JP6410089B2 - Glass for semiconductor element coating - Google Patents

Description

  The present invention relates to glass used for coating a semiconductor element including a PN junction.

  In general, a semiconductor element such as a silicon diode or a transistor is covered with glass on the surface including the PN junction of the semiconductor element from the viewpoint of preventing contamination by outside air. As a result, the surface of the semiconductor element can be stabilized and deterioration of characteristics over time can be suppressed.

  The characteristics required for glass for semiconductor element coating are as follows: (1) The thermal expansion coefficient matches the thermal expansion coefficient of the semiconductor element so that cracks do not occur due to the difference in thermal expansion coefficient with the semiconductor element during coating. (2) To prevent deterioration of the characteristics of the semiconductor element, it can be coated at a relatively low temperature (for example, 900 ° C. or less), and (3) It does not contain impurities such as alkali metal components that adversely affect the characteristics of the semiconductor element. (4) The electrical characteristics after the semiconductor element surface coating includes high reliability such as high reverse breakdown voltage and low leakage current.

Conventionally, as glass for semiconductor element coating, zinc-based glass such as ZnO—B ₂ O ₃ —SiO ₂ , PbO—SiO ₂ —Al ₂ O ₃ or PbO—SiO ₂ —Al ₂ O ₃ —B ₂ Lead glass such as O ₃ system is known, and lead glass such as PbO—SiO ₂ —Al ₂ O ₃ system and PbO—SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ system from the viewpoint of workability. Has become the mainstream (see, for example, Patent Documents 1 to 4).

Japanese Examined Patent Publication No. 1-49653 JP 50-129181 A JP-A-48-43275 JP 2008-162881 A

Since lead components such as PbO are components with a large environmental load, in recent years, their use in electrical and electronic devices is being regulated, and lead-free materials are being developed. Some zinc-based glasses such as ZnO—B ₂ O ₃ —SiO _{2 described} above contain a small amount of a lead component, and some of them are restricted in terms of environment.

On the other hand, glass containing no lead component has a low surface charge density, and it is difficult to deal with medium to high withstand voltage semiconductor elements. As a semiconductor element coating material having a high surface charge density, a material made of glass containing Bi ₂ O ₃ has also been proposed. However, Bi ₂ O ₃ is concerned about the burden on the environment like lead.

  In view of the above, an object of the present invention is to provide a glass for coating a semiconductor element that has a low environmental burden and a high surface charge density.

As a result of intensive studies, the present inventor has found that the above problem can be solved by using a ZnO—B ₂ O ₃ —SiO ₂ glass having a characteristic composition, and proposes the present invention.

That is, the glass for covering a semiconductor element of the present invention is 50% by mass of ZnO (excluding 62%), 19-28% of B ₂ O ₃ , 8-15% of SiO ₂ (however, 8%). Not containing), Al ₂ O ₃ 3 to 12%, and containing substantially no alkali metal component, lead component, Bi ₂ O ₃ , Sb ₂ O ₃ and As ₂ O ₃ .

  In the present invention, “substantially does not contain” means that the glass component is not intentionally added, and does not mean that impurities inevitably mixed are completely excluded. Objectively, it means that the content of the relevant components including impurities is less than 0.1% by mass.

The glass for coating a semiconductor element of the present invention preferably further contains MnO ₂ 0 to 5%, Nb ₂ O ₅ 0 to 5%, and CeO ₂ 0 to 3% by mass.

  The glass powder for covering a semiconductor element of the present invention is characterized by comprising the above glass for covering a semiconductor element.

The semiconductor element coating material of the present invention is selected from 100 parts by mass of the above semiconductor element coating glass powder, TiO ₂ , ZrO ₂ , ZnO, αZnO · B ₂ O ₃ , 2ZnO · SiO ₂ , cordierite and quartz. It contains 0.01 to 5 parts by mass of at least one inorganic powder.

  In particular, when the contact area between the semiconductor element such as Si and the covering glass is very large, it is desirable that the thermal expansion coefficients of the semiconductor element and the covering glass are close to suppress the occurrence of cracks and the like. Although the thermal expansion coefficient of the glass for coating can be adjusted by the crystal component contained in the glass, it is very difficult to appropriately control the amount of precipitated crystals. Therefore, if the above inorganic powder is appropriately added to the glass powder for covering a semiconductor element, these inorganic powders serve as a nucleating agent, so that the amount of precipitated crystals can be controlled relatively easily. As a result, a desired thermal expansion coefficient can be easily achieved.

The glass for coating a semiconductor element of the present invention is 50% by mass of ZnO (excluding 62%), 19-28% of B ₂ O ₃ , 8-15% of SiO ₂ (excluding 8%) in mass%. ), Al ₂ O ₃ 3 to 12%, and contains substantially no alkali metal component, lead component, Bi ₂ O ₃ , Sb ₂ O ₃ and As ₂ O ₃ . Hereinafter, the reason why the content of each component is defined as described above in the glass for coating a semiconductor element of the present invention will be described. In the following description regarding the content of each component, “%” means “% by mass” unless otherwise specified.

