KR102081622B1 - aluminium nitride sintered body having excellent resitivity at high temperature and manufacturing method of the same - Google Patents

Abstract

The present invention relates to a method for producing an aluminum nitride sintered body comprising mixing AlN powder, a sintering aid and urea and press sintering the mixed product, and an aluminum nitride sintered body produced thereby. According to the present invention, it is possible to reduce Al ₂ O ₃ , which is an impurity contained in AlN, to induce a decrease in Al vacancy, which acts as a carrier at high temperatures, to have a high specific resistance at high temperatures, and to have a high density. An aluminum nitride sintered body having a high volume resistance at high temperature can be produced.

Description

Aluminum nitride sintered body having excellent resitivity at high temperature and manufacturing method of the same

The present invention relates to an aluminum nitride sintered body and a method for manufacturing the same, and more particularly, to reduce Al ₂ O ₃ , which is an impurity contained in AlN, and to reduce Al vacancy that acts as a carrier at high temperatures. The present invention relates to a method for producing an aluminum nitride sintered body having a high specific resistance at high temperature, high density and high volume resistivity, and an aluminum nitride sintered body produced thereby.

The crystal structure of aluminum nitride (AlN) is a tetrahedron centered on Al or N as a basic structure. These tetrahedrons cross each other and have a hexagonal wurtzite structure. The interatomic bonds are covalent.

Aluminum nitride (AlN) is stable at high temperatures, has a low dielectric constant and low dielectric loss, excellent electrical insulation, and thermal conductivity of about 320 W / mK, which has physical properties higher than that of metals. In addition, aluminum nitride (AlN) has a coefficient of thermal expansion of about 2.64 × 10 ⁻⁶ / K, which is similar to silicon and can be used as a filler for a substrate material or a polymer package material of a semiconductor.

Due to such physical properties, aluminum nitride (AlN) may be used as a high thermal conductive insulating substrate, a high corrosion resistant material, and an electrostatic chuck material. In particular, many researches on the synthesis method have been made since it can be used in a high-temperature material such as a package of a highly integrated semiconductor chip requiring excellent electrical insulation and heat dissipation or a heat exchanger requiring high thermal conductivity and high corrosion resistance.

Aluminum nitride (AlN) is difficult to sinter due to its strong covalent bond and requires high temperature sintering at 2000 ℃ or higher in order to obtain a compact sintered body. Is needed.

In the case of general ceramic materials used as electrostatic chuck materials, the specific resistance tends to decrease with temperature. In the case of low temperature electrostatic chuck (ESC) material, the change of specific resistance with temperature should be small, and in case of high temperature electrostatic chuck material, high specific resistance should be maintained at high temperature. For example, in recent years, a specific resistance of 10 ⁸ Pa · cm or more is required at a high temperature of 400 ° C in an industrial field. However, general aluminum nitride (AlN) exhibits a specific resistance of about 10 ⁷ Pa · cm at 400 ℃, it is necessary to study to increase the volume resistance at high temperature.

Korean Patent Registration Publication No. 10-1516990

The problem to be solved by the present invention is to reduce Al ₂ O ₃ which is an impurity contained in AlN, has a high specific resistance at high temperature by inducing a decrease in Al vacancy acting as a carrier at high temperature, The present invention provides a method for producing an aluminum nitride sintered body having high density and high volume resistance at high temperature, and an aluminum nitride sintered body produced thereby.

The present invention provides a method for producing an aluminum nitride sintered body comprising the steps of (a) mixing AlN powder, a sintering aid and urea, and (b) pressing and sintering the mixed product.

In step (a), one or more group 2 oxides selected from MgO and SrCO ₃ may be further mixed.

It is preferable that the said group 2 oxide mixes 0.1-5 weight part with respect to 100 weight part of said AlN powders.

In step (a), one or more of Group 4 oxides selected from TiO ₂ and HfO ₂ may be further mixed.

It is preferable that the said Group 4 oxide mixes 0.01-3 weight part with respect to 100 weight part of said AlN powders.

In the step (a), the urea (Urea) is preferably mixed with 0.01 to 2 parts by weight based on 100 parts by weight of the AlN powder.

