JP2004311906A - Laser processing device and laser processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser processing device and a laser processing method which increase the use efficiency or process accuracy of energy and enable a concurrent processing at a plurality of fine sites at a narrow pitch. <P>SOLUTION: The laser processing device comprises optical elements (a micro-lens array 16 and a micro-lens 27) in which a plurality of beams 20 are formed and a focus 22 is formed each beam, and an optical system (reduction transfer optical system 18) for transferring each focus of the beam formed by this optical element to a side of a processing plane 28 to form an image. Further, the laser processing method carries out various laser processings of a processing, reforming or film formation, such as a perforation, etching, doping or annealing, with respect to a processing object (work 26) by using a laser energy generated to a related laser processing device. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser processing apparatus and a laser processing method for performing various types of laser processing such as drilling, etching, doping, annealing, processing, modification, and film formation on an object to be processed using laser energy.
[0002]
[Prior art]
Laser energy is used for various processes such as drilling, etching, doping, annealing, etc., modification, film formation, etc. The following patent documents exist regarding the technology related to this laser processing. doing.
[0003]
[Patent Document 1]
JP 63-220991 A
[0004]
[Patent Document 2]
JP 2001-62578 A
[0005]
[Patent Document 3]
JP-A-4-356392
[0006]
[Patent Document 4]
JP 2001-269789 A
[0007]
Regarding drilling, Patent Document 1 discloses a process using mask projection. In this case, the processed part is processed into an arbitrary shape by using a mask that transmits laser light, and the non-processed part is used with a mask that blocks the laser light. Further, Patent Document 2 discloses a combination of a diffractive optical component and an fsin θ lens. In this case, a diffractive optical component that diffracts laser light to generate a number of beams, and a diffractive optical component are disclosed. In addition, a configuration including an fsin θ lens that condenses a large number of branched beams is disclosed.
[0008]
Regarding microlens array focusing, Patent Document 3 discloses simultaneous multi-point processing of a printed circuit board by arranging circular Fresnel lenses in a plane on a light propagation portion of a mask and focusing laser light. . This is energy efficient. Further, Patent Document 4 discloses a laser that has a minute beam condensing diameter by using a laser having an unstable resonator and reducing a beam divergence angle.
[0009]
In addition, regarding the crystallization of amorphous Si by laser annealing, the current amorphous Si crystallization technology includes forming a laser from a high-power excimer laser into a line beam on an amorphous Si thin film formed on a glass substrate. There is a method of obtaining a polycrystalline Si film by irradiating while scanning the line beam in a direction perpendicular to the line beam and sequentially melting and recrystallizing the entire amorphous Si on the glass substrate. This processing method has already been put into practical use and is mainly used as a manufacturing technique for high-performance TFT (Thin Film Transistor) liquid crystal displays for portable devices. As known literature, for example, Toshiba Review vol. 55, no. 2 (2000) Toru Nishibe et al. “Low-temperature p-Si TFT”.
[0010]
[Problems to be solved by the invention]
By the way, in the process by mask projection (Patent Document 1), the energy of the non-processed part that is shielded from light is wasted, so that the energy efficiency is poor, and if the energy of the processed part is increased, the energy consumption becomes very large. Further, since the apparatus becomes large, when this apparatus is used for production, the production cost tends to increase.
[0011]
In the technology that combines the diffractive optical component and the fsin θ lens (Patent Document 2), the incident beam is diffracted by the diffractive grating and condensed by the fsin θ lens, so that higher-order diffracted light is emitted as the number of holes increases. It is necessary to use it. As the diffraction order increases, the diffraction efficiency decreases. Therefore, a beam intensity distribution is generated in the processing surface, and it is difficult to simultaneously process a large number of holes and control the processing diameter of the large number of holes.
[0012]
In addition, the microlens array condensing (Patent Documents 3 and 4) has the following inconveniences when processing a minute diameter.
[0013]
First, the influence of the beam divergence angle is large. An excimer laser or the like generally used as a high-power ultraviolet laser has a large beam divergence angle. When the beam divergence angle is large, the focal blur becomes large. In general spherical lenses,
Defocus = beam divergence angle x focal length
There is a relationship. For this reason, when the beam divergence angle is large, it is difficult to condense and process to a minute diameter. Therefore, there is a method of using a laser having an unstable resonator and reducing the beam divergence angle. However, the unstable resonator has a complicated optical system and low pulse energy.
[0014]
Second, narrow pitch processing is difficult. The condensing of the spherical lens has the following relationship.
Focal diameter = constant × wavelength / numerical aperture
Numerical aperture = lens radius / focal length
[0015]
From such a relationship, in order to process a minute diameter, it is necessary that the numerical aperture (= lens radius / focal length) of the lens is large. Therefore, it is necessary to increase the lens radius. In order to increase energy efficiency, it is preferable to increase the energy collection rate, and it is desirable that the lens radius is large. On the other hand, since the pitch of the processing point corresponds to the pitch of the lens, the pitch of the processing point is larger than the lens diameter. Therefore, if the lens radius is increased, it becomes difficult to process a narrow pitch.
[0016]
Third, performance degradation occurs due to the influence of processing. In order to process a minute diameter, it is necessary that the numerical aperture of the lens (= lens radius / focal length) be large. Therefore, it is necessary to reduce the focal length. Moreover, it is necessary to shorten the focal length from the viewpoint of reducing the focal blur (= beam divergence angle × focal length).
[0017]
In the configurations disclosed in Patent Documents 3 and 4, the focal distance is almost equal to the working distance (distance between the lens and the workpiece), and if the working distance is small, contaminants adhere to the workpiece during processing. There is a risk of processing defects, lens performance deterioration, and damage due to the influence of heat and heat.
[0018]
Regarding the performance limit due to the grain boundary of TFT, in the formation of conventional low-temperature p-Si, a line beam having a width of several hundreds μm and a length of several hundreds mm is scanned and melted and recrystallized so that numerous crystal nuclei are formed. There are several to tens of grain boundaries in the channel of the transistor that is generated and formed there. For this reason, there are problems such as variations in threshold voltage values and current values, which are important characteristic values of transistors, and an increase in OFF current value, which are not suitable for manufacturing advanced ICs such as memories and MPUs.
[0019]
For high energy consumption, taking crystallization for a pixel switching TFT of liquid crystal as an example, the pitch of the RGB pixels of the liquid crystal is 120 [μm], 40 [μm], for example, and the size of the TFT is changed. For example, if the area ratio is simply calculated as 10 × 10 [μm],
1-{(10 × 10) / (120 × 40)} = 47/48
It becomes. As is apparent from this result, about 98% of the portion is unnecessary and is removed in a later etching step. For this reason, a very large amount of energy is consumed in a portion that is almost discarded, which is useless.
[0020]
Further, regarding the thermal load on the substrate, originally unnecessary energy is supplied to the thin film, so that the substrate is subjected to a thermal load more than necessary. For this reason, it is an obstructive factor for TFTs formed on thermoplastic substrates such as plastics.
[0021]
Accordingly, a first object of the present invention is to provide a laser processing apparatus and a laser processing method with improved energy use efficiency.
[0022]
A second object of the present invention is to provide a laser processing apparatus and a laser processing method with improved processing accuracy.
(Addition)
A third object of the present invention is to provide a laser processing apparatus and a laser processing method that enable simultaneous processing of a plurality of minute portions having a narrow pitch.
[0024]
[Means for Solving the Problems]
In order to achieve the first, second, or third object, the laser processing apparatus of the present invention forms a plurality of beams (20, 70, 74, 86, 92) and a focal point 22 for each beam. Optical elements (microlens array 16 and microlens 27) to be formed, and an optical system (reduction transfer optical system 18) that forms an image by transferring each focal point of the beam formed by the optical elements to the processing surface 28 side. It is set as the structure provided with. The optical element may be either a refractive element or a diffractive element. The surface to be processed is a surface of an object to be irradiated with a laser, and is a light receiving surface that receives laser energy when processing such as processing proceeds. The surface to be processed and the focal point of the beam may coincide, but need not coincide.
[0025]
With such a configuration, the laser beam is condensed into a desired pattern by the optical element, so that the energy use efficiency is high, energy loss is reduced compared to the mask projection method, and there is no blurring of the focus. Compared with the microarray condensing method, the condensing accuracy is high, and the focus pitch can be adjusted with high precision by the optical system, so that the drilling can be performed at a narrow pitch, and the processing accuracy is improved. Depending on the number of focal points of the beam, various laser processes such as drilling, etching, doping, annealing, etc., processing, modification, film formation, etc. can be performed.
[0026]
In order to achieve the first, second or third object, by moving the object to be processed (work 26), the optical element or the optical system in the direction of each optical axis, It is good also as a structure which changes the irradiation area with respect to the said to-be-processed surface of the said beam. With such a configuration, the beam can be adjusted to a desired irradiation area, and the processing range can be controlled with high accuracy.
[0027]
In order to achieve the first, second, or third object, the laser processing method of the present invention includes a step of forming a plurality of beams and forming a focal point for each beam, and applying each focal point of the beam. And transferring the image to the processing surface side to form an image, and subjecting the processing surface to laser processing by beam irradiation.
