JP7219538B2 - glass - Google Patents

Description

TECHNICAL FIELD The present invention relates to highly heat-resistant glass, and for example, to a glass substrate for producing semiconductor crystals for LEDs at high temperatures.

It is known that semiconductor crystals used in LEDs and the like have improved semiconductor properties as the film is formed at a higher temperature.

For this application, a highly heat-resistant sapphire substrate is generally used. Sapphire substrates are also used for other applications when semiconductor crystals are deposited at high temperatures (for example, 700° C. or higher).

JP-A-11-243229

By the way, in recent years, techniques for forming large-area semiconductor crystal films have been actively studied. This technology is also considered promising as a surface emitting light source for large displays.

However, the sapphire substrate is difficult to increase in area and is not suitable for the above applications.

If a glass substrate is used instead of a sapphire substrate, it is considered possible to increase the substrate area. However, since the conventional glass substrate has insufficient heat resistance, it is easily deformed by heat treatment at a high temperature.

When the heat resistance of a conventional glass substrate is increased, the thermal expansion coefficient of the glass substrate is unduly lowered, making it difficult to match the thermal expansion coefficient of the semiconductor crystal. Warping is likely to occur, and cracks are likely to occur in the semiconductor film. Further, when the heat resistance of the glass substrate is increased, the resistance to devitrification is lowered, making it difficult to form a flat glass substrate.

The present invention has been made in view of the above circumstances, and its technical object is to create a glass that has high heat resistance and a high coefficient of thermal expansion and that can be formed into a flat plate shape.

As a result of repeating various experiments, the inventor found that the above technical problems can be solved by limiting the glass composition to a predetermined range, and proposes the present invention. That is, the glass of the present invention has, as a glass composition, SiO ₂ 55 to 80%, Al ₂ O ₃ 11 to 30%, B ₂ O ₃ 0 to 3%, Li ₂ O + Na ₂ O + K ₂ O 0 to 3%, MgO+CaO+SrO+BaO 5-35%, and the strain point is higher than 700°C. Here, " _Li2O + _Na2O + _K2O " refers to the total amount of _Li2O , _Na2O and _K2O . "MgO+CaO+SrO+BaO" refers to the total amount of MgO, CaO, SrO and BaO. Here, the "strain point" refers to a value measured according to the ASTM C336 method.

The glass of the present invention contains Al ₂ O ₃ in a glass composition of 11 mol % or more, a B ₂ O ₃ content of 3 mol % or less, and a Li ₂ O + Na ₂ O + K ₂ O content of 3 mol % or less. Regulating. By doing so, the strain point is remarkably raised, and the heat resistance of the glass substrate can be greatly improved.

Further, the glass of the present invention contains 5 to 25 mol % of MgO+CaO+SrO+BaO in the glass composition. By doing so, the devitrification resistance can be enhanced while increasing the coefficient of thermal expansion.

Second, the glass of the present invention preferably has a B ₂ O ₃ content of less than 1 mol %.

Thirdly, it is preferable that the content of Li ₂ O+Na ₂ O+K ₂ O in the glass of the present invention is 0.2 mol % or less.

Fourth, the glass of the present invention preferably has a molar ratio (MgO+CaO+SrO+BaO)/Al ₂ O ₃ of 0.5-5. Here _, "(MgO+CaO+SrO+BaO)/ _Al2O3 " is a value obtained by dividing the total amount of MgO, CaO, SrO and BaO by the content _{of Al2O3} .

Fifth, the glass of the present invention preferably has a molar ratio MgO/(MgO+CaO+SrO+BaO) of less than 0.5. Here, "MgO/(MgO+CaO+SrO+BaO)" is a value obtained by dividing the content of MgO by the total amount of MgO, CaO, SrO and BaO.

Sixthly, the glass of the present invention preferably has a coefficient of thermal expansion of 40×10 ^-7 /°C or more in the temperature range of 30 to 380°C. Here, the “thermal expansion coefficient in the temperature range of 30 to 380° C.” refers to the average value measured with a dilatometer.

