JP2000026166A - High purity silicon nitride-base corrosion resistant member and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a silicon nitride-base corrosion resistant member comprising a silicon nitride-base sintered compact excellent in heat resistance and capable of suppressing the generation of particles. SOLUTION: At least the surface of the corrosion resistant member brought into contact with a halogen-contg. corrosive gas or its plasma comprises a high purity silicon nitride-base sintered compact having >=95% relative density obtd. by compacting a powder contg. silicon nitride as the principal phase, 1.0-15.0 wt.% (expressed in terms of SiO2) impurity oxygen and <=0.1 wt.%, in total, of impurity metals other than Si and press-firing the resultant compact in a nonoxidizing atmosphere at 1,600-2,000 deg.C and 150-500 kgf/cm2 pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing semiconductors, which has high corrosion resistance especially to fluorine-based and chlorine-based corrosive gases or fluorine-based / chlorine-based plasma, and generates little particles and contamination. The present invention relates to a silicon nitride-based corrosion-resistant member suitable for use as a jig or the like for an inner wall member or a support for supporting an object to be processed, and a method for manufacturing 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 devices 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 because of its high reactivity.

[0003] These members that come into contact with corrosive gas are required to have high corrosion resistance. Conventionally, members other than the object to be processed that come into contact with these plasmas are generally made of glass or quartz.
Materials containing iO ₂ as a main component and metals such as stainless steel and Monel are frequently used.

[0004] In the manufacture of semiconductors, as a susceptor material for supporting and fixing a wafer, an alumina-based sintered body, sapphire, an AlN-based sintered body, or those coated with a surface by a CVD method or the like are used because they have excellent corrosion resistance. ing. Further, a heater coated with graphite or boron nitride is also used.

[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 and AlN sintered compacts and coating materials have better corrosion resistance to fluorine-based gases than the above materials, but when they come in contact with plasma at high temperatures, the corrosion gradually progresses and the surface of the sintered compact crystallizes. There has been a problem that particles are shed, or a reaction product with plasma is deposited and separated to cause particles.

[0006] The generation of such particles is caused by breaking of metal wiring and pattern defects due to ion bombardment and extremely fine particles generated by a gas phase reaction in the course of higher integration of semiconductors and further cleanliness of the process. 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.

[0007] In order to solve such a problem, the present inventors have first made a group 2A or 3A element of the periodic table that forms a stable halide on the material surface against fluorine-chlorine-based plasma. Has been proposed. However, a material containing a Group 2A or 3A element of the periodic table as a main component is stable against fluorine-chlorine-based plasma, but the halide formed on the surface of the material drops off, Particles were generated by the reaction.

[0008]

Means for Solving the Problems The present inventors have repeatedly studied materials which have high corrosion resistance to fluorine-based and chlorine-based corrosive gases or plasmas and can suppress the generation of particles which impair the performance of semiconductors. As a result, silicon nitride,
Compounds with a high atomic bond, such as silicon carbide and diamond, exhibit excellent corrosion resistance.Especially, silicon nitride reacts with plasma and reacts with fluorine or chlorine, forming constituents with high vapor pressure even when the constituent elements react. Since it is released out of the system as a gas, it has been found that there is no risk of generating particles and contaminating the device.

However, since silicon nitride is difficult to sinter,
Addition of a sintering aid was indispensable for densification of the sintered body. This sintering aid component is present at the grain boundaries of silicon nitride crystals in the sintered body. However, when the surface comes into direct contact with a halogen-based corrosive gas or plasma, the sintering aid component depends on the type and conditions of the gas plasma. It has been found that the agent component can be selectively etched or form a reactant with the halogen to cause particle generation.
That is, in order to suppress the generation of particles in plasma in the silicon nitride sintered body, a sintering aid component forming a grain boundary phase is not contained, or the silicon nitride is selectively etched or a reactant does not generate particles. Only the components need to be selected as auxiliaries.

Therefore, according to the present invention, the corrosion resistance of the sintered body can be remarkably improved by substantially using only Si as the metal component as a sintering aid for the silicon nitride based sintered body. It has been found that the generation of particles inside can be suppressed.

[0011] That is, silicon nitride corrosion resistant member of the present invention, the surface which contacts the halogen-based corrosive gas or directly with the plasma, the silicon nitride as a main phase, 1.0 to 15.0 wt oxygen in terms of SiO ₂ %, And the total amount of impurity metals other than Si is 0.1% by weight or less, and the relative density is 95%.
It is characterized by comprising the above sintered body. The grain boundary phase is mainly composed of SiO ₂ and / or Si.
Is composed of ₂ N ₂ O is desirably.

[0012] Further, the manufacturing method is characterized in that silicon nitride is used as a main component and the total amount of impurity metals other than Si is 0.1% by weight.
Hereinafter, a silicon nitride powder containing 1.0 to 15.0% by weight of oxygen in terms of SiO ₂ or a compact thereof is placed in a non-oxidizing atmosphere at 1600 to 2000 ° C. and 150 to 500 kgf / c.
It is characterized by being fired under pressure at m ² .

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The corrosion-resistant member of the present invention is a member whose surface is in direct contact with a halogen-based corrosive gas or plasma such as a fluorine-based or chlorine-based gas. Examples of the fluorine-based gas include SF ₆ , NF ₃ , and the like. CF ₄ , CHF ₃ , ClF ₃ , H
F, etc., and chlorine-based gases such as Cl ₂ , BCl ₃ ,
HCl and the like. When a microwave, a high frequency, or the like is introduced into an 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,
It is made of a silicon nitride sintered body. When silicon nitride reacts with fluorine or chlorine, SiF ₄ or SiCl
Form reactive products with high vapor pressure, such as _4, and are discharged out of the system as a gas, so they do not generate contamination or particles. In addition, since the bonding force between atoms is large, it does not easily react with a halogen-based gas or plasma, and exhibits excellent corrosion resistance.

In order to enhance the corrosion resistance at the site of contact with the plasma, it is desirable that the dense body has a relative density of 95% or more, particularly 98% or more. Further, as the diameter of the silicon wafer increases, the manufacturing equipment and the components themselves also increase in size.Therefore, it is necessary to increase the strength and thermal shock resistance. The relative density of the sintered body needs to be 95% or more in order to improve the heat resistance because the deterioration of parts due to the cycle is regarded as a problem.

Since silicon nitride does not sinter alone, conventionally, in addition to SiO _2, a group 3A element of the periodic table such as a rare earth element, an alkaline earth metal oxide such as MgO, or
Densification is achieved by adding a sintering aid such as l ₂ O ₃ . The structure of the sintered body is composed of a main crystal phase made of silicon nitride and a grain boundary phase formed mainly by a component added as a sintering aid or an impurity component. From the viewpoint of corrosion resistance to halogen-based gas,
Silicon nitride itself is excellent in corrosion resistance because it is composed of a chemically stable compound having a covalent bond itself.However, the corrosion resistance is poor due to the components mixed as the sintering aid and impurities, and the grain boundary phase is locally etched. Or reacts easily with gas.

Therefore, according to the present invention, in order to maintain the sintering property without adding the sintering aid component which deteriorates the corrosion resistance and to the extent that the corrosion resistance is not impaired, the oxygen content is reduced at a predetermined ratio. It is important to include it. That is, the silicon nitride as a main phase, oxygen in terms of SiO ₂ 1.0 to 15.
0% by weight, desirably 2.0 to 10.0% by weight,
It is important that the total amount of impurity metals other than Si be 0.1% by weight or less, particularly 0.05% by weight or less.

Here, the oxygen is the total amount of oxygen in the silicon nitride sintered body, and most of the oxygen is inevitable oxygen in the Si ₃ N ₄ raw material or oxygen in SiO ₂ added intentionally. .

The reason for limiting the composition of the sintered body to the above range is as follows.
If the SiO ₂ conversion amount is less than 1.0% by weight, the sinterability decreases, so that it becomes difficult to densify the sintered body.
If the content is more than 5.0% by weight, the ratio of the grain boundary phase in the sintered body becomes high, and a large amount of Si oxide present in the grain boundary is selectively etched, and the surface is roughened and the grains are removed, resulting in high corrosion resistance. It is because it is damaged.

The silicon nitride sintered body of the present invention is structurally characterized by a main crystal phase composed of silicon nitride and S, O,
There is a grain boundary phase containing N, and the grain boundary phase may be made of glass, but may be made of SiO ₂ or Si ₂ N ₂ O.
It is desirable to include a crystal phase formed by the following. Even if these Si compounds, including the main crystal phase, react with a halogen-based gas or plasma, they generate halides or gases having a high vapor pressure and are discharged out of the system. When the content of the impurity metal other than Si is set to 0.1% by weight or less, selective etching of the grain boundary phase composed of metal impurities other than Si can be performed.
The generation of particles due to the formation of low vapor pressure halide and the contamination of the wafer due to contamination can be suppressed.

The silicon nitride corrosion-resistant member of the present invention is manufactured by the following method. Α having a total amount of metal impurities other than Si of 0.1% by weight or less, particularly 0.05% by weight or less, an average particle diameter of 2 μm or less, and an impurity oxygen amount of 0.5 to 2.0% by weight.
, Or β-type high-purity silicon nitride raw material powder
The total amount of metal impurities other than 0.1% by weight or less
iO ₂ to produce silicon nitride powder containing 1.0 to 15.0 wt% in terms of. As the high-purity silicon nitride raw material powder, it is possible to use the one originally produced with high purity,
It is also possible to obtain a raw material powder containing metal impurities by performing a purification treatment in a chlorine or hydrogen atmosphere at 800 to 1900 ° C. in a vacuum.

When the total amount of metal impurities other than Si in the silicon nitride raw material powder exceeds 0.1% by weight, a low-melting grain boundary phase containing a high concentration of impurities is generated and exposed to a halogen-based corrosive gas or plasma. When used for a long time in an environment where the grain boundary phase component inside the sintered body easily diffuses and moves toward the member surface, erosion proceeds to the inside of the sintered body,
It reduces corrosion resistance and adversely affects semiconductors.

When the amount of oxygen is insufficient with only the silicon nitride powder, an SiO ₂ powder may be appropriately added to and mixed with the silicon nitride raw material powder.

The silicon nitride-based powder is filled in a mold or molded into a desired shape, and heated in a non-oxidizing atmosphere at 1600 to 2000 ° C., particularly 1700 to 1950 ° C., for 150 to 5 minutes.
Pressure calcination is performed at a pressure of 00 kgf / cm ² . As a molding method, a known method such as press molding, cast molding, cold isostatic molding, extrusion molding, sheet molding, or injection molding is employed. The firing atmosphere can be fired at normal pressure in a low temperature range, but at 1800 ° C. or higher where decomposition of silicon nitride occurs,
A nitrogen atmosphere of 1.5 atm or more is preferable in order to prevent decomposition of silicon nitride and promote densification.

As the firing method, 150 to 500 kgf
Hot pressing under a pressure of / cm ² , hot isostatic firing in an inert atmosphere of 1000 atm or more can be employed, but the hot pressing is preferred from the viewpoint of increasing cost and sinterability. Further, in order to improve the density of the sintered body, hot isostatic firing may be further performed after the hot pressing.

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.

By the above calcination, the relative density is 95% or more,
In particular, a sintered body of 98% or more is obtained. If the sintered body has a low density and a large number of pores, the contact area with the gas or plasma increases and the consumption is accelerated. Therefore, the open porosity is desirably 0.2% or less. The obtained sintered body is appropriately subjected to a grinding process to finish it into a product shape 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.

[0028]

EXAMPLE An experiment for evaluating the corrosion resistance to specific plasma was carried out below. Using silicon nitride powder having an average particle size of 0.3 μm and an α ratio of 90%, purity, metal impurities and SiO ₂ added as a sintering aid are combined with those obtained by converting impurity oxygen contained in the raw material into SiO _2. Addition and mixing were performed so that the ratios shown in Table 1 were obtained. This raw material powder was filled in a carbon mold and subjected to hot pressing (HP) in a nitrogen atmosphere under the conditions shown in Table 1.

As a comparative example, a quartz glass having a purity of 99.99% by weight or more was prepared (Sample No. 5). Was also prepared and the sample added Y ₂ O ₃ or alumina as a sintering aid (Sample No.19~23). For these powders,
Hot press (HP) or nitrogen gas pressure firing (GP
By S), similarly, a sintered body was produced in a nitrogen atmosphere under the conditions shown in Table 1.

[0030]

[Table 1]

Using the obtained sintered body, the density of the silicon nitride based sintered body was first measured by the Archimedes method, and the relative density (%) as a ratio to the theoretical density was calculated. The results are shown in Table 2.

(Corrosion Resistance Test 1) A disk having a diameter of 22 cm was mirror-finished on the obtained sintered body so that the surface had a surface roughness (Ra) of 0.1 μm or less, and RIE was performed.
CF ₄ (60sccm) with plasma etching equipment
The wafer was exposed to a fluorine-based plasma of + Ar (60 sccm) at room temperature, and the etching rate and the presence or absence of particles were examined. Etching conditions are pressure 10 Pa, RF output 1 kW,
The plasma irradiation time was 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 2 shows the results.

(Corrosion Resistance Test 2) Further, the film was exposed to chlorine plasma of Cl ₂ (100 sccm) at room temperature using an RIE plasma etching apparatus, and the etching rate and the presence or absence of particles were examined. The etching conditions are a pressure of 4 Pa,
The RF output was 1.8 kW and the plasma irradiation time was 3 hours.
The evaluation method is the same as in the first embodiment. Table 2 shows the results.

[0034]

[Table 2]

According to the results shown in Table 2, the sample No. 6 is Si
Due to the small amount of the O ₂ component, it cannot be densified. As a result, the corrosion resistance is reduced, and 2500 or more particles are generated due to the shedding of particles, which is unusable. In addition, the sample No.
No. 7 excessively contains SiO _2, which is inferior in corrosion resistance to silicon nitride, and selectively etches it to remove the grain boundary phase, and the silicon nitride particles are shed to generate a large amount of particles. ing. Sample No. Nos. 9 and 11 contain an impurity metal in excess of 0.1% by weight, which results in the generation of particles. Sample No. Sample No. 12 has a too low firing temperature. In Nos. 13 and 16, densification was not sufficient due to insufficient press pressure, and a large amount of particles were generated. Sample No. In No. 18, the sintering temperature was too high, silicon nitride was decomposed, and the corrosion resistance was greatly reduced. Sample No. In Nos. 19 and 20, since the grain boundary phase contains Y and Al which react with fluorine to form a solid having a low vapor pressure, the etching rate of the material is lowered, but the reaction product of the grain boundary phase and fluorine is powder. And generate a large amount of particles.

Sample No. 1 according to the present invention. 1-4, 8, 1
Nos. 0, 14, 15, and 17 show about twice or more the corrosion resistance as compared with quartz glass (sample No. 5) which is currently widely used, and generation of particles is suppressed to 1,000 or less. In addition, no deposition of reaction products was observed on the sample surface itself.

[0037]

As described in detail above, according to the present invention,
By using a specified high-purity silicon nitride sintered body as a member exposed to fluorine-based and chlorine-based corrosive gases or plasma, it can withstand long-term durability in high-temperature, high-density fluorine-based and chlorine-based corrosive atmospheres. Since it does not generate contamination and particles, and retains mechanical strength as a large component, it can be used as an apparatus for semiconductor manufacturing, especially a support for supporting an inner wall member of a plasma processing apparatus or an object to be processed. By using it as a member such as a jig,
A semiconductor device of high quality can be manufactured while improving the yield of semiconductor manufacturing.

Continued on the front page (72) Inventor Takeo Fukudome 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima F-term in Kyocera Research Institute (reference) 4G001 BA04 BA32 BA71 BA73 BB04 BB32 BB71 BB73 BC13 BC42 BC43 BC52 BC54 BC55 BD04 BD13 BD37 BD38 BE11 BE33 BE35 5F004 AA15 AA16 BA04 BB13 BB14 BB29 DA00 DA01 DA04 DA11 DA16 DA17 DA18 DA20 DA23 DA29 5F031 DA13 EA02 EA04 MA23 MA28 MA32 PA26 5F045 AA08 BB14 EB03 EC05 EM09

Claims (3)

[Claims] A surface which is in direct contact with a halogen-based corrosive gas or its plasma is mainly composed of silicon nitride,
1.0 to 15.0% by weight in terms of SiO ₂
A high-purity silicon nitride-based corrosion-resistant member comprising a sintered body having a total amount of impurity metals other than 0.1% by weight or less and a relative density of 95% or more. 2. The high-purity silicon nitride-based corrosion-resistant member according to claim 1, wherein the grain boundary phase of the sintered body is mainly composed of SiO ₂ and / or Si ₂ N ₂ O. 3. A method for producing a corrosion-resistant member having a surface directly in contact with a halogen-based corrosive gas or its plasma, wherein silicon nitride is a main component and the total amount of impurity metals other than Si is 0.1% by weight or less. , Oxygen in terms of SiO ₂ .
A silicon nitride-based powder containing 0 to 15.0% by weight or a compact thereof is placed in a non-oxidizing atmosphere at 1600 to 2000 ° C.,
A method for producing a high-purity silicon nitride-based corrosion-resistant member, characterized by firing under pressure at 50 to 500 kgf / cm ² .