JP2000239066A - Corrosionproof member and its production, and member for plasma treatment device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a corrosionproof member excellent in corrosionproofness and suppressed in particle production, to provide a method for producing the member, and to provide a plasma treatment device using the member. SOLUTION: This corrosionproof member is a sintered compact obtained by firing in an inert atmosphere at temperatures of 600-1,400 deg.C such powder as to be <=30 μm in average particle size, consist of a fluoride of at least one metal selected from group IIIA elements and contain a total of <=100 ppm of the metallic elements except the group IIIA elements. The sintered compact thus obtained contains a total of <=100 ppm of the metallic elements except the group IIIA elements, has the average size of the fluoride crystal grains of <=30 μm and a relative density of >=95%. This sintered compact is used as a member subject to direct contact with halogen-based corrosive gases or plasma thereof, in particular as a support for the inner wall members and/or objects to be treated for a plasma treatment device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in the manufacture of semiconductors, in particular, having high corrosion resistance to fluorine-based and chlorine-based corrosive gases or fluorine-based / chlorine-based plasma, and generating little particles or contamination. The present invention relates to a corrosion-resistant member suitable for use as a jig or the like for an inner wall member of a plasma processing apparatus or a support for supporting an object to be processed, a method of 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 advancing. 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 that come into contact with these corrosive gases are required to have high corrosion resistance. Conventionally, the members that come into contact with these plasmas other than the object to be processed are generally made of Si such as glass or quartz.
Materials containing O ₂ as a main component and metals such as stainless steel and Monel are frequently used.

In the manufacture of semiconductors, a silicon-based sintered body such as an alumina-based sintered body, sapphire, an AlN-based sintered body, silicon carbide, or the like is used as a susceptor material for supporting and fixing a wafer in a plasma processing apparatus. Those coated by the CVD method or the like are used because they have excellent corrosion resistance. Further, a heater coated with graphite or boron nitride is also used.

Further, in Japanese Patent Application Laid-Open No. 8-91932, the plasma resistance is improved by using a sintered body of AlF ₃ which is a product of the plasma of an aluminum material as a member to be brought into contact with a corrosive gas. Is disclosed.

[0006]

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. In particular, with the spread of high-density plasma, plasma control has become more important, and a problem has arisen that plasma control is hindered by mixing of constituent elements of an etched member into plasma. Was.

For example, when a quartz member is etched, oxygen is released into the plasma. Particularly, in the case of fluorine-based plasma, a stable etching property can be obtained because the concentration of fluorine radicals changes with the oxygen concentration in the plasma. There was no problem.

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, 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. There has been a problem that crystal grains are shed from the surface of the sintered body, and a reaction product with the plasma is deposited and separated to cause particles.

[0010] The generation of such particles is caused by ion bombardment, breakage of metal wiring due to extremely fine particles generated by a gas phase reaction, and pattern defects, as semiconductors become more highly integrated and processes are further cleaned. There is a possibility that problems such as deterioration of the device characteristics and a decrease in the yield due to the above may occur.

Further, as in JP-8-91932 and JP-as a member for contacting the corrosive gas, when using the sintered body of AlF _3, AlF ₃ is in the high temperature region for sublimation from a relatively low temperature Because it becomes unstable, alumina,
Although corrosion resistance was improved as compared with aluminum nitride and silicon nitride sintered bodies, they were not practically sufficient. Furthermore, Al
Since F ₃ (melting point 1040 ° C.) sublimates at a relatively low temperature, it is necessary to sinter while suppressing sublimation, particularly in atmospheric sintering such as normal-pressure sintering or hot-press sintering. It was difficult to get.

In order to solve such a problem, the inventors of the present invention have proposed that a surface in contact with a fluorine-chlorine-based plasma be formed on a group 2A or 3A of the periodic table capable of forming a halide stable to the plasma. It is proposed to form oxides, nitrides, and carbides containing element-containing sintered bodies, and to form halides containing elements from the 2A and 3A groups of the periodic table, such as CaF _{2, on the} surface of the sintered bodies by plasma. did.

However, a material containing a Group 2A or 3A element of the periodic table as a main component is stable against fluorine and chlorine plasma, but has a thermal expansion coefficient at room temperature of, for example, magnesium oxide 14. × 10 ^-6 / ° C., because of the magnesium fluoride 10 × 10 ^-6 / ℃ and difference, periodic table 2 by thermal cycling are formed in the sintered body surface
There has been a problem that fluoride containing Group A and 3A elements is easily peeled off, and particles are generated due to dropout of a halide formed on the material surface.

In particular, since the melt of CaF ₂ has cleavage, the surface layer and the like easily peels off due to vibration, impact, and the like.
This has caused a large amount of particles to be generated.

[0015]

Means for Solving the Problems The present inventors have repeatedly studied materials which have high corrosion resistance to fluorine-based and chlorine-based corrosive gas or plasma and can suppress generation of particles. By controlling the crystal grain size, the amount of impurities and the density of the fluoride sintered body of the Group 3A group element, especially the lanthanoid rare earth metal, to a specific range,
It has been found that it exhibits high corrosion resistance to fluorine, chlorine-based corrosive gases or plasma, and can suppress the generation of particles.

That is, the corrosion-resistant member of the present invention has at least a surface directly in contact with a halogen-based corrosive gas or its plasma, and the surface is at least one metal fluoride selected from Group 3A elements of the periodic table. Consisting of
The total amount of metal elements other than the Group 3A element of the periodic table is 100 ppm or less in terms of metal, the average particle size of the fluoride crystal particles is 30 μm or less, and the sintered body has a relative density of 95% or more. It is characterized by the following.

Further, the method for producing the same is as follows.
0 μm or less, made of a fluoride of at least one metal selected from Group 3A elements of the periodic table,
The total amount of metal elements other than Group A elements is 100 pp in metal conversion
m or less, or a compact thereof is fired at 600 to 1400 ° C. in an inert atmosphere to densify the powder to a relative density of 95% or more. It is desirable to apply ^two or more pressures.

Further, in the member for a plasma processing apparatus of the present invention, at least a surface of a halogen-based corrosive gas or a surface thereof which is in direct contact with the plasma is made of a fluoride of at least one metal selected from Group 3A elements of the periodic table; A rare earth metal fluoride sintered body in which the total amount of metal elements other than the Group 3A element of the periodic table is 100 ppm or less in terms of metal, the average crystal grain size of the fluoride is 30 µm or less, and the relative density is 95% or more. It is characterized by being formed of a union.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The corrosion-resistant member of the present invention comprises a sintered body of a fluoride of at least one metal selected from Group 3A elements of the periodic table, and has a corrosion resistance to halogen-based plasma, especially fluorine plasma. In view of the above, the total amount of metal elements other than the Group 3A elements of the periodic table is 10
0 ppm or less, desirably 90 ppm or less, especially 50 p
It is important to control the pressure to not more than pm, more preferably not more than 10 ppm.

That is, when the total amount of the metal elements other than the Group 3A element is more than 100 ppm in terms of metal, the metal other than the Group 3A element reacts with the plasma on the plasma contact surface, whereby the etching proceeds, This is because the reactant causes particles.

As the fluoride of the Group 3a element of the periodic table, a material having a high melting point is desirable in terms of corrosion resistance to fluorine plasma, and ScF ₃ (melting point: 1515 ° C.)
LaF ₃ (melting point 1490 ° C.), ErF ₃ (melting point 1350
° C), CeF ₃ (melting point 1324 ° C), YbF ₃ (melting point 1
157 ° C.) and YF ₃ (melting point 1152 ° C.) in this order.

Further, in order to enhance the corrosion resistance to plasma, the relative density of the sintered body needs to be 95% or more, especially 98% or more. This is because if the relative density of the sintered body is less than 95%, the contact area with the plasma increases, so that the corrosion resistance is reduced and the etching proceeds from the pores present on the plasma contact surface.

Also, with the increase in the diameter of silicon wafers,
Since the manufacturing equipment and the components themselves also become larger, it is necessary to increase the strength and thermal shock resistance, and when using a chlorine-based gas and its plasma, deterioration of the components due to thermal cycling becomes a problem. Therefore, the relative density of the sintered body needs to be 95% or more in order to enhance the heat resistance reliability.

The average particle size of the fluoride crystal particles of the sintered body is 30 μm or less, preferably 10 μm or less, and more preferably 1 μm or less.
μm or less, more preferably 0.3 μm or less. That is, if the average particle diameter is larger than 30 μm, the influence on the semiconductor element manufactured in the plasma processing apparatus becomes large in the case of occurrence of particle shedding or the like.

As a method for producing a rare earth metal fluoride sintered body having high corrosion resistance to such a halogen-based plasma, the total amount of metal elements other than the Group 3A element in the periodic table is 100 ppm or less, preferably 100 ppm or less. 90 ppm
Or less, particularly 50 ppm or less, more preferably 10 ppm or less, and the average particle size is 30 μm or less, preferably 10 μm or less.
m or less, particularly 1 μm or less, and further, 0.3 μm or less are prepared. The amount of oxygen contained in the raw material powder is 0.05 to 2.
It is desirable that the content be 0% by weight in order to enhance the sinterability.

When the particle size of the raw material powder is larger than 30 μm, the raw material powder may be pulverized by a desired pulverizing method, for example, a ball mill, a vibrating mill, an attritor mill, a jet mill or the like, and may be used by a mesh pass or the like. It is desirable to remove coarse particles.

Using the powder, a desired shape is formed into a predetermined shape by a desired forming means, for example, a die press, a cold isostatic press, an extrusion molding or the like. The compact at this time is desirably 55% or more in relative density, and if the compact density is lower than 55%, it is difficult to produce a dense body having a relative density of 95% or more in the subsequent sintering process. .

Next, the formed body produced as described above is fired to a relative density of 95% or more, especially 98% or more. In order to densify to a relative density of 95% or more, the compact having the above composition is pressed or normal pressure (non-oxidized) in an inert atmosphere such as vacuum, Ar, N ₂ , CO, H ₂ , HF gas or the like. (Atmospheric gas pressure of 1 atm or more) in a temperature range of 600 to 1400 ° C. In particular, as the inert atmosphere, CO,
H ₂ and HF are most desirable.

In this case, the optimum calcination temperature depends on the element of Group 3A of the periodic table used. For example, for YF ₃ and YbF ₃ , the temperature is 600 to 1100 ° C., preferably 7 to 100 ° C.
The temperature is preferably from 1000 to 1000 ° C., more preferably from 800 to 1000 ° C., and for CeF ₃ and ErF ₃ ,
300 ° C., preferably 900-1200 ° C., and even 1
000-1100 ° C. is desirable, and for LaF ₃ ,
900-1400 ° C, preferably 1000-1350 ° C
Furthermore, 1100-1250 degreeC is desirable.

In the above sintering, it is preferable to perform hot press sintering under a pressure of 50 kg / cm ² or more in order to improve the relative density. Further, nitrogen gas or argon gas is applied to the obtained sintered body. The densification can be further promoted by performing hot isostatic pressure treatment at a temperature of 500 to 1300 ° C. under a pressure of 1000 atm or more.

In the case of hot pressing, carbon may be slightly mixed into the sintered body by the carbon mold, but there is no particular problem as long as the amount is 0.5% by weight or less.

The relative density of 95% produced by the above calcination
In the above sintered body, if there are many open pores on the surface of the sintered body, a contact area with a corrosive gas or plasma is increased and consumption is accelerated. Therefore, the open porosity is 0.2% or less. It is desirable.

Thereafter, the obtained sintered body is appropriately ground to finish the product 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 in contact with the corrosive gas or its plasma is considered.
Is 1 μm or less, particularly 0.5 μm or less, and more preferably 0.1 μm or less.
It is desirable that it is not more than μm.

The fluoride sintered body of the Group 3A element of the periodic table is combined with a fluorine-based or chlorine-based corrosive gas or plasma in a plasma processing apparatus used for manufacturing a semiconductor device. It is suitably used for sites where the surface is in direct contact.

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

According to the present invention, the surface in direct contact with such a halogen-based corrosive gas or its plasma is
By comprising the above-mentioned sintered body of a fluoride of Group 3A element of the periodic table, excellent corrosion resistance and generation of particles can be suppressed.

This is because the Group 3A element fluoride sintered body has low reactivity with fluorine and chlorine, has a high melting point, and is stable at a high temperature without sublimation at a low temperature unlike AlF _3. As a result, the sintering can be performed stably, so that a dense sintered body can be produced.

[0038]

EXAMPLES (Example 1) Average raw material particle diameters shown in Table 1, contents of metals other than Group 3A elements of the periodic table (referred to as impurity amounts)
Was filled in a carbon mold and subjected to hot press firing for 2 hours at a firing temperature shown in Table 1 under a pressure of 200 kg / cm ² in an HF atmosphere.

As comparative examples, SiO ₂ , Al ₂ O ₃ , A
1N and AlF ₃ were fired at the temperatures shown in Table 1 to produce similarly sintered bodies (Sample Nos. 35 to 38).

Using the obtained sintered body, the density of the sintered body was measured by the Archimedes method, and the relative density (%) as a ratio to the theoretical density was calculated. Also, JISR160
The 4-point bending strength was measured based on 1. Further, the average particle size of the fluoride crystal particles was measured by an intercept method. The results are shown in Table 1.

Further, the obtained sintered body was subjected to a corrosion resistance test by the following method. First, the surface of the produced sintered body was mirror-finished to a surface roughness (Ra) of 0.1 μm or less to produce a disk having a diameter of 22 cm, and CF ₄ (60 sccm) + Ar was produced by an RIE plasma etching apparatus. (6
(0 sccm) at room temperature to examine the etching rate and the presence or absence of particles. The etching conditions were a pressure of 10 Pa, an RF output of 1 KW, and a plasma irradiation time of 3 hours. 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. Table 1 shows the results.

