JPH03155694A - Manufacture of aluminum nitride multilayer circuit board - Google Patents

Abstract

PURPOSE:To obtain a multilayer circuit substrate which has excellent adhesion with a conductor line by boring a hole at a via formation position of a green sheet of aluminum nitride and then providing a heating process in a wet nitrogen gas atmosphere. CONSTITUTION:An AlN green sheet is heated over one hour in an N2 ambient atmosphere at a temperature ranging from 50 to 100 deg.C where oxidation takes place due to a trace of water contained H2O. Then, on the surface of the green sheet is formed a boehmite AlO(OH) which is an oxide of Al. By way of a thin film of the boehmite, conductor part paste, such as of W is screen-printed so that a conductor pattern may be formed. The boehmite is dehydrated by heating and is turned into an Al oxide rho-Al2O3. However, it exists as a thin oxide layer adhered to the AlN, which makes it possible to obtain a conductor line which has excellent adhesion to a substrate.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for manufacturing an aluminum nitride multilayer circuit board, the purpose of this invention is to put into practical use a method for manufacturing a multilayer circuit board with excellent adhesion to conductor lines. After drilling a hole at the via formation position, a heating step is performed in a humid nitrogen gas atmosphere, and a conductor track is formed by screen printing a conductor paste on the green sheet. Aluminum nitride is characterized by comprising the steps of: filling the green sheets with I., stacking the green sheets while aligning them, applying pressure to integrate them, and firing the laminate in a nitrogen gas atmosphere. A method for manufacturing a multilayer circuit board is configured.

[Industrial application field]

The present invention relates to a method for manufacturing an aluminum nitride multilayer circuit board.

Due to the need to process a large amount of information at high speed, information processing devices are becoming smaller and larger in capacity, and the degree of integration of semiconductor integrated circuits that form the main body of these devices has improved, and LSI and VLSI have been put into practical use.

These integrated circuits are mounted as chips on a ceramic chip mounting board (interposer) to create an LSI module, which is then mounted on a printed wiring board as a replacement unit. There is Retsu.

As described above, as the degree of integration of semiconductor integrated circuits increases and high-density packaging is performed, the amount of heat generated by devices is also increasing at an accelerating pace.

That is, initially, the amount of heat generated per IC chip was approximately 3.
The amount of heat generated per LSI chip used to be as low as 5W, but now it has increased to about 10W, and this is
When a large number of J-hooks are attached, the amount of heat generated is enormous, and this tends to increase further.

Conventionally, chip mounting substrates for mounting LSI chips and the like have been made of alumina (Aji!z), which has high thermal conductivity and excellent heat resistance.
Os) have been used.

However, alumina has excellent thermal conductivity - 20W/
It is only about a+, which is insufficient as a material for the above-mentioned chip mounting substrate.

Therefore, AlN has a high thermal conductivity of 320 W/mK (theoretical value) and a coefficient of thermal expansion close to that of silicon (Si).
has attracted attention, and efforts are being made to put this substrate into practical use.

In other words, in addition to its excellent thermal conductivity, AIN has a thermal expansion coefficient of 4.4Xl0-'/'C, which is close to the thermal expansion coefficient of Si that constitutes LSI (3°6X 10-''/''C). There are advantages.

[Conventional technology]

Since LSIs and VLSIs that have a flip-chip structure have a large number of terminals, conductor lines such as pads that are patterned on the chip mounting substrate on which multiple semiconductor chips are mounted are becoming finer and more complex. Therefore, it necessarily has a multilayer structure.

Therefore, AIN has a high melting point, and the substrate can be fired at 1800℃.
Because the process is carried out at high temperatures exceeding
is used.

As a method of forming a multilayer wiring board, via holes (Via holes) are formed at the positions of the green sheet where circuit connections are made between layers.
-hole), screen-print a conductor paste made of a high-melting point metal such as W to fill the hole and create a conductor pattern, which is then dried, aligned, laminated, and pressurized. Thereafter, by firing, a multi-ceramic circuit board with circuit connections via vias is formed.

However, AIN has the property of having extremely poor wettability with the conductor metal, which tends to cause cracks and peeling in the conductor line, as well as partial peeling and disconnection in vias that connect between layers. There were problems and improvements were needed.

