CN111403329B - A transfer method of micro-light-emitting diode, display panel and preparation method thereof - Google Patents

Abstract

The application discloses a micro light-emitting diode transfer method, a display panel and a preparation method of the display panel, which are used for improving the transfer efficiency of micro light-emitting diodes and avoiding damaging the micro light-emitting diodes. The embodiment of the application provides a micro light emitting diode transfer method, which comprises the following steps: forming a micro light emitting diode array on a substrate and forming a hydrogenated amorphous layer over the micro light emitting diodes; attaching the hydrogenated amorphous layer to a transfer substrate, and peeling the micro light-emitting diode array from the substrate; aligning and attaching the micro light emitting diode array of the transfer substrate with a target substrate; and adopting an annealing process to the hydrogenated amorphous layer so that the hydrogenated amorphous layer releases hydrogen and the transfer substrate is stripped.

Description

A transfer method of micro-light-emitting diode, display panel and preparation method thereof

technical field

The present application relates to the field of display technology, in particular to a method for transferring micro-light emitting diodes, a display panel and a preparation method thereof.

Background technique

In recent years, micro light-emitting diodes (Micro LEDs), as a new type of self-illuminating display technology, have attracted extensive attention from researchers. Compared with Liquid Crystal Display (LCD), Micro LED display has a simpler structure, and as a self-luminous technology, Micro LED display is superior to LCD in terms of display contrast, response speed, color gamut, viewing angle, etc.; Micro LED display and Compared with organic light-emitting diode (OLED) display, Micro led has certain advantages in terms of brightness, efficiency, and lifespan.

In the current Micro LED technology, the key step is to transfer the Micro LED chip from the temporary substrate to the target substrate. Typical process methods in the prior art include the following two methods: 1. Micro LEDs are picked up and placed by transfer equipment; 2. Micro LEDs are irradiated with laser beams for peeling and transfer. The first process requires the pick-up and placement of Micro LED chips by adjusting the magnitude of the force between the transfer device and the Micro LED. The second process is to irradiate the release layer material with a laser beam, so that the force between the material and the Micro LED is weakened, and the purpose of peeling and transfer is achieved. However, the above two methods have certain limitations. The first method has low peeling and transfer efficiency, and is limited by the size of the pick-up equipment; the second method has a large laser spot and excessive local heat damage. The active layer of Micro LED affects the luminous efficiency of Micro LED.

To sum up, the transfer efficiency of the existing Micro LED transfer process is low, and it is easy to damage the Micro LED and affect the luminous efficiency of the Micro LED.

Contents of the invention

The embodiments of the present application provide a method for transferring micro-light emitting diodes, a display panel and a preparation method thereof, so as to improve the transfer efficiency of micro-light-emitting diodes and avoid damage to the micro-light-emitting diodes.

A method for transferring micro-light emitting diodes provided in an embodiment of the present application, the method comprising:

forming an array of micro light emitting diodes on the base substrate and forming a hydrogenated amorphous layer on the micro light emitting diodes;

bonding the hydrogenated amorphous layer to the transfer substrate, and peeling off the micro-LED array from the base substrate;

Aligning and attaching the micro-LED array on the transfer substrate to the target substrate;

An annealing process is applied to the hydrogenated amorphous layer, so that the hydrogenated amorphous layer releases hydrogen gas, and the transfer substrate is peeled off.

In the transfer method of micro-light emitting diodes provided in the embodiment of the present application, in the process of transferring micro-light-emitting diodes for the first time, the transfer substrate will not be limited by the size and spacing of micro-light-emitting diodes on the base substrate, and the micro-light-emitting diodes can be improved. The transfer efficiency of light-emitting diodes, because the transfer substrate can transfer micro-light-emitting diodes of any size, so the transfer substrate can be used repeatedly, which can save costs. Moreover, in the transfer method of micro-light emitting diodes provided in the embodiment of the present application, a hydrogenated amorphous layer is also provided on the micro-light-emitting diodes. During the first transfer process of the micro-light-emitting diodes, the hydrogenated amorphous layer and the transfer substrate Bonding, after the micro-LED array is aligned and bonded to the target substrate, the hydrogenated amorphous layer can be released by annealing process to separate the hydrogenated amorphous layer from the transfer substrate, so that the micro-LEDs can be separated from the transfer substrate. For stripping, the annealing process is adopted instead of the laser beam irradiation process, so as to avoid the damage of the laser beam to the micro-LED array, ensure the yield rate of the micro-light-emitting diode, and thereby improve the luminous efficiency of the micro-light-emitting diode.

