JP2008093723A - Laser beam fine machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam fine machining apparatus of which the machining efficiency can be enhanced by simultaneously machining a plurality of workpieces, and which can perform highly accurate machining without being conscious of the rotation center of a turntable. <P>SOLUTION: The laser beam fine machining apparatus is equipped with: a workpiece fixture which is formed of a flat plate having the thickness substantially identical to the thickness of a workpiece, and has a plurality of fitting holes which are through in the thickness direction and regulate the position of the fitted workpiece; and the turntable which sucks the workpiece fixture and the workpiece fitted to the fitting hole and rotates them. Each of the plurality of fitting holes is formed away from the rotation center of the workpiece fixture, and the height of a machining surface of the workpiece and of a non-suction surface of the workpiece fixture is substantially same. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser micromachining apparatus that irradiates a machining laser beam to produce fine pits on a machining surface of a workpiece.

  2. Description of the Related Art Conventionally, there is known a laser micromachining apparatus that irradiates a machining target laser beam emitted from an optical machining head onto a plate-like workpiece and produces fine pits on the machining surface of the workpiece. In this laser microfabrication apparatus, there is an apparatus as shown in Patent Document 1, for example, as an apparatus for irradiating a laser beam onto a processing object fixed on a turntable.

In the laser drawing apparatus disclosed in Patent Document 1, a single workpiece is fixed to a turntable so that the rotation center of the turntable and the center of the workpiece are substantially coincident, and the turntable is rotated to rotate. Processing is performed by directly irradiating a processing surface of an object with laser light.
JP 2001-133987 A

  However, in the laser micromachining apparatus having the configuration of the conventional laser drawing apparatus, since the number of processing objects that can be set and processed on the turntable is one, the replacement of the processing object is complicated and the processing tact is long, Efficient processing is difficult.

  When processing is performed by rotating the turntable so that the linear velocity at the position irradiated with the processing laser beam is constant, the turntable rotates when the position irradiated with the processing laser beam is near the rotation center. Since the speed is increased, the accuracy of the rotation control is inferior to the position away from the rotation center. In addition, since the rotational speed is limited, there is a case where control at a constant linear velocity cannot be performed when approaching the center. Furthermore, it is difficult to accurately align the rotation center of the turntable with the center of the workpiece, and it is also difficult to adjust the turntable rotation center to include the radial movement line of the processing laser beam. is there. For this reason, it has been difficult to perform high-precision machining on the workpiece near the rotation center of the turntable.

  The present invention has been made in view of such circumstances, and it is possible to improve the machining efficiency by allowing a plurality of workpieces to be machined simultaneously, without being aware of the rotation center of the turntable. An object of the present invention is to provide a laser micromachining apparatus capable of high-precision machining.

  The laser micromachining apparatus according to claim 1 is a flat plate having substantially the same thickness as the workpiece, and has a plurality of mounting holes that penetrate the thickness direction and regulate the position of the inserted workpiece. A workpiece fixing jig, and a turntable that rotates by adsorbing the workpiece to be processed and the workpiece mounted in the mounting hole, each of the plurality of mounting holes being a workpiece fixing jig. It is provided apart from the center of rotation, and the height of the processing surface of the processing object and the non-adsorption surface of the processing object fixing jig is substantially the same.

  The laser micromachining apparatus according to claim 2 is characterized in that the workpiece fixing jig and the turntable are integrally formed.

  The laser micromachining apparatus according to claim 3 generates a focus error signal based on the reflected light from the workpiece, and focuses servo so that the machining laser beam is focused on the workpiece based on the focus error signal. And a focus servo means for performing an S-shaped detection distance in which an S-shaped waveform is generated in the focus error signal, corresponding to 3 to 10 times the step between the processing surface of the processing object and the non-adsorption surface of the processing object fixing jig. It is characterized by that.

  According to a fourth aspect of the present invention, there is provided a laser micromachining apparatus comprising: a servo circuit for generating a signal for controlling the focal position of the processing laser beam based on the focus error signal; and a cutoff frequency in the servo circuit. Further, it is characterized by being equivalent to 1 / 2.5 to 1/15 of the frequency of the signal component generated by the gap between the workpiece and the mounting hole of the workpiece fixing jig.

