CN109676269B

CN109676269B - Laser pre-segmentation method and device for LED wafer

Info

Publication number: CN109676269B
Application number: CN201910099108.3A
Authority: CN
Inventors: 卢金龙; 张小军; 苑学瑞; 陈红; 盛存国; 卢建刚; 张红江; 尹建刚; 高云峰
Original assignee: Han s Laser Technology Industry Group Co Ltd
Current assignee: Shenzhen Hans Semiconductor Equipment Technology Co Ltd
Priority date: 2019-01-31
Filing date: 2019-01-31
Publication date: 2021-02-23
Anticipated expiration: 2039-01-31
Also published as: CN109676269A; TW202030782A; TWI719787B

Abstract

The invention discloses a laser pre-segmentation method and a laser pre-segmentation device for an LED wafer, wherein the device comprises the following steps: the system comprises an ultrafast laser, a laser transmission assembly, a non-diffraction beam generation module, a focusing objective lens, a visual detection device and a motion platform; the visual detection device is positioned at the upper part of the focusing objective lens, the moving platform is positioned at the lower part of the focusing objective lens and is used for bearing the LED wafer, and the focusing objective lens is an imaging objective lens of the visual detection device; the ultra-short pulse laser beam emitted by the ultra-fast laser device is shaped by the laser transmission assembly to obtain a high-precision circular light spot, then the light spot is incident to the non-diffraction light beam generation module to generate a non-diffraction light beam, and the non-diffraction light beam is focused by the focusing objective lens to form a processing light beam for pre-dividing the LED wafer. The invention can effectively avoid the defects of inclined crack, back collapse, large and small edges and the like caused by the traditional laser cutting, and can also solve the problem of electrode surface damage during the direct-formed non-diffraction beam scribing.

Description

Laser pre-segmentation method and device for LED wafer

Technical Field

The invention relates to the technical field of laser processing, in particular to a laser pre-segmentation method and device for an LED wafer.

Background

As a new generation of lighting technology, LEDs are widely applied to numerous fields of national life by the characteristics of energy conservation, environmental protection, high efficiency and low energy consumption, wherein the LED light source replaces the traditional light source to reduce the energy consumption by more than 50 percent, so the development of the technology has important significance for the commercial development of China and the improvement of the living standard of people. The sapphire substrate is one of the most widely applied materials in the LED industry, and its crystal characteristics (specifically, two directions of easy cutting and difficult cutting perpendicular to each other) cause a certain oblique crack after a wafer is divided into individual devices, and may affect the final yield and performance of the individual devices. Compared with the traditional mechanical scribing and dividing into single devices, the laser stealth scribing technology belongs to non-contact processing and rapidly occupies the market by virtue of numerous advantages. The specific advantages include: the method can cleanly and tidily scribe all LEDs taking sapphire, silicon carbide and the like as substrates at present, can reduce the scribing defects such as edge breakage, microcrack and the like, has narrow scribing line, can improve the number of single devices divided by a wafer in the same area, has strong operability and high efficiency, can reduce the production cost and the like. However, the laser stealth scribing technology adopted in the current LED industry still has certain disadvantages due to the use of gaussian beams directly output by a laser, such as a large improvement space for yield after scribing, a reduction in device performance due to crack expansion of a modified layer, a large oblique crack angle after cutting, and the like.

With the development of the LED industry and the continuous increase of market demand, it puts forward more requirements on the laser wafer scribing technology widely used at present, and the traditional gaussian beam hidden-cutting scribing is not enough to meet the application demand of the development in this field. For example, optical devices with special shapes and sizes suitable for different industries are increasingly applied, the sizes of the predetermined dividing line and a single device are continuously reduced to improve the output quantity, the yield and the performance requirements of the divided single device are higher and higher, and the requirements on the shape of a modified layer, an oblique crack angle, electrode surface damage and the like after scribing are higher and higher. For example, patent CN102194931A discloses a method for improving the brightness of an optical device after being divided by improving a modified layer after laser processing, and patent CN1575909A and patent CN103537805A propose a method for increasing a laser modified layer by multiple spots or multiple processes to obtain a better dividing effect. The documents show the important function of the modification layer optimization on the LED wafer segmentation, and indicate the direction for the promotion of the laser scribing technology.

