WO2012132328A1

WO2012132328A1 - Low-expansion glass and tempered glass

Info

Publication number: WO2012132328A1
Application number: PCT/JP2012/001942
Authority: WO
Inventors: 大正和田; 淳史倉知
Original assignee: 日本板硝子株式会社
Priority date: 2011-03-31
Filing date: 2012-03-21
Publication date: 2012-10-04
Also published as: JPWO2012132328A1; JP5890393B2

Abstract

This low-expansion glass comprises, in mol%, 55 to 75% of SiO₂, 5 to 17% of B₂O₃, 5 to 15% of Al₂O₃, 0 to 10% of MgO, 0 to 10% of CaO, 0 to 5% of SrO, 0 to 1% of BaO, 0 to 6% of ZnO, 0.6 to 4% of Li₂O, 0 to 1% of Na₂O, 0 to 1% of K₂O, 0 to 1% of SnO₂, 0 to 5% of Fe₂O₃, 0 to 30% of TiO₂ and 0 to 10% of CeO₂. The total content of alkali metal oxides is up to 5mol%, while the content of Li₂O exceeds the total content of alkali metal oxides other than Li₂O, each content being expressed in terms of mol%. Further, the low-expansion glass exhibits a dielectric loss tangent of less than 0.0050 as determined under the condition of 25°C and 1GHz.

Description

Low expansion glass and tempered glass

The present invention relates to a low expansion glass and a tempered glass obtained by chemically strengthening the low expansion glass.

A borosilicate glass called Pyrex (registered trademark of Corning) is known as the most versatile and inexpensive low expansion glass. This glass is a SiO ₂ _81% by mass _percentage, B 2 _{O 3} and 13% _Al 2 _{O 3} 2%, including 4% Na ₂ O, the average linear expansion coefficient of up to 350 ° C. from room temperature to about 33 × 10 ⁻⁷ / ° C.

低 Low expansion glass is often bonded to silicon by anodic bonding. In the anodic bonding method, glass and silicon are brought into contact and heated to about 300 to 450 ° C., while applying a high voltage of about several hundred to 1 kV with silicon as the anode side, In this method, the alkali metal ions are moved to the cathode side and electrostatically and chemically strong bonds are formed at the interface between the glass and silicon to bond the two.

As another low expansion glass, Patent Document 1 describes a glass for a silicon pedestal containing no alkali metal. It is described that the deterioration of the element due to migration of alkali metal can be prevented as an effect due to the absence of alkali metal.

Patent Document 2 describes an anodic bonding glass that does not contain Na ₂ O and contains a relatively large amount of Li ₂ O. It is described that the anodic bonding between glass and silicon can be performed at a low temperature (less than 300 ° C.) as an effect by containing a relatively large amount of Li ₂ O. Moreover, does not contain any Na 2 _O, it is described that can suppress the increase in the linear expansion coefficient and volume resistivity of the glass.

Patent Document 3 describes a glass that defines the ratio of Li ₂ O to Al ₂ O ₃ . By adjusting the composition so that the value of (Li ₂ O / Al ₂ O ₃ ) is 0.9 or more, it has a low average linear expansion coefficient while containing a relatively large amount of Li ₂ O, and heat It is described that a glass capable of melting at a relatively low temperature can be obtained without devitrification even in the inter-processing.

Patent Document 4 describes a composition of low expansion glass suitable for a photoresist mask.

Japanese Patent No. 3153710 Japanese Patent No. 3762157 JP 2010-228969 A JP 61-53130 A

The glass described in Patent Document 1 does not contain an alkali metal. Therefore, the number of ions that move when glass and a silicon wafer are bonded by an anodic bonding method is small. In this case, since the Si—O—Si covalent bond is unlikely to form between silicon and glass, there is a concern that the bonding strength is insufficient. It is also predicted that the joining process will take a long time.

When using glass as an electronic component, it is important not only that silicon and glass can be reliably bonded by an anodic bonding method, but also the characteristics of the glass itself. One important characteristic of glass is the dielectric loss tangent (tan δ). As the dielectric loss tangent of glass increases, signal loss (delay) in the high frequency band (mainly the GHz band) increases. The dielectric loss tangent of glass is preferably less than 0.0050, for example, when measured at 25 ° C. and 1 GHz. Corning's glass has a dielectric loss tangent of about 0.0054, and development of glass having a dielectric loss tangent superior to this is expected.

Since the glass described in Patent Document 2 contains a relatively large amount of alkali metal (specifically, Li), its dielectric loss tangent is large.

According to the knowledge of the present inventors, the dielectric loss tangent decreases as the alkali metal content decreases. For example, if the content of Li ₂ O contained in the glass described in Patent Document 3 is adjusted to 1.40% by weight or less, the dielectric loss tangent of the glass when measured under the conditions of 25 ° C. and 1 GHz is 0.00. May be less than 0050. However, in order to satisfy the requirement of (Li ₂ O / Al ₂ O ₃ ) ≧ 0.9, it is necessary to reduce the content of Al ₂ O ₃ to 1.26% by weight or less. Al ₂ O ₃ is a component that forms a glass skeleton, and is also a component that improves the mobility of an alkali metal by taking four-coordination. Therefore, if the content of Al ₂ O ₃ is too small, the alkali metal mobility is lowered, and the anodic bondability is deteriorated.

Since the glass described in Patent Document 4 contains an appropriate amount (1.8 to 3.5% by weight in the examples) of Na ₂ O, it is presumed that anodic bonding is possible. However, according to the knowledge of the present inventors, when Na ₂ O is used alone, the dielectric loss tangent of the glass tends to be excessive.

