Sealing glass as well as preparation method and application thereof

Abstract

The invention provides sealing glass as well as a preparation method and application thereof. The preparation method comprises the following steps: preparing materials according to a sealing glass formula, uniformly mixing, and carrying out first ball milling; the raw materials are subjected to high-temperature melting, clarification, leakage forming and annealing, and lead glass is obtained; crushing lead glass, performing secondary ball milling, sieving, preparing the obtained glass powder into slurry, coating the surface of the to-be-passivated area with the slurry, and performing heat treatment to form a glass passivation layer; and immersing the glass passivation layer into molten toughening molten salt, and carrying out chemical toughening treatment at a designed temperature to synchronously remove sodium ions, so as to obtain the high-strength low-leakage-current sealing glass. The technical problem to be solved is how to prepare the sealing glass which has higher strength and chemical stability on the basis of meeting the performance that low-melting-point glass can be used for electronic device packaging in the prior art, the strength of the sealing glass can reach 300 MPa or above, the expansion coefficient is 35 * 10 <-6 >-50 * 10 <-6 > / DEG C, and the sealing glass is excellent in insulating property and can be applied to electronic device packaging. And the requirements of development in the fields of semiconductor surface passivation and the like on a sealing glass material can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of glass manufacturing, in particular to a sealing glass and a preparation method and application thereof. BACKGROUND

[0002] With the continuous progress of electronic technology, semiconductor devices are facing increasing demands in electrical performance, reliability and size miniaturization. The exposed surface of semiconductor material, as a termination zone of lattice periodic arrangement, has a large number of dangling bonds and other unsaturated bonding states, which causes the surface state to change, and then causes phenomena such as energy band bending and Fermi level pinning, resulting in unstable electrical characteristics of the device. Especially in the PN junction region, mobile ion impurities (such as Na + ) will drift under the action of an external electric field, which not only increases the leakage current and reduces the reverse breakdown voltage, but also affects the long-term working stability of the device. Therefore, passivation treatment of the semiconductor surface has become a key process link to improve the performance and reliability of the device.

[0003] Low-melting point glass powder is a kind of special glass material with a significantly lower glass transition temperature, which has been widely used in the field of electronic components and display devices due to its excellent packaging and protection characteristics. This kind of material can be densified at a relatively low sintering temperature, which helps to avoid damage to the sensitive structure of the semiconductor caused by high temperature, and its good adhesion performance provides effective passivation protection for the chip surface. Although low-melting point glass powder has been used for semiconductor passivation packaging due to its high breakdown voltage and thermal shock resistance, the existing glass materials still have shortcomings in mechanical strength and chemical durability, which makes them prone to damage during subsequent manufacturing processes such as mesa etching and scribing, thereby restricting the final performance and service life of semiconductor devices. SUMMARY

[0004] The main purpose of the present application is to provide a sealing glass and a preparation method and application thereof, and the technical problem to be solved is how to prepare a sealing glass that has higher strength and chemical stability on the basis of the performance of low-melting point glass that can be used for electronic device packaging in the prior art, the strength of which can reach more than 300 MPa, the expansion coefficient of which is 35x10 -6 ~ 50x10 -6 / ℃, the water resistance and alkali ion corrosion resistance of which are good, reaching HGB2 level and A1 level respectively; and the glass medium has low leakage current and high reverse breakdown voltage, the leakage current being less than 0.50 μA (room temperature) and the reverse breakdown voltage being greater than 1400 V, having excellent insulation performance; the comprehensive performance is excellent, which can meet the requirements of the development of the field of semiconductor surface passivation and the like for sealing glass materials, and is suitable for semiconductor packaging scenarios with strict requirements for mechanical durability and electrical characteristics, thereby being more suitable for practical use.

[0005] The technical scheme of the present application is as follows: a preparation method of sealing glass is provided, which comprises the following steps:

[0006] S1: ingredients are prepared according to the sealing glass formula, and then first ball milling is performed after uniform mixing; raw materials are high-temperature melted, clarified, and formed by material leakage, and then annealed to obtain lead glass;

[0007] S2: the lead glass is crushed, second ball milling is performed, and then sieving is performed to obtain glass powder, which is mixed into slurry and coated on the surface of a to-be-passivated region, and then heat treatment is performed to form a glass passivation layer;

[0008] S3: the glass passivation layer is immersed in molten chemical tempering molten salt, chemical tempering treatment is performed at a designed temperature, and sodium ions are simultaneously removed to obtain sealing glass with high strength and low leakage current.

[0009] The technical scheme of the present application is as follows: a preparation method of sealing glass is provided, which comprises the following steps:

[0010] Preferably, in the preparation method, the sealing glass formula comprises, in terms of mass percentage of oxides, 30-40% of silicon dioxide, 30-45% of lead oxide, 4-8% of barium oxide, 1-2% of zinc oxide, 5-10% of aluminum trioxide, 8-15% of boron trioxide, 1-4% of zirconium oxide, and 2-4% of yttrium trioxide, and the total content of the above components is 100%; the mass ratio of the barium oxide and the zinc oxide is 2-4:1; the chemical tempering molten salt comprises lithium nitrate, barium nitrate and zinc nitrate; the mass ratio of the barium nitrate and the zinc nitrate is 3-4:1; and the mass of the lithium nitrate accounts for 0.5-1% of the mass of the chemical tempering molten salt.

[0011] Preferably, in the preparation method, the particle size of the raw materials after the first ball milling is less than 1 μm.

[0012] Preferably, in the preparation method, the high-temperature melting is performed at a temperature of 1550-1620 ℃; and the annealing is performed by keeping the glass at 420-450 ℃ for 3-5 h.

[0013] Preferably, in the preparation method, the annealing is performed by keeping the glass at 420-450 ℃ for 3-5 h.

[0014] Preferably, in the preparation method, the particle size of the glass powder after the second ball milling is 200-2000 nm.

[0015] Preferably, in the preparation method, the heat treatment is performed at 550-620 ℃ for 3-6 h.

