White light Micro-LED chip and preparation method thereof

Abstract

The invention relates to a white light M micro-LED chip and a preparation method thereof, and the preparation method comprises the steps: preparing a substrate, the substrate comprises a plurality of regions to be cut, each region to be cut is a blue light M micro-LED chip, each region to be cut comprises a pixel region, a transition region and an IO region, the pixel region comprises at least one pixel unit, the pixel unit comprises a light-emitting pixel, and the light-emitting pixel is arranged in the transition region; the IO area is used for electrically connecting the pixel unit with an external circuit; coating the whole surface of the substrate with a white light conversion layer; carrying out photoetching treatment on the white light conversion layer, so that the white light conversion layer after photoetching treatment only covers the pixel region of each to-be-cut region; and each area to be cut is cut off from the substrate to obtain a plurality of white light Mi cro-LED chips, and the white light Mi cro-LED chips are packaged. The invention further discloses a white light Micro-LED (Light Emitting Diode) chip. According to the invention, the production efficiency of the white light Mi cro-LED chip can be improved, and the production cost can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a white light Micro-LED chip and a preparation method thereof. Background Art

[0002] With the rapid development of the electric smart car industry, the requirements for on-board ADB (adaptive high beam) are getting higher and higher, requiring on-board ADB to have a headlight chip with higher resolution, more precise control, and higher intelligence, while white light Micro-LED (micro light emitting diode) chips can be well adapted to the above requirements, which also makes white light Micro-LED chips widely used in the automotive field. When manufacturing existing white light Micro-LED chips, after manufacturing the blue light Micro-LED substrate, they are first cut to obtain multiple single blue light chips, and then each blue light chip is packaged. After the packaging is completed, the single blue light chip is coated with white light conversion material to achieve white light conversion, thereby obtaining a white light chip. This preparation method is only applicable to a single Micro-LED chip after packaging. The process is relatively complex, the production efficiency is low, and the manufacturing cost is also high, which cannot meet the needs of efficient production. Summary of the invention

[0003] To this end, the technical problem to be solved by the present invention is to improve the production efficiency of white light Micro-LED chips and reduce production costs.

[0004] In order to solve the above technical problems, the present invention provides a method for preparing a white light Micro-LED chip, comprising the following steps:

[0005] Step 1), preparing a substrate, the substrate comprising a plurality of areas to be cut, each of the areas to be cut is a blue light Micro-LED chip, each of the areas to be cut comprises a pixel area and an IO area, a transition area is provided between the pixel area and the IO area, the pixel area comprises at least one pixel unit, the pixel unit comprises a light-emitting pixel for emitting blue light, and the IO area is used to electrically connect the pixel unit to an external circuit;

[0006] Step 2), coating the entire surface of the substrate with a white light conversion layer;

[0007] Step 3), performing photolithography on the white light conversion layer, so that the white light conversion layer after the photolithography only covers the pixel area of ​​each of the areas to be cut;

[0008] Step 4), cutting each of the to-be-cut areas from the substrate to obtain a plurality of white light Micro-LED chips, and packaging each of the white light Micro-LED chips.

[0009] In one embodiment of the present invention, the white light conversion layer is a photoresist mixed with yellow phosphor.

[0010] In one embodiment of the present invention, the mixing mass ratio of the yellow phosphor and the photoresist in the white light conversion layer is 10% to 80%.

[0011] In one embodiment of the present invention, the mixing mass ratio of the yellow phosphor and the photoresist in the white light conversion layer is 30% to 50%.

[0012] In one embodiment of the present invention, the method of performing photolithography on the white light conversion layer in step 3) so that the white light conversion layer after the photolithography only covers the pixel areas of each of the areas to be cut includes: exposing the white light conversion layer and performing development treatment so that the treated white light conversion layer only covers the pixel areas of each of the areas to be cut.

[0013] In one embodiment of the present invention, the distance between the top surface of the white light conversion layer and the top surface of the pixel unit after the photolithography process in step 3) is a first thickness, and the first thickness is 5 μm to 200 μm.

[0014] In one embodiment of the present invention, after step 3) the white light conversion layer after photolithography processing only covers the pixel area of ​​each of the areas to be cut, in each area to be cut, the distance between the outer edge of the white light conversion layer and the outer edge of the pixel unit on the same side of the outermost side of the pixel area is equal to the first thickness, and the first thickness is the distance between the top surface of the white light conversion layer after photolithography processing and the top surface of the pixel unit.

