WO2019239835A1

WO2019239835A1 - Method for manufacturing microdisplay substrate

Info

Publication number: WO2019239835A1
Application number: PCT/JP2019/020422
Authority: WO
Inventors: 飛坂　優二; 小西　繁; 川合　信
Original assignee: 信越化学工業株式会社
Priority date: 2018-06-15
Filing date: 2019-05-23
Publication date: 2019-12-19
Also published as: TW202032830A; JP2019220511A; JP6914227B2

Abstract

In order to reduce the size of a transistor, a method for manufacturing a microdisplay substrate is provided with which it is possible to manufacture a microdisplay substrate having a large-diameter transparent substrate even when using a small-diameter substrate having a single-crystal Si layer, and with which it is possible to prevent the transmittance of light from dropping even when using an adhesive. In this method, a circuit layer (14) is formed on the surface of a small-diameter first substrate (11) having a single-crystal Si layer, the substrate is then placed in a jig (20), and the circuit-layer-side surface of the first substrate is affixed to a large-diameter second substrate (12) with an adhesive (16). The jig is removed, the back surface of the first substrate is ground, polished, and mirror-finished, and a large-diameter transparent third substrate (13) is directly affixed to the mirror-finished back surface and heat-treated to reinforce the bonding strength of the first substrate and the third substrate. The first substrate and the second substrate are then mechanically separated, the adhesive remaining on the surface of the first substrate is removed, and the circuit layer is exposed, whereby a large-diameter microdisplay substrate is obtained.

Description

Manufacturing method of substrate for micro display

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

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

Small display devices, including projectors, use small display devices called microdisplays, which are magnified so that they can be seen by the viewer and projected onto the screen, or images from the reflective member to the viewer's field of view. It is. Among them, the head-mounted display has been attracting attention as one of wearable terminals because it allows hands-free viewing of information from information terminals. As described in Patent Document 1 and Patent Document 2, the head-mounted display is mounted like glasses and displayed near the eyes, and thus the device itself is required to be downsized.

A small display device called a micro display is used for the head-mounted display. A transmissive liquid crystal panel that controls transmitted light using liquid crystal, and a reflective liquid crystal that reflects light at the electrode and controls the polarization direction of reflected light using liquid crystal. There is a micromirror driving panel that controls the direction of reflected light of the panel and the micromirror.

Each of the above panels refers to a single component of the panel. In fact, a display device requires 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. . Since the transmissive liquid crystal panel emits incoming light in its direction, the front and rear optical systems can be made simple, and the size of the display device can be made compact. Reflective LCD panels output reflected light, but incident light and reflected light are the same surface with respect to the panel surface, so it is necessary to separate the light with an optical component called a polarizing beam splitter (PBS). The device size increases. Since the micromirror driving panel also uses reflected light, an optical component (for example, an internal total reflection prism (TIRPrism)) is required, and the size of the display device is increased.

The pixel circuit of the transmissive liquid crystal panel is made of Si. However, it is difficult to reduce the size of the transistor, which is a switching element of the pixel circuit, with amorphous Si or polycrystalline Si used in a normal liquid crystal panel. It is desirable to use A liquid crystal panel using single crystal Si is called LCOS (Liquid Crystal On On Silicon), and is distinguished from a normal liquid crystal display (LCD). When a pixel circuit is manufactured from single-crystal Si, a Si substrate or an SOI (Silicon-on-Insulator) substrate is usually used. However, since Si does not transmit light, it cannot be used as a display device as it is. Using a SOQ (Silicon on 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 where there is no pixel circuit. .

Patent Document 3 describes a method of manufacturing a pixel circuit substrate by forming a pixel circuit on an SOI substrate, bonding the circuit portion to a transparent substrate with an adhesive, and then removing the SOI substrate. In this way, a normal semiconductor process apparatus can be used, a small and high-performance circuit can be formed, and it can be used for a transmissive liquid crystal panel.

Japanese Patent No. 5678460 JP 2010-032997 A US Pat. No. 5,256,562

As described above, it is conceivable to use an SOQ substrate for manufacturing a microdisplay substrate. However, the SOQ substrate has two problems in using a normal semiconductor process apparatus. One is that it is light transmissive, so a sensor that uses light to check for the presence of a substrate does not detect it. The other is that the electrostatic chuck used in the semiconductor process apparatus cannot be attracted. Because of these problems, it is necessary to modify the semiconductor process equipment, and it is not possible to put it in all the semiconductor process equipment. At present, the semiconductor process apparatus specially adjusted so that a circuit can be formed on an SOQ substrate is limited to a substrate having a small diameter such as an outer diameter of 150 mm, for example, a substrate having a large diameter such as an outer diameter of 200 mm. There is a problem that can not cope.

