JP6914227B2 - Manufacturing method of substrate for micro display - Google Patents

Description

The present invention relates to a method for manufacturing a substrate for a microdisplay.

Liquid crystal panels are generally used as display devices used in televisions, personal computer displays, mobile terminals, and the like. In addition to the method of directly viewing the display panel, there is also a display device of a method of projecting an image such as a projector. Further, as a small display device, there are a head-up display (HUD) and a head-mounted display (HMD). A miniaturized head-mounted display that is a glasses type is called a smart glass.

Small display devices, including projectors, use a small display device called a micro display, which is magnified so that it can be seen by the observer and projected onto a screen, or the image is guided from the reflective member to the observer's field of view. I'm doing it. Among them, the head-mounted display is attracting attention as one of the wearable terminals because it allows hands-free viewing of information on information terminals. As described in Patent Document 1 and Patent Document 2, the head-mounted display is worn like eyeglasses and displayed near the eyes, so that the device itself is required to be miniaturized.

A small display device called a micro display is used for the head mount display. A transmissive liquid crystal panel that controls transmitted light with a liquid crystal, and a reflective liquid crystal that is reflected by an electrode and controls the polarization direction of the reflected light with a liquid crystal. There are panels and micromirror drive panels that control the direction of reflected light from the micromirror.

Each of the above panels refers to a component of a single panel, and in fact, as a display device, a light source, an optical component for guiding light to the panel, an optical component for guiding the emitted light to the output side, and the like are required. .. Since the transmissive liquid crystal panel emits the incoming light in that direction, the front and rear optical systems can be simplified and the size of the display device can be made compact. The reflective liquid crystal panel outputs the reflected light, but since the incident light and the reflected light are on the same surface with respect to the panel surface, it is necessary to separate the light with an optical component called a polarizing beam splitter (PBS), and the display is displayed. The size of the device increases. Since the micromirror drive panel also uses the reflected light, an optical component (for example, an internal total internal reflection prism (TIRPrism)) is required, and the size of the display device becomes large.

The pixel circuit of a transmissive liquid crystal panel is made of Si, but with amorphous Si and polycrystalline Si used in ordinary liquid crystal panels, it is difficult to reduce the size of the transistor that is the switching element of the pixel circuit, and single crystal Si. It is desirable to use. A liquid crystal panel using single crystal Si is called LCOS (LiquidCrystalOnSilicon), and is described separately from a normal liquid crystal display (LCD). When a pixel circuit is manufactured from a single crystal Si, a Si substrate or an SOI (SilicononInsulator) substrate is usually used, but since Si does not transmit light, it cannot be used as it is as a display device. By using an SOQ (Siliconon Quartz) substrate in which a single crystal Si film is formed on a quartz glass substrate, a small transistor can be manufactured and light can be transmitted in a portion without a pixel circuit, which is most suitable for a microdisplay.

Patent Document 3 describes a method of forming a pixel circuit on an SOI substrate, attaching a circuit portion to a transparent substrate with an adhesive, and then removing the SOI substrate to prepare a pixel circuit board. By doing so, a normal semiconductor process device can be used, a small and high-performance circuit can be formed, and the circuit can be used for a transmissive liquid crystal panel.

Japanese Patent No. 5678460 Japanese Unexamined Patent Publication No. 2010-032997 U.S. Pat. No. 5,256,562

As described above, it is conceivable to use an SOQ substrate for manufacturing a substrate for a microdisplay, but the SOQ substrate has two problems in using a normal semiconductor process apparatus. One is that because it is light-transmitting, it is not detected by a sensor that uses light to check for the presence or absence of a substrate. The other is that the electrostatic chuck used in semiconductor process equipment cannot adsorb. Due to these problems, it is necessary to modify the semiconductor process equipment, and it cannot be put into all semiconductor process equipment as it is. Currently, semiconductor process devices specially adjusted to form circuits on SOQ substrates are limited to those with a small diameter, such as an outer diameter of 150 mm, for large diameter substrates such as an outer diameter of 200 mm. Has the problem that it cannot be dealt with.

Further, in the method described in Patent Document 3, as described above, since the SOI substrate is removed after the pixel circuit formed on the SOI substrate is attached to the transparent substrate, light can be transmitted, but the adhesion is achieved. There is a problem that the light transmittance drops due to the presence of the agent. Further, in manufacturing, there may be a problem that air bubbles enter the uneven portion of the circuit or peel off from the adhesive portion during processing.

Therefore, in view of the above problems, in order to reduce the size of the transistor which is the switching element of the pixel circuit, the present invention may use a small-diameter substrate having a single crystal Si layer such as a Si substrate or SOQ substrate. It is an object of the present invention to provide a method for manufacturing a substrate for a microdisplay, which can manufacture a substrate for a microdisplay having a transparent substrate having a large diameter and can prevent a decrease in light transmittance even if an adhesive is used. ..

In order to achieve the above object, the method for manufacturing a substrate for a microdisplay according to the present invention includes a step of preparing a first substrate having a single crystal Si layer and a first surface of the first substrate. , A step of forming a pixel circuit for a pixel electrode and a drive circuit around it, and a transparent third substrate having an outer diameter larger than that of the first substrate and serving as a support substrate for the microdisplay substrate. A step of preparing, a step of preparing a second substrate having the same outer diameter as the third substrate, and a jig for eliminating the difference in outer diameter between the first substrate and the second substrate. The first substrate is placed so that the first surface on which the pixel circuit and the drive circuit are formed is exposed, and the first surface of the first substrate and the second substrate are coated with an adhesive. After removing the jig from the first substrate, the second surface of the first substrate opposite to the first surface is ground to be thinned and further polished. The step of directly bonding the third substrate to the mirrored second surface of the first substrate, and the step of directly bonding the bonded first substrate, first A step of heat-treating the second substrate and the third substrate to strengthen the bonding force between the first substrate and the third substrate, and a direction of peeling the second substrate and the third substrate from each other. The step of mechanically separating the first substrate and the second substrate and the adhesive remaining on the first surface of the first substrate are removed while applying a force to the first substrate. It includes a step of exposing the pixel circuit and the drive circuit.

As the first substrate, an SOQ substrate having a Si layer on a quartz substrate may be used. A glass substrate may be used as the third substrate, and a quartz glass substrate is particularly preferable. The second substrate may be made of the same material as the third substrate.

The jig may have the same outer diameter as the second substrate. The jig may include a recessed portion capable of accommodating the first substrate. That is, the inner diameter of the recessed portion may correspond to the outer diameter of the first substrate. The depth of the recessed portion may be 40 to 70% of the thickness of the first substrate.

The production method of the present invention may further include a step of activating the surface of the third substrate by ozone treatment, etching treatment, plasma treatment, or a combination thereof before the step of laminating the third substrate. good. Further, in the manufacturing method of the present invention, after forming the pixel circuit and the drive circuit on the first surface of the first substrate, a step of further forming a transparent pixel electrode on the pixel circuit is further performed. It may be included. The heat treatment may be carried out at a temperature of 200 to 250 ° C.

As described above, according to the present invention, even if a small-diameter first substrate having a single crystal Si layer is used, after forming a pixel circuit for a pixel electrode and a drive circuit around it on the first surface thereof. , Place it on a jig to eliminate the difference in outer diameter, attach it to the second substrate of large-diameter temporary bonding with an adhesive, and after removing the jig, the second surface of the first substrate. (That is, the back surface) is ground and polished to make a mirror surface, and a third substrate, which is the final substrate having the same outer diameter as the second substrate, is directly bonded to the mirrored back surface and heat-treated. Therefore, by strengthening the coupling force between the first substrate and the third substrate, the second substrate can be easily mechanically separated, so that the first substrate has a small diameter at the time of circuit formation. However, it is possible to manufacture a substrate for a microdisplay in which a circuit is formed on a transparent third substrate having a large diameter. Further, since the first substrate and the third substrate are directly bonded to each other, there is no adhesive between the substrates, and it is possible to prevent the light transmittance from dropping.

It is a schematic flow chart which shows one Embodiment of the manufacturing method of the substrate for micro display which concerns on this invention. It is a plan view and a side sectional view which shows the jig and a 1st substrate shown in FIG. It is sectional drawing which shows the transmissive liquid crystal panel which used the substrate for a microdisplay. It is a top view which shows an example of the circuit layer of the substrate for a microdisplay schematically. It is a top view which shows an example which arranges a plurality of circuit patterns on a 1st substrate.

Hereinafter, an embodiment of the method for manufacturing a substrate for a microdisplay according to the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, in the manufacturing method of the present embodiment, first, an SOQ substrate is prepared as the first substrate 11 ((a) in FIG. 1). The first substrate 11 has a small diameter, and the outer diameter thereof is preferably, for example, 149.5 to 150.5 mm. The thickness of the quartz layer is not particularly limited, but is preferably 600 to 650 μm, for example. The thickness of the single crystal Si layer on the surface layer is determined by the circuit design and process conditions, and is not particularly limited, but is preferably 50 to 300 nm, for example.

Then, a circuit layer 14 including a pixel circuit and a drive circuit around the pixel circuit is formed on the first substrate 11 ((b) in FIG. 1). Although a semiconductor process device is used for circuit formation, a known semiconductor process device in which a load sensor or a suction stage has been adjusted or modified for a transparent substrate can be used. By adjusting the wiring position of the thin film transistor (TFT) of each pixel circuit in the circuit layer 14 so that the wiring functions as a light-shielding film, it is possible to eliminate the need to form a new light-shielding layer. For the portion without wiring, a pattern for shading may be formed at the time of wiring formation. In this case, it is desirable to consider the effect on nearby signal lines.

After forming the circuit layer 14, an ITO (IndiumTinOxide) layer (not shown) serving as a transparent pixel electrode may be formed to form a pattern thereof. Further, after forming the circuit layer 14 or the ITO layer, a protective film (not shown) made of, for example, phenol novolac or polyhydroxystyrene, which is used as a resist material in the photolitho step, may be further formed. It is possible to prevent damage to the circuit layer 14 and the ITO layer in the process. The protective film may be formed at the time of applying the adhesive before bonding, which will be described later.

On the other hand, a third substrate 13 to which the circuit layer 14 is finally transferred is prepared ((c) in FIG. 1).

Since the third substrate 13 needs to transmit light as a substrate for a microdisplay, it needs to be a colorless and transparent substrate. For example, a glass substrate, particularly the same quartz glass as the SOQ substrate may be used, or non-alkali glass or optical glass used for a normal liquid crystal panel may be used. Since the third substrate 13 is directly bonded to the mirror-finished surface of the first substrate 11, the bonded surface is finished to be a mirror surface. As the surface condition, it is preferable that the surface roughness Ra is 1 nm or less, which is common for direct bonding.

In addition, a second substrate 12 for temporary joining with the circuit layer 14 is prepared ((d) in FIG. 1). It is preferable that the second substrate 12 and the third substrate 13 are made of the same material. The reason is to prevent thermal stress from being generated in the heat treatment after the third substrate 13 is directly bonded. When the same material is not used, it is preferable to use a material having ^{a linear expansion coefficient of 1 × 10-6} [/ K] or less in order to prevent thermal stress from being generated. When the thermal stress is large, the first substrate 11 having a thin substrate cannot withstand the thermal stress and is damaged. There is also a method of lowering the heat treatment temperature in order to reduce the thermal stress, but it is not realistic because the bonding force is difficult to be strengthened when the temperature is low.

It is preferable that the size of the third substrate 13 is the size of the finally obtained microdisplay substrate, and the size of the second substrate 12 for temporary bonding is also the same. Specifically, the third substrate 13 and the second substrate 12 have a large diameter, and the outer diameter is preferably 199.5 to 200.5 mm, for example. Although the sizes of the first substrate 11 and the second substrate 12 are different, the second substrate 12 is used to position the first substrate 11 and attach it to the second substrate 12 by using a jig 20 described later. By setting the outer diameters of the third substrate 13 and the third substrate 13 to be the same, the third substrate 13 can be bonded to the second substrate 12 with good reproducibility. The thickness of the third substrate 13 is not particularly limited, but is preferably 300 to 600 μm, for example. The thickness of the second substrate 12 is not particularly limited, but is preferably 600 to 800 μm, for example.

Next, the first substrate 11 and the second substrate 12 are temporarily joined with the adhesive 16 ((e) and (f) in FIG. 1). Since the second substrate 12 is a temporary bond for the grinding process of the first substrate 11 before being bonded to the third substrate 13, the adhesive 16 withstands the grinding process and the third substrate 13 It is preferable that it can be removed after being bonded to. The adhesive 16 is preferably one that has resistance to a chemical solution during grinding and polishing, can withstand the temperature of heat treatment for increasing the bonding force, and is easily peeled off and separated. Examples of such an adhesive 16 include an ultraviolet curable acrylic adhesive such as 3M's trade name WSS, and a thermosetting modified silicone adhesive such as Shin-Etsu Chemical's trade names TA1070T, TA2570V3, and TA4070. Can be mentioned. The latter modified silicone adhesive is more preferable because of its resistance to chemicals.

As the adhesive 16, the adhesive 16 may be applied to the side of the second substrate 12 and the first substrate 1 is bonded to each other for the purpose of protecting the surface of the second substrate 12, but the adhesive 16 is used during grinding. It may adversely affect grinding tools such as grinding wheels. In that case, as shown in FIG. 1 (e), the adhesive material 16 on the circuit 14 is bonded to the second substrate. When the adhesive 16 is applied to the first substrate 11 side, a jig 20 on which the first substrate 1 is placed is used ((e) in FIG. 1).

As shown in FIG. 2, the jig 20 has a substantially disk-like shape having the same outer diameter as the second substrate 12. The jig 20 has an orientation flat 21 on a part of its outer edge so that it can be positioned with the second substrate 12. If the second substrate and the third substrate are notch type, the orientation flat 21 has a V-shaped or U-shaped notch according to the notch type. Further, the surface of the jig 20 is provided with a recessed portion 22 capable of accommodating the first substrate 11. That is, the inner diameter of the recessed portion 22 corresponds to the outer diameter of the first substrate 11. The recessed portion 22 has an orientation flat 23 on a part of its outer circumference so that it can be positioned with the first substrate 11. Further, holes 24 for taking out the first substrate 11 from the recessed portion 22 are formed at both ends of the orientation flat 23 of the recessed portion 22.

The depth of the recessed portion 22 of the jig 20 is preferably 40 to 70%, more preferably 45 to 65%, based on the thickness of the first substrate 11. If the recess 22 is too deep, the adhesive that has squeezed out from the surface 25 of the jig 20 when the adhesive is applied to the first substrate 11 will be second when the second substrate 12 is bonded and pressed. There is a possibility that the jig 20 adheres to the substrate 12 and the jig 20 adheres to the second substrate 12 and cannot be removed. On the other hand, if the recessed portion 22 is too shallow, the shape of the chamfered portion of the edge of the first substrate 11 may be tapered, so that the positional deviation may become large. The jig 20 can be easily and repeatedly used, for example, by using a material (for example, a metal such as aluminum) in which the adhesive can be easily removed or a surface state (for example, a mirror surface).

Then, after removing it from the jig 20, the back surface of the first substrate 11 is ground and polished ((g) in FIG. 1). The purpose of grinding and polishing the back surface is to reduce the thickness of the first substrate 11 and to finish it in a mirror surface state for bonding. The polished first substrate 11a does not need to be thinned until the original substrate disappears, and may have a thickness of 0.7 to 1.2 mm when combined with the third substrate 13 to be bonded. After thinning by grinding, for example, rough polishing is performed on a lap surface plate, primary polishing is performed using cerium oxide on the slurry, and final polishing is performed using colloidal silica to finish the slurry in a mirror surface. By finishing it to a mirror surface, direct bonding becomes possible, and it can be integrated between the first substrate 11a and the third substrate 13 without the presence of inclusions such as adhesives, so that the transmittance of the liquid crystal panel is reduced. It can be prevented.

The back surface of the first substrate 11a and the front surface of the third substrate 13 after such polishing are bonded together ((h) in FIG. 1). At this time, in order to increase the bond strength, it is preferable to activate the surface of the third substrate 13. Examples of the activation include ozone treatment, etching treatment, and plasma treatment, and it is preferable to perform the treatment by any one or a combination of these. By this treatment, organic substances and gas adsorbing substances on the surface of the third substrate 13 are removed, the presence of substances between the substrates immediately after bonding is reduced, and a strong bonding force can be obtained.

Further, the material obtained by laminating the third substrate 13 in this way is heat-treated. By this heat treatment, the bonding force between the first substrate 11a and the third substrate 13 can be increased, and the second substrate 12 can be mechanically separated. The higher the heat treatment temperature, the better, but since it causes deterioration of the adhesive 16, the upper limit thereof is preferably 250 ° C. or lower. The lower limit of the heat treatment is preferably, for example, 200 ° C. or higher. The heat treatment time needs to be longer as the temperature is lower. The temperature and time of the heat treatment may be such that the first substrate 11a and the third substrate 13 are not separated when the second substrate 12 is separated. For example, the temperature may be 200 to 210 ° C. For example, 48 to 72 hours is preferable, and if the temperature is 240 to 250 ° C., 12 to 24 hours is preferable.

Then, the second substrate 12 for temporary bonding is separated ((i) in FIG. 1). In order to separate the second substrate 12 from the first substrate 11a, both the second substrate 12 and the third substrate 13 are adsorbed and fixed by suction devices (not shown), respectively, and these two suction devices are used. Adhesion, which is a bonding surface between the first substrate 11a and the second substrate 12, while applying a force to separate the second substrate 12 and the third substrate 13 from each other by a moving mechanism (not shown) that moves them apart. The blade 17 is inserted into the portion of the agent 16 to form an opening, and further pulling force is continuously applied to separate the second substrate 12 at the portion of the adhesive 16.

After separation, the residue of the adhesive 16 is removed with an organic solvent ((j) in FIG. 1). The organic solvent is not particularly limited as long as it can remove the adhesive 16 without adversely affecting the circuit layer 14, and for example, p-menthane, limonene, or acetone can be used. In this way, a microdisplay substrate can be produced by transferring the circuit layer 14 for the liquid crystal panel of the microdisplay formed on the surface layer of the small-diameter first substrate 11 to the large-diameter third substrate 13.

An example of a liquid crystal panel using the microdisplay substrate produced as described above is shown in FIG. As shown in FIG. 3, the transmissive liquid crystal panel 30 includes a pixel substrate 32 and an opposing substrate 38 arranged to be opposed to each other, and a liquid crystal layer 35 sandwiched between the pair of the substrates. .. The pixel substrate 32 and the opposing substrate 38 are further sandwiched between two polarizing plates 31.

A circuit layer 33 having a plurality of pixel circuits 33a including transistors and peripheral drive circuits 33b is formed on the surface of the pixel substrate 32 on the liquid crystal layer 35 side, and further, the liquid crystal layer 35 side of the circuit layer 33. Is formed with a plurality of pixel electrodes 43. A counter electrode 37 is formed on the surface of the counter substrate 38 on the liquid crystal layer 35 side. A sealing material 36 is arranged between the pixel substrate 32 and the facing substrate 38 so as to surround the liquid crystal layer 35. As the facing substrate 38, a transparent substrate such as a quartz substrate or a glass substrate is used. As shown in FIG. 3, the transmissive liquid crystal panel 30 receives the incident light 1 from the facing substrate 38 side, and receives the polarizing plate 31a, the facing substrate 38, the facing electrode 37, the liquid crystal layer 35, the pixel electrode 34, the pixel circuit 33a, and the pixels. The emitted light 2 is emitted from the pixel substrate 32 side through the substrate 32 and the polarizing plate 31b.

The pixel substrate 32 on which the circuit layer 33 in the transmissive liquid crystal panel 30 is formed corresponds to the substrate for a microdisplay obtained by the method of the present invention. As the circuit layer 33, for example, as shown in FIG. 4, a circuit in which a pixel circuit unit 41 in which a plurality of pixel circuits 33a are formed and a drive circuit unit 42 in which a drive circuit 33b around the pixel circuit unit 33b is formed are arranged. The pattern 40 is formed. The drive circuit unit 42 includes a column selection circuit unit 42a and a row selection circuit unit 42b. The pixel circuit section 41 is a portion through which light passes, but since the wiring of the pixel circuit section 41 is a metal layer, it does not allow light to pass through, and the transistor portion may malfunction when exposed to light. Designed to block light. Therefore, the direction in which light passes is limited to the direction shown in FIG.

The circuit pattern 40 shown in FIG. 4 corresponds to one liquid crystal panel, and as shown in FIG. 5, the circuit pattern 40 is a single first substrate 11 having an orientation flat 51 on a part of the outer edge. Multiple can be placed on the entire surface of. Thereby, a plurality of liquid crystal panels can be manufactured from one substrate. More specifically, the substrate for a microdisplay obtained by this method is bonded to a counter substrate on which a counter electrode is formed, cut into a panel size, and then a liquid crystal is sealed therein to form a liquid crystal panel. Can be done.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[Example 1]
A substantially disk-shaped SOQ substrate having an outer diameter of 150 mm and a thickness of 625 μm was prepared as the first substrate, and a circuit layer was formed on the surface Si layer of 150 nm by a semiconductor process apparatus. Since the Si layer on the surface of the SOQ substrate is a single crystal, the circuit layer was formed by designing a transistor using the same parameters as the Si layer of normal SOI, and using a mask prepared based on this design data. In order to support a transparent substrate, the semiconductor process device used is a transparent body by exchanging or adjusting the load sensor, and the adsorption stage is also compatible with quartz glass. After forming an ITO film on the surface of the SOQ substrate on which the circuit layer was formed in this way, a groove was formed so as to separate the pixels, and a pixel electrode was produced.

As the second substrate and the third substrate, a substantially disk-shaped synthetic quartz glass substrate having an outer diameter of 200 mm and a thickness of 725 μm was prepared. Then, the first substrate is positioned with an orientation flat with the surface on which the circuit layer is formed facing up in the recessed portion having an inner diameter of about 150 mm provided on the surface of a substantially disk-shaped jig having an outer diameter of 200 mm. I put it in. The jig was made of aluminum in consideration of cleaning with an organic solvent for removing the adhesive.

Five jigs having different depths of the recesses are manufactured, an adhesive is applied to the first substrate housed in the recesses, the second substrate is bonded, and the first substrate at that time is bonded. Was tested for misalignment and ease of removal of the jig. The results are shown in Table 1.

The adhesive at the time of temporary joining of the first substrate and the second substrate is considered in consideration of workability at the time of separation later and heat resistance at the time of heat treatment after joining the third substrate. Selected. Here, TA1070T, TA2570V3, and TA4070 manufactured by Shin-Etsu Chemical Co., Ltd., which are thermosetting modified silicone adhesives, were used. That is, TA1070T was 10 μm on the first substrate by spin coating, TA2570V3 was 10 μm on it, and TA4070 was further laminated on it by 90 μm to make a total of 110 μm. TA1070T functions as a circuit protection, TA2570V3 functions as a peeling layer at the time of substrate separation, and TA4070 functions as an adhesive layer with a second substrate. In the bonding of the second substrate, after pressing with a force of 0.1 MPa, the substrate was set horizontally in the oven with the jig attached, and heat treatment was performed at 190 ° C. for 2 hours to cure the adhesive.

As shown in Table 1, in the jigs of Test Examples 1 and 2 in which the recessed portion is relatively shallow, the misalignment of the first substrate occurred. Further, in the jig of Test Example 5 in which the recessed portion is relatively deep, the adhesive protruding from the first substrate adheres to the second substrate, and when the jig is removed, it sticks and cannot be peeled off. .. Therefore, since the depths of the jigs of Test Examples 3 and 4 with little misalignment and easy removal of the jig are 300 mm and 400 mm, the jig has a thickness of 625 μm of the first substrate. It can be seen that the depth of the recessed portion is preferably 40 to 70%.

Next, the back surface of the first substrate to which the second substrate is temporarily joined is ground with a grinding wheel to reduce the thickness of the first substrate, and then rough polishing with a lap surface plate and 1 with cerium oxide. Next polishing and finish polishing with colloidal silica were performed in order, and the back surface of the first substrate was finished to a mirror surface. At this time, processing was performed so that the thickness of the first substrate was 200 μm. After polishing, it was washed in the order of scrub washing, washing with a 2% hydrogen fluoride aqueous solution, and pure water rinsing so that no residue such as slurry remained on the back surface of the first substrate.

Then, the front surface of the third substrate was activated by plasma treatment and bonded to the mirrored back surface of the first substrate. At this time, the second substrate and the third substrate were positioned and bonded by the shape of the outer circumference. The bonding was performed by direct bonding. That is, after placing the first substrate so that the back surface faces upward, the surfaces of the third substrate are overlapped with each other facing downward, and a part of the portion overlapping with the first substrate is pushed to push the substrates together. The bonding was performed by bringing them into contact with each other. Since it is a transparent substrate, the bonding status was visually confirmed.

After bonding, heat treatment was performed at 250 ° C. for 12 hours in order to increase the bonding strength. After the heat treatment, the third substrate is placed on the adsorption stage so that the back surface of the third substrate is on the bottom and the back surface of the second substrate is on the top, and the third substrate is adsorbed and pulled upward to the back surface of the second substrate. A suction tool having a mechanism was attached, and a force was applied in a direction in which the second substrate and the third substrate were separated from each other. While applying that force, the blade was inserted into the adhesive layer at the interface between the first substrate and the second substrate. Due to the insertion of the blade, an opening was created in a part of the adhesive, and a force for peeling the substrates from each other was applied. Therefore, the opening gradually expanded and the separation proceeded. Finally, it was peeled off from the portion bonded to the first substrate by the adhesive, and the separation of the second substrate was completed. At this time, the first substrate was not separated from the third substrate.

After the separation of the second substrate, the residue of the adhesive on the first substrate was removed by immersing it in the organic solvent p-menthane for 5 minutes. In the first substrate bonded to the third substrate, the interface of the direct coupling could not be visually confirmed, and the portion without the circuit was transparent. By direct bonding, it was possible to obtain a substrate for a microdisplay in which the circuit was transferred to a large substrate without deteriorating the transmittance.

[Example 2]
The material of the second substrate and the third substrate was changed from quartz glass to non-alkali glass (trade name EagleXG manufactured by Corning Inc.), the activation of the surface of the third substrate was changed from plasma treatment, or A substrate for microdisplay was obtained in the same procedure as in Example 1 except that the heat treatment conditions were changed from 250 ° C. for 12 hours. Table 2 shows the various changed conditions and the results.

As shown in Table 2, in Test Examples 6 to 9, the second substrate could be separated normally as in Example 1, and the target microdisplay substrate could be obtained safely. However, in Test Examples 10 and 11, when the second substrate was separated, the third substrate was separated from the first substrate, and the target microdisplay substrate could not be obtained. In Test Example 10, although the surface of the third substrate was activated by plasma treatment, the bonding force could not be strengthened because the time was short with respect to the heat treatment temperature, and the first substrate and the third substrate were attached. It is considered that they were separated at the mating interface. In Test Example 11, since the activation treatment was not performed before the third substrate was bonded, the bonding force could not be strengthened even if the heat treatment was performed after that, and at the bonding interface between the first substrate and the third substrate. Probably separated.

1 Incident light 2 Emission light 11 1st substrate 12 2nd substrate 13 3rd substrate 14 Circuit layer 16 Adhesive 17 Blade 20 Jigs 21, 23, 51 Orientation flat 22 Recessed part 30 Transmissive liquid crystal panel 31 Plate plate 32 Pixel board 33 Circuit layer 34 Pixel electrode 35 Liquid crystal layer 36 Sealing material 37 Opposing electrode 38 Opposing substrate 40 Circuit pattern 41 Pixel circuit part 42 Drive circuit part

Claims (6)

This is a method for manufacturing a substrate for a micro display.
A step of preparing a first substrate having a single crystal Si layer,
A step of forming a pixel circuit for a pixel electrode and a drive circuit around it on the first surface of the first substrate,
A step of preparing a transparent third substrate having an outer diameter larger than that of the first substrate and serving as a support substrate for the microdisplay substrate.
A step of preparing a second substrate having the same outer diameter as the third substrate, and
The jig for eliminating the difference in outer diameter between the first substrate and the second substrate is provided so that the first surface on which the pixel circuit and the drive circuit are formed is exposed on the first substrate. A step of mounting and bonding the first surface of the first substrate and the second substrate with an adhesive, and
After removing the jig from the first substrate, a step of grinding and thinning a second surface of the first substrate opposite to the first surface, and further polishing to make a mirror surface. When,
A step of directly joining the third substrate to the mirrored second surface of the first substrate, and a step of bonding the third substrate to the mirrored second surface.
A step of heat-treating the bonded first substrate, second substrate, and third substrate to strengthen the bonding force between the first substrate and the third substrate.
A step of mechanically separating the first substrate and the second substrate while applying a force in a direction of peeling the second substrate and the third substrate from each other.
A manufacturing method including a step of removing the adhesive remaining on the first surface of the first substrate to expose the pixel circuit and the drive circuit. The manufacturing method according to claim 1, wherein the first substrate is an SOQ substrate having a Si layer on a quartz substrate. The manufacturing method according to claim 1 or 2, wherein the third substrate is a glass substrate. Claims 1 to 3 that the jig includes a recessed portion capable of accommodating the first substrate, and the depth of the recessed portion is 40 to 70% of the thickness of the first substrate. The manufacturing method according to any one of the above. Any of claims 1 to 4, further comprising a step of activating the surface of the third substrate by ozone treatment, etching treatment, plasma treatment, or a combination thereof before the step of laminating the third substrate. The manufacturing method according to item 1. The production method according to any one of claims 1 to 5, wherein the heat treatment is carried out at a temperature of 200 to 250 ° C.

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