JP2009020468A - Method for manufacturing micro-mirror - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical scanner, which suppresses the camber of a mirror part without changing the resonance frequency of a swinging mirror part of the optical scanner. <P>SOLUTION: The method for manufacturing the optical scanner 10 comprising the mirror part 1, a beam part 2 supporting the mirror part 1 in a swingable manner, and a frame part 3 holding the beam part 2, includes a film forming process for depositing a reflective film 6 on the surface of the mirror part 1, and an ion implantation process for injecting an ionized material into the surface of the mirror part 1 by an ion implantation method to reduce the surface camber of the mirror part 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a micromirror of an optical scanner used in an image projection apparatus or the like. In particular, the present invention relates to a manufacturing method for suppressing warpage of the surface of a micromirror.

  Optical scanners are used to form projected images in image projection apparatuses, printers, and the like. The optical scanner scans reflected light by irradiating a micromirror having a oscillating reflecting surface with laser light, and forms a projected image on a screen or a photosensitive drum. However, when the flatness of the reflecting surface is deteriorated, the intended purpose cannot be achieved, for example, the characteristics of the reflected beam are deteriorated and the resolution of the projected image is lowered.

  FIG. 4A is a perspective view showing an optical scanning device 100 using a conventionally known micromirror. The optical scanning device 100 includes a mirror unit 101 having a reflecting surface, a beam unit 102 that supports the mirror unit 101, and a frame unit 103 that holds the beam unit 102. The beam portion 102 forms a swing axis for swinging the mirror portion 101. A planar coil 104 is formed in the vicinity of the side of the mirror unit 101, and a rotational torque is applied to the mirror unit 101 due to a change in the magnetic field passing through the plane surrounded by the planar coil 104. The mirror unit 101 has a beam unit 102. Oscillate around the axis. Along with this oscillation, an incident beam 108 such as a laser beam is reflected by the oscillating mirror 101 and emitted as a scanned scanning beam 109.

  FIG. 4B is a schematic diagram illustrating a cross section of the mirror unit 101. The mirror unit 101 includes, for example, a silicon substrate 105, a reflective film 106 made of metal formed on the surface thereof, an oxide film 107 formed on the upper surface of the reflective film 106 and the lower surface of the silicon substrate 105, and the like. In order to prevent the laser light incident on the mirror unit 101 from deteriorating, it is necessary to make the surface of the mirror unit 101 flat. In general, in the region irradiated with the laser beam having the wavelength λ, the unevenness d on the surface of the mirror portion 101 needs to be λ / 4 or less. However, stress remains in the formed thin film under the influence of the film thickness of the reflective film 106, the type and film thickness of the oxide film 107, the temperature at the time of manufacture, and the unevenness d becomes λ / 4 or more.

Patent Document 1 describes a movable body and a torsion bar made of a silicon oxide film, and a planar electromagnetic actuator in which a frame portion is integrally formed. On the surface of the oscillating movable body, a mirror portion in which a reflection film or an insulating film is deposited is formed in the center portion, and a planar coil portion is formed in the peripheral portion. The reflection film and the insulating film at the center are formed by sputtering or vapor deposition. In addition, it is described that a stress film is further formed on the movable body in order to cancel the stress of the coil part and the mirror part and control the warp of the movable body.
JP 2004-264603 A

  According to the method of Patent Document 1, a stress film is deposited on the movable body in order to control the warp of the movable body. However, by depositing this stress film, the mass that the movable body originally had changes, and the rotational moment changes accordingly. As a result, there arises a problem that the resonance frequency in the swing of the movable body (corresponding to the mirror unit 101) changes. The present invention has been made for the purpose of solving the problems of the conventional example.

  The present invention has taken the following means in order to solve the above problems.

  In the invention which concerns on Claim 1, In the manufacturing method of the optical scanner provided with the mirror part, the beam part which supports the said mirror part so that rocking | fluctuation, and the frame part which hold | maintains the said beam part, A light comprising: a film forming step for depositing a reflective film on a surface; and an ion implantation step for injecting a material ionized by an ion implantation method into the mirror portion in order to reduce warpage of the surface of the mirror portion. A scanner manufacturing method was adopted.

2. The method of manufacturing an optical scanner according to claim 1, wherein the film forming step further includes a step of depositing a protective film on a surface of the reflective film.
It was.

  In the invention according to claim 3, the film forming step is a step of depositing a reflective film on one surface of the mirror portion, and the ion implantation step implants an ionized material on the other surface of the mirror portion. The method of manufacturing an optical scanner according to claim 1 or claim 2, wherein

  The invention according to claim 4 is the method for manufacturing an optical scanner according to any one of claims 1 to 3, wherein the ionized material is either oxygen or phosphorus.

