Preparation method of silicon nitride substrate and silicon nitride substrate

Abstract

The invention discloses a preparation method of a silicon nitride substrate and the silicon nitride substrate, and belongs to the field of integrated circuit manufacturing, and the preparation method comprises the following steps: S1, ball milling; s2, forming is conducted; s3, degreasing is conducted; s4, sintering: sintering the degreased sheet to form a silicon nitride sintered substrate; the sintering aid contains enstatite microcrystalline glass, a rare earth compound, silicon nitride, enstatite microcrystalline glass and rare earth compound: 88-93 wt% of silicon nitride, 4-7 wt% of enstatite microcrystalline glass and 2-5 wt% of rare earth compound; the enstatite microcrystalline glass is prepared from the following components: 50-55 wt% of raw ore sodium sand, 1-5 wt% of high alumina, 35-40 wt% of calcined talc for blanks, 1-5 wt% of anorthite, 1-5 wt% of potassium feldspar and 1-5 wt% of albite. The bending strength of the silicon nitride ceramic substrate is improved, cracking deformation is avoided, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuit manufacturing, and in particular to a method for preparing a silicon nitride substrate and the silicon nitride substrate. Background Art

[0002] With the rapid development of new energy vehicles, photovoltaics, wind power, integrated circuits, aerospace, 5G communications, and other fields, and the emergence of third-generation semiconductors, such as SiC and GaN, power electronics are gradually moving towards high power, integration, high frequency, high voltage, and high current. Ceramic substrates serve as chip supports, electrical insulation, and thermal pathways. In the thermal path, the substrate has the highest thermal resistance and must transfer heat to the package housing in a timely manner, requiring high thermal conductivity. Ceramic substrates also need to withstand thermal stresses caused by thermal cycling and temperature gradients, requiring excellent mechanical properties.

[0003] Silicon nitride ceramic substrates are now an important heat dissipation substrate material and are required to have high thermal conductivity and excellent mechanical properties. In the existing preparation process of silicon nitride ceramic substrates, the sintering aid during sintering is magnesium oxide. Although it has high thermal conductivity and excellent mechanical properties, it has the following shortcomings:

[0004] ⑴High manufacturing cost;

[0005] ⑵The substrate has low flexural strength and is prone to deformation and cracking.

[0006] The above background technology is for facilitating understanding of the present invention and is not a known technology disclosed to the general public before the application of the present invention. Summary of the Invention

[0007] In view of the above-mentioned defects, the present invention provides a method for preparing a silicon nitride substrate, which improves the flexural strength of the silicon nitride ceramic substrate, avoids cracking and deformation, and reduces costs.

[0008] The technical solution is: a method for preparing a silicon nitride substrate, comprising the following steps:

[0009] S1, ball milling: silicon nitride and sintering aid are mixed and ball milled to form a ceramic slurry;

[0010] S2, forming: the ceramic slurry is degassed, aged, sieved and then tape-casted to produce silicon nitride green tape;

[0011] S3, degreasing: degreasing the silicon nitride green porcelain tape to remove organic matter from the green body to obtain a degreased sheet;

[0012] S4, sintering: the degreased sheet is sintered to form a silicon nitride sintered substrate;

[0013] Among them, in S1, the sintering aid contains enstatite glass-ceramics and rare earth compounds, and the contents of silicon nitride, enstatite glass-ceramics and rare earth compounds are:

[0014] Silicon nitride 88-93wt%

[0015] Enstatite glass-ceramics 4-7wt%

[0016] Rare earth compound 2-5wt%

[0017] The enstatite glass-ceramic is made of the following ingredients:

[0018] Raw sodium sand 50-55wt%

[0019] High alumina 1~5wt%

[0020] 35-40wt% calcined talc for blank

[0021] Calcium feldspar 1~5wt%

[0022] Potassium feldspar 1~5wt%

[0023] Sodium feldspar 1~5wt%.

