JP6901261B2 - Laser device - Google Patents

Description

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

A wafer in which a plurality of devices such as ICs and LSIs are partitioned by a scheduled division line and formed on the surface is irradiated with a laser beam by a laser device and divided into individual devices to be used for electric devices such as mobile phones and personal computers.

The laser apparatus is composed of at least a holding means for holding the workpiece and a laser beam irradiating means for irradiating the workpiece held by the holding means with a laser beam. The laser beam irradiating means includes a laser beam oscillator that oscillates a laser beam, a condenser that condenses the laser beam oscillated by the laser beam oscillator, and condenses the laser beam on a workpiece held by the holding means, the laser beam oscillator, and the laser beam oscillator. It is composed of an optical system disposed between the condenser and at least guiding a laser beam to a predetermined optical path, and can perform desired processing on the workpiece (see, for example, Patent Document 1). ..

Further, when the wavelength of the laser beam suitable for processing the workpiece is ultraviolet light such as 355 nm and 266 nm, the damage to the optical system is relatively severe, so that the laser beam oscillator oscillates in order to reduce the damage to the optical system. Applicants have developed a laser device that converts the wavelength of the laser beam to be ultraviolet light of 1064 nm, which has less burden on the optical system, and converts it into ultraviolet light of 355 nm, 266 nm, etc. by arranging a wavelength conversion means in front of the condenser. It has been proposed (see Patent Document 2). As the wavelength conversion means, CLBO crystal, BBO crystal, LBO crystal, KTP crystal and the like can be adopted as the non-linear crystal having a wavelength conversion function, and the non-linear crystals are appropriately combined according to the wavelength to be obtained. , Various wavelength conversion methods (SHG, FHK, THG, etc.) can be realized.

Japanese Unexamined Patent Publication No. 2006-108478 Japanese Patent No. 5964621

Although a laser beam of a desired wavelength can be obtained by the above-mentioned laser device, the laser beam converted by the wavelength conversion 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 the strength cannot be obtained and stable processing cannot be performed even if the work piece is irradiated as it is.

Further, since the non-linear crystal constituting the wavelength conversion means described above causes deterioration of the irradiated portion when the same portion is continuously irradiated with the laser beam, it is necessary to appropriately change the irradiation position of the laser beam so that it can be used for a long period of time. However, the crystal structure of a non-linear crystal that realizes wavelength conversion is not always uniform depending on the position where the laser beam is irradiated, and the light intensity distribution after wavelength conversion changes every time the irradiation location is changed. In that sense, there may be a problem of hindering stable processing.

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

To solve the above object, according to the present invention, a holding means for holding a workpiece, a laser beam application means for applying a laser beam to the workpiece held by the holding means, made at least configured from The laser beam irradiating means is a laser device, the wavelength is converted by the laser oscillator, the wavelength converting means for converting the wavelength of the laser beam oscillated by the laser oscillator using a nonlinear crystal, and the wavelength converting means. The optical fiber is configured to include at least a concentrator that concentrates the laser beam on the workpiece held by the holding means and an optical fiber disposed between the wavelength conversion means and the concentrator. Provided is a laser device that shapes the Gaussian distribution of a turbulent laser beam that has passed through the wavelength conversion means.

A harmonic separator is arranged between the wavelength conversion means and the optical fiber, and the laser beam having a wavelength other than the predetermined wavelength is excluded from the laser beam whose wavelength is converted to a predetermined wavelength by the harmonic separator. Can be. Further, a spectroscope arranged between the optical fiber and the condenser to guide a part of the laser beam to the output measurement path, an output measuring means arranged in the output measurement path, the spectroscope and the spectroscope and the same. A transmittance adjusting means disposed between the light collector and the light collector may be provided, and the output of the laser beam irradiating 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 to extend the life of the wavelength conversion crystal.

The laser beam irradiating means in the laser apparatus of the present invention includes a laser oscillator, a wavelength converting means for converting the wavelength of the laser beam oscillated by the laser oscillator using a nonlinear crystal, and a laser beam whose wavelength is converted by the wavelength converting means. It is configured to include at least a concentrator that collects light on the workpiece held by the holding means and an optical fiber disposed between the wavelength conversion means and the concentrator, and the optical fiber is the optical fiber. Since the disturbed laser beam is shaped by passing through the wavelength conversion means, the Gaussian distribution is disturbed due to the laser beam passing through the wavelength conversion means, etc., and even if stable processing cannot be performed as it is, the optical fiber By the action, the laser beam reaching the condenser is shaped so as to approach an appropriate Gaussian distribution, and stable laser processing can be performed.

