CN110605483A - A laser cutting device for LED wafers - Google Patents

Abstract

The invention discloses a laser cutting 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 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

A laser cutting device for LED wafers

technical field

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

Background technique

As a new generation of lighting technology, LED is widely used in many fields of national life due to its energy saving, environmental protection, high efficiency and low energy consumption. Among them, LED light source can reduce energy consumption by more than 50% by replacing traditional light source. Therefore, the development of this technology is very important for my country's Commercial development and the improvement of people's living standards are of great significance. As one of the most widely used materials in the LED industry, sapphire substrates have crystal characteristics (specifically, two directions of easy-cutting and difficult-cutting perpendicular to each other) that cause certain oblique cracks after the wafer is divided into individual devices, which may affect the final The yield rate and performance of a single device. Compared with the traditional mechanical scribing and dividing into individual devices, the laser hidden cutting scribing technology is a non-contact processing and quickly occupies the market with its many advantages. Specific advantages include: all LEDs that currently use sapphire, silicon, silicon carbide, etc. Dividing the number of individual devices has strong operability and high efficiency, and can reduce production costs. However, the laser implicit scribing technology currently used in the LED industry uses the Gaussian beam directly output by the laser, and there are still some shortcomings. For example, there is still a lot of room for improvement in the yield rate after scribing, and crack expansion in the modified layer leads to device performance degradation. , Large oblique crack angle after cutting and other problems.

With the development of the LED industry and the continuous growth of market demand, it puts forward more requirements for the widely used laser wafer scribing technology. The traditional Gaussian beam implicit scribing is no longer enough to meet the application requirements of this field. . For example, more and more optical devices with special shapes and sizes suitable for applications in different industries are used more and more, and the size of the predetermined division line and individual devices is continuously reduced to increase the output quantity, yield rate and performance requirements of individual devices after division It is getting higher and higher, which has higher standards for the modified layer shape, oblique crack angle, electrode surface damage, etc. after scribing. There are more and more researches on laser cutting of LED wafers in this field. For example, the invention patent CN102194931A discloses a method of improving the luminous brightness of the split optical device by improving the modified layer after laser processing. The invention patents CN1575909A and CN103537805A A method to increase the laser modification layer by multi-spot or multiple processing is proposed to obtain better segmentation effect. The above documents all reflect the important role of modification layer optimization for LED wafer segmentation, and also point out the direction for the improvement of laser scribing technology.

Compared with Gaussian beams, non-diffracting beams have the characteristics of no divergence along the propagation direction, extremely small central spot, and self-healing after encountering obstacles during propagation. Applying it to LED wafer scribing is expected to achieve more regular improvements. It can also scribe wafers with narrower dicing lines, which can inject new impetus into the development of laser hidden cutting technology. Using traditional Gaussian light for internal modification, because the modified layer is extremely narrow, it is easy to cause many cracks and large oblique crack angles in the section after cutting; while cutting with non-diffracting beams can be achieved by virtue of the larger width of the modified layer. Realize the cutting of higher quality sections; however, due to the formation method and beam characteristics of the non-diffraction beam in the normal state when cutting Useless) can easily lead to damage to the electrode surface with a low damage threshold. This phenomenon is more obvious on the CH1 surface of the cut LED sapphire substrate due to the small dot pitch and larger pulse energy input. So how to give full play to the advantages of non-diffraction beam and avoid its disadvantages is very important to apply it to LED wafer scribing.

Therefore, the prior art still needs to be improved and developed.

Contents of the invention

In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a laser pre-segmentation method and device for LED wafers, so as to overcome the oblique cracks, back collapse, Defects such as large and small edges, and problems that damage the electrode surface.

Technical scheme of the present invention is as follows:

The present invention provides a laser pre-segmentation device for LED wafers, which includes: an ultrafast laser, a laser transmission component, a non-diffraction beam generation module, a focusing objective lens, a visual detection device, and a motion platform;

The visual inspection device is located on the upper part of the focusing objective lens, and the moving platform is located on the lower part of the focusing objective lens to carry the LED wafer. The focusing objective lens is the imaging objective lens of the visual inspection device;

The ultrafast laser emits an ultrashort pulse laser beam, which is shaped by the laser transmission component to obtain a high-precision circular spot, and then enters the non-diffraction beam generating module to generate a non-diffraction beam, which is then focused by the focusing objective lens to form a pre-segmented LED wafer. processing beam.

