JP6865544B2 - Spatial Light Modulators and Methods for Manufacturing Spatial Light Modulators - Google Patents

Description

The present invention relates to a spatial light modulator and a method for manufacturing a spatial light modulator that spatially modulates the phase, amplitude, etc. of light by a magneto-optical effect and emits the incident light.

Spatial light modulators use optical elements (optical modulation elements) as pixels and arrange them two-dimensionally in a matrix to spatially modulate the phase and amplitude of light, and display technology and recording technology. It is widely used in such fields. Liquid crystals have been used as spatial light modulators in the past, but in recent years, magneto-optical spatial light modulators using magneto-optical materials, which are expected to have high-speed processing and the possibility of miniaturization of pixels of 1 μm or less. Development is in progress.

In a magneto-optical spatial light modulator, the Faraday effect (Kerr effect in the case of reflection) is used to change the direction of polarized light (optical rotation) when light incident on a magnetic material is transmitted or reflected. There is. That is, in the magneto-optical spatial light modulator (hereinafter, spatial light modulator), the magnetization direction of the light modulation element in the selected pixel (selected pixel) and the magnetization direction of the light modulation element in the other pixels (non-selection pixel). The light emitted from the selected pixel and the light emitted from the non-selected pixel are modulated into binary light having a difference in the rotation angle (rotation angle) of the polarization. As a method of changing the magnetization direction of the light modulation element, a magnetic field application method of applying a magnetic field to the light modulation element (for example, Patent Document 1) or a magnetic random access memory (MRAM) for supplying a current to the light modulation element. ), There are a spin injection method (for example, Patent Documents 2 and 3) and a domain wall moving method (for example, Patent Document 4).

Spin injection type spatial optical modulators include spin injection magnetization reversal of CPP-GMR (Current Perpendicular to the Plane Giant Magneto Resistance) elements and TMR (Tunnel Magneto Resistance) elements. The element is mounted as a magnetoresistive element. Generally, a spin injection magnetization reversing element has a laminated structure of at least three layers composed of a non-magnetic film or two magnetic films sandwiching an insulating film (intermediate layer), and electrons are supplied by supplying an electric current perpendicular to the film surface. Spin is injected, and one of the magnetic films acts as a magnetization free layer, and its magnetization direction changes. That is, this magnetization free layer corresponds to the light modulation element of the magnetic field application method. Since the spin injection magnetization reversing element connects a pair of electrodes to the upper and lower surfaces, it is not necessary to form the electrodes as extremely thin wiring with respect to the pixel size as in the magnetic field application type light modulation element, depending on the wiring width. There are few restrictions on the element size. Further, since the drive current of the spin injection magnetization reversing element depends on the current density on the film surface, the smaller the element size (area), the more the current can be suppressed, and the one side is preferably about 500 nm or less for easy magnetization reversal. Is formed to about 100 to 300 nm. A spatial light modulator equipped with such a spin-injection magnetization reversal element constitutes an electrode connected to at least the light input / output side of the spin-injection magnetization reversal element, and here, an electrode connected to the magnetization free layer. The wiring to be used is formed of a transparent electrode material so that light is incident on the spin injection magnetization reversing element. Further, when the spin injection magnetization reversing element is two-dimensionally arranged as a light modulation element to form a spatial light modulator, the wiring (electrode) connected above and the wiring connected below are orthogonal to each other in a plan view. Since it may be formed in a striped shape, the pixels can be further miniaturized as compared with the magnetic field application method. Further, as in Patent Documents 5 and 6, a spin injection magnetization reversing element having a parallel dual pin structure in which an electrode is not connected to the magnetization free layer is applied, and both of the wirings constituting the pair of electrodes are made of good conductor metal electrodes. It can also be formed of material.

In the domain wall movement type spatial light modulator, a fine wire-shaped magnetic film (magnetic thin wire) is mounted as a light modulation element, and a pair of electrodes are connected to both ends thereof. When a current is supplied to the magnetic wire in the wire direction, the domain wall moves in the direction opposite to the current, so that the magnetization direction in a predetermined region changes. In the domain wall moving method, the current required for driving depends on the current density in the wire direction (in the cross section perpendicular to the wire direction), so that the current can be suppressed as compared with the spin injection method. Further, unlike the magnetizing free layer of the spin injection magnetization reversing element, which is difficult to invert the magnetization unless it is a thin film of about 20 nm or less, the magnetic wall movement type spatial light modulator may have a thick magnetic wire up to about 70 nm, and is magnetic. It is easy to increase the optical effect. Further, as applied to MRAM, in order to stably maintain the domain wall generated in the magnetic thin wire, it is preferable to laminate an magnetization fixing layer on both ends of the magnetic thin wire and connect the electrodes (for example). , Patent Document 7).

Further, in the spatial light modulator of the spin injection type or the domain wall movement type, the light modulation element is connected to the wiring constituting one of the electrodes via a transistor formed of MOSFET or the like, similarly to the selection transistor type MRAM. It may be used (for example, Patent Documents 6 and 7). With such a configuration, it is possible to reduce the loss due to the wraparound of the current and reduce the current consumption, and in the spin injection method, it is also possible to detect a write error by the same method as reading the MRAM. it can.

Japanese Patent No. 4596468 Japanese Patent No. 4829850 Japanese Patent No. 5001807 Japanese Patent No. 4939489 Japanese Patent No. 5567969 Japanese Unexamined Patent Publication No. 2013-195594 Japanese Unexamined Patent Publication No. 2011-119537 Japanese Unexamined Patent Publication No. 2005-101186 Japanese Patent No. 2791429 Japanese Patent No. 5401661 Japanese Unexamined Patent Publication No. 2013-243333

In the spatial light modulator, in the spin injection method, light modulation elements composed of three or more layers are arranged two-dimensionally on a substrate, wiring of at least two layers as electrodes, and in order to insulate them from each other. It is provided with an insulating layer to be provided, or is further provided with a transistor. Therefore, the manufacture of the spatial light modulator requires a large number of steps of repeating the film formation and processing of each of these layers, and the time required for product completion (TAT: turn around time) becomes long. In particular, the spin injection magnetization reversal element having a parallel dual pin structure and the optical modulation element of the domain wall movement type have two magnetizing fixed layers separated in the plane, so that the process is complicated.

Therefore, in recent years, the present inventors have focused on a laminated semiconductor device developed for reducing the chip area of a highly integrated semiconductor element (semiconductor device). Since the laminated semiconductor device is manufactured by laminating wafers or chips on which circuits are formed, each wafer can be manufactured on a separate line. Specifically, for example, a wiring constituting one of a pair of electrodes is formed on a wafer, a wiring constituting the other and a light modulation element are formed on another wafer, and these two wafers are bonded together to form light. Join the modulation element and the wiring (electrode).

In such a laminated semiconductor device, in order to mechanically and electrically connect the wirings of each wafer, through electrodes are formed, or bumps or the like are formed on the joint surface of one wafer or chip. A method of crimping at a high temperature or pressure is known (for example, Patent Document 8). However, it is difficult to form a through hole for each fine pixel having a pitch of about 1 μm or less. On the other hand, bonding with bumps may cause damage to the magnetic film of the light modulation element due to heat, and in a spatial light modulator with fine pixels, the width of the wiring is narrow, so sufficient adhesion can be obtained. It is difficult and may peel off.

