JP2001212796A - Laser machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser machining method capable of realizing a fine three-dimensional structure by a simple machining process without using a complicated machining process such as a lithography process. SOLUTION: Laser light from a laser oscillator for continuously radiating optical pulses having the spatial and temporal large energy density at the pulse emitting time not more than 1 picosecond is radiated to a workpiece of a multilayer structure having the different wave length absorptance in a specified pattern and with specified energy density, and the workpiece is machined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method for forming a structure on a workpiece using a laser beam. The present invention also relates to micromachining of materials such as micromachines, ICs and diode devices.

[0002]

2. Description of the Related Art Conventionally, as a means for processing a multi-layered workpiece in which different materials are laminated on each layer into a fine three-dimensional structure on the order of submicron to 10 micron,
Usually, a lithography process is used. According to this, for each layer of a plurality of different materials,
A method of processing a structure through a series of processes such as resist coating, resist patterning exposure, resist development, etching using a resist pattern, and resist ashing is employed.

[0003]

However, when processing a fine three-dimensional structure on the order of submicrons to 10 microns, the above-described lithography process complicates the processing steps, so that the tact time is reduced. On the other hand, there is a problem of cost, and there is a problem that investment in production equipment becomes enormous.

Accordingly, the present invention solves the above problems and provides a laser processing method capable of realizing a fine three-dimensional structure with a simple and simple processing step without using a complicated processing process such as a lithography process. It is intended to do so.

[0005]

SUMMARY OF THE INVENTION The present invention provides a laser processing method configured as described in the following (1) to (5) in order to solve the above-mentioned problems. (1) A laser beam from a laser oscillator that continuously emits a light pulse having a large spatial and temporal energy density with a pulse emission time of 1 picosecond or less is used for processing a multi-layer workpiece having a different wavelength absorptivity of the laser light. And irradiating the workpiece with a predetermined pattern and a predetermined energy density to process the workpiece. (2) The workpiece having the multilayer structure is a plate or a structure formed by laminating or joining a plurality of materials that are translucent at the light wavelength of the laser light and have different light absorptivity. The laser processing method according to (1). (3) The laser processing method according to any one of (1) and (2), wherein the light pulse has a light intensity distribution of a Gaussian beam. (4) The laser processing method according to any one of (1) to (3), wherein the laser oscillator is a laser oscillator having a spatial compression device for light propagation. (5) The laser processing method according to the above (4), wherein the spatial compression device for light propagation has a means for generating a chirped pulse and a longitudinal mode synchronization means using light wavelength dispersion characteristics.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of the present invention using the above configuration, a laser beam output from a laser oscillator which outputs a laser beam having a pulse emission time of 1 picosecond or less is used as the light of the laser beam. Irradiating a plate or a structure formed by laminating or joining a plurality of materials having different light absorptances that are translucent at a wavelength with a predetermined pattern and a predetermined energy density to process and form a structure on the plate or the structure. Accordingly, a portion having a light energy density equal to or higher than the ablation processing threshold of each material can be processed by the relationship between the light intensity distribution of the laser beam and the laser light absorptance of each compounded material. This enables various three-dimensional designs by designing the irradiation light intensity distribution pattern of the laser light flux, the energy density of the irradiation laser light, and the arrangement of materials having different light absorptivity of the irradiation laser light wavelength according to the purpose. Fine processing of a shaped structure becomes possible. Further, the laser processing method can be applied to processing of an ink passage structure of an ink jet recording head having a fine three-dimensional structure.

[0007] The above-mentioned laser used here is called "Next Generation Optical Technology" (published in 1992 by Optronics Co., Ltd., part 1 element technology; generation and compression of ultrashort light pulses, page 24 to). 31), and the like. According to such a femtosecond laser, the temporal energy density is extremely large, and the irradiation time of the laser light is very short. As a result, the sublimation ablation process can be completed before diffusing in the workpiece.

That is, for example, in the case of processing a material such as polysulfone, which is a resin material, the absorption of an energy density of about 15 megawatt / cm ² is the ablation processing threshold value, When the absorptance is about 0.1%, the energy density required for the laser light to be irradiated is about 15 GW / cm ² . Since such a very high energy concentration is required, the output is insufficient with a normal YAG laser or the like, and the temporal energy density is increased by using a laser that oscillates with a pulse emission time of 1 picosecond or less. Needs to be increased. (Some commercially available femtosecond laser oscillators have a pulse emission time of 150 femtoseconds or less and a light energy of 800 microjoules per pulse. That is, the energy density of the emitted laser light is It will be about 5.3 gigawatts level, and it will be 1 if focused on 0.35 cm ² area.
(The energy density reaches 5 gigawatts / cm ² ) In addition, in order to precisely and precisely process the processed shape of the structure to be finely processed, in order to avoid deformation and melting due to heat absorption of laser light, Using a laser whose laser irradiation time is very short and oscillates with a pulse emission time of 1 picosecond or less, the sublimation process is completed before the irradiated laser beam diffuses inside the workpiece as thermal energy. Used.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. First, the outline of the processing method of the present invention will be described with reference to FIG. The laser beam 1 having a Gaussian beam intensity profile emitted from a laser oscillator (not shown) that emits a laser beam in an ultrashort pulse emission time (1 picosecond or less) has a laser beam wavelength absorptance of a multi-layered workpiece. Irradiation is performed on the surface of layer A 2 which is a polysulfone layer colored to 5%. As a result, the laser beam is subjected to about 5% Fresnel reflection on the surface of the A layer 2 and the A layer 2 absorbs 5% of the energy, and the remaining 90% of the laser beam has a laser beam wavelength absorptivity of about 5%. B, a polysulfone layer colored to 20%
Transferred to layer. Next, the B layer absorbs 90% × 20% = 18% of the first irradiation laser energy, and the remaining 90% × 80% = 72% of the laser light has a laser light wavelength absorption rate of about 50%. C, a colored polysulfone layer
Transferred to layer. Next, the C layer absorbs 72% × 50% = 36% of the initial irradiation laser energy, and the remaining 72% × 50% = 36% of the laser light has a laser light wavelength absorption rate of about 30%. D, a colored polysulfone layer
Transferred to layer. Finally, the D layer absorbs 36% × 30% = 11% of the initial irradiation laser energy, and the remaining 36% × 70% = 25% of the laser light passes through the entire workpiece.

Therefore, each of the A layer, the B layer, the C layer, and the D layer
The energy of the laser light absorbed by the layers is
5%, 18%, 36% of first irradiation laser energy
%, 11%. Therefore, the pulse of the laser light to be irradiated
Irradiation energy density is about 300 (= 15 ÷ 0.05)
Megawatt / cm^TwoSet to Gaussian beam intensity
By irradiating with profile, A layer, B layer
Energy of the laser light absorbed by each of the layers C, D and D
Lug density is about 15MW / cm each ^Two, About 5
4 MW / cm^Two, About 108 MW / cm^Two,about
33 MW / cm^TwoAnd the Gaussian beam intensity
By irradiating with profile, polysulfur
The ablation threshold of resin is about 15MW /
cm^TwoAblation threshold
The area irradiated with the energy density not less than the value is the layer A, D
Layer, B layer, and C layer in this order, that is, as shown in FIG.
The processing is performed in a proper shape.

As is apparent from the above description, according to the present embodiment, a laser beam having a predetermined laser beam intensity profile and a predetermined laser irradiation energy density is applied to a plurality of materials having a predetermined layered structure having different light absorptivity to laser light. By irradiating light, processing of three-dimensional three-dimensional structures of various shapes can be performed. In other words, processing of various shapes
This is a design item for each parameter of the arrangement and arrangement of materials having different light absorptivity to laser light, the laser beam intensity profile, and the laser irradiation energy density, and it goes without saying that it can be easily realized. In addition, the workpiece does not need to be limited to a simple layered structure, and may be in a bonded state of free materials such as the presence or absence of overlap.

[0012]

As described above, according to the present invention, the relation between the irradiation light intensity distribution of the laser beam and the laser light absorptivity of each of the stacked materials exceeds the ablation threshold of each material. By processing the part given the light energy density, the irradiation light intensity distribution pattern of the laser beam and the arrangement of the laminated materials with different light absorptance of the irradiation laser light wavelength are designed according to the purpose, Fine processing of various three-dimensionally shaped structures becomes possible. Therefore, according to the present invention, it is possible to form a structure by processing a composite material by a single ultrashort pulse laser irradiation step, that is, in one step, and to use a complicated processing process such as a lithography process. Instead, it is possible to realize a laser processing method capable of processing a fine three-dimensional structure in a simple and simple processing step.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a laser processing method according to an embodiment of the present invention.

FIG. 2 is an example of a processed shape processed by a laser processing method according to an embodiment of the present invention.

[Explanation of symbols]

1: Laser light flux 2: Polysulfone layer (A layer) colored to a laser light wavelength absorption rate of about 5% 3: Polysulfone layer (B layer) colored to a laser light wavelength absorption rate of about 20% 4: Laser light wavelength absorption Polysulfone layer (C layer) colored at a rate of about 50% 5: Polysulfone layer (D layer) colored at a laser beam wavelength absorption rate of about 30%

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B41J 2/16 B41J 3/04 103H

Claims (5)

[Claims] 1. A laser beam emitted from a laser oscillator which continuously emits a light pulse having a large spatial and temporal energy density with a pulse emission time of 1 picosecond or less is applied to a multilayer structure having different wavelength absorptivity of the laser light. A laser processing method comprising irradiating a workpiece with a predetermined pattern and a predetermined energy density to process the workpiece. 2. The multi-layered workpiece is a plate or a structure formed by laminating or joining a plurality of materials that are translucent at the light wavelength of the laser beam and have different light absorptivity. The laser processing method according to claim 1. 3. The laser processing method according to claim 1, wherein the light pulse has a light intensity distribution of a Gaussian beam. 4. The laser processing method according to claim 1, wherein said laser oscillator is a laser oscillator having a spatial compression device for light propagation. 5. The laser processing method according to claim 4, wherein said spatial compression device for light propagation has a means for generating a chirped pulse and a longitudinal mode synchronization means using a light wavelength dispersion characteristic.