JP2010286729A - Magneto-optical spatial light modulator and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magneto-optical spatial light modulator causing little variation between pixels and exhibiting excellent response speed. <P>SOLUTION: The spatial light modulator 1 includes a plurality of pixels 4 arranged in two dimensions on a transparent substrate 7 and reflects light incident from the substrate 7 side to emit the light. A pixel 4 includes a light modulation element 5 changing the polarization direction of the incident light to emit the light, a lower electrode 3 arranged below the light modulation element and containing a crystalline transparent electrode material formed by heating film formation, and an upper electrode 2 arranged on the light modulation element 5 and formed of a metal electrode material. The light transmitted through the substrate 7 to be incident on the pixel 4 is further transmitted through the lower electrode 3 to be incident on the light modulation element 5, and the light further transmitted through the light modulation element 5 is reflected on the upper electrode 2 to be emitted after being transmitted again through the light modulation element 5, the lower electrode 3, and the substrate 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a spatial light modulator that emits incident light by spatially modulating the phase and amplitude of the light by a magneto-optic effect.

  A spatial light modulator uses optical elements (light modulation elements) as pixels and arranges them in a two-dimensional array to spatially modulate the phase, amplitude, etc. of light. Widely used in fields such as equipment, display technology, and recording technology. In addition, since optical information can be processed in two dimensions in parallel, its application to optical information processing technology is also being studied. As a spatial light modulator, liquid crystal has been conventionally used and widely used as a display device, but for holography and optical information processing, since response speed and high definition of pixels are insufficient, in recent years, Development of a magneto-optical spatial light modulator using a magneto-optical material that is expected to be capable of high-speed processing and pixel miniaturization (for example, Patent Documents 1 to 3).

  The magneto-optic spatial light modulator uses the Faraday effect (Kerr effect in the case of reflection), which is emitted when the direction of polarization of the magneto-optic material, ie, the light incident on the magnetic material is transmitted or reflected. is doing. That is, assuming that the magnetization direction of the light modulation element in the selected pixel (selected pixel) is different from the magnetization direction of the light modulation element in the other pixel (non-selected pixel), the light emitted from the selected pixel and the non-selected pixel The emitted light causes a difference in the rotation angle (rotation angle) of the polarized light. As a method of changing the magnetization direction of the light modulation element, in addition to a method of applying a magnetic field to the light modulation element (Patent Documents 1 and 2), there is a method of injecting spin into the light modulation element (Patent Document 3) in recent years. .

  In order to apply a magnetic field to the light modulation element for each pixel, in Patent Documents 1 and 2, current is supplied to the periphery of the light modulation element by extending electrode wiring around the periphery of each pixel. Further, by arranging the wiring between the pixels in this way, incident light and outgoing light to the light modulation element are not blocked by the metal wiring. On the other hand, when spins are injected, a spin injection magnetization reversal element (Non-patent Document 1) such as a GMR (Giant MagnetoResistance) element is used as a light modulation element, and a pair of electrodes are connected above and below the light modulation element. Then, a current is supplied perpendicular to the film surface. In addition, since such a light modulation element (spin injection magnetization reversal element) is once supplied with a current having a predetermined magnitude and direction, the magnetization direction is maintained until a reverse current is supplied. As in Patent Document 3, by arranging strip-like electrodes vertically and horizontally on the upper side and the lower side, respectively, a current that changes the magnetization direction can be supplied to the light modulation element for each pixel. . In this way, in the magneto-optical spatial light modulator using spin injection, a transparent electrode material such as indium zinc oxide (IZO) is used in order to dispose electrodes above and below the light modulation element. In use, the light is configured to pass through the electrode and enter the light modulation element.

Japanese Patent Laying-Open No. 2005-70101 (Claim 2, FIG. 5) JP 2005-221841 A (Claim 1, FIG. 6) Japanese Patent Laying-Open No. 2008-83686 (paragraphs 0067 to 0072, FIG. 4)

E.B.Myers, D.C.Ralph, J.A.Katine, R.N.Louie, R.A.Buhrman, “Current-Induced Switching of Domains in Magnetic Multilayer Devices”, Science August 6, 1999, Vol.285, No.5429, p.867-870

  The spatial light modulators described in Patent Documents 1 and 2 have a structure in which the XY drive lines are arranged along the outer periphery of the pixel, so that it is difficult to form a fine pixel of several μm or less. In addition, if the pixels are further miniaturized in order to use a combined magnetic field by current, there is a problem that crosstalk to adjacent pixels increases.

  On the other hand, since the spatial light modulator described in Patent Document 3 supplies current perpendicularly to the film surface of the light modulation element, it can cope with pixel miniaturization. However, since the electrodes are arranged on the optical paths of the incident light and the outgoing light to the light modulation element, it is necessary to use a transparent electrode material that is greatly inferior in conductivity as compared with the metal electrode material. Is used for the electrode wiring, it is necessary to apply a high voltage with respect to the operating current of the light modulation element, and there is a possibility that the operation may vary among pixels in the pixel array, so there is room for improvement.

  The present invention was devised in view of the above problems, and by applying a spin-injection magnetization reversal element to a pixel, high-definition and high-speed response can be realized, and power saving and operation variation between pixels can be reduced. An object is to provide a possible magneto-optical spatial light modulator.

  In order to solve the above-mentioned problems, the present inventors have improved the conductivity by treating the transparent electrode material at a high temperature, and the light modulation is performed so that the light modulation element is not damaged by the high temperature treatment. In order to form an electrode made of a transparent electrode material before forming the element, a transparent electrode material is applied to the lower electrode disposed under the light modulation element, and light is incident from the lower electrode side. It was.

  That is, a magneto-optical spatial light modulator according to the present invention includes a substrate that transmits light, a plurality of pixels that are two-dimensionally arranged on the substrate, and a pixel that selects one or more pixels from the plurality of pixels. A selection unit; and a current supply unit that supplies a predetermined current to the pixel selected by the pixel selection unit, and reflects and emits the light that passes through the substrate and enters the plurality of pixels. In this magneto-optical spatial light modulator, the pixel has a light modulation element that emits light that has been incident upon selection by the pixel selection unit and changes its polarization direction to a specific direction, and the light modulation element. An upper electrode and a lower electrode connected to the upper and lower sides of the substrate, wherein the lower electrode is at least partially transparent so as to transmit light incident from the substrate side and transmit light emitted from the light modulation element The upper electrode is made of a metal electrode material so as to reflect light incident from the light modulation element.

  With this configuration, the magneto-optical spatial light modulator is configured such that light is transmitted through the substrate and the lower electrode and light is incident and emitted from the substrate side, so that only the lower electrode disposed under the light modulation element is transparent. An electrode material is provided. Therefore, since the light modulation element is laminated after forming the transparent electrode on the substrate, the resistance can be reduced by applying heat treatment or the like to the transparent electrode material without damaging the light modulation element.

  Furthermore, in the magneto-optic spatial light modulator according to the present invention, the lower electrode is disposed in a metal electrode having a through hole formed in a region overlapping the light modulation element in a plan view, and the through hole of the metal electrode. And a transparent electrode formed of the transparent electrode material electrically connected to the light modulation element.

