JP2013060353A - Glass for covering semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide glass which has a low environmental load, excellent chemical durability and low surface charge density and which is especially suitable for covering a semiconductor element for low withstanding voltage.SOLUTION: The glass for covering the semiconductor element is characterized by including, in mass% as glass composition, 52-65% ZnO, 5-20% BO, 15-35% SiOand 3-6% AlOand not substantially containing lead. It is preferable that the glass composition additionally contains 0-5% TaO, 0-5% MnO, 0-5% NbO, 0-3% CeOand SbO.

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 covering semiconductor elements are as follows: (1) The thermal expansion coefficient matches the thermal expansion coefficient of the semiconductor element so that cracks and the like do not occur due to the difference in thermal expansion coefficient from the semiconductor element. (2) In order to prevent deterioration of the characteristics of the semiconductor element, it can be coated at a low temperature (for example, 900 ° C. or less), and (3) it does not contain impurities such as alkali components that adversely affect the surface of the semiconductor element.

Conventionally, as a 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 is used.} Lead glass such as O ₃ system is known, but lead system 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. Glass has become 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 harmful to the environment, their use in electric and electronic equipment is being prohibited in recent years, and lead-free materials are being developed. Some zinc-based glasses such as the ZnO—B ₂ O ₃ —SiO ₂ system described above contain a small amount of lead components and cannot be used from the viewpoint of the environment. In addition, zinc-based glass is inferior in chemical durability as compared with lead-based glass, and its resistance to acid in a post-process after glass firing is relatively weak. Therefore, it was necessary to form a protective film on the surface of the coated glass and perform a subsequent process.

If the glass composition is made SiO ₂ rich in order to improve chemical durability, the surface charge density of the semiconductor element-coated glass layer increases and the reverse breakdown voltage of the semiconductor element improves. There is a problem that the current increases. Therefore, it is necessary to reduce the surface charge density in order to suppress the reverse leakage current in the semiconductor element-coated glass used for the low breakdown voltage semiconductor element that does not require the reverse breakdown voltage so much.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a glass that has a low environmental load, is excellent in chemical durability, has a low surface charge density, and is particularly suitable for coating a semiconductor device for low withstand voltage. .

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

That is, the present invention contains, as a glass composition, by mass%, ZnO 52 to 65%, B ₂ O ₃ 5 to 20%, SiO ₂ 15 to 35%, and Al ₂ O ₃ 3 to 6%, and The present invention relates to a glass for covering a semiconductor element, which is substantially free of a lead component.

The glass for covering a semiconductor element of the present invention suppresses the surface charge density by strictly limiting the content of each component with respect to ZnO—B ₂ O ₃ —SiO ₂ glass, and particularly a semiconductor for low withstand voltage. It is suitable for covering the device and has a high chemical durability. Moreover, since the lead component is not substantially contained, the load on the environment is small.

  In the present invention, “substantially does not contain” means that the corresponding component is not intentionally added as a glass component, 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.

Second, the glass for covering a semiconductor element of the present invention is further composed of Ta ₂ O ₅ 0 to 5%, MnO ₂ 0 to 5%, Nb ₂ O ₅ 0 to 5%, CeO ₂ 0 to 3%. And Sb ₂ O ₃ is preferably contained in an amount of 0 to 3%.

  Thirdly, the present invention relates to a semiconductor element coating material comprising glass powder made of the semiconductor element coating glass.

  By using the semiconductor element coating material, the surface of the semiconductor element can be easily coated.

Fourth, the semiconductor element coating material of the present invention is at least one selected from TiO ₂ , ZrO ₂ , ZnO, ZnO · B ₂ O ₃ and 2ZnO · SiO _{2 with} respect to 100 parts by mass of the glass powder. It is preferable to contain 0.01-5 mass parts inorganic powder.

  In particular, when the contact area between a semiconductor element made of Si or the like and glass is large, it is desirable that the thermal expansion coefficients of glass and Si are close. Thereby, generation | occurrence | production of the crack of the coating glass surface by the thermal expansion coefficient difference of a semiconductor element and glass can be suppressed. Although the thermal expansion coefficient of glass can be adjusted with the crystal component contained in glass, it is difficult to control appropriately the quantity of the crystal which precipitates out of glass. Therefore, if the above-mentioned inorganic powder is appropriately added to the glass 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, it is possible to easily adjust to a desired thermal expansion coefficient.

