Light-emitting chip, lighting device and preparation method of light-emitting chip

Abstract

The invention relates to the technical field of light-emitting chips, in particular to a light-emitting chip, a lighting device and a preparation method of the light-emitting chip. The light-emitting chip comprises a chip substrate and a light conversion layer, the chip substrate comprises a semiconductor layer, and the semiconductor layer is provided with a plurality of micro light-emitting diodes. The light conversion layer is arranged on the semiconductor layer, the light conversion layer comprises a light conversion part and a light isolation part which are sequentially and adjacently arranged, and the array period of one of the micro light-emitting diodes and the light isolation part is integer multiples of the array period of the other one of the micro light-emitting diodes and the light isolation part. The light insulation part comprises a conductor and a reflecting film arranged on the surface of the conductor, and the width of the light insulation part is smaller than or equal to 10 micrometers. According to the invention, the light conversion layers are provided with the light isolation parts, so that light crosstalk between the light conversion layers is avoided. And moreover, the width size of the light insulation part is set to be less than 10 microns, so that the shielding of the light insulation part to the micro light-emitting diode is reduced, the shielding of the light-emitting area and the field intensity of the micro light-emitting diode is reduced, and the risk of crosstalk of light in the structure of the micro light-emitting diode is reduced.

Description

Technical Field

[0001] This application relates to the field of light-emitting chip technology, and in particular to a light-emitting chip, a lighting device, and a method for preparing the light-emitting chip. Background Technology

[0002] From early halogen lamps and xenon lamps to LED (Light emitting diode) lamps and laser headlights, the main focus of car headlights has been on improving brightness and efficiency, as well as providing more colors or different white light color temperatures. But in essence, these headlights project the light spots from the left and right headlights onto the road ahead, illuminating the road ahead with two beams to provide drivers with safety assurance and assistance.

[0003] Currently, in the planning of megapixel-level uLED (Micro Light Emitting Diode) automotive lighting products, the size of a single pixel uLED chip is approximately tens of micrometers. To minimize obstruction of the uLED's light-emitting area and field strength, the light-blocking structure between pixels should theoretically be as narrow as possible. Therefore, the actual requirement for the width of the light-blocking structure between the phosphor layers is less than 10 micrometers to reduce the decrease in uLED brightness. However, the thickness of a typical phosphor layer is approximately between 10 and 50 micrometers. Therefore, fabricating the light-blocking structure defining the pixels within the phosphor layer presents numerous manufacturing challenges. Summary of the Invention

[0004] This application provides a light-emitting chip, a lighting device, and a method for fabricating the light-emitting chip, aiming to solve the main mass production process difficulties of high-reflectivity light-blocking structures and improve the brightness of vehicle lights.

[0005] This application provides a method for fabricating a light-emitting chip in a first aspect, the method comprising:

[0006] A conductive substrate is bonded onto an insulating substrate;

[0007] Photoresist is applied at intervals to the upper surface of the conductive substrate to form spaced cavities and conductors, with a portion of the insulating substrate exposed through the cavities;

[0008] Remove the photoresist;

[0009] The insulating substrate and the conductor are placed in an electroplating solution, and a reflective film is formed on the surface of the conductor. The conductor and the reflective film form a light-blocking part, and the width of the light-blocking part is ≤10μm.

[0010] Fluorescent adhesive is filled into the cavity and cured to form a light conversion part, and the light blocking part and the light conversion part form a light conversion layer;

[0011] The light conversion layer is attached to the chip substrate.

[0012] In this application, by utilizing the difference in conductivity between the insulating substrate and the conductor, the reflective metal will only adhere to the surface of the conductive material during the electroplating of the reflective film. Furthermore, under the premise of uniform flow and distribution of the electroplating solution, the thickness of the reflective film on the surface of the conductor will have a high degree of uniformity.

[0013] Therefore, the electroplating process used in this application to form a reflective film on the surface of a conductor is superior to the evaporation or sputtering processes. This application avoids significant differences in the thickness of the reflective film across different areas of the light-blocking surface, and prevents issues such as roughness in some areas of the reflective film that could lead to a decrease in reflectivity. The electroplating process used in this application to prepare the reflective film facilitates a smooth surface for the light-blocking portion and improves its reflectivity.

[0014] Furthermore, this application uses an electroplating process to fabricate the reflective film, so there is no metal adhering to the light-transmitting area on the surface of the insulating substrate. Therefore, after the electroplating process is completed, there is no need to use processes such as exposure and etching to remove the metal coating in the light-transmitting area, thus solving the difficulties in mass production of high-reflectivity structures.

[0015] In addition, this application uses an electroplating process to create a light-blocking part with a width of less than 10 micrometers, which reduces the obstruction of the light-blocking part to the micro light-emitting diode and increases the overall brightness of the cavity light-emitting chip.

[0016] Among them, the cavity mentioned above refers to a square cavity or a cubic cavity.

[0017] In one possible design, after the insulating substrate and the conductive substrate are bonded together, the method further includes:

[0018] The conductive substrate is ground to reduce its thickness to a first target thickness.

[0019] In this application, CMP (chemical mechanical polishing) and other methods can be used to grind and polish the conductive substrate to reduce its thickness. Specifically, the thickness of the conductive substrate can be reduced to less than 30 μm, so that the thickness of the subsequently formed light-blocking portion is less than 30 μm, and the thickness of the subsequently formed light conversion layer is less than 30 μm. Because the thinner the conductive substrate, the narrower the width of the light-blocking portion is easier to make, thereby reducing the folding of the light-emitting area of ​​the micro-LED and improving the overall brightness emitted by the light-emitting chip.

[0020] In one possible design, during the electroplating process, the metal in the electroplating solution is a metal with a reflectivity ≥70%.

[0021] In this application, the metal can be silver, aluminum, copper, gold, etc. Through this electroplating process, a uniform, dense, and smooth reflective film is formed on the surface of the conductor.

[0022] In one possible design, after the electroplating process is completed, the method further includes:

[0023] The insulating substrate and the light-blocking part are cleaned in a cleaning solvent.

