Silicon nitride substrate and preparation method and application thereof

Abstract

The invention belongs to a silicon nitride ceramic substrate, and particularly relates to a silicon nitride substrate with high thermal conductivity and high bending strength as well as a preparation method and application thereof. In order to improve the thermal conductivity and the bending strength of the silicon nitride substrate, simplify the preparation process and reduce the cost, silicon nitride powder, a sintering aid, a dispersing agent, a plasticizer, a binder and the like are mixed according to a specific proportion, and the silicon nitride substrate with the high thermal conductivity and the high bending strength is prepared through tape casting, glue discharging, pre-sintering, sintering and annealing treatment. According to the silicon nitride substrate, a nitrogen and carbon dioxide glue discharging and pre-sintering integrated technology is adopted, so that a green body is not prone to oxidation, the residual carbon amount is low, and the sintering heat conductivity and densification are improved; in addition, the pre-sintered green body has certain strength and is not prone to being broken when transferred into a sintering furnace, and the product yield is increased. And meanwhile, by adopting the annealing process, the silicon nitride substrate has high heat conductivity and high bending strength. The method is simple and low in raw material cost, and can be widely applied to the field of semiconductor device preparation.

Description

Technical Field

[0001] The present invention relates to a silicon nitride ceramic substrate, and in particular to a silicon nitride substrate with high thermal conductivity and high bending strength, and a preparation method and application thereof. Background Art

[0002] Silicon nitride ceramic substrates, due to their combination of high thermal conductivity, mechanical strength, and electrical insulation, are excellent heat dissipation substrate materials and are widely used in high-power semiconductor devices. Currently, commercially available silicon nitride substrates typically have a thermal conductivity of 80 W / (m·K) and a flexural strength of approximately 700 MPa. As electronic components continue to move toward greater integration, miniaturization, and higher power, higher requirements are being placed on the heat dissipation and mechanical properties of silicon nitride substrates.

[0003] At present, the common methods to improve the thermal conductivity of silicon nitride substrates are: 1) adding non-oxides such as nitride, fluoride, SiC, silicated graphite, BeO or sintering aids with high thermal conductivity; 2) using a combination of three or more composite sintering aids; 3) using molding techniques such as molding (dry pressing), molding + isostatic pressing, and casting + isostatic pressing to increase the initial density of the green body; 4) using vacuum, air, nitrogen, nitrogen + air and other protective atmospheres for debinding; 5) using higher temperatures (≥1900°C) and long-term heat preservation (≥24 h) to promote grain growth; 6) using hot pressing and hot isostatic pressing techniques to further increase the density and thus improve thermal conductivity.

[0004] However, the above preparation methods have their own disadvantages: 1) The preparation process of sintering aids such as nitrides, fluorides, SiC, silicated graphite, BeO, etc. is complicated, the market price is expensive, and the storage conditions of some aids are harsh, which will greatly increase the cost of product preparation; in addition, products such as BeO and fluorides are biotoxic during the preparation process, which increases the difficulty of occupational health management, safety and environmental protection; 2) The use of 3 or more multi-component mixed sintering aids, a wide variety of sintering aids, and complex preparation operations also increase the difficulty of sintering process control; 3) Although the use of molding (dry pressing) and isostatic pressing technology can obtain green bodies with higher initial density in order to obtain high sintering density and thermal conductivity, the molding and isostatic pressing methods are cumbersome to operate and have low production capacity, which is not conducive to mass industrial production; 4) Use air debinding , silicon nitride green body is easily oxidized at high temperature, resulting in a decrease in thermal conductivity; in addition, the temperature for air debinding cannot be too high, usually between 500 and 800 ° C. The strength of the debinded green body is low, and it is easy to break when transferred to the sintering furnace, resulting in a low yield rate; however, when using nitrogen atmosphere or vacuum environment for debinding, the binder is often not completely decomposed, and a lot of carbon remains in the green body, which is not conducive to grain growth and densification process during sintering; 5) Although the method of long-term insulation under high temperature conditions can improve thermal conductivity, when the insulation time is too long and the ceramic substrate is over-burned, it will lead to a decrease in density and an increase in pores, thereby reducing the thermal conductivity to a certain extent; in addition, excessive abnormal growth of grains will lead to a decrease in bending strength; 6) The preparation cost of hot pressing and hot isostatic pressing sintering technology is high, and the production capacity is low, which is not conducive to mass production.

[0005] Therefore, there is an urgent need to develop a new silicon nitride ceramic substrate preparation process with high thermal conductivity, flexural strength, low preparation cost, simple operation method, environmental friendliness and conducive to mass production. Summary of the Invention

[0006] In order to solve the technical problems of low thermal conductivity and flexural strength, complex operation, low cost and environmental pollution in the existing silicon nitride ceramic substrate preparation process, the present invention provides a silicon nitride substrate with high thermal conductivity and high flexural strength, low cost, simple operation method, environmental friendliness and conducive to mass production, as well as its preparation method and application.

[0007] To achieve the above application objectives, the technical solutions adopted in this application are as follows: In a first aspect, the present invention provides a method for preparing a silicon nitride substrate, comprising the following steps: Step S1: mixing ceramic powder consisting of 90-97 wt% silicon nitride powder and a sintering aid, a solvent, and a dispersant, and then mixing the mixture with a glue solution prepared by blending a plasticizer, a binder, and a solvent. The mixed slurry is vacuum degassed to obtain a casting slurry. Step S2: tape-casting the tape slurry to obtain a silicon nitride tape; Step S3: cutting the silicon nitride tape to obtain a silicon nitride green body; Step S4: uniformly coating a layer of isolation powder on the surface of the silicon nitride green body; Step S5: Debinding the green compact after applying the isolation powder in a nitrogen atmosphere and pre-sintering it in a carbon dioxide atmosphere; Step S6: sintering the pre-sintered green body to obtain a silicon nitride ceramic substrate; Step S7: annealing the sintered silicon nitride ceramic substrate.

[0008] In step S1, the mass fraction of silicon nitride powder in the ceramic powder is 93-96 wt%.

[0009] Preferably, the α-phase content of the silicon nitride powder is ≥90%.

[0010] Preferably, the sintering aid is a binary mixture of alkaline earth metal oxide and rare earth oxide in a mass ratio of (1-4):(1-4).

[0011] Preferably, the alkaline earth metal oxide is magnesium oxide or calcium oxide.

[0012] Preferably, the rare earth oxide is yttrium oxide, ytterbium oxide or lanthanum oxide.

[0013] Wherein, in step S1, the contents of the dispersant, plasticizer, binder and solvent are 0.5-3%, 4-15%, 4-15% and 60-80% of the mass of the ceramic powder, respectively.

[0014] Preferably, 1 / 3 to 1 / 2 of the solvent is used for dispersing the ceramic powder, and the remaining amount is used for forming the glue solution. The solvent is a mixture of butanone and anhydrous ethanol in a mass ratio of 1:1 to 3.

[0015] Preferably, the dispersant is selected from at least one of castor oil phosphate, fish oil, polyethylene glycol or polyvinyl pyrrolidone.

[0016] Preferably, the plasticizer is selected from at least one of dibutyl phthalate, butyl benzyl phthalate, glycerol or dioctyl phthalate.

[0017] Preferably, the binder is selected from at least one of polyvinyl butyral, polymethyl methacrylate or polyethylene terephthalate.

[0018] Wherein, in step S1, the solid content of the casting slurry after vacuum degassing treatment is 50-80%.

[0019] Wherein, in step S2, the thickness of the dried silicon nitride green tape is 0.4-1.0 mm.

[0020] In step S3, the length and width dimensions of the silicon nitride green body are 240 mm*180 mm.

[0021] Wherein, in step S4, the isolation powder is boron nitride powder.

[0022] In step S5, during nitrogen debinding, the debinding temperature is 550-750° C., and the holding time is 2-10 h.

[0023] Wherein, in step S5, during pre-sintering under carbon dioxide, the pre-sintering temperature is 750-1000° C., and the holding time is 2-10 h.

[0024] Wherein, in step S6, the sintering temperature is 1850-1900° C., and the holding time is 2-10 h.

[0025] Wherein, in step S6, the sintering atmosphere is nitrogen, and the gas pressure is 0.5-5 MPa.

[0026] Wherein, in step S7, the annealing temperature is 1500-1750° C., and the holding time is 0.5-5 h.

[0027] In step S7, the annealing atmosphere is nitrogen, and the pressure is 0.1-3 MPa.

[0028] In a second aspect, the present invention provides a silicon nitride substrate prepared by the above preparation method.

[0029] The silicon nitride substrate has a thermal conductivity of 95 to 120 W / (m•K) and a bending strength of 720 to 790 MPa.

[0030] In a third aspect, the present invention provides an application of the prepared silicon nitride substrate in the preparation of semiconductor devices.

[0031] Beneficial Effects: The present invention combines silicon nitride powder, sintering aids, and other organic additives (dispersants, plasticizers, binders, and solvents) in specific proportions, followed by tape casting, binder removal, pre-sintering, sintering, and annealing to produce a silicon nitride substrate with high thermal conductivity and high flexural strength. This silicon nitride substrate utilizes a nitrogen and carbon dioxide debinding and pre-sintering process, which prevents oxidation and reduces residual carbon content, facilitating improved thermal conductivity and densification during sintering. Furthermore, the pre-sintered green body possesses a certain strength, preventing breakage during transfer to the sintering furnace and improving product yield.

[0032] The method of the present invention eliminates the complex isostatic pressing process and replaces the inefficient dry pressing, hot pressing, and hot isostatic pressing techniques. By combining specific ratios of raw materials and additives with debinding pre-sintering in nitrogen and carbon dioxide, combined with optimized gas pressure sintering, annealing temperatures, and holding times, a silicon nitride substrate with a high thermal conductivity of 95-120 W / (m•K) and a high flexural strength of 720-790 MPa is produced. The substrate exhibits a dense microstructure with no significant pores, a predominant β phase, and no α-phase diffraction peaks. Furthermore, the raw materials used and the process steps are simple, resulting in low production costs. Silicon nitride substrates produced using the method of the present invention are expected to be widely manufactured and applied in electronic devices such as semiconductors. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a cross-sectional SEM image of the silicon nitride substrate prepared in Example 1 of the present invention; Figure 2 XRD pattern of the silicon nitride substrate prepared in Example 1 of the present invention; Figure 3 This is a cross-sectional SEM image of the silicon nitride substrate prepared in Example 2 of the present invention; Figure 4 XRD pattern of the silicon nitride substrate prepared in Example 2 of the present invention; Figure 5 This is a cross-sectional SEM image of the silicon nitride substrate prepared in Example 3 of the present invention; Figure 6 XRD pattern of the silicon nitride substrate prepared in Example 3 of the present invention; Figure 7 This is a cross-sectional SEM image of the silicon nitride substrate prepared in Example 4 of the present invention; Figure 8 XRD pattern of the silicon nitride substrate prepared in Example 4 of the present invention; Figure 9 XRD pattern of the silicon nitride substrate prepared in Comparative Example 1 of the present invention; Figure 10 This is a backscattered SEM image of the surface of the silicon nitride substrate prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0034] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clear, the application is further described in detail below in conjunction with the embodiments. Unless otherwise defined, all scientific and technical terms used herein have the same meanings as understood by ordinary technicians in this field.

[0035] In one embodiment of the present invention, a method for preparing a silicon nitride substrate is provided, comprising the following steps: Step S1: mixing ceramic powder consisting of 90-97 wt% silicon nitride powder and a sintering aid, a solvent, and a dispersant, and then mixing the mixture with a glue solution prepared by blending a plasticizer, a binder, and a solvent. The mixed slurry is vacuum degassed to obtain a casting slurry. Step S2: tape-casting the tape slurry to obtain a silicon nitride tape; Step S3: cutting the silicon nitride tape to obtain a silicon nitride green body; Step S4: uniformly coating a layer of isolation powder on the surface of the silicon nitride green body; Step S5: Debinding the green compact after applying the isolation powder in a nitrogen atmosphere and pre-sintering it in a carbon dioxide atmosphere; Step S6: sintering the pre-sintered green body to obtain a silicon nitride ceramic substrate; Step S7: annealing the sintered silicon nitride ceramic substrate.

[0036] In some specific embodiments of the present invention, the α-phase content of the silicon nitride powder is ≥90%.

[0037] In some specific embodiments of the present invention, the sintering aid is a binary mixture of alkaline earth metal oxide and rare earth oxide in a mass ratio of (1-4):(1-4).

[0038] Preferably, the alkaline earth metal oxide is magnesium oxide or calcium oxide. Although aluminum oxide is also an alkaline earth metal oxide, the use of aluminum oxide will significantly reduce the thermal conductivity of silicon nitride ceramics. Therefore, magnesium oxide or calcium oxide is preferred in the present invention.

[0039] Preferably, the rare earth oxide is yttrium oxide, ytterbium oxide or lanthanum oxide.

[0040] In some specific embodiments of the present invention, the contents of the dispersant, plasticizer, binder and solvent are 0.5-3%, 4-15%, 4-15% and 60-80% of the mass of the ceramic powder, respectively.

[0041] In some specific embodiments of the present invention, 1 / 3 to 1 / 2 of the solvent is used to disperse the ceramic powder, with the remainder used to form the glue solution. The solvent is a mixture of butanone and anhydrous ethanol in a mass ratio of 1:(1-3). Both butanone and anhydrous ethanol are solvents that can fully dissolve all material components while also being inexpensive and low in toxicity.

[0042] In some specific embodiments of the present invention, the dispersant is selected from at least one of castor oil phosphate, fish oil, polyethylene glycol or polyvinyl pyrrolidone.

[0043] In some specific embodiments of the present invention, the plasticizer is selected from at least one of dibutyl phthalate, butyl benzyl phthalate, glycerol or dioctyl phthalate.

[0044] In some specific embodiments of the present invention, the binder is selected from at least one of polyvinyl butyral, polymethyl methacrylate, and polyethylene terephthalate.

[0045] In some specific embodiments of the present invention, in step S1, the solid content of the casting slurry after vacuum degassing is 50-80%.

[0046] In some specific embodiments of the present invention, in step S2, the thickness of the dried silicon nitride green tape is 0.4-1.0 mm.

[0047] In some specific embodiments of the present invention, in step S3, the length and width dimensions of the silicon nitride green body are 240 mm*180 mm.

[0048] In some specific embodiments of the present invention, in step S4, the isolation powder is boron nitride powder.

[0049] In some specific embodiments of the present invention, in step S5, during nitrogen debinding, the debinding temperature is 550-750°C and the holding time is 2-10 hours. At this temperature and holding time, most organic substances such as dispersants, binders, and plasticizers in the green body can be fully decomposed.

[0050] In some specific embodiments of the present invention, during pre-sintering under carbon dioxide in step S5, the pre-sintering temperature is 750-1000°C, and the holding time is 2-10 hours. The advantages of using these parameters are: 1) the reaction temperature between carbon dioxide and residual carbon needs to be >750°C to ensure that the residual carbon in the green body can fully react with the carbon dioxide during nitrogen debinding; 2) this temperature range ensures higher green body strength, facilitating transfer to the sintering furnace without breakage.

[0051] In some specific embodiments of the present invention, in step S6, the sintering temperature is 1850-1900°C, and the holding time is 2-10 hours. Low sintering temperatures or short holding times can easily result in loose sintering and poor performance. High sintering temperatures or long holding times can cause overburning of the substrate and result in undesirable appearance, such as black spots and edges.

[0052] In some specific embodiments of the present invention, in step S6, the sintering atmosphere is nitrogen at a pressure of 0.5 to 5 MPa. Silicon nitride ceramics generally decompose at temperatures around 1800°C, which is not conducive to the sintering and densification of the product. Therefore, a certain amount of pressure must be applied during the sintering process of the silicon nitride ceramic substrate. If no pressure is applied or the pressure is too low, the product structure will not be dense, and properties such as thermal conductivity and flexural strength will be reduced. Because the gas pressure sintering furnace is a pressure vessel, if the pressure is too high, it will increase safety risks.

[0053] In some specific embodiments of the present invention, in step S7, the annealing temperature is 1500-1750°C and the holding time is 0.5-5 hours. If the annealing temperature is too low, the bending strength will be reduced to a certain extent; if the annealing temperature is too high, there will be excess heat.

[0054] In some specific embodiments of the present invention, in step S7, the annealing atmosphere is nitrogen, and the pressure is 0.1-3 MPa.

[0055] Specific examples will be listed below to explain the scheme of the present invention. Those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not specified in the examples, they are carried out according to the techniques or conditions described in the literature in this area or according to the product specifications. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0056] Example Preparation of Silicon Nitride Substrate Step S1: After mixing ceramic powder, solvent, and dispersant, the mixture is mixed with a glue solution prepared by blending plasticizer, binder, and solvent (the amount of solvent used in the dispersion stage is 1 / 3 of the total solvent amount, and the remaining amount is used for sol). The mixed slurry is vacuum degassed to obtain a casting slurry with a certain solid content; the amount of component addition and slurry information are shown in Table 1.

[0057] In Example 1, the ceramic powder is 93% silicon nitride powder and a sintering aid, and the contents of the dispersant, plasticizer, binder, and solvent are 2%, 9%, 10%, and 70% of the mass of the ceramic powder, respectively. In Example 2, the ceramic powder is 94% silicon nitride powder and a sintering aid, and the contents of the dispersant, plasticizer, binder, and solvent are 2%, 10%, 8%, and 70% of the mass of the ceramic powder, respectively. In Example 3, the ceramic powder is 93% silicon nitride powder and a sintering aid, and the contents of the dispersant, plasticizer, binder, and solvent are 3%, 12%, 13%, and 80% of the mass of the ceramic powder, respectively. Among them, in Example 4, the ceramic powder is 90% silicon nitride powder and sintering aid, and the contents of the dispersant, plasticizer, binder and solvent are 0.5%, 8%, 9% and 65% of the mass of the ceramic powder, respectively.

[0058] Table 1 Raw material components and contents in different experimental groups

[0059] Note: The solid content mentioned above refers to the solid content of the slurry after degassing.

[0060] Step S2: pumping the casting slurry into a casting machine for casting, to obtain a silicon nitride casting green tape with a dry thickness of 0.5 mm (Examples 1 and 2), 0.8 mm (Example 3), and 0.4 mm (Example 4); Step S3: cutting the silicon nitride green tape into square pieces with a length and width of 240 mm*180 mm to obtain silicon nitride green compacts; Step S4: uniformly coating a layer of boron nitride isolation powder on the surface of the silicon nitride green body; Step S5: placing the green body after the isolation powder coating into a debinding furnace for debinding and pre-sintering; the debinding atmosphere is nitrogen, and the debinding temperature and holding time are shown in Table 2; the pre-sintering atmosphere is carbon dioxide, which is used to react with a small amount of residual carbon in the nitrogen atmosphere to generate CO gas and discharge it; the pre-sintering temperature and holding time are shown in Table 2; Step S6: Transfer the pre-sintered green body to a sintering furnace for sintering to obtain a silicon nitride ceramic substrate. The sintering temperature and holding time are shown in Table 2. The atmosphere is nitrogen and the pressure is shown in Table 2. Step S7: annealing the sintered silicon nitride substrate in nitrogen. The annealing temperature, holding time, and pressure are shown in Table 2.

[0061] Table 2 Main process parameters for preparing silicon nitride substrates in different experimental groups

[0062] As shown in Table 3, the residual carbon content of the silicon nitride pre-sintered green bodies prepared in Examples 1 to 4 was 0.05%, 0.03%, 0.02% and 0.04%, respectively. The thermal conductivity of the sintered substrates was 105 W / (m•K), 113.5 W / (m•K), 108.4 W / (m•K) and 95.6 W / (m•K), respectively. The flexural strength was 750 MPa, 764 MPa, 723 MPa and 786 MPa, respectively. The substrate fragmentation rates were 0.5%, 0.6%, 0.3% and 0.6%, respectively. Figure 1 、 3 , 5, and 7 show that the microstructure of the prepared nitrided substrate is dense and no obvious pores are generated; Figure 2 、 4 , 6, and 8 show that the main phase of the silicon nitride substrate is β phase, and no α phase diffraction peak is found, indicating that the phase transformation during the sintering process is complete.

[0063] Table 3 Properties of silicon nitride substrates prepared in the experimental group

[0064] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the addition amounts of ceramic powders silicon nitride, magnesium oxide, and yttrium oxide are 85 g, 10 g, and 5 g, respectively. The other technical solutions are the same as those in Example 1. In this comparative example, the carbon content of the silicon nitride pre-sintered green body prepared is 0.03%, the thermal conductivity of the sintered substrate is 75 W / (m·K), the flexural strength is 650 MPa, and the substrate fragmentation rate is 0.5%. Figure 9 It can be seen that in addition to β-phase silicon nitride, the prepared nitride substrate also contains a second phase formed by sintering. A large amount of second phase will be enriched at the grain boundaries and triangular grain boundaries, which will attenuate both thermal conductivity and bending resistance.

[0065] Comparative Example 2 Comparative Example 2 differs from Example 2 in that the debinding and pre-sintering atmospheres are both nitrogen, the sintering hold time is 72 h, the annealing temperature is 1350°C, and the hold time is 0.5 h. Other technical solutions are the same as Example 2. In this comparative example, the residual carbon content of the silicon nitride pre-sintered body is 0.1%, the thermal conductivity of the sintered substrate is 119.3 W / (m·K), the flexural strength is only 460 MPa, and the substrate fragmentation rate is 0.5%. Although long-term holding at high temperature can improve thermal conductivity, overburning significantly reduces flexural strength.

[0066] Comparative Example 3 Comparative Example 3 differs from Example 3 in that the sintering aid magnesium oxide is replaced by aluminum oxide, and the other technical solutions are the same as Example 3. The silicon nitride pre-sintered body prepared in this comparative example has a residual carbon content of 0.02%. After sintering, the substrate has a thermal conductivity of only 38.4 W / (m·K), a flexural strength of 762 MPa, and a substrate fragmentation rate of 0.4%.

[0067] Comparative Example 4 The difference between Comparative Example 4 and Example 4 is that the atmosphere for debinding and pre-sintering is air, the sintering temperature is 1840°C, and the holding time is 1.5 h; the annealing temperature is 1300°C, and the holding time is 15 min. Other technical solutions are the same as Example 4. In this comparative example, the residual carbon content of the silicon nitride pre-sintered green body is 0.02%, the thermal conductivity of the substrate after sintering is 65 W / (m·K), the flexural strength is only 580 MPa, and the substrate fragmentation rate is 0.4%. Figure 10It can be seen that the microstructure of the prepared nitride substrate is not completely dense, there are many pores, and some grains are not fully developed and grown.

Claims

1. A method for preparing a silicon nitride substrate, characterized in that: The following steps are involved: Step S1: mixing ceramic powder consisting of 90-97 wt% silicon nitride powder and a sintering aid, a solvent, and a dispersant, and then mixing the mixture with a glue solution prepared by blending a plasticizer, a binder, and a solvent. The mixed slurry is vacuum degassed to obtain a casting slurry. Step S2: tape-casting the tape slurry to obtain a silicon nitride tape; Step S3: cutting the silicon nitride tape to obtain a silicon nitride green body; Step S4: uniformly coating a layer of isolation powder on the surface of the silicon nitride green body; Step S5: Debinding the green compact after applying the isolation powder in a nitrogen atmosphere and pre-sintering it in a carbon dioxide atmosphere; Step S6: sintering the pre-sintered green body to obtain a silicon nitride ceramic substrate; Step S7: annealing the sintered silicon nitride ceramic substrate.

2. The method for preparing a silicon nitride substrate according to claim 1, wherein: The sintering aid is a binary mixture of an alkaline earth metal oxide and a rare earth oxide in a mass ratio of (1-4):(1-4), wherein the alkaline earth metal oxide is magnesium oxide or calcium oxide; and the rare earth oxide is yttrium oxide, ytterbium oxide or lanthanum oxide.

3. The method for preparing a silicon nitride substrate according to claim 1, wherein: In step S1 , the contents of the dispersant, plasticizer, binder and solvent are 0.5-3%, 4-15%, 4-15% and 60-80% of the mass of the ceramic powder, respectively.

4. The method for preparing a silicon nitride substrate according to claim 1, wherein: Meet at least one of the following: The solvent is a mixture of butanone and anhydrous ethanol in a mass ratio of 1:(1-3); The dispersant is selected from at least one of castor oil phosphate, fish oil, polyethylene glycol or polyvinyl pyrrolidone; The plasticizer is selected from at least one of dibutyl phthalate, butyl benzyl phthalate, glycerol or dioctyl phthalate; The binder is selected from at least one of polyvinyl butyral, polymethyl methacrylate or polyethylene terephthalate.

5. The method for preparing a silicon nitride substrate according to claim 1, wherein: In step S1, the solid content of the casting slurry after vacuum degassing treatment is 50-80%.

6. The method for preparing a silicon nitride substrate according to claim 1, wherein: In step S5, during debinding under nitrogen, the debinding temperature is 550-750° C., and the holding time is 2-10 h; during pre-sintering under carbon dioxide, the pre-sintering temperature is 750-1000° C., and the holding time is 2-10 h.

7. The method for preparing a silicon nitride substrate according to claim 1, wherein: In step S6, the sintering temperature is 1850-1900° C., the holding time is 2-10 h; the sintering atmosphere is nitrogen, and the pressure is 0.5-5 MPa.

8. The method for preparing a silicon nitride substrate according to claim 1, wherein: In step S7, the annealing temperature is 1500-1750° C., and the holding time is 0.5-5 h; the annealing atmosphere is nitrogen, and the pressure is 0.1-3 MPa.

9. The silicon nitride substrate according to any one of claims 1 to 8.

10. Use of the silicon nitride substrate according to claim 9 in the preparation of semiconductor devices.

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