  ZnO is a component that stabilizes the glass. The content of ZnO is 50 to 62% ZnO (excluding 62%), preferably 55 to 61%. If the ZnO content is too small, the above effect is difficult to obtain. In addition, the coefficient of thermal expansion tends to increase, and as a result, the difference in thermal expansion between the glass and the semiconductor element increases, and there is a risk of cracks occurring in the glass. On the other hand, if the ZnO content is too large, crystallization proceeds rapidly due to the heat treatment during coating, so that it tends to be difficult to coat the surface of the semiconductor element due to insufficient fluidity.

B ₂ O ₃ is a network forming component and has an effect of improving fluidity. The content of B ₂ O ₃ is 19 to 28%, preferably 20 to 25%. If the content of B ₂ O ₃ is too small, fluidity crystallinity becomes strong is impaired, it tends to be difficult to coat the semiconductor element surface. On the other hand, when the content of B ₂ O ₃ is too large, the thermal expansion coefficient tends to be large. As a result, the difference in thermal expansion between the glass and the semiconductor element is increased, and there is a risk that the glass will crack.

SiO ₂ is a network forming component and has an effect of increasing acid resistance. The content of SiO ₂ is 8 to 15% (however, not including 8%), and preferably 9 to 14%. When the content of SiO ₂ is too small, chemical durability tends to decrease. In addition, the coefficient of thermal expansion tends to increase, and as a result, the difference in thermal expansion between the glass and the semiconductor element increases, and there is a risk of cracks occurring in the glass. When the content of SiO ₂ is too large, homogeneity tends to lower.

Al ₂ O ₃ is a component that increases the surface charge density. The content of Al ₂ O ₃ is 3 to 12%, preferably 5 to 10%, and more preferably 5.5 to 9.5%. When the content of Al ₂ O ₃ is too small, the effect is difficult to obtain. On the other hand, when the content of _Al 2 _{O 3} is too large, it tends to be devitrified.

Alkali metal components (such as Li ₂ O, Na ₂ O and K ₂ O) tend to adversely affect the characteristics of the semiconductor element. Therefore, the glass for covering a semiconductor element of the present invention does not substantially contain an alkali metal component. The semiconductor element for covering glass of the present invention, from the viewpoint of reducing the load on the environment, is substantially free of lead component, Sb ₂ O ₃ and As ₂ O _3. Furthermore, as described above, Bi ₂ O ₃ is also a component that is feared to be burdened with the environment. Therefore, the glass for covering a semiconductor element of the present invention does not substantially contain Bi ₂ O ₃ . When Bi ₂ O ₃ is contained, the surface charge density can be easily increased, so that the breakdown voltage is easily increased, but at the same time, the leakage current tends to increase. Therefore, it is effective not to contain Bi ₂ O ₃ substantially from the viewpoint of reducing the leakage current.

The glass for covering a semiconductor element of the present invention can contain MnO ₂ , Nb ₂ O ₅ or CeO ₂ in addition to the above components. These components have the effect of reducing the leakage current of the semiconductor element.

The MnO ₂ content is preferably 0 to 5%, more preferably 0.1 to 3%. When the content of MnO ₂ is too large, there is a tendency that the melting is lowered.

The content of Nb ₂ O ₅ is preferably 0 to 5%, and more preferably 0.1 to 3%. When the content of Nb ₂ O ₅ is too large, there is a tendency that the melting is lowered.

The CeO ₂ content is preferably 0 to 3%, more preferably 0.1 to 2%. When the CeO ₂ is too much, too strong crystallinity, the fluidity tends to decrease.

The glass for coating a semiconductor element of the present invention is preferably in the form of a powder (a glass powder for coating a semiconductor element) from the viewpoint of easily covering the surface of the semiconductor element. In this case, preferably has an average particle diameter D ₅₀ of the glass powder is 25μm or less, more preferably 15μm or less. When the average particle diameter D ₅₀ of the glass powder is too large, or become difficult to paste, or electrophoretic coating tends to become difficult. The lower limit of the average particle diameter D ₅₀ of the glass powder is not particularly limited, in practice it is 0.1μm or more.

  The glass for coating a semiconductor element of the present invention can be obtained by preparing a batch by mixing raw material powders such as oxides, and melting and melting at around 1400 ° C. for about 1 hour. Moreover, the glass powder for semiconductor element coating | cover can be obtained by further grind | pulverizing and classifying with respect to the glass after shaping | molding.

