JP2572103B2 - Manufacturing method of A1N substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding a method for producing a dense and high thermal conductivity AlN substrate, AlN is liable to be decomposed and volatilized in low-pressure sintering, causing cracks and the like. In order to solve the problem of non-densification and to provide AlN with high density and high thermal conductivity, a green sheet of AlN or a laminate thereof in a furnace filled with nitrogen gas at a room temperature and a pressure of 1 to 300 mbar. It is configured as a firing method.

[Industrial applications]

The present invention relates to a dense and high thermal conductivity aluminum nitride (Al
N) A method for manufacturing a substrate.

[Problems to be solved by conventional technology and invention]

The AlN substrate is generally placed in a tunnel furnace under a nitrogen stream at normal pressure.
It is fired at a high temperature of 800 ° C or more for about 10 hours. However, AlN is decomposed in a nitrogen atmosphere at 1 atm, which causes problems such as warpage. Al to reduce decomposition
There is a method of embedding and firing with N powder, but in this case, AlN powder adheres to the substrate and the surface becomes rough. There is also a method in which a weight material is placed and fired to suppress warpage,
In this case, variations in shrinkage, cracks, and the like are likely to occur.

On the other hand, when firing in a high-pressure nitrogen atmosphere, decomposition is unlikely to occur, but the liquid phase generated by the reaction with the sintering aid does not volatilize sufficiently, so that it does not densify and has low thermal conductivity. Become.

Therefore, the present invention suppresses the decomposition of AlN without using embedding powder, and also suppresses the warpage without using a weight material,
It is another object of the present invention to provide a method for baking an AlN substrate that is dense and has high thermal conductivity by sufficiently evaporating a liquid phase.

[Means for solving the problem]

The object of the present invention is to provide a method for producing an AlN substrate, comprising firing an AlN green sheet or a laminate thereof in a furnace filled with nitrogen gas at a pressure of 1 to 300 mbar at room temperature. To achieve.

In order to achieve the above object, the present inventors are in the process of eagerly studying that the liquid phase can be sufficiently volatilized by firing AlN under reduced pressure, and if it is under a certain range of nitrogen pressure in a sealed furnace. The present inventors have found that an AlN fired body with little decomposition of AlN and small warpage can be obtained, and thus completed the present invention.

The nitrogen pressure in the closed furnace is between 1 mbar and 300 mbar at room temperature. When the pressure is lower than this range, the decomposition of AlN becomes remarkable, and when the pressure is higher, volatilization of the liquid phase becomes insufficient and densification does not occur. Preferred nitrogen pressure is 10 mbar to 200 mba at room temperature
range of r.

A green sheet or a laminate thereof for manufacturing an AlN substrate to which the method of the present invention is applied may be a conventional one, and the firing temperature and the firing time may be the same as those in the related art.

[Action]

By firing under reduced pressure, the liquid phase was effectively volatilized, and by regulating the pressure in the closed furnace within a certain range, the warpage of the substrate could be minimized.

〔Example〕

2 wt% of CaO is added to AlN powder, and polyvinyl butyral, dibutyl phthalate (DBP), and ethanol are further added, and a 150 μm-thick AlN green sheet is prepared by a doctor blade method. After lamination, degreasing was performed in nitrogen at 600 ° C. for 4 hours.

These samples were fired at 1800 ° C. for 6 hours under the following conditions.

(1) vacuum, (2) 1 mbar N ₂ gas flow, (3) 10 mbar N ₂ gas flow, (4) 1 mbar N ₂ gas filling, (5) 10 mbar N ₂ gas filling, (6) 30 mbar N ₂ gas filling, (7) 100 mbar N ₂ gas filling, (8) 300 mbar N ₂ gas filling, (9) 400 mbar N ₂ gas filling.

The following table shows the results of examining the obtained fired body for weight reduction, warpage, relative density, and thermal conductivity.

From the above, it is recognized that in the example of the present invention, an AlN substrate having a small warpage, a high density, and a high thermal conductivity can be obtained.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to the method of this invention, the AlN board | substrate which has no warpage, is dense, and has high thermal conductivity is obtained. In addition, since firing is performed with gas sealing, there is an advantage that the amount of gas used is significantly reduced as compared with the case of gas flow. If the aluminum nitride substrate obtained by the present invention is subjected to HIP processing, a more dense substrate can be obtained.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Table Koji 1015 Uedanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Nobuo Kamehara 1015 Uedanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (1)

(57) [Claims] 1. A method for manufacturing an aluminum nitride substrate, comprising firing a green sheet of aluminum nitride or a laminate thereof in a furnace filled with nitrogen gas at a pressure of 1 to 300 mbar at room temperature.