  With this configuration, the magneto-optical spatial light modulator has a lower electrode than the transparent electrode except for the portion that becomes the optical path without providing incident light and outgoing light by providing the transparent electrode only in the portion that becomes the optical path in the lower electrode. These metal electrodes can be used. Therefore, the conductivity of the lower electrode can be improved.

  In the magneto-optic spatial light modulator according to the present invention, the transparent electrode material forming the lower electrode is preferably a crystalline material, and is further formed by heating film formation or post-annealing. More preferably, it is applied.

  With this configuration, the magneto-optical spatial light modulator can reduce the resistance by heat treatment even when a transparent electrode material having a higher resistance than the metal electrode material is used, so that the conductivity of the lower electrode can be improved. .

  The magneto-optic spatial light modulator manufacturing method according to the present invention also includes a magneto-optic that reflects and emits light incident on a plurality of pixels that are two-dimensionally arranged on the substrate through the substrate from below. A method of manufacturing a spatial light modulator, wherein a lower electrode forming step for forming a lower electrode, at least a part of which is made of a transparent electrode material, on the substrate, and light for forming a light modulation element on the lower electrode A modulation element formation step and an upper electrode formation step of forming an upper electrode made of a metal electrode material on the light modulation element, and in the lower electrode formation step, the transparent electrode material is formed by heating film formation, or Post-annealing is performed after forming the transparent electrode material.

  With this configuration, since the transparent electrode material is heat-treated before the light modulation element is formed, the resistance of the transparent electrode material can be reduced without damaging the light modulation element. An improved magneto-optic spatial light modulator can be manufactured.

  According to the magneto-optical spatial light modulator according to the present invention, it is possible to simultaneously achieve a high-definition having a visible light wavelength size (blue: 400 nm) from several μm or less and a high-speed response that is theoretically about several ps. A pixel is provided, power saving can be achieved, and variation in operation between pixels can be reduced. According to the method for manufacturing a magneto-optical spatial light modulator according to the present invention, the magneto-optical spatial light modulator having the above characteristics can be manufactured.

It is a bottom view showing typically the composition of the spatial light modulator concerning a 1st embodiment. FIG. 2 is an enlarged view of a pixel of the spatial light modulator according to the first embodiment, and is a partial cross-sectional view taken along line BB in FIG. It is a schematic diagram explaining the structure of a display apparatus using the spatial light modulator which concerns on 1st Embodiment, and the operation | movement of pixel selection, and is a figure corresponding to AA sectional drawing of FIG. It is a bottom face schematic diagram of a pixel array of a spatial light modulator concerning a 2nd embodiment. It is a top view of the pixel array of the spatial light modulator which concerns on 2nd Embodiment. FIG. 6 is an enlarged view of a pixel of a spatial light modulator according to a second embodiment, and is a DD partial cross-sectional view of FIG. 4. FIGS. 4A and 4B are schematic diagrams for explaining a lower electrode forming step in a method for manufacturing a pixel array of a spatial light modulator according to the second embodiment, wherein FIGS. 4A to 4C and FIGS. Partial sectional views (d) and (h) are plan views. FIGS. 4A and 4B are schematic diagrams for explaining a light modulation element forming step and an upper electrode forming step in the method for manufacturing a pixel array of the spatial light modulator according to the second embodiment. FIGS. -C partial sectional view, (d), (f) are plan views. FIGS. 4A and 4B are schematic views for explaining another lower electrode forming step in the method for manufacturing the pixel array of the spatial light modulator according to the second embodiment, and FIGS. FIG. 4B is a plan view. FIGS. 4A and 4B are schematic views for explaining another lower electrode forming step in the method for manufacturing a pixel array of the spatial light modulator according to the second embodiment, and FIGS. Figures (b) and (f) are plan views. It is a graph which shows the relationship between the film thickness of the transparent electrode and drive voltage in the pixel of an Example.

  Hereinafter, an embodiment for realizing a magneto-optical spatial light modulator according to the present invention (hereinafter referred to as a spatial light modulator as appropriate) will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a bottom view schematically showing the configuration of the spatial light modulator according to the first embodiment of the present invention. Note that the bottom surface (lower surface) in this specification is a light incident surface of the spatial light modulator. Further, the vertical and horizontal directions in the bottom view and the plan view indicate the vertical and horizontal directions in FIG. 1, respectively. FIG. 2 is an enlarged view of a pixel of the spatial light modulator according to the first embodiment of the present invention, and is a partial cross-sectional view taken along line BB in FIG. Below, each element which comprises the spatial light modulator which concerns on this invention is demonstrated.

  The spatial light modulator 1 includes a pixel array 40 including pixels 4 arranged in a two-dimensional array on a substrate 7 as shown in FIG. Further, the spatial light modulator 1 includes a current control unit 10 that selects and drives one or more pixels 4 from the pixel array 40. Note that the substrate 7 is disposed in front of the pixel array 40 in FIG. 1 (not shown). Further, the pixel in this specification refers to a means for displaying information (bright / dark) in the minimum unit of display by the spatial light modulator.

  As shown in FIG. 1, the pixel array 40 includes a plurality of upper electrodes 2, 2,... Striped in plan view, and a plurality of lower electrodes that are also striped and orthogonal to the upper electrode 2 in plan (bottom) view. .., And one pixel 4 is provided for each intersection of the upper electrode 2 and the lower electrode 3. Therefore, the pixels 4 are arranged in a two-dimensional array on the light incident surface of the spatial light modulator 1 to form the pixel array 40. In the present embodiment, the pixel array 40 is exemplified by a configuration including 25 pixels 4 of 5 rows × 5 columns. The upper electrode 2 and the lower electrode 3 are collectively referred to as electrodes 2 and 3 as appropriate. As shown in FIGS. 1 and 2, the pixel 4 includes an upper electrode 2 and a lower electrode 3 as a pair of electrodes in the pixel 4, and a light modulation element 5 sandwiched between the electrodes 2 and 3 from above and below. Is provided. Further, the insulating members 6 are buried between the adjacent upper electrodes 2 and 2, between the light modulation elements 5 and 5, and between the lower electrodes 3 and 3.

  As shown in FIG. 1, the current control unit 10 controls the upper electrode selection unit 12 that selects the upper electrode 2, the lower electrode selection unit 13 that selects the lower electrode 3, and the electrode selection units 12 and 13. A pixel selection unit (pixel selection means) 14 and a power supply (current supply means) 11 for supplying current to the electrodes 2 and 3 are provided. These may be known ones, and appropriate voltages and currents are supplied to reverse the magnetization of the light modulation element 5.

  The upper electrode selection unit 12 selects one or more of the upper electrodes 2, and the lower electrode selection unit 13 selects one or more of the lower electrodes 3, and each supplies a predetermined current from the power source 11. For example, the pixel selection unit 14 selects one or more specific pixels 4 of the pixel array 40 based on an external signal (not shown), and connects the electrodes 2 and 3 connected to the selected pixel 4 to the electrode selection units 12 and 13. To select. The power supply 11 supplies an appropriate voltage / current to reverse the magnetization of the light modulation element 5 provided in the selected pixel 4. With such a configuration, a specific pixel 4 is selected, and a predetermined current is supplied to the light modulation element 5 of this pixel 4 to reverse the magnetization. In FIG. 1, the power source 11 is connected to one end of each of the electrodes 2 and 3 via the electrode selection units 12 and 13, but may be connected to both ends. By connecting to both ends, the response speed can be increased and the operation variation between pixels can be reduced.

