Microdisplay device and method of manufacturing the same

Abstract

The application discloses a micro display device and a preparation method thereof. The micro display device comprises a driving substrate, a first light-emitting unit located on one side of the driving substrate and connected with the driving substrate, and a second light-emitting unit located on the side of the first light-emitting unit away from the driving substrate and connected with the driving substrate. The center of the second light-emitting unit is provided with a first opening. The depth of the first opening is less than or equal to the thickness of the part of the second light-emitting unit surrounding the first opening. The orthographic projection of the first light-emitting unit on the driving substrate is located in the orthographic projection of the first opening on the driving substrate along the thickness direction of the micro display device. The application can improve the light-emitting efficiency of the micro display device.

Description

Technical Field

[0001] This invention relates to the field of display technology, and in particular to a microdisplay device and its fabrication method. Background Technology

[0002] Micro LEDs (Micro Light Emitting Diodes) have advantages such as small size, long lifespan, fast response speed, and low power consumption, and are widely used in fields such as augmented reality (AR), near-eye display (NED), and wearable displays.

[0003] However, the low luminous efficiency of Micro LED technology limits its further application. Summary of the Invention

[0004] This invention provides a microdisplay device and its fabrication method to improve the light extraction efficiency of the microdisplay device.

[0005] According to one aspect of the present invention, a microdisplay device is provided, characterized in that the microdisplay device comprises: Drive substrate; The first light-emitting unit is located on one side of the driving substrate and is connected to the driving substrate; The second light-emitting unit is located on the side of the first light-emitting unit away from the driving substrate and is connected to the driving substrate; the center of the second light-emitting unit is provided with a first opening; the depth of the first opening is less than or equal to the thickness of the portion of the second light-emitting unit surrounding the first opening; along the thickness direction of the microdisplay device, the orthographic projection of the first light-emitting unit on the driving substrate is located within the orthographic projection of the first opening on the driving substrate.

[0006] Optionally, the first opening penetrates the second light-emitting unit; or, the thickness of the portion of the second light-emitting unit corresponding to the first opening is greater than zero and less than or equal to 2 micrometers.

[0007] Optionally, the microdisplay device further includes a first planarization layer covering the first light-emitting unit; the second light-emitting unit is located on the side of the first planarization layer away from the driving substrate; The microdisplay device further includes a first interconnect structure that extends through the first planarization layer and is connected to the second light-emitting unit and the driving substrate.

[0008] Optionally, the microdisplay device further includes a first bonding structure located between the first light-emitting unit and the driving substrate, and a second bonding structure located between the first planarization layer and the second light-emitting unit; one end of the first interconnect structure is connected to the second bonding structure, and the other end of the first interconnect structure is connected to the driving substrate through a padding structure; the padding structure is on the same layer as the first bonding structure.

[0009] Optionally, the microdisplay device further includes a first electrode layer located on the side of the first light-emitting unit away from the driving substrate and connected to the first light-emitting unit; and a second electrode layer located on the side of the second light-emitting unit away from the driving substrate and connected to the second light-emitting unit; The microdisplay device further includes a first pad, a second pad, and a second interconnect structure surrounding the second light-emitting unit; the first pad is connected to the first electrode layer, and the second pad is connected to the second electrode layer; along the thickness direction of the microdisplay device, the second interconnect structure is located between the first pad and the second pad, and is connected to both the first pad and the second pad; and / or, The second electrode layer is reused as the first electrode layer.

[0010] Optionally, the microdisplay device further includes a first ohmic contact structure located on the side of the second light-emitting unit away from the driving substrate; the first ohmic contact structure forms an ohmic contact with the second light-emitting unit; and the first ohmic contact structure is adjacent to the first opening.

[0011] Optionally, the first ohmic contact structure surrounds the first opening.

[0012] Optionally, the microdisplay device further includes a third light-emitting unit; along the thickness direction of the microdisplay device, the third light-emitting unit is located between the first light-emitting unit and the second light-emitting unit; and the orthographic projection of the third light-emitting unit on the driving substrate is located within the orthographic projection of the first opening on the driving substrate; The third light-emitting unit has a second opening; along the thickness direction of the micro-display device, the orthographic projection of the first light-emitting unit on the driving substrate is located within the orthographic projection of the second opening on the driving substrate.

[0013] Optionally, the microdisplay device further includes a third light-emitting unit; along the thickness direction of the microdisplay device, the third light-emitting unit is located between the first light-emitting unit and the driving substrate; and the orthographic projection of the third light-emitting unit on the driving substrate is located within the orthographic projection of the first opening on the driving substrate; The area of ​​the first light-emitting unit on the side away from the driving substrate is larger than the area of ​​the first light-emitting unit on the side close to the driving substrate; the area of ​​the third light-emitting unit on the side away from the driving substrate is larger than the area of ​​the third light-emitting unit on the side close to the driving substrate; the micro-display device further includes a first reflective layer disposed on the sidewall of the first light-emitting unit and a second reflective layer disposed on the sidewall of the third light-emitting unit.

