JPH0146460B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a low expansion glass composition, and more particularly to a low expansion glass composition suitable for use in photoetching masks. Glass masks used in the photoetching method are usually made by applying a film of metallic chromium to a glass plate by vapor deposition or sputtering, then applying a photoresist, and then exposing and baking a projected image from a reticle (intermediate master) onto the coated surface. Then, the photoresist is peeled off by etching or washing with an acid or alkali, and unnecessary portions of the chromium film are removed to form a pattern. This glass mask is used, for example, in the production of integrated circuits.The glass mask with the chromium pattern formed thereon is applied to a silicon substrate coated with photoresist in advance, exposed to light, baked, etched,
By performing cleaning and the like, a substrate with an integrated circuit pattern can be obtained. The preferred conditions for the glass for photo-etching masks are that it can sufficiently withstand the heat generated by the light during the exposure process, that it does not expand or contract, so that a sharp pattern can be drawn on the substrate, and that it is effective for printing photoresists. It can transmit light of short wavelengths and ultraviolet range well, and it can withstand acids and alkalis used in etching and cleaning processes, but it also has to be homogenized enough to transmit light uniformly. It is also important that there are no bubbles, undissolved substances, foreign substances, striae, etc., and that the surface is extremely smooth. (Prior Art) A well-known glass for photo-etching masks is SiO ₂ -B ₂ O ₃ -Na ₂ O-based Pyrex glass (for example, Ceramic Notebook, page 604, published January 15, 1971). However, 80% of SiO ₂ is added in the composition.
% or more, it is difficult to melt at normal glass melting temperatures of 1,500 to 1,550°C, and its high viscosity makes it difficult to break bubbles and make it difficult to obtain a homogeneous glass. In addition, as a known low expansion glass, SiO ₂ 71.0
~75.5wt%, _{Al2O3 2.2} ~3.2wt%, _{B2O3 16.0} ~
21.0wt%, CaO0~0.6wt%, MgO0~0.6wt%,
BaO0~2wt%, ZnO0~1wt%, _Li2O0.4 ~2.2wt
%, _Na2O0.8 ~3.3wt%, _K2O0 ~3.0wt%, _Li2O
+Na ₂ O + K ₂ O 3.3 to 6.0wt% component accounts for 98wt of the total
% or more glass (Japanese Unexamined Patent Publication No. 49-39607),
_SiO2 55~70mol%, _{Al2O3 7} ~13mol%, CaO7~
20mol%, MgO3~13mol%, ZnO3~13mol%,
_K2O or _Na2O0.5-3mol %, PbO0-11mol%,
A photoetching mask glass (Japanese Unexamined Patent Publication No. 41736/1983) containing 0 to 3 mol % of ZrO ₂ is known. However, the former glass _has less _Al2O3 , while
Due to the excessive amount of B ₂ O ₃ , the heat resistance, chemical durability, and alkali resistance are not sufficient, and in addition, it tends to phase separate and become emulsified, so it is not satisfactory for use in photoresist masks. In addition, since the latter glass contains CaO, it inevitably has a high expansion coefficient, making it difficult to obtain a highly accurate pattern.
In addition, when PbO is not contained, the liquidus temperature is high and the melting property is poor.On the other hand, as the PbO content increases, the ultraviolet transmittance deteriorates significantly, and ZrO ₂
If it does not contain ZrO ₂ , it has poor chemical durability and
There was a problem in that as the content of . (Problems to be solved by the invention) Glass of conventional composition has poor heat resistance, chemical durability,
Although it is not fully satisfactory for use in photoresist masks due to problems with meltability, ultraviolet transmittance, expansion coefficient, etc., the present invention provides a glass composition that satisfies these conditions. . (Means for Solving the Problems) The low expansion glass suitable for the photoetching mask according to the present invention has a weight percentage of
_{SiO2 55-68} %, _Al2O3 15-24%, _{B2O3 2-8} %,
MgO3~10%, ZnO3~10%, BaO0~3%,
Na ₂ O 0 to 2%, and the molar ratio (Al ₂ O ₃ +
_B2O3 )/(MgO+ZnO+ _BaO + _Na2O ) is 0.9~
It is characterized by a range of 1.1. The present invention is first based on a composition range with a relatively low liquidus temperature due to the eutectic of SiO ₂ -Al ₂ O ₃ -RO (divalent metal oxide), and furthermore, a suitable amount of B ₂ O ₃ is added. By including it, the liquidus temperature is further lowered, so that it can be sufficiently melted even at normal glass melting temperatures. Note that B ₂ O ₃ , SiO ₂ , and Al ₂ O ₃ are well known as component factors that give low expansion, and MgO and ZnO are also known as divalent metal oxides that give low expansion. However, CaO and PbO are unsuitable for obtaining low expansion because they act negatively and should be avoided. In terms of chemical durability (acid resistance, alkali resistance), Al ₂ O ₃ is generally excellent, followed by SiO ₂ . Next to these, ZnO is excellent among divalent metal oxides, but CaO, PbO, etc. are inferior and are not preferred. Although ZrO ₂ has excellent chemical durability, it is not suitable because it increases the liquidus temperature and makes meltability extremely difficult. Regarding the composition of each individual component in the present invention, if SiO ₂ exceeds 68wt% (hereinafter wt% is simply referred to as %), the viscosity increases and the clarity deteriorates, and if it is less than 55%, the heat The coefficient of expansion increases,
The crystallization rate of devitrification increases. When Al ₂ O ₃ exceeds 24%, the viscosity increases and Al ₂ O ₃ -based striae are particularly likely to occur, but when it is less than 15%, chemical durability deteriorates.