[0015] In one embodiment of the present invention, the method for preparing the substrate in step 1) comprises the following steps,

[0016] Step S11), bonding the epitaxial layer for emitting blue light to the driving wafer through a bonding layer, the driving wafer being provided with an anode contact, the epitaxial layer being a compound semiconductor material, and having a substrate at one end of the epitaxial layer away from the driving wafer;

[0017] Step S12), after removing the substrate, etching the epitaxial layer and the bonding layer to obtain a plurality of independent pixel units, wherein the epitaxial layer in each pixel unit forms a light-emitting pixel for emitting blue light, and the light-emitting pixels in each pixel unit are connected to the anode through the bonding layer and the corresponding anode contact on the driving wafer;

[0018] Step S13), preparing an insulating passivation layer so that the outside of each pixel unit is covered with the passivation layer, and setting an opening in the passivation layer above each pixel unit;

[0019] Step S14), preparing a transparent conductive layer outside the passivation layer, so that the light-emitting pixel of each pixel unit is connected to the cathode through the opening of the passivation layer and the transparent conductive layer;

[0020] Step S15), preparing a cathode connector on the transparent conductive layer, wherein the cathode connector is partially located in the transition region, and preparing a P electrode and an N electrode in the IO region, wherein the N electrode in the IO region is used to be electrically connected to the transparent conductive layer through the cathode connector, and the P electrode in the IO region is used to be electrically connected to the anode contact of the driving wafer, thereby realizing the preparation of the substrate;

[0021] Among them, the substrate includes multiple areas to be cut, each of the areas to be cut forms a blue light Micro-LED chip, each of the areas to be cut includes a pixel area and an IO area, and a transition area is also set between the pixel area and the IO area. The pixel area includes at least one pixel unit, and the IO area is used to electrically connect the pixel unit to an external circuit.

[0022] In one embodiment of the present invention, after preparing the P electrode and the N electrode in the IO region in step S15), a microlens is also prepared so that the pixel units and the microlenses correspond one to one and each of the microlenses is located above the corresponding pixel unit.

[0023] In one embodiment of the present invention, after the microlens is prepared, each of the pixel units is located in the projection of the corresponding microlens on the driving wafer.

[0024] In one embodiment of the present invention, after a plurality of independent pixel units are obtained in step S12), each pixel unit corresponds to the anode contact one by one, and each anode contact is located in the projection of the corresponding pixel unit on the driving wafer.

[0025] The present invention also discloses a white light Micro-LED chip, comprising:

[0026] A blue light Micro-LED chip, wherein the blue light Micro-LED chip comprises a pixel area and an IO area, a transition area is provided between the pixel area and the IO area, the pixel area comprises at least one pixel unit, the pixel unit comprises a light-emitting pixel for emitting blue light, and the IO area is used to electrically connect the pixel unit to an external circuit;

[0027] A white light conversion layer, wherein the white light conversion layer only covers the pixel area of ​​the blue light Micro-LED chip;

[0028] Wherein, the white light conversion layer is used to convert the blue light emitted by the light-emitting pixel into white light.

[0029] In one embodiment of the present invention, the distance between the top surface of the white light conversion layer and the top surface of the pixel unit is a first thickness, and the first thickness is 5 μm to 200 μm.

[0030] In one embodiment of the present invention, the distance between the outer edge of the white light conversion layer and the outer edge of the outermost pixel unit on the same side of the pixel area is equal to the first thickness, and the first thickness is the distance between the top surface of the white light conversion layer and the top surface of the pixel unit.

[0031] In one embodiment of the present invention, each of the pixel units comprises a bonding layer and a light-emitting pixel which are sequentially arranged in a direction away from the driving wafer.

[0032] In one embodiment of the present invention, the outside of the pixel unit is sequentially coated with a passivation layer and a transparent conductive layer, an opening is set at the passivation layer, and the light-emitting pixels of the pixel unit are cathode-connected through the opening at the passivation layer and the transparent conductive layer, and an anode contact is set on the driving wafer, and the light-emitting pixels of the pixel unit are anode-connected through the bonding layer and the corresponding anode contact.

[0033] In one embodiment of the present invention, a cathode connector is connected to the transparent conductive layer, and a portion of the cathode connector is located in the transition zone. The IO zone is provided with a P electrode and an N electrode, and the N electrode of the IO zone is used to be electrically connected to the cathode connector through the transparent conductive layer, and the P electrode of the IO zone is used to be electrically connected to the anode contact of the driving wafer.

[0034] In one embodiment of the present invention, each pixel unit corresponds to the anode contact one by one, and each anode contact is located in the projection of the corresponding pixel unit on the driving wafer.

[0035] In one embodiment of the present invention, the blue light Micro-LED chip further includes a microlens, the microlens corresponds to the pixel unit one by one, the microlens is located above the corresponding pixel unit, and the white light conversion layer covers all the microlenses.