  Next, details of the pixel configuration of the spatial light modulator according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  The upper electrode 2 is disposed on the light modulation element 5 as shown in FIG. 2, and extends in a strip shape in the lateral direction as shown in FIG. One upper electrode 2 supplies current to each of the light modulation elements 5 of the plurality of pixels 4, 4,... Arranged in one horizontal row. On the other hand, the lower electrode 3 is arranged under the light modulation element 5 and extends in a strip shape in the vertical direction. One lower electrode 3 supplies a current to each of the light modulation elements 5 of the plurality of pixels 4, 4,... Arranged in one vertical column. The lower electrode 3 is made of a transparent electrode material so as not to block incident light and outgoing light to the light modulation element 5. On the other hand, the upper electrode 2 is made of a metal electrode material having a high reflectivity in order to reflect the light transmitted through the light modulation element 5 from the lower side (the lower electrode 3 side) and reach the lower side again.

  The upper electrode 2 is made of a general electrode metal material such as a metal such as Cu, Al, Au, Ag, Ta, or Cr, or an alloy thereof. Then, it is processed into a stripe shape by a known method such as a sputtering method, by film formation, photolithography, etching, lift-off method, or the like.

  As shown in FIG. 2, the lower electrode 3 includes a transparent electrode 31 made of a transparent electrode material, and a base layer 32 that is a metal film laminated between the transparent electrode 31 and the light modulation element 5. Thus, when an electrode (wiring) is comprised with a transparent electrode material, it is preferable to provide a metal film between an electrode and the light modulation element 5 connected to this electrode. By interposing the base layer 32, which is a metal film, between the light modulation element 5 and the transparent electrode 31 made of a transparent electrode material having a resistance higher than that of the metal electrode material, the contact between the lower electrode 3 and the light modulation element 5 is achieved. The response speed can be increased by reducing the resistance.

  The transparent electrode 31 is, for example, known indium tin oxide (ITO), gallium zinc oxide (GZO), aluminum oxide-zinc oxide (AZO), or the like. It consists of a crystalline transparent electrode material. By using a crystalline material, resistance can be reduced by heat deposition or post-annealing after deposition. As will be described later, these transparent electrode materials are formed at a high temperature by a known method such as a sputtering method or a vacuum deposition method. Alternatively, post-annealing is performed after the film is formed by the method or the coating method at a low temperature (no heating) such as room temperature. Then, the shape of the lower electrode 3 is processed into a stripe shape by photolithography and etching.

  As the metal constituting the underlayer 32, for example, Au, Ru, Ta, or an alloy composed of two or more of these metals can be used, and these metals are formed by a known method such as a sputtering method. Is done. In order to further reduce the contact resistance by improving the adhesion between the base layer 32 and the layer above it, that is, the magnetization free layer 53 which is the lowermost layer of the light modulation element 5 described later, the metal film that becomes the base layer 32 is It is preferable to form a film continuously with the magnetic material to be the magnetization free layer 53 in a vacuum processing chamber. Since the continuously formed films are usually processed together, as shown in FIG. 2, the underlayer 32 has the same planar view shape as the light modulation element 5, but for example, the transparent electrode 31 (lower electrode) The same planar view shape (band shape) as 3) may be used. Details will be described in the manufacturing method of the pixel 4. If the thickness of the underlayer 32 is less than 1 nm, it is difficult to form a continuous film, while if it exceeds 10 nm, the amount of transmitted light is reduced. Therefore, the preferable thickness of the foundation layer 32 is 1 to 10 nm.

In the spatial light modulator 1 according to the present invention, light is incident on the pixel 4 from the lower side, that is, the substrate 7 side, and the light reflected by the pixel 4 is emitted to the substrate 7 side, so that the substrate 7 is made of a transparent material. Become. In addition, the substrate 7 has heat resistance that can cope with high-temperature processing in the formation of the transparent electrode 31 of the lower electrode 3, and examples thereof include glass, SiO ₂ , Al ₂ O ₃ , and MgO. The insulating member 6 is disposed between the adjacent upper electrodes 2 and 2, between the light modulation elements 5 and 5, and between the lower electrodes 3 and 3 (not shown in FIG. 2), and is made of, for example, SiO ₂ or Al ₂ O _3. Become.

  As shown in FIG. 1, the light modulation element 5 is arranged in a portion where the upper electrode 2 and the lower electrode 3 overlap in a plan (bottom) view, and is sandwiched and connected to the electrodes 2 and 3 from above and below. The planar view shape of the light modulation element 5 is a square in the present embodiment, but is not limited to this. In addition, one light modulation element 5 is arranged for one pixel 4. For example, a plurality of light modulation elements such as (1 × 3), (2 × 2), and the like are provided in one pixel 4 in the surface direction. An element 5 may be provided. The light modulation element 5 is a spin-injection magnetization reversal element, and is a known element such as a CPP-GMR (Current Perpendicular to the Plane Giant MagnetoResistance) element or a TMR (Tunnel MagnetoResistance) element. Become. As shown in FIG. 2, the configuration of the light modulation element 5 is formed by laminating a magnetization free layer 53, an intermediate layer 52, a magnetization fixed layer 51, and a protective layer 54 in this order on the lower electrode 3. Each of these layers is formed into a film by a known method such as a sputtering method or a molecular beam epitaxy (MBE) method, stacked, and processed into the shape by electron beam lithography or the like.

  The magnetization fixed layer 51 and the magnetization free layer 53 are magnetic bodies, and both have in-plane magnetic anisotropy or both have perpendicular magnetic anisotropy. And while the magnetization direction of the magnetization fixed layer 51 is fixed, the magnetization direction of the magnetization free layer 53 is not fixed and can be easily rotated (reversed) by spin injection. The intermediate layer 52 provided between these two layers is formed of an insulator if the light modulation element 5 is a TMR element, and a nonmagnetic conductor if it is a CPP-GMR element. Although these three layers operate as spin injection magnetization reversal elements, a protective layer 54 is provided as the uppermost layer in order to protect these layers (particularly the magnetization fixed layer 51) from damage in the manufacturing process.

The magnetization fixed layer 51 has a thickness of several to several tens of nm. When the magnetization fixed layer 51 has in-plane magnetic anisotropy, the magnetization fixed layer 51 is made of a ferromagnetic metal (FM) or a magnetic semiconductor. Ferromagnetic metals include transition metals such as Fe, Co, Ni and alloys containing them, multilayer films such as FM / PtMn, FM / Ru / FM / PtMn (synthetic pin layers, laminated ferristructure), IrMn, etc. And FM / IrMn and FM / Ru / FM / IrMn, each of which has a magnetic pinned layer of the above structure. In addition, examples of magnetic semiconductors include ZnO: Mn, ZnO: Mn _1-X Fe _X , ZnO: Cr _1-X Mn _{X and the} like based on ZnO, III-V group compound semiconductors as the base, TiO And those based on II-VI group compound semiconductors. On the other hand, in the case of the magnetization fixed layer 51 having perpendicular magnetic anisotropy, a transition metal such as Fe, Co, Ni, and an alloy containing them, a multilayer of [Fe / Pt] × n and [Co / Pt] × n Examples thereof include ferromagnetic metals such as films and alloys containing rare earth such as Sm, Eu, Gd, and Tb.