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 bonded to the transparent substrate, light transmission is possible. There is a problem in that the light transmittance is reduced due to the presence of the agent. Further, in production, there may be a problem that air bubbles enter into the uneven portion of the circuit or peels off from the adhesive portion during processing.

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

In order to achieve the above object, a method for manufacturing a microdisplay substrate according to the present invention comprises: preparing a first substrate having a single-crystal Si layer; and providing a first surface of the first substrate. Forming a pixel circuit for a pixel electrode and a driving circuit therearound, and a transparent third substrate having a larger outer diameter than 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 an outer diameter difference 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 driving circuit are formed is exposed, and the first surface of the first substrate and the second substrate are bonded with an adhesive. And bonding the jig to the first Removing the second surface of the first substrate opposite to the first surface and then thinning and further polishing to make a mirror surface; and Bonding the third substrate to the mirror-finished second surface by direct bonding, heat-treating the bonded first substrate, second substrate, and third substrate, Strengthening the bonding force between the first substrate and the third substrate, and applying the force in a direction to separate the second substrate and the third substrate from each other, Mechanically separating the two substrates, and removing the adhesive remaining on the first surface of the first substrate to expose the pixel circuit and the driving circuit. .

The first substrate may be an SOQ substrate having a Si layer on a quartz substrate. As the third substrate, a glass substrate may be used, 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 recess that can accommodate the first substrate. In other words, the inner diameter of the recess may correspond to the outer diameter of the first substrate. The depth of the recess may be 40 to 70% of the thickness of the first substrate.

The manufacturing 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 bonding the third substrate. good. The manufacturing method of the present invention further includes a step of forming a transparent pixel electrode on the pixel circuit after forming the pixel circuit and the driving circuit on the first surface of the first substrate. May be included. The heat treatment may be performed at a temperature of 200 to 250 ° C.

As described above, according to the present invention, even when the first substrate having a small diameter having a single crystal Si layer is used, after the pixel circuit for the pixel electrode and the peripheral drive circuit are formed on the first surface, Then, place it on a jig for eliminating the difference in outer diameter, attach it to the second substrate of the large-diameter temporary joint 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 that is the final substrate having the same outer diameter as the second substrate is directly bonded to the mirror-finished back surface and heat-treated. Since the second substrate can be easily mechanically separated by strengthening the bonding force between the first substrate and the third substrate, the first substrate has a small diameter at the time of circuit formation. It is possible to manufacture a microdisplay substrate in which a circuit is formed on a transparent third substrate having a large diameter. The ability. In addition, since the first substrate and the third substrate are bonded together by direct bonding, there is no adhesive between the substrates, and the light transmittance can be prevented from decreasing.

It is a typical flowchart which shows one Embodiment of the manufacturing method of the board | substrate for microdisplays which concerns on this invention. It is the top view and side sectional view which show the jig | tool and 1st board | substrate which are shown in FIG. It is sectional drawing which shows the transmissive liquid crystal panel using the board | substrate for microdisplays. It is a top view which shows typically an example of the circuit layer of the board | substrate for microdisplays. It is a top view which shows an example which arrange | positions a some circuit pattern on the 1st board | substrate.

Hereinafter, an embodiment of a method for manufacturing a microdisplay substrate 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 its outer diameter 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 as the surface layer is determined by 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 its peripheral driving circuit is formed on the first substrate 11 ((b) in FIG. 1). Although a semiconductor process apparatus is used for circuit formation, a known semiconductor process apparatus in which a stock sensor or an adsorption stage for a transparent substrate is adjusted or modified can be used.

Note that after the circuit layer 14 is formed, an ITO (Indium Tin Oxide) layer (not shown) to be a transparent pixel electrode may be formed and the pattern may be formed. Further, after forming the circuit layer 14 or the ITO layer, a protective film (not shown) made of, for example, phenol novolak or polyhydroxystyrene, which is used as a resist material in the photolithography process, may be formed. It is possible to prevent damage to the circuit layer 14 and the ITO layer in the step. You may form a protective film at the time of the adhesive agent application before bonding mentioned later.