Compared with Gaussian beams, the non-diffraction beam has the characteristics of no divergence along the propagation direction, extremely small central light spot, self-healing after encountering an obstacle during propagation and the like, is expected to obtain a modified layer with more regular formation when being applied to LED wafer scribing, can scribe a wafer with a narrower cutting channel, and can inject new power for the development of the laser hidden cutting technology. As shown in fig. 3, the conventional gaussian light is adopted for internal modification, and the modification layer is extremely narrow, so that more cracks appear on the cut section and the oblique fracture angle is large; when the non-diffraction light beam is used for cutting, the cutting of a higher-quality section can be realized by virtue of the characteristic that the width of the modified layer is larger; however, when the non-diffracted beam is cut in a normal state, the electrode surface with a low damage threshold is easily damaged due to the formation mode and the beam characteristics (the energy of the front end and the rear end in the propagation direction of the non-diffracted beam is low in a normal state, and the energy is useless for substrate scribing). This phenomenon is more pronounced at the CH1 face of the cut LED sapphire substrate due to the small dot spacing and the larger pulse energy input (fig. 4). It is important how to fully exploit the advantages of the non-diffracted beam and avoid its disadvantages to apply it to LED wafer dicing.

Accordingly, the prior art is yet to be improved and developed.

Disclosure of Invention

In view of the above-mentioned deficiencies of the prior art, an object of the present invention is to provide a method and an apparatus for laser pre-dividing an LED wafer, so as to overcome the defects of bevel crack, back collapse, large and small edges, etc. and the problem of damaging the electrode surface, which are easily caused by the conventional LED wafer pre-dividing method.

The technical scheme of the invention is as follows:

the invention provides a laser pre-segmentation device of an LED wafer, which comprises: the system comprises an ultrafast laser, a laser transmission assembly, a non-diffraction beam generation module, a focusing objective lens, a visual detection device and a motion platform;

the visual detection device is positioned at the upper part of the focusing objective lens, the moving platform is positioned at the lower part of the focusing objective lens and is used for bearing the LED wafer, and the focusing objective lens is an imaging objective lens of the visual detection device;

the ultra-short pulse laser beam emitted by the ultra-fast laser device is shaped by the laser transmission assembly to obtain a high-precision circular light spot, then the light spot is incident to the non-diffraction light beam generation module to generate a non-diffraction light beam, and the non-diffraction light beam is focused by the focusing objective lens to form a processing light beam for pre-dividing the LED wafer.

The laser pre-segmentation device for the LED wafer is characterized in that the laser transmission assembly comprises a laser beam reducing mirror, a hole-shaped attenuation device and a rapid switching optical pulse output control device which are sequentially arranged along the light beam transmission direction;

an ultrashort pulse laser beam emitted by an ultrafast laser firstly passes through a laser beam shrinking mirror to obtain a high-precision light spot with a divergence angle smaller than 1 milliradian and a diameter smaller than 1 millimeter, then passes through a porous attenuation device to improve the roundness of the light spot, and then controls the output of the light beam through a rapid switching light pulse output control device.

The laser pre-segmentation device for the LED wafer is characterized in that the non-diffraction light beam generation module comprises an axicon.

The laser pre-segmentation device for the LED wafer is characterized in that the pulse width of an ultra-short pulse laser beam generated by the ultra-fast laser is less than 1000 picoseconds.

The laser pre-segmentation device for the LED wafer is characterized in that the visual detection device comprises a CCD camera.

The laser pre-segmentation device for the LED wafer comprises a semi-reflecting and semi-transmitting lens, a focusing objective lens and a non-diffraction beam generation module, wherein the semi-reflecting and semi-transmitting lens is arranged between the visual detection device and the focusing objective lens, and the non-diffraction beam generated by the non-diffraction beam generation module firstly enters the semi-reflecting and semi-transmitting lens and then is partially reflected to enter the focusing objective lens.

