JP2000313655A - High-density magnesium oxide-based sintered compact and its production, and member for plasma treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject sintered compact with high corrosion resistance, suitable as a member for plasma treatment apparatuses capable of suppressing particle generation. SOLUTION: This high-density magnesium oxide-based sintered compact is such one as to consist mainly of magnesium oxide, contain 0.1-20 wt.%, on an oxide basis, of at least one kind of rare earth element selected from Yb, Er and Lu, contain <=100 ppm, on a metal basis, of a total of metallic elements other than magnesium and the rare earth element(s), be <=10 μm in the mean size of each of the magnesium oxide crystal grains, and be >=99% in relative density. Furthermore, in this sintered compact, there exists the rare earth metal(s) oxide crystal phase in the grain boundary phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member for a semiconductor manufacturing apparatus which has high corrosion resistance especially to fluorine-based and chlorine-based corrosive gas or fluorine-based / chlorine-based plasma, and generates few particles and contamination. More particularly, the present invention relates to a high-density magnesium oxide sintered body suitable for use as a focus ring, a clamp ring, a bell jar, a dome, and the like in a plasma process, a method for manufacturing the same, and a member for a plasma processing apparatus using the same.

[0002]

2. Description of the Related Art In recent years, the use of plasma, such as a dry process and plasma coating, used for forming highly integrated circuits such as semiconductor elements and liquid crystals has been rapidly progressing. As a plasma process in a semiconductor, a halogen-based corrosive gas such as a fluorine-based gas is used for vapor phase growth, etching and cleaning due to its high reactivity.

[0003] The members which come into contact with these corrosive gases are required to have high corrosion resistance and contain as little impurities as possible which contaminate non-processed materials or cause particles. Conventionally, materials other than the object to be processed that come into contact with the plasma are generally made of a material mainly composed of SiO ₂ such as glass or quartz, or a metal such as stainless steel or Monel.

Further, as a susceptor material for supporting and fixing a wafer at the time of manufacturing a semiconductor, an alumina sintered body, sapphire, A
A 1N sintered body or one obtained by coating these with a surface by a CVD method or the like is used because of its excellent corrosion resistance. Further, a heater coated with graphite or boron nitride is also used. For these materials, the use of high-density plasma has been promoted in order to increase the degree of integration of elements, and non-particle generation without generation of particles has been demanded.

[0005]

However, conventionally used glass and quartz have insufficient corrosion resistance in plasma and are intensely depleted. In particular, when they come into contact with fluorine or chlorine plasma, the contact surface is etched and the surface properties are reduced. There have been problems such as changes that affect etching.

Further, even members made of metal such as stainless steel have insufficient corrosion resistance, so that corrosion has caused defective products especially in semiconductor manufacturing. Alumina, aluminum nitride, and silicon nitride sintered bodies and coating materials have better corrosion resistance to fluorine-based gases than the above materials, but when they come into contact with plasma at high temperatures, corrosion gradually progresses and the sintered bodies There has been a problem that crystal grains are dislodged from the surface of the substrate, and a reaction product with the plasma is deposited and separated to cause particles. The generation of such particles is due to the ion bombardment, breakage of metal wiring due to extremely fine particles generated by the gas phase reaction, defects in the pattern, etc. as semiconductors become more highly integrated and the process becomes even cleaner. There is a possibility that problems such as deterioration of characteristics and reduction of yield may occur.

First, the present inventors have proposed that MgO and Y ₃
A sintered body containing an oxide containing a group 2a or 3a group of the periodic table such as Al ₅ O ₁₂ as a main crystal phase has excellent corrosion resistance, but its crystal grain boundaries are selectively etched by plasma. For the 2a and 3a groups of the periodic table, C
By constituting the grain boundary phase with a compound mainly composed of at least one of r, Co and Ni, it is possible to suppress the progress of corrosion of the grain boundary phase and improve the corrosion resistance of the material itself. (Japanese Patent Laid-Open No. 10-6755).
No. 4).

However, the magnesium oxide based sintered body in such a proposal has a problem that the grain boundary phase forms a crystalline compound of MgO and the added oxide in a ratio of 1: 1. As a result, the corrosion resistance is insufficient. was there. For this reason, it is necessary to study a compound that can promote the densification of MgO and contribute to the enhancement of the corrosion resistance of the grain boundary phase of the MgO-based sintered body.

On the other hand, a dense magnesium oxide sintered body is disclosed in Japanese Patent Application Laid-Open Nos.
JP-A-130828, JP-A-10-158826, and the like have proposed a method of manufacturing a target material made of a magnesium oxide-based sintered body having a relative density of 99.0% or more.

However, although the sintered bodies described therein exhibit excellent characteristics as a target material for forming an MgO film by sputtering, if they are used as a member that comes into direct contact with the plasma, the sintered body will have a starting point at the crystal grain boundary. Since the corrosion reaction by the generated plasma progresses, the corrosion resistance of the material itself is insufficient, and it is necessary to enhance the plasma resistance of the grain boundary phase.

Accordingly, the present invention provides a high-density magnesium oxide-based sintered body which is made of a magnesium oxide-based sintered body, has excellent corrosion resistance to the plasma of the material itself, and suppresses the generation of contamination and particles. It is an object of the present invention to provide a manufacturing method for producing the same, and a member for a plasma processing apparatus using the same, which is excellent in corrosion resistance.

[0012]

Means for Solving the Problems The inventors of the present invention have made an effort to improve the corrosion resistance of fluorine and chlorine-based corrosive gas / plasma and oxygen plasma, and to generate contamination and particles for materials used in the plasma processing of semiconductors. As a result of studying the suppression, it was found that magnesium oxide was the main component, at least one rare earth element selected from Yb, Er and Lu was contained in an amount of 0.1 to 20% by weight in terms of oxide, and Mg and other than the rare earth element were contained. Is 100 ppm or less in terms of metal, the average particle size of the magnesium oxide crystal particles is 10 μm or less, and the relative density is 9 ppm or less.
It has been found that 9% or more and the presence of the oxide crystal phase of the rare earth element in the grain boundary phase has high corrosion resistance to plasma, and has been found to be suitable as a member for a plasma processing apparatus.

[0013] The sintered body may contain at least one selected from the group consisting of Yb ₂ O ₃ , Er ₂ O ₃ , and Lu ₂ O _{3 having} an average particle size of 5 μm or less with respect to a magnesium oxide powder having an average particle size of 5 μm or less. 0.1 to 20% by weight of rare earth element oxide
Is fired at 1400 to 1800 ° C. in a non-oxidizing atmosphere or in air to obtain a relative density of 9
It is manufactured by densifying to 9% or more and precipitating the oxide crystal phase of the rare earth element in the grain boundary phase.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The magnesium oxide sintered body of the present invention is exposed to a halogen-based corrosive gas or plasma such as a fluorine-based or chlorine-based gas used in a semiconductor plasma process, or to O ₂ or Ar plasma. It is suitable as a member for a plasma processing apparatus.

As the fluorine-based gas, SF ₆ , CF ₄ ,
CHF ₃ , ClF ₃ , HF, and the like, and chlorine-based gases include Cl ₂ , BCl ₃ , HCl, and the like. When microwaves or high-frequency waves are introduced into the atmosphere in which these gases are introduced, these gases are removed. It is turned into plasma.

The sintered body of the present invention contains magnesium oxide as a main component, and among the rare earth elements, Yb, Er and L are selected from the viewpoint of enhancing the plasma resistance of the grain boundary phase.
At least one rare earth element selected from the group u is contained at a ratio of 0.1 to 20% by weight in terms of oxide. This is in terms of corrosion resistance to the corrosive gas and plasma,
It is desirable to select a material having a high melting point as the metal oxide constituting the grain boundary phase, and from such a viewpoint, Lu ₂ O ₃ , Y
b ₂ O ₃ , Er ₂ O ₃ (2427 ° C., 2355 ° C., 23
44 ° C.). Other rare earth elements have an oxide melting point lower than 2300 ° C. and are insufficient in corrosion resistance.

