JP4644797B2 - Laser irradiation method and apparatus, fine processing method and apparatus, and thin film forming method and apparatus - Google Patents

Description

  The present invention is, for example, a laser irradiation method and apparatus suitably used for nano-level microfabrication on a solid surface using a laser, nano-level ion emission from the solid surface, non-destructive mass analysis of the solid surface, etc. Further, the present invention relates to a technical field of a fine processing method and apparatus using these and a thin film forming method and apparatus.

In the technical field of microfabrication using this type of laser, technological development using a “femtosecond laser” with an extremely short pulse width is in progress. Here, “femtosecond laser” refers to a femtosecond laser or a laser pulse having a pulse width of 1 picosecond (ps) or less. In addition, a technique for performing fine processing on a solid surface by irradiating the solid surface with a laser at high fluence or low fluence is also known. Here, the “fluence” is an energy density (J / cm ² ) obtained by dividing the output energy per one pulse of the laser by the irradiation sectional area.

  More specifically, in a high fluence region, by irradiating the solid surface with a long pulse laser or a short pulse laser including a femtosecond laser, the ion surface is thermally released from the solid surface heated to a high temperature ( Or the technique which performs desorption ionization is reported (refer nonpatent literature 1, 2, 3).

  On the other hand, a microfabrication method characterized by controlling the size and shape of a hole by controlling the wavelength (that is, frequency control) and polarization of a femtosecond laser with a low fluence has been proposed (patented) Reference 1). Note that “low fluence” generally means that the value of the fluence is relatively small. However, in Patent Document 1, the energy density is such that the material surface evaporates by irradiating the surface of the material with a laser. It is assumed that the fluence near the minimum value (ablation threshold) is shown.

P.A.VanRompay et al, “Pulse-contrast effects on energy distributions of C1 + to C4 + ions for high-intensity 100-fs laser-ablation plasmas”, Applied Surface Science 127-129, pp.1023-1028 (1998) S. Amoruso et al, “Thermal and nonethermal ion emission during high-fluence femtosecond laser ablation of metallic targets”, Appl. Phys. Lett. 77, pp. 3728-3730 (2000) T. Gotz et al, “Short-pulse UV laser ablation of solid and liquid metals: indium”, Appl. Phys. A64, pp. 539 543 (1997) JP 2003-211400 A

  However, according to the techniques of Non-Patent Documents 1 to 3, the laser used is limited to the high fluence region. For this reason, the solid surface is melted by laser irradiation, or the structure of the solid surface is thermally destroyed. Therefore, when considering microfabrication of a solid surface by laser irradiation, in particular, delamination at the atomic and molecular level, ionization at the atomic and molecular level, or non-destructive analysis (ie, only at the atomic and molecular level). However, according to these techniques, there is a problem that it is impossible in practice.

  On the other hand, according to Patent Document 1, the size of the microfabrication is “having a positive correlation with the wavelength”. For example, the size of the microfabrication is changed, including the peeling depth or the ablation rate. In order to control and adjust the size of the fine processing, it is necessary to change the wavelength of the laser. For this reason, according to Patent Document 1, special wavelength control means such as arranging an optical wavelength converter in the laser optical path is required in the optical system, and the apparatus configuration and control are complicated, and the degree of freedom in fine processing is increased. There is a technical problem that is lacking. Furthermore, in the method with wavelength control as described above, there is a technical problem that it is practically difficult to perform separation at the atomic / molecular level or ionization at the atomic / molecular level even when using a femtosecond laser. is there.

  The present invention has been made in view of the above-described problems. For example, it is possible to perform separation at the atomic / molecular level or ionization (that is, desorption ionization) at the atomic / molecular level on the solid surface, and by ablation. Laser irradiation method and apparatus, fine processing method and apparatus on solid surface using these, and thin film forming method and apparatus, which can be suitably used for fine processing, fine ion emission, non-destructive solid surface analysis, etc. The issue is to provide.

In order to solve the above problems, the first laser irradiation method of the present invention irradiates the solid surface by irradiating the solid surface according to a desired peeling depth to be peeled from the solid surface and the material of the solid surface. A setting step for setting an irradiation fluence value for the femtosecond laser in the low fluence region causing non-thermal ionization emission on the surface in the low fluence region; and the set irradiation fluence for the solid surface An irradiation step of irradiating the femtosecond laser at a value of , wherein the setting step includes a first ablation threshold fluence and a second of a plurality of ablation threshold fluences depending on the material within the low fluence region. Set the value of the irradiation fluence within the region between the low ablation threshold fluence and .

According to the first laser irradiation method of the present invention, in the setting step, depending on the desired peeling depth (in other words, desired ablation rate) to be peeled from the solid surface and the material of the solid surface, On the other hand, the value of the irradiation fluence relating to the femtosecond laser to be irradiated is set. For example, in terms of the ablation rate, 0.01 nm / shot (nanometer / shot, where “shot” means one irradiation of a laser pulse), ie, at the atomic / molecular level, If the peel depth is very shallow, the irradiation fluence value is set to 0.1 J / cm ² , for example. The “ablation rate” indicates an ablation depth, that is, a peeling depth (nm) per one laser pulse. In the irradiation process, the solid surface is irradiated with the femtosecond laser at the irradiation fluence value set in the setting process.

  The “femtosecond laser” according to the present invention means a femtosecond order pulse laser having a pulse width shorter than the collision relaxation time for a material such as a metal forming a solid surface. That is, the pulse width itself related to the femtosecond laser is variable according to the material such as metal forming the solid surface. For example, it is 1.12 ps (picosecond) for Al (aluminum), 17.49 ps for Cu (copper), and 0.83 ps for Ti (titanium).

The “low fluence region” according to the present invention means a region near the ablation threshold where nonthermal ionization occurs on the solid surface. More specifically, it typically means within the region between the first lowest ablation threshold fluence and the second lowest ablation threshold fluence. Although the low fluence region varies depending on the material of the solid surface, for example, a fluence region on the order of 15 mJ / cm ^{2 to} 150 mJ / cm ² is cited here.

Particularly in the first laser irradiation method of the present invention, in the setting step, the value of the irradiation fluence is set within a low fluence region that causes non-thermal ionization emission (that is, non-thermal desorption ionization) on the solid surface. In the irradiation step, the femtosecond laser is irradiated with this set value. The femtosecond laser irradiated in the present invention is a “low fluence high intensity laser pulse” having a low fluence and a high light intensity. Here, the “high intensity” or “high light intensity” of the laser according to the present invention is a laser that can be emitted from the solid surface as molecular ions or multivalent molecular ions by irradiating the solid surface with a femtosecond laser. This value is specific to the material of the solid surface. However, in the present invention, the condition for the parameter “light intensity” does not have to be required independently, and if the conditions related to the ablation threshold fluence described above are determined, the relationship of laser intensity (light intensity) = fluence / pulse width. From the formula, it is determined depending on the fluence. Here, in the setting step, in the low fluence region, in a region between the first smallest ablation threshold fluence and the second smallest ablation threshold fluence among the plurality of ablation threshold fluences depending on the material, The value of the irradiation fluence is set. In this way, the value of the irradiation fluence is within a region between the first and second lowest ablation threshold fluences among the plurality of ablation threshold fluences depending on the material of the solid surface, Is set. Such a plurality of ablation threshold fluences can be quantified or tabulated in advance depending on the material of the solid surface. Therefore, once these values are obtained, the value of the irradiation fluence in the setting step is determined according to the material of the solid surface and the desired peeling depth (or ablation rate) that are actually laser irradiation targets. It can be determined uniquely. That is, the irradiation fluence can be set relatively easily.

  Therefore, (i) thermal ionization on the solid surface by high fluence laser irradiation as described in Non-Patent Documents 1 to 3 above or (ii) laser irradiation with a pulse longer than the collision relaxation time instead of femtosecond laser. Peeling or ablation can be performed at the atomic and molecular level without incurring or melting or breaking by heating. At this time, by using an extremely short pulse of a low fluence and a femtosecond laser, a non-thermal ion emission phenomenon occurs on the solid surface, and the solid surface is not heated, at the atomic / molecular level. Peeling is possible. In the present invention, the “atomic / molecular level” indicates a range or unit of nano-order or sub-nano-order near the solid surface, for example, one atom, several atoms, or dozens to dozens of atoms.

  Furthermore, in the above-mentioned Patent Document 1, “adjusting / controlling the wavelength of the laser adjusts / controls the size of the fine processing that has a positive correlation with the wavelength”. In the irradiation step according to the first laser irradiation method of the present invention, the value of the irradiation fluence related to the laser is adjusted / controlled within the low fluence region, so that the peeling depth is adjusted / controlled, in other words, the ablation rate Is to adjust and control. According to the study of the present invention, in the low fluence region, for example, the three-photon absorption process as a multivalent ionization phenomenon becomes dominant or completely dominant as a factor of the ablation phenomenon. This is based on the consideration that the peeling depth or the ablation rate can be adjusted / controlled by adjusting / controlling the value of the irradiation fluence (regardless of the wavelength). That is, according to the present invention, the size of the fine processing can be adjusted and controlled by adjusting and controlling the value of the irradiation fluence without the need to adjust and control the laser wavelength as a parameter as taught in Patent Document 1. Is also possible. Further, as seen as a kind of traditional laser processing, two laser beams to be finely processed by light interference are not required.

  As described above, according to the first laser irradiation method of the present invention, in order to adjust / control the separation depth (ablation rate) or the size of microfabrication including the separation depth and the separation area, The irradiation fluence value within the fluence region is adjusted and controlled. In other words, laser irradiation for causing ablation and laser irradiation for causing nonthermal ionization are performed simultaneously as one laser irradiation. Therefore, a special optical means for adjusting and controlling the laser wavelength such as the “wavelength converter” as in the above-mentioned Patent Document 1 is not necessary, and it is relatively easy to make a peeling depth (ablation rate) or fine processing. This can be adjusted and controlled to a desired value, which is very advantageous in practice.

  In other words, it is possible to release a small amount of molecular ions non-destructively from the solid surface by peeling at the atomic and molecular level, and use it for thin film formation, etc. Therefore, it is possible to release molecular ions (that is, desorb ions) and use them for mass spectrometry and the like, which is very advantageous in practice.

In one aspect of the first laser irradiation method of the present invention, the setting step includes the first ablation threshold fluence F3, th among the ablation threshold fluences present as at least three ablation threshold fluences, and the The irradiation fluence value may be set in a region between the second smallest ablation threshold fluence F2, th.

  With this setting, the value of the irradiation fluence is set within a low fluence region existing between the ablation threshold fluences F3, th and F2, th, for example, in which the three-photon absorption process becomes dominant in the ablation phenomenon. Will be. Even in the case of a femtosecond laser, for example, if it has a wavelength of 800 nm, the photon has a particle property of 1.5 eV. Therefore, non-thermal ionization emission is performed on the solid surface according to the three-photon absorption process. Incidentally, according to the study by the present inventors, the two-photon absorption process is dominant in the ablation phenomenon, between the second smallest ablation threshold fluence F2, th and the third smallest ablation threshold fluence F1, th. In the region, the thermal ionization release phenomenon is confirmed, and the nonthermal ionization release phenomenon as in the present invention is hardly or not confirmed.

  In the aspect relating to the ablation threshold fluence, the setting step is performed in a laser multiphoton absorption process according to the material in a region between the first smallest ablation threshold fluence and the second smallest ablation threshold fluence. The irradiation fluence value may be set according to a characteristic curve of the ablation rate with respect to the irradiation fluence value set in advance.

  If comprised in this way, it will become possible to set the value of irradiation fluence comparatively simply and rapidly according to the characteristic curve which was preset based on the laser multiphoton absorption process, for example, was simulated or modeled.

  In this case, the setting step may set the value of the irradiation fluence according to the characteristic curve set in advance based on a three-photon absorption process as the laser multiphoton absorption process.

  With this setting, it is possible to set the value of the irradiation fluence relatively easily and quickly according to the characteristic curve set in advance based on the three-photon absorption process.

  In another aspect of the first laser irradiation method of the present invention, the setting step sets a value of the light intensity of the femtosecond laser according to the peeling depth and the material (that is, the light intensity is Instead of the value of the irradiation fluence, ie indirectly set, or in addition to the value of the irradiation fluence).

  According to this aspect, in the setting step, depending on the desired peeling depth (ablation rate) and material, the light intensity of the femtosecond laser is set instead of the irradiation fluence value, that is, indirectly, or Set in addition to the value of irradiation fluence. Therefore, by appropriately changing the value of the light intensity related to the femtosecond laser, it is relatively easy (without changing the wavelength), and the separation depth (ablation rate) or the size of the fine processing is set to a desired value. Can be adjusted and controlled. As described above, the condition for the parameter “light intensity” does not need to be independently requested. If the condition relating to the ablation threshold fluence described above is determined, it is determined depending on this.

In order to solve the above-described problem, the second laser irradiation method of the present invention irradiates the solid surface by irradiating the solid surface according to a desired peeling depth to be peeled from the solid surface and the material of the solid surface. A setting step of setting a light intensity value related to the femtosecond laser in the low fluence region causing nonthermal ionization emission on the surface within a range in which the irradiation fluence related to the femtosecond laser does not deviate from the low fluence region. And an irradiation step of irradiating the femtosecond laser with the set light intensity value on the solid surface , wherein the setting step includes the material in which the irradiation fluence is in the low fluence region. 1st lowest ablation threshold fluence and 2nd lowest ablation of multiple ablation threshold fluences depending on Within a range that does not deviate from the area between the threshold fluence, it sets the value of the light intensity.

  According to the second laser irradiation method of the present invention, in the setting step, depending on the desired peeling depth (in other words, desired ablation rate) to be peeled from the solid surface and the material of the solid surface, On the other hand, the value of the light intensity relating to the femtosecond laser to be irradiated is set. In the irradiation process, the solid surface is irradiated with the femtosecond laser with the light intensity value set in the setting process.

  Particularly in the second laser irradiation method of the present invention, in the setting step, the light intensity value is set within a range in which the irradiation fluence value does not deviate from the low fluence region causing non-thermal ionization emission on the solid surface. In the irradiation process, the femtosecond laser is irradiated at this set value. Therefore, as in the case of the first laser irradiation method of the present invention described above, peeling or ablation can be performed at the atomic / molecular level without causing thermal ionization on the solid surface or causing melting or destruction by heating. It can be carried out.

  As described above, according to the second laser irradiation method of the present invention, the value of irradiation fluence does not deviate from the low fluence region in order to adjust and control the peeling depth (ablation rate) or the size of fine processing. Within the range, the light intensity value of the femtosecond laser is adjusted and controlled. In other words, laser irradiation for causing ablation and laser irradiation for causing nonthermal ionization are performed simultaneously as one laser irradiation. Therefore, as in the case of the first laser irradiation method of the present invention described above, an optical means for specially adjusting and controlling the laser wavelength such as the “wavelength converter” as described in Patent Document 1 is unnecessary. Therefore, it is comparatively easy to adjust and control the peeling depth (ablation rate) or the size of fine processing to a desired value, which is very advantageous in practice.

  Also in the second laser irradiation method of the present invention, the same aspects as the various aspects in the first laser irradiation method of the present invention described above can be adopted as appropriate.

  In another aspect of the first or second laser irradiation method of the present invention, the setting step depends on a desired peeling area and the material to be peeled from the solid surface in addition to or instead of the peeling depth. Then, at least one of the irradiation fluence value and the light intensity value is set.

  According to this aspect, in the setting step, the first laser irradiation method is irradiated according to the peeling depth and the peeling area and the material of the solid surface, or according to the peeling area and the material of the solid surface. A fluence value is set, and a light intensity value is set for the second laser irradiation method. Therefore, in the irradiation process, for example, without changing the wavelength of the femtosecond laser, by appropriately changing the value of the irradiation fluence and the light intensity related to the femtosecond laser, not only the peeling depth but also the peeling area. Can be adjusted and controlled. In the present invention, the “peeled area” refers to the area of the part peeled by desorption ionization on the solid surface. Further, the peeling depth and the peeling area may be combined and called “finely processed size” in a broad sense, or the peeled area may be called alone as “finely processed size” in a narrow sense. In any case, according to this embodiment, not only the peeling depth or the ablation rate but also the peeling area and the finely processed size in a broad sense or narrow sense can be controlled by the irradiation fluence or light intensity value related to the femtosecond laser.

  In order to solve the above-described problems, the microfabrication method of the present invention includes the above-described first or second laser irradiation method of the present invention (including various aspects thereof), and the solid surface is made fine by the irradiation step. Process.

  According to the fine processing method of the present invention, since the first or second laser irradiation method of the present invention described above is included, it is possible to perform ultrafine processing at the atomic / molecular level on the solid surface.

  In order to solve the above problems, the thin film forming method of the present invention is released from the solid surface by the above-described first or second laser irradiation method of the present invention (including various aspects thereof) and the irradiation step. A film forming step of forming a film on the film forming body using the molecular ions.

  According to the thin film forming method of the present invention, since the first or second laser irradiation method of the present invention described above is included, the molecular ion released at the atomic / molecular level from the solid surface is used, for example, for a substrate or the like. A thin film can be formed on the non-film-formed body. For example, it is possible to form an extremely thin thin film on the substrate by accelerating the emitted molecular ions by an electric field and colliding with the substrate.

  The first or second laser irradiation method of the present invention described above utilizes molecular ions emitted at the atomic / molecular level from the solid surface in addition to such a fine processing method and thin film forming method. The present invention can also be applied to a method of performing analysis and measurement such as mass spectrometry on the material of the solid surface. For example, the above-described first or second laser irradiation method of the present invention (including various aspects thereof) and the irradiation step released from the solid surface, that is, desorption ionization (desorption ionization). By using the molecular ions, an analysis method including an analysis step of performing non-destructive physical or chemical analysis (including measurement) of the solid surface such as mass spectrometry can be realized.

In order to solve the above problems, the first laser irradiation apparatus of the present invention irradiates the solid surface by irradiating the solid surface according to a desired peeling depth to be peeled from the solid surface and the material of the solid surface. Setting means for setting an irradiation fluence value for the femtosecond laser in the low fluence region causing non-thermal ionization emission on the surface in the low fluence region, and the irradiation fluence set for the solid surface Irradiating means for irradiating the femtosecond laser at a value of , wherein the setting means includes a first ablation threshold fluence and a second ablation threshold fluence depending on the material within the low fluence region. Set the value of the irradiation fluence within the region between the low ablation threshold fluence and .

  According to the first laser irradiation apparatus of the present invention, as in the case of the above-described first laser irradiation method of the present invention, in order to adjust and control the peeling depth (ablation rate) or the size of fine processing. Adjust and control the value of irradiation fluence. Therefore, special optical means for adjusting and controlling the laser wavelength such as the “wavelength converter” as in the above-mentioned Patent Document 1 is not necessary, and it is relatively easy to make the peeling depth (ablation rate) or fine. Since the processing size can be adjusted and controlled to a desired value, it is very advantageous in practice.

  In the first laser irradiation apparatus of the present invention, the same aspects as the various aspects in the above-described first laser irradiation method of the present invention can be adopted as appropriate.

In order to solve the above-described problem, the second laser irradiation apparatus of the present invention irradiates the solid surface by irradiating the solid surface according to a desired peeling depth to be peeled from the solid surface and the material of the solid surface. Setting means for setting a light intensity value related to the femtosecond laser in the low fluence region causing non-thermal ionization emission on the surface within a range in which the irradiation fluence related to the femtosecond laser does not deviate from the low fluence region. And irradiation means for irradiating the femtosecond laser with the set light intensity value on the solid surface, and the setting means includes the material in which the irradiation fluence is in the low fluence region. 1st lowest ablation threshold fluence and 2nd lowest ablation of multiple ablation threshold fluences depending on Within a range that does not deviate from the area between the threshold fluence, it sets the value of the light intensity.

  According to the second laser irradiation apparatus of the present invention, as in the case of the above-described second laser irradiation method of the present invention, in order to adjust and control the peeling depth (ablation rate) or the size of fine processing. The light intensity value of the femtosecond laser is adjusted and controlled within a range where the irradiation fluence value does not deviate from the low fluence region. Therefore, special optical means for adjusting and controlling the laser wavelength such as the “wavelength converter” as in the above-mentioned Patent Document 1 is not necessary, and it is relatively easy to make the peeling depth (ablation rate) or fine. Since the processing size can be adjusted and controlled to a desired value, it is very advantageous in practice.

  In the second laser irradiation apparatus of the present invention, the same aspects as the various aspects in the second laser irradiation method of the present invention described above can be adopted as appropriate.

  In one aspect of the first or second laser irradiation apparatus of the present invention, the irradiation unit is configured to be able to irradiate one laser pulse in a time independent manner from another laser pulse as the laser. .

  According to this aspect, the irradiation means irradiates one laser pulse in a time independent manner from the other laser pulses, so that molecular ions are separated from the solid surface with extremely fine separation corresponding to one laser pulse. It becomes possible to ionize and release in an amount. That is, for example, ultrafine processing at the atomic / molecular level and nondestructive molecular ion release are possible. In addition, when it is desired to release molecular ions with a larger amount of peeling than this, it is possible to irradiate a plurality of laser pulses collectively or continuously by an irradiation means.

  In order to solve the above-described problems, the microfabrication apparatus of the present invention includes the above-described first or second laser irradiation apparatus of the present invention (including various aspects thereof), and the solid surface is finely formed by the irradiation means. Process.

  According to the microfabrication apparatus of the present invention, since the first or second laser irradiation apparatus of the present invention described above is included, as in the case of the microfabrication method of the present invention described above, atoms and molecules are Ultra-fine processing at the level becomes possible.

  In order to solve the above problems, the thin film forming apparatus of the present invention is released from the solid surface by the above-described first or second laser irradiation apparatus of the present invention (including various aspects thereof) and the irradiation means. And a film forming means for forming a film on the film forming body using the molecular ions.

  According to the thin film forming apparatus of the present invention, since the first or second laser irradiation apparatus of the present invention described above is included, as in the case of the thin film forming method of the present invention described above, from the solid surface at the atomic / molecular level. A thin film can be formed on a non-film-forming body such as a substrate, for example, by using the released molecular ions.

  The first or second laser irradiation apparatus of the present invention described above utilizes molecular ions emitted at the atomic / molecular level from the solid surface in addition to such a fine processing apparatus and thin film forming apparatus. The present invention can also be applied to an apparatus that performs analysis and measurement such as mass spectrometry on the material of the solid surface. For example, using the above-described first or second laser irradiation apparatus of the present invention (including various aspects thereof) and molecular ions released from the solid surface by the irradiation means, for example, mass spectrometry, It is possible to realize an analyzer equipped with an analysis means for performing non-destructive physical or chemical analysis (including measurement) of the solid surface.

  In order to solve the above problems, the workpiece of the present invention has a structure that has been finely processed by the above-described first or second laser irradiation method of the present invention (including various aspects thereof).

  According to the workpiece of the present invention, since the fine processing is performed by the above-described first or second laser irradiation apparatus of the present invention, it is possible to realize a workpiece subjected to ultrafine processing at the atomic / molecular level. .

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment of laser irradiation apparatus)
An embodiment of a laser irradiation apparatus will be described with reference to FIGS.

  First, the configuration of the laser irradiation apparatus will be described with reference to FIG. FIG. 1 shows a schematic configuration of the laser irradiation apparatus according to the present embodiment.

  In FIG. 1, the laser irradiation apparatus 1 includes a control device 10, a laser light source device 11, and a condenser lens 12. The control device 10 constitutes an example of “setting means” according to the present invention, and the laser light source device 11 and the condenser lens 12 constitute an example of “irradiation means” according to the present invention.

  The laser light source device 11 receives drive control by the control device 10 and irradiates the femtosecond laser LB toward the target 13 as an example of the solid having the “solid surface” according to the present invention via the condenser lens 12. To do. The laser light source device 11 has an irradiation fluence set by the control device 10 according to the material of the target 13 and a desired peeling depth Dr (or ablation rate) desired when peeling the surface of the target 13. By value, it is configured to generate a femtosecond laser LB. The control device 10 sets the value of the light intensity related to the femtosecond laser LB in addition to or instead of the value of the irradiation fluence related to the femtosecond laser LB in accordance with the material of the target 13 and the desired peeling depth Dr. May be.

  In the present embodiment, the target 13 is disposed in a vacuum container 14 having a window for entering the femtosecond laser LB. However, it does not necessarily have to be arranged in the vacuum vessel 14 in this way. The target 13 is disposed to be inclined by a predetermined angle θ, for example, 45 degrees with respect to the incident axis of the femtosecond laser LB, and thereby, a vacuum vessel 14 of molecular ions desorbed and ionized from the surface of the target 13. Good release into the interior.

  The parameter setting related to the femtosecond laser LB by the control device 10 will be described in detail later. The irradiation fluence value related to the femtosecond laser LB in the low fluence region is determined by the femtosecond laser LB on the surface of the target 13. It is set according to the material of the target 13 and the desired peeling depth Dr so as to cause ionization emission.

  In FIG. 1, the condensing lens 12 is arranged as an optical system in the optical path of the femtosecond laser LB as an optical system. However, other lenses, prisms, mirrors, shutters, and the like are appropriately arranged in the optical path. Furthermore, various laser devices such as a semiconductor laser device and optical components such as various lenses, shutters, polarizing plates, and retardation plates may be appropriately incorporated in the laser light source device 11.

  Next, with reference to FIGS. 2 to 12, the setting of the value of the irradiation fluence related to the femtosecond laser LB in the laser irradiation apparatus 1 having the above-described configuration will be described. Here, the relationship between the value of the irradiation fluence and the ablation rate (corresponding to the peeling depth) on the surface of the target 13 is verified, and further, the ablation rate on the surface of the target 13 is a femtosecond laser LB in the low fluence region. It is verified that it can be adjusted and controlled by the irradiation fluence value or the light intensity value. Based on these verifications, an irradiation fluence value and the like in the laser irradiation apparatus 1 shown in FIG. 1 are set.

  First, the configuration of a laser irradiation / analysis apparatus as an experimental apparatus for verifying the relationship between the value of irradiation fluence and the ablation rate will be described with reference to FIG. FIG. 2 shows a schematic configuration of the laser irradiation / analysis apparatus. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  As shown in FIG. 2, the laser irradiation / analysis apparatus 2 includes a control device 10, a laser light source device 11, a condensing lens 12, and a vacuum vessel 14 in the same manner as the laser irradiation device 1 of FIG. The detection device 16 is configured.

  The detection device 16 is a mass spectrometer that analyzes the mass of molecular ions, for example, by detecting the concentration of molecular ions released or desorbed from the surface of the target 13. Detection information related to the analysis result of the molecular ion mass is input from the detection device 16 to the control device 10 including a CPU (Central Processing Unit) or a system controller, and the detection information is recorded here.

  Subsequently, characteristics of the femtosecond laser having an extremely low fluence and high intensity used in the present embodiment will be described with reference to FIG. FIG. 3 shows the waveform characteristics of the ultrashort pulse laser (ie, femtosecond laser) according to this embodiment.

  As shown in FIG. 3, the ultrashort pulse laser (that is, femtosecond laser) irradiated by the laser light source device 11 depends on, for example, a desired peeling depth to be peeled from the surface of the target 13 and its material. , "Low fluence high intensity laser pulses" that cause non-thermal ionization emission on the surface and are low fluence and high light intensity. Here, the “low fluence” according to the present embodiment is a fluence between the first smallest ablation threshold fluence F3, th and the second smallest ablation threshold fluence F2, th, as will be described in detail later. Means. The “high intensity” or “high light intensity” of the laser according to the present embodiment means a laser intensity (light intensity) exceeding the “ablation threshold laser intensity” as illustrated in FIG. In other words, “high intensity” or “high light intensity” means that a femtosecond laser is irradiated onto a solid surface (in this case, the surface of the target 13) so that the material on the solid surface is converted into molecular ions or multivalent molecular ions. This means the intensity or light intensity of the laser that can be emitted, and this value is specific to the material of the solid surface (here, the surface of the target 13).

In general, the unit of “fluence” is J / cm ² , and the unit of “laser intensity” or “light intensity” is W / cm ² (that is, J / s · cm ² ). Accordingly, the fluence of the laser is obtained by dividing the energy of the laser by the irradiation area, and the laser intensity (light intensity) is obtained by dividing the fluence by the pulse width (time) of the laser. In other words, the laser intensity (light intensity) is obtained by dividing the laser energy by (irradiation area × laser pulse width). Therefore, in this embodiment, the laser intensity or the light intensity is adjusted by adjusting the laser energy, the laser irradiation area, and the laser pulse width. However, in the present embodiment, conditioning for the parameter “light intensity” is not required independently, and depends on this if the conditions relating to the ablation threshold fluences F3, th to F2, th as described later are satisfied. (Ie, from the relational expression laser intensity (light intensity) = fluence / pulse width).

FIG. 3 shows a “low-fluence high-intensity laser pulse” which is a laser having an energy of 300 μJ and a pulse width of 100 fs, and whose irradiation diameter is reduced to 20 μm on the surface of the target 13 by the condenser lens 12 or the like. ing. The definition of “pulse width (laser pulse width)” according to this embodiment is obtained by experimentally examining the time waveform of the laser intensity and measuring the time that is half of the maximum laser intensity. In the case of the laser pulse illustrated in FIG. 3, the fluence is as low as 95 J / cm ² (that is, low fluence), but the laser intensity is extremely high as 10 ¹⁵ W / cm ² (that is, high intensity). ). Incidentally, this laser has a power well exceeding 64.3 million kW (= 6 × 10 ¹⁰ W) at the peak of TEPCO's 2001 power consumption. This is one of the characteristics of an ultrashort pulse laser called a femtosecond laser.

