JPH069275A - Aluminum nitride sintered product and semiconductor device substrate using the same - Google Patents

Abstract

PURPOSE:To obtain an AIN sintered product containing yttrium aluminate so as to surround AlN crystal particles and free from the falling of the AlN particles when polished into a mirror surface, by adding Y2O3 to AlN powder, processing the mixture into particles, compacting the particles, and subsequently sintering the compacted product. CONSTITUTION:Aluminum nitride powder is mixed with yttrium oxide as a sintering auxiliary and an organic binder as a hinder, and subsequently spray- dried into particles. The particles are pressed into a desired shape, or formed into a sheet by a doctor blade method and then processed into the desired shape. The formed green shaped product of the aluminum nitride is defatted and subsequently sintered in a non-oxidative atmosphere to produce the aluminum nitride sintered product having a fine structure in which the crystal particles of the aluminum nitride are surrounded with the yttrium aluminate. The application of a mirror surface polishing to the sintered product gives a polished surface improved in surface roughness characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride sintered body, and more particularly to an aluminum nitride sintered body used after being mirror-polished.

[0002]

2. Description of the Related Art In recent years, semiconductor devices such as semiconductor integrated circuits have been remarkably improved in characteristics such as increase in element integration density, higher speed, and higher output due to multifunctionalization. Along with this, the amount of heat generated from the semiconductor device also remarkably increases, and in order to effectively dissipate the generated heat to the outside, a material having high thermal conductivity is required for the ceramic substrate on which the semiconductor device is mounted. By the way, such an alumina substrate, which is highly versatile as a substrate for a semiconductor device, has a low thermal conductivity of about 20 W / m · k, and has a thermal expansion coefficient larger than that of silicon, which is a material of the semiconductor device. There were problems such as poor bondability. As a material that can solve the problems of alumina, the thermal conductivity is about 190 W /
Aluminum nitride, which has a high m · k and a thermal expansion coefficient close to that of silicon, has been attracting attention. This aluminum nitride sintered body is subjected to mirror-polishing, and a substrate for semiconductor devices, etc., on which a fine wiring pattern made of a thin film or the like is further provided. Is being put to practical use.

[0003]

However, when the above-mentioned aluminum nitride sintered body is subjected to mirror-polishing, defects (voids) are generated on the polished surface due to the dropping of aluminum nitride particles, and the presence of these defects results in semiconductor devices. When the fine wiring pattern is formed on the substrate, there is a problem that the fine wiring has defects such as disconnection and short circuit, and the reliability of the substrate is impaired. The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide an aluminum nitride sintered body in which the aluminum nitride particles are unlikely to fall off when mirror-polished.

[0004]

The aluminum nitride sintered body of the invention according to claim 1 is characterized in that it contains aluminum nitride crystal grains and yttrium aluminate surrounding the aluminum nitride crystal grains. Here, as the aluminum nitride powder used for producing the above-mentioned aluminum nitride sintered body, a fine powder having an average particle diameter of 10 μm or less is used, and particularly preferably 2 μm or less. The yttrium oxide as a sintering aid has an average particle size of 10 μm or less, and particularly preferably 5 μm or less. Furthermore, if a non-translucent substrate (black substrate) is required, the periodic table IIIa, IVa, Va
Group elements or oxides, carbides, borides, nitrides of these elements may be added. In this case, those having an average particle diameter of 10 μm or less are used, and those having an average particle diameter of 5 μm or less are particularly preferable.

The manufacturing process of the aluminum nitride sintered body will be briefly described below. First, an organic binder is added to the above raw material powder as a binder, and wet mixed using an organic solvent or the like. Next, granulated powder is prepared by spray drying and pressed into a desired shape, or a sheet is prepared by a doctor blade method and green-processed into a desired shape to obtain an aluminum nitride green compact. Next, in order to remove the organic binder, heating is performed in air, nitrogen, decomposed gas or the like (degreasing step). In this case, it is necessary to perform degreasing at a temperature not higher than the temperature at which aluminum nitride is oxidized. The degreased aluminum nitride compact thus obtained is placed in a boron nitride container and fired in a non-oxidizing atmosphere. Nitrogen gas is desirable as the non-oxidizing atmosphere. The firing temperature is 1600-21
It is determined in the range of 00 ° C, and particularly preferably in the range of 1650 to 1800 ° C. This is because sintering is not sufficiently performed at 1600 ° C or lower, and decomposition of aluminum nitride itself occurs at 2100 ° C or higher. The sintering is carried out by the atmospheric pressure sintering method, but it may be carried out by the hot pressing method or the pressure sintering method.

The semiconductor device substrate according to the second aspect of the present invention is made of the aluminum nitride sintered body according to the first aspect, and has a surface roughness Rmax of 1.0 μm or less. . This substrate for a semiconductor device is obtained by mirror-polishing the surface of the aluminum nitride sintered body according to claim 1. The surface roughness Rmax is 1.0 μm or less, and more preferably 0.5 μm or less.

[0007]

Since the aluminum nitride sintered body of the invention according to claim 1 has a fine structure in which the aluminum nitride crystal grains are surrounded by the yttrium aluminate, mirror polishing is performed. When applied, the dropping of aluminum nitride crystal particles from the sintered body is suppressed.

Further, the semiconductor device substrate made of the above-mentioned aluminum nitride sintered body has a surface roughness Rmax of 1.0 μm or less because the aluminum nitride particles are prevented from falling off when mirror-polished. Maintain a good surface condition. Therefore, when a fine wiring pattern such as a thin film is formed on the surface of the semiconductor device substrate, defects such as wire disconnection and short circuit are less likely to occur, and the reliability of the semiconductor device substrate is improved.

