JPS6153130A - Low expansion glass - Google Patents

Abstract

PURPOSE:A low-expansion glass that is obtained by using SiO2, Al2O3, B2O3, MgO, ZnO, BaO, Na2O in a specific proportion, thus being suitable for use in photoetching mask. CONSTITUTION:The objective low-expansion glass is composed of 55-68wt% of SiO2, 15-24wt% of Al2O3, 2-8wt% of B2O3, 3-10wt% of MgO, 0.3-10wt% of ZnO, 0-3wt% of BaO, 0-2wt% of Na2O and has (Al2O3+B2O3)/(MgO+ZnO+ BaO+Na2O) of 0.9-11 in moles. Further the molar ratio of Al2O3/B2O3 is preferably 1.4-8. The resultant glass has low expansion, and a pattern of high integration can be drawn, because it is low in expansion. Further, it can sufficiently stand etching and cleaning and the violet rays suitable for photoresists can be well transmitted.

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.

The glass mask used in the photoetching method is usually made by applying a film of metallic chromium to a glass plate by vapor deposition or sputtering, then applying a photoresist, and exposing the applied surface with a projected image from a reticle (intermediate original). The pattern can be obtained by baking the resist, peeling off the shift resist by etching or cleaning with acid or alkali, and removing unnecessary portions of the chromium film to form a pattern.

This glass mask is used, for example, in the production of integrated circuits, and is made by applying the glass mask with the chromium pattern formed on a silicon substrate coated with photoresist in advance, exposing it to light, baking it, etching it, cleaning it, etc. A substrate with an integrated circuit pattern is obtained.

The preferred conditions for glass for photo-etching masks are that it can withstand the heat generated by the light during the exposure process, does not expand or contract, and therefore allows a sharp pattern to be drawn on the substrate, and has a short time that is effective for baking photoresist. In particular, it must be able to transmit light in the ultraviolet range well, and it must be sufficiently resistant to acids and alkalis used in etching and cleaning processes. bubbles, undecomposed water, foreign matter,
It is also important that there are no striae and the surface is extremely smooth.

(Prior Art) A conventionally well-known glass for photoetching masks is SiO2-B2O3-Na2O-based Pyrex glass (for example, Ceramics Notebook, page 604, published January 15, 1989); SiO□8
Since it contains 0% or more, it is difficult to melt at the normal glass melting temperature, that is, 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.

Further, as a known low expansion glass, Si○; 71. .

~75.5 wt%, Al2O, 2,2~3.2 wt
%, B2O3, 16,0-21. Owt%, CaOO~
0.6 wt%, MgO0-5-0,6 wt%, Ba
oo~2Wt,%, ZnOO~I wt%, Li2O0
, 4-2.2 wt%, Na2゜O, 8-3.3 wt%
%, K2O01~3. Owt%, Li2O+Na2O+
2O3.3-6. Owt% component is 98wt% of the whole
The above glass (Japanese Patent Application Laid-Open No. 49-39607), SiO
255-70 m01%, Al2O37-I3 m0
1%, CaO7~2O m01%, MgO3~l 3m
o1%, ZnO3~13 m01%, K2O or Na
2O0.5~3mol1%, pbQ O~l I m01
%, ZrO□0 to 3 mo1% glass for photoetching masks (Japanese Patent Application Laid-open No. 41736/1983) is known.

However, the former glass has less Al2O3, while B2
If there is too much O3, the heat resistance, chemical durability, and alkali resistance are not sufficient, and in addition, the phase tends to separate easily and become opaque, so it is not satisfactory for use in photoresist masks, and the latter Because glass contains CaO, it inevitably has a high coefficient of expansion, making it difficult to obtain a highly accurate putter.If it does not contain PBO, its liquidus temperature is high and its tactility is poor; As the Zr content increases, the ultraviolet transmittance deteriorates significantly.
If it does not contain 0z', it has poor chemical 1itI durability.
There was a problem in that as the content of ZrO2 was increased, the liquidus temperature was significantly increased and the meltability was deteriorated.

(Problems to be solved by the invention) Glass of conventional composition has poor heat resistance, chemical durability, meltability,
Although the glass composition for photoresist masks is not fully satisfactory due to problems in either ultraviolet transmittance or expansion coefficient, the present invention provides a glass composition that satisfies these conditions.