[0024] Furthermore, the enstatite glass-ceramics is prepared by the following steps:

[0025] Q1, drying the raw mineral materials such as sodium sand, high bauxite, calcined talc, calcium feldspar, potassium feldspar, and sodium feldspar separately to remove moisture;

[0026] Q2, weigh raw sodium sand, high bauxite, calcined talc for blank, calcium feldspar, potassium feldspar and sodium feldspar according to the formula, mix them evenly, and place them in an alumina crucible;

[0027] Q3, an alumina crucible is placed in an air sintering furnace for sintering at a heating rate of 1-10°C / min, a melting temperature of 1500-1600°C, and a holding time of 2-4 hours. The melted liquid is then poured into a water tank for water quenching to obtain a glass frit, which is then dry-ground to obtain glass powder.

[0028] Q4, ball milling the glass powder for 1 to 3 hours to form a slurry;

[0029] Q5, the slurry is placed in a spray granulation tower to granulate to obtain spherical powder, which is then dry-pressed into block samples;

[0030] Q6. Obtain enstatite glass-ceramics from bulk samples by a powder sintering method, wherein the heating rate is 1-10°C / min, the nucleation temperature of the enstatite microcrystals is 800-900°C, and the holding time is 1-2h; the crystallization temperature is 1100-1200°C, and the holding time is 2-4h.

[0031] Furthermore, in Q5, the particle size D50 of the spherical powder is 0.5 to 1.0 μm.

[0032] Furthermore, in S2, the aging time is 3 to 665 hours, and the thickness of the green porcelain strip is 0.1 to 0.8 mm; in S3, the degreasing atmosphere is nitrogen, the flow rate is 100 to 300 L / min, the degreasing temperature is 500 to 600°C, the degreasing time is 5 to 10 hours, and the heating rate is 1 to 5°C / min; in S4, the sintering atmosphere is nitrogen, the air pressure is 1 to 3 MPa, the sintering temperature is 1750 to 1850°C, the holding time is 3 to 6 hours, and the heating rate is 1 to 5°C / min.

[0033] Furthermore, the silicon nitride powder is α-Si3N4 with a purity greater than 99% and a particle size D 50 0.4~1.0μm.

[0034] Furthermore, the rare earth compound is one of Yb2O3, Y2O3 or a mixture thereof.

[0035] The present invention also provides a silicon nitride substrate.

[0036] A silicon nitride substrate made of the following main components:

[0037] Silicon nitride 88-93wt%

[0038] Enstatite glass-ceramics 4-7wt%

[0039] Rare earth compound 2-5wt%

[0040] The enstatite glass-ceramic is made of the following ingredients:

[0041] Raw sodium sand 50-55wt%

[0042] High alumina 1~5wt%

[0043] 35-40wt% calcined talc for blank

[0044] Calcium feldspar 1~5wt%

[0045] Potassium feldspar 1~5wt%

[0046] Sodium feldspar 1~5wt%.

[0047] Furthermore, the silicon nitride substrate has a flexural strength greater than 800 MPa, a thermal conductivity greater than 80 W / mk, and a density greater than 3.2 g / cm 3 , warpage ≤0.3%.

[0048] Furthermore, the enstatite glass-ceramics is prepared by the following steps:

[0049] Q1, drying the raw mineral materials such as sodium sand, high bauxite, calcined talc, calcium feldspar, potassium feldspar, and sodium feldspar separately to remove moisture;

[0050] Q2, weigh raw sodium sand, high bauxite, calcined talc for blank, calcium feldspar, potassium feldspar and sodium feldspar according to the formula, mix them evenly, and place them in an alumina crucible;

[0051] Q3, an alumina crucible is placed in an air sintering furnace for sintering at a heating rate of 1-10°C / min, a melting temperature of 1500-1600°C, and a holding time of 2-4 hours. The melted liquid is then poured into a water tank for water quenching to obtain a glass frit, which is then dry-ground to obtain glass powder.