The laser pre-segmentation device for the LED wafer is characterized in that the multiple of the focusing objective lens is more than 10 times, and the numerical aperture is more than 0.3.

The invention also provides a laser pre-segmentation method of the LED wafer, which comprises the following steps:

providing a laser pre-segmentation apparatus as described in any of the above;

after the LED wafer is placed on the motion platform, the visual detection device and the motion platform are adjusted, a predetermined cutting line of the LED is positioned, and the position of a focus point in the sample at the moment is fed back;

opening an ultrafast laser to emit ultrashort pulse laser beams, shaping the ultrashort pulse laser beams through a laser transmission assembly to obtain high-precision circular light spots, and then, enabling the light spots to enter a non-diffraction beam generation module to generate non-diffraction beams and then enter a focusing objective lens;

and adjusting the moving platform and the focusing objective lens to carry out accurate focusing, and focusing the processing light beam formed by focusing through the focusing objective lens to a selected area in the substrate, so that the processing light beam carries out accurate internal modification on the LED wafer along the preset dividing line to realize pre-division.

The laser pre-segmentation method of the LED wafer is characterized in that when the wafer is subjected to laser pre-segmentation, the width of the modified layer is adjusted and controlled through the laser transmission assembly or the diffraction-free beam generation module, and the position of the modified layer is adjusted through the focusing objective and the focusing point of the moving platform.

The laser pre-segmentation method of the LED wafer is characterized in that the diameter of a light beam of the high-precision circular light spot is smaller than 1 mm, and the divergence angle of the high-precision circular light spot is smaller than 1 milliradian.

The invention has the beneficial effects that:

according to the invention, the laser transmission assembly is used for shaping to obtain a high-precision circular light spot, then the incident non-diffraction light beam generation module generates a non-diffraction light beam, the interior of the sapphire substrate is processed to form a modified layer, the cross section of each device obtained after subsequent splitting is regular in shape, the defects of inclined crack, back collapse, large and small edges and the like caused by the traditional laser cutting can be effectively avoided, and the problem of electrode surface damage during direct-formed non-diffraction light beam scribing can be solved; secondly, the obtained low-damage modified layer can improve the strength and the optical performance of a single device after being divided; the large-dot-pitch pre-segmentation can be realized by the method, and higher efficiency can be obtained in actual production.

Drawings

Fig. 1 is a schematic structural diagram of an apparatus for laser pre-dividing an LED wafer according to an embodiment of the present invention.

FIG. 2 is a flow chart of a method for laser pre-dividing an LED wafer according to an embodiment of the present invention.

FIG. 3 is a conventional Gaussian beam to undiffracted beam sapphire substrate undercut cleave plane pair ratio; wherein, (a) the fracture surface after the traditional Gaussian beam cutting has more cracks and the width of the modified layer is narrow, and (b) the modified layer with larger width can be obtained by the non-diffraction beam cutting.

Fig. 4 shows the results of damage to the electrode surface caused by scribing in the direction of the undiffracted beam CH1 formed directly without the laser delivery assembly.

FIG. 5 is a diagram showing the effect of two-directional complete division of the sapphire substrate LED of example 1; wherein, (a) is that the electrode surface has no damage after being cut by the non-diffraction light beam directly formed by the laser transmission component, (b) is that the sapphire surface can obtain excellent straightness, (c) and (d) are respectively the cross section of CH2 and CH1 directions, and the cross section is regularly formed and has no crack.

Fig. 6 is a cross-sectional cutting effect diagram after the adjustment of the light beam transmission assembly in embodiment 2 to achieve the adjustment of the states of different modifying layers in the CH2 direction; wherein, (a) is the cutting of small dot spacing, (b) is the cutting of big dot spacing, (c) is the modification layer position control, (d) is the modification layer width control.