Further, regardless of the metal material or the insulating material, surface activation bonding, hydroxyl group bonding, and atomic diffusion bonding are known as techniques for bonding wafers and chips at a low temperature such as room temperature. The surface-activated bonding is performed by irradiating both bonding surfaces with ions or plasma of the inert gas in an inert gas atmosphere such as Ar, and then bringing them into contact with each other in this environment (for example, Patent Document 9). Although the surface-activated bonding depends on the material to be bonded, the adhesive force is not strong and there is a risk of peeling. In atomic diffusion bonding, a metal such as Al is formed on one or both bonding surfaces in a vacuum or an inert gas atmosphere to a thickness of 0.2 nm to 1 μm, and the formed metal films are brought into contact with each other in this environment. (For example, Patent Document 10). Therefore, in order to electrically connect two or more sets of wiring formed on each wafer, a mask with a wiring pattern is provided so that different wirings exposed on each bonding surface are not short-circuited by a metal film. It is necessary to displace it on the wafer so that it can be detached in the film forming chamber, and as a result, it is difficult to obtain sufficient adhesion due to the narrow width of the wiring as in the case of bonding by bumps. In the hydroxyl group bonding, a hydroxyl group is attached to the bonding surface by washing with water or the like to perform a hydrophilic treatment, and the bonding surfaces are brought into contact with each other for bonding (for example, Patent Document 11). For hydroxyl group bonding, it is necessary to smooth both bonding surfaces to 1 nm or less with an arithmetic mean roughness Ra. When the wafer on which the light modulation element is formed is polished by chemical mechanical polishing (CMP) or the like, the light modulation element is used. May cause damage to.

However, in order to electrically connect these two wafers, high-definition patterning of a metal thin film on a light modulation element or wiring (electrode) is required. Therefore, the manufacturing process of the spatial light modulator has become complicated.

The present invention has been made in view of the above points, and an object of the present invention is to provide a spatial light modulator and a method for manufacturing a spatial light modulator having a simple manufacturing process.

In order to solve the above problems, the spatial light modulator according to one aspect of the present invention is a spatial light modulator in which a first substrate and a second substrate are bonded via a bonding layer.
Here, the first substrate insulates between a first substrate formed in a rectangular shape, a plurality of first electrodes formed toward opposite sides on the first substrate, and adjacent first electrodes. A first insulating layer is provided , and a striped pattern is formed on the surface by the first electrode.

Further, the second substrate includes a second substrate formed in a rectangular shape, a plurality of second electrodes formed on the second substrate in a direction intersecting with the first electrode, and the second electrode on the second electrode. A plurality of light modulation elements projecting from the second electrode at an intersection intersecting with the first electrode and two-dimensionally arranged, and adjacent second electrodes and adjacent light modulation elements are insulated and two-dimensionally arranged. wherein a second insulating layer a part of which is formed so as to protrude before Symbol first substrate side of the light modulation element, convex pattern of the two-dimensional array by said light modulating element is formed on the surface ing.

Further, the bonding layer includes a first metal film formed on the surface of the first substrate and a second metal film formed on the surface of the second substrate, and each of the protruding optical modulations is provided. A joint portion between the first metal film and the second metal film is formed by a part of the element, and a surface portion of the joint layer other than the joint portion is formed as an oxide film.

In the spatial light modulator having such a configuration, a convex pattern is formed on the second substrate by each of the protruding light modulation elements. Then, this convex pattern forms a joint portion with the first metal film formed on the first substrate by forming the second metal film.

According to one aspect of the present invention, a second metal film is formed on each light modulation element protruding from the surface of the second insulating layer to form a joint with the first substrate, so that patterning for bonding is performed. Is unnecessary, and the manufacturing process can be simplified and shortened .

It is a schematic block diagram of the spatial light modulator which concerns on 1st Embodiment of this invention. It is the schematic of the light modulation element used in the spatial light modulator according to the 1st Embodiment of this invention, (a) shows an ON state (bright), (b) shows an OFF state (dark). It is sectional drawing in the direction (Y direction) in which the upper electrode of the spatial light modulator according to the first embodiment of the present invention is extended. It is sectional drawing in the direction (X direction) in which the lower electrode of the spatial light modulator according to 1st Embodiment of this invention is extended, (a) shows the whole view, (b) is the enlarged view of the main part. Shown. It is a figure for demonstrating the spatial light modulator which concerns on 1st Embodiment of this invention, (a) is the external perspective view of the upper substrate which is a 2nd substrate, (b) is the lower part which is a 1st substrate. It is an external perspective view of a substrate. It is an example of the manufacturing process of the lower substrate which is a 1st substrate, and (a) to (c) show each process. It is an example of the manufacturing process of the upper substrate which is a 2nd substrate, and (a) to (g) show each process. It is an example of the joining process of the lower substrate which is a 1st substrate and the upper substrate which is a 2nd substrate, and (a) to (c) show each process. It is sectional drawing in the direction (Y direction) in which the upper electrode of the spatial light modulator according to 2nd Embodiment of this invention is extended, (a) shows the whole view, (b) is the enlarged view of the main part. Shown. It is a figure for demonstrating the spatial light modulator which concerns on 2nd Embodiment of this invention, (a) is the external perspective view of the upper substrate which is a 2nd substrate, (b) is the lower part which is a 1st substrate. It is an external perspective view of a substrate. It is an example of the manufacturing process of the lower substrate which is a 1st substrate, and (a) to (d) show each process. It is an example of the manufacturing process of the upper substrate which is a 2nd substrate, and (a) to (f) show each process. It is an example of the joining process of the lower substrate which is a 1st substrate and the upper substrate which is a 2nd substrate, and (a) to (c) show each process.

A mode for realizing the spatial light modulator according to the present invention will be described with reference to the drawings. Here, each figure is merely schematically shown to the extent that the present invention can be fully understood. Therefore, the present invention is not limited to the illustrated examples. Also, the dimensions in the referenced drawings may be exaggerated for clarity. In each figure, common components and similar components are designated by the same reference numerals, and duplicate description thereof will be omitted.

[First Embodiment]
<< Configuration of Spatial Light Modulator according to First Embodiment >>
FIG. 1 shows an outline of the configuration of the spatial light modulator 1 according to the first embodiment of the present invention. In FIG. 1, a configuration other than the configuration related to light modulation (for example, a substrate, an insulating layer, etc.) is omitted. The spatial light modulator 1 according to the first embodiment of the present invention includes a spin injection type light modulation element 23 that modulates incident light into different binary light (polarizing component) and emits the light in a two-dimensional arrangement. .. The optical modulation element 23 includes an upper electrode 22 extending in the Y direction (vertical direction in FIG. 1) and a lower electrode 12 extending in the X direction (horizontal direction in FIG. 1) orthogonal to the upper electrode 22. It is installed at the intersection and is sandwiched from above and below by the upper electrode 22 and the lower electrode 12 as a pair of electrodes. Each light modulation element 23 is a pixel that points to a means for displaying information (bright / dark) in the smallest unit of display by the spatial light modulator 1.

In the present embodiment, for the sake of brevity, the spatial light modulator 1 includes four (D1 to D4) upper electrodes 22 extending in the Y direction (vertical direction in FIG. 1) and upper electrodes 22. It is provided with four (S1 to S4) lower electrodes 12 extending in the X direction (horizontal direction in FIG. 1) orthogonal to the above. Then, one light modulation element 23 (pixels) is formed at each intersection of the upper electrode 22 and the lower electrode 12, so that the configuration is composed of 16 light modulation elements 23 (pixels) in 4 rows × 4 columns. Illustrated. This also applies to the second embodiment described later.

