JPH0252861B2 - - Google Patents

Description

[Detailed description of the invention]

a. Technical Field of the Invention The present invention relates to a multilayer substrate for mounting semiconductor devices, and more specifically, to a multilayer ceramic circuit board on which a plurality of semiconductor chips such as ICs and LSIs are mounted. b. Background of the technology Although semiconductor devices (such as LSI) have become more sophisticated and highly integrated in recent years,
When configuring a system (or unit) using LSI chips, the conventional mounting method was to attach multiple DIP packages each containing one chip to a printed circuit board. However, with this mounting method, there was a problem with the delay time caused by the wiring and loads that connect the chips, and a method for higher-density mounting was proposed. For example, there is a method of mounting multiple chips on a multilayer circuit board using a synthetic resin material. It has problems such as being small and having a different coefficient of thermal expansion than the semiconductor material of the chip. on the other hand,
Multilayer ceramic circuit boards have better heat resistance and thermal conductivity than those made of synthetic resin, and have a thermal expansion coefficient close to that of chip semiconductors, so various proposals have been made (for example, Takashi Tamura's "For Multi-Chip Packages"). "Ceramic multilayer substrate", Electronic Materials, Vol.21,
No. 11, November 1982, Industrial Research Association Co., Ltd., pp. 64-69,
74, see). c. Prior art and problems When constructing a multilayer ceramic circuit board by firing a mixture of alumina and glass, if the proportion of alumina is high, the firing temperature will also be high; material must be used. However, since these high melting point metal materials have relatively high electrical resistance, it is desirable to use highly conductive metal materials such as copper, gold, silver, or an alloy of any of them. Further, since alumina has a high dielectric constant of 8 to 9.5, which leads to a delay in signal conduction, it is desirable to use a mixture containing a higher proportion of a material with a lower dielectric constant.
Therefore, we increased the proportion of glass, which has a lower melting point and dielectric constant than alumina, to lower the firing temperature to the melting points of these highly conductive metal materials (copper melting point 1083°C, gold melting point 1063°C, silver melting point 961°C). ),
A multilayer ceramic substrate with a lower dielectric constant has been proposed. In this case, it is a fired substrate made of a base made of alumina, borosilicate glass, etc., and a highly conductive material such as copper. For this fired substrate, the firing temperature is set relatively low at 700 to 900°C.
The drawback was that the dielectric strength of the circuit board was low because the binder was not removed sufficiently. In addition, in order to increase the heat dissipation efficiency of the ceramic substrate,
There is a need to improve the thermal conductivity of substrates. d. Purpose of the Invention The purpose of the present invention is to provide a multilayer ceramic circuit board, which is a multilayer board for mounting semiconductor devices, which can perform sufficient binder removal, has improved dielectric strength, and has increased thermal conductivity. It is. e.Structure of the Invention The above-mentioned object has a highly conductive metal wiring layer and is made from a fired mixture of borosilicate glass, alumina, and an inorganic material having a higher thermal conductivity than these and a relatively high melting point. This is achieved by a multilayer substrate for mounting semiconductor devices. The highly conductive metal wiring layer is preferably made of copper, gold, silver, or an alloy of any of these metals. Further, as the inorganic material having high thermal conductivity and a relatively high melting point, beryllia (BeO), silicon carbide (SiC), or diamond (C) powder is preferable. The temperature at which the mixture is fired is preferably higher than conventional temperatures and slightly lower than the melting point of the above-mentioned metal wiring layer in order to sufficiently remove the binder. Mixing ratio with beryllia, silicon carbide or diamond: borosilicate glass: 25-55wt%
(preferably 30-35wt%); Alumina: 50-5wt%
(preferably 40 to 30 wt%); and beryllia, silicon carbide, or diamond: 25 to 55 wt% (preferably 30 to 35 wt%). The use of silicon carbide and diamond also has the advantage of improving the mechanical strength, particularly the hardness, of the substrate. f Examples Hereinafter, the present invention will be explained in more detail with reference to the following examples. Example 1 Alumina powder, borosilicate glass powder, and beryllia powder were placed in a polyethylene pot, and a solvent, a plasticizer, and a resin binder were added, and the mixture was ball-milled for 48 hours to form a slurry. The composition of this slurry is shown in Table 1.

