HK1075243B - Ultra low thermal expansion transparent glass-ceramics - Google Patents

Description

Ultra-low thermal expansion transparent glass ceramic

Technical Field

The present invention relates to a glass ceramic which can be widely used for various precision components requiring ultra-low thermal expansion properties, ultra-surface flatness or high rigidity, and is particularly suitable for use as various components of next-generation semiconductor devices.

In the present specification, the term "difference between the maximum value and the minimum value of Δ L/L" refers to the difference between the maximum value and the minimum value of Δ L/L at a given temperature from 0 ℃, where L represents the length of the glass-ceramic sheet at 0 ℃ and Δ L represents the amount of change in the length of the glass-ceramic at the given temperature.

In the present specification, the term "ultra-low thermal expansion property" refers to a property of a glass-ceramic having 0.0. + -. 0.2X 10 at a temperature of 0 to 50 ℃ C^-70.0. + -. 0.1X 10 ℃ is preferred^-7Average linear thermal expansion coefficient of/° C, and the difference between the maximum value and the minimum value of Δ L/L is 10 × 10^-7Or less, preferably 8X 10^-7Or smaller.

In the present specification, "main crystal phase" refers to all crystal phases having a relatively large precipitation ratio. More specifically, the "main crystal phase" includes all crystal phases each of which has a main peak (highest peak in the crystal phase) having a ratio of X-ray diffraction intensities (hereinafter referred to as "X-ray diffraction intensity ratio") of 30 or more when the X-ray diffraction intensity of the main peak (highest peak) of the crystal phase having the largest precipitation ratio in an X-ray diagram of X-ray diffraction (the vertical axis represents X-ray diffraction intensity, the horizontal axis represents diffraction angle) is assumed to be 100. The X-ray diffraction intensity ratio of the crystal phases other than the main crystal phase should preferably be less than 20, more preferably less than 10, and most preferably less than 5.

Background

In recent lithography, the development of higher density integration in semiconductor circuits has increased the active development of reducing the width of exposed lines. For example, as a next-generation technology, in optical type lithography, a technology using a KrF laser beam having a wavelength of 0.248 μm or an ArF laser beam having a wavelength of 0.193 μm has been actively studied. Also, in order to realize a smaller semiconductor circuit, a variable wavelength system using an EPL (electron projection lithography) and an EUV (extreme ultraviolet) system using extreme ultraviolet rays having a wavelength of 0.0134 μm have been studied.

Such next generation lithographic components used in the manufacture of semiconductors require thermal stability in terms of size, strength, heat resistance and chemical stability, particularly ultra-low thermal expansion performance necessary for dimensional thermal stability.

Si and SiO₂Materials have been used as components of prior art semiconductor devices. The Si material has an average linear thermal expansion coefficient alpha of 30 x 10^-7High thermal expansion material at/° C, SiO with relatively low thermal expansion properties₂The alpha of the material is still 5 multiplied by 10^-7/° c, which is far from satisfactory for the ultra-low thermal expansion performance required for high precision design, it is difficult to use for next generation lithography.

Common transparent glass ceramics and SiO produced by CVD (chemical vapor deposition) can be considered₂-TiO₂Glass is used as a material for eliminating these material defects. However, materials produced by CVD have defects in the form of striations (cord) produced in one direction by the material stack, with the result that the average linear coefficient of thermal expansion of the resulting material has anisotropic propertiesTherefore, it is not satisfactory in terms of dimensional thermal stability.

Except for quartz glass and SiO₂-TiO₂In addition to glass, SiO is known in the field of ordinary transparent glass ceramics₂-Al₂O₃-Li₂O transparent glass-ceramics, which have achieved various low thermal expansion characteristics. For example, Japanese patent publication JP 77137/1991 and U.S. Pat. No. 3, 4851372 disclose glass-ceramics containing TiO as a nucleating agent₂And ZnO₂And additionally contains P as an optional component₂O₅、MgO、CaO、Na₂O and K₂And O. However, these glass-ceramics have a size of 1X 10^-7A high average linear thermal expansion coefficient per deg.c, and highly accurate ultra low thermal expansion properties, object of the present invention, are not considered at all in these publications.

Japanese patent JP 2668057 discloses a composition containing TiO₂And ZrO₂Glass-ceramics as nucleating agents. However, these glass-ceramics also have a refractive index of 0. + -. 5X 10^-7The wide range of linear thermal expansion coefficients per deg.c is averaged, and highly accurate ultra low thermal expansion properties, object of the present invention, are not considered at all in these publications.