[0016] Preferably, in the preparation method, the chemical tempering treatment is performed at a temperature of 420-480 ℃ for 2-4 h.

[0017] The technical scheme of the present application is as follows: The sealing glass for surface passivation of semiconductor devices according to the present application comprises:

[0018] The glass passivation layer is an amorphous Si-O-B-Pb-Zr-Y cross-linking network structure, and comprises, in terms of mass percentage of oxides, 30-40% of SiO2, 30-45% of PbO, 4-8% of BaO, 1-2% of ZnO, 5-10% of Al2O3, 8-15% of B2O3, 1-4% of ZrO2 and 2-4% of Y2O3, and the total content of the above components is 100%; wherein the mass ratio of BaO to ZnO is 2-4:1.

[0019] The tempered surface layer is arranged on the glass passivation layer, and the tempered surface layer is a compressive stress layer formed by ion exchange of the glass passivation layer through Ba 2+ / Li + The depth of the compressive stress layer is greater than or equal to 50 microns, the strength of the sealing glass is greater than 300 MPa, and the expansion coefficient is 35-50*10 -6 / ℃. -6

[0020] The technical scheme of the present application is as follows: The technical scheme of the present application is as follows: The sealing glass for surface passivation of semiconductor devices according to the present application comprises:

[0021] Preferably, the sealing glass is prepared according to the preparation method described above.

[0022] The technical scheme of the present application is as follows: The technical scheme of the present application is as follows: The sealing glass for surface passivation of semiconductor devices according to the present application comprises:

[0023] The technical scheme of the present application is as follows: The technical scheme of the present application is as follows: The sealing glass for surface passivation of semiconductor devices according to the present application comprises:

[0024] ​The core concept of the sealing glass, its preparation method, and its application in this invention is to perform annealing after the glass is melted, clarified, and shaped, rather than the conventional quenching process used in existing sealing glass technologies. On the one hand, annealing can effectively eliminate permanent thermal stress frozen due to uneven cooling. On the other hand, sufficient annealing also helps the glass network structure to fully relax and rearrange atoms, promoting its transition to a more stable metastable equilibrium, thereby stabilizing the physicochemical properties of the glass, such as the coefficient of thermal expansion and dielectric constant, and preventing performance drift caused by structural relaxation during long-term use of the device. The technical solution of this invention forms an amorphous cross-linked network in the glass network through the annealing process. Then, a specific tempering molten salt is designed according to the actual glass formula, so that the amorphous glass network formed by annealing undergoes ion exchange in the tempering molten salt to form a compressive stress layer while removing impurities, thereby improving mechanical strength and exhibiting better electrical properties.

[0025] Based on the above-mentioned inventive concept, this invention, through the rational design of the basic glass composition, first anneals it to form an amorphous Si-OB-Pb-Zr-Y crosslinked network structure glass passivation layer, and then applies Ba to the glass passivation layer. 2+ / Li + Ion exchange is performed to form a compressive stress layer of a certain depth. A tempered surface layer is then applied to the glass passivation layer to achieve a sealing glass strength >300MPa and a coefficient of thermal expansion of 35×10⁻⁶. -6 ~50×10 -6 The temperature is maintained at a constant ℃, preventing breakage and detachment during subsequent use. Simultaneously, the ion exchange process effectively removes sodium ions from the glass during the chemical tempering step, and the introduction of heavy metal ions into the formulation helps reduce leakage current in the glass medium and improves reverse breakdown voltage. This results in a sealing glass that exhibits both high strength and excellent insulation performance and overall reliability, making it particularly suitable for semiconductor packaging applications with stringent requirements for mechanical durability and electrical properties.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Detailed Implementation

[0027] To further clarify the technical means and effects taken by the present application to achieve the intended purpose, the following describes in detail the sealing glass, its preparation method and application, the specific implementation and effects according to the present application, in combination with the accompanying tables and preferred embodiments. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the results in one or more embodiments can be combined in any suitable form. The present application provides these embodiments to make the present application thorough and complete, and fully express the scope of the present application to those skilled in the art. It should be noted that: unless otherwise specifically stated, the relative arrangement of components and steps, the composition of materials, numerical expressions and values described in these embodiments should be interpreted as merely exemplary, not as a limitation.

[0028] The present application provides a sealing glass and its preparation method, which comprises the following steps:

[0029] First, the sealing glass formula is prepared, and after uniform mixing, the first ball milling is performed; the raw materials are high-temperature melted, clarified, and formed by material leakage, and then annealed to obtain lead glass; then the lead glass is crushed, the second ball milling is performed, and the screening is performed, and the obtained glass powder is prepared into a slurry, which is coated on the surface of the area to be passivated, and then heat treated to form a glass passivation layer; finally, the glass passivation layer is immersed in a molten chemical tempering salt, and the sodium ions are removed simultaneously at the designed temperature by chemical tempering treatment, thereby obtaining a sealing glass with high strength and low leakage current.

