JP2006076853A - Method of manufacturing aluminum nitride substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an aluminum nitride substrate by which the occurrence of color shading or stain is suppressed. <P>SOLUTION: The method of manufacturing an aluminum nitride substrate is provided with a sintering process for sintering a formed body at a prescribed sintering temperature TS to obtain a sintered compact and an annealing process for annealing the sintered compact at a prescribed annealing temperature TA. In the annealing process, the sintered compact is heated to a prescribed annealing temperature TA, kept at the annealing temperature TA for a prescribed time and cooled from the annealing temperature TA. The annealing temperature is fixed to satisfy the relation of TA≤TS and a temperature rising rate in the heating of the sintered compact from 1,200°C to the annealing temperature TA is ≤200°C/hr and a temperature dropping rate in the cooling of the sintered compact from the annealing temperature TA to 1,200°C is ≤200°C/hr. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an aluminum nitride substrate.

  Conventionally, for example, as described in Patent Documents 1 and 2, an aluminum nitride substrate is known as a substrate excellent in thermal conductivity and mechanical strength. Such an aluminum nitride substrate is first formed into a plate shape by adding a sintering aid such as yttria or a binder to aluminum nitride powder, and the formed body is sintered at a predetermined sintering temperature. It is obtained by sintering to a sintered body and annealing the sintered body.

Annealing is usually performed by heating the sintered body to a predetermined annealing temperature, maintaining the sintered body at the annealing temperature for a predetermined time, and then cooling the sintered body.
JP 2002-160974 A JP 2002-37670 A

  However, in the conventional manufacturing method, “color unevenness” and “stain” often occur on the surface of the annealed aluminum nitride substrate. Specifically, an aluminum nitride substrate having predetermined mechanical, thermal, and electrical characteristics can be obtained by making the method based on the methods and conditions described in Patent Documents 1 and 2, and in particular, 2 inches (50. When an aluminum nitride substrate having a diameter of 8 mm) or more is processed and molded from a sintered body, “color unevenness” and “stain” are often generated, resulting in poor appearance.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing an aluminum nitride substrate capable of suppressing the occurrence of “color unevenness” and “stains”.

  As a result of intensive studies by the inventor, in the annealing step, the temperature of the sintered body is lowered from the annealing temperature after maintaining the heating rate of the sintered body until the annealing temperature is reached and the predetermined time at the annealing temperature. By controlling the temperature drop rate within the specified range and keeping the annealing temperature below the sintering temperature, annealing can be performed without significantly damaging the good mechanical, thermal and electrical properties obtained during sintering. The inventors have found that it is possible to remarkably suppress the occurrence of “color unevenness” and “stains” on the surface of the sintered body after the process, and arrived at the present invention.

  The method for producing an aluminum nitride substrate according to the present invention includes a sintering process for obtaining a sintered body by sintering a molded body at a predetermined sintering temperature TS, and an annealing process for annealing the sintered body at a predetermined annealing temperature TA. And.

  In this annealing step, the sintered body is heated until it reaches a predetermined annealing temperature TA, then the sintered body is maintained at the annealing temperature TA for a predetermined time, and then the temperature of the sintered body is cooled from the annealing temperature TA.

  In particular, the annealing temperature TA is determined so as to satisfy TA ≦ TS, the heating rate when the sintered body is heated from 1200 ° C. to the annealing temperature TA is 200 ° C./h or less, and the sintered body is annealed. The temperature lowering rate when the temperature is decreased from the temperature TA to 1200 ° C. is 200 ° C./h or less.

  According to the present invention, “stain” and “color unevenness” on the surface of the sintered body after annealing are reduced as compared with the conventional case. Therefore, the yield in manufacturing the aluminum nitride substrate is improved, and the manufacturing cost can be reduced.

  Here, the reason why the “stain” and “color unevenness” of the sintered body after annealing is reduced as compared with the prior art by the manufacturing method of the present invention is not clear. Similarly, the cause of occurrence of “stain” and “color unevenness” is not clear as well.

  In the annealing step, the time for maintaining the sintered body at the annealing temperature TA is preferably 3 to 5 hours. As a result, “stains” and “color unevenness” on the surface of the sintered body after annealing can be further reduced, and the mechanical strength of the sintered body is also sufficient.

  Here, if the time for maintaining the sintered body at the annealing temperature TA is less than 3 hours, the effect of reducing “stain” and “color unevenness” tends to be reduced. On the other hand, if the time for maintaining the sintered body at the annealing temperature TA exceeds 5 hours, the crystal grains grow too much in the sintered body, and the mechanical strength tends to decrease.

  Further, if the annealing temperature TA is further determined to satisfy TA (° C.) ≧ TS (° C.) − 200 ° C. in the annealing step, “stains” and “color unevenness” on the surface of the sintered body after annealing are obtained. Further reduction can be achieved.

  Furthermore, it is preferable that the rate of temperature increase when heating the sintered body from 1200 ° C. to the annealing temperature TA is 50 ° C./h or more, and the rate of temperature decrease when the sintered body is decreased from the annealing temperature TA to 1200 ° C. It is also preferably 50 ° C./h or more. According to these, since the time required for annealing is not so required, high productivity can be realized.

  Moreover, it is preferable that sintering temperature TS is 1800-2100 degreeC, and by this, a precise | minute sintered compact is obtained and the board | substrate with high mechanical strength and heat conductivity can be obtained suitably.

  Further, it is preferable that the sintered body is sliced into a substrate after the sintering step and before the annealing step, and this substrate is annealed in the annealing step.

  According to this, compared with annealing, the time-consuming and laborious sintering process can be easily performed in a bulk state, and mass productivity becomes high. It is also possible to prepare a plate-shaped molded body in advance before the sintering step, and sinter and anneal it.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the aluminum nitride board | substrate which can suppress generation | occurrence | production of "color unevenness" and "stain" is provided.

  A method for manufacturing an aluminum nitride substrate according to an embodiment of the present invention will be described with reference to FIG.

  In this production method, first, a mixed powder containing aluminum nitride powder is obtained, and this mixed powder is molded, sintered, sliced, and annealed to produce an aluminum nitride substrate.

  Specifically, first, a solvent and a binder are added to the aluminum nitride powder, and a slurry containing mixed powder is prepared by adding a sintering aid as necessary, and then the slurry is spray-dried or the like. To form a granulated granule. At the time of slurry preparation, amorphous or crystalline carbon may be added. Subsequently, the granulated product is put into a mold or the like and pressed to form the mixed powder into a lump shape or a plate shape, and a molded body (green) 10 shown in FIG.

  Examples of the sintering aid include oxides such as yttria and calcium oxide. Examples of the binder include acrylic resins. Examples of the solvent include alcohol and toluene.

  The shape of the molded body 10 is a lump (bulk) shape as shown in FIG.

Here, the molded body 10 can also be compressed using a cold isostatic press (CIP), and in this case, the sintering proceeds uniformly and the sintering density can be improved. The pressure during CIP is preferably 50 to 500 MPa (about 500 to 5000 kgf / cm ² ).

  Next, the compact 10 is heated uniformly in a state where it is in contact with the BN powder in a container made of BN, and the compact 10 is sintered at a predetermined sintering temperature TS for a predetermined period of time. The sintered body 20 shown in (b) is manufactured. Sintering temperature TS should just be the temperature which can sinter aluminum nitride, for example, 1000-2500 degreeC, and it is especially preferable to set it as 1800-2100 degreeC. By setting the sintering temperature to 1800 to 2100 ° C., a dense sintered body is obtained, and the mechanical strength and thermal conductivity are increased. Moreover, the sintering time should just be time which can sinter the molded object 10 to sufficient intensity | strength, for example, can be 5 to 50 hours, Preferably, it can be 10 to 25 hours.

  In addition, although the temperature increase rate and temperature decrease rate in sintering are not specifically limited, It is preferable to make it the same as the temperature increase rate and temperature decrease rate in annealing mentioned later.

  Here, HIP, that is, the molded body 10 can be heated while being pressed to obtain the sintered body 20. In this case, an aluminum nitride substrate having particularly few pores can be produced.

  And after such sintering, this sintered compact 20 is cooled to about room temperature, for example.

  Next, as shown in FIG. 1C, the sintered body 20 is sliced to obtain a large number of plate-like sintered bodies 30. In order to reduce “stains” and “color unevenness” on the surface of the sintered body after annealing, the thickness of the sintered body before annealing is preferably 1 mm or less.

  In addition, when other mechanical processings, such as formation of a hole, are further required with respect to the sintered compact 30, it is preferable to perform the next annealing after these mechanical processings are complete | finished.

  Next, the sintered body 30 is annealed at a predetermined annealing temperature for a predetermined time to obtain a sintered body 40 after annealing as shown in FIG.

  In the annealing, each sintered body 30 is embedded in BN powder in a BN container in order to heat uniformly, and the sintered body 30 is heated to a predetermined annealing temperature TA. This is performed by maintaining the annealing temperature TA for a predetermined time (annealing time) and then cooling the temperature of the sintered body 30 from the annealing temperature TA.

  The annealing temperature TA is equal to or lower than the sintering temperature TS, that is, TA ≦ TS. Moreover, it is preferable that the annealing temperature TA further satisfies TA (° C.) ≧ TS (° C.) − 200 ° C. This can further suppress occurrence of “stain” and “color unevenness”.

  Further, the rate of temperature increase when heating the sintered body 30 from 1200 ° C. to the annealing temperature TA is 200 ° C./h or less, and the rate of temperature decrease when the sintered body 30 is decreased from the annealing temperature TA to 1200 ° C. is 200. It shall be below ℃ / h.

  The temperature of the sintered body 30 is raised from room temperature to 1200 ° C., and after maintaining the annealing temperature TA for a predetermined time, the sintered body 30 cooled to 1200 ° C. is further heated from 1200 ° C. to room temperature. The temperature lowering speed at the time of temperature lowering is not particularly limited.

  Here, it is preferable that the rate of temperature increase when the sintered body 30 is heated from 1200 ° C. to the annealing temperature TA is 50 ° C./h or more, and the temperature of the sintered body 30 is decreased from the annealing temperature TA to 1200 ° C. It is preferable that the temperature lowering rate at the time of further is 50 ° C./h or more. According to these, since the time required for annealing can be reduced, high productivity can be realized.

  The annealing time for maintaining the sintered body 30 at the annealing temperature TA is not particularly limited, but is preferably 3 to 5 hours. When the time for maintaining the sintered body 30 at the annealing temperature TA is less than 3 hours, the effect of reducing “stain” and “color unevenness” tends to decrease. On the other hand, if the time for maintaining the sintered body 30 at the annealing temperature TA exceeds 5 hours, crystal grains grow too much in the sintered body 30 and the mechanical strength of the sintered body 40 after annealing tends to decrease. is there.

  Further, the atmosphere in which the annealing process is performed is preferably an inert gas atmosphere.

  The annealed sintered body 40 manufactured by the manufacturing method as described above becomes a high-quality aluminum nitride substrate with less “stains” and “color unevenness” compared to the prior art. Such an aluminum nitride substrate can be used as a substrate for various electronic devices.

  In particular, the manufacturing method according to the present embodiment is highly effective for annealing a substrate having a thickness of 3 mm or less.

  Further, the massive shaped body 10 is sintered to obtain a massive sintered body 20, the massive sintered body 20 is sliced into a plate-like sintered body 30, and the plate-like sintered body 30 is annealed. Therefore, as compared with the case where a plate-shaped molded body is sintered and then the sintered body is annealed, the amount of processing when the molded body is sintered in the sintering furnace can be increased, which is preferable.

  Needless to say, it is possible to manufacture a high-quality aluminum nitride substrate with less “stains” and “color unevenness” even if a plate-shaped molded body is manufactured in advance and sintered and annealed. .

Example 1
Prepare a slurry of aluminum nitride powder with yttria as sintering aid, acrylic resin as binder, toluene and alcohol as solvent, mix this slurry in a ball mill, and then granulate this slurry by spray drying method To form a granulated body. Subsequently, this granulated body was molded at a pressure of 30 MPa in a 4 inch (10.16 cm) × 13 mm size mold, further compressed at 100 MPa with a CIP apparatus, and then at 450 ° C. for 3 hours. The molded body was obtained by degreasing. The compact was sintered at a sintering temperature TS = 1975 ° C. and a sintering time of 20 hours to obtain a sintered body. After cooling the sintered body, the sintered body was sliced to a thickness of 0.5 mm to obtain a large number of plate-like sintered bodies.

  Subsequently, the sintered body was annealed. Here, the annealing temperature TA was 1775 ° C., and the annealing time was 5 hours. Further, the temperature increase rate of the sintered body from room temperature to 1200 ° C. is 600 ° C./h, the temperature increase rate of the sintered body from 1200 ° C. to the annealing temperature TA is 100 ° C./h, and the annealing temperature TA is 1200 ° C. The temperature lowering rate up to 100 ° C./h was set to 600 ° C./h.

(Examples 2-3, Comparative Examples 1-4)
In Example 2, the temperature increase rate of the sintered body from 1200 ° C. to the annealing temperature TA is 50 ° C./h, and the temperature decrease rate from the annealing temperature TA to 1200 ° C. is 50 ° C./h. The same was done.

  In Example 3, the temperature increase rate of the sintered body from 1200 ° C. to the annealing temperature TA was set to 200 ° C./h, and the temperature decrease rate from the annealing temperature TA to 1200 ° C. was set to 200 ° C./h. The same was done.

  Comparative Example 1 was the same as Example 1 except that the rate of temperature decrease from the annealing temperature TA to 1200 ° C. was 300 ° C./h.

  Comparative Example 2 was the same as Example 1 except that the rate of temperature decrease from the annealing temperature TA to 1200 ° C. was 600 ° C./h.

  Comparative Example 3 was the same as Example 1 except that the temperature increase rate of the sintered body from 1200 ° C. to the annealing temperature TA was set to 300 ° C./h.

  Comparative Example 4 was the same as Example 1 except that the temperature increase rate of the sintered body from 1200 ° C. to the annealing temperature TA was 600 ° C./h.

(Examples 4, 5, and 6)
Example 4 was the same as Example 1 except that the annealing time was 3 hours. Example 5 was the same as Example 1 except that the annealing time was 1 hour. Example 6 was the same as Example 1 except that the annealing time was 10 hours.

(Example 7)
Example 7 was the same as Example 1 except that the annealing temperature TA was 1875 ° C.

(Example 8)
Example 8 was the same as Example 7 except that the annealing time was 3 hours.

(Examples 9 and 10)
Example 9 was the same as Example 1 except that the annealing temperature TA was 1975 ° C.

  Example 10 was the same as Example 1 except that the annealing temperature TA was 1675 ° C.

(Comparative Example 5)
Comparative Example 5 was the same as Example 1 except that the annealing temperature TA was 2075 ° C.

(Example 11)
Example 11 was the same as Example 1 except that the sintering temperature TS was 2050 ° C. and the annealing temperature TA was 1850 ° C.

The degree of occurrence of “stains” or “color unevenness” on the surface of each sintered body obtained as described above and the mechanical strength of the sintered body are combined with the conditions of the examples and comparative examples. As shown in FIG. The mechanical strength was measured with a Shimadzu precision universal testing machine. The substrate of Example 1 has a thermal conductivity of 195 W / mK, an average crystal grain size of 17.6 μm, a volume resistance of 10 ¹³ Ω · cm or more, a dielectric breakdown voltage of 14 kV / mm or more, and a strength of about 460 MPa. there were.

  As is apparent from FIG. 2, the annealing temperature TA is determined so as to satisfy TA ≦ TS, and the heating rate when heating the sintered body from 1200 ° C. to the annealing temperature TA is 200 ° C./h or less. In Examples 1 to 11 where the temperature lowering rate when the temperature of the bonded body is lowered from the annealing temperature TA to 1200 ° C. is 200 ° C./h or less, the occurrence of “stains” or “color unevenness” on the substrate surface is suppressed, and the high quality Substrate was obtained. On the other hand, in Comparative Examples 1 to 5 that did not satisfy this condition, a large number of “stains” or “color unevenness” occurred on the substrate surface.

  In particular, as in Examples 1 to 4 and Examples 7 to 11, when the annealing time is 3 to 5 hours, the occurrence of “stains” or “color unevenness” is sufficiently suppressed, and mechanical properties are exhibited. An excellent substrate was obtained.

  Further, in Examples 1 to 6 and Example 11 in which the annealing temperature TA is further determined to satisfy TA (° C.) ≧ TS (° C.) − 200 ° C., “stain” or “color unevenness” is sufficiently generated. Was suppressed.

It is a schematic diagram which shows the manufacturing method of an aluminum nitride board | substrate. It is a table | surface which shows the conditions and results of Examples 1 to 11 and Comparative Examples 1 to 5.

Claims (7)

A sintering step of obtaining a sintered body by sintering the molded body at a predetermined sintering temperature TS;
Annealing the sintered body at a predetermined annealing temperature TA, and
In the annealing step, the sintered body is heated until a predetermined annealing temperature TA is reached, and then the sintered body is maintained at the annealing temperature TA for a predetermined time, and then the temperature of the sintered body is set to the annealing temperature TA. Cooled from
An annealing temperature TA in the annealing step is determined to satisfy TA ≦ TS,
In the annealing step, the heating rate when heating the sintered body from 1200 ° C. to the annealing temperature TA is 200 ° C./h or less, and the temperature of the sintered body is decreased from the annealing temperature TA to 1200 ° C. The manufacturing method of the aluminum nitride board | substrate whose temperature-fall rate is 200 degrees C / h or less.   2. The method of manufacturing an aluminum nitride substrate according to claim 1, wherein in the annealing step, the time for maintaining the sintered body at the annealing temperature TA is 3 to 5 h.   3. The method of manufacturing an aluminum nitride substrate according to claim 1, wherein in the annealing step, the annealing temperature TA is further determined to satisfy TA (° C.) ≧ TS (° C.) − 200 ° C. 4.   4. The production of an aluminum nitride substrate according to claim 1, wherein, in the annealing step, a heating rate when the sintered body is heated from 1200 ° C. to the annealing temperature TA is 50 ° C./h or more. Method.   5. The method for producing an aluminum nitride substrate according to claim 1, wherein in the annealing step, a rate of temperature drop when the sintered body is cooled from the annealing temperature TA to 1200 ° C. is 50 ° C./h or more. .   The method for manufacturing an aluminum nitride substrate according to any one of claims 1 to 5, wherein, in the sintering step, the sintering temperature TS is 1800 to 2100 ° C.   The method for producing an aluminum nitride substrate according to any one of claims 1 to 6, wherein the sintered body is sliced to form a substrate after the sintering step and before the annealing step, and the substrate is annealed in the annealing step. .

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