JPS6273797A - Multilayer ceramic circuit substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multilayer ceramic substrate, particularly a highly thermally conductive multilayer ceramic substrate using tantalum nitride as a conductor.

(Prior art and its problems) With the dramatic progress in semiconductor technology, ICs and LSIs have come to be widely used for industrial and civilian purposes.

In particular, multilayer ceramic substrates are attracting attention as mounting substrates for high-speed operation LSIs with high integration density. This multilayer ceramic substrate can directly mount an LSI, and allows fine multilayer wiring.

Generally, alumina is mainly used as the material for ceramic substrates, but in recent years electrical devices have become smaller and smaller.
There is a strong demand for higher density circuits, and the degree of integration of elements and circuit elements per unit area of a substrate is increasing. On the other hand, LSI
, the chip tends to generate more heat as it operates at higher speeds. As a result, the heat generated by the substrate increases significantly, and a problem arises in that the alumina substrate does not have sufficient heat dissipation properties. Therefore, an insulating substrate that has higher thermal conductivity and better heat dissipation than an alumina substrate has become necessary.

Therefore, a ceramic substrate mainly composed of silicon carbide was developed as a material with excellent heat dissipation properties (Japanese Patent Laid-Open No. 57
-180006). Silicon carbide itself electrically belongs to a semiconductor, has a specific resistance of about 1 to 10 Ω·1, and has no electrical insulation properties, so it cannot be used as an insulating substrate. Furthermore, since silicon carbide has a high melting point and is very difficult to sinter, it is usually sintered using a so-called hot press method in which a small amount of sintering aid is added and pressure is applied at high temperature. When beryllium oxide or boron nitride is used as this sintering aid, it is effective not only for the sintering aid but also for electrical insulation, and the specific resistance of the sintered substrate mainly composed of silicon carbide is 10 to
It becomes Ω・1 or more. However, the dielectric constant, which is one of the important factors in mounting boards such as LSI, is as high as 40 at IMHz, and even with additives, the insulation between particles drops rapidly when the voltage reaches about 5V. Therefore, there is also a problem with the withstand voltage.

Furthermore, although it is possible to create a multilayer ceramic substrate using Be powder, it is difficult in practice due to its toxicity.

On the other hand, from a process point of view, the hot press method must be applied, which not only makes the equipment bulky but also makes it difficult to increase the shape of the substrate, and it also has problems with surface smoothness. There are many problems. Furthermore, for ceramic substrates using silicon carbide, alumina multilayer ceramic substrate technology using the conventional green sheet method is used.1. However, the process is extremely difficult.

The green sheet multilayer ceramic substrate technology referred to herein is the following technology. The sweetened ceramic powder is mixed with an organic vehicle to form a slurry. A sheet having a thickness of about 10 μm to 400 Pm is formed on an organic film by casting this slurry.

After cutting the sheet into a predetermined size and forming through holes to provide electrical conduction between each layer, the sheet was printed using a thick film printing method.
A predetermined conductor pattern is formed. The ceramic green/sheets on which each of these conductor patterns have been formed are laminated and pressed, subjected to a binder removal step, and then fired.

The main properties that a high-density mounting board should have are (
1) It has a low dielectric constant with respect to electrical properties, low dielectric loss, and excellent electrical insulation, (2) sufficient mechanical strength, (3) high thermal conductivity, (4)
The coefficient of thermal expansion is close to that of silicon chips, etc. (5
) It must have excellent surface smoothness, and (6) it must be easy to increase the density.

The above-mentioned ceramic substrates cannot be said to be sufficient in terms of these substrate properties in general.

On the other hand, aluminum nitride has been developed as a material for highly thermally conductive substrates (Japanese Unexamined Patent Publication No. 59-50077, etc.)
. However, this material also has to be sintered at high temperatures, and hot pressing has become the mainstream manufacturing method.
A multilayer wiring board using aluminum nitride has not yet been realized.

(Objective of the invention) The present invention provides high-density, high-density, and
It is an object of the present invention to provide a multilayer ceramic substrate with high thermal conductivity.

(Structure of the Invention) According to the present invention, there is provided a highly thermally conductive multilayer ceramic wiring board characterized in that the ceramic layer is composed of a polycrystalline body containing aluminum nitride as the main component, and the conductor layer is composed of tantalum nitride as the main component. can get.

(Detailed Description of Configuration) The present invention solves the problems of the prior art by adopting the above-mentioned configuration.

First, aluminum nitride, which has high thermal conductivity, was used as an insulating ceramic material constituting the multi-I ceramic substrate. After firing, this material forms a fine structure of polycrystalline aluminum nitride. In order to obtain high thermal conductivity, it is preferable that the amount of oxygen contained in the sintered body is small, and therefore it is preferable to add a reducing agent having a reducing effect as an additive.

