JP2013233556A - Laser machining apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser machining apparatus which is compact in size and low in running cost, and achieves stable performance.SOLUTION: A laser machining apparatus is configured such that a plurality of blue laser diodes each having an average output of not less than 1 W and a wave length of 400 nm to 475 nm serve as a light source; an optical fiber is coupled to each of the blue laser diodes and a plurality of the optical fibers are welded into one optical fiber to form an optical transmission path of one unit; optical transmission paths of not less than three units per one an optical head are provided; a laser power sensor for detecting laser power is provided at an intermediate position of the respective optical fiber of each optical transmission paths; the output of the light source is feedback controlled by the detection result of the laser power sensor; the optical fibers of the respective optical transmission paths are aligned to be connected to the optical head; and a laser beam is shaped in the optical head and is converged by an objective lens to be irradiated to a workpiece.

Description

  The present invention relates to a laser processing apparatus that performs processing to change the shape and material of an object using a laser as a light source.

There has been proposed a laser processing apparatus that performs processing to change the shape and material of an object using a laser as a light source (see, for example, Patent Documents 1 to 14).
As a laser of the light source of this laser processing apparatus, for example, a carbon dioxide gas laser, an excimer laser, which is a gas laser, an Nd: YAG laser, an Nd: YVO ₄ laser, a fiber laser, a diode laser (hereinafter referred to as a laser diode or a laser) LD)).
However, since each laser is not universal for all workpieces, it is necessary to select the optimum wavelength, repetition frequency and energy that the workpiece absorbs.
Since the wavelength of the laser of the light source is determined by the principle and structure of the oscillator, it is necessary to select a light source having an optimum wavelength for the workpiece under limited conditions.
Typical applications of laser processing equipment include metal cutting, drilling, welding, reforming, and scribing.

Among the lasers described above, LDs are remarkably advanced in technology and are well known for thermal processing in the infrared region and for excitation of solid-state lasers.
Single-emitter type LDs with an output of several watts or more, multi-emitter type LDs with an output of over 100 W, and stacked LDs with kW-class output are available.
However, a blue LD (hereinafter referred to as BLD) capable of high output of about 20 W is not available.
Therefore, conventionally, the necessary energy has been obtained by using a plurality of available BLDs each having an output of less than 1 W (see, for example, Patent Documents 11 to 14).

In recent years, laser processing is often used in semiconductor processes.
For example, for the annealing of the silicon substrate, for example, an excimer laser (XeCl) with a wavelength of 308 nm or a Nd: YAG laser with a double wavelength of 1064 nm, that is, a green laser with a wavelength of 532 nm is used.
Each of these lasers has advantages and disadvantages.

The emission wavelength of excimer laser includes a wavelength band with high absorption rate in silicon, but it is selectively absorbed directly only in the surface layer of silicon, so that the excimer laser's strong energy causes roughness on the silicon surface. . Therefore, post-processing such as CMP (chemical mechanical polishing) or etching is required.
In addition, in the excimer laser, the pulse interval of the oscillation pulse may vary to some extent, and the output may decrease due to temporal variation due to gas deterioration.

  Since the green laser has a lower absorptance in silicon than the excimer laser, the efficiency becomes worse, and accordingly, higher energy is required. As a result, particularly in the pulse mode, the surface becomes rough like the excimer laser, and the size of the apparatus needs to be increased.

An annealing apparatus using an excimer laser is very large and requires regular adjustment and maintenance, so that the running cost is high.
In addition, an annealing apparatus using a green laser, for example, when taking out a second harmonic from an Nd: YAG laser has a large attenuation of the laser at the second harmonic generation unit, so that it is necessary to increase the output of the fundamental laser. There is also a need for periodic maintenance of the second harmonic generation unit.

  It has been proposed to use the above-described excimer laser as a light source of an annealing apparatus using a pulse laser (see, for example, Patent Document 2 and Patent Document 3).

It has also been proposed to use an LD-excited solid-state laser as a light source for an annealing apparatus using a pulse laser. For example, a BLD is used as the light source, and the optical transmission system is an optical waveguide. It is assumed that this optical waveguide is actually an optical fiber.
In general, the energy loss is very large at the joint between the BLD and the optical fiber, so that a large energy loss occurs in the transmission system and the optical system.
For this reason, a light source having an energy twice or more of the laser energy irradiated to the workpiece may be used. As an example, a total of 48 optical fibers are connected to each of a number of LDs, for example, 48 BLDs (maximum output 550 mW), and optical transmission is performed with bundled optical fibers. There is an example in which a line beam having a length of several hundred μm, a width of several μm, and a few W is condensed on a workpiece by being aligned, connected to an optical system, and homogenized.

Here, it is assumed that the total energy loss from the output light of the BLD to the workpiece is 50% or more, and it is assumed that it is used at an output of 70% or less of the maximum output in consideration of the life of the BLD. If the upper energy is 7 W, the energy of the light source is 20 W.
For example, the laser energy required for annealing the thin film transistor is CW and the maximum energy is about 5 to 8 W per area of 600 μm × 2.4 μm when the workpiece is irradiated with an ultrafine wire beam. If the irradiation area of the ultrafine beam is small, annealing is possible even at 6 W or less.

