Micro-led chip structure, light source module and preparation method thereof

Abstract

The application provides a micro LED chip, a light source module and a preparation method. The preparation method comprises the following steps: providing an original substrate, one side of the original substrate comprising a first epitaxial layer and an ohmic contact layer which are stacked; providing a non-light-transmitting substrate, one side of the non-light-transmitting substrate comprising an adhesive layer; bonding the non-light-transmitting substrate to the side of the ohmic contact layer through the adhesive layer; peeling off the original substrate to expose the first epitaxial layer; thinning the first epitaxial layer to form a second epitaxial layer; and obtaining the micro LED chip after preparing an LED light-emitting structure and an electrode structure on the second epitaxial layer. The wafer-level bonding preparation process is used to integrally transfer the micro LED epitaxial layer from the light-transmitting sapphire substrate to the non-light-transmitting substrate, and then the micro LED chip is prepared on the non-light-transmitting substrate. When the micro LED chip is used as a light source of a display module, the problem of light cross talk between pixels caused by light transmission of the light-transmitting substrate is solved, and the requirement of the light source equipment which needs accurate light path control is met.

Description

Technical Field

[0001] This invention relates to the field of light-emitting technology, and in particular to a micro-LED chip structure, light source module, and preparation method. Background Technology

[0002] MicroLEDs (miniature light-emitting diodes) are LED devices with chip sizes typically below 50 micrometers. With their superior performance, including high brightness, high contrast, low power consumption, and long lifespan, they have become an important development direction for next-generation display technology, widely used in virtual reality (VR) / augmented reality (AR) displays, backlight modules, outdoor large screens, photopolymer 3D printing, and automotive intelligent lighting. As display pixel density (PPI) continues to increase, higher demands are placed on the optoelectronic performance and structural design of microLED chips.

[0003] In existing microLED chip fabrication processes, a flip-chip microLED combined with a sapphire transparent substrate is typically employed. The sapphire transparent substrate possesses excellent light transmittance and epitaxial growth matching, which is beneficial for light extraction efficiency. However, the sapphire transparent substrate itself also has high photoconductivity. During microLED emission, light easily enters the interior of the sapphire transparent substrate, resulting in reflection and scattering. This leads to optical crosstalk between adjacent microLED chips within each pixel unit of a display device using microLED chips. This optical crosstalk causes beam divergence, reducing image contrast and sharpness, making it difficult to meet the exposure accuracy requirements of applications requiring precise optical path control, such as photopolymer 3D printing.

[0004] In view of this, the present invention proposes a microLED chip structure, a light source module and its fabrication method that can effectively suppress inter-pixel optical crosstalk while maintaining high luminous efficiency and high reliability. In particular, it can meet the application scenarios that require high beam collimation, high pixel independence and high energy utilization efficiency, and has the advantage of simple process. Summary of the Invention

[0005] This invention provides a method for fabricating a microLED chip, a microLED chip structure, and a light source module. Utilizing a wafer-to-wafer bonding process, the microLED epitaxial layer is transferred integrally from a transparent sapphire substrate to a non-transparent substrate. The microLED chip is then fabricated on the non-transparent substrate. When this microLED chip is subsequently used as a light source in a display module, it fundamentally solves the problem of inter-pixel crosstalk caused by light guiding on a transparent substrate, thereby meeting the requirements of applications requiring precise optical path control.

[0006] In one embodiment of the present invention, a method for fabricating a microLED chip is provided, the method comprising: A raw substrate is provided, one side of which includes a first epitaxial layer and an ohmic contact layer stacked together; A non-transparent substrate is provided, one side of which includes an adhesive layer; The non-transparent substrate is bonded to the ohmic contact layer via an adhesive layer; Peel off the original substrate to expose the first epitaxial layer; Thinning the first epitaxial layer to form the second epitaxial layer; and After fabricating the LED light-emitting structure and electrode structure on the second epitaxial layer, a microLED chip is obtained.

[0007] As an optional technical solution, thinning the first epitaxial layer to form the second epitaxial layer includes: forming the second epitaxial layer by ion etching the U-GaN buffer layer on the surface of the first epitaxial layer.

[0008] As an optional technical solution, the thickness of the second epitaxial layer is 1 / 2 of the thickness of the first epitaxial layer.

[0009] As an optional technical solution, fabricating the LED light-emitting structure and electrode structure on the second epitaxial layer includes: The patterned second epitaxial layer forms a stacked first conductive layer, light-emitting layer, and second conductive layer, which serve as the LED light-emitting structure. A first electrode is formed on the first conductive layer, and A second electrode is formed on the second conductive layer, and the first electrode and the second electrode form an electrode structure.

[0010] As optional technical solutions, the following also include: A current blocking layer is prepared, which covers the surface of the LED light-emitting structure away from the non-transparent substrate. A patterned current blocking layer forms a first opening and a second opening, such that a first region of the first conductive layer and a second region of the second conductive layer are exposed from the corresponding first opening and second opening, respectively; and A first electrode is prepared in a first opening, and a second electrode is prepared in a second opening.

[0011] As an optional technical solution, the current blocking layer is an insulating layer.

[0012] As an optional technical solution, the original substrate also includes an optical reflection layer, which is formed on the side of the ohmic contact layer away from the first epitaxial layer.

[0013] As an optional technical solution, the non-transparent substrate is a silicon substrate.

[0014] Another embodiment of the present invention also provides a microLED chip structure, which is prepared by the above-described preparation method.

[0015] As an optional technical solution, the microLED chip structure is a front-emitting structure.

[0016] As an optional technical solution, a lens structure is also included, which is disposed on one side of the light-emitting surface of the microLED chip structure.

[0017] In another embodiment of the present invention, a micro-LED light source module is provided, which includes multiple micro-LED chip structures as described above, wherein the multiple micro-LED chip structures are arranged in a strip shape.

[0018] In summary, this invention provides a method for fabricating a microLED chip, a microLED chip structure, and a light source module. By using wafer-level bonding technology to transfer the epitaxial layer onto a non-transparent substrate, and combining it with an optical reflective layer, the chip becomes a front-emitting structure. The non-transparent substrate effectively absorbs stray light, completely blocking the lateral propagation of light within the substrate, thereby significantly suppressing optical crosstalk between pixels. The front-emitting structure, combined with a high-reflectivity layer, guides more light outwards, reducing light energy loss. In practical applications, such as photopolymer 3D printing, higher exposure intensity and faster processing speeds can be achieved.

[0019] Furthermore, in the micro-LED chip fabrication method provided by this invention, the overall transfer of the epitaxial layer can avoid the precision and yield loss problems in the transfer of a single chip (mass transfer). While replacing it with an opaque substrate, it ensures the high yield and structural integrity of the epitaxial wafer. By thinning the epitaxial layer to 1-2μm, the lateral propagation distance of light in the medium is shortened, scattering and light mixing are reduced, which helps to improve the energy utilization efficiency of the LED light-emitting structure, making the light emission of a single chip closer to a "point light source", with stronger directionality and clearer light spot. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a flowchart of a method for fabricating a microLED chip according to an embodiment of the present invention.

[0022] Figure 2 This is a schematic cross-sectional view of the original substrate in one embodiment of the present invention.

[0023] Figure 3 This is a cross-sectional schematic diagram of a non-transparent substrate according to an embodiment of the present invention.

[0024] Figure 4 This is a schematic cross-sectional view of the original substrate and the non-transparent substrate after bonding in one embodiment of the present invention.

[0025] Figure 5 and Figure 6 This is a cross-sectional schematic diagram of the removal of the original substrate in one embodiment of the present invention.

[0026] Figure 7 This is a cross-sectional schematic diagram of the thinning of the first outer grinding layer in one embodiment of the present invention.

[0027] Figure 8 This is a cross-sectional view of the second epitaxial layer and a partially enlarged view in one embodiment of the present invention.

[0028] Figure 9 This is a cross-sectional schematic diagram of the patterned second epitaxial layer in one embodiment of the present invention.

[0029] Figure 10 This is a cross-sectional schematic diagram of a patterned current blocking layer formed on a patterned second epitaxial layer in one embodiment of the present invention.

[0030] Figure 11 This is a cross-sectional schematic diagram of the first and second electrodes on a patterned current blocking layer in one embodiment of the present invention.

[0031] Figure 12 A cross-sectional schematic diagram showing the placement of a lens on a microLED chip structure. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0034] It should be understood that when describing the structure of a component, when referring to a layer or region as being "above" or "on top of" another layer or region, it can mean that it is directly above the other layer or region, or that it contains other layers or regions between it and the other layer or region. Furthermore, if the component is flipped over, that layer or region will be located "below" or "under" the other layer or region.

[0035] This invention provides a method for fabricating a microLED chip, a microLED chip structure, and a light source module. Through wafer bonding, an epitaxial layer is transferred onto a non-transparent substrate, and the microLED chip structure is completed on one side of the non-transparent substrate. Because the fabricated microLED chip structure is formed on a non-transparent substrate, and the reflective layer on the non-transparent substrate side enables the microLED chip to become a front-emitting structure, when used in a display module, it can overcome the optical crosstalk problem caused by the use of transparent substrates in existing microLED chip structures, improving the energy utilization efficiency of the LED. In 3D printing product applications, the microLED chip of this application, as a light source module, can achieve better exposure intensity and faster processing speed.

[0036] like Figure 1 As shown, the present invention provides a method for fabricating a microLED chip, comprising: S1. Provide a raw substrate, one side of which includes a first epitaxial layer and an ohmic contact layer stacked together; S2. Provide a non-transparent substrate, one side of which includes an adhesive layer; S3. Bond the non-transparent substrate to the ohmic contact layer side via the adhesive layer; S4. Peel off the original substrate to expose the first epitaxial layer; S5. Thinning the first epitaxial layer to form the second epitaxial layer; and S6. After fabricating the LED light-emitting structure and electrode structure on the second epitaxial layer, a microLED chip is obtained.

[0037] The following will combine Figures 2 to 11 illustrate Figure 1 The fabrication process of AMEC LED chips.

[0038] like Figure 2As shown, the original substrate 10 includes a first epitaxial layer 20, an ohmic contact layer 30, and an optical reflective layer 40 sequentially formed on one side surface by methods such as metal-organic chemical vapor deposition (MOCVD). The original substrate 10 is, for example, a sapphire or gallium arsenide substrate; the first epitaxial layer 20 is, for example, a gallium nitride or gallium phosphide epitaxial thin film layer, serving as the light-emitting functional layer of the micro-LED. The ohmic contact layer 30 is used to reduce the contact resistance with subsequent electrodes. The optical reflective layer 40 is used to guide light to the front side of the micro-LED chip; it can be a stacked structure consisting of a high-reflectivity metal (such as aluminum or silver) layer and a high-reflectivity metal protective layer, or it can be a distributed Bragg reflector (DBR) structure.

[0039] like Figure 3 As shown, the opaque substrate 100 includes a bonding layer 200 formed on one side surface. The opaque substrate 100 serves as a new carrier substrate, blocking light transmission within the substrate. The opaque substrate 100 can be selected from high-resistivity silicon substrates, ceramic substrates (such as aluminum nitride AlN), or metal composite substrates. The bonding layer 200 on one side surface of the opaque substrate 100 is used to achieve a strong bond with the functional layers of the original substrate 10. The material of the bonding layer 200 can be selected according to subsequent bonding processes, for example: Au-In or Cu-Sn alloy layers for metal eutectic bonding, or SiO2 layers for oxide bonding.

[0040] like Figures 4 to 6 As shown, the optical reflective layer 40 of the original substrate 10 is bonded to the bonding layer 200 of the non-transparent substrate 100. A laser irradiates the original substrate 10, penetrating the original substrate 10 from the side where the first epitaxial layer 20 is not located, and acts on the contact interface between the first epitaxial layer 20 and the original substrate 10. This causes thermal decomposition of the material at the contact interface, thereby detaching the connection between the first epitaxial layer 20 and the original substrate 10, and thus separating the first epitaxial layer 20 and the original substrate 10. At this time, the bonding layer 200 combines the optical reflective layer 40, the ohmic contact layer 30, and the first epitaxial layer 20, thus transferring the first epitaxial layer 20 to the side of the non-transparent substrate 100.

[0041] In one embodiment, the process of bonding the optical reflective layer 40 and the non-transparent substrate 100 of the original substrate 10 through the bonding layer 200 is, for example, wafer bonding. The wafer bonding process can be selected according to the bonding layer material, such as hot pressing bonding, eutectic bonding or surface activation bonding, to ensure high bonding strength and few interface defects between the two layers.

[0042] In this embodiment, the original substrate 10 is, for example, a sapphire transparent substrate, and the method for separating the first epitaxial layer 20 and the original substrate 10 is laser separation, but it is not limited thereto. In other embodiments of the present invention, the original substrate 10 and the first epitaxial layer 20 can also be separated by an etching process.

[0043] like Figure 7 As shown, the first epitaxial layer 20 is thinned to form the second epitaxial layer 21. The thickness of the second epitaxial layer 21 is approximately half the thickness of the first epitaxial layer 20, roughly 1-2 μm. Thinning the first epitaxial layer 20 refers to removing the outermost U-GaN buffer layer of the first epitaxial layer 20 using an inductively coupled plasma (ICP) etching process. The U-GaN buffer layer is a non-functional layer in the first epitaxial layer 20, which serves to buffer stress, block defects, and provide a lattice basis.

[0044] In this embodiment, the thickness of the first epitaxial layer 20 is reduced to 1-2 μm (i.e., the thickness of the second epitaxial layer 21 is 1-2 μm), further reducing scattering and light mixing in the second epitaxial layer 21 when the microLED chip emits light. This makes the light emission of a single microLED chip closer to a "point light source," resulting in stronger directionality and a clearer light spot. Subsequently, when the microLED chip is combined with a lens or reflector, it is easier to adjust the emission angle to obtain the desired light pattern.

[0045] Continue to refer to Figure 8 In this invention, the second epitaxial layer 21 is a multilayer epitaxial structure, including: a first conductive layer 21a, a light-emitting layer 21b, and a second conductive layer 21c. Taking a gallium nitride epitaxial layer as an example, the first conductive layer 21a is an n-GaN semiconductor layer, the light-emitting layer 21b is a multiple quantum well (MQW), and the second conductive layer 21c is a p-GaN semiconductor layer.

[0046] like Figure 9 and Figure 10 As shown, it also includes patterning the second epitaxial layer 21 using photolithography and etching techniques, so that the first conductive layer 21a, the light-emitting layer 21b, and the second conductive layer 21c are isolated from each other; and forming a current blocking layer 300 on the patterned second epitaxial layer 21, and then patterning the current blocking layer 300 to form a first opening 310 and a second opening 320, wherein a portion of the first conductive layer 21a is exposed through the first opening 310, and a portion of the second conductive layer 21c is exposed through the second opening 320.

[0047] In this embodiment, the circuit barrier layer 300 is an insulating layer, such as SiO2 or SiN. X A thin film layer is used to protect the first conductive layer 21a, the light-emitting layer 21b, and the second conductive layer 21c and to define the current injection region.

[0048] like Figure 10 and Figure 11As shown, a first electrode 410 (n-type electrode) is fabricated in the first opening 310 and a second electrode 420 (p-type electrode) is fabricated in the second opening 320 using methods such as electron beam evaporation or sputtering. The electrode materials typically employ multilayer metal systems, such as Ti / Al / Ti / Au or Cr / Pt / Au, to ensure good ohmic contact and adhesion. Thus, a microLED chip structure is fabricated.

[0049] like Figure 11 As shown, the microLED chip structure of the present invention employs a non-transparent substrate 100, and an optical reflective layer 40 is provided between the non-transparent substrate 100 and the light-emitting layer 21b. The optical reflective layer 40 and the non-transparent substrate 100 enable the microLED chip to be a front-emitting structure. When this LED chip structure is used as a pixel unit in a display module, the light emitted from the self-emitting layer 21b is reflected upwards by the optical reflective layer 40 before being emitted. The non-transparent substrate 100 can absorb the stray light that is not reflected, effectively overcoming the optical crosstalk problem caused by adjacent microLED chip structures in a pixel unit sharing a transparent substrate.

