JP2001007082A - Electrode plate for plasma etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode plate for plasma etchings, where the quantity of its wastage is small to make usable it over a long term and the generation of particles is reduced, by making specific the value of its opened porosity, and by forming it out of a silicon carbide sintered body having the main crystal structure of α-SiC of 6H-type. SOLUTION: The value of the opened porosity of an electrode plate for plasma etchings is 10-40% and is made of a silicon carbide sintered body, having a main crystal structure of 6H-type of α-SiC. The silicon carbide having the main crystal structure of 6H-type of α-SiC is used by the reason that 6H-type of α-SiC is especially superior in its plasma resistance. With the existence of the opened porosity, the base body of the electrode plate is made lightweight to improve its easy usability, and its many holes are prevented from clogging due to the reaction products of the plasma etching. The value of the opened porosity is 10-40%, preferably 15-30%. When the value of the opened porosity is very much smaller than 10%, the porous effect of the electrode plate is reduced, and its inner impurities are hard to be removed from it sufficiently, when cleaning it. When the value of the opened porosity is very much larger than 40%, the mechanical strength of the electrode plate becomes low for a base material, and its plasma resistance is also reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode plate for a plasma generator and a method for manufacturing the same, and more particularly to an electrode plate for a plasma generator used for plasma etching of a semiconductor wafer and the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of a semiconductor integrated circuit (hereinafter, simply referred to as a semiconductor device) increases, the size of a device to be integrated is reduced to a submicron region.
Higher precision micromachining technology is required. In a semiconductor device, a thin film of metal, semiconductor and / or insulator is basically formed on the entire surface of a substrate, and the thin film is selectively etched and removed according to a resist mask pattern.
The process of forming (wiring) and the like is repeatedly performed. In this etching process, dry etching using an etching gas is used instead of wet etching using a chemical solution because processing accuracy is high and fine processing is possible. Etching is mainly used.

Specifically, the dry etching step is typically performed by a parallel plate type plasma etching apparatus or the like in which two upper and lower electrodes face each other. A gas generated by photo-resisting a silicon thin film formed by CVD or sputtering on a silicon wafer in accordance with a circuit pattern, setting it on one of its electrodes, and discharging and decomposing the etching gas introduced into the chamber. The portion where the resist is not masked is etched by plasma to form a fine circuit pattern.

[0004] Under these circumstances, the required performance of an electrode plate for plasma etching has become more sophisticated even in the process of etching a semiconductor wafer. Particularly, during etching, a part of the electrode plate is peeled, and the consumption of the electrode plate is accelerated, or a peeling substance drops on the wafer surface as particles to contaminate the wafer and hinder the formation of a predetermined pattern. Has become.

As materials for the electrode plate for plasma etching, metals such as aluminum and carbon have been conventionally used. However, since these materials cause contamination of semiconductor wafers, these materials have recently been mainly used for polycrystalline silicon or single crystal. Silicon is used. However, silicon has a problem in that plasma resistance is not sufficient, and erosion by plasma gas is apt to occur, and the electrode plate is quickly consumed.

In order to solve these problems, it has been proposed to use a silicon carbide (SiC) sintered body as an electrode plate.

For example, Japanese Patent Application Laid-Open No. Sho 62-10047 discloses that β
Type silicon carbide is used as an electrode plate.
The silicon carbide having the type crystal structure basically has insufficient plasma resistance, and JP-A-62-109317 and JP-A-1-242411 only describe the use of silicon carbide. No consideration is given to what kind of crystallinity is used in the first place.

Japanese Patent Application Laid-Open No. Hei 3-162593 discloses the use of an electrode plate made of β-type silicon carbide by a CVD method containing a small amount of impurities.
It is difficult to manufacture an electrode plate having a thickness of m or more, which is disadvantageous in terms of cost.

On the other hand, as described in JP-A-5-304114, when a β-type silicon carbide film is formed on the surface of a carbon base material such as a graphite material to prevent the scattering of graphite powder, the β-type Since the silicon carbide film is gradually etched by the plasma gas, it has been difficult to use it for a long time.