[0014] According to another aspect of the present invention, a method for fabricating a microdisplay device is provided, for fabricating the microdisplay device as described above, the method comprising: Provide driving substrate; A first light-emitting unit is formed on one side of the driving substrate, and the first light-emitting unit is connected to the driving substrate; A second light-emitting unit is formed on the side of the first light-emitting unit away from the driving substrate, and the second light-emitting unit is connected to the driving substrate; a first opening is provided at the center of the second light-emitting unit; the depth of the first opening is less than or equal to the thickness of the portion of the second light-emitting unit surrounding the first opening; along the thickness direction of the microdisplay device, the orthographic projection of the first light-emitting unit on the driving substrate is located within the orthographic projection of the first opening on the driving substrate.

[0015] The technical solution of this invention employs a microdisplay device comprising a driving substrate, a first light-emitting unit, and a second light-emitting unit. The first light-emitting unit is located on one side of the driving substrate and connected to it; the second light-emitting unit is located on the side of the first light-emitting unit away from the driving substrate and is also connected to it; a first opening is provided at the center of the second light-emitting unit; the depth of the first opening is less than or equal to the thickness of the second light-emitting unit; along the thickness direction of the microdisplay device, the orthographic projection of the first light-emitting unit on the driving substrate lies within the orthographic projection of the first opening on the driving substrate. Stacking the second light-emitting units, which have lower emitted light energy, above the first light-emitting unit ensures that the second light-emitting unit has high light extraction efficiency; simultaneously, the first opening on the second light-emitting unit ensures that the emitted light from the first light-emitting unit can be emitted to the outside of the microdisplay device. In other words, the microdisplay device achieves both high light extraction efficiency for the second light-emitting unit and ensures that the emitted light from the first light-emitting unit can be emitted to the outside of the microdisplay device, resulting in a high display effect.

[0016] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a microdisplay device provided in an embodiment of the present invention; Figure 2 This is a top view of a microdisplay device provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of another micro-display device provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of another micro-display device provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of another micro-display device provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of another micro-display device provided in an embodiment of the present invention; Figure 7 A flowchart illustrating a method for fabricating a microdisplay device according to an embodiment of the present invention; Figures 8 to 23 This is a schematic diagram of the product structure corresponding to the main steps of a method for fabricating a microdisplay device provided in an embodiment of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] Microdisplay devices in related technologies suffer from low light extraction efficiency. Extensive research revealed that this problem arises because, in stacked microdisplay devices, such as those comprising stacked first and second light-emitting units, the photon energy of the emitted light from the first light-emitting unit is greater than the bandgap of the material of the second light-emitting unit. Therefore, the second light-emitting unit strongly absorbs the emitted light from the first light-emitting unit. Conversely, the photon energy of the emitted light from the second light-emitting unit is less than the bandgap of the material of the first light-emitting unit, so it is not absorbed by the first light-emitting unit. Based on this principle, in related technologies, the stacking order of the light-emitting units in microdisplay devices is typically set with the second light-emitting unit at the bottom and the first light-emitting unit at the top. However, because the emitted light energy from the second light-emitting unit is lower, when it is at the bottom, the emitted light must pass through more film layers before reaching the outside of the microdisplay device. Each film layer reflects or absorbs the emitted light to some extent, resulting in lower light extraction efficiency for the second light-emitting unit and higher light extraction efficiency for the first light-emitting unit, leading to poor display performance.

[0022] Based on the above-mentioned technical problems, the present invention proposes the following solutions: Figure 1 This is a schematic diagram of the structure of a microdisplay device provided in an embodiment of the present invention. Figure 2 This is a top view of a microdisplay device provided in an embodiment of the present invention, wherein, Figure 1 The micro-display device located in region Z1 can also be understood as... Figure 2 Cross-sectional view along the A1A2 direction, see reference. Figure 1 and Figure 2 Microdisplay devices include: The device comprises a driving substrate 1, a first light-emitting unit 4, and a second light-emitting unit 10. The first light-emitting unit 4 is located on one side of the driving substrate 1 and is connected to the driving substrate 1; the second light-emitting unit 10 is located on the side of the first light-emitting unit 4 away from the driving substrate 1 and is connected to the driving substrate 1; a first opening gap is provided at the center of the second light-emitting unit 10; the depth of the first opening gap is less than or equal to the thickness of the portion of the second light-emitting unit 10 surrounding the first opening gap; along the thickness direction of the microdisplay device, the orthographic projection of the first light-emitting unit 4 on the driving substrate 1 is located within the orthographic projection of the first opening gap on the driving substrate 1.

[0023] Specifically, the microdisplay device in this embodiment is a multi-color stacked microdisplay device, meaning that the microdisplay device can emit at least two colors of light. The first light-emitting unit 4 and the second light-emitting unit 10 emit different colors. The driving substrate 1 may include a driving circuit layer 111 and contacts 112 located on the driving circuit layer 111. The driving circuit layer 111 is provided with multiple driving circuits, and one driving circuit can drive one or more light-emitting units, wherein the light-emitting unit may be the first light-emitting unit 4 or the second light-emitting unit 10, etc. The specific structure and working principle of the driving substrate 1 are well known to those skilled in the art and will not be described in detail here.

[0024] The photon energy of the emitted light from the first light-emitting unit 4 is greater than the bandgap of the material of the second light-emitting unit 10. Therefore, the second light-emitting unit 10 strongly absorbs the emitted light from the first light-emitting unit 4. Conversely, the photon energy of the emitted light from the second light-emitting unit 10 is less than the bandgap of the material of the first light-emitting unit 4. Therefore, the emitted light from the second light-emitting unit 10 is not absorbed by the first light-emitting unit 4. In this embodiment, the first light-emitting units 4, which have higher photon energy, are stacked at the bottom, while the second light-emitting units 10, which have lower photon energy, are stacked at the top. This allows the emitted light from the second light-emitting unit 10 to exit the microdisplay device without passing through a large number of film layers, thereby greatly improving the light extraction efficiency of the second light-emitting unit 10.

[0025] Furthermore, a first opening gap is provided at the center of the second light-emitting unit 10, and the first light-emitting unit 4 is disposed at the first opening gap. Since no material of the second light-emitting unit 10 is disposed at the first opening gap, or only a very thin layer is provided, the light emitted by the first light-emitting unit 4 is not absorbed or is minimally absorbed by the second light-emitting unit 10. In other words, the microdisplay device can both enable the second light-emitting unit 10 to have high light extraction efficiency, ensure that the light from the first light-emitting unit 4 can be emitted to the outside of the microdisplay device, and make the light extraction efficiencies of the first light-emitting unit 4 and the second light-emitting unit 10 more similar, thereby improving the display effect of the microdisplay device.

[0026] The technical solution of this embodiment employs a microdisplay device including a driving substrate, a first light-emitting unit, and a second light-emitting unit. The first light-emitting unit is located on one side of the driving substrate and connected to it; the second light-emitting unit is located on the side of the first light-emitting unit away from the driving substrate and is connected to it; a first opening is provided at the center of the second light-emitting unit; the depth of the first opening is less than or equal to the thickness of the second light-emitting unit; along the thickness direction of the microdisplay device, the orthographic projection of the first light-emitting unit on the driving substrate lies within the orthographic projection of the first opening on the driving substrate. Stacking the second light-emitting units, which have lower emitted light energy, on top of the first light-emitting unit ensures that the second light-emitting unit has high light extraction efficiency; simultaneously, the first opening on the second light-emitting unit ensures that the emitted light from the first light-emitting unit can be emitted to the outside of the microdisplay device. In other words, the microdisplay device achieves both high light extraction efficiency for the second light-emitting unit and ensures that the emitted light from the first light-emitting unit can be emitted to the outside of the microdisplay device, resulting in a high display effect.

[0027] Optionally, such as Figure 2 As shown, the shape of the first light-emitting unit 4 can be circular; the shape of the four edges of the second light-emitting unit 10 can be rectangular. Of course, the shape of the first light-emitting unit 4 is not limited to a circle, and the shape of the four edges of the second light-emitting unit 10 is not limited to a rectangle.

[0028] Alternatively, in some implementations, such as Figure 1 As shown, the first opening gap penetrates through the second light-emitting unit 10. At this time, there is no material of the second light-emitting unit 10 at the first opening gap that absorbs the emitted light of the first light-emitting unit 4, thus ensuring that the second light-emitting unit 10 can have a high light extraction efficiency at the first opening gap.

[0029] Optionally, in some other embodiments, the thickness of the portion of the second light-emitting unit 10 corresponding to the first opening gap is greater than zero and less than or equal to 2 micrometers. In this embodiment, the first opening gap does not completely penetrate the second light-emitting unit 10, that is, the second light-emitting unit 10 retains a portion at the first opening gap. The thickness of this portion is extremely thin, such as less than or equal to 2 micrometers. The extremely thin second light-emitting unit 10 absorbs less light from the first light-emitting unit 4, which can also ensure that the first light-emitting unit 4 has a high light extraction efficiency.