Detailed Description

The invention provides a laser pre-segmentation method and a laser pre-segmentation device for an LED wafer, and in order to make the purpose, technical scheme and effect of the invention clearer and clearer, the invention is further described in detail below by referring to the attached drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1, fig. 1 shows an LED wafer laser pre-segmentation optical path based on a non-diffracted beam. The embodiment of the invention provides a laser pre-segmentation device 100 for an LED wafer, which comprises: an ultrafast laser 110, a laser transmission assembly 140, a non-diffraction beam generation module 150, a focusing objective lens 170, a vision inspection device 200, and a motion platform 210; the vision inspection device 200 is located above the focusing objective lens 170, the moving platform 210 is located below the focusing objective lens 170 for bearing the LED wafer 220, and the focusing objective lens 170 is an imaging objective lens of the vision inspection device 200; the focusing objective lens 170, the vision detection device 200 and the motion platform 210 form a focusing positioning system for performing cutting positioning and precise focusing in the cutting process of the LED wafer; the ultrafast laser 110 emits an ultrashort pulse laser beam with a pulse width less than 1ns, the ultrashort pulse laser beam is shaped by the laser transmission assembly 140 to obtain a high-precision circular light spot, then the high-precision circular light spot is incident to the non-diffraction light beam generation module 150 to generate a non-diffraction light beam, and the non-diffraction light beam is focused by the focusing objective lens 170 to form a processing light beam for pre-dividing the LED wafer 220.

Further, in this embodiment, the laser transmission assembly includes a laser beam shrinking mirror, a hole-shaped attenuator, and a fast switching optical pulse output control device, which are sequentially disposed along a beam transmission direction; an ultrashort pulse laser beam emitted by an ultrafast laser firstly passes through a laser beam shrinking mirror to obtain a high-precision light spot with a divergence angle smaller than 1 milliradian and a diameter smaller than 1 millimeter, then passes through a porous attenuation device to improve the roundness of the light spot, and then controls the output of the light beam through a rapid switching light pulse output control device. The laser beam shrinking mirror controls the diameter and the divergence angle of a directly generated light beam, and the hole-shaped attenuation device realizes the small light spot roundness control device, so that the generated diffraction-free light beam can meet the corresponding requirements of LED segmentation and has no burn influence on an electrode surface. The response time of the fast switching light pulse output control device is not higher than 1 microsecond, namely the switching interval time is less than 1 microsecond. The hole-shaped attenuation device can improve the roundness by at least 96 percent. The hole attenuation is mainly used for further optimizing the energy subsection of the small light spot, during specific implementation, a small hole can be simply arranged to achieve the effect, preferably, an attenuation sheet with similar effect can be adopted to achieve the effect, and the interaction between light beams under large energy can be avoided.

Further, in this embodiment, the non-diffraction beam generation module includes an axicon or other components or systems capable of achieving the same effect. The pulse width of an ultra-short pulse laser beam generated by the ultra-fast laser is less than 1000 picoseconds, the single pulse energy is not less than 20 microjoules, the laser wavelength is not limited to 1030 nanometers, and the ultra-short pulse laser beam can be focused in a sapphire substrate to modify the sapphire substrate. The visual inspection device includes a CCD camera. Referring to fig. 1, the laser pre-segmentation apparatus 100 further includes a transflective lens 130 disposed between the vision inspection apparatus 200 and the focusing objective lens 170, and the non-diffracted beam generated by the non-diffracted beam generation module 150 is incident on the transflective lens 130 and then partially reflected into the focusing objective lens 170. The focusing objective 170 has a multiple of more than 10 and a numerical aperture of more than 0.3.