Further, in Japanese Patent Application Laid-Open No. 07-211700, an electrode plate is used in which the pores of a porous silicon carbide body are filled with silicon. However, in the case of the porous body containing silicon as described above, there has been a problem that the silicon portion is selectively etched and the generation of plasma becomes unstable.

As described above, the conventional plasma etching electrode made of a porous silicon carbide sintered body has not been sufficiently satisfactory in characteristics.

Further, the miniaturization of semiconductor devices is continually progressing, and at present, the minimum line width of wiring is generally 0.2 μm or less. For this reason, extremely fine dust (a few tenths to one tenth of the line width) on the device surface
Even if so-called particles are attached, pattern irregularities such as disconnection are easily caused, and directly affect the reliability and yield of the device.

[0013] Due to such a situation, in the conventional electrode plate made of a silicon carbide sintered body, a problem that a portion having poor plasma resistance falls off and particles are generated has been solved promptly and more completely. It has been demanded.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrode for plasma etching which can be used for a long time with little consumption, generates less particles, and can generate inexpensive and stable plasma. An object of the present invention is to provide a board and a method for manufacturing the board.

[0015]

According to the present invention, (1)
An electrode plate for plasma etching having gas introduction holes, characterized in that it has an open porosity of 10 to 40% and has a crystal structure of 6H-type sintered silicon carbide mainly composed of α-SiC. An electrode plate for plasma etching is provided.

Further, according to the present invention, there are provided (2) a molding step of molding a mixture of silicon carbide powder and a binder, a sintering step of sintering the obtained molded body, and The method for producing an electrode plate for plasma etching according to any one of claims 1 to 3, further comprising a perforation step of forming a gas introduction hole.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The electrode plate for plasma etching of the present invention is basically made of a silicon carbide sintered body mainly composed of α-SiC having an open porosity of 10 to 40% and a crystal structure of 6H type. Become.

One of the features of the present invention is to use silicon carbide mainly composed of α-SiC having a crystal structure of 6H type. Because it is excellent.

As the silicon carbide mainly composed of 6H-type α-SiC, the content of 6H-type α-SiC in the silicon carbide sintered body is preferably 70% by weight or more. . The more preferable content of the 6H-type α-SiC is 80% by weight or more, and the more preferable content is 90% by weight or more.

In the present invention, 6
In addition to H-type α-SiC, the following α-SiC or β-S
iC may be contained.

For example, as α-SiC, 4H type, 8
H type, 15R type, 21R type, 27R type, 33R type, 51
R-type, 75R-type, 84R-type and 87R-type are exemplified.

The silicon carbide sintered body of the present invention is a porous body having an open porosity of 10 to 40%. The diameter of the pore is not particularly specified, but it is desirable that the pore has an average pore diameter of about 10 to 800 μm, preferably about 20 to 600 μm.

The presence of these open pores makes it possible to reduce the weight of the substrate to make it easier to handle and to prevent clogging by reaction products.

The open porosity is 10 to 40%, preferably 15
３０30%. If the open porosity is much smaller than this, the effect of making it porous is small, and it is difficult to sufficiently remove impurities inside during washing.If it is too large, the strength as a base material will be low, and Plasma resistance decreases.

The electrode plate of the present invention is obtained, for example, as follows. That is, the average particle size is 0.2 to 20 μm
m, preferably about 0.5 to 10 μm, 6H type α-S
iC is used as raw material SiC powder, and a binder such as acrylic resin-based aqueous emulsion, PVA (polyvinyl alcohol), methylcellulose, carboxymethylcellulose, wax and a solvent such as water or alcohol or ether are added and kneaded. And

If the average particle size of the raw material SiC powder is much larger than this, the force of bonding the individual particles at the contact point in the sintered body is weak, and when exposed to the plasma gas, the particles tend to fall off. If the particle size is too small, the weight of the sintered body increases and the plasma resistance deteriorates.

