JP2006130515A - Laser beam machining method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining method and a device therefor realizing stable microfabrication with high precision by an ultrashort pulse laser. <P>SOLUTION: A first machining phenomenon appearing at a threshold fluence lower than a machining threshold fluence required for realizing desired laser beam machining is induced in a fixed region at the surface and inside of the material of the object 6 to be machined by a laser pulse passed through an optical path 2 for lower bulkhead phenomenon induction. The region modified by the first machining phenomenon is irradiated with a threshold fluence stronger than the threshold fluence inducing the first machining phenomenon by a laser pulse passed through an optical path 3 for upper threshold phenomenon induction, and a second machining phenomenon is induced in the above modified region, thus the modified region is preferentially or exclusively machined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for performing laser processing (for example, cutting, breaking, surface and internal modification, refractive index change, ablation, modification of material structure and physical properties, etc.) with an ultrashort pulse laser.

  In ultrashort pulse laser processing, a method of controlling the processing shape by controlling the irradiation fluence, the pulse width, the number of pulses to be irradiated, and the beam spot diameter is known.

For example, Patent Document 1 discloses a method for efficiently generating laser-induced breakdown by controlling a pulse width and a processing threshold fluence. In particular, in ultrashort pulse laser processing, since there is a fluence processing threshold value dependency according to the relationship between fluence and pulse width, the processing shape is controlled by the energy distribution in the beam spot and the processing threshold value. When the energy distribution in the beam spot is a Gaussian distribution, the processing is performed only at the energy irradiation portion that is equal to or greater than the processing threshold, and therefore processing that is equal to or less than the beam spot diameter is possible.
Japanese Patent No. 3283265

  However, in the processing method disclosed in Patent Document 1 described above, even when the laser beam is sufficiently collected and processed, the peripheral effects such as avalanche ionization, alteration, and material stress around the spot cause Since the processing is easily affected by the portion, the processing resolution is lowered. In addition, the energy distribution in the beam spot is likely to vary due to energy fluctuations due to the stability of the laser, and the variation in energy distribution is due to variations in the machining area and unclearness of the machining boundary. It is difficult to perform microfabrication by direct writing of nano-areas that require performance.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a laser processing method and apparatus that realizes highly accurate and stable fine processing using an ultrashort pulse laser.

In one aspect of the laser processing method of the present invention, in laser processing with an ultrashort pulse laser,
Inducing a first processing phenomenon that occurs at a threshold fluence lower than a processing threshold fluence necessary for realizing a desired laser processing in a certain region on the material surface and inside,
By irradiating the altered region altered by the first machining phenomenon with a threshold fluence stronger than the threshold fluence that induces the first machining phenomenon, and inducing a second machining phenomenon in the altered region, Process the altered region preferentially or exclusively;
It is characterized by that.

Moreover, one aspect of the laser processing apparatus of the present invention is a laser processing apparatus using an ultrashort pulse laser,
A first processing means for inducing a first processing phenomenon that occurs at a threshold fluence lower than a processing threshold fluence necessary for realizing a desired laser processing, in a certain region inside the material surface and inside;
By irradiating the altered region altered by the first machining phenomenon with a threshold fluence stronger than the threshold fluence that induces the first machining phenomenon, and inducing a second machining phenomenon in the altered region, A second processing means for processing the altered region preferentially or exclusively;
It is characterized by comprising.

  According to the present invention, first, material alteration is induced on the surface and inside, and only the altered portion is selectively and preferentially processed, so that the influence on the surroundings is extremely reduced. It is possible to provide a laser processing method and apparatus capable of performing micro processing and realizing highly accurate and stable micro processing using an ultrashort pulse laser.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram showing a configuration of a laser processing apparatus according to the first embodiment of the present invention. FIGS. 2A and 2B are views showing the processing mechanism of the first embodiment. FIG. 3 is a diagram showing a surface state of quartz subjected to surface submicron dot processing by the laser processing apparatus according to the present embodiment.

(Constitution)
As shown in FIG. 1, in the laser processing apparatus according to the present embodiment, the laser pulse generated from the ultrashort pulse laser apparatus 1 capable of controlling the number of pulses is used for inducing the lower threshold phenomenon that is the first processing phenomenon. An optical path (hereinafter referred to as a lower threshold phenomenon inducing optical path) 2 and a second processing phenomenon, an upper threshold phenomenon inducing optical path (hereinafter referred to as an upper threshold phenomenon inducing optical path) 3 are branched into each optical path. The set energy attenuator 4 sets the energy suitable for each processing. Then, the laser pulse divided into the two optical paths is returned to the same optical path, and is condensed on the workpiece 6 by the condensing optical system 5. The processing position control is controlled by moving the stage 7.

  Here, after the laser pulse that has passed through the lower threshold phenomenon inducing optical path 2 is irradiated on the workpiece 6, the two laser pulses that have passed through the upper threshold phenomenon inducing optical path 3 are irradiated. An optical path difference is set between the optical paths.

  The workpiece 6 is a metal, a wafer, glass, a crystal material, a biomaterial, or the like.

  Further, it is possible to monitor the processing phenomenon by spectrum observation in the spectroscope 8.

  In the present embodiment, the ultrashort pulse laser device 1 uses a light source that can change a pulse repetition frequency of 1 kHz, a laser wavelength of 800 mm, and a pulse width of 150 fs to 3 ps.

(Function)
In the first embodiment, the laser pulse that has passed through the lower threshold phenomenon inducing optical path 2 induces material alteration, which is the lower threshold phenomenon as the first processing phenomenon, on the surface and inside of the workpiece 6, and the upper threshold Only the altered portion is selectively and preferentially processed by the laser pulse that has passed through the phenomenon inducing optical path 3.

  That is, the laser pulse generated from the ultrashort pulse laser device 1 is focused on the workpiece 6 by the focusing optical system 5. In the lower threshold phenomenon as the first processing phenomenon and the upper threshold phenomenon as the second processing phenomenon, a change is seen in the spectrum scattered from the material surface, so that the light scattered from the workpiece 6 is spectroscope. By observing at 8, the processing phenomenon can be monitored, and the irradiation fluence can be easily set.

  FIGS. 2A and 2B are diagrams showing the mechanism when the lower threshold phenomenon is modified and the upper threshold phenomenon is ablated. As shown in FIG. 2A, the lower threshold phenomenon is reformed on the material surface in the energy region exceeding the threshold fluence. Then, as shown in FIG. 2B, selective ablation of the reforming section 9 can be performed by setting the fluence within the range of the ablation threshold fluence of the bulk and within the range of the ablation threshold of the reforming section. Become.

  For example, the energy region of the threshold fluence that induces the lower threshold phenomenon is in the region from 10 joules per square centimeter to 1 microjoule per square centimeter, and the energy region of the threshold fluence that induces the upper threshold phenomenon is per square centimeter. It is in the region from 10 microjoules to 1 joule per square centimeter. That is, the threshold fluence in the lower threshold phenomenon is determined by setting conditions in the energy region from 10 joules per square centimeter to 1 microjoule per square centimeter, in materials such as metals, glass, resins, and biomaterials. In addition, it is possible to cause internal modification, refractive index change, ablation, modification of material structure and physical properties, and the upper threshold phenomenon can be induced by a condition higher than the threshold fluence in the lower threshold phenomenon.

  In addition, by shaping the beam into the desired beam spot shape using the condensing optical system 5, the beam spot shape can be changed at the time of induction of the lower threshold phenomenon and the upper threshold phenomenon, so that accuracy and machining shape can be freely set. It becomes possible to control to. As described above, by narrowing down the irradiation area of the reforming portion 9, direct drawing processing at a submicron level can be easily performed.

  FIG. 3 shows the results of submicron ablation of the quartz substrate obtained by this embodiment. Thus, according to the present embodiment, highly accurate and stable microfabrication using an ultrashort pulse laser can be realized.

[Second Embodiment]
In the laser processing apparatus according to the first embodiment, a case where the lower threshold phenomenon is ionized inside the material and the upper threshold phenomenon is an internal refractive index change will be described as a second embodiment of the present invention. FIG. 4 is a diagram showing a spectrum result at the time of internal ionization and a spectrum result at the time of changing the internal refractive index when irradiating the inside of glass (BK7). FIG. 5 is a diagram showing the obtained internal refractive index change dots.

(Constitution)
Using the laser processing apparatus described in the first embodiment, the condensing point by the condensing optical system 5 is set inside the glass that is the workpiece 6. As the workpiece 6, BK7 is used, and internal refractive index change dot processing is performed with the lower threshold phenomenon as internal ionization and the upper threshold phenomenon as internal refractive index change.

(Function)
FIG. 4 shows a spectrum observation result by the spectrometer 8 during internal ionization and a spectrum observation result when the internal refractive index changes. As shown in the figure, since there is a difference in the spectrum results, internal ionization and internal refractive index change can be distinguished and controlled.

  FIG. 5 shows the microscopic observation results of the internal refractive index change dots of BK7.

  According to the second embodiment, it is possible to create sub-micron level internal dots.

[Third Embodiment]
FIG. 6 is a diagram showing a configuration of a laser processing apparatus according to the third embodiment of the present invention. The laser processing apparatus according to the present embodiment is a laser processing apparatus capable of batch patterning drawing. In the present embodiment, a DOE (phase type diffractive optical element) 10 is used as a beam energy intensity distribution pattern control method.

(Constitution)
In the laser processing apparatus according to the present embodiment, in the configuration of the laser processing apparatus according to the first embodiment, the DOE 10 is inserted in the lower threshold phenomenon inducing optical path 2, and the lower threshold phenomenon inducing laser pulse is included in the beam. The energy intensity distribution pattern can be controlled. In addition to the DOE 10, there are a beam interference method, a phase plate, and a homogenizer that can control the energy intensity distribution pattern in the beam.

  Both the lower threshold phenomenon and the upper threshold phenomenon perform surface batch irradiation by defocusing. The processing area is determined by the energy profile, the condensing optical system NA, and the beam diameter.

(Function)
In the present embodiment, a DOE 10 is used to create an in-beam energy intensity distribution pattern, a pattern of a lower threshold phenomenon is irradiated on the surface of the material or inside, and uniform beam energy is irradiated when an upper threshold phenomenon is induced.

  That is, since the altered portion along the intensity pattern is created by the lower threshold phenomenon, when the uniform beam energy is irradiated, the altered pattern portion can be selectively processed, and high-quality pattern processing becomes possible.

  Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention.

(Appendix)
The invention having the following configuration can be extracted from the specific embodiment.

(1) In laser processing (cutting, breaking, surface and internal modification, refractive index change, ablation, modification of material structure and physical properties, etc.) using an ultrashort pulse laser,
Inducing a first processing phenomenon (lower threshold phenomenon) that develops at a threshold fluence lower than a processing threshold fluence necessary to realize a desired laser processing, on a material surface and a certain region inside,
The altered region altered by the first machining phenomenon is irradiated with a threshold fluence stronger than the threshold fluence that induces the first machining phenomenon, and a second machining phenomenon (upper threshold phenomenon) is applied to the altered region. Process the altered region preferentially or exclusively by inducing,
The laser processing method characterized by the above-mentioned.

(Corresponding embodiment)
The first to third embodiments correspond to the laser processing method described in (1).

(Function and effect)
When a lower threshold phenomenon induced by a lower threshold fluence than the upper threshold phenomenon, which is the desired processing phenomenon, is formed inside or on the surface of the material, the lower threshold fluence irradiation part (deformed part) is higher than the threshold fluence of the bulk material. The threshold fluence of the threshold phenomenon changes. When the modified part has a modified processing threshold, the irradiated area can be processed preferentially, and when the modified part has a high processing threshold, exclusive processing with the altered part remaining is possible. It becomes. In addition, the processing method using the lower threshold phenomenon simplifies the processing phenomenon and is less susceptible to side effects, so it is possible to create an altered region due to the lower threshold phenomenon in a finer area, with high resolution. Can be realized.

(2) The threshold fluence that induces the second processing phenomenon (upper threshold phenomenon) is set to a threshold fluence that is lower than the threshold fluence of the unmodified bulk material,
Only the altered portion is selectively machined by the difference between the altered portion due to the first processing phenomenon (lower threshold phenomenon) and the processing threshold fluence of the bulk.
(1) The laser processing method according to (1).

(Corresponding embodiment)
The first to third embodiments correspond to the embodiment related to the laser processing method described in (2).

(Function and effect)
If the threshold fluence of the upper threshold phenomenon of the irradiated part altered by the lower threshold phenomenon is lower than the threshold fluence of the unirradiated bulk material, it is lower than the threshold fluence of the unirradiated bulk material By selecting a modified part, it is possible to process only the modified part by leaving a part of the bulk material that has not been modified by irradiating the region including the modified part with a fluence higher than the threshold fluence of the irradiated part. Machining is possible. Since the processing does not exceed the region obtained by the lower threshold phenomenon, it is not affected by the periphery of the irradiation region. Improvement in processing resolution and improvement in processing variation are expected by making the lower threshold phenomenon smaller and reducing the influence on the periphery.

(3) When performing laser ablation with an ultrashort pulse laser as the laser processing,
Create a modified region that is the first processing phenomenon (lower threshold phenomenon) near the material surface as the altered region,
Thereafter, the modified region is removed by laser ablation, which is the second processing phenomenon (upper threshold phenomenon),
(1) The laser processing method according to (1).

(Corresponding embodiment)
The embodiment relating to the laser processing method described in (3) corresponds to the first embodiment.

(Function and effect)
Since the material structure of the modified region in the vicinity of the material surface, which is the lower threshold fluence irradiating portion, is brittle, the ablation threshold is lowered in the modified region. Therefore, since the processing threshold fluence difference with the bulk material around the lower threshold fluence irradiation part occurs, only the modified region is removed by fluence irradiation lower than the ablation threshold of the bulk material, or in the same region ablation with the bulk material Also, the reforming part can be removed preferentially.

(4) The energy region of the threshold fluence that induces the first processing phenomenon (lower threshold phenomenon) is in a region from 10 joules per square centimeter to 1 microjoule per square centimeter,
The energy region of the threshold fluence that induces the second processing phenomenon (upper threshold phenomenon) is in the region from 10 microjoules per square centimeter to 1 joule per square centimeter,
The laser processing method according to any one of (1) to (3).

(Corresponding embodiment)
The first to third embodiments correspond to the embodiment relating to the laser processing method described in (4).

(Function and effect)
The threshold fluence in the lower threshold phenomenon is determined by setting conditions in the region from 10 joules per square centimeter to 1 microjoule per square centimeter, in materials such as metals, glass, resins, and biomaterials. It is possible to cause quality, refractive index change, ablation, modification of material structure and physical properties, and the upper threshold phenomenon can be induced by conditions higher than the threshold fluence in the lower threshold phenomenon.

  (5) A beam is shaped into a desired beam spot shape using a condensing optical system, and beams are mutually generated when the first processing phenomenon (lower threshold phenomenon) and the second processing phenomenon (upper threshold phenomenon) are induced. The laser processing method according to any one of (1) to (3), wherein the spot shape is changed.

(Corresponding embodiment)
The embodiment relating to the laser processing method described in (5) corresponds to the first and second embodiments.

(Function and effect)
By changing the irradiation beam spot shape at the time of the lower threshold phenomenon and the upper threshold phenomenon, it becomes possible to freely control the accuracy and the processing shape. By narrowing down the irradiation area of the modified portion, direct drawing processing at a submicron level can be easily performed.

(6) In the first processing phenomenon (lower threshold phenomenon), an altered portion based on the energy intensity distribution pattern in the beam is created by beam interference or phase control,
A pattern region is created in a lump by irradiating the altered portion with the same or enlarged spot region of the second processing phenomenon (upper threshold phenomenon),
The laser processing method according to any one of (1) to (3).

(Corresponding embodiment)
The embodiment relating to the laser processing method described in (6) corresponds to the third embodiment.

(Function and effect)
An in-beam energy intensity distribution pattern is created using interference, a phase plate, a DOE, a homogenizer, etc., and a pattern of a lower threshold phenomenon is irradiated on the material surface or inside, and uniform beam energy is irradiated when an upper threshold phenomenon is induced. Since the altered portion along the intensity pattern is created by the lower threshold phenomenon, when the uniform beam energy is irradiated, the altered pattern portion can be selectively processed, and high-quality pattern processing becomes possible.

(7) In a laser processing apparatus using an ultrashort pulse laser,
First processing means for inducing a first processing phenomenon (lower threshold phenomenon) that appears at a threshold fluence lower than a processing threshold fluence necessary for realizing desired laser processing, on a material surface and a certain region inside. When,
The altered region altered by the first machining phenomenon is irradiated with a threshold fluence stronger than the threshold fluence that induces the first machining phenomenon, and a second machining phenomenon (upper threshold phenomenon) is applied to the altered region. A second processing means for preferentially or exclusively processing the altered region by inducing,
A laser processing apparatus comprising:

(Corresponding embodiment)
The first to third embodiments correspond to the laser processing apparatus according to (7). In these embodiments, the ultrashort pulse laser device 1, the lower threshold phenomenon inducing optical path 2, the energy attenuator 4, and the condensing optical system 5 correspond to the first processing means, and the ultrashort pulse laser device 1, The upper threshold phenomenon inducing optical path 3, the energy attenuator 4, and the condensing optical system 5 correspond to the second processing means.

(Function and effect)
When a lower threshold phenomenon induced by a lower threshold fluence than the upper threshold phenomenon, which is the desired processing phenomenon, is formed inside or on the surface of the material, the lower threshold fluence irradiation part (deformed part) is higher than the threshold fluence of the bulk material. The threshold fluence of the threshold phenomenon changes. When the modified part has a modified processing threshold, the irradiated area can be processed preferentially, and when the modified part has a high processing threshold, exclusive processing with the altered part remaining is possible. It becomes. In addition, the processing method using the lower threshold phenomenon simplifies the processing phenomenon and is less susceptible to side effects, so it is possible to create an altered region due to the lower threshold phenomenon in a finer area, with high resolution. Can be realized.

FIG. 1 is a diagram showing a configuration of a laser processing apparatus according to the first embodiment of the present invention. FIG. 2A is a diagram showing a modification processing mechanism as a lower threshold phenomenon, and FIG. 2B is a diagram showing an ablation processing mechanism as an upper threshold phenomenon. FIG. 3 is a diagram illustrating a surface state of quartz that has been subjected to surface submicron dot processing by the laser processing apparatus according to the present embodiment. FIG. 4 is a diagram showing a spectrum result at the time of internal ionization and a spectrum result at the time of change in internal refractive index when irradiating the inside of glass (BK7) as a second embodiment of the present invention. FIG. 5 is a diagram showing the obtained internal refractive index change dots. FIG. 6 is a diagram showing a configuration of a laser processing apparatus according to the third embodiment of the present invention.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 1 ... Ultra-short pulse laser apparatus, 2 ... Optical path for lower threshold phenomenon induction, 3 ... Optical path for upper threshold phenomenon induction, 4 ... Energy attenuator, 5 ... Condensing optical system, 6 ... Workpiece, 7 ... Stage, 8 DESCRIPTION OF SYMBOLS ... Spectroscope, 9 ... Modified part, 10 ... DOE (phase type diffractive optical element).

Claims (7)

In laser processing with ultrashort pulse laser,
Inducing a first processing phenomenon that occurs at a threshold fluence lower than a processing threshold fluence necessary for realizing a desired laser processing in a certain region on the material surface and inside,
By irradiating the altered region altered by the first machining phenomenon with a threshold fluence stronger than the threshold fluence that induces the first machining phenomenon, and inducing a second machining phenomenon in the altered region, Process the altered region preferentially or exclusively;
The laser processing method characterized by the above-mentioned. The threshold fluence that induces the second processing phenomenon is set to a threshold fluence that is lower than the threshold fluence of the unmodified bulk material,
Only the altered portion is selectively machined by the difference in the processing threshold fluence between the altered portion and the bulk due to the first machining phenomenon,
The laser processing method according to claim 1. When performing laser ablation with an ultrashort pulse laser as the above laser processing,
Create a modified region that is the first processing phenomenon in the vicinity of the material surface as the altered region,
Thereafter, the modified region is removed by laser ablation, which is the second processing phenomenon.
The laser processing method according to claim 1. The energy range of the threshold fluence that induces the first processing phenomenon is in the range from 10 joules per square centimeter to 1 microjoule per square centimeter;
The threshold fluence energy region inducing the second processing phenomenon is in the region of 10 microjoules per square centimeter to 1 joule per square centimeter;
The laser processing method according to any one of claims 1 to 3.   A beam is shaped into a desired beam spot shape by using a condensing optical system, and the beam spot shape is changed mutually when the first machining phenomenon and the second machining phenomenon are induced. The laser processing method according to any one of 1 to 3. In the first processing phenomenon, an altered portion based on the energy intensity distribution pattern in the beam is created by beam interference or phase control,
A pattern region is created in a lump by irradiating the altered portion with the same or enlarged spot region of the second processing phenomenon,
The laser processing method according to any one of claims 1 to 3. In laser processing equipment using ultra-short pulse laser,
A first processing means for inducing a first processing phenomenon that occurs at a threshold fluence lower than a processing threshold fluence necessary for realizing a desired laser processing, in a certain region inside the material surface and inside;
By irradiating the altered region altered by the first machining phenomenon with a threshold fluence stronger than the threshold fluence that induces the first machining phenomenon, and inducing a second machining phenomenon in the altered region, A second processing means for processing the altered region preferentially or exclusively;
A laser processing apparatus comprising:

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