  Since the glass for semiconductor element coating of the present invention has a low surface charge density, it is particularly suitable for coating a semiconductor element for low withstand voltage, and since it has high chemical durability, deterioration with time can be reduced. Moreover, since the lead component is not substantially contained, the load on the environment is small.

  Hereinafter, the reason for defining each component as described above in the glass for coating a semiconductor element of the present invention will be described. In the following description of the content of each component, “%” means “% by mass” unless otherwise specified.

  ZnO is a component that stabilizes the glass. The content of ZnO is preferably 52 to 65%, particularly 55 to 60%. When there is too little content of ZnO, the devitrification at the time of a fusion | melting will become strong, and it will become difficult to obtain a homogeneous glass. On the other hand, when there is too much content of ZnO, there exists a tendency for acid resistance to become weak.

B ₂ O ₃ is a glass network-forming component and a component that improves fluidity. The content of B ₂ O ₃ is preferably 5 to 20%, particularly preferably 7 to 15%. If the content of B ₂ O ₃ is too small, the fluidity at the time of coating becomes crystalline strongly is impaired, uniform coating on the semiconductor device surface tends to become difficult. On the other hand, when the content of B ₂ O ₃ is too large, or the thermal expansion coefficient increases, the chemical durability tends to decrease.

SiO ₂ is a glass network-forming component and a component that increases acid resistance. The content of SiO ₂ is preferably 15 to 35%, particularly preferably 20 to 33%. When the content of SiO ₂ is too small, there tends to be inferior in chemical durability. On the other hand, if the content of SiO ₂ is too much, devitrification becomes stronger at the time of melting, homogeneous glass is hardly obtained.

Al ₂ O ₃ is a component that stabilizes the glass and adjusts the surface charge density. The content of Al ₂ O ₃ is preferably 3 to 6%, particularly preferably 4 to 5.5%. When the content of Al ₂ O ₃ is too small, it tends to be devitrified. On the other hand, when the content of Al ₂ O ₃ is too large, the surface charge density tends to be too large.

The glass for covering a semiconductor element of the present invention is further used as a component that reduces the surface charge density of the glass and suppresses the occurrence of leakage current, and is further Ta ₂ O _5, MnO ₂ , Nb ₂ O ₅ , CeO ₂ or Sb ₂ O _3. Can be contained.

Ta ₂ O ₅ is a component that has a particularly large effect. The content of Ta ₂ O ₅ is preferably 0 to 5%, particularly preferably 0.1 to 3%. When the content of Ta ₂ O ₅ is too large, there is a tendency that the melting is lowered.

The content of MnO ₂ is preferably 0 to 5%, particularly 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%, particularly 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%, particularly preferably 0.1 to 2%. When the content of CeO ₂ is too large, fluidity during coating crystallinity becomes too strong tends to decrease.
The content of Sb ₂ O ₃ is preferably 0 to 3%, particularly preferably 0.1 to 2%. When the content of Sb ₂ O ₃ is too large, there is a tendency that the melting is lowered.

The glass for covering a semiconductor element of the present invention substantially does not contain a lead component (PbO or the like) from the viewpoint of the environment. Further, alkaline components _(Li 2 O, Na ₂ O and _K 2 O) which adversely affect the semiconductor device surface is also preferably substantially free.

The semiconductor element coating glass of the present invention is preferably in the form of powder. Accordingly, the surface of the semiconductor element can be easily coated using, for example, a paste method or an electrophoretic coating method. In this case, the average particle diameter _{D 50} of the glass powder is 25μm or less, and particularly preferably 15μm or less. When the average particle diameter D ₅₀ of the glass powder is too large, there is a tendency that paste becomes difficult. Also, electrophoretic coating becomes 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 material for coating a semiconductor element of the present invention comprises glass powder made of the glass for coating a semiconductor element (hereinafter also referred to as “glass powder for coating a semiconductor element”). The semiconductor element coating material of the present invention has at least one kind of inorganic powder selected from TiO ₂ , ZrO ₂ , ZnO, ZnO · B ₂ O ₃ and 2ZnO · SiO _{2 as a} core with respect to the glass powder for semiconductor element coating. It may be contained as a forming agent. By adding these inorganic powders, the amount of precipitated crystals can be controlled relatively easily. As a result, it is possible to easily adjust to a desired thermal expansion coefficient.

  The content of these inorganic powders is preferably 0.01 to 5 parts by mass, particularly 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 is small, and it tends to be 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 at the time of coating, and the semiconductor element surface tends to be difficult to coat.

