Glass for coating semiconductor element and sintered body for coating semiconductor element

Abstract

Provided is a glass for coating a semiconductor element, which has little environmental burden and is not susceptible to devitrification in a melting step. This glass for coating a semiconductor element is characterized by containing, in mol%, 40 to 75% of (SiO2 + ZnO), 0 to 20% of B2O3, 5 to 15% of Al2O3, and 8 to 22% of (MgO + CaO) as a glass composition, with Al2O3 / (SiO2 + ZnO) in a molar ratio of 0.2 or less, and containing substantially no lead component.

Description

Technical Field

[0001] The present invention relates to glass for coating semiconductor devices and sintered bodies for coating semiconductor devices. Background Technology

[0002] For semiconductor devices such as silicon diodes and transistors, the surface containing the PN junction is typically covered with glass. This stabilizes the surface of the semiconductor device and suppresses the degradation of its properties over time.

[0003] The characteristics required for glass used to coat semiconductor elements include: (1) the coefficient of thermal expansion must match that of the semiconductor element in order to prevent cracks caused by the difference in coefficients of thermal expansion with the semiconductor element; (2) the coating must be performed at low temperatures (e.g., below 900°C) in order to prevent the degradation of the semiconductor element's properties; (3) the glass must not contain impurities such as alkaline components that would adversely affect the surface of the semiconductor element; etc.

[0004] For a long time, zinc-based glasses such as ZnO-B2O3-SiO2, lead-based glasses such as PbO-SiO2-Al2O3, and PbO-SiO2-Al2O3-B2O3 have been known as coating glasses for semiconductor devices. However, currently, from a workability point of view, lead-based glasses such as PbO-SiO2-Al2O3 and PbO-SiO2-Al2O3-B2O3 have become the mainstream (for example, see Patent Documents 1 to 4).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 48-43275

[0008] Patent Document 2: Japanese Patent Application Publication No. 50-129181

[0009] Patent Document 3: Japanese Patent Publication No. 1-49653

[0010] Patent Document 4: Japanese Patent Application Publication No. 2008-162881 Summary of the Invention

[0011] The technical problem that the invention aims to solve

[0012] However, lead in lead-based glass is an environmentally harmful component. Zinc-based glass, as mentioned above, contains small amounts of lead and bismuth, therefore it cannot be said to be completely harmless to the environment.

[0013] In addition, compared with lead-based glass, zinc-based glass is prone to devitrification during the melting process.

[0014] Therefore, the present invention was made in view of the above circumstances, and its technical objective is to provide a semiconductor element coating glass with low environmental impact and low devitrification during the melting process.

[0015] Technical means for solving problems

[0016] The inventors conducted in-depth research and discovered that the devitrifier generated during the glass melting process is zinc aluminum spinel (ZnAl2O4). In SiO2-ZnO-Al2O3 glass, by limiting the ratio of Al2O3 content to the total content of SiO2 and ZnO, zinc aluminum spinel is less likely to be generated during the glass melting process, and this invention is proposed. Specifically, the glass used for coating semiconductor devices according to the present invention is characterized by containing, in molar percentage: SiO2+ZnO 40%~75%, B2O3 0~20%, Al2O3 5%~15%, (MgO+CaO) 8%~22%, and in molar ratio, Al2O3 / (SiO2+ZnO) is less than 0.2, and substantially contains no lead. Here, "SiO2+ZnO" refers to the total content of SiO2 and ZnO. "MgO+CaO" refers to the total content of MgO and CaO. "Al2O3 / (SiO2+ZnO)" refers to the value obtained by dividing the content of Al2O3 by the total content of SiO2 and ZnO. Furthermore, "substantially free of" means that this component will not be intentionally added as a glass component, but does not mean that unavoidable impurities are completely excluded. Specifically, it means that the content of this component, including impurities, is less than 0.1% by mass.

[0017] The glass used to coat the semiconductor element of the present invention preferably has a coefficient of thermal expansion of 20 × 10⁻⁶ in a temperature range of 30°C to 300°C. -7 / ℃~55×10 -7 / ℃. Here, "coefficient of thermal expansion in the temperature range of 30℃ to 300℃" refers to the value measured using a push-rod type coefficient of thermal expansion measuring device.

[0018] Invention Effects

[0019] According to the present invention, a semiconductor device coating glass with low environmental impact and low devitrification during the melting process can be provided. Detailed Implementation

[0020] The glass used to coat the semiconductor element of the present invention is characterized in that, as a glass composition, it contains, in mole percent: (SiO2 + ZnO) 40%~75%, B2O3 0~20%, Al2O3 5%~15%, and (MgO + CaO) 8%~22%, and in mole ratio, Al2O3 / (SiO2 + ZnO) is 0.2 or less, and it substantially does not contain lead. The reasons for limiting the content of each component are explained below. It should be noted that, unless otherwise specified, the percentage (%) in the following description of the content of each component refers to mole percent. In this specification, the numerical range indicated by “~” refers to the range of values ​​listed before and after “~” as the minimum and maximum values, respectively.