[0052] Q4, ball milling the glass powder for 1 to 3 hours to form a slurry;

[0053] Q5, the slurry is placed in a spray granulation tower to granulate to obtain spherical powder, which is then dry-pressed into block samples;

[0054] Q6. Obtain enstatite glass-ceramics from bulk samples by a powder sintering method, wherein the heating rate is 1-10°C / min, the nucleation temperature of the enstatite microcrystals is 800-900°C, and the holding time is 1-2h; the crystallization temperature is 1100-1200°C, and the holding time is 2-4h.

[0055] Furthermore, the silicon nitride substrate is prepared by the following steps:

[0056] S1, ball milling: silicon nitride and sintering aid are mixed and ball milled to form a ceramic slurry;

[0057] S2, forming: the ceramic slurry is degassed, aged, sieved and then tape-casted to produce silicon nitride green tape;

[0058] S3, degreasing: degreasing the silicon nitride green porcelain tape to remove organic matter from the green body to obtain a degreased sheet;

[0059] S4, sintering: the degreased sheet is sintered to form a silicon nitride sintered substrate.

[0060] Furthermore, in S2, the aging time is 3 to 665 hours, and the thickness of the green porcelain strip is 0.1 to 0.8 mm; in S3, the degreasing atmosphere is nitrogen, the flow rate is 100 to 300 L / min, the degreasing temperature is 500 to 600°C, the degreasing time is 5 to 10 hours, and the heating rate is 1 to 5°C / min; in S4, the sintering atmosphere is nitrogen, the air pressure is 1 to 3 MPa, the sintering temperature is 1750 to 1850°C, the holding time is 3 to 6 hours, and the heating rate is 1 to 5°C / min.

[0061] Principle and effect of the invention:

[0062] The enstatite microcrystals of the present invention replace magnesium oxide and are combined with silicon nitride and rare earth compounds, which reduces the liquid phase formation temperature and increases the liquid phase amount, promotes the process of particle rearrangement, and improves sintering density; the enstatite microcrystals have an extremely low thermal expansion coefficient, so that the green sheet has high thermal stability in the high-temperature sintering zone, which can effectively prevent the green sheet from deformation and cracking; and the production process of the enstatite microcrystals is reduced, and compared with imported magnesium oxide additives, the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 This is a microscopic morphology image of the silicon nitride sintered substrate according to Example 2 of the present invention;

[0064] Figure 2 This is a physical picture of the silicon nitride sintered substrate according to Example 2 of the present invention. DETAILED DESCRIPTION

[0065] The technical solutions of the present invention are described in detail below with reference to specific embodiments. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than for limiting the patent claims of the present invention.

[0066] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "longitudinal", "lateral", "horizontal", "inside", "outside", "front", "back", "top", "bottom", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the inventive product is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0067] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "opened," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integral connection; they may refer to direct connection, indirect connection through an intermediate medium, or internal connection between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0068] In the present invention, unless otherwise specified, all the contents are based on the prior art.

[0069] In the present invention, unless otherwise specified, all materials involved were purchased from the market.

[0070] Example 1

[0071] A method for preparing enstatite microcrystals comprises the following steps:

[0072] Q1, the raw mineral materials such as raw sodium sand, high bauxite, calcined talc for blanks, calcium feldspar, potassium feldspar, sodium feldspar, etc. are dried separately to remove moisture.

[0073] Q2, take the dried raw sodium sand, high bauxite, calcined talc for blanks, calcium feldspar, potassium feldspar, and sodium feldspar from Q1, wherein the raw sodium sand is 50wt%, high bauxite is 5wt%, calcined talc for blanks is 38wt%, calcium feldspar is 2wt%, potassium feldspar is 2wt%, and sodium feldspar is 3wt%, mix them evenly, and place them in an alumina crucible.

