit 7 does not apply a voltage. As a result, the flexible member 2 keeps the reflection film 10 flat and reflects the incident light beam as it is without giving any aberration. On the other hand, when an aberration is given to the incident light beam, the drive circuit 7 applies a voltage between the upper electrode layer 8 and the lower electrode layer 12. As a result, electrostatic stress acts between the upper electrode layer 8 and the lower electrode layer 12, and the flexible member 2 is attracted to the uneven surface 3, deforms the reflective film 10, and enters. A predetermined aberration is given to the light beam.
[0061]
FIG. 5 shows an example of an optical device to which the deformable mirror of FIG. 1 is applied. This optical apparatus performs recording and reproduction on two types of optical disks having different thicknesses.
[0062]
Here, the disc thickness is 0.6 mm (for example, DVD) and l. An optical device that can handle two types of optical disks of 2 mm (for example, CD) will be described as an example.
[0063]
A light source (semiconductor laser) 500 that is a light source of an optical pickup emits a light beam 504. The light beam 504 passes through the collimator lens 502, the beam splitter 503, and the quarter wavelength plate 505 and reaches the beam splitter 506. Subsequently, the beam 504 goes straight, passes through the beam splitter 506 and the quarter-wave plate 507, and reaches the deformable mirror 1.
[0064]
Then, the light reflected by the deformable mirror 1 passes through the quarter-wave plate 507, is reflected by the beam splitter 506, and this reflected light enters the objective lens 508. Then, this light beam is focused on the optical disk 509. The objective lens 508 has a focal length, a numerical aperture (NA), and the like so as to correspond to an optical disc having a disc thickness of 0.6 mm.
[0065]
In this optical apparatus, an accurate recording / reproducing operation can be performed on both an optical disc having a thickness of 1.2 mm and two types of optical discs having a thickness of 0.6 mm. This is realized by changing the state of the deformable mirror 1 in accordance with the thickness of the mounted optical disk 509. In other words, the shape of the flexible member 2 of the deformable mirror 1 is changed, and thereby the focused spot of the light beam emitted from the objective lens 508 is displaced, and this focused spot is supported by the driving motor 517. The optical disc 509 is matched.
[0066]
More specifically, when the thickness of the disk is 1.2 mm, the flexible member 2 of the deformable mirror 1 is deformed to give aberration to the incident light of the objective lens 508, thereby causing The focused spot of the light beam is matched with the optical disc 509, and the recording / reproducing operation of the optical disc 509 is performed in this state.
[0067]
Further, when the disc thickness is 0.6 mm, the flexible member 2 of the deformable mirror 1 is not deformed, a flat mirror is formed, and the incident light of the objective lens 508 is not given aberration, whereby the objective lens The focused spot of the light beam from 508 is matched with the optical disc 509, and the recording / reproducing operation of the optical disc 509 is performed in this state.
[0068]
Therefore, it is necessary to detect the thickness of the optical disk 509 as a premise for deforming the flexible member 2 of the deformable mirror 1. This thickness detection is performed by a thickness detection device (substrate thickness detection device) 515 provided on the upper side of the optical disk 509.
[0069]
The thickness detection device 515 is configured as shown in FIG. 6, for example, and emits the light beam 602 of the light source 600 toward the optical disc 509. The reflected light reflected from the surface of the optical disc 509 enters the optical position detector 601 via the optical path 604 when the thickness of the optical disc 509 is 0.6 mm. Similarly, when the thickness of the optical disk 509 is 1.2 mm, it enters the optical position detector 601 through the optical path 603. If the position of the reflected light is detected by the optical position detector 601, the thickness of the optical disk 509 can be detected. The detection result, that is, the thickness information of the optical disk is reported to the system control device 516, and the system control device 516 that receives the information deforms the deformable mirror 1 as follows.
[0070]
When the disc thickness of the optical disc 509 is 0.6 mm, the system controller 516 does not need to perform aberration compensation, and therefore does not drive the drive circuit 7. In this case, the flexible member 2 of the deformable mirror 1 is not deformed, and the reflective film 10 functions as a plane mirror.
[0071]
When the disc thickness is 1.2 mm, the system control device 516 drives the drive circuit 7 to attract the flexible member 2 of the deformable mirror 1 to the uneven surface 3 of the reference surface substrate 6, and The flexible member 2 is deformed. As a result, a predetermined aberration is given to the light beam reflected by the deformable mirror 1, and the condensed spot of the light beam from the objective lens 508 matches the optical disk 509 having a thickness of 1.2 mm.
[0072]
Here, the deformable mirror 1 is deformed to compensate for aberrations in the case of an optical disk having a thickness of 1.2 mm. Conversely, the deformable mirror 1 is deformed in the case of an optical disk 509 having a thickness of 0.6 mm. It is also possible.
[0073]
However, since the optical disk 509 having a thickness of 0.6 mm has a large recording capacity, the thickness is l. Higher accuracy is required for the optical components used than when reproducing an optical disk such as a 2 mm CD. According to the results of simulations by the inventors, it has been confirmed that the accuracy of the optical components can be reduced by giving aberration to the light beam when recording and reproducing a disk having a thickness of 1.2 mm. Therefore, when the reflective film 10 of the deformable mirror 1 is a plane mirror, when the optical disk 509 having a thickness of 0.6 mm is recorded and reproduced and the flexible member 2 of the deformable mirror 1 is deformed, It is preferable to carry out recording and reproduction of the optical disk 509 having a thickness of 1.2 mm.
[0074]
Next, referring to FIG. 7, a specific cross-sectional shape of the uneven surface 3 of the reference surface substrate 6 for deforming the reflective surface of the deformable mirror 1 (the reflective film 10 of the flexible member 2) into a predetermined shape. (Curved surface shape) will be described.