  If there is no margin in laser output and the laser is used at the maximum standard, the life of the BLD will be shortened and it will be necessary to replace the BLD frequently. In that case, a structure capable of easily exchanging the BLD is desired.

  As an example, there is an example provided with a large number of BLDs, optical fibers, complicated power feedback, autofocus, etc. In this case, the apparatus cost further increases, resulting in an increase in total cost.

JP 2003-86505 A JP 2003-109912 A JP-A-9-129573 JP 2006-135251 A JP 2007-088050 A JP 2007-251196 A International Publication Number 2007/114031 JP 2008-85236 A JP 2009-16376 A JP 2009-49030 A JP 2009-206386 A JP 2009-260133 A JP 2010-103177 A JP 2011-71351 A

If an LD-excited solid-state laser is used as the light source, or a large number of BLDs, for example, 48 BLDs, are used as the light source, the apparatus becomes complicated and large.
In addition, when an optical transmission path is configured by connecting optical fibers to a large number of BLDs one by one, the number of optical transmission paths is large, so that it is difficult to connect to a processing head. Although the BLD drivers are individually controlled, the effect of feedback is low although the circuit is complicated.

In the configurations described in Patent Documents 12 to 14, since an auto power control sensor is provided inside the optical head, it is difficult to accurately feed back a large number of BLD drivers individually. Since the structure of the optical head is complicated and the weight increases, it is not suitable for an apparatus using a movable head system. Moreover, the expandability to a long line beam is low.
In this case, since the entire laser beam from a large number of BLDs is detected by a sensor inside the optical head, even if one BLD or transmission system fails, the rate of decrease in output is small and it is difficult to identify a defective part. .

Patent Document 10 and the like propose a configuration for generating a long and narrow line beam.
However, for example, an optical system that generates a line beam of 600 μm × 2.4 μm is assumed to have a focal length of several mm and a focal depth of several μm, so that the machining table and the workpiece are extremely high accuracy. Is required, and autofocus is also required.

  In addition, a configuration in which an optical fiber is branched into a plurality of lines and arranged linearly has been proposed, but it is difficult to obtain a uniform ultrafine linear beam only by fiber alignment, and as a result, linear traces remain.

When annealing is performed with an excimer laser or a green laser, it is known that the surface becomes rough due to strong energy. Therefore, post-processing by a CMP apparatus, an etching apparatus or the like is required to improve the surface flatness.
The excimer laser is very large and requires a periodic replacement member, which increases the running cost.

  In order to solve the above-described problems, the present invention provides a stable laser processing apparatus that is small in size and low in running cost.

The laser processing apparatus of the present invention is a laser processing apparatus that processes a workpiece by irradiating the workpiece with laser light.
A plurality of blue laser diodes having an average output of 1 W or more and a wavelength of 400 nm to 475 nm are used as light sources, optical fibers are coupled to the blue laser diodes, and a plurality of optical fibers are welded and welded to one optical fiber. With one optical fiber as one unit optical transmission path, each optical head has three or more optical transmission paths, and a laser power sensor for detecting laser power is provided in the middle of the optical fiber in each optical transmission path. The output of the light source is feedback-controlled by the detection result of this laser power sensor, the optical fibers of each optical transmission line are aligned and connected to the optical head, the laser beam is shaped in this optical head, and condensed by the objective lens Then, the workpiece is irradiated.

In the laser processing apparatus of the present invention, the laser power sensor can be configured to detect leakage light from the optical fiber in the optical transmission path.
In the laser processing apparatus of the present invention, an interchangeable slit having an opening for correcting the shape of the laser beam is provided between the connection portion of the optical transmission path to the optical head and the objective lens. It is possible to have a configuration.
In the laser processing apparatus of the present invention, the total irradiation power of the laser beam per optical head can be 6 W or less per unit area of 600 μm × 2.4 μm.
In the laser processing apparatus of the present invention, it is possible to further provide a structure in which three optical transmission paths are provided for each optical head, and seven optical fibers are welded to each optical transmission path.

  Examples of “processing” performed by the laser processing apparatus of the present invention include modification by annealing (crystallization, etc.), local thermal processing of copper and the like, fine welding processing, cutting processing, and the like.

Examples of the material to be processed by the laser processing apparatus of the present invention include materials such as semiconductors such as silicon, dielectrics, and metals such as copper.
Among these, as the silicon material, for example, it is formed on a thin film transistor (TFT), a thin film optical sensor, a silicon wafer, glass, a flexible plastic, or a metal formed on glass (including quartz glass), a flexible plastic, or a metal. Examples thereof include a thin film semiconductor element having a thickness of 10 nm to 1.4 μm, which is represented by a thin film solar cell.
Examples of the dielectric material include a thin film dielectric on a silicon wafer substrate.
In addition, it can be applied to materials such as a SiC substrate, a thin film metal, and a glass substrate.

