A low-temperature hybrid bonding method for preparing a micro-LED display device based on an asymmetric structure

Abstract

This invention discloses a low-temperature hybrid bonding method for fabricating Micro-LED display devices based on an asymmetric structure, relating to the field of display device technology. The method, through asymmetric structure design combined with low-temperature hybrid bonding technology, achieves precise alignment and efficient connection between the Micro-LED chip and the substrate or other components. This reduces the significant thermal stress and deformation that can occur in Micro-LED devices during operation due to the different coefficients of thermal expansion and Young's modulus of the materials used in each component.

Description

Technical Field

[0001] This invention relates to the field of display device technology, and in particular to a low-temperature hybrid bonding method for fabricating Micro-LED display devices based on an asymmetric structure. Background Technology

[0002] With the rapid development of display technology, Micro-LED, as a representative of next-generation display technology, is gradually becoming a research hotspot in the display field due to its significant advantages such as high brightness, low power consumption, long lifespan, and high contrast. The high performance requirements of Micro-LED display devices pose more stringent challenges to their manufacturing processes, especially in the bonding process between the chip and the substrate, where it is necessary to solve the stress impact problem caused by the difference in thermal expansion coefficients in order to improve the structural strength and reliability of the device.

[0003] Currently, bonding processes for Micro-LED display devices mainly include traditional eutectic bonding, metal welding, and the emerging laser mass bonding. However, these technologies all have limitations to varying degrees in practical applications. While eutectic bonding can achieve high bonding strength, the hot-pressing process can easily lead to thermal stress mismatch between the chip and the substrate, affecting the long-term stability of the device. Metal welding can effectively reduce thermal stress, but it is costly and complex. Although laser mass bonding has high precision and efficiency, it also has relatively high requirements for equipment precision and cost.

[0004] Furthermore, traditional bonding processes often face challenges such as uneven interfaces and low alignment accuracy when dealing with the tiny size and high-density arrangement of Micro-LED chips. These problems directly affect bonding quality and device performance. Therefore, developing a novel bonding process to improve the flatness of the bonding interface, reduce thermal stress, and enhance the structural strength and reliability of Micro-LED display devices has become a pressing technical challenge.

[0005] Photosensitive polymer materials, such as photosensitive benzocyclobutene (BCB) and photosensitive polyimide (PI), have been widely used in microelectronic packaging due to their excellent optical properties, thermal stability, and chemical stability. Although these materials can achieve precise patterning through photochemical reactions, the application of photosensitive polymer materials in the hybrid bonding process of Micro-LED display devices still faces challenges such as interface unevenness and insufficient bonding strength. Summary of the Invention

[0006] The purpose of this invention is to provide a low-temperature hybrid bonding method for fabricating Micro-LED display devices based on an asymmetric structure. This method can improve the manufacturing efficiency of Micro-LED display devices by combining asymmetric structure design with hybrid bonding technology under low-temperature conditions.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] A low-temperature hybrid bonding method for fabricating Micro-LED display devices based on asymmetric structures, comprising:

[0009] Step 1: Fabricate Ti / Ni / Au metal electrodes on the surface of a silicon substrate using the damascus process;

[0010] Step 2: Coat the surface of the silicon substrate with a photosensitive polymer as a dielectric layer;

[0011] Step 3: To meet the requirements of the subsequent vapor deposition process, photolithography is used to pattern the polymer.

[0012] Step 4: Apply photoresist again over the dielectric layer to isolate and protect the polymer, and then perform patterning again;

[0013] Step 5: Use electron beam evaporation to deposit indium metal as bumps;

[0014] Step 6: Use the lift-off process to remove excess metal and photoresist to complete the substrate fabrication;

[0015] Step 7: Using a flip-chip bonding machine, pressure and temperature are applied to mix and bond the substrate to obtain a Micro-LED display device with an asymmetric structure.

[0016] Optionally, the photosensitive polymer is a photosensitive benzocyclobutene and / or a photosensitive polyimide that is poorly soluble in reagents such as acetone.

[0017] Optionally, the position of the patterning process in step 4 is the same as the position of the patterning process in step 3.

[0018] Optionally, the flip bonding machine employs a low-temperature bonding method.

[0019] Optionally, the temperature for the low-temperature bonding method is 140°C.

[0020] Optionally, the pressure in step 7 is 20 kg.

[0021] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0022] This invention discloses a low-temperature hybrid bonding method for fabricating Micro-LED display devices based on an asymmetric structure. The method achieves precise alignment and efficient connection between the Micro-LED chip and the substrate or other components through asymmetric structure design combined with hybrid bonding technology under low-temperature conditions. This reduces the large thermal stress and deformation that would occur in the Micro-LED device during operation due to the different thermal expansion coefficients and Young's modulus of the various component materials. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the 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.

[0024] Figure 1 This is a flowchart of the substrate fabrication process in this embodiment;

[0025] Figure 2 This is a schematic diagram of the cross-sectional structure of the device after hybrid bonding in this embodiment. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 are within the scope of protection of the present invention.

[0027] The purpose of this invention is to provide a low-temperature hybrid bonding method for fabricating Micro-LED display devices based on an asymmetric structure. This method can improve the manufacturing efficiency of Micro-LED display devices by combining asymmetric structure design with hybrid bonding technology under low-temperature conditions.