[0036] In one embodiment of the present invention, each of the pixel units is located in a projection of a corresponding microlens on the driving wafer.

[0037] The above technical solution of the present invention has the following advantages compared with the prior art:

[0038] The white light Micro-LED chip and the preparation method thereof described in the present invention improve the process integration, simplify the preparation process, greatly improve the production efficiency of the white light Micro-LED chip, and greatly reduce the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0040] Figure 1 is a preparation flow chart of the white light Micro-LED chip of the present invention;

[0041] Figure 2 Schematic diagram of the substrate area division of the present invention (top view);

[0042] Figure 3 yes Figure 2 A schematic diagram of each area to be cut;

[0043] Figure 4 In one embodiment, Figure 3 The cross-sectional view at a1-a2;

[0044] Figure 5 Another embodiment is along Figure 3 The cross-sectional view at a1-a2;

[0045] Figure 6 yes Figure 4 Schematic diagram of the preparation process of the substrate structure in the structure shown;

[0046] Figure 7 yes Figure 6 A schematic diagram of the process of processing the white light conversion layer after preparing the substrate of the structure shown;

[0047] Figure 8 is a schematic diagram of a substrate structure with a microlens;

[0048] Fig. 9 yes Figure 8 A schematic diagram of the process of processing the white light conversion layer after preparing the substrate of the structure shown;

[0049] Fig.10 is a graph showing the variation of color temperature with the first thickness;

[0050] Description of the Figures in the Specification:

[0051] 10. driving wafer; 101. anode contact;

[0052] 20. pixel unit; 201. light-emitting pixel; 202. bonding layer;

[0053] 30. passivation layer; 40. transparent conductive layer; 50. cathode connector; 60. N electrode; 70. P electrode; 80. microlens;

[0054] 90. White light conversion layer;

[0055] 100, epitaxial layer; 1001, substrate; 110, mask; 120, UV light. DETAILED DESCRIPTION

[0056] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present disclosure and its application or use.

[0057] In the description of the present invention, it should be understood that the terms "vertical", "upper", "lower", "top", "side", "inner", "outer", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0058] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] Example

[0060] See also Figure 1 This embodiment discloses a method for preparing a white light Micro-LED chip, comprising the following steps:

[0061] Step 1), preparing a substrate, the substrate comprising a plurality of areas X to be cut, each of which is a blue light Micro-LED chip, each of which comprises a pixel area A, a transition area B and an IO area C, a transition area B is provided between the pixel area A and the IO area C, the pixel area A comprises at least one pixel unit 20, the pixel unit 20 comprises a light-emitting pixel 201 for emitting blue light, and the IO area C is used to electrically connect the pixel unit 20 to an external circuit;

[0062] Step 2), coating the entire surface of the substrate with a white light conversion layer 90, the white light conversion layer 90 is used to convert the blue light emitted by the blue light Micro-LED chip into white light;

[0063] During coating, a spin coating method may be used so that the white light conversion layer 90 can be more evenly coated on the entire surface of the substrate;

[0064] Step 3), see Figure 2-Figure 3 , the white light conversion layer 90 is subjected to photolithography processing, so that the white light conversion layer 90 after the photolithography processing only covers the pixel area A of each area to be cut, that is, only the pixel area A is covered by the white light conversion layer 90, and the white light conversion layer 90 in the transition area B and the IO area C is removed; wherein, Figure 2 The middle substrate has been divided into a plurality of to-be-cut regions X in advance, and each to-be-cut region X is divided into a pixel region A, a transition region B and an IO region C;

[0065] Step 4), each to-be-cut region X is cut from the substrate to obtain a plurality of independent white light Micro-LED chips (see Figure 3 ), and each white light Micro-LED chip is packaged. That is, each cut-off area X becomes a white light Micro-LED chip, thereby obtaining multiple separate white light Micro-LED chips. The internal structure of the white light Micro-LED chip can be found in Figure 4 or Figure 5 .

[0066] It can be understood that the above-mentioned pixel area in each area to be cut is the area where all the pixel units 20 in the area to be cut are located, including at least one pixel unit 20. The IO area is the area where the input and output ports are located, and various electrodes are arranged thereon, which are used to electrically connect the pixel unit 20 to the external circuit through the input and output ports of the IO area to obtain power supply, display signals, etc.; and the lines leading out of the pixel unit 20 are connected to the input and output ports of the IO area via the transition area. The transition area can separate the pixel area and the IO area by a distance to avoid the pixel area and the IO area being too close to be convenient for packaging.

[0067] The above-mentioned preparation method can realize the whole-surface coating of the white light conversion layer 90 before cutting and packaging, and after one photolithography process, the white light conversion layer 90 only covers the pixel area without blocking the IO area, so that the subsequent cutting and packaging can be carried out smoothly. It has realized white light conversion before cutting the wafer, and after cutting, a plurality of white light Micro-LED chips that can emit white light can be directly obtained. Compared with the prior art that needs to first cut into a plurality of separate blue light chips and package them, and then spray white light conversion materials on each packaged blue light chip one by one to obtain a white light chip, the preparation method of this embodiment improves the process integration, the preparation method is simpler, greatly improves the production efficiency of the white light chip, and greatly reduces the production cost.

[0068] In some embodiments, the white light conversion layer 90 is a photoresist mixed with yellow phosphor to convert the blue light emitted by the pixel unit 20 into white light through the yellow phosphor. That is, the blue light emitted by the pixel unit 20 will form white light after being emitted through the white light conversion layer 90 where the yellow phosphor is located.

[0069] In some embodiments, the method of performing photolithography on the white light conversion layer 90 in step 3) so that the white light conversion layer 90 after the photolithography only covers the pixel area A of each area to be cut X includes: exposing the white light conversion layer 90 and performing development treatment so that the processed white light conversion layer 90 only covers the pixel area A of each area to be cut X.

[0070] The photoresist in the white light conversion layer 90 may be a negative photoresist, for example, Figure 7 or Fig. 9 SU-8 photoresist can be used. Before exposure, a mask 110 is set above the white light conversion layer 90 so that only the pixel area is light-transmissive, while the transition area and the IO area are not light-transmissive. Then, UV light 120 (ultraviolet light) is used for exposure. After exposure, a development process is performed to remove the white light conversion layer 90 covered by the transition area and the IO area, and only the white light conversion layer 90 in the pixel area is retained.

[0071] In some other embodiments, the photoresist in the white light conversion layer 90 may also be a positive photoresist.

[0072] In some embodiments, the mixing mass ratio of the yellow phosphor and the photoresist in the white light conversion layer 90 is 10% to 80%.

[0073] Preferably, the mixing mass ratio of the yellow phosphor and the photoresist in the white light conversion layer 90 is 30% to 50%.

[0074] In some implementations: the distance between the top surface of the white light conversion layer 90 after the photolithography process in step 3) and the top surface of the pixel unit 20 is referred to as the first thickness h, and the first thickness h is 5 μm to 200 μm.

[0075] The mixing ratio of the yellow phosphor and the photoresist in the white light conversion layer 90 and the first thickness h jointly determine the color temperature of the white light Micro-LED chip:

[0076] When the first thickness h remains unchanged, the higher the mixing mass ratio of the yellow phosphor to the photoresist in the white light conversion layer 90 is, the lower the color temperature of the obtained white light Micro-LED chip is.

[0077] When the mixing mass ratio of the yellow phosphor to the photoresist in the white light conversion layer 90 remains unchanged, the greater the first thickness h is, the lower the color temperature of the obtained white light Micro-LED chip is.

[0078] When the mixing mass ratio of the yellow phosphor to the photoresist in the white light conversion layer 90 remains unchanged, the corresponding relationship between the color temperature of the white light Micro-LED chip and the first thickness h is shown in Fig.10 .

[0079] When the first thickness h is 40 μm to 70 μm, the color temperature is relatively stable with a small fluctuation range, and can be maintained at 5000 K to 6000 K.

[0080] When the first thickness h is 30 μm to 40 μm, the color temperature changes in the range of 6000 K to 8000 K, and decreases rapidly as the first thickness h increases.

[0081] Furthermore, in order to make the overall color temperature of the white light Micro-LED chip more uniform, after the white light conversion layer 90 after photolithography processing in step 3) covers only the pixel area A of each area to be cut X, in each area to be cut X, the distance between the outer edge of the white light conversion layer 90 and the outer edge of the pixel unit 20 on the same side of the outermost side of the pixel area is equal to the first thickness h, wherein the first thickness h is the distance between the top surface of the white light conversion layer 90 after photolithography processing and the top surface of the pixel unit 20.

[0082] For example, participation Figure 3-Figure 4 The white light conversion layer 90 after photolithography is rectangular, and has four outer edges, namely, front, back, left and right. The distance between the front outer edge and the outer edge of the outermost pixel unit 20 on the front side of the pixel area is d4, the distance between the rear outer edge and the outer edge of the outermost pixel unit 20 on the rear side of the pixel area is d3, the distance between the right outer edge and the outer edge of the outermost pixel unit 20 on the right side of the pixel area is d2, and the distance between the left outer edge and the outer edge of the outermost pixel unit 20 on the left side of the pixel area is d1, then d1=d2=d3=d4=h.