It is desirable to use a raw material SiC powder having a total content of metal elements of 40 ppm or less, preferably 30 ppm or less, more preferably 20 ppm or less, and most preferably 10 ppm or less.
In the present invention, most of the metal elements in the sintered body are derived from the raw material SiC powder, so that the total of the metal elements contained in the sintered body is reduced to 40 pp.
m or less. The metal element referred to here is
Fe, Cu, Mg, V, Ni, Mn, Na, Al, Ca
Is a harmful element which is taken into a wafer and may cause a decrease in insulation resistance, a decrease in withstand voltage of SiO ₂ , a pn junction leak failure, and the like for a semiconductor device. In the present invention, at least Fe, Cu, Mg, V, Ni, Mn, Na, Al, Ca
Can be reduced to 40 ppm or less.

High-purity raw material S having a low metal element content
There are various production methods for the iC powder, and the Acheson method conventionally used may be used. For example, αC produced by the method described in JP-A-6-298515 may be used.
-SiC is more preferably used. In this method, a carbonaceous raw material such as graphite powder or carbon black and metallic silicon are charged into a silicon carbide crucible and the pressure is 0.2 mm.
After heating at a degree of vacuum of Hg or less to disperse impurities in the starting material, the temperature is raised and the temperature is maintained at 2,000 to 2,200 ° C. in an inert gas atmosphere such as argon or helium. This is to synthesize α-SiC having a high purity.

As the raw material silicon carbide powder, β-SiC powder synthesized by vapor phase synthesis or reaction of silica and carbon can be used. β-SiC is
It is easy to synthesize a higher purity than α-SiC. When β-SiC is used as a raw material, it can be converted to α-SiC by setting the firing temperature to 2,100 ° C. or higher.

If the purity of the raw material SiC powder is not sufficient, the raw material powder is washed with a mixed acid of hydrofluoric acid and nitric acid and pure water to elute and separate impurities in the powder, thereby increasing the purity. be able to.

This molding slurry is molded by a known molding means such as casting, extrusion molding, injection molding or the like using a porous mold such as a gypsum mold to form a molded body, which is preferably dried and demolded. After the binder, it is fired in a non-oxidizing atmosphere to obtain a porous SiC sintered body. Further, the kneaded slurry is dried and granulated, and this is 500 to 2,000 kg.
It is also possible to carry out cold isostatic pressing (rubber pressing) or dry press molding at a pressing pressure of about / cm ² .

The non-oxidizing atmosphere is an atmosphere under a vacuum or reduced pressure, or an inert gas atmosphere such as argon and helium.
Under this atmosphere, the molded body is heated at a temperature of 1,500 to 2,300 ° C, preferably 1,500 to 2,100 ° C, more preferably 1,500 to 2,000 for 10 to 600 minutes.
Preferably 120-500 minutes, more preferably 300
A sintered body is obtained by heating and firing for about 400 minutes. As a furnace for sintering, a commonly used resistance heating furnace is suitably used.

Here, sintering means that each particle of the raw material SiC powder is diffused through its contact point or contact surface (
Mass transfer), is a process of forming a new interface while deforming each other, by heating to the above temperature,
A sufficient diffusion process of atoms is achieved, and the formation of this new interface reduces the surface area of the particles and reduces the free energy of the system.

The sintered body obtained as described above is used as raw material S
It is considered that the filling voids of the iC particles are basically supported, and a porous sintered body is formed. That is, as described above, the starting material particles have a particle size of 0.2 to 20 μm,
Preferably, those having an open porosity of about 10 to 40% are obtained by using those having a diameter of 0.5 to 10 μm.

The sintered body is formed into a desired shape suitable for an electrode plate by a known cutting means for ceramics. The shape may be a square shape, but a disk shape having a diameter of 100 to 300 mmφ, preferably 150 to 250 mmφ and a thickness of 1 to 5 mmt, preferably 2 to 4 mmt.

The electrode plate of the present invention is obtained by forming gas inlet holes in a sintered body having the obtained shape as described above by a perforation process.

In order to uniformly etch the semiconductor wafer, the supplied etching gas must be uniformly ejected from the gas introduction holes. For this purpose, introduction holes having the same diameter and high density are formed. It is desirable to use a shaped electrode.

Accordingly, the gas introduction hole is preferably of a small cylindrical shape, and has a diameter of 0.1 in order to smoothly and uniformly eject and supply the etching gas into the chamber and to prevent the occurrence of strong discharge. It is desirably about 1.0 to 1.0 mmφ, preferably about 0.2 to 0.7 mmφ. In addition, it is desirable that a large number of introduction holes are formed on substantially the entire surface of the substrate, and are uniformly arranged in a shape such as a triangular arrangement, a staggered arrangement, and a dust arrangement.

The density of gas introduction holes is 1 to 1 / cm ^2.
00, preferably 1 to 50, more preferably 1 to
About 30 pieces are formed. If it is less than this, it is difficult to jet out the etching gas uniformly, and if it is more than this,
Not only is processing difficult, but the strength of the substrate is extremely reduced, which is not preferable.

In the drilling step for forming the introduction hole, the drilling may be performed by drilling with a drilling machine and mechanically drilled, or non-mechanically drilled using a laser processing machine, an ultrasonic processing machine or the like. Good.

In the present invention, it is preferable that the sintered body is heated again after the step of piercing the gas introduction holes.

The heat treatment of the perforated sintered body is performed at 1,500 to 2,300 ° C., preferably 1,500 to 2,100 ° C. under vacuum or reduced pressure or in an atmosphere of an inert gas such as argon or helium. , More preferably 1,5
Under a temperature condition of 00 to 2,000 ° C., 10 to 600 minutes, preferably 120 to 500 minutes, and more preferably 300 to 500 minutes.
It is desirable to carry out for about 400 minutes.

By subjecting the perforated sintered body to the heat treatment in this manner, the generation of particles during plasma etching can be extremely reduced or substantially eliminated. Presumably, this is due to the local shear energy or vibration energy applied for drilling during the formation of the gas inlet in the drilling process, due to the bonding force of the crystal grains at or near the inner surface of the hole, that is, the grain boundary of the crystal. It is considered that the bonding force is weakened, and the weakened grain boundary portion is etched and peeled off when exposed to the plasma gas, thereby causing generation of particles. Therefore, it is presumed that the heat treatment of the perforated sintered body can re-sinter the weakened grain boundary portion particularly on the inner wall of the hole, thereby enhancing the bonding force of the crystal grains.

Thus, the electrode plate of the present invention, which has been subjected to the heat treatment after the perforation, has an excellent effect that plasma resistance is sufficiently enhanced and almost no particles are generated during etching.

The specific resistivity of the electrode plate is preferably 10 Ω · cm or less, more preferably 1 Ω · cm or less, for stably generating plasma. In order to control the specific resistivity, an Al film or the like may be deposited on the surface of the electrode plate.

The plasma etching electrode plate according to the present invention has a maximum surface roughness Rm as its surface smoothness.
ax is desirably 5 μm or less. Rmax is 5
If the thickness exceeds μm, the number of powder particles that fall off and adhere to the wafer surface increases because the projections on the rough surface are not consumed evenly when the part is consumed due to the impact of ions generated by the plasma. Not preferred.

Note that Rmax is a value measured according to JIS B-0601 using an electronic surface roughness meter.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. The characteristics of the sintered body were measured by the following methods.

Open porosity: Underwater gravimetric method (Archimedes method)
) Crystal structure: X-ray diffraction Heavy metal content concentration: ICP (inductively coupled plasma) emission spectroscopy Specific resistivity: by silver electrode formation and 4 terminal method.

(I) Production of SiC Sintered Body Example 1 An α-SiC powder having an average particle diameter of 2 μm and having a 6H-type crystal structure was prepared. Then, a 4% by weight aqueous PVA solution was 3.0% by weight based on the silicon carbide powder,
3% by weight of wax was added, wet-mixed, and then dried and granulated.

Next, this granulated powder was filled into a rubber press mold having an outer diameter of 250 mm and a thickness of 10 mm, and
Press molding was performed at a pressure of kg / cm ² to obtain a molded body.

The molded body was fired under vacuum at 1,800 ° C. for 2 hours. The obtained sintered body was cut into a disk shape with an outer diameter of 200 mm and a thickness of 3 mm,
A sintered body base for forming an electrode plate was obtained.

The disk-shaped substrate was subjected to a drilling step by laser processing to form gas introduction holes. The diameter of the gas introduction holes was 0.5 mm, and the number was 4 per 1 cm ² .

Subsequently, the substrate after the perforation step was placed under vacuum for 1,
Heat treatment was performed at 900 ° C. for 2 hours.

The open porosity of the obtained substrate was 25%. The crystal structure was 6H-type α-SiC 100%. The total metal element content was 32 ppm (
The metal element content of the raw material α-SiC powder was 33 ppm. ). The specific resistivity was 0.3 Ω · cm.

[Comparative Example 1] 3 mm thick containing boron
A gas introduction hole having a diameter of 0.5 mm was provided in the single-crystal silicon substrate in the same manner as in Example 1 to obtain an electrode plate for plasma etching.

[Comparative Example 2] The average particle size was 2.
Example 1 except that a 5 μm β-type silicon carbide raw material was used.
An electrode plate for plasma etching was manufactured by the same manufacturing method as that described above.

(II) Etching Test Next, the electrode plates prepared in Examples and Comparative Examples were respectively disposed in a processing chamber (chamber) as upper electrode plates of a parallel plate type plasma etching apparatus. A semiconductor wafer for an etching test was placed on a lower electrode plate with the surface to be etched facing upward. In this semiconductor wafer, an oxide film is formed on a Si substrate, and a photoresist having a predetermined pattern is applied on the oxide film.

This plasma etching apparatus is operated at a pressure of 1 To.
rr, and CHF in the processing chamber with Ar as a carrier.
Supply ₃ gases, 13.6M from high frequency power supply to upper electrode
By applying a high frequency electric field of Hz, the oxide film was etched according to the pattern of the resist.

The processing time for one etching is 80
The number of etchings (the number of times that uniformity of the etching rate can be maintained) was measured as the life.

After etching one wafer under the same conditions as described above for 2 hours, the surface of the wafer was
The above number of particles was measured. The number of particles was measured by irradiating the surface of the wafer with a laser beam and scanning the entire surface of the wafer. Table 1 shows the measurement results of the number of etching times and the number of particles.

[0062]

[Table 1]

[0063]

The electrode plate for plasma etching of the present invention is formed of a silicon carbide sintered body mainly composed of 6H-type α-SiC having an open porosity of 10 to 40% and a crystal structure having a particularly high covalent bond. Therefore, the plasma resistance is excellent, and the life of the electrode plate can be extended.

Further, in the electrode plate for plasma etching of the present invention, since the sintered body is preferably heat-treated and stabilized after the step of piercing the gas introduction holes, generation of particles is substantially prevented.

Continued on the front page (72) Inventor Masaaki Takada 5-6-1 Umai, Takasago-shi, Hyogo Asahi Glass Co., Ltd. F-term (reference) 4G001 BA22 BB22 BB71 BC12 BC13 BC17 BC54 BC71 BC73 BD22 BE02 BE33 4K057 DD03 DE06 DM02 DM10 DN01 5F004 BA04 BB13 BB32 DA16 DA23

Claims (6)

[Claims] 1. An electrode plate for plasma etching having gas introduction holes, having an open porosity of 10 to 40% and a crystal structure of 6H-type silicon carbide sintered body mainly composed of α-SiC. An electrode plate for plasma etching, characterized in that: 2. The heat treatment of the silicon carbide sintered body after the gas introduction holes are formed.
The electrode plate as described. 3. The electrode plate according to claim 1, wherein the total of the contained metal elements is 40 ppm or less. 4. A molding step of molding a mixture of silicon carbide powder and a binder, a sintering step of sintering the obtained molded body,
The method for producing an electrode plate for plasma etching according to any one of claims 1 to 3, further comprising a perforation step of forming gas introduction holes in the obtained sintered body. 5. The method for manufacturing an electrode plate according to claim 4, further comprising a heating step of further heating the sintered body after the perforating step. 6. The method for producing an electrode plate according to claim 4, wherein the heat treatment is performed at 1,500 to 2,300 ° C.