In order to reduce the width of the exposed lines of the integrated circuit and to make the integrated circuit more accurate, various elements used in photolithography for next-generation semiconductor devices are required to have the following properties:

(1) the component should have ultra low thermal expansion properties.

(2) After polishing, the component should have an ultra-flat surface roughness.

(3) To achieve flatness, the average grain diameter of the material should be very small.

(4) The influence of heat and vibration should be minimized.

(5) The element should be free of Na which is liable to cause contamination of the element material during film formation and cleaning₂O and K₂And (4) an O component.

It is therefore an object of the present invention to provide a glass ceramic which eliminates the above-mentioned drawbacks of the prior art materials and realizes an ultra-low thermal expansion property and an ultra-flat surface capable of accommodating the next-generation LSI lithography.

It is another object of the present invention to provide parts for semiconductor devices such as masks, optical mirrors, wafer stages and reticle stages, and various precision elements.

Disclosure of Invention

In order to achieve the above object of the present invention, diligent research and experiments conducted by the inventors of the present invention have resulted in the finding of the present invention that, in a glass ceramic having a glass composition within a specific composition range and a specific main crystal phase, an ultra-low thermal expansion transparent glass ceramic having an average linear thermal expansion coefficient of 0.0. + -. 0.2X 10 within a temperature range of 0 to 50 ℃ of 0.0. + -. 0.2X 10, which is significantly superior to that of the prior art glass ceramic, can be obtained^-7/° C, the difference between the maximum and minimum values of Δ L/L is 10 × 10^-7Or less, preferably composed of fine grains having an average grain diameter of 50 to 90nm, and having a surface roughness after polishing ofOr lower, and is free of PbO, Na₂O、K₂O and B₂O₃Diffusion of ions.

According to the present invention, there is provided a glass ceramic having an average linear thermal expansion coefficient of 0.0. + -. 0.2X 10 in a temperature range of 0 to 50 DEG C^-7/° C, the difference between the maximum and minimum values of Δ L/L is 10 × 10^-7Or below, it contains SiO in a total amount of 86.0 to 89.0 mass%₂、Al₂O₃And P₂O₅。

In one aspect of the invention, P₂O₅With SiO₂Ratio of (A) to (B) and P₂O₅With Al₂O₃In a ratio of

P₂O₅/SiO₂0.1230-0.1450 and

P₂O₅/Al₂O₂ 0.270-0.330。

in another aspect of the present invention, there is provided a glass-ceramic having an average linear thermal expansion coefficient of 0.0. + -. 0.1X 10 in a temperature range of 0 to 50 ℃^-7/° C, the difference between the maximum and minimum values of Δ L/L is 8 × 10^-7Or less, and contains SiO in a total amount of 86.0 to 89.0 mass%₂、Al₂O₃And P₂O₅。

In another aspect of the invention, P is in the glass-ceramic₂O₅With SiO₂Ratio of (A) to (B) and P₂O₅With Al₂O₃In a ratio of

P₂O₅/SiO₂0.1230-0.1450 and

P₂O₅/Al₂O₃ 0.270-0.330。

in another aspect of the invention, the glass-ceramic has a surface roughness (Ra) (arithmetic mean roughness) ofOr lower.

In another aspect of the present invention, the precipitated crystal phase of the glass ceramic has an average particle diameter of 50 to 90 nm.

In another aspect of the invention, the glass-ceramic contains beta-quartz (beta-SiO) as the main crystalline phase₂) And/or beta-quartz solid solution (beta-SiO)₂Solid solution).

In another aspect of the present invention, the glass-ceramic does not contain PbO, Na₂O、K₂O and B₂O₃。

In another aspect of the present invention, a glass-ceramic is obtained by heat-treating (for crystallization) a base glass containing, by mass%,

SiO₂ 53-57％

P₂O₅7.0-8.5% and

Al₂O₃ 23-26％

and is substantially free of PbO, Na₂O、K₂O and B₂O₃The glass-ceramic contains beta-quartz (beta-SiO) as the main crystal phase₂) And/or beta-quartz solid solution (beta-SiO)₂Solid solution).

In another aspect of the invention, the glass-ceramic contains 3.5 to 4.5 mass% Li₂O。

In another aspect of the present invention, the glass-ceramic contains, by mass%,

MgO 0.5-1.5% and/or

0.1-1.5% of ZnO and/or

CaO 0.5-1.5% and/or

BaO 0.5-1.5% and/or

TiO₂1.5-3.0% and/or

ZrO₂1.0-3.0% and/or

As₂O₃ 0.5-1.0％。

In another aspect of the invention, the maximum temperature of the heat treatment for crystallization is 750-.

