JP2629325B2 - Manufacturing method of AlN multilayer substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] The present invention relates to a method for manufacturing an aluminum nitride (AlN) substrate,
In particular, it relates to a method for firing an AlN substrate having a conductor such as tungsten (W) formed on an inner layer or a surface layer. For this purpose, the conductor is sealed in an aluminum nitride (AlN) green sheet and fired. As a sealing method, a green sheet having a conductor pattern or a conductor via formed thereon and a solid green sheet covering an exposed portion of the conductor are laminated.

[Industrial applications]

The present invention relates to a method for manufacturing an AlN substrate, and particularly to a method for firing an AlN substrate having a conductor such as W inside.

In recent years, with the speeding up of computer systems, interposers (interposers, vias for interlayer connection, etc.) and multilayer ceramic substrates have been required.

Since AlN, which has a high thermal conductivity and a thermal expansion coefficient close to that of silicon, is used as a material for interposers and multilayer ceramic substrates, it must be integrally fired with a conductor. There are W, molybdenum (Mo), etc. as conductors that are integrally fired with AlN. However, since AlN has a higher firing temperature than other ceramics, it warps the AlN substrate due to the difference in shrinkage ratio with AlN during firing. This may cause undulation.

For this reason, there is a demand for an AlN substrate that is not warped by integral firing with a conductor.

[Conventional technology]

FIGS. 2 (1) to 2 (3) are schematic cross-sectional views for explaining firing of an AlN substrate according to a conventional example.

As a conventional method of firing an AlN substrate, a plurality of sheets having a W via 3 penetrating the AlN green sheet 2 (second sheet) are used.
(1), or a plurality of sheets (FIG. 2 (2)) having a W pattern 5 printed on the surface of an AlN green sheet 4 are laminated by pressing to obtain a sample 7, which is degreased in nitrogen. The sintering is performed on a boron nitride (BN) setter 8 in a graphite container 6 (FIG. 2 (3)).

However, in this method, the starting temperature of the firing shrinkage of W is lower than that of AlN, and the auxiliary of the green sheet scatters during sintering from the surface of the AlN substrate. Cause.

Further, since carbon is used for the heater of the firing furnace, carbon is mixed into the furnace atmosphere. 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 via on an AlN substrate by simultaneous firing, that is, simultaneously with the substrate firing.

The present invention relates to an AlN film which is co-fired and has no distortion of the AlN substrate and no insulating layer due to peeling and carbonization of the surface metallized layer.
It is an object to obtain a method for manufacturing a substrate.

[Means for solving the problem]

In order to solve the above problems, the conductor must be made of aluminum nitride (Al
N) A method of manufacturing an AlN multilayer substrate characterized by sealing and firing in a green sheet, or as a sealing method, a green sheet having a conductor pattern or a conductor via formed thereon and an exposed portion of the conductor. This is achieved by a method for manufacturing an AlN multilayer substrate, characterized by laminating with a covering solid green sheet.

In this case, a conductor pattern or via-formed Al
A sufficient effect can be obtained by covering the exposed portion of the conductor of the N laminate with a solid green sheet without pressure.

[Action]

1 (1) and 1 (2) are schematic sectional views for explaining the principle of firing an AlN substrate according to the present invention.

FIG. 1A shows a laminate of AlN green sheets 2 having W vias 3 formed thereon, and upper and lower solid AlN green sheets 1.
Are simultaneously laminated.

FIG. 1 (2) shows a laminate of an AlN green sheet 4 having a W pattern 5 printed on its surface and a solid AlN green sheet 1 on the laminate.

Next, in FIG. 2 (3), the laminate prepared in FIG. 1 (1) or FIG. 1 (2) was used as a sample 7 and degreased in nitrogen. Is baked on a setter 8 made of aluminum.

In the sintered body fired as described above, the conductor can be exposed by polishing if necessary, for example, when connecting the inner conductor to the outside.

According to the present invention, as shown in FIG. 1 (1) or (2), a conductor (W via 3 or W
Since the pattern 5) is shielded from the atmosphere in the furnace, the surface condition of the substrate after sintering is good, the conductor is not carbonized, and the conductor is sintered while being wrapped in an AlN green sheet. The difference in rate is reduced, and the warpage of the substrate can be reduced.

The present invention is particularly effective for firing an AlN substrate having a high sintering temperature.

〔Example〕

 Comparative examples and examples will be described with reference to FIG.

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

Comparative Example: A slurry (Slurry) having the composition shown in Table 1 was prepared, and molded using a doctor blade method with a molding gap of 450 μm and a feeding speed of 2.3 m / min to produce a green sheet.

Table 1 Slurry composition (parts by weight) Ceramic AlN 100, CaCO ₃ 5. Binder PVB 10 Plasticizer DBP 10 Dispersion medium Ethanol 50 Here, PVB (Polyvinyl Butyral) is manufactured by Eslek B series (BL-1), manufactured by Sekisui Chemical. Using.

For DBP (Di-n-butyl Phtalate), a special grade reagent manufactured by Wako Pure Chemical Industries, Ltd. was used.

This green sheet was laminated 10 times and laminated (lamination conditions: heating temperature 50 ° C, laminating pressure 45MPa, pressurized for 20 minutes), and 900 through holes of 0.2mmφ were formed in a 20mm square with a drill. The sample filled with W paste was used as a via forming sample corresponding to FIG. 2 (1). A green sheet having a pattern of 300 μm in width and 70 mm in length formed with a commercially available W paste was laminated 10 layers under the same lamination conditions to obtain a multilayer substrate sample corresponding to FIG. 2 (2).

The laminated green sheets for forming vias and the green sheets for the multilayer substrate are degreased in nitrogen at 600 ° C., and each sample is placed in a BN setter 8 in a graphite container 6 shown in FIG. Set on top and hold for 1700-1900 ° C in baking temperature under 1 atmosphere gas flow in nitrogen
The firing was performed for 3 hours.

 Table 2 shows the results of the firing.

The sample for via formation showed a large warp regardless of the firing temperature.

Also, in the multilayer substrate sample, the substrate surface was rough and the substrate was warped. Further, the W pattern on the surface was turned up (indicated as "peeling" in the table), carbonized and turned black, and an insulating layer was formed.

Example 1 (see FIG. 1 (1)): Ten layers of via green sheets 2 of the comparative example, and solid green sheets 1 above and below the green sheets 2 were stacked on top of each other.
After degreasing at 0 ° C., each sample was set on a BN setter 8 in a graphite container 6 shown in FIG. Was carried out for a holding time of 3 hours.

 Note that the above lamination was performed as follows.

After laminating 10 layers under the above-mentioned laminating conditions, a through hole was opened, a W paste was filled in the through-hole, and a solid green sheet was covered above and below the dried green sheet laminate without applying pressure.

Example 2 (refer to FIG. 1 (2)): The green sheet 4 for a multilayer substrate of the comparative example was composed of 10 layers.
A solid green sheet 1 was laminated thereon under the same conditions as in Example 1 and degreased in nitrogen at 600 ° C., and each sample was placed in a graphite container 6 shown in FIG. It was set on the setter 8 and baked for 3 hours at a calcination temperature of 1700 to 1900 ° C. with a gas flow of 1 atm in nitrogen.

 Table 3 shows the results of firing in the examples.

Table 3 shows the following.

In the case of Example 1 (via), the firing temperature is 1700 to 1900 ° C.
No warping of the substrate was observed in the range.

In the case of Example 2 (multilayer substrate), carbonization occurred only at a firing temperature of 1900 ° C., and no such change was observed in a substrate fired in the range of 1700 to 1850 ° C.

The conductor of the sintered body manufactured in the embodiment can be exposed by polishing if necessary.

A setter may be placed as a weight on the sample 7 and fired.

Also, if necessary, green sheets for via formation,
Solid green sheets above and below the green sheet for the multilayer substrate may be simultaneously laminated under pressure.

〔The invention's effect〕

As described above, according to the present invention, it is possible to prevent the warpage of the substrate, the separation and carbonization of the interposer or the wiring pattern, and to contribute to the improvement of the reliability and the yield of the interposer or the multilayer ceramic substrate.

Further, since the bottom is formed in the through hole, the filling of the conductor base becomes easy, and since the three hole is covered, the bleeding of the via caused by the change in the viscosity of the paste is improved.

In addition, by sealing the AlN 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 description of the drawings]

1 (1) and 1 (2) are schematic cross-sectional views illustrating the principle of firing an AlN substrate according to the present invention, and FIGS. 2 (1) to (3) are schematic cross-sectional views illustrating firing of an AlN substrate according to a conventional example. FIG. In the figure, 1 is a solid AlN green sheet, 2 is an AlN green sheet formed with a W via, 3 is a W via, 4 is an AlN green sheet on which a W pattern is printed, 5 is a W pattern, 6 is a graphite container, and 7 is a graphite container. Sample 8 is a BN setter.

Claims (2)

(57) [Claims] 1. A method for manufacturing an AlN multilayer substrate, wherein a conductor is sealed in an aluminum nitride (AlN) green sheet and fired. 2. A sealing method according to claim 1, wherein a green sheet on which a conductor pattern or a conductor via is formed and a solid green sheet covering an exposed portion of the conductor are laminated. A method for manufacturing a multilayer substrate.