[0075]
The cross-sectional shape of the concavo-convex surface 3 may be any shape as long as the reflection surface of the flexible member 2 that deforms following the cross-sectional shape of the concavo-convex surface 3 generates the predetermined aberration.
[0076]
FIG. 7 shows the result of the simulation of the cross-sectional shape of the uneven surface 3 that generates the predetermined aberration. When the reflective film 10 of the deformable mirror 1 acts as a plane mirror, it is in a concave state along the position of depth d = 0 (μm), and when acting as a mirror that compensates for aberrations, the reflective film 10 is curved. It follows the cross-sectional shape along the uneven surface 3 as shown in FIG. The cross-sectional shape of the uneven surface 3 is axially symmetric with respect to an axis passing through the center.
[0077]
Here, originally, it is desirable to make this reflective surface circular so that the reflective surface of the deformable mirror can be deformed in an axial symmetry. On the other hand, as the deformable mirror applied to the optical device, a deformable mirror having an overall diameter of 10 mm or less, preferably about 5 mm is suitable. As a result, the opening 53 of the silicon substrate 50 has a diameter of 8 mm, Desirably, about 4 to 3 mm is appropriate. In this way, if the opening 53 of the silicon substrate 50 is processed into a small circle with good accuracy, there are the following three processing methods.
[0078]
(1) Precision machining by electrical discharge machining
(2) Wet etching
(3) Dry etching
However, these processing methods have the following problems.
[0079]
In the case of (1) above, it is not suitable for mass production. In addition, when the deformable mirror works as a plane mirror, it is necessary to apply a certain tension to the flexible member 2 in order to improve the stability. It is difficult to hold and fix.
[0080]
In the case of (2) above, a circular opening cannot be formed. That is, the silicon substrate 50 requires a certain degree of strength for the purpose of supporting the flexible member 2. Although the size around the opening 53 may be increased, the diameter of the deformable mirror is limited as described above. For this reason, it is necessary to ensure the strength by giving the silicon substrate 50 a certain thickness. The thickness is usually about 0.3 to 1 mm. In this case, since the side etching is performed in the wet etching, it is basically impossible to obtain the opening 50 having the dimensions described above.
[0081]
In the case of the above (3), it is not impossible if a single crystal Si substrate is used as the silicon substrate 50 and trench etching is performed. However, it is not established as a mass production technology at the present time, and the apparatus is expensive and the productivity is not good. That is, the production cost is high.
[0082]
Therefore, in one embodiment of the manufacturing method of the present invention described later, the opening 53 of the silicon substrate 50 is formed by applying anisotropic wet etching called crystal orientation dependency called bulk micromachining.
[0083]
For this anisotropic wet etching, for example, a (100) plane (110) plane single crystal Si substrate, a quartz substrate, or the like is used. However, since it is anisotropic wet etching in which etching is performed at different etching speeds depending on the crystal plane, a circular through-hole cannot be obtained, and the single crystal Si substrate 401 usually has a shape as shown in FIG. A rectangular opening 402 is formed. 8B shows the plan view shape of the etching mask for forming the square opening 402, and the hatching area in FIG. 8C shows the case where the square opening 402 is formed. The shape of the deformable mirror in plan view is shown.
[0084]
If the opening of the silicon substrate 50 is a quadrangle, the uneven surface 3 of the reference surface substrate 6 with which the flexible member 2 comes into contact is circular. Therefore, when the flexible member 2 is deformed, Displacement distribution occurs. There is also a problem from the viewpoint of the strength of the silicon substrate 50. Further, since the area of the opening is increased and the area of the deformation portion of the flexible member 2 is increased, the stability of the reflective surface can be improved when the reflective surface of the flexible member 2 is used as a plane mirror. There is a problem with sex.
[0085]
Therefore, even if anisotropic wet etching is applied, a rectangular shape cannot be adopted as the shape of the opening of the silicon substrate 50, and the opening 53 of the silicon substrate 50 is not provided like the deformable mirror of the present invention. The shape of the octagon must be realized.
[0086]
FIG. 9A shows a silicon substrate 50 made of a single crystal Si substrate.
This silicon substrate 50 is manufactured by applying anisotropic wet etching utilizing crystal orientation dependency, similar to the above-described one having a square opening. In the case of the above-described rectangular opening, the surface with the slowest etching rate appears by etching, whereas when the opening 53 of the silicon substrate 50 is octagonal, the surface with the slowest etching rate is The second slowest surface appears to make it polygonal, and the planar shape is made closer to a circle, thereby solving the problems that occurred with respect to the square opening.
[0087]
Further, by making the opening 53 of the silicon substrate 50 octagonal, the support portion of the silicon substrate 50 that supports the flexible member 2 is increased, and the strength of the silicon substrate 50 is increased. Furthermore, since the area of the deformation portion of the flexible member 2 is reduced, the stability of the reflective surface is increased when the reflective surface of the flexible member 2 is used as a plane mirror.
[0088]
FIG. 10A shows that the flexible member 2 is forcibly brought into contact with the uneven surface 3 of the reference surface substrate 6 having a depth of about 5 μm as shown in FIG. FIG. 10 (b) shows the state of displacement of the flexible member 2 when the opening is octagonal, and the reference member is shown in FIG. 10 (c). 6 shows a state of displacement of the flexible member 2 when it is forcibly brought into contact with the concavo-convex surface 3 of FIG.
[0089]
As is clear from comparing FIGS. 10 (a) and 10 (b), when the opening is a square, the flexible member 2 does not deform into a circle, but when the opening is an octagon, The flexible member 2 is deformed into a circle.