The upper electrode selection unit 2 is connected to the upper electrode 22, while the lower electrode selection unit 3 is connected to the lower electrode 12. Further, the current source 4 and the current control means 5 are connected to the upper electrode selection unit 2 and the lower electrode selection unit 3. The upper electrode selection unit 2, the lower electrode selection unit 3, the current source 4, and the current control means 5 may have a configuration different from that of the spatial light modulator 1.
The upper electrode selection unit 2 selects one electrode from the upper electrodes 22 of D1 to D4, and the lower electrode selection unit 3 selects one electrode from the lower electrodes 12 of S1 to S4. The upper electrode selection unit 2 and the lower electrode selection unit 3 identify one of the plurality of light modulation elements 23 (pixels) in the matrix.

The current source 4 supplies a pulse current to the light modulation element 23. The current source 4 may be configured to supply a direct current.
The current control means 5 controls the upper electrode selection unit 2, the lower electrode selection unit 3, and the current source 4. The current control means 5 controls the direction and magnitude of the current flowing through each of the light modulation elements 23, and spin-injects the current into each of the light modulation elements 23 to reverse the magnetization of the light modulation element 23.

Next, with reference to FIG. 2, the operating principle of the spin-injection type light modulation element 23 will be briefly described. The light modulation element 23 is a CPP-GMR element or a TMR element that utilizes spin injection magnetization reversal and a magneto-optical effect. The light modulation element 23 is mainly composed of a magnetization fixed layer 231, an intermediate layer 232, and a magnetization free layer 233, and an upper electrode 22 is connected to the upper part (free layer 233 side) and a lower part (fixed layer 231 side). The lower electrode 12 is connected.

The magnetization fixing layer 231 is a layer in which the magnetization direction is fixed in a predetermined direction. Here, the arrow in the magnetization fixing layer 231 is an example of the magnetization direction, and in FIG. 2, it is assumed that the magnetization is magnetized downward. The intermediate layer 232 is a tunnel barrier layer located in the middle between the magnetized fixed layer 231 and the magnetized free layer 233. The magnetization free layer 233 is a layer in which the direction of magnetization is reversed depending on the magnitude and direction of the current flowing through the upper electrode 22 and the lower electrode 12. Here, the arrow in the magnetization free layer 233 is an example of the magnetization direction.

For example, when a current is passed from the magnetization free layer 233 side, electrons flow from the bottom to the top. Here, since the magnetization fixing layer 231 is magnetized downward, the electrons of the upward spin that try to enter the magnetization fixing layer 231 are reflected by the magnetization fixing layer 231 and only the electrons of the downward spin are the magnetization fixing layer 231. It passes through the intermediate layer 232 and is injected into the magnetized free layer 233. Therefore, the magnetization of the magnetization free layer 233 is inverted downward (see FIG. 2A). On the other hand, when a current is passed from the magnetization fixed layer 231 side, electrons flow from top to bottom. Here, since the magnetization fixing layer 231 is magnetized downward, among the electrons that have passed through the magnetization free layer 233 and the intermediate layer 232, the electrons having an upward spin opposite to the magnetization direction of the magnetization fixing layer 231 are magnetized and fixed. It is reflected by layer 231. Therefore, a large number of electrons with upward spins are present in the magnetization free layer 233, and the magnetization of the magnetization free layer 233 is inverted upward (see FIG. 2B).

In this way, the light modulation element 23 can control the direction of magnetization of the magnetization free layer 233 by the magnitude and direction of the current flowing from the current source 4. That is, when a transparent electrode material is used for the upper electrode 22, the laser beam applied from the laser light source 92 through the polarizing filter 94a has a polarizing surface that rotates depending on the direction and size of magnetization of the magnetization free layer 233 due to the magneto-optical Kerr effect. ..

Next, a specific configuration of the spatial light modulator 1 according to the first embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a cross-sectional view in the direction (Y direction) in which the upper electrode 22 of the spatial light modulator 1 according to the first embodiment of the present invention is extended. FIG. 4 is a cross-sectional view in the direction (X direction) in which the lower electrode 12 of the spatial light modulator 1 according to the first embodiment of the present invention is extended, FIG. 4A shows an overall view, and FIG. 4B shows an overall view. Is an enlarged view of a main part of FIG. 4 (a). The upper side (Z direction side) of the spatial light modulator 1 is the incident surface of light.

As shown in FIGS. 3 and 4, the spatial light modulator 1 is configured to both include a plate-shaped upper base 21 and a lower base 11, and light modulation is performed between the two stacked bases 21 and 11. The elements 23 are arranged two-dimensionally. The lower base 11 is the first base, and the upper base 21 is the second base. The upper electrode 22 is connected to the upper part of the light modulation element 23, while the lower electrode 12 is connected to the lower part of the light modulation element 23 via the bonding layer 30. As a result, the spatial light modulator 1 is mainly laminated from the bottom in the order of the lower base 11, the lower electrode 12, the bonding layer 30, the light modulation element 23, the upper electrode 22, and the upper base 21.

In the spatial light modulator 1, as described later in the manufacturing method, elements such as the light modulation element 23 are separately formed on the bases 11 and 21 of each substrate, and the lower substrate 10 which is the first substrate (FIG. 5 (FIG. 5). b)) and the upper substrate 20 (see FIG. 5A), which is the second substrate, are manufactured. Then, the upper electrode 22 and the lower electrode 12 are made to face each other so as to intersect (here, orthogonally), and as shown in FIGS. 3 and 4, these two substrates 10 and 20 are one via the bonding layer 30. Manufactured by sticking to. In explaining the configurations of the substrates 10 and 20 individually, the planes (sometimes referred to as the upper surface or the surface) of the substrates 11 and 21 are the sides on which the light modulation elements 23 and the electrodes 12 and 22 are formed. Each element may be described with the side of the base 11 or the base 21 as the base facing down. Hereinafter, each configuration will be described.

<Lower board>
The configuration of the lower substrate 10 which is the first substrate will be described. As shown in FIG. 3, the lower substrate 10 is formed between the lower substrate 11 which is the first substrate, the lower electrode 12 which is the first electrode patterned on the lower substrate 11, and the patterned lower electrode 12. It is composed of an insulating layer 13 which is a first insulating layer formed in.

The lower substrate 11 is, for example, a Si substrate. The lower substrate 11 may be formed with a circuit including an upper electrode selection unit 2, a lower electrode selection unit 3, a current source 4, and a current control means 5 shown in FIG. The lower electrode 12 is patterned on the lower substrate 11 using, for example, a lithography technique. The lower electrode 12 may be a general metal electrode material such as a metal such as Cu, Al, Au, Ag, Ta, Cr or an alloy thereof. The insulating layer 13 is formed between the patterned lower electrodes 12 and insulates between the adjacent lower electrodes 12.

As shown in FIG. 5B, the surface 10a of the lower substrate 10 has the lower electrode 12 and the insulating layer 13 formed on the same plane (plane). It is desirable that the surface roughness of the lower substrate 10 is smaller than that for, for example, CMP (Chemical Mechanical Polishing) treatment.