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1 As shown, to improve the structural strength and reliability of Micro-LED microdisplays and reduce the stress impact caused by the difference in thermal expansion coefficients between the chip and the substrate, this invention provides a low-temperature hybrid bonding method for fabricating Micro-LED display devices based on an asymmetric structure, comprising:

[0030] Step 1: Fabricate Ti / Ni / Au metal electrodes on the surface of a silicon substrate using the damascus process;

[0031] Step 2: Coat the surface of the silicon substrate with a photosensitive polymer as a dielectric layer, such as photosensitive benzocyclobutene (BCB) or photosensitive polyimide (PI). These two materials are difficult to dissolve in reagents such as acetone.

[0032] Step 3: To meet the requirements of the subsequent vapor deposition process, photolithography is used to pattern the polymer.

[0033] Step 4: Apply photoresist again to the polymer layer to isolate and protect the polymer, and pattern it in the same position as in the previous step;

[0034] Step 5: Electron beam evaporation of indium (In) as bumps;

[0035] Step 6: Lift-off process removes excess metal and photoresist. The substrate fabrication flowchart for the above steps is shown below. Figure 1 As shown;

[0036] Step 7: Using a flip-chip bonding machine, hybrid bonding of Micro-LEDs is achieved by applying pressure and temperature. A schematic diagram of the cross-sectional structure of the device after hybrid bonding is shown below. Figure 2 As shown.

[0037] The aforementioned low-temperature hybrid bonding process based on asymmetric structure design aims to improve the manufacturing efficiency of Micro-LED display devices, reduce costs, and optimize the mechanical properties and reliability of the devices. Therefore, it offers the following beneficial effects:

[0038] Due to the small size of Micro LEDs, traditional dispensing processes may encounter precision and uniformity issues when handling such tiny dimensions during manufacturing. Spin coating technology, on the other hand, can more accurately control the distribution of adhesive. However, spin coating of Micro LED chips still presents many problems, such as: (1) Micro LEDs have extremely high requirements for the luminous efficacy and wavelength consistency of LED chips. If not properly controlled during the spin coating process, the emission wavelength of the LED chips may deviate, affecting the display effect; (2) Due to the small size of Micro LED chips, extremely high precision is required during the spin coating process to control the thickness and uniformity of the coating. If not properly controlled, the coating thickness may be uneven, affecting the display effect and device performance. Although etching after spin coating on existing chips and substrates can be considered in Micro LED hybrid bonding, the etching selectivity for materials is poor, the adhesive thickness on the etched surface is often uneven, and plasma may also damage the device surface.

[0039] Therefore, this invention uses an asymmetric structure with adhesive only on the substrate side. A photosensitive polymer is first coated, then photoresist is used to protect the photosensitive polymer, followed by photolithography and subsequent evaporation of bumps, eliminating the need for dry etching. Furthermore, this embodiment uses low-temperature bonding (140°C) to improve the structural strength and reliability of the Micro-LED display device by optimizing the bonding interface and reducing thermal stress.

[0040] Furthermore, the bonding process in this embodiment is an effective method to solve problems such as thermal stress impact and interface unevenness in the bonding process between Micro-LED chips and substrates in the prior art, as specifically demonstrated below:

[0041] (1) Improved bonding quality: By using a photosensitive polymer material as the dielectric layer and achieving precise patterning through photolithography, a low-temperature hybrid bonding process is employed. This invention significantly improves the flatness of the bonding interface and reduces bonding defects caused by interface unevenness.

[0042] (2) Enhanced structural strength: Photosensitive polymer materials have good mechanical support properties, which can form a stable connection between the Micro-LED chip and the substrate, thus enhancing the structural strength of the device.

[0043] (3) Extended service life: Under long-term working conditions, the hybrid bonding process of the present invention can reduce performance degradation caused by thermal stress, reduce the generation of dead pixels, and extend the service life of Micro-LED display devices.

[0044] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0045] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A low-temperature hybrid bonding method for fabricating Micro-LED display devices based on asymmetric structures, characterized in that, include: Step 1: Fabricate Ti / Ni / Au metal electrodes on the surface of a silicon substrate using the damascus process; Step 2: Coat the surface of the silicon substrate with a photosensitive polymer as a dielectric layer; Step 3: To meet the requirements of the subsequent vapor deposition process, photolithography is used to pattern the polymer. Step 4: Apply photoresist again over the dielectric layer to isolate and protect the polymer, and then perform patterning again; Step 5: Use electron beam evaporation to deposit indium metal as bumps; Step 6: Use the lift-off process to remove excess metal and photoresist to complete the substrate fabrication; Step 7: Using a flip-chip bonding machine, pressure and temperature are applied to mix and bond the substrate to obtain a Micro-LED display device with an asymmetric structure. The photosensitive polymer is a photosensitive benzocyclobutene and / or a photosensitive polyimide that is poorly soluble in reagents such as acetone; The position of the patterning process in step 4 is the same as the position of the patterning process in step 3; The flip-chip bonding machine uses a low-temperature bonding method.

2. The low-temperature hybrid bonding method for fabricating Micro-LED display devices based on asymmetric structures according to claim 1, characterized in that, The temperature for the low-temperature bonding method is 140℃.

3. The low-temperature hybrid bonding method for fabricating Micro-LED display devices based on asymmetric structures according to claim 1, characterized in that, The pressure in step 7 is 20 kg.

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