  According to the first aspect of the present invention, there is provided an optical scanner manufacturing method in which a reflective film is deposited on the surface of the mirror portion, and further, an ionized material is injected into the surface of the mirror portion. Thereby, the stress of a mirror part can be adjusted, without changing the mass of a mirror part almost. Therefore, there is an advantage that the flatness of the mirror portion can be improved without affecting the resonance frequency.

  According to invention of Claim 2, the process of depositing a protective film on the surface of a reflecting film is included. Thereby, there is an advantage that the reflection film can be prevented from being damaged due to a decrease in reflectance and a scratch on the reflection film.

  According to the third aspect of the present invention, the ion implantation is performed on the back surface where the reflective film is not formed. Thereby, it has the advantage that it can prevent that a reflective surface is roughened by injection | pouring of the ionized material.

  According to the invention of claim 4, the ionized material is oxygen or phosphorus. This has the advantage that compressive stress or tensile stress can be applied to the region of the mirror part without changing the resonance frequency of the mirror part.

  FIG. 1A shows a schematic top view of an optical scanner 10 manufactured by the manufacturing method of the present invention, and FIG. 1B shows a schematic cross-section of the section XX ′ in FIG. Represents the figure.

  As shown in FIG. 1A, an optical scanner 10 includes a mirror part 1, a beam part 2 that pivotally supports the mirror part 1 from both sides, and a frame part 3 that holds the beam part 2. Yes. The beam portion 2 forms the swing axis of the mirror portion 1, and the mirror portion 1 vibrates with the beam portion 2 as the swing axis. For example, a coil is formed on the peripheral surface of the mirror portion 1 and a magnetic field passing through the surface surrounded by the coil is changed from the outside, thereby giving rotational torque to the mirror portion 1 and using the beam portion 2 as a swing axis. The mirror unit 1 can be vibrated. In addition, a vibrating body made of a piezoelectric body or the like is installed between the beam portion 2 and the frame portion 3, and the vibration of this vibrating body is transmitted from the beam portion 2 to the mirror portion 1, and the beam portion 2 is used as a swing axis. The part 1 can be vibrated.

  In FIG. 1, a storage portion and a lid portion are attached to the lower and upper portions of the optical scanner 10 to form a swinging space of the mirror portion 1, but these storage portion and lid portion are omitted. Further, a coil and a piezoelectric body that cause the mirror unit 1 to swing are also omitted.

  As shown in FIG. 1B, the mirror unit 1 includes a silicon substrate 5, a reflective film 6 made of an aluminum film or the like deposited on the surface of the silicon substrate 5, and a silicon oxide film deposited on the reflective film 6. And the like, and a silicon oxide film 8 formed on the back surface of the silicon substrate. As will be described in detail later, in the silicon oxide film 8 formed on the back surface of the silicon substrate 5, in the back surface region corresponding to the region where the reflective film 6 is formed, the implantation material 9 implanted by the ion implantation method is silicon oxide. The film 8 or the silicon substrate 5 is localized. The material to be injected is, for example, an oxygen atom or a phosphorus atom.

  By localizing the implanted material in the region of the back surface corresponding to the reflective film 6 by the ion implantation method, the internal stress of each formed film is offset, and the wavelength λ of the laser light that irradiates the warp of the mirror portion 1 1/4 or less.

  FIG. 2 is a flowchart showing a method for manufacturing the optical scanner 10 according to the present invention. In particular, a cross-sectional portion of the optical scanner 10 along the XX ′ portion of FIG. 1 is shown. In the present embodiment, a method for simultaneously manufacturing a large number of optical scanners 10 will be described. Hereinafter, the same reference numerals are assigned to the same parts or parts having the same function.

  In FIG. 1A, first, a cleaned silicon substrate 5 is prepared. The silicon substrate has a thickness of about 0.5 mm. Next, a photoresist 11 is uniformly applied to the surface of the silicon substrate 5 by a spinner or the like. Next, the applied photoresist 11 is pre-baked and dried, and a necessary area is exposed using a mask. Next, development processing of the photoresist 11 is performed, and the photoresist 11 is left in regions corresponding to the mirror portion 1, the beam portion 2, and the frame portion 3. FIG. 1B shows a cross section of the photoresist 11 after development. Next, the photoresist 11 is post-baked to bring the photoresist 11 into close contact with the silicon substrate 5.

  Next, the silicon substrate 5 is etched away by dry etching by RIE (reactive ion etching) or the like or wet etching using a solution such as KOH (FIG. 2C). In the case where the silicon substrate 5 is removed by wet etching such as KOH, an etching prevention film such as a silicon oxide film or a resist is previously formed on the back surface of the silicon substrate 5. The state of the silicon substrate after etching shown in FIG. 2C is a state in which the mirror portion 1 is held by the frame portion 3 by the beam portion 2.