<Upper board>
The configuration of the upper substrate 20 which is the second substrate will be described. As shown in FIG. 4A, the upper substrate 20 projects from the upper substrate 21 which is the second substrate, the upper electrode 22 which is the second electrode patterned on the upper substrate 21, and the upper electrode 22. It is composed of a two-dimensionally arranged light modulation element 23 and an insulating layer 24 which is a second insulating layer formed between the patterned upper electrode 22 and the light modulation element 23.

The upper substrate 21 is a transparent substrate such as glass. The upper electrode 22 is a transparent electrode that allows light to pass through, and is patterned on the upper substrate 21 using, for example, a lithography technique. The upper electrode 22 has indium zinc oxide (IZO: Indium Zinc Oxide), indium-tin oxide (ITO: Indium Tin Oxide), tin oxide (SnO ₂ ), antimony oxide-tin oxide system (ATO), zinc oxide ( It is made of known transparent electrode materials such as ZnO), fluorine-doped tin oxide (FTO), and indium oxide (In ₂ O _3). The upper electrode 22 is most preferably IZO in terms of specific resistance and ease of film formation.

The light conversion element 23 is patterned on the upper electrode 22 by using, for example, a lithography technique. As shown in FIG. 4B, the light modulation element 23 here has a four-layer structure in which the magnetization free layer 233, the intermediate layer 232, the magnetization fixing layer 231 and the protective layer 234 are laminated in this order from the upper electrode 22 side. Is.

The magnetization fixing layer 231 and the magnetization free layer 233 are known magnetic materials used for CPP-GMR elements and TMR elements, and in particular, a perpendicular magnetic anisotropy material whose optical rotation angle is increased due to the polar Kerr effect is applied. Is preferable. The magnetization fixing layer 231 and the magnetization free layer 233 are, for example, a multilayer film such as a Co / Pd multilayer film in which a transition metal such as Fe, Co, Ni and a noble metal such as Pd, Pt are repeatedly laminated, Tb-Fe-. Co, an alloy of a rare earth metal and a transition metal such as Gd-Fe (RE-TM alloy), FePt was the L ₁₀ system ordered alloy consists FePd like.

When the light modulation element 23 has a GMR structure, the intermediate layer 232 is preferably made of a non-magnetic metal such as Cu, Ag, and Al, and has a thickness of 1 to 10 nm. In the case of a TMR structure, the intermediate layer 232 is not a non-magnetic metal but is made of MgO, Al ₂ O ₃ , MgAl ₂ O ₄ , and HfO ₂ , and is an extremely thin insulating film having a thickness of about 0.6 to 2 nm. Is preferable.

The protective layer 234 is continuously formed on the magnetic film forming the magnetization fixing layer 231. The protective layer 234 is composed of a single layer of Ta, Ru, and Cu, or two layers of Cu / Ta and Cu / Ru (Cu is the inner (lower layer)) and the like. If the thickness (film thickness) of the protective layer 234 is less than 1 nm, it is difficult to form a continuous film, while even if the thickness exceeds 10 nm, the effect of protecting the magnetization fixing layer 231 in the manufacturing process is further enhanced. Does not improve. Therefore, the thickness of the protective layer 234 is preferably 1 to 10 nm, more preferably 3 to 5 nm.

The insulating layer 24 is formed between the patterned upper electrodes 22 and the light modulation elements 23, and insulates between the adjacent upper electrodes 22 and the adjacent light modulation elements 23. The surface 20a of the upper substrate 20 is composed of a light modulation element 23 and an insulating layer 24, and a step structure is formed by exposing a part of the light modulation element 23 to the insulating layer 24. That is, the insulating layer 24 is formed so that the tip of the light modulation element 23 is exposed to the lower substrate 10 side by a predetermined amount. The exposure amount (protrusion amount) H of the light modulation element 23 (see FIG. 4B) is preferably 0.2 nm or more, and the magnetization fixing layer 231 is prevented from being exposed to the atmosphere during the manufacturing process. Therefore, it is desirable that the thickness is less than the thickness of the protective layer 234. As a result, as shown in FIG. 5A, the exposed light modulation element 23 forms a convex pattern of a two-dimensional array on the surface 20a of the upper substrate 20.

The convex pattern formed by the light modulation element 23 may be formed by various methods, and the method for forming the convex pattern is not particularly limited. The following shows an example of a method for forming a convex pattern.
For example, when backfilling with the insulating layer 24 after patterning and etching the resist of the light modulation element 23 by lithography, the backfilling is made shallower by the thickness of the protective layer 234 than the etching depth. After that, if possible, it is preferable to perform surface flattening treatment with CMP or the like.

Further, when backfilling with the insulating layer 24 after patterning and etching the resist of the light modulation element 23 by lithography, the insulating layer 24 is backfilled with an appropriate thickness (the surface is flattened with CMP or the like if necessary). Only the insulating layer 24 may be etched by a few nm with a reactive gas such as CF _4. At this time, since the light modulation element 23 is hardly etched (because the etching rates of the light modulation element 23 and the insulating layer 24 are different), the convex pattern is easily completed.

Further, when the insulating layer 24 is formed on the upper substrate 21, the resist holes of the pattern of the light modulation element 23 are patterned by photolithography, and after etching, the light modulation element 23 is formed and lifted off. The light modulation element 23 is formed thicker than the depth, and then the lift-off is performed. After that, if possible, it is preferable to perform surface flattening treatment with CMP or the like.

<Joint layer>
The configuration of the bonding layer 30 will be described. As shown in FIG. 4A, the bonding layer 30 joins the lower substrate 10 which is the first substrate and the upper substrate 20 which is the second substrate. As shown in FIG. 4B, the bonding layer 30 is composed of an upper metal thin film 32 formed on the surface of the upper substrate 20 and a lower metal thin film 31 formed on the surface of the lower substrate 10. For example, these metal thin films 31 and 32 are bonded by the atomic diffusion bonding method. The metal thin films 31 and 32 may be formed on the substrates 10 and 20 by a method such as sputtering, and are formed to have a substantially uniform thickness. The metal thin film 32 on the upper side has a convex pattern similar to that of the upper substrate 20. As a result, the lower part of the light modulation element 23 becomes a joint portion 33 that joins the metal thin film 32 on the upper side and the metal thin film 31 on the lower side. In the following, the lower substrate 11, the lower electrode 12, the insulating layer 13, and the metal thin film 31 formed on the surfaces of the lower electrode 12 and the insulating layer 13 may be referred to as a “first substrate”. .. Further, the "second substrate" includes the upper substrate 21, the upper electrode 22, the light modulation element 23, the insulating layer 24, and the metal thin film 32 formed on the surfaces of the light modulation element 23 and the insulating layer 24. May be called.

Further, the bonding layer 30 is composed of two portions, a conductive portion 30a and an insulating portion 30b. The conductive portion 30a is formed in the lower portion of the light modulation element 23 (particularly, near the center of the junction portion 33), and electrically connects the light modulation element 23 and the lower electrode 12. On the other hand, the insulating portion 30b is formed around the conductive portion 30a and in a portion other than the joint portion 33. The conductive portion 30a and the insulating portion 30b are formed by exposing the surfaces of the metal thin films 31 and 32 to the atmosphere by exposing the lower substrate 10 and the upper substrate 20 in a state where the metal thin films 31 and 32 are joined to the atmosphere. Will be done. That is, the surface portion of the bonding layer 30 other than the bonding portion 33 is formed as an oxide film.