In the step (a), the sintering aid is preferably mixed 0.1 to 12 parts by weight based on 100 parts by weight of the AlN powder.

The pressure sintering is preferably carried out at a temperature of 1650 ~ 1900 ℃.

The pressure sintering is preferably performed while applying a pressure of 10 to 30 MPa.

The pressure sintering is preferably carried out in an inert gas atmosphere.

The pressurizing sintering may be performed to heat up to a first temperature of 1350 to 1550 ° C., to maintain at the first temperature, and to be 1650 to 1900 ° C. higher than the first temperature to thermally decompose the urea. It may include the step of raising the temperature up to 2 and the step of sintering by pressing while maintaining at the second temperature.

The pressure sintering is performed by heating to a first temperature of 1650 to 1900 ° C., pressing and sintering while maintaining the temperature at the first temperature, and cooling to a second temperature of 1350 to 1550 ° C. lower than the first temperature. And maintaining at the second temperature.

Moreover, this invention provides the aluminum nitride sintered compact which has a specific resistance higher than 10 <^8> Pa * cm at the temperature of 400 degreeC as a sintered compact manufactured by the said manufacturing method.

According to the present invention, it is possible to reduce Al ₂ O ₃ , which is an impurity contained in AlN, to induce a decrease in Al vacancy, which acts as a carrier at high temperatures, to have a high specific resistance at high temperatures, and to have a high density. An aluminum nitride sintered body having a high volume resistance at high temperature can be produced.

In addition, grain growth is prevented during the sintering process due to Group 2 oxides or Group 4 oxides, so that the mechanical properties, etc., may be excellent, and oxides that lower electron or ion conduction at grain boundaries are distributed. As a result, mobility can be reduced.

1 is a graph showing the density of the AlN sintered body obtained by sintering in an N ₂ atmosphere using AlN powder according to Experimental Example 3, Experimental Example 11 and Experimental Example 15.
2A and 2B are scanning electron microscope (SEM) photographs showing the microstructure of the AlN sintered body prepared according to Experimental Example 3. FIG.
3A and 3B are scanning electron microscope (SEM) photographs showing the microstructure of the AlN sintered body prepared according to Experimental Example 7.
4A and 4B are scanning electron microscope (SEM) photographs showing the microstructure of the AlN sintered body manufactured according to Experimental Example 8. FIG.
5A and 5B are scanning electron microscope (SEM) photographs showing the microstructure of the AlN sintered body prepared according to Experimental Example 9;
6A and 6B are scanning electron microscope (SEM) photographs showing the microstructure of the AlN sintered body prepared according to Experimental Example 13. FIG.
7A and 7B are scanning electron microscope (SEM) photographs showing the microstructure of the AlN sintered body prepared according to Experimental Example 14;
8 is a view showing a sintering profile applied to prepare AlN sintered body prepared according to Experimental Example 1 and Experimental Example 2.
9A is a photograph of an AlN sintered body prepared according to Experimental Example 2, FIG. 9B is a photograph of Pt coated AlN sintered body prepared according to Experimental Example 2 to measure volume resistance, and FIG. 9C is AlN coated with Pt. It is photograph after high temperature resistance measurement of sintered compact.
10A is a photograph of an AlN sintered body prepared according to Experimental Example 1, FIG. 10B is a photograph of Pt coated AlN sintered body prepared according to Experimental Example 1 to measure volume resistance, and FIG. 10C is AlN coated with Pt. It is photograph after high temperature resistance measurement of sintered compact.
11 is a graph showing the change in volume resistance of the AlN sintered body prepared according to Experimental Example 1 and Experimental Example 2.
12 is a graph showing an Arrhenius plot (activation energy) of AlN sintered bodies prepared according to Experimental Example 1 and Experimental Example 2. FIG.
FIG. 13 is a view showing a sintering profile applied to prepare an AlN sintered body prepared according to Experimental Examples 13 to 15. FIG.
14A is a photograph of an AlN sintered body prepared according to Experimental Example 15, FIG. 14B is a photograph of Pt coated AlN sintered body prepared according to Experimental Example 15 to measure volume resistance, and FIG. 14C is AlN coated with Pt. It is photograph after high temperature resistance measurement of sintered compact.
15A is a photograph of an AlN sintered body prepared according to Experimental Example 13, FIG. 15B is a photograph of Pt coated AlN sintered body prepared according to Experimental Example 13 to measure volume resistance, and FIG. 15C is AlN coated with Pt. It is photograph after high temperature resistance measurement of sintered compact.
16 is a graph showing a change in volume resistance of the AlN sintered body prepared according to Experimental Examples 13 to 16.
17 is a graph showing an Arrhenius plot (activation energy) of AlN sintered bodies prepared according to Experimental Examples 13 to 16. FIG.
18 is a view showing a sintering profile applied to prepare an AlN sintered body prepared according to Experimental Examples 7 to 12.
19 is a graph showing a change in volume resistance of the AlN sintered body prepared according to Experimental Examples 7 to 12.
20 is a graph showing an Arrhenius plot (activation energy) of AlN sintered bodies prepared according to Experimental Examples 7 to 12.
21 is a view showing a sintering profile applied to prepare an AlN sintered body prepared according to Experimental Examples 17-22.
22 is a graph showing a change in volume resistance of the AlN sintered body prepared according to Experimental Examples 17 to 22.
FIG. 23 is a graph showing an Arrhenius plot (activation energy) of AlN sintered bodies prepared according to Experimental Examples 17 to 22. FIG.
24 illustrates a sintering profile according to an example.
25 illustrates a sintering profile according to another example.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided to those skilled in the art to fully understand the present invention, and may be modified in various forms, and the scope of the present invention is limited to the embodiments described below. It doesn't happen.