In the laser processing apparatus of the present invention, a plurality of blue laser diodes (BLD) having an average output of 1 W or more and a wavelength of 400 nm to 475 nm are employed as the light source.
The reason will be described below.
Absorption, transmission, and reflection were calculated when single-crystal silicon, polycrystalline silicon, or amorphous silicon was deposited to 50 nm on the buffer layer (SiO ₂ layer, thickness 50 μm) on the glass substrate. This will be described with reference to FIG.
As shown in FIG. 7, the peak of the absorption curve of amorphous silicon is around 450 nm, the center wavelength 52 of the BLD employed in the present invention is 445 nm, and the absorption is equal to or less than that at the center wavelength 51 of the excimer laser. Has characteristics. At the center wavelength 53 of the green laser, it has a lower absorption characteristic than BLD and excimer laser.

Furthermore, since BLD has a broad spectrum compared to excimer lasers and Nd: YAG lasers, there is less concern about interference in the optical system.
In addition, it is difficult to obtain a wavelength of 445 nm with a laser light source other than BLD.
Therefore, it can be said that BLD is an optimal light source for annealing a silicon-based material.

As the BLD of the apparatus of the present invention, for example, NDB7875 (rated output 1.6 W) manufactured by Nichia Corporation can be used. The wavelength of this NDB7875 is 435 nm to 455 nm and is optimal for annealing amorphous silicon.
In addition, since this BLD is multimode and there is no interference between each BLD peculiar to a single mode, the optical system can be simplified.

In the apparatus of the present invention, by adopting a blue laser diode (BLD) as a light source, although it is a weak energy of a CW laser modulated at a frequency of CW or up to 10 kHz, the concentrated energy of amorphous silicon has a high absorption rate. It becomes possible to irradiate a laser.
As a result, surface roughness can be avoided, and an annealing process that does not require post-processing by a CMP apparatus, an etching apparatus, or the like is possible.
Furthermore, the BLD does not require a periodic replacement member like an excimer laser, and the running cost is low.

In the apparatus of the present invention, a plurality of BLDs are used, and one optical fiber (pigtail fiber) is connected to each BLD.
Further, the same number of optical fibers (pigtail fibers) connected to the BLD are bundled together and welded to one optical fiber in the optical transmission line to combine them. One optical fiber of this optical transmission line is taken as one unit.
An optical transmission path of 3 units or more per one optical head is configured.

For example, 21 BLDs are used. Then, a total of 21 optical fibers are connected to each BLD, and seven 21 optical fibers are welded to one optical fiber in the optical transmission line and combined to produce three light beams. Can be grouped into a transmission line.
The loss during the combining can be as low as 10% or less. Further, since the original 21 optical fibers are combined into 3 optical transmission lines, the number of optical transmission lines can be greatly reduced.
In this way, when 21 BLDs are used, if a maximum output of 1 W per BLD is used, it is possible to obtain a 21 W output from less than half of the BLDs with a margin even if loss is considered. .

  When combining with a fiber using a single mode BLD, a multimode is obtained. Therefore, in the present invention, both a single mode and a multimode BLD can be used.

In the device of the present invention, since three or more units of optical transmission paths are configured per optical head, there are three or more BLD drivers, each of which is assigned one unit or more of optical transmission paths to one zone and is controlled by three zones. It becomes possible to do.
In the apparatus of the present invention, a laser power sensor for feedback control of the laser power is provided in the middle of the optical fiber of the optical transmission path, so that a plurality of BLD lasers corresponding to the optical transmission paths of each unit are provided. The power can be monitored independently and fed back to the BLD driver. Furthermore, since the number of BLDs corresponding to one sensor is reduced compared to a configuration in which a sensor is provided in the optical head, if one BLD or one optical fiber connected to the BLD is damaged. In addition, the rate of output decrease detected by the sensor increases, and abnormality detection becomes easier.
In addition, in the device of the present invention, compared to a configuration in which a laser power sensor and an autofocus mechanism are provided in the optical head, no electrical wiring is required, the configuration of the optical head is simplified, the optical head is reduced in size and It becomes possible to reduce the weight. As a result, a plurality of optical heads are installed and the expandability to a long line beam is high. It can also be mounted on movable heads and gantry types.

  Further, in the device of the present invention, when the interchangeable slit having an opening for correcting the shape of the laser beam is provided between the connection portion of the optical transmission path to the optical head and the objective lens, For example, when generating a line beam of 600 μm × 2.4 μm, the laser beam can be corrected or corrected to a shape according to the processing specifications. The slit is not provided for the purpose of removing the edge of the laser beam as used in the excimer laser, but for the purpose of obtaining a shape necessary for the process. Therefore, since a low-magnification objective lens is used, it is possible to increase the depth of focus and facilitate focus adjustment.

According to the laser processing apparatus of the present invention described above, since the optical head can be reduced in size and weight as compared with the conventional apparatus, the entire processing apparatus can also be configured to be small and inexpensive. Become.
As a result, a plurality of optical heads can be installed on the processing table, and parallel laser irradiation is possible, so that the processing time can be shortened.
In addition, since a blue laser diode capable of CW oscillation is used as the light source, the peak power can be reduced as compared with an excimer laser that oscillates pulsed, so that surface roughness on the workpiece during processing is reduced. It is reduced. This eliminates the need for post-processing such as CMP and etching.

