JPH0426541B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION The present invention relates to silicon wafers, particularly those having dimensions 4 to 5.
Protects the surface of inch large diameter silicon wafers,
Or it relates to glass coated for stabilization (passivation). Prior Art The characteristics required for glass for coating silicon wafers include that the coefficient of thermal expansion of the glass matches that of silicon wafers, that good sealing can be achieved by firing in the temperature range of 700 to 900 degrees Celsius, and that it is possible to form electrodes. It has good chemical resistance and acid resistance for the semiconductor manufacturing process, and the electrical properties of the semiconductor element after coating, especially excellent reverse withstand voltage and reverse leakage current properties. Conventionally, this type of coating glass has been ZnO-B ₂ O ₃ -SiO _2- based zinc-based glass, which has ZnO as its main component.
PbO−SiO ₂ system with PbO as the main component or PbO
-B ₂ O ₃ -SiO ₂ -based lead-based glasses have been used.
Among these conventional coating glasses, lead-based glass has the advantage of superior chemical resistance compared to zinc-based glass, but because its coefficient of thermal expansion is larger than that of silicon wafers, silicon wafers may warp after firing. It became difficult to easily create an electrode pattern. This warpage has become more noticeable as silicon wafers have increased in diameter to 4 to 5 inches in recent years. In addition to this, after firing,
Cracks were more likely to form in the glass, and the structure of the mesa silicon wafer had to be changed from a single moat type in which the glass portion was cut to a double moat type in which the silicon portion was cut, resulting in higher production costs. OBJECT OF THE INVENTION The purpose of the present invention is to improve the various properties required for the silicon wafer coating glass mentioned above, particularly to improve the shortcomings in the thermal expansion properties of conventional lead-based glass, and to
To provide a glass for coating which hardly causes cracks in the glass even when it is directly coated on a silicon wafer having a large diameter of ~5 inches and a thin thickness, and the silicon wafer does not warp. Structure of the Invention As a result of various studies, the inventor has found that
It has been found that in order to coat a 5-inch silicon wafer, the thermal expansion coefficient of the coating glass should be 42×10 ^-7 /°C or less, and this is proposed as the present invention. That is, the large-diameter silicon wafer coating glass of the present invention contains PbO45 to 65% in weight percentage;
PbO− consisting of SiO ₂ 32-45%, Al ₂ O ₃ 0.5-15%
_SiO2 -based glass powder or PbO42~65%,
PbO _{- B2O3} -SiO2 glass powder consisting of _0.5-14 % _{B2O3 ,} 15-48% _SiO2 , 1-18% _Al2O3 , _and 10-50% willemite powder by weight , 0.01 to 25% of quartz glass powder, or a mixture of both. Furthermore, the coating glass of the present invention may contain, if necessary, in addition to the above-mentioned components PbO, SiO ₂ , B ₂ O ₃ , and Al ₂ O ₃ .
_MnO2 , _{CeO2 , Sb2O3 , Ta2O5} , _SnO2 , _{Nb2O5 ,}
Each of Bi ₂ O ₃ and ZnO can be contained in an amount of 5% or less. However, MnO ₂ , CeO ₂ , Sb ₂ O ₃ ,
When each component of Ta ₂ O ₅ , SnO ₂ , Nb ₂ O ₅ , and Bi ₂ O ₃ is more than 5%, the glass becomes non-uniform and at the same time the coefficient of thermal expansion becomes high. Further, if the ZnO content is more than 5%, the glass undergoes phase separation and a stable glass cannot be obtained. In addition, the above-mentioned PbO-SiO ₂ system or PbO-B ₂ O ₃
−SiO ₂ glass powder has a softening point of 570 to 790℃,
It is preferable to have a thermal expansion coefficient of 42 to 55×10 ⁻⁷ ° C. ⁻¹ (30 to 300° C.). PbO−SiO ₂ glass and PbO listed in the table below
-B ₂ O ₃ -SiO ₂ composition examples, softening points and thermal expansion coefficients of each glass are shown.

【table】

[Table] Although the above-mentioned lead-based glass powder has overall favorable glass properties, in the coating glass of the present invention, willemite powder is further added to reduce the thermal expansion coefficient to 42×10 ^-7 /°C or less. 10 to 50% and 0.01 to 25% of quartz glass powder, or both. In other words, willemite powder has the effect of lowering the coefficient of thermal expansion of glass, making the glass optimal for sealing large-diameter silicon wafers.This eliminates warping of silicon wafers and makes it possible to form electrode patterns accurately. At the same time, it is possible to prevent cracks in the coated glass. However, if the amount added is less than 10%, if the silicon wafer has a large diameter of 4 to 5 inches and is thin, the coefficient of thermal expansion of the glass cannot be lowered sufficiently, and the silicon wafer tends to warp. Also
If it exceeds 50%, the fluidity of the glass deteriorates and sufficient sealing cannot be obtained. Willemite (Zn ₂ SiO ₄ ) powder is made by combining zinc white and silica powder with ZnO
and SiO ₂ in a molar ratio of 2:1,
After firing at a high temperature of about 1450°C, the resulting sintered body is finely pulverized and used. The amount of quartz glass powder added is preferably 0.01 to 25%, and 0.01% to 25% is suitable.
% or less, the coefficient of thermal expansion of the glass will not decrease sufficiently.
If it is more than 25%, the quartz glass powder and glass will react and fluidity will be impaired, making it impossible to obtain sufficient sealing. In manufacturing the large-diameter silicon wafer coating glass according to the present invention as described above, PbO,
Raw materials for each component such as SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ and the like are mixed and made into a batch, and the mixture is melted and vitrified at a temperature of 1500 to 1600° C. for about 1 hour. After pulverizing this molten glass, it is finely pulverized using a pulverizer such as a ball mill.
Classify at 350 meters. For coating and sealing silicon wafers, the coating glass produced as described above is dispersed in an organic solvent, electrodeposited on the surface of the silicon wafer by electrophoresis, and then the silicon wafer is After drying, heat at 700 to 800℃ in an electric kiln.
Heat for 10 to 15 minutes to seal. Examples Table 3 shows the amounts of willemite powder and quartz glass powder added, thermal expansion coefficients, and sealing temperatures in the present invention using the glass powders shown in Table 1.2.

[Table] Table 3 shows that when one or both of willemite powder and quartz glass powder is added to conventional glass powder, the coefficient of thermal expansion is significantly lowered, and sealing can be performed at a relatively low temperature of 900° C. or less. Furthermore, these glasses are coated on silicon wafers using the electrophoresis method and baked to create a design withstand voltage of 1500~.
When we measured the electrical characteristics of a 2000V semiconductor device, we found that the reverse leakage current was small and the reverse withstand voltage satisfied the design withstand voltage. Effects of the Invention As described above, the large-diameter silicon wafer coating glass of the present invention satisfies the various properties required for silicon wafer coating glass such as electrical properties, and in particular has a thermal expansion coefficient of 42× that is equal to that of silicon.
10 ^-7 /℃ or less, it exhibits excellent properties such as no cracking of the glass and no warping of the silicon wafer even when directly coated on a large diameter and thin silicon wafer with dimensions of 4 to 5 inches. .

Claims (1)

[Claims] 1 In weight percentage, PbO45-65%, _SiO2 32-45
%, PbO- _SiO2 based glass powder consisting of _Al2O3 0.5-15%, _or PbO42-65%, _{B2O3 0.5-14}
PbO consisting of %, _SiO2 15-48%, _{Al2O3 1-18} %
−B ₂ O ₃ −SiO ₂ glass powder, willemite powder 10-50%, quartz glass powder 0.01-25% by weight
Large-diameter silicon wafer coating glass made of one or a mixture of the two.