The intermediate layer 52 is provided between the magnetization fixed layer 51 and the magnetization free layer 53. If the light modulation element 5 is a TMR element, the intermediate layer 52 is made of an insulator such as MgO, Al ₂ O ₃ , HfO ₂ or a laminated film containing an insulator such as Mg / MgO / Mg. The thickness is about 0.5 to 3 nm. If the light modulation element 5 is a CPP-GMR element, the intermediate layer 52 is made of a nonmagnetic metal such as Cu, Au, or Ag and has a thickness of about 3 to 20 nm.

The magnetization free layer 53 is made of a ferromagnetic metal or a magnetic semiconductor and has a thickness of about 1 to 20 nm. As a material for forming the magnetization free layer 53 having in-plane magnetic anisotropy, transition metals such as Fe, Co, and Ni, alloys including them such as CoFe, CoFeB, and NiFe, and two or more of these materials are used. And a ferromagnetic metal such as FM / Ru / FM (synthetic free layer, laminated ferrimagnetic structure). Alternatively, a magnetic semiconductor based on ZnO, such as ZnO: Mn, ZnO: Mn _1-X Fe _X , ZnO: Cr _1-X Mn _X , III-V group compound semiconductor, or II-VI group compound semiconductor is used as a base. Things. On the other hand, as the material for the magnetization free layer 53 having perpendicular magnetic anisotropy, transition metals such as Fe, Co, Ni and alloys containing them, CoPt, CoCr base alloys (CoCr, CoCrPt, CoCrTa, etc.), Examples include [Fe / Pt] × n and [Co / Pt] × n multilayer films, alloys containing rare earth such as Sm, Eu, Gd, and Tb, and ferromagnetic metals such as MnBi.

  The protective layer 54 is composed of a single layer of Ta, Ru, Cu, or two layers of Cu / Ta, Cu / Ru. In addition, when setting it as the said 2 layer, all make Cu inside (lower layer). If the thickness of the protective layer 54 is less than 1 nm, it is difficult to form a continuous film. On the other hand, the effect is saturated even if the thickness exceeds 10 nm. Therefore, the thickness of the protective layer 54 is preferably 1 to 10 nm, and more preferably 3 to 5 nm.

  Next, the pixel selection operation of the spatial light modulator according to the first embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram for explaining the configuration of the display device using the spatial light modulator and the pixel selection operation according to the first embodiment, and corresponds to a cross-sectional view taken along the line AA in FIG. The electrodes 2 and 3 are connected to the current control unit 10 as described above. 3, since the spatial light modulator 1 according to the first embodiment is used for a display device, a light source that irradiates light toward the pixel array 40 below the pixels 4 (pixel array 40). 93, an incident polarization filter 91 that polarizes the light emitted from the light source 93 before entering the pixel array 40, and an output polarization filter 92 that transmits only polarized light in a specific direction from the light emitted from the pixel array 40. A detector 94 that detects light transmitted through the output polarization filter 92 is disposed. Thus, the spatial light modulator 1 is a reflective spatial light modulator that reflects light incident from below the pixel array 40.

  In this embodiment, the light modulation element 5 is a spin-injection magnetization reversal element including a magnetization fixed layer 51 and a magnetization free layer 53 having in-plane magnetic anisotropy, that is, magnetization in the film surface direction. In FIG. 3, the magnetization directions of the magnetization fixed layer 51 and the magnetization free layer 53 are indicated by rightward or leftward arrows. In FIG. 3, the protective layer 54 of the light modulation element 5 is not shown.

  Since light (laser light or the like) emitted from the light source 93 includes various polarization components, the light is transmitted through the incident polarization filter 91 in front of the pixel array 40 to be light of one polarization component. Hereinafter, light of one polarization component is referred to as polarization. This polarized light (incident polarized light) passes through the substrate 7 and enters all the pixels 4 of the pixel array 40 at a predetermined incident angle. In each pixel 4, the incident polarized light passes through the lower electrode 3 and enters the light modulation element 5, is reflected by the light modulation element 5 or the upper electrode 2 thereon, and is emitted from the light modulation element 5 as outgoing polarization. Then, the light passes through the lower electrode 3 again and is emitted from the pixel 4. All the outgoing polarized light emitted from each pixel 4 passes through the substrate 7 again and reaches the outgoing polarization filter 92. The outgoing polarization filter 92 transmits only specific polarized light, here polarized light whose angle θap is rotated with respect to incident polarized light, and this transmitted outgoing polarized light is incident on the detector 94. The polarizing filters 91 and 92 are polarizing plates, respectively, and the detector 94 is an image display means such as a screen. Alternatively, the detector 94 may be imaging means such as a camera.

  The light modulation element 5, which is a spin injection magnetization reversal element, reverses the magnetization direction of the magnetization free layer 53 by injecting electrons having spins in the opposite direction, that is, by supplying current in the opposite direction (spin injection magnetization). To the same direction as the magnetization direction of the magnetization fixed layer 51 or a direction different by 180 °. Specifically, when the upper electrode 2 is set to “−” and the lower electrode 3 is set to “+”, and a current is supplied from the magnetization free layer 53 side to the magnetization fixed layer 51, the magnetization of the magnetization free layer 53 is changed to the magnetization fixed layer 51. It becomes the same direction as the magnetization direction. Hereinafter, this state is referred to as that the magnetization of the light modulation element 5 is parallel (P: Parallel). Conversely, when the upper electrode 2 is set to “+” and the lower electrode 3 is set to “−” and a current is supplied from the magnetization fixed layer 51 side to the magnetization free layer 53, the magnetization of the magnetization free layer 53 becomes the magnetization of the magnetization fixed layer 51. The direction is opposite to the direction. Hereinafter, this state is referred to as anti-parallel (AP) where the magnetization of the light modulation element 5 is antiparallel. As shown in FIG. 3, since the magnetization of the magnetization fixed layer 51 is aligned in one direction (rightward) in all the pixels 4, the magnetization of the magnetization free layer 53 according to the direction of the current from the electrodes 2 and 3. Indicates either right-facing or left-facing. In addition, if the magnetization of the light modulation element 5 indicates either parallel or antiparallel magnetization, the magnetization is maintained until a current for inverting the magnetization is supplied. As described above, since the magnetization is held in the light modulation element 5, the current supplied to the light modulation element 5 is a current that temporarily reaches a current value that reverses the magnetization direction, such as a pulse current. Can do.

  The polarized light incident on the light modulation element 5 is transmitted through the magnetization free layer 53, the intermediate layer 52, and the magnetization fixed layer 51, reflected by the lower surface of the upper electrode 2, and again the magnetization fixed layer 51, the intermediate layer 52, and the magnetization free layer. 53 is transmitted through the magnetization free layer 53 and the magnetization fixed layer 51, which are magnetic materials, the direction of polarization of each of the magnetization free layer 53 and the magnetization fixed layer 51 depends on the Faraday effect. Rotate (rotate) to a predetermined angle (rotation angle). Furthermore, the polarized light incident on the parallel and antiparallel light modulation elements 5 is emitted by rotating in the opposite directions at the optical rotation angle because the magnetization direction of the magnetization free layer 53 differs by 180 °. Therefore, the optical rotation angles in the light modulation elements 5 having parallel and antiparallel magnetization can be expressed by angles different from θp and θap, respectively. Since the magnetization direction of the magnetization fixed layer 51 is constant, the difference between the optical rotation angles θp and θap is determined only by the magnetization free layer 53.

  Alternatively, when the polarized light incident on the light modulation element 5 is transmitted through the magnetization free layer 53, reflected at the interface with the intermediate layer 52, and transmitted again through the magnetization free layer 53, the magnetization direction changes. Since the magnetization free layer 53 is transmitted, a difference between the optical rotation angles θp and θap is similarly generated. As described above, when the light modulation element 5 is reversed in magnetization, the outgoing polarized light becomes polarized light in different directions rotated by the optical rotation angles θp and θap with respect to the incident polarized light in the same direction.

  The outgoing polarized light from the pixels 4 and 4 at both left and right ends of FIG. 3 rotated by an angle θap with respect to the incident polarized light passes through the outgoing polarizing filter 92 and reaches the detector 94, so that the pixel 4 is bright (white). ) Is displayed on the detector 94. On the other hand, since the outgoing polarized light from the central pixel 4 is blocked by the outgoing polarizing filter 92, the pixel 4 is dark (black) and displayed on the detector 94. Thus, light / dark (white / black) can be separated for each pixel, and light / dark can be switched by switching the direction of the current. Note that, as an initial state of the spatial light modulator 1, for example, all the upper electrodes 2 are set to “+” in order to supply a downward current to the light modulation elements 5 of all the pixels 4 so that the whole is displayed white. All of the lower electrode 3 may be set to “−”.

  Here, the magneto-optical effect is larger as the incident angle of light is closer to the parallel to the magnetization direction of the magneto-optical material. Therefore, in the light modulation element 5 having in-plane magnetic anisotropy, the closer the incident angle of light (incident polarization) is to be parallel to the film surface, that is, the film surface direction of the pixel array 40, The difference between the optical rotation angles θp and θap can be increased. However, due to the structure of the pixel array 40, in order for light to enter from the bottom surface of the light modulation element 5, a certain degree of inclination is required for the incident angle. Therefore, the incident angle of light to the pixel 4 in the spatial light modulator 1 is 10 ° to 60 ° with respect to the magnetization direction of the magnetization free layer 53 of the light modulation element 5 in operation, that is, the magnetization direction of the magnetization fixed layer 51. The incident angle is preferably in the range of 30 ° to 80 °. As shown in FIG. 3, in the spatial light modulator 1 of this embodiment, light is incident on the pixel array 40 obliquely. In addition, since the optical paths of both the incident polarized light and the outgoing polarized light are below the pixel array 40, the outgoing polarized light filter 92 and the detector 94 are positioned so as not to block the optical path of the incoming polarized light. Each is arranged at a position that does not block the optical path.

  When the light modulation element 5 includes the magnetization fixed layer 51 and the magnetization free layer 53 having perpendicular magnetic anisotropy, the respective magnetizations are in the vertical direction, and the magnetization of the magnetization free layer 53 is reversed in the upward / downward direction. In this case, the Faraday effect is similarly produced. In addition, it is desirable to make the incident angle of polarized light to the pixel 4 (pixel array 40) provided with such a light modulation element 5 0 ° in order to increase the optical rotation angle, but in this case, the optical path of the outgoing polarized light is incident. It coincides with the optical path of polarization. Therefore, the incident angle is inclined by about 5 ° to 30 ° so that the outgoing polarization filter 92, the detection unit 94, the light source 93, and the incoming polarization filter 91 are arranged so as not to block the optical paths of the incoming polarized light and the outgoing polarized light, respectively. That is, the incident angle of polarized light is preferably 5 ° to 30 °. Alternatively, the incident angle may be 0 °, and a half mirror may be disposed between the incident polarization filter 91 and the pixel array 40 to reflect only the outgoing polarized light laterally. In this case, the output polarization filter 92 and the detector 94 are arranged on the side of the pixel array 40.

Here, the necessary minimum voltage (drive voltage) applied through the electrodes 2 and 3 to supply a current for reversing the spin injection magnetization of the light modulation element 5 is proportional to the resistance of the pixel 4. Therefore, the applied voltage can be lowered as the sum of the resistances of the upper electrode 2, the light modulation element 5, and the lower electrode 3, which are the resistances of the pixels 4, is smaller. The resistance of the light modulation element 5 is determined by the configuration of the light modulation element 5, and the upper electrode 2 is made of a metal electrode material. Therefore, the resistance is negligible compared to the light modulation element 5 and the lower electrode 3 made of a transparent electrode material. Since the value is as small as possible (for example, the specific resistance of Cu: 1.68 × 10 ⁻⁶ Ω · cm), the drive voltage greatly depends on the resistance of the lower electrode 3.

  Common transparent electrode materials include crystalline ITO, GZO, AZO, amorphous IZO, and the like. When a transparent electrode material is applied as the upper electrode, it is necessary to form a film, process, and the like under conditions that do not damage the lower light modulation element, and the temperature is limited to about 200 ° C. or lower. In such a case, IZO (specific resistance: 450 μΩ · cm) that can obtain relatively good conductivity by non-heating (room temperature or the like) film formation is preferably used. In particular, in the case of non-heated film formation, film formation on a resist mask is possible, so that processing by a lift-off method is also possible. On the other hand, a crystalline conductive material such as ITO can increase the crystal grain size and reduce the resistance by heat treatment such as heat film formation or post-annealing after film formation. For example, the specific resistance of ITO formed without heating (room temperature) is 700 to 800 μΩ · cm, but the ITO formed by sputtering at 350 ° C. (substrate temperature) has a specific resistance of 100 μΩ · cm. It is about 1/8 of ITO of heat-deposited film and 1/4 or less for IZO.

In the spatial light modulator 1 according to the first embodiment, the transparent electrode material is directly formed on the substrate 7 as the transparent electrode 31 of the lower electrode 3 so that the processing within the durability range of the material of the substrate 7 is achieved. It becomes possible to perform high-temperature processing such as the above-mentioned heating film formation and post-annealing. Specifically, in the case of applying ITO as the transparent electrode material, a film formation temperature of 200 to 600 ° C. is preferable, or after film formation without heating, at 200 ° C. for 10 min or more in a vacuum (in the atmosphere) It is preferable to perform post annealing for about 30 to 60 minutes. Also, a film can be formed by a coating method that requires firing, and a solution of an ITO raw material (for example, a solution in which a metal salt InI ₃ and SnO ₂ are dissolved in an organic solvent at a mass ratio of 95: 5) is spin-coated on the substrate 7. The organic substance is decomposed by an ordinary baking condition, for example, a heat treatment at 400 to 600 ° C. in the air to form an ITO-only film. Further, as post-annealing, the firing temperature is maintained, and the N ₂ atmosphere containing 0.05 to 0.1% of H ₂ is changed into a N ₂ atmosphere, followed by heat treatment to give oxygen defects in the ITO film. Improve conductivity. Other transparent electrode materials can also be treated so as to have particularly excellent properties such as conductivity and transmittance.

  Thus, by using the transparent electrode 31 with a reduced resistance, that is, the lower electrode 3 with a low resistance, the applied voltage does not need to be excessively increased with respect to the inversion current density of the light modulation element 5, and the spatial light modulator 1 power saving is possible. Further, since it is not necessary to expand the cross-sectional area of the wiring in order to reduce the resistance of the lower electrode 3, the wiring width can be narrowed to further reduce the size of the pixel 4, and the wiring (transparent electrode 31) can be reduced. Thinning is possible, and attenuation of the amount of outgoing light with respect to incident light is suppressed.

  As described above, according to the first embodiment, a spatial light modulator capable of saving power is achieved by using a spin injection light modulation element capable of high-definition and high-speed response. Alternatively, a spatial light modulator capable of further miniaturizing pixels and suppressing attenuation of the amount of emitted light is obtained.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIGS. 4, 5, and 6. FIG. 4 is a bottom view schematically showing the configuration of the pixel array of the spatial light modulator according to the second embodiment. As in the first embodiment, 25 pixels are arranged in an array of 5 rows × 5 columns. Is. FIG. 5 is an enlarged perspective view (upper view) from below of a pixel of the spatial light modulator according to the second embodiment with a part thereof cut away. FIG. 6 is an enlarged sectional view of a pixel according to the second embodiment, and is a DD partial sectional view of FIG. FIG. 4 shows the substrate, and FIG. 5 shows the substrate and the insulating member without illustration. The same elements as those in the first embodiment (see FIGS. 1 to 3) are denoted by the same reference numerals, and the description thereof is omitted. As shown in FIGS. 5 and 6, the pixel 4 </ b> A of the second embodiment has the same configuration as the pixel 4 of the first embodiment, except that the lower electrode 3 </ b> A is provided. That is, the spatial light modulator including the pixel array 40A according to the second embodiment also changes the direction of optical rotation of incident polarized light from below by the spin injection magnetization reversal of the light modulation element 5 as in the first embodiment. Since it is a reflective spatial light modulator that emits downward, the description of its operation is omitted (see FIG. 3).

  In the pixel array 40A of the second embodiment, the lower electrodes 3A, 3A,... Have a stripe shape extending in the vertical direction in the same manner as the lower electrodes 3, 3,. The lower electrode 3A includes a metal electrode 33 in which a plurality of holes (through holes) are formed in a band shape, and a transparent electrode 31A having a shape filled in the holes. The hole of the metal electrode 33 and the transparent electrode 31 </ b> A are provided in a region overlapping the light modulation element 5 in a plan view, that is, immediately below the light modulation element 5. Accordingly, one metal electrode 33 has five holes that are the number of pixels 4A in the vertical direction (row). A transparent electrode 31 </ b> A is provided in the hole of the metal electrode 33 so as to be electrically connected to the lower surface of the light modulation element 5.

  The metal electrode 33 is made of a general electrode metal material similar to the upper electrode 2 of the first and second embodiments, and the transparent electrode 31A is the same as the transparent electrode 31 of the lower electrode 3 of the first embodiment. Since it is comprised with a crystalline transparent electrode material, description is abbreviate | omitted, respectively. In the present embodiment, the transparent electrode 31A is a window through which light enters and exits the light modulation element 5, and the shape (shape of the hole of the metal electrode 33) and size are not particularly limited, but the shape in plan view is If the shape of the light modulation element 5 is small with respect to the plan view, the metal electrode 33 blocks the light and the amount of emitted light is reduced. If it is too large, the metal electrode 33 becomes narrow at the periphery of the hole and the metal electrode 33 The resistance increases and the resistance of the lower electrode 3A increases. Therefore, it is preferable that the planar view shape of the transparent electrode 31 </ b> A is similar to the planar view shape of the light modulation element 5 and is large in the range where the metal electrode 33 does not become narrow at the periphery of the hole. Thus, in the lower electrode 3A, the drive voltage can be further reduced by using the metal electrode having a low resistance as the main material, with the transparent electrode only under the light modulation element 5, that is, the optical path portion. In addition, variations due to the positions of the pixels 4A in the pixel array 40A can be reduced.

  5 and 6, the shape of the transparent electrode 31 </ b> A is a quadrangular prism whose side surface is vertical. However, the shape is not limited to this, and for example, a mesa shape (square frustum) whose side surface is inclined may be used. When the light modulation element 5 side is narrow and widens toward the substrate 7, the contact area between the transparent electrode 31A and the metal electrode 33 is increased, and the contact resistance in the lower electrode 3A can be reduced. Furthermore, as in the spatial light modulator 1 according to the first embodiment (see FIG. 3), when the incident / exit angle of light is oblique (non-perpendicular to the pixel array 40A), the metal electrode 33 for incident / exited light is used. As a result, the amount of the emitted light is improved.

  Further, similarly to the first embodiment, the lower electrode 3A is preferably provided with a base layer 32 made of a metal film between the transparent electrode 31A and the light modulation element 5 to reduce the contact resistance. The underlayer 32 only needs to be provided between the transparent electrode 31A and the light modulation element 5 as in the first embodiment, and has the same planar view shape as the light modulation element 5 as shown in FIGS. It may be formed, may be the same as the transparent electrode 31A, that is, may be formed so as to fill each hole of the metal electrode 33, or may have the same planar view shape (band shape) as the lower electrode 3A. Since the material and thickness of the foundation layer 32 are the same as those of the foundation layer 32 of the lower electrode 3 of the first embodiment, description thereof is omitted.

  As described above, according to the second embodiment, the electrode having the advantages of both the transparent electrode material that does not block light and the low-resistance metal material can further reduce the drive voltage and increase the response speed. The spatial light modulator has a reduced variation in operation between pixels.

[Method of manufacturing spatial light modulator]
Next, as a method for manufacturing a pixel (pixel array) of the spatial light modulator according to the present invention, an example of a method for manufacturing a pixel array according to the second embodiment will be described with reference to FIGS. 7 to 10 are schematic views for explaining a method of manufacturing the pixel array according to the second embodiment, and are respectively a partial cross-sectional view (hereinafter referred to as a cross-sectional view) or a plan view in FIG. FIGS. 7A and 7B are schematic views in the lower electrode forming step, wherein FIGS. 7A to 7C and FIGS. 7E to 7G are cross-sectional views, and FIGS. 7D and 7H are plan views. FIGS. 8A and 8B are schematic views in the light modulation element forming step and the upper electrode forming step. FIGS. 8A to 8C are sectional views, and FIGS. 8D and 8F are plan views. 9 and 10 are schematic views for explaining another method in the lower electrode forming step, in which (a), (c) and (d) of FIG. 9 are cross-sectional views, and (b) is a plan view. 10 (a), (c)-(e) are sectional views, and (b), (f) are plan views. Moreover, in FIGS. 7-10, the code | symbol with () is attached | subjected and shown to the film | membrane before shaping | molding (processing) of each element.

(Lower electrode forming step S10)
As the lower electrode forming step S10, the lower electrode 3A is formed.
First, the transparent electrode 31A is formed (transparent electrode forming step S11e ₀ ). A transparent electrode material is formed on the substrate 7 by sputtering or the like at a high temperature. A resist (PR1) mask is formed on the transparent electrode film in a region to be a window of the transparent electrode 31A by photolithography or the like, and the transparent electrode film is processed into the shape of the transparent electrode 31A by etching such as ion milling ( FIG. 7 (a)). Further, post-annealing may be performed after forming the transparent electrode material at a low temperature (no heating).