[0030] The core idea of the above technical solution is to perform annealing treatment after glass melting, clarification and forming, instead of the conventional quenching process of the sealing glass in the prior art. On the one hand, annealing can effectively eliminate the permanent thermal stress frozen due to uneven cooling, and at the same time, sufficient annealing also helps the glass network structure to fully relax and rearrange atoms, promotes the transition to a more stable metastable state balance, thereby stabilizing the physical and chemical properties of the glass, such as the thermal expansion coefficient and the dielectric constant, to avoid performance drift caused by structural relaxation during long-term use of the device; the technical solution of the present application forms a cross-linked network of amorphous structure through the annealing process; then a specific chemical tempering salt is designed according to the actual formula of the glass, so that the amorphous glass network formed by annealing treatment removes impurities while ion exchange in the chemical tempering salt, thereby better improving the mechanical strength and having better electrical properties. The mechanism is as follows: the chemical tempering salt can provide ions that can exchange with the easily migratable harmful ions in the glass network, such as Na + , which can induce leakage current and affect the electrical stability of the glass. By ion replacement, the mobile ions in the glass are transferred to the molten salt, thereby reducing the ion migration channels in the glass from the root; at the same time, part of the cations entering the glass, such as Ba 2+It can form induced negative charge centers at the interface of the sealed and passivated film layer, further suppressing reverse leakage current and improving the electrical insulation reliability of the glass; specific cations in the tempered molten salt, such as large-radius cations, can exchange with smaller mobile ions on the glass surface, utilizing the difference in ion radii to form a squeezing effect on the glass surface, thereby constructing a stable compressive stress layer; this compressive stress layer can counteract the tensile stress of the glass under external force, significantly improving the mechanical strength of the glass, such as bending strength, and preventing the glass from cracking or falling off during subsequent processing (scratching, corrosion) or service; lithium source components in the tempered molten salt can decompose to generate highly mobile cations, such as Li + These cations can preferentially open up ion migration channels on the glass surface, creating conditions for the large-scale exchange of other cations. At the same time, these cations can also form a transition layer with a gentle compositional gradient and a dense structure on the glass surface. On the one hand, this inhibits the relaxation of the glass surface network at high temperatures, ensuring the long-term stability of the compressive stress layer. On the other hand, it blocks impurity ions in the molten salt from invading the glass network, reducing the damage of external corrosion to the glass structure and improving the chemical stability of the tempered glass. Different types of cations in the tempering molten salt, such as cations that provide compressive stress and cations that play a densifying role, can form a synergistic effect. The former dominates the construction of the compressive stress layer to improve strength, while the latter locks in deep stress through interfacial densification, balancing the brittleness of the glass. This avoids stress concentration caused by the exchange of a single cation, which can lead to microcracks, and also prevents excessive growth of the interfacial layer caused by uneven ion exchange, which can increase brittleness. Ultimately, this achieves a mechanical balance between high strength and low brittleness.

[0031] Based on the above-mentioned inventive concept, this invention first forms an amorphous network structure in the glass through combined annealing treatment, and then chemically tempers it with a specific tempering molten salt. This specific tempering molten salt removes impurity ions from the glass network structure while simultaneously chemically tempering it, thereby ensuring both the mechanical strength and electrical properties of the sealing glass.

[0032] In some specific embodiments of the present invention, the preferred glass formulation is as follows: based on the mass percentage of oxides, it includes 30-40% silicon dioxide, 30-45% lead oxide, 8-15% boron trioxide, 5-10% aluminum trioxide, 1-4% zirconium oxide, 4-8% barium oxide, 1-2% zinc oxide, and 2-4% yttrium trioxide, with the total content of the above components being 100%; wherein the mass ratio of barium oxide to zinc oxide is 2-4:1.

[0033] The following description is based on this formula, but it is not intended to limit the scope of the invention. The functions of each component in the above glass raw material are as follows:

[0034] Silica is the main component of the glass skeleton, which can form a uniform network in the glass. The introduction of silica into the glass can improve the strength, viscosity, thermal stability of the glass, and reduce the thermal expansion coefficient of the glass. If the content of silica is less than 30%, the overall performance of the glass is poor, and it is not easy to obtain high-strength sealing glass. However, if the content of silica is higher than 40%, the required temperature during glass melting process is too high, and defects such as stones are caused, affecting the final performance.

[0035] Lead oxide, as a network modifier and strong fluxing agent, can break the rigid structure of the silicon-oxygen (Si-O) network and reduce the melting temperature of the glass. Lead ions have a strong binding effect on oxygen ions, and the Pb-O bond energy is high, which makes the sealing layer have barrier properties to water vapor and alkali metal ions (such as Na + 、K + ) in the environment; at the same time, the thermal expansion coefficient of the glass is adjusted to match the thermal expansion coefficient of the semiconductor device. If the content of lead oxide is less than 30%, the effect of the fluxing agent is weakened, the glass melting temperature is increased, and the glass flowability is poor, which can easily cause uneven coverage, pinholes or cracks, and the expansion coefficient of the glass is too small to match the expansion coefficient of the semiconductor device. However, if the content of lead oxide is higher than 45%, the glass phase region is unstable, and lead or lead-containing crystals are easily precipitated. Excessive lead oxide, as an external network oxide, can break the continuous network structure of the glass, resulting in a decrease in the hardness and mechanical strength of the sealing layer, and a significant decrease in chemical stability.

[0036] Boron trioxide is an important component of glass and a good fluxing agent. It forms boron-oxygen tetrahedra in the glass, making the structure more compact to improve the viscosity of the glass. If the content of boron trioxide is higher than 15%, the required temperature during glass melting process is too high. Instead of boron-oxygen tetrahedra, boron-oxygen triangles appear in the glass structure, which weakens the glass structure and leads to a decrease in performance, and phase separation occurs. If the content of boron trioxide is less than 8%, sufficient boron-oxygen tetrahedra cannot be formed in the glass, causing the structure of boron to change from layered to framework structure, and boron trioxide and silica cannot form a uniform glass matrix.

[0037] Aluminum trioxide can form a network structure with silica, making the glass structure more compact. The appropriate introduction of aluminum trioxide can significantly improve the chemical stability, mechanical strength and anti-crystallization ability of the glass. By forming a strong Al-O bond to strengthen the network structure, the migration of alkali metal ions is effectively inhibited and the hydrolysis resistance is enhanced. If the content of aluminum trioxide is less than 5%, the network structure degree in the glass is small, and the strength, viscosity and other properties are small, and the network gap is small. If the content of aluminum trioxide is higher than 10%, the required temperature during melting is too high, and defects such as stones are caused, which reduces the thermal expansion coefficient of the glass and makes it difficult to match the semiconductor device, affecting the final performance.

[0038] Zirconia mainly acts as network intermediate to improve chemical durability, mechanical strength and hardness. Its high field strength Zr 4+ Ions can effectively strengthen the glass network, especially significantly enhance the corrosion resistance to alkali. If the content is less than 1%, the strengthening effect is not obvious, and the wear resistance and stability of the glass are limited; if the content is higher than 4%, due to the low solubility of zirconium ions in the glass melt, it is easy to crystallize, which seriously damages the uniformity and density of the glass, and sharply increases the melt viscosity, making melting, homogenization and forming extremely difficult.