[0030] Optionally, continue to refer to Figure 1 The microdisplay device also includes a first planarization layer 14 covering the first light-emitting unit 4; the second light-emitting unit 10 is located on the side of the first planarization layer 14 away from the driving substrate 1; the microdisplay device also includes a first interconnection structure 7, which penetrates the first planarization layer 14 and is connected to the second light-emitting unit 10 and the driving substrate 1.

[0031] Specifically, the first planarization layer 14 is an inorganic or organic material that is transparent to the emitted light of the first light-emitting unit 4. The inorganic material can be one or a combination of at least two of silicon oxide, titanium oxide, silicon nitride, silicon carbide, alumina, and phosphosilicate glass. The organic material can be a polymer of SU-8 and benzocyclobutene (BCB), or a transparent plastic (resin) including spin-coated glass, or a combination of at least two of the above. This embodiment, through the design of the first planarization layer and the first interconnect structure 7, can greatly reduce the fabrication difficulty of the micro-display device. In detail, after the first light-emitting unit 4 is fabricated, it is not necessary to immediately fabricate the second light-emitting unit 10. Instead, the first planarization layer 14 is fabricated first. The first light-emitting unit 4 and the second light-emitting unit 10 do not need to be directly bonded. Therefore, the electrodes of the first light-emitting unit 4 near the second light-emitting unit 10, and the electrodes of the second light-emitting unit 10 near the first light-emitting unit 4, are easier to fabricate, and there is no need to use a complex bonding process to bring out these two electrodes. The first interconnection structure 7 is, for example, a copper pillar, one end of which is electrically connected to the end of the second light-emitting unit 10 near the first light-emitting unit 4, and the other end is electrically connected to the driving substrate 1.

[0032] Optionally, in some embodiments, the second light-emitting unit 10 may correspond to a plurality of first interconnect structures 7.

[0033] Optionally, continue to refer to Figure 1 The microdisplay device also includes a first bonding structure 3 located between the first light-emitting unit 4 and the driving substrate 1, and a second bonding structure 9 located between the first planarization layer 14 and the second light-emitting unit 10; one end of the first interconnect structure 7 is connected to the second bonding structure 9, and the other end of the first interconnect structure 7 is connected to the driving substrate 1 through the padding structure 15; the padding structure 15 is on the same layer as the first bonding structure 3.

[0034] Specifically, the first bonding structure 3 is used to bond the first light-emitting unit 4 to the driving substrate 1, and the second bonding structure 9 is used to bond the second light-emitting unit 10 to the first planarization layer 14. The two bonding structures mentioned above include, but are not limited to, Au-Au, Cu-Cu, Au-Sn, Au-In, ITO-ITO, ITO-Au-ITO, ITO-Ti-ITO, ITO-Ti-Au-ITO, and other similar methods. The raised structure 15 is in the same layer as the first bonding structure 3, meaning they are formed in the same process. The raised structure 15 is bonded to the driving substrate 1 and is used to connect the first interconnect structure 7 to the driving substrate 1. In this embodiment, the first interconnect structure 7 is connected to the driving substrate 1 through the raised structure 15. The depth of the first interconnect structure 7 does not need to be too large, thus further reducing the fabrication difficulty of the micro-display device.

[0035] Optionally, continue to refer to Figure 1The microdisplay device also includes a redistribution layer 2, which is located between the driving substrate 1 and the first light-emitting unit 4, and is used to connect the contacts on the driving substrate 1 to the positions of the electrodes of each light-emitting unit.

[0036] Optionally, in some embodiments, both the first light-emitting unit and the second light-emitting unit include a first semiconductor layer, a light-emitting layer, and a second semiconductor layer sequentially located away from the driving substrate 1. The first semiconductor layer can be a P-type semiconductor layer, and the second semiconductor layer can be an N-type semiconductor layer. Alternatively, the first semiconductor layer can be an N-type semiconductor layer, and the second semiconductor layer can be a P-type semiconductor layer. The material of the semiconductor layer in the light-emitting unit can be a III-V group compound material, etc.

[0037] Optionally, continue to refer to Figure 1 The microdisplay device further includes a first electrode layer 5 located on the side of the first light-emitting unit 4 away from the driving substrate 1 and connected to the first light-emitting unit 4; and a second electrode layer 11 located on the side of the second light-emitting unit 10 away from the driving substrate 1 and connected to the second light-emitting unit 10; the microdisplay device further includes a first pad 6, a second pad 12, and a second interconnect structure 8 surrounding the second light-emitting unit 10; the first pad 6 is connected to the first electrode layer 5, and the second pad 12 is connected to the second electrode layer 11; along the thickness direction of the microdisplay device, the second interconnect structure 8 is located between the first pad 6 and the second pad 12, and is connected to the first pad 6 and the second pad 12.

[0038] Specifically, such as Figure 1As shown, the microdisplay device may further include a common electrode input structure 16, which is used to input signals to the common electrode of each light-emitting unit in the microdisplay device. The common electrode input structure 16 is, for example, a cathode input structure, that is, it inputs the cathode signal of the microdisplay device to provide to each light-emitting unit of the microdisplay device; in this case, the light-emitting units in the microdisplay device have a common cathode structure. The common electrode input structure 16 may include a portion on the same layer as the first electrode layer 5, a portion on the same layer as the first pad 6, a portion on the same layer as the first interconnect structure 7, a portion on the same layer as the second electrode layer 11, and a portion on the same layer as the second pad 12. The first electrode layer 5 is, for example, indium tin oxide (ITO), and the second electrode layer 11 can also be ITO. Because ITO has a large resistance, the voltage drop of the cathode signal received by the light-emitting units farther from the common electrode input structure 16 is different from that received by the light-emitting units closer to the common electrode input structure 16, which will cause uneven display. In this embodiment, a first solder pad 6, a second solder pad 12, and a second interconnect structure 8 made of metal are arranged around the light-emitting unit. The first solder pad 6 and / or the second solder pad 12 are connected to the corresponding film layer in the common electrode input structure 16 in the same layer. That is, the cathode signal input by the common electrode input structure 16 can be transmitted through the metal structure to the corresponding first solder pad 6 and second solder pad 12, and then to the first electrode layer 5 and the second electrode layer 11. Since the resistance of the metal structure is small, the first solder pad 6, the second solder pad 11, and the second interconnect structure 8 play the role of current amplification.

[0039] Furthermore, the first pad 6, the second pad 12, and the second interconnect structure 8 can be configured to surround the second light-emitting unit 10. Since the first pad 6, the second pad 12, and the second interconnect structure 8 are all metal, metal provides good light-shielding. Therefore, the overall structure composed of the first pad 6, the second pad 12, and the second interconnect structure 8 also has a light-shielding effect, preventing light crosstalk between adjacent stacked first and second light-emitting units.

[0040] Optionally, in Figure 1 In the embodiment shown, the first electrode layer 5 and the second electrode layer 11 are disposed independently.

[0041] Optionally, in some other embodiments, the second electrode layer 11 can also be reused as the first electrode layer. Specifically, as... Figure 3 As shown, Figure 3 This is a schematic diagram of another microdisplay device provided in an embodiment of the present invention. Since the second light-emitting unit 10 has a first opening gap that penetrates the second light-emitting unit 10, and the first light-emitting unit 4 is corresponding to the first opening gap, the first opening gap exposes the surface of the first light-emitting unit 4. Therefore, the second electrode layer 11 can directly extend within the first opening gap and connect with the first light-emitting unit 4. Compared to... Figure 1In the embodiment shown, this embodiment can save a process of fabricating the first electrode layer 5, thereby further reducing the process complexity of fabricating microdisplay devices.

[0042] Optionally, Figure 4 This is a schematic diagram of the structure of another microdisplay device provided in an embodiment of the present invention, with reference to... Figure 4 The microdisplay device also includes a first ohmic contact structure 17, which is located on the side of the second light-emitting unit 10 away from the driving substrate 1; the first ohmic contact structure 17 forms an ohmic contact with the second light-emitting unit 10; and the first ohmic contact structure 17 is adjacent to the first opening Gap.

[0043] Specifically, a first ohmic contact structure 17 is provided between the second electrode layer 11 and the second light-emitting unit 10. The first ohmic contact structure 17 can reduce the contact resistance between the second electrode layer 11 and the second light-emitting unit 10. In this embodiment, the first ohmic contact structure 17 is opaque, for example, a metal structure. The first ohmic contact structure 17 is located adjacent to the first opening gap, which can avoid affecting the light emission of the second light-emitting unit 10. In detail, during the etching of the second light-emitting unit 10 to form the first opening gap, sidewall damage occurs due to etching, resulting in some damage to the portion of the second light-emitting unit 10 adjacent to the first opening gap, leading to low light emission efficiency or no light emission. By placing the first ohmic contact structure 17 here, the originally non-light-emitting area on the second light-emitting unit 10 can be utilized, thereby avoiding blocking the light emission of the second light-emitting unit 10, which means that the second light-emitting unit 10 can have a higher light emission efficiency.

[0044] Optionally, continue to refer to Figure 4 The first ohmic contact structure 4 surrounds the first opening gap. In detail, the first ohmic contact structure 4 surrounds the first opening gap, and there is a larger contact area between the first ohmic contact structure 4 and the second light-emitting unit 10, which further reduces the contact resistance.

[0045] Alternatively, in some embodiments, the first ohmic contact structure may be located in other positions, such as spaced apart from the first opening gap.

[0046] Optionally, in some embodiments, the first light-emitting unit 4 is provided with a second ohmic contact structure, which is disposed between the first electrode layer 5 and the first light-emitting unit 4 to form an ohmic contact with the first light-emitting unit 4.

[0047] Optionally, refer to Figures 1 to 4In some embodiments, a transparent insulating layer 18 may be provided between the first electrode layer 5 and the first light-emitting unit 4. The transparent insulating layer 18 may directly cover the first light-emitting unit 4, or a passivation layer may be provided between the transparent insulating layer 18 and the first light-emitting unit 4. By making a hole in the transparent insulating layer 18, the first electrode layer 5 contacts the first light-emitting unit 4 within the hole.

[0048] Optionally, in some embodiments, the microdisplay device further includes a microlens structure 13, which is disposed on the side of the second light-emitting unit 10 away from the driving substrate 1, for converging light.

[0049] Optionally, in some embodiments, the first light-emitting unit 4 emits green light and the second light-emitting unit 10 emits red light.

[0050] Optionally, Figure 5 This is a schematic diagram of the structure of another microdisplay device provided in an embodiment of the present invention, with reference to... Figure 5 The microdisplay device also includes a third light-emitting unit 19; along the thickness direction of the microdisplay device, the third light-emitting unit 19 is located between the first light-emitting unit 4 and the second light-emitting unit 10; and the orthographic projection of the third light-emitting unit 19 on the driving substrate 1 is located within the orthographic projection of the first opening Gap on the driving substrate 1; a second opening Gap2 is provided on the third light-emitting unit 19; along the thickness direction of the microdisplay device, the orthographic projection of the first light-emitting unit 4 on the driving substrate 1 is located within the orthographic projection of the second opening Gap2 on the driving substrate 1.

[0051] Specifically, the emission color of the third light-emitting unit 19 is different from that of the first light-emitting unit 4 and also different from that of the second light-emitting unit 10; for example, the emission color of the third light-emitting unit 19 is blue. The photon energy of the emitted light from the third light-emitting unit 19 is greater than the bandgap of the material of the second light-emitting unit 10, therefore the third light-emitting unit 19 strongly absorbs the emitted light from the first light-emitting unit 4. Conversely, the photon energy of the emitted light from the third light-emitting unit 19 is less than the bandgap of the material of the first light-emitting unit 4, therefore the emitted light from the third light-emitting unit 19 is not absorbed by the first light-emitting unit 4. In this embodiment, the third light-emitting unit 19, with its higher photon energy, is stacked below the second light-emitting unit 10, while the second light-emitting unit 10, with its lower photon energy, is stacked on top. This allows the emitted light from the second light-emitting unit 10 to exit the microdisplay device without passing through a large number of film layers, thereby greatly improving the light extraction efficiency of the second light-emitting unit 10.

[0052] Optionally, Figure 6 This is a schematic diagram of the structure of another microdisplay device provided in an embodiment of the present invention, as shown below. Figure 6As shown, in some embodiments, the microdisplay device further includes a third light-emitting unit 19; along the thickness direction of the microdisplay device, the third light-emitting unit 19 is located between the first light-emitting unit 4 and the driving substrate 1; and the orthographic projection of the third light-emitting unit 19 on the driving substrate 1 is located within the orthographic projection of the first opening Gap on the driving substrate 1; the area of ​​the first light-emitting unit 4 on the side away from the driving substrate 1 is larger than the area of ​​the first light-emitting unit 4 on the side close to the driving substrate 1; the area of ​​the third light-emitting unit 19 on the side away from the driving substrate 1 is larger than the area of ​​the third light-emitting unit 19 on the side close to the driving substrate 1; the microdisplay device further includes a first reflective layer (not shown) disposed on the sidewall of the first light-emitting unit 4, and a second reflective layer (not shown) disposed on the sidewall of the third light-emitting unit 19.

[0053] Specifically, in this embodiment, the third light-emitting unit 19 is disposed on the bottom layer, and the first light-emitting unit 4 is disposed between the third light-emitting unit 19 and the second light-emitting unit 10. The emitted light from the third light-emitting unit 19 is not absorbed by the first light-emitting unit 4, therefore, it is not necessary to provide an opening on the first light-emitting unit 4. Both the first light-emitting unit 4 and the third light-emitting unit 19 have inverted trapezoidal structures with a larger surface area away from the driving substrate 1. Thus, after providing a reflective layer on the sidewall, it is possible to prevent the emitted light from the first light-emitting unit 4 and the third light-emitting unit 19 from incident on the second light-emitting unit 10 and exciting the second light-emitting unit 10 to emit light. At the same time, it can reduce the absorption of the driving substrate and better prevent light crosstalk. In this embodiment, the light emission efficiency of various color light-emitting units is more similar, which can achieve a better brightness balance effect. The reflective layer can be a metal layer or a DBR (Distributed Bragg Reflector), etc.

[0054] Based on the same inventive concept, this invention also provides a method for fabricating a microdisplay device, used to fabricate the microdisplay device provided in any embodiment of this invention. For example... Figure 7 As shown, Figure 7 This is a flowchart illustrating a method for fabricating a microdisplay device according to an embodiment of the present invention. The method includes: Step S110: Provide a driving substrate; Step S120: A first light-emitting unit is formed on one side of the driving substrate, and the first light-emitting unit is connected to the driving substrate. In step S130, a second light-emitting unit is formed on the side of the first light-emitting unit away from the driving substrate, and the second light-emitting unit is connected to the driving substrate; a first opening is provided at the center of the second light-emitting unit; the depth of the first opening is less than or equal to the thickness of the portion of the second light-emitting unit surrounding the first opening; along the thickness direction of the micro-display device, the orthographic projection of the first light-emitting unit on the driving substrate is located within the orthographic projection of the first opening on the driving substrate.

[0055] The micro-display device fabricated by the method described in this embodiment has a second light-emitting unit with high light extraction efficiency. The specific principle can be found in the description of the structure of the micro-display device in this invention, and will not be repeated here.

[0056] Optionally, Figures 8 to 23 This is a schematic diagram of the product structure corresponding to the main steps of a method for fabricating a microdisplay device according to an embodiment of the present invention, with reference to... Figures 8 to 23 The fabrication method of the micro-display device in this embodiment specifically includes: firstly, as shown in the figure... Figure 8 As shown, a driving substrate 1 is provided; then, as Figure 9 As shown, a reconstructed metal block is deposited on the metal contacts on the upper surface of the driving substrate 1 to guide the contacts to the target location. The reconstructed metal block can be, but is not limited to, single-layer or multi-layer combinations of Cr, Pt, Au, Sn, Ti, W, Cu, Ta, TaN, etc. Then, as... Figure 10 As shown, a transparent insulating passivation layer is deposited, and then a redistribution layer 2 is formed by CMP (Chemical Mechanical Polishing). After this step, the redistribution layer 2 and the surface of the transparent insulating passivation layer away from the driving substrate 1 together form a flat surface.

[0057] Then, the step of forming the first light-emitting unit begins. First, as follows... Figure 11 As shown, the first light-emitting unit material layer 41 is bonded to the driving substrate 11 through the first bonding material layer 31 to form a structure as shown. Figure 12 The structure shown. Then, as... Figure 13 As shown, the substrate corresponding to the first light-emitting unit material layer 41 is removed. Then, as... Figure 14 As shown, the first light-emitting unit material layer is etched to form the first light-emitting unit 4. After this step, the first light-emitting unit 4 is fabricated. Then, as... Figure 15 As shown, a passivation layer 20 covering the entire surface can be formed first; then as... Figure 16 As shown, the passivation layer 20 and the first bonding material layer 31 are etched to form the first bonding structure 3 and the raised structure 15. Then, as shown... Figure 17 As shown, a transparent insulating layer 18 is formed covering the entire surface. Then, as... Figure 18 As shown, the transparent insulating layer 18 is etched to expose the surface of the first light-emitting unit 4. Then, as... Figure 19 As shown, the first electrode layer 5 is formed. Then, as... Figure 20 As shown, the metal layer containing the first pad 6 is formed. Then, as... Figure 21 As shown, a first planarization layer 14 is formed. Then, as... Figure 22As shown, the first interconnect structure 7 and the second interconnect structure 8 are formed through micro-nano fabrication. Following this step, the fabrication of the second light-emitting unit proceeds, repeating the processes in the fabrication steps corresponding to the first light-emitting unit, ultimately forming… Figure 23 The structure is shown. Finally, a rectangular array of microlenses is formed through mask patterning, photolithography, high-temperature reflow etching, and etching. Each light-emitting unit has one or more microlenses, which are hemispherical or frustum-shaped. In some embodiments, microlenses composed of inorganic or organic materials are formed through mask patterning, photolithography, and then etching. In some embodiments, microlenses composed of organic materials are formed by mask patterning, photolithography, high-temperature reflow etching, and then etching to form a light-focusing microlens structure above a single light-emitting unit.

[0058] As can be seen from the above fabrication steps of the micro-display device, the micro-display device of this embodiment does not involve advanced bonding processes such as ITO bonding. It only requires simple bonding of the second light-emitting unit to the first planarization layer, resulting in low process complexity.

[0059] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0060] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A microdisplay device, characterized in that, The microdisplay device includes: Drive substrate; The first light-emitting unit is located on one side of the driving substrate and is connected to the driving substrate; The second light-emitting unit is located on the side of the first light-emitting unit away from the driving substrate and is connected to the driving substrate; the center of the second light-emitting unit is provided with a first opening; the depth of the first opening is less than or equal to the thickness of the portion of the second light-emitting unit surrounding the first opening; along the thickness direction of the microdisplay device, the orthographic projection of the first light-emitting unit on the driving substrate is located within the orthographic projection of the first opening on the driving substrate.

2. The microdisplay device according to claim 1, characterized in that, The first opening penetrates the second light-emitting unit; or, the thickness of the portion of the second light-emitting unit corresponding to the first opening is greater than zero and less than or equal to 2 micrometers.

3. The microdisplay device according to claim 1, characterized in that, The microdisplay device further includes a first planarization layer covering the first light-emitting unit; the second light-emitting unit is located on the side of the first planarization layer away from the driving substrate; The microdisplay device further includes a first interconnect structure that extends through the first planarization layer and is connected to the second light-emitting unit and the driving substrate.

4. The microdisplay device according to claim 3, characterized in that, The microdisplay device further includes a first bonding structure located between the first light-emitting unit and the driving substrate, and a second bonding structure located between the first planarization layer and the second light-emitting unit; one end of the first interconnect structure is connected to the second bonding structure, and the other end of the first interconnect structure is connected to the driving substrate through a padding structure; The raised structure is in the same layer as the first bonding structure.

5. The microdisplay device according to claim 1, characterized in that, The microdisplay device further includes a first electrode layer located on the side of the first light-emitting unit away from the driving substrate and connected to the first light-emitting unit; and a second electrode layer located on the side of the second light-emitting unit away from the driving substrate and connected to the second light-emitting unit. The microdisplay device further includes a first pad, a second pad, and a second interconnect structure surrounding the second light-emitting unit; the first pad is connected to the first electrode layer, and the second pad is connected to the second electrode layer; along the thickness direction of the microdisplay device, the second interconnect structure is located between the first pad and the second pad, and is connected to both the first pad and the second pad; and / or, The second electrode layer is reused as the first electrode layer.

6. The microdisplay device according to claim 1, characterized in that, The microdisplay device further includes a first ohmic contact structure located on the side of the second light-emitting unit away from the driving substrate; the first ohmic contact structure forms an ohmic contact with the second light-emitting unit; the first ohmic contact structure is adjacent to the first opening.

7. The microdisplay device according to claim 6, characterized in that, The first ohmic contact structure surrounds the first opening.

8. The microdisplay device according to claim 1, characterized in that, The microdisplay device further includes a third light-emitting unit; along the thickness direction of the microdisplay device, the third light-emitting unit is located between the first light-emitting unit and the second light-emitting unit; and the orthographic projection of the third light-emitting unit on the driving substrate is located within the orthographic projection of the first opening on the driving substrate; The third light-emitting unit is provided with a second opening; Along the thickness direction of the microdisplay device, the orthographic projection of the first light-emitting unit on the driving substrate is located within the orthographic projection of the second opening on the driving substrate.

9. The microdisplay device according to claim 8, characterized in that, The microdisplay device further includes a third light-emitting unit; along the thickness direction of the microdisplay device, the third light-emitting unit is located between the first light-emitting unit and the driving substrate; and the orthographic projection of the third light-emitting unit on the driving substrate is located within the orthographic projection of the first opening on the driving substrate; The area of ​​the first light-emitting unit on the side away from the driving substrate is larger than the area of ​​the first light-emitting unit on the side close to the driving substrate; the area of ​​the third light-emitting unit on the side away from the driving substrate is larger than the area of ​​the third light-emitting unit on the side close to the driving substrate; the micro-display device further includes a first reflective layer disposed on the sidewall of the first light-emitting unit and a second reflective layer disposed on the sidewall of the third light-emitting unit.

10. A method for fabricating a microdisplay device, used to fabricate the microdisplay device according to any one of claims 1-9, characterized in that, The method for fabricating the microdisplay device includes: Provide driving substrate; A first light-emitting unit is formed on one side of the driving substrate, and the first light-emitting unit is connected to the driving substrate; A second light-emitting unit is formed on the side of the first light-emitting unit away from the driving substrate, and the second light-emitting unit is connected to the driving substrate; a first opening is provided at the center of the second light-emitting unit; the depth of the first opening is less than or equal to the thickness of the portion of the second light-emitting unit surrounding the first opening; along the thickness direction of the microdisplay device, the orthographic projection of the first light-emitting unit on the driving substrate is located within the orthographic projection of the first opening on the driving substrate.

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