JPH02159096A - Manufacture of aln multilayer substrate - Google Patents

Abstract

PURPOSE:To eliminate distortion and to prevent development of insulating layer due to removal and carbonization of a surface metallized layer by sealing a conductor inside an aluminum nitride(AlN) green sheet and by burning it. CONSTITUTION:A conductor is sealed inside an aluminum nitride(AlN) green sheet and burnt. As for a sealing method, a green sheet which is provided with a conductor pattern or a conductor via, and a pure green sheet which covers an exposed area of the conductor are laminated. Since a conductor (W via 3, or W pattern 5) is shielded from furnace atmosphere, a surface state of a substrate after sintered is good and a conductor does not carbonized. Furthermore, since the conductor is sintered wrapped in an AlN green sheet, a difference of shrinkage rate is reduced, thereby resulting in reduction of warp of a substrate.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a method for manufacturing an aluminum nitride (^IN) substrate;
In particular, it concerns a method of firing an IN substrate in which a conductor such as tungsten (11) is formed in the inner layer or surface layer.

The objective is to obtain an AIN substrate that is free from distortion and no peeling or carbonization of the surface metallized layer during substrate firing.

The conductor is configured to be sealed within an aluminum nitride (AIN) green sheet and fired. Further, as a sealing method, a green sheet having a conductor pattern or a conductor via formed thereon and a solid green sheet covering the exposed portion of the conductor are laminated.

(Industrial Application Field) The present invention relates to a method for manufacturing an AIN substrate, and particularly to a method for firing an AIN substrate having an inner layer of a conductor such as -.

In recent years, as computer systems have become faster.

Interposers (interposers, vias for interlayer connections, etc.) and multilayer ceramic substrates are required.

AIN, which has high thermal conductivity and a coefficient of thermal expansion close to that of silicon, is used as a material for interposers and multilayer ceramic substrates, so it must be fired together with a conductor. Examples of conductive materials that can be fired together with AIN include - and molybdenum (Mo), but since AIN has a higher firing temperature than other ceramics, the difference in shrinkage rate with AIN during firing causes the difference between AI and AIN.
This causes warping and waviness in the N substrate.

For this reason, there is a demand for an AIN substrate that can be integrally fired with a conductor without warping.

[Conventional technology]

FIGS. 2(1) to 2(3) are schematic cross-sectional views illustrating the firing of an AIN substrate according to a conventional example.

Conventional AIN substrate firing methods include multiple sheets having vias 3 passing through the AIN green sheet 2 (see FIG. 2 (1)), or multiple sheets having a pattern 5 printed on the surface of the AIN green sheet 4. (Second
(Fig. 2)) were laminated using a press to form a sample 7, which was degreased in nitrogen and then fired on a center 8 made of boron nitride (BN) in a graphite container 6 (Fig. 2). (
3)).

However, in this method, the starting temperature of - firing shrinkage is AIN
In addition, the additive of the green sheet scatters from the surface of the AIN substrate during sintering, causing distortion of the AIN substrate and peeling of the printed pattern.

Furthermore, since carbon is used in the heater of the firing furnace, carbon is mixed into the atmosphere inside the furnace. Therefore, the surface layer of the conductor is carbonized and an insulating layer is formed.

[Problems to be Solved by the Invention] Therefore, it has been difficult to form a surface metallized layer or vias on an IN substrate by simultaneous firing, that is, at the same time as the substrate is fired.

An object of the present invention is to provide a method for manufacturing an AIN substrate by simultaneous firing, which does not cause distortion of the AIN substrate, and does not cause peeling of the surface metallized layer or formation of an insulating layer due to carbonization.

[Means to solve the problem]

The solution to the above problem was to replace the conductor with aluminum nitride (AIN).
) A method for manufacturing an AIN multilayer board, characterized by sealing it in a green sheet and firing it, or as the sealing method, a green sheet with a conductor pattern or conductor via formed thereon, and covering the exposed portion of the conductor. This is achieved by a method for manufacturing an AIN multilayer board, which is characterized in that it is laminated with solid green sheets.

In this case, the AI with conductor patterns or vias formed
A sufficient effect can be obtained by covering the exposed conductor part of the N laminate with a solid green sheet without applying pressure.

[Effect]

FIGS. 1(1) and 1(2) are schematic cross-sectional views illustrating the principle of firing an AIN substrate according to the present invention.

FIG. 1(1) shows a stack of AIN green sheets 2 with vias 3 formed thereon and upper and lower solid AIN green sheets 1 simultaneously stacked.

FIG. 1(2) shows a laminate of AIN green sheets 4 having a - pattern 5 printed on their surfaces, and a solid AJN green sheet 1 laminated thereon at the same time.

Next, in FIG. 2 (3), the laminate produced in FIG. 1 (1) or FIG. 1 (2) is used as sample 7, and after degreasing it in nitrogen, the BN Firing is performed on a center 8 made of

The sintered body fired as described above can be polished to expose the conductor if necessary, such as when connecting the inner conductor to the outside.

In the present invention, as shown in FIG. 1 (1) or (2), the conductor (-via 3. or control pattern 5) is isolated from the furnace atmosphere using a solid AIN green sheet l, so that the substrate is not removed after sintering. The surface condition of the conductor is good and the conductor is not carbonized, and
This method takes advantage of the fact that since the conductor is sintered while being wrapped in the AIN green sheet, the difference in shrinkage rate is reduced and the warpage of the substrate can be reduced.

The present invention is particularly effective for firing AIN substrates at high sintering temperatures.

〔Example〕

A comparative example and an example will be explained using FIG. 1.

First, a comparative example is produced under the same conditions as the example.

Comparative example: A slurry having the composition shown in Table 1 was prepared, and a molding gap of 450μ was formed using the doctor blade method.
A green sheet was produced by molding at a feed rate of 2.3 m/+in.

Table 1 Slurry composition (parts by weight) Ceramic AIN 100, CaC0+ 5
゜Binder PVB 10 Plasticizer DBP 10 Dispersion medium Ethanol 50 Here, PVB (Polyvinyl Butyr
al) used S-LEC B series (BL-1) manufactured by Building Block Chemical.

Also, DBP (Di-n-butyI Phtala
te, phthalate-lobetyl) used was a special grade reagent manufactured by Wako Pure Chemical Industries.

These green sheets were stacked in 10 layers (lamination conditions: heating temperature 50°C, lamination pressure 45 MPa for 20 minutes), and 20 through holes of 0.2 msφ were drilled into this.
A sample for forming vias corresponding to FIG. 2 (1) was prepared by forming 900 pieces in the au corner and filling them with a commercially available paste. Further, a pattern of 300 μm in width and 7011 IIl in length was formed on a green sheet using a commercially available paste, and 10 layers were stacked under the same lamination conditions to prepare a sample for a multilayer board corresponding to FIG. 2 (2).

The laminated green sheets for forming vias and green sheets for multilayer substrates were degreased at 600°C in nitrogen, and each sample was placed in a BN glass container 6 in a graphite container 6 as shown in FIG. 2 (3). It was set on the ivy 8 and fired under a gas flow of 1 atm in nitrogen at a firing temperature in the range of 1700 to 1900°C for a holding time of 3 hours.

Table 2 Comparative Example Results Firing Temperature Via Multilayer Board (''C) (Warp) (Warp) (Peeling) (Carbonization) 1700 Yes Yes No No 1
750 Yes Yes No No 1800
Yes Yes Yes Yes 1850
Yes Yes Yes Yes1900
Yes Yes Yes Yes Large warpage was observed in the sample for via formation regardless of the firing temperature.

In addition, the surface of the multilayer substrate sample was rough, and the substrate was warped. Also, one pattern on the surface is turned up.
(Indicated as peeling in the table), carbonized and turned black, and an insulating layer was formed.

Example 1 (see Figure 1 (1)): 10 layers of via green sheets 2 of the above comparative example and solid green sheets 1 were stacked above and below the layers,
After degreasing at 00°C, each sample was set on the BN center 8 in the graphite container 6 shown in FIG.
Firing was performed at 900°C for a holding time of 3 hours.

Note that the above lamination was performed as follows.

After laminating 10 layers under the above lamination conditions, 3 through holes were opened and filled with paste.

Solid green sheets were laminated on the top and bottom of the dried green sheet laminate without applying any pressure.

Example 2 (see FIG. 1 (2)): 10 layers of the multilayer board green sheet 4 of the above comparative example,
A solid green sheet L was laminated thereon under the same conditions as in Example 1, degreased at 600'C in nitrogen, and each sample was placed in a graphite container 6 shown in FIG.
Set it on the center 8 of the manufacturer, and hold it for 3 at a firing temperature in the range of 1700 to 1900"C with a gas flow of 1 atm in nitrogen.
Firing was performed in h.

Table 3 shows the firing results of Examples.

Table 3 Results of Examples Firing Temperature Via Multilayer Board ('C) (Warp) (Warp) (Peeling) (Carbonization) 1700 None None None None 1
750 None None None 1800
None None None 1850
None None None None 1900 None None None Yes Table 3 shows the following.

In the case of Example 1 (via), the firing temperature was 1700-19
No warpage of the substrate was observed in the temperature range of 00°C.

In the case of Example 2 (multilayer substrate), the firing temperature was 1900°C.
Carbonization occurred only in the case of 1,700°C to 1,850°C, and no such change was observed in the substrates fired in the range of 1,700 to 1,850°C.

The conductor of the sintered body produced in the example can be exposed by polishing, if necessary.

It is also possible to place seven ivy vines on top of the sample 7 as a weight for firing.

Furthermore, if necessary, the solid green sheets above and below the green sheets for forming vias for multilayer substrates may be simultaneously laminated under pressure.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to prevent warping of the substrate, peeling and carbonization of the interposer or wiring pattern, and contribute to improving reliability and yield of the interposer or multilayer ceramic substrate.

Furthermore, since a bottom is formed in the through hole, filling with the conductive paste is facilitated, and since the through hole is covered, bleeding of the via caused by changes in paste viscosity is improved.

Furthermore, by sealing the AIN substrate with a solid green sheet, the atmosphere around the substrate during firing can be made uniform, and the firing conditions on the substrate surface can be made uniform.

[Brief explanation of the drawing]

FIGS. 1(1) and 1(2) are schematic cross-sectional views illustrating the principle of firing the ^IN substrate according to the present invention. FIGS. 2(1) to 2(3) are schematic cross-sectional views illustrating the firing of an AIN substrate according to a conventional example. In fig. l is solid AIN green sheet. 2 - AIN green sheet with vias formed. 3 is - Bahia. 4 is an AIN green sheet with an enemy pattern printed on it. is H pattern. is a graphite container. is a sample. The center is made of BN (11 vias formed in Fig. 1).

Claims (2)

[Claims] (1) A method for manufacturing an AIN multilayer board, which comprises sealing a conductor within an aluminum nitride (AIN) green sheet and firing it. (2) As the sealing method according to claim 1, the AIN multilayer board is characterized in that a green sheet on which a conductor pattern or conductor vias are formed and a solid green sheet covering the exposed portion of the conductor are laminated. manufacturing method.