[0039] Barium oxide is a divalent network exoskeleton oxide, with large ionic radius and strong alkalinity. It can increase the refractive index, density, luster and chemical stability of the glass. At the same time, it can increase the thermal expansion coefficient of the glass, match the expansion coefficient of the sealing body, and reduce the interfacial thermal stress. In addition, the introduction of barium oxide helps to improve the dielectric constant of the glass, and the dielectric loss is small. As high field strength cations, barium ions will produce induced charges at the junction of the sealing passivation film layer after sealing passivation, forming negative centers and reducing reverse leakage current. A small amount of barium oxide can accelerate the melting of glass, but too much will cause the second bubble of fining. If the content of barium oxide is less than 4%, its effect on accelerating glass melting is not obvious, and the process and thermal matching of the glass may not meet the requirements; when the content of barium oxide is greater than 8%, the chemical stability of the glass will decrease, the structural strength will decrease, and the glass may increase the tendency of crystallization, increase the tendency of crystallization, and react with oxygen, making it difficult to clarify the melt, and the erosion of refractory materials is more serious, while hindering ion exchange and affecting the final performance.

[0040] Zinc oxide as a network intermediate can effectively reduce the melting temperature and high temperature viscosity of the glass, improve the fluidity and spreadability, and thus ensure the formation of a dense and defect-free sealing layer. At the same time, zinc oxide can improve the chemical stability of the glass, especially the alkali resistance, and effectively inhibit the tendency of glass crystallization. In addition, zinc oxide can adjust the thermal expansion coefficient to better match the semiconductor device and reduce thermal stress. If the content is less than 1%, the fluxing and strengthening effect is limited; if the content is higher than 2%, zinc spinel crystals may be precipitated due to the exceeding of its solubility, which may lead to glass devitrification and reduce its chemical stability.

[0041] By synergistically combining the fluxing and thermal expansion regulating properties of barium oxide with the network stabilizing and crystallization inhibiting properties of zinc oxide, a balance is achieved between suitable process temperature, a matching coefficient of thermal expansion with the substrate, excellent chemical stability, and long-term structural stability in the sealing glass. If the mass ratio of barium oxide to zinc oxide is greater than 4:1, the glass network structure becomes too loose due to excessive network modifications. While this helps lower the melting temperature, it severely degrades the chemical stability of the passivation layer, reduces its water resistance, and significantly increases the coefficient of thermal expansion, leading to a risk of thermal stress mismatch with semiconductor devices. If the mass ratio of barium oxide to zinc oxide is less than 2:1, the high-temperature viscosity of the glass melt increases sharply, worsening its fluidity and spreadability, leading to higher process temperatures and easily inducing the precipitation of zinc-related crystalline phases, thus compromising the uniformity of the sealing glass.

[0042] Yttrium trioxide is a rare earth oxide, which can be obtained by introducing a high-field Y... 3+ Ions effectively strengthen the glass network structure, significantly improving the density and chemical stability of the passivation layer, especially enhancing its resistance to active corrosive media such as fluoride ions. Simultaneously, the introduction of Y₂O₃ effectively suppresses glass phase separation tendency, improves high-temperature viscosity stability, and ensures that the sealing glass maintains an amorphous and uniform state during heat treatment. Furthermore, its trivalent nature effectively compensates for the space charge formed by the migration of alkali metal ions in the glass network, optimizing the interfacial electric field distribution and dielectric properties. If the yttrium trioxide content is less than 2%, the glass network structure lacks a high electric field strength due to the absence of Y₂O₃. 3+ The strengthening effect of ions leads to insufficient compactness, resulting in a significant decrease in the chemical stability of the glass, especially its resistance to hydrolysis and its ability to inhibit ion migration. Simultaneously, the glass's resistance to crystallization weakens, making it prone to phase separation or crystallization during high-temperature processing, thus compromising its amorphous homogeneity. When the yttrium trioxide content exceeds 4%, excessive Y... 3+ Ions, due to their limited solubility in the glass melt, drastically increase the high-temperature viscosity of the glass, severely deteriorating the melt's fluidity and spreadability, making glass forming difficult and prone to defects such as uneven coverage. Simultaneously, excess Y₂O₃ acts as a heterogeneous nucleation site, greatly increasing the glass's crystallization tendency and leading to the precipitation of crystals such as yttrium silicates. This not only causes devitrification but also introduces micro-stress due to the difference in thermal expansion coefficients between the crystalline and glass phases, deteriorating the mechanical integrity and insulation properties of the sealing glass. Furthermore, it affects ion exchange, resulting in poor tempering.

[0043] Fine raw material particle size is the basis for obtaining a highly chemically uniform, no unmelted grain, no glass melt with stripe defect, by ball milling process to the accurate reduction of raw material particle size, can significantly increase the contact area between each component, thereby greatly promoting the solid phase reaction rate and mass transfer efficiency in the subsequent melting process. Effective to reduce the complete melting temperature of glass and shorten the melting time, not only is conducive to energy saving and consumption reduction, but also can avoid the excessive loss of volatile components (such as B2O3, PbO, etc.) caused by high temperature and long time heating, ensure that the final glass composition is consistent with the design ratio, so as to ensure that the passivation layer formed finally is uniform in composition and structure on a microscale, avoid the problems of uneven electrical properties, internal stress concentration or decreased corrosion resistance caused by local composition fluctuation, significantly improve the reliability and yield of semiconductor devices. If the raw material particle size is greater than 1 microns, the specific surface area of each component will be significantly reduced, which will seriously hinder the solid phase reaction kinetics and mass transfer efficiency in the high temperature melting process. Therefore, the complete melting requires a significant increase in melting temperature or prolonging the melting time, resulting in energy waste, and causing the severe volatilization of low boiling point components (such as B2O3, PbO, etc.), which makes the actual composition of the final glass deviate from the design ratio, and the performance out of control. In addition, the coarse particles that are not completely melted or the intermediate phases that are not completely reacted will remain as foreign matter in the glass melt, forming a micro-heterogeneous zone. These defects will become stress concentration points, ion migration fast channels or electrical weak points after being formed into a glass seal, which will seriously degrade the density, insulation strength and chemical stability of the passivation layer. The particle size of the raw material after the first ball milling is preferably <1 μm.

[0044] The above glass raw material components contain refractory components such as silicon oxide and aluminum oxide. If the melting temperature is lower than 1550℃, the thermodynamic driving force is insufficient, resulting in incomplete solid phase reaction, and the raw material is difficult to fully melt and homogenize, which is easy to produce unmelted particles or component segregation, forming micro defects; at the same time, the glass melt viscosity is high, and the internal bubbles are difficult to effectively remove, which finally leads to poor density of the passivation layer, reduced insulation strength, and risk of leakage channel. If the melting temperature is higher than 1620℃, it will cause excessive volatilization of B2O3, PbO and other components in the composition, resulting in deviation of the actual glass composition from the design formula, and uncontrollable performance; at the same time, high temperature will aggravate the corrosion of refractory materials, introduce foreign impurities to contaminate the glass liquid, and significantly increase the energy consumption. In addition, too high temperature may cause the valence change of some functional components, affecting the dielectric properties of the glass. In order to ensure complete melting of the raw material and stability of the components, the temperature of high temperature melting is preferably 1550-1620℃.

[0045] According to the inventive concept of the present application, the glass is first annealed to form an amorphous glass network, and then chemically tempered and ion-extracted simultaneously. According to the above glass component design, the annealing process is preferably performed by keeping the glass at 420-450℃ for 3-5h. The annealing process is used instead of the quenching process commonly used for sealing glass, mainly because annealing can effectively eliminate the permanent thermal stress frozen due to uneven cooling. If quenching process is used, although rapid solidification can be achieved, it will lead to the formation of a large internal stress gradient in the glass. This high internal stress will make the sealing glass prone to micro-crack initiation and even macro-cracking during subsequent processing or service, seriously weakening its mechanical integrity and protection ability for semiconductor devices. At the same time, quenching makes the glass structure loose, and the ion migration resistance is small. In addition, full annealing helps the glass network structure to fully relax and rearrange atoms, promoting its transition to a more stable metastable equilibrium, thereby stabilizing the physical and chemical properties of the glass (such as thermal expansion coefficient, dielectric constant), avoiding performance drift due to structural relaxation during long-term use of the device. If the annealing temperature is lower than 420℃, the atoms and ions in the glass will have difficulty moving, and they will not have enough time to form a stable state, resulting in low efficiency. If the annealing temperature is higher than 450℃, the energy consumption will be too high, and new internal stress will be generated in the glass, which may lead to crystallization or component phase separation, destroying the amorphous uniformity. If the annealing time is less than 3h, the effect of eliminating internal stress cannot be achieved, and the annealing is not sufficient. If the annealing time is more than 5h, the effect of eliminating internal stress will not increase, the energy consumption will increase, and unnecessary structural relaxation or slight crystallization may occur, which will have a negative impact on the performance stability.

[0046] The particle size distribution of the glass powder in the prepared slurry is a decisive step to ensure the performance and form a high-quality sealing layer. The appropriate fine particle size can ensure the good dispersibility and rheology of the glass powder in the organic carrier, thereby obtaining a slurry with excellent coating uniformity, avoiding scratching, caking or clogging problems caused by too large particles. And it has higher specific surface area and surface energy, which can significantly reduce the softening flow temperature of the glass and accelerate the sintering kinetics in the subsequent heat treatment (sintering) process, thereby realizing rapid densification of the passivation layer at a relatively low process temperature, forming a continuous film with no pores, flat and strong adhesion. Thus, the dielectric strength, breakdown voltage and barrier ability against sodium ion migration and other pollution of the passivation layer are significantly improved. Therefore, the particle size of the glass powder after the second ball milling is preferably 200-2000 nm. If the particle size of the glass powder is greater than 2000 nm, the specific surface area will be significantly reduced, and problems such as sedimentation, uneven dispersion, etc. will occur during the subsequent preparation of the slurry, affecting the uniformity of the coating. At the same time, the large particles are difficult to fully melt and flow during sintering and densification, and are prone to form micro-pores, interface cavities and other defects, which significantly deteriorate the densification, insulation strength and ion migration resistance of the passivation layer, becoming a potential weak point of device reliability. If the particle size of the glass powder is less than 200 nm, although it is beneficial to sintering and densification, the extremely high specific surface area will result in too large viscosity and poor leveling of the slurry, which is also not conducive to process operation. In addition, the ultra-fine powder is prone to agglomeration, which will cause local unevenness, and the too high surface energy will narrow the sintering window, which is easy to cause excessive shrinkage or stress cracking of the sealing layer.

[0047] The technical scheme of the present application forms a glass passivation layer by heat treatment of the glass slurry coated on the surface of the area to be passivated. According to the above glass component design, the heat treatment is preferably carried out at 550-620℃ for 3-6h. If the temperature is lower than 550℃ or the time is less than 3h, the glass powder does not reach a fully softened flow state, and the mass transfer power is insufficient, so complete densification cannot be achieved. This will result in a large number of micro-pores and interface defects remaining in the passivation layer, which will significantly reduce the densification, insulation strength and moisture resistance of the passivation layer, and cannot effectively block external ion pollution, which will seriously affect the reliability of the device. If the temperature is greater than 620℃ or the time is greater than 6h, it may cause excessive volatilization of the glass component, aggravate the crystallization tendency, or have an adverse interface reaction with the underlying semiconductor device. Not only will it change the preset physicochemical properties of the passivation layer, but also may damage the existing structure of the chip, introduce interface states, and cause degradation of the electrical properties of the device. At the same time, over-burning will easily cause excessive flow of the glass layer, resulting in uneven thickness and edge climbing, affecting the geometric appearance.

[0048] The tempering molten salt needs to be adjusted according to the glass component design. According to the above glass component design, the tempering molten salt preferably comprises lithium nitrate, barium nitrate and zinc nitrate; the mass ratio of the barium nitrate to the zinc nitrate is 3-4:1; and the lithium nitrate accounts for 0.5-1% of the mass of the tempering molten salt. The barium nitrate and the zinc nitrate can provide more effective barium ions and zinc ions, so that the molten salt exchanges with ions with smaller ion radius in the glass to form multiple stress layers, thereby improving the strength performance after strengthening, the network space stability of the glass and the alkali resistance of the glass; meanwhile, the possible Na ions in the glass are replaced, and the ion migration ability of the glass is reduced; the barium ions entering the glass will generate induced charges at the junction of the sealing passivation film layer, form negative centers, and reduce the reverse leakage current. The interfacial densification of zinc can effectively lock the deep compressive stress formed by the promotion of barium, and achieve the ideal combination of high surface compressive stress and large stress layer depth. If the mass ratio of the barium nitrate to the zinc nitrate is greater than 4:1, excessive barium oxide will cause excessive reaction, resulting in micro-cracks on the surface of the glass, and thereby reducing the strength; if the mass ratio of the barium nitrate to the zinc nitrate is less than 3:1, the excessive zinc content will cause excessive growth of the interfacial layer, and increase the brittleness. The lithium ions produced by the decomposition of lithium nitrate in the molten salt have the smallest ion radius and the highest migration activity. These Li + ions can be preferentially exchanged with the sodium ions on the surface of the glass before the barium ions. This pre-exchange process effectively dredges the ion migration channels on the surface of the glass, and creates favorable conditions for the subsequent large-scale diffusion of ions, so that a deeper ion exchange layer and a higher surface compressive stress can be obtained under the same temperature and time. The introduction of lithium ions helps to form a stress layer with a more gentle composition gradient and a more dense structure on the surface of the glass. On the one hand, this can significantly inhibit the relaxation effect of the network structure on the surface of the glass during the high-temperature ion exchange process, so that the obtained compressive stress is more stable; on the other hand, the dense layer can effectively block the erosion of impurity ions in the molten salt to the glass network, thereby improving the chemical stability of the passivated glass after tempering. If the content of lithium nitrate is less than 0.5%, it will not have the corresponding effect; if the content of lithium nitrate is greater than 1%, it will cause excessive Li + exchange, because the too small ion radius cannot generate sufficient compressive stress, which may instead lead to a decrease in the effectiveness of the stress layer, and intensify the erosion of the molten salt tank; meanwhile, too many lithium ions in the glass will increase the ion migration ability and increase the reverse leakage current.

[0049] According to the above glass component design and the above preferred tempering molten salt component, the chemical tempering treatment temperature is preferably 420-480℃, and the time is 2-4h. If the tempering temperature is lower than 420℃, the ion exchange efficiency is low, the stress layer depth and the stress value are both very low; if the tempering temperature is higher than 480℃, the surface of the glass is prone to stress relaxation, and the mechanical strength of the glass decreases sharply; if the time is less than 2h, the chemical tempering time is too short, and the effect is insufficient; if the time is greater than 4h, the chemical tempering time is too long, and the efficiency is reduced.

[0050] By the technical scheme, the application provides a sealing glass prepared by the method, which is used for surface passivation of a semiconductor device and comprises a glass passivation layer; the glass passivation layer is an amorphous Si-O-B-Pb-Zr-Y cross-linking network structure; the glass passivation layer comprises, in terms of mass percentage of oxides, 30-40% of silicon dioxide, 30-45% of lead oxide, 4-8% of barium oxide, 1-2% of zinc oxide, 5-10% of aluminum oxide, 8-15% of boron trioxide, 1-4% of zirconium oxide and 2-4% of yttrium trioxide, and the total content of the above components is 100%; the mass ratio of the barium oxide and the zinc oxide is 2-4:1; the sealing glass further comprises a strengthened surface layer; the strengthened surface layer is arranged on the glass passivation layer; the strengthened surface layer is a compressive stress layer formed by ion exchange of Ba 2+ / Li + .

[0051] The application obtains a basic glass system suitable for subsequent chemical strengthening treatment by reasonably designing glass components, and simultaneously realizes the strength improvement and removal of harmful impurities of the glass by a molten salt ion exchange process, so as to prepare the sealing glass with high mechanical strength and excellent electrical properties. The appropriate amount of lead oxide and barium oxide and other components introduced in the basic glass not only ensure the low-temperature sealing performance, but also provide a structural basis for ion exchange in the subsequent chemical strengthening process. In the strengthening treatment, the composite molten salt system containing lithium nitrate, barium nitrate and zinc nitrate not only forms a compressive stress layer on the surface by the exchange of Ba 2+ and other large-radius ions and small-radius ions in the glass, which significantly improves the strength of the glass, but also effectively replaces the easily migratable sodium ions in the glass network, thereby reducing the ion conductivity of the glass, inhibiting the generation of leakage current and improving the insulation reliability of the packaged device.

[0052] The strength of the sealing glass prepared by the application is greater than 300 MPa, and the expansion coefficient is 35*10 -6 ~ 50*10 -6 / ℃.

[0053] In the above technical scheme, the application obtains a basic glass system suitable for subsequent chemical strengthening treatment by reasonably designing glass components, and simultaneously realizes the strength improvement and removal of harmful impurities of the glass by a molten salt ion exchange process, so as to prepare the sealing glass with high mechanical strength and excellent electrical properties. The appropriate amount of lead oxide and barium oxide and other components introduced in the basic glass not only ensure the low-temperature sealing performance, but also provide a structural basis for ion exchange in the subsequent chemical strengthening process. In the strengthening treatment, the composite molten salt system containing lithium nitrate, barium nitrate and zinc nitrate not only forms a compressive stress layer on the surface by the exchange of Ba +The exchange of ions with equal radius and small radius ions in the glass forms a compressive stress layer on the surface, significantly improves the strength of the glass, and effectively replaces the easily migratable sodium ions in the glass network, thereby reducing the ion conductivity of the glass, inhibiting the generation of leakage current, and improving the insulation reliability of the packaged device.