[0090]
The state of displacement of the flexible member 2 is obtained by FEM (Finite Element Method) simulation. Although not shown, the distribution of stress acting on the flexible member 2 shows the same tendency.
[0091]
Next, a method for manufacturing the silicon substrate 50 of FIG. 1, which is an embodiment of the manufacturing method of the present invention, will be described with reference to FIG. This silicon substrate 50 has a {100} plane (normal (100) plane) as shown in FIG. 110 ] A single crystal Si substrate 71 having an orientation flat in the orientation (usually <011> orientation) is used. The thickness of the single crystal Si substrate 71 is preferably about 0.3 to 1 mm.
[0092]
As shown in FIG. 11 (b), this single crystal Si substrate 71 is oxidized to form each etching SiO mask. ₂ Layers 51a and 51b are formed.
[0093]
In order to improve the accuracy of anisotropic wet etching, which will be described later, Si having good selectivity by an etchant. _Three N _Four More preferably, the layer is formed by low pressure CVD and this is used as an etching mask.
[0094]
Next, as shown in FIG. 11C, the SiO formed on the back surface of the single crystal Si substrate 71, that is, the back surface opposite to the surface on which the flexible member 2 is formed, by photolithography and RIE. ₂ The layer 51b is patterned, and an etching mask 60 for forming the opening 53 is formed.
[0095]
Next, as shown in FIG. 11 (d), an adhesion layer 61 such as Ta, Cr, Nb or the like is formed on the surface of the single crystal Si substrate 71 by sputtering or EB vapor deposition, and thereafter, flexible A seed layer 62 for forming the member 2 by an electroplating method to be described later is formed. Usually, the adhesion layer 61 and the seed layer 62 are continuously formed.
[0096]
Next, as shown in FIG. 11E, an Ni layer 63 having a thickness of 8 μm, for example, serving as a base material of the flexible member 2 is formed by electroplating.
[0097]
Next, as shown in FIG. 11F, the upper electrode 58 and the like for applying a voltage to the flexible member 2 driven by electrostatic force are patterned.
[0098]
In this embodiment, the electroplating method is used. However, an electroless plating method may be used, and the surface of the single crystal Si substrate 71 is doped with a P-type impurity to form an etch stop layer. It may be formed to prevent etching of the flexible member 2 to be formed later.
[0099]
Next, as shown in FIG. 11G, anisotropic wet etching is performed on the single crystal Si substrate 71 using, for example, 40 wt% KOH aqueous solution at 60 ° C., and then SiO 2 ₂ Unnecessary portions of 51a are removed by, for example, RIE to form the silicon substrate 50 and the opening 53. Accordingly, a part of the adhesion layer 61, the seed layer 62, and the Ni layer 63 becomes the flexible member 2, and the flexible member 2 is held flat by the opening 53.
[0100]
At this time, as shown in FIG. 9A, the {111} plane appears first by etching, and this {111} plane is 54.7 with respect to the (100) plane of the single crystal Si substrate 71. Make an angle of °. Further, the (010) plane and the (001) plane appear second, and the (010) plane and the (001) plane are perpendicular to the (100) plane.
[0101]
The etching rate of the {111} plane is very small and appears almost faithfully in the etching mask 60. Further, since the (010) plane and the (001) plane have the same orientation as the (100) plane of the single crystal Si substrate 71 covered with the etching mask 60, etching is performed at the same etching rate as the (100) plane. Is done.
[0102]
If the size and shape of the etching mask 60 are appropriately set, it is possible to control the dimensions of the (010) plane and the (001) plane when the opening 53 penetrates. Further, the {111} plane, the (010) plane, and the (001) plane form an angle of 45 ° (135 °) with each other when projected onto the (100) plane and viewed in plan. If this is utilized, an octagonal opening 53 can be formed by both {111} and {100} surfaces, and a regular octagonal opening 53 can be obtained with higher accuracy.
[0103]
Although the silicon substrate 50 and the flexible member 2 of the deformable mirror are completed as described above, if necessary, as shown in FIG. 11 (h), Al, Au or the like is formed on the surface of the flexible member 2. The reflective film 10 may be formed.
[0104]
Next, a specific shape of the etching mask for satisfactorily reproducing the octagonal opening 53 will be described.
[0105]
First, in the case of the rectangular opening 402 in FIG. 8A described above, a single crystal Si substrate 401 having an orientation flat with a (100) plane and a <011> orientation is applied. Then, the single crystal Si substrate 401 is masked with a rectangular etching mask having horizontal and vertical sides, and then the single crystal Si substrate 401 is patterned. By this etching mask, the (111) plane and the (1-1-1) plane appear horizontally with respect to the orientation flat (011) plane, and the (1-11) plane and the (11-1) plane are (011). Appears perpendicular to the surface. The {111} plane intersects with the (100) plane of the single-crystal Si substrate 401 at 54.7 °, but the shape projected onto the (100) plane and viewed in plan can be seen from the surface. Even when viewed from the back side, as shown in FIGS.
[0106]
On the other hand, in the case of the octagonal opening 53 of the present invention, as described above, it forms 45 ° with respect to the orientation flat in the <011> orientation of the single crystal Si substrate 71, and the single crystal Si substrate 51 For the (100) plane, which is the surface, four {100} planes perpendicular to the previous {111} plane appear and are combined.
[0107]
In the manufacturing method of the above embodiment, the etching mask SiO ₂ Layer 51a (or Si _Three N _Four Layer) and the etching rate of the {111} plane of the single-crystal Si substrate 71 is 200-400 or less of the etching rate of the (100) plane through which the opening 53 passes. In order to form the octagonal opening 53, the (010) plane and the (001) plane appear together with the {111} plane. These (010) plane and (001) plane are etched at an etching rate of about 20 μm / hour like the (100) plane. However, other higher-order planes such as {110} plane and {210} plane are still used. The etching rate is slower than that of the surface.