In specific implementation, a 125-micron thick sapphire substrate LED wafer can be used for pre-segmentation. Fig. 1 is a schematic diagram of an LED wafer laser pre-dividing apparatus based on diffraction-free light beams, in which a processing light beam generated by a laser 110 enters a focusing objective 170 through a reflector 120 and a semi-reflective and semi-transparent mirror 130, and the semi-reflective and semi-transparent mirror 130 can be matched with a visual inspection apparatus 200 and the focusing objective 170 to achieve processing, observation, cutting and positioning; the light beam is shaped by a specific laser transmission assembly 140 before passing through the non-diffraction beam generation module 150, and the finally formed non-diffraction beam passes through a lens 160 and then enters a focusing objective lens (50 times, NA is 0.5) to form a beam for processing and pre-divide the wafer 220 placed on the motion system 210. The selection of modified layer morphology may be achieved by adjustment of the particular laser delivery assembly 140 during actual processing. The key point for realizing the effect of the invention is that the specific laser transmission component 140 shapes the laser beam and then passes through the non-diffraction beam generation module 150, wherein the light beam firstly passes through a laser beam reducing mirror (the reducing range is adjustable) to obtain a light spot with a divergence angle smaller than 0.8 milliradian and a diameter smaller than 1 millimeter, then the light beam directly output by the laser is shaped by a method of improving the roundness of the small light spot through a porous attenuation device, and a fast switch light pulse output control device in the component is positioned behind the attenuation device.

Further, in this embodiment, the laser cutting apparatus further includes a control system for controlling the ultrafast laser 110, the laser transmission assembly 140, the focusing objective 170, the vision inspection apparatus 200, and the motion platform 210, so as to control the wafer or the focusing objective during the processing process and automatically control the cutting positioning and the focusing process.

Referring to fig. 2, an embodiment of the present invention further provides a method for laser pre-dividing an LED wafer, where the method includes:

step S100, providing the laser pre-segmentation device;

s200, after the LED wafer is placed on a motion platform, adjusting a visual detection device and the motion platform, positioning a preset segmentation line of the LED and feeding back the position of a focus point in a sample;

step S300, opening an ultrafast laser to emit ultrashort pulse laser beams, shaping the ultrashort pulse laser beams through a laser transmission assembly to obtain high-precision circular light spots, and then, enabling incident undiffracted light beams to enter a focusing objective lens after the undiffracted light beams are generated by an incident undiffracted light beam generating module;

and S400, adjusting the motion platform and the focusing objective lens to carry out accurate focusing, focusing the processing light beam formed by focusing the focusing objective lens on a selected area in the substrate, and carrying out accurate internal modification on the LED wafer (sapphire substrate) along the preset splitting line by the processing light beam to realize pre-splitting.

In the specific implementation, a preset dividing line of an LED is positioned in the visual monitoring equipment and the control system thereof, the position of a focusing point in a sample at the moment is fed back, a non-diffraction light beam required by processing is focused on a selected area in the substrate through a related element, and finally, the processed light beam is subjected to accurate internal modification on the sapphire substrate along the preset dividing line under the motion control and visual monitoring system to realize pre-division.

Further, in this embodiment, the diameter of the light beam of the high-precision circular light spot is smaller than 1 mm, and the divergence angle is smaller than 1 mrad. When the wafer is subjected to laser pre-segmentation, the width of the modified layer is adjusted and controlled through the laser transmission assembly or the diffraction-free beam generation module, and the position of the modified layer is adjusted through the focusing objective and the focusing point of the moving platform. The diffraction-free light beam generated by the specific laser transmission assembly acts inside the sapphire substrate, and the width and the position of the formed modified layer are adjustable. The width of the modified layer can be controlled by the non-diffraction beam generation system or the laser transmission assembly, the position of the modified layer can be realized by motion control and adjustment of the focus position of the vision system, and the modified layer can be selected according to actual requirements when the subsequent splitting effect is ensured.

Furthermore, in the embodiment, after the modified layer is processed by the non-diffraction light beam, a single straight crack can be observed on the surface of the sapphire, and the splitting is convenient; even if the two directions are crossed for cutting, no direction deviation exists at the intersection of the two cracks, and the problems of inclined crack and back collapse in actual production can be effectively solved. After the processing parameters are optimized, the modified layers of the sapphire in the two cutting directions are well formed, no crack can appear except the modified regions, and the optical performance and the strength of a single device after being divided can be ensured. When the sapphire is cut in two directions, the ideal processing effect can be obtained only by modifying at different point intervals, and the processing point interval in one direction can reach at least 20 micrometers, so that the possibility of high-efficiency automatic processing or processing cost reduction is provided.

