JP2001294487A - Black aluminum nitride sintered compact and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a black aluminum nitride sintered compact maintaining intrinsic characteristics of the aluminum nitride, such as high thermal conductivity or high resistance to plasma and a method of producing the same. SOLUTION: The black aluminum nitride sintered compact is composed of aluminum nitride and yttrium aluminate and has a lightness index L*, defined by JIS Z 8729-1994, of <45. The black aluminum nitride sintered compact is obtained by adding >=0.1 and <=10 wt.%, expressed in terms of outer percentage and yttrium element, based on aluminum nitride, of a yttrium compound to an aluminum nitride powder, then forming and sintering at 1450 to 1900 deg.C under a reduced pressure atmosphere of <=10 Torr for at least 1 hr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a black aluminum nitride sintered body and a method for producing the same, and more particularly, to
The present invention relates to a black aluminum nitride sintered body suitably used as a member for a semiconductor manufacturing apparatus such as a susceptor for lamp heating and a method for manufacturing the same.

[0002]

2. Description of the Related Art Aluminum nitride has characteristics such as high thermal conductivity and high plasma resistance, excellent mechanical strength, electrical insulation and corrosion resistance, and a coefficient of thermal expansion close to that of silicon. For this reason, aluminum nitride
Widely used for electroceramic members such as LEDs for optical communication. It is also suitably used for a member such as a susceptor on which a wafer is placed in a CVD process or the like in semiconductor manufacturing.

[0003] Aluminum nitride is a material that is difficult to sinter. Therefore, during normal pressure sintering, a sintering aid made of a compound containing a rare earth element such as yttrium is added, and a sintered body is formed by liquid phase sintering. Is generally manufactured. However, the aluminum nitride sintered body manufactured by the above method is apt to cause unevenness of color tone, which is not preferable in appearance.
In addition, in a member such as a susceptor for lamp heating, temperature unevenness is likely to occur on a mounted wafer due to the color tone unevenness. Such temperature unevenness of the wafer is caused by CV
This leads to unevenness in the film thickness formed on the wafer in the D step, which causes a reduction in the yield in the semiconductor manufacturing step.

[0004] For this reason, in order to reduce the color tone unevenness of the aluminum nitride sintered body and increase the heating efficiency of the lamp, a method of blackening the aluminum nitride sintered body has been conventionally studied. For example, JP-A-3-290371 discloses that titanium oxide, molybdenum oxide and / or chromium oxide are added to aluminum nitride as a coloring agent component, and yttria (Y ₂ O ₃ ) is added as a sintering aid. The added black or gray aluminum nitride sintered body is shown. Japanese Patent No. 2767979 discloses a method in which tungsten and / or molybdenum are added as a blackening agent.

[0005]

However, the method of adding a blackening agent (colorant) such as a transition metal as described above involves introducing a foreign element into the aluminum nitride sintered body, Phonon scattering due to solid solution of a different element in the crystal may lower the thermal conductivity. In addition, segregation of the foreign element compound at the grain boundary may decrease the plasma resistance. As described above, although the addition of the blackening agent is effective in blackening the aluminum nitride sintered body, it has the side effect of impairing the characteristics of aluminum nitride such as high thermal conductivity and high plasma resistance. Further, when such a foreign element is introduced into a susceptor or the like, it causes undesired contamination of a mounted wafer, which is not preferable.

[0006] Japanese Patent Application Laid-Open No. 9-48669 discloses that
An aluminum nitride sintered body containing AlON as a subphase is shown, but such a subphase may reduce the thermal conductivity and plasma resistance of the aluminum nitride sintered body.

As described above, in the prior art proposed as a means for blackening an aluminum nitride sintered body, although it is effective for blackening, the characteristics of aluminum nitride are impaired. It could not be said that it was for practical use such as members for semiconductor manufacturing equipment.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and does not impair the features of aluminum nitride such as high thermal conductivity and high plasma resistance.
It is another object of the present invention to provide a black aluminum nitride sintered body having a uniform color tone. Moreover, the present invention further provides the above-described aluminum nitride without impairing the features thereof.
It is an object of the present invention to provide a method for producing black aluminum nitride, which can uniformly blacken the sintered body.

[0009]

According to the present invention, there is provided a semiconductor device comprising aluminum nitride and yttrium aluminate.
Lightness index L ^* defined in ISZ 8729-1994
Is less than 45, and a black aluminum nitride sintered body is provided. According to the present invention, as a preferred embodiment of the black aluminum nitride sintered body, the value of the lightness index L ^* is less than 40, and a black aluminum nitride sintered body, and a thermal conductivity thereof. Is 10
Black aluminum nitride sintered bodies characterized by being at least 0 W / m · K are provided.

