JPH03205322A - Semiconductor coating glass - Google Patents

Abstract

PURPOSE:To obtain the title glass ensuring the generation of its warpage to be suppressed even in the case of large diameter with satisfying glass characteristics by formulating PbO, SiO2 and Al2O3 at a specified weight ratio. CONSTITUTION:A formulation composed of (1) 45-49wt.% of PbO, (2) 46-49wt.% of SiO2 and (3) 2-6wt.% of Al2O3 is heated, melted and ground to obtain the objective glass 40-45X10<-7>/ deg.C in the mean thermal expansion coefficient (alphas) up to the temperature 1/2 (Tg+Tf) of the median point between the glass transition temperature (Tg) and the yield temperature (Tf) and suitable for direct coating on e.g. the surface of a silicon wafer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to protecting or stabilizing the surface including the PN junction of individual semiconductor elements such as diodes, thyristors, and transistors made of silicon single crystal. ), and particularly relates to a glass for semiconductor coating suitable for directly coating the surface of a silicon wafer.

[Prior art] The properties required for this glass for semiconductor coating are (
l) The coefficient of thermal expansion of the glass is compatible with that of the semiconductor element, ■ The sealing temperature must be 800°C or less, as the characteristics of semiconductor elements such as silicon may deteriorate at high temperatures; (3) The semiconductor element (4) After coating, the glass must have an appropriate amount of negative charge that matches the design of the semiconductor device, and have excellent reverse leakage current characteristics. (5) It has excellent chemical resistance because it is exposed to various chemicals in semiconductor manufacturing processes such as electrode formation.

Traditionally, this type of glass has been ZnO-B203-SiO2-based zinc-based glass whose main component is ZnO, and pb-based glass.
PbO-5102 series or PbO- with o as the main component
Lead-based glasses of the B203-Si02 series have been used.

[Problems to be Solved by the Invention Among the conventional glasses mentioned above, lead-based glass has the advantage of superior chemical resistance compared to zinc-based glass;
On the other hand, since the coefficient of thermal expansion is larger than that of a silicon wafer, the silicon wafer tends to warp after baking, making it difficult to form an electrode pattern. The occurrence of warpage in silicon wafers has become more and more noticeable as silicon wafers have increased in diameter from 3 to 5 inches in recent years.

The object of the present invention is to provide a semiconductor coating glass that is made of lead-based glass and satisfies all of the above-mentioned required characteristics, and in particular, a semiconductor coating glass that can suppress the occurrence of warping even when used on large-diameter silicon wafers. It is to provide.

[Means for Solving the Problems] As a result of various studies conducted by the present inventors in order to achieve the above-mentioned objective, the inventors have found that the temperature at which the coating glass is thought to be fixed to the element from 30°C, i.e. Glass transition point (T
g) and the temperature between the yielding point (Tf) (Tg+Tf/2)
The average coefficient of thermal expansion (hereinafter referred to as α8) up to 40 to 45
Setting the temperature to
Is it possible to obtain a glass for semiconductor coating that satisfies this characteristic and also satisfies all of the other required characteristics mentioned above by comprising three components, 1Sin2 and Al2O3, and by mixing these components in appropriate proportions? I discovered that.

That is, the glass for semiconductor coating of the present invention contains PbO 45-49%, Sh0248-49, Al2O in weight percentage.
a It is characterized by having a composition of 2 to 6%.

In the present invention, PbO 1Sin. , Al2O3 are set in the above composition ranges for the following reasons.

If PbO is less than 45%, the viscosity of the glass becomes high and sealing becomes difficult, and if it is more than 48%, α8 becomes 45XIO.
-7/''C, which is not preferable.

If Si02 is less than 46%, α6 is 45X 10
If it is greater than -7/°C and more than 49%, the viscosity of the glass becomes too high and sealing becomes difficult.

When A1■03 is less than 2%, the glass becomes unstable and tends to devitrify, and when it is more than 6%, the reverse leakage current becomes large.

The glass of the present invention is composed of three components: PbO 2 , SI02, and Al203, and it is better to avoid adding other components since this tends to have an adverse effect on the properties of the glass. For example, when B203 is added, many pores tend to remain in the glass after coating, and the reverse withstand voltage of the glass increases.
Deteriorates the characteristics of reverse leakage current. Furthermore, when ZnO is added, the glass not only becomes unstable and easily devitrified, but also deteriorates the electrical properties. Furthermore, Mg
Addition of RO such as O , Ca0 1SrO 1BaO is not preferred because α8 becomes larger than 45×10 −7 /′C and at the same time the viscosity of the glass increases, making sealing difficult.

[Examples] The glass for semiconductor coating of the present invention will be explained in detail based on Examples.

The following table shows the glass composition, softening point, coefficient of thermal expansion, α8, and silicon wafer warpage of Examples of the present invention (Samples N[1 1 to 6) and Comparative Examples (Sample Ha 7 ).

The following margin is 151 (% by weight) Each sample of N[L to 7 in the table was prepared as follows, taking sufficient care not to mix with an alkali component.

A raw material batch prepared to give a glass having the composition shown in the table in weight percent was melted at a temperature of 1500 to 1600°C for 1 hour, roll-formed, finely pulverized in a pulverizer such as a ball mill, and classified using 350 mesh.

For coating and sealing the semiconductor element, the coating glass produced as described above was dispersed in an organic solvent and electrodeposited on the surface of the semiconductor element by electrophoresis. Next, after drying this semiconductor element, it was heated in an electric firing furnace at 800 to 900° C. for 10 to 15 minutes to seal it.

The softening point in the table was measured using a differential thermal analyzer for the above-mentioned finely pulverized coating glass, and the thermal expansion coefficient and α1 were determined by press-forming each sample into a rod shape and subjecting it to the same heat treatment as when baking a silicon wafer. It was calculated from the thermal expansion curve measured using a well-known dilatometer using the fired product. The warpage of the silicon wafer was determined by coating and sealing each glass onto a 4-inch wafer using the method described above, placing the wafer on a horizontal surface, and measuring the difference in height between the center and the periphery.

As is clear from the table, each sample of NIl1 to NIl6, which is an example, has a thermal expansion coefficient of 41 to 43X 10-'/''C and α
6 had a coefficient of thermal expansion of 42 to 45X 10-7/'C, and the warpage of the silicon wafer was as low as 25 to 40 μm, whereas the comparative sample of Na 7 had a thermal expansion coefficient of 44
X 10-7/''C, which was close to that of the example, but α8 was large, 50X1G-'/'C, and the silicon wafer's anti-rehabilitation l was 25 μm, which was a high value.

In addition, the glass of sample N [1 1 to 6 was designed to withstand voltage 1000V.
When we measured the reverse leakage current of a semiconductor device made by coating it on a silicon semiconductor, it showed a value of 10μ8 or less, and when we measured the reverse withstand voltage (when the reverse leakage current reached 1μA). All values were good, showing values of 900 to iooov. Furthermore, to check the chemical resistance, a block of fired glass powder was prepared at 25°C with 37% HCI: 4.
When the block was immersed in a solution of 9% HF=9:1 for 1 minute and the thickness reduction was measured, it showed a small value of 4 to 6 μm, indicating that it had good chemical resistance.

[Effects of the Invention] As described above, the glass of the present invention satisfies all the characteristics required of a glass for semiconductor coating, and can suppress the occurrence of warpage, especially when used for large-diameter silicon wafers.

Claims (1)

[Claims] (1) PbO45-49% by weight percentage, SiO_24
A glass for semiconductor coating characterized by having a composition of 6 to 49% and Al_2O_32 to 6%.