  Next, the metal electrode 33 is formed (metal electrode formation step S12m). A metal electrode material is formed with the resist remaining on the transparent electrode 31A (FIG. 7B), and the resist PR1 is removed together with the metal electrode film (33) thereon using a resist stripping solution (lift-off). FIG. 7 (c), (d)). Then, a resist (PR2) mask is formed on the lower electrode 3A, that is, the wiring region on the metal electrode film (33) + the transparent electrode 31A (FIG. 7E), and the metal electrode film (33) is etched to form the metal electrode 33. (Fig. 7 (f)).

  Next, the insulating member 6 is formed between the metal electrodes 33 and 33 (between the lower electrodes 3A and 3A) by a lift-off method (insulating member forming step S13b). That is, an insulating material is formed with the resist PR2 remaining, and the insulating film 6 is deposited between the lower electrodes 3A and 3A by removing the resist PR2 together with the insulating film thereon (FIG. 7G). (H)). Alternatively, after processing the metal electrode 33, the resist PR2 is removed, and then an insulating material is formed and embedded between the metal electrodes 33 and 33, and the transparent electrode 31A is formed by etching, CMP (Chemical Mechanical Polishing), or the like. The insulating film may be removed to remove the insulating film until the upper surface is exposed.

(Light modulation element forming step S20)
As described above, since the base layer 32 and the layers serving as the light modulation element 5 on the lower electrode 3A are preferably formed continuously, the transparent electrode 31A and the metal electrode 33 formed on the substrate 7 are used. On the insulating member 6 between the metal electrodes 33 and 33, the underlayer 32, the magnetization free layer 53, the intermediate layer 52, the magnetization fixed layer 51, and the protective layer 54 are successively formed in sequence. They are stacked (FIG. 8 (a)). A resist (PR3) mask is formed on the protective layer film (54) in the region to be the light modulation element 5, and the laminated film of the protective layer film (54) to the metal film (32) is processed by electron beam lithography or the like. The light modulation element 5 and the base layer 32 are formed (FIG. 8B). An insulating material is formed with the resist PR3 left, and the resist PR3 is removed together with the insulating film thereon, thereby depositing an insulating member 6 between the light modulation elements 5 and 5 (FIG. 8C). (D)). Alternatively, after processing the light modulation element 5 and the base layer 32, the resist PR3 is removed, and then an insulating material is formed and embedded between the light modulation elements 5 and 5, and the upper surface of the light modulation element 5 by etching or CMP ( The insulating film may be removed until the protective layer 54) is exposed to form the insulating member 6.

(Upper electrode forming step S30)
Next, the upper electrode 2 is formed. A resist mask is formed on the insulating member 6 between the light modulation elements 5 and 5 in a region between the stripe-shaped wirings orthogonal to the lower electrode 3A (between the upper electrodes 2 and 2), and a metal electrode material is formed thereon. The upper electrode 2 is formed by removing the resist together with the metal electrode material thereon (lift-off). Finally, the insulating member 6 is deposited between the upper electrodes 2 and 2 (and above) to form the pixel 4A (pixel array 40A) (FIGS. 8E and 8F).

  When the pixel array 40 according to the first embodiment is formed, the transparent electrode 31 is formed by processing the transparent electrode material formed on the substrate 7 into a stripe shape of the shape of the lower electrode 3 in the lower electrode formation step S10. After that, the insulating member 6 is deposited between the transparent electrodes 31 and 31 (between the lower electrodes 3 and 3). Thereafter, it can be manufactured in the steps S20 and S30.

The lower electrode 3A (transparent electrode 31A, metal electrode 33) can also be formed by the following method described with reference to FIGS. 7 and 9 (lower electrode formation step S10A).
First, the transparent electrode 31A is formed on the substrate 7 in the same manner as described above (transparent electrode forming step S11e). Here, after forming the transparent electrode 31A (FIG. 7A), the resist PR1 is further removed. The transparent electrode 31A can also be formed by a lift-off method. In this case, the transparent electrode material is formed without heating, the resist is removed, and post-annealing is performed thereafter.

  Next, the insulating member 6 is formed by a lift-off method in a region (inter-wiring region) between the lower electrodes 3A and 3A (insulating member forming step S12b). A resist (PR4) mask is formed on the substrate 7 + transparent electrode 31A in the region to be the lower electrode 3A, that is, the wiring region (FIGS. 9A and 9B), and an insulating material is formed on the resist (PR4) mask. PR4 is removed together with the insulating film thereon (FIG. 9C).

  Next, the metal electrode 33 is formed (metal electrode formation step S13m). A metal electrode film is formed and embedded between the transparent electrodes 31A and 31A and between the insulating members 6 and 6 (FIG. 9D), and until the upper surfaces of the transparent electrode 31A and the insulating member 6 are exposed by CMP or the like (33) is removed to form a metal electrode 33 (FIGS. 7G and 7H). Thus, by forming the metal electrode 33 after the transparent electrode 31A and the insulating member 6, it is possible to apply Cu, which is difficult to dry-etch. First, the insulating member 6 in the region between the lower electrodes 3A and 3A is formed, and a resist mask having a window (region to be the transparent electrode 31A) is formed thereon (on the substrate 7 + insulating member 6), and lift-off is performed. The transparent electrode 31A can be formed by the method and post-annealing to obtain the state shown in FIG.

  Further, the lower electrode 3A can be formed by forming the metal electrode 33 first and then embedding a transparent electrode material in the hole to form the transparent electrode 31A. An example will be described with reference to FIG. 10 (lower electrode forming step S10B).

First, the metal electrode 33 is formed on the substrate 7 by a lift-off method or the like (metal electrode formation step S11m). Next, the insulating member 6 is formed between the metal electrodes 33 and 33 (between the lower electrodes 3A and 3A, the region between the wirings) by a lift-off method (insulating member forming step S12b ₁ ). A resist (PR5) mask is formed on the metal electrode 33 and the region above the hole, which is slightly narrower (thin) than the region to be the lower electrode 3A (FIGS. 10A and 10B), and an insulating material is formed thereon. Then, the resist PR5 is removed together with the insulating film thereon (FIG. 10C).

  Next, the transparent electrode 31A is formed (transparent electrode forming step S13e). A transparent electrode material is formed to be slightly thicker than the metal electrode 33 and embedded in the hole of the metal electrode 33 (FIG. 10D). A resist (PR6) mask is formed on the transparent electrode film (31A) in a region that is slightly larger than the planar view shape of the hole of the metal electrode 33, and the transparent electrode film (31A) is processed by etching (FIG. 10E). ), The resist PR6 is removed (FIG. 10F). In the lower electrode 3A formed by this method, the transparent electrode 31A has a thickness thicker than that of the metal electrode 33 and is laminated on the upper surface of the metal electrode 33 at the periphery of the hole.