Next, regarding the conductor layer, multiple conductor layers such as a power supply layer, a ground layer, and fine signal lines are formed on a ceramic layer made of aluminum nitride, and these multiple conductor layers are provided in the ceramic layer. It is electrically connected via a peer hole.

Therefore, the wiring density of the mounting board can be greatly increased, and the heat generated from elements such as LSI can be efficiently dissipated to the outside.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram showing an embodiment of a highly thermally conductive multilayer ceramic substrate according to the present invention. 1 is an insulating ceramic layer, which is mainly composed of polycrystalline aluminum nitride. Reference numeral 2 denotes a conductor layer for signal lines, power supply, etc., which is formed entirely of tantalum nitride as a main component, and the layers are electrically connected through peer holes 3 formed in the insulating ceramic layer. A die pad 4 and a bonding pad 5 are formed on the multilayer ceramic substrate configured in this way so that an LSI chip can be mounted, and in order to take out a signal from the mounting board or input a signal into the board. An input/output pad 6 is formed on the back surface of the board. Heat generated from the LSI chip mounted on the substrate is spread into the ceramic substrate via the die pad 4. Due to the high thermal conductivity of the ceramic substrate, heat diffusion becomes an efficient pressure chamber, and it is possible to prevent the LSI chip from increasing in temperature due to heat generation.

The method for manufacturing the wiring board of this example is as follows. Ceramic materials constituting the substrate of the present invention include:
C as an additive to improve the sinterability of aluminum nitride
*C, is mixed. First, aluminum nitride powder, Cac, and powder were weighed and wet mixed in an organic solvent using a ball mill for 48 hours.

This mixed powder is dispersed in a solvent with an organic binder that easily decomposes in a neutral atmosphere, such as polycaprolactone or polyacrylate resin, and the viscosity is 3000-70.
Create a slurry in the range of 00 ep. The slurry is cast onto an organic film to form a green sheet so as to have a uniform thickness K of about 10 μm to 200 Prn.

Next, this green sheet is peeled off from the 11-layer film, and then peer holes are formed for electrically connecting each layer. The pier holes formed here were punched out mechanically using a punch and a gourd, but they can also be punched out by other methods such as laser machining.

A conductive paste containing a tantalum compound as a main component, which becomes tantalum nitride when fired in a nitrogen atmosphere or other neutral atmosphere or a reducing atmosphere, is screened onto the green sea in which the pier holes are formed. A predetermined pattern is printed in a predetermined position using a printing method.The desired number of each green sheet with conductors printed in this way is stacked and heated.Then, it is cut using a cutter into the required cedar shape, and heated at 1400℃. Firing in a non-oxidizing atmosphere at ~2000℃.During firing, 400t
The binder was sufficiently removed at a temperature of ~6001:9.

The characteristics of the fabricated substrate are shown in the table.

Hereinafter, as the white conductor paste material, T a N, T a H
, T a CI h.

and TaBr, were used.

The amount of CaC shown here is a value when aluminum nitride is taken as 100. Further, the amount of frit is a value relative to the combined weight of the conductor material and the frit material.

As a result of measuring the electrical characteristics of the created substrate, the specific resistance was l
O'xΩ・1 or more, and the galvanic rate is 13.7 (IMHz
), 'faiK loss is less than lXl0-'' (IMHz
)Met. It can be seen that the electrical characteristics are also at least the same as those of conventional boards, and are sufficient as a mounting board.

On the other hand, CaO, B as additives to aluminum nitride
oo, YIO, CuO, Ago, BaC1,5rC1
.

N*@C@, KsC@, Cuc, , Mg
Even when C1, kg@C@, Z rc@, etc. were used, the effect of improving the sinterability of aluminum nitride was obtained.

(Effects of the Invention) As is clear from the examples, the multilayer ceramic wiring board of the present invention can easily form a two-wire circuit that connects all conductors such as signal lines and power supply layers. It is possible to obtain a highly thermally conductive multilayer ceramic substrate which is also effective against thermal grazing properties.

The thermal conductivity of the conventionally used alumina substrate is 17W/
mK, which indicates that the thermal conductivity of the substrate of the present invention is at a very high level. In terms of thermal tensile coefficient, whereas the alumina substrate has a C55X 1 o-'/, the substrate of the present invention has a smaller value, which is closer to the thermal expansion coefficient of a silicon chip, which is advantageous. be.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a highly thermally conductive multilayer ceramic substrate showing an embodiment of the present invention. l...Insulating ceramic layer, 2
. . . conductor layer, 3 . . . peer hole, 4 . . . pad, 5 .

Claims (1)

[Claims] A multilayer ceramic wiring board comprising a ceramic layer containing aluminum nitride as a main component and a conductor containing tantalum nitride as a main component.