Seventh, the glass of the present invention preferably has a strain point of 800° C. or higher.

Eighth, the glass of the present invention preferably has a (temperature at 10 ^2.5 dPa·s−strain point) of 900° C. or less. Here, "temperature at high temperature viscosity of 10 ^2.5 dPa·s" refers to a value measured by a platinum ball pull-up method.

Ninth, the glass of the present invention preferably has a temperature of 1750° C. or lower at a viscosity of 10 ^2.5 dPa·s.

Tenth, the glass of the present invention preferably has a flat plate shape.

Eleventh, the glass of the present invention is preferably used as a substrate for growing semiconductor crystals.

The glass of the present invention has a glass composition of SiO ₂ 55 to 80%, Al ₂ O ₃ 11 to 30%, B ₂ O ₃ 0 to 3%, Li ₂ O + Na ₂ O + K ₂ O 0 to 3% in mol%. , MgO+CaO+SrO+BaO containing 5-35%. The reason why the content of each component is regulated as described above will be explained below. In addition, in description of each component, the following % display points out mol%.

A suitable lower range of _SiO2 is 55% or more, 58% or more, 60% or more, 65% or more, especially 68% or more, and a suitable upper range is preferably 80% or less, 75% or less, 73% or less, 72% or less, 71% or less, particularly 70% or less. If the content of SiO ₂ is too small, defects due to devitrified crystals containing Al ₂ O ₃ are likely to occur, and the strain point tends to be lowered. In addition, the high-temperature viscosity decreases, and the liquidus viscosity tends to decrease. On the other hand, if the _SiO2 content is too high, the coefficient of thermal expansion will unduly decrease, and the high-temperature viscosity will increase, resulting in a decrease in meltability and the formation of devitrified crystals containing _SiO2 . Become.

A preferable lower limit range of Al ₂ O ₃ is 11% or more, 12% or more, 13% or more, 14% or more, particularly 15% or more, and a preferable upper limit range is 30% or less, 25% or less, 20% or less, 18% or less, 17% or less, particularly 16% or less. If the content of Al ₂ O ₃ is too small, the strain point tends to decrease, or the high-temperature viscosity increases, which tends to lower the meltability. On the other hand, if the Al ₂ O ₃ content is too high, devitrified crystals containing Al ₂ O ₃ are likely to occur.

The molar ratio SiO ₂ /Al ₂ O ₃ is preferably 2 to 6, 3 to 5.5, 3.5 to 5.5, 4 to 5 from the viewpoint of achieving both a high strain point and high devitrification resistance. .5, 4.5-5.5, especially 4.5-5. " _SiO2 / _Al2O3 " is _a value obtained by dividing the content of _SiO2 by the content of _{Al2O3 .}

A preferred upper limit of B ₂ O ₃ is 3% or less, 1% or less, less than 1%, especially 0.1% or less. If the B ₂ O ₃ content is too high, the strain point may be significantly lowered.

A preferred upper limit range of Li ₂ O+Na ₂ O+K ₂ O is 3% or less, 1% or less, 1% or less, 0.5% or less, particularly 0.2% or less. If the content of Li ₂ O+Na ₂ O+K ₂ O is too high, the properties of the semiconductor crystal formed on the glass may deteriorate. The preferred upper limits of Li ₂ O, Na ₂ O and K ₂ O are 3% or less, 1% or less, less than 1%, 0.5% or less, 0.3% or less, and particularly 0.2%. It is below.

The preferable lower limit range of MgO+CaO+SrO+BaO is 5% or more, 7% or more, 9% or more, 11% or more, 13% or more, especially 14% or more, and the preferable upper limit range is 35% or less, 30% or less, 25% or less. , 20% or less, 18% or less, 17% or less, in particular 16% or less. If the content of MgO+CaO+SrO+BaO is too small, the liquidus temperature rises significantly, making it easier for devitrified crystals to form in the glass, or increasing the high-temperature viscosity, which tends to lower the meltability. On the other hand, if the content of MgO+CaO+SrO+BaO is too high, the strain point tends to decrease, and devitrified crystals containing alkaline earth elements tend to form.