[0108]
Therefore, etching is performed after forming an etching mask 60 covering the hatched region as shown in FIG. Depending on the shape of the etching mask 60, the (010) plane and the (001) plane appear preferentially until the {111} plane appears, and the over-etching proceeds considerably. As a result, the opening 53 has an octagonal shape. Become.
[0109]
Since the octagonal opening 53 is formed based on the above principle, the {111} plane, (010) plane and (001) plane constituting the octagon do not directly reflect the shape and dimensions of the etching mask 60. Therefore, it is necessary to adjust the shape and dimensions of the etching mask 60 as appropriate.
[0110]
Next, the shape and dimension of the opening 53 of the silicon substrate 50 with respect to the etching mask 60 will be described with reference to FIGS. 9B and 9C. FIG. 9B shows a cross section taken along X1-X1 ′ in FIG. 9A, and FIG. 9C shows a cross section taken along X2-X2 ′ in FIG. 9A.
[0111]
As shown in FIG. 9B, for the (010) plane and the (001) plane, when the thickness of the silicon substrate 50 is T and the side etch (undercut) amount by etching is W, the side etch amount W is This substantially corresponds to the thickness T of the silicon substrate 50. Therefore, W = T, and the separation distance between the opposing sides of the octagon forming the opening 53 is larger by 2 * T than the separation distance between the sides forming the etching mask 60.
[0112]
Further, as shown in FIG. 9C, the {111} plane comes out inside the etching mask 60. When the amount is V, V = T / tan (54.7 °). The distance between the opposing sides of the octagon forming the opening 53 is smaller than the distance between the sides forming the etching mask 60 by 2 * T / tan (54.7 °).
[0113]
FIG. 12 is a schematic perspective view showing the octagon forming the opening 53 and the etching mask 60 in an easy-to-understand manner and showing the silicon substrate 50 from the back side. The hatched area in FIG. 12A shows the shape of the etching mask 60, the hatched area in FIG. 12B shows the planar shape of the deformable mirror, and the hatched area in FIG. The shape of the back side is shown. When the shape of the opening 53 is projected onto the (100) plane of the single-crystal Si substrate 51 and viewed in plan, it becomes an octagon as shown in FIG.
[0114]
Next, the relationship between the shape and dimensions when the etching mask 60 and the opening 53 of the silicon substrate 50 are viewed in plan will be described with reference to FIG.
[0115]
As described above, in order to make the opening 53 of the silicon substrate 50 octagonal, the etching mask 60 is made octagonal, and the four sides of the etching mask 60 are formed on the silicon substrate 50 (single crystal Si substrate). 71) along {110}, and the remaining four sides may be along the {100} plane of the silicon substrate 50.
[0116]
In order to make the opening 53 close to a regular octagon, the lengths of the opposing sides of the etching mask 60 are made equal. That is, the length of each side of the etching mask 60 that is horizontal or vertical with respect to the orientation flat in the <011> orientation is made equal, and the length of each side that forms 45 ° with respect to the orientation flat in the <011> orientation is also made equal. To do.
[0117]
Here, the length of each side of the etching mask 60 that is horizontal or vertical with respect to the orientation flat in the <011> orientation is A, and the length of each side that forms 45 ° with respect to the orientation flat in the <011> orientation is B. In addition, for each side of the octagon when the opening 53 is projected onto the (100) plane, the length of each side that is horizontal or perpendicular to the orientation flat in the <011> orientation is L1. The length of each side forming 45 ° with respect to the orientation flat in the <011> direction is L2. Further, as apparent from the above description, the distance between the sides of the length L1 is smaller than the distance between the sides of the length A by 2 * T / tan (54.7 °) The distance between the sides of the length L2 is larger than the distance between the sides of the length B by 2 * T.
[0118]
From these relationships, the lengths A and B of each side of the etching mask 60 are expressed by the following equations (7) and (8).
A = L1-2 * T * (1 / tan (54.7 °) + √ (2)) (7)
B = L2 + 2 * T * (1 / tan (54.7 °) + √ (2)) (8)
In order to make the opening 53 close to a substantially regular octagon, A <B and L1 = L2 = L and L = (L1 + L2) / 2L. Accordingly, the following (9) and (10) are derived from the above equations (7) and (8).
[0119]
A = L-2 * T * (1 / tan (54.7 °) + √ (2)) (9)
B = L + 2 * T * (1 / tan (54.7 °) + √ (2)) (10)
From these equations (9) and (10), the lengths A and B of the respective sides are obtained, and the etching mask 60 composed of these sides is employed to form the opening 53 of the silicon substrate 50. The opening 53 can be a substantially regular octagon.
[0120]
However, since it is extremely difficult to form the opening 53 of the silicon substrate 50 into a regular octagon, it must be expressed as a substantially regular octagon. The reason is that the {111} plane of the silicon substrate 50 hardly recedes, but the {100} plane recedes at a rate of about 20 μm / hour due to overetching or the like. It is difficult to avoid an error in the length of the substrate, it is difficult to align the etching mask 60 on the single crystal Si substrate 71 with high accuracy, and a slight deviation occurs. It may be said that the thickness of the substrate 71 also has some variation with respect to the standard.
[0121]
When actually producing a prototype, it was found that there was a total variation of 6%, with a variation of about 3% for the former two reasons and a variation of 3% for the latter one reason. Therefore, in order to realize a perfect regular octagon as the shape of the opening 53 of the silicon substrate 50, the back calculation is performed in consideration of these variations, and the following equations (1) and (2) are used. The lengths A and B of each side of the etching mask 60 need to be set.