In another aspect of the present invention, there is provided a mask for lithography using these glass-ceramics.

In another aspect of the present invention, there is provided an optical system mirror for lithography using these glass ceramics.

In another aspect of the invention, a wafer stage or reticle stage for lithography using these glass-ceramics is provided.

In another aspect of the present invention, there is provided a precision instrument part using these glass-ceramics.

According to the present invention, there is provided an excellent, ultra-low thermal expansion transparent glass-ceramic material having mechanical strength capable of coping with a film forming process at high temperature and stress caused by multilayer film formation, and also having high temperature resistance, allowing ultra-flatness of the substrate surface for manufacturing highly precise elements, low diffusion of alkali components from the substrate during film formation or annealing at high temperature, excellent light transmission properties and ultra-low thermal expansion properties, and capable of realizing highly precise ultra-precise parts, semiconductor elements and structural elements. Also provided are semiconductor device parts and precision instrument parts using the glass-ceramic material.

Also, the glass ceramic of the present invention can be manufactured by melting raw materials of a base glass at a relatively low temperature and heat-treating the base glass at a low crystallization temperature of 800 ℃ or less, compared to the prior art glass ceramic, and thus, the glass ceramic can be manufactured at a relatively low cost.

Drawings

In the drawings, there is shown in the drawings,

FIG. 1 is a graph illustrating the Δ L/L curves over the range of 0 ℃ to 50 ℃ for examples 1, 2, 5 and 7;

FIG. 2 is a graph illustrating the Δ L/L curves in the range of 0 ℃ to 50 ℃ for example 1 and comparative examples 1 and 2;

FIG. 3 is an enlarged view of the microstructure of example 1 obtained by a transmission electron microscope; and

fig. 4 is an enlarged view of the microstructure of comparative example 1 obtained by a transmission electron microscope.

Detailed Description

The reasons for defining the thermal and physical properties, the main crystal phase and the crystal grain diameter, the surface roughness and the composition of the glass-ceramic of the present invention as described above will be described below.

As for the average linear thermal expansion coefficient, as described above, in semiconductor devices and ultra-precision instruments, material thermal expansion properties capable of coping with the trend toward higher precision are required. For this purpose, the material should have a temperature of 0.0. + -. 0.2X 10 in the range from 0 to 50 ℃^-7/. degree.C., more preferably 0.0. + -. 0.1X 10^-7Average linear thermal expansion coefficient of/° C, and the difference between the maximum value and the minimum value of Δ L/L is 10 × 10^-7Or less, more preferably 8X 10^-7Or lower.

As for the surface roughness and the crystal grain diameter after polishing, as described above, in semiconductor devices and ultra-precision instruments, the relationship between the average crystal grain diameter and the surface roughness is important for maintaining the flatness of the substrate surface that can cope with the trend toward higher precision. For this reason, the surface roughness Ra after polishing should preferably beOr less, more preferablyOr lower. In order to easily obtain this flatness, the average crystal grain diameter of the precipitated crystals should preferably be 90nm or less, more preferably 80nm or less. On the other hand, in order to obtain the desired mechanical strength of the glass-ceramic, the average crystal grain diameter should preferably be 50nm or more, more preferably 60nm or more.

This is an important factor in determining the average linear thermal expansion coefficient with respect to the main crystal phase precipitated in the glass ceramic. In the glass ceramic of the present invention, the average linear thermal expansion coefficient of the glass ceramic as a whole within the desired range is obtained by forming a main crystal phase having a negative average linear thermal expansion coefficient. For this purpose, the glass-ceramic should preferably comprise beta-quartz (beta-SiO)₂) Or a solid solution of beta-quartz (beta-SiO)₂Solid solution) as the main crystalline phase. In the present specification, "β -quartz solid solution" refers to β -quartz containing interstitial and/or substitutional elements or elements other than Si and O. In the glass ceramic of the present invention, in particular, a preferable β -quartz solid solution is a crystal in which Al is used⁺³By replacement of Si by atoms⁺⁴And adding Li⁺、Mg⁺²And Zn⁺²The atoms are kept in equilibrium.

The reason for limiting the various components to the above-mentioned number ranges will now be described. The amounts of the respective components are expressed in mass%.

SiO₂Composition is a very important component, by heat treatment of the base glass, SiO₂The above-mentioned crystals as the main crystal phase are generated. If the amount of this component is 53% or more, crystal precipitation in the produced glass ceramic is stable and its texture (texture) hardly becomes coarse, so that the mechanical strength of the glass ceramic is improved and the surface roughness of the glass ceramic after polishing becomes small, if the amount of this component is 57% or less, the base glass is easily melted and formed and the uniformity of the glass ceramic is improved. In order to more easily obtain these effects, the lower limit of this component is preferably 54%, and the more preferred lower limit is 54.5%. Similarly, the preferred upper limit for this component is 56%, with a more preferred upper limit of 55.8%.

When reacting with SiO₂When components coexist, P₂O₅The ingredients are effective for improving the melting property and transparency of the base glass and also for stabilizing the thermal expansion property after crystallization by heat treatment to a desired value. In the glass-ceramic of the present invention, if P₂O₅The amount of the component (C) is 7.0% or moreThese effects are remarkably improved, and if the amount of this component is 8.5% or less, the base glass has excellent resistance to devitrification, which prevents coarsening of the glass-ceramic structure due to a decrease in resistance to devitrification during the crystallization process, and thus, the mechanical strength of the glass-ceramic is improved. In order to more easily obtain these effects, the lower limit of this component is preferably 7.3%, and the more preferred lower limit is 7.4%. Similarly, the preferred upper limit for this component is 7.9%, with a more preferred upper limit of 7.7%.

If Al is present₂O₃When the amount of the component (C) is 23 to 26%, the base glass is easily melted, and as a result, the homogeneity of the resulting glass ceramic is improved and the glass ceramic has excellent chemical durability. Also, if the amount of this component is 26% or less, the devitrification resistance of the base glass is improved, which prevents the coarsening of the glass-ceramic structure due to the decrease in devitrification resistance during the crystallization, and as a result, the mechanical strength of the glass-ceramic is improved. In order to more easily obtain these effects, the lower limit amount of this component is preferably 24%, and the more preferable lower limit is 24.2%. Similarly, the preferred upper limit of this component is 25%, and the more preferred upper limit is 24.7%.

If SiO₂、Al₂O₃And P₂O₅The total amount of (B) is 86.0-89.0%, P₂O₅With SiO₂A ratio of (A) to (B) of 0.1230-0.1450, and P₂O₅With Al₂O₃The ratio of (b) is 0.270 to 0.330, the low thermal expansion performance in the temperature range of 0 to 50 ℃ is remarkably improved, thereby obtaining ultra low thermal expansion performance. To more easily obtain these effects, SiO₂、A1₂O₃And P₂O₅The preferred lower limit of the total amount is 86.5%, the more preferred lower limit of the total amount is 86.7%₂O₅With SiO₂The preferred lower limit of the ratio is 0.1310, and the more preferred lower limit thereof is 0.1320. P₂O₅With Al₂O₃The preferable lower limit of the ratio is 0.290, and the more preferable lower limit thereof is 0.300. SiO 2₂、Al₂O₃And P₂O₅The preferred upper limit of the total amount is 88.0%, whichA more preferred upper limit is 87.8%. P₂O₅With SiO₂The preferable upper limit of the ratio is 0.1420, and the more preferable upper limit thereof is 0.1400. P₂O₅With Al₂O₃The preferred upper limit of the ratio is 0.320.

Li₂O, MgO and ZnO are important components constituting the solid solution of β -quartz. Furthermore, the importance of these components is that when these components are mixed with SiO₂And P₂O₅When the components coexist in a specific composition range, the components improve the low thermal expansion property of the glass ceramic and reduce the deflection (deflections) of the glass ceramic at high temperatures, and significantly improve the melting property and transparency of the base glass.

If Li is present₂The above effect is remarkably improved when the amount of the O component is 3.5% or more, and the homogeneity of the base glass is greatly improved by the improvement of the melting property of the glass. Moreover, the precipitation of the desired crystalline phase increases significantly. Also, if the amount of this component is 4.5% or less, the low thermal expansion property is significantly improved, so that an ultra-low thermal expansion property can be easily obtained, and the devitrification resistance of the base glass is improved, which prevents the texture of the glass ceramic from being coarsened due to the decrease in devitrification resistance during crystallization, and as a result, the mechanical strength of the glass ceramic is improved. In order to more easily obtain these effects, the lower limit of this component is preferably 3.8%, and the more preferable lower limit is 3.9%. Similarly, a preferred upper limit for this component is 4.1%.

If the amount of the MgO component is 0.5% or more, the above effect is remarkably improved, and if the amount of this component is 1.5% or less, the low thermal expansion performance is remarkably improved, so that the ultra low thermal expansion performance can be obtained. In order to more easily obtain these effects, the lower limit of this component is preferably 0.6%, and the more preferred lower limit is 0.7%. Similarly, the preferred upper limit for this component is 1.4%, with a more preferred upper limit of 1.3%.

If the amount of the ZnO component is 0.1% or more, the above effect is remarkably improved, and if the amount of this component is 1.5% or less, the low thermal expansion property is remarkably improved, so that the ultra-low thermal expansion property can be obtained, and the devitrification resistance of the base glass is improved, which prevents coarsening of the glass-ceramic structure due to a decrease in devitrification resistance during crystallization, and as a result, the mechanical strength of the glass-ceramic is improved. In order to more easily obtain these effects, the lower limit of this component is preferably 0.2%, and the more preferred lower limit is 0.3%. Similarly, the preferred upper limit of this component is 1.2%, and the more preferred upper limit is 0.9%.

The two components, CaO and BaO, are present as a glass matrix, which is a portion of the glass ceramic other than precipitated crystals in the glass ceramic. These components are important as components for fine adjustment between the crystal phase and the glass matrix to improve the ultra-low thermal expansion property and the melting property.

If the amount of the CaO component is 0.5% or more, the melting and refining effects are remarkably obtained, and if the amount of this component is 1.5% or less, the low thermal expansion property is remarkably improved, so that the ultra-low thermal expansion property can be obtained, and the devitrification resistance of the base glass is improved, which prevents coarsening of the glass-ceramic structure due to a decrease in devitrification resistance during crystallization, and as a result, the mechanical strength of the glass-ceramic is improved. In order to more easily obtain these effects, the lower limit of this component is preferably 0.6%, and the more preferred lower limit is 0.7%. Similarly, the preferred upper limit for this component is 1.4%, with a more preferred upper limit of 1.3%.

If the amount of the BaO component is 0.5 to 1.5%, the low thermal expansion property is remarkably improved, so that an ultra-low thermal expansion property can be easily obtained, and the devitrification resistance of the base glass is improved, which prevents the coarsening of the texture of the glass ceramic due to the decrease in devitrification resistance during the crystallization, and as a result, the mechanical strength of the glass ceramic is improved. In order to more easily obtain these effects, the lower limit of this component is preferably 0.6%, and the more preferred lower limit is 0.7%. Similarly, the preferred upper limit for this component is 1.4%, with a more preferred upper limit of 1.3%.

As nucleating agent, TiO₂And ZrO₂Ingredient is notMay or may not be present. If TiO is present₂The amount of the component (A) is 1.5% or more, and ZrO₂When the amount of the component is 1.0% or more, a desired crystal phase may be precipitated. If the amounts of these two components are respectively 3% or less, the occurrence of unmelted portions of the glass is prevented, thereby increasing the melting property of the glass and improving the uniformity of the glass. To more easily obtain these effects, TiO₂The lower limit of the component (B) is preferably 1.7%, and the lower limit is more preferably 1.9%. ZrO (ZrO)₂The lower limit of the component (B) is preferably 1.3%, and the lower limit is more preferably 1.6%. TiO 2₂The upper limit of the component (B) is preferably 2.9%, and more preferably 2.8%. ZrO (ZrO)₂The upper limit of the component (B) is preferably 2.7%, and more preferably 2.4%.

As may be added during melting of the glass material₂O₃As a clarifying agent (refining agent) to obtain a homogeneous preparation. To obtain this effect, preferably 0.5-1.0% of this ingredient should be added.

In addition to the above components, SrO, B may be added in a total amount of 2% or less in order to finely adjust the properties of the glass-ceramic within a range not to impair the properties of the glass-ceramic₂O₃、F₂、La₂O₃、Bi₂O₃、WO₃、Y₂O₃、Gd₂O₃And SnO. One or more coloring components such as CoO, NiO, MnO or the like may be added in a total amount of 2% or less₂、Fe₂O₃And Cr₂O₃. However, in the case where the glass ceramic of the present invention is used for applications requiring high light transmittance, it is preferable that these coloring components are not contained.

