KR102153324B1 - Manufacturing method of aluminum nitride-yttria composite ceramics - Google Patents

Abstract

The present invention includes the steps of forming a slurry by mixing AlN powder, Y ₂ O ₃ powder and MgO powder with a solvent, drying the slurry to form a composite powder, and molding the composite powder. It relates to a method of manufacturing an aluminum nitride-yttria composite ceramic comprising the step of sintering the resultant product. According to the present invention, an aluminum nitride-yttria composite ceramic having high electrical resistance as a whole can be manufactured by increasing the resistance due to grain boundaries by adding MgO powder.

Description

Manufacturing method of aluminum nitride-yttria composite ceramics}

The present invention relates to a method of manufacturing aluminum nitride-yttria composite ceramics, and more particularly, by adding MgO powder to increase resistance due to grain boundaries, thereby producing aluminum nitride-yttria composite ceramics having high overall electrical resistance. It relates to a method that can be manufactured.

Aluminum nitride (AlN) has a theoretical thermal conductivity of 320 W/m·K, and is widely used as a plasma-resistant ceramic material in semiconductor manufacturing processes that require a uniform temperature distribution of a wafer.

In particular, in recent years, it has been widely used as a material for an electrostatic chuck, which is a component that fixes a wafer by electrostatic attraction. In order to function as an electrostatic chuck, thermal characteristics are also important, but in order to attract a wafer by generating electrostatic force on the substrate surface, the electrical characteristics of the material having high resistance and high dielectric constant are also very important.

There are two known mechanisms for fixing wafers using electrostatic force, the Coulomb method and the Johnson-Rabeck method. In the Coulomb method, the high-resistance dielectric between the wafer and the electrode fixes the wafer with electrostatic force generated when a high voltage of about 1000 to 3000 V is applied to the electrode. On the other hand, the Johnson-Rabeck type uses the electrostatic force with the wafer generated by the charge carrier moving to the surface of the dielectric when a voltage of several hundred V is applied to the electrode to a dielectric having a resistance of 10 ⁹ ∼ 10 ¹³ Ω·cm. The mechanism of the existing Johnson-Ravec type electrostatic chuck is explained to be due to the fixing force generated when the charge carrier of the dielectric is an electron or a hole.

In recent years, semiconductor processes that require high-precision lithography at high temperatures are increasing, and thus ceramic materials capable of maintaining electrostatic force at high temperatures are required. Therefore, there is a demand for a material that maintains electrical resistance even at high temperatures (>1E8 ohm cm @500 degrees) and has a high dielectric constant. However, in the case of a dielectric material such as AlN that is actually used, ions in addition to electrons or holes become charge carriers. In ceramics, systematic impedance analysis for ion conduction at particle and grain boundaries is very poor.

In the case of an AlN material widely used as an electrostatic chuck material, it is manufactured using AlN powder manufactured by a carbothermal method. AlN commercial powder produced by the carburization process generally contains around 1 wt% of oxygen. Therefore, when using Y ₂ O ₃ as a sintering aid, a significant amount of Al ₂ O ₃ components in the AlN raw material and Y ₂ O ₃ react to form Yttrium-Aluminate such as YAG (Y ₃ Al ₅ O ₁₂ ), and the rest It is known that about 0.5 wt% of oxygen is dissolved in AlN particles through an ionic compensation reaction as shown in Scheme 1 below.

[Scheme 1]

Korean Patent Publication No. 10-1402501

An object to be solved by the present invention is to provide a method for manufacturing aluminum nitride-yttria composite ceramics having a high overall electrical resistance by adding MgO powder to increase resistance due to grain boundaries.

The present invention comprises the steps of (a) mixing AlN powder, Y ₂ O ₃ powder and MgO powder with a solvent to form a slurry, (b) drying the slurry to form a composite powder, and (c) the It provides a method of manufacturing an aluminum nitride-yttria composite ceramics comprising the steps of forming the composite powder and (d) sintering the formed product.

The slurry may be formed by further mixing Ta ₂ O ₅ powder in step (a).

In the step (a), the slurry may be formed by further mixing WO ₃ powder.

The slurry may be formed by further mixing TiO ₂ powder in step (a).

In step (a), HfO ₂ powder may be further mixed to form the slurry.

In step (a), the slurry may be formed by further mixing SrO powder.

The Y ₂ O ₃ powder is preferably mixed with 0.1 to 7 parts by weight based on 100 parts by weight of the AlN powder.