A = L-2 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (1)
B = L + 2 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (2)
FIG. 14 shows a schematic shape of an etching mask in the second embodiment of the manufacturing method of the present invention.
[0122]
In the second embodiment, it is assumed that the silicon substrate 50 and the opening 53 are downsized as the deformable mirror is downsized.
[0123]
On the other hand, in the deformable mirror of the first embodiment, the deformable mirror is relatively large, the etching mask 60 used for etching the single crystal Si substrate 71 is octagonal, and has four lengths A. There are four sides of length B and the condition of A> 0 is satisfied. By substituting the condition of A> 0 into the above equation (1), the following equation (11) can be obtained. As long as the etching mask 60 is octagonal, if this equation (11) is not satisfied, The opening 53 of the silicon substrate 50 cannot be formed in an octagon.
L> 2 * T * (1 / tan (54.7 °) + √ (2)) (11)
However, if the opening 53 of the silicon substrate 50 is reduced and the etching mask is also reduced accordingly, A = 0, so that the shape of the etching mask is not an octagon but a square etching as shown in FIG. A mask 81 is formed.
[0124]
When the single-crystal Si substrate 71 is covered with the etching mask 81 and the single-crystal Si substrate 71 is etched, {111} planes appear from the vertices of the rectangle forming the etching mask 81, and { 100} plane appears.
[0125]
Therefore, each side of the quadrangle that forms the etching mask 81 needs to exist along a {100} plane perpendicular to the (100) plane that is the surface of the single crystal Si substrate 71.
[0126]
When the direction of each side of the quadrilateral of the etching mask 81 is determined in this way, the quadrilateral of the etching mask 81 is a rectangle. However, if the lengths of adjacent sides of the rectangle are different, the lengths of the octagonal sides 91, 95 and 93, 97 and 90, 94 and 92, 96 forming the opening 53 shown in FIG. 14 are different. End up. To make it closer to a regular octagon, the sides of this rectangle must be equal in length, that is, square.
[0127]
Here, when A = 0 is substituted into the above equation (1), the following equation (12) is derived.
L = 2 * T * (1 / tan (54.7 °) + √ (2)) (12)
Further, substituting this equation (12) into the above equation (2) and replacing it with B = C leads to the following equation (13).
[0128]
C = 4 * T * (1 / tan (54.7 °) + √ (2)) (13)
C obtained by the equation (13) is the length of one side of the square of the etching mask 81. When the single crystal Si substrate 71 is covered with the square etching mask 81 and the single crystal Si substrate 71 is etched, The opening 53 of the silicon substrate 50 is a substantially regular octagon, and the length of each side of the substantially regular octagon is L.
[0129]
Here, in the same manner as the etching mask 60 of the first embodiment, in order to make the opening 53 of the silicon substrate 50 into a regular octagon in consideration of 6% variation, after considering these variations, It is necessary to perform back calculation and set the lengths A and B of each side of the etching mask 81 based on the following (3).
C = 4 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (3)
FIG. 15 shows a schematic shape of an etching mask in the third embodiment of the manufacturing method of the present invention.
[0130]
In the third embodiment, it is assumed that the silicon substrate 50 and the opening 53 are further miniaturized as the deformable mirror is further miniaturized.
[0131]
On the other hand, the deformable mirror of the second embodiment is premised on satisfying the condition of the above expression (12), and when this condition is not satisfied and the following expression (14) is satisfied, that is, simply Compared with the thickness T of the crystalline Si substrate 71, the opening 53 of the silicon substrate 50. The When the length L of one side of the octagon to be formed is short and the octagon is small, even if the octagon can be created, as shown in FIGS. The distance V to one side of the octagon that forms the opening 53 and the distance W from one side of the quadrangle that forms the etching mask 81 to one side of the octagon that forms the opening 53 cannot be adjusted separately. A regular octagon cannot be formed because the relationship between the lengths L1 and L2 of the sides of the octagon that forms is L1> L2.
[0132]
L <2 * T * (1 / tan (54.7 °) + √ (2)) (14)
Incidentally, as is clear from the above description of FIGS. 9B and 9C, the {111} plane of the silicon substrate 50 is smaller than the etching mask pattern, and the {100} plane is larger than the etching mask pattern ( Side etching enters). Therefore, when the square etching mask is deformed in advance so that side etching is performed on the {111} surface by an amount smaller than the octagonal shape after completion of etching, the result is as follows. Thus, an etching mask 82 having the shape shown in FIG. 15 is obtained. If this etching mask 82 is used, the opening 53 of the silicon substrate 50 can be formed in a substantially regular octagon.
[0133]
The shape of the etching mask 82 includes a rectangular area 83 and wedge-shaped areas 84 extending radially from the corners of the rectangular area 83. A pair of lines connecting the apexes of the wedge-shaped regions 84 facing each other exist along the {110} plane perpendicular to the surface of the single-crystal Si substrate 71, and each side of the rectangular region 83 is a single-crystal Si substrate. The single crystal Si substrate 71 is covered with the etching mask 82 so that the single crystal Si substrate 71 exists along the {100} plane perpendicular to the surface, and the single crystal Si substrate 71 is etched. Accordingly, the length L of one side of the octagon forming the opening 53 of the silicon substrate 50 is shorter than the thickness T of the single-crystal Si substrate 71, and this octagon is substantially regular octagon even when the octagon is small. Can be close to a square.
[0134]
Further, in order to make the opening 53 of the silicon substrate 50 closer to a regular octagon, the length of a pair of lines connecting the apexes of the wedge-shaped regions 84 facing each other of the etching mask 82 is D, and each of the rectangular regions 83 is When the distance between the sides is E and the distance between the wedge-shaped regions 84 on each side of the rectangular region 83 is F, the following equations (15), (16), and (17) may be satisfied. .