The present invention has been made paying attention to such a conventional problem, and an object of the present invention is to provide a low expansion glass capable of anodic bonding and having a low dielectric loss tangent.

In this specification, the term “anodic bondability” includes not only the bonding strength but also the meaning of ease of anodic bonding. The ease of forming anodic bonding will be described later in detail.

As described above, an appropriate amount of alkali metal is indispensable to ensure excellent anodic bonding properties. However, alkali metals have the property of increasing the dielectric loss tangent of glass. That is, for glass containing an alkali metal, anodic bondability and dielectric loss tangent are essentially in a trade-off relationship.

Based on these findings, the present inventors have closely investigated the relationship between the type of alkali metal, the content of alkali metal, and the dielectric loss tangent of glass in the high frequency band (GHz band). As a result, it was found that Li has a lower ability to increase the dielectric loss tangent of glass compared to other alkali metals such as Na and K. As a result, the following present invention has been completed.

That is, the present invention
Displayed in mol%,
SiO ₂ : 55 to 75%,
B ₂ O ₃ : 5 to 17%,
Al ₂ O ₃ : 5 to 15%,
MgO: 0 to 10%,
CaO: 0 to 10%,
SrO: 0-5%
BaO: 0 to 1%,
ZnO: 0 to 6%,
Li ₂ O: 0.6-4%,
Na ₂ O: 0 to 1%,
K ₂ O: 0 to 1%,
SnO ₂ : 0 to 1%
Fe ₂ O ₃ : 0 to 5%,
TiO ₂ : 0-30%, and CeO ₂ : 0-10%,
Including
The total content of alkali metal oxides is 5 mol% or less,
displayed in mol%, the content of Li ₂ O, well above the total content of alkali metal oxides other than Li ₂ O,
Provided is a low expansion glass having a dielectric loss tangent of less than 0.0050 at measurement conditions of 25 ° C. and 1 GHz.

In another aspect of the present invention, the alkali metal is brought into contact with a molten salt containing a monovalent cation having an ionic radius larger than that of the alkali metal ion contained in the low expansion glass. Ions are exchanged with the monovalent cation to provide a tempered glass having a compressive stress layer formed on the surface.

According to the present invention, Li ₂ O is the most contained as the alkali metal oxide. Accordingly, the dielectric loss tangent of the glass is smaller than when only the same amount of alkali metal oxide other than Li ₂ O is contained. Further, (total content) The content of alkali metal oxides but is relatively small, other components such as Al ₂ O ₃ is properly adjusted. Therefore, even if the content of the alkali metal oxide is small, for example, the mobility of the alkali metal when forming the anodic bonding is sufficiently high. Therefore, the low expansion glass of the present invention has excellent anodic bonding properties. Thus, according to the present invention, it is possible to provide a low expansion glass having not only excellent anodic bonding properties but also low dielectric loss tangent. In addition, according to the present invention, there is provided a tempered glass in which a compression stress layer is formed on the surface by ion-exchange of alkali metal ions contained in the low expansion glass with monovalent cations having a larger ion radius. Can do.

Hereinafter, the reason for prescribing the range of the content of each component of the low expansion glass will be described. Unless otherwise specified, the numerical value representing the content (content rate) is expressed in mol%.

(SiO ₂ )
SiO ₂ is an essential component for forming a glass network. SiO ₂ is also a component that enhances the durability, particularly acid resistance, of the glass. Therefore, the content of SiO ₂ is too small acid resistance of the glass may be insufficient. Therefore, the lower limit of the content of SiO ₂ is 55%. The lower limit of the content of SiO ₂ is preferably 60%, more preferably 63%. On the other hand, if the content of SiO ₂ is too large melting properties of the glass may be reduced significantly. Therefore, the upper limit of the content of SiO ₂ is 75%. The upper limit of the content of SiO ₂ is preferably 72%, and more preferably 70%. The range of the content of SiO ₂ can be specified by any combination of these upper and lower limits.

(B ₂ O ₃ )
B ₂ O ₃ is an essential component that forms a glass network. If the content of B ₂ O ₃ is too small, the devitrification temperature is significantly increased, and the meltability of the glass may be significantly decreased. In addition, the productivity of glass may be affected. Therefore, the lower limit of the content of B ₂ O ₃ is 5%. The lower limit of the content of B ₂ O ₃ is preferably 7%, and more preferably 9%. On the other hand, if the content of B ₂ O ₃ is too large, the durability of the glass may be insufficient. Therefore, the upper limit of the content of B ₂ O ₃ is 17%. The upper limit of the content of B ₂ O ₃ is preferably 13%. The range of the content of B ₂ O ₃ can be specified by any combination of these upper and lower limits.

(Al ₂ O ₃ )
Al ₂ O ₃ is an essential component that plays a role of forming a glass network and a role of modifying the glass network. If the content of Al ₂ O ₃ is too small, phase separation may occur. Further, as described above, when the content of Al ₂ O ₃ is too small, the mobility of the alkali metal is lowered, and the anodic bondability may be greatly deteriorated. Therefore, the lower limit of the content of Al ₂ O ₃ is 5%. The lower limit for the content of Al ₂ O ₃ is preferably 8%. On the other hand, if the content of Al ₂ O ₃ is too large, the linear expansion coefficient and the devitrification temperature may be significantly increased. Therefore, the upper limit of the content of Al ₂ O ₃ is 15%. The upper limit of the content of Al ₂ O ₃ is preferably 13%, and more preferably 12%. The range of the content of Al ₂ O ₃ can be specified by any combination of these upper and lower limits.

Al ₂ O ₃ is contained in the low-expansion glass of the present invention more than Li ₂ O, regardless of whether it is expressed in mol% or mass%.

(Alkaline earth metal oxide)
Alkaline earth metal oxides, that is, MgO, CaO, SrO, and BaO are optional components that modify the glass network and are components that improve the meltability of the glass. If the content of the alkaline earth metal oxide is too large, the linear expansion coefficient may be significantly increased. Therefore, the upper limit of the content of MgO is, for example, 10%, preferably 7%, more preferably 5%. The upper limit of the content of CaO is, for example, 10%, preferably 8%, more preferably 7%. The upper limit of the content of SrO is, for example, 5%, preferably 3%, more preferably 2%. The upper limit of the content of BaO is, for example, 1%, preferably 0.5%. In particular, since BaO has a large load on the environment, the low expansion glass of the present embodiment may not substantially contain BaO.

“Substantially free” means not intentionally included unless, for example, it is inevitably mixed with industrial raw materials. Specifically, it means a content of less than 0.1%, preferably less than 0.01%.

On the other hand, appropriate amounts of MgO and CaO bring about the effect of lowering the devitrification temperature as well as the effect of improving the meltability of the glass. Therefore, MgO may be contained, for example, 1% or more, preferably 2% or more. Similarly, CaO may be contained, for example, 1% or more, preferably 2.5% or more, more preferably 3% or more.

Note that CaO and SrO have the ability to strongly bind alkali metals. Therefore, when there is too much these content, there exists a possibility of causing the significant fall of anodic bondability. In addition, since CaO and SrO have a large ability to change the linear expansion coefficient, if the content thereof is too large, it may be difficult to adjust the linear expansion coefficient to a desired range. Therefore, the upper limit of the total content of CaO and SrO is, for example, 9%, preferably 7%, more preferably 6%.

(ZnO)
ZnO is an optional component having the same effect as the alkaline earth metal oxide, and is generally also a component that improves glass forming ability. When there is too much content of ZnO, devitrification temperature may rise significantly. Therefore, the upper limit of the ZnO content is 6%, preferably 2.5%.

The total content of MgO, CaO, SrO, BaO and ZnO is, for example, 5 to 13%, preferably 7 to 13%, more preferably in consideration of the linear expansion coefficient, meltability, anodic bondability, and the like. It may be adjusted to a range of 9 to 11%.

The ranges of the contents of MgO, CaO, SrO, BaO and ZnO can be specified by any combination of the above upper limit and lower limit, respectively.

(Alkali metal oxide)
Alkali metal oxide is an essential component that improves anodic bonding. At the time of anodic bonding, alkali metal ions move to the cathode, thereby causing a covalent bond between non-crosslinked oxygen ions in the glass and silicon at the interface. The alkali metal oxide is a component that modifies the glass network, and has an effect of appropriately cutting the glass network, lowering the melting temperature of the glass, and keeping the viscosity of the glass melt low. On the other hand, if the content of the alkali metal oxide is too large, the linear expansion coefficient and the dielectric loss tangent may be significantly increased.

Here, not all alkali metal oxides have the same ability to increase the dielectric loss tangent. Among alkali metal oxides, Li ₂ O has a relatively low ability to increase the dielectric loss tangent of glass. Therefore, if Li ₂ O is mainly used as the alkali metal oxide, a glass having both excellent anodic bonding properties and low dielectric loss tangent can be provided. Since Li ⁺ has a high mobility during anodic bonding, the use of Li ₂ O as an essential alkali metal oxide is preferable.

Specifically, first, the total content of alkali metal oxides is set to 5% or less. In addition, the content of Li ₂ O is limited to a range of 0.6 to 4%. The content of Li ₂ O is expressed in mol% and exceeds the total content of alkali metal oxides other than Li ₂ O. By satisfying these conditions, it is possible to ensure excellent anodic bondability and prevent the dielectric loss tangent from becoming too high.

The total content of alkali metal oxides is preferably 3% or less. The upper limit of the content of Li ₂ O is preferably 3%, more preferably 2%. The lower limit of the content of Li ₂ O is preferably 1%. The range of the content of Li ₂ O can be specified by any combination of these upper and lower limits.

As an alkali metal oxide other than Li ₂ O, at least one selected from Na ₂ O and K ₂ O may be contained as an optional component. The upper limit of the content of Na ₂ O is, for example, 1%, preferably 0.5%, more preferably 0.25%. The upper limit of the content of K ₂ O is, for example, 1%, preferably 0.5%.

The low expansion glass of this embodiment may contain 0.05% or more of at least one selected from Na ₂ O and K ₂ O. The content of Na ₂ O and the content of K ₂ O are each smaller than the content of Li ₂ O. Na ₂ O may be contained in the low expansion glass at a ratio of 0.1% or more. Similarly, K ₂ O may be contained in the low expansion glass at a ratio of 0.1% or more. According to the knowledge obtained by the present inventors from the examples described later, when a small amount of Na ₂ O and / or K ₂ O is contained in the low expansion glass together with Li ₂ O, an increase in dielectric loss tangent is suppressed. However, excellent anodic bondability can be imparted to the low expansion glass.

The range of the content of Na ₂ O and K ₂ O can be specified by any combination of the above upper limit and lower limit, respectively.

