JP2018103232A - Laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser device that enables an intensity distribution of a laser beam that has passed through wavelength conversion means, to be shaped into an adequate Gaussian distribution (normal distribution).SOLUTION: The laser device implement at least: holding means for holding a workpiece (wafer 10); and laser beam emitting means 24 for projecting a laser beam to the workpiece held by the holding means. The laser beam emitting means 24 includes at least: a laser oscillator 24b; wavelength conversion means 24c for converting a wavelength of the laser beam emitted by the laser oscillator 24b; a light collector 24a for focusing the laser beam on the workpiece held by the holding means, the laser beam having the wavelength converted by the wavelength conversion means; and optical fiber FB disposed between the wavelength conversion means and the light collector. The optical fiber is configured to shape a Gaussian distribution of the laser beam that has disturbed intensity distribution as the laser beam has passed through the wavelength conversion means.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a laser device capable of making the light intensity distribution of a laser beam after being oscillated from a laser oscillator and passing through a wavelength converting means an appropriate Gaussian distribution.

  A wafer formed by dividing a plurality of devices such as IC and LSI on a surface by dividing lines is irradiated with a laser beam by a laser device to be divided into individual devices and used for electric devices such as mobile phones and personal computers.

  The laser apparatus includes at least a holding unit that holds a workpiece and a laser beam irradiation unit that irradiates the workpiece held by the holding unit with a laser beam. The laser beam irradiating means includes a laser beam oscillator that oscillates a laser beam, a laser beam that is oscillated by the laser beam oscillator, a condenser that focuses the laser beam on a workpiece held by a holding unit, the laser beam oscillator, and the laser beam oscillator An optical system that is disposed between the condenser and guides at least a laser beam to a predetermined optical path, and can perform desired processing on the workpiece (see, for example, Patent Document 1). .

  In the case of ultraviolet light with a laser beam wavelength of 355 nm, 266 nm, etc. suitable for processing the workpiece, the damage to the optical system is relatively severe, so the laser beam oscillator oscillates to reduce damage to the optical system. A laser apparatus that converts the wavelength of the laser beam to 1064 nm infrared light with a small burden on the optical system and converts it into ultraviolet light of 355 nm, 266 nm, etc. by arranging wavelength converting means in front of the condenser is provided by the present applicant. It has been proposed (see Patent Document 2). As the wavelength conversion means, a CLBO crystal, a BBO crystal, an LBO crystal, a KTP crystal, or the like can be adopted as a nonlinear crystal having a wavelength conversion function, and the nonlinear crystals are appropriately combined depending on the wavelength to be obtained. Various wavelength conversion methods (SHG, FHK, THG, etc.) can be realized.

JP 2006-108478 A Japanese Patent No. 5964621

  Although the laser beam having a desired wavelength can be obtained by the laser device described above, the laser beam converted by the wavelength converting means is disturbed with respect to the ideal Gaussian distribution assumed in the design, and the laser processing assumed in the design. There is a problem that strength cannot be obtained, and stable processing cannot be performed even if the workpiece is irradiated as it is.

  In addition, the non-linear crystal constituting the wavelength converting means described above causes deterioration of the irradiated portion if the same portion is continuously irradiated with the laser beam, so that it is necessary to appropriately change the irradiation position of the laser beam so that it can be used for a long time. However, the nonlinear crystal that realizes wavelength conversion does not necessarily have a uniform crystal structure depending on the position irradiated with the laser beam, and the light intensity distribution after wavelength conversion changes every time the irradiation location is changed. In a sense, the problem of inhibiting stable processing may occur.

  The present invention has been made in view of the above-mentioned facts, and its main technical problem is to provide a laser device capable of shaping the Gaussian distribution of the laser beam after passing through the wavelength converting means so as to approach the ideal Gaussian distribution. There is to do.

  In order to solve the above-mentioned main technical problem, according to the present invention, at least achieved from a holding means for holding a workpiece and a laser beam irradiation means for irradiating a workpiece held on the holding means with a laser beam. A laser device, wherein the laser beam irradiation unit holds a laser oscillator, a wavelength conversion unit that converts the wavelength of the laser beam oscillated by the laser oscillator, and a laser beam whose wavelength is converted by the wavelength conversion unit in the holding unit A condenser for condensing light on the processed workpiece, and an optical fiber disposed between the wavelength converting means and the condenser, and the optical fiber passes through the wavelength converting means. Thus, a laser device for shaping the Gaussian distribution of the disturbed laser beam is provided.

