JP2001199762A - Corrosion-resisting ceramic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a corrosion-resisting ceramic material having high corrosion resistance to corrosive gases and plasmas, especially to halogen-based gases of which the representative is a fluorine-based gas and further to a plasma generated therefrom, and suitably used for an inner-wall material, a jig, etc., of a plasma treatment unit, etc. SOLUTION: This corrosion-resisting ceramic material comprises a spinel ceramic material which contains MgO and Al2O3 as main components, wherein the composition ratio of MgO to Al2O3 is in the range of 0.76-2.33 by weight, and crystalline particles of the material have an average particle diameter of <3 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion-resistant ceramic material suitably used as an inner wall material or a jig in a plasma processing apparatus or a plasma apparatus for producing semiconductors and liquid crystals.

[0002]

2. Description of the Related Art In recent years, the environment in a semiconductor manufacturing apparatus has been increased due to the rapid integration of semiconductor memories, an increase in the number of repetitions of etching, impurity diffusion, and ion implantation steps, and an increase in plasma output due to miniaturization. It is severe compared to. As a result, ceramics having excellent high-temperature resistance and corrosion resistance have been used in many processes as members in semiconductor manufacturing equipment.

[0003] Among them, for example, in dry etching for forming a pattern, a halogen-based gas is activated by plasma and used. Is required. Under such circumstances, a material mainly containing SiO ₂ such as glass or quartz, or alumina, aluminum nitride, or the like has been frequently used for a portion exposed to the plasma other than the object to be processed. Was.

[0004]

However, conventionally used materials containing SiO ₂ as a main component, such as glass and quartz, do not have sufficient corrosion resistance to plasma. The device member itself is etched, and the surface properties are changed, and there are inconveniences that a sharp hole is formed by local etching.

Alumina, aluminum nitride and the like are more stable to halogen-based gas plasmas than those containing SiO ₂ as a main component, but they are less stable when exposed to plasma at high temperatures. However, there is a problem in that the corrosion reaction proceeds, crystal particles are degranulated from the surface of the member, and particles are easily generated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is intended to provide a corrosion-resistant ceramic having high corrosion resistance to corrosive gases and plasmas, particularly halogen-based corrosive gases and plasmas represented by fluorine. The purpose is to provide the material.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, in a spinel ceramic material containing MgO and Al ₂ O ₃ as main components, M
By controlling the composition ratio of gO and Al ₂ O ₃ (MgO / Al ₂ O ₃ ) to an appropriate range and controlling the average particle size of the crystal grains constituting the ceramic material to an appropriate range, the corrosiveness is improved. The present inventors have found that a plasma of a gas and a corrosive gas, particularly a halogen-based corrosive gas typified by a fluorine-based gas, and that the plasma show high corrosion resistance, have completed the present invention.

That is, the present invention relates to MgO and Al ₂ O ₃
Is a spinel-based ceramic material whose main component is
The composition ratio of MgO and Al ₂ O ₃ is 0.67 to
2.33 and the average grain size of the crystal grains is 3
a corrosion-resistant ceramic material characterized by being less than μm.

Here, in the corrosion-resistant ceramic material of the present invention, it is preferable that 70% or more of the crystal particles have a particle size of 3 μm or less. Also, MgO and Al ₂ O
The content of the impurity components to the total 100 parts by weight of ₃ 3
It is preferable that the amount is not more than 1 part by weight and the porosity is not more than 1%.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. The corrosion-resistant ceramic material of the present invention is a spinel ceramic material containing MgO and Al ₂ O ₃ as main components, and a preferred form thereof is a sintered body. Of the film is also included. Spinel is usually represented by MgAl ₂ O ₄ , and is a compound in which MgO and Al ₂ O ₃ are combined at a theoretical ratio of 1: 1 in a molar ratio and 28.6: 71.4 in a weight ratio. here,
When the composition ratio of MgO and Al ₂ O ₃ was changed, only the MgAl ₂ O ₄ crystal was present at the theoretical ratio,
O is a two-phase crystal structure of long if MgO + MgAl ₂ O ₄ excess, whereas, if an excessive _Al 2 _{O 3 Al} 2 O
₃ + MgAl ₂ O _{4 has} a two-phase crystal structure. In the present invention, MgO is increased from the theoretical ratio to obtain MgO + MgAl ₂
The composition ratio of MgO / Al ₂ O ₃ is defined so as to be two phases of O ₄ .

