WO2021237511A1

WO2021237511A1 - Transfer substrate of micro-leds and preparation method therefor

Info

Publication number: WO2021237511A1
Application number: PCT/CN2020/092610
Authority: WO
Inventors: 翟峰; 唐彪
Original assignee: 重庆康佳光电技术研究院有限公司
Priority date: 2020-05-27
Filing date: 2020-05-27
Publication date: 2021-12-02

Abstract

A transfer substrate of Micro-LEDs and a preparation method therefor. The transfer substrate comprises: a support plate (1), and a bonding adhesive layer (2) disposed on the support plate (1); and a plurality of bonding rubber bumps (3) are formed on the side surface of the bonding adhesive layer (2) away from the support plate (1). By means of forming the plurality of bonding rubber bumps (3) on the surface of the bonding adhesive layer (2), the bonding rubber bumps (3) can deform and are used for bonding connection with Micro-LEDs, and internal stress generated by inhibiting the bonding of a bonding adhesive and the Micro-LEDs on a warped epitaxial growth substrate is dispersed, thus reducing the amount of stress on the bonding adhesive layer (2), so that when the Micro-LEDs and the transfer substrate are temporarily bonded, the bonding adhesive can more completely adhere the Micro-LEDs, thereby reducing the differences in adhesive force at the center and the periphery of a temporary substrate caused by the warping of the epitaxial growth substrate, so that the Micro-LEDs on the epitaxial growth substrate can all bond with the bonding adhesive on the transfer substrate, thus eliminating the phenomenon of bonding rings.

Description

Micro-LED transfer substrate and preparation method thereof

Technical field

The present invention relates to the field of semiconductor technology, in particular to a transfer substrate of Micro-LED and a preparation method thereof.

Background technique

Micro-LED displays are a new generation of display technology. Compared with existing LED liquid crystal displays, Micro-LED displays have higher photoelectric efficiency, higher brightness, higher contrast, and lower power consumption, and can also be combined with flexible panels to achieve flexible display. However, in the actual panel preparation process, tens of millions of LEDs need to be stripped from the epitaxial growth substrate, and then transferred to the drive backplane.

The process of stripping the Micro-LED from the epitaxial growth substrate is as follows: first use a temporary bonding material to bond the Micro-LED to the temporary substrate, and then use laser lift-off technology to peel the Micro-LED from the epitaxial growth substrate to transfer the Micro-LED To the temporary substrate. However, because the growth temperature of Micro-LED on the epitaxial growth substrate of Micro-LED is as high as about 1000℃, and the material of the LED crystal layer is usually gallium nitride, the lattice parameters and thermal expansion coefficient of gallium nitride and the epitaxial growth substrate are different. Larger, the substrate will warp when the temperature drops to room temperature, as shown in Figure 1. The temporary substrate has good flatness, so when bonding with the Micro-LED on the epitaxial growth substrate, the flatness difference between the two is obvious, and the adhesion of the Micro-LED and the bonding glue at different positions on the epitaxial growth substrate is different. Bonding ring phenomenon. In addition, during laser lift-off, the gallium nitride connected between the Micro-LED and the epitaxial growth substrate decomposes and generates an impact force. If the impact force cannot be effectively transferred or released, the Micro-LED will chip or drift.

Therefore, the existing technology needs to be improved and developed.

Summary of the invention

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a Micro-LED transfer substrate and a preparation method thereof, which aims to solve the large difference in the adhesive force of the temporary bonding between the bonding glue and the Micro-LED, and to buffer the laser The problem that the stress generated by the decomposition of gallium nitride during stripping cannot be effectively transferred or released, thereby effectively improving the laser stripping yield.

The technical scheme of the present invention is as follows:

A transfer substrate of Micro-LED, wherein the transfer substrate comprises:

Support plate

The bonding adhesive layer is arranged on the support plate;

A plurality of bonding glue protrusions are formed on the surface of the bonding glue layer facing away from the supporting plate.

In the transfer substrate, the shape of the protrusion includes one of a hemispherical shape and a circular pyramid shape.

In the transfer substrate, in the plurality of protrusions, the distance between two adjacent bonding glue protrusions and the bottom diameter of the bonding glue protrusions are both 1 to 5 μm.

