JP2606155B2 - Multilayer wiring board, method for manufacturing the same, and method for manufacturing sintered silica used therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic substrate used for a microwave integrated circuit requiring particularly low dielectric loss, a method of manufacturing the same, and a silica sintered body used therefor.

[0002]

2. Description of the Related Art In recent years, with the progress of higher integration and higher frequency of semiconductor chips, demands for lower dielectric constant and lower transmission loss of ceramic multilayer wiring substrates have been increasing.
As the low dielectric constant substrate, those having a dielectric constant of about 4 to 5 by a composite of borosilicate glass and quartz or a composite of borosilicate glass and cordierite have been put to practical use. This is insufficient for the requirement for dielectric loss in high frequency bands such as microwaves.

As a microwave material having a low dielectric constant, there is silica. Silica is reported to have a relative dielectric constant of 3.8 and a Qf product of 15,000 [GHz]. Further, for a ceramic multilayer wiring board, it is required to use a low-resistance metal as a wiring material from the viewpoint of transmission characteristics. However, the firing temperature of silica is much higher than the melting point of gold, silver, copper, and the like, which are known as low resistance metals, and it has been difficult to form multilayer wiring by simultaneous firing.

[0004]

In order to utilize the low dielectric constant and low dielectric loss factor of silica as a material for a multilayer wiring board, it is necessary to sinter silica in a temperature range not higher than the melting point of the low-resistance metal described above. Will be needed.

[0005] JP-A-2-302362 discloses a BPO
There is disclosed a technique in which the firing temperature is adjusted to 950 to 1100 ° C. by adding ₄ % by weight or more to SiO ₂ . Temperature range 100 where silver or copper can be used as wiring material
In order to fire at 0 ° C. or less, the amount of addition needs to be 20% by weight or more. Although this material shows a low value in terms of the dielectric constant, it is not desirable that the amount of the additive is large in terms of the dielectric loss.

An object of the present invention is to provide a multilayer wiring board having a low dielectric constant and a low dielectric loss factor by enabling silica to be fired at a low temperature, and a method of manufacturing the same.

[0007]

Means for Solving the Problems The characteristics of the multilayer wiring substrate according to the present invention, the insulating layer is SiO ₂ from 95.0 to 99.5 wt%, alkali metal compound 0-5.0 wt%, the alkaline earth metal compound 0-5.0 wt%, or SiO ₂ 95.
0 to 99.0% by weight, consists of B ₂ O ₃ 1.0 to 5.0 wt%, the melting point is in the temperature range of 800 to 1200 ° C. A
It is to have the above-mentioned low-resistance conductor such as u, Ag, Cu, Ag-Pd as a conductor layer.

[0008] Silica sintered body forming the insulating layer, a fine powder of silica having an average particle size of 5 to 500 nm SiO ₂
Of a mixed powder of the raw material powder and a predetermined amount of an alkali metal compound, an alkaline earth metal compound, or B ₂ O _3, and a partial pressure of 0.005
It is obtained by baking at 800 to 1200 ° C. in an atmosphere containing water vapor at a pressure of 0.85 atm or more.

When this is used as a multilayer wiring board, a slurry is prepared from the above-mentioned mixed powder, binder and solvent, and a green sheet is formed therefrom.
Wiring is printed on this green sheet, and after laminating them, it is manufactured by integrally firing at 800 to 1200 ° C. in an atmosphere containing water vapor having a partial pressure of 0.005 to 0.85 atm. Can be.

[0010]

The silica sintered body according to the present invention has an average particle size of 5-5.
The SiO ₂ is 00nm as a raw material powder, which alkali metal compound or alkaline earth metal compound 0.5-5 wt% or B ₂ O ₃ 1-5% by weight was added, 0.005 atm and a partial pressure It can be obtained by firing at 800 to 1200 ° C. in an atmosphere containing water vapor of 0.85 atm or less. It is difficult to obtain a silica powder having an average particle size of less than 5 nm, and if the average particle size is larger than 500 nm, sintering at 1200 ° C. or less becomes difficult.
The average particle size of the raw material powder needs to be in the range of 5 to 500 nm. More preferably, the range is 5 to 50 nm. Further, addition of an alkali metal, an alkaline earth metal and B ₂ O ₃ has an effect of promoting the progress of sintering. Even when no additive is added, sintering can be performed by increasing the firing time, but the firing time can be shortened by adding an appropriate amount. At this time, the effect is not recognized when the addition amount of the alkali metal compound and the alkaline earth metal is 1% by weight or less. Also,
With B ₂ O ₃ , no effect is observed at 0.5% by weight or less. The effect increases as the amount added increases, but 5% by weight
Addition of the above leads to an increase in the dielectric constant. Therefore, the addition amount is 1 for alkali metals and alkaline earth metals.
In the case of B ₂ O ₃ , the range of 0.5 to 5% by weight is appropriate. More preferably, addition of 3 to 5% by weight is desirable. As the alkali metal and alkaline earth metal compounds, carbonates, oxides, hydroxides, fluorides and the like can be used. The method of mixing these compounds with silica powder is not particularly limited, but the weighed powder is dispersed in a solution as shown in the flowchart of FIG.
It is desirable to dissolve and uniformly mix the metal compound.
Further, as shown in FIG. 1 (b), a silica powder may be added to a solution in which only a metal salt is dissolved, and mixed so as to coat the silica powder. After mixing, the powder can be uniformly mixed by drying and removing the solvent. Therefore, it is preferable to use a metal compound having high solubility in a solvent.

Regarding the firing atmosphere, the sinterability improves as the content of water vapor increases,
If the pressure is less than 5 atm, the effect will not be recognized. Further, it is difficult to create a water vapor atmosphere having a partial pressure of 0.85 atm or more. Therefore, it is desirable to bake in the range of 0.005 to 0.85 atm, more preferably in the range of 0.3 to 0.7 atm. By firing under these conditions, a silica sintered body can be obtained at a firing temperature of 800 to 1200 ° C.

In the case of manufacturing a multilayer wiring board, a green sheet on which a conductive layer is formed is prepared, and a laminate of the green sheets is fired to be integrated to obtain a multilayer wiring board. Alternatively, a conductive layer may be formed on a previously sintered silica sintered body and then integrated to form a multilayer wiring board.

[0013]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited to the following Examples without departing from the scope of the invention.

Example 1 1, 3 and 5% by weight of Li ₂ CO _{3 based} on amorphous silica powder having an average particle size of 5 nm
The mixture was added and mixed with a ball mill using pure water as a dispersion medium.
By drying the mixed solution, Li ₂ CO ₃ is uniformly attached to the surface of the silica powder, and the raw material powder is obtained by granulation (FIG. 1 (a)). The obtained raw material powder is added to a solution of polyvinyl butyral dissolved in a solvent containing ethanol as a main component, and uniformly mixed to obtain a viscosity of 3000.
A slurry having a viscosity of 〜１０10000 cps was produced. Similarly, the Li ₂ CO ₃ component is replaced with Na ₂ CO ₃ , K ₂ CO ₃ , R
A slurry was prepared with the replacement of b ₂ CO ₃ . These slurries were prepared by slip casting method.
A green sheet is formed so as to have a thickness of 0 to 200 μm. A green laminate was obtained by hot pressing the produced green sheet. This green laminate is subjected to 800, 1 atmosphere in an atmosphere containing water vapor at a partial pressure of 0.5 atm, nitrogen and oxygen.
Calcination was performed at 2,000 and 1,200 ° C. for 5 hours.

The sample to which Li ₂ CO ₃ was added reached a relative density of 96.0% or more, and showed sufficient sinterability (Table 1). Similarly, Na ₂ CO ₃ , K ₂ CO ₃ and Rb
_The samples to which ₂ CO ₃ was added also showed sufficient sintering (Tables 2, 3 and 4).

The alkali metal having the effect of addition may be used as Li ₂ O, K ₂ O, Rb ₂ O or the like in addition to carbonate.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

[Table 4]

Example 2 MgO was added to amorphous silica powder having an average particle size of 5 nm in an amount of 1, 3 and 5% by weight, and a ball mill was mixed using pure water as a dispersion medium. After mixing, drying is performed to remove water, and MgO
Was uniformly adhered. This mixed powder was granulated to obtain a raw material powder. The obtained mixed powder was added to a solution obtained by dissolving polyvinyl brillal in a solvent containing ethanol as a main component, and uniformly mixed to prepare a slurry having a viscosity of 3000 to 10,000 cps. Similarly, the MgO portion is replaced with Ca
A slurry was prepared with the replacement of CO ₃ and SrCO ₃ . These slurries are formed into green sheets so as to have a thickness of 50 to 200 μm by a slip casting film forming method. A green laminate was obtained by hot pressing the produced green sheet. This green laminate was fired at 800, 1000, 1200 ° C. for 5 hours in an atmosphere containing water vapor at a partial pressure of 0.5 atm, nitrogen and oxygen.

The obtained sintered body had a relative density of 96.0% or more, and sufficient sinterability was recognized (Tables 5, 6 and 7). It was also observed that the closer the density of the sample to 100%, the higher the light transmittance.

The alkaline earth metal to be added is MgC
O ₃ , CaO, or SrO may be used.

[0024]

[Table 5]

[0025]

[Table 6]

[0026]

[Table 7]

Example 3 2% by weight of K ₂ CO ₃ and Ca were added to the amorphous silica powder described in Examples 1 and 2.
CO ₃ was added 2 wt%, to prepare a mixed powder uniformly deposited an additive to silica powder surface in the same manner as in Example 1 and 2. A green sheet was produced from the obtained mixed powder using the same method as in Examples 1 and 2. The green sheets were laminated and hot-pressed to form a green laminate, which was baked at 1000 ° C. for 5 hours in an atmosphere containing 0.5 atm of water vapor, nitrogen and oxygen at a partial pressure.

The obtained sintered body showed translucency, and when the fracture surface was observed with a scanning electron microscope, it was confirmed that the sintered body was sufficiently dense (Table 8). .

[0029]

[Table 8]

Example 4 B ₂ O ₃ was added to amorphous silica powder having an average particle diameter of 10 nm by 1, 3 and 5% by weight, and slurry was prepared in the same manner as in Example 1. , A green sheet and a green laminate. The prepared green laminate was fired at 800, 1000 and 1200 ° C. for 5 hours in an atmosphere containing water vapor of 0.5 atm, nitrogen and oxygen at a partial pressure (Table 9).

Each of the obtained fired bodies reached a relative density of 96.0% or more, and sufficient sinterability was confirmed. The appearance was translucent, and when the fracture surface was observed, it was confirmed that it was a dense sintered body.

[0032]

[Table 9]

Example 5 A coarse powder of amorphous silica having an average particle size of about 10 μm was pulverized using a dry pulverizer.
When the average particle size of the obtained powder was measured, it was 0.5 μm. B ₂ O ₃ was added to this amorphous silica powder in an amount of 1, 3 and 5% by weight, and a laminate was produced in the same manner as in Example 4. This laminate was set to a partial pressure of 0.85
1200 atmospheres in an atmosphere containing water vapor, oxygen and nitrogen.
Baking was performed at 10 ° C. for 10 hours.

The density of the sintered body of the obtained sample reached 96.0%, and had a sufficient strength. Average particle size 0.5
It was confirmed that sufficient sintering was completed at 1200 ° C. using μm amorphous silica powder as a raw material powder.

Example 6 A laminate was prepared in the same manner as in Example 1 from a mixed powder obtained by adding 5% by weight of B ₂ O ₃ to amorphous silica powder having an average particle size of 5 nm. This laminated body is subjected to 1, 5, 10 at 1200 ° C. in an atmosphere containing water vapor at a partial pressure of 0.005 atm and nitrogen and oxygen.
And firing for 20 hours.

If the firing time is 1 hour, the sintering proceeds insufficiently and the sample has no strength. Increasing the firing time to 5 or 10 hours increases the density, and over 20 hours, the relative density becomes 96% or more. Observation of the fracture surface with a scanning electron microscope confirmed that sufficient sintering had progressed. Thus, it was confirmed that the amorphous silica powder could be sintered at 1200 ° C. by adding 0.005 atm of water vapor to the firing atmosphere.

Example 7 In the same manner as in Example 2, a green sheet having a thickness of 100 μm and comprising 97% by weight of SiO _{2 and} 3% by weight of MgO was prepared. As the SiO ₂ powder, an amorphous silica powder having an average particle size of 5 nm was used. A via hole having a diameter of 180 μm was formed in this green sheet, and a copper paste was embedded therein. In addition, a conductor pattern was printed. Twenty green sheets subjected to these treatments were laminated, heated to 110 ° C. and press-molded at a pressure of 20 MPa to produce a green laminate. The green laminate was fired at 1000 ° C. for 5 hours in an atmosphere containing water vapor at 0.5 atm, nitrogen and oxygen at a partial pressure.

The insulating layer of the multilayer wiring board thus obtained exhibited the same properties as the sintered body obtained in Example 2. The measured dielectric constant was 5.0 at 10 GHz and the dielectric loss tangent (tan δ) was 7 × 10 −4. The specific resistance of the Cu conductor was 3 μΩ · cm, which was good as a low-resistance conductor.

Comparative Example 1 Li ₂ CO ₃ as an additive
Na ₂ CO ₃ , K ₂ CO _3, and Rb ₂ CO ₃ were added to amorphous silica powder having an average particle size of 5 nm in the same manner as in Example 1 so as to be 10% by weight. Using each of the produced raw material powders, a green laminate was produced in the same manner as in Example 1. In addition, a raw laminate was similarly produced using amorphous silica powder having an average particle size of 5 nm to which no additive was added as a raw material powder. These five types of samples were placed in an atmosphere containing water vapor, nitrogen, and oxygen at a partial pressure of 0.5 atm.
Firing was performed at 800, 1000 and 1200 ° C. for 5 hours (Tables 1, 2, 3 and 4).

Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃
In the samples to which Rb ₂ CO ₃ was added, sufficient sintering was observed at each firing temperature. However, when the relative dielectric constant of each sample was measured at 1 MHz, it was confirmed to be 4.0 or more. From the viewpoint of dielectric properties, the addition amount of 5% by weight or more is inappropriate. In addition, it was confirmed that the sample of silica alone was not sufficiently sintered and the relative density was 92.0%. Since the relative density of the sample to which each additive was added at 1% by weight or more in Example 1 reached 96.0% or more, adding these alkali metals at 1% by weight or more improved the sinterability. I understand.

Comparative Example 2 MgO, CaC as additives
Example 2 Amorphous silica powder having an average particle diameter of 5 nm was prepared so that O ₃ and SrCO ₃ each became 10% by weight.
Was added in the same manner as described above. Using each of the produced raw material powders, a green laminate was produced in the same manner as in Example 2. These three kinds of samples were fired at 800, 1000 and 1200 ° C. for 5 hours in an atmosphere containing water vapor, nitrogen and oxygen at a partial pressure of 0.5 atm (Tables 5, 6 and 7).

Each sample had a relative density of 98.0% or more, and sufficient sintering was recognized. However, when the relative dielectric constant of each sample was measured at 1 MHz, it was 4.0.
This was confirmed. From the viewpoint of the dielectric properties, the addition amount of 5% by weight or more is inappropriate.

Comparative Example 3 B ₂ O ₃ was added by 10% by weight to amorphous silica powder having an average particle diameter of 10 nm in the same manner as in Example 4 to obtain a raw material powder. Was adjusted. Using this raw material powder, a green laminate was produced in the same process as in Example 4. This is divided into a partial pressure of 0.5 atm in an atmosphere containing water vapor, nitrogen and oxygen, 800, 1000
And calcination at 1200 ° C. for 5 hours (Table 9).

When the sintering temperature was 800 ° C., it was confirmed from the relative density that the sintering was sufficient. However, since the relative dielectric constant was 4.5 (1 MHz), the amount of addition was small in view of the dielectric properties. 10% by weight is unsuitable. In addition, if the firing temperature is 1
It was confirmed that melting was performed at 000 ° C. or higher. From the above, it is determined that the amount of B ₂ O ₃ added is preferably 5% by weight or less.

[0045]

As described above, according to the present invention, a silica sintered body characterized by a low dielectric constant and a low dielectric loss can be produced by using Au, A
It is obtained by firing in a temperature range equal to or lower than the melting point of a low-resistance conductor such as g, Cu and Ag-Pd. In addition, this makes it possible to manufacture a multilayer wiring board in which the low-resistance conductors are provided by co-firing.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of sample preparation in the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 silica powder 2 Li ₂ CO ₃ aqueous solution 3 SiO ₂ 4 Li ₂ CO ₃ 5 green sheet 6 silica sintered body

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-30196 (JP, A) JP-A-60-17181 (JP, A) JP-A-55-128899 (JP, A) JP-A-63-1988 74957 (JP, A)

Claims (7)

(57) [Claims] 1. An insulating layer and a conductor layer comprising 95.0 to 99.5% by weight of SiO _{2, 0 to} 5.0% by weight of an alkali metal compound, and 0 to 5.0% by weight of an alkaline earth metal compound. A multilayer wiring board characterized by the above-mentioned. _2. 95.0 to 99.0% by weight of SiO ₂ , B ₂
O ₃ 1.0 to 5.0 a multilayer wiring board characterized by comprising an insulating layer and a conductor layer consisting wt%. 3. The multilayer wiring board according to claim 1, wherein the conductive layer is made of at least one of Au, Ag, Ag-Pd, and Cu. 4. A silica fine powder having an average particle size of from 5 to 500 nm in an amount of 95.0 to 99.5% by weight and an alkali metal compound 0
~ 5.0% by weight and alkaline earth metal compound 0 ~ 5.0.
Powder 95.0 to 99.0 weight percent silica mixture weight percent, or an average particle diameter of 5~500nm and B ₂ O
₃ A mixture of 1.0 to 5.0% by weight is mixed with a binder and a solvent to form a slurry. After shaping the slurry, the mixture is subjected to a partial pressure of 0.005 to 0.85 atm. Sintering at 800 to 1200 ° C. 5. A silica fine powder having an average particle diameter of 5 to 500 nm, 95.0 to 99.5% by weight and an alkali metal compound 0
~ 5.0% by weight and alkaline earth metal compound 0 ~ 5.0.
Powder 95.0 to 99.0 weight percent silica mixture weight percent, or an average particle diameter of 5~500nm and B ₂ O
₃ After press-forming a mixture of 1.0 to 5.0% by weight,
A method for producing a silica sintered body, characterized by firing at 800 to 1200 ° C. in an atmosphere containing water vapor at a partial pressure of 0.005 to 0.85 atm. 6. A fine silica powder having an average particle diameter of 5 to 500 nm in an amount of 95.0 to 99.5% by weight and an alkali metal compound 0
~ 5.0% by weight and alkaline earth metal compound 0 ~ 5.0.
Powder 95.0 to 99.0 weight percent silica mixed powder of% by weight or average particle size, a 5~500nm and B ₂ O
₃ A mixed powder of 1.0 to 5.0% by weight,
A green sheet is prepared as a slurry by mixing with a solvent, a conductor layer is formed on this green sheet, and after laminating these layers, in an atmosphere containing water vapor at a partial pressure of 0.005 to 0.85 atm. 800-1200
3. The method according to claim 1, wherein the sintering is carried out at a temperature of one degree.
A method for manufacturing the multilayer wiring board according to the above. 7. The method for manufacturing a multilayer wiring board according to claim 1, wherein a conductive layer is formed on the silica sintered body according to claim 4 and laminated and integrated.