Patent Grant
10759691
The present invention relates to a glass substrate, a laminated substrate, and a method for producing a glass substrate.
As for image sensors, such as a chip size package (CSP), etc., a mode of protection by sticking a glass substrate onto a silicon substrate is known, and a glass for silicon pedestal in which an elongation percentage by thermal expansion is made close to an elongation percentage by thermal expansion of a silicon substrate to be bonded to a glass is proposed (see, for example, Patent Document 1).
In addition, in the semiconductor assembly process so far, a series of assembly processes in which after cutting a silicon substrate and a glass substrate in a wafer state, respectively, the silicon substrate and the glass substrate are stuck to each other, followed by die bonding, wire bonding, molding, and so on, are performed. In recent years, the wafer-level package technology in which a silicon substrate and a glass substrate in a full-scale wafer state are stuck to each other and subjected to an assembly process, followed by cutting is in the limelight as a next-generation CSP technology.
In order to stick the silicon substrate and the glass substrate to each other, a heat treatment step is required. In the heat treatment step, for example, a laminated substrate obtained by sticking the silicon substrate and the glass substrate to each other at a temperature of 200° C. to 400° C. is subjected to temperature decrease to room temperature. At this time, if there is a difference in thermal expansion coefficient between the silicone substrate and the glass substrate, a large residual strain (residual deformation) is caused in the silicon substrate due to the difference in thermal expansion coefficient.
In the wafer-level package technology, since the silicon substrate and the glass substrate are stuck to each other in the wafer state, even as for the difference in thermal expansion coefficient, which has not been problematic so far, the residual strain is liable to be caused in the silicon substrate. In addition, in the heat treatment step, it is required that an alkali ion is not diffused from the glass substrate into the silicon substrate.
Patent Document 1: Japanese Patent No. 3153710
Patent Document 1 proposes a glass for silicon pedestal which is characterized in that a ratio α1/α2 of an elongation percentage α1 by thermal expansion of a glass to an elongation percentage α2 by thermal expansion of a silicon substrate to be bonded to the glass is a value ranging from 0.8 to 1.2. However, regarding the glasses of the working examples disclosed in Patent Document 1, the coincidence of thermal expansion coefficient with the silicon substrate is insufficient, so that in the wafer-level package technology, a residual strain is liable to be generated in the silicone substrate.
Then, the present invention provides a glass substrate and a method for producing a glass substrate, in which in a heat treatment step of sticking a silicon substrate and a glass substrate to each other, an alkali ion is hardly diffused into the silicon substrate, and a residual strain generated in the silicon substrate is small. Or, the present invention provides a laminated substrate using the foregoing glass substrate.
A glass substrate of the present invention has:
an average thermal expansion coefficient α50/100 at 50° C. to 100° C. of 2.70 ppm/° C. to 3.20 ppm/° C.;
an average thermal expansion coefficient α200/300 at 200° C. to 300° C. of 3.45 ppm/° C. to 3.95 ppm/° C.;
a value α200/300/α50/100 obtained by dividing the average thermal expansion coefficient α200/300 at 200° C. to 300° C. by the average thermal expansion coefficient α50/100 at 50° C. to 100° C. of 1.20 to 1.30; and
a content of an alkali metal oxide being 0% to 0.1% as expressed in terms of a molar percentage based on oxides.
A laminated substrate of the present invention includes: the above-described glass substrate; and a silicon substrate laminated on the glass substrate.
Additionally, a laminated substrate of the present invention includes: a glass substrate; and a silicon substrate laminated on the glass substrate,
a difference Δα50/100 (=α50/100−αSi50/100) between an average thermal expansion coefficient α50/100 at 50° C. to 100° C. of the glass substrate and an average thermal expansion coefficient αSi50/100 at 50° C. to 100° C. of the silicon substrate is −0.25 ppm/° C. to 0.25 ppm/° C.,
a difference Δα200/300 (=α200/300−αSi200/300) between an average thermal expansion coefficient α200/300 at 200° C. to 300° C. of the glass substrate and an average thermal expansion coefficient αSi200/300 at 200° C. to 300° C. of the silicon substrate is −0.25 ppm/° C. to 0.25 ppm/° C.,
(Δα200/300−Δα50/100) is −0.16 ppm/° C. to 0.16 ppm/° C., and
a content of an alkali metal oxide in the glass substrate is 0% to 0.1% as expressed in terms of a molar percentage based on oxides.
A method for producing a glass substrate of the present invention is a method including:
a melting step of heating glass raw materials to obtain a molten glass;
a refining step of removing bubbles from the molten glass;
a forming step of forming the molten glass into a sheet-like shape to obtain a glass ribbon; and
a cooling step of gradually cooling the glass ribbon to a room temperature state,
in which the resulting glass substrate has a composition including, as expressed in terms of a molar percentage based on oxides:
SiO2: 50% to 75%;
Al2O3: 6% to 16%;
B2O3: 0% to 15%;
MgO: 0% to 15%;
CaO: 0% to 13%;
SrO: 0% to 11%; and
BaO: 0% to 9.5%,
a content of an alkali metal oxide is 0% to 0.1% as expressed in terms of a molar percentage based on oxides, and
the composition of the resulting glass substrate and an average cooling rate R (unit: ° C./min) from a temperature at which a viscosity of the glass ribbon in the cooling step is 1013 dPa·sec to a temperature at which the viscosity thereof is 1014.5 dPa·sec satisfy the following condition (1), condition (2), condition (3), and condition (4):
{0.0177×(content of SiO2)−0.0173×(content of Al2O3)+0.0377×(content of B2O3)+0.0771×(content of MgO)+0.1543×(content of CaO)+0.1808×(content of SrO)+0.2082×(content of BaO)+0.0344×log10 R} is 2.70 to 3.20; Condition (1):
{0.0181×(content of SiO2)+0.0004×(content of Al2O3)+0.0387×(content of B2O3)+0.0913×(content of MgO)+0.1621×(content of CaO)+0.1900×(content of SrO)+0.2180×(content of BaO)+0.0391×log10 R} is 3.13 to 3.63; Condition (2):
{0.0177×(content of SiO2)+0.0195×(content of Al2O3)+0.0323×(content of B2O3)+0.1015×(content of MgO)+0.1686×(content of CaO)+0.1990×(content of SrO)+0.2179×(content of BaO)+0.0312×log10 R} is 3.45 to 3.95; and Condition (3):
0.0111×(content of SiO2)+0.0250×(content of Al2O3)+0.0078×(content of B2O3)+0.0144×(content of MgO)+0.0053×(content of CaO)+0.0052×(content of SrO)+0.0013×(content of BaO)−0.0041×log10 R} is 1.20 to 1.30, Condition (4):
in which the content of SiO2, the content of Al2O3, the content of B2O3, the content of MgO, the content of CaO, the content of SrO, and the content of BaO are respectively a content of each of the components contained in the resulting glass as expressed in terms of a molar percentage based on oxides.
In the present specification, the content of each of the components in the glass substrate and in the method for producing the same is expressed in terms of a molar percentage based on oxides unless otherwise indicated.
The present invention is able to provide a glass substrate and a method for producing a glass substrate, in which in a heat treatment step of sticking a silicon substrate and a glass substrate to each other, an alkali ion is hardly diffused into the silicon substrate, and a residual strain generated in the silicon substrate is small. Or, the present invention is able to provide a laminated substrate using the foregoing glass substrate.
An embodiment of the present invention is hereunder described.
The glass substrate according to an embodiment of the present invention is small in a difference in thermal expansion coefficient from the silicon substrate, and therefore, in the heat treatment step of sticking to the silicon substrate or the sequent heat treatment, the generation of a residual strain to be caused due to the difference in thermal expansion coefficient can be suppressed. For that reason, the glass substrate according to an embodiment of the present invention is suitable as a glass substrate for image sensors, such as MEMS, CMOS, CTS, etc., for which miniaturization of element due to the wafer-level package is effective.
In addition, the glass substrate according to an embodiment of the present invention is suitable as a cover glass for display devices for projection application, for example, a cover glass of LCOS (liquid crystal on silicon). For example, in the LCOS or image sensors, after forming an electronic circuit on a silicon substrate, the cover glass is adhered to the silicon substrate with a resin or a glass frit as an adhesive material. When the silicon substrate and the cover glass are coincident with or extremely close to each other in terms of a thermal expansion coefficient, a stress generated on the adhesive interface when the temperature varies at the time of device production or use is reduced. Thereby, a reduction of color unevenness to be caused due to photoelastic deformation, or an improvement of long-term reliability can be expected.
Furthermore, the glass substrate according to an embodiment of the present invention is suitable as a bored substrate of glass interposer (GIP) or a support glass for semiconductor backgrind. The glass substrate according to an embodiment of the present invention can be suitably used for any application for glass substrate to be used through sticking to a silicon substrate.
In the glass substrate according to an embodiment of the present invention, an average thermal expansion coefficient α50/100 at 50° C. to 100° C. is 2.70 ppm/° C. to 3.20 ppm/° C. α50/100 is preferably 2.80 ppm/° C. or more, more preferably 2.90 ppm/° C. or more, still more preferably 2.91 ppm/° C. or more, and especially preferably 2.92 ppm/° C. or more. In addition, α50/100 is preferably 3.10 ppm/° C. or less, more preferably 3.00 ppm/° C. or less, still more preferably 2.96 ppm/° C. or less, and especially preferably 2.94 ppm/° C. or less.
