Glass for covering semiconductor elements and semiconductor covering material using the same

Abstract

To provide a semiconductor element coating glass that has a small change of negative charge amount in the glass and high acid resistance in a bias test.SOLUTION: The semiconductor element coating glass contains, as a glass composition, in mol%, 55-85% of SiO2, 12-40% of PbO, 0.1-10% of Al2O3, and 0.1-6% of GeO2+Ta2O5+Nb2O5+Bi2O3.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a glass for covering semiconductor elements and a semiconductor covering material using the same. [Background technology]

[0002] In general, the surfaces of semiconductor elements such as silicon diodes and transistors, including the PN junctions, are covered with glass, which stabilizes the surface of the semiconductor elements and prevents their characteristics from deteriorating over time.

[0003] The properties required for glass for covering semiconductor elements include: (1) a thermal expansion coefficient that matches that of the semiconductor element to prevent cracks due to differences in the thermal expansion coefficient between the semiconductor element and the glass; (2) the glass must be capable of covering the semiconductor element at low temperatures (for example, 900°C or less, and particularly 860°C or less) to prevent deterioration of the characteristics of the semiconductor element; and (3) the glass must be free of impurities such as alkaline components that have adverse effects on the surface of the semiconductor element.

[0004] Conventionally, zinc-based glasses such as ZnO-B2O3-SiO2-based glasses and lead-based glasses such as PbO-SiO2-Al2O3-based glasses and PbO-SiO2-Al2O3-B2O3-based glasses have been known as glasses for covering semiconductor elements. However, from the standpoint of workability, lead-based glasses such as PbO-SiO2-Al2O3-based glasses and PbO-SiO2-Al2O3-B2O3-based glasses are currently mainstream (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 58-64424 [Patent Document 2] Special Publication No. 11-236239 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, in addition to the characteristics (1) to (3), glass for semiconductor coating is required to have the following characteristics: (4) after coating, the amount of charge in the glass becomes an appropriate amount of negative charge (initial NFB) that matches the design of the semiconductor device, and (5) during bias testing by heating and applying voltage, the change in the amount of negative charge in the glass is small. In particular, characteristic (5) is considered important in order to increase the reliability of semiconductor elements.

[0007] One type of glass that shows little change in negative charge due to bias testing is zinc-based glass. However, zinc-based glass has low acid resistance and may be corroded by acid during the manufacturing process of semiconductor devices, preventing it from performing to its full potential.

[0008] The present invention has been made in view of the above circumstances, and its technical object is to provide a glass for covering semiconductor elements which exhibits small change in the amount of negative charge in a bias test and has high acid resistance. [Means for solving the problem]

[0009] As a result of intensive research, the present inventors have found that the above technical problems can be solved by adding at least one of GeO2, Ta2O5, Nb2O5 and Bi2O3 to PbO-SiO2-Al2O3-based glass, and propose this invention. That is, the glass for covering semiconductor elements of the present invention is characterized by containing, in mole percent, SiO2 55-85%, PbO 12-40%, Al2O3 0.1-10%, and GeO2+Ta2O5+Nb2O5+Bi2O3 0.1-6% as a glass composition. Here, "GeO2+Ta2O5+Nb2O5+Bi2O3" refers to the total amount of GeO2, Ta2O5, Nb2O5 and Bi2O3. In addition, the glass for covering semiconductor elements of the present invention preferably contains GeO2 at a content of 0.1-6%.

[0010] As described above, the glass for covering semiconductor elements of the present invention has the range of each component regulated. This allows the glass to have a small change in the amount of negative charge in a bias test and high acid resistance. As a result, the semiconductor elements can be covered appropriately.

[0011] The material for covering a semiconductor element of the present invention preferably contains 75 to 100 mass % of glass powder made of the above-mentioned glass for covering a semiconductor element, and 0 to 25 mass % of ceramic powder.

[0012] The semiconductor element coating material of the present invention has a thermal expansion coefficient of 20×10 in the temperature range of 30 to 300° C. -7 / ℃~55×10 -7 / ° C. Here, the term "coefficient of thermal expansion in the temperature range of 30 to 300° C." refers to a value measured using a push rod type thermal expansion coefficient measuring device. Effect of the Invention

[0013] According to the present invention, it is possible to provide a glass for covering a semiconductor element which exhibits small change in the amount of negative charge in the glass in a bias test and has high acid resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The glass for covering semiconductor elements of the present invention is characterized by containing, in mole percent, SiO2 55-85%, PbO 12-40%, Al2O3 0.1-10%, and GeO2+Ta2O5+Nb2O5+Bi2O3 0.1-6% as a glass composition. The reason for limiting the content of each component as described above is explained below. In the following explanation of the content of each component, % means mole percent unless otherwise specified.

[0015] SiO2 is a component that enhances acid resistance. The SiO2 content is preferably 55 to 85%, 60 to 80%, and particularly preferably 65 to 75%. If the SiO2 content is too low, the acid resistance is likely to decrease and vitrification is difficult. On the other hand, if the SiO2 content is too high, the firing temperature becomes high, which is likely to deteriorate the characteristics of the semiconductor element in the coating process. In addition, the melting temperature becomes too high, making vitrification difficult.

[0016] PbO is a component that lowers the firing temperature. The PbO content is preferably 12-40%, 14-36%, 16-32%, and particularly preferably 18-28%. If the PbO content is too low, the firing temperature becomes high, which tends to deteriorate the characteristics of the semiconductor element in the coating process. In addition, the melting temperature becomes too high, making vitrification difficult. On the other hand, if the PbO content is too high, the thermal expansion coefficient becomes too high, which results in significant warping of the wafer.

[0017] Al2O3 is a component that stabilizes glass. The content of Al2O3 is preferably 0.1 to 10%, 2 to 8%, 2 to 7%, and particularly preferably 3 to 6%. If the content of Al2O3 is too low, vitrification becomes difficult. On the other hand, if the content of Al2O3 is too high, the firing temperature may become too high.

[0018] GeO2, Ta2O5, Nb2O5 and Bi2O3 are all components that stabilize the glass skeleton and suppress the change in the amount of negative charge due to bias testing. The total amount of these components is preferably 0.1 to 6%, 0.3 to 5%, 0.5 to 4%, and particularly preferably 0.5 to 3.5%. The individual contents of these components are also preferably 0.1 to 6%, 0.3 to 5%, 0.5 to 4%, and particularly preferably 0.5 to 3.5%. In particular, it is preferable that GeO2 is 0.1 to 6%. If the contents of these components are too small, the change in the amount of negative charge due to bias testing becomes large. On the other hand, if the contents of these components are too large, it becomes difficult to obtain electrical properties suitable for semiconductor coating.

[0019] In addition to the above components, other components may be incorporated. For example, B2O3, CaO, SrO, BaO, MnO2, CeO2, Sb2O3, etc. may each be contained up to 7% (preferably up to 3%). The total amount of other components is preferably 7% or less, particularly 3% or less.

[0020] From the viewpoint of the influence on semiconductor elements, it is preferable that the glass is substantially free of alkali metal oxides (Li2O, Na2O, and K2O) that adversely affect the surface of semiconductor elements. Here, "substantially free of alkali metal oxides" means that the content of alkali metal oxides in the glass composition is less than 0.1 mol%.

[0021] The glass for covering a semiconductor element of the present invention is preferably in a powder form, that is, in the form of glass powder. If it is processed into glass powder, it can be easily used to cover the surface of a semiconductor element by, for example, a paste method or an electrophoretic coating method.

[0022] Average particle size of glass powder D 50 is preferably 25 μm or less, particularly 15 μm or less. 50 If the average particle diameter D of the glass powder is too large, it becomes difficult to form a paste. It also becomes difficult to apply the paste by electrophoresis. 50 The lower limit of the average particle diameter D is not particularly limited, but in reality it is 0.1 μm or more. 50 " is a value measured on a volume basis and refers to a value measured by a laser diffraction method.

[0023] The glass for covering semiconductor elements of the present invention can be obtained, for example, by blending raw material powders of each oxide component into a batch, melting the batch at about 1500°C for about 1 hour to vitrify the batch, and then molding the batch (and then crushing and classifying the batch, if necessary).

[0024] The semiconductor element coating material of the present invention preferably contains 75 to 100 mass% glass powder and 0 to 25 mass% ceramic powder, more preferably contains 85 to 100 mass% glass powder and 0 to 15 mass% ceramic powder, further preferably contains 95 to 100 mass% glass powder and 0 to 5 mass% ceramic powder, and particularly preferably contains more than 99 to 100 mass% glass powder and 0 to less than 1 mass% ceramic powder. The addition of ceramic powder makes it easier to adjust the thermal expansion coefficient. On the other hand, if the content of ceramic powder is too high, the softening flowability is impaired, making it difficult to coat the surface of the semiconductor element.

[0025] Average particle size of ceramic powder D 50 is preferably 30 μm or less, particularly 20 μm or less. 50 If the average particle diameter D of the ceramic powder is too large, the surface smoothness of the coating layer is likely to decrease. 50 The lower limit is not particularly limited, but is practically 0.1 μm or more.

[0026] In the semiconductor element coating material of the present invention, the thermal expansion coefficient in the temperature range of 30 to 300° C. is preferably 20×10 -7 / ℃~55×10 -7 / ℃, especially 30×10 -7 / ℃~50×10 -7 If the thermal expansion coefficient is outside the above range, cracks, warping, etc. are likely to occur due to the difference in thermal expansion coefficient with the semiconductor element.