[0083] In some embodiments, see Figure 6 , the method for preparing the substrate in step 1) comprises the following steps:

[0084] Step S11), bonding the epitaxial layer 100 for emitting blue light to the driving wafer 10 through the bonding layer 202, the driving wafer 10 is provided with an anode contact 101, the epitaxial layer 100 is a compound semiconductor material, and one end of the epitaxial layer 100 away from the driving wafer 10 has a substrate 1001;

[0085] The epitaxial layer 100 includes a P-type semiconductor layer, an active layer, an N-type semiconductor layer and a substrate 1001 which are sequentially arranged in a direction away from the driving wafer 10;

[0086] The driving wafer 10 may be a CMOS driving wafer.

[0087] Step S12), after removing the substrate 1001, the epitaxial layer 100 and the bonding layer 202 are etched to obtain a plurality of independent pixel units 20, wherein the epitaxial layer 100 in each pixel unit 20 forms a light-emitting pixel 201 for emitting blue light, and the light-emitting pixel 201 in each pixel unit 20 is anode-connected via the bonding layer 202 and the corresponding anode contact 101 on the driving wafer 10;

[0088] It can be understood that the light-emitting pixel 201 in each independent pixel unit 20 includes a P-type semiconductor layer, an active layer, and an N-type semiconductor layer sequentially arranged in a direction away from the driving wafer 10, wherein the active layer is used to emit blue light, and the P-type semiconductor layer is connected to the anode through the bonding layer 202 and the corresponding anode contact 101 on the driving wafer 10;

[0089] Preferably, after obtaining multiple independent pixel units 20 in step S12), each pixel unit 20 corresponds to the anode contact 101 one by one, and each anode contact 101 is located in the projection of the corresponding pixel unit 20 on the driving wafer 10, so as to better avoid the anode contact 101 being exposed and contacting the transparent conductive layer 40 (cathode), thereby causing leakage and short circuit.

[0090] Step S13), preparing an insulating passivation layer 30, so that the outside of each pixel unit 20 is covered with the passivation layer 30, so that the P-type semiconductor layer and the N-type semiconductor layer in the pixel unit 20 are insulated and isolated, and an opening is set in the passivation layer 30 above each pixel unit 20;

[0091] Step S14), preparing a transparent conductive layer 40 outside the passivation layer 30, so that the light-emitting pixel 201 of each pixel unit 20 is in contact with the transparent conductive layer 40 through the opening at the passivation layer 30 to achieve cathode connection; that is, the N-type semiconductor layer in the light-emitting pixel 201 is electrically connected to the transparent conductive layer 40 through the opening at the passivation layer 30;

[0092] Step S15), preparing a cathode connector 50 on the transparent conductive layer 40, wherein the cathode connector 50 is partially located in the transition region and extends to the IO region, and preparing a P electrode 70 (anode) and an N electrode 60 (cathode) in the IO region, wherein the N electrode 60 in the IO region is used to be electrically connected to the transparent conductive layer 40 through the cathode connector 50, and the P electrode 70 in the IO region is used to be electrically connected to the anode contact 101 of the driving wafer 10, thereby realizing the preparation of the substrate;

[0093] Among them, Figure 2 As shown, the substrate includes a plurality of to-be-cut regions X, each of which is a blue light Micro-LED chip. Figure 3 As shown, each area to be cut X includes a pixel area A and an IO area C, a transition area B is further provided between the pixel area A and the IO area C, the pixel area A includes at least one pixel unit 20, and the IO area C is used to electrically connect the pixel unit 20 to an external circuit.

[0094] It can be understood that all pixel units 20 in each area X to be cut are located in the pixel area A of the area X to be cut, and the transition area B is used to separate the pixel area A and the IO area C by a certain distance to avoid the two being too close to affect subsequent packaging.

[0095] like Figure 2 As shown, the above-mentioned area X to be cut, as well as the pixel area A, transition area B and IO area C inside the area to be cut can be marked in advance on the driver wafer 10. For example, the driver wafer 10 can be marked before the epitaxial layer 100 and the driver wafer 10 are bonded.

[0096] When the P electrode 70 and the N electrode 60 are prepared in the IO region, multiple groups can be prepared as needed, each group including a P electrode 70 and an N electrode 60. It can be understood that the P and N electrodes 60 in each group are independent of each other and do not form contact.

[0097] In some embodiments, the cathode connector 50 is disposed around each pixel unit 20. For example, a cathode metal layer is plated on the entire upper surface of the transparent conductive layer 40, and excess cathode metal is removed by a photoresist stripping method to expose the transparent conductive layer 40 on the upper portion of the pixel unit 20, and only the cathode metal around the pixel unit 20 is retained as the cathode connector 50.