[0024] In this application, after the electroplating process is completed, the parts formed by the above steps are placed in pure water or solvent to clean them and remove residual electroplating solution and other possible contaminants or residues.

[0025] In one possible design, the fluorescent adhesive is filled into the cavity by spraying or molding.

[0026] In this application, the spraying process is as follows: after the fluorescent powder is mixed into fluorescent adhesive, the fluorescent adhesive is sprayed onto the cavity in a manner similar to a spray gun, and air bubbles in the fluorescent adhesive can be removed by means of negative pressure, etc.

[0027] The molding process is as follows: the sample is placed in the fixture, fluorescent adhesive is applied to the sample surface or inside the container, the thickness of the fluorescent adhesive is controlled by applying pressure with the fixture (top cover), and finally the fluorescent adhesive is cured by UV light irradiation or heating.

[0028] In one possible design, after the fluorescent adhesive has cured, the method further includes:

[0029] The fluorescent adhesive is ground to remove the portion of the fluorescent adhesive that is above the light-blocking part.

[0030] In this application, the fluorescent adhesive above the light-blocking part is removed by grinding, polishing or CMP (chemical mechanical polishing) to avoid the appearance of a layer of fluorescent adhesive on the light-blocking side, which would cause light crosstalk.

[0031] In one possible design, before bonding the light conversion layer to the chip substrate, the method further includes:

[0032] The insulating substrate is ground to reduce its thickness to a second target thickness.

[0033] In this application, after the grinding and polishing process is completed, the thickness of the insulating substrate can be reduced to less than 100μm by grinding and polishing or CMP (chemical mechanical polishing), and the components formed in the above steps can be cut into chips of a specific size by laser or cutting wheel.

[0034] In one possible design, after bonding the light conversion layer to the chip substrate, the method further includes:

[0035] Remove the insulating substrate.

[0036] In this application, the insulating substrate can be removed by means of laser irradiation or grinding and polishing to further reduce the possibility of crosstalk of light within the insulating substrate.

[0037] In one possible design, the height of the light-blocking part is ≤50μm.

[0038] A second aspect of this application provides a light-emitting chip, which is fabricated using the above-described method for preparing a light-emitting chip, comprising:

[0039] A chip substrate, the chip substrate including a semiconductor layer, the semiconductor layer being provided with a plurality of micro light-emitting diodes;

[0040] A light conversion layer is disposed on the semiconductor layer. The light conversion layer includes a light conversion part and a light blocking part arranged sequentially adjacent to each other. In the micro light-emitting diode and the light blocking part, the array period of one is an integer multiple of the array period of the other.

[0041] The light-blocking part includes a conductor and a reflective film disposed on the surface of the conductor, and the width of the light-blocking part is ≤10μm.

[0042] In this application, after light is emitted by the micro light-emitting diode in the semiconductor layer, it must pass through the structure of the micro light-emitting diode itself, the adhesive layer, the light conversion layer and the insulating substrate before it can be directed toward the target. By setting a light-blocking part in the light conversion layer, crosstalk between the light conversion layers is avoided.

[0043] Meanwhile, by setting the width of the light-blocking part to be less than 10 micrometers, this application increases the channel for light to pass through the light conversion part, reduces the obstruction of the light-blocking part on the micro light-emitting diode, thereby reducing the obstruction of the light-emitting area and field strength of the micro light-emitting diode, reducing the risk of crosstalk of light in the structure of the micro light-emitting diode itself, and increasing the brightness of the light-emitting chip.

[0044] In addition, a reflective film is provided on the surface of the light-blocking part. The surface reflectivity of the light-blocking part is highly positively correlated with the field strength of the micro light-emitting diode. When the surface reflectivity of the light-blocking part is higher, the brightness of the light-emitting chip is higher. Conversely, when the surface reflectivity of the light-blocking part is lower, the brightness of the light-emitting chip is lower.

[0045] Therefore, this application provides a light-blocking part in the light conversion layer, which reduces the possibility of crosstalk between the light conversion layer and the structure of the light-emitting diode itself, thereby improving the luminous brightness of the light-emitting chip.

[0046] In one possible design, the light-emitting chip further includes an insulating substrate disposed on the light conversion layer, the insulating substrate having a light transmittance ≥90%.

[0047] In this application, the insulating substrate is made of a transparent material, such as glass or sapphire. By setting the light transmittance of the insulating substrate to ≥90%, the brightness of the light emitted by the light-emitting chip is ensured.

[0048] In one possible design, the dominant wavelength of the light emitted by the micro-LED is between 430nm and 500nm.

[0049] In this application, a blue light-emitting diode (LED) can be used. The blue LED, combined with a light conversion layer, emits white light to suit various applications. The dominant wavelength of the light emitted by the blue LED is between 430nm and 500nm.

[0050] Alternatively, micro-LEDs of other colors can be selected. The light emitted by the micro-LEDs can also be converted into other colors after passing through the light conversion layer. The specific color can be set according to actual needs.

[0051] A third aspect of this application provides a lighting device comprising the light-emitting chip described above.

[0052] In this application, the lighting device can be a lighting module on a vehicle lighting system. In addition to traditional lighting purposes, the lighting device can also be used for intelligent vehicle lights that implement road navigation guidance and interactive message transmission in a pixelated display.

[0053] Secondly, besides its application in intelligent vehicle lighting, the lighting device is also suitable for laser beam scanning (LBS) intelligent vehicle lighting applications. When using blue lasers (light emitted by micro-light-emitting diodes) with array mirror devices such as digital micromirror devices (DMDs) as pixelated vehicle light sources, a light conversion layer is required to convert the blue light into white light. Regardless of whether the blue laser light enters the light conversion layer through transmission or reflection to form a white light spot, crosstalk will still occur within the light conversion layer, causing a decrease in the contrast of the white light spot. Therefore, when using blue lasers as intelligent vehicle light sources, the light conversion layer with light-blocking components can effectively improve image contrast.