[0135]
D = L * (1 + √ (2)) + 2 * T / tan (54.7 °) (15)
E = L * (1 + √ (2)) − 2 * T (16)
F = L (17)
Here, in the same manner as the etching mask 60 of the first embodiment, in order to make the opening 53 of the silicon substrate 50 into a regular octagon in consideration of 6% variation, after considering these variations, It is necessary to perform reverse calculation and set D, E, and F based on the following equations (4), (5), and (6).
D = L * (1 + √ (2)) + 2 * T / tan (54.7 °) ± 6% (4)
E = L * (1 + √ (2)) − 2 * T ± 6% (5)
F = L (6)
[0136]
【The invention's effect】
As described above, according to the present invention, the reflecting surface of the flexible member is deformed following the cross-sectional shape of the curved surface portion. For this reason, if the shape accuracy of the curved surface portion is kept high, the deformed shape of the reflecting surface can be determined with high accuracy, and aberration correction can be performed with high accuracy.
[0137]
In addition, since the opening inside the support frame that borders the outer peripheral edge of the flexible member is formed in an octagonal shape, stress applied to the flexible member is substantially applied to the entire flexible member during deformation. It can be evenly distributed, the deformability of the flexible member is improved, and the life is improved. Moreover, it is easy to hold | maintain the reflective surface of this flexible member to a plane at the time of no deformation | transformation, and this state can be maintained stably. The shape of the opening inside the support frame is most preferably a regular octagon.
[0138]
On the other hand, the shape of the curved surface portion may be any shape as long as it can correct the aberration specified in advance. In an optical device equipped with this deformable mirror, the reflecting surface of the flexible member is held flat, and no aberration is given to incident light on the reflecting surface of the flexible member, and the flexible member is It is possible to selectively set a state in which a predetermined aberration is given to light incident on the reflecting surface of the flexible member by sucking the curved surface of the reference surface substrate and elastically deforming the flexible member. Thereby, a plurality of optically different lights can be generated.
[0139]
As described in claim 2, the support frame is preferably formed from a single crystal Si substrate having a {100} plane and an orientation flat with a [110] orientation, whereby each of the claims 3, 8 and The manufacturing method of the deformation | transformation mirror as described in 12 is attained.
[0140]
According to the manufacturing method of the third aspect, the opening of the support frame is formed by coating the single crystal Si substrate with the etching mask and then etching the single crystal Si substrate. There are four sides of the octagon along the {110} plane that is rectangular and is perpendicular to the surface of the single crystal Si substrate covered by the etching mask, and the single crystal Si covered by the etching mask. There are four other sides of the octagon along the {100} plane perpendicular to the surface of the substrate.
[0141]
When the single crystal Si substrate is etched under such conditions, an octagonal one can be obtained as the opening of the support frame.
[0142]
As described in claim 4, before etching the single crystal Si substrate, a flexible member is laminated on the single crystal Si substrate, and thereafter, the single crystal is not etched without etching the flexible member. The Si substrate may be etched to form the support frame opening.
[0143]
As a result, the support frame and the flexible member can be formed simultaneously. Also, if the surface of the single crystal Si substrate is flattened, the flexible member to be laminated can be formed in a flat shape. The reflective surface of the sex member can be held flat.
[0144]
The four sides along the octagonal {110} plane forming the etching mask are equal to each other, and the other four sides along the octagonal {100} plane are equal to each other. Is good.
[0145]
As a result, the four sides on the octagonal {110} plane forming the opening of the support frame are equal to each other, and the other four sides on the octagonal {100} plane are equal to each other. The octagon is shaped.
[0146]
7. The length of the four sides along the octagonal {110} plane forming the etching mask as defined in claim 6 is A, and the length of the other four sides along the octagonal {100} plane is as follows. Assuming that B is A, it is preferable that A <B.
[0147]
Thereby, the octagon that forms the opening of the support frame can be reproduced well.
[0148]
More preferably, the thickness of the support frame is T, the average value of the lengths of the sides of the octagon forming the opening of the support frame is L, and L> 2 * T * Assuming that (1 / tan (54.7 °) + √ (2)), the lengths A and B of the sides of the octagon forming the etching mask are expressed by the following equations (1) and (2).
A = L-2 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (1)
B = L + 2 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (2)
In this case, the octagon that forms the opening of the support frame is a regular octagon.
[0149]
According to the manufacturing method of claim 8, the opening of the support frame is formed by covering the single crystal Si substrate with the etching mask and then etching the single crystal Si substrate. Is a quadrangle, and there are four sides of the quadrangle along the {100} plane perpendicular to the surface of the single crystal Si substrate covered by the etching mask.
[0150]
Here, it is assumed that the opening of the support frame is slightly small, and the length A of four sides along the octagonal {110} plane forming the etching mask is 0 (A = 0). When the single crystal Si substrate is etched under the condition described in Item 8, an octagonal opening can be obtained as the opening of the support frame.
[0151]
As described in claim 9, before etching the single crystal Si substrate, a flexible member is laminated on the single crystal Si substrate, and thereafter, the single crystal is not etched without etching the flexible member. The Si substrate may be etched to form the support frame opening.
[0152]
As a result, the support frame and the flexible member can be formed simultaneously. In addition, the flexible member laminated on the single crystal Si substrate can be formed in a flat shape, and after the etching is finished, the reflective surface of the flexible member is held flat by the opening of the support frame. be able to.
[0153]
As described in claim 10, the quadrangle forming the etching mask may be a square.
[0154]
More preferably, as described in claim 11, the thickness of the support frame is T, the average value of the lengths of the sides of the octagon forming the opening of the support frame is L, and L = 2 * T * Assuming (1 / tan (54.7 °) + √ (2)), the length C of one side of the square forming the etching mask is expressed by the following equation (3).