[0054] The strength of the sealing glass tested is greater than 300 MPa, and the expansion coefficient is 35-50x10-6 / ℃.

[0055] The application also provides an application of the sealing glass in the field of semiconductor surface passivation technology.

[0056] The application will be further described below in conjunction with specific examples, but it should not be understood as limiting the scope of protection of the application. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the application still belong to the scope of protection of the application.

[0057] Unless otherwise specified, the materials and reagents involved below are commercially available goods well known to those skilled in the art; unless otherwise specified, the methods described are well-known methods in the art. Unless otherwise defined, the technical terms or scientific terms used should be the usual meaning understood by those skilled in the art in the field of the application.

[0058] The test methods of various performance indicators in the embodiments of the application are as follows:

[0059] The expansion coefficient is tested according to the method of GB / T 16920-2015 "Determination of average linear expansion coefficient of glass".

[0060] The strength is tested according to the method of GB / T 37781-2019 "Glass material flexural strength test method".

[0061] The leakage current and reverse breakdown voltage are tested according to the method of GB / T 17573-1998 "Semiconductor devices Discrete devices and integrated circuits Part 1: General".

[0062] Example 1

[0063] According to the predetermined composition of high-strength sealing glass (in mass percentage), each component in the raw material is weighed and mixed uniformly: 30% of silicon dioxide, 45% of lead oxide, 5% of aluminum trioxide, 12% of boron oxide, 1% of zirconium oxide, 4% of barium oxide, 1% of zinc oxide and 2% of yttrium trioxide, the raw material ratio is shown in Table 1; wherein the mass of SiO2 is 200g, and the mass of the rest components corresponds; the uniformly mixed raw material is ball milled into a powder with a particle size of 900nm, placed in a melting furnace for high-temperature melting at 1550℃, the glass melt obtained by melting is clarified, and then is formed by leakage, and then is annealed at 420℃ for 3h to obtain lead glass. The lead glass is ball milled and crushed, and sieved to obtain a glass powder with a particle size of 200nm; the glass powder is used to prepare a glass slurry, the glass slurry is coated on the surface of the area to be passivated by a rotary coating method, and then is heat treated at 550℃ for 3h to form a glass passivation layer; then it is immersed in a molten chemical tempering molten salt to perform chemical tempering treatment, and a strengthened sealing glass is obtained; wherein the chemical tempering molten salt comprises lithium nitrate, barium nitrate and zinc nitrate, and the mass ratio of barium nitrate to zinc nitrate is 3:1; the amount of lithium nitrate added is 0.5% based on the mass of the chemical tempering molten salt; the chemical tempering temperature is 420℃, and the chemical tempering time is 2h; the process parameters are shown in Table 2. It is tested that the strength of the prepared sealing glass is 320MPa, the expansion coefficient is 40×10 -6 / ℃, the leakage current is 0.45μA (room temperature), the reverse breakdown voltage is 1450V, and the performance of the sealing glass is shown in Table 3.

[0064] Examples 2-17

[0065] The preparation method of Examples 2-17 is the same as that of Example 1, the raw material ratio of each component in the raw material of each example is shown in Table 1, the process parameters of each step are shown in Table 2, and the performance of the sealing glass is shown in Table 3.

[0066] Comparative Example 1

[0067] The difference between the present comparative example and Example 1 is that the present comparative example does not have annealing in the melting process, and the rest steps and parameters are the same as those of Example 1. It is tested that the strength of the prepared sealing glass is 135MPa, the expansion coefficient is 58×10 -6 / ℃, the leakage current is 1.9μA (room temperature), and the reverse breakdown voltage is 940V.

[0068] Comparative Example 2

[0069] The difference between the present comparative example and Example 1 is that the mass ratio of barium nitrate to zinc nitrate is 1:1 (as shown in Table 2), and the rest steps and parameters are the same as those of Example 1. It is tested that the strength of the prepared sealing glass is 180MPa, the expansion coefficient is 50×10 -6 / ℃, leakage current 3.8 μA (room temperature), reverse breakdown voltage 728 V.

[0070] Comparative Example 3

[0071] The difference between the present comparative example and Example 1 is that no lithium nitrate is added in the tempering molten salt of the present comparative example (as shown in Table 2), and the rest of the steps and parameters are the same as those of Example 1. The strength of the prepared sealing glass is 120 MPa, and the expansion coefficient is 53 x 10 -6 / ℃, leakage current 4.2 μA (room temperature), reverse breakdown voltage 701 V.

[0072] The raw material component proportions and preparation process conditions of Examples 1-17 and Comparative Examples 1-3 are summarized in Tables 1 and 2 below.

[0073] Table 1 Raw material component proportions of Examples 1-17 and Comparative Examples 1-3

[0074]

[0075]

[0076] Table 2 Preparation process conditions of Examples 1-17 and Comparative Examples 1-3

[0077]

[0078]

[0079] Note: ① Particle size after first ball milling / nm, ② Melting temperature / ℃, ③ Annealing temperature / ℃, ④ Annealing time / h, ⑤ Particle size after second ball milling / nm, ⑥ Heat treatment temperature / ℃, ⑦ Heat treatment time / h, ⑧ Barium nitrate / zinc nitrate, ⑨ Lithium nitrate (wt%), ⑩ Tempering temperature / ℃, Tempering time / h.