  Therefore, according to the present invention, it is possible to realize a small-sized laser processing apparatus with low running cost and stable performance.

It is a schematic block diagram (block diagram) of one embodiment of the laser processing apparatus of the present invention. A and B are schematic plan views of the optical head of FIG. FIG. 2 is an enlarged view of the vicinity of the fiber power sensor unit of FIG. 1. It is sectional drawing which shows the state of the fiber in the fiber welding module of FIG. It is a front view which shows the state of the fiber in the fiber welding module of FIG. It is sectional drawing of the other example of welding of a fiber. It is a figure which shows the relationship between the wavelength of light and an absorptivity with respect to a single crystal silicon, a polycrystalline silicon, and an amorphous silicon. It is a top view which shows the example of a movement of a to-be-processed object in the case of surface modification and annealing. It is a figure which shows the analysis result of the K-spectrum of the silicon layer crystallized with the laser processing apparatus of this invention. It is a figure which shows the result of the X-ray-diffraction method of the silicon layer crystallized with the laser processing apparatus of this invention.

Hereinafter, the best mode for carrying out the invention (hereinafter referred to as an embodiment) will be described.
FIG. 1 shows a schematic configuration diagram (block diagram) of an embodiment of a laser processing apparatus of the present invention.
The laser processing apparatus shown in FIG. 1 is roughly divided into a light source unit 2 using a laser diode as a light source, an optical head 15 for irradiating a workpiece with laser light, and a space between the light source unit 2 and the optical head 15. An optical fiber to be connected, a processing table 27 that holds and moves the workpiece, an output control unit 43 that controls the output of the laser, and a computer 41 are provided.

The light source unit 2 includes a driver unit 1, a BLD unit 3, and a BLD power supply / control unit 4.
The driver unit 1 includes three BLD drivers 1-1, 1-2, and 1-3. Each BLD driver 1-1, 1-2, and 1-3 independently drives seven BLDs.
The BLD unit 3 includes a first BLD unit (BLD1-7) 3-1, a second BLD unit (BLD8-14) 3-2, and a third BLD unit (BLD15-21) each including seven BLDs. 3-3.
Each BLD (1-21) is coupled to an optical fiber by an optical connector 5 and is in a so-called pigtail state. The optical connector 5 is composed of 21 groups, 3 groups, 7 groups corresponding to the three BLD units 3-1, 3-2 and 3-3 and the number of the BLDs.
By being connected by the optical connector 5, the BLD and the optical fiber can be easily attached and detached, so that maintenance work can be easily performed.

  As the BLD, for example, NDB7875 (rated output 1.6 W) manufactured by Nichia Corporation can be used.

Pigtail fibers 1 to 7 (6-1), pigtail fibers 8 to 14 (6-2), and pigtail fibers 15 to 21 (6-3) are accommodated in one optical fiber protective tube 13. Are connected to the fiber combiner box 10.
The fiber combiner BOX 10 includes a fiber welding module 7, a fiber power sensor unit 8, and a fiber power sensor amplifier 11 therein. In addition, three sets of optical connectors 12-1, 12-2, 12-3 are provided at the right end.

Each pigtail fiber is welded to one fiber line from seven pigtail fibers inside the fiber welding module 7.
The state of the fiber in the fiber welding module 7 is shown in the sectional view of FIG. 4 and the front view of FIG.
As shown in FIG. 5, seven pigtail fibers are welded to one fiber line (transmission fiber).
As shown in FIG. 4, seven pigtail fiber cores 46 and clad 46-1 are welded to the core 45 part of one fiber line.
The diameters of the core and cladding of each fiber are, for example, the diameter of the core 46 of the pigtail fiber is 105 μm, the diameter of the cladding 46-1 of the pigtail fiber is 125 μm, and the diameter of the core 45 of the transmission fiber is 300 μm. The diameter of the cladding 45-1 of the transmission fiber is 330 μm.
In addition, in the welding location 7-1 of the fibers 1-7, the welding location 7-2 of the fibers 8-14, and the welding location 7-3 of the fibers 15-21, the tip of the core 46 of the seven pigtail fibers is Polished to be contained within the core 45 of the transmission fiber.

Here, FIG. 6 shows a sectional view of another example of fiber welding.
FIG. 6 shows a cross-sectional view when five, three, two, and nineteen fibers are welded to one transmission fiber.
When 19 fibers are welded to one, a higher-power BLD light source can be configured than when seven fibers are welded to one.
Also, as can be seen from FIGS. 4 and 6, when 7 or 19 fibers are welded together into one, they can be combined into a shape close to a circle, which has the advantage of improving the area utilization efficiency. Have.