Meanwhile, 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 microdisplay substrate, it is necessary to be a colorless and transparent substrate. For example, the same quartz glass as that of the glass substrate, particularly 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 bonding surface is finished to be a mirror surface. The surface state is preferably a surface roughness Ra of 1 nm or less, which is common for direct bonding.

In addition, a second substrate 12 for provisional bonding with the circuit layer 14 is prepared ((d) in FIG. 1). The second substrate 12 and the third substrate 13 are preferably made of the same material. The reason is to prevent thermal stress from being generated by the heat treatment after directly bonding the third substrate 13. 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 thickness cannot withstand the thermal stress and is damaged. Although there is a method of lowering the heat treatment temperature in order to reduce the thermal stress, the bonding strength is not realistic because it is difficult to strengthen when the temperature is low.

The size of the third substrate 13 is preferably the size of the finally obtained microdisplay substrate, and the second substrate 12 for temporary bonding is preferably the same size. Specifically, the third substrate 13 and the second substrate 12 have a large diameter, and both outer diameters are preferably, for example, 199.5 to 200.5 mm. Although the sizes of the first substrate 11 and the second substrate 12 are different, the first substrate 11 is positioned and bonded to the second substrate 12 using a jig 20 to be described later. Since the third substrate 13 and the third substrate 13 have the same outer diameter, 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) of FIG. 1). Since the second substrate 12 is temporarily joined 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. Those which can be removed after being bonded to each other are preferred. The adhesive 16 is preferably one that can withstand the temperature of heat treatment for increasing the bonding force and can be easily peeled off and separated, in addition to being resistant to chemicals during grinding and polishing. Examples of such an adhesive 16 include UV curable acrylic adhesives such as trade names WSS manufactured by 3M, and thermosetting modified silicone adhesives such as trade names TA1070T, TA2570V3, and TA4070 manufactured by Shin-Etsu Chemical Co., Ltd. Is mentioned. The latter modified silicone adhesive is more preferred because of its resistance to chemicals.

For the purpose of protecting the surface of the second substrate 12, the adhesive 16 may be applied to the second substrate 12 side and bonded to the first substrate 1. It may adversely affect grinding tools such as grinding wheels. In that case, bonding to the second substrate is performed with the adhesive 16 on the circuit 14 as shown in FIG. When the adhesive 16 is applied to the first substrate 11 side, a jig 20 for placing the first substrate 1 is used ((e) of FIG. 1).

2, the jig 20 has a substantially disk shape having the same outer diameter as that of the second substrate 12. The jig 20 has an orientation flat 21 at 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 types, the orientation flat 21 is formed into a V-shaped or U-shaped notch accordingly. In addition, a recess 22 that can accommodate the first substrate 11 is provided on the surface of the jig 20. That is, the inner diameter of the recess 22 corresponds to the outer diameter of the first substrate 11. The recess 22 has an orientation flat 23 at a part of its outer periphery so that it can be positioned with the first substrate 11. In addition, holes 24 for taking out the first substrate 11 from the recess 22 are formed at both ends of the orientation flat 23 of the recess 22.

The depth of the recess 22 of the jig 20 is preferably 40 to 70%, more preferably 45 to 65% of the thickness of the first substrate 11. If the recess 22 is too deep, the adhesive that protrudes from the surface 25 of the jig 20 when the adhesive is applied to the first substrate 11 will cause the second substrate 12 to adhere to the second substrate 12 and pressurize it. It may adhere to the substrate 12 and the jig 20 may be fixed to the second substrate 12 and cannot be removed. On the other hand, if the dent 22 is too shallow, the shape of the chamfered portion of the edge of the first substrate 11 may be a tapered shape, which may increase the positional deviation. The jig 20 can be easily and repeatedly used, for example, by using a material (for example, a metal such as aluminum) from which the adhesive can be easily removed or a surface state (for example, a mirror surface).

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

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

Further, the thus-bonded third substrate 13 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 temperature of the heat treatment, the better. However, the upper limit of the upper limit is preferably 250 ° C. or less because it causes deterioration of the adhesive 16. The lower limit of the heat treatment is preferably 200 ° C. or higher, for example. The heat treatment time needs to be longer as the temperature is lower. The temperature and time of the heat treatment may be any conditions as long as 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 are preferable, and if the temperature is 240 to 250 ° C., 12 to 24 hours are preferable.