  Next, with reference to FIGS. 4 and 5 in addition to FIG. 2, the experiment will be further described in order to verify the relationship between the value of irradiation fluence and the ablation rate. Here, FIG. 4 shows an example of conditions relating to various parameters and various equipment related to the laser irradiation / analysis apparatus shown in FIG. 2, and FIG. 5 shows the conditions in the laser irradiation / analysis apparatus shown in FIG. An optical arrangement of a laser light source device and a CCD (Charged Coupled Device) camera for verification is shown. In FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

As illustrated in the list of FIG. 4, in the laser irradiation / analysis apparatus 2, various parameters, various equipment, and various conditions relating to the target 13 are set. That is, as the target 13, a metal sample Cu, Al, Fe,... Is selected, and its size is set to 5 × 5 cm. The femtosecond laser LB has a wavelength of 800 nm (nanometer) or the like. In particular, the light intensity (energy) is variable between 0.21 and 600 μJ, and accordingly, the irradiation fluence is variable between 10 mJ / cm ^{2 and} 28 J / cm ² .

  As shown in FIG. 5, in the laser irradiation / analysis apparatus 2, in addition to the laser light source apparatus 11, a CCD camera 31 and the like for imaging the surface of the target 13 (not shown in FIG. 2) are included in the optical system. It has been incorporated. In FIG. 5, other components such as the detection device 16 and the control device 10 shown in FIG. 2 are omitted.

  In FIG. 5, a laser light source device 11 generates a femtosecond laser light source device (fs laser) 11a that generates a femtosecond laser Lfs for causing non-thermal ablation, and a laser La for optical alignment. Helium-neon gas laser light source (He-Ne laser) 11b. The femtosecond laser Lfs passes through the mirror 21, the laser La passes through the optical plate 25 for controlling the polarization state and the mirror 26, and is then synthesized at the half mirror (dichroic mirror) 22 to be combined with the laser LB on the same optical path. Is done. Further, the laser LB reaches a half mirror (dichroic mirror) 34. Of the lasers LB, the femtosecond laser Lfs is reflected by the half mirror 34 and irradiated onto the surface of the metal sample as the target 13 via the condenser lens 12. On the other hand, the alignment laser La among the lasers LB passes through the half mirror 34 and is used for alignment. The state of the surface of the metal sample that is ablated by the femtosecond laser Lfs is reflected by the reflected light Lr that reaches the CCD camera 31 through the condenser lens 12, the half mirror 34, the lens 33, and the mirror 32. 31 is used to capture an image.

  Next, referring to FIG. 6 to FIG. 12, the relationship between the irradiation fluence and the ablation rate obtained by the laser irradiation / analysis apparatus 2 as described above, in particular, three ablations identified on the characteristic curve indicating this relationship. The threshold fluence and the low fluence region showing the new ablation physics defined by these thresholds will be described. 6 shows the relationship between the irradiation fluence obtained by the laser irradiation / analysis apparatus 2 and the ablation rate. FIG. 7 shows the laser pulse width obtained by the laser irradiation / analysis apparatus 2 and the ablation threshold (ablation threshold fluence). ). 8 to 10 show the ion signal intensity detected by the laser irradiation / analysis apparatus 2 with respect to the time axis (horizontal axis), respectively. FIG. 11 shows the relationship between temperature and distribution density for Cu (copper), and FIG. 12 shows the relationship between incident laser energy and ion signal intensity for Cu obtained by the laser irradiation / analysis apparatus 2.

When the laser irradiation / analysis apparatus 2 described with reference to FIGS. 2 to 5 is used, the irradiation fluence (laser irradiation fluence (J / cm ² )) and the ablation rate (nm / shot) illustrated in FIG. A relationship is obtained. However, here, the target 13 is Cu (copper), the wavelength of the femtosecond laser Ffs is 800 nm, the pulse width is 70 fs (femtosecond), and other conditions are as illustrated in FIG. .

As shown in FIG. 6, according to the discrete experimental data indicated by black circles, the characteristic curve indicating the relationship between irradiation fluence and ablation rate has three ablation threshold fluences in ascending order of ablation. It is confirmed that threshold fluences F3, th (= 0.018 J / cm ² ), F2, th (= 0.18 J / cm ² ) and F1, th (= 0.25 J / cm ² ) exist. .

  Here, “ablation rate” means the depth (peeling depth) of the crater formed on the surface of the target 13 per laser pulse, and is expressed by the following equation (1).

L = α ⁻¹ ln (F / Fth) (1)
However,
α ^-1 : light penetration length (cm),
F: Irradiation fluence (J / cm ² )
Therefore, from the equation (1), the three ablation threshold fluences Fth (F3, th, F2, th, F1, th) described above are evaluated from the irradiation fluence F where L = 0.

  More generally, when the laser spatial profile is expressed by a Gaussian function, the crater diameter Γ is expressed by the following equation (2).

Γ = a {ln (F / Fth)} ^0.5 (2)
However, a: Diameter of the incident laser beam Therefore, in this case, from the equation (2), the above-mentioned three ablation threshold fluences Fth (F3, th, F2, th, F1, th) are respectively Γ Evaluation is made from an irradiation fluence F of = 0.

  As described above, as shown in the equations (1) and (2), the ablation threshold fluence can be evaluated by two methods.

  6 is a characteristic curve on a log-log graph, the existence of these three ablation threshold fluences F3, th, F2, th and F1, th is somewhat difficult to see. Is plotted on a graph with only the horizontal axis (laser irradiation fluence axis) as a logarithm, as is clear from the above equations (1) and (2), these three ablation threshold fluences F3, th, F2, The presence of th and F1, th can be easily and clearly confirmed visually.

As shown in FIG. 7, on the characteristic curve showing the relationship between the laser pulse width (s) and the ablation threshold fluence (J / cm ² ), these three ablation threshold fluences F3, th, F2, th and F1, th Have properties that change depending on the pulse width of the femtosecond laser Lfs. Here, since the femtosecond laser Lfs has a pulse width shorter than the collision relaxation time in the target 13, the pulse width related to the femtosecond laser Lfs is variable according to the material of the surface of the target 13. For example, in the case of Cu, for example, 17.49 ps. (In this example, as in the case of FIG. 6, the target 13 is Cu (copper) and the wavelength of the femtosecond laser Ffs is 800 nm.) Thus, the three ablation threshold fluences F3, th, F2, Since th and F1, th change with the pulse width, respectively, it can be said that the laser intensity is also an important parameter depending on the pulse width (see FIG. 3). By changing the condensing optical system, the laser irradiation area on the surface of the target 13 changes, so that the laser intensity can be changed. That is, it is possible to adjust the time interval contributing to ablation to be longer or shorter. However, in the present embodiment, conditioning for the parameter “light intensity” is not required independently, and depends on this if the conditions relating to the ablation threshold fluences F3, th to F2, th as described above are satisfied. To be determined.

As can be seen from FIGS. 6 and 7, the “low fluence region” according to the present embodiment is a region between the first smallest ablation threshold fluence F3, th and the second smallest ablation threshold fluence F2, th. means. Therefore, the low fluence region varies depending on the material of the target 13, but in the example shown in FIG. 6 (that is, the example where the target is Cu), 0.018 J / cm ^{2 to} 0.18 J / cm ^2. The fluence region is a low fluence region. In other words, the fluence region of 0.018 J / cm ^{2 to} 0.18 J / cm ² means a region in the vicinity of the ablation threshold where nonthermal ionization occurs on the surface of the target 13 made of Cu.

In FIG. 6, a characteristic curve L ₃ (ξ ₃ ) simulated or modeled based on the three-photon absorption process is shown by a solid line. This characteristic curve L ₃ (ξ ₃ ) is consistent with the experimental data indicated by the black circles in the region between the ablation threshold fluence F3, th and the ablation threshold fluence F2, th, that is, in the low fluence region. It is confirmed.

Here, when m-th order multiphoton absorption occurs, if the absorption coefficient ζ _m (cm ^m / W ^m−1 ) is known, the ablation rate L _m (cm / shot) can be explained analytically, It is represented by the following formula (3).

L _m = 1 / {(m−1) ζ _m }
× {(E _th / τ _p ζ _m ) ^{((1-m) / m)} − (F / τ _p ) ^1-m } (3)
However,
m ≧ 2
τ _p (s): width of laser pulse,
E _TH (J / cm ³ ): Energy required to melt a unit volume of solid with heat of fusion And the condition for L _m = 0 is the ablation threshold fluence F _th and is expressed by the following equation (4): The

F _th = (E _th / ζ _m ) ^{1 / m} τ _p ^{((1-m) / m)} = β _m τ _p ^{((1-m) / m)} (4)
As can be seen from the equations (3) and (4) above, the ablation threshold fluence F3, th depends on the pulse width, and depends on the three-photon absorption process shown by the characteristic curve L ₃ (ξ ₃ ) in FIG. It is explained as a thing.

In FIG. 6, a characteristic curve ^{Lσ that} is simulated or modeled based on the two-photon absorption process is indicated by a broken line. This characteristic curve L ^sigma, the region between the ablation threshold fluence F2, th the ablation threshold fluence F1, and th, i.e., in the high fluence region adjacent to the low fluence region, and is consistent with the experimental data shown by black circles Is confirmed. In this high fluence region, the two-photon absorption process becomes dominant in the ablation phenomenon, and a thermal ionization emission phenomenon occurs.

Further, in FIG. 6, a characteristic curve L ^{1 that} is simulated or modeled based on the one-dimensional two-temperature thermal diffusion process is indicated by a one-dot chain line. The characteristic curve L ¹ is the ablation threshold fluence F1, at high high fluence region than th, it can be confirmed that that is consistent with the experimental data shown by black circles.

  As described above, when the femtosecond laser Ffs is used, the “three-photon absorption process” becomes notably or completely dominant as a factor of the ablation phenomenon in the low fluence region. In the case of the femtosecond laser Lfs, for example, when the wavelength is 800 nm, the photon has a particle property of 1.5 eV. Therefore, non-thermal ionization emission (non-thermal desorption ionization) is performed on the surface of the target 13 in accordance with the three-photon absorption process. On the contrary, in the high fluence region deviating from the low fluence region according to this embodiment, little or no non-thermal ionization emission phenomenon as in this embodiment has been confirmed, and the thermal ionization emission phenomenon is remarkable. It is confirmed.

Next, with reference to FIGS. 8 to 10, the characteristic curve L ₃ (ξ ₃ ) based on the two-photon absorption process in the low fluence region showing the novel ablation physics will be further verified. More specifically, an ionization emission process and a laser multiphoton absorption process (or a three-photon absorption process) based on molecular ions emitted from the surface of the target 13 measured by the detection apparatus 16 in the laser irradiation / analysis apparatus 2. ). Here, the pulse width of the femtosecond laser Lfs having a wavelength of 800 nm is fixed to 130 fs, and a lens with f (focal length) = 250 mm is used as the condenser lens 12. The surface of the Cu metal sample as the target 13 is irradiated with the femtosecond laser Lfs while changing the irradiation fluence in the range of 15 to 700 mJ / cm ² . Then, molecular ions emitted from the surface of the target 13 are measured by a time-of-flight mass analyzer (TOF) as an example of the detection device 16. The measurement results obtained in this way are shown in FIGS. 8 to 10 show the irradiation energy of the femtosecond laser Lfs in this order as 27 μJ (relatively high energy), 17 μJ (relatively medium energy), and 8.7 μJ (relatively low energy). Is.

As shown in FIG. 8 to FIG. 10, under these measurement conditions, in any case, peaks corresponding to Cu ³⁺ and Cu ²⁺ are measured, that is, polyvalent copper ions are remarkably released. It is confirmed. 8 to 10, the peak in the vicinity of 3 μs is due to hydrogen ions caused by the measurement environment, and is not particularly related to the verification related to the new ablation physics.

FIG. 11 shows the valence of copper ions (Cu ⁺ , Cu ²⁺ , Cu ³⁺ ) and copper (Cu) with respect to the temperature (k) when the ablation related to the measurement as described above is calculated by a thermal process. Distribution is shown. On the other hand, FIG. 12 shows the valence distribution of copper ions (Cu ⁺ , Cu ²⁺ , Cu ³⁺ ) and copper (Cu) with respect to the incident laser energy (μJ) obtained by the measurement of the present embodiment as described above. Is shown. In FIG. 12, the peak seen when the incident laser energy is around 9 μJ indicates the ion signal intensity when no signal is obtained, and is not particularly relevant to the verification related to the new ablation physics. .

  From FIG. 11 and FIG. 12, it is presumed that the ablation or ionization emission phenomenon in the low fluence region shown in FIG. 6 occurs not in the thermal process but in the non-thermal process. As described above, in the low fluence region, the multiphoton absorption process or the three-photon absorption process becomes dominant or completely dominant as a factor of the ablation phenomenon, and multivalent ions are generated as molecular ions. The result supports the discussion.

  As described above with reference to FIGS. 2 to 12, the surface of the target 13 can be ablated or ionized very softly at the atomic / molecular level, in other words, with a pulse related to one femtosecond laser. . At this time, a non-thermal ablation phenomenon in which only multivalent ions other than monovalent ions are remarkably released or a non-thermal ionization phenomenon has not been reported before the present invention.

  Further, in the present embodiment, the case where Cu is appropriately used as the metal is illustrated, but the same non-thermal ablation phenomenon or non-thermal ionization phenomenon is confirmed for all the metals illustrated in the table of FIG. . In summary, the fluence dependence of the ablation rate described with reference to FIG. 6 and the like is composed of three logarithmic components having different slopes even when all the metals are the target 13, and the ablation threshold fluence is There are three (F3, th, F2, th and F1, th), respectively. And about any metal, it is thought that the pulse dependence of ablation threshold fluence follows the multiphoton absorption process or the three-photon absorption process.

Subsequently, referring to FIG. 13 and FIG. 14, according to the present embodiment, it is not necessary to control the wavelength of the femtosecond laser Lfs, and the size of fine processing including the peeling depth of the surface of the target 13 or the peeling area is included. The point that can be controlled is verified. FIG. 13 shows the waveform of the femtosecond laser Lfs used in this embodiment. FIG. 14 shows the peeling depth for each position (μm) around the irradiation position when the irradiation fluence (J / cm ² ) and the number of pulses (shots number) related to the femtosecond laser Lfs irradiated to the target 13 are changed. (Ablation depth (μm)).

  As shown in FIGS. 13 and 14, even if the pulse width is 70 fs and the wavelength is fixed to 800 nm, the peeling depth and the peeling area can be changed by changing the irradiation fluence as shown in FIG. .

  Therefore, the relationship between the irradiation fluence value, the peeling depth and the peeling area, or the relationship between the irradiation fluence and the microfabrication size can be obtained in advance by experiment, empirical, theoretical or simulation. For example, fine processing with a desired peeling depth and peeling area or a desired fine processing size can be realized by adjusting and controlling the value of irradiation fluence and the number of irradiation pulses.

  Subsequently, referring to FIGS. 15 to 17, according to the present embodiment, the interval of the periodic structure formed on the surface of the target 13 by laser ablation can be controlled without the need to control the wavelength of the femtosecond laser Lfs. Verify the point. Here, FIG. 15 and FIG. 16 each show a periodic structure formed on the surface of the target 13 by irradiation with the femtosecond laser Lfs. FIG. 17 shows the relationship between the interval between the periodic structures and the irradiation fluence.

  As illustrated in FIG. 15, a periodic structure having an interval depending on the wavelength of the femtosecond laser Lfs is formed on the surface of the target 13 by irradiation with the femtosecond laser Lfs. For example, a periodic structure having a height of 200 nm is formed in the surface of the target 13 at a distance of 0.5 μm. This state can be visually understood from FIG. 16 in which the peeling depth at each position on the surface of the target 13 is shown by shading. If the CCD camera 31 shown in FIG. 5 is used, such a grayscale image is observed on the surface of the target 13.

  Such a periodic structure is caused by a standing wave generated by interference between a laser as incident light and a plasma wave (or scattered wave) formed on the surface of the target 13. Further, the interval between the periodic structures also depends on the polarization direction of the laser.

  More specifically, the interval d of the periodic structure is expressed by the following formula (5).

d = λ / (1 ± sin θ) (5)
However,
λ: Laser wavelength θ: Laser incident angle Since λ = 800 nm and θ = 0 in this example, d = λ = 800 nm.

  As shown in FIG. 17, according to this embodiment, the interval in such a periodic structure can be reduced by reducing the value of the irradiation fluence without changing the wavelength. In particular, in the low fluence region, the interval between the periodic structures can be remarkably narrowed compared to the high fluence region.

  As described above with reference to FIG. 13 to FIG. 17, in the case of ablation using the femtosecond laser Lfs, the peeling depth and peeling area on the surface of the target 13, and further, the interval of the periodic structure is determined by the irradiation fluence value. Can be controlled by.

  Further, in the present embodiment, the case where Cu is appropriately used as the metal is exemplified, but the same control is possible for all the metals exemplified in the table of FIG. In summary, even when various metals are used as the target 13, the separation depth and the separation area on the surface of the target 13, and the interval of the periodic structure having an interval narrower than the laser wavelength are controlled by the value of the irradiation fluence. it can.

In view of the above discussion with reference to FIGS. 2 to 17, in the laser irradiation apparatus 1 according to the present embodiment shown in FIG. 1, the irradiation fluence value is determined by the surface of the target 13 in the setting process by the control apparatus 10 or the like. causing non-thermal ionization released into the low fluence region (in the example of FIG. ^{6, 0.018J / cm 2 ~0.18J /} cm 2 in area) are set at. In the irradiation process by the laser light source device 11 or the like, the femtosecond laser LB is irradiated with this set value. Therefore, according to the laser irradiation apparatus 1, atoms or molecules can be obtained without causing thermal ionization on the surface of the target 13 by high fluence laser irradiation or by long pulse laser irradiation, or causing melting or destruction by heating. Separation or ablation can be performed at the level. At this time, by using an extremely short pulse of a low fluence and a femtosecond laser, a non-thermal ion emission phenomenon occurs on the surface of the target 13, and the surface is not heated, at the atomic / molecular level. It becomes possible to peel off.

  As described above in detail with reference to FIGS. 1 to 17, according to the laser irradiation apparatus 1 (see FIG. 1) according to the present embodiment, a desired peeling depth on the surface of the target 13 or a desired fineness. In order to adjust and control the size of processing, the value of the irradiation fluence of the femtosecond laser LB in the laser light source device 11 is adjusted and controlled under the drive control by the control device 10. Alternatively, the light intensity value of the femtosecond laser LB is adjusted and controlled. Therefore, for example, the optical means for adjusting and controlling the laser wavelength such as the “wavelength converter” as in the above-mentioned Patent Document 1 is not necessary, and it is relatively easy to perform ultrafine processing on the surface of the target 13. An extremely small amount of ionized emission from the surface of the target 13 becomes possible.

  Note that the three ablation threshold fluences F3, th, F2, th and F1, th as illustrated in FIG. 6 can be quantified or tabulated in advance depending on the material of the surface of the target 13. Therefore, once these values are obtained, the value of the irradiation fluence in the setting process by the control device 10 (see FIG. 1) is changed to the material of the target 13 that is actually the target of laser irradiation and the desired peeling depth. Accordingly, it can be determined uniquely. That is, it is possible to set the irradiation fluence value by the control device 10 in the actual irradiation with relative ease.

  In addition, the laser irradiation / analysis apparatus 2 shown in FIG. 2 can be used as an analysis apparatus that performs non-destructive mass analysis or the like on the sample surface using the target 13 as a sample.

(Micro processing equipment)
An embodiment of a microfabrication apparatus of the present invention will be described.

  The microfabrication apparatus according to the present embodiment has the same configuration as the laser irradiation apparatus shown in FIG. In other words, if the laser irradiation apparatus 1 shown in FIG. 1 is used as a target for fine processing, the fine processing apparatus according to this embodiment can be realized as it is.

  According to the microfabrication apparatus of the present embodiment, as in the case of the laser irradiation apparatus 1 described above, the irradiation fluence related to the femtosecond laser Lfs is adjusted and controlled in the low fluence region, so・ Ultra-fine processing at the molecular level is possible.

  In this case, preferably, under the drive control by the control device 10, the laser light source device 11 is configured to be able to irradiate one laser pulse in a time independent manner from the other laser pulses as the femtosecond laser LB. . Thus, by irradiating one laser pulse in a time independent manner from the other laser pulses, molecular ions are ionized and released from the surface of the target 13 with a very fine separation amount corresponding to one laser pulse. It becomes possible.

  In FIG. 1, the target 13 is tilted by θ. However, in the case of a microfabrication apparatus that does not particularly use the released molecular ions, it is not always necessary to tilt the target 13 in this way. You may adjust (theta) suitably according to a shape and a grade.

  According to the microfabrication apparatus according to the present embodiment, formation of nanostructures with a laser wavelength or less, tripology, micro-drilling with a laser wavelength or less, semiconductor crystallization, creation of a communication microdevice, μ-TAS (Total Analysis System), Wide application to MEMS (Micro Electro Mechanical System) etc. becomes possible.

(Thin film forming equipment)
An embodiment of the thin film forming apparatus of the present invention will be described with reference to FIG. FIG. 18 shows a schematic configuration of the thin film forming apparatus. In FIG. 18, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  As shown in FIG. 18, the thin film forming apparatus 3 includes a control device 10, a laser light source device 11, a condensing lens 12, and a vacuum container 14, similar to the laser irradiation device 1 of FIG. It comprises a base 202 and a power supply device 203 to be placed. The base 202 and the power supply device 203 constitute an example of the “film forming unit” according to the present invention.

  The base 202 is set at a predetermined potential by the power supply device 203 and holds the film formation target 201 at a predetermined potential. As a result, when forming a thin film, molecular ions released from the target 13 in response to irradiation with the femtosecond laser LB collide with the film formation target 201 in a manner similar to the existing sputtering technique, and the film formation target A thin film composed of molecular ions is formed on 201.

  Note that an ion accelerator or an electric field application device (not shown in FIG. 18) may be provided in the vacuum vessel 14 so that molecular ions emitted from the target 13 are accelerated and then collide with the film formation target 201. Good.

  Therefore, according to this embodiment, as in the case of the laser irradiation apparatus 1 described above, for example, non-film formation of a semiconductor device substrate or the like is performed using molecular ions emitted from the surface of the target 1 at the atomic / molecular level. An extremely thin thin film can be formed on the body 201.

  Note that the laser light source device 11 may be configured to irradiate a plurality of laser pulses collectively or continuously under drive control by the control device 10. Thereby, molecular ions can be released from the target 13 with a large amount of peeling, and the film forming speed in the thin film forming apparatus 3 can be increased.

  In the embodiment described above, not only metals but also semiconductors, insulators, compounds, biomaterials and a wide range of solids can be used as the target 13. In particular, since it is easy to increase the laser intensity, an insulator or the like can be ablated as the target 13 with relatively no problem. Alternatively, since the laser is irradiated at a low fluence, a compound or biological sample that is easily destroyed can be ablated as the target 13 with relatively no problem. For this reason, the present invention provides extremely important technology over a wide range of fields such as nanotechnology, information technology, environmental technology, biotechnology, and manufacturing technology where miniaturization proceeds.

  The present invention is not limited to the above-described embodiments, and can be changed as appropriate without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and a laser irradiation method involving such changes. In addition, an apparatus, an apparatus, a fine processing method and apparatus, and a thin film forming method and apparatus are also included in the technical scope of the present invention.

It is a block diagram which shows schematic structure of the laser irradiation apparatus which concerns on embodiment of this invention. 1 is a block diagram showing a schematic configuration of a laser irradiation / analysis apparatus according to an embodiment of the present invention. It is a characteristic view which shows the waveform characteristic of the ultra-short pulse laser (namely, femtosecond laser) which concerns on embodiment of this invention. It is a table | surface which shows an example of the conditions which concern on various parameters, various equipment, etc. in the laser irradiation and analysis apparatus which concern on embodiment. It is a block diagram which shows optical arrangement | positionings, such as a laser light source apparatus and a CCD camera for verification, in the laser irradiation / analysis apparatus according to the embodiment. It is a characteristic view which shows the relationship between the irradiation fluence obtained by the laser irradiation and analysis apparatus which concerns on embodiment, and an ablation rate. It is a characteristic view which shows the relationship between the laser pulse width obtained by the laser irradiation and analysis apparatus which concerns on embodiment, and an ablation threshold value. It is a characteristic view (the 1) which shows the ion signal strength detected with the laser irradiation and analysis device concerning an embodiment to a time axis (horizontal axis). It is a characteristic view (the 2) which shows the ion signal strength detected with the laser irradiation and analysis device concerning an embodiment to a time axis (horizontal axis). It is a characteristic view (the 3) which shows the ion signal strength detected with the laser irradiation and analysis device concerning an embodiment to a time axis (horizontal axis). It is a characteristic view which shows the relationship between the temperature and distribution density about Cu (copper). It is a characteristic view which shows the relationship between the incident laser energy and ion signal intensity | strength about Cu obtained by the laser irradiation and analysis apparatus concerning embodiment. It is a wave form diagram which shows the waveform of the femtosecond laser Lfs used in embodiment. It is a characteristic view which shows the peeling depth with respect to each position centering on the irradiation position in the case of changing the irradiation fluence and pulse number concerning the femtosecond laser Lfs in the embodiment. It is a characteristic view (graph) which shows the periodic structure formed in the surface of a target by irradiation of femtosecond laser Lfs in an embodiment. FIG. 6 is a characteristic diagram (shading diagram) showing a periodic structure formed on the surface of a target by irradiation with a femtosecond laser Lfs in the embodiment. It is a characteristic view which shows the relationship between the space | interval of a periodic structure, and irradiation fluence in embodiment. It is a block diagram which shows schematic structure of the thin film forming apparatus which concerns on embodiment of this invention.

Explanation of symbols

1. Laser irradiation device (microfabrication device)
2 ... Laser irradiation / analysis device 3 ... Thin film forming device 10 ... Control device 11 ... Laser light source device 12 ... Condensing lens 13 ... Target 14 ... Vacuum vessel 16 ... Detection device

Claims (15)

A femtosecond laser in a low fluence region that causes non-thermal ionization emission to the solid surface by irradiating the solid surface according to the desired peel depth to be peeled from the solid surface and the material of the solid surface A setting step of setting an irradiation fluence value according to the above in the low fluence region;
Irradiating the femtosecond laser with the set irradiation fluence value on the solid surface , and
In the low fluence region, the setting step includes the irradiation fluence in a region between a first ablation threshold fluence and a second ablation threshold fluence among a plurality of ablation threshold fluences depending on the material. Set the value of
The laser irradiation method characterized by the above-mentioned. In the setting step, among the ablation threshold fluences present as at least three as the plurality of ablation threshold fluences, the setting step is performed between the first smallest ablation threshold fluence F3, th and the second smallest ablation threshold fluence F2, th. in the region, the laser irradiation method according to claim 1, characterized in that setting the value of the irradiation fluence. The setting step includes an irradiation fluence that is preset based on a laser multi-photon absorption process in accordance with the material in an area between the first smallest ablation threshold fluence and the second smallest ablation threshold fluence. laser irradiation method according to claim 1 or 2, characterized in that in accordance with the characteristic curve of the ablation rate for the value, it sets the value of the irradiation fluence. The laser irradiation method according to claim 3 , wherein the setting step sets the value of the irradiation fluence according to the characteristic curve set in advance based on a three-photon absorption process as the laser multiphoton absorption process. . Said setting step, in response to said peeling depth and the material, the laser irradiation method claimed in any one of 4, characterized in that setting the value of the light intensity of the femtosecond laser. A femtosecond laser in a low fluence region that causes non-thermal ionization emission to the solid surface by irradiating the solid surface according to the desired peel depth to be peeled from the solid surface and the material of the solid surface A setting step for setting the value of the light intensity according to a range in which the irradiation fluence related to the femtosecond laser does not deviate from the low fluence region;
Irradiating the femtosecond laser at the set light intensity value on the solid surface , and
In the setting step, the irradiation fluence is an area between the first ablation threshold fluence and the second smallest ablation threshold fluence among the plurality of ablation threshold fluences depending on the material as the low fluence area. Set the light intensity value within a range that does not deviate from
The laser irradiation method characterized by the above-mentioned. In the setting step, in addition to or instead of the peeling depth, depending on a desired peeling area and the material to be peeled from the solid surface, at least one of the irradiation fluence value and the light intensity value is set. It sets, The laser irradiation method as described in any one of Claim 1 to 6 characterized by the above-mentioned. A micromachining method comprising the laser irradiation method according to any one of claims 1 to 7 , wherein the solid surface is micromachined by the irradiation step. The laser irradiation method according to any one of claims 1 to 7 ,
A film forming step of forming a film on a film formation body using molecular ions released from the solid surface by the irradiation step. A femtosecond laser in a low fluence region that causes non-thermal ionization emission to the solid surface by irradiating the solid surface according to the desired peel depth to be peeled from the solid surface and the material of the solid surface Setting means for setting the value of the irradiation fluence in the low fluence region;
Irradiating means for irradiating the femtosecond laser with the set irradiation fluence value on the solid surface ;
The setting means includes the irradiation fluence in the low fluence region within a region between a first ablation threshold fluence and a second ablation threshold fluence among a plurality of ablation threshold fluences depending on the material. Set the value of
The laser irradiation apparatus characterized by the above-mentioned. A femtosecond laser in a low fluence region that causes non-thermal ionization emission to the solid surface by irradiating the solid surface according to the desired peel depth to be peeled from the solid surface and the material of the solid surface A setting means for setting the value of the light intensity according to the above within a range in which the irradiation fluence related to the femtosecond laser does not deviate from the low fluence region;
Irradiating means for irradiating the femtosecond laser with the set light intensity value on the solid surface ;
The setting means includes an area between the first ablation threshold fluence and the second smallest ablation threshold fluence among the plurality of ablation threshold fluences depending on the material, the irradiation fluence being in the low fluence area. Set the light intensity value within a range that does not deviate from
The laser irradiation apparatus characterized by the above-mentioned. The laser irradiation apparatus according to claim 10 or 11 , wherein the irradiation unit is configured to be able to irradiate one laser pulse as the laser in a time independent manner from other laser pulses. 13. A micromachining apparatus comprising the laser irradiation apparatus according to any one of claims 10 to 12 , wherein the solid surface is micromachined by the irradiation means. The laser irradiation apparatus according to any one of claims 10 to 12 ,
A thin film forming apparatus comprising: a film forming unit configured to form a film on an object to be formed using molecular ions released from the solid surface by the irradiation unit. A workpiece having a structure subjected to fine processing by the laser irradiation method according to any one of claims 1 to 7 .

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