[0054] Furthermore, this application uses conductive materials to fabricate the conductor and employs electroplating to create a reflective film on the surface of the conductor. This structure can be used not only in automotive headlights but also in highly directional ULED displays for ARF / VR glasses. Currently, ultra-high resolution (thousands of PPI and above) microdisplays require various projection lens groups to magnify the image for user viewing. For example, by using a wet etching process to naturally form a reflective cup structure with a specific tilt angle on the surface of a conductive silicon wafer, and then electroplating to create a reflective metal film on the silicon wafer surface, the manufacturing cost of this type of micro-reflective cup can be effectively reduced. Attached Figure Description

[0055] Figure 1 SEM image of the surface morphology of the metal vapor-deposited sidewall of the light-blocking structure;

[0056] Figure 2 A schematic diagram showing a reflective metal shielding the light-transmitting area.

[0057] Figure 3 This is a schematic diagram of the light-emitting chip provided in this application in one embodiment;

[0058] Figure 4 This is a schematic diagram of the light-emitting chip provided in this application in another embodiment;

[0059] Figure 5 A flowchart illustrating the method for fabricating the light-emitting chip provided in this application;

[0060] Figure 6 A flowchart illustrating the method for fabricating the light-emitting chip provided in this application;

[0061] Figure 7 A flowchart illustrating the method for fabricating the light-emitting chip provided in this application;

[0062] Figure 8 This is a schematic diagram illustrating the fabrication of a light-emitting chip by thinning the fluorescent adhesive to different thicknesses as provided in this application.

[0063] Figure label:

[0064] 1′-Chip;

[0065] 11′-Transparent substrate;

[0066] 12′-Fluorescent layer;

[0067] 121′-Fluorescent part;

[0068] 122′ - Light-blocking structure;

[0069] 122a′-Body part;

[0070] 122b′-Reflective coating;

[0071] 1-Light-emitting chip;

[0072] 11-Chip substrate;

[0073] 111-Drive backplane;

[0074] 112 - Metallic solder ball;

[0075] 113 - Semiconductor layer;

[0076] 113a - Micro LED;

[0077] 114 - Filler adhesive;

[0078] 12-Adhesive layer;

[0079] 13-Light conversion layer;

[0080] 131 - Light conversion unit;

[0081] 132-Light isolation part;

[0082] 132a - Conductor;

[0083] 132b - Reflective film;

[0084] 14-Insulating substrate;

[0085] 2-Conductive substrate;

[0086] 21-Cavity;

[0087] 3-Etching mask. Detailed Implementation

[0088] With the rapid advancement of technology, new pixelated intelligent automotive lighting systems such as Adaptive Front-Lighting System (AFS) and Adaptive Driving Beam (ADB) are gaining attention from major automakers and the industry. Compared to traditional automotive lighting systems that simply illuminate the road ahead, Adaptive Front-Lighting System (AFS) and Adaptive Driving Beam (ADB) incorporate a pixelated concept, dividing the lighting area into tens of thousands of blocks. Through the differences in brightness between these blocks, the previously simple function of road illumination is enhanced with added value, including road guidance, information display, preventing direct glare from oncoming drivers' eyes, and even providing some entertainment features. Among various pixelated technologies for automotive lighting, micro light emitting diodes (uLEDs) possess inherent pixelated lighting and display characteristics. When paired with a driver backplane such as complementary metal oxide semiconductor (CMOS) or printed circuit board (PCB), they can become pixelated automotive light sources. Compared to other technologies such as laser beam scanning (LBS), they have significant advantages in terms of low cost, small size, and ease of assembly.

[0089] In the display fields of mobile phones, smartwatches, and large-screen TVs, micro light-emitting diodes (uLEDs) are considered highly likely to replace organic light-emitting diodes (OLEDs) as the mainstream next-generation display technology due to their high efficiency, high brightness, long lifespan, and high contrast. In these standard full-color applications, millions of red, green, and blue microlight-emitting diode (uLED) chips, each tens of micrometers in size, are transferred and bonded to driving backplanes such as thin-film transistors (TFTs) or printed circuit boards (PCBs). This process, known as "mass transfer," has extremely high requirements for bonding accuracy, speed, and yield, and is widely regarded in the industry as the biggest manufacturing process challenge for the industrialization of micro light-emitting diode (uLED) display technology. However, when micro-light-emitting diode (uLED) chips are used in pixelated automotive lights, unlike when uLEDs are used in full-color displays, where millions of uLEDs require millions of surface mount processes, the uLED chips used in smart automotive lights share at least one semiconductor layer. In other words, a lighting chip with 10,000 uLEDs can be considered as one large LED chip with more than 10,000 p-type and n-type electrodes. Therefore, when bonding uLED chips to driver backplanes such as Complementary Metal Oxide Semiconductor (CMOS), mass transfer technology is not used. Instead, high-density, high-precision thermal compression bonding (TCB) and other mature bonding technologies are employed, which greatly improves the performance of uLEDs. The feasibility of mass production of diode and uLED automotive lights.

[0090] Unlike uLED (microlight emitting diode) display systems in mobile phones, watches, and large-screen TVs, which use red, green, and blue uLED chips to mix the light emitted to create various colors, including white light, the mainstream solution in uLED smart car lighting applications currently uses blue uLED chips mixed with phosphors to produce white light in order to reduce process complexity and manufacturing costs. This architecture uses only one color of uLED chip, instead of red, green, and blue, thus eliminating the need for mass transfer and significantly reducing the complexity of uLED surface mount technology. However, when micro light emitting diode (uLED) smart car light chips share p or n-type structures, the possibility of crosstalk between pixels increases. In particular, when the blue light emitted by the micro light emitting diodes (uLEDs) of each pixel enters the phosphor layer, phenomena such as the isotropic emission characteristics of fluorescence and the scattering of different colors of light by encountering phosphor particles will reduce the imaging contrast of the micro light emitting diode (uLED) smart car light, resulting in problems such as blurry and unclear projected images.