[0011] Specifically, in theory ratio of MgAl ₂ O _4, although the weight ratio of MgO / _Al 2 _{O 3} is about 0.4, in the present invention, the MgO / _Al 2 _{O 3} 0. 67
To 2.33. Thereby, MgAl ₂ O ₄
Better corrosion resistance can be obtained than in the case of only crystals or in the case of two phases of Al ₂ O ₃ + MgAl ₂ O ₄ .

In the present invention, the weight ratio of the composition ratio of MgO to Al ₂ O ₃ is in the range of 0.67 to 2.33. This is because when the content is less than 2.33 and the amount of excess MgO is too large, the corrosion resistance to halogen-based corrosive gas represented by fluorine and halogen-based plasma is reduced in any case.

In the present invention, in addition to the above-mentioned composition, the average particle diameter of the crystal grains constituting the ceramic material is set to less than 3 μm. The average particle size can be determined, for example, by using a SEM
It can be determined by observation and the like, and by image analysis and the like. In the present invention, the crystal grain size of the ceramic material is defined in order to improve corrosion resistance when exposed to a halogen-based corrosive gas and a halogen-based plasma,
Another reason is to suppress generation of particles.

That is, as in the present invention, when the average grain size of the crystal grains is less than 3 μm, the grain boundary phase of the ceramic material is thin, so that when the ceramic material is exposed to a halogen-based corrosive gas and a halogen-based plasma. The etching rate becomes slow, and the generation of particles is suppressed, so that excellent corrosion resistance can be obtained. On the other hand, when the average grain size of the crystal grains is 3 μm or more, the thickness of the grain boundary phase becomes large, and the portion is selectively etched, so that the etching rate is undesirably increased.

Note that Japanese Patent Application Laid-Open No. 10-330150 discloses
Means that MgO is at least 15% by weight and Al ₂O₃85% by weight
MgO, MgO + MgAl contained in the following range
₂O₄, MgAl₂O₄, Al₂O₃+ MgAl₂O₄
And the average particle size of these crystal phases
Having a porosity of 3 μm or more and a porosity of 0.2% or less
Box sintered body is disclosed.
Is 3 μm or more, the thickness of the grain boundary phase increases,
The corrosion resistance in the interphase was significantly reduced. Like this
Et al., The invention disclosed in JP-A-10-330150 and the present invention.
The difference from the invention is clear.

When considering the average particle size, the state of the distribution of the particle size also poses a problem. That is, this is a case where particles having a very small particle size are dispersed in particles having a relatively large particle size, and the overall average particle size is 3%.
If it is less than μm, it is assumed that corrosion resistance is reduced due to grain boundaries between particles having a large particle size. In order to prevent such a decrease in corrosion resistance, in the present invention, 70% of the crystal particles having a particle size of 3 μm or less are used.
In the above state, the average particle diameter is preferably 3 μm or less.

Next, in the corrosion-resistant ceramic material of the present invention, MgO and other than _Al 2 _{O 3} component is a main component, i.e. the content of impurity components are, MgO and _Al 2 O
It is preferable that the total amount of ₃ is not more than 3 parts by weight and the porosity is not more than 1% based on 100 parts by weight.

This is because, in semiconductor manufacturing equipment and the like, contamination by impurities is a problem, and a high-purity member having a purity of 95% or more is required. In the present invention, a preferable range of the impurity component is as follows. , MgO and Al ₂ O _{3 in} a total of 3 parts by weight or less based on 100 parts by weight in total.
Note that such impurity components include SiO ₂ , Ca
O, Na ₂ O, Fe ₂ O _{3 and the} like.

Further, in the corrosion-resistant ceramic material of the present invention, the preferable range of the porosity is set to 1% or less.
If pores exist in the ceramic material and the pores appear on the surface, a significant corrosion reaction occurs in that part,
This is because there is a possibility that the deterioration of the surface state may become severe.
That is, by setting the porosity to 1% or less, it is possible to effectively prevent deterioration of the surface properties due to corrosion from the pores.

The above-mentioned method for producing a corrosion-resistant ceramic material according to the present invention includes producing a material having a fine structure in which the crystal grain size satisfies predetermined conditions and the porosity is preferably 1% or less. Any method can be used as long as it is possible. For example, a method of mixing the raw material powder to have a desired composition, and then molding and sintering can be used as conventionally widely used, such as hot pressing (HP) treatment or hot isostatic pressing. By performing (HIP) treatment or the like, a sintered body having extremely low porosity may be obtained. Such a sintering method is suitably used when the entire member used for various devices is made of the corrosion-resistant ceramic material of the present invention.

In addition to the sintering method, a method of forming a film of the corrosion-resistant ceramic material of the present invention on the surface of a base material of various ceramics and metals using a film forming method such as thermal spraying or sputtering is also used. be able to. These film forming methods can be used even when the shape of the member is simple.However, the method is applied only to the case where the shape of the member is complicated, or only to a part of the gas exposed to corrosive gas or corrosive gas plasma. When it is preferable to form the corrosion-resistant ceramic material of the invention,
It is preferably used.

As will be described in detail in an embodiment described later,
For the spinel ceramic material of the present invention, CF ₄ and O were used by using a parallel plate electrode type plasma etching apparatus.
_When plasma etching was performed in a mixed gas atmosphere of No. ₂ , compared with conventionally used quartz glass and the like,
It was confirmed that the etching rate (corrosion rate) was low, and the composition had high corrosion resistance to halogen plasma.

As described above, the ceramic material of the present invention has high corrosion resistance especially to fluorine-based corrosive gas and fluorine-based plasma. Examples of the fluorine-based gas include SF ₆ , CHF _{3, and the} like in addition to CF _{4. When} a microwave or the like is introduced into the gas atmosphere, these gases are turned into plasma. Examples of the halogen gas other than the fluorine-based gas include a chlorine-based gas such as Cl ₂ , BCl ₃ , HCl, and CCl ₄ , and a bromine-based gas such as Br ₂ , HBr, and CBr _4. May be introduced, but the ceramic material of the present invention exhibits good corrosion resistance to these corrosive gases.

Therefore, the ceramic material of the present invention can be used in plasma devices such as various semiconductor manufacturing devices and liquid crystal manufacturing devices by utilizing the corrosion resistance to the above-mentioned halogen-based corrosive gas or corrosive gas plasma.
At least a part thereof is suitably used as a member of a portion exposed to an environment such as a corrosive gas. In such a member, the entire member may be made of the ceramic material, or only a portion exposed to a corrosive gas or a plasma of a corrosive gas may be made of the ceramic material.

[0025]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. MgAl ₂ O ₄ powder having a purity of 99% and MgO powder having a purity of 99.9% were prepared so as to have a predetermined composition ratio.
The mixture was ground for an hour to obtain a mixed powder. This mixed powder is uniaxially pressed at 50 MPa, for 1 minute, at 150 MPa by cold isostatic pressing.
a Molding was performed for 1 minute.

Next, the molded body was sintered at 1500 to 1650 ° C. for 1 to 6 hours using an air furnace to produce a sintered body. Further, with respect to some of the sintered bodies, thereafter, using argon (Ar) as a pressure medium, 1400 ° C. or 1500 ° C.
At 177 MPa (1800 kgf / cm ² )
HIP processing was performed for a time to produce a sintered body having a relative density of 100% (Examples 1 to 7). Table 1 shows the manufacturing conditions of the samples according to Examples 1 to 7.

[0027]

[Table 1]

For comparison, powder is produced and molded in the same manner as described above, and the grain growth is promoted by elongating the firing time so that the average grain size becomes 3 μm or more. Sintering was performed, and further, a part of the sintered bodies was subjected to HIP treatment in the same manner to produce sintered bodies (Comparative Examples 1 to 5). In addition, quartz glass was prepared as Comparative Example 6. Table 1 also shows the manufacturing conditions of the samples according to these comparative examples.