The semiconductor element coating material of the present invention is selected from TiO ₂ , ZrO ₂ , ZnO, αZnO · B ₂ O ₃ , 2ZnO · SiO ₂ , cordierite and quartz with respect to the glass powder for coating a semiconductor element. It contains at least one inorganic powder as a nucleating agent. The content of the inorganic powder is preferably 0.01 to 5 parts by mass and more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the semiconductor element coating glass powder. When the content of the inorganic powder is too small, the amount of precipitated crystals decreases, making it difficult to achieve a desired thermal expansion coefficient. When the content of the inorganic powder is too large, the amount of precipitated crystals increases so that the fluidity is impaired and the semiconductor element surface tends to be difficult to coat.

Note that the smaller the particle size of the inorganic powder, the smaller the particle size of the precipitated crystals and the denser the structure of the coating material, so that the mechanical strength tends to increase. Therefore, it is preferable that the average particle diameter D ₅₀ of the inorganic powder is 5μm or less, more preferably 3μm or less. The lower limit of the average particle diameter D ₅₀ of the inorganic powder is not particularly limited, in practice it is 0.1μm or more.

The surface charge density of the glass for covering a semiconductor element and the material for covering a semiconductor element of the present invention is 4 × 10 ¹¹ / cm ² or more for a semiconductor device having a voltage of 1000V and 9 × 10 for a semiconductor device having a voltage of 1500V or more. It is preferable that it is ¹¹ / cm ² or more. As the surface charge density increases, the breakdown voltage increases, but at the same time, the leakage current tends to increase. Therefore, when applied to a semiconductor element of about 1000 to 1500 V, the surface charge density is, for example, 12 × 10 ¹¹ / cm ² or less, further 10 × 10 ¹¹ / cm ^{2 in} order to suppress the leakage current and balance the breakdown voltage. It is preferable to adjust to cm ² or less.

The thermal expansion coefficient (30 to 300 ° C.) of the semiconductor element coating glass and the semiconductor element coating material of the present invention is, for example, 20 to 60 × 10 ⁻⁷ / ° C., or 30 depending on the thermal expansion coefficient of the semiconductor element. It adjusts suitably in the range of -50 * 10 < ^-7 > / degreeC.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples.

  Table 1 shows examples of the present invention and comparative examples.

Each sample was produced as follows. First, a raw material powder was prepared so as to have the glass composition shown in Table 1, and a batch was prepared. After the molten glass was formed into a film, it was pulverized with a ball mill and classified using a 350 mesh sieve to obtain a glass powder for covering a semiconductor element (average particle diameter D ₅₀ : 12 μm).

  The thermal expansion coefficient and surface charge density of the obtained glass powder for coating a semiconductor element were measured. In Example 6, measurement was performed on a semiconductor element coating glass powder added with 0.1 part by mass of ZnO powder to 100 parts by mass. The results are shown in Table 1.

  The thermal expansion coefficient was measured in a temperature range of 30 to 300 ° C. using a dilatometer.

  The surface charge density was measured as follows. First, glass powder was dispersed in an organic solvent, adhered to the silicon plate surface by electrophoresis so as to have a constant film thickness, and then fired to form a glass layer. After forming an aluminum electrode on the glass layer, the change in electric capacity in the glass was measured using a CV meter, and the surface charge density was calculated.

As apparent from Table 1, the samples of Examples 1 to 5 had a surface charge density as high as 5 × 10 ¹¹ / cm ² or more. This is a surface charge density equivalent to that of a lead glass such as a conventional PbO—SiO ₂ —Al ₂ O ₃ system or PbO—SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ system. Therefore, the semiconductor element coating glasses (semiconductor element coating materials) of Examples 1 to 6 are suitable for coating of medium to high breakdown voltage semiconductor elements.

On the other hand, the sample of Comparative Example 1 has a low surface charge density of 1 × 10 ¹¹ / cm ² , indicating that it is not suitable for coating a medium to high breakdown voltage semiconductor element.

Claims (5)

Containing 50% to 62% ZnO (excluding 62%), 19% to 28% B ₂ O ₃ , 12.5 % to 15 % SiO ₂ , 4 % to 12% Al ₂ O ₃ , and alkali metal A glass for covering a semiconductor element, which does not substantially contain a component, a lead component, Bi ₂ O ₃ , Sb ₂ O ₃ and As ₂ O ₃ . Moreover, in _{mass%, MnO 2 0~5%, Nb} 2 O 5 0~5%, and a semiconductor element coated glass according to claim 1, characterized in that it contains _CeO 2 0 to 3%.   Surface charge density is 7 × 10 ¹¹ / Cm ² It is the above, The glass for semiconductor element coating | cover of Claim 1 or 2 characterized by the above-mentioned. The glass powder for semiconductor element coating which consists of the glass for semiconductor element coating as described in any one of Claims 1-3 . 100 parts by mass of the semiconductor element coating glass powder according to claim 4 and at least one selected from TiO ₂ , ZrO ₂ , ZnO, αZnO · B ₂ O ₃ , 2ZnO · SiO ₂ , cordierite and quartz. A semiconductor element coating material comprising 0.01 to 5 parts by mass of an inorganic powder.