[0091] To address the aforementioned issue of decreased display contrast, the proposed solutions include: (1) Each pixel's microlight emitting diode (uLED) chip is completely independent from the phosphor layer through which the light emission direction passes. Light-blocking material structures are filled or fabricated between pixels to ensure complete brightness non-interference between pixels. Specifically, the uLEDs are bonded to the driver backplane using mass transfer or similar methods. Light crosstalk between the phosphor layers is prevented by metal plating, filling with opaque adhesive, or filling with highly reflective materials. Since the light emitted by uLEDs has a certain diffusion angle, if there is no light-blocking structure within the phosphor adhesive, different uLEDs may excite the same area of ​​phosphor adhesive, leading to decreased display contrast (similar to incorrectly brightening the same pixel).

[0092] (2) Micro light emitting diode (uLED) chips still share n-type or p-type semiconductors, but the phosphor layer that the light emission direction passes through is filled or light-blocking material structure is made in the middle according to the pixel configuration. This can avoid crosstalk between phosphor layers, but there is a possibility of crosstalk between micro light emitting diode (uLED) chips.

[0093] As mentioned above, if we want micro LEDs (uLEDs) to be completely optically independent and free from crosstalk, then the micro LED chips must be completely independent. In this case, thousands to tens of thousands of micro LED chips cannot share a common n-type or p-type semiconductor layer to avoid light crosstalk. When such a large number of micro LED chips are mass-transfer bonded to the driver backplane, problems such as misalignment between individual chips and bonding failures can lead to yield issues. Especially when automotive lighting involves safety issues, a 100% yield may be required. Currently, even with rework, the overall yield of mass transfer technology is still far from 100%.

[0094] Currently, in the planning of megapixel-level micro LED (uLED) automotive lighting products, the size of a single pixel uLED chip is approximately tens of micrometers. To minimize obstruction of the uLED's light-emitting area and field strength, the light-blocking structure between pixels should theoretically be as narrow as possible. Therefore, the actual requirement for the width of the light-blocking structure between the phosphor layers is less than 10 micrometers to reduce the decrease in uLED brightness. However, the thickness of a typical phosphor layer is approximately between 10 and 50 micrometers. Therefore, fabricating the light-blocking structure defining the pixels within the phosphor layer presents numerous manufacturing challenges.

[0095] For example, after phosphor is mixed with silicone and sprayed and cured onto the surface of a micro light emitting diode (uLED) chip, it is very difficult to achieve trench etching with a width of less than ten micrometers using dry etching or wet etching methods, and it is also difficult to create a light-blocking structure in the phosphor trench by depositing a reflective film, a metal film, or filling it with reflective and light-absorbing materials. Currently, there is no mature process solution in the industry.

[0096] Another manufacturing process involves first fabricating the light-blocking structure and then filling the light-transmitting areas within it with phosphor material. This approach has high mass production feasibility because it utilizes semiconductor manufacturing processes such as wafer bonding, dry etching, and mirror coating. However, regardless of whether the light-blocking structure is fabricated first or the phosphor layer is coated first, the high visible light reflectivity of the light-blocking structure surface has a direct and significant impact on the overall brightness and luminous efficiency of the micro light emitting diode (uLED) automotive headlight. According to simulation calculations, assuming the surface of the light-blocking structure has 100% reflectivity, the white light intensity of the uLED headlight is 1. When the reflectivity of the light-blocking structure surface drops to 90%, the white light intensity of the uLED headlight will drop to 0.7. When the reflectivity of the light-blocking structure surface further drops to 50%, the white light intensity of the uLED headlight will only be about 0.4. Actual measurements show that using white scattering materials to make the light-blocking structure also causes the luminous intensity of the blue light-emitting diode (uLED) to decrease by more than 30%. This proves that in addition to a high aperture ratio, the high reflectivity of the light-blocking material surface is also a key requirement for improving headlight performance.

[0097] To improve the reflectivity of light-blocking structures, two main approaches can be adopted: using materials with inherently high reflectivity and creating a reflective layer on the surface of a non-reflective material. Materials with high reflectivity may include adhesives containing scattering particles and highly reflective metals. First, let's discuss materials with inherently high reflectivity. It is challenging to fabricate a wall-like checkerboard structure with a scattering particle film measuring over 10µm in width and 20µm in height. Furthermore, the reflectivity of adhesives with scattering particles is generally below 90%. Therefore, considering both the morphology and reflectivity of the light-blocking structure, materials with scattering particles are not an ideal choice. Another approach is to use a light-blocking structure with high reflectivity. For example, a light-blocking structure tens of micrometers thick can be made using electroplating. Metals such as silver or aluminum, which are commonly used as reflective metals in the visible light band, can be used. However, the electroplating process for aluminum is complicated and unreliable, and the cost of electroplating thick silver is also very expensive. Therefore, making a thick metal light-blocking structure on the epitaxial layer of a micro light-emitting diode (uLED) by electroplating faces great challenges in terms of both process difficulty and cost.

[0098] On the other hand, if a highly reflective metal or distributed Bragg reflector (DBR) reflective layer is deposited on the surface of other materials by means of vapor deposition, two key problems will be encountered: (1) such as Figure 1 The image shows a schematic SEM image of the surface morphology of the metal vapor-deposited sidewall of the light-blocking structure. The light-blocking structure is tens of micrometers high. The coating thickness and flatness of the sidewall are difficult to control, which may result in insufficient or deviated film thickness, affecting the reflectivity of the metal or the distributed Bragg reflector (DBR).

[0099] Specifically, evaporation / sputtering processes are generally highly directional. For example, when a deep trench is dug on a wafer to deposit / sputter a metal film, the thickness of the metal film in the area near the opening of the trench will inevitably be greater than that in the deeper area.

[0100] For example, if a trench is 5µm wide and 20µm deep, when performing metal evaporation / sputtering, the metal thickness within the 5µm trench depth may be similar to that on the wafer surface. However, as the trench depth increases, the metal film thickness on the trench sidewalls gradually decreases. This phenomenon is mainly because, regardless of whether the metal film is made by evaporation or sputtering, metal atoms will be directed straight from the evaporation material or target towards the sample. Therefore, most of the metal atoms will adhere to the wafer surface or the bottom of the trench. Although the angle of incidence of metal atoms on the wafer can be increased by rotating the sample, since the width of the trench is less than its depth, the metal film thickness on the sidewalls at the deepest part of the trench will ultimately be much less than the metal film thickness at the trench opening.