In addition, there exists a tendency for the particle diameter of a precipitation crystal | crystallization to become small and the mechanical strength to become large, so that the particle diameter of the said inorganic powder is small. Therefore, the average particle diameter _{D 50} of the inorganic powder is 5μm or less, and particularly preferably 3μm or less. The lower limit of the average particle diameter D ₅₀ of the inorganic powder is not particularly limited, but realistically is 0.1μm or more.

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

The surface charge density of the semiconductor element coating material is, for example, 6 × 10 ¹¹ / cm ² or less, particularly 5 × 10 ¹¹ / cm ² or less when used for a semiconductor element of 1000 V or less. The surface charge density is a value measured by the method described in Examples described later.

  The glass for coating a semiconductor element of the present invention is prepared, for example, by preparing raw material powders of respective oxide components to form a batch, melting at about 1500 ° C. for about 1 hour, and vitrifying, and then molding (and then pulverizing as necessary) , Classification) can be obtained.

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

  Table 1 shows Examples 1 to 6 and Comparative Examples 1 to 3 of the present invention.

Each sample was produced as follows. First, raw material powders were prepared so as to have the glass composition shown in the table, and batchwise melted at 1500 ° C. for 1 hour to be vitrified. Subsequently, after forming the molten glass into a film and then pulverized by a ball mill, and classified with a 350 mesh sieve, the mean particle diameter D ₅₀ was obtained 12μm glass powder (semiconductor element coating material). In Example 4, ZnO powder was added to the obtained glass powder to obtain a semiconductor element coating material.

  The thermal expansion coefficient, surface charge density, and acid resistance of the semiconductor element coating material were measured or evaluated by the following methods. The results are shown in Table 1.

  A thermal expansion coefficient shows the value measured in the temperature range of 30-300 degreeC using the dilatometer.

  The surface charge density was measured as follows. First, the semiconductor element coating material was dispersed in an organic solvent, adhered to the silicon substrate surface by electrophoresis so as to have a constant film thickness, and baked to form a sintered layer. After forming the aluminum electrode on the surface of the sintered layer, the change in electric capacity in the sintered layer was measured using a CV meter, and the surface charge density was calculated.

  The acid resistance was evaluated as follows. First, a semiconductor element coating material is press-molded to a size of about 20 mm in diameter and about 4 mm in thickness, fired to produce a pellet-like sample, and the mass after dipping this sample in 30% nitric acid at 25 ° C. for 1 minute. The mass change per unit area was calculated from the decrease and used as an index of acid resistance. In addition, it is excellent in acid resistance, so that the said mass change amount is small.

As is apparent from Table 1, the semiconductor element coating materials of Examples 1 to 6 have a surface charge density as low as 6 × 10 ¹¹ / cm ² or less, and the mass loss by the acid resistance test is 1.0 mg / cm 2. ^{It is 2} or less and it turns out that it is excellent in acid resistance. Therefore, it can be seen that the semiconductor element coating materials of Examples 1 to 6 are suitable for coating a low breakdown voltage semiconductor element and are excellent in chemical durability.

On the other hand, the samples of Comparative Examples 1 and 2 had a surface charge density as low as 6 × 10 ¹¹ / cm ² or less, but the mass loss by the acid resistance test was 3.5 mg / cm ² or more, which was inferior in acid resistance. Moreover, although the mass loss by the acid resistance test of the sample of Comparative Example 3 was as small as 0.4 mg / cm ² , the surface charge density was as large as 15 × 10 ¹¹ / cm ² .

Claims (4)

As a glass composition, in _{wt%, ZnO 52~65%, B 2} O 3 5~20%, containing SiO 2 15 to 35% and _Al 2 _O 3 _3~6%, and substantially the lead component A glass for covering a semiconductor element, which is not contained. Furthermore, a _{composition, Ta 2 O 5 0~5%,} MnO 2 0~5%, Nb 2 O 5 0~5%, in that it contains CeO 2 0 to 3% and _Sb 2 _O 3 0~3% The glass for coating a semiconductor element according to claim 1, wherein the glass is used for coating a semiconductor element.   A semiconductor element coating material comprising glass powder made of the semiconductor element coating glass according to claim 1. The glass powder 100 parts by _weight, comprising TiO _2, ZrO 2, ZnO, at least one inorganic powder selected from ZnO _· B 2 _{O 3,} and 2ZnO · SiO ₂ containing 0.01 to 5 parts by weight The semiconductor element coating material according to claim 3.