JP2006289441A - Method and apparatus for laser beam machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for laser beam machining, by which method and apparatus, a fine machining operation, such as removal and re-formation, can be accurately performed over a required range even by the multiple photon absorption process. <P>SOLUTION: An area of a workpiece 5 wider than the area of the converged spot of a pulsed laser beam is processed by a machining operation, such as a removal machining, by scanningly irradiating the workpiece 5 with the pulsed laser beam, which is radiated from a main light source 21 and has a pulse width smaller than 10 ps, and is called as, for example, femto-second (fs) laser and pico-second (ps) laser. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser processing method and a laser processing apparatus for processing a workpiece by irradiating pulsed laser light.

In manufacturing a member such as a thin film composed of a conductor such as an insulator, a semiconductor, or a metal, processing such as removal or shaping other than a predetermined portion is performed in order to make the shape and properties desired. Yes.
As a technique used for such processing, for example, wet etching with an etching solution such as an acid or dry etching with an etching gas can be cited.

Wet etching is one method that has been established historically, and the process can be performed with a relatively inexpensive apparatus configuration.
However, since it is necessary to go through steps such as resist coating, patterning exposure, selective removal using an etching solution, washing, and drying, the procedure is complicated. Moreover, it has been pointed out as a problem that immersion in an etching solution may not be appropriate depending on the shape and type of a sample to be removed, that is, a workpiece, and that fine patterning is difficult.

A dry etching technique such as Reactive Ion Etching (RIE) has been known for the above-described problems in wet etching, in particular, that fine patterning is difficult.
However, in this dry etching, although fine patterning can be realized, the basic process is the same as in wet etching, the procedure is complicated, and the etching apparatus is more expensive than in wet etching. In addition, it is necessary to consider the control of the atmospheric gas, which takes time.

In addition to these etching techniques, a technique for removing and shaping a member to be processed by irradiating it with a pulsed laser beam has been proposed and widely used (see, for example, Patent Document 1).
However, when the pulse width of the laser beam is, for example, on the order of nanoseconds (ns), even in the peripheral part where the laser beam is not directly irradiated by the thermal melting of the material constituting the member and the accompanying thermal diffusion Melting and deformation will occur.
Accordingly, any of the above-described methods has problems in terms of convenience, simplicity, cost, selectivity, and the like.

On the other hand, by selecting a shorter pulse width in the above-described pulse laser light irradiation, for example, by irradiating the pulse laser light with a short pulse width of less than 10 picoseconds, such as femtosecond order, selective to the workpiece Processing methods for removing and shaping have been proposed.
According to such a method of irradiating a short pulse width laser beam, unlike the case of irradiating a pulse laser beam having a pulse width of 10 picoseconds or more, such as the nanosecond order described above, the heat is diffused to the surroundings. Since pulse light irradiation with a short period is possible, the material constituting the member can be directly evaporated without going through a melting process by a so-called multiphoton absorption process that does not cause thermal diffusion.
JP 09-190995 A

  However, since the multi-photon absorption process by irradiation with such a short pulse width laser light proceeds only at the focused focal position, it is constant by widening the spot on the member surface as in the thermal process described above. It is difficult to perform so-called area removal that performs light irradiation over an area.

  Further, as described above, in the case of irradiation with pulsed laser light having a pulse width of 10 picoseconds or more, thermal diffusion occurs, so it is difficult to selectively remove or shape only a minute range. There is a similar problem in the depth direction. For example, when processing a member having a laminated structure composed of two or more materials whose melting points and boiling points are close to each other, only the uppermost layer is selectively removed. It was considered difficult.

  The present invention has been made in view of such problems, and its purpose is to selectively remove or shape a predetermined portion of a workpiece to be processed, that is, fine, while suppressing the occurrence of thermal melting and thermal diffusion. An object of the present invention is to provide a laser processing method and a laser processing apparatus capable of performing processing.

The laser processing method according to the present invention scans and irradiates a pulsed laser beam having a pulse width of less than 10 picoseconds, so that the member to be processed is at least partially wider than the focused spot of the pulsed laser beam. It is characterized by being removed over a period.
Thus, by performing scanning irradiation with short pulse laser light, thermal melting and thermal diffusion in the workpiece are suppressed as in the case of a thermal process.

The laser processing apparatus according to the present invention scans and irradiates a pulsed laser beam having a pulse width of less than 10 picoseconds, so that the workpiece is at least partially wider than the focused spot of the pulsed laser beam. It can be removed over a wide area.
By adopting a configuration in which processing is performed by laser light irradiation, for example, the degree of freedom of the device configuration is increased as compared with the above-described device for performing wet etching or dry etching.

  According to the laser processing method of the present invention, a pulse laser beam having a pulse width of less than 10 picoseconds, for example, a pulse laser beam called a femtosecond (fs) laser or a picosecond (ps) laser is scanned and irradiated. Since the member is removed over a wide range compared to the focused spot of the pulse laser beam, it is possible to perform removal and shaping over a desired range, that is, fine processing with high accuracy while using a multiphoton absorption process. It becomes.

  According to the laser processing apparatus of the present invention, the workpiece is removed over a wider range than the focused spot of the pulse laser beam by scanning and irradiating the pulse laser beam with a pulse width of less than 10 picoseconds. Therefore, it is possible to suppress thermal melting and thermal diffusion in the workpiece and to refine the machining on the workpiece in an apparatus configuration with a high degree of freedom.

  Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment of laser processing apparatus>
First, an embodiment of a laser processing apparatus according to the present invention will be described with reference to FIG.
As shown in FIG. 1, the laser processing apparatus 1 according to this embodiment includes at least a light source system 2, an optical system 3, and an irradiation system 4.

  The light source system 2 in the present embodiment includes, for example, a main light source 21 by Tsunami (Ti: Sapphire Laser; center wavelength 800 nm, pulse width 100 fs or less, repetition frequency 80 MHz) manufactured by Spectra-Physics, which is an oscillator, and Spectra, which is a regenerative amplifier, for example. Auxiliary light source 22 and amplifier 23 by Spitfire (central wavelength 800 nm, pulse width 100 fs or less, repetition frequency 1 Hz to 1 kHz) manufactured by Physics Co., Ltd., mirror 24 for guiding pulse laser light from the main light source 21 to the amplifier 23, and the main light source 21 And an adjuster 25 for aligning the phase and deflection of the light from the auxiliary light source 22.

  The optical system 3 in this embodiment includes, for example, an ND filter (Neutral Density Filter) 31 that adjusts the amount of pulsed laser light from the light source system 2, and an in-plane alignment adjustment mirror that defines an optical path that leads to the irradiation system 4. 32 and 33 and an afocal optical system 34 for adjusting the optical axis alignment.

The irradiation system 4 in this embodiment transmits a light from the mirror 41 introduced from the optical system 3 and the light from the mirror 41, and detects light from the objective lens side described later, for example, by a CCD (Charge Coupled Device). A beam splitter 42 that reflects on a container (not shown), an objective lens 43 that condenses the light from the mirror 41, and a workpiece 5 that is an object to be irradiated with the condensed pulsed laser light are placed. A stage 44 to be illuminated, an illumination light source 45 serving as an illumination of the stage 44, and a filter 46 for adjusting the amount of light of the illumination light source 45.
The irradiation system 4 is configured as a so-called microscope optical system. The stage 44 is controlled by, for example, a computer (not shown), and can be moved and selected in at least a two-dimensional plane substantially orthogonal to the optical axis of the pulse laser beam.

In this laser processing apparatus 1, the pulse width and irradiation energy of the pulsed laser light introduced from the light source system 2 through the optical system 3 to the irradiation system 4 are made to correspond to the materials constituting the workpiece 5, respectively. By adjusting each other, it is desirable to select a value that allows the member material to evaporate without melting through the multiphoton absorption process in the irradiated portion of the member 5 to be processed.
Note that when the pulse width is 10 picoseconds or more, the number of materials through which the multiphoton absorption process proceeds is extremely small, and thermal melting and thermal diffusion based on the one-photon absorption process proceeds. The width is preferably selected to be less than 10 picoseconds, desirably less than 1 picosecond, and particularly desirably 1 to 500 femtoseconds or less.

According to the laser processing apparatus 1 having this configuration, it is possible to scan and irradiate the workpiece 5 with pulsed laser light having a pulse width of less than 10 picoseconds, for example, by moving the stage 44 and selecting a position. That is, it becomes possible to remove at least a part of the workpiece 5 over a wider range than the focused spot of the pulsed laser beam, and perform processing such as shaping on the workpiece 5.
Therefore, according to the laser processing apparatus 1 according to the present embodiment, compared with an apparatus for performing wet etching or dry etching, the degree of freedom in the apparatus configuration is improved, and thermal melting and thermal diffusion in the workpiece are suppressed. As a result, it is possible to reduce the size of the workpiece and increase the accuracy. Furthermore, the cost can be reduced because the process is simplified and the atmosphere is less restricted than etching.

<Embodiment of Laser Processing Method>
Next, an embodiment of the laser processing method according to the present invention will be described with reference to FIG. 2, taking as an example the case of using the laser processing apparatus shown in FIG.

In the laser processing method according to the present embodiment, a pulse laser beam having a pulse width of less than 10 picoseconds,
By scanning and irradiating the workpiece, at least a part of the workpiece is removed or shaped over a wider range than the focused spot of the pulse laser beam. In addition,
In laser light irradiation, pulse laser light with a pulse width of less than 10 picoseconds is focused and irradiated, so that only the uppermost thin film can be directly evaporated from a solid by a multiphoton absorption process. Unlike the case of thin film removal by, it does not involve thermal melting.
Further, because of the multiphoton absorption process, extremely fine selective removal can be achieved with a resolution below the diffraction limit at the time of light collection. Multiphoton absorption occurs only at a certain level of light intensity. Therefore, when a focused beam is used to focus laser light on an irradiated material with such energy that multiphoton absorption occurs, the same laser beam is emitted. This is because there is a very high possibility that multiphoton absorption occurs only in the vicinity of the center. This is because the intensity profile of the focused beam has a Gaussian distribution or a profile conforming to it, so that the required intensity is not reached near the outer periphery of the profile, and the transpiration process by irradiation with focused femtosecond laser. Therefore, selective removal can be performed. In other words, in the case where a substance divergence occurs due to multiphoton absorption, that is, in the process of changing directly from a solid to a gas, since it does not liquefy, the influence on the ground is less likely to occur, so selective removal is possible. .

  First, as shown in FIG. 2A, in a plane perpendicular to the optical axis of the pulse laser beam on the surface of the workpiece, a scan is performed so that the focused spot S moves in the first direction axis, for example, the horizontal direction, As shown in FIG. 2B, removal or shaping, that is, processing is performed over a predetermined width that is wide at least in the lateral direction as compared with the focused spot S of the pulse laser beam.

Subsequently, as shown in FIG. 2C, the irradiation position, that is, the vertical feed of the spot S, that is, the vertical direction of the second direction axis, that is, the spot S, is performed, and at least partly different from the point S ₁ where scanning is started _first. adjust the position of the focusing spot S in position S _2, to start scanning again.
By feeding in the vertical direction, it is possible to scan and irradiate a wide range as compared with the focused spot S not only in the width direction but also in the vertical direction, that is, two-dimensionally.

Thus, by combining the scan with respect to the first direction axis, ie, the horizontal direction, and the feed with respect to the second direction axis, ie, the vertical direction, that is, the rescan is performed from the position of S ₃ , S ₄ ,. By repeating and starting, as shown in FIGS. 2D and 2E, it becomes possible to perform two-dimensional scanning irradiation with a short pulse width laser beam.

In addition, when processing a conductor such as a metal, a semiconductor, and an insulator by irradiation with a short pulse width laser beam having a pulse width of 100 femtoseconds, in addition to suppressing thermal diffusion, a so-called skin effect Because of the property that light is contained only within a few nm to 10 nm from the surface of the object to be irradiated, it can be removed only to a depth of several nm at the maximum by one pulse irradiation.
However, for example, when the member material can be removed to a depth of 5 nm by one pulse irradiation, the member has a depth of 15 nm by three pulse irradiations, 25 nm by five pulse irradiations, and a depth of 50 nm by ten pulse irradiations. Since the material can be removed, it is possible to dig a member by a so-called drilling technique by performing laser light irradiation with such two or more pulse irradiations.

  Therefore, in the laser processing method according to the present embodiment, in order to remove a member over a wider range than the focused spot S at a target removal depth, the number of drilling operations for one focused spot S is By selecting the optimum scanning speed, scanning order and method by combining scanning optical system elements such as scanning speed, irradiation beam focusing performance, and laser pulse repetition frequency, any range can be selectively removed. Thus, so-called area processing can be performed.

  In other words, by determining the scanning speed so that the pulses are almost adjacent to each other in consideration of the beam diameter φ (Airy Disc size φ to 1.22Xλ / NA) uniquely determined from the light collection performance and wavelength, and the repetition frequency of the pulses. In addition, it is possible to perform pulse irradiation with almost no gap for a predetermined removal length, and it is possible to realize irradiation for each pulse in a pseudo manner. Further, if the scanning interval with the next scanning line is φ / 2, for example, it is equivalent to the irradiation of two pulses, so that the pseudo interval can be obtained by appropriately adjusting the scanning interval in this way. The number of irradiation pulses can be controlled.

Further, it is desirable that the scanning irradiation of the pulsed laser light is performed not only so that the respective focused spots S are at least partially adjacent but also at least partially overlap each other.
This is because, for example, in laser light irradiation with a Gaussian distribution, the energy of the laser light is not sufficiently supplied at the outer portion in each focused spot S, and the central portion of each focused spot S, for example, the diameter r. This is because the transpiration of the member material by the multiphoton absorption process proceeds only within the range of about 0.6 r or less. Therefore, when processing is actually performed, it is desirable that the respective focused spots S overlap each other at least 20% or more, particularly desirably 30% or more with respect to the diameter.

In addition, after performing scanning in advance, when performing scanning again after feeding in the second direction axis, that is, in the vertical direction, particularly when performing light irradiation partially overlapping with already irradiated portions, It is desirable that the rescan be performed with a lower laser energy or a smaller number of pulses as compared to a scan performed in advance.
This is because, in the rescan, the portion that has already been removed by the laser beam irradiation is included in the irradiation range, and the irradiated part in the rescan is adjacent to the portion that has already been removed. The target depth can be obtained with lower laser energy or fewer pulses than when drilling without scanning, because the environment is likely to receive concentrated energy and transpiration is likely to proceed. This is because it is possible to perform desired processing such as removal.

  In the laser processing method according to the present invention, the mode of scanning and feeding can be selected as appropriate. That is, in the present embodiment, scanning is performed so that each focused spot is adjacent or overlapping, feed or slide is performed so that each scanning is adjacent or overlapping, and each scan is made substantially parallel to each other. However, the laser processing method according to the present invention is not limited to this.

For example, as shown in FIGS. 3A and 3C, for the rescan after feeding, S ₂ is performed by performing the first scan in the vertical direction, for example, near the end of the area to be finally processed. not only is started from the position, for example, when starting from the position of S ₄ is also already possible to start the adjacent or overlapping rescan locations machining is made, a lower laser energy or fewer pulses Processing can be done with numbers.

Further, for example, as shown in FIGS. 4A to 4C, the first scan is not started from the end of the area to be finally processed in the horizontal direction, but by starting from the position of S ₁ near the center, for example. after each scan starting from ₂ to S ₅ position, the position of S ₆ adjacent to duplicate S _1, by the S ₁ starts to scan in the opposite direction, by already places the machining is made Many adjacent or overlapping rescans can be performed, and processing can be performed with lower laser energy or fewer pulses.

  Further, for example, the respective focused spots in the scan can be formed intentionally at intervals. The feed for the second direction axis does not necessarily have to be performed in a direction orthogonal to the scan for the first direction axis, and the scan directions before and after the feed do not necessarily have to be parallel to each other. And the feed direction axis can be appropriately selected under the condition that they are at least partially different.

  According to such a laser processing method, for example, in the case of a thermal process, a pulse laser beam called a femtosecond (fs) laser or a picosecond (ps) laser is irradiated by scanning. Since the thermal melting and thermal diffusion are suppressed and the workpiece is removed over a wide range compared to the focused spot of the pulse laser beam, it can be removed over the desired range while using the multiphoton absorption process. And shaping, that is, fine processing can be performed with high accuracy.

<Example>
An embodiment of the laser processing method according to the present invention will be described.
First, a description will be given of a processing result for a laminated structure in which the uppermost layer is made of Ag by the laser processing method according to the present invention.
FIGS. 5A and 5B show a 700 nm thick resin film and a 125 nm thick ITO (Indium Thin Oxide) film (both shown in the figure, respectively) formed on a 0.7 mm thick glass substrate (not shown). (Not shown) shows the results of the laser processing method according to the present invention and the drilling without scanning performed on an Ag (silver) film having a thickness of 50 nm (measured value: 60 nm).
In this embodiment, processing by the laser processing method according to the present invention uses an optical system having a numerical aperture of 0.95 and an Airy disc size of about 1.0 μm, a center wavelength of 800 nm, a repetition frequency of 333 MHz, and irradiation energy. Under the condition of 1.6 J / cm ² , scanning at a scanning speed of about 313 μm / s was repeated 40 times over a width of 300 μm in the horizontal direction at a feed interval of 0.5 μm. On the other hand, the processing by drilling without scanning was performed using the same optical system, and 5 pulses were performed under the conditions of a center wavelength of 800 nm, a repetition frequency of 100 MHz, and an irradiation energy of 1.6 J / cm ² .

In the case of the laser processing method according to the present invention, as shown in FIG. 5A, an Ag film having a thickness of about 200 nm covers a range of 20 μm wide (arrow a shown) and a depth of about 66 nm (arrow b shown). It can be seen that the removal was almost complete. Although there is an overetching of about several nm, it can be suppressed to 5% or less with respect to the thickness of the Ag film and 10% or less with respect to the removal depth.
From this result, according to the laser processing method according to the present invention, the processing accuracy is higher than the result in the case of drilling without scanning shown in FIG. 5B (Ag film thickness of about 50 nm, removal width of 1 μm, removal depth of 53 nm). It is possible to selectively remove or shape a predetermined portion of the upper layer, for example, the Ag layer, without spotting the ITO film and without removing the ITO film serving as the underlayer. Was confirmed.

That is, according to the laser processing method of the present invention, since it is a process of directly evaporating from a solid using a multiphoton absorption process at the time of removal, damage or melting of the underlayer can be suppressed or avoided. 982 ° C.) and Ag (melting point 961 ° C.), and even when processing a laminated structure with materials having extremely close melting points and boiling points, it is possible in principle to properly remove only the upper layer, for example, the uppermost layer. Conceivable.
Furthermore, since removal is performed by a multiphoton absorption process, extremely fine selective removal is possible with a resolution below the diffraction limit at the time of light collection.

Next, the processing result for the Cr (chrome) thin film on the soda lime glass substrate by the laser processing method according to the present invention will be described.
6A and 6B show the removal of about 500 μm (shown by arrow f) over the Cr thin film over a range of 100 μm in length and 10 μm in width (shown by arrow e) by the laser processing method according to the present invention. The result of having processed and the examination result of the numerical aperture in laser beam irradiation are shown.

As shown in FIG. 6A, according to the laser processing method of the present invention, even if the material constituting the member to be processed is other than Al, the peripheral portion extends over a range wider than the laser beam spot by scanning irradiation. It was confirmed that processing can be performed with high accuracy while suppressing the raised height (shown by the arrow g) generated in 12.5 nm or less, that is, 5% or less of the removal depth.
In addition, since the raised height in a peripheral part will be broken by an impact etc. and will cause a new dust if this is large, it is preferable to make it as small as possible and 20% or less with respect to the removal depth. According to the present example, it was confirmed that the height of the swell could be reduced by the processing method according to the present invention even when compared with the processing result by the conventional thermal process as shown in FIG.

As shown in FIG. 6B, the relationship between the removal depth (Zapped Depth) and the swell height (Edge Height) when the laser energy (Fluence) is changed is examined for each numerical aperture of laser light irradiation. As a result, regardless of the numerical aperture, it was confirmed that the rise of the peripheral edge could be reduced most when 2.5 J / cm ² was used.

Next, the results of examining the transmittance of the soda lime glass substrate as the underlayer after removing the Cr thin film by the laser processing method according to the present invention for each laser energy (Fluence) will be described.
As shown in FIG. 8, since it can be confirmed that the transmittance of the ground layer after processing, that is, soda lime glass shows a high value regardless of the laser energy, the Cr thin film is removed by the removing method according to the present invention. In this case, it was confirmed that the soda lime glass substrate serving as the underlayer was hardly roughened and the damage was small.

  As mentioned above, although the embodiment of the laser processing method and the laser processing apparatus according to the present invention has been described, the materials used in the description of this embodiment, the combination thereof, and the numerical conditions such as dimensions are only preferred examples, The dimensional shape and the arrangement relationship in each figure used for explanation are also schematic. That is, the present invention is not limited to this embodiment.

For example, by irradiating a workpiece with a pulse laser beam having a pulse width of 10 picoseconds or more in advance, and then performing the laser machining method according to the present invention, the unevenness of the workpiece can be reduced or lowered. Processing can be performed to a range close to the formation.
Further, for example, in addition to the irradiation of the pulse laser beam, the member can be deformed as necessary by performing the irradiation of the second pulse laser beam that enables the deformation of the member to be processed. The invention can be variously modified and changed.

It is a schematic diagram which shows the structure of an example of the laser processing apparatus which concerns on this invention. Each of A to E is a schematic view for explaining an example of a laser processing method according to the present invention. Each of A and B is a schematic diagram for explaining another example of the laser processing method according to the present invention. AC is a schematic diagram for explaining another example of the laser processing method according to the present invention. A and B are photographs used to explain an example of the laser processing method according to the present invention. Each of A and B is a schematic diagram for explaining an example of a laser processing method according to the present invention. It is a schematic diagram with which it uses for description of the conventional laser processing method as a comparative example. It is a schematic diagram with which it uses for description of an example of the laser processing method which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laser processing apparatus, 2 ... Light source system, 3 ... Optical system, 4 ... Irradiation system, 5 ... Member to be processed (irradiated body), 21 ... Main light source, 22 ... Auxiliary light source, 23 ... Amplifier, 24 ... Mirror, 25 ... Adjuster, 31 ... ND filter, 32 ... Mirror, 33 ... Mirror, 34 ... Afocal Optical system, 35 ... lens, 36 ... slit, 37 ... lens, 41 ... mirror, 42 ... beam splitter, 43 ... objective lens, 44 ... stage, 45 ... .Light source, 46 ... filter

Claims (14)

By scanning and irradiating a pulsed laser beam having a pulse width of less than 10 picoseconds, at least a part of the workpiece is removed over a wider range than the focused spot of the pulsed laser beam. Laser processing method. The laser processing method according to claim 1, wherein the scanning irradiation is performed two-dimensionally. The laser processing method according to claim 2, wherein the scanning irradiation is performed by scanning with respect to a first direction axis and feed with respect to a second direction axis. The laser processing method according to claim 3, wherein refeeding can be performed by using the feed at a location that is at least partially different from a location where the scan has been performed in advance. The laser processing method according to claim 3, wherein refeeding can be performed at least partially adjacent to a portion where the scan has been performed in advance by the feed. After performing the scan in advance, it is possible to perform a rescan by the feed,
The laser processing method according to claim 3, wherein the rescan is performed with a lower laser energy than the previously performed scan. After performing the scan in advance, it is possible to perform a rescan by the feed,
The laser processing method according to claim 3, wherein the rescan is performed with a smaller number of pulses than the previously performed scan. The laser processing method according to claim 1, wherein the scanning irradiation is performed with at least a part of each of the focused spots overlapping each other. The laser processing method according to claim 7, wherein the overlap is generated by 20% or more with respect to a diameter of the focused spot. 2. The laser processing method according to claim 1, wherein the scanning irradiation is performed by selecting the size and interval of each of the focused spots, the pulse width, and the scanning speed. The workpiece has at least a laminated structure of a base layer and an upper layer formed on the base layer,
The laser processing method according to claim 1, wherein at least a part of the upper layer is removed by the scanning irradiation. The laser processing method according to claim 1, wherein the workpiece is irradiated with a pulse laser beam having a pulse width of 10 picoseconds or more in advance. 2. The laser processing method according to claim 1, wherein, in addition to the irradiation with the pulsed laser beam, irradiation with a second pulsed laser beam that enables deformation of the workpiece is performed. By scanning and irradiating a pulse laser beam with a pulse width of less than 10 picoseconds, it is possible to remove at least a part of the workpiece over a wider range than the focused spot of the pulse laser beam. A laser processing apparatus characterized by the above.