Hereinafter, the inert gas atmosphere is used to mean a gas atmosphere containing an inert gas such as argon (Ar), helium (He), nitrogen (N ₂ ).

Method for producing an aluminum nitride sintered body according to a preferred embodiment of the present invention, (a) mixing AlN powder, sintering aid and urea (Urea) and (b) pressure sintering the mixed product.

In step (a), one or more group 2 oxides selected from MgO and SrCO ₃ may be further mixed.

It is preferable that the said group 2 oxide mixes 0.1-5 weight part with respect to 100 weight part of said AlN powders.

In step (a), one or more of Group 4 oxides selected from TiO ₂ and HfO ₂ may be further mixed.

It is preferable that the said Group 4 oxide mixes 0.01-3 weight part with respect to 100 weight part of said AlN powders.

In the step (a), the urea (Urea) is preferably mixed with 0.01 to 2 parts by weight based on 100 parts by weight of the AlN powder.

In the step (a), the sintering aid is preferably mixed 0.1 to 12 parts by weight based on 100 parts by weight of the AlN powder.

The pressure sintering is preferably carried out at a temperature of 1650 ~ 1900 ℃.

The pressure sintering is preferably performed while applying a pressure of 10 to 30 MPa.

The pressure sintering is preferably carried out in an inert gas atmosphere.

The pressurizing sintering may be performed to heat up to a first temperature of 1350 to 1550 ° C., to maintain at the first temperature, and to be 1650 to 1900 ° C. higher than the first temperature to thermally decompose the urea. It may include the step of raising the temperature up to 2 and the step of sintering by pressing while maintaining at the second temperature.

The pressure sintering is performed by heating to a first temperature of 1650 to 1900 ° C., pressing and sintering while maintaining the temperature at the first temperature, and cooling to a second temperature of 1350 to 1550 ° C. lower than the first temperature. And maintaining at the second temperature.

The aluminum nitride sintered compact according to a preferred embodiment of the present invention is a sintered compact manufactured by the above production method and has a specific resistance higher than 10 ⁸ Pa · cm at a temperature of 400 ° C.

Hereinafter, a method of manufacturing the aluminum nitride sintered body according to a preferred embodiment of the present invention will be described in more detail.

AlN powder, sintering aid and urea are prepared as starting materials and mixed.

The urea (Urea) is preferably mixed with 0.01 to 2 parts by weight based on 100 parts by weight of the AlN powder. Urea may react with Al ₂ O ₃ , an impurity contained in AlN, to be converted to AlN, or ammonia generated by decomposition at high temperature may cause nitrification. The reduced Al ₂ O ₃ content reduces Al vacancy, which is the primary carrier substituted, and reduces the positively charged O _N species. Since O _N species form an ionic pair with Al vacancies, the activation energy (Ea) decreases when a nitriding reaction occurs. When the urea (Urea) is used as a starting material, it is possible to reduce Al ₂ O ₃ , which is an impurity contained in AlN, and to induce a decrease in Al vacancy, which acts as a carrier at high temperatures, at high temperatures. It can have a high specific resistance.

It is preferable that the said sintering aid mixes 0.1-12 weight part with respect to 100 weight part of said AlN powders. The sintering aid may be an oxide containing rare earth elements, for example, Y, Er, Sm, La, Yb, and the like. More specifically, examples may include Y ₂ O ₃ Er ₂ O ₃ , Sm ₂ O ₃ , La ₂ O ₃ , Yb ₂ O ₃ , and the like. Aluminum nitride (AlN) is difficult to sinter due to the property of strong covalent bonds and pressure sintering at a temperature of 2000 ° C. or higher is required to obtain a compact sintered body. When the sintering aid is added, there is an advantage that it can be sintered at a temperature of 1650 ~ 1900 ℃.

In the case of general ceramic materials used as electrostatic chuck materials, the specific resistance tends to decrease with temperature. In the case of low temperature electrostatic chuck (ESC) material, the change of specific resistance with temperature should be small, and in case of high temperature electrostatic chuck material, high specific resistance should be maintained at high temperature. For example, in recent years, a specific resistance of 10 ⁸ Pa · cm or more is required at a high temperature of 400 ° C in an industrial field. However, general aluminum nitride (AlN) shows a specific resistance of about 10 ⁷ Pa.cm at 400 degreeC.

In order to maintain a high resistivity at high temperature, there are two methods of reducing electron conductivity and ion conductivity carrier, or reducing mobility. In order to reduce the carrier (carrier) it is necessary to minimize the generation of the carrier by removing the impurities of the raw material as much as possible.

Mobility can be reduced by depositing an oxide layer that lowers electron or ion conduction at grain boundaries.

In view of these points, as the starting material, one or more group 2 oxides selected from MgO and SrCO ₃ may be further mixed. It is preferable that the said group 2 oxide mixes 0.1-5 weight part with respect to 100 weight part of said AlN powders. For example, when MgO, a Group 2 oxide, is added, it is dissolved in the AlN matrix during the sintering process, Mg can be substituted for Al, oxygen can be substituted for nitrogen, and the substituted Mg and oxygen have negative and positive charges, respectively. do. As another possibility, MgO may react with impurity-containing Al ₂ O ₃ to form a spinel phase, in which case the spinel phase present at the interface interferes with the movement of ions and electrons. do. This reduced activation energy prevents a sharp decrease in resistance at high temperatures. In addition, when the Group 2 oxide is added, grain growth is hindered in the sintering process to be described later, which may have excellent mechanical properties. In addition, since the Group 2 oxides that lower electron or ion conductivity are distributed at grain boundaries, mobility can be reduced.

In addition, as the starting material, one or more Group 4 oxides selected from TiO ₂ and HfO ₂ may be further mixed. It is preferable that the said Group 4 oxide mixes 0.01-3 weight part with respect to 100 weight part of said AlN powders. For example, when TiO ₂ , a Group 4 oxide, participates, Ti is substituted with Al and oxygen is substituted with nitrogen to create Al vacancies, and the substituted Ti and oxygen have a positive charge. It forms an ionic pair with the vacancy, which results in an increase in activation energy. In addition, when the Group 4 oxide is added, grain growth is hindered in the sintering process to be described later, which may have excellent mechanical properties. In addition, since the Group 4 oxides that lower electron or ion conduction are distributed at grain boundaries, mobility can be reduced.