Then, the temporarily bonded second substrate 12 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 adsorption devices (not shown), respectively. Adhesion that is a bonding surface of 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 the substrates apart. The blade 17 is inserted into the part of the agent 16 to form an opening, and a force for further pulling off is continuously applied to separate the second substrate 12 at the part 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 manner, a microdisplay substrate in which the circuit layer 14 for the liquid crystal panel of the microdisplay formed on the surface layer of the first substrate 11 having a small diameter is transferred to the third substrate 13 having a large diameter can be manufactured.

FIG. 3 shows an example of a liquid crystal panel using the microdisplay substrate manufactured as described above. As shown in FIG. 3, the transmissive liquid crystal panel 30 includes, as shown in FIG. 3, a pixel substrate 32 and a counter substrate 38 that are disposed to face each other, and a liquid crystal layer 35 that is sandwiched between the pair of substrates. . The pixel substrate 32 and the counter substrate 38 are further sandwiched between two polarizing plates 31.

On the surface of the pixel substrate 32 on the liquid crystal layer 35 side, a circuit layer 33 having a plurality of pixel circuits 33 a including transistors and the peripheral drive circuit 33 b is formed. Further, the circuit layer 33 on the liquid crystal layer 35 side is formed. A plurality of pixel electrodes 43 are formed. 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 disposed between the pixel substrate 32 and the counter substrate 38 so as to surround the liquid crystal layer 35. The counter substrate 38 is also a transparent substrate such as a quartz substrate or a glass substrate. As shown in FIG. 3, the transmissive liquid crystal panel 30 receives incident light 1 from the counter substrate 38 side and receives a polarizing plate 31a, a counter substrate 38, a counter electrode 37, a liquid crystal layer 35, a pixel electrode 34, a pixel circuit 33a, and a pixel. The outgoing 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 a microdisplay substrate 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 peripheral drive circuit 33b is formed are arranged. A pattern 40 is formed. The drive circuit unit 42 includes a column selection circuit unit 42a and a row selection circuit unit 42b.

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

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

[Example 1]
A substantially disk-shaped SOQ substrate having an outer diameter of 150 mm and a thickness of 625 μm was prepared as a first substrate, and a circuit layer was formed by a semiconductor process apparatus on the surface Si layer of 150 nm. Since the surface Si layer of the SOQ substrate is a single crystal, the circuit layer was formed using the same parameters as those of a normal SOI Si layer and using a mask prepared based on the design data. The used semiconductor process apparatus corresponds to a transparent substrate, so that the in-stock sensor is made compatible with the transparent body by replacement or adjustment, and the adsorption stage is also made compatible with quartz glass. After the ITO film was formed 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.

A substantially disc-shaped synthetic quartz glass substrate having an outer diameter of 200 mm and a thickness of 725 μm was prepared as the second substrate and the third substrate, respectively. Then, the first substrate is positioned by positioning it with an orientation flat with the surface on which the circuit layer is formed facing the recess 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 stored it. The jig was made of aluminum in consideration of cleaning with an organic solvent for removing the adhesive.

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

In addition, the adhesive at the time of temporary joining which bonds a 1st board | substrate and a 2nd board | substrate considers the workability | operativity at the time of isolate | separating later, and the heat resistance at the time of the heat processing after joining a 3rd board | substrate. Selected. Here, TA1070T, TA2570V3, and TA4070 manufactured by Shin-Etsu Chemical Co., Ltd., which are thermosetting modified silicone adhesives, were used. That is, 10 μm of TA1070T, 10 μm of TA2570V3, and 90 μm of TA4070 were further laminated on the first substrate by spin coating, for a total of 110 μm. TA1070T functions as a circuit protection, TA2570V3 functions as a release layer during substrate separation, and TA4070 functions as an adhesive layer with the second substrate. The second substrate was bonded by pressing with a force of 0.1 MPa, then set horizontally in an oven with the jig attached, and subjected to a heat treatment at 190 ° C. for 2 hours to cure the adhesive.

As shown in Table 1, in the jigs of Test Examples 1 and 2, where the dent portion was relatively shallow, the first substrate was displaced. Further, in the jig of Test Example 5 in which the dent portion was relatively deep, the adhesive protruding from the first substrate adhered to the second substrate, and was fixed when the jig was removed and could not be peeled off. . Therefore, since the depths of the jigs of Test Examples 3 and 4 in which the displacement was small and the jigs were easy to be removed were 300 mm and 400 mm, the jigs had a thickness of 625 μm with respect to the first substrate thickness of 625 μm. It can be seen that the depth of the recess is preferably 40 to 70%.