(Another Means to Solve the Problem) The low expansion glass suitable for the photoetching mask according to the present invention has a SiO2 content of 55 to 68% by weight.
, AI□0315-24%, 82O32-8%, MgO
3~l O 3%, Na2O0~2% Te<ri
V), in Kamol ratio (Al2O3+B2O3)/
(MgO+ZnO+BaO+Na2O) is 0.9 to 1.
It is characterized by being in the range of 1.

The present invention is based on SiO2-A12O3-RO (SiO2-A12O3-RO) (a composition range with a relatively low liquidus temperature due to eutectic synthesis of divalent metal oxides), and further contains a suitable amount of B2O3. Second, the liquidus temperature is further lowered so that it can be sufficiently melted even at normal glass melting temperatures.

In addition, B2O3, SiO□, and Al2O3 are well known as component factors that give low expansion, and among divalent metal oxides, MgO1ZnO is known to give low expansion, but caOlPbO has low expansion. Since it has a negative effect, it is inappropriate and should be avoided.

Chemical durability (acid resistance, alkali resistance) is generally Am2
O3 is excellent, followed by SiO2. Next to these, ZnO is eroded among divalent metal oxides, but OaO%PbO and the like are inferior and are not preferred. Although ZrO2 has excellent chemical durability, it is not suitable because it increases the liquidus temperature and makes meltability extremely difficult.

Referring to the individual component compositions of the present invention,
When SiO2 exceeds 68 wt% (hereinafter wt% is simply referred to as "silicon"), the viscosity increases and the clarity deteriorates.
If it is less than 5%, the coefficient of thermal expansion becomes high and the rate of crystallization of devitrification becomes low. A1□o3 24%? If the content exceeds 15%, the viscosity increases and Al2O3 striae are likely to occur, but if the content is less than 15%, the chemical durability deteriorates. Among divalent metal oxides, MgO is effective in reducing the coefficient of thermal expansion, but 10
If it exceeds 3%, chemical durability, especially acid resistance, will be significantly deteriorated, and if it is less than 3%, clarity will also deteriorate. ZnO also has a relatively low coefficient of thermal expansion and is effective in reducing viscosity! In particular, MgO has excellent chemical durability, so it compensates for the disadvantages of MgO, but if it is less than 3%, its effect is small, and if it exceeds 10%, the crystallization rate of devitrification increases and workability deteriorates. This is not desirable because it causes B2O3 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 NanoO~2H and/or BaOO~3H are introduced as optional components in the form of nitrates or sulfur salts, good results can be obtained in terms of foam removal and homogeneity. In addition,
When Na2O 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, As2O3
If 0.5% or less of the total weight is added, the foam-cutting effect can be obtained in an extremely short period of time.

Therefore, if the glass has this composition range, the liquidus temperature will be 11
Since it is below 50℃, the normal glass melting temperature is 1500℃.
It can be sufficiently melted at ~1550℃, has a low coefficient of thermal expansion (25~b), and can therefore be used to form highly integrated/large patterns on substrates in the production of integrated circuits. It can withstand etching and cleaning with alkali, etc., and has a transition temperature of around 700°C, so it has excellent heat resistance.

Furthermore, when applying i-light to a substrate, ultraviolet rays are often used as light beams in a short wavelength range suitable for printing photoresist. However, B2O3 and Al2O3 in glass tend to form non-bridging oxygen to some extent compared to milk 02, and as is well known, non-bridging oxygen has the property of absorbing ultraviolet rays, which is not preferable. It is presumed that introducing oxides of alkali metals and divalent metals in a balanced manner makes it difficult to form non-bridging oxygen.
As a result, absorption of ultraviolet rays can be reduced.

That is, (B2O3+Al□03)/(MgO+ZnO
+BaO+Na2O) if the molar ratio is 0.9 to 1.1, the lower limit of ultraviolet transmission in 2-thickness glass is 22O~
250-, and it is clear that it is easier to transmit ultraviolet rays than, for example, about 280 to 300 wn in JP-A No. 58-41736.

