JP5188085B2 - Aluminum nitride corrosion-resistant member and semiconductor manufacturing apparatus member - Google Patents

Description

  The present invention relates to an aluminum nitride corrosion-resistant member suitable for use as a member for a semiconductor manufacturing apparatus such as a heater material or an electrostatic chuck material.

Conventionally, an aluminum nitride (AlN) sintered body exhibits high corrosion resistance against halogen gas, and thus has been widely used as a member for semiconductor manufacturing equipment such as a heater material for heating a semiconductor wafer and an electrostatic chuck material. For example, when an aluminum nitride sintered body is used as an electrostatic chuck material, a holding method using a Johnson-Rahbek force is useful in order to realize high adsorption force and desorption response. Therefore, it is necessary to control the volume resistivity to about 10 ⁸ to 10 ¹² [Ω · cm] within the operating temperature range. From such a background, the inventors of the present invention disclosed in Patent Document 1 that the volume resistivity is increased from 10 ⁸ to 10 ⁸ at room temperature by adding a small amount of yttrium oxide (Y ₂ O ₃ ) to high purity aluminum nitride. It has been disclosed that it can be controlled within a range of 10 ¹² [Ω · cm]. In addition, the inventors of the present invention disclosed in Patent Document 2 that, by adding cerium oxide (CeO ₂ ) to high-purity aluminum nitride, the volume resistivity is 10 ⁸ to 10 ¹² [Ω · cm] at room temperature. It was disclosed that it can be controlled within the range. On the other hand, Patent Document 3 discloses a method for reducing the resistance of an aluminum nitride sintered body by adding conductive ceramics such as titanium nitride to aluminum nitride in an amount of 22 [vol%] or more.
Japanese Patent No. 3457495 JP 2001-163672 A Japanese Patent Laid-Open No. 5-286767

As described above, the substrate material used for the electrostatic chuck application needs to obtain a volume resistivity of about 10 ⁸ to 10 ¹² [Ω · cm] in order to obtain an adsorption force based on the Johnson-Rahbek principle. Some ceramic members used in the manufacturing apparatus may be required to have a lower resistance value depending on the application. For example, in a plasma etching apparatus or the like, a ring-shaped ceramic member is placed around the electrostatic chuck in order to prevent corrosion due to halogenated gas on the electrostatic chuck substrate. Conventionally, as this ring-shaped member, Insulating ceramics were used. However, in order to generate a uniform and stable plasma on the wafer placed on the electrostatic chuck, it is desirable to use a ring member exposed around the wafer having a volume resistivity equivalent to that of the wafer. ing. Therefore, it is necessary to impart conductivity of 10 ⁴ [Ω · cm] or less, which is a semiconductor region equivalent to, for example, a silicon wafer, to the base material of the ring-shaped member.
However, according to the techniques described in Patent Documents 1 and 2, the volume resistivity range of the aluminum nitride sintered body at room temperature can be further expanded to the low resistance side of about several hundred to 10 ¹² [Ω · cm]. For example, the applicable range of the aluminum nitride sintered body to a member for a semiconductor manufacturing apparatus or the like that requires conductivity cannot be expanded. Furthermore, the technique described in Patent Document 3 is applicable to an aluminum nitride sintered body having a relative resistance of 1 [Ω] or less, but is 10 ¹² [Ω · cm, which is an area usable in an electrostatic chuck region. It is estimated that it is difficult to expand the resistance control range to In addition, due to the large amount of conductive ceramic added, the characteristics (thermal expansion coefficient, corrosion resistance, chemical stability, etc.) inherent to aluminum nitride may be impaired, and volume resistivity can be reduced by adding as little as possible. Additives that can achieve resistance values are desired.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an aluminum nitride corrosion-resistant member that retains the characteristics inherent to aluminum nitride and is controlled in resistance over a wide range.

As a result of intensive studies, the inventors of the present application have found that when calcium is contained in an aluminum nitride-based sintered body to produce a calcium-aluminum oxide phase, the calcium-aluminum oxide phase is aluminum nitride. By forming a network structure in the porous ceramics and continuing three-dimensionally and functioning as a conductive path, the room temperature volume resistivity can be sufficiently lowered without impairing the characteristics unique to aluminum nitride, and several hundred to 10 ¹² [Ω・ It was discovered that resistance could be reduced to cm].

  Hereinafter, the present invention will be specifically described based on examples.

[Example 1]
In Example 1, first, calcium carbonate (CaCO ₃ ) was weighed to 4.66 [mol%] with respect to aluminum nitride (AlN), and then a nylon pot and cobblestone were used with isopropyl alcohol as a solvent. For 4 hours. In addition, as AlN, the commercial powder (average particle diameter 0.7 [micrometer]) synthesize | combined by CVD method was used. As CaCO ₃ , a commercial powder having a purity of 99.1 [%] and an average particle size of 3.1 [μm] was used.

Next, the slurry obtained by wet mixing was taken out, dried in a nitrogen stream at 110 [° C.], passed through a sieve and granulated to obtain a blended raw material powder. Furthermore, the raw material powder was uniaxially pressed at a pressure of 20 [MPa] to produce a disk-shaped molded body having a size of about φ50 [mm] and a thickness of 20 [mm]. Thereafter, the obtained disk-shaped molded body was housed in a firing graphite mold and fired by a hot press method to obtain an aluminum nitride sintered body of Example 1. The firing atmosphere was a vacuum (1 × 10 ⁻² [Pa] or less) from room temperature to 1600 [° C.], and nitrogen gas with a pressure of 0.15 [MPa] was introduced at a temperature higher than that. Moreover, after hold | maintaining at a calcination temperature for 2 hours, it cooled to room temperature.

[Example 2]
In Example 2, it was weighed so that CaCO ₃ was 1.95 [mol%] and samarium oxide (Sm ₂ O ₃ ) was 0.05 [mol%], and the firing atmosphere was from room temperature to 1000 [° C.]. Evacuates the furnace (1 × 10 ⁻² [Pa] or less) and introduces nitrogen gas at a pressure of 0.15 [MPa] from 1000 [° C.] to a firing temperature of 1600 [° C.] at the firing temperature. An aluminum nitride sintered body of Example 2 was obtained by manufacturing under the same conditions as Example 1 except that the holding time was 4 hours. As Sm ₂ O ₃ , a commercial powder having a purity of 99.9 [%] or more and an average particle size of about 1.2 [μm] was used.

Example 3
In Example 3, the production was performed under the same conditions as in Example 2 except that CaCO ₃ was 1.95 [mol%] and europium oxide (Eu ₂ O ₃ ) was 0.05 [mol%]. Thus, an aluminum nitride sintered body of Example 3 was obtained. Eu ₂ O ₃ used was a commercial powder having a purity of 99.9 [%] or more and an average particle size of about 1.8 [μm].

[Examples 4 to 7]
In Examples 4 to 7, CaCO ₃ , strontium carbonate (SrCO ₃ ) or cerium oxide (CeO ₂ ) was weighed as shown in Table 1 and manufactured under the firing conditions shown in Table 1. 4 to 7 aluminum nitride sintered bodies were obtained. However, AlN uses a commercially available reduced nitride powder, and the firing atmosphere is a vacuum (1 × 10 ⁻² [Pa] or less) from room temperature to 1000 [° C.] as in Example 2, and 1000 [° C. ] To a firing temperature of 1600 [° C.] or 1800 [° C.], nitrogen gas having a pressure of 0.15 [MPa] was introduced. SrCO ₃ is a commercially available powder having a purity of 99.4 [%] or more and an average particle size of about 3.0 [μm], and CeO ₂ is a purity of 99.9 [%] or more and an average particle size of about 1.1 [μm]. ] Commercially available powder was used.

[Comparative Examples 1 and 2]
In Comparative Examples 1 and 2, CaCO ₃ and Eu ₂ O ₃ were weighed as shown in Table 1, and the furnace was vacuumed from room temperature to 1000 [° C.] at the firing temperature shown in Table 1 as in Example 2. (1 × 10 ⁻² [Pa] or less) and from 1000 [° C.] to a firing temperature of 1600 [° C.] or 1800 [° C.] by introducing nitrogen gas with a pressure of 0.15 [MPa] Thus, aluminum nitride sintered bodies of Comparative Examples 1 and 2 were obtained.

[Evaluation]
About each aluminum nitride sintered compact of the said Examples 1-7 and Comparative Examples 1 and 2, content of Ca, O, and Me (metal elements added in addition to calcium: Sr, Sm, Eu, Ce) is determined by chemical analysis. The open porosity, bulk density, room temperature volume resistivity [Ω · cm], crystal phase, thermal conductivity [W / m · K], and activation energy [eV] were evaluated. The Ca and Me contents were determined by inductively coupled plasma (ICP) emission spectrum analysis, and the O content was quantified by an inert gas melting infrared absorption method. The open porosity and bulk density were measured by Archimedes method using pure water as a medium.

  The room temperature volume resistivity was measured in the atmosphere by a method according to JIS_C2141, and when the activation energy was obtained, it was measured from room temperature to about 400 [° C.] in vacuum. Specifically, the test piece shape is φ50 [mm] × 1 [mm], the main electrode diameter 20 [mm], the guard electrode inner diameter 30 [mm], the guard electrode outer diameter 40 [mm], and the voltage application electrode diameter Each electrode was formed of silver so as to be 40 [mm]. The applied voltage was 0.1 to 500 [V / mm], and the volume resistivity was calculated by reading the current one minute after the voltage was applied. The activation energy was calculated from room temperature and a volume resistivity of 400 [° C.].

The crystal phase was identified by an X-ray diffractometer (rotating anti-cathode X-ray diffractometer, RINT manufactured by Rigaku Corporation) (measurement conditions: CuKα radiation source, 50 [kV], 300 [mA], 2θ = 10 to 70 [° ]). The thermal conductivity was measured by a laser flash method. The measurement results are shown in Table 2 below.

As apparent from Table 2, the room temperature volume resistivity of the aluminum nitride sintered bodies of Examples 1 to 7 is lower than the room temperature volume resistivity of the aluminum nitride sintered bodies of Comparative Examples 1 and 2, and both are 1 × It became clear that it was below 10 ¹² [Ω · cm]. Further, when comparing the crystal phase of the aluminum nitride sintered body of Examples 1 to 7 and the crystal phase of the aluminum nitride sintered body of Comparative Examples 1 and 2, the aluminum nitride sintered bodies of Examples 1 to 3 and 5 are It was revealed that the Ca ₁₂ Al ₁₄ O ₃₃ phase was abundant, and in Examples 6 and 7, there were many Ca ₃ Al ₂ O ₆ phases.

1 and 2 show X-ray diffraction profiles obtained from the aluminum nitride sintered bodies of Example 5 and Example 6, respectively. As is apparent from FIGS. 1 and 2, as a component other than AlN, many Ca ₁₂ Al ₁₄ O ₃₃ phases and Ca ₃ Al ₂ O ₆ phases are generated. FIG. 3 shows the X-ray diffraction profile of the aluminum nitride sintered body of Example 4. The observed peaks have the same structure as the Ca ₁₂ Al ₁₄ O ₃₃ phase and the Ca ₁₂ Al ₁₄ O ₃₃ phase. It is located between the Sr ₁₂ Al ₁₄ O ₃₃ phase, which is known to take This is presumed that Ca and Sr are in solid solution with each other, and a solid solution of Ca ₁₂ Al ₁₄ O ₃₃ phase and Sr ₁₂ Al ₁₄ O ₃₃ phase is generated.

When the polished surface of the aluminum nitride sintered bodies of Examples 1 to 5 was observed using a scanning electron microscope (SEM), a white phase having a contrast different from that of AlN was observed. Further analysis by EDX revealed that the continuous grain boundary phase contains at least Ca, Al, and O, and from the comparison with the crystal phase identified from the XRD profile, the Ca ₁₂ Al ₁₄ O ₃₃ phase (or addition) It has been clarified that the Ca ₁₂ Al ₁₄ O ₃₃ phase in which the metal element is dissolved is present as a continuous grain boundary phase. Moreover, when the polished surface of the aluminum nitride of Examples 6 and 7 was observed and analyzed by EDX, the continuous grain boundary phase contained at least Ca, Al, and O, and was obtained from the XRD profile. Ca ₃ Al ₂ O ₆ phase from the comparison of the crystal phase (or the added Ca ₃ Al ₂ O ₆ phase metal element forms a solid solution) that is present as a grain boundary phase which serializes revealed. 4 and 5 are SEM photographs of the polished surface of the aluminum nitride sintered bodies of Examples 2 and 6, respectively. Therefore, the aluminum nitride sintered bodies of Examples _1-5, as Ca _{12 Al} 14 _{O 33} phase (or the added _Ca 12 _Al 14 _{O 33} phase metal element forms a solid solution) grain boundary phase continuous reduction is Since it plays the role of a conductive path when it exists, it is estimated that the volume resistivity is reduced as compared with the aluminum nitride sintered bodies of Comparative Examples 1 and 2. In the aluminum nitride sintered bodies of Examples 6 and _7, be present as a grain boundary phase Ca 3 _Al 2 _{O 6} phase (or added metal element is dissolved has been _Ca 3 _Al 2 _{O 6} phase) was serialized Therefore, it is estimated that the volume resistivity is lowered as compared with the aluminum nitride sintered bodies of Comparative Examples 1 and 2. 6 and 7 show the temperature characteristics of the volume resistivity of the aluminum nitride sintered bodies of Examples 2 and 3. FIG. When the activation energy was calculated using the room temperature and the volume resistivity of 400 [° C.] for the aluminum nitride sintered bodies of Examples 2 and 3, they were 0.15 [eV] and 0.25 [eV], respectively. All activation energies were 0.4 [eV] or less. Moreover, when the heat conductivity was measured about the aluminum nitride sintered compact of Examples 1-7, all the heat conductivity was 60 [W / m * K] or more.

  As is apparent from the above description, according to the aluminum nitride sintered bodies of Examples 1 to 7, it is possible to achieve a reduction in resistance without impairing the characteristics unique to aluminum nitride. In addition, according to the aluminum nitride sintered bodies of Examples 1 to 7, the volume resistivity range of aluminum nitride at room temperature can be expanded to the low resistance side. The applicable range of aluminum nitride can be expanded. Since the aluminum nitride sintered body of the present invention does not substantially contain alkali metal, boron or the like, it does not become an impurity source even when applied to a member for a semiconductor manufacturing apparatus.

  As mentioned above, although the embodiment to which the invention made by the present inventors was applied has been described, the present invention is not limited by the description and the drawings that form part of the disclosure of the present invention according to this embodiment. That is, it should be added that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above embodiments are all included in the scope of the present invention.

The X-ray-diffraction profile obtained from the aluminum nitride sintered compact of Example 5 is shown. The X-ray-diffraction profile obtained from the aluminum nitride sintered compact of Example 6 is shown. The X-ray-diffraction profile obtained from the aluminum nitride sintered compact of Example 4 is shown. The SEM photograph of the surface of the aluminum nitride sintered compact of Example 2 is shown. The SEM photograph of the surface of the aluminum nitride sintered compact of Example 6 is shown. The temperature dependence of the volume resistivity of the aluminum nitride sintered compact of Example 2 is shown. The temperature dependence of the volume resistivity of the aluminum nitride sintered compact of Example 3 is shown.

Claims (6)

The main component is aluminum nitride (AlN), and has a continuous grain boundary phase containing at least calcium (Ca), aluminum (Al), and oxygen (O), and the grain boundary phase functions as a conductive path,
See contains at least one of the grain boundary phase is Ca ₁₂ Al ₁₄ O ₃₃ phase and Ca ₃ Al ₂ O ₆ phase,
An aluminum nitride corrosion-resistant member having a volume resistivity of 1 × 10 ¹² [Ω · cm] or less at room temperature in the air .   2. The aluminum nitride corrosion-resistant member according to claim 1, wherein a rare earth metal and / or an alkaline earth metal is dissolved in the grain boundary phase. 3.   3. The aluminum nitride corrosion-resistant member according to claim 2, wherein the grain boundary phase is at least one selected from the group consisting of strontium (Sr), samarium (Sm), europium (Eu), and cerium (Ce). An aluminum nitride corrosion-resistant member in which a seed metal element is dissolved. Of claims 1 to 3, a nitride aluminum corrosion-resistant member according to any one, that the activation energy at 400 [° C.] following temperatures above room temperature is 0.4 [eV] or less An aluminum nitride corrosion-resistant member characterized by The aluminum nitride corrosion-resistant member according to any one of claims 1 to 4, wherein the aluminum nitride corrosion-resistant member has a thermal conductivity of 60 [W / m · K] or more. A member for a semiconductor manufacturing apparatus, wherein at least a part of the aluminum nitride corrosion-resistant member according to any one of claims 1 to 5 is formed.