[0042]

[Table 1]

According to the results shown in Table 1, the samples Nos. 1, 11
Since the sintering temperature is low and the relative density cannot be densified to 95% or more, the corrosion resistance is reduced, and 30 or more particles are generated by grain shedding, which is unusable.
Sample No. 16 melted at a high firing temperature. Further, Sample Nos. 10, 18, 23, 29 and 34 in which the average particle size of the raw material powder exceeded 30 μm were not densified, and the corrosion resistance was reduced. Further, the sample N in which the total amount of metal elements other than Group 3A element of the periodic table is more than 100 ppm in terms of metal.
In o.9 and 17, generation of a large amount of particles was observed.

On the other hand, Si other than fluoride of Group 3A element
Regarding the sintered body of O ₂ , Al ₂ O ₃ , and AlN, the corrosion resistance was insufficient even though it was a dense sintered body having a high purity and a crystal grain size of 30 μm or less. In addition, the AlF ₃ sintered body did not sufficiently densify due to sublimation and decomposition progressed during firing.

On the other hand, the sample Nos.
8, 12-15, 19-22, 24-28, 30-33
Has a relative density of 95% or more and an etching rate of 25 °
/ Min. Hereinafter, in particular, 15 ° / min. Hereafter, the particle generation amount is 15 pieces / 8 inch wafer or less, especially 10 pieces /
It showed good corrosion resistance of 8 inch wafer or less.

Example 2 The average particle size is 0.2 μm, the content of metal elements other than Group 3A of the periodic table (impurity amount) 90 pp
m of YF ₃ powder at a pressure of 3 ton / cm ² and CI
After the P molding, the baking temperature is 9 in an Ar atmosphere of 1 atm.
Atmosphere firing (PLS) was performed at 00 ° C. The obtained sample was evaluated in the same manner as in Example 1. As a result, the relative density was 95% or more, the average crystal grain size was 1.5 μm, and the etching rate was 25 ° / min. In addition, good corrosion resistance of a wafer having a particle generation amount of 15/8 inch was exhibited.

Similarly, the average particle size is 0.1 μm,
L of 85 ppm of metal element content (impurity amount) other than group A
Using aF ₃ powder, CIP processing was performed at a pressure of 3 ton / cm ² and CIP molding was performed.
Atmosphere firing (PLS) was performed at 250 ° C. When the same evaluation as in Example 1 was performed on the obtained sample,
Relative density 97%, average crystal grain size 0.8 μm, etching rate 17 ° / min. , Particle generation 10 /
The 8-inch wafer exhibited good corrosion resistance.

[0048]

As described in detail above, according to the present invention,
The member exposed to a fluorine-based or chlorine-based corrosive gas or plasma is made of a fluoride of at least one metal selected from Group 3A elements of the periodic table.
The total amount of Group A metal elements is 100 ppm or less in terms of metal, the average particle size is 30 μm or less, and the relative density is 95%.
% Of the sintered body, it has long-term durability in high-temperature, high-density fluorine-based and chlorine-based corrosive atmospheres, does not generate contamination or particles, and has mechanical properties as large parts. Because it retains strength, it can be used as a jig such as an inner wall member of a plasma processing apparatus or a support for supporting an object to be processed, which is mainly used for semiconductor manufacturing. Can be manufactured.

Claims (4)

[Claims] 1. A method according to claim 1, further comprising a surface in direct contact with at least a halogen-based corrosive gas or a plasma thereof, said surface being mainly composed of a fluoride of at least one metal selected from Group 3A elements of the periodic table. The total amount of metal elements other than Group 3A elements is 100 ppm or less in terms of metal, and the average particle size of the fluoride crystal particles is 30 μm or less, and the sintered body has a relative density of 95% or more. Corrosion resistant member. 2. A method for producing a member having at least a surface in direct contact with a halogen-based corrosive gas or its plasma, comprising at least one metal selected from Group 3A elements of the periodic table having an average particle size of 30 μm or less. A powder having a total content of metal elements other than the Group 3A element of the periodic table, which is 100 ppm or less in terms of metal, or a compact thereof, which is fired at 600 to 1400 ° C. in an inert atmosphere to obtain a relative density A method for producing a corrosion-resistant member, wherein the member is densified to 95% or more. 3. The method for producing a corrosion-resistant member according to claim ² , wherein a pressure of 50 kg / cm ² or more is applied during said firing. 4. A method according to claim 1, further comprising a surface in direct contact with at least a halogen-based corrosive gas or a plasma thereof, wherein said surface comprises a fluoride of at least one metal selected from Group 3A elements of the periodic table. It is made of a rare earth metal fluoride sintered body having a total amount of metal elements other than the Group 3A element of 100 ppm or less in terms of metal, an average particle diameter of the fluoride crystal particles of 30 μm or less, and a relative density of 95% or more. A member for a plasma processing apparatus, comprising: