JPH01183469A - Sintered aluminum nitride - Google Patents

Abstract

PURPOSE:To increase the denseness and thermal conductivity in addition to easy sintering properties, by adding alkaline earth element-rare earth element-Al compound as at least one of the subphases to AlN as the main component. CONSTITUTION:80-99.99wt.% of a powder of crystalline AlN particles of less than 4 micron average particle size and 0.01-7wt.% oxygen content are combined with totally 0.01-80wt.%, based on the oxides, of a mixture from a compound of alkaline earth metal (R) selected from Mg, Ca, Sr, Ba or the like, and another compound of rare earth metal (Ln) selected from Sc, Y, La, Ce, Sm, Eu, Tm, Tb, Dy, Nd, Gd, Pr, Ho, Er, Yb at 0.9-0.1 Ln/(Ln+R) weight ratio, crushed and mixed in a ball mill to prepare the starting formulation. The formulation is mixed with a binder, formed, defatted by heating in a N2 gas flow, sintered at 1,500-1,950 deg.C under normal pressure to give the title sintered product containing AlN as the main component and R-Ln-Al compound as at least one part of subphases.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an aluminum nitride sintered body, and particularly to an easily sinterable aluminum nitride sintered body having a novel composition.

(Prior technology) Aluminum nitride (Al!N) has many excellent properties, such as maintaining high strength from room temperature to high temperature, not getting wet with molten metal, and having high electrical insulation and high thermal conductivity. It is attracting attention as a new material because of its properties. Especially in recent years,
A. Research on the application of 11'N sintered bodies to heat dissipating substrates has been actively conducted, and as a result, due to improvements in raw materials and sintering technology, the thermal conductivity was at its limit of 100 W/m-k until a few years ago. However, it has now been improved to 260 W/m-k.

Incidentally, the A/N sintered body is usually manufactured by molding 1t'N powder by a desired method and then sintering it. Sintering is performed by the pressureless sintering method or the hot press method, but since A and 47N are difficult to sinter, sintering aids are used in the pressureless sintering method in order to obtain a dense sintered body. It is necessary to add

Compounds of alkaline earth elements and compounds of rare earth elements are known as sintering aids for lt'N. These compounds react with oxygen that is unavoidably mixed into the A-N powder raw material during sintering, and form an R-1J7-0 yarn pore compound (R:
alkaline earth elements) and Ln-Al-〇-based compounds (Ln
; rare earth elements) and densifies the sintered body. In addition, the oxygen contained in the A, i7N powder raw material is
Generates 0 prefecture Hokuai products, Al! A solid solution in N particles
Although the inherent high thermal conductivity of N is reduced, the above-mentioned alkaline earth element compounds and rare earth element compounds as sintering aids react with oxygen and fix this product as a grain boundary phase. Sintering aids also contribute to high thermal conductivity.

By adding a sintering aid to the A-N powder raw material in this way, it is certainly possible to achieve densification and high thermal conductivity of the A, l'N sintered body, but the above-mentioned sintering aid All of these materials require sintering at a high temperature of 1,700 to 1,900°C.

In order for A/N sintered bodies to be widely utilized, several issues remain, one of which is reducing the sintering temperature. Reducing the sintering temperature is extremely important from the viewpoint of cost reduction.

In particular, when considering the application of A1N sintered bodies to semiconductor substrates, it is possible to consider replacing them with alumina substrates, which are currently widely used, and in such a situation, thorough cost reduction is necessary.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and has excellent sinterability and can achieve sufficient densification at a lower sintering temperature than conventional The present invention aims to provide an aluminum nitride sintered body.

[Structure of the Invention] (Means for Solving Problem M) The present invention provides an aluminum nitride characterized by containing aluminum nitride as a main component and containing an alkaline earth element rare earth element aluminum compound as at least a part of the subphase. It is a sintered body.

As the alkaline earth element rare earth element aluminum compound, for example, an alkaline earth element is R1 a rare earth element is L
When n is an example, R-Ln-A No. 0 type oxides can be mentioned. Here, the alkaline earth element is Mg
5Ca, 5rSBa, especially Ca
SS r%Ba is preferred. As a rare earth element, S c
SY, LasCe, Sm, Eu, Tag, T
b S Dy, Nd.

Examples include Gd5Pr, Ho5Er, Yb, etc.
Particularly preferred are Y, La, and Ce.

The composition ratio of A-N crystal particles in the above-mentioned A-N sintered body is:
It is desirable to set it as 80-99.99 weight% of the whole.

Next, a manufacturing method for obtaining the lt'N sintered body of the present invention will be explained.

First, a predetermined amount of a rare earth element compound and an alkaline earth element compound are added to A and NN powders, and then ground and mixed using a ball mill or the like to prepare a raw material.

However, in the case of pressureless sintering, a binder is further added to the pulverized and mixed material using the ball mill, etc., and the raw material is prepared by kneading, granulating, and sizing. As the A-N powder, it is desirable to use one containing 0.01 to 7% by weight of oxygen. This A, 17N powder has an average particle size of 4 μm or less, and it is desirable to use 2 μm or less for low-temperature sintering. Examples of the rare earth element compound include Sc, Y,
, Las Ce5SsSEuST1Tb%Dys Nd
s Gd5Pr, Hos Er, Yb oxides, fluorides, carbides, or compounds that become oxides, fluorides, or carbides by sintering can be used;
A mixture of more than one species may be used. Examples of the alkaline earth element compounds include Mg1Ca SSr, Ba
oxides, fluorides, carbides or sintered oxides,
Compounds that form fluorides and carbides can be used, and these may be used alone or in a mixture of two or more. As with the A and ffN powders, it is desirable to use powders with an average particle size of 4 μm or less, more preferably 2 μm or less as these rare earth element compounds and alkaline earth element compounds.

Further, it is desirable that the amount of the rare earth element compound and the alkaline earth element compound added to the A-N powder ranges from 0.01 to 20% by weight in total in terms of their respective oxide states. The reason for this is that the amount of these compounds added is 0.0
If it is less than 1% by weight, it will be difficult to generate the desired subphase of the rare earth element alkaline earth element aluminum compound.
On the other hand, if the amount of these compounds added exceeds 20% by weight, there is a risk that heat resistance, mechanical strength and thermal conductivity will decrease. A more preferable amount of the rare earth element compound and alkaline earth element compound is in the range of 0.01-17% by weight.

Next, the raw material containing the binder is molded using a mold, hydrostatic pressure, sheet molding, or the like, and then the molded body is heated in a N2 gas stream to remove the binder. Subsequently, the molded body is placed in a container made of graphite or aluminum nitride, and pressureless sintering is performed at 1550 to 1950°C in an N2 gas atmosphere. On the other hand, in the case of hot press sintering, the raw materials prepared by pulverizing and mixing in the ball mill are hot pressed at the same temperature as above. At this time, A with high thermal conductivity
, 1800 to 1950°C when obtaining a t'N sintered body, and 15°C when giving priority to low temperature sinterability over high thermal conductivity.
Sintering is performed at 50 to 1700°C.

A, t' of the AiN sintered body manufactured by the above-mentioned sintering
When the constituent phases other than N are identified by powder X-ray diffraction, Ln
Depending on the addition ratio of /H, only ■Ln-A No〇 system exists,
■R-Ln-A no O system and Ln-Aj? Coexistence of -0 system, ■Only R-Ln-A No〇 system exists, ■R-Ln-A No〇 system and R-Al! -0 system coexists, ■R-, A No ○ system only exists, and so on.

In addition, in a raw material composition in which the amount of oxygen in the A-N powder is large and the amounts of the Ln compound and R compound added are small, an A-N-0 yarn pore compound may be formed in addition to the above-mentioned constituent phases.

In the present invention, the R-Ln-A no. AiN sintered body is used.

In addition, in order to generate the R-Ln-A, ff-〇-based oxide as the subphase mentioned above, it is necessary to combine rare earth elements (Ln) and alkaline earth elements (R), depending on the properties of the A-N powder. The addition ratio of Ln/(Ln +R) in weight ratio is 0.9
It is desirable to set it in the range of ~0.1. That is, when adding Y2O3 as a Ln compound and CaO as an R compound to A, 17N powder, Y203 in weight ratio
/ (Y203+Ca0) is in the range of 0.9 to 0.1, so that at least CaYAJ! as a constituent phase other than A and t'N! 04 and Ca YAlO-based unknown phase (Ca
YAJ! 307) is generated.

(Function) According to the present invention, since the main component is aluminum nitride and contains an alkaline earth element rare earth element aluminum compound as at least a part of the subphase, a lower sintering temperature is required than in the past. densification has been achieved,
Moreover, an aluminum nitride sintered body with high thermal conductivity can be obtained.

(Example of the invention) Examples of the present invention will be described in detail below.

Examples 1 to 3 First, A-N powder containing 0.86% by weight of oxygen as an impurity and having an average particle size of 1.8 μm was added with an average particle size of 0.8 μm.
Mixed powder of Y2O3 and CaCo3 (mixing ratio; Y
A raw material was prepared by adding 3% by weight of 2O3/CaO (3=1) and crushing and mixing using a ball mill. Subsequently, 5% by weight of an acrylic binder was added to this raw material and granulated, followed by press molding at a pressure of 500 psi/i to obtain a green compact with dimensions of approximately 30 cMX 30 n x 8 α.

Subsequently, this green compact was heated to 700° C. in a nitrogen gas atmosphere to remove the binder. Next, AJ! Set in a container made of N sintered body and heated under nitrogen gas atmosphere.
Three types of A/N sintered bodies were produced by pressureless sintering at temperatures of 600°C, 1700°C, and 1800°C for 2 hours.

Examples 4 to 21 Using A-N powder shown in Table 1 below as raw materials and a mixed powder as an additive (however, CaO is added in the form of CaCO3), under the conditions shown in Table 1. Eighteen types of AiN sintered bodies were manufactured in the same manner as in Example 1 except for sintering.

