JPS5812216B2 - handmade glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glass for coating semiconductor devices such as double-studded silicon rectifiers having electrodes of molybdenum, tungsten, or the like.

Generally, the electrical characteristics of a semiconductor element are greatly influenced by the characteristics of its surface, so it is necessary to protect the surface from the atmosphere.

Conventional surface protection methods include protecting the surface of a semiconductor element with an insulating film, such as forming an oxide film on the surface of a silicon semiconductor, and attaching silicon oxide or silicon nitride to the semiconductor surface by vapor phase decomposition. , or methods of encapsulating the entire semiconductor element with an organic polymer material are known.

However, each of the above methods is insufficient in terms of moisture resistance and reliability, and in order to obtain sufficient moisture resistance and reliability, a method of sealing the product in a metal cap has been adopted, but as a result, However, the manufacturing process is complicated and very expensive, making it impractical.

In this respect, methods such as directly covering the P-N junction of a semiconductor element with glass or encapsulating the entire element with glass fully satisfy the above characteristics and are advantageous in terms of manufacturing and cost. It can fully satisfy the requirements of recent semiconductor devices, such as miniaturization, thinning, nonflammability, and high reliability.

When covering a semiconductor device with glass, the following conditions are required for the glass.

(a) 40-50X10-7/℃ (30-30
It must have a coefficient of thermal expansion of 0°C). It must flow sufficiently at temperatures that do not impair the performance of semiconductor devices, i.e., at temperatures below 750°C, and it must fit well with the electrodes and silicon of semiconductor devices. (-) It must be coated with glass. (d) When attaching electrodes or plating the semiconductor device, the glass must have sufficient chemical durability so that it will not be damaged by chemicals and the electrical characteristics of the semiconductor device will not be impaired. Hitherto, as this type of glass, borosilicate glass, zinc monoborate glass, lead monoborosilicate glass, etc. have been known, but as shown below, all of them fully satisfy the above requirements. It wasn't for nothing.

In other words, although borosilicate glass satisfies the requirements (a) and (d) above, it has a high sealing temperature of 750°C or higher, and if it is directly coated on a semiconductor, it may impair the electrical characteristics of the semiconductor device. Therefore, the above requirements (1) and (3) cannot be met.

Although zinc monoborate resistant glass meets requirements (a), (c), and (c), it cannot meet requirement (d) because of its poor chemical resistance.

Although borosilicate glass meets the above requirement (d), it has a high coefficient of thermal expansion and is poorly compatible with semiconductor conductive parts, making it impossible to obtain a completely hermetic seal.

The purpose of the present invention is to solve the above-mentioned drawbacks of conventional sealing glasses and to meet all of the above requirements (a) to (d). It is an object of the present invention to provide a satisfactory glass for semiconductor coating.

The composition range and preferred composition range of the glass for semiconductor coating of the present invention are as shown below (wt%).The preferred composition range means that a semiconductor device with excellent electrical properties, particularly reverse withstand voltage properties, can be easily obtained. Refers to the composition range.

(Composition range) (Preferred composition range Zn0 18% to 40% 28% to 38%B
20315 width ~ 35% 18 width ~ 29% Al2033
%~15chi 5%~13%SiO 5%~13
・Part 8 to 11 Pb0 10% to 30%
20% to 26 Mg0 0% to 7 CeO2 O Width to 5 to Sb2030 to 1 The aim is to maintain adhesion to the glass and improve chemical durability by adding appropriate amounts of AI203 and PbO to the glass system.

Therefore, even if a semiconductor coated with the glass of the present invention is subjected to direct plating or other chemical treatments, the glass does not deteriorate, and the electrical characteristics of the semiconductor device are permanently maintained.

Figure 1 shows the glass of the present invention shown in Table 1 (Glass A),
This figure shows the etching rate when zinc monoborate glass (glass B) and lead monoborosilicate glass (glass C) were treated with a plating solution (tin sulfate). It has chemical durability comparable to that of borosilicate glass (Glass C).