Among divalent metal oxides, MgO is effective in reducing the coefficient of thermal expansion, but when it exceeds 10%, it significantly deteriorates chemical durability, especially acid resistance, and when it is less than 3%, it also deteriorates clarity. . ZnO also has a relatively low coefficient of thermal expansion, is effective in reducing viscosity, and has excellent chemical durability, so it
Although it compensates for the drawbacks of MgO, if it is less than 3%, these effects will be small, and if it exceeds 10%, it will increase the rate of crystallization of devitrification and deteriorate workability, which is not preferable. B ₂ O ₃ acts as a solvent and reduces the coefficient of thermal expansion, but if it exceeds 8%, it deteriorates heat resistance and chemical durability, and if it is less than 3%, its action as a solvent is insufficient. Furthermore, if 0 to 2% of Na ₂ O and/or 0 to 3% of BaO are introduced in the form of nitrate or sulfate as optional components, good results can be obtained in terms of foam removal and homogeneity. In addition, when Na ₂ O and BaO are used together, it is sufficient to keep the former at 1% or less and the latter at 1.5% or less. In addition, if AS ₂ O ₃ is added in an amount of 0.5% or less based on the total weight, the foam breaking effect can be obtained in an extremely short time. However, since the liquidus temperature of glass in this composition range is 1150°C or lower, it can be sufficiently melted at the normal glass melting temperature of 1500 to 1550°C, and the coefficient of thermal expansion (25 to 300°C) is 25 to 35 Because it is extremely low at 10 ^-7 cm/cm, °C, it is possible to create sharp patterns with a high degree of integration on substrates in the production of integrated circuits, for example, and because it is highly chemically durable, it can withstand etching with acids, alkalis, etc. It withstands washing well, has a transition temperature of around 700℃, and has excellent heat resistance. Furthermore, when exposing a substrate, ultraviolet rays are often used as light beams in a short wavelength range suitable for printing photoresists. However, B ₂ O ₃ in glass,
Al ₂ O ₃ has _a slight tendency to form non-bridging oxygen compared to SiO ₂ , and as is well known, non-bridging oxygen has the property of absorbing _ultraviolet rays, so it is not preferable. It is presumed that by introducing oxides of alkali metals and divalent metals into ₂ O ₃ in a balanced manner, it becomes difficult to form non-bridging oxygen, and as a result, absorption of ultraviolet rays can be reduced. That is, (B ₂ O ₃ + Al ₂ O ₃ )/(MgO + ZnO +
If the molar ratio of BaO + Na ₂ O) is 0.9 to 1.1, then 2 mm
The lower limit of ultraviolet transmission in thick glass is 220 to 250
For example, in Japanese Patent Application Laid-Open No. 58-41736,
It is clear that ultraviolet rays can easily pass through around 280 to 300 mm. In addition, when the Al ₂ O ₃ /B ₂ O ₃ molar ratio is close to 1 in this composition range, the obtained glass is likely to undergo phase separation,
It has therefore been experimentally shown that there is a tendency for emulsification. To prevent phase separation, Al ₂ O ₃ /
It is preferable that the B ₂ O ₃ molar ratio is 1.4 or more. On the other hand, if the Al ₂ O ₃ /B ₂ O ₃ molar ratio exceeds 8, the liquidus temperature will become high, which will have a negative effect on meltability. Also, Al ₂ O ₃ /
If the B ₂ O ₃ molar ratio is less than 1.4, especially less than 1, chemical durability etc. will be adversely affected. (Examples) The present invention will be described in detail below based on Examples. No. 1 to No. 8 in Table 1 are examples of glass compositions of the present invention, and No. 11 to No. 15 are comparative examples. Of which No.11~No.13
indicates a case outside the glass composition range of the present invention, No. 14 is an example of a glass composition based on JP-A-58-41736, and No. 15 is an example of a glass composition based on JP-A-49-39607. This is an example. In the preparation of glass, _{the glass raw materials are optical silica sand as a SiO2 source, aluminum hydroxide as an Al2O3 source, boric acid as a B2O3 source , magnesium} carbonate as an MgO source, and zinc white as a ZnO source _. ,
Barium nitrate was used as a BaO source, sodium nitrate was used as a Na ₂ O source, and in both cases, arsenous acid was added at 0.3% based on the total weight as a clarifying promoter. These raw materials were weighed according to the target composition, thoroughly stirred and mixed, then put into a platinum crucible, held at 1550°C for 4.5 hours in an indirect heating electric furnace, and then allowed to cool in the furnace to obtain a glass sample. A part of the obtained glass was processed into a rod shape, and the expansion coefficient (25° to 300°C) and transition point from the expansion bending point were determined using a push-rod linear dilatometer, and the results are shown in Table 1. In addition, a part of the glass was processed into a square piece, held in an electric furnace at 1100℃ and 1150℃ for 3 hours each, and then rapidly cooled.
The solid and liquid states of each were observed under a microscope to determine the liquidus temperature range. In Table 1, A indicates that the liquidus temperature is 1100℃ or less, B indicates 1100 to 1150℃, and C indicates that the liquidus temperature exceeds 1150℃.
It was displayed in Furthermore, a plate glass sample having a thickness of 2 mm with both sides polished smooth was prepared, and its spectral transmittance was measured using a spectrophotometer, and the lower limit of transmittance in the ultraviolet region was determined and shown in Table 1. Similarly, regarding the above plate glass, after masking about 1/2 of the glass surface with wax, one is coated with 100%
℃3N HCl for 2 hours, and then washed with water. The masking was peeled off and the cloudy state of the eroded area relative to the masked area (non-immersed area) was observed visually and under a mirror.
The other samples were immersed in 2N NaOH at 100°C for 2 hours and observed using the same method as above. In Table 1, cases where no difference from the non-immersed area was observed were ranked as A, cases where some cloudiness was observed were ranked as B, and cases where cloudiness was evident were ranked as C. In Table 1, the glasses No. 1 to No. 8 according to the present invention had well-balanced good values in all measurement results. Comparative example No. 11 is inferior in thermal expansion coefficient, and No. 12 is inferior in thermal expansion coefficient.
No. 13 has a high lower limit of transmission in the ultraviolet region, and No. 13 has a slight emulsion phenomenon due to phase separation. Further, No. 15 is inferior in thermal expansion coefficient, alkali resistance, and heat resistance, and No. 14 is inferior in thermal expansion coefficient, and has a high lower limit of transmission in the ultraviolet region. (Effects of the Invention) As described above, the glass of the present invention has low expansion for use in photo-etching masks, so it is possible to form highly integrated patterns on substrates, and it has excellent chemical durability, so it cannot be etched with acids or alkalis. It exhibits the outstanding effects of being sufficiently resistant to cleaning, well transmitting ultraviolet rays suitable for baking photoresists, sufficiently melting at ordinary glass melting temperatures, and having sufficient heat resistance. Of course, it has the advantage that it can be used not only for photo-etching masks, but also for a wide range of fields, such as sealed beams for automobile headlights, bulbs for mercury lamps, heat-resistant tableware such as jars and coffee pots, physical and chemical products such as beakers and flasks, and interior parts of microwave ovens. It has the following. 【table】

Claims (1)

[Claims] 1. In weight percent, SiO ₂ 55-68%, Al ₂ O ₃ 15
~24%, _{B2O3 2} ~8%, MgO3~10%, ZnO3~
10%, BaO0~3%, _{Na2O0 ~} 2%, and the molar ratio is ( _Al2O3 + _{B2O3 )} /(MgO+ZnO+
A low expansion glass characterized in that BaO + Na ₂ O) is in the range of 0.9 to 1.1. 2. The low expansion glass according to claim 1 _, wherein the _Al2O3 / _B2O3 molar ratio is in the _range of 1.4 to 8.