From another point of view, when at least one selected from Na ₂ O and K ₂ O is contained in the low expansion glass, the ratio of the content of Li ₂ O to the total content of Na ₂ O and K ₂ O ( Li ₂ O / (Na ₂ O + K ₂ O)) can be a value greater than 2. Thereby, the above-described effects can be fully enjoyed. As an example, the upper limit of the ratio (Li ₂ O / (Na ₂ O + K ₂ O)) is 80. At this time, the content of Li ₂ O is 4%, and the content of Na ₂ O or K ₂ O is 0.05%.

As known to those skilled in the art, by mixing different types of alkali ions in the glass, the properties of the glass greatly deviate from the additivity. This phenomenon is called “mixed alkali effect”.

However, the present inventors have found that when a small amount of Na ₂ O and / or K ₂ O is contained together with Li ₂ O in a low expansion glass, the phenomenon in which the increase in dielectric loss tangent deviates from additivity is the usual mixing. It is different from the alkali effect and is considered to be a phenomenon peculiar to the high frequency band. The reason is as follows.

In general, the mixed alkali effect is prominent when the ratio of two types of alkali components is 1: 1. However, as will be apparent from the examples described later, the effect of suppressing the increase in dielectric loss tangent is obtained advantageously when Li ₂ O: Na ₂ O = 5: 1. The mixed alkali effect is considered to be a phenomenon based on alkali movement. On the other hand, at a frequency of 1 GHz, the alkali in the glass only deforms or vibrates, so it is unrelated to the movement of the alkali.

(SnO ₂ )
Since SnO ₂ has a clarification action, it may be contained in the low expansion glass at a ratio of 0.05% or more, preferably 0.1% or more, for example. However, if the SnO ₂ content is too large, devitrification and phase separation may occur. Therefore, the upper limit of the content of SnO ₂ is, for example, 1%, preferably 0.2%. The range of the content of SnO ₂ can be specified by any combination of these upper and lower limits.

(Fe ₂ O ₃ , TiO ₂ , CeO ₂ )
Usually, Fe is present in the glass in the state of Fe ²⁺ or Fe ³⁺ . Fe ³⁺ is a component that ^improves the ultraviolet absorption characteristics of glass, and Fe ²⁺ is a component that ^improves the heat ray absorption characteristics. Therefore, Fe is not essential, but may be used as a component for adjusting the optical properties of the glass. Moreover, Fe may be inevitably mixed by industrial raw materials. Fe, expressed as Fe ₂ O ₃ , may be contained in the low expansion glass at a ratio of 0.01% or more, preferably 0.5% or more, for example. However, if Fe is excessively contained, the low expansion glass may be excessively colored, or the difficulty in producing the low expansion glass may increase. This is because Fe absorbs infrared rays well and may increase the temperature non-uniformity of the glass melt. Therefore, the upper limit of the Fe content is expressed as Fe ₂ O ₃ , for example, 5.0%, preferably 2.0%, more preferably 1.0%.

When using the low expansion glass of this embodiment as an electronic component, the low expansion glass may be processed with a laser. In this case, the low expansion glass is required to have a property of absorbing a laser. A small amount of Fe facilitates laser absorption and facilitates processing using a laser, such as drilling. For the same purpose, TiO ₂ and / or CeO ₂ may be contained in the low expansion glass. That is, the low expansion glass of the present embodiment may include at least one selected from the group consisting of Fe ₂ O ₃ , TiO ₂ and CeO ₂ as a laser absorption component. Since Fe has a clarification action and is extremely inexpensive, the use of Fe ₂ O ₃ as a laser absorbing component is preferred.

For example, adjusting the content of the laser absorbing components (Fe ₂ O ₃ , TiO ₂ and CeO ₂ ) so that the absorption coefficient of the low expansion glass with respect to a laser having a specific wavelength λ of 535 nm or less is 50 cm ⁻¹ or less. Can do. The absorption coefficient is preferably in the range of 3 to 20 cm ⁻¹ , more preferably 3 to 10 cm ⁻¹ .

Examples of the laser for processing the low expansion glass include Nd: YAG laser harmonics, Nd: YVO ₄ laser harmonics, and Nd: YLF laser harmonics. The harmonic is, for example, a second harmonic, a third harmonic, or a fourth harmonic. The wavelength of the second harmonic of these lasers is in the vicinity of 532 to 535 nm, the wavelength of the third harmonic is in the vicinity of 355 to 357 nm, and the wavelength of the fourth harmonic is in the vicinity of 266 to 268 nm. is there. By using these lasers, low expansion glass can be processed at low cost.

Taking the above viewpoint into consideration, the lower limit of the content of TiO ₂ is, for example, 1%, preferably 3%. The lower limit of the CeO ₂ content is, for example, 0.2%, preferably 0.5%. However, if these are excessively contained, devitrification and phase separation may occur. Therefore, the upper limit of the content of TiO ₂ is, for example, 30%, preferably 20%, more preferably 10%. Similarly, the upper limit of the content of CeO ₂ is, for example, 10%, preferably 5%, more preferably 2%.

The range of the content of Fe ₂ O ₃ , TiO ₂ and CeO ₂ can be specified by any combination of the above upper limit and lower limit, respectively.

_The absorption coefficient per 1mol of Fe ₂ O 3, TiO ₂ and CeO _2, ^{respectively,} 12.5 cm -1, is 1.0 cm ^-1 and 5.9 cm ^-1. When the contents of Fe ₂ O ₃ , TiO ₂ and CeO ₂ are X, Y and Z, respectively, the absorption coefficient based on these components is represented by “12.5X + Y + 5.9Z”. The maximum value of (X + Y + Z) that satisfies 3 <(12.5X + Y + 5.9Z) <50 is 30 (mol%), and the minimum value is 0.3 (mol%).

The low expansion glass of the present invention may consist essentially of the components described above. Moreover, the low expansion glass of this invention does not need to contain substantially components other than an above-described component. Furthermore, the low expansion glass of this invention may consist of an above-described component.

(Other ingredients)
In order to produce a low expansion glass, a generally known fining agent, for example, a chloride such as NaCl, a fluoride such as CaF ₂ , arsenous acid, antimony oxide or the like may be added in a small amount to the raw material. The component of the fining agent may remain in the low expansion glass as long as it does not significantly affect the characteristics such as dielectric loss tangent and bonding strength. However, it is preferable that substances having a large environmental load, such as arsenous acid and antimony oxide, are not substantially contained.

(Dielectric loss tangent)
In recent years, the use of devices called MEMS (Micro Electro Mechanical Systems) produced by making full use of semiconductor technology has been expanded mainly in the fields of automobiles, mobile phones, biochemistry, and the like. Acceleration sensors, pressure sensors, etc. have already been applied to automobiles and the like, and the application range has expanded to optical MEMS, such as optical waveguide sensors and optical switching devices. As one of the components of MEMS, the low expansion glass of the present invention can be widely used for applications such as an electronic substrate, an electrically insulating substrate, a pedestal for supporting silicon (silicon wafer).

デバイス Devices using low expansion glass often handle high frequency signals. Therefore, the low expansion glass preferably has a dielectric loss tangent of less than 0.0050 under the measurement conditions of an air temperature of 25 ° C. and a frequency of 1 GHz. The lower limit of the dielectric loss tangent is not particularly limited, but a dielectric loss tangent less than 0.001 is unrealistic.

(Devitrification temperature)
The low expansion glass of the present embodiment has a devitrification temperature in the range of 950 to 1150 ° C., for example, by having the composition in the above range. When the devitrification temperature is low, the glass can be produced stably. Of course, it is not essential that the devitrification temperature is within the above range.

(Average linear expansion coefficient)
The low expansion glass of this embodiment preferably has an average coefficient of linear expansion in the range of 32 × 10 ⁻⁷ / ° C. to 40 × 10 ⁻⁷ / ° C. when measured in the range of 25 to 450 ° C. Yes. If the average linear expansion coefficient is within this range, the problem of residual stress after anodic bonding is unlikely to occur, and the strength of anodic bonding between glass and silicon is easily ensured. In addition, the low expansion glass of the present embodiment is less likely to be warped or damaged due to stress at the bonded portion even when bonded to silicon or the like by a method other than anodic bonding. Moreover, the low expansion glass of this embodiment is less likely to cause a problem due to thermal stress even when a silicon thin film is formed on the surface and a circuit such as a thin film transistor is further formed. The average linear expansion coefficient can be obtained by measuring the elongation of a sample between 25 ° C. and 450 ° C. with a differential thermal dilatometer and dividing the elongation by the value of temperature change.

(Chemical enhancement)
The low expansion glass of the present invention can be chemically strengthened, and the tempered glass of the present invention can be obtained by chemically strengthening the low expansion glass of the present invention. Chemical strengthening is a technique for forming a compressive stress layer on the glass surface by replacing alkali metal ions contained on the glass surface with monovalent cations having a larger radius.

The tempered glass of the present invention can be used, for example, as a circuit board material. Specifically, a through-hole is provided in tempered glass, one surface is bonded to silicon, and a conductive wiring material containing a metal such as copper, aluminum, or silver is connected to silicon through the through-hole from the other surface. A usage pattern for wiring is conceivable. In such a usage pattern, since the metal generally has a large coefficient of linear expansion, there is a possibility that breakage may occur due to the thermal stress difference between the low expansion glass of the present invention and the wiring material. However, according to the tempered glass of the present invention, the risk of breakage due to the thermal stress difference with the wiring material can be reduced by the compressive stress layer formed on the surface. Moreover, if the tempered glass of this invention is used as a glass substrate of the panel part of a touch panel display, for example, since the surface of the tempered glass is strengthened by the compression stress layer, the protective glass of a touch panel display may be made unnecessary.

The chemical strengthening of the low expansion glass of the present invention can be performed by bringing the low expansion glass into contact with a molten salt containing a monovalent cation having an ionic radius larger than that of the alkali metal ion contained in the low expansion glass. Thereby, the alkali metal ion contained in the low expansion glass of the present invention is substituted with a monovalent cation having a larger ion radius, and a compressive stress layer is formed on the surface. Specifically, lithium ions or sodium ions contained in the low expansion glass of the present invention are replaced with monovalent cations having a larger ion radius. As the molten salt, a molten salt of sodium nitrate or potassium nitrate, or a mixed salt thereof can be used. It is preferable to use a molten salt of potassium nitrate from the viewpoint of imparting a high compressive stress to the compressive stress layer. Moreover, when using the tempered glass of this invention by said usage form, it is preferable to chemically strengthen with respect to the low expansion glass in which the through-hole was formed previously. However, you may make it form a through-hole in tempered glass after performing chemical strengthening.

In the tempered glass of the present invention, the 50% fracture load described later is preferably 1500 gf (gram force) or more, more preferably 1700 gf or more, and further preferably 1800 gf or more.