[0080] Table 3 Sealing glass performance test data of Examples 1-17 and Comparative Examples 1-3

[0081]

[0082]

[0083] As can be seen from the test data of Examples 1-17 above, the strength of the sealing glass prepared by the method of the present application is greater than 300 MPa, and the expansion coefficient is 35-50 x 10 -6 / ℃, leakage current is less than 0.50 μA (room temperature), and reverse breakdown voltage is greater than 1400 V. In the examples 1 to 17, the mass ratio of barium nitrate and zinc nitrate is between 3:1 and 4:1. The suitable mass ratio range is selected to enable barium nitrate and zinc nitrate to provide more effective barium ions and zinc ions, so that the molten salt exchanges with the ions with smaller ion radius in the glass to form multiple stress layers, thereby improving the strength performance after strengthening, the network space stability of the glass, and the alkali resistance of the glass; meanwhile, the possible Na ions in the glass are replaced, and the ion migration ability of the glass is reduced; the barium ions entering the glass will generate induced charges at the interface of the sealing passivation film layer after the sealing passivation, form negative centers, and reduce the reverse leakage current. The interfacial densification of zinc can effectively lock the deep compressive stress formed by barium promotion, so as to obtain an ideal combination of high surface compressive stress and large stress layer depth, thereby improving the strength performance after strengthening, and the strength of the obtained glass can be greater than 300 MPa. Compared with example 1, the lithium nitrate in example 16 is increased from 0.5 wt% to 1 wt%, and a deeper ion exchange layer and a higher surface compressive stress can be obtained under the same temperature and time, thereby improving the strength of the glass. Compared with example 1, the strengthening temperature in example 17 is increased to 480 ℃, and the time is prolonged to 4 h, so that the strengthening effect can be strengthened, and the strength of the glass can be improved.

[0084] Compared with example 1, the melting process of comparative example 1 does not have an annealing process, but uses the quenching process in the prior art. The glass does not undergo annealing but uses the quenching process, so that the glass maintains a loose structure at high temperature, the ion migration resistance is low, and the thermal expansion coefficient increases, resulting in a decline in the final performance of the glass.

[0085] In the strengthening molten salt of comparative example 2, the mass ratio of barium nitrate to zinc nitrate is 1:1. Barium nitrate and zinc nitrate can provide more effective barium ions and zinc ions, so that the molten salt exchanges with the ions with smaller ion radius in the glass to form multiple stress layers, thereby improving the strength performance after strengthening, the network space stability of the glass, and the alkali resistance of the glass. The mass ratio of barium nitrate to zinc nitrate is 1:1, and the excessive zinc content can cause the interface layer to grow excessively, thereby increasing the brittleness.

[0086] In comparative example 3, no lithium nitrate is added to the strengthening molten salt. Lithium ions help to form a stress layer with a more gentle composition gradient and a more dense structure on the surface of the glass, which can significantly inhibit the relaxation effect of the network structure of the glass surface during the high-temperature ion exchange process, so that the compressive stress obtained is more stable; on the other hand, the dense layer can effectively block the erosion of impurity ions in the molten salt to the glass network, thereby improving the chemical stability of the passivated glass after strengthening. Without adding lithium nitrate, the comprehensive performance of the glass will be significantly reduced.

[0087] The technical features in the claims and / or the specification of the present application can be combined, and the combination manner is not limited to the combination obtained by reference in the claims. The technical solutions obtained by combining the technical features in the claims and / or the specification are also within the protection scope of the present application.

[0088] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present application are still within the scope of the technical solutions of the present application.

Claims

1. A method for preparing sealing glass, characterized in that, It includes the following steps: S1 is prepared according to the sealing glass formula, mixed evenly, and then ball-milled; the raw materials are melted at high temperature, clarified, formed by leakage, and annealed to obtain lead glass; S2 involves crushing the lead glass, then ball milling and sieving it to obtain glass powder, which is then mixed into a slurry, applied to the surface of the area to be passivated, and heat-treated to form a glass passivation layer. S3 involves immersing the glass passivation layer in molten tempering salt and chemically tempering it at the designed temperature, simultaneously removing sodium ions to obtain a high-strength, low-leakage-current sealing glass.

2. The preparation method according to claim 1, characterized in that, The sealing glass formulation, by mass percentage of oxides, comprises 30-40% silicon dioxide, 30-45% lead oxide, 4-8% barium oxide, 1-2% zinc oxide, 5-10% aluminum oxide, 8-15% boron trioxide, 1-4% zirconium oxide, and 2-4% yttrium trioxide, with a total content of 100%. The mass ratio of barium oxide to zinc oxide is 2-4:

1. The tempering molten salt comprises lithium nitrate, barium nitrate, and zinc nitrate; the mass ratio of barium nitrate to zinc nitrate is 3-4:1; and the mass percentage of lithium nitrate is 0.5-1% of the tempering molten salt.

3. The preparation method according to claim 1 or 2, characterized in that, The particle size of the raw material after the first ball milling is <1μm.

4. The preparation method according to claim 2, characterized in that, The high-temperature melting temperature is 1550-1620℃; the annealing involves holding the glass at 420-450℃ for 3-5 hours.

5. The preparation method according to claim 1 or 2, characterized in that, After the second ball milling, the particle size of the glass powder is 200–2000 nm.

6. The preparation method according to claim 2, characterized in that, The heat treatment is performed at 550–620°C for 3–6 hours.

7. The preparation method according to claim 2, characterized in that, The chemical tempering treatment is carried out at a temperature of 420–480°C for 2–4 hours.

8. A sealing glass, characterized in that, The sealing glass is used for surface passivation of semiconductor devices and includes: The glass passivation layer has an amorphous Si-OB-Pb-Zr-Y cross-linked network structure; based on the mass percentage of oxides, it includes 30-40% silicon dioxide, 30-45% lead oxide, 4-8% barium oxide, 1-2% zinc oxide, 5-10% aluminum oxide, 8-15% boron oxide, 1-4% zirconium oxide, and 2-4% yttrium oxide, with the total content of the above components being 100%; wherein the mass ratio of barium oxide to zinc oxide is 2-4:1; A tempered surface layer is disposed on the glass passivation layer; the tempered surface layer is formed by permeating the glass passivation layer with Ba. 2+ / Li + The compressive stress layer formed by ion exchange has a depth ≥ 50 μm; the strength of the sealing glass is > 300 MPa, and the coefficient of thermal expansion is 35 × 10⁻⁶. -6 ~50×10 -6 / ℃.

9. The sealing glass according to claim 8, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

10. An application of the sealing glass according to claim 8 or 9 in the field of semiconductor surface passivation technology.

Images