JPH0794474A - High speed particle beam processing device - Google Patents

Abstract

PURPOSE:To ease a restriction on space charge generated in an ion acceleration region for obtaining a highly dense particle beam by establishing an electron source and an electron acceleration means in the latter part of an ion extracting means. CONSTITUTION:A microwave and a magnetic field are supplied to a quartz discharge tube 1 and supplied gas is turned into plasma. Further, a 2-sheet set electron accelerating group 4 and an ion accelerating electrode group 5 are set up inside the quartz discharge tube 1 for being separated into electron outgoing plasma 6 and ion outgoing plasma 7 by these electrode groups. Then, the potential of an electrode on the side coming in contact with electron outgoing plasma 6 of the electron accelerating electrode group 4 is made potential V3 lower than potential V1 of an electrode coming in contact with ion outgoing plasma 7. Thereby, electrons can be taken out from electron outgoing plasma 6 for distributing electrons to an ion accelerating region of the ion acceleraing electrode group 5. In this way, space charge due to ions inside the ion- accelerating region can be relaxed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high speed particle beam processing apparatus for performing surface treatment such as etching of semiconductor device materials.

The etching technique is a technique for irradiating the surface of a semiconductor device material with accelerated ions or neutral particles to induce a physical or chemical surface reaction to process the material surface into an arbitrary shape. . With this technique, fine processing is performed to form the wiring of an ultra-high integrated circuit.

[0003]

2. Description of the Related Art In a conventional apparatus, there are mainly two types of methods as means for accelerating incident ions on a sample to be processed. One is a method in which a high-frequency electric field is applied to a sample to be processed placed in plasma, and the potential of the sample to be processed is made lower than that of the plasma to accelerate and inject ions in the plasma to the sample to be processed. . The other is a method in which a flat plate-shaped electrode group having a plurality of minute holes is arranged so as to be in contact with plasma, and ions emitted from the minute holes accelerated by the electrode group are incident on a sample to be processed.

[0004]

In the conventional apparatus, when the ions are accelerated toward the sample to be processed, the potential near the ion emission surface in the acceleration region (between the ion sheath or the extraction electrode) is weakened by the space charge due to the ions. There was a problem that a sufficient amount of ion beam could not be extracted. This effect is particularly remarkable when the energy for extracting ions (corresponding to the extraction voltage) is relatively low as in etching.

[0005]

In the present invention, in order to solve the above problems, an electron source and an electron accelerating means are installed after the ion extracting means.

[0006]

By the above (means for solving the problem), the space charge due to the ions in the ion acceleration region and the ion flight region is accelerated from the electron source, neutralized by the extracted electrons, and the density of the extracted ions is increased. Realized reduction of ion beam divergence. By this action, the surface processing speed of the sample to be processed can be increased and the processing accuracy can be improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the basic structure of an apparatus according to an embodiment of the present invention. In the configuration shown in FIG. 1, the microwave generated by the microwave generation means 2 and the magnetic field generated by the magnetic field generation means 3 are supplied to the quartz discharge tube 1 to bring the gas introduced into the quartz discharge tube 1 into a plasma state. Also, in the quartz discharge tube 1, two pieces 1
An electron accelerating electrode group 4 and an ion accelerating electrode group 5 having a set of a plurality of micropores are provided, and the electrode group separates an electron extracting plasma 6 and an ion extracting plasma 7. The electrode used in this example was made of graphite.

Next, the operation will be described. First, a positive potential V ₁ is applied to the ion extraction electrode and the electron extraction electrode that are in contact with the plasma 7. This positive potential V ₁ causes plasma 7
Of the plasma potential Vp from V ₁
The value is higher (V ₁ + Vp). Next, the potential of the other ion accelerating electrode is set to the ground potential or a potential V ₂ lower than it, so that the ions in the plasma 7 are accelerated by the potential difference (V ₁ + V ₂ ) between the ion extracting electrodes, The sample 8 to be processed is irradiated. This state is similar to the conventional device. The potential distribution near the ion extraction electrode group 5 and the space charge due to the ions at this time are shown in FIG. Figure 2
Since the extracted ions are distributed in the ion acceleration region as shown in (a), a positive space charge 12 is generated in the ion acceleration region. The positive space charge 12 is somewhat weakened by the space charge 13 of low energy electrons in the plasma.
Therefore, the total space charge 14 of ions and electrons between the electrodes is as shown in FIG. Between the electrodes, the potential distribution 15 in the ion acceleration region changes as shown in FIG. 2A due to the space charge of the ions and the electrons as a whole, compared with the case where there is no space charge. As a result, the potential at the ion emission surface is weakened and the amount of extracted ions is limited. This phenomenon is called space charge limitation. In the region where the extraction ion current is restricted by the space charge restriction, the extraction current increases in proportion to the cube of the potential difference V between the extraction electrodes, as shown in "Equation 1". Where Jsi is the extraction current density, ε ₀ is the vacuum permittivity,
Z is the valence of the ions, e is the unit charge, mi is the mass of the ions, and V is the potential difference between the extraction electrodes. Further, the width of the ion sheath when the potential difference V between the extraction electrodes is set to ds, and d
And ds are assumed to have almost the same size.

[0009]

[Equation 1]

It can be seen that when the ions are extracted at a relatively lower energy than "Equation 1," the extraction ion current is particularly limited, and the ions cannot be extracted at a sufficient density. Therefore, in the present invention, the potential of the electrode of the electron accelerating electrode group 4 in contact with the electron extracting plasma 6 is set to a potential V ₃ lower than the potential V _{1 of the} electrode in contact with the ion extracting plasma 7. As a result, electrons can be extracted from the electron extraction plasma 6 and distributed in the ion acceleration region of the ion acceleration electrode group 5. Figure 2
It shows in (b). FIG. 2B shows a total space charge distribution 17 in the case where the space charges 16 due to accelerated electrons are added to FIG. 2A, and a potential distribution 18 resulting therefrom. FIG. 2B shows a case where the acceleration energy of electrons is equal to or more than the acceleration energy of ions. As shown in FIG. 2B, the accelerated electrons can distribute the electrons over a wide area within the ion acceleration area. In particular, when the acceleration energy is equal to or higher than the acceleration energy of the ions, it is possible to discharge the ions together with the ions from the ion acceleration electrode group 5 to the sample 8 to be processed. In this case, the space charge of the electrons not only relaxes the space charge limitation of extracting the ions, but also relaxes the space charge during flight of the ion beam and reduces the scattering of the ion beam. Due to the above effects, the space charge due to the ions in the ion acceleration region is relaxed, and even when the ions are extracted with relatively low energy, "Equation 2"
The ion beam can be extracted at a current density close to the saturated ion current density shown in. Here, Jpi is the saturated ion current density, ni is the plasma density, Z is the valence of ions, e is the unit charge, k is the Boltzmann constant, Te is the electron temperature, and mi is
Is the mass of the ion.

[0011]

[Equation 2]

In FIG. 3, the ion accelerating means is the sample 1 to be processed.
In this example, 9 is directly exposed to plasma 20 and a high frequency electric field is applied to the sample 19 to be processed by the high frequency electric field applying means 21. By applying a high frequency electric field, the potential of the sample to be processed 19 can be adjusted with respect to the plasma 20, and the ions can be accelerated by the electric field in the ion sheath formed at the boundary between the surface of the sample to be processed and the plasma 20. it can. In this case also, the space charge of the ions in the ion sheath weakens the potential distribution in the vicinity of the ion emission surface and limits the amount of extracted ions. Therefore, as in the embodiment shown in FIG. 1, by setting the electrode of the electron accelerating electrode group 22 in contact with the plasma 20 to a positive potential and the electrode in contact with the electron extracting plasma 23 to the ground potential or a potential lower than that, the electron extracting plasma 2 is generated.
Electrons are accelerated from 3 and can be distributed in the ion sheath, which is the ion acceleration region. The electrons weaken the positive space charge in the ion sheath, relax the space charge limitation, and irradiate the sample to be processed with a high-density ion beam. In the embodiment shown in FIG. 3, the magnetic field generated by the magnetic field generating means 24 and the microwave generated by the microwave generating means 25 were used to form the plasma. CHF is used as the gas to be introduced
₃ was used to etch the silicon oxide film on the surface of the processed sample 9.

FIG. 4 is an application of the embodiment shown in FIG. 1. In addition to the electron extraction plasma 30 and the ion extraction plasma 31, a radical supply plasma 33 is provided on the front surface of the sample 32 to be processed.
It is an example in the case of forming. The electron extracting plasma 30, the ion extracting plasma 31, and the radical supplying plasma 33 are generated by the same magnetic field generating means 34 and microwave generating means 35. Further, in this embodiment, a mixed gas of CHF ₃ and argon was used as a gas to be introduced, and the silicon oxide film on the surface of the sample 32 to be processed was etched. In the embodiment shown in FIG. 4, the reaction of the reactive radicals from the plasma 33 for supplying radicals on the surface of the sample 32 to be processed is assisted by the energy of the ion beam extracted by the electrode group 36 for ion acceleration to perform high-speed etching. . Also at this time, by supplying electrons to the ion acceleration region by the electron acceleration electrode group 37, the amount of extracted ions can be increased and the processing speed can be significantly increased for the reason described above.