Further, according to the present invention, the yttrium compound is added to the aluminum nitride powder in an amount of 0.1% by weight or more to aluminum nitride in terms of an yttrium element.
0% by weight or less, and after molding, 1450 ° C. or more and 1900 ° C.
A method for producing a black aluminum nitride sintered body, comprising a step of firing for 1 hour or more in a reduced pressure atmosphere of 10 Torr or less at 10 ° C. or less. According to the present invention, as a preferred embodiment of the method for producing a black aluminum nitride sintered body, the firing temperature is 1600 ° C. or more and 1850 ° C. or less. A method is provided.

Further, according to the present invention, JIS Z 87
An aluminum nitride sintered body having a value of the lightness index L ^* according to 29-1994 of 40 or more is 1450 ° C. or more and 1900 ° C.
A method for producing a black aluminum nitride sintered body characterized by performing a heat treatment at a temperature of not more than 10 ° C. under a reduced pressure atmosphere of not more than 10 Torr for not less than 1 hour. According to the present invention, as a preferred embodiment of the method for producing a black aluminum nitride sintered body, the heat treatment temperature is 1600 ° C. or more and 18% or more.
A method for producing a black aluminum nitride sintered body, which is at 50 ° C. or lower, is provided.

[0012] The black aluminum nitride sintered body of the present invention comprises:
It is characterized in that it is made of aluminum nitride and yttrium aluminate and is blackened without impairing various properties inherent to aluminum nitride, such as high thermal conductivity and high plasma resistance.

In order to obtain such a blackened sintered body composed of aluminum nitride and yttrium aluminate, the present invention uses a yttrium compound as a sintering aid and mixes it with a specific amount of aluminum nitride powder. The body or its degreased body is fired for a predetermined time under the above-mentioned specific reduced-pressure and high-temperature conditions, or the sintered body produced from the molded body or its degreased body by a conventional method is subjected to the above-mentioned specific reduced-pressure and high-temperature conditions. Heat treatment is performed for a predetermined time. The yttrium compound reacts with the impurity oxygen component contained in the aluminum nitride during firing to produce liquid phase yttrium aluminate. When this yttrium aluminate is heated under a reduced-pressure atmosphere, a number of oxygen ion defects are generated in the crystal, and the light absorption resulting therefrom causes the yttrium aluminate to take on a black color. In the aluminum sintered body of the present invention, such a black yttrium aluminate is uniformly dispersed in the sintered body, so that the color tone of the aluminum nitride sintered body is uniform and black without unevenness.

In the black aluminum nitride sintered body of the present invention, the degree of blackening is determined according to JIS Z8729-1994.
"Color display method-L ^* a ^* b ^* color system and L ^* u ^* v ^*
The lightness index L ^* is less than 45 when "color system" is used as a criterion. The sintered body having L ^* larger than the value specified in the present invention is not sufficiently blackened, and when a susceptor for mounting a semiconductor wafer is manufactured using the sintered body having such a color tone, the temperature uniformity due to lamp heating is reduced. Sex cannot be achieved sufficiently. As described above, the black aluminum nitride sintered body of the present invention is made of aluminum nitride and yttrium aluminate, and does not include a blackening agent (colorant) such as a transition metal. Excellent properties such as high plasma resistance are maintained.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically. As described above, the black aluminum nitride sintered body according to the present invention is made of aluminum nitride and yttrium aluminate. This yttrium aluminate is an oxide resulting from the sintering aid. Therefore, in order to obtain the black aluminum nitride sintered body according to the present invention, it is necessary to add an yttrium compound as a sintering aid.

The yttrium compound to be added is not particularly limited, but oxides such as yttrium oxide,
Examples thereof include halides such as yttrium fluoride, nitrates such as yttrium nitrate, carboxylate salts such as yttrium oxalate, and carbonates. Among these, yttrium oxide or yttrium fluoride is preferable, and yttrium oxide is most preferable because it is stable and easy to handle.

The amount of the yttrium compound to be added is 0.1 percent in terms of yttrium element relative to aluminum nitride.
It is preferable that the content is not less than 10% by weight and not more than 10% by weight. This amount is preferably determined by the amount of the impurity oxygen component contained in the aluminum nitride. This is because, in the firing step, the yttrium compound reacts with the impurity oxygen component contained in the aluminum nitride to generate liquid phase yttrium aluminate.

The amount of the yttrium compound added is 0.1
If the amount is less than% by weight, an insufficient amount of the liquid phase is generated,
It is difficult to obtain a dense sintered body. Also, even if
Even when a dense sintered body is obtained, the amount of yttrium aluminate contained in the sintered body is small, so that blackening cannot be sufficiently achieved. On the other hand, if the addition amount exceeds 10% by weight, the thermal conductivity decreases due to the production of an excessive amount of yttrium aluminate, which is a low thermal conductive substance, and the excess liquid phase is produced, so that in the firing step, The aluminum nitride sintered body may be deformed. This addition amount is more preferably 0.5% by weight or more and 5% by weight or less in terms of an yttrium element based on aluminum nitride.

When yttrium aluminate is heated under a reduced-pressure atmosphere, a large number of oxygen ion defects are introduced into its crystal, and the crystal takes on a black color due to light absorption resulting therefrom.
By uniformly dispersing such black yttrium aluminate in the aluminum nitride sintered body, the aluminum nitride sintered body is uniformly blackened.

The criterion for blackening is JIS 87
29-1994 "L ^* a ^* b ^* color system and L ^* u ^* v ^*
It is simple to use the "method of displaying an object color by a color system". Preferably, the value of the lightness index L ^* by this method is less than 45. If it is less than 45, the appearance color tone of the aluminum nitride sintered body will be black, and the surface temperature uniformity will be maintained even when the lamp is heated. This L
The value of ^* is more preferably less than 40.

The impurities contained in the aluminum nitride are as follows:
It is preferable that the number is as small as possible. Impurities reduce thermal conductivity and plasma resistance. Therefore, it is preferable to use a high-purity aluminum nitride powder having a total amount of impurities other than oxygen of less than 1000 ppm as a raw material.
Furthermore, in the process of producing a black aluminum nitride sintered body such as a firing step or a heat treatment step, it is necessary to give sufficient consideration so that impurities are not mixed.

The black aluminum nitride sintered body preferably has a thermal conductivity of 100 W / m · K or more. 1
If it is at least 00 W / m · K, it can be suitably used as a member for semiconductor manufacturing equipment such as a susceptor for lamp heating.

In order to produce the black aluminum nitride according to the present invention, a predetermined amount of an yttrium compound is added to aluminum nitride powder, and after molding, a temperature of 1450 ° C. to 190 ° C.
Baking is performed for 1 hour or more at 0 ° C. or less under a reduced pressure atmosphere of 10 Torr or less. Thus, after molding, 1450 ° C. or more and 19
The baking for 1 hour or more under a reduced pressure atmosphere of 10 Torr or less at 00 ° C. or less is for introducing oxygen ion defects into the yttrium aluminate crystal.

In the above treatment, the firing temperature is 1450 ° C.
If the pressure is less than 10 Torr or more than 10 Torr, the oxygen ion defects are not sufficiently introduced, and the aluminum nitride sintered body cannot be sufficiently blackened. Therefore, the treatment is preferably performed under a reduced pressure atmosphere having a firing temperature of 1600 ° C. or more and 1 Torr or less. When the firing temperature is 19
When the temperature exceeds 00 ° C., the decomposition and volatilization of yttrium aluminate becomes severe, the amount of yttrium aluminate contained in the aluminum nitride sintered body decreases, and the effect of blackening decreases. More preferably, the firing temperature is 1850 ° C or lower.

As described above, the firing step in a reduced pressure atmosphere requires at least one hour. When the time is less than 1 hour, introduction of oxygen ion defects into the yttrium aluminate crystal does not proceed sufficiently, and the effect of blackening does not sufficiently appear. For example, in the case of aluminum nitride having a thickness of about 25 mm, about 3 mm
By the firing step in a reduced-pressure atmosphere for a long time, the inside of the aluminum nitride sintered body can be sufficiently blackened. Further, in the case of thick aluminum nitride, it is necessary to adjust the firing step time according to the thickness.

The method for producing black aluminum nitride according to the present invention can be carried out by performing a heat treatment in a reduced pressure atmosphere in the firing step as described above. Also,
After an aluminum nitride sintered body is once obtained by a normal firing step, the aluminum nitride sintered body is heated at 1450 ° C.
The heat treatment can be performed by performing a heat treatment at a temperature of 1900 ° C. or less and a reduced pressure atmosphere of 10 Torr or less for 1 hour or more. According to this method, JIS Z 8729-1
Even if the value of the lightness index L ^* according to 994 is an aluminum nitride sintered body of 40 or more, a black aluminum nitride sintered body having a value of the lightness index L ^* of 40 or less can be obtained.

