JPH11283973A - Manufacture of electrode for plasma etching apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrode for plasma etching device, which has a superior corrosion resistance with respect to etching active gas which is used favorably to a reaction ion-etching device which is used in an etching process for manufacturing a semiconductor device or the like. SOLUTION: This method of manufacturing this electrode is a method in which an SiO2 material is reacted with an Al film, until the component of an SiO2 is substantially spent remaining in the SiO2 material, by dipping the SiO2 material into the molten Al film to convert the SiO2 material into an Al-Al2 O3 composite material, and after this composite material is subjected to form work, the surface of the composite material is subjected to dry-etching treatment to remove an Si film, which exists on the surface of the composite material and is liberated by the reaction, then the surface of the composite material is subjected to anodic oxidation treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrode for a plasma etching apparatus, and more particularly, to a method for manufacturing a semiconductor device. The present invention relates to a method for manufacturing an electrode for a plasma etching apparatus having excellent corrosivity.

[0002]

2. Description of the Related Art In etching in a semiconductor manufacturing process, a parallel plate type plasma apparatus is often used. In this apparatus, a pair of parallel plate type electrodes are arranged in an etching chamber, a wafer is mounted on the lower electrode, and a high frequency power supply is applied to one of the electrodes, for example, the electrode on which the wafer is mounted. And the other opposing electrode is grounded, and a high-frequency voltage is applied while a reactive gas such as a CF ₄ or O ₂ mixed gas is flowed under reduced pressure in this chamber to generate a reactive gas plasma, The wafer is etched by a synergistic effect of the generated neutral active species and gas ions. Conventionally, an aluminum electrode having a large number of gas blowing holes is used as a counter electrode of the wafer mounting side electrode, and the surface of the aluminum electrode is subjected to anodizing treatment (alumite treatment) for improving corrosion resistance. Is given.

In this etching process, Si,
When etching a material such as SiO ₂ or Si ₃ N _4, a fluorine-based gas such as CF ₄ or NF ₃ is used. These gases are activated in the plasma to become neutral active species and reactive gas ions, and perform an etching action on the wafer. At the same time, these neutral active species and reactive gas ions are applied to the electrodes. It also acts on the electrodes, damaging the electrodes. In particular, the aluminum oxide film layer formed by the anodizing treatment (alumite treatment) generally has a thickness of several tens of μm to a maximum of 100 μm, and has a large number of fine holes and fine holes on the surface of the oxide film. There was a defect, and it could not be said that it had sufficient corrosion resistance to the erosion of the fluorine-based gas active species. Therefore, there has been a strong demand for an electrode that has sufficient corrosion resistance to fluorine-based gas plasma, prevents contamination of the processed wafer due to material deterioration, and can withstand long-term use.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to have a sufficient corrosion resistance to corrosive gases containing plasma active species such as neutral active species and reactive gas ions, and to obtain such extremely strong corrosion. It is an object of the present invention to provide a method for manufacturing an electrode for a plasma etching apparatus having excellent durability and capable of stably performing the function as an electrode for a long period of time even in an inert gas atmosphere.

[0005]

According to the present invention, SiO 2 is used.
₂ By immersing the material in molten Al,
React with Al until the O ₂ component no longer remains,
After converting to an Al ₂ O ₃ composite material and shaping the composite material, the surface thereof is dry-etched to remove Si generated by the reaction present on the surface and then anodized. A method for manufacturing an electrode for a plasma etching apparatus is provided. In the method of the present invention, Si which is a constituent element of the SiO ₂
l to replace the Al with the SiO ₂ material.
converted into 1-Al ₂ O ₃ composite material and the resulting Al-Al
By anodizing the surface of the ₂ O ₃ composite material, a surface layer having a dense structure composed of an alumina and aluminum anodic oxide coating layer having excellent corrosion resistance to fluorine-based plasma is formed on the surface. Is a remarkable feature.

The so-called alumite coating layer obtained by anodizing the surface of a metallic aluminum material has a large number of fine pores (10 ⁹ to 10) perpendicular to the base metal (aluminum) on the surface.
10 ¹¹ cm ^-2 ), and has a coating structure in which a very thin bowl-shaped layer called a barrier layer is present at the bottom of the pores. The thickness of the entire alumite coating layer is usually about several tens of μm,
It is extremely thin, at most about 100 μm, and its structure is not necessarily dense and has many fine defects.
It further increases due to thermal shock and the like. The so-called sealing treatment of sealing the alumite film having such fine defects by immersing it in boiling water or bringing it into contact with pressurized steam is also generally performed. However, in this sealing treatment, the alumina component is hydrated with the boiling water or pressurized steam to form an alumina hydrate, and the pores are filled by volume expansion of the coating at this time to seal the pores. It is easy to cause problems such as hydration deterioration during the use period of, and it is difficult to say that it has sufficient corrosion resistance against strong corrosive gas erosion. In addition, once the coating is broken and the erosion starts, the erosion progresses rapidly because the inside is made of extremely reactive aluminum metal, and immediately deteriorates to such an extent that it cannot withstand use.