In the embodiment shown in FIGS. 1 and 4, the sample to be processed is irradiated with accelerated ion beams. As shown in FIG. 5, a mesh-shaped charged particle removing electrode group 41 is provided on the front surface of the sample to be processed. By arranging them, the charged particles are blocked and the sample 42 to be processed can be processed only by neutral particles having no electric charge. A neutral particle beam is formed by causing an ion beam to fly in the gas phase to cause a charge exchange reaction with low-speed neutral particles in the gas phase. The processing using only the neutral particles has an effect of reducing damage such as deterioration of breakdown voltage when processing the insulating film.

6 is different from the embodiment shown in FIGS. 1, 3, 4 and 5 in the case where the electrons are supplied to the ion acceleration region by accelerating the thermoelectrons emitted from the filament 52 by the acceleration electrode 53. This is an example.

In the embodiments shown in FIGS. 1, 3, 4, 5, and 6, the case where a magnetic field and an electromagnetic wave in the microwave region are used for plasma formation is shown. However, it goes without saying that the effect of the present invention is the same even for plasma formed by a high frequency electric field in the radio frequency region.

In the above embodiments, the case where the high speed particle beam according to the present invention is directly applied to the sample to be processed for the surface treatment is described. However, it goes without saying that the present invention can also be applied to sputtering a specific material with the high-speed particle beam according to the present invention and depositing the scattered material on another substrate prepared elsewhere.

In the embodiments shown in FIGS. 1, 4, 5, and 6, the incident angle of the ion beam or the neutral particle beam to the sample to be processed is changed by changing the angle of the sample stand or the angle of the ion extracting electrode. By doing so, it becomes possible to adjust the processed shape by adding the function.

Further, in the embodiments described above, only the effect of relaxing the space charge limitation in the ion extraction of the present invention is described. However, by supplying an electron beam to the plasma for extracting ions with a similar configuration and adjusting the acceleration energy appropriately, the collision cross section of electrons and gas molecules in the gas phase can be increased, and the acceleration energy of the electrons The plasma density of the plasma for extracting ions can be adjusted by the current density. The density of the extracted ion beam can be increased by increasing the plasma density of the plasma for extracting ions. A specific example will be described with reference to FIG. Ion acceleration electrode group 5 from plasma 7 in FIG.
Therefore, when the ion beam is extracted, the current density of the ion beam is greatly influenced by the state of the plasma 7. In particular, the plasma density is an important parameter that determines the limit of the ion current that can be extracted. In the conventional configuration (the configuration in which the electron beam cannot be supplied to the ion extracting plasma), it is difficult to stably and arbitrarily adjust the plasma state of the ion extracting plasma (corresponding to the plasma 7 in FIG. 1). By irradiating the plasma 7 with an electron beam from the plasma 6 through the electron acceleration electrode group 4 according to the present invention, the gas molecules in the plasma 7 region are ionized and the plasma density in the region is supplied with gas pressure or microwave power. It is possible to change without changing the amount. The ionization probability of a gas molecule in a gas phase due to an electron beam increases as the energy of the electron beam increases in the range of about 20 (eV) to 1 (keV). Journal of Chemical Physics, Vol. 43, (1965) pp. 1464-147, examined by Rapp et al.
Page 9 (THE JOURNAL OF CHEMICAL
PHYSICS, Vol43 (1965) 1464
˜1479). Also, energy of several tens (eV) is required to extract the electron beam at a practical current density. From these, the electron beam energy is 30 (eV)
With the above, it is possible to efficiently cause ionization and increase the plasma density. Especially 100 (e
In the vicinity of V) to 300 (eV), the ionization efficiency is high and the amount of the electron beam that can be extracted is sufficient, which is efficient. In addition to the effect of relaxing the space charge limitation by the above effects, it is possible to increase the plasma density of the ion extraction plasma and improve the ion extraction characteristics independently of the plasma generation conditions such as the ion extraction voltage or gas pressure. Becomes In the above embodiments, the electron beam irradiation to the ion extracting plasma was described as being extracted from the plasma formed independently of the ion extracting plasma. However, the electron gun is arranged in the plasma generation region and is emitted from the electron gun. It goes without saying that the same effect can be obtained by using the electron beam.

[0020]

According to the present invention, the positive space charge in the ion acceleration region when extracting ions from the plasma is neutralized by the charge of the electrons from the electron accelerating means provided after the ion accelerating means, and the ion beam is extracted. The space charge limitation can be relaxed. As a result, the density of the high-density ion beam or the neutral particle beam formed by the charge exchange reaction of the ion beam can be improved, and the processing speed can be increased.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the principle of the present invention.

FIG. 3 is a diagram showing a configuration of an apparatus according to another embodiment of the present invention (No. 1).

FIG. 4 is a diagram showing a configuration of an apparatus according to another embodiment of the present invention (No. 2).

FIG. 5 is a diagram showing a configuration of an apparatus according to another embodiment of the present invention (No. 3).

FIG. 6 is a diagram showing the configuration of an apparatus according to another embodiment of the present invention (No. 4).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Quartz discharge tube, 2 ... Microwave generation means, 3 ... Magnetic field generation means, 4 ... Electron acceleration electrode group, 5 ... Ion acceleration electrode group, 6 ... Electron extraction plasma, 7 ... Ion extraction plasma, 8 ... sample to be processed, 9 ... waveguide, 10 ... sample stage, 11 ... plasma, 12 ... positive space charge, 13 ... low energy electron space charge, 14 ... ion and electron total space charge, 15 ... potential distribution , 16 ... Space charge due to accelerated electrons, 17 ... Synthetic space charge, 18 ... Potential distribution, 19
... Work sample, 20 ... Plasma, 21 ... High frequency electric field applying means, 22 ... Electron acceleration electrode group, 23 ... Electron extraction plasma, 24 ... Magnetic field generating means, 25 ... Microwave generating means, 26 ... Matching circuit, 27 ... Waveguide, 28 ... Sample stage, 29 ... Quartz discharge tube, 30 ... Electron extraction plasma, 31 ... Ion extraction plasma, 32 ... Work sample, 33 ... Radical supply plasma, 34 ... Magnetic field generating means, 35 ... microwave generation means, 36 ... ion acceleration electrode group, 37 ... electron acceleration electrode group, 38 ... waveguide, 39 ...
Quartz discharge tube, 40 ... Sample stage, 41 ... Electrode for removing charged particles,
42 ... Work sample, 43 ... Electron acceleration electrode group, 44 ... Ion acceleration electrode group, 45 ... Electron extraction plasma, 4
6 ... Plasma for extracting ions, 47 ... Plasma for supplying radicals, 48 ... Microwave generating means, 49 ... Magnetic field generating means, 50 ... Sample stage, 51 ... Quartz discharge tube, 52 ... Filament, 53 ... Accelerating electrode, 54 ... Ions Extraction plasma, 55 ... Ion acceleration electrode group, 56 ... Work sample,
57 ... Sample stage, 58 ... Quartz discharge tube, 59 ... Microwave generating means, 60 ... Magnetic field generating means, 61 ... Waveguide.

Claims (25)

[Claims] 1. An electron source and a means for accelerating the electron at a position on the plasma side with respect to the position of the means for forming plasma in a gas phase, a means for extracting ions from the plasma, and a means for extracting the ions. , When accelerating the ions by the means for extracting the ions, the space charge generated by the charge of the ions in the acceleration region of the ions is neutralized by the charge of the electrons extracted from the means for accelerating the electrons, A high-speed particle beam processing device characterized by forming a high-density particle beam by relaxing the space charge limitation. 2. A high-speed particle beam processing apparatus, wherein the plasma generating means according to claim 1 is composed of a magnetic field generating means and an electromagnetic wave generating means in a microwave region. 3. A high-speed particle beam processing apparatus, wherein the plasma generating means according to claim 1 is constituted by a high frequency generating means in a radio frequency region. 4. The means for extracting ions according to claim 1 is composed of two flat plate-shaped electrodes having a plurality of micropores.
High-speed particle beam processing equipment characterized by accelerating ions by the potential difference between electrodes. 5. The electron accelerating means according to claim 1 is composed of two flat plate-shaped electrodes having a plurality of fine holes, and the electrons are accelerated by a potential difference between the two electrodes. High-speed particle beam processing equipment. 6. A high-speed particle beam machining apparatus, wherein the flat plate-shaped electrode having a plurality of micropores according to claim 4 or 5 is made of graphite. 7. The plasma formed by the plasma forming means according to claim 2 or 3 is divided into two regions by the ion extracting and electron accelerating means according to claim 4 or 5, and both ions and electrons are generated by the same plasma source. The high-speed particle beam processing apparatus according to claim 1, wherein the high-speed particle beam processing apparatus is drawn out. 8. One of the two flat plate-shaped electrodes having a plurality of micropores according to claim 4 or 5 defines the plasma potential, and the other electrode defines the plasma potential. The high-speed particle beam processing apparatus according to claim 1 or 7, wherein ions or electrons are accelerated by setting a potential different from that. 9. The high-speed particle beam processing apparatus according to claim 1, wherein an electron gun is arranged in plasma for extracting ions, and the electrons emitted from the electron gun are accelerated and irradiated to the ion extracting means. 10. The high-speed particle beam processing apparatus according to claim 1, wherein the extracted ion beam causes a charge exchange reaction with neutral particles in a gas phase to cause neutralization. High-speed particle beam processing equipment characterized by using particle beams. 11. A plasma is formed on the front surface of the ion extracting means according to claim 7, and the surface of the sample to be processed is treated with the reactive particles and the ion beam from the plasma or the neutral particle beam according to claim 10. The high-speed particle beam processing apparatus according to claim 1, characterized in that. 12. The high-speed particle beam processing apparatus according to claim 1, wherein a mesh-shaped electrode group for removing charged particles is arranged on the front surface of the sample to be processed. 13. The high-speed particle beam processing according to claim 1, wherein the energy of the electrons with which the ion extraction electrode is irradiated is ½ or more of the extraction energy of the ions. apparatus. 14. The high-speed particle according to claim 1, wherein the plasma forming gas is a mixture of argon and a chlorofluorocarbon gas, and the sample surface to be processed is etched. Wire processing equipment. 15. The high-speed particle according to claim 1, wherein the gas that forms plasma is a mixture of argon and a halogen-based gas, and the surface of the sample to be processed is etched. Wire processing equipment. 16. The high-speed particle beam processing apparatus according to claim 1, wherein the gas forming the plasma is a halogen gas alone, and the sample surface to be processed is etched. . 17. The plasma forming gas is a rare gas simple substance, and the sputter etching of the surface of the sample to be processed is performed, and any one of claims 1 to 9 or 11 to 13 is provided. The high-speed particle beam processing apparatus according to any one of the above. 18. The structure according to claim 1, wherein the ion beam or the neutral particle beam according to claim 10 can be incident on the surface of the sample to be processed at an arbitrary angle. The high-speed particle beam processing apparatus described in. 19. A sample to be processed is exposed to plasma, and a high frequency electric field is applied to the sample to be processed to accelerate ions incident on the sample to be processed, and the plasma is directed toward the sample to be processed in the plasma. A means for accelerating electrons therein, any one of claims 1 to 3, any one of claims 5, 6, 8 or 9 or claim 13 to 1
The high-speed particle beam processing apparatus according to any one of 7. 20. A specific material is sputtered with the high-speed particle beam according to claim 1, and the scattered specific material is deposited on another substrate to form a film of the specific material. High-speed particle beam processing equipment characterized by performing. 21. In the electron accelerating means according to claim 1, by making the acceleration energy of the electrons equal to or more than the acceleration energy of the ions, the electrons are distributed not only in the ion acceleration region but also in the ion flight region, A high-speed particle beam processing apparatus characterized by reducing ion beam divergence due to space charge in the ion flight region. 22. An electron source and a means for accelerating electrons at a position on the plasma side with respect to the position of the means for forming plasma in a gas phase, a means for extracting ions from the plasma, and a means for extracting the ions, When extracting an ion beam from the plasma by the means for extracting the ions, the density of the ion beam for extracting the plasma density of the plasma is increased by irradiating the plasma with an electron beam by the electron source and a means for accelerating the electrons. A high-speed particle beam processing device characterized by being adjustable. 23. A high-speed particle beam processing apparatus, wherein the energy of an electron beam with which the plasma for extracting ions according to claim 22 is irradiated is 30 eV or more. 24. The plasma formed by the plasma forming means according to claim 22 is divided into two regions by the ion extracting means and the electron accelerating means according to claim 22, and both ions and electrons are generated by the same plasma source. High-speed particle beam processing device characterized by pulling out. 25. An electron gun is arranged in the plasma for extracting ions, the electrons emitted from the electron gun are accelerated, and the plasma for extracting ions is irradiated.
The described high-speed particle beam processing apparatus.