JP5057202B2 - Microstructure manufacturing method and manufacturing apparatus - Google Patents

Description

  The present invention relates to a fine structure manufacturing method, a manufacturing apparatus, and a device obtained thereby, and in particular, a fine structure manufacturing method, a manufacturing apparatus capable of forming a desired fine pattern with good reproducibility, and the same. It relates to the device obtained by

A fine pattern formed using a pulsed laser beam has various industrial uses such as antireflection, phase delay, and marker, and in recent years, interest in improving a fine processing technique is increasing.
For example, a method of forming a nano-periodic structure on a material surface by irradiating the material with a linearly polarized femtosecond laser has been proposed (for example, see Non-Patent Document 1).
However, there are various theories about the mechanism of fine pattern formation by ultrashort pulse laser beam, and it is not clear how the desired fine pattern can be obtained by controlling the laser parameters. There was a problem that was difficult.

In addition, a method has been proposed in which the phases of a plurality of ultrashort pulse laser beams are controlled to interfere with each other and a workpiece is processed using a light intensity distribution due to the interference (for example, Patent Document 1). reference).
Yuzawa Izawa et al., 66th JSAP Scientific Lecture Proceedings 2005, p.992, 8p-B-12 JP 2003-25085 A

  However, although this method can obtain a certain fine pattern by controlling the light intensity distribution, the structure of the fine pattern obtained is also affected by the material and physical properties of the workpiece. It is desired to provide a processing method capable of realizing a desired fine pattern with good reproducibility without being affected by physical properties.

Therefore, an object of the present invention is to provide a manufacturing method and a manufacturing apparatus of a fine structure capable of forming a desired fine pattern with good reproducibility.
Moreover, an object of this invention is to provide the device obtained by the manufacturing method of the said outstanding fine structure.

As a result of intensive studies, the present inventor has found that a desired fine pattern can be realized with good reproducibility by employing a method for producing a specific fine structure, and has completed the present invention.
That is, the present invention is (1) a method of manufacturing a microstructure using a pulse laser that emits a multiphoton absorbing pulse laser beam, comprising a first exposure step and a second exposure step, One exposure step includes a first branching step of branching the multiphoton absorbing pulsed laser beam into a plurality of diffracted beams using a diffractive optical element, and two diffracted beams among the plurality of branched diffracted beams A first selection step using a spatial filter, condensing the two diffracted beams, and irradiating the workpiece with the first interference light by the two diffracted beams, A first irradiation step of removing the surface of the workpiece in a region of a predetermined threshold value or more in the intensity distribution of one interference light, wherein the second exposure step uses the multiphoton absorbing pulsed laser beam. The diffractive optical element A second branching step for branching into a plurality of diffracted beams using the first and second diffracted beams among the plurality of diffracted beams branched in the second branching step using the spatial filter. A selection step, a phase difference providing step for providing a phase difference between the two diffracted beams selected by the second selection step, and condensing the two diffracted beams to which the phase difference is provided, By irradiating the workpiece with the second interference light by the two diffracted beams to which the phase difference has been given, the workpiece in a region of a predetermined threshold value or more in the intensity distribution of the second interference light. It viewed including a second irradiation step of removing the surface of the, in the first irradiation step and the second irradiation step, the multiphoton absorption of pulsed laser beam having a wavelength and a diameter, cross the two diffracted beams Angle, focus Distance, as well as a manufacturing method of a fine structure characterized by adjusting at least one of the phase difference.

The present invention may have the following features.
(2) The microstructure according to (1), wherein the multiphoton absorbing pulse laser beam is an ultrashort pulse laser beam having a pulse width of 10 × 10 ⁻¹⁵ seconds to 10 × 10 ⁻¹² seconds. Manufacturing method of
(3) The method for producing a microstructure according to (1) or (2), wherein the diffracted beam applied to the workpiece is circularly polarized light;
(4) The method for producing a microstructure according to (1) or (2), wherein the diffracted beam applied to the workpiece is linearly polarized light;
(5) A diffractive optical element for branching a multiphoton absorbing pulsed laser beam into a plurality of diffracted beams, a first lens for condensing the plurality of diffracted diffracted beams, and two of the plurality of diffracted beams. A spatial filter that allows only two diffracted beams to pass through, a phase difference plate that gives a phase difference to the two diffracted beams, and condensing the two diffracted beams to produce interference light by the two diffracted beams. A second lens that irradiates a workpiece, the wavelength and diameter of the multiphoton absorbing pulsed laser beam, the crossing angle of the two diffracted beams, the focal length of the first lens, the first lens The focal length of the second lens and at least one of the phase differences can be adjusted, and the surface of the workpiece is removed in a region of a predetermined threshold value or more in the intensity distribution of the interference light. Fine Concrete body manufacturing apparatus;
(6) The fine structure manufacturing apparatus according to (5), wherein the diffractive optical element has a periodic structure of a surface shape or a refractive index distribution; and (7) the retardation plate includes the two diffraction plates. The fine structure manufacturing apparatus according to (5) or (6), wherein a thickness or a refractive index is different between a portion where one diffracted beam is incident and a portion where another diffracted beam is incident .

  According to the present invention, a desired fine pattern can be formed with high reproducibility. According to the method for manufacturing a fine structure of the present invention, a desired fine pattern can be formed on the surface or inside thereof with good reproducibility without being affected by the material and physical properties of the workpiece. The fine structure manufacturing apparatus of the present invention has a simple and stable apparatus configuration.

Next, an embodiment of the present invention will be described. The following embodiment is an example for explaining the present invention, and is not intended to limit the present invention only to this embodiment. The present invention can be implemented in various forms without departing from the gist thereof.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Microstructure manufacturing equipment)
A microstructure manufacturing apparatus 10 according to an embodiment of the present invention is shown in FIG.
As shown in FIG. 1, the microstructure manufacturing apparatus 10 splits a pulse laser 11 that emits a multiphoton-absorbing pulse laser beam, a shutter 12, a mirror 13, and the pulse laser beam into a plurality of diffraction beams. Diffractive optical element 14, a first lens 15 that collects and stabilizes a plurality of branched diffracted beams, a spatial filter 16 that passes only two of the diffracted beams, and two The phase difference plate 17 that gives a phase difference to the diffracted beam and the second lens 18 that condenses the two diffracted beams.

In the present embodiment, the multiphoton absorbing pulse laser beam emitted from the pulse laser 11 has a pulse width of 10 × 10 ⁻¹⁵ seconds to 10 × 10 ⁻¹² seconds, a wavelength of 800 nm, and an average output of 1 mJ. (However, the pulse repetition is 1 KHz). The diameter (D1) of the ultrashort pulse laser beam is 6 mmφ.
In this embodiment, an ultrashort pulse laser beam is used, but the present invention is not limited to this, and any multiphoton absorbing pulse laser beam may be used.

  In the present embodiment, the focal length f1 of the first lens 15 is 500 mm, and the focal length f2 of the second lens 18 is 10 mm.

FIG. 2A shows a side view of the diffractive optical element 14 and FIG. 2B shows a side view of the retardation plate 17.
As shown in FIG. 2A, the diffractive optical element 14 has a binary structure having two levels of a gap h (= 889 nm) with a period P (= 100 μm), and the surface shape is periodic. It has a structure. The diffractive optical element 14 is produced on a quartz substrate by laser drawing and ion etching.
Note that the diffractive optical element 14 is not limited to a binary structure, and for example, the surface shape may be a periodic structure having a sine (cosine) curved surface shape, or the appearance is flat and the internal refractive index is low. A periodically distributed periodic structure may be formed.

As shown in FIG. 2B, the phase difference plate 17 has a step with a gap g (= 889 nm) on the surface. That is, the thickness of the phase difference plate 17 is different between the portion where one of the two diffracted beams is incident and the portion where the other diffracted beam is incident, and the difference between the two diffracted beams is different. Can be given a predetermined optical path difference (phase difference π). The phase difference plate 17 is produced on a quartz substrate by laser drawing and ion etching.
The gap g of the phase difference plate 17 is 889 nm for the phase difference π, 444 nm for the phase difference π / 2, and 222 nm for the phase difference π / 4.
The phase difference plate 17 is not limited to a stepped shape having a different thickness. For example, the phase difference plate 17 may have a flat appearance and a different refractive index in the left and right regions.

(Manufacturing method of fine structure)
Next, a method for manufacturing a fine structure using the manufacturing apparatus 10 will be described.
3A and 3B are diagrams schematically showing formation of a fine pattern on the surface of the workpiece by the interference light intensity distribution, where FIG. 3A shows the first exposure and FIG. 3B shows the second exposure. FIG. 4A is an enlarged view of the diffracted beam irradiation region of the workpiece after the first exposure, and FIG. 4B is an enlarged view of the diffracted beam irradiation region of the workpiece after the second exposure. is there.

[First exposure]
As shown in FIG. 1, the ultrashort pulse laser beam emitted from the pulse laser 11 passes through the shutter 12, is reflected by the mirror 13, and is branched into a plurality of diffracted beams by the diffractive optical element 14. The light is condensed and stabilized by the lens 15. Next, only two diffracted beams pass through the spatial filter 16 disposed in the vicinity of the condensing surface of the lens. The two diffracted beams that have passed through are condensed by the second lens 18 and irradiated onto the workpiece 19.
The two diffracted beams interfere with each other at a predetermined crossing angle θ to generate a periodic interference light intensity distribution. By this interference light intensity distribution, a fine pattern having the same period as the interference light intensity distribution is formed on the surface of the workpiece. The exposure time by the diffracted beam is about several millimeters, and the exposure time is controlled by the shutter 12.

As shown in FIG. 4A, in the first exposure, a fine pattern having a period d (= 1 μm) is formed on the surface of the workpiece by the interference light intensity distribution.
The period d of the interference light intensity distribution is given by the following equation.
[Equation 1]
d = λ / (2 sin θ) = (f2 / f1) (P / 2)
(Where λ is the wavelength of the ultrashort pulse laser, θ is the crossing angle, f1 is the focal length of the first lens, and f2 is the focal length of the second lens.)
For example, if λ = 800 nm and the crossing angle θ = 24 degrees, the period d of the interference light intensity distribution is 1.0 μm.

Further, as shown in FIG. 3A, when the workpiece is irradiated with an ultrashort pulse laser beam, the surface of the workpiece is removed only for an intensity distribution equal to or higher than a certain threshold value. A pattern is formed. The area D2 from which the surface of the workpiece is removed is given by the following equation.
[Equation 2]
D2 = (f2 / f1) D1
(Where D1 is the diameter of the laser beam, f1 is the focal length of the first lens, and f2 is the focal length of the second lens.)
For example, if f1 = 500, f2 = 10, and D1 = 6 mm, the width D2 of the removal region is 120 μm.

[Second exposure]
After the first exposure, the interference light generated by the two diffracted beams is the same as the first exposure except that a phase difference (π) is given between the two diffracted beams using the phase difference plate 17. A fine pattern is formed on the surface of the workpiece by the intensity distribution.
As shown by the broken line in FIG. 3B, the surface of the workpiece is removed at a position shifted by a half cycle (d / 2) with respect to the region removed by the first exposure. As a result, FIG. As shown in (b), a fine pattern with a period of 0.5 μm is formed.

In the above-described embodiment, the case where the phase difference is set to π has been described. However, a relief structure with a finer period can be formed by further reducing the phase difference and repeating interference exposure.
In the above embodiment, the case where the fine pattern is formed on the surface of the material opaque to the diffraction beam wavelength has been described. However, even if the fine structure is formed inside the material transparent to the diffraction beam wavelength. Good.
Moreover, in the manufacturing method of the microstructure of this invention, it is good also as performing a 2nd exposure process first and then performing a 1st exposure process.

As shown in the above embodiment, according to the fine structure manufacturing method and manufacturing apparatus of the present invention, the size and shape of the fine pattern are quantitative by adjusting the period and phase difference of the interference light intensity distribution. To be determined. The period of the interference light intensity distribution and the magnitude of the phase difference are determined by adjusting the specifications of the elements and components that constitute the laser interference exposure system shown in FIG. Therefore, according to the fine structure manufacturing method and manufacturing apparatus of the present invention, a desired fine pattern can be formed with extremely high reproducibility.
That is, in the method for manufacturing a fine structure according to the present invention, a desired fine pattern can be realized with good reproducibility by adjusting at least one of the wavelength and diameter of the diffracted beam, the crossing angle, the focal length, and the phase difference. Can do.

The laser interference exposure system shown in FIG. 1 is extremely stable against disturbance because the two diffracted beams branched from each other are close to each other and the time required for the interference exposure is as short as several milliseconds. Less susceptible to vibrations and air fluctuations.
In general, laser interference exposure systems are sensitive to air fluctuations, and in order to ensure stability, the exposure system is placed on an anti-vibration bench, and the exposure system and anti-vibration bench are covered with a strong cover. Although a treatment such as covering is necessary and the equipment is expensive, the fine structure manufacturing method and manufacturing apparatus of the present invention are extremely stable against disturbances, so that stable exposure is possible. The system can be realized with a simple apparatus configuration.

  Furthermore, according to the fine structure manufacturing method and manufacturing apparatus of the present invention, a desired fine pattern can be formed with good reproducibility on the surface or inside thereof without being affected by the material and physical properties of the workpiece. .

(Example)
A fine pattern was formed on the workpiece by the fine structure manufacturing method and manufacturing apparatus described in the above embodiment. As the ultrashort pulse laser beam, a diffracted beam having a period d of the interference light intensity distribution of 2.0 μm is used, respectively, circularly polarized light, linearly polarized light (TE polarized light; parallel polarized light), and linearly polarized light (TM polarized light; orthogonal). Processing was performed under different pulse polarization conditions (polarization).
FIGS. 5 to 7 show electron micrographs obtained by photographing fine patterns formed using circularly polarized light, linearly polarized light (TE polarized light), and linearly polarized light (TM polarized light) diffraction beams.

As shown in FIG. 5, when a circularly polarized diffracted beam was used, a uniform fine processing pattern having a period of d / 2 (= 1.0 μm) was obtained after the second exposure.
Also, as shown in FIGS. 6 and 7, even when a linearly polarized diffracted beam was used, a finely processed pattern having a period of d / 2 (= 1.0 μm) was obtained after the second exposure. Furthermore, it has been found that when processed under pulse conditions of linearly polarized light, a fine structure can be obtained in a direction parallel to the polarization azimuth by superimposing it on a desired fine processing pattern. That is, as shown in FIG. 6, when a TE-polarized diffracted beam is used, a fine structure is obtained in the vertical direction (TE-polarized azimuth) in the figure superimposed on a desired fine processing pattern. . When a TM-polarized diffraction beam is used, as shown in FIG. 7, a fine structure is obtained in the horizontal direction (TM-polarized direction) in the figure by superimposing the pattern on the desired microfabrication pattern. It is done.

(Application examples)
The method for manufacturing a microstructure of the present invention is useful for manufacturing various devices that require formation of a microstructure pattern. The liquid material is selected according to the desired device function.
For example, a fine pattern formed by interference exposure may be transferred to a substrate by etching to produce a substrate having a fine structure.

Examples of the device include an optical thin film device, a semiconductor thin film device, marking, a micro mechanical component, and the like.
Applications to optical thin film devices include, for example, photonic structures used for light-emitting elements such as antireflection films, retardation plates, optical waveguides, polarizing elements, alignment films, LED elements, EL elements, etc. A density optical disk, and the like.
Application to a semiconductor device includes preparation of an electrode pattern of a SAW element (surface acoustic wave element), an insulating film pattern of a semiconductor element, a wiring pattern, an organic TFT semiconductor film, and the like.
Examples of marking applications include, for example, marking that uses the recognizability of a fine structure. A pattern or character consisting of a fine structure is formed on a part of an electronic component, etc. Perform production management.
As an application example to a micro mechanical component, for example, an application to a gear can be cited. The friction coefficient is controlled by forming a fine structure on the surface of the component and modifying the surface.

FIG. 1 shows a microstructure manufacturing apparatus 10 according to an embodiment of the present invention. 2A is a side view of the diffractive optical element 14, and FIG. 2B is a side view of the phase difference plate 17. It is a figure which shows typically the fine pattern formation on the to-be-processed body surface by interference light intensity distribution, (a) shows 1st exposure, (b) shows 2nd exposure. (A) is an enlarged view of the diffracted beam irradiation region of the workpiece after the first exposure, and (b) is an enlarged view of the diffracted beam irradiation region of the workpiece after the second exposure. It is the electron micrograph which image | photographed the fine pattern formed using the circularly polarized ultrashort pulse laser beam. It is the electron micrograph which image | photographed the fine pattern formed using the ultra-short pulse laser beam of a linear TE polarization. It is the electron micrograph which image | photographed the fine pattern formed using the ultra-short pulse laser beam of a linear TM polarization.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fine structure manufacturing apparatus, 11 Pulse laser, 12 Shutter, 13 Mirror, 14 Diffractive optical element, 15 1st lens, 16 Spatial filter, 17 Phase difference plate, 18 2nd lens

Claims (7)

A method of manufacturing a fine structure using a pulsed laser that emits a multiphoton absorbing pulsed laser beam,
A first exposure step and a second exposure step;
The first exposure step includes
A first branching step of branching the multi-photon absorbing pulsed laser beam into a plurality of diffracted beams using a diffractive optical element;
A first selection step of selecting two diffracted beams among the plurality of branched diffracted beams using a spatial filter;
By condensing the two diffracted beams and irradiating the workpiece with the first interference light by the two diffracted beams, the intensity distribution of the first interference light is in a region of a predetermined threshold value or more. A first irradiation step of removing the surface of the workpiece,
The second exposure step includes
A second branching step of branching the multiphoton absorbing pulsed laser beam into a plurality of diffracted beams using the diffractive optical element;
A second selection step of selecting two diffracted beams among the plurality of diffracted beams branched by the second branching step using the spatial filter;
A phase difference providing step of providing a phase difference between the two diffracted beams selected by the second selection step;
The two diffracted beams having the phase difference are condensed, and the workpiece is irradiated with second interference light by the two diffracted beams having the phase difference. A second irradiation step of removing the surface of the workpiece in a region of a predetermined threshold value or more in the intensity distribution of two interference light;
Only including,
In the first irradiation step and the second irradiation step, at least one of the wavelength and diameter of the multiphoton absorbing pulsed laser beam, the crossing angle of the two diffracted beams, the focal length, and the phase difference is adjusted. It is characterized by
A manufacturing method of a fine structure. 2. The method for manufacturing a microstructure according to claim 1, wherein the multiphoton absorbing pulse laser beam is an ultrashort pulse laser beam having a pulse width of 10 × 10 ⁻¹⁵ seconds to 10 × 10 ⁻¹² seconds.   The method for manufacturing a fine structure according to claim 1 or 2, wherein the diffracted beam irradiated to the workpiece is circularly polarized light.   The method of manufacturing a fine structure according to claim 1 or 2, wherein the diffracted beam irradiated to the workpiece is linearly polarized light. A diffractive optical element for splitting a multiphoton absorbing pulsed laser beam into a plurality of diffracted beams;
A first lens for condensing the plurality of branched diffracted beams;
A spatial filter that passes only two of the plurality of diffracted beams;
A phase difference plate that gives a phase difference to the two diffracted beams;
A second lens for condensing the two diffracted beams and irradiating a workpiece with interference light from the two diffracted beams;
Including
At least one of the wavelength and diameter of the multiphoton absorbing pulsed laser beam, the crossing angle of the two diffracted beams, the focal length of the first lens, the focal length of the second lens, and the phase difference Adjustable,
An apparatus for manufacturing a fine structure, wherein the surface of the workpiece is removed in a region of a predetermined threshold value or more in the intensity distribution of the interference light.   The fine structure manufacturing apparatus according to claim 5, wherein the diffractive optical element has a periodic structure of a surface shape or a refractive index distribution.   The thickness or refractive index of the retardation plate is different between a portion where one of the two diffracted beams is incident and a portion where another diffracted beam is incident. Microstructure manufacturing equipment.