  The laser micromachining apparatus according to claim 5 is characterized in that the object to be machined is an LED wafer.

  According to the first aspect of the present invention, since a plurality of mounting holes for mounting a workpiece to be processed are provided in the workpiece fixing jig, and a plurality of workpieces can be processed simultaneously, the processing efficiency can be improved. Is possible. In addition, each of the mounting holes is provided apart from the rotation center of the workpiece fixing jig, and the workpiece is fixed at a position away from the rotation center of the workpiece fixing jig. It is not necessary to consider the problem that high-precision machining is difficult, and high-precision machining is possible without being aware of the center of rotation.

  According to the invention of claim 2, since the workpiece fixing jig and the turntable are integrally formed, it is only necessary to fix the workpiece to the turntable, and the working efficiency can be improved. .

  According to the invention of claim 3, the S-shaped detection distance in which the S-shaped waveform is generated in the focus error signal generated based on the reflected light from the processing object for performing the focus servo is defined as the processing surface of the processing object. Since it is equivalent to 3 to 10 times the step with the non-adsorption surface of the workpiece fixing jig, the focal position of the laser beam for processing is fixed to the processing surface of the workpiece and the workpiece even when there is a step. Focus servo can be performed so as to match the non-adsorbing surface of the jig, and processing is not interrupted, so that efficient processing is possible.

  According to the invention of claim 4, the cutoff frequency of the servo circuit that generates a signal for controlling the focal position of the processing laser beam is set between the processing object and the mounting hole of the processing object fixing jig. The servo circuit ignores the disturbance even if the focus error signal is disturbed in the place where there is a gap. Therefore, the focus position of the processing laser beam does not change so that the focus servo is not released, and the processing is not interrupted, so that efficient processing is possible.

  According to the invention of claim 5, the object to be processed is an LED wafer, and it is possible to produce an LED with high light extraction efficiency by producing fine irregularities on the surface of the LED wafer with high accuracy.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The laser micromachining apparatus according to the embodiment of the present invention irradiates a processing laser beam emitted from an optical machining head onto a disk-shaped workpiece and produces fine pits on the machining surface of the workpiece. 1 is an explanatory diagram for explaining an example of the configuration of a laser micromachining apparatus according to the present invention, FIG. 2 is an explanatory diagram of a wafer fixing jig of the laser micromachining apparatus, and FIG. 3 is an S-shaped detection of the laser micromachining apparatus. FIG. 4 is an explanatory diagram showing the distance, and FIG. 4 is a configuration diagram showing the configuration of the laser micromachining apparatus.

  In FIG. 1, a wafer 5 is a disk-shaped workpiece such as an LED wafer, and the surface is a processed surface 5a for producing fine pits. The wafer fixing jig 10 constituting the laser micromachining apparatus 1 of the present invention has a disk shape that is substantially the same thickness as the wafer 5 and has a plurality of mounting holes 10a that penetrate in the thickness direction and into which the wafer 5 can be inserted. Has been. The mounting hole 10 a is provided apart from the rotation center of the wafer fixing jig 10. The turntable 12 is a table that rotates the wafer 5. The turntable 12 includes a plurality of suction ports 12 a on the entire surface, and is configured to be able to suck the wafer fixing jig 10 and the wafer 5. The optical processing head 200 emits processing laser light for producing fine pits from a laser light source provided therein.

  As shown in FIG. 4, the laser micromachining apparatus 1 includes the optical machining head 200, a controller 600 including a display device 602 and an input device 604, an HF signal amplification circuit 102, a focus error signal generation circuit 104, and a focus servo. The circuit 106, the drive circuit 108, the light emission signal generation circuit 204, the processing laser drive circuit 202, the spindle motor 300, the spindle motor control circuit 302, the feed motor 400, the field motor control circuit 402, and the like.