[0027]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to the following examples. [Example 1] Example sample Nos. In Table 1 were added to aluminum nitride powder. Yttrium oxide powder was added at the respective ratios shown in 1 to 12 (converted to yttrium element with respect to aluminum nitride, extrinsic ratio).
Mix for 5 hours. To this, a methanol solution of polyvinyl butyral was added as a binder so that polyvinyl butyral was 3% by weight with respect to the aluminum nitride powder, and further mixed by a ball mill for 1 hour to obtain a slurry. This slurry is granulated by a spray dryer, and subjected to uniaxial molding at 30 MPa.
It was formed by a cold isostatic press of 00 MPa. The obtained molded body was degreased at a maximum temperature of 600 ° C. in an air atmosphere. The obtained degreased body was fired at 1850 ° C. under a reduced pressure condition shown in Table 1 under a nitrogen atmosphere.

The surface of the obtained aluminum nitride sintered body was subjected to surface grinding by surface grinding, and the lightness index L ^* was measured using a spectrophotometer (CM-508d manufactured by Minolta Co., Ltd.). The thermal conductivity of the sintered body was measured by a laser flash type thermal conductivity measuring device. After processing a thin piece of 10 mm x 10 mm x 2 mm from the sintered body,
The surface is mirror-polished and the center line average roughness (Ra) is 0.1
Samples of 5 μm or less were prepared. This sample was placed in an RIE plasma etching apparatus, and 10 Pa, RF output 1 k
It was exposed to a fluorine-based plasma of W, CF ₄ + Ar for 5 hours, and this was repeated 50 times. The Ra of the sample after this exposure was measured, and the plasma resistance was evaluated. The evaluation method was ○ when Ra was less than 0.2 and Δ when Ra was 0.2 or more. Further, from the sintered body, a diameter of 50 mm,
A sample having a thickness of 5 mm was prepared, this sample was heated from below by an infrared lamp, and the time required for the temperature measurement value of the thermocouple installed at the center of the upper surface to reach 600 ° C. was measured. Tables 1 and 2 show the results of the above tests and measurements.

Comparative Example 1 Comparative Example Sample No.
Under the conditions shown in 1 to 6, the same test and measurement as in Example 1 were performed on the sample manufactured in the same manner as in Example 1. The results are shown in Table 1.

[0030]

[Table 1]

[0031]

[Table 2]

As shown in Tables 1 and 2, when the addition amount of yttrium oxide is less than 0.1% by weight or more than 10% by weight, the lightness index L ^* is 45 or more (Comparative Sample No. 1 and 2), Example sample Nos. 1 to
The value is higher than 5 and the white color is strong. On the other hand, as shown in Examples 1 to 5, when the addition amount of yttrium oxide is in the range of 0.1% by weight to 10% by weight, the lightness index L ^* is less than 45, and the blackening is reduced. Have been.

The temperature at the time of decompression in the firing step is
When the temperature is lower than 1450 ° C. or higher than 1900 ° C., the lightness index L ^* is 45 or more (Comparative Samples Nos. 3 and 4). The value is higher than that of 6 to 9, and the white color is strong. On the other hand, as shown in Examples 6 to 9, the temperature at the time of pressure reduction was 1450 ° C.
In the case of, the lightness index L ^* is less than 45, and blackening is achieved.

Further, when the decompression time in the firing step is less than 1 hour (Comparative Sample No. 5) or when the pressure exceeds 10 Torr (Comparative Sample No. 5).
6) also has a lightness index L ^* of 45 or more, and is a sample of Example Sample No. 10 or Example Sample No. 11 and 1
This is a higher value than 2. That is, in the comparative example, the blackening of the aluminum nitride sintered body was insufficient, whereas in the example, the lightness index L ^* was less than 45, and blackening was achieved.

In each of the sample samples, the thermal conductivity was 100 W / m · K or more, and the time required to reach 600 ° C. was shorter than that of the comparative sample. The blackening also improves the lamp heating efficiency. In the example samples, the plasma resistance to the fluorine-based plasma was also good.

[Example 2] Yttrium oxide powder was added to aluminum nitride powder in an amount of 2% by weight (in terms of the yttrium element relative to aluminum nitride, external ratio), and an appropriate amount of methanol was added to a ball mill using an aluminum nitride ball. And mixed for 15 hours. To this, a methanol solution of polyvinyl butyral was added as a binder, and polyvinyl butyral was added to the aluminum nitride powder for 3 times.
%, And further mixed by a ball mill for 1 hour to obtain a slurry. The slurry was granulated by a spray dryer, uniaxially molded at 30 MPa, and further molded by a cold isostatic press of 100 MPa. The obtained molded body is placed under an air atmosphere.
Degreasing was performed at a maximum temperature of 600 ° C. The obtained degreased body is
It was fired at 1850 ° C. under a nitrogen atmosphere. The obtained aluminum nitride sintered body was used for the sample No. in Example 3 in Table 3. The heat treatment was performed under the conditions shown in 13 and 14. A sample was prepared in the same manner as in Example 1 from the aluminum nitride sintered body after the heat treatment, and the same tests and measurements as in Example 1 were performed on the sample. Table 3 shows the results.

Comparative Example 2 An aluminum nitride sintered body obtained by the same manufacturing method as in Example 2 was used in Comparative Sample No. Heat treatment was performed under the conditions shown in FIG.
A sample was prepared in the same manner as in Example 1 from the aluminum nitride sintered body after the heat treatment, and the same tests and measurements as in Example 1 were performed on the sample. Table 3 shows the results.

[0038]

[Table 3]

As shown in Table 3, by heating a normal aluminum nitride sintered body in a reduced pressure atmosphere for 1 hour or more, the lightness index L ^* was 45 without lowering the thermal conductivity and plasma resistance. Could be less than. That is, it was recognized that blackening was sufficiently achieved.

Comparative Example 3 In order to compare the black aluminum nitride sintered body according to the present invention with a conventional aluminum nitride sintered body to which a blackening agent was added, Comparative Example Sample N shown in Table 4 was used.
o. Aluminum nitride sintered bodies to which the respective blackening agents were added as shown in Nos. 8 to 13 were produced. A sample was prepared from the obtained aluminum nitride sintered body in the same manner as in Example 1, and the same tests and measurements as in Example 1 were performed on the sample. Table 4 shows the results.

[0041]

[Table 4]

As shown in Table 4, Comparative Example Sample No. 8 to 13 indicate that the lightness index L ^* is 45
And blackening was achieved, but the thermal conductivity was 100 W
/ M · K, and the plasma resistance also decreased.

[0043]

As described above, the black aluminum nitride sintered body according to the present invention does not impair the characteristics of aluminum nitride, such as high thermal conductivity and high plasma resistance, and is suitable for semiconductor manufacturing equipment such as susceptors for lamp heating. It can be suitably used for members. Further, according to the method for producing a black aluminum nitride sintered body of the present invention, the sintered body can be uniformly blackened without impairing the characteristics of the aluminum nitride. Furthermore, the production method according to the present invention does not introduce a foreign element such as a blackening agent into the aluminum nitride sintered body, so that the obtained black aluminum nitride sintered body is used for a semiconductor manufacturing member or the like. Can be used.

Continued on the front page (72) Inventor Shigeko Muramatsu 30 Soya, Hadano-shi, Kanagawa F-term in Toshiba Ceramics Development Co., Ltd. F-term (reference) 4G001 BA09 BA36 BC52 BD03 BD13 BD18 BD23 BD37 BE39

Claims (7)

[Claims] 1. A black aluminum nitride sintered body comprising aluminum nitride and yttrium aluminate, wherein the value of a lightness index L ^* specified in JIS Z 8729-1994 is less than 45. 2. The black aluminum nitride sintered body according to claim 1, wherein the value of the lightness index L ^* is less than 40. 3. The black aluminum nitride sintered body according to claim 1, having a thermal conductivity of 100 W / m · K or more. 4. An aluminum nitride powder is added with an yttrium compound in an external ratio of 0.1% by weight or more and 10% by weight or less in terms of yttrium element with respect to aluminum nitride.
After molding, at 1450 ° C or higher and 1900 ° C or lower, 10 Torr
A method for producing a black aluminum nitride sintered body, comprising a step of firing for 1 hour or more under the following reduced-pressure atmosphere. 5. The sintering temperature is 1600 ° C. or higher and 185 ° C.
The method for producing a black aluminum nitride sintered body according to claim 4, wherein the temperature is 0 ° C or lower. 6. An aluminum nitride sintered body having a value of a lightness index L ^* of 40 or more according to JIS Z 8729-1994 is obtained at a temperature of 1450 ° C. to 1900 ° C. and 10 Torr.
A method for producing a black aluminum nitride sintered body, comprising performing heat treatment for at least one hour in the following reduced pressure atmosphere. 7. The heat treatment temperature is 1600 ° C. or higher and 18.
The method for producing a black aluminum nitride sintered body according to claim 6, wherein the temperature is 50 ° C or lower.