[0050] In addition, the present invention also provides a micro-LED light source module, which includes multiple such... Figure 11 The micro-LED chip structure in the image is composed of multiple micro-LED chips arranged in a long strip, which is used as the light source module of 3D printing equipment.

[0051] like Figure 12 As shown, the microLED chip structure provided by the present invention also includes an optical microlens 500, which is disposed in the light-emitting direction of the microLED chip structure. It is a convex lens structure used to converge the light-emitting angle and collimate the light path.

[0052] In summary, this invention provides a microLED chip and its fabrication method that effectively suppresses optical crosstalk, improves beam collimation, and enhances energy utilization efficiency by transferring the epitaxial layer at the wafer level to a non-transparent substrate and combining epitaxial thinning with a front-side reflective structure. This method is simple, highly compatible with existing semiconductor processes, and offers a new technological path for realizing high-performance, high-reliability microLED display and lighting devices.

[0053] The present invention has been described by the above-described embodiments; however, these embodiments are merely examples for implementing the present invention. Furthermore, the technical features involved in the different embodiments of the present invention described above can be combined with each other as long as they do not conflict with each other. It must be pointed out that the disclosed embodiments do not limit the scope of the present invention. On the contrary, any modifications and refinements made without departing from the spirit and scope of the present invention are within the scope of patent protection of the present invention.

Claims

1. A method for fabricating a microLED chip, characterized in that, The preparation method includes: A raw substrate is provided, one side of which includes a first epitaxial layer and an ohmic contact layer stacked together; A non-transparent substrate is provided, wherein one side of the non-transparent substrate includes an adhesive layer; The opaque substrate is bonded to one side of the ohmic contact layer via the adhesive layer; The original substrate is peeled off to expose the first epitaxial layer; Thinning the first epitaxial layer to form a second epitaxial layer; and After fabricating the LED light-emitting structure and electrode structure on the second epitaxial layer, the microLED chip is obtained.

2. The preparation method according to claim 1, characterized in that, Thinning the first epitaxial layer to form the second epitaxial layer includes: The second epitaxial layer is formed by ion etching the U-GaN buffer layer on the surface of the first epitaxial layer.

3. The preparation method according to claim 2, characterized in that, The thickness of the second epitaxial layer is 1 / 2 of the thickness of the first epitaxial layer.

4. The preparation method according to claim 1, characterized in that, Fabricating an LED light-emitting structure and an electrode structure on the second epitaxial layer includes: The second epitaxial layer is patterned to form a stacked first conductive layer, a light-emitting layer, and a second conductive layer, wherein the first conductive layer, the light-emitting layer, and the second conductive layer constitute the LED light-emitting structure; A first electrode is formed on the first conductive layer, and A second electrode is formed on the second conductive layer, and the first electrode and the second electrode constitute the electrode structure.

5. The preparation method according to claim 4, characterized in that, Also includes: A current blocking layer is prepared, which covers the surface of the LED light-emitting structure away from the non-transparent substrate. The current blocking layer is patterned to form a first opening and a second opening, such that a first region of the first conductive layer and a second region of the second conductive layer are exposed from the corresponding first opening and second opening, respectively. as well as The first electrode is prepared in the first opening, and the second electrode is prepared in the second opening.

6. The preparation method according to claim 5, characterized in that, The current blocking layer is an insulating layer.

7. The preparation method according to claim 1, characterized in that, The original substrate further includes an optical reflection layer formed on the side of the ohmic contact layer away from the first epitaxial layer.

8. The preparation method according to claim 1, characterized in that, The non-transparent substrate is a silicon substrate.

9. A micro-LED chip structure, characterized in that, The microLED chip structure is prepared by the method described in any one of claims 1-8.

10. The microLED chip structure according to claim 9, characterized in that, The microLED chip has a front-emitting structure.

11. The microLED chip structure according to claim 10, characterized in that, It also includes a lens structure, which is disposed on one side of the light-emitting surface of the microLED chip structure.

12. A micro-LED light source module, characterized in that, The microLED light source module includes a plurality of microLED chip structures as described in any one of claims 9-11, wherein the plurality of microLED chip structures are arranged in a strip shape.

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