Next, an enlarged view of the vicinity of the fiber power sensor unit 8 of the fiber combiner BOX 10 of FIG. 1 is shown in FIG.
As shown in FIGS. 1 and 3, fiber power sensors 8-1, 8-2 and 8-3 are provided in the three fiber lines 9-1, 9-2 and 9-3, respectively. .
The fiber power sensors 8-1, 8-2 and 8-3 transmit energy passing through the respective fiber lines 9-1, 9-2 and 9-3 from the fiber lines 9-1, 9-2 and 9-3. The leak light 73 is detected by measuring with the photo sensor 74.
Then, the minute signal 75 obtained by the photosensor 74 is converted to 0 V to 10 V that can be easily measured by the fiber sensor amplifier 11 shown in FIG. 1 to become a fiber power sensor signal 11-1.
The fiber power sensor signal 11-1 is sent from the fiber combiner BOX 10 to the output control unit 43 and received by the A / D, D / A, DIO (digital input / output) unit 29 in the output control unit 43. Is done.

As shown in FIG. 1, the three sets of fiber lines 9-1, 9-2, and 9-3 are respectively connected to the transmission fiber 14 by the three sets of optical connectors 12-1, 12-2, and 12-3. -1, 14-2, 14-3.
The transmission fibers 14-1, 14-2 and 14-3 pass through the optical fiber protection tube 13 and are coupled to the optical head 15.

  The optical head 15 includes a homogenizer 16, a group lens 17, a slit 18, and an objective lens 19.

As shown in FIG. 1, the transmission fibers 14-1, 14-2 and 14-3 are connected to the homogenizer 16 inside the optical head 15.
The homogenizer 16 homogenizes the laser light from the transmission fibers 14-1, 14-2, 14-3.
The group lens 17 is disposed at the subsequent stage of the homogenizer 16 and is configured by combining a plurality of lenses. The lenses adjacent to each other can be either in contact with each other or not in contact with each other.

The slit 18 is disposed between the group lens 17 and the objective lens 19 and has an opening for correcting the shape of the laser beam.
The slit 18 has a pull-out knob protruding outside the optical head 15, and the slit 18 can be pulled out and replaced using this knob.
The shape of the opening of the slit 18 can be various shapes such as a circle, an ellipse, a spindle, a square, a rectangle, and an extra fine wire.

Laser beams from the transmission fibers 14-1, 14-2, and 14-3 are shaped by the combined lens 17 into a shape necessary for the processing process. Further, the laser beam is shaped by the slit 18.
Then, the shaped laser beam 20 is collected by the objective lens 19 and irradiated onto the workpiece 21 shown in FIG.

Here, a schematic plan view of the optical head 15 viewed from each of two orthogonal directions is shown in FIGS. 2A and 2B.
In FIG. 2A, three transmission fibers 14-1, 14-2, 14-3 are arranged.
The laser beam that has passed through the homogenizer 16, the combined lens 17, the slit 18, and the objective lens 19 is, for example, an elongated spot 70 having a length of 600 μm. Here, as shown at the right end of FIG. 2A, the vertical direction of FIG.
In FIG. 2B, three transmission fibers 14-1, 14-2, and 14-3 are overlapped.
The laser beam that has passed through the homogenizer 16, the combined lens 17, the slit 18, and the objective lens 19 is, for example, a short spot 71 having a length of 2.4 μm. Here, as shown at the right end of FIG. 2B, the vertical direction of FIG. 2B is the Y direction.
More preferably, the output of each BLD is set so that the total irradiation power of the laser beam from the optical head per unit area is 6 W or less using the 600 μm × 2.4 μm spot as a unit area.

  In place of the homogenizer 16 and the assembled lens 17 shown in FIGS. 1 and 2, an optical waveguide as described in Patent Document 12 or the like, or an optical waveguide and a combined lens can be used.

  On the processing table 27, a holding unit that holds the workpiece 21, and a laser power sensor 22 that detects laser light applied to the workpiece 21 are provided. A laser power sensor amplifier 23 is connected to the laser power sensor 22.

As shown in FIG. 1, a laser beam 20 emitted from an objective lens 19 is irradiated onto a workpiece 21. At this time, the workpiece 21 is focused using the first focus adjustment 25 and the second focus adjustment 25-1. The first focus adjustment 25 moves the processing table 27 side, for example, the holding portion of the workpiece 21 up and down. The second focus adjustment 25-1 moves the optical head 15 side, for example, the objective lens 19 or the entire optical head 15 up and down.
The movement 26 in the XY direction of the workpiece 21 is set by a program of the machining table 27 according to the machining process.

Here, an example of movement of a workpiece when surface modification or annealing is performed by the laser processing apparatus of the present embodiment is shown in the plan view of FIG.
The workpiece 63 is irradiated with a laser line beam 56 emitted from the optical head 15. The vertical direction in FIG. 8 corresponds to the X direction shown in FIG. 2A, and the horizontal direction in FIG. 8 corresponds to the Y direction shown in FIG. 2B.
As shown in FIG. 8, the Y-direction movement 58 of the workpiece is performed at a high speed of about 300 mm to 500 mm / second because the movement distance is long. The movement 60 in the X direction of the workpiece is performed at a low speed of about 50 mm / second because the movement distance is short.
When the entire surface of the workpiece 63 is modified and annealed, a laser overlap 59 is required, as indicated by the region surrounded by the broken line in the figure.
The amount of overlap 59, the laser energy, and the shape of both ends of the laser beam are adjusted so as to obtain surface uniformity.
An annealed range 57 is obtained by movements 58, 60 in the XY direction of the workpiece.