The material of the bonding layer 30 is preferably a material having a large self-diffusion coefficient for bonding and easily oxidizing in the atmosphere, and chromium (Cr) and nickel (Ni) are added to aluminum (Al) and iron (Fe). Alloys are suitable. Further, the thickness of each of the metal thin films 31 and 32 is preferably about several nm, considering the strength of the joint and the need to completely oxidize the portion other than the joint portion 33.

<< Manufacturing method of spatial light modulator according to the first embodiment >>
Next, a method of manufacturing the spatial light modulator 1 according to the first embodiment will be described.
The spatial light modulator 1 according to the present embodiment manufactures the lower substrate 10 and the upper substrate 20 shown in FIG. 5 by forming the light modulation elements 23 and the electrodes 12 and 22 on the substrate 11 or the substrate 21, respectively. Then, the upper electrode 22 and the lower electrode 12 are made to face each other so as to intersect (here, orthogonally), and these two substrates 10 and 20 are laminated to be manufactured. Hereinafter, each step will be described.

<Manufacturing process of lower substrate>
The manufacturing process of the lower substrate 10 which is the first substrate will be described. As the manufacturing process of the lower substrate 10, the same method as the manufacturing process of a general semiconductor device can be applied. For example, a case where the lower substrate 10 is manufactured by photolithography will be described with reference to FIG.

_{First, an insulating film 13p such as SiO 2} is formed on a lower substrate 11 such as Si (see FIG. 6A), and the insulating film 13p is formed using a resist 41 that opens the formation position of the lower electrode. A hole in the lower electrode pattern is formed in the lower electrode pattern (see FIG. 6 (b)). Next, after forming a film of copper or the like as a lower electrode material, the resist 41 is lifted off to form a pattern of the lower electrode 12 (see FIG. 6C). As a result, the lower substrate 10 which is the first substrate is completed.

<Manufacturing process of upper substrate>
The manufacturing process of the upper substrate 20 which is the second substrate will be described. In the manufacturing process of the upper substrate 20, a part of the light modulation element 23 is exposed to the insulating layer 24 to form a convex pattern of a two-dimensional array by the light modulation element 23 on the surface 20a of the upper substrate 20. As long as it can be done, various methods can be used. Here, a case where a convex pattern is formed in a step of backfilling the insulating layer 24 after forming the upper electrode 22 and the light modulation element 23 by using a lithography technique will be described with reference to FIG. 7. After forming the insulating layer 24 first, the convex pattern may be formed by the light modulation element 23 in the step of forming the light modulation element 23.

First, an upper electrode film 22p such as indium zinc oxide, which is an upper electrode material, is formed on a transparent upper substrate 21 such as glass (see FIG. 7A), and openings other than the positions where the upper electrodes are formed are opened. The upper electrode film 22p formed by using the resist 42 is etched into the upper electrode pattern (see FIG. 7B). Next, the etched portion is _{backfilled with SiO 2} to form a part 24p of the insulating layer 24, and then the resist 42 is lifted off to form a pattern of the upper electrode 22 (see FIG. 7C).

Next, a light modulation element layer 23p made of a metal film or a magnetic film for forming the magnetization free layer 233, the intermediate layer 232, the magnetization fixing layer 231 and the protective layer 234 of the light modulation element 23 is formed (FIG. 7 (FIG. 7). d)), the light modulation element layer 23p formed by using a resist 43 that opens other than the formation position of the light modulation element is etched into the light modulation element pattern (see FIG. 7E).

Next, the insulating layer 24 is formed by backfilling the etched portion with SiO ₂ , and then the light modulation element layer 23 is patterned in a two-dimensional array by lifting off the resist 43 (see FIG. 7 (f)). ). Then, if necessary, the surface is flattened by CMP treatment, and then only the insulating layer 24 is etched by a few nm with a reactive gas such as _{CF 4 to form a convex pattern (see FIG. 7 (g)).} At this time, since the etching rates of the light modulation element 23 and the insulating layer 24 are different, the light modulation element 23 is hardly etched. Therefore, the convex pattern (step structure) can be easily completed.

As a result, the upper substrate 20 which is the second substrate is completed. Since it is desirable that the surface roughness of the upper substrate 20 is small in the joining step, it is preferable that the surface 20a of the upper substrate 20 is finally subjected to CMP (Chemical Mechanical Polishing) treatment or the like.
In the step of backfilling the etched portion shown in FIG. 7 (f) with SiO ₂ , the convex pattern may be formed by backfilling the etched portion shallower by the thickness of the protective layer 234 than the etching depth. As a result, the etching step shown in FIG. 7 (g) can be omitted. Also at this time, it is preferable to flatten the surface by CMP treatment or the like.

Further, here, the case where the convex pattern is formed in the step of backfilling the insulating layer 24 after forming the upper electrode 22 and the light modulation element 23 by using the lithography technique has been described, but the insulating layer 24 is formed first. After that, the convex pattern may be formed in the step of forming the light modulation element 23. In that case, for example, the insulating layer 24 is formed on a transparent upper substrate 21 such as glass, the resist holes of the light modulation element pattern are patterned by photolithography, and after etching, the light modulation element layer 23p is formed and formed. The light modulation element 23 is patterned by performing lift-off. At this time, the light modulation element layer 23p is formed thicker than the etching depth, and lift-off is performed. After that, if possible, it is preferable to flatten the surface by CMP treatment or the like.

<Joining process between upper substrate and lower substrate>
After manufacturing the upper substrate 20 (see FIG. 5 (a)) which is the second substrate and the lower substrate 10 (see FIG. 5 (b)) which is the first substrate, joining these both substrates 10 and 20 together. The process will be described with reference to FIG. Here, it is assumed that the atomic diffusion bonding method is used for bonding both substrates 10 and 20. The atomic diffusion bonding method makes it possible to bond an object at room temperature without applying a large pressure by utilizing atomic diffusion at the grain boundaries and surfaces of a metal thin film.

Metal thin films 31 and 32 were formed on the surfaces of the lower substrate 10 and the upper substrate 20 in a vacuum by a method such as sputtering (see FIG. 8A), and then the metal thin films 31 and 32 formed in the same vacuum were formed. They are brought into contact with each other and joined (see FIG. 8B). At this time, since the convex pattern is formed on the surface 20a of the upper substrate 20 by the light modulation element 23, the lower part of the light modulation element 23 is the metal thin film 32 on the upper side and the metal thin film 31 on the lower side. It becomes a joint portion 33 to join. As a result, the bonding layer 30 composed of the two metal thin films 31 and 32 is formed.

The materials of the metal thin films 31 and 32 are preferably materials having a large self-diffusion coefficient for bonding and easily oxidizing in the atmosphere, and aluminum (Al) and iron (Fe) are mixed with chromium (Cr) or nickel (Ni). The added alloy is suitable. Further, the thickness of the metal thin films 31 and 32 is preferably about several nm in consideration of the bonding strength and the oxidation range in the subsequent steps.

Next, the bonded and integrated substrates 10 and 20 are taken out of the vacuum space and exposed to the atmosphere. As a result, the surfaces of the formed metal thin films 31 and 32 are oxidized to form an oxidized region (insulating portion 30b). The insulating portion 30b has a role of protecting the entire joint portion 33 from being oxidized and a role of an insulating layer for insulating between each electrode 12 and each light modulation element 23.