On the other hand, in the method of the present invention, first, an SiO ₂ molded body such as quartz glass is immersed in a high-purity Al melt under reduced pressure or an inert gas atmosphere, and Al and SiO
_{And 2} until substantially no SiO ₂ component remains, thereby obtaining an Al ₂ O ₃ —Al— (Si) composite material. In this reaction, Si reduced by the reaction of Al with SiO ₂ dissolves in the Al melt and gradually shifts to the melt phase as the immersion time elapses, so that when the reaction is completed, it remains in the composite material. The amount of Si contained is relatively small. The composite material thus obtained has a three-dimensional structure in which a solid solution of Al and a small amount of Si is densely filled between an Al ₂ O ₃ matrix having a three-dimensional network structure.

Next, the Al ₂ O ₃ -Al- (Si)
After removing a small amount of free Si present on the surface of the composite material by dry etching and washing the treated surface, the composite is transferred to an electrolytic cell such as a sulfuric acid electrolytic cell and subjected to anodizing treatment and sealing treatment to perform plasma etching. Electrode. The electrode for a plasma etching apparatus obtained by the method of the present invention has an aluminum anodic oxide film formed on an Al ₂ O ₃ matrix exposed portion occupying most of the surface and an Al solid solution present on the surface. Since it is composed of a part, the surface structure is dense and shows excellent corrosion resistance to fluorine plasma. Further, even if the oxide film surface layer is damaged and broken for some reason, a solid solution of Al and a small amount of Si is formed into a fine island shape between Al ₂ O ₃ matrices having a three-dimensional network structure. Since the structure is densely packed and present, the erosion is limited only to the solid solution portion such as Al, and does not further expand. Therefore, the electrode for a plasma etching apparatus manufactured by the method of the present invention has advantages such as an increase in electrode life and a reduction in particles generated from the electrode, and a reduction in maintenance cost and an improvement in element yield in a device manufacturing process. Have.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in more detail. In the method of the present invention, first, as illustrated in FIG. 1, for example, under reduced pressure or under an inert atmosphere,
The plate-shaped SiO ₂ material 1 for an electrode is immersed in a molten metal aluminum 2 melted in a crucible 3 to react SiO ₂ with Al. In FIG. 1, reference numeral 4 denotes a heater for heating the crucible 3. At this time, as shown by the following equation (1), 4Al + 3SiO ₂ → 2Al ₂ O ₃ + 3Si (1) The substitution reaction between Si and Al in SiO ₂ constituting the material proceeds. In the method of the present invention, this reaction is completed by continuing the immersion until substantially no SiO ₂ component of the raw material remains. As the reaction progresses after the immersion time, Si reduced by Al is generated in the raw material, but Si is dissolved in the Al melt, and most of the Si elutes from the raw material to the melt phase side. Therefore, at the time of completion of the reaction, the SiO ₂ material has a structure structure of Al—Al in which a solid solution of Al and a very small amount of a solid solution of Si are densely filled between an Al ₂ O ₃ matrix having a three-dimensional network structure. Converted to ₂ O ₃ composite.

Next, the Al—Al ₂ O ₃ composite material is pulled up and taken out, and the metal Al adhering to the surface is removed. The method of removing the metal Al adhered to the surface is not necessarily limited to this. For example, the composite material is heated at a temperature 30 to 200 ° C. higher than the temperature of the Al melt.
It is preferable to use a method of performing heat treatment under reduced pressure or an inert gas atmosphere to volatilize excess Al adhering to the composite and remove residual strain generated in the composite.

Thereafter, the plate-like Al-Al ₂ O ₃ composite material is processed into a predetermined electrode shape by grinding, electric discharge machining or the like. Al-Al by grinding and electric discharge machining
_As the electrode shape processing of the ₂ O ₃ composite material 10, for example, FIG.
As shown in the figure, a large number of small through holes 13 for etching gas outflow are densely formed in the center portion 11 of the disk surface or the like.
In the peripheral portion 12 of the board, screw holes 14 for attachment to a plasma etching apparatus are formed at predetermined intervals.

Then, the surface of the shape-processed material electrode plate is released by dry etching such as downflow etching using a mixed gas of CF ₄ and a small amount of O _{2 in} a discharge chamber separation type dry etching apparatus. Remove Si. Further, the surface of the material electrode plate is washed with, for example, a 5% aqueous solution of sodium hydroxide to which a trace amount of sodium gluconate is added to remove the impurity layer on the surface, and sufficiently washed with pure water.

Thereafter, as shown in FIG. 2, for example, the substrate is transferred to an electrolytic cell such as a sulfuric acid electrolytic cell, and the surface of the material electrode plate is subjected to anodizing treatment. The anodic oxidation treatment on the surface of the Al-Al ₂ O ₃ composite in the form of an electrode plate is performed in substantially the same manner as the usual so-called alumite treatment of aluminum metal. That is, as shown in FIG. 2, for example, in an acidic solution 7 such as sulfuric acid, oxalic acid, phosphoric acid, etc., an Al—Al ₂ O ₃ composite is used as an anode 5 and a platinum plate or the like as a cathode 6, and current is applied between both electrodes ( Power supply 9)
The Al metal portion on the surface of the composite is oxidized to form an aluminum oxide film on the surface. Incidentally, in FIG.
Is an air supply pipe provided for performing the above-mentioned treatment while blowing air and stirring.

In the present invention, when sulfuric acid is used as the bath solution, an aqueous sulfuric acid solution having a concentration of 10 to 15% by weight is preferably used at a temperature of 20 to 25 ° C. and an Al ³⁺ concentration of 3 to 1
It is preferable to perform the electrolytic oxidation treatment under the conditions of 0 g / l and a current density of 0.7 to 1.5 A / dm ² for about 60 to 250 minutes under air blowing and stirring. Thereafter, the anodized product is sufficiently washed with water, and the surface oxide film is sealed by boiling water treatment or steam treatment to obtain an electrode for a plasma etching apparatus.

In the present invention, the SiO ₂ material used for producing the electrode of the plasma etching apparatus is a high-purity SiO ₂ material.
The use of quartz glass is preferred from the viewpoint that a disk-shaped material having a certain size can be easily obtained and that it can be easily processed into a predetermined shape. However, other SiO ₂ materials may be used. However, it is preferably amorphous in consideration of the reactivity with Al. The purity of the material is preferably as high as possible because the material is used for manufacturing an electrode of a plasma etching apparatus, and it is preferable to use a material having an impurity concentration of 100 ppm or less. The metal Al used as the molten Al also has a purity of 99%.
As described above, it is preferable to use high purity aluminum of 99.9% or more. The reaction between the SiO ₂ material and the Al melt is usually performed at 900 to 1200 ° C, preferably 1000 to 1150 ° C. Reaction temperature 90
If the temperature is lower than 0 ° C., the material becomes brittle and dense, and cracks are likely to occur. On the other hand, when the reaction temperature is 120
When the temperature is higher than 0 ° C., the material tends to be deformed, and it is difficult to obtain a material having a desired shape.

As described above, in the method of the present invention, the reaction is terminated when substantially all of the raw material SiO ₂ has been converted to Al ₂ O ₃ . Conversion A obtained by this reaction
The composition of the 1-Al ₂ O ₃ composite is such that Al is 20 to 35.
% And Al ₂ O ₃ are preferably in the range of 65 to 80%. When Al is less than 20% (when Al ₂ O ₃ is large), the electric resistance as an electrode becomes too high, and unreacted substances such as internal pores and SiO ₂ tend to increase, which is not preferable. On the other hand, when Al is more than 35% (Al ₂
When O ₃ is small), the ratio of the exposed area of Al on the surface of the composite is increased, and the area ratio of the anodic oxide film formed on the surface is increased, so that the defect tends to increase, and the corrosion resistance is slightly reduced. . It is preferable that the amount of free Si produced by the reducing action of Al is as small as possible. However, if it is 4% or less, there is no significant effect on the performance as an electrode including corrosion resistance, and it is acceptable.

[0017]

[Example] "Production of electrode" SiO ₂ disk (Φ8 inch,
(5.5 mm thick) was supported on a crucible in the reactor shown in FIG. 1 and preheated, and the metal Al in the lower crucible was heated and melted. When the temperature of the molten Al reaches about 1050 ° C., the SiO ₂ material is immersed in the molten Al,
₂ and Al were reacted. Almost all of the Si in the raw material SiO ₂ was replaced with Al, and when the reaction was completed (reaction time: 5 hours), the molten Al was pulled out of the bath and removed to remove metal Al adhering to the surface. Then, Al-Al
_The disc material converted into the ₂ O ₃ composite material was formed into a target electrode shape by forming a gas permeable hole and a screw hole, and performing surface grinding and polishing. The Al—Al ₂ O ₃ composite processed into this electrode shape was set in a discharge chamber-separated dry etching apparatus, and CF ₄ was set at 150 sccm.
Dry etching (downflow etching) was performed using a mixed gas of 75 sccm of O ₂ to remove free Si on the surface. Subsequently, it is immersed for about 1 minute while rocking in a mixed aqueous solution of 5% sodium hydroxide and 0.1% sodium gluconate at a liquid temperature of 50 ° C. and etched to completely remove fluoride and oils and fats adhered to the surface. Was.

Next, this composite material electrode was set in a sulfuric acid electrolytic cell as shown in FIG. 2 and anodizing treatment was performed under the conditions shown in Table 1 below. At this time, the anodic oxidation treatment was performed at a sulfuric acid concentration of 10% by weight, a temperature of 20 ° C., and Al ³⁺
1, the current density was set to 1.0 A / dm ^2, and an electrolysis treatment was performed for 100 minutes while blowing and stirring with air. After sufficiently washing the obtained electrode with water, it was subjected to sealing treatment with boiling water to obtain an electrode for a parallel plate type plasma etching apparatus of the present invention.

[Etching Experiment] The above-mentioned electrode manufactured by the method of the present invention and a conventional alumite-treated aluminum electrode (thickness of anodized aluminum layer: 10 μm) were each set in a parallel plate type plasma etching apparatus, and their performances were compared. The test was performed. The apparatus used for the experiment was a parallel plate type reactive ion etching apparatus, which caused the electrodes to discharge under the following experimental conditions (reactive ion etching conditions).
Particles deposited on the surface of the dummy wafer were measured using a wafer surface inspection device.

“Reactive ion etching conditions” Gas: CF ₄ + H ₂ mixed gas (hydrogen gas mixing ratio 15 vol%) 40 sccm High frequency: 13.56 MHz 1 kw Gas pressure: 25 mTorr Wafer used: Φ6 inch glassy carbon dummy wafer Etching time: 100min / pc (sheet) x 25pc (sheet)

As a result of measuring the particles on the dummy wafer, the number of particles of the product of the present invention (the surface anodized Al—Al ₂ O ₃ composite material) was 34, on the average of 25 dummy wafers. The number of particles of the conventional product (alumite-treated aluminum) was 124. As described above, it was found that the product of the present invention generated less dust from the electrode than the conventional product, and hardly deteriorated during use of the electrode.

[0022]

As described above, the electrode for a plasma etching apparatus manufactured by the method of the present invention has a high-purity A having a three-dimensionally uniform alumina matrix skeleton.
Since the surface of the l-Al ₂ O ₃ composite is anodized, the probability of defects occurring in the oxide film is extremely low as compared with the conventional product, and the corrosion resistance to fluorine plasma,
Has excellent durability. Accordingly, the semiconductor device has a long life and can be used for a long period of time, and generates less particles, which contributes to an improvement in yield in a semiconductor manufacturing process.

[Brief description of the drawings]

FIG. 1 is a schematic view of a reactor for reacting a SiO ₂ material and molten Al used in the method of the present invention.

FIG. 2 is a schematic view of an anodizing tank used in the method of the present invention.

FIG. 3 is a plan view showing an example of a shape of an electrode for a plasma etching apparatus of the present invention.

[Explanation of symbols]

1 SiO ₂ material 2 metal aluminum melt 3 crucible 4 heater 5 anode 6 cathode 7 acid solution 8 air supply pipe 9 Power 10 Al over Al ₂ O ₃ composite material 11 board center 12 board peripheral portion 13 through hole 14 threaded bore

Claims (6)

[Claims] 1. A method of immersing a SiO ₂ material in molten Al until the SiO ₂ component substantially no longer remains.
After converting to an Al-Al ₂ O ₃ composite material by shaping the composite material, the surface of the composite material is dry-etched to remove Si generated by the reaction present on the surface, and then removed. A method for producing an electrode for a plasma etching apparatus, comprising anodizing the surface. 2. The method according to claim 1, wherein the SiO ₂ material is plate-shaped quartz glass. 3. The method according to claim 1, wherein a reaction temperature of the Al—Al ₂ O ₃ composite material reaction is 900 to 1200 ° C. Method. 4. The material composition of the Al—Al ₂ O ₃ composite material, wherein Al is in a range of 20 to 35% by weight and Al ₂ O ₃ is in a range of 65 to 80% by weight. A method for manufacturing an electrode for a plasma etching apparatus according to claim 3. 5. The method according to claim 1, wherein the anodic oxidation treatment is performed at a concentration of 10 to 15%.
The plasma etching apparatus according to any one of claims 1 to 4, wherein the plasma etching apparatus is performed at a temperature of 20 to 25 ° C in a sulfuric acid electrolytic bath using a weight% sulfuric acid solution while stirring by blowing air. Method of manufacturing electrodes. 6. The Al—Al ₂ O whose electrode shape has been processed.
₃ composites further after the anodic oxidation treatment, process for the preparation of a plasma etching apparatus for electrode according to any one of claims 1 to 5, characterized in that the boiling water sealing treatment.