  FIG. 8 shows an example of processing by moving the workpiece. However, since the structure of the optical head of the present invention is simple and light, the optical head may be moved to perform laser scanning.

  The output control unit 43 includes an A / D, D / A, DIO unit 29, a laser power / setting / feedback circuit 30, a remote / local switching / safety circuit 31, a 24V DC power supply 33, a computer interface 34, and a modulation signal interface logic 35. A modulation / CW switching circuit 36 is provided.

As described above, the A / D, D / A, and DIO unit 29 receives the fiber power sensor signal 11-1 amplified by the fiber power sensor amplifier 11. In the A / D, D / A, and DIO unit 29, a correction value of the laser output is obtained from the fiber power sensor signal 11-1. The A / D, D / A, DIO unit 29 and the processing table 27 are connected by a processing table interface 28, and the A / D, D / A, DIO unit 29 and the BLD of the light source unit 2 are connected. The power supply / control unit 4 is connected by an LD power supply / control unit / interface 39.
The correction value of the laser output is fed back to the BLD power source / control unit 4 of the light source unit 2 by the laser power / setting / feedback circuit 30. A remote / local switching / safety circuit 31 and a laser power setting interface 32 are provided between the laser power / setting / feedback circuit 30 and the BLD power source / control unit 4 of the light source unit 2.
The remote / local switching / safety circuit 31 suppresses laser output at power-on and emergency stop. It is also possible to switch between setting the laser power setting value with a dial or using a PC recipe.
The computer interface 34 is connected to the computer 41 through the computer interface 40 outside the output control unit 43. The computer interface 34 and the laser power sensor amplifier 23 connected to the laser power sensor 22 of the processing table 27 are connected by a laser power sensor interface 24.

This apparatus basically oscillates a CW laser, but is configured to be able to switch between CW and a pseudo pulse, that is, QCW.
For this purpose, the output control unit 43 is provided with a modulation signal interface logic 35 and a modulation / CW switching circuit 36, and a function generator 37 is provided in connection with the modulation / CW switching circuit 36.
The modulation signal interface logic 35 sets local annealing by a one-shot signal or a burst signal.
The modulation / CW switching circuit 36 modulates the signal from the modulation signal interface logic 35 with the modulation signal from the function generator 37 and sends it to the BLD power supply / control unit 4 of the light source unit 2. A modulation interface 38 is connected between the modulation / CW switching circuit 36 and the BLD power supply / control unit 4 of the light source unit 2.

  The function generator 37 to be used can modulate the oscillation frequency from 0.1 Hz to 4 MHz, but considering the response of the BLD drivers 1-1, 1-2, and 1-3, the upper limit for annealing The frequency is 100 kHz.

The energy obtained by the modulation does not exceed the peak energy of the CW laser and is different from a pulse laser such as an excimer laser or a YAG laser.
The merit of pulsing the CW laser by this modulation is the control of the amount of heat during annealing. It is possible to control the amount of heat by adjusting the modulation frequency and the duty cycle.

The process recipe is stored in the computer 41.
The computer 41 is provided with laser table control software, and this laser table control software allows the A / D, A, D, and the like from the computer interface 34 in the output control unit 43 via the computer interface 40. Distributed to the D / A and DIO units 29 to set the laser power, offset value, gain, feedback ratio, and the like.
The laser power detected by the laser power sensor 22 is sent to the computer 41 through the laser power sensor interface 24 and the computer interface 40 in the output control unit 43 and connected to the computer 41 for display. It is displayed on a screen (not shown).

  The light source unit 2, the fiber combiner box 10, the processing table 27, the output control unit 43, and the computer 41 are supplied with power by an AC power source (not shown).

The laser light oscillated from the BLD of the light source unit 2 can use either single mode or multi mode.
The single mode has an advantage that it is easy to collect light by the optical head 15 because it has one wavelength component.
The multimode has an advantage that laser light is easily mixed when the fibers are grouped into one unit without interference and easy to handle.

FIG. 8 shows a case where the laser is continuously oscillated when scanning in the Y direction, and processing such as annealing is performed on the continuous region.
In the laser processing apparatus of the present embodiment, laser oscillation is switched on / off while scanning in the Y direction, so that a laser beam is irradiated to discrete regions and processing such as modification by annealing is performed. Is also possible. As a result, it is possible to irradiate only the region of the semiconductor layer, which covers only the portion where the circuit element is formed and irradiates the laser beam discretely.

  In FIG. 1, one optical head 15 is provided on the processing table 27, but a plurality of optical heads may be provided per one processing table 27.