[0101] (2) such as Figure 2 The diagram shows a reflective metal shielding the light-transmitting area. Chip 1' includes a transparent substrate 11' and a phosphor layer 12' disposed on the transparent substrate 11'. The phosphor layer 12' includes a phosphor portion 121' and a light-blocking structure 122'. The light-blocking structure 122' includes a body portion 122a' and a reflective coating 122b'. The reflective coating 122b' is disposed on the surface of the body portion 122a' and the light-transmitting area of ​​the phosphor portion 121'. Since the phosphor portion 121' area must remain transparent, this area will be shielded by the coating during metal or distributed Bragg reflector (DBR) coating. Figure 2 (The area within the dashed circle) is difficult to precisely remove using selective dry / wet etching or other methods, especially the metal or distributed Bragg reflector (DBR) coating in this region.

[0102] In summary, it can be understood that the above methods still have many problems or shortcomings in achieving the light-blocking structure within the fluorescent layer, requiring new process solutions to address them.

[0103] Therefore, this embodiment provides a light-emitting chip to solve the above-mentioned technical problems.

[0104] like Figure 3 The diagram shows a schematic of a light-emitting chip 1. Along the propagation direction Z of the light emitted by the chip 1, the chip 1 includes a chip substrate 11, an adhesive layer 12, a light conversion layer 13, and an insulating substrate 14 arranged sequentially. The chip substrate 11 includes a driving backplate 111, metal solder balls 112, and a semiconductor layer 113.

[0105] Specifically, the semiconductor layer 113 and the driving backplane 111 are fixedly connected by solder balls 112. The semiconductor layer 113 contains at least two micro light-emitting diodes (uLEDs) 113a, with each solder ball 112 connecting one uLED. A filler adhesive 114 is provided between the uLEDs 113a and the driving backplane 111 to enhance the stability of the connection between the uLEDs 113a and the driving backplane 111.

[0106] Along the direction of light propagation Z, the light conversion layer 13 is disposed above the semiconductor layer 113, and the light conversion layer 13 and the semiconductor layer 113 are connected by an adhesive layer 12. The adhesive layer 12 is made of optical adhesive, which is colorless and transparent, has a light transmittance of more than 90%, good bonding strength, can be cured at room temperature or medium temperature, and has low curing shrinkage.

[0107] Along the light propagation direction Z, the insulating substrate 14 is disposed above the light conversion layer 13. The light conversion layer 13 and the insulating substrate 14 are bonded and fixed by molecular bonding or transparent adhesive. The light transmittance of the insulating substrate 14 is ≥90%, ensuring that the insulating substrate 14 has good light transmittance, thereby ensuring the brightness of the light emitted by the light-emitting chip 1.

[0108] The light conversion layer 13 mainly includes a light conversion part 131 and a light blocking part 132 arranged adjacent to each other. The light blocking part 132 includes a conductor 132a and a reflective film 132b disposed on the surface of the conductor 132a. The width of the light blocking part 132 is ≤10μm.

[0109] In this embodiment, when light is emitted from the micro light-emitting diode 113a of the semiconductor layer 113, it must pass through the structure of the micro light-emitting diode 113a itself, the adhesive layer 12, the light conversion layer 13 and the insulating substrate 14 before it can be directed toward the target. By providing a light-blocking part 132 in the light conversion layer 13, crosstalk between the light conversion layers 13 is avoided.

[0110] Meanwhile, by setting the width of the light-blocking part 132 to be less than 10 micrometers, this embodiment increases the channel for light to pass through the light conversion part 131, reduces the obstruction of the micro light-emitting diode 113a by the light-blocking part 132, thereby reducing the obstruction of the light-emitting area and field strength of the micro light-emitting diode 113a, reducing the risk of crosstalk of light in the structure of the micro light-emitting diode 113a itself, and increasing the light-emitting brightness of the light-emitting chip 1.

[0111] In addition, a reflective film 132b is provided on the surface of the light-blocking part 132. The reflectivity of the surface of the light-blocking part 132 is highly positively correlated with the field strength of the micro light-emitting diode 113a. When the reflectivity of the surface of the light-blocking part 132 is higher, the brightness of the light-emitting chip 1 is higher. Conversely, when the reflectivity of the surface of the light-blocking part 132 is lower, the brightness of the light-emitting chip 1 is lower.

[0112] Therefore, in this embodiment, a light-blocking part 132 is provided in the light conversion layer 13 to reduce the possibility of crosstalk between the light conversion layer 13 and the micro light-emitting diode 113a itself, thereby improving the light-emitting brightness of the light-emitting chip 1.

[0113] Please continue to refer to this. Figure 3 Within the light conversion layer 13, the light-blocking portion 132 divides the light conversion layer 13 into multiple parts (light conversion portions 131). The distribution principle of the light-blocking portion 132 can be designed according to the distribution of the micro light-emitting diodes 113a, dividing the light conversion portions 131 into the same partitioned configuration as the micro light-emitting diodes 113a. That is, in the micro light-emitting diodes 113a and the light-blocking portion 132, the array period of one is an integer multiple of the array period of the other.

[0114] For example, when the period of the pixel of the micro-LED 113a is 100μm, if the period of the light-blocking portion 132 is also 100μm, then the micro-LED 113a and the light-blocking portion 132 have the same period. If the period of the light-blocking portion 132 is 200μm, then two micro-LEDs 113a correspond to one light conversion portion 131. In this case, the period of the light-blocking portion 132 is twice that of the micro-LED 113a, and so on.

[0115] This embodiment reduces the possibility of crosstalk when the light emitted by the micro-light-emitting diodes 113a enters the light conversion layer 13 by arraying the micro-light-emitting diodes 113a and the light-blocking parts 132, thereby improving the contrast of the final emitted light color.

[0116] Among them, at least 50% of the light-emitting areas of the micro-LEDs 113a have a size ≤40×40μm. 2 Alternatively, the size of the light-emitting area of ​​the micro LED 113a can be set to other sizes, which can be set according to the actual situation. This embodiment does not limit it here.

