Temporary bonding method for laser lift-off of Mini / MicroLED whole-surface chip structure and supporting structure of Mini / MicroLED whole-surface chip structure

Abstract

The invention relates to the technical field of semiconductor manufacturing, in particular to a high-yield and crack-free temporary bonding method for laser lift-off of a Mini / MicroLED COW whole-surface chip structure. According to the method, a composite membrane material composed of double-sided acrylic UV viscosity-reducing glue and a PET rigid base material is adopted. And high pressure is applied in a vacuum environment to complete bonding of the temporary substrate and the COW, so that large-area and high-density embedding of the acrylic acid adhesive layer and the surface structure of the chip is realized. And carrying out UV exposure to promote the phase change of the acrylic adhesive layer, and curing the acrylic adhesive layer from an initial soft viscoelastic state to a high-modulus hard acrylic support structure. The hard supporting surface and the vacuum embedded structure act together, so that excellent internal stress resistance is provided, and cracks in laser lift-off and subsequent processes are effectively prevented. Meanwhile, after the cured structure is subjected to subsequent permanent bonding, the visbreaking layer can be activated through simple UV irradiation, and residue-free and easy-to-separate de-bonding of the temporary substrate and the PET film material is realized.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a temporary bonding method for a laser lift-off (LLO) process applied to the entire surface structure of a Mini / Micro LED wafer-level chip (COW). Background Art

[0002] 1. Laser lift-off (LLO) requirements Laser lift-off technology uses a high-energy laser beam to decompose the buffer layer at the interface between GaN and the sapphire substrate. It is a key step in separating the Mini / MicroLED epitaxial layer from the sapphire substrate.

[0003] 2. Challenges of Full-Surface Structure: Mini / MicroLEDs in a COW state typically have a chip structure consisting of a continuous full-surface film layer, including a GaN epitaxial layer, a SiO2 dielectric layer, a DBR layer, etc. Such film layers typically accumulate significant internal stress during the growth / deposition process.

[0004] 3. Deficiencies of existing temporary bonding technology:

[0005] Polyimide (PI) adhesive: The widely used PI adhesive usually requires an additional laser stripping step during subsequent debonding, and is prone to producing a large amount of difficult-to-clean adhesive residue, resulting in a complex process and increased costs.

[0006] Double-sided acrylic UV detackifying adhesive: Although debonding is relatively convenient (using UV detackifying), in the absence of an effective supporting structure, this type of soft adhesive is difficult to resist the release of stress within the film layer during the laser stripping process or subsequent processing, and can easily induce large-area stress cracks, film fractures, and even chip structure detachment, resulting in low yield and inability to support subsequent processes. Summary of the Invention

[0007] The purpose of the present invention is to provide a temporary bonding solution that can effectively support the entire chip structure film layer with high internal stress (such as GaN epitaxial layer, SiO2 dielectric layer, DBR layer, etc.) during the laser lift-off process to prevent stress cracks and achieve high yield and residue-free transfer to the subsequent permanent bonding process, so as to solve the problems raised in the above background technology.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a temporary bonding method for laser lift-off of a Mini / MicroLED full-surface chip structure, comprising the following steps:

[0009] S1. Provide composite film material: Lay the PET rigid substrate coated with acrylic UV adhesive on both sides on the temporary bonding substrate;

[0010] S2. Vacuum high-pressure bonding: Under vacuum conditions, the composite film is applied to the entire COW structure, including the GaN epitaxial layer, metal electrode layer, dielectric layer, DBR layer, and the patterned sapphire substrate surface, and a pressure of 50-2000 kPa is applied to embed the acrylic adhesive layer into the surface microstructure.

[0011] S3, UV in-situ curing: irradiating UV light through the temporary substrate to transform the acrylic adhesive layer into a high modulus rigid acrylic support shell;

[0012] S4, laser lift-off: Laser lift-off is performed from the patterned sapphire substrate side to obtain a crack-free entire chip structure film;

[0013] S5, UV debonding: After permanent bonding, UV light is irradiated to activate the adhesion-reducing layer and remove the temporary substrate and composite film material.

[0014] Preferably, the initial elastic modulus of the acrylic UV viscosity-reducing adhesive is less than 10 MPa, and the modulus after UV curing is greater than 1 GPa.

