Seed crystal bonding glue and preparation method and application thereof

Abstract

The invention discloses a seed crystal bonding glue and a preparation method and application thereof, and relates to the field of silicon carbide processing technology. The glue comprises the following components in parts by weight: 40-70 parts of water-based epoxy resin, 30-60 parts of anhydrous ethanol, 0.2-0.5 parts of wetting agent, 0.1-0.3 parts of leveling agent, and 0.2-0.6 parts of silane coupling agent. The glue can be applied to a process of hot pressing curing by spraying. The present invention can solve the use problems of low efficiency, uniform coating, poor bonding quality and poor growth quality of crystals of current seed crystal bonding glue.

Description

Technical Field

[0001] The invention relates to the technical field of silicon carbide processing, and in particular to a seed crystal bonding glue and a preparation method and application thereof. Background Art

[0002] Silicon carbide seed crystal bonding is an important technology in the preparation of semiconductor materials. It uses a specific adhesive to fix the silicon carbide seed crystal to the growth substrate to ensure the quality and uniformity of crystal growth. However, the glue commonly used currently has a series of problems in the use and coating process: Low efficiency: Single-component glue is usually applied evenly to the surface of the seed crystal by manual scraping. This method is not only time-consuming and labor-intensive, but also inefficient and cannot meet the needs of large-scale production. Low yield: The manual scraping method has great instability, which can easily lead to uneven glue coating, thereby affecting the bonding quality of the seed crystal and the growth quality of the crystal. Therefore, the yield is difficult to guarantee.

[0003] Patent document number CN119082851A provides a silicon carbide seed crystal bonding process and a bonding auxiliary device, including the following steps: S1, material preparation: prepare the bearing base to be bonded, the positioning tooling for positioning, and the bonding glue; S2, bonding positioning: the bearing base is positioned and fixed by the positioning tooling, and the bonding area of ​​the auxiliary tube and the upper end of the bearing base is positioned; S3, glue spraying: the bonding glue is sprayed in the bonding area of ​​the upper end of the bearing base; S4, glue leveling: the auxiliary tube is controlled to be pressed against the upper end of the bearing base, and the air blowing device is controlled to blow gas toward the surface of the bonding glue while controlling the directional rotation of the air blowing device; S5, vacuum exhaust: after the glue is leveled, the auxiliary tube is vacuumed through the vacuum pipe to accelerate the discharge of bubbles in the glue; S6, seed crystal bonding. This invention solves the technical problem of uniform and flat silicon carbide seed crystal bonding glue, and the glue leveling is processed in a non-contact manner, thereby improving the efficiency of seed crystal bonding. However, the above process steps are complicated and require an additional vacuum pumping device.

[0004] Patent document number CN118147755A relates to a method for bonding silicon carbide seed crystals, which method includes the following steps: preparing bonding glue, the components of the bonding glue include resin, filler and additives; preheating, vacuumizing and reheating the prepared bonding glue; bonding the silicon carbide seed crystal to the graphite holder with the bonding glue and baking the bonding glue during the bonding process. By separately preparing a bonding glue with a high residual carbon content to improve the bonding effect of the silicon carbide seed crystal at high temperature, the subsequent silicon carbide single crystal growth process is made more stable; at the same time, by pretreating the bonding glue before bonding and cooperating with the baking operation during the bonding process, the gas and volatile substances in the bonding glue can be reduced as much as possible, so that the glue layer can only volatilize very small bubbles or even non-volatile bubbles at high temperature, reducing or avoiding large-area exposure of the back of the silicon carbide seed crystal, and preventing the back of the silicon carbide seed crystal from sublimating or even burning through. However, there are still trace bubbles in the glue layer of the above process during the experiment, which leads to poor ablation. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned background technology, one of the purposes of the present invention is to provide a seed crystal bonding glue, comprising the following components in parts by weight: 40-70 parts of water-based epoxy resin, 30-60 parts of anhydrous ethanol, 0.2-0.5 parts of wetting agent, 0.1-0.3 parts of leveling agent, and 0.2-0.6 parts of silane coupling agent. The scheme adopts 40-70 parts of water-based epoxy resin as the main adhesive, and its excellent water dispersibility and film-forming property ensure that the glue can form a uniform and dense bonding layer between the seed crystal and the graphite paper, effectively avoiding the bonding weaknesses caused by the uneven distribution of the glue. At the same time, 30-60 parts of anhydrous ethanol are added as a solvent in the formula, which not only helps to improve the fluidity of the glue, making the glue easier to spread evenly on the surface of the seed crystal, but also can quickly evaporate in the subsequent hot pressing process, reduce residue, and further reduce the risk of bubble generation. In addition, the addition of 0.2-0.5 parts of wetting agent significantly enhances the wetting ability of the glue on the surface of the seed crystal and graphite paper, ensuring that the glue can penetrate into tiny gaps and achieve closer contact, thereby improving the bonding strength and uniformity. The introduction of 0.1-0.3 parts of leveling agent promotes the natural leveling of the glue on the surface of the seed crystal by adjusting the surface tension of the glue, further eliminating the uneven thickness that may occur during the coating process. Finally, the addition of 0.2-0.6 parts of silane coupling agent acts as a bridge to connect the graphite paper and the water-based epoxy resin, which not only enhances the interfacial bonding between the two, but also reduces the formation of small bubbles inside the glue and at the interface through its chemical activity, effectively preventing the ablation problem caused by the expansion of bubbles during the hot pressing process.

[0006] Preferably, the water-based epoxy resin is one or more of phenolic epoxy resin, water-based epoxy resin emulsion, and non-ionic amine adduct. Phenolic epoxy resin is known for its high heat resistance, high strength and chemical stability, and can significantly improve the high temperature resistance and mechanical strength of the bonding glue. Water-based epoxy resin emulsion is conducive to the uniform coating of glue between seed crystals and graphite paper due to its good dispersibility and environmental protection, while reducing pollution to the environment. Non-ionic amine adducts have good flexibility and adhesion, which helps to improve the adaptability of glue to surfaces of different materials. Combining one or more of these three types of epoxy resins can give full play to their respective advantages and form a complementary effect, thereby further improving the comprehensive performance of seed crystal bonding glue and ensuring the firmness and stability of bonding.

[0007] Preferably, the water-based epoxy resin is a phenolic epoxy resin and a nonionic amine adduct, and the weight ratio of the two is 1: (0.5-0.8). Combining the phenolic epoxy resin and the nonionic amine adduct in a weight ratio of 1: 0.6 is based on an in-depth understanding and optimization consideration of the performance of both. The high heat resistance and high strength of the phenolic epoxy resin provide a solid foundation for the glue, while the flexibility and adhesion of the nonionic amine adduct can make up for the shortcomings of the phenolic epoxy resin in certain aspects. By precisely controlling the ratio of the two, a balance and optimization of performance can be achieved, so that the glue has high strength and heat resistance while also having good flexibility and adhesion.

[0008] Preferably, the epoxy equivalent of the waterborne epoxy resin is 150-500. The epoxy equivalent of the waterborne epoxy resin is controlled within the range of 150-500 based on comprehensive considerations of the curing speed, crosslinking density and mechanical properties of the glue.

[0009] Preferably, the wetting agent is one or more of EO / EP block copolymer and siloxane twin structure surfactant. EO / EP block copolymer has a good balance of hydrophilicity and lipophilicity, and can form a uniform wetting layer on the surface of the seed crystal and graphite paper, which helps to evenly coat the glue between the two. The siloxane twin structure surfactant can form a stable adsorption layer at the interface due to its unique molecular structure, reduce surface tension, further promote the wetting and penetration of the glue, and help to discharge the bubbles originally between the glue and the bonding surface.

[0010] Preferably, the leveling agent is one or more of polyacrylate and anionic emulsifier. Polyacrylate has good film-forming and leveling properties, and can form a smooth and uniform film layer on the surface of the glue, which helps to eliminate problems such as uneven thickness and bubbles that may occur during the coating process. The anionic emulsifier, due to its unique molecular structure and charge properties, can form a stable dispersion system inside the glue, prevent particle agglomeration and sedimentation, thereby maintaining the uniformity and stability of the glue, and is conducive to the discharge of bubbles originally between the glue and the bonding surface.

[0011] Preferably, the silane coupling agent is a siloxane organic compound. The silicon-oxygen bond in the siloxane organic compound molecule has a high bond energy and stability, and can form a strong chemical bond between the inorganic material (such as graphite paper) and the organic glue, thereby enhancing the interfacial bonding force between the two. In addition, the siloxane organic compound also has good compatibility and dispersibility, and can form a uniform mixing system with other components in the glue to avoid phase separation and agglomeration.

[0012] Preferably, the viscosity (25°C) of the seed crystal bonding glue is 100-1000mPa.s. The presence of bubbles will affect the uniformity and density of the bonding layer, thereby reducing the bonding strength. The inventors have found through experiments that the glue in this viscosity range can better eliminate bubbles and reduce the generation of bubbles during the spraying process. This is because the glue with moderate viscosity can form stable droplets during spraying, preventing the air inside the droplets from being wrapped in to form bubbles.

[0013] In order to solve the above technical problems, the second object of the present invention is to provide a method for preparing a seed crystal bonding glue, comprising the following steps:

[0014] S0: Dispersing the water-based epoxy resin in the anhydrous ethanol solution according to the ratio, stirring evenly, to obtain a premix;

[0015] S1: adding a wetting agent, a leveling agent, and a silane coupling agent to the premix according to a proportion, and stirring evenly to obtain a mixture;

[0016] S2: Filter the mixture with filter paper to obtain seed crystal bonding glue.

[0017] In order to solve the above technical problems, the third purpose of the present invention provides the use of the above seed crystal bonding glue in hot pressing curing after spraying.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The technical solution of the seed crystal bonding glue of the present invention improves the wettability, leveling and adhesion of the glue and the bonding substrate by optimizing the component ratio, introducing an organic solvent into the glue to dilute the resin, reducing the viscosity, and adding auxiliary agents such as a wetting agent, a leveling agent and a silane coupling agent, thereby improving the bonding quality.

[0020] (2) The seed crystal bonding glue formula of the present invention has low viscosity and good substrate wetting performance, and is suitable for spraying glue film by a glue sprayer. After spraying, the glue film has excellent leveling and adhesion, and the glue film is free of bubbles, which will not cause ablation of the seed crystal during crystal growth.

[0021] (3) The preparation method of the seed crystal bonding glue provided by the present invention is simple and easy to implement, and is suitable for mass production. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with examples. These examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually carried out according to conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets. Any non-substantial changes and substitutions made by those skilled in the art on the basis of the present invention belong to the scope of protection claimed by the present invention.

[0023] The following Table 1 lists the sources and types of raw materials used in the examples and comparative examples of the present application. Unless otherwise specified, the reagents were all commercially available.

[0024] Table 1 - Sources and models of raw materials in the examples of this application

[0025]

[0026]

[0027] Examples 1-9

[0028] A seed crystal bonding glue, whose components and contents are shown in Table 2, includes water-based epoxy resin, anhydrous ethanol, a wetting agent, a leveling agent, and a silane coupling agent.

[0029] The preparation method of the seed crystal bonding glue comprises the following steps: stirring at a speed of

[0030] (1) The preparation temperature is 23±2°C and the humidity is 15%-25%. Anhydrous ethanol is first added according to the ratio, the stirring speed is adjusted to 600 rpm / min, and then the water-based epoxy resin is added. The mixture is dissolved and stirred at room temperature for 10 minutes until it is completely dissolved to obtain a premix;

[0031] (2) adjusting the speed to 1200-1500 rpm / min, slowly adding the wetting agent, leveling agent, and silane coupling agent in a dropwise manner, stirring for 10 min until they are completely dissolved, and obtaining a mixture;

[0032] (3) filtering the mixture of step (2) through qualitative filter paper to remove undissolved impurities in the glue to obtain seed crystal bonding glue.

[0033] Comparative Example 1

[0034] Commercially available seed crystal glue was used as a comparative example.

[0035] Table 2 - Content of each component in Examples 1-7

[0036]

[0037]

[0038] Testing methods;

[0039] Viscosity test method: According to the rotational viscometer method in GB / T 10247-2008, NDJ-5S was used to measure the viscosity of the glue. The prepared glue was placed in a glass bottle at a constant temperature of 25°C for 30 minutes. The instrument parameters were set as follows: rotor 1#, speed 12 rpm, sample time 15s, unit mpa.s. When the sample result was stable, the average value of the test results was taken after three tests and the value was recorded. The test results are shown in Table 3.

[0040] Hot-pressing and curing the adhesive film: The bonding surfaces of the graphite paper and the seed crystal need to be sprayed with isopropyl alcohol solution, wiped clean with a dust-free cloth, and placed in a 60°C oven for 10 minutes. Place the graphite paper and seed crystal sprayed with glue in a drying oven for 10 minutes to remove the solvent, then fit the bonding surfaces together and perform hot-pressing and curing according to the set process. After the hot-pressing and curing of the adhesive film is completed, observe the surface for bubbles, uneven glue spots, and the thickness of the film. It should be noted that due to the high viscosity of the seed crystal glue in Comparative Example 1, the spraying process cannot be used, and only the conventional hand-coating process can be used. The test results are shown in Table 3;

[0041] Surface condition after seed crystal growth: The hot-pressed seed crystal, graphite paper, and crucible cover are used for subsequent crystal growth. When the growth of the silicon carbide crystal is completed, observe whether the surface of the silicon carbide crystal in contact with the glue is ablated. The test results are shown in Table 3.

[0042] The results of the above test method are shown in Table 3.