C = 4 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (3)
In this case, the octagon that forms the opening of the support frame is a regular octagon.
[0155]
Furthermore, according to the manufacturing method of claim 12, the opening of the support frame is formed by covering the single crystal Si substrate with an etching mask and then etching the single crystal Si substrate. Has a shape composed of a rectangular area and wedge-shaped areas extending radially from each corner of the rectangular area, and a pair of lines connecting the vertices of the wedge-shaped areas facing each other are formed by the etching mask. It exists along the {110} plane perpendicular to the surface of the coated single crystal Si substrate, and each side of the square region is {100} perpendicular to the surface of the single crystal Si substrate coated with the etching mask. Exists along the plane.
[0156]
Here, it is assumed that the opening of the support frame is very small, and when the single crystal Si substrate is etched under the conditions described in claim 10, an octagonal shape is formed as the opening of the support frame. Can be obtained.
[0157]
As described in claim 13, before etching a single crystal Si substrate, a flexible member is laminated on the single crystal Si substrate, and thereafter, the single crystal is not etched without etching the flexible member. The Si substrate may be etched to form the support frame opening.
[0158]
As a result, the support frame and the flexible member can be formed simultaneously. Moreover, the flexible member laminated | stacked on a single crystal Si substrate can be formed in planar shape, and the reflective surface of a flexible member can be hold | maintained at a plane by the opening part of a support frame.
[0159]
Preferably, as described in claim 14, the thickness of the support frame is T, the average length of each side of the octagon forming the opening of the support frame is L, and L <2 * T * ( 1 / tan (54.7 °) + √ (2)), the length of the line connecting the vertices of the wedge-shaped regions facing each other in the shape of the etching mask is D, and the length of each side of the rectangular region is The separation distance is represented by E, and the distance between each wedge-shaped region on each side of the rectangular region is represented by the following equations (4), (5), and (6).
D = L * (1 + √ (2)) + 2 * T / tan (54.7 °) ± 6% (4)
E = L * (1 + √ (2)) − 2 * T ± 6% (5)
F = L (6)
In this case, the octagon that forms the opening of the support frame is a regular octagon.
[Brief description of the drawings]
FIG. 1 is a plan view showing a first embodiment of a deformable mirror according to the present invention;
FIG. 2 is a cross-sectional view showing a deformable mirror broken along line XX in FIG.
3 is a bottom view showing the deformable mirror of FIG. 1. FIG.
4 is an exploded perspective view showing the deformable mirror of FIG. 1 in an exploded manner.
5 is a block diagram showing an example of an optical device to which the deformable mirror of FIG. 1 is applied.
6 is a schematic configuration diagram showing the thickness detection device in FIG. 5;
7 is a graph showing the cross-sectional shape of the uneven surface of the deformable mirror in FIG. 1;
8A is a perspective view showing a single crystal Si substrate in which a rectangular opening is formed, FIG. 8B shows a plan view shape of an etching mask on the single crystal Si substrate, and FIG. 8C shows the single crystal Si substrate. The figure which shows the planar view shape of the deformable mirror formed using the crystalline Si substrate
9A is a perspective view showing a silicon substrate of the deformable mirror in FIG. 1, FIG. 9B is a cross-sectional view taken along X1-X1 ′ in FIG. 1A, and FIG. 9C is X2- in FIG. Diagram showing a cross section along X2 '
FIG. 10A is a graph showing a state of displacement of a flexible member when the opening of the silicon substrate is square and the flexible member is forcibly brought into contact with an uneven surface; ) Is a graph showing the displacement state of the flexible member when the opening is octagonal and the flexible member is forcibly brought into contact with the uneven surface, and (c) is the uneven shape of the flexible member. The figure which shows the state which is made to contact the surface forcibly
11 shows a procedure for manufacturing a silicon substrate of the deformable mirror of FIG. 2, wherein (a) shows a single crystal Si substrate and (b) shows SiO 2. ₂ (C) shows the etching mask formation step, (d) shows the adhesion layer and seed layer formation step, (e) shows the Ni layer formation step, and (f) shows The patterning process of an upper electrode etc. is shown, (g) shows an anisotropic wet etching process, (h) is a figure which shows the film-forming process of a reflecting film
12A shows the shape of an etching mask covering the silicon substrate of the deformable mirror in FIG. 1, FIG. 12B shows the planar shape of the deformable mirror, and FIG. 12C shows the back surface of the opening of the silicon substrate. Figure showing the shape of the side
13 is a plan view showing the shape of the opening and the etching mask of the silicon substrate of the deformable mirror in FIG. 1;
FIG. 14 is a plan view showing a schematic shape of an etching mask in the second embodiment of the manufacturing method of the present invention;
FIG. 15 is a plan view showing a schematic shape of an etching mask in the third embodiment of the manufacturing method of the present invention;
FIGS. 16A and 16B are diagrams showing the relationship between the shape and dimensions of an etching mask and an opening. FIGS.
FIG. 17 is a block diagram showing a configuration of a conventional optical pickup.
FIG. 18 is a diagram showing a configuration of an optical pickup using a conventional deformable mirror.
FIG. 19 is a diagram showing a configuration of a conventional deformable mirror.
