JP2757874B2 - Method for firing aluminum nitride substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for firing an aluminum nitride (AlN) substrate. In firing, no fusion occurs at a predetermined green sheet and a desired position thereof, and the firing of the AlN substrate is mass-produced. A method for baking an aluminum nitride substrate having a wiring pattern on a surface thereof, the method comprising: baking a plurality of aluminum nitride green sheets having a wiring pattern on the surface; And firing with a green sheet interposed therebetween.

[Industrial applications]

 The present invention relates to a method for firing an AlN substrate.

In accordance with recent demands for faster computer systems,
Interposers and multilayer ceramic substrates are required. Since aluminum nitride (AlN), which has a high thermal conductivity and a thermal expansion coefficient close to that of silicon, is also used as a material for interposers and multilayer ceramic substrates, studies including simultaneous firing with conductors (W, Mo, etc.) have been conducted. Have been done. But,
In order to sinter AlN, sintering at a high temperature is necessary, and in a batch type sintering furnace, the cost varies greatly depending on the setting method. For this reason, there is a demand for a method of firing the AlN substrate using a setting method for reducing costs.

[Conventional technology]

As a conventional method of firing an AlN substrate, as shown in FIG. 5, a wiring pattern forming green sheet (substrate) 3 is placed one by one on a boron nitride (BN) setter 1 or the like, and a plurality of the combinations are stacked on graphite or graphite. There is a method of firing in the BN container 4. In this set, a BN spacer 7 is arranged between the BN setters 1 and no load is applied to each green sheet 3. However, in this method, only one green sheet 3 can be fired per BN setter 1, and the firing space is reduced due to the thickness and number of BN setters.

Although not shown, there is a method of stacking green sheets directly on a BN setter and firing in a graphite or BN container in order to reduce costs. However, in this method, when a load is strongly applied to a portion between the substrates during firing, the substrates are fused to each other at that portion.

[Problems to be solved by the invention]

Therefore, an object of the present invention is to mass-produce AlN substrates without firing at a desired green sheet and a desired position during firing. Another object of the present invention is to reduce warpage during firing.

[Means for solving the problem]

According to the present invention, there is provided a method for firing an aluminum nitride substrate including a step of firing a plurality of aluminum nitride green sheets having a wiring pattern on a surface thereof,
The problem is solved by a method for firing an aluminum nitride substrate, comprising laminating and firing an aluminum nitride green sheet having the wiring pattern on a surface thereof with a fusion preventing green sheet having a tungsten pattern formed on the surface interposed therebetween. .

Further, according to the present invention, there is provided a method for firing an aluminum nitride substrate including a step of firing an aluminum nitride green sheet, the method comprising the steps of: forming a tungsten pattern for preventing fusion on a surface edge of a solid green sheet; The problem is solved by a method of firing an aluminum nitride substrate, which is characterized in that the sheets are laminated with a sheet interposed.

(Operation)

According to the present invention, since the green sheets are densely laminated and fired as a laminated body, mass production becomes possible, and a wiring pattern of a fusion forming portion is formed in advance at the edge of the green sheet between desired green sheets. Since the fused portion is cut, formation of the fused portion is prevented in a desired green sheet.

As the wiring pattern used in the present invention, tungsten paste, other high-melting-point metal paste such as Mo and Ti, Zr,
TiB ₂ , ZrB ₂ , TiN, ZrN, or the like can be used.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a view showing a manufacturing process of an AlN multilayer circuit board having a conductor pattern of W, Mo, etc., (1) an AlN ceramic slurry adjusting process, (2) a green sheet forming process by a doctor blade method, and (3). A green sheet punching step, (4) a hole forming step for forming a via hole, (5) a step of forming a conductor wiring pattern such as W or Mo on the perforated green sheet, and (6) a green having a wiring pattern formed thereon. (7) a degreasing step of heat-treating the laminated green sheet laminate to remove the organic binder; and (8) a degreased laminate having a predetermined temperature profile, a predetermined atmosphere, and the like. Then, heat treatment is performed under predetermined heat treatment conditions to manufacture an AlN multilayer circuit board on which a conductor pattern such as W, Mo, Ti, Zr, TiB ₂ , ZrB ₂ , TiN, and ZrN is formed. The present invention particularly relates to the above steps (6) to (8). FIG. 2 shows a process chart of the above steps (4) to (6) performed in the present invention, wherein (a) shows a punched and formed AlN green sheet 22, and (b) shows a via hole in the AlN green sheet 22. A hole is formed to form the conductor wiring pattern 23 and then a conductor paste, which is a mixture of the above-described powder of the conductor material, an organic solvent and a thixotropic agent (such as castor oil), is screen-printed on the green sheet 22 to form the conductor wiring pattern 24 and the via 23. To form

(C) The green sheet 22 on which the conductor wiring patterns 24 and the vias 23 are formed is laminated in a plurality of layers. For example, the green sheet 22 on which the conductor wiring pattern 24 and the via 23 are formed is
The layers are laminated, and a pressurized temperature of 70 ° C., a pressure of 50 MPa, and a holding time of 30 are formed into an integrated multilayered body 25.