Optionally, forming an array of micro-light emitting diodes on the base substrate and forming a hydrogenated amorphous layer on the micro-light-emitting diodes and the light-emitting diodes, specifically includes:

Forming each film layer of the micro light emitting diode on the base substrate;

Depositing an inorganic amorphous material on the micro-light emitting diode by using a plasma-enhanced chemical vapor deposition process to form a hydrogenated amorphous layer;

A patterning process is adopted for each film layer of the micro-light emitting diode and the hydrogenated amorphous layer to form patterns of the micro-light-emitting diode array and the hydrogenated amorphous layer.

Optionally, the inorganic amorphous material is deposited by a plasma-enhanced chemical vapor deposition process in an environment of one or a combination of the following gases: silane, ammonia, hydrogen;

The inorganic amorphous material includes one or a combination of the following: silicon nitride, silicon oxide, silicon oxynitride.

Optionally, before forming each film layer of the micro-light-emitting diode on the base substrate, the method further includes:

A buffer layer is formed on the base substrate.

In the micro-LED transfer method provided in the embodiment of the present application, a buffer layer is provided between the film layers of the micro-light-emitting diode and the base substrate, so as to avoid the crystallization of each film layer of the micro-light-emitting diode directly on the substrate. The problem of mismatch.

Optionally, before attaching the hydrogenated amorphous layer to the transfer substrate, the method further includes:

A bonding layer is formed on the transfer substrate.

In the micro-LED transfer method provided in the embodiment of the present application, a bonding layer is provided on the transfer substrate, which is more conducive to bonding the hydrogenated amorphous layer to the transfer substrate.

Optionally, peeling the micro-LED array from the base substrate specifically includes:

The base substrate and the micro light emitting diodes are separated by a laser lift-off process.

Optionally, before aligning and bonding the micro-LED array on the transfer substrate to the target substrate, the method further includes:

forming a pattern of bonding electrodes on the target substrate;

After aligning and bonding the micro-LED array on the transfer substrate to the target substrate, the method further includes:

Welding the micro light emitting diode array and the bonding electrodes.

Optionally, an annealing process is used for the hydrogenated amorphous layer, which specifically includes:

A rapid annealing process is adopted for the hydrogenated amorphous layer in a temperature environment greater than 500°C.

A method for preparing a display panel provided in an embodiment of the present application, the method comprising:

Prepare an array substrate; the array substrate includes sub-pixel regions of multiple colors;

The micro-light-emitting diodes corresponding to the color of the sub-pixel area are sequentially transferred to the sub-pixel area of the array substrate by using the micro-light-emitting diode transfer method provided in the embodiment of the present application.

The embodiment of the present application provides a display panel, which is manufactured by using the method for preparing a display panel provided in the embodiment of the present application.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings that need to be used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For Those of ordinary skill in the art can also obtain other drawings based on these drawings without making creative efforts.

FIG. 1 is a schematic diagram of a method for transferring a micro-light emitting diode provided in an embodiment of the present application;

Fig. 2 is the current-voltage curve diagram of the micro light-emitting diode annealed in the temperature environment of 500 ℃ provided by the embodiment of the present application;

FIG. 3 is a schematic diagram of another method for transferring micro-light emitting diodes provided in the embodiment of the present application;

FIG. 4 is a schematic diagram of a method for manufacturing a display panel provided in an embodiment of the present application.

Detailed ways

The embodiment of the present application provides a method for transferring micro-light emitting diodes, as shown in Figure 1, the method includes:

S101, forming an array of micro light emitting diodes on a base substrate and forming a hydrogenated amorphous layer on the micro light emitting diodes;

S102, attaching the hydrogenated amorphous layer to the transfer substrate, and peeling off the micro light emitting diode array from the base substrate;

S103. Align and attach the micro-LED array on the transfer substrate to the target substrate;

S104. Using an annealing process on the hydrogenated amorphous layer, so that the hydrogenated amorphous layer releases hydrogen gas, and peels off the transfer substrate.

In the micro-LED transfer method provided in the embodiment of the present application, in addition to the base substrate for growing the micro-light-emitting diode and the target substrate for micro-light-emitting diode transfer, the transfer substrate is also used as a temporary substrate to carry out the first micro-light-emitting diode on the base substrate. In one transfer, after peeling off the base substrate, a second transfer is performed on the micro-light emitting diodes, aligning and bonding the micro-light-emitting diode arrays to the target substrate, and then peeling off the micro-light-emitting diodes from the transfer substrate.

In the transfer method of micro-light emitting diodes provided in the embodiment of the present application, in the process of transferring micro-light-emitting diodes for the first time, the transfer substrate will not be limited by the size and spacing of micro-light-emitting diodes on the base substrate, and the micro-light-emitting diodes can be improved. The transfer efficiency of light-emitting diodes, because the transfer substrate can transfer micro-light-emitting diodes of any size, so the transfer substrate can be used repeatedly, which can save costs. Moreover, in the transfer method of micro-light emitting diodes provided in the embodiment of the present application, a hydrogenated amorphous layer is also provided on the micro-light-emitting diodes. During the first transfer process of the micro-light-emitting diodes, the hydrogenated amorphous layer and the transfer substrate Bonding, after the micro-LED array is aligned and bonded to the target substrate, the hydrogenated amorphous layer can be released by annealing process to separate the hydrogenated amorphous layer from the transfer substrate, so that the micro-LEDs can be separated from the transfer substrate. For stripping, the annealing process is adopted instead of the laser beam irradiation process, so as to avoid the damage of the laser beam to the micro-LED array, ensure the yield rate of the micro-light-emitting diode, and thereby improve the luminous efficiency of the micro-light-emitting diode.

Optionally, step S101 forms a micro-LED array on the base substrate and forms a hydrogenated amorphous layer on the micro-LEDs and the light-emitting diodes, specifically including:

S1011, forming each film layer of the micro light emitting diode on the base substrate;

S1012. Depositing an inorganic amorphous material on the micro-LED by using a plasma enhanced chemical vapor deposition (PlasmaEnhanced Chemical Vapor Deposition, PECVD) process to form a hydrogenated amorphous layer;

S1013. Using a patterning process on each film layer of the micro-LEDs and the hydrogenated amorphous layer to form a pattern of the micro-LED array and the hydrogenated amorphous layer.

Optionally, forming each film layer of the micro light emitting diode on the base substrate specifically includes:

A first semiconductor layer, an active layer, a second semiconductor layer and a second electrode layer are sequentially formed on the base substrate.

The base substrate may be, for example, a sapphire epitaxial wafer. The material of the second electrode layer may include, for example, one of the following or a combination thereof: nickel (Ni), gold (Au). The material of the active layer may include multiple quantum wells (Multiple Quantum Well, MQW), for example. In addition, the material of the first semiconductor layer may include, for example, n-type gallium nitride (n-GaN), and the material of the second semiconductor layer may include, for example, p-type gallium nitride (p-GaN).

Optionally, a patterning process is used for each film layer of the micro-light emitting diodes and the hydrogenated amorphous layer to form the pattern of the micro-light-emitting diode array and the hydrogenated amorphous layer, which specifically includes:

Coating photoresist on the hydrogenated amorphous layer, performing exposure, development, and etching processes to form micro-light-emitting diode arrays and patterns of the hydrogenated amorphous layer;

Remove photoresist.

Optionally, before attaching the hydrogenated amorphous material to the transfer substrate, the method further includes:

Through the laser lift-off process, the micro light emitting diodes in the area other than the micro light emitting diodes to be transferred are irradiated at fixed points, and the micro light emitting diodes in the area other than the micro light emitting diodes to be transferred are removed.