It is a 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 work piece. 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 a laser beam before being shaped by the laser beam irradiation means of this invention, and the light intensity distribution of a laser beam after being shaped.

Hereinafter, the laser apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an overall perspective view of a laser processing device 2 including a laser device 20 configured based on the present invention. The laser apparatus 20 includes at least a holding means 22 for holding the workpiece and a laser beam irradiating means 24 for irradiating the workpiece held by the holding means 22 with a laser beam. The holding means 22 holds the workpiece (wafer 10) held by the annular frame F via the adhesive tape T enlarged to the upper left in the drawing, and the laser processing apparatus 2 is described above. In addition to the laser device 20, a moving means 23 arranged on the stationary base 2a to move the holding means 22 and a vertical wall portion 51 erected on the side of the moving means 23 on the stationary base 2a. 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 irradiating means 24 constituting the main part of the laser device 20 of the present invention is built in the horizontal wall portion 52 of the frame body 50, and the configuration thereof will be described in detail.

The holding means 22 has a rectangular X-direction movable plate 30 mounted on the base 2a so as to be movable in the X direction indicated by the arrow X in the drawing, and an X movablely movable in the Y direction indicated by the arrow Y in the drawing. A rectangular Y-direction movable plate 31 mounted on the directional movable plate 30, a cylindrical support plate 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 support column 32. And include. The cover plate 33 is provided with a holding table 34 for holding a circular workpiece extending upward through an elongated hole formed on the cover plate 33, and a porous material is provided on the upper surface of the holding table 34. A circular suction chuck 35 formed from the above and extending substantially horizontally is arranged. The suction chuck 35 is connected to a suction means (not shown) by a flow path passing through the support column 32. 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 is orthogonal to the X direction. The planes defined in the X and Y directions are substantially horizontal.

The moving means 23 includes an X-direction moving means 40 and a Y-direction moving means 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 X-direction movable plate 30 is X along the guide rail on the base 2a. Move forward and backward in the direction. The Y-direction moving means 42 converts the rotational motion of the motor into a linear motion via the ball screw, transmits it to the Y-direction movable plate 31, and transmits the Y-direction movable plate 31 along the guide rail on the X-direction movable plate 30. Moves forward and backward in the Y direction. Although not shown, the X-direction moving means 40 and the Y-direction moving means 42 are provided with position detecting means, respectively, in the X-direction position, the Y-direction position, and the circumferential direction of the holding table 34. The rotation position is accurately detected, 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, and 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 is placed on a holding table 34 in a state where a plurality of devices 14 are partitioned by a planned division line 12 and formed on the surface thereof, and are supported by an annular frame F via an adhesive tape T. Be retained. Then, the laser beam irradiating means 24 is operated to irradiate the laser beam LB, and the above-mentioned X-direction moving means 40 and Y-direction moving means 42 are operated to perform ablation processing on the planned division line 12 and the division starting point. Form 100.

FIG. 2 shows an example of the laser beam irradiating means 24 constituting the laser apparatus 20 of the present invention. The laser beam irradiating means 24 irradiates a desired laser beam LB (for example, a wavelength of 355 nm) from the above-mentioned concentrator 24a, and has a laser oscillator 24b that oscillates a laser beam LB1 having a wavelength of 1064 nm as a fundamental wave. A wavelength conversion means 24c that converts a laser beam LB1 into a laser beam LB2 having a wavelength of 355 nm, a harmonic separator 24d that outputs a laser beam LB3 that excludes unnecessary wavelength components from the laser beam LB2 output from the wavelength conversion means 24c, and the harmonic. A light intensity distribution shaping means 24f composed of a condenser lens 24e for condensing the laser beam LB3 output from the separator 24d, an optical fiber FB on which the laser beam LB4 condensed by the condensing lens 24e is incident, and the light. A collimating lens 24 g that shapes the laser beam LB4'that has a Gaussian distribution shaped by the optical fiber FB of the intensity distribution shaping means 24f into parallel light, and a part of the laser beam LB5 that has been made parallel light, for example, to the extent that processing is not affected. A spectroscope 24h that reflects an extremely small ratio (1%) of the laser beam LB6'to the output measurement path side and transmits the remaining laser beam LB6 to the condenser 24a side, and a spectroscope 24h that is reflected by the spectroscope 24h and is reflected in the output measurement path. The output is adjusted to a desired output by controlling the transmission rate of the output measuring means 24i including the light receiving element for measuring the light amount value of the guided output measurement laser beam LB6'and the laser beam LB6 transmitted through the spectroscope 24h. The condenser 24a is provided with a transmission rate adjusting means (attenuator) 24j for emitting a laser beam LB7 having a desired output, and the laser beam LB7 is a condenser lens (not shown) constituting the condenser 24a. The waiha 10 held on the holding table 34 is irradiated with the desired laser beam LB.

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

The wavelength conversion means 24c of the laser beam irradiation means 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, and the conversion method is a conversion method for the wavelength of a laser beam serving as a fundamental wave. It is selected in consideration of the wavelength of the laser beam to be obtained, the output of the laser beam when it is finally used for processing, and the like.

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

The first LBO crystal 24c1 and the second LBO crystal 24c2 constituting the wavelength conversion means 24c are provided with incident position changing means (not shown). It is known that a non-linear crystal having a wavelength conversion function deteriorates when a laser beam is irradiated at the same position for a long time, and it enters the optical path of the laser beam LB1 of the fundamental wave at a predetermined time or at a predetermined number of incidents. On the other hand, it is configured so that the incident position is changed. As a result, the life of the nonlinear crystal constituting the wavelength conversion means 24c can be extended. When the laser beam is incident at all the positions where the laser beam can be incident, the first LBO crystal 24c1 and the second LBO crystal 24c2 are exchanged. The laser apparatus of the present invention has a configuration as described above, and its operation will be further described.

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

When the operator instructs the laser processing apparatus of the present invention to start irradiating the laser beam, the laser oscillator 24b oscillates the laser beam LB1 having a wavelength of 1064 nm and incidents the laser beam LB1 on the wavelength conversion means 24c. The first LBO crystal 24c1 and the second LBO crystal 24c2 constituting the wavelength conversion means 24c convert wavelengths as described above, but the laser beam LB1 incident on the first LBO crystal 24c1 is complete. It is not converted to a wavelength of 532 nm, but is emitted in a state where a laser beam having a wavelength of 1064 nm remains at a predetermined ratio. 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 are emitted from the laser beam emitted from the second LBO crystal 24c2, that is, the wavelength conversion means 24c. In addition to the converted laser beam having a wavelength of 355 nm, the laser beam LB2 also includes a laser beam having a wavelength of 1064 nm and a wavelength of 532 nm that remain unconverted. Therefore, in the laser beam irradiating means 24 of the present embodiment, the above-mentioned harmonic separator 24d is arranged on the optical axis through which the laser beam LB2 passes, unnecessary wavelength components are eliminated, and the wavelength is mainly 355 nm. The laser beam LB3 is emitted.

Here, the laser beam LB3 will be described. In FIGS. 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. The light intensity distribution according to the cross-sectional position of the optical axis of the laser beam is schematically represented by. In this embodiment, the radius of the optical axis of the laser beam oscillated from the laser oscillator 24b is N mm. As shown in FIG. 3A, the laser beam LB2 that has passed through the wavelength conversion means 24c does not have an ideal Gaussian distribution with the center of the optical axis as the peak, and has a disordered shape. .. It is presumed that this turbulence is caused by the fact that the crystal structure constituting the nonlinear crystal constituting the wavelength conversion means 24c is not always constant, and the inside of the nonlinear crystal is irradiated with a laser beam at a predetermined position for a long time. 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 focused and irradiated at a predetermined position, the desired peak energy cannot be obtained and the desired processing expected by the laser processing conditions is not performed. Problems can arise. Therefore, in the present invention, the laser beam whose wavelength has been converted by the wavelength conversion means 24c is incident on the optical fiber FB arranged at any of the wavelength conversion means 24c and the condenser 24a. More specifically, according to FIG. 2, in the present embodiment, the laser beam LB3 emitted from the harmonic separator 24d is focused so as to be incident on one end surface FBa of the optical fiber FB constituting the light intensity distribution shaping means 24f. It incidents on the lens 24e and collects light. The focal point of the laser beam LB4 focused by the condenser lens 24e is adjusted so as to be at the position of one end surface 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 its length is set to about 1 m.

Here, the laser beam LB4 incident on the optical fiber FB repeatedly reflects on the side wall surface in the optical fiber FB, travels repeatedly, and is emitted from the other end FBb. Since the laser beam LB4'emitted from the other end FBb of the optical fiber FB is diffused as it is, it is converted into parallel light by the collimated lens 24g and becomes the laser beam LB5.

The laser beam LB5 emitted from the optical fiber FB and made into parallel light passes through the optical fiber FB, so that a peak of light intensity appears at the center of the optical axis as shown in FIG. 3 (b). It is shaped to approach the ideal Gaussian distribution, which declines smoothly toward the outside. Therefore, by passing through the wavelength conversion means 24c, the disordered Gaussian distribution as shown in FIG. 3 (a) is shaped into the ideal Gaussian distribution as shown in FIG. 3 (b), and the desired processing is performed. Will be 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 means 24j is controlled based on the output information of the output measuring means 24i, becomes a laser beam LB7, and is incident on the condenser 24a. As a result, the laser beam LB shaped to have an ideal Gaussian distribution and then focused 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, in the above-described embodiment, the wavelength of the laser beam of the fundamental wave oscillated from the laser oscillator is set to 1064 nm, and the wavelength conversion means 24c for converting the fundamental wave into a wavelength of 355 nm using two LBO crystals is used. However, the present invention is not limited to this, for example, when converting a laser beam having a wavelength of 1064 nm into a laser beam having a wavelength of 266 nm using a KTP crystal and a CLBO crystal, or a wavelength of 1064 nm. Can be applied to a laser device used by converting the laser beam of No. 1 into a wavelength of 532 nm using one KTP crystal. Further, the basic wave is not limited to the case where a laser oscillator 24b that oscillates a laser beam having a wavelength of 1064 nm is used, and 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 can also be applied to a laser device that uses a laser oscillator that oscillates as a wave.

Further, in the above-described embodiment, the spectroscope 24h and the output measuring means 24i are arranged on the downstream side of the light intensity distribution shaping means 24f, but the present invention is not limited to this, and immediately after the harmonic separator 24d. It may be arranged in. Further, 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 means 24 to be applied, the output of the laser beam required for processing, or the disturbance of the Gaussian distribution due to the wavelength conversion means 24c. It is adjusted appropriately according to the condition.

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

2: Laser processing device 10: Waha 20: Laser device 22: Holding means 23: Moving means 24: Laser beam irradiation means 24a: Condenser 24b: Laser oscillator 24c: Wavelength conversion 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)

Holding means for holding a workpiece, comprising: at least configured made the laser device from a laser beam application means for applying a laser beam to the workpiece held by the holding means,
The laser beam irradiating means holds a laser oscillator, a wavelength converting means for converting the wavelength of the laser beam oscillated by the laser oscillator using a nonlinear crystal, and a laser beam whose wavelength is converted by the wavelength converting means in the holding means. It is configured to include at least a condenser that concentrates on the work piece and an optical fiber disposed between the wavelength conversion means and the condenser.
The optical fiber is a laser device that shapes the Gaussian distribution of a turbulent laser beam that has passed through the wavelength conversion means. A harmonic separator is disposed between the wavelength conversion means and the optical fiber, and the harmonic separator excludes a laser beam having a wavelength other than the predetermined wavelength from the laser beam whose wavelength has been converted to a predetermined wavelength by the wavelength conversion means. The laser device according to claim 1. A spectroscope arranged between the optical fiber and the condenser to guide a part of the laser beam to the output measurement path, and an output measuring means arranged in the output measurement path.
Transmittance adjusting means disposed between the spectroscope and the condenser,
With
The laser apparatus according to claim 1, wherein the output of a laser beam irradiating a work piece held by the holding means is adjusted by the transmittance adjusting means. The laser apparatus according to claim 1, further comprising a configuration in which 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.

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