Comparative Examples 1 to 6 Six types were prepared in the same manner as in Example 1, except that A-N powder and additives shown in Table 1 below were used as raw materials, and sintered under the conditions shown in Table 1. An A/N sintered body was manufactured.

Thus, the density of each A/N sintered body obtained in Examples 1 to 21 and Comparative Examples 1 to 6 was measured. Also, each 14'N
The sintered body was ground to a diameter of 101111 mm and a thickness of 3.5 x m.
Thermal conductivity at room temperature was measured using the disks as test pieces by the Zaralash method. Furthermore, the constituent phases other than A and ffN of the N sintered body were identified by powder X-ray diffraction. The results are also listed in Table 1. In addition,
The unknown phase in Table 1 is a Ca-YA-no-O complex oxide, and its composition is currently estimated to be Ca-YA-307.

In addition, Ca O/(Y203 +C
The relationship between the weight ratio of a O), density, and thermal conductivity is shown in FIG. In addition, the opening plotted in Fig. 1 indicates the A/N sintered body with the sintering condition set at 1600°C, and the opening plotted in Figure 1 indicates the A/N sintered body with the sintering condition set at 1700°C. O indicates the A/N sintered bodies in which the sintering conditions were set at 1800°C.In the examples and comparative examples, the sintering conditions were set at 1600°C and 1.
The constituent phases other than A/N of the A, ffN sintered body set at 800°C are shown in Figs. 2 and 3. Further, FIG. 4 shows the powder X-ray diffraction spectrum of the A, ffN sintered body of Example 15.

Note that O in FIG. 4 indicates the diffraction peak of A7N.

As is clear from Table 1 and Figures 1 to 4 above, Ca
The A, i'N sintered bodies of this example containing a -YA No ○ type composite oxide as a subphase are the A and i'N sintered bodies of Comparative Examples 1 to 3 containing a Ca -A No ○ type oxide as a subphase. It can be seen that improved thermal conductivity and densification can be achieved at a lower sintering temperature compared to the sintered bodies and the jl'N sintered bodies of Comparative Examples 4 to 6, which contain Y-A No ○ type oxide as a subphase. .

Examples 22 to 40 A-N powder shown in Table 2 below as a raw material and a mixed powder that is an additive in an amount of 1 to 7% by weight relative to the A-N powder (however, CaO is in the form of Ca003) Except for sintering under the conditions shown in Table 2,
Nineteen types of A, i'N sintered bodies were manufactured by the same method as in Example 1.

As in Example 1, the AiN sintered bodies of Examples 22 to 40 were found to have density, thermal conductivity at room temperature determined by laser flash method, thermal conductivity determined by powder X-ray diffraction, and constituent phases other than A-N determined by powder X-ray diffraction. Identification was carried out. The results are also listed in Table 2.

Examples 41 to 60 Mixed powder of A and NN powders shown in Table 3 below as raw materials and additives (however, CaO is in the form of CaCO3, S
rO is added in the form of SrCO3),
Twenty types of A/N sintered bodies were manufactured in the same manner as in Example 1, except that the sintered bodies were sintered under various conditions shown in Table 3.

However, the lJ of Examples 41 to 60? Regarding the N sintered body, as in Example 1, density, thermal conductivity at room temperature by laser flash method, thermal conductivity, and lt' by powder X-ray diffraction
Constituent phases other than N were identified. The results are also listed in Table 3.

[Effects of the Invention] As detailed above, according to the present invention, by having a structure in which aluminum nitride is the main component and at least a part of the subphase contains an alkaline earth element rare earth element aluminum compound, Sufficient densification can be achieved at a lower sintering temperature, and an aluminum nitride sintered body with high thermal conductivity can be provided.

[Brief explanation of the drawing]

Figure 1 shows the sintering temperatures of 1600°C, 1700°C, and 1800°C.
CaO/ in the AiN sintered body obtained by setting
(Y203 +Ca O) (7) Characteristic diagram showing the relationship between weight ratio, density, and thermal conductivity. Figures 2 and 3 show A/N sintering with sintering conditions set at 1600°C and 1800°C, respectively. Weight ratio of Ca O/(Y203 +Ca O) in the body and ll? A characteristic diagram showing the relationship with constituent phases other than N, and FIG. 4 is a characteristic diagram showing the powder X-ray diffraction spectrum of the A-N sintered body of Example 15. Applicant's representative Patent attorney Takehiko Suzue CaO/(Y203+CaO) 11am100151 diagram

Claims (2)

[Claims] (1). An aluminum nitride sintered body comprising aluminum nitride as a main component and containing an alkaline earth element rare earth element aluminum compound as at least a part of a subphase. (2). Claim 1: The alkaline earth element rare earth element aluminum compound is an oxide of the R-Ln-Al-O system, where R is the alkaline earth element and Ln is the rare earth element.
The described aluminum nitride sintered body.