[0117] In some embodiments, the micro-light-emitting diode 113a may be a blue micro-light-emitting diode 113a, which, together with the light conversion layer 13, emits white light to suit various applications. The dominant wavelength of the light emitted by the blue micro-light-emitting diode 113a is between 430nm and 500nm.

[0118] Alternatively, other colors of micro-light-emitting diodes 113a can be selected. The light emitted by micro-light-emitting diodes 113a can also be converted into other light colors after passing through the light conversion layer 13. The specific color can be set according to actual needs.

[0119] In some embodiments, periodic optical elements may be disposed on the surface of the light conversion layer 13 along the light propagation direction Z, thereby achieving the effect of modifying the light field pattern. Specifically, the surface of the light conversion layer 13 may utilize periodic structures such as micromirror arrays (MLAs) or photonic crystals to change or adjust the final light pattern.

[0120] like Figure 4 The diagram shown is a schematic of a light-emitting chip 1 in another embodiment. Along the propagation direction Z of the light emitted by the chip 1, the chip 1 includes a chip substrate 11, an adhesive layer 12, and a light conversion layer 13 sequentially disposed. The chip substrate 11 includes a driving backplate 111, metal solder balls 112, and a semiconductor layer 113. Compared to... Figure 3 The light-emitting chip 1 in the middle, Figure 4 The light-emitting chip 1 eliminates the insulating substrate 14 to reduce light loss. However, the insulating substrate 14 is an indispensable component in the fabrication of the light-emitting chip 1, and its fabrication method is described in detail below.

[0121] To prepare the light-emitting chip 1 described above, this embodiment also provides a method for preparing the light-emitting chip 1, which is used to form such a chip. Figure 3 and Figure 4 At least a portion of the light-emitting chip 1 shown. (As...) Figures 5 to 7 The diagram shows a flowchart of a method for fabricating a light-emitting chip 1. This method may specifically include the following steps:

[0122] Please refer to Figure 5 S11: Attach the conductive substrate 2 onto the insulating substrate 14.

[0123] In this step, the insulating substrate 14 is made of a transparent material, such as glass or sapphire. The conductive substrate 2 can be made of materials such as silicon, gallium arsenide, or gallium nitride. The conductive substrate 2 can be attached to the insulating substrate 14 by molecular bonding or bonding with transparent adhesive.

[0124] Please refer to Figure 5 S12: After the insulating substrate 14 and the conductive substrate 2 are bonded together, the method further includes: grinding the conductive substrate 2 to reduce the thickness of the conductive substrate 2 to a first target thickness.

[0125] In this step, the conductive substrate 2 can be polished using methods such as CMP (chemical mechanical polishing) to reduce its thickness. Specifically, the thickness of the conductive substrate 2 can be reduced to less than 30 μm, so that the thickness of the subsequently formed light-blocking portion 132 is less than 30 μm, and thus the thickness of the subsequently formed light conversion layer 13 is less than 30 μm. Because the thinner the conductive substrate 2, the narrower the width of the light-blocking portion 132 is, the less it obstructs the light-emitting area of ​​the micro-LED 113a, thereby improving the overall brightness emitted by the light-emitting chip 1.

[0126] Please refer to Figure 6 S13: Photoresist is applied at intervals to the upper surface of the conductive substrate 2 to form spaced cavities 21 and conductors 132a, and part of the insulating substrate 14 is exposed through the cavity 21.

[0127] In this step, photoresist is coated on the conductive substrate 2, and an etching mask 3 is fabricated according to the designed light-blocking part 132. The etching mask 3 is then placed on the photoresist, and a portion of the conductive substrate 2 is etched away until light is transmitted. At this point, the light-transmitting area can be an insulating substrate 14, a molecular bonding layer, a transparent adhesive layer, etc. Here, cavity 21 refers to a directional cavity or a cubic cavity.

[0128] Alternatively, in some embodiments, other processes may be used to fabricate the conductor 132a on the insulating substrate 14. Exemplarily, the conductor 132a may be formed by wet etching of the conductive substrate 2, by screen printing, by gravure printing, by 3D printing, or by direct spraying.

[0129] Please refer to Figure 6 S14: Remove photoresist.

[0130] In this step, the etching mask 3 material is removed by means of photoresist removal solution, plasma etching (including dry etching processes such as RIE (reactive ion etching) or ICP (inductively coupled plasma etching), which can be used to remove organic materials including photoresist.

[0131] Please refer to Figure 6 S14: The insulating substrate 14 and the conductor 132a are placed in the electroplating solution, and a reflective film 132b is formed on the surface of the conductor 132a. The conductor 132a and the reflective film 132b form a light-blocking part 132. The width of the light-blocking part 132 is ≤10μm and the height of the light-blocking part 132 is ≤50μm.

[0132] In this step, the component formed in the above steps is placed in an electroplating solution. A negative voltage is applied to the conductor 132a, and a positive voltage is applied to the metal in the electroplating solution. The metal in the electroplating solution is a metal or other material with a reflectivity ≥70%, such as silver, aluminum, copper, or gold. Through this electroplating process, a uniform, dense, and flat reflective film 132b is formed on the surface of the conductor 132a.

[0133] In this step, due to the difference in conductivity between the insulating substrate 14 and the conductor 132a, the reflective metal will only adhere to the surface of the conductive conductor 132a during the electroplating of the reflective film. Furthermore, under the premise of uniform flow and distribution of the electroplating solution, the thickness of the reflective film 132b on the surface of the conductor 132a will have a high degree of uniformity.

[0134] Therefore, this embodiment uses electroplating to form a reflective film 132b on the surface of the conductor 132a, which is superior to using evaporation or sputtering processes. This embodiment avoids significant differences in the thickness of the reflective film 132b across different areas of the light-blocking portion 132 surface, and prevents issues such as roughness in some areas of the reflective film 132b, which could lead to a decrease in reflectivity. The electroplating process used in this embodiment to prepare the reflective film 132b facilitates a smooth surface on the light-blocking portion 132, thereby improving its reflectivity.