As described above, in the spatial light modulator 1 and the manufacturing method thereof according to the first embodiment, a part of the light modulation element 23 is exposed to the insulating layer 24, so that the surface 20a of the upper substrate 20 is light-modulated. A convex pattern is formed by the element 23. Then, this convex pattern becomes a joint portion 33 with the lower substrate 10 (specifically, the lower electrode 12) by forming the metal thin film 32 into a film. Therefore, the spatial light modulator 1 according to the first embodiment does not require patterning of the metal thin films 31 and 32 for bonding, so that the manufacturing process can be simplified and shortened.
The surfaces of the metal thin films 31 and 32 are oxidized by being exposed to the atmosphere after joining the substrates 10 and 20. This oxide film serves as a protective role for preventing the entire joint portion 33 from being oxidized and as an insulating layer that insulates between each electrode and between each element.

[Second Embodiment]
In the spatial light modulator 1 according to the first embodiment, the light modulation element is exposed from the insulating layer to form a joint portion having a convex pattern (step structure) of a two-dimensional array. In the second embodiment, in the spatial light modulator 1A, the lower electrode is exposed from the insulating layer to form a joint portion having a linear convex pattern (step structure).

<< Configuration of Spatial Light Modulator according to the Second Embodiment >>
A specific configuration of the spatial light modulator 1A according to the second embodiment of the present invention will be described with reference to FIG. 9A and 9B are cross-sectional views in the direction (Y direction) in which the upper electrode 22 of the spatial light modulator 1A according to the second embodiment of the present invention is extended. FIG. 9A shows an overall view, and FIG. 9B shows an overall view. Is an enlarged view of a main part of FIG. 9A. The upper side (Z direction side) of the spatial light modulator 1A is the light incident surface.

As shown in FIG. 9, the spatial light modulator 1A is configured to include both the plate-shaped upper base 21 and the lower base 11, and the light modulation element 23 is placed between the two stacked bases 21 and 11. It is arranged in two dimensions. The lower base 11 is the first base, and the upper base 21 is the second base. The upper electrode 22 is connected to the upper part of the light modulation element 23, while the lower electrode 12 is connected to the lower part of the light modulation element 23 via the bonding layer 30A. As a result, the spatial light modulator 1A is mainly laminated from the bottom in the order of the lower base 11, the lower electrode 12, the bonding layer 30A, the light modulation element 23, the upper electrode 22, and the upper base 21.

In the spatial light modulator 1A, as described later in the manufacturing method, elements such as the light modulation element 23 are separately formed on the basis of the substrates 11 and 21, and the lower substrate 10A which is the first substrate (FIG. 10 (FIG. 10). b)) and the upper substrate 20A (see FIG. 10A), which is the second substrate, are manufactured. Then, the upper electrode 22 and the lower electrode 12 are made to face each other so as to intersect (here, orthogonally), and as shown in FIG. 9, these two substrates 10A and 20A are bonded together via the bonding layer 30A. Manufactured. In explaining the configurations of the substrates 10A and 20A individually, the planes (sometimes referred to as the upper surface or the surface) of the substrates 11 and 21 are the sides on which the light modulation elements 23 and the electrodes 12 and 22 are formed. Each element may be described with the side of the base 11 or the base 21 as the base facing down. Hereinafter, each configuration will be described.

<Lower board>
The configuration of the lower substrate 10A, which is the first substrate, will be described. As shown in FIG. 9A, the lower substrate 10A includes a lower substrate 11 which is a first substrate, a lower electrode 12 which is a first electrode patterned on the lower substrate 11, and a patterned lower electrode. It is composed of an insulating layer 13A which is a first insulating layer formed between the twelve.

The lower substrate 11 is, for example, a Si substrate. The lower electrode 12 is patterned on the lower substrate 11 using, for example, a lithography technique. The lower electrode 12 may be a general metal electrode material such as a metal such as Cu, Al, Au, Ag, Ta, Cr or an alloy thereof. The insulating layer 13A is formed between the patterned lower electrodes 12 and insulates between the adjacent lower electrodes 12.

The surface 10Aa of the lower substrate 10A is composed of a lower electrode 12 and an insulating layer 13A, and a step structure is formed by exposing a part of the lower electrode 12 to the insulating layer 13A.
That is, the insulating layer 13A is formed so that the tip of the lower electrode 12 is exposed to the upper substrate 20A side by a predetermined amount. The exposure amount (protrusion amount) H of the lower electrode 12 is preferably 0.2 nm or more, for example. As a result, as shown in FIG. 10B, a linear convex pattern is formed on the surface 10Aa of the lower substrate 10A by the exposed lower electrodes 12.

The convex pattern formed by the lower electrode 12 may be formed by various methods, and the method for forming the convex pattern is not particularly limited. The following shows an example of a method for forming a convex pattern.
For example, when backfilling with the insulating layer 13A after patterning and etching the resist of the lower electrode 12 by lithography, the backing is made shallower than the thickness of the lower electrode 12. After that, if possible, it is preferable to perform surface flattening treatment with CMP or the like.

Further, when backfilling with the insulating layer 13A after patterning and etching the resist of the lower electrode 12 by lithography, the insulating layer 13A is backfilled with an appropriate thickness (the surface is flattened with CMP or the like if necessary), and CF Only the insulating layer 13A may be etched by a few nm with a reactive gas such as _4. At this time, since the lower electrode 12 is hardly etched (because the etching rates of the lower electrode 12 and the insulating layer 13A are different), the convex pattern is easily completed.

Further, when the insulating layer 13A is formed on the lower substrate 11, the resist holes of the pattern of the lower electrode 12 are patterned by photolithography, and the resist holes of the pattern of the lower electrode 12 are etched, and then the film formation and lift-off of the lower electrode 12 are performed, the depth of the etching is increased. The lower electrode 12 is formed thickly before lift-off. After that, if possible, it is preferable to perform surface flattening treatment with CMP or the like.

<Upper board>
The configuration of the upper substrate 20A, which is the second substrate, will be described. As shown in FIG. 9A, the upper substrate 20A protrudes from the upper substrate 21 which is the second substrate, the upper electrode 22 which is the second electrode patterned on the upper substrate 21, and the upper electrode 22. It is composed of a two-dimensionally arranged light modulation element 23 and an insulating layer 24A which is a second insulating layer formed between the patterned upper electrode 22 and the light modulation element 23.

The upper substrate 21, the upper electrode 22, and the light modulation element 23 are as described in the first embodiment. That is, the upper substrate 21 is a transparent substrate such as glass. The upper electrode 22 is a transparent electrode that allows light to pass through. The optical conversion element 23 is formed on the upper electrode 22 by using, for example, a lithography technique, and has a four-layer structure of a magnetization free layer 233, an intermediate layer 232, a magnetization fixing layer 231 and a protective layer 234.

The insulating layer 24A is formed between the patterned upper electrodes 22 and the light modulation elements 23, and insulates between the adjacent upper electrodes 22 and the adjacent light modulation elements 23. As shown in FIG. 10A, the surface 20Aa of the upper substrate 20A has the light modulation element 23 and the insulating layer 24A formed in the same plane (plane). It is desirable that the surface roughness of the upper substrate 20A is smaller than that for, for example, CMP (Chemical Mechanical Polishing) treatment.

<Joint layer>
The configuration of the bonding layer 30A will be described. As shown in FIG. 9A, the bonding layer 30A joins the lower substrate 10A, which is the first substrate, and the upper substrate 20A, which is the second substrate. As shown in FIG. 9B, the bonding layer 30A is composed of an upper metal thin film 32A formed on the surface of the upper substrate 20A and a lower metal thin film 31A formed on the surface of the lower substrate 10A. For example, these metal thin films 31A and 32A are bonded by the atomic diffusion bonding method. The metal thin films 31A and 32A may be formed on the substrates 10A and 20A by a method such as sputtering, and are formed to have a substantially uniform thickness. The metal thin film 31A on the lower side has a convex pattern similar to that of the lower substrate 10A. As a result, the upper portion of the lower electrode 12 becomes a joint portion 33A that joins the metal thin film 32A on the upper side and the metal thin film 31A on the lower side.

Further, the bonding layer 30A is composed of two portions, a conductive portion 30Aa and an insulating portion 30Ab. The conductive portion 30Aa is formed in the upper portion of the lower electrode 12 (particularly near the center of the joint portion 33A), and electrically connects the light modulation element 23 and the lower electrode 12. On the other hand, the insulating portion 30Ab is formed around the conductive portion 30Aa and in a portion other than the joint portion 33A. The conductive portion 30Aa and the insulating portion 30Ab are formed by exposing the surfaces of the metal thin films 31A and 32A to the atmosphere by exposing the lower substrate 10A and the upper substrate 20A in a state where the metal thin films 31A and 32A are joined to the atmosphere. Will be done. That is, the surface portion of the bonding layer 30A other than the bonding portion 33A is formed as an oxide film.

The material of the bonding layer 30A is preferably a material having a large self-diffusion coefficient for bonding and easily oxidizing in the atmosphere, and chromium (Cr) and nickel (Ni) are added to aluminum (Al) and iron (Fe). Alloys are suitable. Further, the thickness of each of the metal thin films 31A and 32A is preferably about several nm in consideration of the strength of the joint and the need to completely oxidize the portion other than the joint portion 33A.

<< Manufacturing method of spatial light modulator according to the second embodiment >>
Next, a method of manufacturing the spatial light modulator 1A according to the second embodiment will be described.
The spatial light modulator 1A according to the present embodiment manufactures the lower substrate 10A and the upper substrate 20A shown in FIG. 10 by forming the light modulation element 23 and the electrodes 12 and 22 on the substrate 11 or the substrate 21, respectively. Then, the upper electrode 22 and the lower electrode 12 are made to face each other so as to intersect (here, orthogonally), and these two substrates 10A and 20A are laminated to be manufactured. Hereinafter, each step will be described.

<Manufacturing process of lower substrate>
The manufacturing process of the lower substrate 10A, which is the first substrate, will be described. In the manufacturing process of the lower substrate 10A, it is sufficient that a part of the lower electrode 12 is exposed to the insulating layer 13A so that a convex pattern formed by the lower electrode 12 can be formed on the surface 10Aa of the lower substrate 10A. The method can be used. Here, a case where the lower substrate 10A is manufactured by photolithography will be described with reference to FIG.

_{First, an insulating film 13p such as SiO 2} is formed on a lower substrate 11 such as Si (see FIG. 11A), and the insulating film 13p formed by using a resist 41 that opens the formation position of the lower electrode. A hole in the lower electrode pattern is formed in the lower electrode pattern (see FIG. 11B). Next, copper or the like, which is a lower electrode material, is formed into a film, and then the resist is lifted off to form a pattern of the lower electrode 12 (see FIG. 11C).

Then, if necessary, the surface is flattened by CMP treatment, and then _{only the insulating layer 13A is etched by a few nm with a reactive gas such as CF 4} to form a convex pattern by the lower electrode 12 (FIG. 11 (d)). reference). At this time, since the etching rates of the lower electrode 12 and the insulating layer 13A are different, the lower electrode 12 is hardly etched. Therefore, the convex pattern (step structure) can be easily completed.
As a result, the lower substrate 10A, which is the first substrate, is completed. Since it is desirable that the surface roughness of the lower substrate 10A is small in the joining step, it is preferable that the surface 10Aa of the lower substrate 10A is finally subjected to CMP (Chemical Mechanical Polishing) treatment or the like.

In the step of forming a film of copper or the like, which is the lower electrode material shown in FIG. 11C, the lower electrode 12 may be formed thicker than the etching depth to perform lift-off. As a result, the etching step shown in FIG. 11D can be omitted. Also at this time, it is preferable to flatten the surface by CMP treatment or the like.

Further, a convex pattern may be formed in a step of backfilling the insulating layer 13A after forming the lower electrode 12 by using a lithography technique. In that case, when backfilling with the insulating layer 13A, the insulating layer 13A is backfilled shallower than the thickness of the lower electrode 12. Also in this case, it is preferable to flatten the surface by CMP treatment or the like.

<Manufacturing process of upper substrate>
The manufacturing process of the upper substrate 20A, which is the second substrate, will be described. As the manufacturing process of the upper substrate 20A, the same method as the manufacturing process of a general semiconductor device can be applied. For example, a case where the upper substrate 20A is manufactured by photolithography will be described with reference to FIG.

First, an upper electrode film 22p such as indium zinc oxide, which is an upper electrode material, is formed on a transparent upper substrate 21 such as glass (see FIG. 12A), and openings other than the positions where the upper electrodes are formed are opened. The upper electrode film 22p formed by using the resist 42 is etched into the upper electrode pattern (see FIG. 12B). Next, the etched portion is _{backfilled with SiO 2} to form a part 24p of the insulating layer 24A, and then the resist 42 is lifted off to form a pattern of the upper electrode 22 (see FIG. 12C).

Next, a light modulation element layer 23p made of a metal film or a magnetic film for forming the magnetization free layer 233, the intermediate layer 232, the magnetization fixing layer 231 and the protective layer 234 of the light modulation element 23 is formed (FIG. 12 (FIG. 12). d)), the light modulation element layer 23p formed by using a resist 43 that opens other than the formation position of the light modulation element is etched into the light modulation element pattern (see FIG. 12E).

Next, the etched portion is _{backfilled with SiO 2} to form the insulating layer 24A, and then the resist 43 is lifted off to form the light modulation element layer 23 in a two-dimensional array (see FIG. 12 (f)). ).
As a result, the upper substrate 20A, which is the second substrate, is completed. Since it is desirable that the surface roughness of the upper substrate 20A is small in the joining step, it is preferable that the surface 20Aa of the upper substrate 20A is finally subjected to CMP (Chemical Mechanical Polishing) treatment or the like.

<Joining process between upper substrate and lower substrate>
After manufacturing the upper substrate 20A (see FIG. 10A) which is the second substrate and the lower substrate 10A (see FIG. 10B) which is the first substrate, joining these two substrates 10A and 20A together. The process will be described with reference to FIG. Here, it is assumed that the atomic diffusion bonding method is used for bonding both substrates 10A and 20A. The atomic diffusion bonding method makes it possible to bond an object at room temperature without applying a large pressure by utilizing atomic diffusion at the grain boundaries and surfaces of a metal thin film.