When α50/100 falls within the above-described range, since the difference in thermal expansion coefficient from the silicon substrate is small, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the residual strain generated in the silicon substrate can be made small while securing a process margin.
The “average thermal expansion coefficient α50/100 at 50° C. to 100° C.” as referred to herein is an average thermal expansion coefficient as measured by the method prescribed in JIS R3102 (1995), in which a temperature range of measuring the thermal expansion coefficient is 50° C. to 100° C.
The terms “A to B” expressing the above-described numerical value range are used in order to mean that the numerical values described before and after that are included as a lower limit value and an upper limit value, and in the following present specification, the terms “A to B” are used as the same meanings unless otherwise indicated.
In the glass substrate according to an embodiment of the present invention, an average thermal expansion coefficient α200/300 at 200° C. to 300° C. is 3.45 ppm/° C. to 3.95 ppm/° C. α200/300 is preferably 3.55 ppm/° C. or more, more preferably 3.65 ppm/° C. or more, especially preferably 3.66 ppm/° C. or more, and most preferably 3.68 ppm/° C. or more. In addition, α200/300 is preferably 3.85 ppm/° C. or less, more preferably 3.75 ppm/° C. or less, especially preferably 3.73 ppm/° C. or less, and most preferably 3.71 ppm/° C. or less.
When α200/300 falls within the above-described range, since the difference in thermal expansion coefficient from the silicon substrate is small, failures, such as generation of a residual strain to be caused due to the difference in thermal expansion coefficient from the silicon substrate, etc., can be meaningfully suppressed while securing a process margin on the occasion of sticking the glass substrate according to an embodiment of the present invention to the silicon substrate.
In addition, when α200/300 is 3.55 ppm/° C. to 3.85 ppm/° C., since the difference in thermal expansion coefficient from the silicon substrate is sufficiently small, the failures to be caused due to the difference in thermal expansion coefficient can be more suppressed.
The “average thermal expansion coefficient α200/300 at 200° C. to 300° C.” as referred to herein is an average thermal expansion coefficient as measured by the method prescribed in JIS R3102 (1995), in which a temperature range of measuring the thermal expansion coefficient is 200° C. to 300° C.
In the glass substrate according to an embodiment of the present invention, a value α200/300/α50/100 that is a value obtained by dividing the average thermal expansion coefficient α200/300 at 200° C. to 300° C. by the average thermal expansion coefficient α50/100 at 50° C. to 100° C. is 1.20 to 1.30. When α200/300/α50/100 is 1.20 to 1.30, since the difference in thermal expansion coefficient from the silicon substrate is small, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the residual strain generated in the silicon substrate is small. α200/300/α50/100 is preferably 1.24 to 1.27.
In the glass substrate according to an embodiment of the present invention, the content of an alkali metal oxide is 0% to 0.1%. Here, the alkali metal oxide refers to Li2O, Na2O, K2O, and the like. When the content of the alkali metal oxide is 0.1% or less, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the alkali ion is hardly diffused into the silicon substrate. The content of the alkali metal oxide is more preferably 0.05% or less, and still more preferably 0.02% or less, and it is especially preferred that the alkali metal oxide is not substantially contained. Here, it is meant by the terms “the alkali metal oxide is not substantially contained” that the alkali metal oxide is not contained at all, or the alkali metal oxide may be contained as an impurity which is unavoidably included on the production.
It is preferred that the glass substrate according to an embodiment of the present invention has a composition including:
SiO2: 50% to 75%;
Al2O3: 6% to 16%;
B2O3: 0% to 15%;
MgO: 0% to 15%;
CaO: 0% to 13%;
SrO: 0% to 11%; and
BaO: 0% to 9.5%.
SiO2 is a component of forming a structure of glass. When the content of SiO2 is 50% or more, heat resistance, chemical durability, and weather resistance become satisfactory. When the content of SiO2 is 75% or less, meltability becomes satisfactory while viscosity at the time of glass melting does not become excessively high. The content of SiO2 is preferably 60% or more, and more preferably 64% or more. In addition, the content of SiO2 is preferably 70% or less, and more preferably 68% or less.
When the content of Al2O3 is 6% or more, weather resistance, heat resistance, and chemical durability become satisfactory, and a Young's modulus becomes high. When the content of Al2O3 is 16% or less, meltability becomes satisfactory while viscosity at the time of glass melting does not become excessively high, and devitrification hardly takes place. The content of Al2O3 is preferably 8% or more, and more preferably 11% or more. In addition, the content of Al2O3 is preferably 14% or less.
Although B2O3 is not an essential component, when B2O3 is contained, meltability becomes satisfactory while viscosity at the time of glass melting does not become excessively high, and devitrification hardly takes place. When the content of B2O3 is 15% or less, a glass transition temperature can be made high, and a Young's modulus becomes high. The content of B2O3 is more preferably 3% or more. In addition, the content of B2O3 is preferably 12% or less, and more preferably 6% or less.
Although MgO is not an essential component, when MgO is contained, meltability becomes satisfactory while viscosity at the time of glass melting does not become excessively high, weather resistance is improved, and a Young's modulus becomes high. When the content of MgO is 15% or less, devitrification hardly takes place. The content of MgO is preferably 4% or more, and more preferably 6% or more. In addition, the content of MgO is preferably 10% or less, more preferably 9.5% or less, and still more preferably 9% or less.
Although CaO is not an essential component, when CaO is contained, meltability becomes satisfactory while viscosity at the time of glass melting does not become excessively high, and weather resistance is improved. When the content of CaO is 13% or less, devitrification hardly takes place. The content of CaO is preferably 4% or more. In addition, the content of CaO is preferably 10% or less, and more preferably 8% or less.
Although SrO is not an essential component, when SrO is contained, meltability becomes satisfactory while viscosity at the time of glass melting does not become excessively high, and weather resistance is improved. When the content of SrO is 11% or less, devitrification hardly takes place. The content of SrO is preferably 0.5% or more. In addition, the content of SrO is preferably 8% or less, and more preferably 3% or less.
Although BaO is not an essential component, when BaO is contained, meltability becomes satisfactory while viscosity at the time of glass melting does not become excessively high, and weather resistance is improved. When the content of BaO is 9.5% or less, devitrification hardly takes place. The content of BaO is preferably 3% or less, and more preferably 2% or less.
In the glass substrate according to an embodiment of the present invention, a total content of CaO, SrO, and BaO is preferably 7% or more. When the total content of CaO, SrO, and BaO is 7% or more, devitrification hardly takes place. The total content of CaO, SrO, and BaO is more preferably 7.5% or more, and still more preferably 8.0% or more.
In the glass substrate according to an embodiment of the present invention, it is preferable to satisfy a relation of {(content of Al2O3)≥(content of MgO)}. When the relation of {(content of Al2O3)≥(content of MgO)} is satisfied, it is easy to make the average thermal expansion coefficient of the glass substrate to conform to the average thermal expansion coefficient of the silicon substrate, and in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the residual strain generated in the silicon substrate is small.
In the glass substrate according to an embodiment of the present invention, a devitrification viscosity (ηTL) is preferably 103.8 dPa·sec or more. When the devitrification viscosity is 103.8 dPa·sec or more, forming can be stably performed. The devitrification viscosity is more preferably 104.0 dPa·sec or more, and still more preferably 104.2 dPa·sec or more.
In the glass substrate according to an embodiment of the present invention, when used as a cover glass of CMOS sensor, in order to make it harder to absorb a visible light, the content of Fe2O3 is preferably 200 ppm or less as expressed in terms of parts per million mass based on oxides. The content of Fe2O3 is more preferably 150 ppm or less, still more preferably 100 ppm or less, and especially preferably 50 ppm or less.
In the glass substrate according to an embodiment of the present invention, in order to make a thermal conductivity high and to make the meltability satisfactory, it is preferred to contain Fe2O3 in an amount of more than 200 ppm and 1,000 ppm or less as expressed in terms of parts per million mass based on oxides. When the content of Fe2O3 is more than 200 ppm, it is possible to make the thermal conductivity of the glass substrate high and to make the meltability satisfactory. When the content of Fe2O3 is 1,000 ppm or less, absorption of a visible light does not become excessively strong.
The content of Fe2O3 is more preferably 300 ppm or more, still more preferably 400 ppm or more, and especially preferably 500 ppm or more. The content of Fe2O3 is more preferably 800 ppm or less, still more preferably 700 ppm or less, and especially preferably 600 ppm or less.
In the glass substrate according to an embodiment of the present invention, for example, SnO2, SO3, Cl, F, or the like may be contained as a refining agent.
In the glass substrate according to an embodiment of the present invention, in order to improve weather resistance, solubility, devitrification properties, ultraviolet shielding, infrared shielding, ultraviolet transmission, infrared transmission, and so on, for example, ZnO, Li2O, WO3, Nb2O5, V2O5, Bi2O3, MoO3, P2O5, Ga2O3, I2O5, In2O5, Ge2O5, and the like may be contained.
In the glass substrate according to an embodiment of the present invention, in order to improve the chemical durability of glass, ZrO2, Y2O3, La2O3, TiO2, and SnO2 may be contained in an amount of 2% or less, preferably 1% or less, and more preferably 0.5% or less in total in the glass. Among those, Y2O3, La2O3, and TiO2 also contribute to an improvement of the Young's modulus of glass.
In the glass substrate according to an embodiment of the present invention, taking into consideration an environmental load, it is preferred that As2O3 and Sb2O3 are not substantially contained. In addition, taking into consideration stable float forming, it is preferred that ZnO is not substantially contained.
In the glass substrate according to an embodiment of the present invention, an average thermal expansion coefficient α100/200 at 100° C. to 200° C. is preferably 3.13 ppm/° C. to 3.63 ppm/° C., and more preferably 3.23 ppm/° C. to 3.53 ppm/° C. When α100/200 falls within the above-described range, since the difference in thermal expansion coefficient from the silicon substrate is small, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the residual strain generated in the silicon substrate can be made small while securing a process margin.
α100/200 is still more preferably 3.33 ppm/° C. or more, especially preferably 3.34 ppm/° C. or more, and most preferably 3.35 ppm/° C. or more. In addition, α100/200 is still more preferably 3.43 ppm/° C. or less, especially preferably 3.41 ppm/° C. or less, and most preferably 3.38 ppm/° C. or less.
The “average thermal expansion coefficient α100/200 at 100° C. to 200° C.” as referred to herein is an average thermal expansion coefficient as measured by the method prescribed in JIS R3102 (1995), in which a temperature range of measuring the thermal expansion coefficient is 100° C. to 200° C.
In the glass substrate according to an embodiment of the present invention, a Young's modulus thereof is preferably 80 GPa or more. When the Young's modulus is 80 GPa or more, a warpage or cracks of the glass substrate generated in a cooling step on the occasion of producing a glass substrate can be suppressed. In addition, breakage to be caused due to contact with the silicon substrate or peripheral members or the like can be suppressed. The Young's modulus is more preferably 81 GPa or more, still more preferably 82 GPa or more, and especially preferably 84 GPa or more.
In addition, the Young's modulus is preferably 100 GPa or less. When the Young's modulus is 100 GP or less, the glass becomes less-brittle, whereby fracture or chipping at the cutting or dicing process of the glass substrate can be suppressed. The Young's modulus is more preferably 90 GPa or less, and still more preferably 87 GPa or less.
In the glass substrate according to an embodiment of the present invention, a thickness thereof is preferably 1.0 mm or less. When the thickness is 1.0 mm or less, the image sensor can be miniaturized. The thickness is more preferably 0.8 mm or less, still more preferably 0.7 mm or less, and especially preferably 0.5 mm or less.
In the addition, the thickness is preferably 0.1 mm or more. When the thickness is 0.1 mm or more, breakage to be caused due to contact with the silicon substrate or peripheral members or the like can be suppressed. In addition, gravitational sag of the glass substrate can be suppressed. The thickness is more preferably 0.2 mm or more, and still more preferably 0.3 mm or more.
In the glass substrate according to an embodiment of the present invention, an area thereof is preferably 0.03 m2 or more. When the area is 0.03 m2 or more, a silicon substrate having a large area can be used, and a large number of image sensors can be produced from one sheet of laminated substrate. The area is more preferably 0.04 m2 or more, and still more preferably 0.05 m2 or more.
In addition, in the glass substrate according to an embodiment of the present invention, since α200/300 is 3.45 ppm/° C. to 3.95 ppm/° C., and α200/300/α50/100 is 1.20 to 1.30, even when the area is 0.03 m2 or more, the residual strain generated in the silicon substrate in the heat treatment step of sticking the silicon substrate and the glass substrate to each other is small. The area is preferably 0.1 m2 or less. When the area is 0.1 m2 or less, handling of the glass substrate becomes easy, and breakage to be caused due to contact with the silicon substrate or peripheral members or the like can be suppressed. The area is more preferably 0.08 m2 or less, and still more preferably 0.06 m2 or less.
In the glass substrate according to an embodiment of the present invention, a density thereof is preferably 2.60 g/cm3 or less. When the density is 2.60 g/cm3 or less, the glass substrate is lightweight. In addition, gravitational sag of the glass substrate can be reduced. The density is more preferably 2.55 g/cm3 or less, and still more preferably 2.50 g/cm3 or less.
In addition, the density is preferably 2.20 g/cm3 or more. When the density is 2.20 g/cm3 or more, a Vickers hardness of the glass becomes high, so that the glass surface can be made to be hardly scratched. The density is more preferably 2.30 g/cm3 or more, still more preferably 2.40 g/cm3 or more, and especially preferably 2.45 g/cm3 or more.
In the glass substrate according to an embodiment of the present invention, a density of defect contained in the glass substrate is preferably one or less per cm2. The defect contained in the glass substrate refers to a bubble, a scratch, a metal impurity such as platinum, etc., a residual raw material, and the like existing on the surface or inside of the glass substrate, a size of which is 1 mm or less and 0.5 μm or more. When the defect is larger than 1 mm, it can be easily discriminated through visual inspection, and it is easy to exclude a substrate having a defect. When the defect is smaller than 0.5 μm, since the defects are thoroughly small, even when applied as the cover glass of CMOS sensor or LCOS, there is no concern that such a defect affects characteristics of element.
In the conventional semiconductor assembly process, the assembly process was performed after cutting a glass substrate, and therefore, in the case where the glass substrate involves a defect, the substrate involving such a defect could be excluded at the initial stage. On the other hand, in the wafer-level package, since singulation of the laminated substrate is performed at the very end of the assembly process, in the case where the glass substrate involves a defect, what the glass substrate involving such a defect can be excluded is made at the very end of the assembly process. Thus, in the wafer-level package, in the case where the density of defect of the glass substrate increases, an increase of costs becomes large, and therefore, high-quality control of defect is required. The density of defect is more preferably 0.1 or less per cm2, and still more preferably 0.01 or less per cm2.
A shape of the glass substrate according to an embodiment of the present invention may be any of a circle, an ellipse, or a rectangle. In order to make the shape of the glass substrate conform to a shape of the silicon substrate, a notch may be provided in an end of the glass substrate, and in the case where the glass substrate is circular, a part of the outer periphery of the glass substrate may be a straight line.
In the glass substrate according to an embodiment of the present invention, a glass transition point (also referred to as Tg) is preferably 700° C. or higher. When Tg is 700° C. or higher, a dimensional change of the glass substrate in the heat treatment step can be suppressed to be small. Tg is more preferably 720° C. or higher, and still more preferably 740° C. or higher.
In the glass substrate according to an embodiment of the present invention, a fictive viscosity thereof is preferably 1011.0 dPa·sec to 1014.1 dPa·sec. In order to regulate the fictive viscosity to 1011.0 dPa·sec to 1014.1 dPa·sec, it is necessary to make a cooling rate after forming of the glass substrate corresponding to 1° C./min to 1,200° C./min. When the fictive viscosity is 1011.0 dPa·sec to 1014.1 dPa·sec, the average thermal expansion coefficient of the glass substrate becomes close to the average thermal expansion coefficient of the silicone substrate, and the residual strain generated in the silicon substrate in the heat treatment step of sticking the silicon substrate and the glass substrate to each other is small. The fictive viscosity of the glass substrate is more preferably 1012.1 dPa·sec to 1013.1 dPa·sec (corresponding to a cooling rate of 1° C./min to 1,200° C./min).
The fictive viscosity (η) of the glass can be calculated according to the following equation (4) (G. W. Scherer, “Relaxation in Glass and Composites”, Wiley, New York (1986), p. 159).
log10 η=12.3−log10|q| (4)
Here, the unit of η is dPa·sec, and q is an assumed cooling rate, a unit of which is ° C./s.
The assumed cooling rate q is determined from the glass substrate by the following method. Plural small glass pieces are cut out from one sheet of glass substrate having a thickness of 1 mm or less. For example, a small piece of 1 cm square is cut out as the small glass piece. The cut-out plural small glass pieces are respectively heat treated and cooled at various cooling rates V, and physical property values of the respective small glass pieces are measured. A cooling start temperature is preferably a sufficiently high temperature at which any influence is not given by the cooling rate. Typically, the cooling start temperature is preferably approximately (Tg+50° C.) to (Tg+150° C.).
Although the physical property values for carrying out the measurement are not particularly restricted, a density, physical property values in a close relation with the density (for example, a refractive index), and so on are preferred. A calibration curve A is prepared by plotting the cooling rate (log10 V) on the x-axis and plotting the physical property values of the respective heat-treated small glass pieces on the y-axis. From the physical property values of a small glass piece not having been subjected to a heat treatment, the assumed cooling rate q of the glass substrate is determined according to the prepared calibration curve A.
In the glass substrate according to an embodiment of the present invention, a temperature at which the viscosity becomes 102 dPa·sec (also referred to as T2) is preferably 1,800° C. or lower. T2 is more preferably 1,750° C. or lower, still more preferably 1,700° C. or lower, and especially preferably 1,650° C. or lower.
In the glass substrate according to an embodiment of the present invention, a temperature at which the viscosity becomes 104 dPa·sec (also referred to as T4) is preferably 1,350° C. or lower. T4 is more preferably 1,300° C. or lower, still more preferably 1,275° C. or lower, and especially preferably 1,250° C. or lower. Taking into consideration easiness for securing other physical properties, T4 is 1,100° C. or higher.
In the glass substrate according to an embodiment of the present invention, a glass devitrification temperature thereof is preferably 1,325° C. or lower. The glass devitrification temperature is more preferably 1,300° C. or lower, still more preferably 1,275° C. or lower, and especially preferably 1,250° C. or lower. The glass devitrification temperature is one obtained in the following manner. That is, pulverized glass particles are put into a platinum-made dish and heat treated for 17 hours in an electric furnace controlled at a fixed temperature; after the heat treatment, the observation with an optical microscope is performed; and an average value between a maximum temperature at which a crystal is precipitated in the inside of the glass and a minimum temperature at which a crystal is not precipitated is defined as the devitrification temperature.
It is preferred that the glass substrate according to an embodiment of the present invention satisfies the followings:
{0.0177×(content of SiO2)−0.0173×(content of Al2O3)+0.0377×(content of B2O3)+0.0771×(content of MgO)+0.1543×(content of CaO)+0.1808×(content of SrO)+0.2082×(content of BaO)+0.0344×(12.3+log10 60−log10 η)} is 2.70 to 3.20;
{0.0181×(content of SiO2)+0.0004×(content of Al2O3)+0.0387×(content of B2O3)+0.0913×(content of MgO)+0.1621×(content of CaO)+0.1900×(content of SrO)+0.2180×(content of BaO)+0.0391×(12.3+log10 60−log10 η)} is 3.13 to 3.63;
{0.0177×(content of SiO2)+0.0195×(content of Al2O3)+0.0323×(content of B2O3)+0.1015×(content of MgO)+0.1686×(content of CaO)+0.1990×(content of SrO)+0.2179×(content of BaO)+0.0312×(12.3+log10 60−log10 η)} is 3.45 to 3.95; and
{0.0111×(content of SiO2)+0.0250×(content of Al2O3)+0.0078×(content of B2O3)+0.0144×(content of MgO)+0.0053×(content of CaO)+0.0052×(content of SrO)+0.0013×(content of BaO)−0.0041×(12.3+log10 60−log10 η)} is 1.20 to 1.30.
Here, the content of SiO2, the content of Al2O3, the content of B2O3, the content of MgO, the content of CaO, the content of SrO, and the content of BaO are respectively a content of each of the components contained in the resulting glass; and η is a fictive viscosity (unit: dPa·sec).
When these are satisfied, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the residual strain generated in the silicon substrate can be made small while securing a process margin.
{0.0177×(content of SiO2)−0.0173×(content of Al2O3)+0.0377×(content of B2O3)+0.0771×(content of MgO)+0.1543×(content of CaO)+0.1808×(content of SrO)+0.2082×(content of BaO)+0.0344×(12.3+log10 60−log10 η)} is more preferably 2.80 or more, still more preferably 2.90 or more, especially preferably 2.91 or more, and most preferably 2.92 or more.
In addition, {0.0177×(content of SiO2)−0.0173×(content of Al2O3)+0.0377×(content of B2O3)+0.0771×(content of MgO)+0.1543×(content of CaO)+0.1808×(content of SrO)+0.2082×(content of BaO)+0.0344×(12.3+log10 60−log10 η)} is more preferably 3.10 or less, still more preferably 3.00 or less, especially preferably 2.96 or less, and most preferably 2.94 or less.
{0.0181×(content of SiO2)+0.0004×(content of Al2O3)+0.0387×(content of B2O3)+0.0913×(content of MgO)+0.1621×(content of CaO)+0.1900×(content of SrO)+0.2180×(content of BaO)+0.0391×(12.3+log10 60−log10 η)} is more preferably 3.23 or more, still more preferably 3.33 or more, especially preferably 3.34 or more, and most preferably 3.35 or more.
In addition, {0.0181×(content of SiO2)+0.0004×(content of Al2O3)+0.0387×(content of B2O3)+0.0913×(content of MgO)+0.1621×(content of CaO)+0.1900×(content of SrO)+0.2180×(content of BaO)+0.0391×(12.3+log10 60−log10 η)} is more preferably 3.53 or less, still more preferably 3.43 or less, especially preferably 3.41 or less, and most preferably 3.38 or less.
{0.0177×(content of SiO2)+0.0195×(content of Al2O3)+0.0323×(content of B2O3)+0.1015×(content of MgO)+0.1686×(content of CaO)+0.1990×(content of SrO)+0.2179×(content of BaO)+0.0312×(12.3+log10 60−log10 η)} is more preferably 3.55 or more, still more preferably 3.65 or more, especially preferably 3.66 or more, and most preferably 3.68 or more.
In addition, {0.0177×(content of SiO2)+0.0195×(content of Al2O3)+0.0323×(content of B2O3)+0.1015×(content of MgO)+0.1686×(content of CaO)+0.1990×(content of SrO)+0.2179×(content of BaO)+0.0312×(12.3+log10 60−log10 η)} is more preferably 3.85 or less, still more preferably 3.73 or less, especially preferably 3.71 or less, and most preferably 3.65 or less.
Furthermore, 0.0111×(content of SiO2)+0.0250×(content of Al2O3)+0.0078×(content of B2O3)+0.0144×(content of MgO)+0.0053×(content of CaO)+0.0052×(content of SrO)+0.0013×(content of BaO)−0.0041×(12.3+log10 60−log10 η)} is more preferably 1.24 or more.
In addition, 0.0111×(content of SiO2)+0.0250×(content of Al2O3)+0.0078×(content of B2O3)+0.0144×(content of MgO)+0.0053×(content of CaO)+0.0052×(content of SrO)+0.0013×(content of BaO)−0.0041×(12.3+log10 60−log10 η)} is more preferably 1.27 or less.
In the glass substrate according to an embodiment of the present invention, a weight loss value relative to a hydrofluoric acid aqueous solution (HF) (hereinafter also expressed as “HF weight loss value”) is preferably 0.05 (mg/cm2)/min or more and 0.20 (mg/cm2)/min or less. Here, the HF weight loss value means a loss value per unit area and unit time ((mg/cm2)/min) on the occasion of dipping the glass substrate at 25° C. in a 5 mass % hydrofluoric acid aqueous solution.
There is a case where the glass substrate according to an embodiment of the present invention is, after being stuck to the silicon substrate, installed directly as a part of a device. For example, the glass substrate is installed as a cover glass into a device. In such a case, in order to miniaturize the device, it is preferred to subject the glass substrate to chemical thinning. For that reason, in the glass substrate according to an embodiment of the present invention, it is preferred that a thinning rate is high. As an index of the thinning rate of the glass substrate, the HF weight loss value can be adopted.
When the HF weight loss value is 0.05 (mg/cm2)/min or more, the productivity of the thinning step become satisfactory, and hence, such is preferred. When the HF weight loss value is 0.20 (mg/cm2)/min or less, a failure, such as the matter that an etching depth of the glass substrate as generated in the thinning step becomes heterogeneous, whereby smoothness of the glass substrate surface is impaired, etc., can be prevented from occurring, and hence, such is preferred.
The HF weight loss value is more preferably 0.07 (mg/cm2)/min or more, still more preferably 0.09 (mg/cm2)/min or more, and especially preferably 0.11 (mg/cm2)/min or more. In addition, the HF weight loss value is more preferably 0.18 (mg/cm2)/min or less, still more preferably 0.16 (mg/cm2)/min or less, and especially preferably 0.14 (mg/cm2)/min or less.
In addition, the glass substrate according to an embodiment of the present invention can be applied as a cover glass of a display device for projection application, for example, LCOS. In such a case, when a photoelastic constant of the glass substrate is high, the glass substrate has birefringence due to a stress generated in a packaging step of device or at the time of use of device. As a result, there is a concern that a color change is caused in the light coming into the device, thereby causing an image quality failure, such as color unevenness, etc.
In order to prevent such an image quality failure from occurring, in the glass substrate according to an embodiment of the present invention, a photoelastic constant is preferably 31 nm/(MPa·cm) or less, more preferably 30.5 nm/(MPa·cm) or less, still more preferably 30 nm/(MPa·cm) or less, and especially preferably 29.5 nm/(MPa·cm) or less.
In addition, in the glass substrate according to an embodiment of the present invention, an α-ray emitting quantity is preferably 0.5 C/cm2·h or less, more preferably 0.3 C/cm2·h or less, especially preferably 0.1 C/cm2·h or less, and most preferably 0.05 C/cm2·h or less. The unit C means the count number.
For example, the glass substrate according to an embodiment of the present invention is applied to a cover glass of a device, such as an image sensor, etc. In this case, when an α-ray generated from the glass substrate comes into a device, such as an image sensor, etc., there is a concern that a hole-electron pair is induced by energy of the α-ray, resulting in occurrence of a soft error instantaneously generated in an image, such as a bright spot or a white spot. Then, by using a glass substrate with a small α-ray emitting quantity, such a failure is readily prevented from occurring. When a high-purity raw material with a small content of a radioactive isotope and a small α-ray emitting quantity is used as the raw material of the glass substrate, the α-ray emitting quantity can be decreased. In addition, in the melting/refining step of glass, by making a radioactive isotope not include into the molten glass from a furnace material or the like of glass manufacturing equipment, the α-ray emitting quantity can be effectively decreased. In addition, the “α-ray emitting quantity” can be measured by a gas flow proportional counter measuring apparatus or the like.
An average thermal expansion coefficient αSi50/100 at 50° C. to 100° C. of the silicon substrate is preferably 2.91 ppm/° C. to 2.97 ppm/° C. When αSi50/100 is 2.91 ppm/° C. to 2.97 ppm/° C., sticking to the glass substrate of the present invention becomes easy. αSi50/100 is more preferably 2.92 ppm/° C. or more, and still more preferably 2.93 ppm/° C. or more. In addition, αSi50/100 is more preferably 2.94 ppm/° C. or less.
An average thermal expansion coefficient αSi100/200 at 100° C. to 200° C. of the silicon substrate is preferably 3.34 ppm/° C. to 3.40 ppm/° C. When αSi100/200 is 3.34 ppm/° C. to 3.40 ppm/° C., sticking to the glass substrate of the present invention becomes easy. αSi100/200 is more preferably 3.36 ppm/° C. or more, and still more preferably 3.37 ppm/° C. or more. In addition, αSi100/200 is more preferably 3.38 ppm/° C. or less.
An average thermal expansion coefficient αSi200/300 at 200° C. to 300° C. of the silicon substrate is preferably 3.66 ppm/° C. to 3.72 ppm/° C. When αSi200/300 is 3.66 ppm/° C. to 3.72 ppm/° C., sticking to the glass substrate of the present invention becomes easy. αSi200/300 is more preferably 3.68 ppm/° C. or more, and still more preferably 3.69 ppm/° C. or more. In addition, αSi200/300 is more preferably 3.70 ppm/° C. or less.
The laminated substrate according to an embodiment of the present invention is formed through lamination of the above-described glass substrate and the silicon substrate. Since the difference in thermal expansion coefficient between the silicon substrate and the glass substrate is small, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the residual strain generated in the silicon substrate is small. The laminated substrate is obtained by, for example, sticking the glass substrate and the silicon substrate to each other while interposing a resin therebetween.
At this time, the thickness of the resin, the thermal expansion coefficient of the resin, the heat treatment temperature at the time of sticking, and the like may influence a warpage of the whole of the laminated substrate. In the laminated substrate according to an embodiment of the present invention, by controlling the thermal expansion coefficient as in the glass substrate according to an embodiment of the present invention as described above, the warpage of the whole of the laminated substrate can be reduced, and therefore, a process margin, such as the thickness of the resin, the thermal expansion coefficient of the resin, the heat treatment temperature at the time of sticking, etc., can be widened. In the laminated substrate according to an embodiment of the present invention, the above-described glass substrate according to an embodiment of the present invention can be applied.
The laminated substrate according to an embodiment of the present invention is formed through lamination of the glass substrate and the silicon substrate, and a difference Δα50/100 (=α50/100−αSi50/100) between the average thermal expansion coefficient α50/100 at 50° C. to 100° C. of the glass substrate and the average thermal expansion coefficient αSi50/100 at 50° C. to 100° C. of the silicon substrate is −0.25 ppm/° C. to 0.25 ppm/° C.
In addition, a difference Δα200/300 (α200/300−αSi200/300) between the average thermal expansion coefficient α200/300 at 200° C. to 300° C. of the glass substrate and the average thermal expansion coefficient αSi200/300 at 200° C. to 300° C. of the silicon substrate is −0.25 ppm/° C. to 0.25 ppm/° C. Since the difference in thermal expansion coefficient between the silicon substrate and the glass substrate is small, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the residual strain generated in the silicon substrate is small.
Δα50/100 is more preferably −0.15 ppm/° C. or more, still more preferably −0.10 ppm/° C. or more, especially preferably −0.05 ppm/° C. or more, and most preferably −0.03 ppm/° C. or more. Δα50/100 is more preferably 0.15 ppm/° C. or less, still more preferably 0.10 ppm/° C. or less, especially preferably 0.05 ppm/° C. or less, and most preferably 0.03 ppm/° C. or less.
Δα200/300 is more preferably −0.15 ppm/° C. or more, still more preferably −0.10 ppm/° C. or more, especially preferably −0.05 ppm/° C. or more, and most preferably −0.03 ppm/° C. or more. Δα200/300 is more preferably 0.15 ppm/° C. or less, still more preferably 0.10 ppm/° C. or less, especially preferably 0.05 ppm/° C. or less, and most preferably 0.03 ppm/° C. or less.
In the laminated substrate according to an embodiment of the present invention, a difference Δα100/200 (=α100/200−αSi100/200) between the average thermal expansion coefficient α100/200 at 100° C. to 200° C. of the glass substrate and the average thermal expansion coefficient αSi100/200 at 100° C. to 200° C. of the silicon substrate is preferably −0.25 ppm/° C. to 0.25 ppm/° C. When Δα100/200 is −0.25 ppm/° C. to 0.25 ppm/° C., since the difference in thermal expansion coefficient between the silicon substrate and the glass substrate is small, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the residual strain generated in the silicon substrate is small.
Δα100/200 is more preferably −0.15 ppm/° C. or more, still more preferably −0.10 ppm/° C. or more, especially preferably −0.05 ppm/° C. or more, and most preferably −0.03 ppm/° C. or more. Δα100/200 is more preferably 0.15 ppm/° C. or less, still more preferably 0.10 ppm/° C. or less, especially preferably 0.05 ppm/° C. or less, and most preferably 0.03 ppm/° C. or less.
In the laminated substrate according to an embodiment of the present invention, a difference between Δα200/300 and Δα50/100 (Δα200/300−Δα50/100) is −0.16 ppm/° C. to 0.16 ppm/° C. When (Δα200/300−Δα50/100) is −0.16 ppm/° C. to 0.16 ppm/° C., since the difference in thermal expansion coefficient from the silicon substrate is small, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the residual strain generated in the silicon substrate is small. (Δα200/300−Δα50/100) is preferably −0.12 ppm/° C. or more, and more preferably −0.08 ppm/° C. or more. In addition, (Δα200/300−Δα50/100) is preferably 0.12 ppm/° C. or less, and more preferably 0.08 ppm/° C. or less.
Next, the method for producing a glass substrate according to an embodiment of the present invention is described.
In the case of producing the glass substrate according to an embodiment of the present invention, a melting step of heating glass raw materials to obtain a molten glass, a refining step of removing bubbles from the molten glass, a forming step of forming the molten glass into a sheet-like shape to obtain a glass ribbon, and a cooling step of gradually cooling the glass ribbon to a room temperature state are included.
In the melting step, raw materials are prepared so as to have a composition of a glass sheet to be obtained, and the raw materials are continuously put into a melting furnace and heated preferably to approximately 1,450° C. to 1,650° C. to obtain a molten glass.
For the raw materials, oxides, carbonates, nitrates, hydroxides, halides such as chlorides, and so on can be used. In the case where the melting or refining step includes a step where the molten glass comes into contact with platinum, there is a case where minute platinum particles elute into the molten glass and are included as a impurity into the resulting glass sheet. However, the use of a nitrate raw material brings about an effect for preventing elution of this platinum impurity from occurring.
As the nitrate, strontium nitrate, barium nitrate, magnesium nitrate, calcium nitrate, and so on can be used. Use of strontium nitrate is more preferred. As for the particle size of the raw materials, from raw materials having a large particle diameter of several hundred microns to an extent of not causing an unmelted residue to raw materials having a small particle diameter of several microns to an extent that they are not scattered at the time of shipment of raw materials and are not coagulated as secondary particles can be properly used. It is also possible to use a granulated body. In order to prevent scattering of raw materials from occurring, it is also possible to properly regulate the moisture content of raw materials. Melting conditions, such as β-OH, oxidation-reduction degree or redox of Fe [Fe2+/(Fe2++Fe3+)], etc., can be properly regulated and used.
Next, the refining step is a step of removing bubbles from the molten glass obtained in the above-described melting step. As the refining step, a degassing method by means of pressure reduction may be applied. In addition, in the glass substrate in the present invention, SO3 or SnO2 can be used as a refining agent. As the SO3 source, a sulfate of at least one element selected from Al, Mg, Ca, Sr, and Ba is preferred; a sulfate of an alkaline earth metal is more preferred; and above all, CaSO4.2H2O, SrSO4, and BaSO4 are especially preferred because their action to make the bubbles large is remarkable.
As the refining agent in the degassing method by means of pressure reduction, it is preferred to use a halogen, such as Cl, F, etc. As the Cl source, a chloride of at least one element selected from Al, Mg, Ca, Sr, and Ba is preferred; a chloride of an alkaline earth metal is more preferred; and above all, SrCl2.6H2O and BaCl2.2H2O are especially preferred because not only their action to make the bubbles large is remarkable, but also their deliquescency is small. As the F source, a fluoride of at least one element selected from Al, Mg, Ca, Sr, and Ba is preferred; a fluoride of an alkaline earth metal is more preferred; and above all, CaF2 is still more preferred because an action to make the solubility of the glass raw materials large is remarkable.
Next, the forming step is a step of forming the molten glass from which bubbles have been removed in the above-described refining step into a sheet-like shape to obtain a glass ribbon. As the forming step, the float process of forming a molten glass into a sheet-like shape by being flown onto a molten metal to obtain a glass ribbon is applied.
Next, the cooling step is a step of gradually cooling the glass ribbon obtained in the above-described forming step to a room temperature state. As for the cooling step, the glass ribbon is gradually cooled to a room temperature state such that an average cooling rate of from a temperature at which the viscosity is 1013 dPa·sec to a temperature at which the viscosity is 1014.5 dPa·sec becomes R. After cutting the gradually cooled glass ribbon, the glass substrate is obtained.
In the method for producing a glass substrate according to an embodiment of the present invention, the composition of the resulting glass substrate includes, as expressed in terms of a molar percentage based on oxides:
SiO2: 50% to 75%;
Al2O3: 6% to 16%;
B2O3: 0% to 15%;
MgO: 0% to 15%;
CaO: 0% to 13%;
SrO: 0% to 11%; and
BaO: 0% to 9.5%.
The content of the alkali metal oxide is 0% to 0.1%.
In addition, in the method for producing a glass substrate according to an embodiment of the present invention, the composition of the resulting glass substrate and the average cooling rate R (unit: ° C./min) from a temperature at which the viscosity of the glass ribbon in the cooling step is 1013 dPa·sec to a temperature at which the viscosity thereof is 1014.5 dPa·sec satisfy the following conditions (1) to (4).
{0.0177×(content of SiO2)−0.0173×(content of Al2O3)+0.0377×(content of B2O3)+0.0771×(content of MgO)+0.1543×(content of CaO)+0.1808×(content of SrO)+0.2082×(content of BaO)+0.0344×log10 R} is 2.70 to 3.20. Condition (1):
{0.0181×(content of SiO2)+0.0004×(content of Al2O3)+0.0387×(content of B2O3)+0.0913×(content of MgO)+0.1621×(content of CaO)+0.1900×(content of SrO)+0.2180×(content of BaO)+0.0391×log10 R} is 3.13 to 3.63. Condition (2):
{0.0177×(content of SiO2)+0.0195×(content of Al2O3)+0.0323×(content of B2O3)+0.1015×(content of MgO)+0.1686×(content of CaO)+0.1990×(content of SrO)+0.2179×(content of BaO)+0.0312×log10 R} is 3.45 to 3.95. Condition (3):
0.0111×(content of SiO2)+0.0250×(content of Al2O3)+0.0078×(content of B2O3)+0.0144×(content of MgO)+0.0053×(content of CaO)+0.0052×(content of SrO)+0.0013×(content of BaO)−0.0041×log10 R} is 1.20 to 1.30. Condition (4):
Preferably, the following conditions (1) to (4) are satisfied.
{0.0177×(content of SiO2)−0.0173×(content of Al2O3)+0.0377×(content of B2O3)+0.0771×(content of MgO)+0.1543×(content of CaO)+0.1808×(content of SrO)+0.2082×(content of BaO)+0.0344×log10 R} is 2.80 to 3.10. Condition (1):
{0.0181×(content of SiO2)+0.0004×(content of Al2O3)+0.0387×(content of B2O3)+0.0913×(content of MgO)+0.1621×(content of CaO)+0.1900×(content of SrO)+0.2180×(content of BaO)+0.0391×log10 R} is 3.23 to 3.53. Condition (2):
{0.0177×(content of SiO2)+0.0195×(content of Al2O3)+0.0323×(content of B2O3)+0.1015×(content of MgO)+0.1686×(content of CaO)+0.1990×(content of SrO)+0.2179×(content of BaO)+0.0312×log10 R} is 3.55 to 3.85. Condition (3):
0.0111×(content of SiO2)+0.0250×(content of Al2O3)+0.0078×(content of B2O3)+0.0144×(content of MgO)+0.0053×(content of CaO)+0.0052×(content of SrO)+0.0013×(content of BaO)−0.0041×log10 R} is 1.24 to 1.27. Condition (4):
Here, the content of SiO2, the content of Al2O3, the content of B2O3, the content of MgO, the content of CaO, the content of SrO, and the content of BaO are respectively a content of each of the components contained in the resulting glass. When the conditions (1) to (4) are satisfied, it is possible to produce a glass substrate in which the residual strain generated in the silicon substrate in the heat treatment step can be made small.
In the above-described glass substrate according to the present embodiment, since the content of the alkali metal oxide is 0.1% or less, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, an alkali ion is hardly diffused into the silicon substrate. In addition, since the average thermal expansion coefficient α50/100 at 50° C. to 100° C. is 2.70 ppm/° C. to 3.20 ppm/° C., the average thermal expansion coefficient α200/300 at 200° C. to 300° C. is 3.45 ppm/° C. to 3.95 ppm/° C., and the value α200/300/α50/100 obtained by dividing the average thermal expansion coefficient α200/300 at 200° C. to 300° C. by the average thermal expansion coefficient α50/100 at 50° C. to 100° C. is 1.20 to 1.30, the difference in thermal expansion coefficient from the silicon substrate is small, and the residual strain generated in the silicon substrate is small.
The present invention is not limited to the above-described embodiments. Modifications, improvements, and the like within the range where the object of the present invention can be achieved are included in the present invention.
For example, in the case of producing a glass substrate according to an embodiment of the present invention, in the forming step, the molten glass may be formed into a sheet-like shape by applying the fusion process, the press forming process, or the like.
In addition, in the case of producing a glass substrate according to an embodiment of the present invention, a platinum crucible may be used. In the case of using a platinum crucible, in the melting step, raw materials are prepared so as to have a composition of a glass substrate to be obtained; a platinum crucible having the raw materials charged therein is put into an electric furnace and heated preferably to approximately 1,450° C. to 1,650° C.; a platinum stirrer is inserted; and stirring is performed for 1 to 3 hours to obtain a molten glass.
In the forming step, the molten glass is flown onto a carbon sheet to form a glass sheet. In the cooling step, the glass in a sheet form is gradually cooled to a room temperature state and then cut, thereby forming a glass substrate.
In addition, the glass substrate obtained after cutting may be heated to, for example, approximately (Tg+50° C.), followed by gradually cooling to a room temperature state. According to this way, the fictive viscosity η can be regulated.
The following modes are also included in the present embodiment.
A glass substrate having:
an average thermal expansion coefficient α50/100 at 50° C. to 100° C. of 2.80 ppm/° C. to 3.10 ppm/° C.;
an average thermal expansion coefficient α200/300 at 200° C. to 300° C. of 3.55 ppm/° C. to 3.85 ppm/° C.;
a value α200/300/α50/100 obtained by dividing the average thermal expansion coefficient α200/300 at 200° C. to 300° C. by the average thermal expansion coefficient α50/100 at 50° C. to 100° C. of 1.20 to 1.30; and
a content of an alkali metal oxide being 0% to 0.1% as expressed in terms of a molar percentage based on oxides.
The glass substrate as set forth in Appendix 1, having a composition including, as expressed in terms of a molar percentage based on oxides:
SiO2: 50% to 75%;
Al2O3: 6% to 16%;
B2O3: 0% to 15%;
MgO: 0% to 15%;
CaO: 0% to 13%;
SrO: 0% to 11%; and
BaO: 0% to 9.5%.
The glass substrate as set forth in Appendix 1 or 2, in which a total content of CaO, SrO, and BaO is 7% or more as expressed in terms of a molar percentage based on oxides; a relation of {(content of Al2O3)≥(content of MgO)} is satisfied; and a devitrification viscosity is 103.8 dPa·sec or more.
The glass substrate as set forth in any one of Appendixes 1 to 3, having an average thermal expansion coefficient α100/200 at 100° C. to 200° C. of 3.23 ppm/° C. to 3.53 ppm/° C.
The glass substrate as set forth in any one of Appendixes 1 to 4, having a content of Fe2O3 being 200 ppm or less as expressed in terms of parts per million mass based on oxides.
The glass substrate as set forth in any one of Appendixes 1 to 5, having a Young's modulus of 80 GPa or more.
The glass substrate as set forth in any one of Appendixes 1 to 6, having a thickness of 1.0 mm or less.
The glass substrate as set forth in any one of Appendixes 1 to 7, having an area of 0.03 m2 or more.
The glass substrate as set forth in any one of Appendixes 1 to 8, having a fictive viscosity is 1011.0 to 1014.1 dPa·sec.
The glass substrate as set forth in any one of Appendixes 1 to 10, in which:
{0.0177×(content of SiO2)−0.0173×(content of Al2O3)+0.0377×(content of B2O3)+0.0771×(content of MgO)+0.1543×(content of CaO)+0.1808×(content of SrO)+0.2082×(content of BaO)+0.0344×(12.3+log10 60−log10 η)} is 2.80 to 3.10;
{0.0181×(content of SiO2)+0.0004×(content of Al2O3)+0.0387×(content of B2O3)+0.0913×(content of MgO)+0.1621×(content of CaO)+0.1900×(content of SrO)+0.2180×(content of BaO)+0.0391×(12.3+log10 60−log10 η)} is 3.23 to 3.53;
{0.0177×(content of SiO2)+0.0195×(content of Al2O3)+0.0323×(content of B2O3)+0.1015×(content of MgO)+0.1686×(content of CaO)+0.1990×(content of SrO)+0.2179×(content of BaO)+0.0312×(12.3+log10 60−log10 η)} is 3.55 to 3.85; and
{0.0111×(content of SiO2)+0.0250×(content of Al2O3)+0.0078×(content of B2O3)+0.0144×(content of MgO)+0.0053×(content of CaO)+0.0052×(content of SrO)+0.0013×(content of BaO)−0.0041×(12.3+log10 60−log10 η)} is 1.24 to 1.27.
Here, the content of SiO2, the content of Al2O3, the content of B2O3, the content of MgO, the content of CaO, the content of SrO, and the content of BaO are respectively a content of each of the components contained in the resulting glass as expressed in terms of a molar percentage based on oxides; and η is a fictive viscosity (unit: dPa·sec).
A laminated substrate including: the glass substrate as set forth in any one of Appendixes 1 to 10; and a silicon substrate laminated on the glass substrate.
A laminated substrate including: a glass substrate; and a silicon substrate laminated on the glass substrate,
a difference Δα50/100 (=α50/100−αSi50/100) between an average thermal expansion coefficient α50/100 at 50° C. to 100° C. of the glass substrate and an average thermal expansion coefficient αSi50/100 at 50° C. to 100° C. of the silicon substrate is −0.15 ppm/° C. to 0.15 ppm/° C.;
a difference Δα200/300 (=α200/300−αSi200/300) between an average thermal expansion coefficient α200/300 at 200° C. to 300° C. of the glass substrate and an average thermal expansion coefficient αSi200/300 at 200° C. to 300° C. of the silicon substrate is −0.15 ppm/° C. to 0.15 ppm/° C.;
(Δα200/300−Δα50/100) is −0.12 ppm/° C. to 0.12 ppm/° C.; and
a content of an alkali metal oxide in the glass substrate is 0% to 0.1% as expressed in terms of a molar percentage based on oxides.
The laminated substrate as set forth in Appendix 12, in which a difference Δα100/200 (=α100/200−αSi100/200) between an average thermal expansion coefficient α100/200 at 100° C. to 200° C. of the glass substrate and an average thermal expansion coefficient αSi100/200 at 100° C. to 200° C. of the silicon substrate is −0.15 ppm/° C. to 0.15 ppm/° C.
A method for producing a glass substrate, the method including:
a melting step of heating glass raw materials to obtain a molten glass;
a refining step of removing bubbles from the molten glass;
a forming step of forming the molten glass into a sheet-like shape to obtain a glass ribbon; and
a cooling step of gradually cooling the glass ribbon to a room temperature state,
in which the resulting glass substrate has a composition including, as expressed in terms of a molar percentage based on oxides:
SiO2: 50% to 75%;
Al2O3: 6% to 16%;
B2O3: 0% to 15%;
MgO: 0% to 15%;
CaO: 0% to 13%;
SrO: 0% to 11%; and
BaO: 0% to 9.5%,
a content of an alkali metal oxide is 0% to 0.1% as expressed in terms of a molar percentage based on oxides, and
the composition of the resulting glass substrate and an average cooling rate R (unit: ° C./min) from a temperature at which a viscosity of the glass ribbon in the cooling step is 1013 dPa·sec to a temperature at which the viscosity thereof is 1014.5 dPa·sec satisfy the following condition (1), condition (2), condition (3), and condition (4):
{0.0177×(content of SiO2)−0.0173×(content of Al2O3)+0.0377×(content of B2O3)+0.0771×(content of MgO)+0.1543×(content of CaO)+0.1808×(content of SrO)+0.2082×(content of BaO)+0.0344×log10 R} is 2.80 to 3.10; Condition (1):
{0.0181×(content of SiO2)+0.0004×(content of Al2O3)+0.0387×(content of B2O3)+0.0913×(content of MgO)+0.1621×(content of CaO)+0.1900×(content of SrO)+0.2180×(content of BaO)+0.0391×log10 R} is 3.23 to 3.53; Condition (2):
{0.0177×(content of SiO2)+0.0195×(content of Al2O3)+0.0323×(content of B2O3)+0.1015×(content of MgO)+0.1686×(content of CaO)+0.1990×(content of SrO)+0.2179×(content of BaO)+0.0312×log10 R} is 3.55 to 3.85; and Condition (3):
0.0111×(content of SiO2)+0.0250×(content of Al2O3)+0.0078×(content of B2O3)+0.0144×(content of MgO)+0.0053×(content of CaO)+0.0052×(content of SrO)+0.0013×(content of BaO)−0.0041×log10 R} is 1.24 to 1.27. Condition (4):
Here, the content of SiO2, the content of Al2O3, the content of B2O3, the content of MgO, the content of CaO, the content of SrO, and the content of BaO are respectively a content of each of the components contained in the resulting glass.
In the glass substrate, the glass substrate obtained by the method for producing a glass substrate, and the laminated substrate using the glass substrate as described in the Appendixes, since the difference in thermal expansion coefficient between the glass substrate and the silicon substrate is thoroughly small, the failures to be caused due to the difference in thermal expansion coefficient can be more suppressed.
The present invention is hereunder specifically described by reference to the Examples, but it should be construed that the present invention is not limited thereto.
Various glass raw materials, such as silica sand, etc., were compounded so as to have a glass composition as shown in each of Tables 1 to 7, 0.1% to 1% of a sulfate as converted into SO3, 0.16% of F, and 1% of Cl as expressed in terms of a molar percentage based on oxides relative to 100% of the raw materials of the objective composition were added, and the contents were melted for 3 hours under heating at a temperature of 1,550° C. to 1,650° C. by using a platinum crucible. In the melting, a platinum stirrer was inserted, and stirring was performed for 1 hour to achieve homogenization of glass. Subsequently, the molten glass was flown out and formed into a sheet-like shape; thereafter, the glass in a sheet-like shape was put into an electric furnace at a temperature of approximately (Tg+50° C.); and the electric furnace was subjected to temperature decrease at a cooling rate R (° C./min) and cooled until the glass reached room temperature.
With respect to the resulting glasses, a density (unit: g/cm3), an average thermal expansion coefficient (unit: ppm/° C.), a glass transition point Tg (unit: ° C.), a Young's modulus (unit: GPa), T2 (unit: ° C.), T4 (unit: ° C.), a devitrification temperature (unit: ° C.), a devitrification viscosity log10 ηTL (unit: dPa·sec), and a fictive viscosity log10 η (unit: dPa·sec) were measured and shown in Tables 1 to 7. In addition, (1) to (4) shown in Tables 1 to 7 are as follows.
0.0177×(content of SiO2)−0.0173×(content of Al2O3)+0.0377×(content of B2O3)+0.0771×(content of MgO)+0.1543×(content of CaO)+0.1808×(content of SrO)+0.2082×(content of BaO)+0.0344×(12.3+log10 60−log10 η) (1):
0.0181×(content of SiO2)+0.0004×(content of Al2O3)+0.0387×(content of B2O3)+0.0913×(content of MgO)+0.1621×(content of CaO)+0.1900×(content of SrO)+0.2180×(content of BaO)+0.0391×(12.3+log10 60−log10 η) (2)
0.0177×(content of SiO2)+0.0195×(content of Al2O3)+0.0323×(content of B2O3)+0.1015×(content of MgO)+0.1686×(content of CaO)+0.1990×(content of SrO)+0.2179×(content of BaO)+0.0312×(12.3+log10 60−log10 η) (3):
0.0111×(content of SiO2)+0.0250×(content of Al2O3)+0.0078×(content of B2O3)+0.0144×(content of MgO)+0.0053×(content of CaO)+0.0052×(content of SrO)+0.0013×(content of BaO)−0.0041×(12.3+log10 60−log10 η) (4):
The values in the parentheses in the tables are those determined through calculations. The residual amount of Fe2O3 in the glass was 50 ppm to 200 ppm as expressed in terms of parts per million mass based on oxides, and the residual amount of SO3 in the glass was 10 ppm to 100 ppm as expressed in terms of parts per million mass based on oxides. Measurement methods of respective physical properties are shown as follows.
(Average Thermal Expansion Coefficient)
The average thermal expansion coefficient was measured with a differential thermal expansion meter (TMA) in accordance with the method prescribed in JIS R3102 (1995). The measurement temperature range of α50/α100 is from 50° C. to 100° C., the measurement temperature range of α100/α200 is from 100° C. to 200° C., and the measurement temperature range of α200/α300 is from 200° C. to 300° C.
(Difference in Average Thermal Expansion Coefficient from Silicon Substrate)
With respect to a silicon substrate (manufactured by Shin-Etsu Chemical Co., Ltd.), average thermal expansion coefficients αSi50/100, αSi100/200, and αSi200/300 were measured, and respective differences in average thermal expansion coefficient Δα50/100, Δα100/200, and Aα200/300 from the glass substrate were determined. Here, Δα50/100, Δα100/200, and Δα200/300 are as follows.
