JP2000007440A - Silicon nitride-base corrosion resistant member and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide 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 and its production method. SOLUTION: A power contg. β-silicon nitride as a principal phase, 0.1-3 wt.% (expressed in terms of RE2O3) rare earth element (RE), 1-5 wt.% (expressed in terms of Al2O3) aluminum and 1-6 wt.% (expressed in terms of SiO2) excess oxygen in an Al2O3 to RE2O3 ratio of 1-6 and an SiO2 to RE2O3 ratio of 2-15 and contg. <=0.1 wt.%, in total, of other cationic impurities is compacted and pressureless-fired at 1,700-1,800 deg.C in a non-oxidizing atmosphere contg. gaseous SiO to obtain the objective corrosion resistant member comprising a silicon nitride-base sintered compact having >=90% relative density. The member has a surface in contact with corrosive gas or plasma composed of the above sintered compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is suitably used as an inner wall material or a jig in a plasma processing apparatus having a high corrosion resistance to chlorine-based corrosive gas or its plasma or a plasma apparatus for manufacturing semiconductor / liquid crystal. And a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, the use of plasma in processes such as a dry process and a plasma coating process for manufacturing semiconductors and liquid crystals has rapidly advanced. As a plasma process in semiconductor / liquid crystal production, a halogen-based corrosive gas such as a chlorine-based gas is used for vapor-phase growth deposition, etching and cleaning because of its high reactivity. Members that come into contact with these corrosive gases and plasma are required to have high corrosion resistance.

Conventionally, members that come into contact with these corrosive gases other than the object to be treated and the plasma thereof are generally:
Materials mainly composed of SiO ₂ such as glass and quartz, and corrosion-resistant metals such as stainless steel and Monel are often used.

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

[0005]

However, conventionally used glass and quartz have inadequate corrosion resistance in plasma and are intensely depleted. In particular, when they come into contact with chlorine-based plasma, the contact surface is etched and the surface properties change. Thus, problems such as affecting the etching conditions have occurred.

[0006] Further, even members made of metal such as stainless steel have insufficient corrosion resistance, causing problems such as generation of particles due to corrosion. Particularly, in semiconductor manufacturing, one of the major causes for increasing the defective product generation rate is one. Had one.

[0007] Alumina sintered bodies, sapphire, AlN sintered bodies, or those obtained by surface-coating them by the CVD method or the like, have higher corrosion resistance to chlorine-based corrosive gases and their plasmas than the above materials. However, when it comes into contact with the plasma at a high temperature, the corrosion gradually progresses, and in the end, there arises a problem that particles are generated from the surface due to the reaction product particles with the gas and the crystallization of the crystal particles.

In order to solve such a problem, it has also been proposed to use a material mainly composed of Group 2A or 3A element of the periodic table, which forms a stable chlorinated material on the surface of the material with respect to chlorine-based plasma. However, with the further increase in the degree of integration of semiconductors and the further cleanliness of the process, there is a risk that ion bombardment and extremely fine particles generated by reaction in the gas phase may cause defects.

Accordingly, an object of the present invention is to provide a silicon nitride-based corrosion-resistant member made of a silicon nitride-based sintered body having excellent heat resistance and capable of suppressing corrosion resistance and generation of particles, and a method of manufacturing the same.

[0010]

DISCLOSURE OF THE INVENTION The present inventors have studied a ceramic material having high corrosion resistance which can suppress generation of particles which impair the performance of a semiconductor even in a chlorine-based corrosive gas or plasma. A compound having a high covalent bond with Si as a constituent element such as silicon or silicon carbide has excellent corrosion resistance performance, and as a corrosion resistant member for a semiconductor or a liquid crystal manufacturing apparatus, there are many members requiring electrical insulation, and Since excellent thermal shock resistance is required, attention was paid to the fact that silicon nitride is suitable for a wide range of corrosion resistant members.

[0011] Then, as a result of diligent research on the optimum composition as a corrosion-resistant member using the silicon nitride-based sintered body, a sintering aid is an essential component for achieving densification by sintering. Depending on the binder component, the corrosion resistance greatly differs, among which the addition amount of the rare earth element compound is reduced as much as possible, by adding a predetermined amount of alumina and silica,
The present inventors have found that the corrosion resistance of a silicon nitride-based sintered body can be significantly improved without impairing the sinterability, and have led to the present invention.

That is, in the silicon nitride-based corrosion-resistant member of the present invention, the surface in direct contact with a corrosive gas or plasma has β-silicon nitride as a main phase, and rare earth elements are converted to oxides (RE ₂ O ₃ ). .1～3% by weight, each comprise aluminum and 1 to 5% by weight in terms of oxide (Al ₂ O _3), the excess oxygen at a ratio of 1-6 wt% in terms of SiO ₂ (SiO _2), and Al ₂ O ₃ / RE ₂ O ₃ is in the range of 1 to 6, and SiO ₂ / RE ₂ O ₃ is in the range of 2 to 15,
The sintered body has a total amount of other cationic impurities of 0.1% by weight or less and a relative density of 90% or more. The rare earth element is Yb
₂ O ₃ is most desirable.

[0013] Further, the production method is characterized in that a silicon nitride raw material powder having a total amount of cationic impurities of 0.1% by weight or less is used.
And 0.1 to 3% by weight in terms of oxide of rare earth element (RE ₂ O _3), in terms of oxide of aluminum (Al ₂ O ₃₎ 1
-5% by weight, and excess oxygen in terms of SiO ₂ (SiO ₂ ) of 1-6% by weight, and Al ₂ O ₃ / RE ₂ O ₃ is 1-6, and SiO ₂ / RE ₂ O ₃ is It is characterized in that a powder in the range of 2 to 15 is molded and fired. The firing is desirably normal pressure firing.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The corrosion-resistant member of the present invention is a member which is in direct contact with a corrosive gas of a chlorine-based gas or its plasma. As the chlorine-based gas, Cl ₂ , SiCl ₄ ,
BCl ₃ , HCl and the like can be mentioned. 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, such a corrosive gas of a chlorine-based gas or a surface thereof which comes into direct contact with plasma is formed of a silicon nitride sintered body containing silicon nitride as a main component. When silicon nitride reacts with chlorine,
Since a reactant having a low vapor pressure such as SiCl ₄ is generated and hardly reacts with a chlorine-based gas or plasma containing no oxygen, it exhibits excellent corrosion resistance to a chlorine-based gas.
From the viewpoint of thermal shock resistance and strength, it is necessary that at least the inside of the sintered body has a relative density of 90% or more, particularly 95%.

Since silicon nitride does not sinter alone, it has heretofore been a group 3A element of the periodic table such as a rare earth element,
Alkaline earth metal oxides such as MgO, Al ₂ O ₃ , Si
Densification is achieved by adding a sintering aid such as O ₂ . 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 chlorine-based gas,
Silicon nitride is excellent in corrosion resistance because it is composed of a chemically stable compound having a covalent bond itself, but is inferior in corrosion resistance depending on the sintering aid and components mixed as impurities.
The grain boundary phase is locally etched or easily reacts with the gas.

Therefore, according to the present invention, in order to reduce the content of the rare earth compound and maintain the sinterability to the extent that corrosion resistance is not impaired, Al ₂ O ₃ , Si
It is important to add the O _2. That is, β-silicon nitride is used as a main phase, and rare earth elements are converted into oxides (RE ₂ O
₃ ) 0.1 to 3% by weight, preferably 0.5 to 2% by weight
And aluminum is 1 to 5 in terms of oxide (Al ₂ O ₃ ).
Wt%, preferably 2-4 wt%, and excess oxygen
1-6% by weight ₂ equivalent (SiO _2), preferably 2 to 4
% And Al ₂ O ₃ / RE ₂ O ₃ is 1 to
6, preferably 2 to 4 and SiO ₂ / RE ₂ O ₃ of 2
It is important that the total amount of other cationic impurities is within a range of from 0.1 to 15, preferably from 4 to 10, and not more than 0.1% by weight.

Here, the amount of excess oxygen is obtained by subtracting the amount of oxygen combined with the rare earth element and Al contained in the sintered body in a stoichiometric composition from the total amount of oxygen in the silicon nitride sintered body. Most of the remaining oxygen amount is the unavoidable oxygen amount in the Si ₃ N ₄ raw material or SiO ₂ added intentionally.
The oxygen inside.

The reason for limiting the composition of the sintered body to the above range is as follows.
When the rare earth element is 0.1% by weight or less, when the alumina is 1% by weight or less, or when the excess oxygen amount (SiO ₂ ) is 1% by weight or less, the sinterability deteriorates, This is because dense porcelain cannot be obtained and a large amount of particles are generated in the plasma. When the rare earth oxide is 3% by weight or more, or when the alumina is 5% by weight.
If it is more than the above, or if the excess oxygen amount (SiO ₂ ) is 6
If the content is not less than% by weight, the corrosion resistance deteriorates. If the ratio is out of the above range, the sinterability deteriorates and the corrosion resistance deteriorates.

The rare earth elements in the present invention include Y, Ce, La, Yb, Er, Lu, Dy, Nd,
Sm, Gd and the like can be mentioned, and among them, Yb is most suitable because it can be densified with a small amount of addition. Also, N
When cationic impurities such as a, Ca, Mg, Fe, Cr, and Ni are mixed as particles into a semiconductor manufacturing apparatus, they may adversely affect the characteristics of the semiconductor or may cause grain boundaries with respect to the sintered body. In order to promote erosion, the total amount thereof in terms of metal is 0.1% by weight or less, particularly 0.0% by weight.
It is necessary that the content be 5% by weight or less.

The silicon nitride-based corrosion-resistant member of the present invention is manufactured by the following method. First, as a starting material, N
A silicon nitride powder is prepared in which the total amount of cationic impurities such as a, Ca, Mg, Fe, Cr, and Ni is 0.1% by weight or less. This raw material powder can be used in either α-type or β-type having an average particle diameter of 2 μm or less and an impurity oxygen amount of 0.5 to 2.0% by weight.

When the total amount of cationic impurities in the silicon nitride raw material powder exceeds 0.1% by weight, a low-melting grain boundary phase containing impurities at a high concentration is generated and exposed to a chlorine-based corrosive gas or plasma. When used for an extended period of time in an environment, the grain boundary phase component inside the sintered body easily diffuses and moves toward the surface of the member, so that erosion proceeds inside the sintered body and reduces corrosion resistance, Adversely affect

Next, in the silicon nitride raw material powder, 0.1 to 3% by weight of a rare earth element oxide in terms of oxide, and 1 to 5% by weight of aluminum in terms of oxide (Al ₂ O ₃ ), Excess oxygen is 1 to 6% by weight in terms of SiO ₂ (SiO ₂ ), Al ₂ O ₃ / RE ₂ O ₃ is 1 to 6, and SiO ₂ / R
Add and mix so that E ₂ O ₃ is in the range of 2 to 15.

In order to improve the density of the sintered body, these powders or aggregates made of these powders are pulverized by a known powder mixing method such as a ball mill to an average particle size of 3 μm or less, preferably 2 μm or less. It is desirable to do.

The mixed powder is formed into a desired molding means, for example,
It is formed into an arbitrary shape of a corrosion resistant member by a die press, a cold isostatic press, an injection molding, an extrusion molding or the like, and is fired.
The firing is performed at 1700 to 1800 ° C., preferably 1750 to 1800 ° C. in a non-oxidizing atmosphere such as nitrogen containing SiO gas.
It is desirable to carry out in a temperature range of ° C.

As the sintering method, normal pressure calcination, hot pressing, nitrogen gas pressure calcination, hot isostatic pressure calcination, etc. can be adopted. However, normal pressure calcination is preferred from the viewpoint of cost and sintering of large products. According to such a sintering method, it can be easily applied to a large member having a complicated shape, and a member having high corrosion resistance can be efficiently manufactured.

By the above-mentioned firing, a sintered body having a relative density of 90% or more is obtained. In the case where the sintered body has a low density and a large number of pores, the contact area with the gas or the plasma increases and the consumption speed increases. In particular, the relative density is preferably 95% or more. The obtained sintered body is subjected to appropriate grinding,
Finish the product with the specified dimensions.

In order to enhance the corrosion resistance, it is desirable that the surface which directly contacts the plasma has a surface roughness (Ra) of 1 μm or less, preferably 0.1 μm or less.

[0030]

EXAMPLE An experiment for evaluating the corrosion resistance to specific plasma was carried out below. First, a sintering aid was added and mixed at a ratio shown in Table 1 with respect to α-type silicon nitride powder having an average particle diameter of 0.7 μm and a cation metal impurity amount other than silicon of 200 ppm,
After being formed, it was baked at 1750 ° C. for 5 hours in a nitrogen atmosphere. The amount of SiO ₂ contained in the table is the total amount of excess oxygen contained in the raw material and the added silica powder.

For the obtained sintered body, first, the density of the silicon nitride based sintered body was measured by the Archimedes method, and the relative density (%), which was a ratio to the theoretical density, was calculated. Then, the surface roughness (R) of the surface that directly contacts the plasma
Grinding and mirror finishing were performed so that a) became 0.1 μm or less.

Next, the above sintered body was subjected to BCl ₃ (100 sccm) using an RIE plasma etching apparatus.
Was exposed at room temperature to the presence of particles on the sintered body. Etching conditions are pressure 4P
a, RF output was 1.8 kW, and plasma irradiation time was 240 hours. The presence / absence of particles is detected by using laser scattering to detect irregularities on the surface of the wafer and using a particle counter for silicon wafers that can count the shape and number of irregularities. The number of particles of 0.3 μm or more per 8-inch wafer Are shown in Table 1.

[0033]

[Table 1]

As is clear from the results in Table 1, the amount of the sintering aid was smaller than the composition range of the present invention, or the amount of Al ₂ O ₃ /
Sample No. ₂ having large RE ₂ O ₃ and SiO ₂ / RE ₂ O ₃ .
In 6, 10, 20, 22, and 25, the density of the sintered body does not increase, and 3000 or more particles are generated, which is not usable. Further, the amount of the sintering aid is larger than the composition range of the present invention, or Al ₂ O ₃ / RE ₂ O ₃ , SiO ₂ / RE ₂ O
Sample No. ₃ is small. In Nos. 8, 12, 18, and 24, although the density of the sintered body is high, the corrosion resistance is reduced, and 3000 or more particles are generated, which is not usable. Further, the sample No. 3 in which the total amount of other cationic impurities exceeded 0.1% by weight. Even with 27, although the density of the sintered body is high, the corrosion resistance is reduced, and 3000 or more particles are generated, which is not usable.

On the other hand, within the scope of the present invention,
The generation of particles on the silicon wafer was controlled to 1000 or less, and no deposition of reaction products was observed on the sample surface itself.

[0036]

As described in detail above, according to the present invention,
By using a silicon nitride sintered body with a limited sintering aid composition as a member exposed to chlorine-based corrosive gas or plasma, it is possible to obtain a material that suppresses the reactivity with plasma and generates less particles. And corrosion resistance in a severe chlorine-based corrosive atmosphere can be improved.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yumiko Ito 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Inside the Kyocera Research Institute (72) Inventor Koji Kusaka 1-3-7 Honcho, Nirasaki-shi, Yamanashi Bunkodo Building 2F Kyocera Corporation Yamanashi Sales Office (72) Inventor Yasuhiro Nakabori 1-1-1, Yamashita-cho, Kokubu-shi, Kagoshima Kyocera Corporation Kagoshima Kokubu Plant F-term (reference) 4G001 BA03 BA04 BA08 BA32 BA71 BA73 BB03 BB04 BB08 BB32 BB71 BB73 BD36 BD37 BD38 BE33 4G075 AA30 AA53 BC06 BC10 CA02 CA47 FB04 FC09

Claims (6)

[Claims] A surface which is in direct contact with a corrosive gas or plasma has a main phase of β-silicon nitride, contains 0.1 to 3% by weight of a rare earth element in terms of oxide (RE ₂ O ₃ ), and contains aluminum. and 1 to 5% by weight in terms of oxide (Al ₂ O _3), wherein each of excess oxygen at a ratio of 1-6 wt% in terms of SiO ₂ (SiO _2), and the _{Al 2 O 3 / RE 2 O} 3 1 to
6. A sintered body having a SiO ₂ / RE ₂ O ₃ within the range of 2 to 15 and a total amount of other cationic impurities of 0.1% by weight or less and a relative density of 90% or more. Characteristic silicon nitride corrosion resistant member. 2. The silicon nitride-based corrosion-resistant member according to claim 1, wherein the rare earth element oxide is Yb ₂ O ₃ . 3. The silicon nitride-based corrosion-resistant member according to claim 1, wherein the plasma is chlorine plasma. 4. A method for producing a corrosion-resistant member having a surface which is in direct contact with a corrosive gas or its plasma, wherein a silicon nitride raw material powder having a total amount of cationic impurities of 0.1% by weight or less is mixed with a rare earth element. In oxide conversion (RE ₂ O ₃ )
And 0.1 to 3% by weight of aluminum, in terms of oxide (A
l ₂ O ₃ ), 1 to 6% by weight of excess oxygen in terms of SiO ₂ (SiO ₂ ), and Al ₂ O ₃
/ RE ₂ O ₃ is 1 to 6 and SiO ₂ / RE ₂ O ₃ is 2
A method for producing a silicon nitride-based corrosion-resistant member, comprising molding and firing a powder within the range of from 15 to 15. 5. The method for producing a silicon nitride-based corrosion-resistant member according to claim 4, wherein the rare earth element oxide is Yb ₂ O ₃ . 6. The method according to claim 4, wherein the firing is normal pressure firing.