[0135] Furthermore, in this embodiment, the reflective film 132b is fabricated using an electroplating process. No metal will be attached to the light-transmitting area on the surface of the insulating substrate 14. Therefore, after the electroplating process is completed, it is not necessary to use processes such as exposure and etching to remove the metal coating in the light-transmitting area, thus solving the difficulty of mass production of high-reflectivity structures.

[0136] In addition, in this embodiment, an electroplating process is used to fabricate a light-blocking part 132 with a width of less than 10 micrometers, which reduces the obstruction of the light-blocking part 132 on the micro light-emitting diode 113a and enhances the overall brightness of the light-emitting chip 1.

[0137] S15: After the electroplating process is completed, the method further includes: cleaning the insulating substrate 14 and the light-blocking part 132 in a cleaning solvent.

[0138] In this step, after the electroplating process is completed, the parts formed in the above steps are placed in pure water or solvent to clean them and remove residual electroplating solution and other possible contaminants or residues.

[0139] Please refer to Figure 7 S16: Fill the cavity 21 with fluorescent glue and cure it to form a light conversion part 131. The light blocking part 132 and the light conversion part 131 form a light conversion layer 13.

[0140] In this step, fluorescent adhesive can be filled into the cavity 21 using a spraying or molding process. The specific steps are as follows: First, fluorescent adhesive is prepared by mixing phosphors, quantum dots (quantum dots are semiconductor materials scaled to tens of nanometers in size, capable of absorbing light and converting it into another color, similar to phosphors), or other color-conversion materials (color conversion refers to the ability to absorb one color of light and convert it into another; besides phosphors or quantum dots, some phosphorescent materials or semiconductor films also have similar functions) with adhesive materials (silicone, epoxy resin, etc.) to form fluorescent adhesive, which is then filled into the cavity 21 between adjacent light-blocking portions 132. Then, pressure or vacuum is applied to prevent air bubbles from remaining in the cavity 21, which could lead to incomplete filling of the fluorescent adhesive.

[0141] It should be noted that the color transfer material is generally in powder form, so it is mixed with adhesive-like materials (which may also contain solvents) and then applied to the cavity 21. Since the adhesive has a certain degree of viscosity and the width of the light-blocking part 132 is only tens of micrometers, the adhesive can easily remain on the surface of the light-blocking part 132 and cannot completely penetrate into the cavity 21.

[0142] To solve the above problems, the simplest solution is to apply fluorescent adhesive to the surface of the conductor 132a and then place the sample into a vacuum chamber to create a negative pressure environment. This will remove the air from the cavity 21 and allow the fluorescent adhesive to flow into it. Another solution is to apply pressure to the surface of the light-blocking part 132 after applying the fluorescent adhesive, using a scraper or similar tool. This will also help the fluorescent adhesive penetrate into the cavity 21.

[0143] After the fluorescent adhesive is filled into the cavity 21, it is cured by heating, baking, or ultraviolet irradiation. The thickness of the fluorescent adhesive is controlled by the amount of adhesive poured and the thickness of the mold. Generally, the thickness of the fluorescent adhesive is greater than the thickness of the light-blocking part 132.

[0144] It should be noted that the fluorescent adhesive is liquid after being applied. Therefore, the sample can be placed in the mold and the fluorescent adhesive can be applied to the surface of the light-blocking part 132. Then, a mold similar to a lid can be used to press down and control the thickness of the adhesive after curing.

[0145] S16: After the fluorescent adhesive has cured, the method further includes: grinding the fluorescent adhesive to remove the portion of the fluorescent adhesive above the light-blocking part 132.

[0146] In this step, the fluorescent adhesive above the light-blocking part 132 is removed by grinding, polishing or CMP (chemical mechanical polishing) to avoid a layer of fluorescent adhesive on one side of the light-blocking part 132, which would cause light crosstalk.

[0147] like Figure 8The diagram shows a schematic of the process of preparing a light-emitting chip 1 by thinning the fluorescent adhesive to different thicknesses. Due to grinding errors, the thickness of the fluorescent adhesive after grinding may be greater than (shown in the left image after thinning), equal to (shown in the middle image after thinning), or less than (shown in the right image after thinning) the height of the light-blocking portion 132. That is, on the light-emitting chip 1, along the light propagation direction Z, the conductor 132a will have one or two planes that are not covered by metal (without the reflective film 132b), namely the surface of the back micro-light-emitting diode 113a, or the surface facing the back micro-light-emitting diode 113a.

[0148] S17: Before bonding the light conversion layer 13 to the chip substrate 11, the method further includes: grinding the insulating substrate 14 to reduce the thickness of the insulating substrate 14 to a second target thickness.

[0149] In this step, after the grinding and polishing process is completed, the thickness of the insulating substrate 14 can be reduced to less than 100μm by grinding and polishing or CMP (chemical mechanical polishing), and the components formed in the above steps can be cut into chips of specific sizes by laser or cutting wheel.

[0150] It should be noted that if an insulating substrate 14 with a thickness of less than 100 μm is used at the beginning of the fabrication process, the insulating substrate 14 is prone to cracking during processing, and this phenomenon is more likely to occur when the wafer area is larger. Therefore, the thickness of the insulating substrate 14 is reduced by grinding after the fabrication process is completed.

[0151] Please refer to Figure 7 S18: The light conversion layer 13 is attached to the chip substrate 11.

[0152] In this step, transparent adhesive is applied to the surfaces of the light conversion part 131 and the light blocking part 132 along the light propagation direction Z, and then they are flip-mounted and aligned onto the chip substrate 11. At this time, it is ensured that the array period of one of the micro light-emitting diodes 113a and the light blocking part 132 on the chip substrate 11 is an integer multiple of the array period of the other. The specific reason is the same as described above, and will not be repeated here in this embodiment.

[0153] After the light conversion layer 13 is bonded to the chip substrate 11, the transparent adhesive can be cured by heating or ultraviolet irradiation. After curing, the thickness of the transparent adhesive is less than 10 μm, forming the adhesive layer 12. Furthermore, the light transmittance of the adhesive layer 12 is ≥90%.

[0154] Please refer to Figure 7 S18: After bonding the light conversion layer 13 to the chip substrate 11, the method further includes: removing the insulating substrate 14.

[0155] In this step, the insulating substrate 14 can be removed by means of laser irradiation or grinding and polishing to further reduce the possibility of crosstalk of light within the insulating substrate.

[0156] It should be noted that, during the fabrication process, the light-blocking portion 132 and the light-converting portion 131 require a carrier plate to provide sufficient mechanical strength for support; otherwise, several light-blocking portions 132, each only tens of micrometers wide, cannot exist independently and complete the entire process. Therefore, the insulating substrate 14 can be removed in a subsequent step of the fabrication process.

[0157] This embodiment also provides a lighting device, which includes the aforementioned light-emitting chip 1. The lighting device can be a lighting module in a vehicle lighting system. In addition to traditional lighting applications, the lighting device can also be used for intelligent vehicle lights that implement road navigation guidance and interactive message transmission in a pixelated display.

[0158] Secondly, in addition to its application in intelligent vehicle lighting scenarios, the lighting device is also suitable for laser beam scanning (LBS) intelligent vehicle lighting applications. When using blue laser (light emitted by micro-light-emitting diodes) with array mirror devices such as digital micromirror devices (DMDs) as pixelated vehicle light sources, a light conversion layer is required to convert the blue light into white light. Regardless of whether the blue laser light enters the light conversion layer 13 and forms a white light spot through transmission or reflection, crosstalk will still occur within the light conversion layer 13, causing a decrease in the contrast of the white light spot. Therefore, when using blue laser as an intelligent vehicle light source, the light conversion layer with a light-blocking part 132 can effectively improve image contrast.

[0159] In addition, in this embodiment, a conductive material is used to fabricate the conductor 132a, and an electroplating process is used to fabricate a reflective film 132b on the surface of the conductor 132a. This structure can be used not only in automotive lights but also in highly directional uLED displays for AR / VR glasses. Currently, ultra-high (thousands of PPI and above) microdisplays all require various projection lens groups to achieve the goal of magnifying images for users to view. For example, by using a wet etching process to naturally form a reflective cup structure with a specific tilt angle on the surface of a conductive silicon wafer, and then using electroplating to fabricate a reflective metal film on the silicon wafer surface, the manufacturing cost of this type of micro-reflective cup can be effectively reduced.

[0160] The same or similar parts between the various embodiments in this specification can be referred to mutually. In particular, the device embodiments and terminal embodiments are basically similar to the method embodiments, so the description is relatively simple.

[0161] The above descriptions are merely specific implementations of the embodiments of this application, but the protection scope of the embodiments of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the embodiments of this application should be covered within the protection scope of the embodiments of this application. Therefore, the protection scope of the embodiments of this application should be determined by the protection scope of the claims.

Claims

1. A light-emitting chip, characterized in that, The light-emitting chip includes: A chip substrate, the chip substrate including a semiconductor layer, the semiconductor layer being provided with a plurality of micro light-emitting diodes; A light conversion layer is disposed on the semiconductor layer. The light conversion layer includes a light conversion part and a light blocking part arranged sequentially adjacent to each other. In the micro light-emitting diode and the light blocking part, the array period of one is an integer multiple of the array period of the other. The light-blocking part includes a conductor and a reflective film disposed on the surface of the conductor, and the width of the light-blocking part is ≤10μm.

2. The light-emitting chip according to claim 1, characterized in that, The light-emitting chip also includes an insulating substrate disposed on the light conversion layer, and the light transmittance of the insulating substrate is ≥90%.

3. The light-emitting chip according to claim 1, characterized in that, The main wavelength of the light emitted by the micro-LED is between 430nm and 500nm.

4. A lighting device, characterized in that, The lighting device includes a light-emitting chip as described in any one of claims 1 to 3.

5. A method for fabricating a light-emitting chip, used to manufacture the light-emitting chip according to any one of claims 1 to 3, characterized in that, The method includes: A conductive substrate is bonded onto an insulating substrate; Photoresist is applied at intervals to the upper surface of the conductive substrate to form spaced cavities and conductors, with a portion of the insulating substrate exposed through the cavities; Remove the photoresist; The insulating substrate and the conductor are placed in an electroplating solution, and a reflective film is formed on the surface of the conductor. The conductor and the reflective film form a light-blocking part, and the width of the light-blocking part is ≤10μm. Fluorescent adhesive is filled into the cavity and cured to form a light conversion part, and the light blocking part and the light conversion part form a light conversion layer; The light conversion layer is attached to the chip substrate.

6. The method for preparing a light-emitting chip according to claim 5, characterized in that, After the insulating substrate and the conductive substrate are bonded together, the method further includes: The conductive substrate is ground to reduce its thickness to a first target thickness.

7. The method for preparing a light-emitting chip according to claim 5, characterized in that, In the electroplating process, the metal in the electroplating solution is a metal with a reflectivity of ≥70%.

8. The method for preparing a light-emitting chip according to claim 5, characterized in that, After the electroplating process is completed, the method further includes: The insulating substrate and the light-blocking part are cleaned in a cleaning solvent.

9. The method for preparing a light-emitting chip according to claim 5, characterized in that, The fluorescent adhesive is filled into the cavity by spraying or molding.

10. The method for preparing a light-emitting chip according to claim 5, characterized in that, After the fluorescent adhesive has cured, the method further includes: The fluorescent adhesive is ground to remove the portion of the fluorescent adhesive that is above the light-blocking part.

11. The method for fabricating a light-emitting chip according to claim 5, characterized in that, Before bonding the light conversion layer to the chip substrate, the method further includes: The insulating substrate is ground to reduce its thickness to a second target thickness.

12. The method for preparing a light-emitting chip according to claim 5, characterized in that, After bonding the light conversion layer to the chip substrate, the method further includes: Remove the insulating substrate.

13. The method for preparing a light-emitting chip according to claim 5, characterized in that, The height of the light-blocking part is ≤50μm.

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