  Next, as shown in FIG. 2D, a reflective film 6 made of aluminum or the like is deposited on the mirror portion 1 of the silicon substrate 5 to form a film. The reflective film 6 is deposited by a vacuum evaporation method such as a sputtering method or an electron beam evaporation method. When the reflective film 6 is deposited, the reflective film 6 is deposited only in the region of the mirror portion 1 using a metal mask. Alternatively, the reflective film 6 may be formed on the entire surface of the silicon substrate 5, and then the reflective film 6 may be left only in the region of the mirror portion 1 by photolithography and etching processes. The reflective film 6 can be formed by depositing a thin film of gold or silver in addition to aluminum. The material of the reflective film 6 is appropriately selected according to the light to be scanned.

  Next, as shown in FIG. 2E, a protective film 7 is deposited on the surface of the silicon substrate 5. As the protective film 7, a silicon oxide film is deposited by PCVD (plasma chemical vapor deposition) or reactive sputtering. A silicon oxide film 8 is deposited on the entire back surface of the silicon substrate 5 by the same method. The protective film 7 formed on the surface is formed for protecting the surface of the reflective film 6 while preventing the surface of the reflective film 6 from being oxidized and reducing the reflection efficiency. The silicon oxide film 8 formed on the back surface of the silicon substrate 5 is for preventing the mirror portion 1 from warping due to internal stress of the silicon oxide film when the protective film 7 formed on the front surface is a silicon oxide film. Provided. As the protective film 7, other transparent films such as a silicon nitride film and a silicon oxynitride film can be used instead of the silicon oxide film. In that case, in order to prevent warping of the silicon substrate 5, it is preferable to deposit a similar thin film on the back surface by the same method.

  Next, as shown in FIG. 2F, ionized material is ion-implanted into the silicon oxide film 8 on the back surface of the silicon substrate 5. Ion implantation is a method in which atoms and molecules are ionized and accelerated by an electric field, and the kinetic energy is used to inject into an object. Specifically, the elements and molecules to be implanted in the ion source are ionized, the ionized material is selected by passing through a mass analyzer, and accelerated from several KeV to several tens MeV by an accelerator. The ion implantation can also be performed in the region where the reflective film 6 is formed on the surface of the silicon substrate 5. However, since the surface of the reflective film 6 may be roughened by ion implantation, it is preferably performed from the back surface of the silicon substrate 5 as shown in FIG. At the time of ion implantation, the mask 13 is masked so that at least the ion material is not implanted into the beam portion 2. This is to prevent the torsional elastic coefficient of the beam part 2 from being changed by ion implantation into the beam part 2 and the resonance frequency of the mirror part 1 from changing. Further, instead of the mask 13, a resist may be applied to at least the back surface of the beam portion 2 to prevent ions from being implanted into the beam portion 2.

  The material to be ion-implanted differs depending on the warp direction and warpage of the silicon substrate. For example, when the mirror unit 1 has a convex warp on the back side, oxygen ions are implanted from the silicon oxide film 8 side. When oxygen ions are implanted into the silicon oxide film 8 side, tensile stress is generated on the surface. Thereby, the convex curvature of the said back surface can be reduced and the flatness of the mirror part 1 can be improved. On the other hand, when the mirror part 1 has a concave warp on the back side, phosphorus ions are implanted into the silicon oxide film 8 side. When phosphorus ions are implanted into the silicon oxide film 8, a compressive stress is generated on the surface. Thereby, the concave curvature of the said back surface can be reduced and the flatness of the mirror part 1 can be improved.

  The acceleration energy of ions during ion implantation is preferably 10 KeV (kiloelectron volts) to 3 MeV (megaelectron volts). In the case of acceleration energy of 3 MeV or more, the surface of the silicon oxide film 8 or the silicon substrate is damaged, which is not preferable. Lower. The implantation depth of the material to be ion implanted is preferably about 10 nm (nanometer) to 1 μm (micrometer). The injection material is unevenly distributed near the surface of the silicon oxide film 8 or the silicon substrate 5. Thereby, compressive stress and tensile stress can be generated more effectively.

  The material for ion implantation is not limited to oxygen or phosphorus. An ionizable material such as nitrogen (N), hydrogen (H), boron (B), or argon (Ar) can be used.

  Even when ion atoms are implanted, the change in the mass of the mirror portion 1 is negligible. Therefore, a change in mass of the mirror unit 1 can be ignored, and it does not affect the rotating Morton that uses the beam unit 2 of the mirror unit 1 as the swing axis. Therefore, the ion implantation method is suitable for controlling the warpage of the mirror unit 1.

  Next, as shown in FIG. 2G, the adjacent frame portions 3 are separated along the cutting line 14. Next, as shown in FIG. 2 (h), the frame portion 3 is bonded and fixed on the storage portion 15 and covered with a lid portion (not shown).