[0009]

EXAMPLES The present invention will be specifically described below with reference to examples. In this example, the characteristics (density, thermal conductivity, surface roughness, surface state) of the aluminum nitride sintered body according to the present invention were evaluated. (1) Preparation of test product Aluminum nitride (AlN) powder having an average particle diameter of 1.2 μm, yttrium oxide powder (Y ₂ O ₃ ) having an average particle diameter of 1.4 μm as a sintering aid, and an average particle diameter of 0 as a colorant. 0.7 μm titanium dioxide powder (TiO ₂ ) was blended in the proportion shown in Table 1. The test products in Table 1 are No. Nos. 1 to 4 are implemented products. 5
9 to 9 indicate comparative products, which will be similarly displayed below.

[0010]

[Table 1]

Regarding the above-mentioned test product, as shown in Table 2,
Test product No. Nos. 1, 3, 5, 6 and 8 were made into granulated powder by adding a binder to the powders shown in Table 1, and the granulated powder was heated to about 10 at room temperature.
It was molded under pressure of 00 kg / cm ² . In addition, the test product No. 2, 4, 7, and 9 were formed by adding a binder to the powders in Table 1 to prepare green sheets by the doctor blade method, and stacking the sheets. Further, after degreasing these molded bodies in the atmosphere, as shown in Table 2,
It was housed in a container made of boron nitride, a container made of carbon or a container made of aluminum nitride, and baked at 1730 ° C. for 6 hours in a nitrogen atmosphere.

[0012]

[Table 2]

(2) Evaluation of characteristics Results of measurement of density and thermal conductivity characteristics of the above-mentioned sintered body and surface roughness characteristics (maximum roughness R after polishing the mirror surface of the sintered body).
Table 3 shows the measurement results of max and centerline average roughness Ra) and the observation results of the surface state. Specular polishing of the sintered body is #
After rough polishing with 325 diamond whetstone, perform intermediate finishing polishing with # 2000 diamond abrasive grains.
Mirror finishing polishing was performed using 8000 diamond abrasive grains. In addition, the measurement of each characteristic was performed using the method normally used about a ceramic sintered compact. In addition, the surface was visually observed using a reflection microscope (metallurgical microscope).

[0014]

[Table 3]

As is clear from the results shown in Table 3, the test products (excluding No. 5 because it is unsintered) have almost the same density and thermal conductivity, and the sintering is performed sufficiently. ing. However, when each test product was mirror-polished, no aluminum nitride particles were found to have fallen off from the polished surfaces of test products 1 to 4 (implemented product), and the polished surfaces of test products 6 to 9 (comparative product) were not. It was confirmed that the aluminum nitride particles fell off. And, while the test products 1 to 4 (implemented products) all have a maximum surface roughness Rmax of 0.5 μm or less, the test products 6 to 9 (comparative products) all have a maximum surface roughness Rmax of 4.2 μm or more. And a remarkable difference is recognized.

Further, a test product No. which is a typical example of the implemented products is used.
1 and a test product No. which is a typical example of the comparative product. Regarding No. 6, the crystal structures of the fractured surface and the mirror-polished surface were observed with a scanning electron microscope. Here, FIG. 1 is a photograph showing the crystal structure of the fractured surface of the practical product, and FIG. 2 is a photograph showing the crystal structure of the mirror-polished surface of the practical product. 3 is a photograph showing the crystal structure of the fractured surface of the comparative product, and FIG. 4 is a photograph showing the crystal structure of the mirror-polished surface of the comparative product. The horizontal lines in FIGS. 1 to 4 represent a length of 10 μm. In the embodied product, the aluminum nitride crystal particles (gray portion) are present so as to be surrounded by yttrium aluminate (white portion), and the aluminum nitride crystal particles do not fall off.
On the other hand, the comparative product is aluminum nitride crystal particles (gray part)
Yttrium aluminate (white portion) is present in a random state, and the dropout of the aluminum nitride crystal particles (black portion) is clearly observed.

That is, in the aluminum nitride sintered body having a fine structure in which the aluminum nitride crystal grains according to the present invention are surrounded by the yttrium aluminate crystals, yttrium aluminate is randomly distributed in the conventional aluminum nitride crystal grains. Compared with the aluminum nitride sintered body of the structure that exists in the state, the aluminum nitride particles do not fall off from the polished surface when mirror-polished.
The maximum surface roughness Rmax characteristic was improved by about one digit.

The semiconductor device substrate obtained by subjecting the aluminum nitride sintered body having the improved fine structure according to the present invention to the mirror-polishing process produces a fine particle pattern when a fine wiring pattern is formed on the surface of the substrate. The reliability as a substrate for a semiconductor device is improved without causing defects such as disconnection and short circuit due to falling off.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing a crystal structure of a fractured surface of an aluminum nitride sintered body according to an implementation product (test product No. 1) of the present invention.

FIG. 2 is an electron micrograph showing a crystal structure of a mirror-polished surface of an aluminum nitride sintered body according to the same product.

FIG. 3 is an electron micrograph showing a crystal structure of a fractured surface of an aluminum nitride sintered body according to a comparative product (test product No. 6).

FIG. 4 is an electron micrograph showing a crystal structure of a mirror-polished surface of an aluminum nitride sintered body according to the comparative product.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Kanda 14-18 Takatsuji-cho, Mizuho-ku, Nagoya City Nippon Special Ceramics Co., Ltd.

Claims (2)

[Claims] 1. An aluminum nitride sintered body comprising aluminum nitride crystal grains and yttrium aluminate surrounding the aluminum nitride crystal grains. 2. A substrate for a semiconductor device comprising the aluminum nitride sintered body according to claim 1 and having a surface roughness Rmax of 1.0 μm or less.