  A harmonic separator is disposed between the wavelength converting means and the optical fiber, so that laser light having a wavelength other than the predetermined wavelength is excluded from the laser light wavelength-converted to a predetermined wavelength by the harmonic separator. Can be. A spectroscope disposed between the optical fiber and the concentrator and guiding a part of the laser beam to an output measurement path; output measurement means disposed in the output measurement path; the spectroscope; A transmittance adjusting means disposed between the condenser and the output of the laser beam applied to the workpiece held by the holding means may be adjusted by the transmittance adjusting means. . Further, the wavelength conversion crystal constituting the wavelength conversion means may be appropriately shifted from the optical path of the laser beam oscillated by the laser oscillator so as to extend the life of the wavelength conversion crystal.

  The laser beam irradiating means in the laser apparatus of the present invention is held by the laser oscillator, the wavelength converting means for converting the wavelength of the laser beam oscillated by the laser oscillator, and the laser beam whose wavelength is converted by the wavelength converting means. A condenser for collecting light on the workpiece, and an optical fiber disposed between the wavelength converting means and the condenser, and the optical fiber passes through the wavelength converting means. Since the laser beam is distorted by the laser beam, the Gaussian distribution is disturbed by the laser beam passing through the wavelength converting means, etc. The resulting laser beam is shaped so as to approach an appropriate Gaussian distribution, and stable laser processing can be performed.

It is drawing which shows the whole perspective view of the laser processing apparatus to which the laser apparatus of this invention was applied, and the perspective view of the wafer which is a workpiece. It is a block diagram for demonstrating the structure of the laser beam irradiation means which comprises the laser apparatus of FIG. It is a schematic diagram for demonstrating the light intensity distribution of the laser beam before shaping | molding by the laser beam irradiation means of this invention, and the light intensity distribution of the laser beam after shaping.

  Hereinafter, a laser apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an overall perspective view of a laser processing apparatus 2 including a laser apparatus 20 configured according to the present invention. The laser device 20 includes at least a holding unit 22 that holds a workpiece and a laser beam irradiation unit 24 that irradiates the workpiece held by the holding unit 22 with a laser beam. The holding means 22 holds the workpiece (wafer 10) held on the annular frame F via the adhesive tape T shown in the upper left part of the figure, and the laser processing apparatus 2 is described above. In addition to the laser device 20, a moving means 23 disposed on the stationary base 2 a for moving the holding means 22, and a vertical wall 51 erected on the side of the moving means 23 on the stationary base 2 a A frame body 50 including a horizontal wall portion 52 extending in the horizontal direction from the upper end portion of the vertical wall portion 51 is provided. The optical system of the laser beam irradiation means 24 constituting the main part of the laser device 20 of the present invention is built in the horizontal wall 52 of the frame 50, and the configuration will be described in detail later.

  The holding means 22 includes a rectangular X-direction movable plate 30 that is mounted on the base 2a so as to be movable in the X direction indicated by an arrow X in the figure, and an X that is movable in the Y direction indicated by an arrow Y in the figure. A rectangular Y-direction movable plate 31 mounted on the directional movable plate 30, a cylindrical column 32 fixed to the upper surface of the Y-direction movable plate 31, and a rectangular cover plate 33 fixed to the upper end of the column 32. Including. The cover plate 33 is provided with a holding table 34 for holding a circular workpiece extending upward through a long hole formed on the cover plate 33, and a porous material is disposed on the upper surface of the holding table 34. A circular suction chuck 35 that is formed from and extends substantially horizontally is disposed. The suction chuck 35 is connected to suction means (not shown) by a flow path passing through the support column 32. Note that the X direction is the direction indicated by the arrow X in FIG. 1, and the Y direction is the direction indicated by the arrow Y and orthogonal to the X direction. The plane defined by the X direction and the Y direction is substantially horizontal.

  The moving unit 23 includes an X direction moving unit 40 and a Y direction moving unit 42. The X-direction moving means 40 converts the rotational motion of the motor into a linear motion via a ball screw and transmits it to the X-direction movable plate 30, and moves the X-direction movable plate 30 along the guide rail on the base 2a. Advance and retreat in the direction. The Y-direction moving means 42 converts the rotational motion of the motor into a linear motion via a ball screw, transmits it to the Y-direction movable plate 31, and moves along the guide rail on the X-direction movable plate 30. Are advanced and retracted in the Y direction. Although not shown, the X direction moving means 40 and the Y direction moving means 42 are respectively provided with position detecting means, and the position of the holding table 34 in the X direction, the Y direction, and the circumferential direction are arranged. The rotational position is accurately detected, and the X-direction moving means 40 and the Y-direction moving means 42 are driven based on a signal instructed from the control means described later, so that the holding table 34 can be accurately positioned at an arbitrary position and angle. It is possible.

  As shown in FIG. 1, the wafer 10 has a plurality of devices 14 defined on the surface by dividing lines 12 and is supported on an annular frame F via an adhesive tape T on a holding table 34. Retained. Then, while the laser beam irradiating unit 24 is operated to irradiate the laser beam LB, the X-direction moving unit 40 and the Y-direction moving unit 42 are operated to perform ablation processing on the planned dividing line 12 and to start the division. 100 is formed.

  In FIG. 2, an example of the laser beam irradiation means 24 which comprises the laser apparatus 20 of this invention is shown. The laser beam irradiation means 24 irradiates a desired laser beam LB (for example, wavelength 355 nm) from the above-described condenser 24a, and a laser oscillator 24b that oscillates a laser beam LB1 having a wavelength of 1064 nm as a fundamental wave; A wavelength converter 24c for converting the laser beam LB1 into a laser beam LB2 having a wavelength of 355 nm, a harmonic separator 24d for outputting a laser beam LB3 from which an unnecessary wavelength component is removed from the laser beam LB2 output from the wavelength converter 24c, and the harmonic A light intensity distribution shaping unit 24f configured by a condensing lens 24e that condenses the laser beam LB3 output from the separator 24d, and an optical fiber FB into which the laser beam LB4 collected by the condensing lens 24e is incident; The collimating lens 24g for shaping the laser beam LB4 'shaped with the Gaussian distribution by the optical fiber FB of the degree distribution shaping means 24f into parallel light, and a part of the laser beam LB5 made into the parallel light, for example, so as not to affect the processing. A spectroscope 24h that reflects an extremely small proportion (1%) of the laser beam LB6 ′ to the output measurement path side and transmits the remaining laser beam LB6 to the collector 24a side, is reflected by the spectroscope 24h, and enters the output measurement path. By adjusting the transmittance of the laser beam LB6 transmitted through the spectroscope 24h by adjusting the output measurement means 24i composed of a light receiving element that measures the light amount value of the guided laser beam LB6 ′ for output measurement, A transmittance adjusting means (attenuator) 24j for emitting a laser beam LB7 having a desired output to the condenser 24a; With which, laser LB7 is irradiated to the wafer 10 held on the holding table 34 is the desired laser LB is condensed by the condenser lens (not shown) constituting the light-concentrating device 24a.

  Although the laser beam LB6 ′ reflected by the spectroscope 24h is a part of the laser beam LB5, the ratio of the light reflected by the spectroscope 24h is constant. The output of the laser beam LB6 transmitted through the device 24h is substantially measured. Note that each of the above-described units constituting the laser device 20 is controlled by a control unit (not shown). For example, measurement information measured by the output measurement unit 24i is sent to the control unit and executed by the control unit. Based on the value calculated by the control program, the transmittance adjusting means 24j is controlled, and the laser beam LB irradiated to the workpiece is adjusted to a desired output.

  The wavelength conversion unit 24c of the laser beam irradiation unit 24 will be described in more detail. As a means for converting the wavelength of a general laser beam, a conversion method using a non-linear crystal such as an LBO crystal, a CLBO crystal, or a KTP crystal is known. Is selected in consideration of the wavelength of the laser beam to be obtained, the output of the laser beam when finally used for processing, and the like.

  As shown in FIG. 2, the wavelength conversion means 24c in the present embodiment includes a first LBO crystal 24c1 and a second LBO crystal 24c2. A pulsed laser beam LB1 having a wavelength of 1064 nm is oscillated as a fundamental wave by the laser oscillator 24b and is incident on the wavelength converting means 24c. The laser beam LB1 is incident on a predetermined end surface of the first LBO crystal 24c1 constituting the wavelength converting means 24c, and the laser beam having a wavelength of 1064 nm is converted into a laser beam having a wavelength of 532 nm and emitted from the other end surface. The laser beam emitted from the other end surface of the first LBO crystal 24c1 is further incident on a predetermined end surface of the second LBO crystal 24c2, and converted into a laser beam LB2 having a wavelength of 355 nm, so that the second LBO crystal. The light is emitted from the other end face of 24c2, that is, from the wavelength converting means 24c.

  The first LBO crystal 24c1 and the second LBO crystal 24c2 constituting the wavelength converting means 24c are provided with incident position changing means (not shown). It is known that a nonlinear crystal having a wavelength conversion function is deteriorated by irradiating a laser beam at the same position for a long time, and enters the optical path of the fundamental laser beam LB1 for a predetermined time or every predetermined number of times of incidence. On the other hand, the incident position is changed. Thereby, the lifetime of the nonlinear crystal constituting the wavelength converting means 24c is extended. When the laser beam is incident on all the incident positions, the first LBO crystal 24c1 and the second LBO crystal 24c2 are exchanged. The laser device of the present invention has a configuration generally as described above, and the operation thereof will be further described.

Note that the above-described laser device can have the following configuration.
Laser oscillator: 1064 nm (Nd: YAG laser)
Average output: 1-10W
Repeat frequency: 1 kHz to 1 MHz
Pulse width: 100 fs to 100 ns

  When the operator instructs the laser processing apparatus of the present invention to start laser beam irradiation, a laser beam LB1 having a wavelength of 1064 nm is oscillated from the laser oscillator 24b and is incident on the wavelength converting means 24c. The first LBO crystal 24c1 and the second LBO crystal 24c2 constituting the wavelength conversion means 24c convert the wavelength as described above, but the laser beam LB1 incident on the first LBO crystal 24c1 is completely However, it is not converted into a wavelength of 532 nm, but is emitted with a laser beam having a wavelength of 1064 nm remaining at a predetermined rate. Therefore, a laser beam having a wavelength of 532 nm and a laser beam having a wavelength of 1064 nm are incident on the second LBO crystal 24c2, and the laser beam emitted from the second LBO crystal 24c2, that is, emitted from the wavelength conversion means 24c. In addition to the converted laser beam with a wavelength of 355 nm, the laser beam LB2 includes a laser beam with a wavelength of 1064 nm and a wavelength of 532 nm that remains without being converted. Therefore, in the laser beam irradiation means 24 of the present embodiment, the above-described harmonic separator 24d is disposed on the optical axis through which the laser beam LB2 passes, and unnecessary wavelength components are eliminated, and the laser beam irradiation unit 24 is mainly configured with a wavelength of 355 nm. A laser beam LB3 is emitted.

  Here, the laser beam LB3 will be described. 3A and 3B, the horizontal axis represents the cross-sectional position (mm) where the center position of the optical axis of the laser beam is “0”, and the vertical axis represents the light intensity at the cross-sectional position of the optical axis. Thus, the light intensity distribution according to the cross-sectional position of the optical axis of the laser beam is schematically represented. In the present embodiment, the radius of the optical axis of the laser beam oscillated from the laser oscillator 24b is Nmm. As shown in FIG. 3A, the laser beam LB2 that has passed through the wavelength conversion unit 24c does not have an ideal Gaussian distribution having a peak at the center of the optical axis, but has a distorted shape. . This disturbance is presumed to be caused by the fact that the crystal structure constituting the nonlinear crystal constituting the wavelength converting means 24c is not always constant, and the laser beam is irradiated to a predetermined position for a long time to enter the nonlinear crystal. This is a phenomenon that can occur even when deterioration occurs. When the light intensity distribution is disturbed in this way, even if the laser beam is condensed and irradiated at a predetermined position, the desired peak energy cannot be obtained, and the desired processing assumed by the laser processing conditions is not performed. Problems can arise. Therefore, in the present invention, the laser beam whose wavelength is converted by the wavelength converting unit 24c is incident on the optical fiber FB disposed between the wavelength converting unit 24c and the condenser 24a. More specifically, based on FIG. 2, in this embodiment, the laser beam LB3 emitted from the harmonic separator 24d is condensed so as to be incident on one end face FBa of the optical fiber FB constituting the light intensity distribution shaping means 24f. The light enters the lens 24e and is condensed. The focal point of the laser beam LB4 collected by the condensing lens 24e is adjusted to be at the position of the one end face FBa of the optical fiber FB, and the laser beam LB4 is incident on the optical fiber FB. The optical fiber FB has, for example, a diameter of about 1.0 mm and a length of about 1 m.

  Here, the laser beam LB4 incident on the optical fiber FB travels repeatedly on the side wall surface in the optical fiber FB, and is emitted from the other end FBb. Since the laser beam LB4 ′ emitted from the other end portion FBb of the optical fiber FB is diffused as it is, it is converted into parallel light by the collimator lens 24g to be a laser beam LB5.

  When the laser beam LB5 emitted from the optical fiber FB and converted into parallel light passes through the optical fiber FB, a peak of light intensity appears at the center of the optical axis as shown in FIG. It is shaped to approach an ideal Gaussian distribution that falls smoothly as it goes outward. Therefore, by passing through the wavelength converting means 24c, the distorted Gaussian distribution as shown in FIG. 3A is shaped into an ideal Gaussian distribution as shown in FIG. Makes it easier to perform.

  The output of the laser beam LB5 whose light intensity distribution is shaped into the shape shown in FIG. 3B is measured based on the spectroscope 24h and the output measuring means 24i, and the laser beam LB6 is emitted from the spectroscope 24h. At the same time, the transmittance adjusting unit 24j is controlled based on the output information of the output measuring unit 24i, and is incident on the condenser 24a as a laser beam LB7. As a result, the laser beam LB that has been shaped so as to have an ideal Gaussian distribution and then condensed is applied to the wafer 10 on the holding table 34.

  The present invention is not limited to the above-described embodiment, and various modifications can be assumed. For example, the above-described embodiment is applied to the case where the wavelength of the fundamental laser beam oscillated from the laser oscillator is 1064 nm and the wavelength conversion unit 24 c that converts the fundamental wave into a wavelength of 355 nm using two LBO crystals is used. However, the present invention is not limited to this example. For example, a laser beam having a wavelength of 1064 nm is converted into a laser beam having a wavelength of 266 nm using a KTP crystal and a CLBO crystal, or the wavelength is 1064 nm. This laser beam can be applied to a laser device that is used by converting it to a wavelength of 532 nm using one KTP crystal. Further, the present invention is not limited to the case where the laser oscillator 24b that oscillates a laser beam having a wavelength of 1064 nm is used as the fundamental wave. For example, a laser beam having another wavelength such as a YVO4 laser (wavelength 1054 nm) or an LD laser (wavelength 650 to 905 nm) is basically used. It is also possible to apply to a laser apparatus using a laser oscillator that oscillates as a wave.

  In the above-described embodiment, the disposition position of the spectroscope 24h and the output measurement unit 24i is disposed on the downstream side of the light intensity distribution shaping unit 24f. However, the present invention is not limited to this, and immediately after the harmonic separator 24d. You may make it arrange | position to. Furthermore, the diameter and length of the optical fiber FB described above are merely examples, and the wavelength of the fundamental wave of the laser beam irradiation unit 24 to be applied, the output of the laser beam necessary for processing, or the disturbance of the Gaussian distribution by the wavelength conversion unit 24c. It is adjusted appropriately according to the condition.

  In the embodiment described above, an example in which the laser device of the present invention is applied to a laser processing device for processing a wafer has been shown, but the present invention is not limited to this, for example, a shape measuring device using a laser beam, etc. It can also be applied to. The present invention does not exclude application to any apparatus using a laser that is effective in shaping the Gaussian distribution of a laser beam.

2: Laser processing apparatus 10: Wafer 20: Laser apparatus 22: Holding means 23: Moving means 24: Laser beam irradiation means 24a: Condenser 24b: Laser oscillator 24c: Wavelength converting means 24d: Harmonic separator 24e: Condensing lens 24f: Light intensity distribution shaping means 24g: collimating lens 24h: spectrometer 24i: output measuring means 24j: transmittance adjusting means 34: holding table 40: X-direction moving means 42: Y-direction moving means FB: optical fiber

Claims (4)

A laser device achieved at least from a holding means for holding a workpiece, and a laser beam irradiation means for irradiating a workpiece with a laser beam to the workpiece held by the holding means,
The laser beam irradiating means includes a laser oscillator, a wavelength converting means for converting the wavelength of the laser beam oscillated by the laser oscillator, and a laser beam whose wavelength is converted by the wavelength converting means on a workpiece held by the holding means. A condenser for condensing, and an optical fiber disposed between the wavelength converting means and the condenser,
The optical fiber is a laser device that shapes a Gaussian distribution of a laser beam disturbed by passing through the wavelength converting means.   A harmonic separator is disposed between the wavelength converting means and the optical fiber, and the harmonic separator excludes laser light having a wavelength other than the predetermined wavelength from the laser light wavelength-converted to a predetermined wavelength by the wavelength converting means. The laser device according to claim 1. A spectroscope disposed between the optical fiber and the concentrator and guiding a part of the laser beam to the output measurement path; and output measurement means disposed in the output measurement path;
A transmittance adjusting means disposed between the spectroscope and the condenser;
With
The laser apparatus according to claim 1, wherein the output of the laser beam applied to the workpiece held by the holding unit is adjusted by the transmittance adjusting unit.   2. The laser device according to claim 1, wherein the wavelength conversion crystal constituting the wavelength conversion means is appropriately shifted from the optical path of the laser beam oscillated by the laser oscillator to extend the life of the wavelength conversion crystal.