[0028]
According to such processing, as described above, by condensing the laser beam in a desired pattern, the energy utilization efficiency is high, energy loss is reduced compared with the mask projection method, and the focus blur is reduced. Compared with the microlens array focusing method, the focusing accuracy is high, and the focus pitch can be adjusted with high precision by the optical system, so drilling can be performed at a narrow pitch, and high processing accuracy is achieved. can get. As a result, various laser processes such as drilling, etching, doping, annealing, etc., processing / modification / film formation, etc. can be performed in accordance with the number of focal points of the beam.
[0029]
In order to achieve the first, second, or third object, the laser treatment is performed by irradiating the surface to be processed a plurality of times and setting an irradiation area of the beam to the surface to be processed. The same or different may be used. That is, the beam irradiation may be completed once, but in the present invention, it is possible to perform laser processing by multiple times of beam irradiation. In this case, if the irradiation area is the same, multiple processing for the same region is performed. Thus, if the irradiation areas are made different, it is possible to selectively form a processing portion corresponding to the number of times of irradiation and a processing portion where the number of times of irradiation is small. Such a process enables various laser processes such as drilling and modification with different diameters.
[0030]
In order to achieve the first, second or third object, the object to be processed, the optical element or the optical system having the surface to be processed is moved in the direction of each optical axis, thereby the object to be processed of the beam. You may make it change the irradiation area with respect to a surface. According to such processing, the beam is adjusted to a desired irradiation area, and the processing range can be controlled.
[0031]
In order to achieve the first, second, or third object, the laser treatment includes perforation, surface modification, or heat treatment on the surface to be processed, and the surface to be processed depends on the number of focal points of the beam. The processes may be performed simultaneously. That is, the laser processing method according to the present invention is applied to various types of processing according to the magnitude of the laser beam and energy.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
A laser processing apparatus according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an outline of a laser processing apparatus. In the laser processing apparatus 2, the laser apparatus 4 is a generation source that generates laser light 6, and is configured by, for example, an excimer laser apparatus including a stable resonator. In order to reduce the influence of the beam divergence angle, the laser device 4 may use an unstable resonator or an injection-locked type. For example, a device capable of energy control is used. The generated laser beam 6 is applied to an expansion optical system 10 as a first optical system via an attenuator 8. The attenuator 8 is a beam intensity adjusting filter as a means for attenuating energy. For example, an attenuator 8 having several steps of transmittance and an automatic switching mechanism for the transmittance is used.
[0033]
The magnifying optical system 10 is a means for magnifying the laser beam 6 from a narrow beam to a wide beam, and changes the beam dimension according to the size of the processing or processing area so that energy can be used effectively. In this case, the expansion of the beam reduces the beam divergence angle and reduces the out-of-focus blur, so it is preferable to enlarge the beam larger. In this case, intensity distribution optical means for changing the intensity distribution may be provided. Further, when a wide beam can be obtained by the laser device 4, the magnifying optical system 10 is unnecessary. The laser beam 6 that has passed through the magnifying optical system 10 is guided in a desired direction through a mirror 12. The mirror 12 is a means for changing the direction of the laser light 6 and may include two or more mirrors for adjusting the optical axis. In this embodiment, the laser beam 6 reflected by the mirror 12 in the direction orthogonal to the optical axis of the magnifying optical system 10 is guided in the upper surface direction of the stage 14.
[0034]
Above the stage 14, a microlens array 16 is installed as a second optical system, and a reduction transfer optical system 18 is installed as a third optical system. The microlens array 16 is an optical unit that forms a plurality of beams 20 from the wide beam obtained by the magnifying optical system 10 and forms a focal point 22 for each beam 20. The vertical position can be adjusted. In this embodiment, one microlens array 16 is disclosed. However, two or more microlens arrays having greatly different energy collection degrees may be installed, and a plurality of microlens arrays may be switched and used. The reduction transfer optical system 18 is means for transferring the focal point 22 formed on the microlens array 16 side to the processing surface 28 side of the work 26 that is the processing object of the stage 14 and imaging the focal point 30. .
[0035]
A quartz plate 32 is installed on the lower surface side of the reduction transfer optical system 18 as a protective member. This quartz plate 32 is installed so that contaminants scattered during processing do not adhere to the optical system and deteriorate the performance. Yes. The quartz plate 32 can be easily replaced at the time of contamination, and the protective member is not limited to the quartz plate 32 as long as it has a good transmission characteristic and can withstand the laser. By installing the quartz plate 32, the optical system of the reduction transfer optical system 18 is protected from contaminants flying from the workpiece 26 side.
[0036]
A gas flow mechanism 36 and an exhaust mechanism 38 are installed on the upper surface side of the stage 14 with the processing space 34 on the lower surface side of the reduction transfer optical system 18 interposed therebetween. The gas flow mechanism 36 is composed of a fan or the like, and is an injecting unit for an inert gas such as nitrogen or helium or a gas G such as air. The gas flow mechanism 36 is configured so as to prevent contaminants scattered during processing from adhering to the optical system. Shed. The exhaust mechanism 38 installed on the opposite side of the gas flow mechanism 36 is a means for sucking the gas G supplied to the processing space 34 and exhausting it to the outside, and cleans the processing space 34 and the like.
[0037]
The stage 14 is an XY stage for changing a processing position such as processing, and can be moved in the directions of the arrows L and R by the horizontal movement mechanism 40 and in the direction perpendicular to the paper surface, and the arrows U and D by the vertical movement mechanism 42. It can move in the direction. By the movement in the horizontal direction or the vertical direction, the horizontal position and the vertical position of the processing surface 28 of the workpiece 26 are adjusted. That is, the position can be adjusted in the three-dimensional direction. A height adjustment and angle adjustment mechanism for optical adjustment may be provided. Further, the stage 14 is provided with a mechanism capable of gripping an object to be processed such as the workpiece 26. For example, the stage 14 is constituted by an adsorption stage, and a material that is not damaged by a beam penetrating during processing is used.
[0038]
Next, the microlens array 16 and the reduction transfer optical system 18 of the laser processing apparatus 2 will be described with reference to FIG. FIG. 2 shows an outline of the microlens array 16 and the reduction transfer optical system 18. As described above, the microlens array 16 forms a plurality of beams 20 from the laser light 6 that has been changed to a wide beam by the magnifying optical system 10, and the focal point 22 is formed on the virtual processing surface 25 for each beam 20. Since it is an optical means to be formed, a microlens 27 is provided as a plurality of minute optical elements according to the number of beams 20 to be formed.
[0039]
The microlens array 16 includes a large number of minute optical elements, and includes a refractive lens, a Fresnel lens, binary optics, and the like. In this case, it is not necessarily the same light collection as a general spherical lens. It includes those that can be formed into an arbitrary intensity distribution. For example, by using a diffractive lens having a beam intensity distribution in which a convex b having a smaller area and a higher height than the convex a is superimposed on the center of one convex a, a deep small-diameter hole described later is used. And simultaneous processing of shallow large-diameter holes. The microlens array 16 may be in the form of either a refractive element or a diffractive element. The microlens array 16 is composed of a refractive element and a diffractive element, but a diffractive element such as a hologram may be used instead of the microlens array 16. Although not shown, a mechanism for adjusting the height, tilt and angle of the microlens 27 may be provided so that the optical system can be adjusted.
[0040]
Further, the reduction transfer optical system 18 transfers the focal point 22 formed on the micro lens array 16 side to the processing surface 28 side of the work 26 that is the processing object of the stage 14 and forms an image as the focal point 30. That is, the focal plane of the microlens 27 is reduced and transferred to form an image plane. Basically, the image plane is formed on the work surface to perform the work, but the image plane may be formed on a plane moved in the direction perpendicular to the work surface. By using an optical system that is perpendicularly incident on the work surface, a perfect circular and vertical hole can be formed. The design is such that the working distance between the reduction transfer optical system 18 and the surface to be processed 28 of the workpiece 26 is long, and the aberration is corrected. Focus pitch P on the surface to be processed 28 ₂ Is the focal pitch P on the virtual surface 25 ₁ It is narrower. As a result, the focus density can be increased. Focal pitch P ₂ Is the processing point pitch on the surface 28 to be processed.
[0041]
For example, as shown in FIG. 3, the reduction transfer optical system 18 includes convex lenses 44, 46 and 48, a concave lens 50 and convex lenses 52, 54 and 56, but a beam formed on the virtual processing surface 25. Various optical systems are used for optical processing for transferring 20 and the focal point 22 to the processing surface 28 side and combining them as the focal point 30 and reducing the focal interval, and the optical system is limited to the optical system shown in FIG. It is not a thing.
[0042]
The pitch control of the reduction transfer optical system 18 will be described with reference to FIG. 4 with respect to the focal point 22 on the virtual processed surface 25 and the focal point 30 of the processed surface 28. 4A shows a focal point 22 formed on the virtual processing surface 25, and FIG. 4B shows a focal point 30 formed on the processing surface.
[0043]
As shown in FIG. 4A, when a plurality of focal points 22 are formed on the virtual processing surface 25 by the microlens array 16, ₁ Is the pitch between the focal points 22, in this case the distance between the center points. d ₁ Is the ideal focal diameter of the focal point 22, u ₁ Is out of focus. Further, as shown in FIG. 4B, at the focal point 30 formed on the processing surface 28 through the reduction transfer optical system 18, P ₂ Is the pitch between the focal points 30 (processing point pitch), and is the distance between the center points. d ₂ Is the ideal focal diameter of the focal point 30, u ₂ Is out of focus. Here, when the reduction ratio of the reduction transfer optical system 18 is M,
d ₂ = M × d ₁ ... (1)
u ₂ = M × u ₁ ... (2)
P ₂ = M × P ₁ ... (3)
Is established.
[0044]
Further, the area control of the focal points 22 and 30 by the microlens array 16 and the reduction transfer optical system 18 will be described with reference to FIG. 5A and 5B show changes in the focal point formed by the microlens array 16.
[0045]
The focal length f of the micro lens 27 is shifted from the virtual processing surface 25, and the diameter d of the focal point 22 on the virtual processing surface 25. ₁ For example, the focal point 220 (diameter d shown in FIG. ₁ '), The diameter d of the focal point 30 on the processing surface 28 side is increased. ₂ Can be increased. On the contrary, the diameter d of the focal point 22 on the virtual processing surface 25. ₁ Is reduced, the diameter d of the focal point 30 on the processing surface 28 side. ₂ Can be reduced. Here, if f is the focal length of the microlens 27 and D is the aperture diameter of the microlens 27, the distance W. D. 1 is
W. D. 1 = (D−d ₁ ) × (f / D) (4)
It becomes. By such control, the processing point diameter of the processing target surface 28 is easily controlled.
[0046]
Next, processing by the laser processing apparatus 2 will be described.
[0047]
The laser device 4 oscillates the laser beam 6 by controlling the energy to be constant. When control is performed with energy capable of stable oscillation and the beam intensity on the surface to be processed 28 is large, the attenuator 8 is adjusted so as to obtain an appropriate beam intensity. Processing such as processing is performed on the processing target surface 28 of the workpiece 26 under appropriate conditions of the beam intensity and the integrated irradiation time of the beam. By adjusting the conditions, for example, a hole having a controlled depth can be processed in addition to the through hole.
[0048]
When the focal position of the microlens 27 is aligned with the virtual processing surface 25 on the reduction transfer optical system 18 side, the working surface 28 is condensed in a beam waist shape, so that the accuracy of the working distance is reduced and the processing spot diameter is reduced. Easy to control. Then, by shifting the focal position of the micro lens 27 from the virtual processing surface 25 and increasing the beam diameter on the virtual processing surface 25, the processing point diameter can be increased. In this case, as shown in FIG. 6, the reduction transfer optical system 18 may be moved upward or downward as indicated by arrows U and D by the vertical movement mechanism 58 to adjust the processing spot diameter.
[0049]
When two or more microlens arrays having greatly different energy collection degrees are used by switching, the energy at the surface to be processed 28 is greatly different, so that the beam intensity is adjusted. In this beam intensity adjustment method, the laser energy control target value is adjusted. The other method is adjusted by switching the transmittance of the attenuator 8. There is also a method of adjusting the beam intensity by enlarging or reducing the beam irradiated to the microlens 27 by the beam forming optical system.
[0050]
Such a laser processing apparatus and laser processing method have the following features and advantages.
[0051]
(1) Energy utilization efficiency is greatly improved. Since the laser beam 6 is condensed into a desired pattern by using the microlens array 16 and cut out, the energy utilization efficiency is greatly improved over the mask projection method.
[0052]
(2) A large number of holes can be processed simultaneously. That is, the laser light 6 is condensed into a desired pattern using the microlens array 16 and cut out, and the virtual processing surface 25 formed by the focal planes or the virtual processing surface 25 translated in the vertical direction from the focal planes. Since the image surface is formed by transferring, it is possible to simultaneously process a large number of holes at the same time without causing distribution according to location unlike the combination method of the diffractive optical component and the fsin θ lens.
[0053]
(3) The influence of the beam divergence angle is small. The virtual processing surface 25 can be reduced and transferred, and by the reduction transfer, the amount of defocus on the virtual processing surface 25 caused by the beam divergence angle is reduced on the processing surface 28. As a result, it is possible to concentrate and process the fine diameter. Since the influence of the beam divergence angle is reduced, it is not always necessary to use an unstable resonator laser having a complicated optical system and low pulse energy.
[0054]
(4) Processing at any pitch such as narrow pitch processing is possible. If the virtual processed surface 25 is reduced and transferred, the focus pitch formed on the virtual processed surface 25 may be larger than the processing pitch on the processed surface 28. Further, the focal diameter of the virtual processing surface 25 is larger than the focal diameter of the processing surface 28, and the numerical aperture of the lens (lens radius ÷ focal length) is smaller than that of the conventional microlens array focusing method. In the case of the same focal length, the lens diameter can be reduced. From this point, a narrow pitch of the focal point can be easily obtained. As a result, narrow pitch pattern processing can be performed on the processing surface 28 of the workpiece 26.
[0055]
(5) Performance degradation of the laser processing apparatus due to the influence of processing is prevented. By setting the reduction transfer optical system 18 so that the working distance between the reduction transfer optical system 18 and the surface 28 to be processed becomes longer, the influence of contaminants and heat during processing from the workpiece 26 is reduced. Further, since the gas flow mechanism 36 for preventing the adhesion of contaminants is provided, the influence thereof is further reduced. Thereby, performance degradation due to the influence of processing is prevented.
[0056]
Further, since a quartz plate 32 for preventing the adhesion of contaminants is installed between the reduction transfer optical system 18 and the work 26, when the contaminants adhere, the quartz plate 32 is replaced to replace the apparatus. The degraded performance can be easily improved. Any material that has good transmission characteristics and can withstand the laser beam 6 can be used in place of the quartz plate 32.
[0057]
(Second Embodiment)
Next, FIG. 7 shows an outline of a laser processing apparatus according to the second embodiment of the present invention. In the laser processing apparatus 2 according to this embodiment, in order to prevent oxidation during processing of the workpiece 26 which is an object to be oxidized such as Si, gas replacement is performed in which laser processing is performed in an inert gas such as nitrogen or argon. A vacuum chamber 60 is provided for the purpose. The laser beam 6 is introduced into the vacuum chamber 60 through the optical window 64 without breaking the atmosphere of the vacuum chamber 60. A stage 66 is installed to hold the workpiece 26 as an object to be processed such as a substrate in the vacuum chamber 60. Since other configurations are the same as those of the first embodiment, description of each part is omitted.
[0058]
According to such a laser processing apparatus 2, the virtual processing surface 25 is first provided by including the microlens 27 and the reduction transfer optical system 18 in which the condensing diameter on the processing surface 28 is, for example, 1 μm. For example, it is adjusted so that it is transferred to and coincides with the processing surface 28 of the work 26 on which an amorphous Si thin film is formed, and the laser irradiated region is set to a temperature slightly higher than the melting point of amorphous Si. One pulse of the laser beam 6 having the energy is irradiated. As a result, a part of the region irradiated with the laser is melted and crystallized, and fine crystal grains can be formed.
[0059]
Subsequently, the laser beam 6 having an energy set so that the irradiation region is higher than the melting point of the amorphous Si and lower than the melting point of the crystalline Si in a region having an area larger than the previous irradiation area including the previous irradiation region. Irradiate 1 pulse. As a result, the portion other than the fine crystal grains formed in the irradiation region is melted and crystal growth occurs using the fine crystal grains as crystal growth nuclei, so that a large single grain Si crystal is formed.
[0060]
At this time, in order to irradiate the laser beam 6 to a region having a larger area than the previous irradiation area including the previous irradiation region, the microlens array 16 is moved up and down to cover the surface shifted from the focal plane of the microlens array 16. Transfer to the processing surface 28. In this case, the reduction transfer optical system 18 may be moved, or the processing surface 28 of the work 26 may be moved up and down.
[0061]
(Third embodiment)
Next, a laser processing method according to the third embodiment of the present invention will be described with reference to FIGS. 8 and 9 show a laser seeding heat treatment method using the laser processing apparatus 2 according to the second embodiment.
[0062]
As shown in FIG. 8A, a TFT element creation region TD is set in the amorphous silicon film 68 as an initial state. When a laser beam 70 having a minute diameter of, for example, about 1 μm is incident on the center of the TFT element creation region TD using the laser processing apparatus 2 as shown in FIG. The micro area 72 is melted at the center. The melted portion is crystallized, and the minute region 72 is changed from amorphous silicon to crystalline silicon such as single crystal or polycrystalline silicon by laser treatment. As shown in FIG. 8C, the diameter of the minute region 72 is determined by the diameter of the laser beam 70. According to the laser processing apparatus 2, the diameter of the laser beam 70 is narrowed down with high accuracy, and accordingly, a minute region 72 having a highly accurate diameter is formed, and a plurality of minute regions 72 are formed.
[0063]
Then, as shown in FIG. 9A, the laser processing apparatus 2 irradiates a laser beam 74 having a width of about 10 μm, for example. For example, the laser beam 74 is set to have a width within a range surrounding the TFT element formation region TD with the single crystal or polycrystalline silicon in the minute region 72 as the center. In this case, the laser beam 74 is set to a beam intensity and energy intensity that are not lower than the melting point of amorphous silicon and lower than the melting point of crystalline silicon. The setting of the energy intensity is adjusted by the laser device 4 or the attenuator 8 or the like. As a result, the irradiation with the laser beam 74 selectively melts the amorphous silicon portion, and the amorphous silicon is in a molten state in a wide range region 75 around the crystalline silicon portion.
[0064]
When such laser treatment is performed, as shown in FIG. 9B, the microregion 72 is centered, that is, the crystalline silicon of the microregion 72 is used as a nucleus, and a crystal is formed in the melted portion of amorphous silicon. Growth occurs. An arrow 76 indicates the direction of crystal growth. In FIG. 9B, a minute region 72 indicates a single crystal or polycrystalline silicon portion, a region 78 indicates a crystal growth portion, a region 75 indicates a molten portion, and a region 82 indicates an amorphous silicon portion.
[0065]
Through the above process, as shown in FIG. 9C, a single crystal or polycrystalline silicon having a large crystal grain size is formed in a region 75 wider than the TFT element formation region TD.
[0066]
Such a laser processing apparatus and laser processing method have the following features and advantages.
[0067]
(1) Single grain Si can be formed, and performance limits due to grain boundaries can be overcome. A single grain crystal is a crystal in which no clear grain boundary exists in the region, and ideally, the region is composed of one single crystal. Therefore, utilizing the fact that the melting point of amorphous Si is approximately 300 ° C. lower than that of crystalline Si, first, laser light 6 having an energy such that the temperature is slightly higher than the melting point of amorphous Si in a minute region of 1 μm or less on the amorphous Si thin film. , And a part of the surface of the part is melted and recrystallized to form crystal nuclei. Next, a laser beam 6 having an energy higher than the melting point of amorphous Si and lower than the melting point of crystalline Si is irradiated to a region of about 10 μm centering on that portion, and the crystal nucleus formed earlier is irradiated. By crystal growth, a single grain Si crystal of about 10 μm is formed.
[0068]
(2) Energy consumption can be reduced. An example of crystallization for a pixel switching TFT of liquid crystal will be described. If the pitch of the RGB pixels of the liquid crystal is 120 μm and 40 μm vertically and horizontally and the TFT size is 10 μm × 10 μm, simply calculating by area ratio, the energy is (10 × 10) / (120 × 40) = 1/48 Crystallization is possible. In the crystallization by the line beam in the actual manufacturing process, scanning is performed by overlapping about 95% of the line width in order to solve the insufficiency of crystal growth due to generation of a large number of crystal nuclei. This corresponds to the laser irradiation of about 20 times in the same place. According to the laser processing apparatus 2 of the present invention, since there are two steps of crystal nucleation and crystal growth, it is assumed that the laser irradiation energy to the minute point for the first nucleation is the same energy as the second time. However, the laser energy of 2 / (20 × 48) = 1/480 is sufficient.
[0069]
(3) It is possible to reduce the thermal load on the workpiece such as a substrate. The fact that the energy required for the Si crystal is very small leads to a significant reduction in the thermal load on the substrate. If the throughput of the processing according to the present invention is the same as that of the prior art, the thermal load on the substrate per unit time is 1/480. This makes it possible to replace existing substrates for crystallization using high-quality glass with thermoplastic materials such as plastics, which is economical and applicable to various flexible electronic devices. Is possible.
[0070]
(Fourth embodiment)
Next, a laser processing method according to the fourth embodiment of the present invention will be described with reference to FIGS. FIG. 10 and FIG. 11 show a method for forming micro-holes with micro-sitting using the laser processing apparatus 2 according to the first or second embodiment.
[0071]
In this embodiment, as shown in FIG. 10A, a polyimide plate 84 is irradiated with a laser beam 86 having a relatively large area as an object to be processed. In this case, the laser beam 86 is applied to the etching region 88 (irradiation area = R) of the polyimide plate 84. By this laser etching, a hole 90 is formed as shown in FIG. Then, as shown in FIG. 10C, the laser irradiation is stopped when the depth h of the hole 90 reaches a desired depth.
[0072]
At this point, as shown in FIG. 11A, laser etching is performed by irradiating a region r smaller than the previous irradiation area R with a laser beam 92. As shown in FIG. 11B, a hole 94 is dug by laser etching. When the laser irradiation is stopped when the hole 94 has penetrated and the process is terminated, a large hole 90 having a depth h and a diameter R is formed, as shown in FIG. A small-diameter hole 94 is formed.
[0073]
In this way, the minute diameter hole 94 is formed together with the minute counterbore hole 90 by the two-stage laser processing.
[0074]
In such a laser processing process, the energy density of the laser on the actual workpiece surface is one of the important parameters. This energy density is determined by the output energy from the laser of the light source and mainly the configuration of the optical path from the laser to the workpiece by the optical system, and the energy density in the process is determined by the output of the laser and the attenuator 8 placed in the optical path. Adjusted.
[0075]
In the case of this two-stage process, for example, in the processing of a hole with a counterbore, laser irradiation is performed on a large area and then on a small area in the first setting. At this time, if light is condensed on the area of the second stage with the same laser output and attenuator setting as in the first stage, the energy density becomes larger than the condition of the first stage, but the energy density necessary for etching is Since they are almost the same, the adjustment is performed by the laser device 4 and the attenuator 8, and the processing is performed so that the energy density is substantially the same.
[0076]
In this embodiment, the holes 90 and 94 can be formed by a processing apparatus having a configuration excluding the vacuum chamber 60 and the optical window 64 using the laser processing apparatus 2 shown in FIG.
[0077]
(Other embodiments)
The laser processing apparatus and laser processing method of the present invention may be configured as follows. In the direct pattern etching process, the workpiece 26 is held in an etching gas activated by the laser beam 6, and only a region irradiated with the laser is etched by irradiating the workpiece 26 with a laser beam. As a result, a desired pattern can be selectively etched in one step.
[0078]
Further, it can be directly used for pattern film forming processing. For example, the work 26 is held in a reactive gas in which a reaction progresses by the laser beam 6 and a solid substance is deposited, and the laser irradiation is performed on the workpiece 26, so that only the region irradiated with the laser can be formed. As a result, a desired pattern can be formed in one step.
[0079]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
a Various laser processes such as drilling, etching, doping, annealing, and the like, processing / modification / film formation, etc., with increased utilization efficiency of laser energy can be realized.
b The processing accuracy of various laser processes such as drilling can be increased and deterioration on the processing apparatus side can be prevented.
[Brief description of the drawings]
FIG. 1 is a diagram showing a laser processing apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram showing processing of a microlens array and a reduction transfer optical system.
FIG. 3 is a diagram illustrating an example of a reduction transfer optical system.
FIGS. 4A and 4B show a form of a focal point formed by the reduction transfer optical system, FIG. 4A is a diagram showing a focal point on the virtual processing surface side, and FIG. 4B is a diagram showing a focal point on the processing surface side.
FIGS. 5A and 5B show a condensing form of a microlens, FIG. 5A is a diagram showing a standard condensing state, and FIG. 5B is a diagram showing a condensing form in a state where a focal position is adjusted.
FIG. 6 is a view showing a modification of the laser processing apparatus according to the first embodiment.
FIG. 7 is a diagram showing a laser processing apparatus according to a second embodiment of the present invention.
FIG. 8 is a diagram showing laser seeding heat treatment by a laser processing method according to a third embodiment of the present invention.
FIG. 9 is a diagram showing a laser seeding heat treatment by a laser processing method according to a third embodiment.
FIG. 10 is a diagram showing a counter boring process by a laser processing method according to a fourth embodiment of the present invention.
FIG. 11 is a diagram illustrating a counter boring process by a laser processing method according to a fourth embodiment.
[Explanation of symbols]
16 Micro lens array (optical element)
18 Reduction transfer optical system
20 beams
22, 30 focus
26 Workpiece (object to be processed)
27 Microlens (optical element)
28 Surface to be treated
70, 74, 86, 92 Laser beam

Claims (6)

An optical element for forming a plurality of beams and forming a focal point for each beam;
An optical system that forms an image by transferring each focal point of the beam formed by the optical element to the surface to be processed;
The laser processing apparatus characterized by having provided the structure. A configuration is provided in which an irradiation area of the beam to the processing surface is changed by moving the processing object having the processing surface, the optical element, or the optical system in each optical axis direction. The laser processing apparatus according to claim 1. Forming a plurality of beams and forming a focal point for each beam;
Transferring each focal point of the beam to the surface to be processed to form an image, and performing laser processing on the surface to be processed by beam irradiation; and
A laser processing method comprising: 4. The laser processing method according to claim 3, wherein in the laser processing, the surface to be processed is irradiated a plurality of times and the irradiation area of the beam to the surface to be processed is the same or different. . 4. The laser according to claim 3, wherein an irradiation area of the beam to the processing surface is changed by moving a processing object, an optical element or an optical system having the processing surface in each optical axis direction. Processing method. 6. The laser processing includes drilling, surface modification, or heat treatment on the surface to be processed, and performing processing corresponding to the number of focal points of the beam on the surface to be processed at the same time. Laser processing method.

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