The starting material may be mixed in various ways such as a ball mill, planetary mill, attrition mill, and the like. Hereinafter, the mixing process by the ball mill method is demonstrated concretely. The starting materials are charged and mixed in a ball milling machine. The starting material is mixed evenly by rotating at a constant speed using a ball mill. The ball used in the ball mill may use a ball made of ceramics such as alumina and zirconia, and the balls may be all the same size or may have a ball having two or more sizes together. Adjust the size of the ball, milling time and revolutions per minute of the ball mill. For example, in consideration of the particle size, the size of the ball can be set in the range of about 1 mm to 50 mm, and the rotational speed of the ball mill can be set in the range of about 100 to 1000 rpm. The ball mill is preferably carried out for 1 to 24 hours in consideration of the target particle size and the like. By the ball mill, the starting materials are uniformly mixed.

Pressure sinter the mixed product. The pressure sintering is preferably performed while applying a pressure of 10 to 30 MPa. The pressure sintering is preferably carried out in an inert gas atmosphere. The pressure sintering is preferably carried out at a temperature of 1650 ~ 1900 ℃. If the sintering temperature is less than 1650 ℃, the thermal or mechanical properties of the sintered body may be poor due to incomplete sintering, and if the sintering temperature is higher than 1900 ℃, it is not only economical due to high energy consumption but also excessive grain growth resulting in the mechanical properties of the sintered body This may not be good. It is preferable to increase the temperature to a sintering temperature at a temperature increase rate of 1 to 50 ° C./min. If the temperature increase rate is too slow, productivity may take a long time, and if the temperature increase rate is too fast, thermal stress may be applied due to a rapid temperature increase. Since it is possible to raise the temperature at a temperature increase rate in the above range, it is preferable. In addition, the sintering is preferably maintained for 10 minutes to 24 hours at the sintering temperature. If the sintering time is too long, it is not only economically difficult to expect more sintering effects because of the high energy consumption, and when the sintering time is small, the physical properties of the sintered body may be poor due to incomplete sintering.

The pressurized sintering, as shown in Figure 24, in order to thermally decompose the urea (Urea) step (S1) to the first temperature (T1) of 1350 ~ 1550 ° C and at the first temperature (T1) Pressing and sintering while maintaining (S2), the step (S3) of raising the temperature to a second temperature (T2) of 1650 ~ 1900 ℃ higher than the first temperature (T1) and the second temperature (T2) It may also include step S4.

The pressurized sintering step, as shown in Fig. 25, the step (S1) of raising the temperature to the first temperature (T1) of 1650 ~ 1900 ℃, and the step of pressing and sintering while maintaining at the first temperature (T1) (S2 ), And cooling to a second temperature T2 of 1350 to 1550 ° C. lower than the first temperature T1, and a step S4 of maintaining it at the second temperature T2. .

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

AlN powder (Tokuyama Co.) and sintering aid Y ₂ O ₃ (HC Stark Co., C-grade) were used as starting materials, and Urea (Daejung Co., Ltd.,> 98%) was added as an additive. MgO (high purity chemistry,> 99.99%) and TiO _{2 (} Sigma Aldrich,> 99.9%) were optionally added.

The starting material was ball milled at 100 rpm for 24 hours with ethanol and 3 mm alumina balls to obtain a slurry.

The slurry was dried at 40 ° C. for 3 hours using an evaporator, and powder was obtained using a sieve of 200 mesh.

The powder obtained by sieving was sintered at a pressure of 15 to 20 MPa at a sintering temperature of 1700 to 1800 ° C. using a pressure sintering furnace (Cermotech, Korea) in an N ₂ atmosphere. It heated up at the temperature increase rate of 10 degrees C / min to the said sintering temperature. Table 1 below shows the content ratio and sintering conditions of each raw material.

