JPH068189B2 - Oxide dielectric material - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an oxide dielectric material, and more specifically, it is excellent in electrical properties and mechanical properties, and particularly excellent for circuit boards capable of firing at low temperature. Oxide dielectric material.

[Technical Background of the Invention and its Problems] With the development of microelectronics (ME), miniaturization of office automation equipment and home electronics equipment has been rapidly promoted, and miniaturized microelectronic equipment has become a familiar existence. is there. A relatively high-density multilayer wiring board is widely used in microelectronic devices, and alumina ceramics have been mainly used as the material from the viewpoint of electrical characteristics, mechanical characteristics, and mass productivity. Such a multilayer wiring board can be obtained by alternately laminating dielectric layers and conductor layers, which normally have a role of interlayer insulation, and then firing them integrally.

Alumina (Al ₂ O ₃ ) has excellent insulation characteristics, but the firing temperature is as high as 1500 to 1600 ℃, so the conductor layers that can be used are molybdenum (Mo), tungsten (W), etc. that can withstand this firing temperature. Limited to those made of refractory metals. This M
Since o, W, etc. have a large specific resistance, there is a limit to the reduction of the wiring width, which not only goes against the demand for downsizing of the device by high-density wiring, but also uses a high temperature in a reducing atmosphere for firing. Therefore, it becomes difficult to maintain and manage the firing apparatus, which hinders the reduction of man-hours.

On the other hand, platinum-silver (Pt-Ag), which has a smaller specific resistance than W, Mo, etc.
Considering the use of a paste of silver-gold (Ag-Au), copper (Cu), etc., it is desired that the firing temperature of the dielectric material is about 1000 ° C or lower. In response to such demands, there is one that uses a glass-based ceramic containing lead oxide as a main component as a dielectric (Japanese Patent Laid-Open No. 58-78496). This material is Al ₂ O ₃
Although the firing temperature is lower than that of, it is not yet sufficient.
Further, in a system containing lead oxide, the lead oxide is partially reduced during firing in a low partial pressure oxygen atmosphere (for Cu paste sintering), and is precipitated as metallic lead. This significantly lowers the volume resistivity of the insulating layer made of a dielectric material, causing a signal leak between the wirings.

Furthermore, as high-density wiring and higher speed have progressed due to the miniaturization of the device, the influence of the dielectric layer relating to signal seeding cannot be ignored. For example, the permittivity (ε) greatly affects the signal propagation delay time (general formula τ: delay time per 1 cm) and ε are preferably small. Further, the dielectric loss (tan δ) greatly affects the signal loss, and when tan δ is large, an electromagnetic field is formed in the dielectric layer around the wiring by the signal current and converted into heat energy, which leads to signal loss. This thermal energy leads to a rise in the temperature of the substrate, which causes troubles such as IC chip destruction and solder melting. Therefore, it is desired that tan δ be small.

It is desirable that the dielectric constant and the dielectric loss of the dielectric material used for such a substrate be small, and conventional Al ₂ O ₃ and glass-based ceramics (ε: 7 to 20, tan δ: 2 × 10 ⁻³ to 4 × 10 6). ^-3
(At 1MHz)) was not enough.

[Object of the Invention] An object of the present invention is to solve the above-mentioned problems, and to provide an oxide dielectric material which has excellent electrical properties and mechanical properties and can be fired at a low temperature.

[Outline of the Invention] In the present invention, Mg, Si, B and Ba are converted into oxides, respectively, and M
Constituting 20-40% by weight of gO, 34-40% by weight of SiO _2, 9-28% by weight of BaO and 4-12% by weight of B ₂ O ₃ and constituting a glass ceramic of Mg ₂ SiO ₄ forsterite and barium borosilicate glass. And an oxide dielectric material.

Silicon dioxide (SiO ₂ ) in the dielectric material of the present invention plays a role of forming a solid solution with magnesium oxide during firing, forming Mg SiO ₂ forsterite, and forming a melt with boron oxide and barium oxide. If the ratio converted to SiO ₂ is less than 34% by weight, the magnesium oxide and the rest of the components will be separated and firing will not be possible, and if it exceeds 40% by weight, the volume resistance will deteriorate due to migration of the conductor paste. Occurs. It is preferably 36 to 38% by weight.

Magnesium oxide (MgO) plays a role of imparting mechanical strength to the dielectric material of the present invention by forming a compound by partially forming a solid solution with silicon dioxide. If it is less than 20 wt% in terms of MgO is generally falls below the 15 Kg / mm ² required 6 Kg / mm ² with a sufficient flexural resistance degree can not be obtained, when it exceeds 40 wt% in terms of MgO is Sintering below 1000 ° C becomes impossible and low temperature sintering cannot be achieved. It is preferably 27 to 32% by weight.