It has been experimentally found that when the Al2O3/B2O3 molar ratio is close to 1 within this composition range, the resulting glass tends to undergo phase separation and therefore tends to become emulsified. In order to prevent phase separation, it is preferable that the Al2O3/B2O3 molar ratio is 1.4 or more;
When the /B2O3 molar ratio exceeds 8, the liquidus temperature will be high, which will have a negative effect on meltability. Furthermore, if the Al2O3/B2O3 molar ratio is smaller than 1.4, especially less than 1, it will adversely affect chemical durability and the like.

(Example) The present invention will be explained in detail below based on examples.

/IG, 1 to 8 in Table 1 are examples of glass compositions of the present invention,
Boiled 11 to AI 5 are comparative examples. Of which A+1~Jf
fi13 indicates a case outside the glass composition range of the present invention, A14 is an example of a glass composition based on JP-A-58-41736, and 415 is an example of a glass composition based on JP-A-49-3960.
This is flJ with a glass composition based on No. 7.

In the preparation of glass, glass raw materials include optical silica sand as a SiO□ source, aluminum hydroxide as an Al2O3 source, boric acid as a B2O3 source, magnesium carbonate as an MgO source, zinc white as a ZnO source, and barium nitrate as a BaO source. using sodium nitrate as a Nano source,
In each case, 0.3% of arsenic acid was added to 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, and heated in an indirect heating electric furnace for 15 minutes.
It was held at 50° C. for 4.5 hours, 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 DEG to 300 DEG C.) and the transition point from the expansion bending point were determined using a push rod type linear expansion needle and are shown in Table 1.

In addition, a part of the glass is processed into a square piece and heated to 110 mm in an electric furnace.
The samples were held at 0°C and 1150°C for 3 hours each and then rapidly cooled, and the solid and liquid states of each were observed under a microscope to determine the liquidus temperature range.

In Table 1, the degree of non-immersion is 1100℃ or less: A, 1100
~1150℃ 13. Temperatures exceeding 1150°C were designated as C.

Furthermore, a sheet glass sample was prepared with both surfaces smoothed using a two-sided polishing machine, and its spectral transmittance was measured using a spectrophotometer.The lower limit of transmittance in the ultraviolet region was determined and is shown in Table 1.

Similarly, regarding the above plate glass, approximately 1/2 of the glass surface
After masking with wax, one was heated to 100℃3NH.
After immersing in C1 for 2 hours and washing 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 microscope. Others are 100℃ 2N NaOH
The specimens immersed in water for 2 hours were observed using the same method as above.

In addition, if there is no difference from the non-immersed part in Table 1, 2A,
B1 for the case where &υ is recognized slightly; C for the case where cloudy is obvious.
It is displayed in rank.

In Table 1, the glasses Nos. 1 to A8 according to the present invention obtained well-balanced and good values in all measurement results. Comparative examples All
is inferior in thermal expansion coefficient, Al2 has a high lower limit of transmission in the ultraviolet region, and Ify and Al3 exhibit a slight emulsion phenomenon due to phase separation.

Furthermore, KA15 is inferior in thermal expansion coefficient, alkali resistance, and heat resistance, and Al 4 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 is suitable for photo-etching masks because it has low expansion, so it is possible to form patterns with a high degree of integration on the substrate, and because it has excellent chemical durability, it can withstand etching with acids and alkalis. It exhibits the outstanding effects of being sufficiently resistant to cleaning, transmitting ultraviolet rays suitable for photoresist baking, sufficiently bath melting at ordinary glass melting temperatures, and having sufficient heat resistance.
6 Of course, 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, pulp 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. This has the advantage that.

(Margin below)

Claims (1)

[Claims] 1) In weight percent, SiO_255-68%, Al
_2O_315-24%, B_2O_32-8%, Mg
O3~10%, ZnO3~10%, BaO0~3%, N
a_2O 0 to 2%, and the molar ratio (Al_2O_
3+B_2O_3)/(MgO+ZnO+BaO+Na
_2O) is in the range of 0.9 to 1.1. 2) Al_2O_3/B_2O_3 in molar ratio is 1.4~
8. The low expansion glass according to claim 1, wherein the low expansion glass is in the range of 8.