Optionally, the inorganic amorphous material is deposited by PECVD in an environment of one or a combination of the following gases: silane (SiH ₄ ), ammonia (NH ₃ ), hydrogen (H ₂ );

The inorganic amorphous material includes one or a combination of the following: silicon nitride (SiN _x ), silicon oxide (SiO _x ), silicon oxynitride (SiO _x N _y ).

In specific implementation, the range of x in SiN _x can be, for example, 1 to 1.3, the range of x in SiO _x can be, for example, 1 to 2, the range of x in SiO _x N _y can be, for example, 1 to 2, and the range of y For example, it may be 1 to 1.3.

It should be noted that the film deposited by the PECVD process is a hydrogenated amorphous film. The hydrogenated amorphous layer formed in the embodiment of the present application can be, for example: hydrogenated amorphous silicon nitride (a-SiNx: H), hydrogenated amorphous oxide Silicon (a- _SiOx :H), hydrogenated amorphous silicon oxynitride (a-SiON:H). The function of hydrogenation is to passivate the dangling bonds in the amorphous material, so that its defect density is greatly reduced. Taking the amorphous material as SiN _x as an example, the gas in the PECVD process can be a mixed gas of SiH ₄ , NH ₃ and H ₂ , and the H content can be regulated by changing the proportion of H ₂ in the mixed gas during specific implementation. For example, when it is necessary to deposit a-SiN _x :H with a thickness of 300 nanometers (nm), the ratio of H ₂ in the mixed gas may range from 10% to 30%.

Optionally, before forming each film layer of the micro-light-emitting diode on the base substrate, the method further includes:

A buffer layer is formed on the base substrate.

That is, the buffer layer is disposed between the base substrate and the first electrode.

In the micro-LED transfer method provided in the embodiment of the present application, a buffer layer is provided between the film layers of the micro-light-emitting diode and the base substrate, so as to avoid the crystallization of each film layer of the micro-light-emitting diode directly on the substrate. The problem of mismatch.

In specific implementation, for example, before each layer of the micro-light emitting diode is epitaxially grown on the sapphire substrate, a layer of material grown at low temperature, for example, GaN with a thickness of 20nm can be grown, or aluminum nitride (AlN) with a thickness of 50nm can be grown. , followed by an annealing process to form a buffer layer. Ni/Au electrodes can also be prepared on a sapphire substrate by a magnetron sputtering process, and a buffer layer can be formed by annealing at a high temperature of 500 degrees; the thickness of Ni can be, for example, 15nm, and the thickness of Au can be, for example, 1000nm. Then, each film layer of the micro-light emitting diode is epitaxially grown on the buffer layer, thereby avoiding a large dislocation density generated by the growth of each layer of the micro-light-emitting diode, and obtaining a film layer of a micro-light-emitting diode device with higher lattice quality.

Optionally, before step S103 bonding the hydrogenated amorphous layer to the transfer substrate, the method further includes:

A bonding layer is formed on the transfer substrate.

In the micro-LED transfer method provided in the embodiment of the present application, a bonding layer is provided on the transfer substrate, which is more conducive to bonding the hydrogenated amorphous layer to the transfer substrate.

During specific implementation, the transfer substrate can be, for example, a glass substrate, and the material of the bonding layer can be, for example, metal, polyimide (Polyimide, PI), anisotropic conductive film (Anisotropic Conductive Film, ACF), polydimethyl Silicone (Polydimethylsiloxane, PDMS) and other materials, the bonding layer is preferably a high temperature resistant material.

In the micro-LED transfer method provided in the embodiment of the present application, the bonding layer on the transfer substrate does not need to be patterned, so that the transfer substrate is not limited by the size and spacing of the micro-LEDs on the base substrate, and alignment is not required. , can improve the transfer efficiency of micro-light emitting diodes, and the transfer substrate can transfer micro-light-emitting diodes of any size, that is, the transfer substrate can be used repeatedly, thereby saving costs.

Optionally, peeling the micro-LED array from the base substrate specifically includes:

The base substrate and the micro light emitting diodes are separated by a laser lift-off process.