[0098] like Figure 6 As shown, in some embodiments, when preparing the substrate, the microlens 80 may not be prepared. After the substrate of this form is prepared, the subsequent coating and processing of the white light conversion layer 90 is referred to in Figure 7 ;

[0099] like Figure 8As shown, in other methods, when preparing the substrate, after preparing the P electrode and the N electrode in the IO area in step S15), a microlens 80 is also prepared so that the pixel units 20 and the microlenses 80 correspond one to one, and each microlens 80 is located on the upper part of the corresponding pixel unit 20.

[0100] Furthermore, after the microlens 80 is prepared, each pixel unit 20 is located in the projection of the corresponding microlens 80 on the driving wafer 10 to better converge the light-emitting angle and improve the light-emitting brightness.

[0101] like Figure 8 After the substrate with the microlens 80 is prepared, the subsequent process of coating and processing the white light conversion layer 90 is shown in FIG. Fig. 9 .

[0102] like Figure 4 As shown, this embodiment discloses a white light Micro-LED chip prepared by the above preparation method, including a blue light Micro-LED chip and a white light conversion layer 90;

[0103] The blue light Micro-LED chip includes a pixel area and an IO area, and a transition area is set between the pixel area and the IO area. Figure 4 The A, B, and C regions represent the pixel region, transition region, and IO region, respectively. The pixel region includes at least one pixel unit 20, and the pixel unit 20 includes a light-emitting pixel 201 for emitting blue light. The IO region is used to electrically connect the pixel unit 20 to an external circuit. It can be understood that all pixel units 20 in the blue light Micro-LED chip are located in the pixel region.

[0104] The white light conversion layer 90 only covers the pixel area of ​​the blue light Micro-LED chip, but not the transition area and IO area;

[0105] The white light conversion layer 90 is used to convert the blue light emitted by the light-emitting pixel 201 into white light.

[0106] Furthermore, the white light conversion layer 90 is a photoresist mixed with yellow phosphor.

[0107] In some embodiments, the pixel unit 20 may be circular, square, polygonal, etc.

[0108] In some embodiments, the width D of the pixel unit 20 is 2 μm to 200 μm.

[0109] In some embodiments, in a white light Micro-LED chip, a distance between a top surface of the white light conversion layer 90 and a top surface of the pixel unit 20 is a first thickness h, and the first thickness h is 5 μm to 200 μm.

[0110] Furthermore, in the white light Micro-LED chip, the distance between the outer edge of the white light conversion layer 90 and the outer edge of the pixel unit 20 on the same side of the outermost side of the pixel area is equal to the first thickness h, and the first thickness h is the distance between the top surface of the white light conversion layer 90 and the top surface of the pixel unit 20. This setting can make the overall color temperature of the white light Micro-LED chip more uniform.

[0111] In some embodiments, each pixel unit 20 includes a bonding layer 202 and a light-emitting pixel 201 which are sequentially arranged in a direction away from the driving wafer 10 , the bonding layer 202 is a metal layer, and the light-emitting pixel 201 is used to emit blue light.

[0112] Among them, the light-emitting pixel 201 in each pixel unit 20 includes a P-type semiconductor layer, an active layer and an N-type semiconductor layer arranged in sequence along the direction away from the driving wafer 10, wherein the active layer is used to emit blue light, and the P-type semiconductor layer is connected to the anode through the bonding layer 202 and the corresponding anode contact 101 on the driving wafer 10.

[0113] Furthermore, in the white light Micro-LED chip, the outside of the pixel unit 20 is sequentially coated with a passivation layer 30 and a transparent conductive layer 40, the passivation layer 30 is an insulating layer, an opening is provided above the passivation layer 30, and the light-emitting pixels 201 of the pixel unit 20 are all in contact with the transparent conductive layer 40 through the opening at the passivation layer 30 to achieve cathode connection, and an anode contact 101 is provided on the driving wafer 10;

[0114] The P-type semiconductor layer of the light-emitting pixel 201 of the pixel unit 20 is connected to the corresponding anode contact 101 through the bonding layer 202, and the N-type semiconductor layer in the light-emitting pixel 201 is connected to the cathode by contacting the transparent conductive layer 40 through the opening at the passivation layer 30.

[0115] In the above-mentioned white light Micro-LED chip, each pixel unit 20 can be driven individually by the driving wafer 10 to emit light.

[0116] In some embodiments, in a white light Micro-LED chip, a cathode connector 50 is connected to the transparent conductive layer 40, and a portion of the cathode connector 50 is located in the transition zone. A P electrode 70 and an N electrode 60 are provided in the IO zone. The N electrode 60 in the IO zone is used to be electrically connected to the transparent conductive layer 40 through the cathode connector 50 (cathode connection), and the P electrode 70 in the IO zone is used to be electrically connected to the anode contact 101 of the driving wafer 10 (anode).