The density of each of the thus obtained sintered bodies was measured by the Archimedes method, and the porosity was obtained. As shown in Table 1, the results were in the range of 0 to 0.05% in all samples, and it was confirmed that all samples were dense. In addition, in order to measure the particle size of the sintered body, the sintered body was mirror-polished, then subjected to thermal etching, and the average particle size was determined from SEM observation. The average particle size measured is also shown in Table 1.

Here, FIG. 1 shows SEM photographs of the polished surface after thermal etching of Example 1 and FIG. 2 shows SEM photographs of Comparative Example 2 respectively. In Example 1, 3 μm
It was confirmed that crystal particles having the above-mentioned particle size were hardly observed, and that the particles were dense enough that hardly any pores were observed. On the other hand, in Comparative Example 2, many fine pores were observed between the crystal grains, and those having a crystal grain size of 3 μm or more were also observed. Was observed.

Next, each sample was etched for about 2 hours using a parallel plate electrode type plasma etching apparatus with a frequency of 2.45 GHz and an output of 800 W in an atmosphere in which the volume ratio of CF ₄ to O ₂ was 4: 1. This was performed by plasma etching. Then, an etching rate was calculated by measuring a change in weight of each sample before and after etching.

The results are as shown in Table 1. In Examples 1 to 7 satisfying the conditions of the present invention, the etching rate was lower than that in Comparative Examples 1 to 6, and the erosion rate by the plasma containing CF ₄ gas was used. Is high, that is, it shows high corrosion resistance to plasma containing CF ₄ gas.

FIG. 3 is a view of Example 1 having the polished surface (fine structure) shown in FIG. 1, and FIG. 4 is a comparative example 2 having a polished surface (fine structure) shown in FIG. 3 is an SEM photograph showing the structure of each of FIGS. In Example 1, degradation such as intergranular corrosion and grain shedding was hardly observed, whereas in Comparative Example 2, grain shedding was confirmed to have occurred significantly. The grain removal in Comparative Example 2 was not only because there were many fine pores at the grain boundaries, but also because the crystal grains were large, the grain boundary layer was thick and the structure was prone to intergranular corrosion. It is also considered that this was involved.

[0034]

As described above, according to the present invention, MgO and Al ₂
A spinel ceramic material containing O ₃ as a main component, wherein the composition ratio between MgO and Al ₂ O ₃ is 0.67 by weight.
２2.33, and the average particle size of the crystal particles is 3 μm.
By setting the value to less than the above value, a corrosive gas and a plasma of the corrosive gas, particularly a halogen-based corrosive gas represented by a fluorine-based gas, and a ceramic material having high corrosion resistance to the plasma can be obtained. By applying such a material to a member that is exposed to the gas or plasma atmosphere, such as a semiconductor manufacturing apparatus, it is possible to dramatically improve the durability of the apparatus.

[Brief description of the drawings]

FIG. 1 is an SEM photograph showing a microstructure of Example 1 relating to a corrosion-resistant ceramic material of the present invention.

FIG. 2 is an SEM photograph showing a microstructure of Comparative Example 2.

FIG. 3 is an SEM photograph showing a structure after plasma etching of Example 1 shown in FIG. 1;

FIG. 4 is an SEM photograph showing a structure after plasma etching of Comparative Example 2 shown in FIG. 2;

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Claims (3)

[Claims] 1. A spinel ceramic material containing MgO and Al ₂ O ₃ as main components, wherein the MgO and Al ₂ O ₃
A corrosion-resistant ceramic material, characterized in that the composition ratio of O ₃ is in the range of 0.67 to 2.33 by weight, and the average particle size of the crystal particles is less than 3 μm. 2. The corrosion-resistant ceramic material according to claim 1, wherein 70% or more of the crystal particles have a particle size of 3 μm or less. 3. The method according to claim 1, wherein the content of the impurity component is 3 parts by weight or less and the porosity is 1% or less based on 100 parts by weight of the total of MgO and Al ₂ O _3. The corrosion-resistant ceramic material according to claim 2.