The MgO powder is preferably mixed with 0.1 to 10 parts by weight based on 100 parts by weight of the AlN powder.

The sintering is preferably performed at a sintering temperature of 1500 to 1620°C.

After the sintering, the step of annealing at a temperature lower than the sintering temperature may be further included.

The annealing is preferably performed at a temperature of 1300 to 1550°C.

According to the present invention, an aluminum nitride-yttria composite ceramic having high electrical resistance as a whole can be manufactured by increasing the resistance due to grain boundaries by adding MgO powder.

1 is an aluminum nitride-yttria composite ceramics prepared by adding 1.0 wt% of Y ₂ O ₃ according to Experimental Example 1, prepared by adding 1.0 wt% of Y ₂ O ₃ and 2.0 wt% of MgO according to Experimental Example 2 X-ray diffraction of aluminum nitride-yttria composite ceramics, and aluminum nitride-yttria composite ceramics prepared by adding 1.0 wt% Y ₂ O ₃ and 2.0 wt% MgO and annealing according to Experimental Example 3 (X -ray diffraction (XRD) is a diagram showing the analysis result.
2 is a diagram showing the microstructure of aluminum nitride-yttria composite ceramics prepared according to Experimental Examples 1 to 3. FIG.
3 is a diagram showing an EDX (Energy Dispersive X-ray Spectroscopy) mapping image of aluminum nitride-yttria composite ceramics prepared according to Experimental Examples 1 to 3. FIG.
4 is a diagram showing DC electrical conductivity and activation energy according to temperature under an electric field of 100V/mm for the aluminum nitride-yttria composite ceramics manufactured according to Experimental Example 3. FIG.
5 is a view showing the electrical conductivity of the aluminum nitride-yttria composite ceramics prepared according to Experimental Examples 1 to 3 according to temperature under an electric field of 100V/mm.
6A and 6B are diagrams showing changes in impedance spectra of aluminum nitride-yttria composite ceramics manufactured according to Experimental Example 1. FIG.
7A and 7B are diagrams showing changes in the impedance spectrum of the aluminum nitride-yttria composite ceramics manufactured according to Experimental Example 2.
8A and 8B show changes in the impedance spectrum of the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 3.
9 shows an impedance spectrum using the ZVIEW program to configure an equivalent circuit in consideration of polarization by particles, grain boundaries, and electrodes, and resistance and capacitance corresponding to each polarization through numerical fitting. It is a diagram showing the (capacitance) value.
FIG. 10 is a diagram showing electrical conductivity according to temperature by separating resistance of an intragranular and grain boundary, and calculating activation energy.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following examples are provided so that the present invention may be sufficiently understood by those of ordinary skill in the art, and may be modified in various other forms, and the scope of the present invention is limited to the examples described below. It does not become.

In the detailed description of the invention or in the claims, when any one component "includes" another component, it is not construed as being limited to only the component unless otherwise stated, and other components are further included. It should be understood that it may contain.

A method of manufacturing an aluminum nitride-yttria composite ceramic according to a preferred embodiment of the present invention includes the steps of (a) mixing AlN powder, Y ₂ O ₃ powder and MgO powder in a solvent to form a slurry, and (b) the Drying the slurry to form a composite powder, (c) forming the composite powder, and (d) sintering the formed product.

The slurry may be formed by further mixing Ta ₂ O ₅ powder in step (a).

In the step (a), the slurry may be formed by further mixing WO ₃ powder.

The slurry may be formed by further mixing TiO ₂ powder in step (a).

In step (a), HfO ₂ powder may be further mixed to form the slurry.

In step (a), the slurry may be formed by further mixing SrO powder.

The Y ₂ O ₃ powder is preferably mixed with 0.1 to 7 parts by weight based on 100 parts by weight of the AlN powder.

The MgO powder is preferably mixed with 0.1 to 10 parts by weight based on 100 parts by weight of the AlN powder.

The sintering is preferably performed at a sintering temperature of 1500 to 1620°C.

After the sintering, the step of annealing at a temperature lower than the sintering temperature may be further included.

The annealing is preferably performed at a sintering temperature of 1300 to 1550°C.

A method of manufacturing an aluminum nitride-yttria composite ceramic according to a preferred embodiment of the present invention will be described in more detail.

As starting materials, AlN powder, Y ₂ O ₃ powder and MgO powder are prepared.

