JPS6215494B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION This invention relates to improved glass compositions for use in semiconductor coatings. [Technical background of the invention and its problems] The surface of silicon semiconductor devices such as diodes and transistors is protected with multi-component glass,
The technique of so-called glass percussion, which increases the reliability of devices, is known. A type of glass used for this passivation is, for example,
There is a so-called lead-based glass containing a large amount of PbO, as described in Japanese Patent No. 42-17837. This type of glass has the advantage of good chemical durability and high suitability for semiconductor manufacturing processes. On the other hand,
There have been problems with the high temperature stability of devices packaged with this type of glass. In other words, in the so-called BT test, in which a glass-coated element is held at high temperature under reverse bias to examine changes in electrical characteristics, conventional lead-based glass could only withstand temperatures of up to 130°C. However, for elements that require high reliability, a temperature of at least 150°C or higher is required. [Object of the Invention] An object of the present invention is to provide a lead-based glass composition for semiconductor passivation having good stability at high temperatures. [Summary of the invention] One of the glass compositions for semiconductor coating of the present invention is
_SiO2 35-50 weight (wt)%, _{Al2O3 1.5-10wt} %,
PbO35-50wt%, _{B2O3 0-10wt} %, RO (However, R
is at least one of Mg, Ca, Sr, Ba) 0.1~5wt
% of the composition, and the other is composed of an oxide mixture of the above composition.
It is characterized in that it contains at least 1 wt% of at least one of ZrO ₂ , InO ₃ , CeO ₂ and V ₂ O ₃ . The numerical limitations of the above composition are based on the following reasons. SiO ₂ is an essential component as a glass-forming oxide. This SiO ₂ has the effect of reducing the coefficient of thermal expansion of glass and making it compatible with that of silicon. If it is less than 35wt%, it lacks compatibility with silicon, and if it exceeds 50wt%, it is insufficient to make the glass flow. The firing temperature becomes extremely high, exceeding the possible limits of heat treatment of the silicon element itself. Also
Al ₂ O ₃ is also essential as a subcomponent for glass formation, and if it is less than 1.5 wt%, the glass will undergo phase separation and cannot be homogenized. On the other hand, glasses with a composition exceeding 10 wt% have the disadvantage of significantly increasing the reverse leakage current of devices coated with them, making them unsuitable for passivation. PbO is the main component of glass and is an essential component for developing the electrical properties necessary for passivation.
If it is less than 35 wt%, the electrical properties such as device breakdown voltage will be insufficient, while if it exceeds 50 wt%, the thermal expansion of the glass will become too large, causing defects such as cracks. B ₂ O ₃ is a subcomponent that reduces the viscosity of glass, and its addition has the advantage of lowering the melting temperature, but if it exceeds 10 wt%, it can cause phase separation in the glass and cause heterogeneity. Become. R.O.
These components are essential for improving thermal stability, which is the main objective of the present invention. If it is less than 0.1 wt%, the effect will not be exhibited, but if it exceeds 5 wt%, undesirable properties such as the occurrence of cracks due to an increase in the coefficient of thermal expansion will appear. As mentioned above, RO
It has been found that a lead-based partition glass with improved thermal stability can be obtained by adding .
It has been found that the thermal properties can be further improved by adding at least one of ZrO ₂ , In ₂ O ₃ , CeO ₂ and V ₂ O ₅ . It has been found that when the amount exceeds 1 wt%, the thermal stability is rather impaired. These glasses are made using normal melting methods.
After being pulverized into powder, it is attached to the element surface using, for example, a doctor blade method, and then fired at a temperature at which the glass becomes light and fluid, thereby completing a glass perseveration element. [Effects of the Invention] According to the present invention, it has better BT characteristics than lead-based glass, and also has a coefficient of thermal expansion close to that of silicon without causing phase separation, thereby increasing the breakdown voltage of semiconductors and stabilizing the protective effect for a long time. It is possible to obtain a glass composition that can exhibit the following characteristics. [Embodiments of the Invention] Next, embodiments of the present invention will be specifically described using drawings and tables. First, two types of glasses as shown in Table 1 were selected as basic compositions A and B. These glasses are made from high-purity silica, alumina, red lead, borax, etc., mixed to a target composition, and then heated at 1450℃ in a platinum crucible.
It was obtained by melting it. These two basic glass compositions
A glass in which a portion of PbO was replaced with RO (R = Mg, Ca, Sr, Ba) was prepared in a similar manner. Table 2 shows the types and concentrations of substituted oxides. The obtained glass is crushed, and the obtained powder is coated on a silicon diode element 1 with a pressure resistance standard of 600V using the doctor blade method. A glass film 2 as shown in the figure was formed, an Al electrode 3 was formed on the p side, and a solder electrode 4 was formed on the n side to obtain a mesa diode. The reverse leakage current of these diodes at 550V at room temperature is A
It was 0.05 to 0.2 μA for the basic composition system of B, and 0.8 to 3 μA for the basic composition system of B, both of which were within the standard of 10 μA or less. Also added RO additives~
There was a tendency for the leakage current to be lower in the glass than the basic composition glass. The obtained diode was treated under a reverse applied voltage of 500 V at 150 °C for 100 hours, and then again at room temperature with V
-I characteristics were measured, and changes in leakage current before and after heat treatment were investigated. The results obtained are summarized in Table 3.
The thermal property stabilizing effect of the RO component is obvious.

【table】

【table】

【table】

[Table] Next, the basic compositions of the glasses shown in Table 2 were selected, and glasses in which ZrO ₂ , In ₂ O ₃ , CeO ₂ and V ₂ O ₅ were added by PbO substitution were prepared in the same manner. A glass insulation diode was fabricated using the same method as described above, and changes in leakage current before and after the BT treatment described above were investigated. Table 4 summarizes the types and concentrations of additives and changes in leakage current. There was no significant difference in the initial value of leakage current between the base glass and the base glass. It can be seen that these additives reduce the increase in leakage current before and after BT treatment. The basic composition as a reference example is ZrO ₂ , In ₂ O ₃ , CeO ₂ and V ₂ O ₅
Similar experiments were conducted on four types of glass containing 2.0wt% of
It exceeded 10 times.

[Other embodiments of the invention]

Four types of glasses with different basic compositions and additives were made in a similar manner. Table 5 shows the target composition. This glass was coated onto a diode in the same manner as before to produce a glass cladding diode as shown in FIG. All initial values of the elements were within the specifications. These devices were subjected to BT treatment in the same manner as before, and changes in leakage current were investigated.
The results are shown in Table 5. The change in leakage current is within a factor of 2, which is very good compared to the 100 times or more increase typically exhibited by this type of lead-based glass without additives.

【table】 [Brief explanation of the drawing]

The drawing is a schematic diagram of a mesa diode used to evaluate the electrical characteristics of a glass film. 1...Silicon diode element, 2...Glass film, 3...Aluminum electrode, 4...Solder electrode.

Claims (1)

[Claims] 1 SiO ₂ 35-50% by weight, Al ₂ O ₃ 1.5-10% by weight,
PbO35-50% by weight, _{B2O3 0-10} % by weight, RO (R is at least one of Mg, Ca, Sr, Ba) 0.1
A glass composition for semiconductor coating, characterized in that it consists of an oxide mixture having a composition of ~5% by weight. ₂ SiO2 35-50% by weight, _{Al2O3 1.5-10} % by weight,
PbO35-50% by weight, _{B2O3 0-10} % by weight, RO (R is at least one of Mg, Ca, Sr, Ba) 0.1
ZrO 2 , ZrO ₂ ,
1. A glass composition for coating a semiconductor, comprising 1% by weight or less of at least one of In ₂ O ₃ , CeO ₂ and V ₂ O ₅ .