The depth of the compressive stress layer formed on the tempered glass of the present invention is preferably 5 μm or more. The compressive stress applied to the outermost surface is preferably 200 MPa or more.

The relationship between the above components that can be contained in the low expansion glass of the present invention and the chemical strengthening property will be described below. When the content of Al ₂ O ₃ is too small decreases the mobility of the alkali metals, the chemical reinforcing may be reduced. Therefore, the lower limit of the content of Al ₂ O ₃ is 5% as described above, and preferably 8%.

CaO and SrO have the ability to bind alkali metals. Therefore, when there is too much content of these, chemical strengthening property may fall. Therefore, the upper limit of the total content of CaO and SrO is, for example, 9%, preferably 7%, more preferably 6%, as described above.

The alkali metal oxide is a component that improves chemical strengthening properties. Alkali metal ions contained in the glass derived from the alkali metal oxide are components that improve the glass strength by applying compressive stress to the surface by exchanging with monovalent cations having a larger ion radius. Since Li ⁺ easily moves during chemical strengthening, it is preferable to use Li ₂ O as an essential component among alkali metal oxides. When the total content of alkali metal oxides and the content of Li ₂ O satisfy the above conditions, chemical strengthenability can be ensured. From the viewpoint of improving chemical strengthenability, the content of Li ₂ O is preferably 1 to 4%, more preferably 1.2 to 3.5%, and even more preferably 1.5 to 3%.

Further, since the diffusion rate of sodium ions and potassium ions exchanged during chemical strengthening can be increased and the depth of the compressive stress layer can be increased, other alkali metal oxides (Na ₂ O, K) can be used together with Li ₂ O. ₂ O). From the viewpoint of increasing the depth of the compressive stress layer, it is preferable to include 0.05% or more of at least one selected from Na ₂ O and K ₂ O.

On the other hand, sodium ions have a larger ionic radius than lithium ions, and the compressive stress on the glass surface generated by exchange with potassium ions in the molten salt is smaller than lithium ions. Further, sodium ions do not generate compressive stress when exchanged with sodium ions in the molten salt. The ionic radius of potassium ions is larger than that of sodium ions, and no compression stress is generated by exchange with potassium ions in the molten salt. Potassium ions, on the other hand, lower the compressive stress when exchanged with sodium ions in the molten salt, and in some cases generate tensile stress. Therefore, from the viewpoint of generating a sufficient compressive stress, preferably the ratio of Li ₂ O is greater than 2 in _{_{Li 2 O / (Na 2 O}} + K 2 O). The alkali metal oxide that coexists with Li ₂ O is preferably Na ₂ O rather than K ₂ O.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

A batch was obtained by weighing and mixing oxides, carbonates, nitrates, sulfates and the like as glass raw materials so that the composition shown in Example 1 of Table 1 was obtained. The obtained batch was put in a platinum crucible and heated in an electric furnace set with an atmospheric temperature of 1400 to 1650 ° C. to melt the batch. The molten glass was kept for 4 to 5 hours in the crucible with proper stirring. Thereafter, molten glass was poured into a carbon or stainless steel mold and gradually cooled to 25 ° C. Thereby, the glass sample of Example 1 was obtained. In the same manner, glass samples of Examples 2 to 23 and Comparative Examples 1 to 9 were obtained.

(Devitrification temperature)
The devitrification temperature of the glass of an Example and a comparative example was measured with the following method. Glass crushed to a particle size of 1.0 to 2.8 mm was placed in a platinum boat and heated in an electric furnace with a temperature gradient (900 to 1400 ° C.) for 24 hours. The devitrification temperature was determined from the maximum temperature of the electric furnace corresponding to the crystal appearance position. The results are shown in Tables 1 to 3. Note that the temperature in the electric furnace is determined in advance, and the glass placed in a predetermined place is heated at a temperature corresponding to the place. The devitrification temperature is a temperature at which crystals start to grow and grow in the molten glass.

(Calculation of average linear expansion coefficient)
In order to measure the linear expansion coefficient, a cylindrical test piece having a diameter of 5.0 mm and a length of 18.0 mm was cut from each glass sample. The coefficient of thermal expansion of each test piece was measured using a differential thermal dilatometer, and the average coefficient of linear expansion from 25 to 450 ° C. was calculated. The results are shown in Tables 1 to 3.

(Measurement of dielectric loss tangent)
In order to measure the dielectric loss tangent, a prismatic test piece having a size of 1.4 mm × 1.4 mm × 80.0 mm was cut from each glass sample. The dielectric loss tangent (tan δ) of the test piece was measured using a network analyzer (E8361A manufactured by Agilent Technologies) and a cavity resonator. The measurement frequency was 1 GHz, the measurement temperature was 25 ° C., and the humidity was 50%. The results are shown in Tables 1 to 3.

(Measurement of anodic bonding current)
From each glass sample, a glass substrate having a flat surface with a width of 50 mm × 50 mm was cut out. Next, a silicon wafer having the same dimensions as the glass substrate was superimposed on the glass substrate, and the glass substrate and the silicon wafer were brought into contact with a carbon electrode heated to 400 ° C. After sufficiently heating the glass substrate and the silicon wafer, a voltage of 1000 V was applied between the glass substrate and the silicon wafer (the glass substrate side is the cathode). And the electric current which flowed between the glass substrate and the silicon wafer in the period until 5 minutes pass after starting the application of a voltage was measured. However, since the current value varies depending on the dimensions of the carbon electrode, the obtained current value was converted to a current value per unit area. Furthermore, the obtained current value was converted into a current value per unit time. The results are shown in Tables 1 to 3.

The measured anodic bonding current does not directly represent the strength of the anodic bonding. However, those skilled in the art often measure the anodic bonding current as an indicator of anodic bonding properties. This is because a large anodic bonding current means that the mobility of alkali metal is high, which means that anodic bonding can be easily performed and high-strength anodic bonding can be formed. According to the knowledge of the present inventors, when the value obtained by measuring and converting the anodic bonding current under the above-described conditions is ² μA / mm ² · min or less, the bonding speed is very slow (anodic bonding process). It takes a long time) and poor bonding may occur.

(Chemical enhancement)
The glass samples of Example 1, Example 8, and Example 23 shown in Tables 1 and 2 were cut into a shape of 130 mm × 70 mm × 0.7 mm. The cut glass sample was immersed in a molten salt of potassium nitrate at 480 ° C. for 8 hours for chemical strengthening to obtain a strengthened glass sample.

The 50% breaking load was measured for the tempered glass sample and the glass sample not subjected to chemical strengthening by the following method. In an environment with a temperature of 25 ° C and a humidity of 60%, a micro Vickers hardness tester (MVK-G2 manufactured by Akashi Co., Ltd.) is used for any five locations on the surface of the glass sample using a diamond indenter (a square pyramid indenter with a facing angle of 136 °) A 300 gf load was applied for 15 seconds to create a square impression. About the sample glass which added the load, it left still for 5 minutes except the load. Thereafter, it was observed with an optical microscope whether cracks were generated on the extended line connecting the center of the square of the indentation and the vertex of the square. The presence or absence of cracks was confirmed at each vertex of the five indentations, and the fracture probability P was determined by dividing the number of cracks generated by the total number of vertices of 20. The load applied to the glass sample was changed to 500 gf, 1000 gf, and 2000 gf, and the fracture probability P of the glass sample with respect to each load was similarly determined. With respect to two loads adjacent to each other across the fracture probability P = 50%, a fracture load with a fracture probability P of 50% was obtained by linear interpolation from the respective fracture probabilities, and was set as the 50% fracture load of the glass sample. The results are shown in Table 4.

Further, with respect to the tempered glass sample obtained by performing chemical strengthening on Example 23, the compressive stress on the outermost surface and the depth of the compressive stress layer were measured using a surface stress meter “FSM-6000” manufactured by Orihara Seisakusho. The measurement results are also shown in Table 4.

As shown in Tables 1 to 3, Examples 1 to 23 mainly containing Li ₂ O as an alkali metal oxide all exhibited low dielectric loss tangents (less than 0.0050). In addition, as long as the measurement was performed, each example had an anode junction current of ² μA / mm ² · min or more, an average linear expansion coefficient in the range of 32 × 10 ⁻⁷ / ° C. to 40 × 10 ⁻⁷ / ° C., and A sufficiently low devitrification temperature was exhibited.

Example 8 contained 3% Li ₂ O and exhibited a dielectric loss tangent of 0.0049. Comparative Example 1 contained 1.5% Na ₂ O and exhibited a dielectric loss tangent of 0.0057. Comparative Example 2 contained 1.5% K ₂ O and exhibited a dielectric loss tangent of 0.0059. That is, Example 8 exhibited a dielectric loss tangent smaller than those of Comparative Examples 1 and 2 even though it contained twice the molar amount of alkali metal oxide as Comparative Examples 1 and 2. This suggests that Li ₂ O can be advantageously used as the alkali metal oxide in order to avoid an excessive increase in the dielectric loss tangent of the glass.

Examples 11 and 18 have the same composition except for alkali metal oxides. Example 11 contains 1.5% Li ₂ O as the alkali metal oxide. Example 18 contains 1.25% Li ₂ O and 0.25% Na ₂ O as the alkali metal oxide. That is, the content of the alkali metal oxide of Example 11 is equal to the content of the alkali metal oxide of Example 18. Nevertheless, the dielectric loss tangent of Example 11 was 0.0034, the dielectric loss tangent of Example 18 was 0.0032, and the dielectric loss tangent of Example 18 was 0.0002 smaller than that of Example 11. This suggests that when a small amount of Na ₂ O is contained in the low expansion glass together with Li ₂ O, it is possible to impart excellent anodic bondability to the low expansion glass while suppressing an increase in dielectric loss tangent. . A similar phenomenon was seen between Examples 1 and 2. Moreover, it is predicted that the same phenomenon appears when a small amount of K ₂ O is used.

This phenomenon appears remarkably when the ratio of the content of Li ₂ O to the total content of Na ₂ O and K ₂ O (Li ₂ O / (Na ₂ O + K ₂ O)) is greater than 2. It is predicted. For example, the ratio of Example 16 is 2, the dielectric loss tangent of Example 16 is 0.0034, and is equal to the dielectric loss tangent of Example 11. In Example 16, it is not clear whether a small amount of K ₂ O is contained together with an appropriate amount of Li ₂ O, so that the effect of suppressing the increase in dielectric loss tangent appears.

Examples 11, 13, and 14 have substantially the same composition except for the content of Al ₂ O ₃ . With the increase in the content of Al ₂ O ₃ , the anodic bonding current increased. This suggests that Al ₂ O ₃ has a function of increasing alkali metal mobility.

Comparative Example 3 contains 1.5% Li ₂ O and 1.5% Na ₂ O. Comparative Example 4 contains 1.5% Li ₂ O and 1.5% K ₂ O. That is, Comparative Examples 3 and 4 each contain the same molar amount of alkali metal oxide as Example 8. And the comparative example 3 showed the dielectric loss tangent of 0.0049. This value is equal to the dielectric loss tangent of Example 8. Comparative Example 4 showed a dielectric loss tangent of 0.0052. This value is smaller than the dielectric loss tangent (0.0059) of Comparative Example 2 containing K ₂ O alone as an alkali metal oxide.

The above fact is that when Na ₂ O or K ₂ O is used in combination with Li ₂ O, a smaller dielectric loss tangent can be obtained with reference to the dielectric loss tangent when Na ₂ O or K ₂ O is used alone. It suggests. However, the average linear expansion coefficient of Comparative Example 3 was larger than the average linear expansion coefficient of Example 8. Moreover, the devitrification temperature of Comparative Example 3 was lower than the devitrification temperature of Example 8. Further, the dielectric loss tangent of Comparative Example 4 was higher than the preferable dielectric loss tangent reference value (0.0050), and similarly to Comparative Example 3, it showed a large average linear expansion coefficient and a low devitrification temperature.

The absorption coefficients of Examples 1, 2, and 19 to 22 at a wavelength of 355 nm were measured, and were found to be 1.39 cm ⁻¹ , 1.61 cm ⁻¹ , 8.77 cm ⁻¹ , 3.87 cm ⁻¹ , 3.93 cm ⁻ , respectively. ¹ and 6.46 cm ⁻¹ . The absorption coefficient was calculated according to the following method. A test piece of 20 mm × 20 mm × 3 mm was cut out from each glass sample. Using these test pieces, transmittance and reflectance at a wavelength of 355 nm were measured. The absorption coefficient was calculated from the measured transmittance, reflectance, and test piece thickness (3 mm).

As shown in Table 4, the tempered glass samples obtained by chemically strengthening the glass samples of Example 1, Example 8 and Example 23 have a considerably larger 50% fracture load than the glass samples not subjected to chemical strengthening. The value is shown. Further, the 50% fracture load of the tempered glass sample obtained by chemically strengthening the glass sample of Example 8 having a Li ₂ O content higher than that of Example 1 is the tempered glass obtained by chemically strengthening the glass sample of Example 1. It was larger than that of the sample. This suggests that the strength of the tempered glass as the Li 2 _O content in the low-expansion glass is large becomes high. Further, in the tempered glass sample of Example 23, a compressive stress layer depth that was not observed in the tempered glass sample of Example 8 was observed. This suggests that the compressive stress layer is deepened by allowing Na ₂ O to coexist with Li ₂ O.

The low expansion glass and tempered glass of the present invention can be widely used for applications such as an electronic substrate, an electrically insulating substrate, a pedestal for supporting silicon (silicon wafer).

Claims

Displayed in mol%,
SiO 2 : 55 to 75%,
B 2 O 3 : 5 to 17%,
Al 2 O 3 : 5 to 15%,
MgO: 0 to 10%,
CaO: 0 to 10%,
SrO: 0-5%
BaO: 0 to 1%,
ZnO: 0 to 6%,
Li 2 O: 0.6-4%,
Na 2 O: 0 to 1%,
K 2 O: 0 to 1%,
SnO 2 : 0 to 1%
Fe 2 O 3 : 0 to 5%,
TiO 2 : 0-30%, and CeO 2 : 0-10%,
Including
The total content of alkali metal oxides is 5 mol% or less,
displayed in mol%, the content of Li 2 O, well above the total content of alkali metal oxides other than Li 2 O,
A low expansion glass having a dielectric loss tangent of less than 0.0050 under measurement conditions of 25 ° C. and 1 GHz.
The low expansion glass according to claim 1, wherein the content of Li 2 O is in the range of 1 to 4 mol%.
The low expansion glass according to claim 1, comprising 0.05% or more of at least one selected from Na 2 O and K 2 O, expressed in mol%.
Including at least one selected from Na 2 O and K 2 O;
The low expansion glass according to claim 1, wherein a ratio of the content of Li 2 O to the total content of Na 2 O and K 2 O (Li 2 O / (Na 2 O + K 2 O)) is greater than 2.
The low expansion glass according to claim 1, wherein the total content of MgO, CaO, SrO, BaO and ZnO is in the range of 5 to 13%, expressed in mol%.
The low-expansion glass according to claim 1, wherein the total content of CaO and SrO is 9% or less, expressed in mol%.
Including at least one selected from the group consisting of Fe 2 O 3 , TiO 2 and CeO 2 as a laser absorption component,
The low expansion glass according to claim 1, wherein the content of the laser absorbing component is adjusted so that the absorption coefficient of the low expansion glass with respect to a laser having a specific wavelength λ of 535 nm or less is 50 cm -1 or less.
2. The low expansion glass according to claim 1, wherein the average linear expansion coefficient at 25 to 450 ° C. is in the range of 32 to 40 × 10 −7 / ° C.
Contacting the low expansion glass according to any one of claims 1 to 8 with a molten salt containing a monovalent cation having an ionic radius larger than that of an alkali metal ion contained in the low expansion glass, Tempered glass having a compressive stress layer formed on the surface by ion exchange of alkali metal ions with the monovalent cation.
The tempered glass according to claim 9, wherein the molten salt is potassium nitrate.
The tempered glass according to claim 9, wherein the compressive stress of the compressive stress layer is 200 MPa or more.