【table】

[Table] This slurry was formed into a green sheet with a thickness of 0.34 mm by the doctor blade method. This green sheet was cut into a predetermined shape and punched to form a via hole. Copper paste with a viscosity adjusted to 300 to 1000 P (poise) was applied by screen printing and filled into the via holes, and then a conductive wiring pattern that would become the signal layer or power layer was formed on the green sheet. Stack these green sheets and heat them to 130℃ for 30 minutes.
Laminated under pressure of 30MPa. The laminated unfired substrates were fired in a nitrogen atmosphere to prevent the copper paste from oxidizing. Firing was performed by first heating at a temperature of 810°C for 10 hours in a nitrogen atmosphere containing water (7% H ₂ O) to remove the resin binder, and then in a nitrogen atmosphere with an oxygen concentration of 5 ppm or less. This was done by heating at a temperature of 1000°C for 10 hours. It is better to keep the oxygen concentration as low as possible, but commercially available nitrogen gas contains 2 to 3 ppm of oxygen, so although some oxygen is present, there is no problem in practice as long as it is at this level. The multilayer ceramic circuit board made in this way has a high firing density of over 98.5% and a low dielectric constant of 5.2, so the transmission delay of the circuit board is 80PS/cm.
and small, and the carbon residue of the resin binder is
Since the content was as low as 30 ppm, it exhibited high dielectric strength. In addition, the thermal conductivity is 0.133 Cal/cm・sec・deg,
This is the case of a sintered substrate of a mixture of 50wt% alumina and 50wt% borosilicate glass as a comparative example.
Greater than 0.011Cal/cm・sec・deg. Example 2 A green sheet having a conductive pattern of copper paste was formed in the same process as in Example 1 using silicon nitride powder instead of the beryllia powder in Example 1 and using the slurry composition shown in Table 2.

[Table] The obtained green sheets were stacked and laminated under a pressure of 30 MPa for 30 minutes while heating to 130°C. The laminated and integrated product was fired in a nitrogen atmosphere so that the copper paste in Example 1 would not be oxidized. Firing was performed by first heating at 810°C for 8 hours in a nitrogen atmosphere containing water (7% H ₂ O), then heating at 1000°C for 5 hours in a nitrogen atmosphere with an oxygen concentration of 5 ppm or less. This was done by heating for a period of time. The multilayer ceramic circuit board made in this way has a high firing density of over 98.5% and a low dielectric constant of 5.0, so the transmission delay of the circuit board is 79PS/cm.
It is small in size and contains only 30 ppm of carbon residue, so it exhibits high dielectric strength. Also, the thermal conductivity is
It was 0.09 Cal/cm・sec・deg. Example 3 Synthetic diamond powder (particle size of about 5 μm) was used instead of the beryllia powder in Example 1, and slurry compositions A and B in Table 2 were prepared using the same process as in Example 1 to form a copper paste conductor pattern. A green sheet was formed.

【table】

[Table] The obtained green sheets were stacked and laminated under a pressure of 35 MPa for 30 minutes while heating to 130°C. The laminated and integrated product was fired by heating at a temperature of 1000° C. for 30 minutes in a nitrogen atmosphere so that the copper paste in Example 1 would not be oxidized. The multilayer ceramic circuit board made in this way has a high firing density of over 98.5% and a low dielectric constant of 5.5, so the transmission delay of the circuit board is 82PS/cm.
It is small in size and contains only 30 ppm of carbon residue, so it exhibits high dielectric strength. Further, the thermal conductivity and hardness of the obtained fired substrate were as shown in Table 4. As a comparative example, 50wt% alumina and 50wt% borosilicate glass
Table 4 also shows the thermal conductivity and hardness of a mixture fired substrate made under the same conditions.

[Table] g Effects of the Invention According to the present invention, it has a highly conductive metal wiring layer made of copper, etc., and the resin binder is sufficiently decomposed and scattered, resulting in high dielectric strength and thermal conductivity due to less carbon residue. A multilayer substrate for mounting a semiconductor device made of a ceramic fired body with a high efficiency can be obtained. The multilayer substrate of the present invention can also be used in a ceramic package that accommodates one LSI chip.

Claims (1)

[Claims] 1. A semiconductor having a highly conductive metal wiring layer and consisting of a fired mixture of borosilicate glass, alumina, and an inorganic material having a higher thermal conductivity than these and a relatively high melting point. Multilayer board for device mounting. 2. The multilayer board according to claim 1, wherein the highly conductive metal wiring layer is made of copper, gold, silver, or an alloy of any of these metals. 3. The multilayer substrate according to claim 1, wherein the inorganic material is beryllia. 4. The multilayer substrate according to claim 1, wherein the inorganic material is silicon carbide. 5. The multilayer substrate according to claim 1, wherein the inorganic material is diamond.