[0074] Q3 is sintered in an air sintering furnace with a heating rate of 5°C / min, a melting temperature of 1550°C, and a holding time of 3 hours. The molten liquid is then poured into a water tank for water quenching to obtain a glass frit, which is then dry-ground to obtain glass powder.

[0075] Q4, weigh the glass powder, triolein, ethyl cellulose and water in Q3, including 43wt% glass powder, 2wt% triolein, 5wt% ethyl cellulose and 50wt% deionized water, place them in a planetary ball mill, add 2 / 3 of the volume of alumina ceramic balls, and ball mill for 2h to obtain a slurry.

[0076] Q5, place the slurry in a spray granulation tower to obtain spherical powder with a D50 particle size of 0.5 to 1.0 microns, and then dry-press it into a block sample at a pressure of 60 MPa.

[0077] Q6, the bulk sample was sintered to obtain enstatite glass-ceramics by powder sintering method; the heating rate was 5°C / min, the nucleation temperature of the enstatite microcrystals was 850°C, and the holding time was 2h; the crystallization temperature was 1200°C, and the holding time was 4h.

[0078] In this embodiment,

[0079] The enstatite microcrystals prepared in this example are used in the following Examples 2 to 6.

[0080] Example 2

[0081] A preparation method of a high-strength silicon nitride substrate comprises the following steps:

[0082] S1, ball milling: Weigh silicon nitride, enstatite microcrystals, and yttrium oxide to obtain a mixed powder, add a dispersant, a binder, and an organic solvent, wherein the dispersant accounts for 3% by weight of the mixed powder, the binder accounts for 10% by weight of the mixed powder, and the organic solvent accounts for 150% by weight of the mixed powder, and ball mill the mixture for 30 hours to obtain a ceramic slurry.

[0083] S2, tape casting: degas the ceramic slurry, control the slurry viscosity to 10000 ~ 15000cps, then age for 5h, sieve, and then connect the tape casting head to start tape casting molding, control the tape casting machine head height to 0.2 ~ 1.0, and after drying, obtain a green ceramic tape with a thickness of 0.1 ~ 0.8mm.

[0084] S3, degreasing: Place the green porcelain strip in a degreasing furnace to remove organic matter in the body. The degreasing atmosphere is nitrogen, the flow rate is 100-300 L / min, the degreasing temperature is 500-600°C, the degreasing time is 10 hours, and the heating rate is 1-5°C / min. After the organic matter in the body is fully removed, a degreased sheet is obtained.

[0085] S4, sintering: Finally, the degreased sheet is placed in a gas pressure sintering furnace for sintering. The sintering atmosphere is nitrogen, the gas pressure is 1-3 MPa, the sintering temperature is 1800°C, the holding time is 5 hours, and the heating rate is 1-5°C / min; finally, a silicon nitride sintered substrate is obtained.

[0086] In this embodiment S1, silicon nitride 91wt%, enstatite microcrystals 6wt%, yttrium oxide 3wt%. In this embodiment, the silicon nitride powder is α-Si3N4 powder with a purity greater than 99%, and a particle size D50 of 0.4-1.0μm.

[0087] The microscopic morphology of the silicon nitride sintered substrate obtained in this embodiment is shown in FIG. Figure 1 , the actual picture is as follows Figure 2 .

[0088] Comparative Example 1

[0089] This comparative example is different from Example 2 in that: in S1, 6 wt % of enstatite microcrystals is replaced by 6 wt % of magnesium oxide.

[0090] Example 3

[0091] Compared with Example 2, this comparative example differs in that: in S1, silicon nitride is 91 wt%, enstatite microcrystals are 7 wt%, and yttrium oxide is 2 wt%.

[0092] Example 4

[0093] Compared with Example 2, this comparative example differs in that: in S1, silicon nitride is 91 wt%, enstatite microcrystals are 5 wt%, and yttrium oxide is 4 wt%.