Metal thin films 31A and 32A were formed on the surfaces of the lower substrate 10A and the upper substrate 20A in a vacuum by a method such as sputtering (see FIG. 13A), and then the metal thin films 31A and 32A formed in the same vacuum were formed. They are brought into contact with each other and joined (see FIG. 13 (b)). At this time, since the convex pattern is formed on the surface 10A of the lower substrate 10A by the lower electrode 12, the upper portion of the lower electrode 12 joins the upper metal thin film 32A and the lower metal thin film 31A. It becomes the joint portion 33A to be formed. As a result, the bonding layer 30A composed of the two metal thin films 31A and 32A is formed.

The materials of the metal thin films 31A and 32A are preferably materials having a large self-diffusion coefficient for bonding and easily oxidizing in the atmosphere, and aluminum (Al) and iron (Fe) with chromium (Cr) and nickel (Ni). The added alloy is suitable. Further, the thickness of the metal thin films 31A and 32A is preferably about several nm in consideration of the bonding strength and the oxidation range in the subsequent steps.

Next, the bonded and integrated substrates 10A and 20A are taken out from the vacuum space and exposed to the atmosphere. As a result, the surfaces of the formed metal thin films 31A and 32A are oxidized to form an oxidized region (insulating portion 30Ab). The insulating portion 30Ab has a role of protecting the entire joint portion 33A from being oxidized and a role of an insulating layer for insulating between each electrode 12 and each light modulation element 23.

As described above, in the spatial light modulator 1A and the manufacturing method thereof according to the second embodiment, the lower electrode 12 is exposed on the surface 10Aa of the lower substrate 10A by exposing a part of the lower electrode 12 to the insulating layer 13A. A convex pattern is formed by. Then, this convex pattern becomes a joint portion 33A with the upper substrate 20A (specifically, the light modulation element 23) by forming a metal thin film 31A. Therefore, the spatial light modulator 1A according to the second embodiment does not require patterning of the metal thin films 31A and 32A for bonding, so that the manufacturing process can be simplified and shortened.
The surfaces of the metal thin films 31A and 32A are oxidized by being exposed to the atmosphere after joining the two substrates 10A and 20A. This oxide film serves as a protective role for preventing the entire joint portion 33A from being oxidized and as an insulating layer that insulates between each electrode and between each element.

[Modification example]
Although the embodiments of the present invention have been described above, the present invention is not limited to this, and can be carried out within a range that does not change the gist of the claims.

In each embodiment, the case where the optical conversion element 23 is arranged on the upper substrates 20 and 20A side (upper electrode 22 side) has been described, but the optical conversion element 23 is arranged on the lower substrates 10 and 10A side (lower electrode 12 side). May be disposed. In that case, the optical conversion element 23 is formed on the lower electrode 12 by using, for example, lithography technology, and is laminated in the order of the magnetization fixing layer 231, the intermediate layer 232, the magnetization free layer 233, and the protective layer 234 from the lower electrode 12 side. It has a four-layer structure. Then, in the convex pattern, the tip of the optical conversion element 23 arranged on the lower substrate 10 is exposed to the insulating layer 13, or the tip of the upper electrode 22 is exposed to the insulating layer 24. To do. That is, in each embodiment, the "first substrate" is the lower substrate 10, 10A and the "second substrate" is the upper substrate 20, 20A, but in this case, the "first substrate" is the upper substrate 20, 20A. The "second substrate" is the lower substrate 10, 10A.

Further, in each embodiment, after all the substrates 10, 20 or the substrates 10A, 20A are manufactured, the metal thin films 31, 31A, 32, 32A are formed on the surfaces of the substrates 10, 10A, 20, 20A. It was. However, the steps before joining the respective substrates 10, 20 or 10A, 20A (for example, the steps of manufacturing the respective substrates 10, 10A, 20, 20A and forming the metal thin films 31, 31A, 32, 32A). Therefore, the order of (which may be collectively referred to as a "board preparation process") is not limited to this. For example, the substrate preparation step is an order in which the upper substrate 20 which is the second substrate is manufactured to form the metal thin film 32, and then the lower substrate 10 which is the first substrate is manufactured to form the metal thin film 31. You may.

1,1A Spatial light modulator 2 Upper electrode selection part 3 Lower electrode selection part 4 Current source 5 Current control means 10,10A Lower substrate (first substrate)
11 Lower substrate (first substrate)
12 Lower electrode (first electrode)
13,13A Insulation layer (first insulation layer)
20,20A Upper board (second board)
21 Upper base (second base)
22 Upper electrode (second electrode)
23 Light Modulation Element 24, 24A Insulation Layer (Second Insulation Layer)
231 Magnetized fixed layer 232 Intermediate layer 233 Magnetized free layer 234 Protective layer 30,30A Bonding layer 31,31A Metal thin film (first metal film)
32, 32A metal thin film (second metal film)
33,33A Joint

Claims (3)

A spatial light modulator in which a first substrate and a second substrate are bonded via a bonding layer.
The first substrate is a first substrate that insulates between a first substrate formed in a rectangular shape, a plurality of first electrodes formed toward opposite sides on the first substrate, and adjacent first electrodes. It is provided with an insulating layer, and a striped pattern is formed on the surface by the first electrode.
The second substrate includes a second substrate formed in a rectangular shape, a plurality of second electrodes formed on the second substrate in a direction intersecting with the first electrode, and the first electrode on the second electrode. A plurality of light modulation elements projecting from the second electrode at intersections intersecting with the electrodes and two-dimensionally arranged, and the two-dimensionally arranged light modulation elements while insulating between the adjacent second electrodes and the adjacent light modulation elements. A second insulating layer formed so that a part of each light modulation element projects toward the first substrate side is provided, and a convex pattern of a two-dimensional arrangement is formed on the surface by the light modulation element. ,
The bonding layer includes a first metal film formed on the surface of the first substrate and a second metal film formed on the surface of the second substrate, and the protruding optical modulation elements of the respective photomodulators. Spatial photomodulation characterized in that a joint portion between the first metal film and the second metal film is formed by a part thereof, and a surface portion of the joint layer other than the joint portion is formed as an oxide film. vessel. A protective layer is formed on the first substrate side of the light modulation element.
The spatial light modulator according to claim 1, wherein the amount of protrusion of the light modulation element is less than the thickness of the protective layer. A first substrate formed in a rectangular shape, a plurality of first electrodes formed toward opposite sides on the first substrate, a first insulating layer that insulates between adjacent first electrodes, the first electrode, and the like. A first substrate having a first metal film formed on the surface of the first insulating layer, a second substrate formed in a rectangular shape, and a plurality of formed on the second substrate in a direction intersecting with the first electrode. 2nd electrode, a plurality of photomodulators protruding from the 2nd electrode at an intersection intersecting with the 1st electrode on the 2nd electrode, and 2 adjacent second electrodes and adjacent light A second insulating layer formed so as to insulate between the modulation elements and to project a part of each of the optical modulation elements arranged in two dimensions, a second insulating layer formed on the surface of the optical modulation element and the second insulating layer. A substrate preparation step for preparing a second substrate having two metal films, and
A joining step in which the first electrode and the second electrode face each other so as to intersect each other, and the portion of the second metal film covering each light modulation element and the opposing portion of the first metal film are joined.
It consists of an oxide film forming step of oxidizing the surfaces of parts other than the joint portion of the first metal film and the second metal film after joining.
On the first substrate, a striped pattern is formed under the first metal film by the first electrode.
On the second substrate, a convex pattern of a two-dimensional array is formed under the second metal film by the light modulation element.
A method for manufacturing a spatial light modulator.

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