JPH08197266A - Method for processing material by using photoirradiation - Google Patents

Abstract

PURPOSE: To obtain a method for processing a material which increases a processing speed and uses photoirradiation with lessened damage by irradiating a work with at least >=2 kinds of beams of different wavelengths simultaneously or parting by a prescribed spacing. CONSTITUTION: The quaternary higher harmonic wave of an Nd:YAG laser 10 is condensed as exciting light by a lens 12 and is made incident into a Raman cell 14 packed with gaseous hydrogen as a Raman medium. A lens 16 for condensing the vacuum UV Raman laser beam which is the Raman conversion light formed by Raman scattering of the quaternary higher harmonic wave of the Nd:YAG laser 10 by the Raman cell 14 and quartz glass 18 as the work to be irradiated with the vacuum UV Raman laser beam condensed by the lens 16 are disposed in a region A held in vacuum from the Raman cell 14. The vacuum UV Raman laser beam has 15 pieces of discontinuous oscillation lines divided to a wavelength 594nm from a wavelength 122nm and the quartz glass 18 is simultaneously pulse irradiated with such beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of processing a substance using light irradiation, and more particularly, to a method of processing a substance having a large energy gap, that is, a so-called difficult-to-process material. The present invention relates to a method for processing a substance using suitable light irradiation.

[0002]

2. Description of the Related Art It is generally known that when a high-intensity light is irradiated on a surface of a substance having absorption for the light, a phenomenon called ablation occurs.

[0003] The phenomenon of ablation is caused by, for example, irradiating a pulse of high-intensity laser light to a surface of a substance having absorption with respect to the laser light, thereby performing a photodissociation process and a thermal process on the surface of the material. This is a phenomenon in which molecular bonds and atomic bonds in the irradiation area are broken and decomposed, and a high-density plasma state is generated, whereby the decomposed molecules and atoms are scattered.

Conventionally, ablation has been widely used to study fine processing of a solid surface by scattering molecules and atoms on a material surface and thin film forming processing by the scattering particles, and some of them have been put to practical use. I have.

In the conventional processing of a substance by ablation, a laser beam of a single wavelength is irradiated on the surface of the substance by a pulse, and an excimer laser mainly in an ultraviolet region is used as a laser light source.

[0006]

However, in the conventional method of processing a substance using a single-wavelength laser beam, a high-power vacuum ultraviolet laser does not exist. There has been a problem that processing without damage is difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to increase the processing speed of material processing using ablation and reduce damage. An object of the present invention is to provide a method for processing a substance using light irradiation.

[0008]

In order to achieve the above-mentioned object, a method for processing a substance using light irradiation according to the present invention comprises the steps of: A method for processing a substance using light irradiation of irradiating light of different wavelengths, wherein at least one of the two or more kinds of light of different wavelengths absorbs the material to be processed and has The light of the first wavelength that causes electronic excitation from the valence band to the conduction band of the processing material, and at least one other light of the two or more different wavelengths of light is the material to be processed. Is a light of the second wavelength that causes absorption of the excitation level.

The light of the second wavelength is light having a longer wavelength than the first wavelength and having a large energy.

[0010]

The object is irradiated with light having a wavelength that absorbs the object to be processed and including light that causes electronic excitation from the valence band to the conduction band of the object to be processed. Electronic excitation from the valence band to the conduction band occurs in the material to be processed.

[0011] In this state, the absorption edge of light in the material to be processed is shifted to the longer wavelength side, and absorption occurs even when irradiated with light of a longer wavelength having large energy. Become. Therefore, the material to be processed is irradiated with the light of the first wavelength and the light of the second wavelength that causes the absorption of the excited level to the material to be processed, simultaneously or at a predetermined interval. Ablation can occur.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for processing a substance using light irradiation according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an apparatus for carrying out a method for processing a substance using light irradiation according to an embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes an Nd: YAG laser as a light source. The fourth harmonic (wavelength 266 nm) of the Nd: YAG laser 10 is condensed by a lens 12 as excitation light, and is used as a Raman medium. The light is incident on a Raman cell 14 filled with hydrogen gas.

The region A kept in vacuum from the Raman cell 14 is Nd: YA by the Raman cell 14.
A lens 16 for condensing vacuum ultraviolet Raman laser light as Raman-converted light obtained by Raman scattering the fourth harmonic of the G laser 10, and a workpiece irradiated with vacuum ultraviolet Raman laser light condensed by the lens 16 A quartz glass 18 is provided as a substance.

The vacuum ultraviolet Raman laser beam emitted from the Raman cell 14 has a wavelength of 122 nm to 594 wavelength.
Vacuum ultraviolet Raman laser light (hereinafter referred to as “full-wavelength vacuum ultraviolet Raman laser light”) having 15 discontinuous oscillation lines up to nm and having all of these wavelength components is applied to the quartz glass 18. On the other hand, pulse irradiation is performed simultaneously.

FIG. 2 shows a case where the quartz glass 18 is simultaneously pulsed with a full-wavelength vacuum ultraviolet Raman laser beam by the apparatus shown in FIG. 1 and a case where Nd: The pulse irradiation of the fourth harmonic (wavelength 266 nm) of the YAG laser
9 is a graph of an experimental result showing a relationship between a pulse number and an ablation depth.

The energy density of both the full-wavelength vacuum ultraviolet Raman laser light and the fourth harmonic of the Nd: YAG laser was 2.1 J / cm ² .

As shown in FIG. 2, the simultaneous irradiation of all-wavelength vacuum ultraviolet Raman laser light with a pulse radiates the fourth harmonic (wavelength 26) of a single wavelength Nd: YAG laser.
When the pulse number is the same, the ablation depth is about 1.5 times larger than that of the pulse irradiation of the same pulse number, and the processing speed is high.

Also, in the processing shape, FIG.
As shown in (a) and (b), there was a great difference between simultaneous pulse irradiation of full-wavelength vacuum ultraviolet Raman laser light and pulse irradiation of the fourth harmonic of a single wavelength Nd: YAG laser.

That is, FIGS. 3A and 3B show the quartz glass 1.
When a metal mask having a pattern of a square through hole having a side of 25 μm is placed on 8 and 50 pulses of full-wavelength vacuum ultraviolet Raman laser light are simultaneously irradiated (FIG. 3A).
And 50 pulses of the fourth harmonic (wavelength 266 nm) of a single wavelength Nd: YAG laser (FIG. 3)
3B is a micrograph of the processed surface of the quartz glass 18 in FIGS.

The energy density of both the full-wavelength vacuum ultraviolet Raman laser beam and the fourth harmonic of the Nd: YAG laser was 2.1 J / cm ² .

As shown in FIG. 3A, when 50 pulses of full-wavelength vacuum ultraviolet Raman laser light are simultaneously irradiated, a regular distribution reflecting the spatial intensity distribution by diffraction of the full-wavelength vacuum ultraviolet Raman laser light is obtained. A relatively flat machined surface was obtained. No cracks occurred around the processed part.

On the other hand, when the fourth harmonic of a single wavelength Nd: YAG laser was irradiated, as shown in FIG. 3B, irregular asperities and thermal damage were also confirmed on the processed surface. .
Further, cracks also occurred around the processed portion.

FIGS. 4A and 4B show the quartz glass 1.
Respect 8, if the energy density is 5 pulses simultaneously irradiating the entire wavelength vacuum ultraviolet Raman laser beam 20 J / cm ² and (FIG. 4 (a)), the energy density of 20 J / cm ²
FIG. 4B is a photomicrograph of the surface of the quartz glass 18 when five pulses of the fourth harmonic (wavelength 266 nm) of the single wavelength Nd: YAG laser are applied (FIG. 4B).

The micrographs of FIGS. 4 (a) and 4 (b) show the same results as those of FIGS. 3 (a) and 3 (b).

Here, the mechanism of processing by ablation when the full-wavelength vacuum ultraviolet Raman laser light is simultaneously pulsed onto the quartz glass 18 will be described. This processing mechanism is based on the single-wavelength laser in the prior art. The mechanism of processing by ablation in light pulse irradiation is completely different.

That is, among the wavelength components of the full-wavelength vacuum ultraviolet Raman laser beam irradiated at the same time, the wavelength of 160 nm or less having a photon energy larger than the energy gap of 8 eV that has an absorption in the quartz glass 18 and is at first absorbed. Electronic excitation from the valence band to the conduction band occurs.
In this state, the absorption edge shifts to the longer wavelength side, and the fundamental wave of the Raman conversion having the largest energy among all wavelengths of vacuum ultraviolet Raman laser light, that is, the excitation light wavelength 26
It causes absorption of the fourth harmonic of a 6 nm Nd: YAG laser. This situation is shown in FIGS.

That is, FIG. 5 shows the measurement of the change in the transmittance of quartz glass 18 with time for the wavelength component of 266 nm in the quartz glass 18 when the full-wavelength vacuum ultraviolet Raman laser light is simultaneously pulsed onto the quartz glass 18. The results are shown, and FIG. 6 shows the pulse waveform of a wavelength component at a wavelength of 160 nm that would cause electronic excitation,
Irradiation of such a short wavelength component in the full-wavelength vacuum ultraviolet Raman laser light reduces the transmittance of the wavelength component of 266 nm to a maximum of about 36%. Such a phenomenon is caused by absorption by an excited level (ESA: Excited S).
In this case, the absorption by the excitation level makes it possible to effectively ablate the quartz glass 18.

In the above-described embodiment, a full-wavelength vacuum ultraviolet Raman laser beam containing three or more wavelength components is used. However, the present invention is not limited to this. Light of at least two wavelengths, that is, light of a wavelength component that causes electronic excitation from the valence band of the glass 18 to the conduction band and light of a wavelength component that causes absorption of an excitation level to the quartz glass 18. May be simultaneously irradiated.

In the above-described embodiment, the pulsed irradiation with the full-wavelength vacuum ultraviolet Raman / laser laser beam was performed simultaneously. However, as shown in FIGS. Since there is a slight shift between the pulse waveform of the wavelength component that causes electronic excitation from the electronic band to the conduction band and its absorption in the quartz glass 18, the quartz glass 18 is moved by the time of the shift. On the other hand, the irradiation of light having a wavelength component that causes absorption from the valence band of the quartz glass 18 to the conduction band and that causes absorption of an excitation level with respect to the quartz glass 18 is shifted. It may be.

Further, in the above-described embodiment, light having a wavelength component which absorbs the quartz glass 18 and causes electronic excitation from the valence band to the conduction band of the quartz glass 18;
Light of at least two types of wavelengths, that is, light of a wavelength component that causes absorption of an excitation level to the quartz glass 18, is radiated to the quartz glass 18 by the same system. You may do so.

Further, the light of the wavelength component that absorbs the quartz glass 18 and causes electronic excitation from the valence band to the conduction band of the quartz glass 18 does not have to be a laser beam. A lamp having a photon energy larger than the gap may be used. That is, even if the light of such a lamp is irradiated, electronic excitation to the upper level occurs,
By irradiating an appropriate laser beam in that state, absorption by an excitation level occurs, and ablation can be performed.

In the above embodiment, only the processing of the quartz glass 18 by ablation has been described. However, a thin film may be formed by depositing scattered molecules and scattered atoms by ablation.

In the above embodiment, the quartz glass 18 is selected as the material to be processed, and the wavelength component of the wavelength component that absorbs the quartz glass 18 and causes electronic excitation from the valence band of the quartz glass 18 to the conduction band is generated. A case has been described where full-wavelength vacuum ultraviolet laser light by Raman conversion is used as light including at least two types of wavelength components, that is, light and light having a wavelength component that causes absorption of an excitation level to the quartz glass 18. However, these are merely examples, and it is a matter of course that the material to be processed and the type of light may be appropriately selected without being limited thereto.

[0036]

According to the present invention, as described above, the processing speed of material processing using ablation can be increased, and a high-intensity laser with a short wavelength in the vacuum ultraviolet region can be obtained. It becomes possible to efficiently process difficult-to-process materials having a large energy gap, which are difficult to process because they do not exist.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an apparatus for performing a method of processing a substance using light irradiation according to an embodiment of the present invention.

FIG. 2 shows a case where quartz glass is simultaneously pulse-irradiated with a full-wavelength vacuum ultraviolet Raman laser beam by the apparatus shown in FIG. 1, and a case where a Nd: YAG laser is used as a single-wavelength laser beam as in the prior art. 4th harmonic (wavelength 266n
10 is a graph of experimental results showing the relationship between the number of pulses and the ablation depth when m) is irradiated with pulses.

FIGS. 3 (a) and 3 (b) are micrographs of a processed quartz glass surface, and FIG.
FIG. 3 is a photomicrograph when 50 pulses of full-wavelength vacuum ultraviolet Raman laser light were simultaneously irradiated on a metal mask having a pattern of a square through hole having a side of 25 μm, and FIG.
3B shows the fourth harmonic (wavelength 266n) of a single wavelength Nd: YAG laser under the same conditions as FIG.
m) is a micrograph when 50 pulses are irradiated.

4 (a) and 4 (b) are photomicrographs of a processed quartz glass surface, and FIG. 4 (a) is a full-wavelength vacuum ultraviolet with an energy density of 20 J / cm ² with respect to quartz glass. FIG. 4B is a micrograph of a case where five pulses of Raman laser light are simultaneously irradiated. FIG. 4B shows a single wavelength Nd: YA having an energy density of 20 J / cm ² with respect to quartz glass.
It is a microscope photograph at the time of irradiating 5 pulses of the 4th harmonic (wavelength 266nm) of G laser.

FIG. 5 is a graph showing a measurement result of a change in transmittance with time of a wavelength component of a wavelength of 266 nm in quartz glass when a quartz glass is simultaneously pulse-irradiated with full-wavelength vacuum ultraviolet Raman laser light.

FIG. 6 is a graph showing a pulse waveform of a wavelength component having a wavelength of 160 nm.

[Explanation of symbols]

 Reference Signs List 10 Nd: YAG laser 12 lens 14 Raman cell 16 lens 18 quartz glass A region held in vacuum

Continuation of front page (72) Inventor Koichi Toyoda 2-1 Hirosawa, Wako-shi, Saitama Pref. RIKEN

Claims (4)

[Claims] 1. A method for processing a substance using light irradiation for irradiating at least two or more types of light having different wavelengths simultaneously or at predetermined intervals to a substance to be processed, wherein the two or more different types of light are irradiated. The light of at least one wavelength among the light of the wavelength is light of a first wavelength that absorbs the material to be processed and causes electronic excitation from a valence band to a conduction band of the material to be processed, At least one other light of the two or more different wavelengths is light of a second wavelength that causes absorption of an excitation level to the material to be processed. Method of processing substances using 2. The method according to claim 1, wherein the light having the second wavelength is light having a wavelength longer than the first wavelength and having a large energy. 3. The material to be processed is quartz glass, and at least two or more types of light having different wavelengths, which are irradiated on the material to be processed simultaneously or at predetermined intervals, are N
2. The method for processing a substance using light irradiation according to claim 1, wherein d is a pulsed laser beam of a vacuum ultraviolet Raman laser for Raman scattering the fourth harmonic of a YAG laser in hydrogen gas. 4. The material to be processed is quartz glass, the light of the first wavelength is a pulsed laser light having a wavelength of 160 nm or less, and the light of the second wavelength is a pulsed laser light having a wavelength of 266 nm. A method for processing a substance using light irradiation according to claim 1.