Table 1 also shows that a silicon semiconductor element with a reverse withstand voltage of 1500V is coated with the glasses A, B, and C, and the reverse withstand voltage when the reverse leakage current of the nuclear semiconductor device is 1 μA is determined by plating (tin sulfate). The results of measurements taken before and after were shown. Regarding the semiconductor devices coated with glasses B and C, the reverse withstand voltage deteriorated in the heat after plating, but the semiconductor devices coated with glass A according to the present invention deteriorated in reverse withstand voltage. The reverse withstand voltage did not change at all even after plating, and the surface of the semiconductor element and the PN junction were completely protected.

The reason for limiting the composition as described above in the present invention is as follows.

When the ZnO content is less than 18% by weight, the coefficient of thermal expansion increases and at the same time it becomes easy to devitrify, impairing fluidity, and when it is more than 40% by weight, chemical durability deteriorates.

When B203 is less than 15% by weight, the glass rapidly devitrifies, making it difficult to vitrify, and when it is more than 35% by weight, it becomes difficult to obtain homogeneous glass and at the same time the durability deteriorates.

When Al203 is less than 3% by weight, the chemical durability becomes extremely poor, and when it is more than 15% by weight, it becomes difficult to vitrify.

When the Si02 content is less than 5% by weight, the chemical durability deteriorates, and when it is more than 13% by weight, the viscosity of the glass increases and sealing becomes difficult.

When PbO is less than 10% by weight, the sealing temperature becomes too high, and when it is more than 30% by weight, PbO in the glass is easily reduced and at the same time the luminous expansion coefficient becomes too high.

Adding MgO, CeO2, and Sb203 makes it easier to obtain homogeneous glass, and at the same time improves the adhesion of the glass to metal parts and silicon during coating, resulting in a highly reliable semiconductor device.

However, when MgO has a weight range of 7 or more, the coefficient of thermal expansion becomes too high, when Ce02 has a weight range of 5 or more, it is difficult to obtain a homogeneous glass, and when Rb203 has a weight range of 1-weight or more, foaming occurs during sealing. is more likely to occur.

When producing the coating glass of the present invention, as in the usual glass melting method, oxides of each element or starting materials containing them are prepared to a desired composition, mixed, and then placed in a platinum-rhodium alloy crucible. and melted at a temperature of 1300 to 1400°C for 1 to 2 hours.

The molten glass is poured between water-cooled stainless steel rollers to form a thin ribbon, or poured into pure water to be pulverized.
After drying, 350 mesh N was applied using an alumina ball mill.
Size A - Next, if you want to coat a semiconductor device with this glass, mix the glass powder described in (h) with pure water or an organic substance such as isopropyl alcohol or arsenic acetate, and apply it to the surface of the semiconductor device. Alternatively, the above-mentioned glass powder is dispersed in an organic substance such as acetone or isopropyl alcohol, and applied to the surface of a semiconductor element or a P-N junction by a sedimentation method using centrifugation or an electrophoresis method. Attach it to the area.

Furthermore, the semiconductor device coated with this glass is heated in an electric furnace controlled at a desired temperature for an appropriate period of time to volatilize and remove water or organic media, and then the glass is softened and fluidized to form a glass coating.

Examples of the present invention will be described below.

Table 2 shows the glass compositions and properties of Examples of the present invention.

The etching rate in Table 2 is 10% H2S at 50°C.
This figure shows the decrease in the thickness of the glass surface when a glass sample of 10 x 10 x 5 mm was immersed in 04 or 10 HF solution for 1 minute.

The glass for semiconductor coating of the present invention having a composition as shown in the above table has a thermal expansion coefficient of about 40 to 50
It has a sealing temperature of 0 to 740°C, and solves all the conventional problems of glass chemical durability, fluidity, adhesion between glass and semiconductor elements, and maintaining the electrical characteristics of semiconductor devices. This is what I did.

It is particularly suitable for coating semiconductor devices in which a chemical treatment such as plating is applied to the semiconductor after the glass coating is formed.

[Brief explanation of drawings]

Figure 1 shows the glass of the present invention (Glass A), the zinc monoborate glass (Glass B), and the lead monoborosilicate glass (Glass C).
) is compared with the etching speed when immersed in tin sulfate plating solution.

Claims (1)

[Claims] 1 Weight percentage: 18~40% ZnO, 15%~
35% B203t3-15 articles Al2035-1
3% SiO, 10% to 30% pbo, θ% to 7% MgO, O% to 5% Ce02, O% to 1% Sb20
Glass for semiconductor coating consisting of 3.