JPH06310473A - Fine machining device and method therefor - Google Patents

Abstract

PURPOSE:To expand the object to be machined of a fine machining device by laying out a pair of counter electrodes where voltage is applied so that electric field is applied to a material to be machined in the incidence direction of laser beams in a vacuum bath and the material to be machined can be electrified. CONSTITUTION:An object 1 to be machined is installed between counter electrodes 4 and 5 inside a vacuum bath 9 where pressure is reduced. Laser beams 2 are applied via a crystal window so that a machining hole can be formed on the surface of the object 1 to be machined by focusing light with a lens 3. The counter electrodes 4 and 5 are laid out so that electric field can be applied to the object 1 to be machined in the vertical direction which is the machining direction by a high-voltage power supply 6 and the laser beams 2 through the crystal window are applied to the object 1 to be machined from an opening 10 provided at the counter electrode 4, thus applying magnetic field in the vertical direction by a high magnetic field coil 7, thus preventing machining residues from remaining at a site to be machined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine processing technique, and more particularly to a technique for forming a fine trench hole with a high aspect ratio.

[0002]

2. Description of the Related Art Conventionally, microfabrication devices and methods include focused ion beam (FIB) microfabrication devices (Shiokawa, Journal of Precision Engineering 55/2/1989, P32-36) and micro electric discharge machines. There is. These are excellent methods for forming fine trench holes. The FIB device realizes sub-μm level processing.

[0003]

However, the FIB
Since the device is processed by ions, it is not possible to use an object to be processed which may cause crystalline damage due to the high-energy ions, and the shape of the processing hole is V-shaped, and a re-adhesion layer exists in the processing layer. Therefore, there are various problems. Further, in the case of fine electric discharge machining, the processing accuracy is determined by the thickness (thinness) of the electrode to be discharged, and the processing target is limited to a conductive object. In both cases, since the residue generated during processing is a neutral substance, it is necessary to use an air flow or a liquid flow to remove this residue from the processing site, but if the diameter of the processing hole is small, it will be difficult to remove it. Since the FIB device is in a vacuum, it is difficult to remove it by using a fluid, and redeposition occurs. Therefore, there is a problem that these restrictions are the limits of processing.

[0004]

In order to solve the above-mentioned problems, the structure of the first invention is a fine processing apparatus which causes laser ablation at a predetermined portion of a material to be processed by irradiation of a laser beam to perform processing. A vacuum chamber provided with a table for placing a processing material therein and having a transmission window for the laser beam, and arranged so that an electric field is applied to the material to be processed in the vacuum chamber in the incident direction of the laser beam. And a pair of counter electrodes to which a voltage is applied so that the material to be processed is charged. The structure of the first related invention is a magnetic field coil arranged so that a magnetic field is applied in the same direction as the incident direction, and electromagnetically induces charged particles generated from the material to be processed by laser ablation to form a processed portion. It is characterized by having a guiding means for moving from. The configuration of the second related invention is to apply a second magnetic field in a direction perpendicular to the transmission window,
It is characterized by having an excluding means for electromagnetically excluding the charged particles moved by receiving the induction so as not to hit the transmission window. The structure of the third related invention is characterized in that the vacuum chamber has a gas supply means for exposing at least one reactive gas to the material to be processed as needed during processing.

According to another aspect of the invention, the material to be processed is irradiated with a laser beam in a vacuum of a negative pressure or higher to cause laser ablation to scatter ionized charged particles, and the material to be processed is scattered. Voltage is applied so that the charged particles are electrically charged, and an electric field applied in the incident direction of the laser beam and a magnetic field applied in the same direction as the incident direction cause the charged particles scattered from the material to be processed to be electromagnetic. It is characterized in that the charged particles that have moved are further electromagnetically induced by a second magnetic field so as not to hit the quartz window into which the laser beam is introduced. The structure of the related invention of this invention is
It is characterized in that the laser beam irradiation is performed in a pulsed manner, and processing and residue removal are performed alternately.

[0006]

Function A laser beam made into an extremely fine beam by a condenser lens is irradiated through a quartz window to a predetermined portion of the material to be processed in a vacuum chamber having a negative pressure or more. At the same time, a voltage is applied to the counter electrode of the material to be processed to charge the surface. The material to be processed that has been irradiated with laser causes laser ablation, and atoms, ions, and electrons fly out from the processing site.
Since an electric field is applied to this area in the same direction as the laser beam direction, the ejected charged particles receive Coulomb force and make a motion determined by the electric field strength, charge amount, particle mass, etc. Moving. The atoms that have jumped out in neutrality are also ionized and moved away because they collide with the electrons that have jumped out.

[0007]

[Effects of the Invention] Since no processing residue remains on the processing site, the processing can be formed deep within the reach of the laser beam. Even a non-conductive material could be processed to form a high aspect ratio hole. As a general rule, there is no worry of contamination because it is not etched with other substances. Further, since the machining and the residue removal are alternately performed by the pulse operation, the machining progresses efficiently.

[0008]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 is a schematic cross-sectional view of a vacuum chamber for carrying out the present invention. A processing target 1 is installed between opposing electrodes 4 and 5 in a vacuum chamber 9 whose pressure is reduced by a vacuum pump (not shown). A laser beam 2 passes through a quartz window 8 and is focused by a lens 3 to 2 μm or less so as to form a processing hole perpendicular to the surface of the processing target 1. The laser is Ar with a wavelength of 193 nm
Laser ablation is generated by using an F excimer laser, and it is movable in the horizontal direction so that a predetermined portion can be irradiated. The counter electrodes 4 and 5 are arranged by the high-voltage power source 6 so that an electric field is applied to the object 1 to be processed in the vertical direction, and the laser beam 2 transmitted through the quartz window 8 is provided on the counter electrode 4 above. The object to be processed 1 is irradiated through the opening 10. A magnetic field is applied in the vertical direction by the high magnetic field coil 7.

As shown in detail in FIG. 2, when the laser beam 2 is irradiated, the object 1 to be processed absorbs the light energy of the laser, and it is described in the literature (Laser Research Vol. 18, No. 4, P3).
Laser ablation occurs as described in 2-40). Then, the place where the laser to be processed hits becomes the state of plasma 12, and the velocity energy is several e from there.
Ions 13 having a high kinetic energy of about V to several hundred eV jump out. For example, when the object to be processed is a metal or the like, the ions are positively charged. Therefore, if a voltage of tens of volts or more, preferably several hundreds of volts or more is applied to the counter electrode so that the object to be processed is positively charged, a large Coulomb force is applied, and the processing is performed. It moves towards a negatively charged counter electrode on the top surface of the object. Further, here, when a magnetic field 11 parallel to the direction of the processed hole is applied as shown in FIG. 2B, the emitted particles that are ionized receive Lorentz force,

Where r is mv / qB, m is the weight of ions, v is the velocity in the direction perpendicular to the magnetic field, q is the number of charges, and B is the magnetic flux density. A circular motion is performed by drawing a radius r. At the same time, since the Coulomb force is moving toward the counter electrode 4, ions are eventually ejected from the processed portion while making a spiral motion. Since the object 1 to be processed is charged with the same electric charge as the ions, the object 1 receives a slight repulsion from the side wall of the processed hole and is less likely to cause collision (see FIG. 3). That is, the ions are ejected in any direction, but due to these effects, redeposition does not occur and they are removed from the processed hole.

A large amount of the ions 13 that have left the object 1 to be processed pass through the opening 5 into which the laser beam is incident and head toward the quartz window 8, so there is a risk that they will be attached at the window. Therefore, below the window, a magnetic field 14 perpendicular to the window is used to change the traveling direction of the ions toward the quartz window 8 by a coil (not shown) to prevent the ions from adhering to the window. Ions that have jumped out into the vacuum chamber are exhausted by a vacuum pump for lowering the degree of vacuum.

Regarding the electrons ejected by laser ablation, considering the case where the velocity energy is emitted at 1 eV or less, when the magnetic flux density B is 5000 [G], the radius r becomes a motion of 6.8 μm or less, Even if the radius is less than this level, the electrons collide with other non-ionized atoms to be ionized while rotating in the machining hole, thereby preventing reattachment of atoms and improving machining efficiency. This is because 100% of the atoms in plasma are not ionized. Even if the velocity is other than this, there is an effect that the electrons are ionized by collision while they are in the plasma. However, since electrons also receive Coulomb force, they move to the side of the object to be processed, and hit the object to be absorbed by the potential.

The object to be processed can be any solid substance that absorbs laser, and includes metals, ceramics, polymer compounds and the like, and is considered to have a wide range of applications. However, the laser beam needs to be a laser having an energy higher than the wavelength of ultraviolet rays in order to give the atom for ionization to the atom to be processed.

The high magnetic field coil 7 for rotating the ions in the processed hole is installed outside the vacuum chamber in FIG.
Even if it is installed inside the vacuum chamber, the effect is the same, and rather the magnetic field strength can be increased. Further, an etching gas may be introduced during processing by the gas supply means to enhance the processing effect by utilizing a normal etching reaction. In this case, the reaction product is also ionized and removed by the laser.

If the laser irradiation is not pulsed but pulsed, plasma generation due to high energy density irradiation and ion ejection state during non-irradiation alternate, and efficient hole processing is realized. In this embodiment, the electric field and the magnetic field are applied, but the effect is obtained even when only the electric field is applied.

As described above, in the processing apparatus and the processing method according to the present invention, since the residue does not adhere to the processing wall, a very deep hole can be processed. Further, it is possible to perform the hole processing particularly efficiently, and the processing target is not limited to the conductive object, and the range of fine processing can be expanded.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a microfabrication device showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a processing target portion.

FIG. 3 is an explanatory diagram of an ionized state of a processed hole.

FIG. 4 is a cross-sectional view of the processing device as viewed from above.

[Explanation of symbols]

 1 Processing Target 2 Laser Beam 3 Condensing Lens 4, 5 Counter Electrode 6 High Voltage Power Supply 7 High Magnetic Field Coil 8 Quartz Window 9 Vacuum Chamber 10 Opening 11 Magnetic Field Direction 12 Plasma 13 Ions (Processing Waste) 14 Magnetic Field for Direction Change 15 Insulation Body 16 Positive charge on the surface to be processed

Claims (6)

[Claims] 1. A microfabrication apparatus for performing laser ablation at a predetermined portion of a material to be processed by laser beam irradiation, wherein a table for installing the material to be processed is provided inside, and a transmission window for the laser beam is provided. A vacuum chamber, and a pair of opposed electrodes that are arranged so that an electric field is applied to the material to be processed in the vacuum chamber in the incident direction of the laser beam, and a voltage is applied so that the material to be processed is charged. A microfabrication device comprising an electrode. 2. A magnetic field coil arranged so that a magnetic field is applied in the same direction as the incident direction, and electromagnetically induces charged particles generated from the material to be processed by laser ablation to move the charged particles from the processing site. The microfabrication apparatus according to claim 1, further comprising means. 3. Excluding means for electromagnetically excluding the charged particles moved by receiving a second magnetic field in a direction perpendicular to the transmission window so as not to hit the transmission window. The fine processing apparatus according to claim 1, wherein: 4. The microfabrication apparatus according to claim 1, wherein the vacuum chamber is provided with a gas supply means for exposing at least one reactive gas to the material to be processed as needed during processing. . 5. A material to be processed is irradiated with a laser beam in a vacuum of a negative pressure or higher to cause laser ablation and ionized charged particles are scattered, so that the material to be processed is charged. The charged particles scattered from the material to be processed are electromagnetically moved from the processing site by a voltage applied and an electric field applied in the direction of incidence of the laser beam and a magnetic field applied in the same direction as the direction of incidence. In addition, the fine machining method is characterized in that the moved charged particles are further electromagnetically induced by a second magnetic field so as not to hit the quartz window into which the laser beam is introduced. 6. The fine processing method according to claim 5, wherein the laser beam irradiation is performed in a pulsed manner, and the processing and the residue removal are performed alternately.