[Explanation of symbols]
1 Deformable mirror
2 Flexible members
3 Uneven surface
7 Drive circuit
8 Upper electrode layer
9 Insulating layer
10 Reflective film
12 Lower electrode layer
50 Silicon substrate
53 opening
54 Spacer layer
55 Wiring section
56 Wiring pad
59 Chamfer
60, 81, 82 Etching mask
71 Single crystal Si substrate
500 light source
502 collimator lens
503,506 Beam splitter
505, 507 quarter wave plate
508 Objective lens
509 Optical disc
515 Thickness detection device
517 Driving motor
601 Optical position detection device

Claims (14)

A film-like flexible member having a reflective surface on its surface for reflecting incident light;
A support frame formed of a single crystal Si substrate and having an opening formed inside to support the outer peripheral edge of the flexible member;
A curved surface portion is disposed in the circular region that is opposed to the support frame with the flexible member interposed therebetween, and that faces the inside of the opening and forms a space that allows elastic deformation of the flexible member. Provided with a substrate ,
The opening of the support frame is formed in the octagon,
The flexible member is supported by the support frame so as to cover the opening and the space in a state where the reflecting surface is flat.
The curved surface portion of the substrate gives a predetermined aberration to light incident on the reflecting surface through the opening when the flexible member is elastically deformed and closely contacts the curved surface portion. A deformable mirror characterized by being formed . 2. The deformable mirror according to claim 1, wherein the support frame has a {100} plane and a side parallel to an orientation flat of [110] orientation. A method of manufacturing a deformable mirror according to claim 2,
The single-crystal Si substrate, eight coated with square etch mask having an opening, includes an etching process that to form the opening of the support frame by the single-crystal Si substrate is wet-etched,
In the etching process, four sides of the octagon of the opening in the etching mask , ie, two sides parallel to each other and two sides perpendicular to the two sides, are perpendicular to the surface of the single crystal Si substrate. such with a state along the {110} plane, as a positive octagonal other four sides of the opening is, in a state along the vertical {100} plane and the monocrystalline Si substrate surface A method of manufacturing a deformable mirror , comprising arranging the etching mask . Before the etching step, comprising the step of laminating the flexible member to the single crystal SI substrate in the etching step, the flexible member without etching, etching the single crystal SI substrate The method of manufacturing a deformable mirror according to claim 3 , wherein the opening of the support frame is formed by: The length of the four sides along the {110} plane of the octagonal the openings in the etching mask are equal to each other, and mutually the length of the other four sides along the該Hachi square of the {100} plane A method of manufacturing a deformable mirror according to claim 3 , which is equal to Wherein said octagonal the opening in the etching mask {110} of the four sides along the surface of each length is A, and該Hachi square of the {100} other four along the surface sides of the respective 6. The method of manufacturing a deformable mirror according to claim 5 , wherein A <B, where B is a length. Wherein the thickness of the support frame is T, the average value of the lengths of the sides of the octagon of the opening in the support frame and L, L> 2 * T * (1 / tan (54.7 °) + √ (2))
The method of manufacturing a deformable mirror according to claim 5, wherein the lengths A and B of each side of the octagon of the opening in the etching mask are represented by the following expressions (1) and (2).
A = L-2 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (1)
B = L + 2 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (2) In the manufacturing method of the deformation | transformation mirror of Claim 2,
The single-crystal Si substrate, and covered by an etching mask having an opening square, the single-crystal Si substrate includes an etching step of forming an opening in the support frame by wet etching,
In the etching step, the four sides of the rectangle of the openings in the etching mask, the so a state along the vertical {100} plane and the single crystal Si substrate surface, placing the etch mask A method of manufacturing a deformable mirror characterized by the above . Before the etching step, comprising the step of laminating the flexible member to the single crystal Si substrate in the etching step, the flexible member without etching, etching the single-crystal Si substrate The method of manufacturing a deformable mirror according to claim 8 , wherein the opening of the support frame is formed by: The method of manufacturing a deformable mirror according to claim 8, wherein the quadrangle of the opening in the etching mask is a square. Wherein the thickness of the support frame is T, the average value of the lengths of the sides of the octagon of the opening in the support frame and L, L = 2 * T * (1 / tan (54.7 °) + √ (2))
The method of manufacturing a deformable mirror according to claim 10, wherein a length C of one side of the square of the opening in the etching mask is represented by the following expression (3).
C = 4 * T * (1 / tan (54.7 °) + √ (2)) ± 6% (3) The method of manufacturing a deformable mirror according to claim 2,
The single-crystal Si substrate, and covered by an etching mask having an opening, the single-crystal Si substrate includes an etching step of forming an opening in the support frame by wet etching,
The opening of the etching mask has a rectangular region and a wedge-shaped region extending radially from each corner of the rectangular region along a diagonal direction ,
In the etching step, the diagonal lines connecting the apexes of the wedge-shaped regions facing each other of the openings in the etching mask are in a state along the {110} plane perpendicular to the surface of the single crystal Si substrate. The etching mask is arranged so that each side of the rectangular region of the opening in the etching mask is in a state along a {100} plane perpendicular to the surface of the single crystal Si substrate. Of manufacturing a deformable mirror. Before the etching step, comprising the step of laminating the flexible member to the single crystal Si substrate in the etching step, the flexible member without etching, etching the single-crystal Si substrate The method of manufacturing a deformable mirror according to claim 12 , wherein the opening of the support frame is formed by: Wherein the thickness of the support frame is T, the average value of the lengths of the sides of the octagon of the opening in the support frame and L, L <2 * T * (1 / tan (54.7 °) + √ (2))
The respective lengths of the diagonal lines connecting the vertices of the respective wedge-shaped region facing each other of the openings in the etching mask D, each side of the distance E facing each other of the rectangular region in the opening, and of the square The method of manufacturing a deformable mirror according to claim 12, wherein the length F of each side located between the wedge-shaped regions in the region is represented by the following expressions (4), (5), and (6).
D = L * (1 + √ (2)) + 2 * T / tan (54.7 °) ± 6% (4)
E = L * (1 + √ (2)) − 2 * T ± 6% (5)
F = L (6)

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