The amorphous semiconductor layer can be crystallized by irradiating an amorphous semiconductor layer (such as a silicon layer) with blue semiconductor laser light using the laser processing apparatus of this embodiment. it can.
At this time, since crystallization is performed by laser light irradiation, crystallization can be performed in a relatively short time.
In addition, since the laser light is emitted by blue semiconductor laser light having continuous wave CW, a crystalline semiconductor layer excellent in flatness, uniformity and crystallinity can be obtained stably and with good reproducibility.

By using the laser processing apparatus of the present embodiment, the blue semiconductor laser light is irradiated, so that it is difficult to crystallize by excimer laser irradiation, and a relatively thick semiconductor layer having a thickness of 300 nm to 1.4 μm is formed. In contrast, crystallization can be performed with good flatness.
Further, since the absorption efficiency of the blue semiconductor laser light into the silicon film is relatively high, it is possible to crystallize with good flatness even for a silicon film having a thin film thickness of 20 to 400 nm.

  Note that the laser processing apparatus of this embodiment is not limited to the above-described modification such as crystallization of the amorphous semiconductor layer or annealing, but various processing (semiconductors, metals, dielectrics) It can also be used for surface or internal modification, thermal processing, welding, cutting, substrate scribing, and the like.

According to the configuration of the laser processing apparatus of the present embodiment, since a blue semiconductor laser diode (BLD) is used as a light source, a periodic replacement member such as an excimer laser is not necessary, and the running cost can be reduced.
In addition, when amorphous silicon is irradiated, the absorption rate in amorphous silicon is high and concentrated energy can be irradiated, so it is possible to avoid surface roughness caused by excimer laser irradiation. Thus, post-processing by a CMP apparatus, an etching apparatus, or the like is not necessary.

According to the configuration of the laser processing apparatus of the present embodiment, 21 pigtail fibers connected to 21 BLDs, respectively, are welded together in units of 7 to form one fiber. After making the transmission fiber, it is connected to the optical head 15.
Thereby, compared with the case where 21 pigtail fibers are connected to the optical head, the configuration of the optical head can be simplified, and the weight and size can be reduced.
In addition, since the laser beam from the 21 BLDs is gathered into 3 units and irradiated onto the workpiece, it is possible to control by the so-called 3-zone method by controlling the laser spot of each unit.

Furthermore, in the laser processing apparatus of the present embodiment, the fiber power sensors 8-1, 8-2, and 8-3 for feedback control of the laser power include three units of three fiber lines 9-1 and 9-2. , 9-3.
For this reason, it becomes possible to independently monitor the laser power of the seven BLDs corresponding to the fiber lines of each unit and feed back to the BLD driver. Since the number of BLDs corresponding to one sensor is reduced from 21 to 7, compared with the configuration in which the sensor is provided in the optical head, it is assumed that one BLD or one optical fiber connected to the BLD. When the sensor is damaged, the rate of output decrease detected by the sensor increases, and the abnormality detection becomes easy. Further, as compared with a configuration in which a laser power sensor and an autofocus mechanism are provided in the optical head, no electrical wiring is required. From this point of view, the configuration of the optical head 15 is simplified and the optical head 15 is reduced in size. And weight reduction.
Since the optical head 15 can be reduced in size and weight, a plurality of optical heads 15 can be installed on one processing table 27 to form a long line beam. It is also possible to easily scan the optical head 15 as a movable type.
In addition, for example, if a plurality of optical heads 15 are installed on the processing table 27 to perform parallel laser irradiation, the processing time can be shortened.

  Further, in the laser processing apparatus of the present embodiment, a replaceable slit 18 having an opening for correcting the shape of the laser beam is provided between the combined lens 17 of the optical head 15 and the objective lens 19. . Thereby, for example, when generating a line beam of 600 μm × 2.4 μm, the laser beam can be corrected or corrected to a shape according to the processing specifications.

From the above, the laser processing apparatus of the present embodiment makes it possible to configure the entire processing apparatus to be small and inexpensive.
And it becomes possible to implement | achieve the laser processing apparatus of the stable performance with small and low running cost.

In the above-described embodiment, 21 BLDs are grouped into one unit of optical transmission path for every seven BLDs and connected to the optical head 15 as three units of optical transmission path.
In the present invention, the number of BLDs per unit optical transmission line can be plural (two or more), and the number of units of optical transmission lines connected to the optical head is three units or more. Is possible.
If the number of units of the optical transmission line is 3 units or more, it is possible to perform control by the 3-zone method by assigning 1 unit or more to one zone.
Further, if the number of units of the optical transmission path is 5 units or more, it is possible to perform control by a 5-zone method (both end portions, the central portion, and a portion between them).
Even when the number of units of the optical transmission path is 3 units or more, the configuration of the optical head can be simplified and reduced in weight compared to the configuration in which the same number of optical fibers as the number of BLDs are connected to the optical head. .

  Next, the amorphous semiconductor layer was actually crystallized by the laser processing apparatus of the present invention using a blue semiconductor laser diode, and the characteristics were examined.

First, a high-purity Si target was sputtered on a glass substrate by RF sputtering using Ar gas as a sputtering discharge inert gas to form an amorphous silicon layer having a thickness of 50 nm.
The amorphous silicon layer was crystallized using the laser processing apparatus of the present invention.
The wavelength of the emitted light is set to 445 nm, the output is set to 4.0 W, the scanning speed of the laser line beam 56 shown in FIG. 8 is set to 500 mm / s, and the overlap 59 is provided as shown in FIG. Crystallization was performed.
Further, crystallization was carried out in the same manner with outputs of 5.0 W and 7.0 W, respectively.

  In the case of a thick film having a thickness of 50 nm, since the temperature gradient is hardly observed in the vertical direction of the film during crystallization, the entire film can be heated uniformly. As a result, uniform fine crystals having a crystal grain size of about 50 nm are generated.

Furthermore, about the obtained silicon layer, the analysis of the K-spectrum which is the absorptivity by spectroscopic ellipsometry, and the crystal orientation by the X-ray diffraction method were identified.
The K-spectrum for each output is shown in FIG.
Moreover, the result of the X-ray diffraction method when the output is 4.0 W is shown in FIG.

FIG. 9 shows that a clear peak appears in the K-spectrum, and the entire film is sufficiently crystallized.
Further, FIG. 10 clearly shows that the (111) plane peak clearly appears as a sharp peak and is sufficiently crystallized.

Further, surface roughness of the obtained silicon layer was evaluated by AFM.
As a result, the surface roughness was 5 nm (rms) or less.
Generally, the magnitude of surface roughness known by excimer laser annealing of ultraviolet light pulses is 10 nm (rms) or more.
Therefore, it was found that a silicon layer with very little surface roughness was obtained as compared with excimer laser annealing using ultraviolet light pulses.

  The present invention is not limited to the above-described embodiments and examples, and various other configurations can be taken without departing from the gist of the present invention.

1 Driver unit, 1-1, 1-2, 1-3 BLD driver, 2 Light source unit, 3 BLD unit, 4 BLD power supply / control unit, 5 Optical connector, 6-1, 6-2, 6-3 Pigtail Fiber, 7 Fiber welding module, 7-1 Welding location of fibers 1-7, 7-2 Welding location of fibers 8-14, 7-3 Welding location of fibers 15-21, 8 Fiber power sensor unit, 8-1, 8-2, 8-3 Fiber power sensor, 9-1, 9-2, 9-3 Fiber line, 10 Fiber combiner BOX, 11 Fiber power sensor amplifier, 11-1 Fiber power sensor signal, 12-1, 12- 2,12-3 Optical connector, 13 Optical fiber protection tube, 14-1, 14-2, 14 3 Transmission fiber, 15 Optical head, 16 Homogenizer, 17 Pair lens, 18 Slit, 19 Objective lens, 20 Laser beam, 21 Work piece, 22 Laser power sensor, 23 Laser power sensor amplifier, 24 Laser power sensor sensor Interface, 25 first focus adjustment, 25-1 second focus adjustment, 27 machining table, 28 machining table interface, 29 A / D, D / A, DIO unit, 30 laser power, setting and feedback circuit, 31 Remote / local switching / safety circuit, 32 Laser power setting interface, 33 DC24V power supply, 34, 40 Computer interface, 35 Modulation signal interface logic, 36 Modulation / CW Switch circuit, 37 function generator, 38 modulation interface, 39 LD power supply / control unit interface, 41 computer, 43 output controller, 45 transmission fiber core, 45-1 transmission fiber cladding, 46 pigtail fiber core 46-1 Pigtail fiber cladding, 56 Laser line beam, 58 Workpiece movement in Y direction, 59 Overlap, 60 Workpiece X direction, 63 Workpiece, 70, 71 Spot, 73 Leakage light , 74 Photosensor, 75 Small signal

Claims (5)

A laser processing apparatus for processing a workpiece by irradiating the workpiece with a laser beam,
A plurality of blue laser diodes having an average output of 1 W or more and a wavelength of 400 nm to 475 nm are used as a light source.
An optical fiber is coupled to each of the blue laser diodes,
A plurality of the optical fibers are welded to one optical fiber, and the welded single optical fiber is used as one unit optical transmission path, and the optical transmission path includes three or more units per optical head,
A laser power sensor for detecting laser power is provided in the middle of the optical fiber of each optical transmission line, and the output of the light source is feedback controlled according to the detection result of the laser power sensor,
Optical fibers of each of the optical transmission paths are aligned and connected to the optical head,
A laser processing apparatus in which a laser beam is shaped in the optical head, condensed by an objective lens, and irradiated onto the workpiece.   The laser processing apparatus according to claim 1, wherein the laser power sensor is configured to detect leakage light from an optical fiber in the optical transmission path.   2. An interchangeable slit having an opening for correcting the shape of the laser beam is provided between a connection portion of the optical transmission path to the optical head and the objective lens. Or the laser processing apparatus of Claim 2.   4. The laser processing apparatus according to claim 1, wherein the total irradiation power of the laser beam per one optical head is 6 W or less per unit area of 600 μm × 2.4 μm. 5.   5. The laser processing apparatus according to claim 1, comprising three units of the optical transmission path per optical head, wherein seven optical fibers are welded to each of the optical transmission paths. .

Images