  In the above-described embodiment, when the planar coil for generating the swing is formed in the periphery of the upper surface of the mirror portion 1 and the lead-out wiring is formed on the beam portion 2 and the pad is formed on the surface of the frame portion 3, the above steps are performed. After forming the pattern of the reflective film 6 in (d) or after forming the protective film 7 in the step (e), a pattern is formed by depositing a conductor made of aluminum or the like. When the mirror unit 1 is swung by the piezoelectric vibrating body, an electrode is formed on the surface of the frame unit 3 after forming the protective film 7 in the step (e) or after ion implantation in the step (f). Next, the piezoelectric vibrator is bonded and fixed across the beam portion 2 and the frame portion 3.

  Further, a large number of storage portions 15 corresponding to the plurality of frame portions 3 shown in FIG. 2 (g) are continuously formed at the same time, and a sheet in which a large number of frame portions 3 are continuously formed is continuously formed. The optical scanner 10 may be laminated and fixed to the storage unit 15 and then divided by dicing.

  In addition, although a laser printer or an optical scanning display (such as a retinal scanning display or a laser display) is known as an apparatus using an optical scanner, application of the present invention is effective in improving resolution reduction, In particular, it is effective in an optical scanning display in which the stability of the optical scanning frequency is important in that the resonance frequency can be stabilized.

  FIG. 3 is a flowchart showing another embodiment of the method for manufacturing an optical scanner according to the present invention. The same portions or portions having the same function are denoted by the same reference numerals.

  As shown in FIG. 3A, a cleaned silicon substrate 5 is first prepared. Next, as shown in FIG. 3B, silicon oxide films 17 are formed on both surfaces of the silicon substrate 5 by thermal oxidation. Next, as shown in FIG. 3C, a reflective film made of aluminum or the like is deposited on the silicon oxide film 17 and patterned so as to leave the reflective film 6 in the region of the mirror portion 1 by photolithography and etching processes. To do.

  Next, a protective film 7 made of a silicon oxide film or the like is deposited on the entire surface of the silicon substrate 5. Next, a photoresist is applied to the back surface of the silicon substrate 5, and the photoresist in the corresponding region of the mirror portion 1 is removed to form an opening for ion implantation. Next, as shown in FIG. 3E, ion implantation is performed from the back surface to localize the implantation material 9. As already described, the ion implantation is performed by accelerating oxygen ions, phosphorus ions, and the like. Next, as shown in FIG. 3 (f), a photoresist 11 is applied to the surface of the silicon substrate 5, exposed and developed, and the photoresist in the region to be etched is removed. Next, as shown in FIG. 3G, the protective film 7, the silicon oxide film 17, the silicon substrate 5, and the silicon oxide film 17 on the back surface are removed by dry etching or wet etching in this order, and FIG. As shown, the photoresist 11 is removed. The subsequent steps are the same as those in FIGS. 2 (g) and 2 (h).

  In this embodiment, since the silicon oxide film 17 is formed on the back surface of the silicon substrate 5 by thermal oxidation, it is necessary to form a mask such as a resist on the back surface of the silicon substrate 5 when the silicon substrate 5 is wet-etched. There is an advantage that there is no.

  In the above description, the optical scanner using the silicon substrate has been described, but the present invention is not limited to this. A metal made of stainless steel, a metal oxide, glass, ceramics, or the like can be used as the substrate.

1A and 1B are a schematic top view and a cross-sectional view of an optical scanner according to an embodiment of the present invention. It is a flowchart which shows the manufacturing method of the optical scanner which concerns on embodiment of this invention. It is a flowchart which shows the manufacturing method of the optical scanner which concerns on embodiment of this invention. It is a perspective view of a conventionally well-known optical scanner, and sectional drawing of a mirror part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mirror part 2 Beam part 3 Frame part 5 Silicon substrate 6 Reflective film 7 Protective film 8 Silicon oxide film

Claims (4)

In a method for manufacturing an optical scanner, comprising: a mirror part; a beam part that supports the mirror part so as to be swingable; and a frame part that holds the beam part.
A film forming step of depositing a reflective film on the surface of the mirror portion; and an ion implantation step of injecting a material ionized by an ion implantation method into the mirror portion in order to reduce warpage of the surface of the mirror portion. An optical scanner manufacturing method.   The method of manufacturing an optical scanner according to claim 1, wherein the film forming step further includes a step of depositing a protective film on a surface of the reflective film.   The film forming step is a step of depositing a reflective film on one surface of the mirror portion, and the ion implantation step is a step of injecting ionized material into the other surface of the mirror portion. A method for manufacturing the optical scanner according to claim 1.   The method of manufacturing an optical scanner according to claim 1, wherein the ionized material is either oxygen or phosphorus.

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