JPH1022273A - Rotary electrode used for high-efficiency processing method by high-density radical reaction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent secondary electrons from being emitted from the surface of the rotary electrode, stably maintain low-temperature plasma which is electrically neutral, and stabilize processing characteristics by forming an insulator film on the surface of the rotary electrode. SOLUTION: A spherical rotary electrode 1 has an insulator film 16, which has superior anticorrosiveness against neutral radicals (mainly, halogen radicals) and small dielectric loss at high frequencies, on its spherical surface. A columnar rotary electrode 1, has a similar insulator film 16 formed on its columnar surface. Thus, the insulator film is formed on the rotary electrode to prevent secondary electrons from being emitted out of the electrode surface. Therefore, the low-temperature plasma which is electrically neutral can stably be maintained and the processing characteristics can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating electrode used in a high-efficiency processing method by a high-density radical reaction, and more particularly to a semiconductor or a conductor such as silicon single crystal or an insulator such as glass or ceramic having defects or heat. The present invention relates to a rotating electrode suitable for carrying out a high-efficiency processing method by a high-density radical reaction that can be processed with high accuracy and high efficiency without introducing a deteriorated layer.

[0002]

2. Description of the Related Art A conventional dicing method using a diamond wheel is used for cutting a silicon single crystal or the like. Since this processing principle is based on the brittle fracture caused by fine cracks, there is no crystallographic controllability of the processing surface, and deep damage equivalent to the finished processing thickness is always given, and the cutting is performed in this way. When semiconductor devices are manufactured using wafers, the yield is poor,
In addition, the electrical performance is reduced, and this is one of the factors that limit the limit of the degree of integration. This is all the case for the processing of various functional materials.

Accordingly, the present inventor has disclosed in Japanese Patent Application Laid-Open No. 1-1258.
As disclosed in Japanese Patent Publication No. 29, neutral radicals of a reaction gas by high-density plasma generated by an electrode to which a high frequency is applied are supplied to a processing surface of a workpiece to form a processing surface with the neutral radicals. Volatile substances generated by radical reactions with atoms or molecules are vaporized and removed, and high precision is achieved without introducing defects or thermally altered layers in semiconductors such as silicon single crystals or conductors or insulators such as glass or ceramics. There has already been proposed a distortion-free precision processing method (plasma CVM method) capable of processing into a uniform shape. Where CVM
Is an abbreviation for Chemical Vaporization Machining.

That is, a work and an electrode are arranged in an atmosphere gas containing a reaction gas, and a high-frequency voltage is applied between the work and the electrode to generate neutral radicals based on the reaction gas in the vicinity of the electrode. It is. At this time, when the processing electrode is a wire electrode, the workpiece is cut or grooved. When the processing electrode is a flat electrode, the workpiece is smoothed or mirror-finished. The transfer processing for transferring the shape to the workpiece can be performed.

[0005] When cutting a workpiece, it is effective to use a wire electrode. However, in a cutting process using a normal wire electrode, a sufficient amount of reactive gas is introduced into a cutting groove formed in the process. Cannot be supplied to the electrode, the input power to the electrode is low, and in mirror polishing using a flat electrode having a wide area and a smooth surface, the reaction gas cannot be sufficiently supplied to the central portion in the processing gap. ,
At that portion, the density of neutral radicals becomes low. as a result,
In the case of cutting, the processing speed decreases with the progress of the processing, and in the case of mirror finishing, unevenness in the processing amount occurs due to the difference in the processing speed between the peripheral portion and the central portion of the electrode.

Therefore, the present inventor has proposed a cutting method using a flat gas supply nozzle which can be inserted into a machining groove (Japanese Patent Laid-Open No.
162523) and a processing method in which a gas supply hole is provided in a support holding a processing electrode (Japanese Patent Laid-Open No. 4-33763).
No. 5, JP-A-5-96500, JP-A 6-1
No. 68924) and a processing method in which a gas supply means is provided on the processing electrode itself and a reaction gas is forcibly supplied to a processing gap between the processing electrode and the workpiece (Japanese Patent Laid-Open No. Hei 4-24661).
No. 84, JP-A-5-234942, JP-A-6
No. 85059), and a maximum processing speed of several tens of μm / min has been achieved. This processing speed is a value far exceeding common sense of conventional plasma dry etching,
Industrially, it is not enough to cut a workpiece having a large wall thickness or to polish a large area.

[0007]

The processing speed is greatly related to the density of neutral radicals in the vicinity of the processing portion of the workpiece, that is, the concentration of the reactive gas for generating the neutral radicals and the input power. It is speculated that the reason why the processing speed could not be significantly improved by any of the conventional methods was that the supply of the reaction gas and the exhaust of the used gas were insufficient, and the limit value of the input power was low. Is done. The reason that the supply of the reaction gas and the exhaustion of the used gas are insufficient is that the plasma CVM according to the present invention has a very high gas atmosphere pressure of 1 atm or more and a processing gap of usually 10 to 2 atmospheres.
It is thought that this is because the gas is so narrow as 00 μm, and the viscous resistance of the gas is large. Further, the reason why the limit value of the input power is low is that the electric field concentrated portion of the processing electrode is heated and is thermally damaged. For example, when cutting using a wire electrode in a gas atmosphere of 1 atm, the concentration of the reaction gas (SF ₆ ) is 1 to several percent, and the input power is about 40 W / c.
m is the limit and the processing speed achieved by it is 2
0 to 30 μm / min. In addition, when reactant gas is ejected from the gas supply nozzle or gas supply hole, there is a disadvantage that the density of the reactant gas varies in density and the machining amount is partially different, and a truly uniform machined surface cannot be obtained. Was inherent.

[0008] These problems have been solved by rotating the rotating electrode at a high speed. That is, by rotating the rotating electrode at high speed, the atmosphere gas is entrapped on the rotating electrode surface to form a gas flow crossing the processing gap, thereby increasing the density of neutral radicals in the processing gap and greatly increasing the processing speed. At the same time, the discharge of volatile substances generated by the radical reaction is promoted and a new reaction gas can always be supplied. Further, the outer peripheral portion of the rotating electrode moves at a high speed with respect to the processing progress portion. The concentration of high-frequency power is not limited to one location of the rotating electrode, but always moves and is air-cooled, so the limit value of input power is increased, thereby increasing the high-frequency power supplied to the rotating electrode and generating neutral radicals Efficiency could be improved.

However, the increase in the limit value of the high-frequency power supplied to the rotating electrode causes a new problem that the plasma becomes unstable and the plasma temperature rises. In other words, since the rotating electrode is made of metal, the ions, which are charged particles in the plasma, collide with the metal surface and emit secondary electrons, so that the electron density in the plasma becomes excessively large compared to the ion density. It is extremely difficult to maintain a neutral state. When the electron density in the plasma becomes excessive, in the case of high-pressure plasma, it shifts to arc discharge, which is a local dielectric breakdown, and tends to fall into an uncontrollable state. It causes thermal damage.

In view of the above situation, the present invention is intended to solve the problem by preventing secondary electrons from being emitted from the surface of a rotating metal electrode and generating an electrically neutral and low-temperature plasma. It is used for high-efficiency processing method by high-density radical reaction, which can stabilize processing characteristics by stably maintaining and can dramatically increase the limit value of input power and increase processing speed. The point is to provide a rotating electrode.

[0011]

SUMMARY OF THE INVENTION According to the present invention, there is provided a rotating electrode provided in a gas atmosphere containing a reactive gas and an inert gas and a processing gap of a workpiece while maintaining a processing gap. By rotating the electrode at a high speed and entraining the gas on the surface of the rotating electrode to form a gas flow crossing the processing gap, a high frequency voltage is applied to the rotating electrode to generate plasma in the processing gap, and to generate a plasma based on the reaction gas. Generates a neutral radical, vaporizes and removes a volatile substance generated by a radical reaction between the neutral radical and an atom or molecule constituting a processing portion of the workpiece, and removes the rotating electrode and the workpiece. A rotating electrode used in a processing method in which processing is performed by relatively displacing, and an insulator having high corrosion resistance to neutral radicals is provided on at least a surface corresponding to a plasma generation region. By configuring the rotating electrode used in high-efficiency machining method due to the high density radical reaction by forming a film, we tried to solve the aforementioned problems.

Here, by forming an insulating film on the surface of the rotating electrode, even if ions in the plasma collide with the surface of the rotating electrode, the insulating film prevents secondary electrons from being emitted. An electrically neutral state is maintained, so that low-temperature plasma can be stably maintained.

The insulator film is a ceramic film or an ethylene tetrafluoride resin film, and the material of the rotating electrode is aluminum;
Preferably, the insulator film is an alumina film formed by alumite treatment.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The high-efficiency processing method using a high-density radical reaction according to the present invention generates activated reactive radicals (free radicals) in the vicinity of a processing portion of a workpiece. Utilizing a radical reaction (free radical reaction) between neutral radicals and atoms or molecules constituting the workpiece, the generated volatile substances are vaporized and removed, and the rotating electrode and the workpiece are relatively moved. Based on the principle of processing, the shape of the rotating electrode, especially the shape of the electric field concentrating part that directly contributes to the processing, cutting processing, polishing processing, numerical control processing of arbitrary shape, dicing processing, and even shape Transfer processing and free-curve cutting can be performed. The radical in the present invention is a concept in plasma physics (plasma etching, plasma CVD, etc.), and is a broad concept including excited ones in addition to those having unpaired electrons.

Here, as a method of generating radicals, plasma dry etching has conventionally been carried out by using plasma which can be easily generated by electric discharge at a vacuum degree of about 1 Torr or less (10 ⁻³ to 1 Torr). I have. Since the purpose of plasma dry etching is to remove only the surface layer of the workpiece, the processing speed does not matter so much. However, the processing speed is very important in the processing intended for the present invention, and the neutral radical The aforementioned low-density plasma having a low density cannot be used. For example, 5 inches (about 12 inches in diameter)
Considering the cutting of a silicon wafer of 7 mm), a processing speed of 100 μm / min requires 21 hours, and a processing speed of 1 mm / min requires 2.1 hours. A processing speed of at least several hundred μm / min is required.

The processing speed depends not only on the magnitude of the high frequency power supplied to the rotating electrode, but also on the type of neutral radical, ie, the type of reactive gas, the type of inert gas for diluting it, and Since it largely depends on the material of the workpiece, it is necessary to select the optimum reaction gas and inert gas according to the workpiece. This reaction gas is excited in the plasma generated by the input of high-frequency power to generate neutral radicals. More specifically, in a gas atmosphere containing a reaction gas and an inert gas of 0.1 to 10 atm, preferably 1 atm or more, the rotating electrode and the workpiece are provided with a predetermined processing gap, A high frequency voltage is applied to the rotating electrode to generate plasma, and neutral radicals based on the reaction gas are generated in the plasma. The generation efficiency of neutral radicals based on the reaction gas in the plasma also depends on the type of inert gas constituting the plasma. For example, when the workpiece is silicon single crystal or quartz glass, SF ₆ is suitable for the reactive gas, and He is suitable for the inert gas. Other reactive gases include fluorine-based CF ₄ and chlorine-based Cl ₂ , CCl ₄ , PCl.
₅ and other inert gases such as Ne, Ar
Etc. Each of these gases may be used alone or in combination.

Therefore, assuming that the optimum types of the reactive gas and the inert gas are selected in accordance with the material of the workpiece, in order to increase the processing speed, how the reactive gas should be introduced into the processing area. It is important as a practical matter how to efficiently supply and exhaust a large amount and how to efficiently supply energy to the reaction gas.

Further, since the processing amount (depth) is proportional to the processing time when the processing speed is constant, a desired processing amount can be obtained by controlling the processing time. The processing time is determined by the stop time or the average stay time of the rotating electrode with respect to the processing progress portion of the workpiece.

Therefore, the gist of the present invention is to maintain a processing gap between a rotary electrode disposed in a gas atmosphere containing a reaction gas and an inert gas and a processing progress portion of a workpiece while maintaining a processing gap. By rotating the rotating electrode at a high speed and entraining gas on the surface of the rotating electrode to form a gas flow crossing the processing gap, a high frequency voltage is applied to the rotating electrode to generate plasma in the processing gap and generate a reaction gas. A neutral radical based on the volatile radical generated by a radical reaction between the neutral radical and an atom or a molecule constituting a processing part of the workpiece to be removed by vaporization, and the rotating electrode and the workpiece are removed. In a high-efficiency processing method by a high-density radical reaction that progresses the processing by relatively displacing, the surface corresponding to at least the plasma generation region of the rotating electrode, Forming a high corrosion resistance insulating coating on sexual radicals, to prevent the emission of secondary electrons, despite the increasing input power, it is to maintain the low temperature of the plasma stably.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be further described with reference to the embodiments shown in the accompanying drawings. FIG. 1 is a simplified explanatory view of a processing apparatus showing a typical embodiment of the present invention, in which 1 is a rotating electrode, 2 is a workpiece, 3 is a high-frequency power supply, 4 is a matching device, 5 is a feed drive mechanism, Reference numeral 6 denotes a rotary drive mechanism, 7 denotes a control device, and 8 denotes a gap measuring device.

An endless rotating electrode 1 and a workpiece 2 are disposed inside a chamber (not shown), and a reaction gas and an inert gas determined according to the material of the workpiece 2 are supplied thereto. Atmosphere gas containing is sealed or circulated. The pressure of the atmospheric gas is practically about 0.1 to 10 atm, and is preferably 1 atm or more from the viewpoint of processing efficiency. A machining gap G of 10 to several hundreds of micrometers is formed between the endless portion 9 of the rotary electrode 1 and the processing progress portion 10 of the workpiece 2.
From the power supply 3 via a matching device 4 for matching the impedance of the power supply 3 and the load.
By supplying high frequency power to the rotating electrode 1, a high electric field is formed in a processing gap G between the rotating electrode 1 and the processing part 10, and a plasma of an atmospheric gas existing in the region is generated. The reaction gas present in the region is excited and activated to generate neutral radicals, and volatile substances generated by a radical reaction between the neutral radicals and atoms or molecules constituting the workpiece 2 are vaporized to advance processing. It is removed from the part 10. The feed drive mechanism 5 maintains the processing gap G to cause the above-described radical reaction, and relatively shifts the rotary electrode 1 and the workpiece 2 to generate a volatile substance from the processing progress portion 10. Is vaporized and the processing proceeds.

Further, by rotating the rotary electrode 1 at a high speed by the rotary drive mechanism 6, the outer peripheral portion 9 contributing to the processing is moved at a high speed with respect to the processing advancing section 10 and gas is discharged on the rotary electrode surface 11. The entrainment forms a gas flow that crosses the processing gap G, and a large amount of a reactive gas and an inert gas for generating neutral radicals are supplied to a region between the outer peripheral portion 9 and the processing progress portion 10. In the illustrated example, the rotating electrode 1 has a flat disk shape and is suitable for cutting.

The high-frequency power source 3 and the feed drive mechanism 5
Are controlled by a control device 7 composed of a personal computer. Also, in order that the rotating electrode 1 and the workpiece 2 do not come into contact with each other and short-circuit the high-voltage circuit,
Alternatively, in order to maintain a predetermined machining gap G, the displacement of the support frame 12 of the rotary drive mechanism 6 and the workpiece 2 is detected by the gap measuring device 8 and the signal is sent to the control device 7 to send the signal to the feed drive mechanism. 5 is controlled. The feed drive mechanism 5 is a mechanism that appropriately combines an elevating stage (adjustment and maintenance of the processing gap G), an XY stage, and a rotary stage, and moves the workpiece 2 relative to the rotary electrode 3 three-dimensionally. It is made movable. The work piece 2 is made of an insulator 13 incorporated in the feed drive mechanism 5.
, And is held by a conductive mounting table 14 fixed to the base. When the workpiece 2 to be processed is an insulator or a semiconductor, high-frequency power is supplied between the rotating electrode 1 and the mounting table 14, or high-frequency power is supplied to the rotating electrode 1 and the mounting table 14 is By grounding, the input power is concentrated on the machining gap G. Mounting table 14 used for this purpose
Function as auxiliary electrodes. When the workpiece 2 is a conductor, high-frequency power can be supplied directly to the rotating electrode 1 and the workpiece 2. Although not shown, a gas containing a volatile substance generated by the radical reaction is exhausted from a suction port arranged near the rotating electrode, and the gas is passed through a filter to remove the volatile substance. It is also possible to re-enter the chamber.

In the present embodiment, the frequency of the high frequency power supply 3 is 150 MHz, and the power can be supplied by varying the power from several hundred to 1,000 W. Since the electric field intensity in the processing gap G is about 10 ⁶ V / m, the voltage applied to the outer peripheral portion 9 of the rotating electrode 1 is about 100 to 1,000 V, depending on the size of the processing gap G. It is. The rotation speed of the rotary electrode 1 depends on the peripheral speed (or diameter), but the larger the rotation speed, the higher the processing speed tends to be, and in this embodiment, 5,000 to 18,000.
It is processed at rpm.

The rotating electrode 1 shown in FIGS. 2 and 3 is suitable for polishing (smoothing). FIG.
Shows a shape in which the rotating shafts 15 and 15 are fixed to the spherical rotating electrode 1, and FIG. 3 shows a shape in which the rotating shafts 15 and 15 are fixed coaxially to the cylindrical rotating electrode 1. I have.

The spherical rotary electrode 1 shown in FIG. 2 has an insulator coating on its spherical surface which has excellent corrosion resistance to neutral radicals (mainly halogen radicals) and has a small dielectric loss at high frequencies. 16 (see FIG. 2).
(b)). In addition, in the cylindrical rotating electrode 1 shown in FIG. 3, an insulating film 16 similar to the above is formed on the cylindrical surface (see FIG. 3B). Here, it is sufficient if the insulator film 16 is formed on the surface of the rotating electrode 1 corresponding to the plasma generation region, but in this embodiment, it is formed on substantially the entire surface. Note that the plasma generation region corresponds to the outer peripheral portion 9 which is an electric field concentration portion. Further, the insulator film 16 may be formed so as to form a concave portion on the surface of the rotating electrode 1 and fill the concave portion.

As the type of the insulating film 16, ceramics such as alumina (Al ₂ O ₃ ) or zirconia (ZrO ₂ ) or a fluorine-based gas is often used as a reaction gas, so that AlF ₃ , MgF ₂ , CaF ₂ , NiF ₂
And the like, or a tetrafluoroethylene resin. Here, the ceramic coating is formed on the surface of the rotating electrode 1 with high accuracy by thermal spraying or the like. When the material of the rotating electrode 1 is aluminum, it is also preferable to form an alumina coating on the surface by alumite treatment.

[0028]

According to the rotary electrode used in the high-efficiency processing method by the high-density radical reaction of the present invention as described above,
By forming an insulator film on the surface of the rotating electrode,
Since the emission of secondary electrons from the electrode surface can be prevented, electrically neutral and low-temperature plasma can be stably maintained, and the processing characteristics can be stabilized. Therefore, the limit value of the high-frequency power that can be applied to the plasma can be drastically increased by the synergistic effect with the cooling effect obtained by the high-speed rotation of the rotating electrode,
An increase in processing speed can be realized. In addition, by using alumina or the like having excellent corrosion resistance to neutral radicals as the material of the insulator film, it is possible to improve the durability of the rotating electrode and prevent contamination of the surface of the workpiece by the electrode material. it can.

[Brief description of the drawings]

FIG. 1 is a simplified explanatory view of a processing apparatus showing an embodiment of the present invention.

2A and 2B show a spherical rotating electrode, wherein FIG. 2A is an overall perspective view of the rotating electrode, and FIG. 2B is a sectional view of the rotating electrode.

3A and 3B show a cylindrical rotating electrode, wherein FIG. 3A is an overall perspective view of the rotating electrode, and FIG. 3B is a sectional view of the rotating electrode.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 rotating electrode 2 workpiece 3 high-frequency power supply 4 matching device 5 feed drive mechanism 6 rotation drive mechanism 7 control device 8 gap measuring device 9 outer peripheral portion 10 processing progress portion 11 surface 12 support frame 13 insulator 14 mounting table 15 rotation shaft 16 Insulator coating

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H05H 1/30 H05H 1/30

Claims (4)

[Claims] 1. A rotating electrode is rotated at a high speed while maintaining a machining gap between a rotating electrode disposed in a gas atmosphere containing a reaction gas and an inert gas and a processing portion of a workpiece. A gas flow is formed across the processing gap by entraining gas on the surface of the rotating electrode, and a high-frequency voltage is applied to the rotating electrode to generate plasma in the processing gap, thereby generating neutral radicals based on the reaction gas. Volatile substances generated by the radical reaction between the neutral radicals and the atoms or molecules that make up the processing part of the workpiece are vaporized and removed, and the rotating electrode and the workpiece are relatively displaced to perform the processing. A rotating electrode used for a processing method that is advanced, wherein an insulating film having high corrosion resistance to neutral radicals is formed on at least a surface corresponding to a plasma generation region. Rotating electrode used for high-efficiency processing by high-density radical reaction. 2. The rotary electrode according to claim 1, wherein said insulator film is a ceramic film. 3. The rotating electrode used in the high-efficiency processing method by high-density radical reaction according to claim 1, wherein the material of the rotating electrode is aluminum, and the insulator film is an alumina film formed by alumite treatment. 4. The rotary electrode according to claim 1, wherein the insulator film is a tetrafluoroethylene resin film.