Barium oxide acts as a network-modifying oxide on a network-forming oxide such as silicon dioxide or boron oxide, which forms glass by itself, forms a stable glass phase, and plays a role of lowering the sintering temperature. If it is less than 9% by weight in terms of BaO, the sintering temperature rises, making it difficult to perform low-temperature sintering at 1000 ° C or lower.
If it exceeds 28% by weight in conversion, foaming phenomenon occurs during sintering, and the mechanical strength decreases to 15 kg / mm ² or less. It is preferably 16 to 20% by weight.

Boron oxide becomes a network-forming oxide and forms a glass phase with silicon dioxide and barium oxide. It also plays a role in promoting the sintering of the compound of magnesium oxide and silicon dioxide and the glass to obtain both glass-ceramics. If it is less than 4% by weight, low temperature sintering at 1000 ° C or less becomes difficult, and if it exceeds 12% by weight, there are many fluid components and it becomes impossible to maintain the molded shape, and bubbles remain on the surface and paste Printability, accuracy, etc. It is preferably 7 to 9% by weight.

The material of the present invention may be obtained by mixing each constituent element with an oxide or a salt that changes to an oxide by firing as a raw material, and firing and then sintering, or Mg ₂ SiO ₄ and B ₂ O ₃ —SiO _{2. 2-} BaO glass may be used as a raw material, crushed, mixed and sintered. In this case, it is difficult to sinter Mg ₂ SiO ₄ alone, and a sintering aid such as Al ₂ O ₃ is generally contained. Usually 1 to 3 wt% in Mg ₂ SiO ₄
Included to some extent. If too much, the firing temperature of the material of the present invention
Although it is as high as about 1000 ° C. or higher, it does not have a bad influence on the material of the present invention as long as the amount is about the amount of the sintering aid. Further, the glass component also contains an unavoidable component in the production, but no problem occurs if it is in the amount of impurities.
For example, CaO, SrO, K ₂ O, TiO ₂ , Fe ₂ O ₃ , Na ₂ O, ZrO _{2 and the} like can be mentioned. Usually 5% by weight or less, preferably 2% by weight
There is no problem if it is below. It may also contain PbO, but as mentioned above, it adversely affects the electrical characteristics.
The limit is about 0.1% by weight.

The material of the present invention constitutes a glass ceramic of Mg ₂ SiO ₄ and B ₂ O ₃ —SiO ₂ —BaO glass. Although the amount of Mg ₂ SiO ₄ is determined almost by the amount of MgO, when Mg ₂ SiO ₄ is in the range of 40 to 80% by weight, it is possible to obtain those having excellent properties such as mechanical strength. Since it is most excellent in the vicinity of 60% by weight, the range of 55 to 65% by weight is the more preferable range. If the amount of glass is large, the mechanical strength will be poor, and if it is small, the sintering temperature will be high.

Next, a method for producing the oxide derivative material of the present invention will be described.

A predetermined amount of Mg ₂ SiO ₄ forsterite and barium borosilicate glass was weighed, and an average particle size of 1.0 to 1.
Mix and pulverize to about 9 μm to obtain raw material powder. Next, a binder, a solvent and the like are added to this powder to make a slurry. The binder and solvent can be appropriately selected, for example, PVB (polyvinyl butyral) as a binder 5 to 20% by weight, solvent 1,1,1-trichloroethane 25 to 35% by weight, n-butanol to 100% by weight of raw material powder. 10-22% by weight, tetrachloroethylene 8-19% by weight,
Tributyl phosphate of 4 to 13% by weight is used.
At the time of mixing, the viscosity should be about 500 cps because of uniform dispersion of the raw materials. Thereafter, this slurry is degassed, air dissolved in the slurry is degassed, and the viscosity is set to about 20000 cps in order to flatten the surface of the green sheet formed in a later step and to adjust the strength and the like.

Using the slurry, a green sheet is prepared by a general method, and firing is performed in the air and a nitrogen atmosphere to obtain the oxide derivative material of the present invention.

In the above-mentioned method, forsterite and glass were used as raw materials, but the constituent raw materials (MgO, SiO ₂ , BaO, B ₂ O ₃ or various salts replacing oxides by firing) are mixed,
Forsterite may be formed by baking or the like. A slight deviation from the stoichiometric ratio does not affect the present invention.
Further, in this case, it is effective to contain 1 to 3% by weight of Al ₂ O ₃ as a sintering aid of Mg ₂ SiO ₄ .

Especially SiO 36-33 wt%, MgO 27-32 wt%, BaO 16-20
%, B ₂ O ₃ containing 7 to 9% by weight is ε: 6.8
~ 7.0, tan δ: 4 × 10 ⁻⁴ or less, volume resistance: 7 × 10 ¹⁴
It is particularly preferable because it has the above characteristics and can be fired at a low temperature of 960 ° C. or lower.

Since the dielectric material of the present invention does not contain lead oxide, there is no fear of precipitation of metallic lead, and the firing atmosphere is not selected. Therefore, various conductor pastes can be used, and the advantage of manufacturing a circuit board is great.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Examples of the Invention] Examples 1 to 9 Forsterite (Mg ₂ SiO ₄ ) and barium borosilicate glass were weighed in a predetermined ratio, and an average particle size of 1.0 to 2.0 μm was obtained using a nonaqueous wet mixing mill or the like. Mix and pulverize to a degree,
The raw material powder was used. Next, PVB (polyvinyl butyral) as a binder, 1,1,1-trichloroethane, n-butanol, and tetrachloroethylene as a solvent are added to this raw material powder.
Tributyl phosphate and the like were added to adjust the slurry.
The viscosity was set to about 500 cps for uniform dispersion. Thereafter, this slurry was degassed, air dissolved in the slurry was degassed, and the viscosity was set to about 20000 cps in order to flatten the surface of the green sheet formed in a later step and adjust the strength.

Similarly, those outside the scope of the present invention (Comparative Examples 1 to 5) were also produced.

Using this slurry, a green sheet was prepared by a general method. The characteristics are shown in the table. The firing was performed in the air and a nitrogen atmosphere to obtain the oxide derivative material of the present invention.

ε, tanδ and ρ are printed concentrically with 325 mesh screen printing of Ag paste on both sides of a disc-shaped sample, dried and then baked at 750 ° C for 20 minutes in the air, 17.5m
The measurement was performed by forming a circular electrode of mφ × 15 μm. ε, tanδ
Is the value at 1MHz, and ρ is 10 ° C at 25 ° C and 50% humidity.
It is the minimum value after 00 V application for 1 minute.

In the table, composition after sintering is also shown. Al ₂ O ₃
Is a sintering aid in forsterite, and impurities are alkali metals, ZnO, and the like.

In all cases, PbO was 0.07% by weight or less.

As is clear from the table, the dielectric material of the present invention can be sintered at a low temperature of 1000 ° C. or lower, and has a resistance strength of 15 kg /
mm ² or more, excellent mechanical properties, dielectric constant (ε): 7-8.
0, dielectric loss tangent (tan δ): 3 × 10 ^{−4 to} 6 × 10 ^−4, and volume resistance (Rv): 9 × 10 ^{13 to} 1.3 × 10 ¹⁵ , electrical characteristics should be satisfied. Therefore, in order to be able to fire those having such good characteristics at a low temperature,
For example, conventional tungsten (W) as a conductor paste,
Instead of molybdenum (Mo), copper (Cu), silver (Ag) -palladium (P
d), low resistance material such as silver (Ag) -gold (Au) and resistance paste such as RuO can be used, and high density wiring aiming at downsizing of the device and reduction of the number of manufacturing steps can be achieved. .

In contrast, Comparative Example 5 satisfies the required mechanical properties, but the firing temperature is 1000 ° C. or higher, and Comparative Example 3 is 1000 ° C.
It can be fired below ℃, but it does not satisfy the required mechanical properties. Comparative Example 1 cannot satisfy the required firing temperature and mechanical characteristics, and Comparative Examples 2 and 4 cannot satisfy the required firing temperature, mechanical characteristics and electrical characteristics, and are difficult to use in practice.

[Effects of the Invention] As described in detail above, since the oxide dielectric material of the present invention has excellent electrical properties and mechanical properties and can be fired at a low temperature, for example, integral sintering is not possible. Since it is required for a multilayer wiring board or has a small ε and tanδ, it can be expected to be used as a board for a high-density hybrid on which LSI is mounted, and its practical value is extremely large.

Claims (3)

[Claims] 1. Mg, Si, B, and Ba are converted into oxides, respectively, and are converted into oxides of 20 to 40% by weight of MgO, 34 to 40% by weight of SiO _{2, and} 9 to _{2 of} BaO.
An oxide dielectric material comprising 8% by weight and 4 to 12% by weight of B ₂ O ₃ to form a glass ceramic of Mg ₂ SiO ₄ forsterite and barium borosilicate glass. _2. 40-80% by weight of Mg ₂ SiO ₄ forsterite
The oxide dielectric material according to claim 1, which contains. 3. 55 to 65% by weight of Mg ₂ SiO ₄ forsterite
The oxide dielectric material according to claim 1, which contains.