Further, the total amount of Mg and metal elements other than the rare earth elements is 100 ppm or less in terms of metal, preferably 9 ppm or less.
0 ppm or less, especially 50 ppm or less, furthermore 10 pp
It is important to control to less than m. If the total amount of the above metal elements is more than 100 ppm in terms of metal, Mg and a metal other than the rare earth element react with the plasma, whereby the etching proceeds, and the reaction product causes particles. Impurities in the primary raw material are controlled to be reduced by elevating the temperature to a vacuum before firing.

Further, in order to enhance the corrosion resistance to plasma, the relative density of the sintered body is 99% or more, especially 99.5.
%. This is because if the relative density of the sintered body is less than 99%, a large amount of pores and the like on the surface increase the area of contact with the plasma, thereby deteriorating the corrosion resistance and the pores existing on the plasma contact surface. This is because the etching proceeds from the beginning.

The average particle size of the MgO crystal particles of the sintered body is 10 μm or less, preferably 5 μm or less, and more preferably 1 μm or less. That is, the average particle size is 1
If the particle size is larger than 0 μm, the influence on the inside of the semiconductor manufacturing apparatus becomes large when the particles are shattered.

Furthermore, the rare earth element as a sintering aid is contained in the grain boundaries of the MgO main crystal particles in the sintered body of the present invention. According to the present invention, the rare earth element in this grain boundary phase is It is important that is precipitated as an oxide crystal phase. This is because when the grain boundary phase is a glass phase, the corrosion resistance of the grain boundary phase is reduced, and the grain boundary phase is etched from the grain boundary, or when the precipitated crystal phase is a composite oxide crystal phase of MgO and a rare earth element oxide. This is because grain boundaries are selectively etched due to lower corrosion resistance than the rare-earth element oxide single crystal phase.

The raw material powder used for producing the high-density magnesium oxide sintered body having high corrosion resistance as described above has a mean particle size of 5% for magnesium oxide powder.
A powder having a size of not more than μm, preferably not more than 2 μm, particularly preferably not more than 1 μm is desirable. If the average particle size exceeds 5 μm, the sinterability is reduced and the densification is insufficient. As the magnesium oxide powder, a powder produced by a gas phase method or an electrofusion method can be used.

Further, Yb ₂ O ₃ , Er ₂ O ₃ , Lu ₂ O
It is desirable that at least one rare earth element oxide powder selected from ₃ has an average particle size of 5 μm or less, preferably 2 μm or less. In the case of coarse particles exceeding 5 μm, the contribution to the sintering of magnesium oxide is reduced due to a decrease in surface energy, resulting in insufficient densification.

The amount of the rare earth element oxide to be added is 0.1 to 20 with respect to the magnesium oxide powder.
Weight, preferably 0.1 to 10% by weight, especially 0.5 to 5%
% By weight. If the addition amount is less than 0.1% by weight, the sintering promoting effect cannot be obtained, and if it exceeds 20% by weight, the sintering temperature rises, so that abnormal grain growth of MgO particles is caused. This is because it cannot be controlled to 10 μm or less.

The powder is formed into a desired shape by a desired forming means, for example, a die press, a cold isostatic press, an extrusion or the like. The compact at this time is desirably 55% or more in relative density. If the density of the compact is lower than 55%, it is difficult to produce a dense body having a relative density of 99% or more in the subsequent sintering process. is there.

Next, the formed body produced as described above is fired to a relative density of 99% or more, especially 99.5% or more.
Densification to a relative density of 99% or more can be obtained by firing a molded body having the above composition in a non-oxidizing atmosphere or in air.

In this case, the optimum firing temperature is 1400-1.
800 ° C., preferably 1450-1750 ° C., more preferably 1500-1700 ° C. If the temperature is lower than 1400 ° C., the densification becomes insufficient.
This leads to abnormal growth of gO crystal grains.

In the above sintering, it is desirable to perform hot press sintering under a pressure of 50 kgf / cm ² or more in order to improve the relative density. Further, the obtained sintered body is subjected to N ₂ , Hot isostatic pressure treatment may be performed in Ar gas. In the case of hot pressing,
Carbon may be slightly mixed into the sintered body due to the carbon mold, but there is no particular problem if the amount is 0.5% by weight or less.