[0015] Preferably, the vacuum high pressure bonding environment pressure is ≤10 -3 Pa, bonding time 30-180 seconds.

[0016] The composite support structure includes, from bottom to top: a temporary bonding substrate;

[0017] First acrylic UV adhesive layer;

[0018] PET rigid substrate (thickness 20-100μm);

[0019] Second acrylic UV adhesive layer;

[0020] After UV curing, the two layers of acrylic adhesive form a rigid acrylic support shell covering the PET substrate.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a high-yield, crack-free temporary bonding method for laser peeling of Mini / MicroLED COW full-surface chip structures. The method uses a composite film material composed of "double-sided acrylic UV detackifying adhesive + PET rigid substrate". High pressure is applied in a vacuum environment to complete the bonding of the temporary substrate and COW, so that the acrylic adhesive layer and the chip surface structure can be embedded in a large area and high density. UV exposure is then carried out to cause the acrylic adhesive layer to undergo a phase change, solidifying from the initial soft viscoelastic state to a hard acrylic support structure with a high modulus. The hard support surface and the vacuum embedded structure work together to provide excellent resistance to internal stress, effectively preventing cracks in laser peeling and subsequent processes. At the same time, after the cured structure is permanently bonded, the detackifying layer can be activated by simple UV irradiation, achieving residue-free and easy-to-separate debonding of the temporary substrate and the PET film material. This method significantly improves the full-surface peeling yield (>99%), eliminates the risk of cracks, and avoids the complicated laser debonding and residual adhesive cleaning steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a COW structure diagram of the present invention;

[0025] Figure 2 A structural view of a temporary substrate according to the present invention;

[0026] Figure 3 This is a structural diagram of the viscosity-reducing adhesive and the temporary substrate of the present invention;

[0027] Figure 4 This is a structural diagram of the COW and the temporary substrate after bonding via UV viscosity-reducing adhesive;

[0028] Figure 5 This is a structural diagram of UV exposure after temporary bonding of the present invention;

[0029] Figure 6 This is a structural view of the COW chip structure after peeling off.

[0030] Description of reference numerals:

[0031] 1. GaN epitaxial layer; 2. Metal electrode layer; 3. Dielectric layer and DBR layer; 4. Patterned sapphire substrate; 5. Temporary bonding substrate; 6. Acrylic UV adhesive; 7. PET substrate; 8. UV light source. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] See also Figures 1 to 6 , the present invention provides a technical solution:

[0034] A temporary bonding method for laser lift-off of a Mini / MicroLED full-surface chip structure, comprising the following steps:

[0035] S1. Providing a composite film material: Laminating a PET rigid substrate 7 coated on both sides with acrylic UV viscosity-reducing adhesive to a temporary bonding substrate 5;

[0036] S2. Vacuum high-pressure bonding: Under vacuum, the composite film is covered on the entire surface of the COW structure, including the GaN epitaxial layer 1, the metal electrode layer 2, the dielectric layer and the DBR layer 3, and the surface of the patterned sapphire substrate 4. A pressure of 50-2000 kPa is applied to embed the acrylic adhesive layer 6 into the surface microstructure.

[0037] S3, UV in-situ curing: irradiating UV light 8 through the temporary substrate 5 to transform the acrylic adhesive layer 6 into a high modulus rigid acrylic support shell;

[0038] S4, laser lift-off: laser lift-off is performed from the patterned sapphire substrate 4 side to obtain a crack-free entire chip structure film;

[0039] S5, UV debonding: After permanent bonding, UV light is irradiated to activate the adhesion-reducing layer, and the temporary substrate 5 and the composite film material are removed.

[0040] The initial elastic modulus of the acrylic UV viscosity-reducing adhesive is less than 10 MPa, and the modulus after UV curing is greater than 1 GPa.

[0041] Vacuum high pressure bonding environment pressure ≤10 -3 Pa, bonding time 30-180 seconds.

[0042] The composite support structure comprises, from bottom to top: a temporary bonding substrate 5;

[0043] First acrylic UV adhesive layer 6;

[0044] PET rigid substrate 7 (thickness 20-100 μm);

[0045] Second acrylic UV adhesive layer 6;

[0046] After UV curing, the two layers of acrylic adhesive form a rigid acrylic support shell covering the PET substrate.

[0047] Through vacuum high-pressure bonding + UV in-situ curing, the double-sided acrylic adhesive / PET composite film is transformed into a rigid support:

[0048] Vacuum high pressure fitting, such as Figure 4 As shown:

[0049] Apply 50-2000kPa pressure in a vacuum environment of ≤10-3Pa to completely fill the COW surface microstructure with acrylic glue 6, eliminate bubbles and form a mechanical lock.

[0050] UV phase change mechanisms, such as Figure 5 As shown:

[0051] UV irradiation triggers a photocuring reaction, and the elastic modulus of the acrylic adhesive 6 increases from <10MPa to >1GPa, forming a rigid acrylic shell covering the PET substrate 7

[0052] Triple anti-cracking mechanism:

[0053] The rigid acrylic shell resists longitudinal stress;

[0054] The PET substrate 7 provides lateral stiffness;

[0055] Dispersed shear stress at the microstructured interface

[0056] LLO yield > 99% (compared to existing technology < 85%);

[0057] Debonding time ≤ 30 seconds, residual glue rate 0%;

[0058] The bending strength of the supporting structure is increased by 5 times

[0059] Key parameters:

[0060] elements Parameter range PET substrate thickness 20-100μm Acrylic adhesive layer thickness on one side 5-50μm Vacuum bonding pressure 50-2000kPa UV curing energy <![CDATA[100-2000mJ / cm 2 ]]>

[0061] Process example (see Figure 3-6 ):

[0062] Attach the composite film (6 / 7 / 6) to the temporary glass substrate ( Figure 3 );

[0063] COW and composite film vacuum high pressure bonding ( Figure 4 );

[0064] UV curing through glass substrate ( Figure 5 );

[0065] Laser peeling of sapphire substrate to obtain complete film ( Figure 6 )

[0066] The present invention aims to overcome the shortcomings of the existing technology and provide a low-cost, high-yield temporary bonding method to solve the following core problems faced by Mini / Micro LED COW full-surface structures during the laser lift-off process:

[0067] a) Stress crack control: effectively supports the entire film layer with high internal stress to prevent cracks or breakage during laser peeling and transfer.

[0068] b) High peeling yield: Achieve high yield (>99%) of damage-free peeling of the entire surface structure.

[0069] Simplified debonding and no residue: Avoid the use of expensive PI laser debonding equipment, making the debonding process simple, fast and without residual adhesive residue.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A temporary bonding method for laser lift-off of a Mini / MicroLED full-surface chip structure, characterized in that: The following steps are involved: S1. Providing a composite film material: Laminating a PET rigid substrate (7) coated on both sides with acrylic UV adhesive to a temporary bonding substrate (5); S2, vacuum high-pressure bonding: in a vacuum environment, the composite film material is covered on the entire surface of the COW structure, including the GaN epitaxial layer (1), the metal electrode layer (2), the dielectric layer and the DBR layer (3) and the surface of the patterned sapphire substrate (4), and a pressure of 50-2000 kPa is applied to embed the acrylic adhesive layer (6) into the surface microstructure; S3, UV in-situ curing: irradiating UV light (8) through the temporary substrate (5) to transform the acrylic adhesive layer (6) into a high modulus rigid acrylic support shell; S4, laser lift-off: performing laser lift-off from the patterned sapphire substrate (4) side to obtain a crack-free entire chip structure film; S5. UV debonding: After permanent bonding, UV light is irradiated to activate the adhesion-reducing layer and remove the temporary substrate (5) and the composite film material.

2. The temporary bonding method for laser lift-off of a full-surface Mini / MicroLED chip structure according to claim 1, characterized in that: The initial elastic modulus of the acrylic UV viscosity-reducing adhesive is less than 10 MPa, and the modulus after UV curing is greater than 1 GPa.

3. The temporary bonding method for laser lift-off of a full-surface Mini / MicroLED chip structure according to claim 1, characterized in that: Vacuum high pressure bonding environment pressure ≤10 -3 Pa, bonding time 10-180 seconds.

4. A composite support structure for use in the method of claim 1, characterized in that From bottom to top, it includes: a temporary bonding substrate (5); A first acrylic UV adhesive layer (6); PET rigid substrate (7), thickness 20-100 μm; A second acrylic UV adhesive layer (6); After UV curing, the two layers of acrylic adhesive form a rigid acrylic support shell covering the PET substrate.

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