[0021] SiO2 and ZnO are components that stabilize the glass. The SiO2 + ZnO content is 40%~75%, preferably 45%~70%, 50%~68%, or 53%~65%, and particularly preferably 55%~64%. If there is too little SiO2 + ZnO, zinc aluminum spinel is prone to precipitate during the melting process. On the other hand, if there is too much SiO2 + ZnO, the softening point of the glass is prone to increase significantly.

[0022] The SiO2 content is preferably 25%~40%, 22%~38%, or 24%~36%, and particularly preferably 26%~34%.

[0023] The ZnO content is preferably 15%~40%, 22%~38%, or 24%~36%, and particularly preferably 26%~34%.

[0024] B2O3 is a component that forms the mesh of glass and improves its softening and fluidity. The content of B2O3 is 0-20%, preferably 0-18%, and particularly preferably 0-16%. If the content of B2O3 is too high, there is a tendency for the coefficient of thermal expansion to increase inappropriately and the acid resistance to decrease.

[0025] Al₂O₃ is a component that stabilizes glass. The Al₂O₃ content is 5% to 15%, preferably 6% to 14%, 7% to 13%, 8% to 12%, or 8% to 11%, and particularly preferably 9% to 10%. If the Al₂O₃ content is too low, vitrification is difficult. On the other hand, if the Al₂O₃ content is too high, zinc aluminum spinel tends to precipitate during the melting process. Furthermore, the softening point of the glass tends to rise significantly.

[0026] In terms of molar ratio, Al2O3 / (SiO2+ZnO) should be 0.2 or less, preferably 0.19 or less, and particularly preferably 0.18 or less. If Al2O3 / (SiO2+ZnO) is too high, zinc-aluminum spinel is prone to precipitate during the melting process. There is no particular lower limit for Al2O3 / (SiO2+ZnO), but in practice it is above 0.07.

[0027] MgO and CaO are components that reduce the viscosity of glass. The MgO+CaO content is 8% to 22%, and particularly preferably 10% to 20%. If there is too little MgO+CaO, the softening temperature of the glass is likely to rise. On the other hand, if the MgO+CaO content is too high, the coefficient of thermal expansion may become too high, or the acid resistance or insulation may decrease.

[0028] The MgO content is preferably 2% to 20%, 3% to 15%, and particularly preferably 4% to 13%.

[0029] The preferred CaO content is 2% to 20%, 3% to 15%, and particularly preferred is 4% to 13%.

[0030] In addition to the above-mentioned components, other components (such as SrO, BaO, MnO2, Ta2O5, Nb2O5, CeO2, Sb2O3, etc.) may be contained in 7% or less (preferably 3% or less).

[0031] From an environmental perspective, it is preferable that the semiconductor device is substantially free of lead (e.g., PbO) and substantially free of Bi2O3, F, and Cl. Furthermore, it is preferable that it is also substantially free of alkaline components (Li2O, Na2O, and K2O) that could adversely affect the surface of semiconductor devices.

[0032] The coefficient of thermal expansion of the glass used to coat the semiconductor element of the present invention is preferably 20 × 10⁻⁶ in the temperature range of 30°C to 300°C. -7 / ℃~55×10 -7 / ℃, preferably 30×10 -7 / ℃~50×10 -7 / ℃. If the coefficient of thermal expansion is outside the above range, cracks, warping, etc., are likely to occur due to the difference in thermal expansion coefficient with that of the semiconductor element.

[0033] The glass used to coat the semiconductor element in this invention is preferably in powder form. If it is processed into powder, the surface of the semiconductor element can be easily coated using, for example, a paste method or an electrophoretic coating method.

[0034] The average particle size D of the glass powder 50 Preferably, the particle size is 25 μm or less, and particularly preferably 15 μm or less. If the average particle size D of the glass powder... 50 If the particle size is too large, paste formation becomes difficult. Furthermore, paste coating using electrophoresis also becomes challenging. It should be noted that the average particle size D of the glass powder... 50 There is no specific lower limit, but in reality it is above 0.1 μm. It should be noted that "average particle size D..." 50 "This is a value determined based on volume, referring to a value determined using laser diffraction."

[0035] The glass used to coat the semiconductor element of the present invention can also be mixed with ceramic powder as needed to form a composite powder. Adding ceramic powder makes it easy to adjust the coefficient of thermal expansion.

[0036] The ceramic powder content is preferably less than 25 parts by weight, and particularly preferably less than 20 parts by weight, relative to 100 parts by weight of glass powder. If the ceramic powder content is too high, the softening and fluidity of the glass will be impaired, making it difficult to coat the surface of semiconductor devices.

[0037] Average particle size D of ceramic powder 50 Preferably, the particle size is 30 μm or less, and particularly preferably 20 μm or less. If the average particle size D of the ceramic powder... 50 If the particle size is too large, the surface smoothness of the coating layer is easily reduced. The average particle size D of the ceramic powder... 50 There is no specific lower limit, but in reality it is above 0.1μm.

[0038] Next, an example of a method for manufacturing a semiconductor element coating glass and a semiconductor element coating sintered body according to the present invention will be described.

[0039] First, the raw material powder, prepared in a manner that yields the desired glass composition, is melted at 1300°C to 1550°C for 1 to 2 hours until a homogeneous glass is obtained. Next, the obtained molten glass is shaped into a film or similar form, then pulverized and graded to produce powdered glass for coating semiconductor devices.

[0040] Next, a powdered semiconductor element coating glass is deposited on the surface of the semiconductor element, for example using a paste method or electrophoretic coating method. Then, by heat treatment, the semiconductor element coating glass deposited on the surface of the semiconductor element becomes a sintered body for semiconductor element coating that does not precipitate crystals. In addition, the sintered body for semiconductor element coating preferably has the same composition range as the glass composition of the semiconductor element coating glass.

[0041] Example

[0042] The present invention will now be described in detail based on embodiments. However, the following embodiments are merely examples. The present invention is not limited to these embodiments in any way.

[0043] Table 1 shows the embodiments (samples No. 1 to No. 4, No. 9, No. 10) and comparative examples (samples No. 5 to No. 8) of the present invention.

[0044] [Table 1]

[0045]

[0046] The samples were prepared as follows. First, the raw material powder was prepared in batches according to the glass composition shown in the table, and then vitrified by melting at 1500°C for 1 hour. Next, the molten glass was formed into a film, pulverized using a ball mill, and classified using a 350-mesh sieve to obtain an average particle size D. 50 It is a 12μm glass powder.

[0047] For each sample, the coefficient of thermal expansion and resistance to devitrification were evaluated. The results are shown in Table 1.

[0048] The coefficient of thermal expansion is a value measured using a push-rod type thermal expansion coefficient measuring device within a temperature range of 30℃ to 300℃.

[0049] Resistance to devitrification was evaluated as follows. 100g of each sample's glass film was placed in a platinum crucible and kept at 1150°C for 24 hours. Devitrification (zinc-aluminum spinel) was visually confirmed. Then, the crucible was kept at 1400°C for 10 minutes. If no devitrification (zinc-aluminum spinel) was visually confirmed, the result was rated "0"; if devitrification (zinc-aluminum spinel) was confirmed, the result was rated "×". It should be noted that X-ray diffraction was used to determine the devitrification, confirming it as zinc-aluminum spinel.

[0050] As shown in Table 1, samples No.1~No.4, No.9, and No.10 have a devitrification resistance of 0 and a coefficient of thermal expansion of 20×10⁻⁶. -7 / ℃~55×10 -7 / ℃. It should be noted that when samples No.1 to No.4 were fired for 10 minutes at the temperatures listed in the table, no crystals were precipitated.

[0051] On the other hand, among samples No.5 to No.8, due to the excessive Al2O3 / (SiO2+ZnO), the devitrification resistance was ×, and they were considered to be glasses that might cause obstacles to the melting process.

Claims

1. A glass coating for a semiconductor element, characterized in that, As a glass composition, it contains, in molar percentage: (SiO2+ZnO) 40%~75%, B2O3 0~20%, Al2O3 5%~15%, (MgO+CaO) 8%~22%, and in molar ratio, Al2O3 / (SiO2+ZnO) is less than 0.2, and it does not contain lead.

2. The glass used to coat semiconductor devices according to claim 1, characterized in that, The coefficient of thermal expansion in the temperature range of 30℃ to 300℃ is 20×10. -7 / ℃~55×10 -7 / ℃.

3. A sintered body for coating semiconductor devices, characterized in that, As a component, it contains, in molar percentage: (SiO2+ZnO) 40%~75%, B2O3 0~20%, Al2O3 5%~15%, (MgO+CaO) 8%~22%, and in molar ratio, Al2O3 / (SiO2+ZnO) is less than 0.2, and it does not contain lead.

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