Next, after the back surface of the first substrate temporarily bonded to the second substrate is ground with a grinding wheel to reduce the thickness of the first substrate, rough polishing with a lapping surface plate, 1 with cerium oxide Next polishing and finish polishing with colloidal silica were sequentially performed to finish the back surface of the first substrate to a mirror surface. At this time, the first substrate was processed to have a thickness of 200 μm. After polishing, scrub cleaning, cleaning with 2% hydrogen fluoride aqueous solution, and pure water rinsing were performed in this order so that no residue such as slurry remained on the back surface of the first substrate.

Then, the 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 together in the shape of the outer periphery. Bonding was performed by direct bonding. That is, after the first substrate is placed so that the back surface of the first substrate faces upward, the surfaces of the third substrate are overlapped with each other downward, and a portion of the portion overlapping the first substrate is pushed to put the substrates together. Bonding was performed by bringing them into contact. Since it is a transparent substrate, the state of bonding was visually confirmed.

After bonding, heat treatment was performed under conditions of 250 ° C. and 12 hours in order to increase the bonding strength. After the heat treatment, the third substrate is placed on the suction stage so that the back surface of the third substrate is facing down and the back surface of the second substrate is facing up, and the third substrate is attracted and pulled up 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 the force, the blade was inserted into the adhesive layer which is the interface between the first substrate and the second substrate. The opening was created in a part of the adhesive by inserting the blade, and the force to peel off the substrates was applied, so that the opening gradually spread and separation progressed. Finally, it was peeled off from the portion bonded to the first substrate with 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 separation of the second substrate, the adhesive residue on the first substrate was removed by immersing it in an organic solvent p-menthane for 5 minutes. The first substrate bonded to the third substrate could not visually confirm the interface of the direct bonding, and was transparent in a portion without a circuit. It was possible to obtain a microdisplay substrate in which the circuit was transferred to a large substrate without deteriorating the transmittance by direct bonding.

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

As shown in Table 2, in Test Examples 6 to 9, as in Example 1, the second substrate could be normally separated, 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, the surface of the third substrate was activated by plasma treatment, but because the time was short with respect to the temperature of the heat treatment, the bonding strength could not be strengthened, and the first substrate and the third substrate were stuck. It is thought 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 strength could not be strengthened even if the heat treatment was performed thereafter, and the bonding interface between the first substrate and the third substrate was not achieved. Probably separated.

DESCRIPTION OF SYMBOLS 1 Incident light 2 Outgoing light 11 1st board | substrate 12 2nd board | substrate 13 3rd board | substrate 14 Circuit layer 16 Adhesive 17 Blade 20

Jig

21, 23, 51 Orientation flat 22 Recessed part 30 Transmission type liquid crystal panel 31 Polarizing plate 32 pixel substrate 33 circuit layer 34 pixel electrode 35 liquid crystal layer 36 sealing material 37 counter electrode 38 counter substrate 40 circuit pattern 41 pixel circuit unit 42 drive circuit unit

Claims

A manufacturing method of a substrate for microdisplay,
Providing a first substrate having a single-crystal Si layer;
Forming a pixel circuit for a pixel electrode and a peripheral drive circuit on the first surface of the first substrate;
Providing a transparent third substrate having a larger outer diameter than the first substrate and serving as a support substrate for the microdisplay substrate;
Providing a second substrate having the same outer diameter as the third substrate;
The first substrate is exposed to a first surface on which the pixel circuit and the drive circuit are formed in a jig for eliminating a difference in outer diameter between the first substrate and the second substrate. Placing 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, grinding and thinning the second surface of the first substrate opposite to the first surface, and further polishing to make a mirror surface When,
Bonding the third substrate to the mirror-finished second surface of the first substrate by direct bonding;
Heat-treating the bonded first substrate, second substrate, and third substrate to enhance the bonding force between the first substrate and the third substrate;
Mechanically separating the first substrate and the second substrate while applying a force in a direction to peel the second substrate and the third substrate from each other;
Removing the adhesive remaining on the first surface of the first substrate to expose the pixel circuit and the driving 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.
The jig includes a recess capable of accommodating the first substrate, and the depth of the recess is 40 to 70% of the thickness of the first substrate. The manufacturing method of any one of these.
5. The method according to claim 1, 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 bonding the third substrate. 2. The production method according to item 1.
The production method according to any one of claims 1 to 5, wherein the heat treatment is performed at a temperature of 200 to 250 属 C.