Furthermore, in this embodiment, the wafer surface has a predetermined dividing line and is divided into a plurality of optical device arrays, and the method focuses the laser beam along the predetermined dividing line inside the wafer substrate to form the modified layer and achieve the desired dividing effect. The method is characterized in that the interior of a sapphire substrate is processed to form a modified layer based on a non-diffraction beam generated after passing through a specific laser transmission assembly, and the width of the modified layer formed by processing can be selected according to the thickness of the substrate or the actual processing requirement so as to meet different actual application requirements. The sections of all devices obtained by the pre-segmentation method after subsequent splitting are regularly formed, the problems of inclined crack and electrode surface damage caused by traditional laser cutting can be effectively avoided, and the strength and the optical performance of a single device after cutting can be improved. The actual cutting of the sapphire substrate wafer shows that the large-point-space machining and cutting can be realized through the adjustment of the transmission assembly, and higher efficiency can be obtained in the actual production; and the electrode surface can not be burnt after the modification layer is changed.

The laser pre-segmentation method of the LED wafer has the advantages that: 1) based on the method, the generated diffraction-free light beam can be used for adjusting the width of the modified layer, wafer scribing with different specifications and processing requirements can be met, and the section forming of a single separated device is remarkably improved compared with that of the traditional laser scribing; 2) by the method, the single device with regular formation can be cut even if the distance between processing points is more than 20 micrometers, so that the laser action area is greatly reduced, and the possibility of improving the scribing efficiency and the luminous performance and the strength of the single device after cutting is provided; 3) the method can well maintain the straightness of the cracks even at the intersection point after the two directions are subjected to crossed scribing, and can provide a solution for solving the defects of back chipping, large and small edges and the like.

The invention is illustrated in detail below with specific examples:

example 1

The aforementioned machining apparatus is provided and the laser delivery assembly 140 is adjusted to obtain a circular beam of about 1 mm in diameter. After the selected sapphire substrate LED wafer is placed on a processing platform, the surface of the sapphire substrate is accurately found through a coaxial imaging vision system, and then an objective lens is moved for a certain distance through a motion control system to enable a processing light beam (the wavelength of the selected laser is 1030 nanometers, the pulse width is adjustable, and the directly output light spot is about 3 millimeters) to be focused on the selected position inside the sapphire. After the determination of the processing position is completed, the horizontal direction and the vertical direction are pre-divided respectively under the selected process parameters (the pulse width is 13 picoseconds, and the single pulse energy is 30 microjoules) (considering the manufacturing process of the sapphire substrate wafer, the processing point distance between the two directions is 6 microns and 24 microns respectively). After laser pre-segmentation, an automatic splitting device is adopted to completely separate the wafer into various devices for observation and separation and section effect.

From the results obtained in example 1, fig. 5 shows that the pre-segmentation and the subsequent splitting are performed in two directions, and the forming rules are that, in particular, the cracks formed after the sapphire substrate is cut in two directions can be completely vertical at the intersection point, and are in sharp contrast to the black spot on the electrode surface after the non-diffraction beam formed after the laser in fig. 4 is directly transmitted is cut, and the electrode surface after the pre-segmentation has no damage. Compared with the traditional section cut by the Gaussian beam (figure 3), the section shape, the oblique fracture and the electrode surface protection degree of the method are obviously improved.

