JPS6025374B2 - Glass for semiconductor coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device including a PN junction, particularly a silicon semiconductor device.
This relates to a coating glass that passes through one diode.

Generally, the surface of a semiconductor element is coated with glass in order to prevent the semiconductor element from being contaminated by outside air, stabilize the surface of the element, and prevent deterioration of its characteristics.

Conventionally, ZNO-B03-Si was used as this type of coated glass.
02-Pb○ type glass was used. However, in semiconductor devices coated with conventional coating glass, the design breakdown voltage is 1
Even if a 000V silicon element is used, the reverse withstand voltage is 600V.
Only a so-called soft breakdown (shown in FIG. 1A) with a large reverse leakage current of about V was obtained. However, in recent years, there has been a demand for highly reliable semiconductor devices with a reverse withstand voltage of 1,500 to 2,000 V and a hard breakdown (indicated by the opening in Figure 1) with extremely low reverse leakage current. Ta. However, with the conventional coating glass, even if two silicon elements with a design breakdown voltage of 1000V were laminated, a sufficient result could not be obtained.
Moreover, it was extremely disadvantageous in terms of cost. The present invention eliminates the above drawbacks and provides a coating glass suitable for highly reliable semiconductor devices. Another object of the present invention is to provide a highly reliable semiconductor device with high reverse breakdown voltage and extremely low reverse leakage current.

The glass for semiconductor coating of the present invention has NN0 50 in weight%.
．． 0-70.0%, B203 20.0-30.0%,
Si025.0~15.0%, Pb00.5~10.0
%, Bi2030.1~20.0%, NQ05 0.1
~5.0%, SQ03 0.1~2.0%, Mountain 203
It has a composition of 0-3.0%.

Further, a semiconductor device coated with glass having the above composition has a high reverse breakdown voltage and a reverse leakage current of 4.

The coating glass of the present invention is Zn0-B2Q-Si02-
Bi203 and Nb205 are added to Pb○ type glass as essential components. The present invention combines Bi203 and N
Due to the coexistence of b2Q, the surface charge density (N
FB) becomes extremely stable and is controlled to have an appropriate amount of positive charge.

Therefore, a semiconductor device with high reverse breakdown voltage and extremely low reverse leakage current can be obtained. Glass A shown in Table 1 is an example of a Z-core-B203-Si02-Pbo glass; glass B has Bi203 added thereto, and glass C has Bi203 and Nb2Q added thereto.

These glasses A, B, and C are each coated on a silicon element with a designed withstand voltage of 2000 V, and the withstand voltage (reverse leakage current is 1
We investigated the reverse voltage (reverse voltage) distribution when the voltage became A. The results are shown in FIG. When glass A, which does not contain either Bi203 or Nb205 in Table 1, is coated, the breakdown voltage distribution varies widely and the reverse breakdown voltage is low.

Glass B containing Bi203 shows a considerable improvement, but glass C containing both Bi203 and N et al.
The reverse breakdown voltage was high and the breakdown voltage distribution was extremely good. The coating glass of the present invention contains 50.0 to 70.0% of N by weight.
, B203 20.0-30.0%, Si02 5.0
~15.0%, Pb0 0.5~10.0%, Bi20
3 0.1-20.0%, N et al. 050.1-5.0%,
Sb203 0.1~2.0%, N203 0~3.0
It has a composition of %. The reason for limiting the composition to this is as follows. When Zn○ is less than 50.0%, the coefficient of thermal expansion becomes too large and vitrification becomes difficult.

When it exceeds 70.0%, crystallization progresses rapidly, and the coating surface becomes unable to flow sufficiently, making it impossible to obtain a good coating.

When &03 is less than 20.0%, the glass tends to devitrify, and when it is more than 30.0%, it becomes difficult to obtain a homogeneous glass.

When Si02 is less than 5.0%, the glass tends to devitrify, and when it is more than 15.0%, it becomes difficult to obtain a homogeneous glass.

When Pb○ is less than 0.5%, the glass tends to devitrify,
Fluidity deteriorates, making it difficult to obtain a good coating.

Furthermore, the surface charge density (NFB) tends to fluctuate, making it difficult to obtain desired semiconductor characteristics. If it exceeds 10.0%, the glass will be easily reduced during sealing.

When Bi203 is less than 0.1%, the desired reverse breakdown voltage and reverse leakage current characteristics cannot be obtained, and when it is more than 20.0%, the coefficient of thermal expansion becomes too large and it becomes difficult to obtain uniform glass. . When NQ05 becomes 0.1% or less, the above-mentioned effect of coexistence with Bi203 cannot be obtained, and 10
% or more, it becomes difficult to melt and it becomes impossible to obtain a homogeneous glass, and at the same time, the positive charge on the surface of the silicon element increases and the reverse leakage current becomes large.

A〆203 stabilizes the glass and improves its chemical durability, but if it is added in an amount of 3.0% or more, the viscosity of the glass increases and it becomes difficult to obtain a good coating.

Adding Sb203 enhances the effect of Bi203 and improves the solubility of glass, but if it is less than 0.1%, the effect is weak, and if it is added more than 2.0%, there is no appreciable change in the effect. .

ZNO-B203-Si02-POO coated glass,
When Ce02, which is commonly added, is added to the coated glass of the present invention, the crystallinity of the glass becomes strong and the fluidity deteriorates, making it impossible to obtain a good coating, so the addition of Ce02 is not preferable.

Table 2 shows the composition of Examples of the coating glass of the present invention and 30
Thermal expansion coefficient and coating sealing temperature at ~300°C are shown.

The raw materials prepared to have the composition shown in Table 2 are sufficiently melted and vitrified, and then ground into fine powder.

This glass powder is mixed with pure water or an organic solvent to form a slurry, which is applied to the surface of the silicon element and heated to a sealing temperature. Since alkali in glass significantly impairs the properties of semiconductors, sufficient care must be taken to prevent alkali from being mixed in as impurities in raw materials or during processes such as melting and pulverization. A semiconductor device manufactured by coating a silicon element with a design breakdown voltage of 2000V with the coating glass of the present invention is an excellent device that exhibits extremely stable properties of reverse breakdown voltage of 2000V and hard breakdown with a single Sea J-con element. there were.

[Brief explanation of the drawing]

FIG. 1 shows the reverse withstand voltage and reverse leakage current of a semiconductor device, in which A shows a device covered with a secondary covering glass, and an opening shows a device covered with a covering glass of the present invention. Figure 2 shows the breakdown voltage distribution of glass-molded silicon diodes, where A is the conventional Zn○-B2Q-Si02-
POO glass coated, B is A glass coated with Bi
Glass coated with 203 added, C is the same as A
is coated with glass to which Bi203 and Nb2Q are added. Figure 1 Figure 2

Claims (1)

[Claims] 1 NnO50.0-70.0% by weight, B_2O_3
20.0~30.0%, SiO_25.0~15.0%
, PbO0.5~10.0%, Bi_2O_30.1~
20.0%, Nb_2O_50.1~5.0%, Sb_
2O_30.1~2.0%, Al_2O_30~3.0
Glass for semiconductor coating with a composition of %.