In the glass ceramic of the present invention, a main crystal phase having a negative average linear thermal expansion coefficient is precipitated, and a glass ceramic having an ultra-low thermal expansion property as a whole is obtained by combining this main crystal phase with a glass matrix having a positive average linear thermal expansion coefficient. For this reason, the glass-ceramic preferably does not contain a crystalline phase having a positive average linear thermal expansion coefficient such as lithium disilicate (lithium silicate), lithium silicate, α -quartz, and,Alpha-cristobalite, alpha-tridymite, Zn-petalite and other petalites, wollastonite, forsterite, diopside, nepheline, clinoptilolite, anorthite, celsian, gehlenite, willemite, mullite, corundum, wollastonite A and solid solutions of these crystals. Moreover, in order to maintain excellent mechanical strength, the glass ceramic should preferably be free of hafnium tungstate, zirconium tungstate and other tungstates, magnesium titanate, barium titanate, manganese titanate and other titanates, mullite, 2Ba3SiO₂、Al₂O₃·5SiO₂And solid solutions of these crystals.

In order to accommodate the lithography for the next-generation semiconductor devices, the thermal conductivity and young's modulus of the glass-ceramic of the present invention should preferably be the following values. The thermal conductivity should preferably be 1.0-2.0W/(m.k) to rapidly dissipate heat from the material being heated during the film forming process or electron beam irradiation. A more preferable lower limit of the thermal conductivity is 1.5W/(m.k) and/or a more preferable upper limit of the thermal conductivity is 1.9W/(m.k). When glass ceramics are used as precision components, the young's modulus is important for preventing the occurrence of fine defects in making the components light, ultra-precision grinding, and ultra-fine machining, and also for reducing the adverse effects caused by external factors such as vibrations caused by various causes. A preferred Young's modulus ranges from 85 to 95GPa, with a more preferred range being a lower limit of 90GPa and/or an upper limit of 94 GPa.

The ultra-low thermal expansion transparent glass-ceramic of the present invention is manufactured by the following method.

The glass materials were weighed, mixed, placed in a crucible, and melted at a temperature of 1500-.

After the base glass is obtained by melting the raw materials, the base glass is shaped into a desired shape by casting and/or thermoforming in a mold.

Then, the base glass is heat-treated to obtain a glass ceramic. First, for nucleation, the base glass is maintained at a temperature of 650-750 deg.C, preferably with a lower limit of 680 deg.C and an upper limit of 720 deg.C.

After nucleation, the base glass is crystallized at a temperature of 750-800 ℃. If the temperature is less than 750 ℃, the main crystal phase grows insufficiently, and if the temperature is more than 800 ℃, the base glass is easily deformed due to softening or remelting. More preferred crystallization temperatures are a lower limit of 770 ℃ and/or an upper limit of 790 ℃.

Further, a mask, an optical system mirror, a wafer stage and a reticle stage, and elements for precision instruments are manufactured by molding a glass ceramic into a desired shape, and subjecting the glass ceramic to lapping, polishing, and film forming processes as necessary.

Examples

Embodiments of the present invention will now be described. Tables 1 and 2 show the compositions (examples 1 to 7) of the ultra-low thermal expansion transparent glass-ceramics of the present invention and prior art Li₂O-Al₂O₃-SiO₂Examples of the composition of the low expansion glass ceramics (comparative examples 1 and 2), and their highest heat treatment temperature, average crystal grain diameter, surface roughness (Ra) after polishing, average linear thermal expansion coefficient in the temperature range of 0 to 50 ℃, and difference between the maximum value and the minimum value of Δ L/L. The compositions of the respective examples and comparative examples are expressed in mass%.

It should be noted that the present invention is not limited by these examples.

TABLE 1

Examples

1 2 3 4 5

SiO₂ 55.00 55.50 55.50 55.50 55.50

P₂O₅ 7.60 7.50 7.60 7.55 7.60

Al₂O₃ 24.40 24.50 24.40 24.45 24.40

Li₂O 4.00 3.95 3.95 3.95 3.97

MgO 1.00 1.00 1.00 1.00 1.00

ZnO 0.50 0.50 0.50 0.50 0.50

CaO 1.00 1.05 1.05 1.05 1.03

BaO 1.00 1.00 1.00 1.00 1.00

TiO₂ 2.50 2.30 2.30 2.30 2.30

ZrO₂ 2.00 2.00 2.00 2.00 2.00

As₂O₃ 1.00 0.70 0.70 0.70 0.70

P₂O₅/SiO₂ 0.1382 0.1351 0.1369 0.1360 0.1369

P₂O₅/Al₂O₃ 0.311 0.306 0.311 0.309 0.311

SiO₂+Al₂O₃+P₂O₅ 87.00 87.50 87.50 87.50 87.50

Maximum crystallization temperature (. degree. C.)