When the sintered body has a low density and a large number of pores, the contact area with the gas or plasma is increased and the consumption is accelerated. Therefore, the open porosity is preferably 0.2% or less. desirable.

The obtained sintered body is appropriately ground to finish it into a product having a predetermined size. At this time, in order to enhance the corrosion resistance, the surface roughness (Ra) of the surface of the sintered body that comes into contact with the corrosive gas or the plasma thereof is 1 μm or less, particularly 0.5 μm or less, and further 0.1 μm or less. Is desirable.

[0030]

EXAMPLES As shown in Table 1, sintered bodies were prepared using a plurality of types of MgO raw material powders having different average particle diameters and purity and rare earth element oxides, and physical properties were evaluated. First, a raw material powder was wet-crushed in a ball mill using ultrapure water as a solvent, and a slurry was prepared using polyvinyl alcohol as an organic binder. A high-purity imide ball was used as a medium for wet disintegration. The raw material powder obtained by granulating this slurry by spray drying is 0.8 ton /
It was molded by a mold press under a load of cm ² and degreased in air at 500 ° C.

The degreased body thus produced is subjected to a vacuum exhaust treatment at 1200 ° C. for the purpose of purification.
Under the conditions shown in Table 1 in a temperature range of 420 to 2000 ° C., firing was performed in air or vacuum, and various characteristics of the obtained magnesium oxide-based sintered body were measured.

As a comparative example, M with a purity of 99.9% was used.
A sintered body of gO (sample No. 1) was prepared. In addition, SiO
₂ and Al ₂ O ₃ were fired at the temperatures shown in Table 1 to produce sintered bodies in the same manner (Sample Nos. 22 and 23).

For the evaluation of the characteristics, the sintered body density was determined by measuring the bulk density by the Archimedes method and calculating the relative density to the theoretical density. The amount of metal other than Si in the sintered body is Na,
Each element of K, Ca, Al, Fe, Ni, and Cr was quantified by ICP analysis, and the total amount was described. The average particle size of MgO crystal particles was calculated by the intercept method, and the grain boundary crystal phase was identified by X-ray diffraction measurement. The results are shown in Table 1.

Regarding the plasma resistance of the sintered body, RIE
(Reactive Ion Etching) The following two test methods were used to evaluate with a device, and the results are shown in Table 2.

(1) A disk-shaped evaluation sample having a diameter of 22 cm was prepared by polishing the surface of the sintered body so that the surface had a surface roughness (Ra) of 0.1 μm or less. Then, BCl ₃ + Cl ₂ gas was introduced, plasma was generated at a high frequency, and a chlorine plasma irradiation test was performed at room temperature. The pressure in the apparatus was maintained at 10 Pa, and a high frequency of 13.56 MHz and 1 kW was used.
The etching rate was calculated based on the weight change before and after the test. The presence / absence of particles was determined by placing an 8-inch Si wafer on a disk after plasma irradiation, detecting the unevenness of the contact surface of the wafer by laser scattering, and counting the number of particles of 0.3 μm or more with a particle counter.

(2) Evaluation method The evaluation sample prepared in the same manner as in (1) was exposed to CF ₄ + CHF ₃ + Ar plasma at room temperature in an RIE plasma etching apparatus, and the etching rate and the presence or absence of particles were investigated. did. The etching conditions were such that a plasma was generated by introducing a high frequency of 13.56 MHz at a pressure of 10 Pa and an RF output of 1 KW and a plasma irradiation time of 3 hours. Others are the same as the evaluation method (1). Table 2 shows the test results.

[0037]

[Table 1]

[0038]

[Table 2]

According to the results of Tables 1 and 2, the sample No.
Nos. 1 and ₂ have a small amount of added Yb ₂ O ₃ and a relative density of
%, The corrosion resistance is reduced and more than 30 particles are generated by threshing.
Does not stand use. In Sample No.7 is the reverse, Yb ₂ O ₃
When the amount added is more than 20% by weight, the sinterability decreases,
At 50 ° C., densification was not possible. In the sample No. 8 in which the sintering temperature was increased to 2000 ° C. and densification was performed, the corrosion resistance was excellent due to abnormal grain growth of MgO crystal particles, but a large number of particles were generated due to shedding.

Further, in Sample No. 15 in which the particle size of the MgO raw material powder exceeded 5 μm and in Sample No. 19 in which the particle size of the Yb ₂ O ₃ raw material powder exceeded 5 μm, densification was not possible, and the corrosion resistance was reduced. Sample No. 20 in which the total amount of metal elements other than the alkaline earth metal and the rare earth element was more than 100 ppm in terms of metal, generation of a large amount of particles was observed. In sample No. 21, the rare earth oxide was Y
₂ O ₃ was used, and the grain boundary crystal phase was formed of MgO.Y ₂ O _3, and had low corrosion resistance. On the other hand, for the sintered bodies of SiO ₂ and Al ₂ O _{3 of} Samples Nos. 22 and 23, a dense sintered body was obtained, but the corrosion resistance was insufficient.

Sample Nos. 3 to 6, 9 to 14,
16 to 18 are dense M having a relative density of 99% or more.
It is a gO type sintered body, and Yb ₂ O is used as a rare earth element oxide.
₃ , at least one selected from Er ₂ O ₃ and Lu ₂ O ₃
The grain boundary phase is formed from the oxide of the rare earth element alone by the addition of the rare earth element oxide, and the plasma resistance of the material itself is enhanced.
It is greatly improved as compared with. Further, since the total amount of the impurity metal is suppressed to 100 ppm or less and the average particle diameter is also suppressed to 10 μm or less, the impurity metal compound and the reaction product are left, and the crystallization of the amorphous phase due to the particle shattering and the plasma impact is caused. The generation of particles was suppressed, and in test 1, an etching rate of 45 ° / min or less, and a good corrosion resistance of a 30-particle / 8-inch wafer with a particle generation of 30 were shown. Test 2 also showed excellent corrosion resistance of 25 ° / min or less and a particle generation of 15/8 inch wafers or less.

[0042]

As described in detail above, according to the present invention,
By using a magnesium oxide sintered body having the specified characteristics as a member exposed to fluorine or chlorine corrosive gas or plasma, it can be used for a long time in a high-temperature, high-density fluorine or chlorine corrosive atmosphere. It has properties and does not generate contamination or particles,
By using it as a jig such as an inner wall member of a semiconductor manufacturing apparatus, in particular, an inner wall member of a plasma processing apparatus or a support for supporting an object to be processed, it is possible to improve a semiconductor manufacturing yield and to manufacture a high-quality semiconductor element. it can.

Claims (3)

[Claims] 1. The method according to claim 1, wherein the main component is magnesium oxide;
0.1 to 20% by weight of at least one rare earth element selected from the group consisting of r and Lu in terms of oxide; the total amount of magnesium and metal elements other than the rare earth element is not more than 100 ppm in terms of metal; A high-density magnesium oxide sintered body characterized in that the average particle diameter of the particles is 10 μm or less, the relative density is 99% or more, and the rare earth element oxide crystal phase exists in the grain boundary phase. 2. A method according to claim 1, wherein a magnesium oxide powder having an average particle size of 5 μm or less is mixed with Yb ₂ O ₃ or Er _{2 having} an average particle size of 5 μm or less.
A molded body obtained by adding at least one rare earth element oxide selected from O ₃ and Lu ₂ O ₃ at a ratio of 0.1 to 20% by weight is added in a non-oxidizing atmosphere or in air.
A high-density magnesium oxide-based sintered body characterized in that it is fired at 0 to 1800 ° C., densified to a relative density of 99% or more, and precipitated an oxide crystal phase of the rare earth element in a grain boundary phase. Method. And a surface which is in direct contact with at least a halogen-based corrosive gas or its plasma, said surface being mainly composed of magnesium oxide, and Yb ₂ O ₃ , Er ₂ O ₃ ,
0.1 to 20% by weight of at least one rare earth element oxide selected from Lu ₂ O ₃ , and the total amount of magnesium and metal elements other than the rare earth element is 100 p
pm or less, the average particle size of the magnesium oxide crystal particles is 10 μm or less, the relative density is 99% or more, and the rare earth element oxide crystal phase is present in the grain boundary phase. A member for a plasma processing apparatus, comprising: