JP2011143421A - Laser beam machining method, laser beam machining device and optical filter unit for laser beam machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform laser beam machining with high accuracy by raising the evenness of the energy intensity distribution of a Gaussian type leaser beam. <P>SOLUTION: The laser beam machining device includes: a laser beam oscillator 1 for emitting a laser beam the energy intensity distribution of which has the Gaussian type; a beam expander 3 for expanding the beam diameter of the laser beam; an optical filter unit 7 for evening the energy intensity distribution of the laser beam the beam diameter of which is expanded and a condensing lens 8 for converging the laser beam and emitting it to a part of an object W to be machined. The optical filter unit 7 has at least one optical filter having structure in which a light shading zone for shading the light and a light transmissive light transmitting zone which spread radially from the center part of a substrate toward the outer peripheral part are provided on a flat substrate 71a and the light transmissive zone is made into a shape which is widened gradually toward the outer peripheral part of the substrate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a processing technique using a laser beam, and more particularly, to a method and an apparatus suitable for use in excavating a groove using a laser beam in an object to be processed when manufacturing a solar cell.

The laser beam (laser light) is coherent light having the same phase, and the laser oscillator used as the light source is a solid laser (YVO ₄ laser, YAG laser, sapphire laser, etc.), gas laser (carbon dioxide laser), depending on the type of laser medium. , Argon ion lasers, etc.), semiconductor lasers, dye lasers, excimer lasers, free electron lasers, etc., but the laser beam emitted from such a laser oscillator has the energy intensity at the center of the optical axis in the lowest order mode. Becomes a Gaussian type in which the energy intensity gradually decreases as the distance from the center of the optical axis increases. This is called a Gaussian beam, but high-precision processing cannot be performed with a Gaussian laser beam.

  For example, when a thin film solar cell is manufactured by patterning using a Gaussian beam, a scribe groove G to be formed only in the transparent electrode Te as shown in FIG. As shown in FIG. 9 (b), the lower silicon layer Si bites into the lower layer, or the transparent electrodes Te to be insulated and divided by the scribe grooves G are connected without being divided. Cause problems.

  For this reason, when high-precision laser processing is required, an optical device called a beam homogenizer is often used to divide and superimpose the Gaussian beam to flatten its energy intensity. Since the optical apparatus is configured by combining a plurality of prisms, reflectors, lenses, and the like, it is extremely expensive.

  Therefore, in Patent Document 1, a phase plate having different thicknesses in the central region and the outer region is used, and the energy intensity distribution of the Gaussian beam is flattened through the Gaussian beam.

JP 05-326716 A

  However, in Patent Document 1, the central region of the phase plate is made thinner than the outer region so that the Gaussian beam transmitted through the phase plate generates a half-wave phase difference between the central portion and the peripheral portion. High precision processing technology is required for the production of the plate itself.

  According to Patent Document 1, the energy intensity of the light component transmitted through the outer region of the phase plate is made to interfere with the light component transmitted through the central region while allowing most of the Gaussian beam to pass through the central region of the phase plate. Therefore, the laser beam (light component transmitted through the central region) obtained by the transmission of the phase plate has a large intensity difference between the center and the peripheral portion of the optical axis, and the energy intensity distribution is not necessarily flattened. That's not enough.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to increase the flatness of the energy intensity distribution of a Gaussian laser beam so that high-precision laser processing can be performed.

In order to achieve the above-mentioned object, the present invention provides a flat substrate, a light-blocking light-blocking zone that spreads radially from the center to the outer periphery of the substrate, and a light-transmitting light that spreads radially by the light-blocking zone. A light-transmitting zone is provided, and the light-transmitting zone is a method of performing laser processing on an object to be processed using an optical filter having a structure in which the light-transmitting zone is gradually widened toward the outer peripheral portion of the substrate.
The diameter of a laser beam having a Gaussian-type energy intensity distribution emitted from a laser oscillator is enlarged and incident on the optical filter, and the laser beam transmitted through the optical filter is focused and irradiated on a part to be processed. A laser processing method is provided.

The present invention also provides a laser oscillator that emits a laser beam having a Gaussian energy intensity distribution;
A beam expander that expands the beam diameter of the laser beam emitted from the laser oscillator;
An optical filter unit for flattening an energy intensity distribution of a laser beam having a beam diameter expanded by the beam expander;
A condensing lens that focuses the laser beam transmitted through the optical filter unit and irradiates a portion of the object to be processed,
The optical filter unit includes a flat substrate, a light shielding zone that spreads radially from the center to the outer periphery of the substrate, and a light transmissive zone that spreads radially and is divided by the light shielding zone. Is provided, and the light transmitting zone has at least one optical filter having a structure in which the light transmitting zone gradually becomes wider toward the outer peripheral portion of the substrate.

  Furthermore, the present invention provides a flat substrate, a light shielding zone that spreads radially from the center to the outer periphery of the substrate, and a light transmissive zone that spreads radially and is divided by the light shielding zone. And two optical filters having a structure in which the translucent zone is gradually widened toward the outer peripheral portion of the substrate. An optical filter unit is provided.

  According to the present invention, a flat substrate is provided with a light shielding zone that spreads radially from its center to the outer periphery, and a light transmissive zone that spreads radially and is divided by the light shielding zone. Since an optical filter having a structure in which the translucent zone gradually becomes wider toward the outer peripheral portion of the substrate is transmitted through a laser beam having a Gaussian-type energy intensity distribution, an expensive optical device is used. Accordingly, it is possible to flatten the energy intensity distribution of the Gaussian laser beam and perform high-precision laser processing.

  In addition, in the case where two optical filters having a specific structure as described above are connected to each other so as to be relatively rotatable, the two are relatively rotated and moved in accordance with the material of the workpiece. The amount of light energy transmitted can be adjusted.

The perspective view which shows the principal part of the laser processing apparatus which concerns on this invention Schematic diagram of the laser processing equipment Sectional drawing which shows the optical filter unit with which the laser processing apparatus is equipped A perspective view showing an optical filter unit Plan view showing an optical filter constituting the optical filter unit Diagram showing energy intensity distribution of laser beam Explanatory drawing which shows the effect | action of the optical filter which concerns on this invention Diagram showing enlarged contours of grooves formed by laser scribing Schematic showing the mode of grooves formed by a laser beam

  Hereinafter, the present invention will be described in detail with reference to the drawings. First, FIG. 1 shows a main part of a laser processing apparatus according to the present invention and its configuration will be described. The laser processing apparatus includes two laser irradiation systems 10. Both laser irradiation systems 10 have the same configuration, and each includes a laser oscillator 1 that emits a laser beam having a Gaussian-type energy intensity distribution as a laser light source.

In this example, the laser oscillator 1 is a YVO ₄ laser, emits a laser beam having a wavelength of 532 nm and a beam diameter of 500 μm, and a rotary rear tenuator 2 that attenuates and adjusts the energy of the laser beam on its optical axis, and its rotary A beam expander 3 for expanding the beam diameter of the laser beam output from the attenuator 2 is provided.

  As shown in FIG. 2, the beam expander 3 is a lens unit including a plano-concave lens 3a and a convex lens 3b. In this example, the beam expander 3 causes a laser beam from the laser oscillator 1 to have a beam diameter of 500 μm (0. 5 mm) to 4 mm, and output as parallel light having a beam diameter of 4 mm.

  In FIGS. 1 and 2, 4 is a plane mirror for converting the optical axis direction of the laser beam emitted from the beam expander 3, and 5 is a semi-transparent mirror (half-beam) for dividing the laser beam totally reflected by the plane mirror 4 into two directions. Mirror 6, 6 is a reflecting mirror that totally reflects the laser beam transmitted through the semi-reflecting mirror 5 in the same direction as the laser beam reflected by the semi-reflecting mirror 5, and the laser beam reflected by the semi-reflecting mirror 5 and the reflecting mirror 6. A condenser lens 8 is disposed on the optical axis via an optical filter unit 7.

  The optical filter unit 7 has an optical element (optical filter) for flattening the energy intensity distribution of a laser beam of Gaussian type, and includes a plane mirror 4 and a half mirror 5 or a reflection mirror from the beam expander 3. A laser beam having a Gaussian-type energy intensity distribution is incident through the mirror 6. The condensing lens 8 converges the laser beam transmitted through the optical filter unit 7 and irradiates the part of the workpiece W. The workpiece W is, for example, a laminated plate serving as a base material for a thin film solar cell, which is fixed on a movable table (not shown) and is perpendicular to the optical axis of the laser beam from the condenser lens 8. Moved to.

  Here, referring to the configuration of the optical filter unit 7, the optical filter unit 7 is configured by two optical filters 71 and 71 facing each other as shown in FIG. In FIG. 3, reference numeral 72 denotes an outer frame that holds the optical filter 71. The outer frame 72 is configured by coupling a ring-shaped fixed frame 72a and a movable frame 72b so as to be relatively rotatable. The two optical filters 71 and 71 are fixed concentrically to the fixed frame 72a and the movable frame 72b, respectively, in a state where one surface is in contact with each other. Accordingly, the two optical filters 71 and 71 can also be rotated relative to each other by the relative rotation of the fixed frame 72a and the movable frame 72b. In this example, the fixed frame 72a is fixed to the frame of the laser processing apparatus, and the other of the movable frame 72b and the optical filter 71 can be rotated with respect to one of the fixed frame 72a and the optical filter 71 fixed thereto. It is like that.

  Further, as is apparent from FIG. 4, the outer peripheral surfaces of the fixed frame 72a and the movable frame 72b are provided with a scale m so that the relative rotational movement amounts of the two optical filters 71 and 71 can be grasped. It is possible.

  Next, in FIG. 5, the optical filter 71 has a colorless and transparent flat glass plate 71a having a thickness of 1.5 mm as a substrate, and a circular pattern portion P having a diameter of 62.5 mm is provided on the substrate 71a. . The pattern portion P is composed of a light shielding zone Pe that spreads radially from the center of the substrate 71a toward the outer periphery, and a light transmissive zone Pt that spreads radially and is divided by the light shielding zone Pe. The light shielding zone Pe and the light transmitting zone Pt appear alternately in the circumferential direction of the pattern portion P.

  As is clear from FIG. 5, the light shielding zone Pe and the light transmitting zone Pt are in the form of an elongated arc that gradually becomes wider toward the outer peripheral portion of the substrate 71a, and the spread angle (wedge angle) of each is in this example. 2.25 degrees. In this example, a metal film is attached to one surface of a transparent substrate 71a to form a light-shielding zone Pe that spreads radially, and a light-transmitting light-transmitting zone Pt is formed between the light-shielding zones Pe. A light-shielding metal plate or the like may be used, and a radial cutout hole may be formed in the metal plate to form a light-transmitting zone Pt while leaving the space as the light-shielding zone Pe.

  The two optical filters 71 constitute the optical filter unit 7 by facing the two so as to be relatively rotatable as described above. The optical filter unit 7 is arranged in front of the condenser lens 8 so that the center of the optical filter 71 (radiation center of the light shielding zone Pe and the light transmitting zone Pt) coincides with the center of the optical axis of the laser beam. It is arranged on the optical path of the laser beam.

  Here, the laser processing method using the laser processing apparatus including the optical filter unit 7 configured as described above and the operation of the optical filter 71 will be described. First, as a laser processing method according to the present invention, a transparent electrode is insulated on a workpiece W (for example, a laminated plate in which a transparent electrode layer is provided on a transparent insulating substrate as a base material of a thin film solar cell). The outline of the case where the scribe grooves to be divided are formed will be described below. The workpiece W is fixed on a movable table (not shown) below the condensing lens 8 and simultaneously with the irradiation of the laser beam from the condensing lens 8. It is moved in the direction at a constant speed.

  On the other hand, a laser beam having a Gaussian-type energy intensity distribution is emitted from a laser oscillator 1 serving as a light source of the laser beam toward a rotary tenuator 2. The energy of the laser beam is attenuated by the rotary tenuator 2 and then incident on the beam expander 3. The beam expander 3 converts the laser beam into parallel light having a beam diameter of 4 mm, for example. Then, the laser beam whose beam diameter is enlarged is incident on the optical filter unit 7 through the plane mirror 4, the semi-transparent mirror 5, and the reflecting mirror 6, and the optical filter unit 7 makes a Gaussian type as shown in FIG. The energy intensity distribution A (intensity distribution in the cross section of the optical axis) is flattened as shown in FIG.

  That is, in the partially enlarged view of the optical filter 71 shown in FIG. 7, the laser beams that have passed through the adjacent transparent zone Pt at the position of radius R are respectively in the D1-D1 direction and D2-D2 orthogonal to the transparent zone Pt. Although it diffracts in the direction and spreads to the outer peripheral side as shown by a one-dot chain line while interfering with the diffracted light of the laser beam transmitted through the light transmitting zone Pt on the outer peripheral side, the width of the light transmitting zone Pt is larger than that on the outer peripheral side. Since the inner peripheral side is narrow, diffraction becomes more prominent on the inner peripheral side of the translucent zone Pt. For this reason, the optical energy at the center of the optical axis of the laser beam transmitted through the radiation center of the light transmitting zone Pt is diverged in the outer peripheral direction, and as a result, the energy intensity distribution is flattened.

  Then, the laser beam whose energy intensity distribution is flattened is incident on the condensing lens 8 from the optical filter unit 7, and the beam diameter is focused to about 50 μm by the condensing lens 8 to be on the surface of the workpiece W. Is irradiated. For this reason, according to the present invention, it is possible to accurately form a groove having a predetermined depth with a width corresponding to the beam diameter with respect to the workpiece W and having a flat bottom.

  FIG. 8 is an enlarged diagram showing the outline of the groove formed in the workpiece W by laser scribing. FIG. 8A shows a laser beam whose energy intensity distribution is flattened by the optical filter unit 7, and FIG. As shown in FIG. 4, it is understood that a Gaussian laser beam not using the optical filter unit 7 is used.

  The optical filter unit 7 may have a configuration in which the single optical filter 71 is held by the outer frame 72. However, in the configuration in which the two optical filters 71 and 71 are coupled to each other so as to be relatively rotatable as described above, The state in which the light shielding zone Pe is aligned in the optical axis direction is set to the maximum amount of light energy transmission, and the light energy emitted from the plurality of optical filter units 7 is adjusted so as to be constant. Can be corrected, or the amount of light energy transmitted can be adjusted in the direction of decreasing according to the material of the workpiece W or the like.

Although the present invention has been described above, the laser oscillator 1 is not limited to the YVO ₄ laser, but other solid-state lasers (YAG laser, sapphire laser, etc.), gas lasers (carbon dioxide laser, argon ion laser, etc.), semiconductor lasers, A dye laser, an excimer laser, a free electron laser, and the like may be used.

  In the above example, the light shielding zone Pe and the light transmitting zone Pt of the optical filter 71 have the same shape and the same area, but the light shielding zone Pe and the light transmitting zone Pt have the same circumference according to the wavelength of the laser beam to be used. The upper width may be 1: 2 to 3 or the like.

DESCRIPTION OF SYMBOLS 1 Laser oscillator 2 Rotating rear tenuator 3 Beam expander 4 Plane mirror 5 Semi-transparent mirror 6 Reflecting mirror 7 Optical filter unit 71 Optical filter 71a Substrate P Pattern part Pe Light-shielding zone Pt Translucent zone 8 Condensing lens

Claims (3)

A flat substrate is provided with a light shielding zone that spreads radially from the center to the outer periphery of the substrate and a light transmissive zone that spreads radially and is divided by the light shielding zone. The optical zone is a method of performing laser processing on an object to be processed using an optical filter having a structure in which the optical zone is gradually widened toward the outer peripheral portion of the substrate.
The diameter of a laser beam having a Gaussian-type energy intensity distribution emitted from a laser oscillator is enlarged and incident on the optical filter, and the laser beam transmitted through the optical filter is focused and irradiated on a part to be processed. And a laser processing method. A laser oscillator that emits a laser beam having a Gaussian type energy intensity distribution;
A beam expander that expands the beam diameter of the laser beam emitted from the laser oscillator;
An optical filter unit for flattening an energy intensity distribution of a laser beam having a beam diameter expanded by the beam expander;
A condensing lens that focuses the laser beam transmitted through the optical filter unit and irradiates a portion of the object to be processed,
The optical filter unit includes a flat substrate, a light shielding zone that spreads radially from the center to the outer periphery of the substrate, and a light transmissive zone that spreads radially and is divided by the light shielding zone. And a light-transmitting zone having at least one optical filter having a structure in which the light-transmitting zone gradually becomes wider toward the outer peripheral portion of the substrate. A flat substrate is provided with a light shielding zone that spreads radially from the center to the outer periphery of the substrate and a light transmissive zone that spreads radially and is divided by the light shielding zone. An optical filter unit for laser processing, comprising two optical filters having a structure in which an optical zone is gradually widened toward an outer peripheral portion of the substrate.

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