Compound vol% Sintering Temperature (℃) Sintering time (h) Pressure (MPa) Experimental Example 1
AlN (H-grade) Y ₂ O ₃ 3.0 wt% 1800 5 15 Experimental Example 2 Y ₂ O ₃ 9.0 wt% 1800 5 15 Experimental Example 3 AlN (E-grade) Y ₂ O ₃ 9.0 wt% 1800 5 20 Experimental Example 4

AlN (H-grade) MgO 2.0 wt% 1600 10 15 Experimental Example 5 Y ₂ O ₃ 1.0 wt%
MgO 2.0 wt% 1600 10 15 Experimental Example 6 Y ₂ O ₃ 1.0 wt%
MgO 1.0 wt% 1600 10 15 Experimental Example 7

AlN (H-grade) Y ₂ O ₃ 9.0 wt%
MgO 1.0 wt% 1700 10 15 Experimental Example 8 Y ₂ O ₃ 9.0 wt%
MgO 2.0 wt% 1700 10 15 Experimental Example 9 Y ₂ O ₃ 9.0 wt%
MgO 3.0 wt% 1700 10 15 Experimental Example 10
AlN (E-grade)
Y ₂ O ₃ 9.0 wt%
MgO 1.0 wt% 1700 10 15 Experimental Example 11 Y ₂ O ₃ 9.0 wt%
MgO 2.0 wt% 1700 10 15 Experimental Example 12 Y ₂ O ₃ 9.0wt%
SrCO ₃ 2.0wt% 1700 10 15 Experimental Example 13
AlN (H-grade) Y ₂ O ₃ 9.0 wt%
TiO ₂ 0.2 wt% 1800/1450 3/2 15 Experimental Example 14 Y ₂ O ₃ 9.0 wt%
TiO ₂ 0.5 wt% 1800/1450 3/2 15 Experimental Example 15 AlN (E-grade)
Y ₂ O ₃ 9.0 wt%
TiO ₂ 0.2 wt% 1800/1450 3/2 15 Experimental Example 16 Y ₂ O ₃ 9.0 wt%
HfO ₂ 0.2wt% 1800/1450 3/2 15 Experimental Example 17

AlN (E-grade)
Y ₂ O ₃ 9.0 wt%
urea 0.25 vol% 1400/1800 3/1 20 Experimental Example 18 Y ₂ O ₃ 9.0 wt%
urea 0.25 vol% 1400/1800 3/5 20 Experimental Example 19 Y ₂ O ₃ 9.0 wt%
urea 0.5 vol% 1400/1800 3/1 20 Experimental Example 20 Y ₂ O ₃ 9.0 wt%
urea 0.5 vol% 1400/1800 3/5 20 Experimental Example 21 Y ₂ O ₃ 9.0 wt%
urea 0.1 vol%
MgO 2.0 wt% 1700 10 15 Experimental Example 22 Y ₂ O ₃ 9.0 wt%
urea 0.1 vol%
TiO ₂ 0.2 wt% 1700 10 15

According to Experimental Example 3, Experimental Example 11 and Experimental Example 15, the density of the AlN sintered body obtained by press-sintering in an N ₂ atmosphere using AlN powder was measured and shown in FIG. 1.

Referring to FIG. 1, the density of the AlN sintered compact (Experimental Example 3) without the additive (additive) was 98.6%, and the density of the AlN sintered compact (Experimental Example 11) obtained by adding MgO 2.0 wt% as the additive. Was 98.7%, and the density of the AlN sintered compact (Experimental Example 15) obtained by adding TiO ₂ 0.2wt% as an additive was 98.6%.

2A and 2B are scanning electron microscope (SEM) photographs showing the microstructure of the AlN sintered body manufactured according to Experimental Example 2, and FIGS. 3A and 3B are micrographs of the AlN sintered body prepared according to Experimental Example 7 Scanning electron microscope (SEM) picture showing the structure, Figures 4a and 4b is a scanning electron microscope (SEM) picture showing the microstructure of the AlN sintered body prepared according to Experimental Example 8, Figure 5a and 5b is Experimental Example 9 Scanning electron microscope (SEM) picture showing the microstructure of the AlN sintered body prepared according to, Figures 6a and 6b is a scanning electron microscope (SEM) picture showing the microstructure of the AlN sintered body prepared according to Experimental Example 13, 7A and 7B are scanning electron microscope (SEM) photographs showing the microstructure of the AlN sintered body prepared according to Experimental Example 14.

2A to 7B, the AlN sintered body using Y ₂ O ₃ as a sintering aid has a grain size of 1 to 2 μm, but MgO and TiO ₂ When grains were added, grain growth was disturbed and observed to be about 0.5 to 1 μm. And as the addition amount increased, the particle size decreased further.

The high voltage electrical characteristics of the AlN sintered bodies were evaluated. The measurement conditions were 200 V at room temperature to 500 ° C.

In the case of general ceramic materials used as electrostatic chuck materials, the specific resistance tends to decrease with temperature. In the case of low temperature electrostatic chuck (ESC) material, the change of specific resistance with temperature should be small. In case of high temperature electrostatic chuck material, high specific resistance should be maintained at high temperature. For example, in recent years, a specific resistance of 10 ⁸ Pa · cm or more is required at a high temperature of 400 ° C in an industrial field. However, general aluminum nitride (AlN) shows a specific resistance of about 10 ⁷ Pa.cm at 400 degreeC.

In order to maintain a high resistivity at high temperature, there are two methods of reducing electron conductivity and ion conductivity carrier, or reducing mobility. In order to reduce the carrier (carrier) it is necessary to minimize the generation of the carrier by removing the impurities of the raw material as much as possible.

Mobility can be reduced by depositing an oxide layer that lowers electron or ion conduction at the grain boundaries.

8 shows a sintering profile applied to prepare AlN sintered body prepared according to Experimental Example 1 and Experimental Example 2. 9A is a photograph of an AlN sintered body prepared according to Experimental Example 2, FIG. 9B is a photograph of Pt coated AlN sintered body prepared according to Experimental Example 2 to measure volume resistance, and FIG. 9C is AlN coated with Pt. It is photograph after high temperature resistance measurement of sintered compact. 10A is a photograph of an AlN sintered body prepared according to Experimental Example 1, FIG. 10B is a photograph of Pt coated AlN sintered body prepared according to Experimental Example 1 to measure volume resistance, and FIG. 10C is AlN coated with Pt. It is photograph after high temperature resistance measurement of sintered compact. 11 is a graph showing a change in volume resistance of the AlN sintered body prepared according to Experimental Example 1 and Experimental Example 2, Figure 12 is an Arrenhenus plot of the AlN sintered body prepared according to Experimental Example 1 and Experimental Example 2 Graph showing (activation energy).

8 to 12, in Experimental Example 1 and Experimental Example 2 using AlN (H-grade), the activation energy (E _a ) increases as the content of Y ₂ O ₃ used as a sintering aid increases. Appeared.

FIG. 13 shows a sintering profile applied to prepare an AlN sintered body prepared according to Experimental Examples 13 to 16. FIG. 14A is a photograph of an AlN sintered body prepared according to Experimental Example 15, FIG. 14B is a photograph of Pt coated AlN sintered body prepared according to Experimental Example 15 to measure volume resistance, and FIG. 14C is AlN coated with Pt. It is photograph after high temperature resistance measurement of sintered compact. 15A is a photograph of an AlN sintered body prepared according to Experimental Example 13, FIG. 15B is a photograph of Pt coated AlN sintered body prepared according to Experimental Example 13 to measure volume resistance, and FIG. 15C is AlN coated with Pt. It is photograph after high temperature resistance measurement of sintered compact. FIG. 16 is a graph showing a change in volume resistance of AlN sintered bodies prepared according to Experimental Examples 13 to 15, and FIG. 17 is an Arrhenius plot of AlN sintered bodies prepared according to Experimental Examples 13 to 16. Graph showing (activation energy).

When TiO ₂ , a Group 4 oxide, is used as an additive, chemical reactions such as the following Scheme 1 are expected.

Scheme 1

TiO ₂ + 2AlN → Ti _Al ＇+ 2O _N ＇ + V _Al '''

Ti substitutes Al and oxygen substitutes nitrogen to create Al vacancy. Substituted Ti and oxygen have a positive charge, forming an ionic pair with the Al vacancy, which results in an increase in activation energy. When Group 4 oxide is added, the activation energy (Ea) is 0.4 to 0.42 eV, which is equivalent to or higher than 0.41 eV of AlN (h-grade) without adding Group 4 oxide.

18 shows a sintering profile applied to prepare an AlN sintered body prepared according to Experimental Examples 7 to 12. FIG. 19 is a graph showing a change in volume resistance of AlN sintered bodies prepared according to Experimental Examples 7 to 12, and FIG. 20 is an Arrhenius plot of AlN sintered bodies prepared according to Experimental Examples 7 to 12. Graph showing (activation energy).

When using Group 2 oxides (MgO) as additives, there are two possibilities.

When dissolved on an AlN matrix, Mg substitutes for Al and oxygen for nitrogen. This reaction is shown in Scheme 2 below. Substituted Mg and oxygen each have a positive and a positive charge.

Scheme 2

MgO + AlN → Mg ' _Al + O˙ _N

Another possibility is to form spinel in reaction with impurity-containing Al ₂ O ₃ . This reaction is shown in Scheme 3 below. The spinel phase present at the interface serves to hinder the movement of ions and electrons.

Scheme 3

MgO + AlN → MgAl ₂ O ₃

When Group 2 oxide is added, the activation energy (Ea) is ˜0.36 eV, which is lower than 0.41 eV of AlN (h-grade) not added. This may be estimated to form a spinel phase rather than MgO to form a new ionic pair to remove impurities Al ₂ O ₃ . This reduced activation energy prevents a sharp decrease in resistance at high temperatures.

21 shows a sintering profile applied to prepare AlN sintered body prepared according to Experimental Examples 17-22. FIG. 22 is a graph showing a change in volume resistance of AlN sintered bodies prepared according to Experimental Examples 17 to 22, and FIG. 23 is an Arrhenius plot of AlN sintered bodies prepared according to Experimental Examples 17 to 22. Graph showing (activation energy).

When urea is added to the AlN matrix, chemical reactions such as in Scheme 4 below are expected.

Scheme 4

Al ₂ O ₃ + CO (NH) ₂ → 2AlN + CO ₂ + N ₂

As shown in Scheme 4, urea reacts directly with Al ₂ O _{3 as an} impurity to convert to AlN, or ammonia generated by decomposition at high temperature as in Scheme 5 may cause nitriding reaction.

Scheme 5

Al ₂ O ₃ + NH ₃ + CO → 2AlN + H ₂ O + CO

The reduced Al ₂ O ₃ content reduces Al vacancy, which is the primary carrier substituted, and reduces the positively charged O _N species. Since O _N species form an ionic pair with Al vacancy, activation energy (Ea) is expected to decrease when nitriding occurs, and the calculated E _a is 0.30 to 0.45. eV, which is lower than 0.41 eV of AlN (H-grade) without urea, and Ea decreases as the urea content increases. Judging.

As mentioned above, although the present invention has been described in detail with reference to preferred embodiments, the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. This is possible.

Claims (13)

(a) mixing AlN powder, sintering aid, SrCO ₃ , HfO ₂ and urea; And
(b) press sintering the mixed result;
The pressure sintering,
Heating up to a first temperature of 1350 to 1550 ° C. to pyrolyze the urea;
Maintaining at the first temperature;
Heating up to a second temperature of 1650-1900 ° C. higher than the first temperature;
Pressing and sintering while maintaining at the second temperature;
Cooling to a third temperature of 1350-1550 ° C. lower than the second temperature; And
Maintaining at the third temperature;
The sintering aid is mixed 0.1 to 12 parts by weight based on 100 parts by weight of the AlN powder,
The SrCO ₃ is mixed with 0.1 to 5 parts by weight based on 100 parts by weight of the AlN powder,
The HfO ₂ is mixed with 0.01 to 3 parts by weight based on 100 parts by weight of the AlN powder,
The urea (Urea) is a manufacturing method of the aluminum nitride sintered body, characterized in that mixing 0.01 to 2 parts by weight based on 100 parts by weight of the AlN powder.
delete delete delete delete delete delete The method of claim 1, wherein the pressure sintering is performed at a temperature of 1650 ~ 1900 ℃.
The method of claim 1, wherein the pressure sintering is performed while applying a pressure of 10 to 30 MPa.
The method of claim 1, wherein the pressurizing is performed in an inert gas atmosphere.
delete delete An aluminum nitride sintered body produced by the method according to claim 1 having a specific resistance higher than 10 ⁸ Pa · cm at a temperature of 400 ° C.

Images