In the transfer substrate, the ratio of the height of the protrusion to the diameter of the bottom is in the range of 1:1 to 1:3.

In the transfer substrate, the thickness of the bonding adhesive layer is 10-60 μm.

The transfer substrate, wherein the bonding adhesive layer includes one of a silicone-based bonding adhesive layer, an acrylic-modified silicone-based bonding adhesive layer, an acrylic bonding adhesive layer, and a polyurethane-based bonding adhesive layer. kind.

In the transfer substrate, the support plate includes one of a glass plate and a sapphire plate.

A method for preparing the transfer substrate of Micro-LED as described above, which comprises the following steps:

Provide a silicon plate, and etch a plurality of grooves on the surface of the silicon plate;

Coating a bonding adhesive layer on the surface of the silicon plate on the side with the groove;

Providing a support plate on the side of the bonding adhesive layer away from the silicon plate and curing the bonding adhesive layer;

Separating the cured bonding adhesive layer from the etched silicon plate to obtain the transfer substrate of the Micro-LED.

In the preparation method, the shape of the groove includes one of a hemispherical shape and a conical shape.

In the preparation method, in the plurality of grooves, the interval between adjacent grooves is 1 to 5 μm; the groove diameter of the grooves is 1 to 5 μm.

In the preparation method, the ratio of the depth of the groove to the diameter of the notch is 1:1 to 1:3.

In the preparation method, the method for forming the bonding adhesive layer includes one of a spin coating method and a slit coating method.

A method for transferring Micro-LEDs, which includes the following steps:

An epitaxial growth substrate is provided, the epitaxial growth substrate includes a base and a Micro-LED disposed on the base;

Disposing the transfer substrate of the Micro-LED as described above on the epitaxial growth substrate, so that the bonding glue protrusion structure of the transfer substrate is in contact with the epitaxial growth substrate;

Applying pressure to the transfer substrate toward the epitaxial growth substrate, so that the Micro-LED on the epitaxial growth substrate adheres to the transfer substrate;

The base of the epitaxial growth substrate is separated from the Micro-LED, and the Micro-LED is transferred to the transfer substrate.

In the method for transferring the Micro-LED, wherein the epitaxial growth substrate is a warped epitaxial growth substrate; the transfer substrate of the Micro-LED as described above is arranged on the epitaxial growth substrate so that the The contact between the bonding glue protrusion structure of the transfer substrate and the epitaxial growth substrate includes:

The side of the transfer substrate with the bonding glue protrusions is arranged on the side of the warped epitaxial growth substrate with the Micro-LED, so that the bonding glue protrusion structure is in contact with the Micro-LED.

In the method for transferring the Micro-LED, wherein the base of the epitaxial growth substrate is a sapphire base, and the separating the base of the epitaxial growth substrate from the Micro-LED includes:

The laser lift-off technology is used to separate the sapphire substrate from the Micro-LED.

Beneficial effects: The present invention forms a plurality of bonding glue protrusions on the surface of the bonding glue layer, and the bonding glue protrusions can be deformed and used for bonding and connection with the Micro-LED, thereby dispersing the bonding glue and the bonding glue. The internal stress generated by the pressing and bonding of the Micro-LED on the warped epitaxial growth substrate reduces the internal stress of the bonding adhesive layer, so that when the Micro-LED and the transfer substrate are temporarily bonded, the bonding adhesive can be more effective. Completely adhere to the Micro-LED, reduce the difference in the adhesive force between the center and the periphery of the temporary substrate due to the warpage of the epitaxial growth substrate, so that the Micro-LED on the epitaxial growth substrate can be combined with the bonding adhesive on the transfer substrate Bonding eliminates the phenomenon of bonding rings.

Description of the drawings

Figure 1 is a schematic diagram of a warped epitaxial growth substrate.

Fig. 2 is a schematic diagram of a Micro-LED transfer substrate provided by an embodiment of the present invention.

FIG. 3 is a schematic flow chart of a method for preparing a transfer substrate for Micro-LED according to an embodiment of the present invention.

FIG. 4 is a flowchart of a method for transferring Micro-LEDs according to an embodiment of the present invention.

5 is a schematic diagram of the contact between a warped epitaxial growth substrate and a transfer substrate in a method for transferring a Micro-LED according to an embodiment of the present invention.

FIG. 6 is a schematic diagram of a transfer result of a method for transferring a Micro-LED provided by an embodiment of the present invention.

FIG. 7 is a schematic diagram of laser irradiation of a method for transferring Micro-LED provided by an embodiment of the present invention.

Detailed ways

The present invention provides a method, system and storage medium for adjusting the image of a display. In order to make the objectives, technical solutions and effects of the present invention clearer and clearer, the present invention will be described in further detail below. It should be understood that the specific embodiments described here are only used to explain the present invention, but not used to limit the present invention.

An embodiment of the present invention provides a Micro-LED transfer substrate. As shown in FIG. 2, the transfer substrate includes: a support plate 1; a bonding adhesive layer 2 disposed on the support plate 1; A plurality of bonding glue protrusions 3 are formed on the surface of the glue layer 2 facing away from the support plate.

Specifically, as shown in Figure 1, Figure 1 is a schematic diagram of a warped epitaxial growth substrate. Due to the high temperature of epitaxial growth, warping of the epitaxial growth substrate will occur. When the plane bonding glue and epitaxial growth of the temporary substrate are used When the Micro-LED on the substrate is press-bonded, a pressure is applied to the temporary substrate so that the Micro-LED on the warped part of the epitaxial growth substrate can be bonded with the bonding glue, resulting in the bond of the non-warped part of the epitaxial growth substrate. The internal stress of the glue is relatively large, and the internal stress of the bonding glue in contact with the warped part is relatively small. When the pressure is relieved, the molecular chain conformation of the bonding glue material with greater internal stress changes, and the van der Waals force with the Micro-LED material changes, resulting in a decrease in the bonding adhesive force of this part, and the bond with less internal stress The adhesive strength is moderate, which results in different adhesive strengths at different positions of the adhesive on the epitaxial growth substrate, and the phenomenon of bonding rings appears. Therefore, in this embodiment, a plurality of bonding glue protrusions 3 are provided on the flat bonding glue layer 2. During the compression bonding process between the epitaxial growth substrate and the transfer substrate, the plurality of bonding glue protrusions 3 undergo adaptive deformation. , Disperse part of the internal stress of the bonding glue in contact with the Micro-LED on the unwarped part of the epitaxial growth substrate, and reduce the internal stress of the bonding glue of the bonding glue layer 2, so that the Micro-LED and the transfer When the substrate is temporarily bonded, the bonding glue can adhere to the Micro-LED more completely, reducing the difference in the adhesion between the center and the periphery of the temporary substrate due to the warpage of the epitaxial growth substrate, so that the Micro-LED on the epitaxial growth substrate -LEDs can be bonded with the bonding glue on the transfer substrate, eliminating the phenomenon of bonding rings.

In one embodiment, the bottom shape of the bonding glue protrusion 3 can be any shape, and the shape of the protrusion 3 is also not limited, but it is necessary to ensure that there is sufficient space between the protrusions 3 so that the protrusions 3 3 After being deformed, it will not cover the part of the surface of the bonding adhesive layer 2 that is not connected to the protrusion 3. Preferably, the shape of the bonding glue protrusion 3 includes one of a hemispherical shape and a circular pyramid shape.

Further, in the plurality of bonding glue protrusions 3, the interval between two adjacent bonding glue protrusions and the bottom diameter of the bonding glue protrusions are both 1˜5 μm. Specifically, the interval between adjacent bonding glue protrusions 3 and the bottom diameter should not be too wide or too narrow. Proper interval and bottom width can produce suitable adaptive deformation to disperse the internal stress of the partial bonding glue and avoid bonding glue. The adhesive force fails. At the same time, in the process of laser lift-off of the epitaxial growth substrate, it is avoided that the laser lift-off causes the non-vertical deformation of the ordered bonding glue bumps 3 to cause the drift of the Micro-LED.

Further, the ratio of the height of the bonding glue protrusion 3 to the bottom diameter is in the range of 1:1 to 1:3. Specifically, the ratio of the height of the bonding glue protrusion 3 to the bottom diameter has a certain effect on the deformation. When the ratio of the height to the bottom diameter is small, the bonding glue protrusion 3 cannot produce effective deformation to cause dispersed bonding. When the ratio of internal stress received by the adhesive layer 2 is too large, the deformation transition of the bonding adhesive protrusion 3 during the laser peeling of the epitaxial substrate will cause the drift of the Micro-LED. Preferably, the ratio of the height of the bonding glue protrusion 3 to the bottom diameter is 1:1.

In one embodiment, the thickness of the bonding adhesive layer 2 is 10-60 μm. Preferably, the thickness of the bonding adhesive layer 2 is 20 μm.

In one embodiment, the bonding adhesive layer 2 includes one of a silicone-based bonding adhesive layer, an acrylic-modified silicone-based bonding adhesive layer, an acrylic bonding adhesive layer, and a polyurethane-based bonding adhesive layer. kind. Preferably, the bonding adhesive layer is polydimethylsiloxane.

In one embodiment, the support plate 1 includes one of a glass plate and a sapphire plate.

The embodiment of the present invention also provides a method for preparing the transfer substrate of the Micro-LED as described above. As shown in FIG. 3, the preparation method includes the steps:

S10. Provide a silicon plate, and etch a plurality of grooves on the surface of the silicon plate;

S20. Coating a bonding adhesive layer 2 on the surface of the silicon plate 4 having a groove after the etching;

S30, setting a support plate 1 on the side of the bonding adhesive layer 2 away from the etched silicon plate and curing the bonding adhesive layer 2;

S40: Separate the cured bonding adhesive layer 2 from the support plate 1 and the etched silicon plate 4 to obtain the transfer substrate 3 of the Micro-LED.

Specifically, the silicon plate is first coated with photoresist, and after exposure and development, a plurality of grooves are etched on the surface of the silicon plate. The shape and size of each groove are consistent with the bonding glue convex on the transfer substrate of the Micro-LED. The size from 3 is the same. A layer of release agent is applied to the surface of the etched silicon plate 4 on the side with the groove, and the release agent can assist the separation of the bonding glue and the etched silicon plate 4. After drying the release agent, use the bonding glue to coat the bonding glue layer 2 on the side with the groove on the etched silicon plate 4, and at the same time, the bonding glue layer 2 faces the etched silicon plate 4 On one side, a bonding glue bump 3 connected to the bonding glue layer 2 is formed. Then set the support plate 1 on the bonding adhesive layer 2, and cure the coated bonding adhesive layer 2 and the bonding adhesive protrusions 3, and finally the cured bonding adhesive layer 2 and the bonded bonding The glue bump 3 is separated from the etched silicon plate 4, thereby obtaining the transfer substrate.

In one embodiment, the shape of the groove includes one of a hemispherical shape and a circular pyramid shape.

In one embodiment, in the plurality of grooves, an interval between two adjacent grooves is 1 to 5 μm; the groove diameter of the groove is 1 to 5 μm.

In one embodiment, the ratio of the depth of the groove to the diameter of the notch is 1:1 to 1:3.

In one embodiment, the materials of the bonding adhesive layer 2 and the plurality of bonding adhesive protrusions 3 include, but are not limited to, silicone-based materials, acrylic-modified silicone-based materials, acrylic-based materials, and polyurethane-based materials. Kind of. Specifically, the material for preparing the plurality of bonding glue protrusions 3 and the bonding glue layer 2 should have a small difference with the surface energy of the support plate 1 and a large difference with the surface energy of the etched silicon plate 4. After the bonding glue is cured, combined with the release agent previously coated on the surface of the etched silicon plate 4, the bonding glue bumps 3 and the bonding glue layer 2 can be separated from the etched silicon plate 4 at the same time, The bonding adhesive layer 2 and the supporting board 1 are bonded together, thereby obtaining the transfer substrate of the Micro-LED. Preferably, the material of the bonding adhesive layer 2 and the plurality of bonding adhesive protrusions 3 is polydimethylsiloxane, and the supporting plate 1 is a glass plate or a sapphire plate. The surface energy of polydimethylsiloxane has a small difference from the surface energy of glass or sapphire, but it has a large difference with the surface energy of silicon materials. The surface of the etched silicon plate 4 is coated with a release agent in advance to assist the silicon material Separate from the interface of polydimethylsiloxane.

In an embodiment, the forming method of the bonding adhesive layer 2 includes one of a spin coating method and a slit coating method.