[0043] Table 3 - Performance test results of embodiments and comparative examples

[0044]

[0045]

[0046] It can be seen from the above table that the viscosity (25°C) of the seed crystal bonding glue prepared in the embodiment of the present invention is 300-850mpa.s. According to the test results of the inventor, the viscosity (25°C) has good spraying performance in the range of 100-1000mpa.s, which can greatly reduce the amount of glue used and greatly improve the production efficiency of glue coating. The hot pressing cured adhesive film is free of bubbles, and after the seed crystal grows, there is no visible ablation on the surface where the silicon carbide crystal and the glue are in contact, and there is no unevenness, and the coating of the adhesive layer is uniform. Moreover, compared with the hand-coating process of comparative example 1, the thickness of the cured adhesive film of the embodiment using spraying is smaller, reaching 0.05-0.1mm, while the thickness of the cured adhesive film of the hand-coating process is generally 0.2-0.3mm. Since the coating thickness can be further reduced, the time consumption of the hot pressing process can be reduced as a whole, from the original 4.5h to 2h.

[0047] From the comparison between Examples 1-3 and Example 4, it can be seen that reducing the proportion of anhydrous ethanol solvent will lead to a moderate decrease in the uniformity of the hot pressing curing adhesive, but has little effect on the crystals grown from the seed crystals.

[0048] The crystal interface fluctuations will lead to inconsistent nitrogen doping concentrations, and the cut wafers will have uneven colors, affecting the yield of subsequent chip production. By comparing Example 5 with Example 4, it can be seen that increasing the proportion of wetting agent and reducing the leveling agent is conducive to further improving the surface flatness of the crystal. The inventor believes that this adjustment not only enhances the wettability and uniform distribution ability of the glue, but also provides more favorable conditions for the growth of the crystal by limiting the excessive flow of the glue. The combined effect of these factors significantly improves the surface flatness of the crystal.

[0049] The film has lines, which means that the film is slightly uneven here, but the degree is relatively minor. Bumps are likely to appear here during crystal growth. From the comparison between Example 7 and Example 8, it can be seen that at the same compounding ratio, the hot press-cured film obtained by the combination of phenolic epoxy resin and non-ionic amine adduct has no lines, the quality of the grown crystals is better, and the surface of the crystals is smoother.

[0050] From the comparison between Example 9 and Example 1, it can be seen that the selection of the twin structure surfactant of siloxane as the wetting agent not only promotes the wetting of the substrate and the penetration of the glue by reducing the surface tension and improving the wetting performance, but also significantly improves the bonding quality and strength by reducing bubble generation and improving the adhesion of the film.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A seed crystal bonding glue, characterized in that: The invention comprises the following components in parts by weight: 40-70 parts of waterborne epoxy resin, 30-60 parts of anhydrous ethanol, 0.2-0.5 parts of wetting agent, 0.1-0.3 parts of leveling agent and 0.2-0.6 parts of silane coupling agent.

2. The seed crystal bonding glue according to claim 1, characterized in that: The waterborne epoxy resin is one or more of phenolic epoxy resin, waterborne epoxy resin emulsion, and non-ionic amine adduct.

3. The seed crystal bonding glue according to claim 2, characterized in that: The waterborne epoxy resin is a phenolic epoxy resin and a non-ionic amine adduct, and the weight ratio of the two is 1: (0.5-0.8).

4. The seed crystal bonding glue according to claim 1, characterized in that: The epoxy equivalent of the waterborne epoxy resin is 150-500.

5. The seed crystal bonding glue according to claim 1, characterized in that: The wetting agent is one or more of EO / EP block copolymer and siloxane twin structure surfactant.

6. The seed crystal bonding glue according to claim 1, characterized in that: The leveling agent is one or more of polyacrylate and anionic emulsifier.

7. The seed crystal bonding glue according to claim 1, characterized in that: The silane coupling agent is a siloxane organic compound.

8. The seed crystal bonding glue according to claim 1, characterized in that: The viscosity (25° C.) of the seed crystal bonding glue is 100-1000 mPa.s.

9. A method for preparing the seed crystal bonding glue according to any one of claims 1 to 8, characterized in that: The following steps are involved: S0: Dispersing the water-based epoxy resin in the anhydrous ethanol solution according to the ratio, stirring evenly, to obtain a premix; S1: adding a wetting agent, a leveling agent, and a silane coupling agent to the premix according to a proportion, and stirring evenly to obtain a mixture; S2: filtering the mixture with filter paper to obtain seed crystal bonding glue.

10. Use of the seed crystal bonding glue as claimed in any one of claims 1 to 8 in hot pressing curing after spraying.

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