[Problem to be solved by the invention]

AIN is suitable as a constituent material for multilayer ceramic circuit boards because of its high thermal conductivity and thermal expansion coefficient close to that of Si.

However, since AlN does not react with most metals, it has poor wettability with metals, and therefore has a problem of poor adhesion with conductor lines such as W formed on the substrate. The challenge is to put into practical use a good method for manufacturing multilayer circuit boards.

[Means to solve the problem]

The above problem involves the process of drilling a hole at the via formation position in the N green sheet, then heating it in a humid N2 gas atmosphere, screen printing a conductive paste on the green sheet to form a conductor line, and , the process of drilling the holes includes filling the part with conductive paste, stacking the green sheets while aligning them, applying pressure to integrate them, and firing this laminate in an N2 gas atmosphere. This problem can be solved by configuring a method for manufacturing an AfN multilayer circuit board.

[Effect]

The present invention forms a hydroxide of A1 on this surface as a method of improving the wettability of metal to iN.

That is, when an IN green sheet is heated for 1 hour or more in a humid N2 atmosphere at 50 to 100°C, oxidation is carried out by the trace amount of water (N20) it contains, and hydroxylation of Al occurs on the surface of the green sheet. Boehmite (10
(OH) ) is formed.

The present invention forms a conductive pattern by screen printing a conductive paste such as W through a thin film of boehmite. This boehmite is dehydrated by heating and becomes Al oxide (T-A1aO@), but AiN Since it is present as a thin oxide layer in close contact with the substrate, a conductor line with excellent adhesion to the substrate can be obtained.

〔Example〕

3.6 Calcium carbonate (CaCOs) as a sintering aid
Aj2N powder containing % by weight was mixed with a ball mill using a butyral resin as a binder, a fatty acid ester as a dispersant, and ethyl alcohol as a solvent.
After kneading for a period of time, a green sheet with a thickness of 300 μm and a density of 1.70 g/CI' was formed by the doctor blade method.

This green sheet was punched to a size of 90 m + square, and 100 via holes each having a diameter of 200 μm were formed using a punch.

Next, this green sheet was exposed to a humid 1\iNa gas flow for 1 hour at varying temperatures from 50 to 100 t, and then W paste was screen printed to form conductor lines and fill the via holes.

The W paste was prepared by adding ethyl cellulose as a binder and butyl carpitol acetate as a solvent to W powder having a particle size of 0.8 μm, and kneading the mixture.

Next, the green sheet 6 formed in this way
After the sheets were aligned and stacked so that the via positions matched, they were integrated by applying pressure at a temperature of 50'C and a stacking pressure of 50 MPa.

After degreasing this laminate by heating it at 600'C in a Nt air flow for 4 hours, it was stored in an IN baking container and fired at varying temperatures in the range of 1500 to 1800°C, resulting in a multilayer structure. A circuit board was formed.

The airtightness of the thus formed substrate was examined using a helium (He) leak detector as a measure of the adhesion between the conductor line and the substrate.

Table 1 Table 1 shows the presence or absence of oxidation treatment in wet N2 according to the present invention.
It shows the relationship between the temperature of wet N2 gas, the firing temperature of the laminated green sheets, and whether or not the vias are airtight.

Here, in the column showing the airtightness of the vias, an x mark indicates that there are 80 or more leaks out of 100 vias, a Δ mark indicates that there are 20 or less leaks out of 100 vias, and a 0 mark indicates that there are 20 or less leaks out of 100 vias. The leak is less than 1 oiii in the via of 100 @, and the ◎ mark indicates the one with no leak.From the results in this table, it is heat-treated at a hot water temperature of 50 to 100 °C in a humid N2 gas stream and heated to 1600 °C. It can be seen that good results can be obtained by firing with the above conditions.

The reason why the results are poor when heated at 150° C. in a humid 11N2 gas stream is that the binder is softened and the ^lN green sheet is deformed.

Rigidization is possible.

〔Effect of the invention〕

Claims (1)

[Claims] A step of drilling holes in an aluminum nitride green sheet at via formation positions and then heating in a humid nitrogen gas atmosphere, and screen-printing a conductive paste on the green sheet to form conductor lines. a step of stacking the green sheets while aligning them and integrating them by applying pressure; and a step of firing the laminate in a nitrogen gas atmosphere. A method for manufacturing an aluminum nitride multilayer circuit board, comprising: