JPH0114185B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a glass composition for sealing alumina with high ultraviolet transmittance, and particularly to a glass composition used as an ultraviolet transmitting window in an alumina ceramic package for EP-ROM. EP-ROM is Erasable Programmable-
Abbreviation for Read Only Memory. It is a read-only memory semiconductor whose program memory can be erased by UV irradiation. An alumina ceramic package is used as the support for this, and a window for UV irradiation is attached to it. It is being The glass used for this window must have high ultraviolet transmittance, and the window glass and alumina package must be hermetically sealed by direct sealing, so the sealing properties between the glass and alumina are good. In particular, it is necessary that the coefficient of thermal expansion of glass matches that of alumina.
In other words, the specific required characteristics of the window glass used in the alumina package for EP-ROM are that it has an ultraviolet transmittance of 60% or more at a glass thickness of 1 mm for ultraviolet light with a wavelength of 253.7 nm; Thermal expansion coefficient is 50-58 in the temperature range of 30-380℃
×10 ^-7 /°C. To further explain this required thermal expansion coefficient, when sealing with alumina, the difference in shrinkage between glass and alumina from the temperature at which glass and alumina stick to room temperature is
If compressive stress is applied to the glass side within the range of 200 to 1000 ppm, a safe compression seal with excellent airtightness and high strength is possible. now,
Since the thermal expansion coefficient of alumina is 65 to 70 × 10 ^-7 /℃, in order to obtain the compression seal as described above, the thermal expansion coefficient of glass must be 50 to 58 ×
It is necessary that the temperature is 10 ^-7 /℃. If the coefficient of thermal expansion is larger than this range, the compressive stress applied to the glass becomes smaller, and eventually the stress reverses and tensile stress is generated in the glass, making it impossible to maintain airtightness.
Moreover, the strength decreases, and cracks are more likely to occur in the glass due to thermal shock or the like. If the coefficient of thermal expansion is small, the shrinkage difference between glass and alumina exceeds 1000 ppm, which applies extremely large stress to each of the alumina and glass, making it easy for cracks to occur in the glass or alumina due to thermal shock, etc. Conventionally, quartz glass has been used as ultraviolet transmitting glass. This has a wall thickness of 1 mm and has a very high ultraviolet transmittance of approximately 90% at a wavelength of 253.7 nm, but its thermal expansion coefficient is approximately 5×
Due to its low temperature of 10 ^-7 /℃, it is not suitable for alumina sealing. There is also No.9741 glass manufactured by Corning in the United States. This glass has a wall thickness of 1 mm and has a UV transmittance of over 88% at a wavelength of 253.7 nm, but a thermal expansion coefficient of 37~
Due to its small temperature of 39×10 ^-7 /℃, it is not suitable for sealing alumina. It has been known that iron mixed into glass as an impurity increases the ultraviolet absorption of glass. This is because Fe ³⁺ has a large absorption in ultraviolet light. Therefore, in order to reduce the ultraviolet absorption of glass and increase its transmittance, it is necessary to reduce the iron content, which is an impurity, and to reduce Fe ³⁺ by reducing the glass to a ^reduced state. It is necessary to do so. Bringing the glass to a reduced state is accomplished by adding a reducing agent into the glass batch. As a reducing agent, carbon powder, metal aluminum, tartaric acid, Lotusel salt,
Sucrose etc. can be used. The iron content of such impurities needs to be 50 ppm or less in terms of Fe ₂ O ₃ weight content. The absorption of ultraviolet rays by glass is caused by
It was found that this phenomenon was not caused solely by Fe ³⁺ absorption, but was strongly influenced by the glass component. The reason why quartz glass has extremely high UV transmittance is Fe ³⁺
It depends on how little impurities there are, but the glass component
Due to _SiO2 being single. Generally, when an alkali metal oxide or alkaline earth metal oxide is added as a glass component, absorption occurs in the ultraviolet region. Currently, 50 to 58× is used as alumina sealing glass.
When considering a glass composition to have a coefficient of thermal expansion of 10 ^-7 /℃, it is necessary to add an alkali metal oxide or alkaline earth metal oxide equivalent to a weight content of 6 to 14 to the glass composition. be. However, adding such amounts of alkali metal oxides and alkaline earth metal oxides increases ultraviolet absorption, and even if iron as an impurity is kept below 50 ppm and melting is done with the addition of a reducing agent, the It is difficult to obtain glass with a high UV transmittance. The inventors have discovered that alkali metal oxides (R ₂ O),
As a result of studying how to suppress ultraviolet absorption by alkaline earth metal oxides (RO), we found that Al ₂ O ₃ and B ₂ O ₃
discovered that it has the effect of suppressing this ultraviolet absorption. It has been found that by increasing the content of Al ₂ O ₃ and B ₂ O ₃ in glass containing alkali metal oxides, ultraviolet absorption decreases and ultraviolet transmittance increases. Al ₂ O ₃ also increases chemical durability, but if the content is too high, meltability deteriorates. B ₂ O ₃ acts as a flux and helps melt the glass, but if the content is too high, the water resistance of the glass will deteriorate, and the amount of volatilization from the glass surface will increase during glass melting, resulting in non-uniformity of the glass. lead to transformation. As a result of such studies, the present inventors have arrived at the present invention having the following contents. The present invention is designed to allow safe compression sealing with alumina ceramics at temperatures between 30 and 380°C.
It has a coefficient of thermal expansion of 50 _to 58×10 ^-7 _/ ℃ in the temperature range of is 60% or more, and contains the following components, i.e. SiO ₂ 61~67, Al ₂ O ₃ 5~
8, _B2O3 20~ ₂₅ , _R2O7 ~10, RO0~2, F20 _~
2, where R ₂ O is Li ₂ O + Na ₂ O + K ₂ O
RO is MgO, CaO, SrO, BaO, ZnO, which is an ultraviolet transmitting glass for sealing alumina. Next, the reasons for limiting the composition of the glass of the present invention will be explained. When SiO ₂ is more than 67%, the solubility of the glass deteriorates and the coefficient of thermal expansion becomes too small, and when it is less than 61%, the ultraviolet transmittance decreases and the chemical durability of the glass deteriorates. When Al ₂ O ₃ is more than 8%, solubility deteriorates, and when it is less than 5%, ultraviolet transmittance decreases and chemical durability deteriorates. When B ₂ O ₃ is more than 25%, chemical durability deteriorates, and when it is less than 20%, ultraviolet transmittance decreases and solubility deteriorates. When the alkali metal oxide content of R ₂ O is more than 1.0%, the thermal expansion coefficient becomes too large and the ultraviolet transmittance decreases, while when it is less than 7%, the thermal expansion coefficient becomes too small and the solubility decreases. Deteriorate. The alkaline earth metal oxide in RO has the effect of improving the solubility and chemical durability of glass, but when it exceeds 2%, the ultraviolet transmittance decreases. _F2 is
It is effective for melting glass and breaking bubbles, but 2%
When the amount is higher, the glass becomes emulsified and the amount of harmful fluorine volatilized increases. The table below shows examples of glasses of the invention.

[Table] The glass samples of the above examples were prepared as follows. The prepared batch was placed in a platinum crucible so as to have the glass composition of the example, and melted in an electric furnace for 4 hours. Metallic aluminum is used as a reducing agent during melting.
Added 0.1% by weight. After melting, it was poured onto a carbon plate to obtain a plate-shaped sample. This plate-shaped sample was cut into small pieces and polished to a thickness of 1 mm for ultraviolet transmittance measurement. In addition, a plate-shaped sample was flame-processed to a length of 50 mm.
A bar-shaped sample with a diameter of 3.5 mm and a diameter of 3.5 mm was prepared and used for measuring the coefficient of thermal expansion. The glass of the present invention as described above has high ultraviolet transmittance, has excellent adhesive properties with alumina ceramic, and can be used for compression sealing with improved airtightness and strength. It is particularly suitable as a window for transmitting ultraviolet rays.

Claims (1)

[Claims] 1. It has a thermal expansion coefficient of 50 to 58 x 10 ^-7 /°C in the temperature range of 30 to 380°C so that it can be safely compression sealed with alumina ceramics,
The weight content of Fe ₂ O ₃ as an impurity is 50 ppm or less, and the transmittance of ultraviolet rays with a wavelength of 253.7 nm is 60% or more at _a wall thickness of 1 mm. 67, _{Al2O35 ~} 8,
Consists of B ₂ O ₃ 20-25, R ₂ O 7-10, RO 0-2, F ₂ 0-2, where R ₂ O is Li ₂ O + Na ₂ O + K ₂ O, and RO is MgO, CaO, SrO, BaO , UV-transparent glass for alumina sealing, which is ZnO. 2 EP that erases memory by ultraviolet irradiation
The ultraviolet transmitting glass for alumina sealing according to claim 1, which is used as an ultraviolet transmitting window in an alumina package supporting a ROM semiconductor.