780 770 770 780 785

Average grain diameter (nm)

50 70 70 60 50

Surface roughness 1.0 1.5 1.3 1.1 1.5

Average linear thermal expansion coefficient

(10^-7/℃)(0℃-50℃) 0.02 0.04 0.03 -0.02 0.06

Δ L/L (highest-lowest) (10)^-7)

(0℃-50℃) 2.1 2.8 7.8 6.2 2.2

TABLE 2

Examples Comparative example

6 7 1 2

SiO₂ 55.50 55.50 53.00 55.00

P₂O₅ 7.35 7.50 8.00 8.00

Al₂O₃ 24.65 24.50 23.50 24.00

Li₂O 3.95 3.95 3.80 4.00

MgO 1.00 1.00 Na₂O0.70 1.00

ZnO 0.50 0.50 1.80 0.50

CaO 1.05 1.00 2.00 1.00

BaO 1.00 1.05 2.50 1.00

TiO₂ 2.30 2.30 2.30 2.50

ZrO₂ 2.00 2.00 1.40 2.00

AS₂O₃ 0.70 0.70 0.80 1.00

P₂O₅/SiO₂ 0.1324 0.1351 0.1509 0.1455

P₂O₅/Al₂O₃ 0.298 0.306 0.3400.333

SiO₂+Al₂O₃+P₂O₅ 87.50 87.50 84.50 87.00

Maximum crystallization temperature (. degree. C.)

780 785 850 800

Average grain diameter (nm)

80 90 110 120

Surface roughness 2.0 2.5 7 6

Average linear thermal expansion coefficient

(10^-7/℃)(0℃-50℃) 0.08 0.04 -0.23 0.25

Δ L/L (highest-lowest) (10)^-7)

(0℃-50℃) 3.8 1.1 10.3 10.1

Comparative example 1 is example 4 of Japanese patent publication JP Hei 3-77137 and US patent US4851372, and comparative example 2 is example 7 of Japanese patent JP 2668057.

To manufacture the glass-ceramics of these examples, raw materials such as oxides, carbonates and nitrates were mixed together, melted at a temperature of about 1450 ℃ C. and 1550 ℃ C, and stirred to make them homogeneous, after which they were shaped into the desired shape and cooled to provide the formed glass. The formed glass is then heat treated at a temperature of 650-750 ℃ for about 1-12 hours to nucleate, and thereafter, at a temperature of 750-785 ℃ for about 1-12 hours to crystallize, thereby providing the desired glass-ceramic. The glass-ceramic is then lapped and polished to a fine finish.

The surface roughness of the glass-ceramic was measured using a NanoScope 3A D3000 atomic force microscope manufactured by Nihon Veeco k.

The average linear thermal expansion coefficient was measured using a Fizeau interferometer-type precision expansion measuring instrument.

The test portion was in the shape of a cylinder having a diameter of 30mm and a length of about 27 mm.

To measure the coefficient of thermal expansion, the test part was placed in an oven capable of controlling the temperature with an optical flat plate (optical flat plate) in contact with the opposite surface of the test part so that interference fringes caused by a HeNe laser could be observed. Then, the temperature of the test portion is changed to observe the change of the interference fringes, thereby measuring the amount of change in the length of the test portion with the change in temperature. In actual measurement, the test portion is measured under the conditions of temperature rise and temperature fall, and then the average value of the amount of change in length of the test portion under these two conditions is used as Δ L.

With respect to calculating the average linear thermal expansion coefficient, the average linear thermal expansion coefficient α (/ deg.c) is calculated using the following formula:

α＝(ΔL/L)/ΔT

where α represents the average linear thermal expansion coefficient, Δ T represents the range of temperatures over which measurements are taken, and L represents the length of the test section.

As shown in tables 1 and 2 and FIGS. 1 to 4, the ultra-low thermal expansion transparent glass-ceramic of the present invention has a crystallization temperature of 785 ℃ or less, a fine crystal grain diameter of 90nm or less, and a surface roughness Ra after polishingOr a lower excellent flat surface. The glass ceramic of the present invention also exhibits an ultra-low thermal expansion property, an average linear thermal expansion coefficient in the range of 0 to 50 ℃ of 0. + -. 0.1 or less, and a difference between the maximum and minimum values of Δ L/L of 7.8X 10^-7Or lower.

The thermal conductivity of the ultra-low thermal expansion transparent glass ceramic is 1.6-1.8W/(m.K), and the Young modulus is 90-93 GPa. Further, with respect to the light transmittance, the wavelength at which 80% of the 5mm thick sample of comparative example 1 transmits is 430nm, that of comparative example 2 is 425nm, and that of the example of the present invention is 395-415nm, indicating excellent light transmittance values.

The glass-ceramics of the present invention are suitable for parts of semiconductor devices such as masks for lithography, optical mirrors, wafer stages and reticle stages, parts for quartz exposure equipment (exposure equipment), parts for large-scale mirrors, and other various precision parts such as parts of standard balance and prototype machines and parts of test instruments. Further, since the glass ceramics of the present invention are high in transparency, they are also suitable for filter substrates, light-transmitting masks for lithography, and the like, which require high light transmittance. For all other purposes, the glass-ceramics of the invention can be used effectively for the manufacture of lightweight articles, owing to their excellent mechanical strength.

Claims (13)

1. Glass-ceramic having an average linear coefficient of thermal expansion of 0.0 + -0.2X 10 in the temperature range from 0 to 50 DEG C^-7/° C, the difference between the maximum and minimum values of Δ L/L is 10 × 10^-7Or less and contains SiO in a total amount of 86.7 to 89.0 mass%₂、Al₂O₃And P₂O₅And further comprises

SiO₂53 to 57% by mass

Li₂O3.5-4.5% by mass

P₂O₅7.0 to 8.5% by mass

Al₂O₃23 to 26% by mass

MgO 0.5-1.5% by mass

0.1 to 1.5 mass% of ZnO

CaO 0.5-1.5 mass%

BaO 0.5-1.5% by mass

TiO₂1.5 to 3.0% by mass

ZrO₂1.0 to 3.0% by mass

As₂O₃0.5 to 1.0 mass% of P wherein₂O₅With SiO₂And P and₂O₅with Al₂O₃The ratio between the mass% of:

P₂O₅/SiO₂0.1230-0.1450 and

P₂O₅/Al₂O₃ 0.270-0.330。

2. the glass-ceramic as defined in claim 1 having an average linear coefficient of thermal expansion of 0.0 ± 0.1 x 10 in the temperature range of 0 to 50 ℃^-7/° C, the difference between the maximum and minimum values of Δ L/L is 8 × 10^-7Or lower.

3. The glass-ceramic as defined in claim 1 or 2, wherein the surface roughness Ra, expressed as arithmetic mean roughness, isOr lower.

4. The glass-ceramic as defined in claim 1 or 2, wherein the average grain diameter of the precipitated phase is 50 to 90 nm.

5. The glass-ceramic as defined in claim 1 or 2, which contains β -quartz and/or β -quartz solid solution as a main crystal phase.

6. The glass-ceramic as defined in claim 1 or 2, which is free of PbO, Na₂O、K₂O and B₂O₃。

7. The glass-ceramic as defined in claim 1 or 2, which contains β -quartz and/or β -quartz solid solution as a main crystal phase, and is obtained by crystallizing a base glass by heat-treating the base glass, said base glass containing:

SiO₂53 to 57% by mass

P₂O₅7.0 to 8.5% by mass

Al₂O₃23 to 26% by mass

Li₂O3.5-4.5% by mass

MgO 0.5-1.5% by mass

0.1 to 1.5 mass% of ZnO

CaO 0.5-1.5 mass%

BaO 0.5-1.5% by mass

TiO₂1.5 to 3.0% by mass

ZrO₂1.0 to 3.0% by mass

As₂O₃0.5 to 1.0 mass%.

8. The glass-ceramic as defined in claim 1 or 2, which contains β -quartz and/or β -quartz solid solution as a main crystal phase, and is obtained by crystallizing a base glass by heat-treating the base glass, said base glass containing:

SiO₂53 to 57% by mass

P₂O₅7.0 to 8.5% by mass

Al₂O₃23 to 26% by mass

Li₂O3.5-4.5% by mass

MgO 0.5-1.5% by mass

0.1 to 1.5 mass% of ZnO

CaO 0.5-1.5 mass%

BaO 0.5-1.5% by mass

TiO₂1.5 to 3.0% by mass

ZrO₂1.0 to 3.0% by mass

As₂O₃0.5 to 1.0% by mass

And substantially free of PbO, Na₂O、K₂O and B₂O₃。

9. The glass-ceramic as defined in claim 1 or 2, wherein the maximum temperature of the heat treatment for crystallization is 750-.

10. A mask for lithography using the glass-ceramic as defined in claim 1 or 2.

11. An optical system mirror for lithography, which uses the glass-ceramic defined in claim 1 or 2.

12. A wafer stage or reticle stage for use in photolithography using the glass-ceramic defined in claim 1 or 2.

13. A part for precision instruments, which uses the glass-ceramic defined in claim 1 or 2.