By processing so that the transparent electrode 31A is left in a region larger than the hole of the metal electrode 33 in this way, there is no gap on the side surface of the hole of the metal electrode 33, and the connection between the metal electrode 33 and the transparent electrode 31A is ensured. Can be retained. In the transparent electrode forming step S13e, the transparent electrode 31A may be formed by forming a mask having a reverse pattern of the resist PR6, performing lift-off, and post-annealing before forming the transparent electrode material. Further, the transparent electrode formation step S13e, before the insulating member forming step S12b _1, can also be performed by the lift-off method.

  As mentioned above, although the form for implementing this invention was described, this invention is not limited to these embodiment, A various change is possible in the range shown to the claim.

  In order to confirm the effect of the present invention, the relationship between the drive voltage and the resistance of the transparent electrode was determined for the pixel of the spatial light modulator according to the second embodiment of the present invention by simulation using a computer.

The specification of the model pixel 4A is a wiring width of 1 μm, and the transparent electrode 31A of the lower electrode 3A is a square of 0.5 μm square in plan view. The lower electrode 3A includes a base layer 32: Ru (3) on the transparent electrode 31A, and the light modulation element 5 starts from the lower layer (on the base layer 32 of the lower electrode 3A) to the magnetization free layer 53: GdFe (10), intermediate A CPP-GMR element constituted of layer 52: Cu (6), magnetization fixed layer 51: CoFe (1) / TbFeCo (20), and protective layer 54: Ru (3) was formed. The numbers in parentheses indicate the film thickness (unit: nm). The current density required for the spin injection magnetization reversal of the CPP-GMR element having such a configuration is | 2 | × 10 ⁷ A / cm ² . Then, two light modulation elements 5 formed in a plan view size of 0.15 μm × 0.4 μm were arranged in one pixel 4A in the short side direction. Specifically, in plan view, two light modulation elements 5 and 5 are arranged side by side at an interval of 0.1 μm on the center of the transparent electrode 31A, and three sides (another one) of each light modulation element 5 are arranged. The distance from the end of the transparent electrode 31 </ b> A (except the side facing the light modulation element 5) was 0.05 μm. Note that the light modulation elements 5 and 5 were considered to undergo magnetization reversal without being affected by electrical and magnetic influences.

For the metal electrode 33 and the upper electrode 2 of the lower electrode 3A, Cu (specific resistance: 1.68 × 10 ⁻⁶ Ω · cm) was applied, and the resistance was set to 0 in the calculation. In addition, ITO (specific resistance ρ = 100 μΩ · cm) formed at 350 ° C. is applied to the transparent electrode 31A, and IZO (specific resistance ρ = 450 μΩ) as a comparative example of a transparent electrode material formed without heating. Cm) was applied. The resistance Rd of the light modulation elements 5 and 5 and the underlying layers 32 and 32 thereunder is 1Ω.

In one pixel 4A, the current | I _STS | required to reverse the spin injection magnetization of the light modulation elements 5 and 5 is calculated to be 24 mA. The voltage applied from the end of the transparent electrode 31A (interface with the metal electrode 33), which is supplied to the light modulation element 5 at the center of the transparent electrode 31A having a 0.5 μm square when viewed in plan, is the current | I _STS | Driving voltage) V was calculated from V = | I _STS | × (Re + Rd) (Re: resistance of transparent electrode).

  The resistance Re of the transparent electrode 31A was obtained from Re = ρ × (distance) / (cross-sectional area). The distance (maximum) of the transparent electrode 31A is the length (0.25 μm) from the end to the center in plan view, and the cross-sectional area is the product of the length of one side (0.5 μm) in plan view and the film thickness. . FIG. 11 is a graph showing the result of calculating the driving voltage for each of the transparent electrodes 31A of ITO and IZO with the film thickness changed, with the horizontal axis representing the film thickness of the transparent electrode 31A and the vertical axis representing the driving voltage.

As described above, since the driving voltage is proportional to the specific resistance of the transparent electrode 31A and the reciprocal of the film thickness, as shown in FIG. 11, the transparent electrode 31A made of ITO by heating film formation with a low specific resistance is driven to be lower. The pixel 4A can be operated by voltage, and the driving voltage can be lowered as the film thickness of the transparent electrode 31A is increased. In the transparent electrode 31A having a film thickness of 0.5 μm, the driving voltage when IZO is used is 132 mV, and the voltage reaches 45.6 mV to reach | I _STS | at the end of the light modulation element 5 (distance 0.05 μm). It takes about 3 times as much. On the other hand, when the ITO of the embodiment according to the present invention is used, the driving voltage can be operated at a low voltage of 48 mV, and 28.8 mV at the end of the light modulation element 5, so that the difference in the pixels is small. . For example, when the driving voltage is 100 mV, the film thickness needs to be 0.71 μm or more when IZO is used, whereas the transparent electrode 31A using ITO by heating film formation has a film thickness of 0. It may be 158 μm or more. As described above, since the transparent electrode with reduced resistance can be applied, the transparent electrode can be operated with a low driving voltage, or the thickness of the transparent electrode 31A can be reduced to improve the amount of transmitted light.

1 Spatial light modulator (magneto-optic spatial light modulator)
10 Current control unit 11 Power supply (current supply means)
14 Pixel selection unit (pixel selection means)
40, 40A pixel array 4, 4A pixel 2 upper electrode 3, 3A lower electrode 31, 31A transparent electrode 32 underlayer 33 metal electrode 5 light modulation element 51 magnetization fixed layer 52 intermediate layer 53 magnetization free layer 54 protective layer 6 insulating member 7 substrate

Claims (5)

A substrate that transmits light, a plurality of pixels that are two-dimensionally arranged on the substrate, a pixel selection unit that selects one or more pixels from the plurality of pixels, and a pixel selected by the pixel selection unit A magneto-optical spatial light modulator that reflects and emits light that has passed through the substrate and is incident on the plurality of pixels.
The pixel includes a light modulation element that emits light that is incident upon being selected by the pixel selection unit with its polarization direction changed to a specific direction, and an upper electrode and a lower part that are connected above and below the light modulation element. An electrode,
The lower electrode is formed of a transparent electrode material so as to transmit light incident from the substrate side and transmit light emitted from the light modulation element,
The magneto-optical spatial light modulator according to claim 1, wherein the upper electrode is made of a metal electrode material so as to reflect light incident from the light modulation element.   The lower electrode includes a metal electrode having a through hole formed in a region overlapping the light modulation element in plan view, and the transparent electrode material disposed in the through hole of the metal electrode and electrically connected to the light modulation element The magneto-optical spatial light modulator according to claim 1, further comprising: a transparent electrode formed by:   The magneto-optical spatial light modulator according to claim 1, wherein the transparent electrode material forming the lower electrode is a crystalline material.   4. The magneto-optical spatial light modulator according to claim 3, wherein the transparent electrode material forming the lower electrode is formed by heating film formation or post-annealing. In a method for manufacturing a magneto-optical spatial light modulator that transmits light reflected from a lower side and incident on a plurality of pixels arranged two-dimensionally on the substrate, and then emits the reflected light.
A lower electrode forming step of forming a lower electrode, at least a part of which is made of a transparent electrode material, on the substrate; a light modulating element forming step of forming a light modulating element on the lower electrode; and An upper electrode forming step of forming an upper electrode made of a metal electrode material,
In the lower electrode forming step, the transparent electrode material is formed by heating film formation, or post annealing is performed after forming the transparent electrode material.

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