[0027] In the semiconductor element coating material of the present invention, the softening point is preferably 880° C. or less, 860° C. or less, and particularly preferably 840° C. or less. If the softening point is too high, the firing temperature becomes high, and there is a risk of impairing the characteristics of the semiconductor element in the coating process. Here, the "softening point" is the temperature of the fourth inflection point obtained by macro-type differential thermal analysis. EXAMPLES

[0028] The present invention will be described in detail below based on examples. Note that the following examples are merely illustrative and the present invention is not limited to the following examples in any way.

[0029] Table 1 shows examples of the present invention (samples Nos. 1 to 7) and comparative examples (samples Nos. 8 to 11).

[0030] [Table 1]

[0031] Each sample was prepared as follows. First, raw material powders were mixed to obtain the glass composition shown in the table to prepare a batch, which was then melted at 1500°C for 1 hour to form a vitrified glass. The molten glass was then formed into a film, which was then crushed in a ball mill and classified using a 350 mesh sieve to obtain the average particle diameter D 50 In sample No. 4, cordierite powder (average particle diameter D 50 10% by mass of ZnO (12 μm) was added to prepare a composite powder.

[0032] The softening point, firing temperature, thermal expansion coefficient, electrical properties, acid resistance, and change in negative charge were evaluated for each sample. The results are shown in Table 1.

[0033] The softening point is the temperature of the fourth inflection point obtained by macro-type differential thermal analysis. The firing temperature is a temperature 20°C higher than the softening point.

[0034] The thermal expansion coefficient is a value measured in a temperature range of 30 to 300°C using a push rod type thermal expansion coefficient measuring device.

[0035] The electrical properties were measured as follows. First, glass powder was attached to a silicon wafer by electrophoresis, and then the wafer was baked for 15 minutes at the baking temperature shown in the table. Aluminum was evaporated onto the glass surface of the silicon wafer thus obtained as an electrode, and the amount of negative charge was measured. The amount of negative charge was 1×9 11 / cm 2 ~10×911 / cm 2 The cases were marked as "○" and the others as "×".

[0036] Acid resistance was evaluated as follows. Each sample was press molded into a size of about 20 mm in diameter and 4 mm in thickness, then fired at the firing temperature in the table to prepare a pellet-shaped sample. This sample was then immersed in 30% nitric acid at 25°C for 1 minute, after which the mass change per unit area was calculated from the mass loss. If the mass change per unit area was 1.0 mg / cm 2 Less than 1.0mg / cm 2 The above was marked as "X".

[0037] The change in the amount of negative charge was evaluated as follows. First, glass powder was attached to a silicon wafer by electrophoresis, and then baked for 15 minutes at the baking temperature shown in the table. Aluminum was evaporated onto the glass surface of the silicon wafer thus obtained as an electrode. Next, this silicon wafer was placed in a thermostatic chamber at 150°C and held for 24 hours with a voltage of 400V applied between the back surface of the silicon wafer and the electrode, after which the electrical characteristics were evaluated and the change in the amount of negative charge measured was found to be 5 x 10 11 / cm 2 If it was less than this, it was marked as "○" and otherwise it was marked as "×".

[0038] As is clear from Table 1, samples Nos. 1 to 7 have a thermal expansion coefficient of 44×10 -7 / ℃~49×10 -7 / ° C., the firing temperature was 860° C. or less, and the electrical characteristics, acid resistance, and negative charge change were also evaluated as being good. Therefore, Samples Nos. 1 to 7 are considered to be suitable as semiconductor element coating materials.

[0039] On the other hand, sample No. 8 did not vitrify because the melting temperature was too high. Sample No. 9 did not have good electrical properties. Sample No. 10 had too large a change in the amount of negative charge. Sample No. 11 had poor acid resistance.

Claims

1. The glass composition is, in mol%, SiO ２ 55-85%, PbO 12-40%, Al ２ O ３ 0.1-10%, GeO 2 0.1-6%, B 2 O 3 0-7%, GeO ２ +Ta ２ O ５ +Nb ２ O ５ +Bi ２ O ３ A glass for covering semiconductor elements, comprising 0.1 to 6% of alumina.

2. A material for covering a semiconductor element, comprising 75 to 100 mass % of a glass powder made of the glass for covering a semiconductor element according to claim 1, and 0 to 25 mass % of a ceramic powder.

3. The thermal expansion coefficient in the temperature range of 30 to 300°C is 20 x 10 －７ / ℃~55×10 －７ 3. The semiconductor element coating material according to claim 2, wherein the temperature is 100° C. / ° C.

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