The preferable lower limit range of MgO is 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, particularly 5% or more, and the preferable upper limit range is 15% or less, 10% or less, 8% or less. , in particular below 7%. If the content of MgO is too small, the meltability tends to decrease, and the devitrification of crystals containing alkaline earth elements tends to increase. On the other hand, if the content of MgO is too high, precipitation of devitrified crystals containing Al ₂ O ₃ is promoted, resulting in a decrease in liquidus viscosity and a significant decrease in strain point. MgO has the effect of increasing the coefficient of thermal expansion, but the effect is the smallest among alkaline earth oxides.

A preferable lower limit range of CaO is 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, particularly 7% or more, and a preferable upper limit range is 20% or less, 15% or less, 12% or less. , 11% or less, 10% or less, in particular 9% or less. If the content of CaO is too small, the meltability tends to deteriorate. On the other hand, if the content of CaO is too high, the liquidus temperature rises and devitrification crystals are likely to occur in the glass. In addition, CaO has a large effect of improving the liquidus viscosity and improving the meltability without lowering the strain point compared to other alkaline earth oxides, and also increases the thermal expansion coefficient more than MgO. Great effect.

The preferred lower limit range of SrO is 0% or more, 1% or more, especially 2% or more, and the preferred upper limit range is 10% or less, 8% or less, 7% or less, 6% or less, 5% or less, especially 4%. It is below. If the content of SrO is too small, the strain point tends to be lowered. On the other hand, when the content of SrO is too high, the liquidus temperature rises, devitrification crystals tend to form in the glass, and the meltability tends to decrease. Furthermore, when the content of SrO increases in coexistence with CaO, the resistance to devitrification tends to decrease. SrO has a greater effect of increasing the coefficient of thermal expansion than MgO and CaO.

A preferable lower limit range of BaO is 0% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, particularly 8% or more, and a preferable upper limit range is 15% or less and 12% or less. , 11% or less, in particular 10% or less. If the BaO content is too low, the strain point and thermal expansion coefficient tend to decrease. On the other hand, if the content of BaO is too high, the liquidus temperature rises and devitrification crystals are likely to occur in the glass. In addition, meltability tends to decrease. BaO has the greatest effect of increasing the coefficient of thermal expansion and the strain point among the alkaline earth metal oxides.

From the viewpoint of increasing devitrification resistance, the lower limit range of the molar ratio MgO/CaO is preferably 0.1 or more, 0.2 or more, 0.3 or more, and particularly 0.4 or more, and the upper limit range is preferably 2 or less, 1 or less, 0.8 or less, 0.7 or less, particularly 0.6 or less. In addition, "MgO/CaO" refers to the value obtained by dividing the content of MgO by the content of CaO.

From the viewpoint of increasing devitrification resistance, the lower limit range of the molar ratio BaO/CaO is preferably 0.2 or more, 0.5 or more, 0.6 or more, 0.7 or more, particularly 0.8 or more, and the upper limit The range is preferably 5 or less, 4.5 or less, 3 or less, 2.5 or less, especially 2 or less. In addition, "BaO/CaO" refers to the value obtained by dividing the content of BaO by the content of CaO.

Considering the balance between strain point and meltability, the lower limit of the molar ratio (MgO+CaO+SrO+BaO)/Al ₂ O ₃ is preferably 0.5 or more, 0.6 or more, 0.7 or more, and particularly 0.8 or more. , the upper limit range is preferably 5.0 or less, 4.0 or less, 3.0 or less, 2.0 or less, 1.5 or less, 1.2 or less, particularly 1.1 or less.

The molar ratio MgO/(MgO+CaO+SrO+BaO) is preferably 0.6 or less, less than 0.5, 0.4 or less, 0.3 or less, 0.2 or less, especially 0.1 or less. MgO is a component that significantly lowers the strain point, and in a region where the MgO content is low, the effect of lowering the strain point is remarkable. Therefore, it is preferable that the content of MgO in the alkaline earth metal oxide is small.

7×[MgO]+5×[CaO]+4×[SrO]+4×[BaO] is preferably 100% or less, 90% or less, 80% or less, 70% or less, 65% or less, especially 60% or less . All of the alkaline earth metal elements have the effect of lowering the strain point, but the smaller the ionic radius of the element, the greater the effect. Therefore, if the upper limit range of 7 × [MgO] + 5 × [CaO] + 4 × [SrO] + 4 × [BaO] is regulated so that the proportion of alkaline earth elements with small ionic radii does not increase, the strain point is preferentially can be increased to [MgO] indicates the content of MgO, [CaO] indicates the content of CaO, [SrO] indicates the content of SrO, and [BaO] indicates the content of BaO. And "7 × [MgO] + 5 × [CaO] + 4 × [SrO] + 4 × [BaO]" is 7 times [MgO], 5 times [CaO], 4 times [SrO] and 4 times It refers to the total amount of [BaO].

21 × [MgO] + 20 × [CaO] + 15 × [SrO] + 12 × [BaO] is preferably 200% or more, 210% or more, 220% or more, 230% or more, 240% or more, 250% or more, especially 300% ~1000%. All of the alkaline earth metal elements have the effect of increasing the meltability, but the effect is greater for elements with smaller ionic radii. Therefore, if the lower limit range of 21 × [MgO] + 20 × [CaO] + 15 × [SrO] + 12 × [BaO] is regulated so that the proportion of alkaline earth elements with small ionic radii is large, the meltability is prioritized. can be increased to However, if 21*[MgO]+20*[CaO]+15*[SrO]+12*[BaO] is too large, the strain point may be lowered. Incidentally, "21 × [MgO] + 20 × [CaO] + 15 × [SrO] + 12 × [BaO]" is 21 times [MgO], 20 times [CaO], 15 times [SrO] and 12 times It refers to the total amount of [BaO].

In addition to the above components, the following components may be introduced into the glass composition.

ZnO is a component that enhances meltability, but if it is contained in a large amount in the glass composition, the glass tends to devitrify and the strain point tends to decrease. The content of ZnO is therefore preferably 0-5%, 0-3%, 0-0.5%, 0-0.3%, especially 0-0.1%.

_ZrO2 is a component that increases Young's modulus. The content of ZrO ₂ is preferably 0-5%, 0-3%, 0-0.5%, 0-0.2%, especially 0-0.02%. If the content of ZrO ₂ is too high, the liquidus temperature rises and devitrification crystals of zircon tend to precipitate.

TiO ₂ is a component that lowers high-temperature viscosity and enhances meltability, and is a component that suppresses solarization. Thus, the content of TiO ₂ is preferably 0-5%, 0-3%, 0-1%, 0-0.1%, especially 0-0.02%.

P ₂ O ₅ is a component that enhances resistance to devitrification, but if it is contained in a large amount in the glass composition, the glass tends to undergo phase separation and become milky, and there is a risk of a significant drop in water resistance. Therefore, the content of P ₂ O ₅ is preferably 0-5%, 0-4%, 0-3%, 0-2%, 0-1%, 0-0.5%, especially 0-0 .1%.

SnO ₂ is a component that has a good clarification action in a high temperature range and also a component that lowers the high temperature viscosity. The SnO ₂ content is preferably 0-1%, 0.01-0.5%, 0.01-0.3%, in particular 0.04-0.1%. When the SnO ₂ content is too high, devitrified crystals of SnO ₂ tend to precipitate.

As described above, _the glass of the present _invention preferably contains SnO ₂ as a fining agent. etc.) may be added up to 1%.

As ₂ O ₃ , Sb ₂ O ₃ , F, and Cl also act effectively as refining agents, and the glass of the present invention does not exclude the inclusion of these components, but from an environmental point of view, these components are Each content is preferably less than 0.1%, particularly less than 0.05%.

If the SnO ₂ content is 0.01 to 0.5% and the Rh ₂ O ₃ content is too high, the glass tends to be colored. Note that Rh ₂ O ₃ may be mixed from the platinum production vessel. The content of Rh ₂ O ₃ is preferably 0-0.0005%, more preferably 0.00001-0.0001%.

_SO3 is a component that is mixed from raw materials as an impurity. If the _SO3 content is too high, bubbles called reboiling may be generated during melting or molding, which may cause defects in the glass. be. A preferred lower range of _SO3 is 0.0001% or more, and a preferred upper range is 0.005% or less, 0.003% or less, 0.002% or less, especially 0.001% or less.

The content of rare earth oxides (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc.) content is preferably less than 2% , 1% or less, less than 0.5%, in particular less than 0.1%. In particular, the content of La ₂ O ₃ +Y ₂ O ₃ is preferably less than 2%, less than 1%, less than 0.5%, especially less than 0.1%. The content of La ₂ O ₃ is preferably less than 2%, less than 1%, less than 0.5%, especially less than 0.1%. If the rare earth oxide content is too high, batch costs tend to increase. _In addition, " _{Y2O3 + La2O3} " is the total amount _{of Y2O3} and _{La2O3 .}

The glass of the present invention preferably has the following properties.

The density is preferably 3.20 g/cm ³ or less, 3.00 g/cm ³ or less, 2.90 g/cm ³ or less, especially 2.80 g/cm ³ or less. If the density is too high, it will be difficult to achieve weight reduction of the electronic device.

The thermal expansion coefficient in the temperature range of 30 to 380° C. is preferably 40×10 ⁻⁷ /° C. or higher, 42×10 ⁻⁷ /° C. or higher, 44×10 ⁻⁷ /° C. or higher, 46×10 ⁻⁷ /° C. or higher. , particularly preferably 48×10 ⁻⁷ to 80×10 ⁻⁷ /°C. If the thermal expansion coefficient in the temperature range of 30 to 380° C. is too low, the thermal expansion coefficients of the semiconductor crystal (for example, nitride semiconductor crystal) and the glass substrate do not match, and the glass substrate tends to warp or the semiconductor crystal cracks. easily occur.

The strain point is preferably above 700.degree. If the strain point is too low, the heat treatment temperature cannot be increased, making it difficult to improve the semiconductor properties of the semiconductor crystal.

The SiO ₂ —Al ₂ O ₃ —RO (RO indicates alkaline earth metal oxide) glass according to the present invention is generally difficult to melt. For this reason, the improvement of meltability becomes a subject. If the meltability is enhanced, the defect rate due to bubbles, foreign matter, etc. is reduced, so that a large amount of high-quality glass substrates can be supplied at low cost. On the other hand, if the high-temperature viscosity is too high, it becomes difficult to promote defoaming in the melting process. Therefore, the temperature at a high temperature viscosity of 10 ^2.5 dPa·s is preferably 1750° C. or less, 1700° C. or less, 1680° C. or less, 1670° C. or less, 1650° C. or less, particularly 1630° C. or less. The temperature at a high-temperature viscosity of 10 ^2.5 dPa·s corresponds to the melting temperature, and the lower the temperature, the better the meltability.

(Temperature at 10 ^2.5 dPa·s−Strain point) is preferably 900° C. or less, 850° C. or less, particularly 800° C. or less from the viewpoint of achieving both a high strain point and a low melting temperature.

Devitrification resistance is important when molding into a flat plate shape. Considering the forming temperature of the SiO ₂ —Al ₂ O ₃ —RO glass according to the present invention, the liquidus temperature is preferably 1450° C. or lower, 1400° C. or lower, particularly 1300° C. or lower. Further, the liquidus viscosity is preferably 10 ^3.0 dPa·s or more, 10 ^3.5 dPa·s or more, particularly 10 ^4.0 dPa·s or more. The "liquidus temperature" is measured by passing through a 30-mesh (500 µm) standard sieve, placing the glass powder remaining on the 50-mesh (300 µm) in a platinum boat, holding it in a temperature gradient furnace for 24 hours, and precipitating crystals. Refers to the measured value of temperature. "Liquidus viscosity" refers to a value obtained by measuring the viscosity of a glass at the liquidus temperature by a platinum ball pull-up method.

The glass of the present invention can be molded by various molding methods. For example, a glass substrate can be formed by an overflow down-draw method, a slot down-draw method, a redraw method, a float method, a roll-out method, or the like. If the glass substrate is formed by the overflow down-draw method, it becomes easier to produce a glass substrate with high surface smoothness.

When the glass of the present invention has a flat plate shape, the plate thickness is preferably 1.0 mm or less, 0.7 mm or less, 0.5 mm or less, and particularly 0.4 mm or less. The smaller the plate thickness, the easier it is to reduce the weight of the electronic device. On the other hand, the thinner the plate thickness, the more easily the glass substrate bends. However, since the glass of the present invention has a high Young's modulus and a high specific Young's modulus, problems due to bending hardly occur. The plate thickness can be adjusted by adjusting the flow rate during molding, the plate drawing speed, and the like.

In the glass of the present invention, the strain point can be increased by decreasing the β-OH value. The β-OH value is preferably 0.45/mm or less, 0.40/mm or less, 0.35/mm or less, 0.30/mm or less, 0.25/mm or less, 0.20/mm or less, In particular, it is 0.15/mm or less. If the β-OH value is too large, the strain point tends to decrease. In addition, if the β-OH value is too small, the meltability tends to decrease. The β-OH value is therefore preferably greater than or equal to 0.01/mm, in particular greater than or equal to 0.05/mm.

Methods for lowering the β-OH value include the following methods. (1) Select raw materials with low water content. (2) adding components (Cl, _SO3, etc.) that reduce the water content in the glass; (3) Reduce the moisture content in the furnace atmosphere. (4) _N2 bubbling in the molten glass; (5) Use a small melting furnace. (6) Increase the flow rate of molten glass. (7) Adopt an electric melting method.

Here, the "β-OH value" refers to the value obtained by measuring the transmittance of the glass using FT-IR and using the following formula.
β-OH value = (1/X) log (T ₁ /T ₂ )
X: Glass thickness (mm)
T ₁ : Transmittance (%) at reference wavelength 3846 cm ⁻¹
T ₂ : Minimum transmittance (%) near hydroxyl group absorption wavelength 3600 cm ⁻¹

The present invention will be described in detail below based on examples. It should be noted that the following examples are merely illustrative. The present invention is by no means limited to the following examples.

Tables 1-4 show examples of the invention (Sample Nos. 1-63).

Each sample was prepared as follows. First, a glass batch prepared by mixing glass raw materials so as to have the glass composition shown in the table was placed in a platinum crucible and melted at 1600 to 1750° C. for 24 hours. When the glass batch was melted, it was homogenized by stirring using a platinum stirrer. Then, the molten glass was poured onto a carbon plate and formed into a flat plate. For each sample obtained, the density ρ, the coefficient of thermal expansion α, the strain point Ps, the annealing point Ta, the softening point Ts, the temperature at a high temperature viscosity of 10 ^4.0 dPa s, the temperature at a high temperature viscosity of 10 ^3.0 dPa s Temperature, temperature at high temperature viscosity of 10 ^2.5 dPa·s, liquidus temperature TL, and liquidus viscosity logηTL were evaluated.

The density ρ is a value measured by the well-known Archimedes method.

The coefficient of thermal expansion α is an average value measured with a dilatometer in a temperature range of 30 to 380°C.

The strain point Ps, annealing point Ta, and softening point Ts are values measured according to ASTM C336 or ASTM C338.

The temperature at a high-temperature viscosity of 10 ^4.0 dPa·s, the temperature at a high-temperature viscosity of 10 ^3.0 dPa·s, and the temperature at a high-temperature viscosity of 10 ^2.5 dPa·s are values measured by a platinum ball pull-up method.

The liquidus temperature TL was determined by pulverizing each sample, passing through a 30-mesh (500 μm) standard sieve, placing the glass powder remaining on the 50-mesh (300 μm) in a platinum boat, and holding it in a temperature gradient furnace for 24 hours. This is the temperature at which devitrification (devitrification crystals) was observed in the glass when the platinum boat was taken out. The liquidus viscosity logηTL is a value obtained by measuring the viscosity of the glass at the liquidus temperature TL by the platinum ball pull-up method.

The β-OH value is a value calculated by the above formula.

As is clear from Tables 1 to 4, sample no. Nos. 1 to 63 have high strain points and high thermal expansion coefficients, and are resistant to devitrification so that they can be molded into flat plates. Therefore, sample no. 1 to 63 are considered suitable as substrates for crystal growth of semiconductor crystals (eg, nitride semiconductor crystals, particularly gallium nitride semiconductor crystals) at high temperatures.

The glass of the present invention has a high strain point and a high coefficient of thermal expansion, and has good devitrification resistance. Therefore, the glass of the present invention is suitable for display substrates such as OLED displays and liquid crystal displays, in addition to substrates for producing semiconductor crystals at high temperatures, and is particularly suitable for display substrates driven by LTPS and oxide TFTs. It is suitable as

Claims (11)

Glass composition, in mol %, SiO ₂ 55-80%, Al 2 O ₃ 13-30%, B ₂ O ₃ 0-1%, Li ₂ O + Na ₂ O + K ₂ O 0-3 _% , MgO + CaO + SrO + BaO 5-35% , SnO ₂ 0.01-1%, MgO 0-15%, CaO 0-15%, SrO 0-10%, BaO 2.5-15%, Y ₂ O ₃ +La ₂ O ₃ less than 0.5% containing, the molar ratio (MgO + CaO + SrO + BaO) / Al ₂ O ₃ is 1.33 or less, the molar ratio SiO ₂ /Al ₂ O ₃ is 3.99375 to 6, the liquidus viscosity is 10 ^3.0 dPa s or more, A glass having a thermal expansion coefficient of 40×10 ^-7 /°C or higher in a temperature range of 30 to 380°C and a strain point higher than 700°C. _2. A glass according to claim 1, characterized in that the content of _B2O3 is less than 1 mol %. 3. The glass according to claim 1, wherein the content of _Li2O + _Na2O + _K2O is 0.2 mol % or less. 4. The glass according to claim 1, wherein the molar ratio (MgO+CaO+SrO+BaO)/Al ₂ O ₃ is 0.5-1.33. The glass according to any one of claims 1 to 4, characterized in that the molar ratio MgO/(MgO + CaO + SrO + BaO) is less than 0.5. 6. The glass according to claim 1, wherein the content of Al ₂ O ₃ is 14 mol % or more. The glass according to any one of claims 1 to 6, which has a strain point of 800°C or higher. The glass according to any one of claims 1 to 7, wherein (temperature at 10 ^2.5 dPa·s - strain point) is 900°C or less. The glass according to any one of claims 1 to 8, wherein the temperature at a viscosity of 10 ^2.5 dPa·s is 1750°C or less. The glass according to any one of claims 1 to 9, which has a flat plate shape. 11. The glass according to any one of claims 1 to 10, which is used as a substrate for producing a semiconductor crystal.