(D) A solid AlN green sheet for preventing fusion of the AlN multilayer circuit boards on the upper surface of the green sheet placed on the integrated multilayer laminate 25 or a □ (frame-like) or parallel pattern-like The AlN green sheet 26 on which the fusion prevention pattern 27 is formed is formed.

(E) The fusion-preventing green sheet 26 formed in the step (d) is interposed between the integrated multilayered laminates 25 of the green sheets formed in the step (c), and without pressing, Stack multiple times on a setter 27 such as BN.

FIG. 3 is a plan view showing a fusion prevention green sheet 34 in which a fusion prevention parallel pattern 33 is formed on an AlN green sheet 32 as a fusion prevention green sheet.
The figure shows one embodiment of the method of the present invention in which the above-mentioned green sheet integrated multilayered body and the non-fused or unfused green sheets on which the unfused pattern is formed are alternately laminated and fired. FIG.

The pattern 33 shown in FIG. 3 is made of, for example, W (tungsten) as a wiring material, and is formed on the AlN green sheet 32. In FIG. 4, BN setter 1 is placed in BN container 4.
Multilayer laminate with integrated green sheet on which wiring pattern is formed
25 and fusing prevention green sheets 26 are alternately laminated,
An AlN sintered substrate 6 for preventing (correcting) warpage is provided on the top of the substrate. Even if the AlN sintered substrate is not provided, the warpage is prevented as compared with the conventional case, but it is more preferable to provide the AlN sintered substrate 6 for correction.

In the examples of the present invention, (1) Preparation of green sheet A slurry having the composition shown in Table 1 was prepared, and a forming gap of 450 μm and a feeding speed of 2.3 m / min were measured using a doctor blade.
To form a green sheet.

(2) Formation of W pattern This green sheet was punched into a square of 90 mm, and a pattern having a width of 300 µm was formed using a commercially available tungsten (W) paste.

(3) Lamination of Green Sheets The prepared pattern-formed green sheets were laminated as a set of 10 sheets under the following conditions. (Pressure temperature 70 ° C, pressure 50MP
a, retention time 30 min) 25 is the laminate.

Samples 25 laminated under the above conditions and green sheets 26 for preventing fusion formed with a pattern for preventing fusion were alternately stacked.

That is, finally, 10 AlN multilayer circuit boards are formed.

(4) Degreasing and firing In the graphite container 40, an integrated multilayered laminated body 25 of green sheets having a setter 1W pattern of BN and a green sheet 26 for preventing fusion are alternately stacked on each other and set as shown in FIG. did. Table 2 shows the results of sintering the sample after removing the organic binder at 1000 ° C. under a gas flow of 1 atmosphere in nitrogen. The lower two multilayer circuit boards were fused in the set of ten green sheet integrated multilayer bodies. However, peeling was possible. That is, since only the W paste of the frame pattern or the parallel pattern for preventing fusion was fused, the surface roughness at the center of the substrate was good, and W had a metallic luster. Also, no warping was observed in each substrate, and the results of the warping were good as shown in Table 2.

Comparative Example 1 A slurry having the composition shown in Table 1 was prepared in the same manner as above,
Using a doctor blade, molding was performed at a molding gap of 450 μm and a feeding speed of 2.3 m / min to produce a green sheet. This green sheet is punched into □ 90mm, and the green sheet punched into 90mm square is 300μm wide with a commercially available W paste.
Was formed. The prepared pattern-forming green sheets were laminated as a set of ten sheets under the following conditions. (Pressure temperature 70 ° C, pressure 50MPa, holding time 30min). Each sample of the green sheet-integrated multilayered laminate was stacked on a BN setter in a graphite container as shown in FIG.
The green sheet integrated laminate was degreased at 1000 ° C. in a gas pressure gas flow, and then fired at a firing temperature of 1800 ° C. and a holding time of 3 hours. Table 2 shows the results of the firing. The number of fired multi-layer circuit boards was three, and the surface was bad and W was blackened. In addition, the fired body of the multilayer circuit board was warped.

Embodiment 2 FIG. 5 is a plan view showing a fusion-prevention green sheet 26 'in which a fusion-prevention pattern (W paste) 52 is printed around the periphery of the surface, and FIG. 6 shows the green sheet. FIG. 6 is a sectional view showing a second embodiment of the present invention in which the layers are stacked and fired.

(1) Preparation of green sheet A slurry having the composition shown in Table 1 was prepared in the same manner, and a forming gap of 450 μm and a feed rate of 2.3 were measured using a doctor blade.
Molding was performed at m / min to produce a green sheet. This green sheet was punched into a 90 mm square. Drilling for via formation was performed on the green sheet, and a conductive paste was screen-printed to form a conductive pattern on the green sheet.

(2) Lamination of Green Sheets Ten green sheets formed with the conductor pattern formed in (1) were laminated as a set under the following conditions to obtain a green sheet integrated multilayer laminate. (Pressure temperature 70 ° C, pressure 50MP
a, holding time 30 min) (3) Formation of a fusion-preventing green sheet A commercially available W paste was applied to a solid green sheet with a width of 300 mm.
A pattern of μm and □ 70 mm was formed.

For pattern formation, use a commercially available W paste with a width of 300 μm,
A 70 mm-shaped pattern (frame) was formed on the edge of the green sheet surface as shown in FIG. Table 3 shows the results of the same degreasing, setting, and baking as described above in the same steps as in Example 1. The lower two sheets were fused together when 10 sheets were set. However, peeling was possible. The surface roughness at the center of the substrate was good because only the W paste at the edge of the green sheet was fused. In this embodiment, the peripheral portion including the above-mentioned fused portion was cut and used. As shown in FIG. 6, the AlN sintered substrate 6 for correction is provided on the uppermost portion of the green sheet, but the warpage can be reduced as in the previous embodiment without the substrate.

Comparative Example 2 A slurry having the composition shown in Table 1 was prepared, and molded using a doctor blade at a molding gap of 450 μm and a feeding speed of 2.3 m / min to produce a green sheet. This green sheet was punched into □ 90 mm and laminated in 10 layers. In nitrogen
After degreasing at 1000 ° C, 10 samples were stacked on each other and set on a BN setter in a graphite container as shown in Fig. 7, and fired at 1800 ° C and a holding time of 3 hours at a gas pressure of 1 atmosphere in nitrogen gas flow. went. Table 2 shows the results of the firing. Bottom 4 sheets were fused among 10 sheets. Also, the two lowermost layers are
It was completely fused, and the third and fourth sheets could be peeled off, but the surface condition of the fused central part was bad.

[Effects of the Invention] As described above, according to the present invention, mass productivity is improved and the setting method at the time of firing is simplified. In addition, the fused portion is no longer a desired green sheet, and warpage is reduced, which greatly contributes to improvement of quality and yield. In the embodiment, an example using a graphite container has been described, but a BN container may be used.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a manufacturing process of an AlN multilayer circuit board having a conductor pattern of W, Mo, etc. FIG. 2 is a diagram showing a step of forming a via hole among the steps shown in FIG. 3 is a diagram illustrating a wiring pattern forming green sheet in which a wiring pattern is formed on an AlN substrate green sheet 2 from a hole forming step for forming a multilayered green sheet on which a wiring pattern is formed. FIG. 4 is a plan view, FIG. 4 is a schematic cross-sectional view showing one embodiment of the method of the present invention in which the green sheets and green sheets on which a wiring pattern is not formed are alternately laminated and fired, and FIG. FIG. 6 is a plan view showing a green sheet on which a pattern (W paste) is printed around, and FIG. 6 is a schematic sectional view showing a second embodiment of the present invention in which the green sheets are laminated and fired; FIG. 7 is a schematic cross-sectional view for explaining a conventional technology. 1. BN setter, 2. Green sheet (AlN substrate), 3. Pattern forming green sheet, 4. Graphite or BN container, 5. Wiring pattern (W paste etc.), 6. AlN sintered substrate (For straightening), 7 ... BN spacer.

Claims (1)

(57) [Claims] 1. A method for baking an aluminum nitride substrate, comprising baking a plurality of aluminum nitride green sheets having a wiring pattern on a surface thereof, wherein the aluminum nitride green sheet having the wiring pattern on the surface is formed with a tungsten pattern on the surface. A firing method for an aluminum nitride substrate, comprising laminating and firing with interposed green sheets for preventing fusion.