[0094] Example 5

[0095] Compared with Example 2, this comparative example differs in that: in S1, silicon nitride is 91 wt%, enstatite microcrystals are 4.5 wt%, and yttrium oxide is 4.5 wt%.

[0096] Example 6

[0097] Compared with Example 2, this comparative example differs in that: in S1, silicon nitride is 91 wt%, enstatite microcrystals are 4 wt%, and yttrium oxide is 5 wt%.

[0098] The thickness of the substrates prepared in Comparative Example 1 and Examples 2 to 6 was 0.32±0.032 mm.

[0099] The silicon nitride substrates prepared in Examples 2 to 6 and Comparative Example 1 were tested, and their structures were shown in Table 1 below.

[0100] Table 1

[0101] <![CDATA[Apparent density (g / cm 3 )]]> Flexural strength (Mpa) Thermal conductivity (W / mK) Warpage (‰) Example 2 3.25 850 85 1 Comparative Example 1 3.24 800 83 3 Example 3 3.22 820 81 3 Example 4 3.19 795 83 5 Example 5 3.17 760 84 6 Example 6 3.16 745 84 6

[0102] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon nitride substrate, characterized in that: The following steps are involved: S1, ball milling: silicon nitride and sintering aid are mixed and ball milled to form a ceramic slurry; S2, forming: the ceramic slurry is degassed, aged, sieved and then tape-casted to produce silicon nitride green tape; S3, degreasing: degreasing the silicon nitride green porcelain tape to remove organic matter from the green body to obtain a degreased sheet; S4, sintering: the degreased sheet is sintered to form a silicon nitride sintered substrate; Among them, in S1, the sintering aid contains enstatite glass-ceramics and rare earth compounds, and the contents of silicon nitride, enstatite glass-ceramics and rare earth compounds are: Silicon nitride 88-93wt% Enstatite glass-ceramics 4-7wt% Rare earth compound 2-5wt% The enstatite glass-ceramic is made of the following ingredients: Raw sodium sand 50-55wt% High alumina 1~5wt% 35-40wt% calcined talc for blank Calcium feldspar 1~5wt% Potassium feldspar 1~5wt% Sodium feldspar 1~5wt%.

2. The method for preparing a silicon nitride substrate according to claim 1, wherein: The enstatite glass-ceramics is prepared by the following steps: Q1, drying the raw mineral materials such as sodium sand, high bauxite, calcined talc, calcium feldspar, potassium feldspar, and sodium feldspar separately to remove moisture; Q2, weigh raw sodium sand, high bauxite, calcined talc for blank, calcium feldspar, potassium feldspar and sodium feldspar according to the formula, mix them evenly, and place them in an alumina crucible; Q3, an alumina crucible is placed in an air sintering furnace for sintering at a heating rate of 1-10°C / min, a melting temperature of 1500-1600°C, and a holding time of 2-4 hours. The melted liquid is then poured into a water tank for water quenching to obtain a glass frit, which is then dry-ground to obtain glass powder. Q4, ball milling the glass powder for 1 to 3 hours to form a slurry; Q5, the slurry is placed in a spray granulation tower to granulate to obtain spherical powder, which is then dry-pressed into block samples; Q6. Obtain enstatite glass-ceramics from bulk samples by a powder sintering method, wherein the heating rate is 1-10°C / min, the nucleation temperature of the enstatite microcrystals is 800-900°C, and the holding time is 1-2h; the crystallization temperature is 1100-1200°C, and the holding time is 2-4h.

3. The method for preparing a silicon nitride substrate according to claim 2, wherein: In Q5, the D50 particle size of the spherical powder is 0.5 to 1.0 microns.

4. The method for preparing a silicon nitride substrate according to any one of claims 1 to 3, wherein: In S2, the aging time is 3 to 665 hours, and the thickness of the green porcelain strip is 0.1 to 0.8 mm; in S3, the degreasing atmosphere is nitrogen, the flow rate is 100 to 300 L / min, the degreasing temperature is 500 to 600°C, the degreasing time is 5 to 10 hours, and the heating rate is 1 to 5°C / min; in S4, the sintering atmosphere is nitrogen, the air pressure is 1 to 3 MPa, the sintering temperature is 1750 to 1850°C, the holding time is 3 to 6 hours, and the heating rate is 1 to 5°C / min.

5. The method for preparing a silicon nitride substrate according to claim 4, wherein: The silicon nitride powder is α-Si3N4 with a purity greater than 99% and a particle size of D 50 0.4~1.0μm; or / and The rare earth compound is one of Yb2O3, Y2O3 or a mixture thereof.

6. A silicon nitride substrate, characterized in that Made with the following main ingredients: Silicon nitride 88-93wt% Enstatite glass-ceramics 4-7wt% Rare earth compound 2-5wt% The enstatite glass-ceramic is made of the following ingredients: Raw sodium sand 50-55wt% High alumina 1~5wt% 35-40wt% calcined talc for blank Calcium feldspar 1~5wt% Potassium feldspar 1~5wt% Sodium feldspar 1~5wt%.

7. The silicon nitride substrate according to claim 6, wherein The silicon nitride substrate has a flexural strength of >800 MPa, a thermal conductivity of >80 W / mk, and a density of >3.2 g / cm 3 , warpage ≤0.3%.

8. The silicon nitride substrate according to claim 6, wherein The enstatite glass-ceramics is prepared by the following steps: Q1, drying the raw mineral materials such as sodium sand, high bauxite, calcined talc, calcium feldspar, potassium feldspar, and sodium feldspar separately to remove moisture; Q2, weigh raw sodium sand, high bauxite, calcined talc for blank, calcium feldspar, potassium feldspar and sodium feldspar according to the formula, mix them evenly, and place them in an alumina crucible; Q3, an alumina crucible is placed in an air sintering furnace for sintering at a heating rate of 1-10°C / min, a melting temperature of 1500-1600°C, and a holding time of 2-4 hours. The melted liquid is then poured into a water tank for water quenching to obtain a glass frit, which is then dry-ground to obtain glass powder. Q4, ball milling the glass powder for 1 to 3 hours to form a slurry; Q5, the slurry is placed in a spray granulation tower to granulate to obtain spherical powder, which is then dry-pressed into block samples; Q6. Obtain enstatite glass-ceramics from bulk samples by a powder sintering method, wherein the heating rate is 1-10°C / min, the nucleation temperature of the enstatite microcrystals is 800-900°C, and the holding time is 1-2h; the crystallization temperature is 1100-1200°C, and the holding time is 2-4h.

9. The silicon nitride substrate according to claim 6, wherein The silicon nitride substrate is prepared by the following steps: S1, ball milling: silicon nitride and sintering aid are mixed and ball milled to form a ceramic slurry; S2, forming: the ceramic slurry is degassed, aged, sieved and then tape-casted to produce silicon nitride green tape; S3, degreasing: degreasing the silicon nitride green porcelain tape to remove organic matter from the green body to obtain a degreased sheet; S4, sintering: the degreased sheet is sintered to form a silicon nitride sintered substrate.

10. The silicon nitride substrate according to claim 6, wherein In S2, the aging time is 3 to 665 hours, and the thickness of the green porcelain strip is 0.1 to 0.8 mm; in S3, the degreasing atmosphere is nitrogen, the flow rate is 100 to 300 L / min, the degreasing temperature is 500 to 600°C, the degreasing time is 5 to 10 hours, and the heating rate is 1 to 5°C / min; in S4, the sintering atmosphere is nitrogen, the air pressure is 1 to 3 MPa, the sintering temperature is 1750 to 1850°C, the holding time is 3 to 6 hours, and the heating rate is 1 to 5°C / min.

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