  Next, a procedure for producing fine pits on the processed surface 5a of the wafer 5 by the laser fine processing apparatus 1 of the present invention will be described with reference to FIG. First, as shown in FIG. 1A, a wafer fixing jig 10 is placed on the turntable 12 and sucked. Next, as shown in FIG. 1B, the wafer 5 is inserted into and attached to the mounting hole 10 a of the wafer fixing jig 10 placed on the turntable 12. Thus, by inserting the wafer 5 into the mounting hole 10 a of the wafer fixing jig 10, the wafer 5 is in a state where the processed surface 5 a is substantially flush with the non-adsorption surface of the wafer fixing jig 10. The position is fixed to the turntable 12 while being regulated. In this state, the wafer 5 and the wafer fixing jig 10 are rotated, and the processing laser beam is irradiated toward the processing surface 5a on the surface of the rotating wafer 5, as shown in FIG.

  Next, a specific operation of the laser micromachining apparatus 1 will be described with reference to FIG. When laser processing start is input from the input device 604, the controller 600 starts operation to the feed motor control circuit 402, spindle motor control circuit 402, spindle motor control circuit 302, light emission signal generation circuit 204, and processing laser drive circuit 202. Instruct. The initial radial position at which the processing laser light is irradiated is set in advance in the feed motor control circuit 402 from the input device 604 via the controller 600. When an operation start instruction is issued from the controller 600, the feed motor control circuit 402 The radial position is calculated from the pulse signal output from the encoder in the feed motor 400, and the feed motor 400 is driven so as to reach the set initial radial position. As a result, the processing laser light is irradiated from a slightly inner radial position or a slightly outer radial position from the wafer 5.

  Then, the controller 600 always calculates the radial position from the pulse signal output from the encoder in the feed motor 400, and from the radial interval and linear velocity of the fine pits input in advance from the input device 604, The feed speed for moving the radial position irradiated with the processing laser beam is calculated just by the radial interval of the fine pits in one rotation, and the feed motor control circuit 402 is instructed. The feed motor control circuit 402 calculates the feed speed from the pulse signal output from the encoder in the feed motor 400, and drives the feed motor 400 so that the feed speed matches the instructed speed. Further, the controller 600 calculates a rotation speed for the linear velocity at the position irradiated with the processing laser light to be the input linear velocity from the calculated radial position and the input linear velocity, and the spindle motor The control circuit 302 is instructed. The spindle motor control circuit 302 calculates the rotational speed from the pulse signal output from the encoder in the spindle motor 300, and drives the spindle motor 300 so that the rotational speed becomes the designated speed.

  The controller 600 calculates the timing of the light emission signal from the circumferential interval and the linear velocity of the fine pits input from the input device 604 and instructs the light emission signal generation circuit 204. The light emission signal generation circuit 204 generates a light emission signal that is a pulse signal at the instructed light emission timing, and outputs the light emission signal to the processing laser drive circuit 202. The processing laser drive circuit 202 generates a processing laser drive signal (a pulse signal composed of a high level and a low level) from the input light emission signal, and outputs it to the laser irradiator of the optical processing head 200. The optical processing head 200 receives the reflected light from the processing laser light with the divided photo director, and outputs a signal corresponding to the received light amount to the HF signal amplification circuit 102. The HF signal amplification circuit 102, the focus error signal generation circuit 104, the focus servo circuit 106, and the drive circuit 108 perform control of the focal position of the processing laser beam by driving the objective lens of the optical processing head 200, that is, focus servo. . As a result, fine pits are formed at intervals on the processed surface 5a irradiated with the processing laser light.

  Thus, according to the laser microfabrication apparatus 1 of the present embodiment, a plurality of mounting holes 10a for mounting the wafer 5 are provided in the wafer fixing jig 10, and a plurality of wafers 5 can be processed simultaneously. It is possible to improve processing efficiency. Further, since each of the mounting holes 10a is provided apart from the rotation center of the wafer fixing jig 10 and the wafer 5 is fixed at a position away from the rotation center of the wafer fixing jig 10, high accuracy is provided at the rotation center. Therefore, it is not necessary to consider the problem of difficult machining, and high-precision machining is possible without being aware of the center of rotation.

Although the processing surface 5a has been described as substantially the same surface as the non-adsorption surface of the wafer fixing jig 10, actually, as shown in FIG. 2, the processing surface 5a and the non-adsorption surface of the wafer fixing jig 10 There is a step Δt between them. If this step Δt is larger than the control range of the focal position of the processing laser beam, the focus servo will be lost at the place where there is a step. Even if the step Δt is smaller than the control range of the focal position of the processing laser beam, if it is not sufficiently small, the focus servo may be lost at a place where there is a step. Therefore, in the laser micromachining apparatus 1 of the present embodiment, the controllable range of the focal position of the processing laser beam, which is variable by adjusting the optical system of the optical machining head, that is, the focal position of the machining laser beam is set in one direction. 4, the S-shaped detection distance _Sp−p , which is the distance from the vertex to the vertex of the S-shaped waveform generated in the focus error signal output from the focus error signal generation circuit 104 in FIG. 3 times to 10 times Δt. This relationship is shown in Equation 1 (equation for 3.5 times).

By determining the S _- shaped detection distance S _p-p in this way, the focal position of the processing laser beam can be changed even in a place where there is a step between the processing surface 5a and the non-adsorption surface of the wafer fixing jig 10. Since the focus servo can be performed so as to match the non-adsorption surface of 5a and the wafer fixing jig 10, and the processing is not interrupted, efficient processing is possible.

  Further, in order to be able to regulate the position of the wafer 5 by the mounting hole 10a of the wafer fixing jig 10, the outer periphery of the wafer 5 and the diameter of the mounting hole 10a are substantially the same diameter, but actually, as shown in FIG. As described above, there is a gap Δx between the outer periphery of the wafer 5 and the mounting hole 10a. When this gap Δx is present, the focus error signal is disturbed, and the focus servo circuit 106 that generates and outputs a signal for controlling the focal position of the processing laser beam based on the focus error signal in FIG. 4 is based on the disturbance of the focus error signal. Output a signal, and the focal position of the processing laser beam fluctuates so that the focus servo is out. Therefore, in the laser microfabrication apparatus 1 of the present embodiment, the cutoff frequency set in the focus servo circuit 106 is equivalent to 1 / 2.5 to 1/15 of the frequency of the signal component generated by the gap Δx. . This relationship is expressed by Equation 2 (an expression in the case of 1/2 times). V [m / s] is the linear velocity of the wafer 5 and the wafer fixing jig 10 at the position where the processing laser beam is irradiated.

  By determining the cutoff frequency of the focus servo circuit 106 in this way, even if the focus error signal is disturbed in a place where there is a gap between the outer periphery of the wafer 5 and the mounting hole 10a, the focus servo circuit 106 ignores the disturbance. Thus, since the servo signal is generated, the focal position of the laser beam for processing does not fluctuate so that the focus servo is removed, and the processing is not interrupted, so that efficient processing is possible.

As described above, fine pits are formed on the processing surface 5a of the wafer 5 by the processing laser light while the focus servo is performed by setting the S-shaped detection distance _Spp and the cutoff frequency of the focus servo circuit 106 to appropriate values. Will be made. Specifically, first, a light emission signal whose light emission timing is controlled by the light emission signal generation circuit 204 is generated by an instruction from the controller 600, and the light emission signal is generated by the processing laser drive circuit 202 as a drive signal for processing laser light. The laser beam for processing is irradiated from the optical processing head 200 toward the processing surface 5a of the wafer 5.

  The optical processing head 200 receives the reflected light from the wafer 5 by the divided photodetector and outputs a signal corresponding to the received light amount to the HF signal amplification circuit 102. The HF signal amplification circuit 102 amplifies the input signal and outputs it to the focus error signal generation circuit 104. The focus error signal generation circuit 104 generates a focus error signal and outputs the focus error signal to the focus servo circuit 106. The focus servo circuit 106 generates a signal for controlling the focal position of the processing laser beam and outputs the signal to the drive circuit 108. Based on the input signal, the drive circuit 108 drives the objective lens in the optical machining head 200 in a direction parallel to the optical axis of the objective lens, and controls so that the focal position of the machining laser beam matches the machining surface 5a.

  In the present embodiment, the case where the wafer fixing jig 10 and the turntable 12 are formed as separate bodies has been described. However, it is also possible to form them integrally and use them. By integrating them, it is not necessary to fix the wafer fixing jig 10, and it is only necessary to fix the wafer 5 to the turntable 12, and work efficiency can be improved.

  In the present embodiment, the wafer 5 has been described as an LED wafer. However, the laser micromachining apparatus 1 of the present invention can produce fine pits on the machining surface 5a with high accuracy, and thus the LED 5 is particularly LED. Suitable for wafer processing. Specifically, it is possible to produce an LED with high light extraction efficiency by producing fine irregularities on the surface of the LED wafer with high accuracy by the laser microfabrication apparatus of the present invention. In addition, although the wafer 5 was demonstrated as an LED wafer, it is not limited to this, What kind of thing may be sufficient as long as it can produce a fine pit by irradiating the laser beam for a process.

  Further, in the present embodiment, the laser beam emitted from the optical processing head 200 is only the processing laser beam, and the reflected light of the processing laser beam on the processing surface 5a of the wafer 5 or the non-adsorption surface of the wafer fixing jig 10 is used. The focus error signal is generated based on the focus error signal and the focus servo is performed based on the focus error signal. However, the reflected light for generating the focus error signal may not be the reflected light of the processing laser light. That is, two laser beams of a processing laser beam and a servo laser beam are emitted from the optical processing head 200, and only the reflected light of the servo laser beam is detected, and a focus error signal is generated based on the reflected light. You may make it do.

  As described above, according to the present invention, it is possible to improve the machining efficiency by allowing a plurality of workpieces to be machined simultaneously, and high-precision machining can be performed without being aware of the rotation center of the turntable. A possible laser micromachining apparatus can be provided.

It is explanatory drawing explaining the structure of the laser fine processing apparatus which concerns on this invention. It is explanatory drawing of the wafer fixing jig of the laser fine processing apparatus. It is explanatory drawing which shows S character detection distance of the laser fine processing apparatus. It is a block diagram which shows the structure of the laser fine processing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser fine processing apparatus 5 ... Wafer 10 ... Wafer fixing jig 12 ... Turntable 12a ... Suction port 102 ... HF signal amplification circuit 104 ... Focus error signal generation circuit 106 ... focus servo circuit 108 ... drive circuit 200 ... optical processing head 202 ... processing laser drive circuit 204 ... light emission signal generation circuit 300 ... spindle motor 302 ... Spindle motor control circuit 400 ... Feed motor 402 ... Feed motor control circuit 600 ... Controller 602 ... Display device 604 ... Input device

Claims (5)

In a laser micromachining apparatus that irradiates a machining target laser beam emitted from an optical machining head onto a plate-like workpiece and produces fine pits on the machining surface of the workpiece,
A processing object fixing jig having a plate shape substantially the same thickness as the processing object, penetrating in the thickness direction and having a plurality of mounting holes for restricting the position of the inserted processing object;
The workpiece fixing jig and a turntable that rotates by sucking the workpiece mounted in the mounting hole,
Each of the plurality of mounting holes is provided apart from the rotation center of the workpiece fixing jig,
A laser micro-machining apparatus, wherein the processing surface of the processing object and the non-adsorption surface of the processing object fixing jig have substantially the same height.   2. The laser micromachining apparatus according to claim 1, wherein the workpiece fixing jig and the turntable are integrally formed. A focus servo unit configured to generate a focus error signal based on reflected light from the processing object and perform focus servo so that the processing laser beam is focused on the processing object based on the focus error signal; ,
An S-shaped detection distance at which an S-shaped waveform is generated in the focus error signal is equivalent to 3 to 10 times the step between the processing surface of the processing object and the non-adsorption surface of the processing object fixing jig. The laser micromachining apparatus according to claim 1 or 2. The focus servo means includes a servo circuit that generates a signal for controlling the focal position of the processing laser beam based on the focus error signal;
The cutoff frequency in the servo circuit is equivalent to 1 / 2.5 to 1/15 of the frequency of the signal component generated by the gap between the workpiece and the mounting hole of the workpiece fixture. 4. The laser micromachining apparatus according to claim 3, wherein   The laser processing apparatus according to claim 1, wherein the processing object is an LED wafer.

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