The embodiment of the present invention also provides a Micro-LED transfer method. As shown in FIG. 4, the transfer method includes the steps:

S100. An epitaxial growth substrate 20 is provided. The epitaxial growth substrate 20 includes a base 4 and a Micro-LED 5 arranged on the base layer;

S200, disposing the transfer substrate 10 of the Micro-LED as described above on the epitaxial growth substrate 20, so that the bonding glue bump 3 structure of the transfer substrate 10 is in contact with the epitaxial growth substrate 20;

S300, applying pressure to the transfer substrate 10 toward the epitaxial growth substrate 20, so that the Micro-LED 5 on the epitaxial growth substrate 20 adheres to the transfer substrate 10;

S400: Separate the base 4 of the epitaxial growth substrate 20 from the Micro-LED 5, and transfer the Micro-LED 5 to the transfer substrate 10.

Specifically, as shown in FIG. 4, the epitaxial growth substrate 20 provided in this embodiment is obtained by epitaxially growing a Micro-LED 5 array on the substrate 4. Since the epitaxial growth temperature is as high as about 1000°C during the epitaxial growth process, The lattice parameters and thermal expansion coefficients of the Micro-LED 5 crystal layer material and the base 4 material are quite different. The epitaxial growth substrate 20 will warp after being cooled to room temperature. Generally speaking, the circular epitaxial growth substrate with a diameter of 4 inches The degree of warpage is about 60 μm (the distance from the highest point of warpage to the plane of the unwarped portion of the epitaxial growth substrate). Using an ordinary temporary substrate to bond the Micro-LED array on the warped epitaxial growth substrate with the bonding glue, a bonding ring phenomenon will occur, and the bonding degree of the Micro-LED inside and outside the bonding ring is inconsistent with the bonding glue. In this case, if the base layer is peeled from the Micro-LED, the peeling effect between the inside and outside of the bonding ring will be inconsistent. Usually, the Micro-LED in the bonding ring cannot be peeled off, resulting in a lower peel yield. After the bonding glue bumps 3 of the transfer substrate 10 using the Micro-LED provided in this embodiment are in contact with the Micro-LED 5 on the warped epitaxial growth substrate 20, a pressure is applied to the transfer substrate 10 toward the epitaxial growth substrate 20 , The multiple bonding glue bumps 3 on the transfer substrate 10 undergo adaptive deformation, which disperses the partial pressure of the bonding glue that is not in contact with the warped part, and reduces the internal stress of the bonding glue of the bonding glue layer 2 , So that the Micro-LED 5 on the epitaxial growth substrate 20 can be adhered to the transfer substrate 10, thereby eliminating the bonding ring phenomenon, so that the Micro-LED 5 on the epitaxial growth substrate 20 can be bonded to the transfer substrate 10 Glue bonding, the result after the transfer of the Micro-LED is shown in Figure 6.

In one embodiment, as shown in FIG. 5, the base 4 of the epitaxial growth substrate 20 is separated from the Micro-LED 5 by using a laser lift-off technology. The base 4 may be but not limited to a sapphire substrate. The laser lift-off technology makes contact with the base 4 The crystal layer material of the Micro-LED 5 decomposes, and the gas generated after decomposition produces an impulse, which causes the bonding glue protrusion 3 on the transfer substrate 10 to deform laterally. Due to the deformation of the bonding glue protrusion 3, the gas is relieved The generated impulse prevents the stress from being concentrated on the Micro-LED 5 or the flat bonding glue, reduces the risk of damage and drift of the Micro-LED 5, thereby further improving the yield of laser stripping.

In summary, in the present invention, by forming a plurality of bonding glue protrusions on the surface of the bonding glue layer, the bonding glue protrusions can be deformed and used for bonding and connection with Micro-LEDs, thereby dispersing due to the bonding The internal stress generated by the pressure bonding between the glue and the Micro-LED on the warped epitaxial growth substrate reduces the internal stress on the bonding glue layer, so that when the Micro-LED and the transfer substrate are temporarily bonded, the bonding glue It can adhere to the Micro-LED more completely and reduce the difference in the adhesion of the bonding glue between the center and the periphery of the temporary substrate due to the warpage of the epitaxial growth substrate, so that the Micro-LED on the epitaxial growth substrate can be bonded to the transfer substrate. Adhesive bonding eliminates the phenomenon of bonding rings. At the same time, in the process of using laser lift-off technology, the adaptive structural deformation of the bonding glue bumps can also effectively transfer the stress of the Micro-LED crystal material decomposition on the Micro-LED during laser lift-off, and prevent the Micro-LED from breaking under the force. Corner chipping or drift problems, thereby effectively improving the laser lift-off yield.