Δα50/100=α50/100αSi50/100
Δα100/200=α100/200−αSi100/200
Δα200/300=α200/300−αSi200/300
The average thermal expansion coefficients αSi50/100, αSi100/200, and αSi200/300 of the silicon substrate were 2.94 ppm/° C., 3.37 ppm/° C., and 3.69 ppm/° C., respectively.
(Glass Transition Point Tg)
The measurement was performed with TMA in accordance with the method prescribed in JIS R3103-3 (2001).
(Density)
About 20 g of a bubble-free glass lump was measured by the Archimedean method.
(Young's Modulus)
A glass having a thickness of 0.5 mm to 10 mm was measured by the ultrasonic pulse method.
(T2)
A viscosity was measured with a rotary viscometer, and a temperature T2 (° C.) at which the viscosity reached 102 dPa·sec was measured.
(T4)
A viscosity was measured with a rotary viscometer, and a temperature T4 (° C.) at which the viscosity reached 104 dPa·sec was measured.
(Glass Devitrification Temperature)
The glass devitrification temperature is one obtained in the following manner. That is, pulverized glass particles are put in a platinum-made dish and heat treated for 17 hours in an electric furnace controlled at a fixed temperature; after the heat treatment, the observation with an optical microscope is performed; and an average value between a maximum temperature at which a crystal is precipitated in the inside of the glass and a minimum temperature at which a crystal is not precipitated is defined as the devitrification temperature.
(Devitrification Viscosity)
A coefficient of the Fulcher's equation was determined from the measurement results of glass viscosity of the molten glass at high temperatures (1,000° C. to 1,600° C.) by using a rotary viscometer, and the glass viscosity at the glass devitrification temperature was determined from the Fulcher's equation using the coefficient.
(HF Weight Loss Value)
The HF weight loss value was measured in the following manner. A glass sheet obtained above was cut, and the both surfaces thereof were subjected to mirror polishing to obtain a glass sample of 40 mm in square and having a thickness of 1 mm. This glass sample was cleaned and then dried, and a weight thereof was measured. Subsequently, the glass sample was dipped in a 5 mass % hydrofluoric acid kept at 25° C. for 20 minutes, cleaned, and then dried. The weight after dipping was measured, and the weight loss value was calculated from the weight before dipping. If a chemical liquid is stirred during dipping, an etching rate fluctuates. Therefore, stirring was not carried out. A surface area was calculated from the sample dimensions, and the weight loss value was divided by the surface area and further divided by the dipping time, thereby determining the weight loss value (HF weight loss value) per unit area and unit time.
(Photoelastic Constant)
The measurement was performed by the circular plate compression method (“Measurement of Photoelastic Constant of Glass for Chemical Strengthening by Method of Compression on Circular Plate”, Ryosuke Yokota, Journal of Ceramic Society of Japan, 87[10], 1979, p. 519-522).
Examples 1 to 60 and 66 to 87 are concerned with working examples, and Examples 61 to 65 are concerned with comparative examples.
In the glass substrates of the present invention of Examples 1 to 60 and 66 to 87 which are concerned with the working examples, since the content of the alkali metal oxide is 0.1% or less, in the heat treatment step of sticking the silicone substrate and the glass substrate to each other, the alkali ion is not diffused into the silicon substrate. In addition, since the average thermal expansion coefficient α50/100 at 50° C. to 100° C. is 2.70 ppm/° C. to 3.20 ppm/° C., the average thermal expansion coefficient α200/300 at 200° C. to 300° C. is 3.45 ppm/° C. to 3.95 ppm/° C., and the value α200/300/α50/100 obtained by dividing α200/300 by α50/100 is 1.20 to 1.30, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the residual strain generated in the silicon substrate easily becomes small.
In the glass substrates of Examples 61 to 65 which are concerned with the comparative examples, the range of at least one of α50/100, α200/300, and α200/300/α50/100 falls outside the scope regarding the glass substrate according to an embodiment of the present invention. Or, in the glass substrates of Examples 61 to 65, at least one of Δα50/100, Δα200/300, and (Δα200/300−Δα50/100) falls outside the scope regarding the glass substrate according to an embodiment of the present invention. Alternatively, in the glass substrates of Examples 61 to 65, at least one of the composition of the resulting glass substrate and the conditions (1) to (4) falls outside the scope regarding the glass substrate according to an embodiment of the present invention. For that reason, in the heat treatment step of sticking the silicon substrate and the glass substrate to each other, the residual strain generated in the silicon substrate is liable to become large.
Next, when each of a glass substrate of Example 88 and a glass substrate of Example 89 was brought into contact with a silicon substrate and then subjected to a heat treatment, a diffusion amount of the alkali metal oxide into the silicon substrate was measured by the secondary ion mass spectrometry (SIMS), and the results are shown in
For the SIMS measurement, ADEPT 1010, manufactured by ULVAC-PHI, INC. was used. A Cs ion was used for a primary ion of the SIMS. As secondary ion species, 28Si− and 23Na+ were measured. In the heat treatment of the silicon substrate having been brought into contact with the glass substrate, the temperature was raised from room temperature to 200° C. for 10 minutes, and after keeping at 200° C. for 1 hour, cooling to room temperature was performed for 10 minutes. The compositions of Examples 88 and 89 are shown in Table 8.
Example 88 is one in which 0.03% in outer percentage of Na2O that is the alkali metal oxide was added to Example 6 and is concerned with a working example. Example 89 is one in which 0.32% in outer percentage of Na2O that is the alkali metal oxide was added to Example 61 and is concerned with a comparative example. In
It is noted from
The glass substrate according to the present invention is small in a difference in thermal expansion coefficient from the silicon substrate, and therefore, in the heat treatment step of sticking to the silicon substrate or the sequent heat treatment, the generation of a residual strain to be caused due to the difference in thermal expansion coefficient can be suppressed. For that reason, the glass substrate according to the present invention is suitable as a glass substrate for image sensors, such as MEMS, CMOS, CIS, etc., for which miniaturization of element due to the wafer-level package is effective.
In addition, the glass substrate according to an embodiment of the present invention is suitable as a cover glass for display devices for projection application, for example, a cover glass of LCOS (liquid crystal on silicon). For example, in the LCOS or image sensors, after forming an electronic circuit on a silicon substrate, the cover glass is adhered to the silicon substrate with a resin or a glass frit as an adhesive material. The glass substrate according to the present invention as the cover glass is small in a difference in thermal expansion coefficient from the silicon substrate, and therefore, a stress generated on the adhesive interface when the temperature varies at the time of device production or use is reduced. Thereby, a reduction of color unevenness to be caused due to photoelastic deformation, or an improvement of long-term reliability can be expected.
Furthermore, the glass substrate according to the present invention is suitable as a bored substrate of glass interposer (GIP) or a support glass for semiconductor backgrind. In addition, the glass substrate of the present invention can be suitably used for any application for glass substrate to be used through sticking to a silicon substrate.
While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. It is to be noted that the present application is based on a Japanese patent application filed on Feb. 6, 2015 (Japanese Patent Application No. 2015-022719) and a Japanese patent application filed on Dec. 10, 2015 (Japanese Patent Application No. 2015-241303), the entireties of which are incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-022719 | Feb 2015 | JP | national |
| 2015-241303 | Dec 2015 | JP | national |
This application is a Continuation of PCT/JP2015/053047, which was filed on Feb. 2, 2016. This application is based upon and claims the benefit of priority to Japanese Application No. 2015-241303, which was filed on Dec. 10, 2015, and to Japanese Application No. 2015-022719, which was filed on Feb. 6, 2015.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20060003884 | Nishizawa | Jan 2006 | A1 |
| 20090270242 | Yanase et al. | Oct 2009 | A1 |
| 20090294773 | Ellison | Dec 2009 | A1 |
| 20110318561 | Murata | Dec 2011 | A1 |
| 20120302063 | Markham | Nov 2012 | A1 |
| 20130267402 | Nishizawa | Oct 2013 | A1 |
| 20140091419 | Hasegawa et al. | Apr 2014 | A1 |
| 20150093561 | Tokunaga | Apr 2015 | A1 |
| 20150160386 | Takemura | Jun 2015 | A1 |
| Number | Date | Country |
|---|---|---|
| 3153710 | Apr 2001 | JP |
| 2004-315354 | Nov 2004 | JP |
| 2009-286689 | Dec 2009 | JP |
| 2011-20864 | Feb 2011 | JP |
| 2013-257532 | Dec 2013 | JP |
| WO 2010107111 | Sep 2010 | WO |
| WO 2013099970 | Jul 2013 | WO |
| WO 2013183681 | Dec 2013 | WO |
| WO2013183681 | Dec 2013 | WO |
| 2014034386 | Mar 2014 | WO |
| Entry |
|---|
| International Search Report and Written Opinion dated Mar. 29, 2016 in PCT/JP2016/053055, 17 pages (with English translation). |
| International Search Report dated Mar. 29, 2016 in PCT/JP2016/053047, filed on Feb. 2, 2016 (with English translation). |
| Written Opinion dated Mar. 29, 2016 in PCT/JP2016/053047, filed on Feb. 2, 2016. |
| Number | Date | Country | |
|---|---|---|---|
| 20170327408 A1 | Nov 2017 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2016/053017 | Feb 2016 | US |
| Child | 15666862 | US |
