JP2005250173A - Laser irradiating method and laser irradiation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser irradiation method and a laser irradiation apparatus with high use efficiency of laser light. <P>SOLUTION: A desired image is obtained on an object by irradiating the object with a laser beam via an image forming element. The image forming element uses a reflective element 11 which can form a two-dimensional image by switching a plurality of micromirrors 11b into at least two directions. Or, as for the image forming element, a reflective element having a plurality of micromirrors aligned in at least two directions to form a two-dimensional image can be used. A hologram image is formed in the image forming element so as to impart a phase difference into laser beams of at least two series assigned to at least two directions, and these beams are made to interfere with each other and to irradiate the object. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laser irradiation method and a laser irradiation apparatus. More specifically, the present invention relates to a laser irradiation method and an irradiation apparatus for obtaining a desired image on an irradiated object by irradiating the irradiated object with a laser beam through an image forming element.

As conventional examples of laser irradiation methods, those described in the following patent documents are known.
JP 7-290264 A JP-A-9-248686

  In the prior art, a phase hologram transmission sheet in which interference fringes are formed is used as an image forming element. However, since the transmission sheet attenuates when the laser beam is transmitted, the laser utilization efficiency is not good.

  In view of such a conventional situation, an object of the present invention is to provide a laser irradiation method and a laser irradiation apparatus with high utilization efficiency of laser light.

In order to achieve the above object, the laser irradiation method according to the present invention is characterized by a method for obtaining a desired image on an irradiated object by irradiating the irradiated object with a laser beam through an image forming element. And
The image forming element is a reflective element capable of forming a two-dimensional image by switching a plurality of fine mirrors in at least two directions.

Another feature of the present invention is a method for obtaining a desired image on an irradiated object by irradiating the irradiated object with a laser beam through an image forming element,
The image forming element is a reflecting element in which a plurality of fine mirrors are oriented in at least two directions to form a two-dimensional image.

  In each of the above features, when a hologram image is formed on the image forming element, a phase difference is imparted to at least two laser beams distributed in at least two directions, and these beams are interfered to irradiate an irradiated object Good.

  Further, in order to improve the gradation, at least a pair of two-line laser beams reflected by at least two different portions of the image forming element may be irradiated to the same portion of the irradiation object.

  The image forming element is a first and second reflecting element that sequentially reflects the laser beam and guides it to the irradiated object, and accumulates on each reflecting element to form a desired image on the irradiated object. Each possible hologram image is formed, a phase difference is given to at least two laser beams distributed in the at least two directions by the first reflecting element, and these beams are caused to interfere with each other on the second reflecting element. You may irradiate on a to-be-irradiated object.

  On the other hand, the laser beam reflected by the reflecting element and distributed in the at least two directions is reflected to the original optical path as a return beam by the reflecting mirror, and one of the forward beam and the return beam is set to a phase different from the other by the rotating element. The return beam may be reflected toward the irradiated object by a polarization separation element provided between the laser light source and the rotation element.

  It is desirable that the polarization directions of at least two systems of laser beams distributed in the at least two directions are matched by a polarization adjuster. It is also desirable that an image transfer element of the reflection element is interposed in each of the optical paths of at least two systems of laser beams distributed in at least two directions. If a reduction means for reducing the image formed on the reflective element and irradiating the irradiated object is provided, fine processing becomes possible. If necessary, a modulation means for modulating the frequency of the laser beam can be provided to further improve the processing accuracy.

  A fluence adjusting element for adjusting the fluence of the laser beam may be provided, and the irradiation position of the irradiated object may be moved relative to the laser beam, and irradiation may be performed in a plurality of times. Thereby, the degree of exposure and ablation of the divided parts of the plurality of parts can be made constant. In addition, by changing the irradiation intensity, the number of exposures, and the time between the divided irradiation regions, it is possible to change the degree of partial exposure or ablation according to the purpose.

  The present invention is used, for example, in applications in which ablation processing or exposure is performed by irradiating the irradiated object.

  On the other hand, the laser irradiation apparatus used in any of the above laser irradiation methods for obtaining a desired image on an irradiation object by irradiating the irradiation object with a laser beam through an image forming element has a plurality of features. And a reflective element capable of forming a two-dimensional image by switching the fine mirror in at least two directions.

  According to the features of the laser irradiation method and the irradiation apparatus according to the present invention, it is possible to minimize the attenuation of light while giving image information to the laser incident light, and to improve the utilization efficiency of the laser light for processing. Became. In particular, by using a reflective element that can form a two-dimensional image by switching a plurality of fine mirrors in at least two directions, various patterns or shapes can be processed on the irradiated object. . Further, by using a reflective element in which a plurality of fine mirrors are oriented in at least two directions to form a two-dimensional image, that is, a fixed reflective element having a design, inexpensive mass production processing is possible.

  In addition, by providing the first and second reflective elements, a final image with higher accuracy can be obtained. In addition, the optical system can be made compact by reflecting the laser beam reflected by the reflecting element to the original optical path as a return beam by the reflecting mirror. Furthermore, the resolution can be improved by irradiating at least one pair of two-system laser beams reflected by at least two different portions of the image forming element to the same portion of the object to be irradiated.

  Other objects, configurations, and effects of the present invention will become apparent from the following embodiments of the present invention.

  Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings as appropriate. First, a first embodiment of the present invention will be described with reference to FIGS. The laser irradiation apparatus 1 according to the present invention generally irradiates the surface of the irradiation object 100 with the laser light from the laser light source 2 through the image forming element 3, the first optical path element 4, the second optical path element 5, and the reduction lens 7. Then, the object to be irradiated 100 is ablated or exposed.

  As the image forming element 3 in the present embodiment, a reflective element 11 called DMD (digital mirror device, trade name) is used. As shown in FIG. 2, the reflecting element 11 includes a plurality of fine mirrors 11b arranged on a flat plate-like substrate 11a so as to spread two-dimensionally in the direction perpendicular to the paper surface, and the drive unit 11c is controlled by a computer. The angle of 11a is changed. In the figure, the fine mirror 11b is controlled to be tilted in two states as indicated by reference numerals A1 and A2, respectively, so that the forward beam Lf is the first and second forward beams Lf1 and L2 in the first and second directions D1 and D2, respectively. The light is distributed to Lf2 and guided to the reduction lens 7 by the first and second optical path elements 4 and 5, respectively.

  FIG. 3 is a block diagram showing the input / output relationship of a two-dimensional image, and will be described with reference to the conversion to the hologram of FIG. First, the original image 101 is Fourier-transformed by the lens 7 ′ to the image forming element 3 and transferred as a phase hologram. Further, the hologram image of the image forming element 3 is transferred by the lens 7 ′ while interfering on the substrate, and the final image is obtained. 103 is formed. The original image 101 is represented by the following equation E in consideration of image transfer by the laser 2. ω is an angular velocity, t is time, and k is a time constant.

  E (y, z) = U (y, z) exp {i (ωt−kx) + φ (y, z)} (1)

  Then, the original image 101 is Fourier-transformed F by the following expression by the processing of the PC 9 and is displayed two-dimensionally by the following expression I as a digital phase hologram image on the image forming element 3, that is, the reflecting element 11.

I (y, z) = 1 (when φ (y, z) = 0)
I (y, z) =-1 (when φ (y, z) = π) (2)
Here, the phase φ included in the equation (2) is as follows.
φ (y, z) = arg [F {E (y, z)}]
When −π / 2 <φ (y, z) <π / 2, φ (y, z) = 0
When π / 2 <φ (y, z) <3π / 2 φ (y, z) = π

The phase hologram image distributed to the first and second optical path elements 4 and 5 is subjected to inverse Fourier transform F ⁻¹ by interference synthesis on the irradiation object 100 via the reduction lens 7, and the final image is obtained by the following equation E 103 is synthesized.

E (y, z) = F ⁻¹ {I (y, z) ^1/2 } (3)

  In addition, since the original wavefront is not formed only by performing the inverse Fourier transform on the Fourier transform image 102, the calculation may be repeated to improve the generation accuracy of the final image 103. Similarly, in the following embodiments, the intermediate image 102 may be obtained by Fresnel transformation, and the final image 103 may be obtained by inverse calculation. However, since the computation time is required, the Fourier transformation for the purpose of the hologram is superior.

  More specifically, the first optical path element 4 includes a first relay mirror group 14 and a relay lens 13 that transfers a reflection image of the reflection element 11, and the second optical path element 5 includes a second relay mirror group 15. The relay lens 13 is included. The interval between 15a and 15b of the second relay mirror group 15 is constant. In contrast, the first relay mirror group 14 functions as a phase adjuster 6 that adjusts the phase difference between the first forward beam Lf1 and the second forward beam Lf2 by adjusting the distances between 14a and 14c and 14b. .

  The reduction lens 7 reduces the images carried by the first and second forward beams Lf1 and Lf2, and adjusts the laser light of these two systems so that they interfere with each other under appropriate conditions by the phase adjuster 6 before being irradiated. An image is imprinted on the object 100. It is desirable that one of the first and second forward beams Lf1 and Lf2 is provided with a polarization adjuster 17 for matching the polarization direction to the other. Moreover, you may interpose the modulation | alteration means 16 which modulates the wavelength (frequency) of the output light of the laser light source 2 according to processing precision.

  Here, the laser light source 2 means a light source of coherent light, for example, cw laser, pulse laser, He-Cd laser, Ar laser, excimer laser, YAG laser, femtosecond laser, He-Ne laser, dye laser. A semiconductor laser or the like can be used. The beam expander 10 is a magnifying optical system that spreads laser light as parallel light, and a Kepler type lens set, a Galileo type lens set, or a Cassegrain mirror (lens barrel) can be used. The relay lens 13 may be any lens that can transfer an image. For example, a projection lens is used. There are Kepler type and Galileo type relay lenses 13 as well, but the former is appropriate to make the device compact, and the latter is appropriate when using high power light. The phase adjuster 6 only needs to generate a phase difference by adding a difference in optical distance. In addition to the delay line as described above, a Babenesoleil plate, a prism set, an optically accurate glass plate, etc. Can be used. The polarization adjuster 17 uses a difference in refractive index between horizontal deflection and vertical deflection to shift the axial direction of one direction to match the beam changing direction, and a wave plate or the like is used.

  In use, the data of the original image 101 is input to the PC 9 and the Fourier transform image 102 is generated using the above equation (2). Based on this Fourier transform image 102 information, the drive unit 11c of the reflection element 11 is controlled, and the Fourier transform image 102 is drawn on the surface of the reflection element 11 by adjusting the fine mirror 11b. Then, the images distributed to the first and second forward beams Lf1 and Lf2 are formed as a final image 103 on the irradiation object 100 by the reduction lens 7 and processed or developed on the surface of the irradiation object 100. .

  Next, another embodiment of the present invention will be described. In the following embodiments, the same reference numerals are given to the same components as those in the above embodiment.

  In the second embodiment shown in FIG. 5, first and second reflective elements 21 and 22 that are arranged face to face are used as the image forming element 3. The first and second optical path elements 4 and 5 disposed between the first and second reflecting elements 21 and 22 are provided with a pair of relay lenses 23 and 23 via relay mirrors 24, respectively. In the first forward beam Lf 1, a Babinet soleil plate 25 is disposed as the phase adjuster 6 described above.

  The outgoing beam Lf incident on the first reflecting element 21 is distributed to the first and second outgoing beams Lf 1, Lf 2, further reflected by the second reflecting element 22, and an image is synthesized. 100 mapped onto the surface. The intermediate image 102 displayed on the first reflective element 21 is converted into the original image 103 through image synthesis by the first and second optical path elements 4 and 5 and image synthesis on the second reflective element 22. The display of the first and second reflecting elements 21 and 22 is calculated by the PC 9.

  In the third embodiment shown in FIG. 6, the distributed first and second forward beams Lf1 and Lf2 are again inverted 180 degrees as the return beam Lb by the first and second reflecting mirrors 31 and 32 to the reflecting element 11. The difference is that the reflected light is reflected and mapped to the irradiation object 100 via the rotating element 35. One of the first and second reflecting mirrors 31 and 32 is provided with a phase adjuster 6 capable of changing the mirror surface position in the mirror surface vertical direction. For example, a piston mirror that can be finely adjusted in position by a piezo element is employed as one of the first and second reflecting mirrors 31 and 32. By adjusting the position of one of the mirrors by this phase adjuster 6, a phase difference is generated between the first and second forward beams Lf1 and Lf2.

  Between the beam expander 10 and the reflection element 11, a polarization separation element 34 and a rotation element 35 are sequentially arranged. The polarization separation element 34 is an element that separates polarized light according to the difference between the s wave and the p wave, and the output of the laser light source 2 and the polarization direction are matched so as to transmit the forward beam Lf. The rotating element 35 transmits the forward beam Lf toward the reflecting element 11 without changing the polarization direction, but the returning beam Lb returning from the reflecting element 11 to the polarization separating element 34 rotates the plane of polarization during transmission. As the rotation element 35, for example, a Faraday rotation element that gives a predetermined polarization angle (for example, 6 to 7 degrees) only to incident light in one direction by rotating the polarization of light in an optical rotation direction determined by the direction of a magnetic field is used. The rotating element 35 may transmit the return beam Lb as it is and rotate the polarization direction of only the forward beam Lf. The return beam Lb reflected as the composite image is reflected 90 degrees by the polarization separation element 34 tilted about 45 degrees in the direction of the forward beam Lf, and transferred onto the irradiation object 100 via the reduction lens 7.

  FIG. 7A schematically shows a part of the first embodiment in the xy plan view in FIG. 1, and the laser beam reflected from one first reflecting portion 11x in the reflecting element 11 is covered. Since the composition is performed on the irradiated object 100, the gradation is limited. Therefore, as seen in the fourth embodiment of FIG. 7B, the laser light separated in two directions by each of the two first reflecting portions 11x and the second reflecting portion 11y in the reflecting element 11 is paired with a pair of optical paths. The degree of gradation can be improved by interfering and synthesizing each of the element groups 40 and 40 and further performing synthetic transfer onto the irradiated object 100 using a pair of synthesis mirrors 41 and 41. That is, the hologram image formed on the reflective element 11 with respect to the original image is separated from the first or second reflective portion 11x or 11y depending on the gradation. Note that the number of reflection portions on the reflection element 11 is not limited to two locations of the first and second reflection portions 11x and 11y, and three or more reflection portions may be provided to further improve the gradation. The reflecting portions do not have to be on the same reflecting element 11, and a plurality of reflecting elements 11 may be provided to improve the gradation.

  In the fifth embodiment shown in FIGS. 8A and 9, the reflective element 11 is configured such that the fine mirror 11b is tilt-controlled in three stages by the PC 9 described above. In FIG. 8, one xy plane is inclined in three stages, but the three-stage inclination may be three-dimensionally performed. Reflected light of the reflecting element 11 distributed in the three directions D1 to D3 forms a composite image 103 on the irradiated object 100 via the first, second and third optical path elements 4, 5 and 8 and the reduction lens 7. Interfere synthesis. The phase adjuster 6 may be provided in any one of the first, second, and third optical path elements 4, 5, and 8. In the present embodiment, as in the fourth embodiment, the gradation of the composite image 103 can be improved, and incident light may be distributed in four or more directions.

  In each of the above embodiments, a DMD in which the angle of the fine mirror 11 b can be changed is used as the image forming element 3. However, as shown in the sixth embodiment of FIG. 8B, the fixed reflection mirror in which the plurality of fine mirrors 51 are two-dimensionally oriented in the plurality of directions A1 to A3 and the reflection directions D1 to D3 are fixedly set. 50 may be used as the image forming element 3.

  In each of the above embodiments, when the irradiation area is larger than the fixed range of one time, the irradiation position of the irradiation object is moved relative to the light, and the irradiation is performed in a plurality of times. Good. In this case, by adjusting the irradiation intensity with an element that adjusts the fluence of the portion irradiated with light between the divided irradiation regions irradiated in multiple times, for example, a variable ND filter, a variable attenuator, etc. The degree of exposure and ablation can be made constant. In addition, by changing the irradiation intensity, the number of times of exposure, and the time between the divided irradiation regions, it is possible to change the degree of partial exposure or ablation according to the purpose. The fluence adjusting element is desirably installed in a portion where the beam is not separated, that is, between the laser light source 2 and the image forming element 3, for example, at the position of reference numeral 16 in FIG.

  In each of the above embodiments, the intermediate image 102, the original image 101, and the final image 103 are converted by the hologram method or the Fresnel method. However, other realizable conversion methods may be used. The above embodiments can be implemented in combination with each other.

  The laser irradiation method and irradiation apparatus of the present invention can be used for ablation processing or exposure using laser light.

It is a figure which shows the optical system of a laser irradiation apparatus. It is a conceptual diagram of an image forming element (reflection element). It is a block diagram of a laser irradiation apparatus. It is a figure which shows the relationship between an image forming element and a coordinate. FIG. 3 is a view corresponding to FIG. 1 showing a second embodiment of the present invention. FIG. 3 is a view corresponding to FIG. 1 showing a third embodiment of the present invention. The relationship between a reflective element and an optical path element is shown. (A) shows a case where a single section of the reflective element is used, and (b) shows a case where two sections on the reflective element are used. FIG. 3 is a view corresponding to FIG. 2 showing another embodiment of the reflecting element, where (a) shows a case where a movable mirror is used, and (b) shows a case where a fixed fine mirror is used. It is a block diagram of the laser irradiation apparatus using the reflective element of FIG.

Explanation of symbols

1: laser irradiation device, 2: laser light source, 3: image forming element, 4: first optical path element, 5: second optical path element, 6: phase adjuster, 7: reduction lens (reduction means), 7 ′: lens 8: Third optical path element, 9: PC (personal computer), 10: Beam expander, 11: Reflective element, 11a: Substrate, 11b: Fine mirror, 11c: Drive unit, 11g: Reflector, 11x: First reflection Part, 11y: second reflection part, 13: relay lens (transfer element), 14: first relay mirror group, 15: second relay mirror group, 16: modulation means, 17: polarization adjuster, 21: first reflection Element: 22: Second reflection element, 23: Relay lens (transfer element), 24: Relay mirror, 25: Babynesoleil plate (phase adjuster), 31: First reflection mirror, 32: Second reflection mirror, 33: Relay lens, 34 : Polarization separating element, 35: Rotating element, 40: Optical path element group, 41: Synthetic mirror, 50: Fixed reflecting element, 51: Fine mirror, 100: Irradiated object, Original image: 101, Fourier transform image 102, Final image 103, L: Laser beam, Lf: Outbound beam, Lf1: First outbound beam, Lf2: Second outbound beam, Lb: Return beam, D1: First direction, D2: Second direction, D3: Third direction

Claims (13)

A laser irradiation method for obtaining a desired image on an irradiated object by irradiating the irradiated object with a laser beam through an image forming element,
The laser irradiation method, wherein the image forming element is a reflective element capable of forming a two-dimensional image by switching a plurality of fine mirrors in at least two directions. A laser irradiation method for obtaining a desired image on an irradiated object by irradiating the irradiated object with a laser beam through an image forming element,
The laser irradiation method, wherein the image forming element is a reflective element in which a plurality of fine mirrors are oriented in at least two directions to form a two-dimensional image. A hologram image is formed on the image forming element, a phase difference is given to at least two systems of laser beams distributed in at least two directions, and these beams are caused to interfere with each other to irradiate an irradiated object. The laser irradiation method according to claim 1 or 2. The at least one pair of two-system laser beams reflected at at least two different portions in the image forming element are irradiated to the same portion of the irradiated object in order to improve the gradation level. A laser irradiation method according to any one of the above. The image forming element is a first and second reflecting element that sequentially reflects the laser beam and guides it to the irradiated object,
Hologram images capable of being accumulated on the respective reflecting elements to form a desired image on an object to be irradiated are formed, and at least two systems of laser beams distributed in the at least two directions by the first reflecting element. 5. The laser irradiation method according to claim 1, wherein a phase difference is imparted to the first reflection element, and these beams are caused to interfere with each other on the second reflecting element to be irradiated onto the irradiated object. The laser beam reflected by the reflecting element and distributed in at least two directions is reflected on the original optical path as a return beam by a reflecting mirror, and one of the forward beam and the return beam is rotated by a rotating element to a phase different from the other. The laser irradiation method according to claim 1, wherein the return beam is reflected to the irradiated object side by a polarization separation element provided between the laser light source and the rotation element. The laser irradiation method according to claim 1, wherein polarization directions of at least two systems of laser beams distributed in at least two directions are matched by a polarization adjuster. The laser irradiation method according to claim 1, wherein an image transfer element of the reflection element is interposed in each of optical paths of at least two systems of laser beams distributed in the at least two directions. The laser irradiation method according to claim 1, further comprising a reduction unit that reduces an image formed on the reflection element and irradiates the irradiated object. The laser irradiation method according to claim 1, further comprising a modulation unit that modulates a frequency of the laser beam. A fluence adjusting element for adjusting the fluence of the laser beam is provided, the irradiation position of the irradiated object is moved relative to the laser beam, and irradiation is performed in a plurality of times. The laser irradiation method according to any one of 10. The laser irradiation method according to claim 1, wherein ablation processing or exposure is performed by irradiating the irradiation object. The laser irradiation apparatus used in the laser irradiation method according to any one of claims 1 to 11, wherein a desired image is obtained on an irradiated object by irradiating the irradiated object with a laser beam through an image forming element. A laser irradiation apparatus comprising a reflective element capable of forming a two-dimensional image by switching a plurality of fine mirrors in at least two directions.

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