[0117] One end of the cathode connector 50 is electrically connected to the transparent conductive layer 40 , and the other end extends through the transition region to the IO region and is electrically connected to the N electrode 60 in the IO region.

[0118] Furthermore, in the white light Micro-LED chip, each pixel unit 20 corresponds to the anode contact 101 one by one, and each anode contact 101 is located in the projection of the corresponding pixel unit 20 on the driving wafer 10, so as to better avoid the anode contact 101 being exposed and contacting the transparent conductive layer 40 (cathode), thereby causing leakage and short circuit.

[0119] exist Figure 4 In the white light Micro-LED chip shown, no microlens 80 is provided.

[0120] In another white light Micro-LED chip, such as Figure 5 As shown, the blue light Micro-LED chip also includes a microlens 80 , and the microlens 80 corresponds to the pixel unit 20 one by one. The microlens 80 is located above the corresponding pixel unit 20 , and the white light conversion layer 90 covers all the microlenses 80 .

[0121] It can be understood that the top surface of the white light conversion layer 90 is higher than the apex of the microlens 80 .

[0122] Furthermore, in order to better converge the light-emitting angle and improve the light-emitting brightness, in the white light Micro-LED chip, each pixel unit 20 is located in the projection of the corresponding microlens 80 on the driving wafer 10.

[0123] The white light Micro-LED chip prepared by the preparation method of the above embodiment has a better light-emitting effect and is more conducive to efficient mass production.

[0124] All of the above optional technical solutions can be combined in any way to form optional embodiments of the present invention, that is, any multiple embodiments can be combined to meet the needs of different application scenarios. They are all within the protection scope of this application and will not be described one by one here.

[0125] It should be noted that the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing a white light Micro-LED chip, characterized in that: The following steps are included: Step 1), preparing a substrate, the substrate comprising a plurality of areas to be cut, each of the areas to be cut is a blue light Micro-LED chip, each of the areas to be cut comprises a pixel area and an IO area, a transition area is provided between the pixel area and the IO area, the pixel area comprises at least one pixel unit, the pixel unit comprises a light-emitting pixel for emitting blue light, and the IO area is used to electrically connect the pixel unit to an external circuit; Step 2), coating the entire surface of the substrate with a white light conversion layer; Step 3), performing photolithography on the white light conversion layer, so that the white light conversion layer after the photolithography only covers the pixel area of ​​each of the areas to be cut; Step 4), cutting each of the to-be-cut areas from the substrate to obtain a plurality of white light Micro-LED chips, and packaging each of the white light Micro-LED chips.

2. The preparation method according to claim 1, characterized in that: The white light conversion layer is a photoresist mixed with yellow fluorescent powder.

3. The preparation method according to claim 2, characterized in that: The mixing mass ratio of the yellow fluorescent powder and the photoresist in the white light conversion layer is 10% to 80%.

4. The preparation method according to claim 3, characterized in that: The mixing mass ratio of the yellow fluorescent powder and the photoresist in the white light conversion layer is 30% to 50%.

5. The preparation method according to claim 2, characterized in that: The method of performing photolithography on the white light conversion layer in step 3) so that the white light conversion layer after photolithography only covers the pixel areas of each of the areas to be cut includes: exposing and developing the white light conversion layer so that the processed white light conversion layer only covers the pixel areas of each of the areas to be cut.

6. The preparation method according to claim 1, characterized in that: The distance between the top surface of the white light conversion layer after the photolithography process in step 3) and the top surface of the pixel unit is a first thickness, and the first thickness is 5 μm to 200 μm.

7. The preparation method according to claim 1, characterized in that: After step 3) that the white light conversion layer after photolithography processing only covers the pixel area of ​​each of the areas to be cut, in each area to be cut, the distance between the outer edge of the white light conversion layer and the outer edge of the pixel unit on the same side of the outermost side of the pixel area is equal to the first thickness, and the first thickness is the distance between the top surface of the white light conversion layer after photolithography processing and the top surface of the pixel unit.

