JPS6341861B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention covers glass for semiconductor coating, and in particular covers the entire semiconductor device, such as a silicon diode having a PN junction, including electrodes, with a thick glass layer. The present invention relates to a sealing glass composition suitable for producing a so-called molded semiconductor. The properties required of glass for semiconductor coating include that the coefficient of thermal expansion of the glass after sealing matches the silicon of the semiconductor element and the metal of molybdenum or tungsten that is the electrode material, and that the characteristics of semiconductor elements such as silicon at high temperatures are required. The sealing temperature must be 750°C or lower to avoid the risk of deterioration, and the semiconductor after sealing must have excellent electrical characteristics and high reliability. The object of the present invention is to have the electrical properties of the semiconductor after sealing among the various properties required of the glass for semiconductor coating, specifically, to have high reverse withstand voltage and extremely low reverse leakage current. It is an object of the present invention to provide a glass for semiconductor coating that exhibits a so-called hard breakdown waveform and has excellent blocking characteristics. In addition, when the reverse withstand voltage is lower than hard breakdown and the reverse leakage current is large, so-called soft breakdown occurs.
breakdown), resulting in a lack of semiconductor reliability. The present inventors have discovered that by adding a predetermined amount of willemite powder to a ZnO--B ₂ O ₃ --SiO ₂ --PbO-based glass powder, a glass for semiconductor coating that meets the above objective can be obtained. The coating glass of the present invention has the main components in weight% of ZnO45 to 75, _{B2O3 15} to 35, SiO2 ₂ to 20,
This composition is made by adding 0.01 to 20.0% by weight of willemite powder to glass powder consisting of 0.5 to 10 PbO. In the coating glass of the present invention, the range of each component of the glass powder is limited as described above. When ZnO is less than 45%, the thermal expansion coefficient becomes too large, and when it is more than 75%, the glass tends to devitrify. When B ₂ O ₃ is less than 15%, the glass tends to devitrify, and when it is more than 35%, homogeneous glass cannot be obtained and the coefficient of thermal expansion becomes too large. When SiO ₂ is less than 2%, the glass tends to devitrify, and when it is more than 15%, it becomes difficult to obtain a homogeneous glass. When PbO is less than 0.5%, the fluidity of the glass deteriorates and sufficient sealing cannot be obtained, and when PbO is more than 10%, the coefficient of thermal expansion becomes too large. In addition to the above components, this glass powder also contains CeO ₂ , Sb ₂ O ₃ ,
It may contain a small amount of Al ₂ O ₃ , Nb ₂ O ₅ , Bi ₂ O ₃ or the like. The glass for semiconductor coating of the present invention contains willemite (2ZnO.SiO ₂ ) as an inorganic refractory additive, a so-called "filler", to the glass powder described above.
It is made by mixing powders in a weight ratio of 0.01 to 20.0%. The addition of this filler causes the glass to crystallize, changing the initial semiconductor surface charge density (initial NFB) to an appropriate value, and at the same time making it possible to immobilize mobile ions in the glass. This makes it possible to obtain a semiconductor device with high reverse withstand voltage and extremely low reverse leakage current. This willemite powder filler is
The above effect is exhibited when the content is 0.01% or more, but 20
When the content exceeds %, crystallization is promoted too much, fluidity is reduced, the coating on the semiconductor element becomes poor, and it becomes difficult to obtain airtight sealing. The table below shows samples of Examples of the glass for semiconductor coating of the present invention, and the lower row shows the thermal expansion coefficient and coating sealing temperature.

[Table] Characteristic evaluation of reverse withstand voltage and reverse leakage current as initial characteristics of semiconductors was performed by coating the coating glass of the present invention listed in the above table on the PN junction surface of a silicon diode, drying it, and then The tests were carried out on sealed samples. When the waveform in the opposite direction was confirmed using a curve tracer, it was found that the diode sample coated with the glass of the present invention had a leakage current of 1 μA or less, and
The waveform showed a hard breakdown at a high voltage close to the design breakdown voltage of 1700 to 2000V. The blocking characteristics of semiconductors can be confirmed by fabricating a diode with a MOS structure and performing BT processing on it to examine its electrical stability under high temperature bias. The blocking properties of the coating glass samples of the present invention listed in the above table were evaluated. That is, the coating glass of the present invention is sealed to a thickness of about 5μ on n-type silicon, and an aluminum electrode is deposited on it to form a MOS (metal-oxide-silicon).
Fabricate a diode structure, apply BT treatment to it,
That is, after applying a voltage of 400V at 200°C for 2 hours with the aluminum electrode on the + side and the aluminum electrode on the - side, the amount of change in the surface charge density (NFB) of the MOS structure, so-called △NFB When measured, it was 0 to 4×10 ¹¹ /cm ² . This result shows that the semiconductor using the coating glass of the present invention has excellent blocking properties.

Claims (1)

[Claims] 1 The main components are ZnO45~75, _{B2O313 ~}
35. Glass for semiconductor coating made by adding 0.01 to 20.0% by weight of willemite powder to glass powder consisting of 2 to 20 SiO ₂ and 0.5 to 10 PbO.