Optionally, before aligning and bonding the micro-LED array on the transfer substrate to the target substrate, the method further includes:

forming a pattern of bonding electrodes on the target substrate;

After aligning and bonding the micro-LED array on the transfer substrate to the target substrate, the method further includes:

Welding the micro light emitting diode array and the bonding electrodes.

In a specific implementation, a gold (Au) thin film or a gold-tin alloy (AuSn) thin film may be deposited on the target substrate, and then a patterning process is performed to form a pattern of bonding electrodes.

Optionally, an annealing process is used for the hydrogenated amorphous layer, which specifically includes:

A rapid annealing process is adopted for the hydrogenated amorphous layer in a temperature environment greater than 500°C.

The current-voltage curve of the micro-LED annealed in a temperature environment of 500° C. is shown in FIG. 2 .

Next, take an example to illustrate the transfer method of the micro light emitting diode provided in the embodiment of the present application. As shown in FIG. 3, the transfer method of the micro light emitting diode includes the following steps:

S201, sequentially forming a buffer layer 2, n-GaN 3, MQW4, p-GaN5 and a second electrode 11 on the sapphire substrate 1;

Wherein, the second electrode 11 is used as an anode, and the second electrode may be, for example, a Ni/Au electrode;

S202. Deposit an inorganic amorphous material on the second electrode layer 11 by using a PECVD process to form a hydrogenated amorphous layer 6;

The thickness of the hydrogenated amorphous layer may be, for example, 300 nm;

S203, process the hydrogenated amorphous layer 6, the second electrode layer 11, p-GaN 5, MQW4, n-GaN 3 and the buffer layer 2 by a patterning process to form a micro-light emitting diode array, a pattern of the hydrogenated amorphous layer and a buffer layer pattern, and through the laser lift-off process, the micro light emitting diodes in the area outside the micro light emitting diode to be transferred are irradiated at fixed points, and the micro light emitting diodes in the area other than the micro light emitting diode to be transferred are removed;

S204, bonding the hydrogenated amorphous layer 6 on the sapphire substrate 1 to the transfer substrate 7 provided with the bonding layer 8;

S205, peeling off the sapphire substrate 1 through a laser lift-off process;

S206, using the transfer substrate to align and bond the buffer layer 2 to the target substrate 9 provided with the bonding electrode 10;

S207, using a high-temperature rapid annealing process, so that the hydrogenated amorphous layer 6 releases hydrogen and separates from the bonding layer 8, and makes the buffer layer 2 and the bonding electrode 10 welded;

S208 , using a dry etching process to expose part of the n-GaN 3 , and using a coating and patterning process to form an ohmic contact electrode 12 on the n-GaN 3 as a cathode.

A method for preparing a display panel provided in an embodiment of the present application, as shown in FIG. 4 , includes:

S301. Prepare an array substrate; the array substrate includes sub-pixel regions of multiple colors;

S302. Using the micro light emitting diode transfer method provided in the embodiment of the present application, sequentially transfer the micro light emitting diodes corresponding to the color of the sub pixel area to the sub pixel area of the array substrate.

Taking a display panel including red sub-pixels, blue sub-pixels, and green sub-pixels as an example, during specific implementation, the above-mentioned light-emitting diode transfer method provided by the embodiment of the present application is used to grow red micro-light emitting diodes, blue light micro-emitting diodes, green light emitting diodes, and transfer the red light emitting diodes, blue light emitting diodes and green light emitting diodes to the red sub-pixel area, the blue sub-pixel area and the green sub-pixel area respectively.

The embodiment of the present application provides a display panel, which is manufactured by using the display panel preparation method provided in the embodiment of the present application.

To sum up, in the transfer method of the micro light emitting diode, the preparation method of the display panel, and the display panel provided in the embodiment of the present application, the transfer substrate will not be affected by the substrate substrate during the first transfer process of the micro light emitting diode. The limitation of the size and spacing of the micro-light emitting diodes on the micro-light-emitting diode can improve the transfer efficiency of the micro-light-emitting diode. Since the transfer substrate can transfer micro-light-emitting diodes of any size, the transfer substrate can be used repeatedly, which can save costs. Moreover, in the transfer method of micro-light emitting diodes provided in the embodiment of the present application, a hydrogenated amorphous layer is also provided on the micro-light-emitting diodes. During the first transfer process of the micro-light-emitting diodes, the hydrogenated amorphous layer and the transfer substrate Bonding, after the micro-LED array is aligned and bonded to the target substrate, the hydrogenated amorphous layer can release hydrogen gas by using an annealing process, so that the hydrogenated amorphous layer is separated from the transfer substrate, so that the micro-LEDs can be separated from the transfer substrate. For stripping, the annealing process is adopted instead of the laser beam irradiation process, so as to avoid the damage of the laser beam to the micro-LED array, ensure the yield rate of the micro-light-emitting diode, and thereby improve the luminous efficiency of the micro-light-emitting diode.

Obviously, those skilled in the art can make various changes and modifications to the application without departing from the spirit and scope of the application. In this way, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these modifications and variations.

Claims (9)

1. A transfer method of micro-light-emitting diode, is characterized in that, described method comprises: Forming an array of micro-light emitting diodes on the base substrate and depositing an inorganic amorphous material on the micro-light-emitting diodes by using a plasma-enhanced chemical vapor deposition process to form a hydrogenated amorphous layer; bonding the hydrogenated amorphous layer to the transfer substrate, and peeling off the micro-LED array from the base substrate; Aligning and attaching the micro-LED array on the transfer substrate to the target substrate; Using an annealing process on the hydrogenated amorphous layer, so that the hydrogenated amorphous layer releases hydrogen gas, and peels off the transfer substrate; Before attaching the hydrogenated amorphous layer to the transfer substrate, the method further includes: A bonding layer is formed on the transfer substrate; the bonding layer is between the transfer substrate and the hydrogenated amorphous layer. 2. The method according to claim 1, characterized in that, forming an array of micro-light-emitting diodes on the base substrate and forming a hydrogenated amorphous layer on the micro-light-emitting diodes above the light-emitting diodes, specifically comprising: Forming each film layer of the micro light emitting diode on the base substrate; Depositing an inorganic amorphous material on the micro-light emitting diode by using a plasma-enhanced chemical vapor deposition process to form a hydrogenated amorphous layer; A patterning process is adopted for each film layer of the micro-light emitting diode and the hydrogenated amorphous layer to form patterns of the micro-light-emitting diode array and the hydrogenated amorphous layer. 3. The method according to claim 2, wherein the inorganic amorphous material is deposited by plasma-enhanced chemical vapor deposition in an environment of one of the following gases or a combination thereof: silane, ammonia, hydrogen; The inorganic amorphous material includes one or a combination of the following: silicon nitride, silicon oxide, silicon oxynitride. 4. The method according to claim 2, characterized in that, before each film layer of the micro-light emitting diode is formed on the base substrate, the method also includes: A buffer layer is formed on the base substrate. 5. The method according to claim 1, wherein the micro-LED array is peeled off from the base substrate, specifically comprising: The base substrate and the micro light emitting diodes are separated by a laser lift-off process. 6. The method according to claim 1, wherein, before aligning and bonding the micro-LED array on the transfer substrate with the target substrate, the method further comprises: forming a pattern of bonding electrodes on the target substrate; After aligning and bonding the micro-LED array on the transfer substrate to the target substrate, the method further includes: Welding the micro light emitting diode array and the bonding electrodes. 7. The method according to claim 1, wherein an annealing process is used for the hydrogenated amorphous layer, specifically comprising: A rapid annealing process is adopted for the hydrogenated amorphous layer in a temperature environment greater than 500°C. 8. A method for preparing a display panel, characterized in that the method comprises: Prepare an array substrate; the array substrate includes sub-pixel regions of multiple colors; Using the method for transferring micro-light emitting diodes according to any one of claims 1 to 7, the micro-light-emitting diodes corresponding to the colors of the sub-pixel regions are sequentially transferred to the sub-pixel regions of the array substrate. 9. A display panel, characterized in that the display panel is manufactured by the method according to claim 8.

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