8. The preparation method according to claim 1, characterized in that: The method for preparing the substrate in step 1) comprises the following steps, Step S11), bonding the epitaxial layer for emitting blue light to the driving wafer through a bonding layer, the driving wafer being provided with an anode contact, the epitaxial layer being a compound semiconductor material, and having a substrate at one end of the epitaxial layer away from the driving wafer; Step S12), after removing the substrate, etching the epitaxial layer and the bonding layer to obtain a plurality of independent pixel units, wherein the epitaxial layer in each pixel unit forms a light-emitting pixel for emitting blue light, and the light-emitting pixels in each pixel unit are connected to the anode through the bonding layer and the corresponding anode contact on the driving wafer; Step S13), preparing an insulating passivation layer so that the outside of each pixel unit is covered with the passivation layer, and setting an opening in the passivation layer above each pixel unit; Step S14), preparing a transparent conductive layer outside the passivation layer, so that the light-emitting pixel of each pixel unit is connected to the cathode through the opening of the passivation layer and the transparent conductive layer; Step S15), preparing a cathode connector on the transparent conductive layer, wherein the cathode connector is partially located in the transition region, and preparing a P electrode and an N electrode in the IO region, wherein the N electrode in the IO region is used to be electrically connected to the transparent conductive layer through the cathode connector, and the P electrode in the IO region is used to be electrically connected to the anode contact of the driving wafer, thereby realizing the preparation of the substrate; Among them, the substrate includes multiple areas to be cut, each of the areas to be cut forms a blue light Micro-LED chip, each of the areas to be cut includes a pixel area and an IO area, and a transition area is also set between the pixel area and the IO area. The pixel area includes at least one pixel unit, and the IO area is used to electrically connect the pixel unit to an external circuit.

9. The preparation method according to claim 8, characterized in that: In step S15), after the P electrode and the N electrode are prepared in the IO region, a microlens is also prepared so that the pixel units and the microlenses correspond one to one and each of the microlenses is located on the upper part of the corresponding pixel unit.

10. The preparation method according to claim 9, characterized in that: After the microlens is prepared, each of the pixel units is located in the projection of the corresponding microlens on the driving wafer.

11. The preparation method according to claim 9, characterized in that: After a plurality of independent pixel units are obtained in step S12), each pixel unit corresponds to the anode contact one by one, and each anode contact is located in the projection of the corresponding pixel unit on the driving wafer.

12. A white light Micro-LED chip, characterized in that: include, A blue light Micro-LED chip, wherein the blue light Micro-LED chip comprises a pixel area and an IO area, a transition area is provided between the pixel area and the IO area, the pixel area comprises at least one pixel unit, the pixel unit comprises a light-emitting pixel for emitting blue light, and the IO area is used to electrically connect the pixel unit to an external circuit; A white light conversion layer, wherein the white light conversion layer only covers the pixel area of ​​the blue light Micro-LED chip; Wherein, the white light conversion layer is used to convert the blue light emitted by the light-emitting pixel into white light.

13. The white light Micro-LED chip according to claim 12, characterized in that: The distance between the top surface of the white light conversion layer and the top surface of the pixel unit is a first thickness, and the first thickness is 5 μm to 200 μm.

14. The white light Micro-LED chip according to claim 12, characterized in that: The distance between the outer edge of the white light conversion layer and the outer edge of the outermost pixel unit on the same side of the pixel area is equal to the first thickness, which is the distance between the top surface of the white light conversion layer and the top surface of the pixel unit.

15. The white light Micro-LED chip according to claim 12, characterized in that: Each of the pixel units comprises a bonding layer and a light-emitting pixel which are sequentially arranged in a direction away from the driving wafer.

16. The white light Micro-LED chip according to claim 15, characterized in that: The outside of the pixel unit is sequentially covered with a passivation layer and a transparent conductive layer, an opening is arranged at the passivation layer, and the light-emitting pixels of the pixel unit are cathode-connected through the opening at the passivation layer and the transparent conductive layer, an anode contact is arranged on the driving wafer, and the light-emitting pixels of the pixel unit are anode-connected through the bonding layer and the corresponding anode contact.

17. The white light Micro-LED chip according to claim 16, characterized in that: A cathode connector is connected to the transparent conductive layer, and a portion of the cathode connector is located in the transition zone. The IO zone is provided with a P electrode and an N electrode. The N electrode in the IO zone is used to be electrically connected to the cathode connector through the transparent conductive layer, and the P electrode in the IO zone is used to be electrically connected to the anode contact of the driving wafer.

18. The white light Micro-LED chip according to claim 16, characterized in that: Each pixel unit corresponds to the anode contact one by one, and each anode contact is located in the projection of the corresponding pixel unit on the driving wafer.

19. The white light Micro-LED chip according to claim 12, characterized in that: The blue light Micro-LED chip also includes a microlens, and the microlens corresponds to the pixel unit one by one. The microlens is located above the corresponding pixel unit, and the white light conversion layer covers all the microlenses.

20. The white light Micro-LED chip according to claim 19, characterized in that: Each of the pixel units is located in the projection of the corresponding microlens on the driving wafer.

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