Example 2

The method comprises the steps of placing a selected long-grain LED wafer of a sapphire substrate (selecting a direction in which sapphire is relatively easy to cut for comparison and explanation) on a processing table, accurately finding the surface of the sapphire substrate through a visual system of coaxial imaging, fixing a focusing objective substance through a motion control system to enable laser to be focused on a specific area inside the sapphire for internal modification as an experiment I, and adjusting the energy distribution of incident laser through an attenuation device (adjusting different attenuation ratios in a circular light spot) in the experiment process to realize cutting at different point intervals under the condition of modifying layers with the same width. In addition, under the condition that the width of the modified layer and the distance between the cutting points are determined, the incident light energy distribution is adjusted by matching with the laser transmission assembly, the position of the focal point of the objective lens can be adjusted after being positioned at different positions in the sapphire, and the condition is taken as experiment three. Further, under the condition that the focusing position of the focusing objective lens is determined, the adjustment of the effective length of the diffraction-free light beam output by the focusing objective lens and the energy distribution of the outer ring of the diffraction-free light beam can be realized through the control of the beam shrinking device of the laser transmission assembly, and the adjustment and control of the width of the sapphire inner modified layer can be realized, wherein the condition is used as a second experiment. After the steps are completed, the LED wafer which is divided into strips by the laser pre-segmentation device is observed, separated and sectioned by the automatic splitting device.

From the results obtained in example 2, fig. 6 shows that the method can realize the segmentation of different modified layer forms in cooperation with the adjustment of the laser transmission assembly and the segmentation parameters. It is worth noting that even if the modified layer is located at the lower part of the sapphire substrate, better cutting can be achieved, and no influence is caused on the electrode surface (fig. 6c), which ensures that all the advantages of non-diffraction beam cutting are fully exerted to the LED wafer scribing. Furthermore, the width of the modified layer can be adjusted by matching with the adjustment of the transmission assembly, and wafer scribing with different specifications can be easily realized.

It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.

Claims

1. A laser pre-segmentation device for an LED wafer is characterized by comprising: the system comprises an ultrafast laser, a laser transmission assembly, a non-diffraction beam generation module, a focusing objective lens, a visual detection device and a motion platform;

the laser transmission assembly comprises a laser beam reducing mirror, a hole-shaped attenuation device and a rapid switching optical pulse output control device which are sequentially arranged along the beam transmission direction, wherein an ultrashort pulse laser beam emitted by the ultrafast laser firstly passes through the laser beam reducing mirror to obtain a high-precision light spot, then passes through the hole-shaped attenuation device to improve the roundness of the light spot, and then the rapid switching optical pulse output control device controls the output of the light beam;

2. The laser pre-dividing device for the LED wafer as claimed in claim 1, wherein the divergence angle of the high-precision light spot is less than 1 milliradian, and the diameter of the high-precision light spot is less than 1 millimeter.

3. The laser pre-dividing apparatus for LED wafers as set forth in claim 1, wherein the non-diffractive beam generating module comprises an axicon.

4. The laser pre-dividing apparatus for LED wafers as set forth in claim 1, wherein the ultra-short pulse laser beam generated by the ultra-fast laser has a pulse width of less than 1000 picoseconds.

5. The laser pre-dividing device for the LED wafer as claimed in claim 1, wherein the visual inspection device comprises a CCD camera.

6. The laser pre-dividing device for the LED wafer as claimed in claim 1, wherein the laser pre-dividing device further comprises a semi-reflective and semi-transparent mirror disposed between the vision inspection device and the focusing objective lens, and the non-diffracted beam generated by the non-diffracted beam generating module is incident to the semi-reflective and semi-transparent mirror and then partially reflected to the focusing objective lens.

7. The laser pre-dividing apparatus for LED wafers as set forth in claim 1, wherein the focusing objective lens has a multiple of more than 10 and a numerical aperture of more than 0.3.

8. A laser pre-segmentation method of an LED wafer is characterized by comprising the following steps:

providing a laser pre-segmentation apparatus as set forth in any one of claims 1 to 7;

9. The method for laser pre-dividing the LED wafer as claimed in claim 8, wherein during the laser pre-dividing of the wafer, the width of the modified layer is adjusted and controlled by the laser transmission assembly or the non-diffraction beam generation module, and the position of the modified layer is adjusted by the focusing objective and the focusing point of the moving platform.

10. The method as claimed in claim 8, wherein the high-precision circular spot has a beam diameter of less than 1 mm and a divergence angle of less than 1 mrad.