It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or changes can be made based on the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims

A transfer substrate of Micro-LED, characterized in that the transfer substrate comprises:

Support plate

The bonding adhesive layer is arranged on the support plate;

A plurality of bonding glue protrusions are formed on the surface of the bonding glue layer facing away from the supporting plate.
The transfer substrate according to claim 1, wherein the shape of the bonding glue protrusion includes one of a hemispherical shape and a circular pyramid shape.
The transfer substrate according to claim 2, wherein, among the plurality of bonding glue protrusions, the interval between two adjacent bonding glue protrusions and the bottom of the bonding glue protrusions The diameter is 1～5μm.
The transfer substrate according to claim 3, wherein the ratio of the height of the bonding glue protrusion to the diameter of the bottom is in the range of 1:1 to 1:3.
The transfer substrate according to claim 1, wherein the thickness of the bonding adhesive layer is 10-60 μm.
The transfer substrate according to claim 1, wherein the bonding adhesive layer comprises a silicone-based bonding adhesive layer, an acrylic-modified silicone-based bonding adhesive layer, an acrylic bonding adhesive layer, and a polyurethane-based bonding adhesive layer. A kind of glue layer.
The transfer substrate according to claim 1, wherein the supporting plate comprises one of a glass plate and a sapphire plate.
A method for preparing the transfer substrate of Micro-LED according to any one of claims 1 to 7, characterized in that it comprises the steps of:

Provide a silicon plate, and etch a plurality of grooves on the surface of the silicon plate;

Coating a bonding glue layer on the surface of the etched silicon plate on one side of the groove;

Providing a support plate on the side of the bonding adhesive layer away from the etched silicon plate and curing the bonding adhesive layer;

Separating the cured bonding adhesive layer from the etched silicon plate to obtain the transfer substrate of the Micro-LED.
The preparation method according to claim 8, wherein the shape of the groove includes one of a hemispherical shape and a conical shape.
The preparation method according to claim 9, characterized in that, in the plurality of grooves, the interval between two adjacent grooves is 1 to 5 μm; the groove diameter of the grooves is 1 to 5 μm. 5μm.
The preparation method according to claim 10, wherein the ratio of the depth of the groove to the diameter of the groove is 1:1 to 1:3.
The preparation method according to claim 8, wherein the forming method of the bonding adhesive layer includes one of a spin coating method and a slit coating method.
A method for transferring Micro-LED, which is characterized in that it comprises the steps:

An epitaxial growth substrate is provided, the epitaxial growth substrate includes a base and a Micro-LED disposed on the base;

Disposing the transfer substrate of the Micro-LED according to any one of claims 1 to 7 on the epitaxial growth substrate, so that the bonding glue protrusion structure of the transfer substrate is in contact with the epitaxial growth substrate;

Applying pressure to the transfer substrate toward the epitaxial growth substrate, so that the Micro-LED on the epitaxial growth substrate adheres to the transfer substrate;

The base of the epitaxial growth substrate is separated from the Micro-LED, and the Micro-LED is transferred to the transfer substrate.
The method for transferring the Micro-LED according to claim 13, wherein the epitaxial growth substrate is a warped epitaxial growth substrate; The transfer substrate disposed on the epitaxial growth substrate so that the bonding glue protrusion structure of the transfer substrate contacts the epitaxial growth substrate includes:

The side of the transfer substrate with the bonding glue protrusions is arranged on the side of the warped epitaxial growth substrate with the Micro-LED, so that the bonding glue protrusion structure is in contact with the Micro-LED.
The method for transferring a Micro-LED according to claim 13, wherein the substrate is a sapphire substrate, and the separating the substrate of the epitaxial growth substrate from the Micro-LED comprises:

The laser lift-off technology is used to separate the sapphire substrate from the Micro-LED.