AlN powder, Y ₂ O ₃ powder and MgO powder are mixed in a solvent to form a slurry. The Y ₂ O ₃ powder is preferably mixed with 0.1 to 7 parts by weight based on 100 parts by weight of the AlN powder. The MgO powder is preferably mixed with 0.1 to 10 parts by weight based on 100 parts by weight of the AlN powder.

The solvent may be water (H ₂ O), alcohols such as ethanol, methanol, and the like.

The slurry may be formed by further mixing Ta ₂ O ₅ powder. The Ta ₂ O ₅ powder is preferably mixed with 0.1 to 5 parts by weight based on 100 parts by weight of the AlN powder.

The slurry may be formed by further mixing WO ₃ powder. The WO ₃ powder is preferably mixed with 0.1 to 5 parts by weight based on 100 parts by weight of the AlN powder.

TiO ₂ powder may be further mixed to form the slurry. The TiO ₂ powder is preferably mixed in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the AlN powder.

The slurry may be formed by further mixing HfO ₂ powder. The HfO ₂ powder is preferably mixed with 0.1 to 5 parts by weight based on 100 parts by weight of the AlN powder.

The slurry may be formed by further mixing SrO powder. The SrO powder is preferably mixed with 0.1 to 5 parts by weight based on 100 parts by weight of the AlN powder.

The mixing may use a ball milling process or the like. In the description of the ball milling process, the starting material is charged into a ball milling machine together with a solvent. Mix mechanically by rotating at a constant speed using a ball mill. The balls used in the ball milling are preferably made of ceramic materials such as alumina and zirconia, and all of the balls may be of the same size, or balls having two or more sizes may be used together. Adjust the size of the ball, milling time, and rotation speed per minute of the ball mill. For example, the size of the ball may be set in the range of 1 mm to 50 mm, and the rotation speed of the ball mill may be set in the range of 50 to 500 rpm. Ball milling is preferably performed for 10 minutes to 48 hours for uniform mixing and the like. The mixture that has undergone the wet mixing process as described above is finely divided to form a slurry state.

The slurry is dried to form a composite powder. The drying is preferably performed at a temperature of about 40 to 90°C.

The composite powder is molded. For the molding, various methods such as commonly known pressure molding and injection molding may be used.

The molded result is sintered. The sintering is preferably performed at a sintering temperature of 1500 to 1620°C. During sintering, it is desirable to keep the pressure inside the furnace constant. The sintering is preferably carried out in an oxidizing atmosphere (eg, oxygen (O ₂ ) or air atmosphere).

After the sintering, the step of annealing at a temperature lower than the sintering temperature may be further included. The annealing is preferably performed at a temperature of 1300 to 1550°C. The annealing is preferably carried out in an oxidizing atmosphere (eg, oxygen (O ₂ ) or air atmosphere).

In the following, experimental examples according to the present invention are specifically presented, and the present invention is not limited to the experimental examples presented below.

In the case of an AlN material widely used as an electrostatic chuck material, it is manufactured using AlN powder manufactured by a carbothermal method. AlN commercial powder produced by the carburization process generally contains around 1 wt% of oxygen. Therefore, when using Y ₂ O ₃ as a sintering aid, a significant amount of Al ₂ O ₃ components in the AlN raw material and Y ₂ O ₃ react to form Yttrium-Aluminate such as YAG (Y ₃ Al ₅ O ₁₂ ), and the rest It is known that about 0.5 wt% of oxygen is dissolved in AlN particles through an ionic compensation reaction.

Several studies have been conducted on the effect of oxygen ions substituted at the nitrogen sites on the electrical conductivity of AlN ceramics. However, in the case of doping with a transition metal or metal oxide, studies on the effect on the electrical conductivity of grains and grain boundaries have not been sufficiently conducted. When TiO ₂ is doped at a low concentration, defects generated by Ti form an ion pair with Al vacancy, reducing the mobility of the charge carrier, and reducing the mobility of the charge carrier and the grain and grain boundaries. grain boundary) decreases in conductivity. However, when various metal oxides (M _x O _y , M=M ^+III , M ^+IV , M ^+V ) are added, the solid solution in the crystal grains of M _x O _y or the secondary phase (M _x Al _y O _z ) The effect of generation on electrical resistance has not been systematically studied. In the case of MgO addition, which is known to increase the resistance at high temperature when added to AlN sintered body, the mechanism of increasing resistance is expected to be different because the electron value (oxidation number) is different when substituted and thus the defects generated are different. There is no bar. In addition, studies on the distribution and electrical properties of Mg according to process conditions such as sintering temperature and sintering time have not been systematically conducted.

In this experiment, MgO was added to AlN and the sintering conditions were changed, and the electrical conductivity in the grain and grain boundaries changed accordingly was to be observed using impedance spectroscopy. In connection with the result of transmission electron microscope (TEM) analysis, this study attempted to reveal the correlation between the microstructure and the electric conduction mechanism. Based on these results, this study attempted to investigate the effect of AlN's electrical conduction mechanism on the function of AlN material as a high-temperature electrostatic chuck material.

<Experimental Example 1>

As raw material powder, AlN powder (Grade H, Tokuyama Soda Co. Ltd., Japan, 1.1 μm) was used, and Y ₂ O ₃ powder (99.99%, HC STARCK, USA) was used.

Mixing AlN powder as raw material powder, Y ₂ O ₃ powder, and anhydrous alcohol (Sigma Aldrich, USA) as a solvent in a 250 ml container, and preparing a slurry through ball milling for 20 hours I did. The Y ₂ O ₃ powder was mixed with 1.0 wt% of the AlN powder as a raw material powder.

The prepared slurry was maintained at 50 for 3 hours using a rotary evaporator and dried.

The obtained powder was put into a graphite mold with a diameter of 40 mm, 7 to 8 g, and a pressure of 15 MPa was pressed.

Then, the temperature was raised to 1600° C. at 5° C./min per minute, maintained for 5 hours, sintered, and cooled by furnace to obtain an aluminum nitride-yttria composite ceramic.

<Experimental Example 2>

As raw material powder, AlN powder (Grade H, Tokuyama Soda Co. Ltd., Japan, 1.1 μm) was used, and Y ₂ O ₃ powder (99.99%, HC STARCK, USA) was used.

In a 250 ml container, mix raw material powder AlN powder, Y ₂ O ₃ powder, MgO powder (99,99%, high purity chemistry, Japan), and anhydrous alcohol (Sigma Aldrich, USA) as a solvent for 20 hours. A slurry was prepared through ball milling. The Y ₂ O ₃ powder was mixed with 1.0 wt% of the AlN powder as a raw material powder. The MgO powder was mixed with 2.0 wt% of the AlN powder as a raw material powder.

The prepared slurry was maintained at 50 for 3 hours using a rotary evaporator and dried.

The obtained powder was put into a graphite mold with a diameter of 40 mm, 7 to 8 g, and a pressure of 15 MPa was pressed.

Then, the temperature was raised to 1600° C. at 5° C./min per minute, maintained for 5 hours, sintered, and cooled by furnace to obtain an aluminum nitride-yttria composite ceramic.

<Experimental Example 3>

As raw material powder, AlN powder (Grade H, Tokuyama Soda Co. Ltd., Japan, 1.1 μm) was used, and Y ₂ O ₃ powder (99.99%, HC STARCK, USA) was used.

In a 250 ml container, mix raw material powder AlN powder, Y ₂ O ₃ powder, MgO powder (99,99%, high purity chemistry, Japan), and anhydrous alcohol (Sigma Aldrich, USA) as a solvent for 20 hours. A slurry was prepared through ball milling. The Y ₂ O ₃ powder was mixed with 1.0 wt% of the AlN powder as a raw material powder. The MgO powder was mixed with 2.0 wt% of the AlN powder as a raw material powder.

The prepared slurry was maintained at 50 for 3 hours using a rotary evaporator and dried.

The obtained powder was put into a graphite mold with a diameter of 40 mm, 7 to 8 g, and a pressure of 15 MPa was pressed.

Then, the temperature was raised to 1600°C at 5°C/min per minute, maintained for 5 hours, and then sintered, cooled to 1500°C at 5°C/min per minute, and maintained for 10 hours for annealing, followed by furnace cooling to aluminum nitride-yttria. Composite ceramics were obtained.

The density of the specimen obtained by sintering was measured by the Archimedes method. Changes in the crystal phase were observed using an X-ray diffraction analyzer (D/max-2500, RIGAKU, Japan). In order to measure the volume resistance, a platinum electrode was deposited using a sputtering method. Resistance measurement was performed using a high resistance meter (Keysight B2985A, USA) to measure the resistance value after 60 seconds after applying a voltage of 100 V/mm in the 25 ~ 550 ℃ section. For impedance analysis, the specimen was processed in a 10 × 10 × 1 mm standard. Each specimen was measured at a temperature range of 25~550℃ using an impedance analyzer (Solatron impedance analyzer SI1260, UK). (OSC: 1.0V, 0.1 Hz ~ 3.0 MHz) The measured impedance value was analyzed using ZVIEW software (Version 2.9c, Scribner Associates, Inc). The microstructure of the sintered body was observed using Cs-TEM (JEM-ARM200F, JEOL, Japan) (200 kV).

Aluminum nitride-yttria composite ceramics prepared by adding 1.0 wt% Y ₂ O ₃ according to Experimental Example 1, aluminum nitride prepared by adding 1.0 wt% Y ₂ O ₃ and 2.0 wt% MgO according to Experimental Example 2- X-ray diffraction (X-ray diffraction) of yttria composite ceramics, and aluminum nitride-yttria composite ceramics prepared by adding 1.0 wt% of Y ₂ O ₃ and 2.0 wt% of MgO and annealing according to Experimental Example 3. ; XRD) The analysis results are shown in FIG. 1.

Referring to FIG. 1, as a result of the analysis, the main crystal phase of all three specimens was an AlN phase. The Yttrium Aluminum Garnet (YAG, Y ₃ Al ₅ O ₁₂ ) phase as well as the Al ₂ O ₃ phase was observed as a secondary phase. In the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 2 and the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 3, secondary phases of YAlO ₃ (YAP) and MgAl ₂ O ₃ (MSP) could be seen. . The AlN raw material used in these experimental examples is prepared by carburization and contains about 0.8 wt% of oxygen. Assuming that this oxygen is in the form of oxide, YAG and YAP are added by adding Y ₂ O ₃ and MgO. , It is thought that the crystal phase of MSP is precipitated.

2 shows the microstructure of the aluminum nitride-yttria composite ceramics prepared according to Experimental Examples 1 to 3, and FIG. 3 shows the aluminum nitride-yttria composite ceramics prepared according to Experimental Examples 1 to 3 EDX (Energy Dispersive X-ray Spectroscopy) mapping image is shown. In FIG. 2, (a) is a transmission electron microscope (TEM) photograph of the aluminum nitride-yttria composite ceramics manufactured according to Experimental Example 1, and (b) is a transmission electron microscope (a) magnified. TEM) is a photograph, (c) is a transmission electron microscope (TEM) photograph showing the grain boundaries of the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 1, and (d) is prepared according to Experimental Example 2. Is a transmission electron microscope (TEM) photograph of the aluminum nitride-yttria composite ceramics, (e) is a transmission electron microscope (TEM) photograph showing an enlarged view of (d), and (f) is a nitride prepared according to Experimental Example 2. It is a transmission electron microscope (TEM) photograph showing the grain boundary of the aluminum-yttria composite ceramics, (g) is a transmission electron microscope (TEM) photograph of the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 3 , (h) is a transmission electron microscope (TEM) photograph magnified in (g), and (i) is a transmission electron microscope showing the grain boundary of the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 3. This is a (TEM) picture. In FIG. 3, (a) is an EDX mapping image of the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 1, and (b) is an EDX mapping image of the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 2. , (c) is an image of EDX mapping of aluminum nitride-yttria composite ceramics prepared according to Experimental Example 3.

2 and 3, in the aluminum nitride-yttria composite ceramics manufactured according to Experimental Example 1, as shown in FIGS. 2A to 2C, the YAG secondary phase was observed independently from the AlN column. On the other hand, in the aluminum nitride-yttria composite ceramics prepared by doping MgO according to Experimental Examples 2 and 3, a liquid film composed of Y, Al, Mg, O, and N was observed at the grain boundary. No independent secondary phase was observed (see (d) to (i) in FIG. 2).

In Fig. 3 (a), which is an EDX mapping image of the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 1, it can be seen that the YAG oxide composed of (Y, Al, O) exists as a secondary phase. As shown in (b) of Figure 3, in the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 2, it can be seen that Mg mainly exists in the grain boundary, and the aluminum nitride-yttria composite prepared according to Experimental Example 3 In ceramics, as shown in Fig. 3(c), it was confirmed that Mg, which was at the critical level, diffused into the inside grain after annealing.

AlN ceramics are known to have a large dependence on the extrinsic part of the donor rather than the intrinsic property of the electron conductivity. When oxygen ions are dissolved in AlN grains, in addition to ionic compensation as shown in Scheme 1, an electronic compensation mechanism such as Scheme 2 is also possible.

[Scheme 2]

In AlN ceramics, the ionic compensation mechanism is far superior to the electronic compensation mechanism, and it can be estimated that the ratio of ionic compensation and electronic compensation is determined by the final heat treatment conditions and doping elements. In general, it is known that the lower the heat treatment temperature, the more predominantly ionic compensation occurs than electronic compensation.

FIG. 4 shows DC electrical conductivity and activation energy according to temperature under an electric field of 100V/mm for the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 3. In FIG. 4, red: RT, black: 100 °C, blue: 200 °C, Cyan: 300 °C, pink: 400 °C, and green: 500 °C are respectively shown.

5 is a view showing the electrical conductivity of the aluminum nitride-yttria composite ceramics prepared according to Experimental Examples 1 to 3 according to temperature under an electric field of 100V/mm.

4 and 5, the volume resistance rapidly increased with time and then saturated after a certain period of time. This is judged as a polarization effect by an electrode in which a charge carrier is blocked at the electrode and current flow is gradually blocked. Looking at the change in the flow of current over time, the aluminum nitride-yttria composite ceramics prepared according to Experimental Examples 1 to 3 show a similar shape, but when measured at 400°C or higher, the current flows within a relatively short time. It can be seen that this is saturated. In this experiment, since a platinum electrode was used, the flow of electrons is not disturbed at the interface between the electrode and the specimen, but may be limited by the flow of ions. This is the expected result when the major charge carrier of AlN is an ion defect, which is a vacancy in the Al site. Accordingly, it can be seen that the movement of ions and electrons contributes to the total current flow at the beginning of the DC resistance measurement, but the flow of ions is gradually restricted by the electrode, and finally only movement by electrons contributes to the current flow.

The results of FIG. 5 were measured only at a relatively high temperature of 200° C. or higher due to the measurement limit of the measuring device. Looking mainly at the high-temperature data of 200°C or higher, the aluminum nitride-yttria composite ceramics prepared according to Experimental Examples 2 and 3 were 1 order or more higher than the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 1. It can be seen that and are showing higher activation energy. This means that the concentration of carriers that dominate the electron conductivity has decreased or that the mobility has been changed with the addition of Mg. When MgO is added to the AlN matrix, the following reaction can occur.

[Scheme 3]

[Scheme 4]

[Scheme 5]

According to Scheme 3, the electronic compensation mechanism according to the addition of Y ₂ O ₃ to the AlN matrix was found, which is similar to Scheme 2. This is thought to be because electron transporters are generated by adding Y ₂ O ₃ even though the ionic radius of Y ³⁺ (0.9Å) is somewhat larger than Al ^{3 +} (0.54Å). Equation 4 shows that the positive and negative carriers increase, respectively, so that the net carrier charge remains unchanged. In the case of Scheme 5, a hole carrier is generated in an N ₂ atmosphere, but the electronic contribution resulting from the reaction of Scheme 3 can be reduced by the addition of MgO. As a result, as shown in Scheme 4, when comparing the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 1 and the aluminum nitride-yttria composite ceramics prepared by doping MgO according to Experimental Examples 2 and 3, MgO It can be seen that the conductivity of electrons decreases by more than several orders by the addition of. It can be interpreted that this is due to the decrease in electron carriers by MgO doping (refer to Scheme 5). In addition, when the activation energy according to the temperature was calculated, in the case of the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 2 and Experimental Example 3, the activation energy of electrical conductivity was 1.19 eV and 1.17 eV, respectively, according to Experimental Example 1. In the case of the prepared aluminum nitride-yttria composite ceramics, the activation energy was 0.86 eV. Thus, it appears that the result of reducing the mobility by MgO doping was also obtained. In the case of AlN ceramics, it is known that the conductivity due to ion conduction cannot be ignored, and impedance spectral analysis and microstructure analysis were performed to accurately analyze the effect of particles or grain boundaries.

The complex impedance spectrum according to the temperature (RT-550 degrees) was measured for the aluminum nitride-yttria composite ceramics prepared according to Experimental Examples 1 to 3. First, the capacitance C _p according to the measurement frequency f and the resulting dielectric constant ε were calculated using the following equation (1) from the complex impedance ( Z _real , Z _imag ) assuming the parallel connection of the resistor and the capacitor.

[Equation 1]

The dielectric constant of ceramics is largely divided into three regions according to the frequency range, and it is known that there are three different polarization mechanisms depending on the frequency. The high frequency band is considered to be due to particles, and it can be estimated as the effect of grain boundaries in the range of 10 ⁴ Hz and ion polarization in the range of 10 ² Hz or less.

6A and 6B show changes in the impedance spectrum of the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 1, and FIGS. 7A and 7B are the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 2. It shows the change of the impedance spectrum, and FIGS. 8A and 8B show the change of the impedance spectrum of the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 3. FIG.

Using the ZVIEW program, the impedance spectrum is composed of an equivalent circuit in consideration of polarization caused by particles, grain boundaries, and electrodes, and resistance and capacitance corresponding to each polarization through numerical fitting. The value was calculated as shown in FIG. 9. In FIG. 9, '1Y' denotes the aluminum nitride-yttria composite ceramics manufactured according to Experimental Example 1, and '1Y2M' denotes the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 2, and '1Y2M-A' Represents the aluminum nitride-yttria composite ceramics prepared according to Experimental Example 3.

In all temperature ranges, the grain boundary resistance (grain boundary term) is 1~2 orders higher than that of the grain resistance (grain term), and the grain resistance and grain boundary resistance are significantly changed by doping. Showing. In the case of the aluminum nitride-yttria composite ceramics (1Y2M) prepared according to Experimental Example 2, the grain resistance decreased compared to the aluminum nitride-yttria composite ceramics (1Y) prepared according to Experimental Example 1 according to MgO doping, but the experiment In the case of the aluminum nitride-yttria composite ceramics (1Y2M-A) prepared according to Example 3, the grain resistance was 1 order compared to the aluminum nitride-yttria composite ceramics (1Y) prepared according to Experimental Example 1 at a high temperature of 300 degrees or more. It could be seen that the increase was increased. This is considered to be because the effect of increasing the resistance by annealing is greater in the high temperature region than the effect of reducing the resistance by doping with MgO.

)이 생성되고( 반응식 4 참조) 주된 운반자인 Al 공극(

) 의 농도가 입계에서 지수적으로(exponentially) 감소하면서 공핍(depletion) 현상이 일어나게 된다. Al 공극는 입계에서 보다 높은 쇼트키 장벽을 느끼게 되고 따라서 입계에서의 저항은 증가한다. 특히 실험예 3에 따라 제조된 질화알루미늄-이트리아 복합 세라믹스(1Y2M-A)의 경우 도 3의 (c)에서 볼 수 있는 것과 같이 어닐링 후 Mg가 입내로 확산되었으며, 이것이 입계저항을 한층 더 증가시킨 것으로 생각된다. As can be seen in FIG. 9, it can be seen that the resistance due to the grain boundary is higher than the internal resistance and dominates the resistance in the high temperature portion. That is, it means that controlling the resistance of the grain boundary is a major factor in increasing the high temperature resistance of the AlN sintered body. In the case of the aluminum nitride-yttria composite ceramics (1Y2M) prepared by doping MgO according to Experimental Example 2, the resistance at a high temperature of 300°C or higher was higher than that of the aluminum nitride-yttria composite ceramics (1Y) prepared according to Experimental Example 1. It can be seen that in the case of the aluminum nitride-yttria composite ceramics (1Y2M-A) manufactured according to Experimental Example 3, an increase of about 1 order is increased by >1 order at all temperatures. This can be interpreted because a liquid film with high insulating properties occurs at the grain boundary, or because a large amount of Mg is precipitated at the grain boundary to increase the Schottky barrier. When Mg ions having a divalent positive charge replace Al ions, defects having negative charges (

) Is created (see Scheme 4) and the main carrier, Al pore (

) As the concentration of) decreases exponentially at the grain boundary, depletion occurs. Al voids feel a higher Schottky barrier at the grain boundary and thus the resistance at the grain boundary increases. In particular, in the case of the aluminum nitride-yttria composite ceramics (1Y2M-A) prepared according to Experimental Example 3, Mg diffused into the grain after annealing as shown in FIG. 3(c), which further increases the intergranular resistance. I think it was.

In FIG. 10, the resistance of the intragranular and grain boundaries was separated to indicate the electrical conductivity according to the temperature, and the activation energy was calculated. In the case of the aluminum nitride-yttria composite ceramics (1Y2M) prepared according to Experimental Example 2 and the aluminum nitride-yttria composite ceramics (1Y2M-A) prepared according to Experimental Example 3, the activation energy of the electrical conductivity in the mouth was 0.264 eV and It was 0.163 eV, and the activation energy of the aluminum nitride-yttria composite ceramics (1Y) prepared according to Experimental Example 1 had a value of 0.62 eV, respectively. The increase in activation energy in the aluminum nitride-yttria composite ceramics (1Y2M) prepared according to Experimental Example 2 and the aluminum nitride-yttria composite ceramics (1Y2M-A) prepared according to Experimental Example 3 is considered to be the effect of MgO doping. do. In the case of the aluminum nitride-yttria composite ceramics (1Y) prepared according to Experimental Example 1, the activation energy of the grain boundary was 1.184 eV, and the aluminum nitride-yttria composite ceramics (1Y2M) prepared according to Experimental Example 2 and Experimental Example 3 In the case of the aluminum nitride-yttria composite ceramics (1Y2M-A) prepared according to the method, it was 1.252, 1.387 eV. The increase in the activation energy for the grain boundary of the aluminum nitride-yttria composite ceramics (1Y2M) prepared according to Experimental Example 2 was caused by the phenomenon that Mg precipitated at the grain boundary as described above, thereby increasing the Schottky barrier against the movement of Al pores. It means that a liquid film with high insulating properties has occurred at the grain boundary as described above in the microstructure analysis. And in the aluminum nitride-yttria composite ceramics (1Y2M-A) prepared according to Experimental Example 3, the grain boundary resistance was further increased, and the activation energy was further increased because Mg was more diffused to the grain boundary by annealing, or the resistance was high. The phase (eg Spinel phase, MgAl ₂ O ₆ ) is generated in a wider range, and thus it can be considered that the grain boundary resistance is further increased. However, looking at the XRD analysis results, no change in the crystal phase such as an increase in the spinel phase was observed even after annealing. Therefore, it is presumed that the mobility decreased due to an increase in the Schottky barrier due to diffusion of Mg.

Through complex impedance spectroscopy and microstructure analysis, the ion conductivity and electron conductivity of MgO-doped AlN ceramics were analyzed according to the temperature of the grain boundary and the inside of the grain. DC conductivity, which is believed to contribute most of electron conduction, is significantly lowered by more than 1 order by the addition of MgO, and activation energy is also increased. As a result of impedance analysis, when MgO is added, resistance by particles decreases, while resistance and activation energy by grain boundaries increase. This is because Mg precipitates at grain boundaries to increase the Schottky barrier, or liquid films with high resistance to grain boundaries. It is considered to be because this ion conduction is reduced. This is in good agreement with the microstructure analysis results showing the presence of an amorphous liquid phase containing Mg evenly distributed at the grain boundaries between grains. On the other hand, in the case of annealing after addition of MgO, the resistance of the grain boundary further increases, which is thought to be because the doped Mg ions further increase the resistance of the grain boundary.

In the above, a preferred embodiment of the present invention has been described in detail, but the present invention is not limited to the above embodiment, and various modifications are possible by those of ordinary skill in the art.

Claims (11)

(a) forming a slurry by mixing AlN powder, Y ₂ O ₃ powder and MgO powder with a solvent;
(b) drying the slurry to form a composite powder;
(c) molding the composite powder; And
(d) sintering the molded resultant in an oxidizing atmosphere at a sintering temperature of 1500 to 1620°C,
After the sintering, the method of manufacturing an aluminum nitride-yttria composite ceramics, further comprising annealing in an oxidizing atmosphere at a temperature lower than the sintering temperature.
The method of claim 1, wherein the slurry is formed by further mixing Ta ₂ O ₅ powder in step (a).
The method of claim 1, wherein the slurry is formed by further mixing WO ₃ powder in step (a).
The method of claim 1, wherein the slurry is formed by further mixing TiO ₂ powder in step (a).
The method of claim 1, wherein the slurry is formed by further mixing HfO ₂ powder in step (a).
The method of claim 1, wherein the slurry is formed by further mixing SrO powder in step (a).
The method of claim 1, wherein the Y ₂ O ₃ powder is mixed with 0.1 to 7 parts by weight based on 100 parts by weight of the AlN powder.
The method of claim 1, wherein the MgO powder is mixed with 0.1 to 10 parts by weight based on 100 parts by weight of the AlN powder.
delete delete The method of claim 1, wherein the annealing is performed at a temperature of 1300 to 1550°C.

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