The laser pre-segmentation device for LED wafers, wherein the laser transmission component includes a laser beam shrinker, a hole-shaped attenuation device, and a fast switching optical pulse output control device arranged in sequence along the beam transmission direction;

The ultrashort pulse laser beam emitted by the ultrafast laser first passes through the laser beam reducer to obtain a high-precision spot with a divergence angle of less than 1 milliradian and a diameter of less than 1 mm, then passes through a hole-shaped attenuation device to improve the roundness of the spot, and then passes through the fast switching light The pulse output control device controls the output of the light beam.

In the laser pre-segmentation device for LED wafers, the non-diffraction beam generating module includes an axicon.

In the laser pre-segmentation device for LED wafers, the pulse width of the ultrashort pulse laser beam generated by the ultrafast laser is less than 1000 picoseconds.

In the laser pre-segmentation device for LED wafers, the visual inspection device includes a CCD camera.

The laser pre-segmentation device for LED wafers, wherein the laser pre-segmentation device further includes a semi-reflective half lens arranged between the visual inspection device and the focusing objective lens, and the non-diffraction beam generated by the non-diffraction beam generation module is first The incident half-mirror is then partially reflected into the focusing objective.

The laser pre-segmentation device of the LED wafer, wherein, the multiple of the focusing objective lens is greater than 10 times and the numerical aperture is greater than 0.3.

The present invention also provides a laser pre-segmentation method for LED wafers, which includes the steps of:

Provide the laser pre-segmentation device described in any one of the above;

After placing the LED wafer on the motion platform, adjust the visual inspection device and the motion platform to locate the predetermined dividing line of the LED and feedback the position of the focal point in the sample at this time;

Turn on the ultrafast laser to emit an ultrashort pulse laser beam, which is shaped by the laser transmission component to obtain a high-precision circular spot, and then enters the non-diffraction beam generating module to generate a non-diffraction beam, and then enters the focusing objective lens;

Adjust the motion platform and the focusing objective lens for precise focusing, and focus the processing beam formed by the focusing objective lens on the selected area inside the substrate, so that the processing beam can carry out precise internal modification of the LED wafer along the predetermined dividing line to achieve pre-segmentation.

The laser pre-segmentation method of the LED wafer, wherein, when the wafer is pre-segmented by laser, the width of the modified layer is adjusted and controlled by the laser transmission component or the non-diffraction beam generation module, and the position of the focus point is adjusted by the focusing objective lens and the moving platform. The adjustment realizes the adjustment of the position of the modified layer.

The laser pre-segmentation method of the LED wafer, wherein the high-precision circular spot has a beam diameter of less than 1 mm and a divergence angle of less than 1 milliradian.

The beneficial effects of the present invention are:

In the present invention, the high-precision circular spot is obtained by shaping the laser transmission component, and then the incident non-diffraction beam generating module generates a non-diffraction beam, processes the inside of the sapphire substrate and forms a modified layer, and the cross-section of each device obtained after subsequent splitting is regular. , can effectively avoid defects such as oblique cracks, back collapse, and large and small edges caused by traditional laser cutting, and can also solve the problem of electrode surface damage when scribing with a directly formed non-diffraction beam; secondly, the obtained low-damage modified layer can improve the cutting The strength and optical performance of the final single device; and processing by this method can achieve large dot pitch pre-segmentation, and higher efficiency can be obtained in actual production.

Description of drawings

FIG. 1 is a schematic structural diagram of a laser pre-segmentation device for an LED wafer according to an embodiment of the present invention.

Detailed ways

The present invention provides a laser pre-segmentation method and device for LED wafers. In order to make the purpose, technical solution and effect of the present invention clearer and clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Referring to FIG. 1, FIG. 1 shows the laser pre-segmentation optical path of the LED wafer based on the non-diffraction beam. An embodiment of the present invention provides a laser pre-segmentation device 100 for LED wafers, which includes: an ultrafast laser 110, a laser transmission component 140, a non-diffracting beam generation module 150, a focusing objective lens 170, a visual inspection device 200, and Motion platform 210; visual detection device 200 is positioned at the top of focusing objective lens 170, and moving platform 210 is positioned at the bottom of focusing objective lens 170 for carrying LED wafer 220, and focusing objective lens 170 is the imaging objective lens of visual detection device 200; Focusing objective lens 170, visual detection device 200 and motion platform 210 constitute a focus positioning system for cutting positioning and precise focusing during the cutting process of LED wafers; the ultrafast laser 110 emits an ultrashort pulse laser beam with a pulse width less than 1 ns, which is shaped by the laser transmission component 140 to obtain The high-precision circular spot is incident on the non-diffracting beam generating module 150 to generate a non-diffractive beam, and then focused by the focusing objective lens 170 to form a processing beam for pre-segmenting the LED wafer 220 .

In the present invention, the high-precision circular spot is obtained by shaping the laser transmission component, and then the incident non-diffraction beam generating module generates a non-diffraction beam, processes the inside of the sapphire substrate and forms a modified layer, and the cross-section of each device obtained after subsequent splitting is regular. , can effectively avoid defects such as oblique cracks, back collapse, and large and small edges caused by traditional laser cutting, and can also solve the problem of electrode surface damage when scribing with a directly formed non-diffraction beam; secondly, the obtained low-damage modified layer can improve the cutting The strength and optical performance of the final single device; and processing by this method can achieve large dot pitch pre-segmentation, and higher efficiency can be obtained in actual production.

Further, in this embodiment, the laser transmission component includes a laser beam shrinker, a hole-shaped attenuation device, and a fast switching optical pulse output control device arranged in sequence along the beam transmission direction; the ultrashort pulse laser beam emitted by the ultrafast laser, First, the laser beam reducer is used to obtain a high-precision spot with a divergence angle of less than 1 milliradian and a diameter of less than 1 mm, and then the hole-shaped attenuation device is used to improve the roundness of the spot, and then the output of the beam is controlled by a fast-switching optical pulse output control device. The laser beam reducer controls the diameter and divergence angle of the directly generated beam, and the hole-shaped attenuation device realizes the small spot roundness control device to ensure that the generated non-diffraction beam can meet the corresponding requirements of LED segmentation and has no impact on the electrode surface. Burn effects. The response time of the fast switching optical pulse output control device is not higher than 1 microsecond, that is, the switching interval is less than 1 microsecond. The hole-shaped attenuation device can improve the roundness by at least 96%. The hole attenuation is mainly to further optimize the energy division of the small spot. In practice, a small hole can be simply set to achieve the effect. Preferably, an attenuation sheet with a similar effect can be used to avoid the gap between the beams under high energy. interaction.

Further, in this embodiment, the non-diffracting beam generating module includes an axicon or other components or systems that can achieve the same effect. The pulse width of the ultrashort pulse laser beam generated by the ultrafast 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 can be focused inside the sapphire substrate for modification processing. The visual inspection device includes a CCD camera. 1, the laser pre-segmentation device 100 also includes a half mirror 130 arranged between the visual inspection device 200 and the focusing objective lens 170, and the non-diffraction beam generated by the non-diffraction beam generation module 150 is first incident on the half mirror. Lens 130 then partially reflects into focusing objective 170 . The multiple of the focusing objective lens 170 is greater than 10 times and the numerical aperture is greater than 0.3.

During specific implementation, a 125-micron-thick sapphire substrate LED wafer can be used for pre-segmentation. Fig. 1 is the schematic diagram of the LED wafer laser pre-segmentation device based on the non-diffraction beam used in the present invention, the processing beam produced by the laser 110 enters the focusing objective lens 170 through the reflector 120 and the half mirror 130, and the half mirror 130 simultaneously It can cooperate with the visual inspection device 200 and the focusing objective lens 170 to realize processing observation and cutting positioning; before the beam passes through the non-diffraction beam generating module 150, it needs to undergo relevant shaping by a specific laser transmission component 140, and the finally formed non-diffraction beam passes through the lens 160 Enter the focusing objective lens (50 times, NA is 0.5) to form beams that can be used for processing and pre-segment the wafer 220 placed on the motion system 210 . In actual processing, the modification layer morphology can be selected by adjusting the specific laser transmission component 140 . The specific laser transmission component 140 shapes the laser beam and then passes through the non-diffraction beam generation module 150 is the key to the realization of the effect of the invention. Here, the beam first passes through the laser beam shrinker (adjustable narrowing range) to obtain a divergence angle of less than 0.8 milliradians and a diameter of For a spot smaller than 1 mm, the beam directly output by the laser is shaped by a hole-shaped attenuation device to improve the roundness of the small spot. The fast-switching optical pulse output control device in the module is located behind the attenuation device.

Further, in this embodiment, the laser cutting device also includes a control system for controlling the ultrafast laser 110, the laser transmission assembly 140, the focusing objective lens 170, the visual inspection device 200, and the motion platform 210, which can realize processing The control of the process wafer or focusing objective lens can realize the automatic control of cutting positioning and focusing process.

In the specific implementation, the predetermined dividing line of the LED is located in the visual monitoring equipment and its control system, and the position of the focus point in the sample is fed back at this time, and then the non-diffraction beam required for processing is focused on the selected surface inside the substrate through relevant components. Finally, under the motion control and visual monitoring system, the processing beam is extended along the predetermined dividing line to carry out precise internal modification on the sapphire substrate to achieve pre-segmentation.

Further, in this embodiment, the high-precision circular spot has a beam diameter of less than 1 mm and a divergence angle of less than 1 milliradian. During the laser pre-segmentation of the wafer, the width of the modified layer is adjusted and controlled by the laser transmission component or the non-diffracting beam generation module, and the position of the modified layer is adjusted by adjusting the focus position of the focusing objective lens and the moving platform. The non-diffraction beam generated by the specific laser transmission component acts on the inside of the sapphire substrate, and the width and position of the modified layer formed can be adjusted. The width of the modified layer can be controlled by the non-diffracting beam generation system or the laser transmission component, and the position of the modified layer can be realized by motion control and adjustment of the focus position of the vision system, which can be selected according to actual needs when ensuring the effect of subsequent splits.

Further, in this embodiment, a single straight crack can be observed on the sapphire surface after processing the modified layer with a non-diffracting beam, and the splitting is convenient; even when the two directions are cross-cut, there is no direction deviation at the intersection of the two cracks , which can effectively solve the problem of oblique cracking and back collapse in actual production. After optimizing the processing parameters, the modified layers in both cutting directions of sapphire are well formed and no cracks appear except in the modified area, which can ensure the optical performance and strength of a single device after division. When cutting sapphire in two directions, the ideal processing effect can be obtained only by modifying the point spacing at different points, and the processing point pitch in one direction can reach at least 20 microns, which provides the possibility for efficient automatic processing or reduced processing costs.

Further, in this embodiment, the surface of the wafer has a predetermined dividing line and has been divided into multiple optical device arrays. In this method, the laser beam is focused on the inside of the wafer substrate along the predetermined dividing line to form a modified layer and achieve Expected segmentation effect. This method is based on the non-diffraction beam generated by a specific laser transmission component to process the inside of the sapphire substrate to form a modified layer. The width of the modified layer formed by the processing can be selected according to the thickness of the substrate or actual processing requirements to meet different practical application requirements. . The cross section of each device obtained by the pre-segmentation method after the subsequent slitting is regular, which can effectively avoid the problems of oblique cracks and electrode surface damage caused by traditional laser cutting, and can also improve the strength and optical performance of a single device after cutting. The actual cutting of the sapphire substrate wafer found that through the adjustment of the transmission component, the processing and cutting of large point spacing can be realized, and higher efficiency can be obtained in actual production; it is also possible to avoid burns on the electrode surface after changing the position of the modified layer.

The advantages of the laser pre-segmentation method for LED wafers of the present invention are: 1) Based on this method, the generated non-diffraction beam can be used for adjusting the width of the modified layer, which can meet wafer dicing of different specifications and processing requirements, and separate Compared with the traditional laser scribing, the cross-sectional shaping of a single device is significantly improved; 2) Even if the distance between processing points is greater than 20 microns, the division of a single device can still be achieved through this method, which greatly reduces the laser active area and improves the scribing efficiency. It is possible to improve the luminous performance and intensity of a single device; 3) The straightness of the crack can be well maintained even at the intersection point after cross-scribing in two directions by this method, which can provide a solution for defects such as back chipping and large and small edges.

The present invention is described in detail below with specific embodiment:

Example 1

The foregoing processing device is provided, and the laser transmission assembly 140 is adjusted to obtain a circular beam with a diameter of about 1 mm. After the selected sapphire substrate LED wafer is placed on the processing platform, the surface of the sapphire substrate is accurately found through the coaxial imaging vision system, and then the objective lens is moved by a certain distance through the motion control system to make the processing beam (the wavelength of the selected laser is 1030 nm And the pulse width is adjustable, and the direct output light spot is about 3 mm) focused on the selected position inside the sapphire. After completing the above processing position determination steps, under the selected process parameters (pulse width 13 picoseconds, single pulse energy 30 microjoules), pre-segment the horizontal and vertical directions respectively (in view of the manufacturing process of the sapphire substrate wafer, the two directions The processing point spacing is 6 microns and 24 microns, respectively). After laser pre-segmentation, an automatic splitting device is used to completely separate the wafer into individual devices to observe the separation and cross-section effects.

Example 2

Place the selected sapphire substrate long-grain LED wafer (select the direction where sapphire is relatively easy to cut for comparison) on the processing table and accurately find the surface of the sapphire substrate through the coaxial imaging vision system, and then use the motion control system to focus The material of the objective lens is fixed so that the laser is focused on a specific area inside the sapphire for internal modification. As Experiment 1, the energy distribution of the incident laser is adjusted by the attenuation device during the experiment (adjustment of different attenuation ratios in the circular spot) to achieve the same width of the modified layer. Cutting with different point spacing. In addition, when the width of the modified layer and the distance between the cutting points are determined, the laser transmission component is used to adjust the energy distribution of the incident light, and the position of the modified layer can be adjusted after the focal point of the objective lens is set at different positions inside the sapphire. Conditions as experiment three. Further, in the case of determining the focal position of the focusing objective lens, the effective length of the non-diffraction beam output by the focusing objective lens and the energy distribution of the outer circle can be adjusted through the control of the beam shrinker device of the laser transmission component, and the adjustment of the width of the modified layer inside the sapphire can be realized. This condition was used as Experiment 2. After completing the above steps, use an automatic splitting device to separate the wafers into strips of LED wafers after laser pre-segmentation to observe the separation and cross-section effects.

It should be understood that the application of the present invention is not limited to the above examples, and those skilled in the art can make improvements or transformations according to the above descriptions, and all these improvements and transformations should belong to the protection scope of the appended claims of the present invention.

Claims (7)

1. A laser cutting device for LED wafers, comprising: 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 located at the focusing objective lens In the upper part, the moving platform is located at the lower part of the focusing objective lens to carry the LED wafer. The focusing objective lens is the imaging objective lens of the visual inspection device; the ultrafast laser emits an ultrashort pulse laser beam, which is shaped by the laser transmission component to obtain a high-precision circular spot, and then The incident non-diffracting beam generation module generates a non-diffraction beam, which is then focused by a focusing objective lens to form a processing beam for pre-segmenting LED wafers. 2. The laser cutting device for LED wafers according to claim 1, wherein the laser transmission assembly includes a laser beam shrinker, a hole-shaped attenuation device, and a fast switching optical pulse output arranged in sequence along the beam transmission direction. Control device; the ultrashort pulse laser beam emitted by the ultrafast laser first passes through the laser beam reducer to obtain a high-precision spot with a divergence angle of less than 1 milliradian and a diameter of less than 1 mm, and then passes through the hole-shaped attenuation device to improve the roundness of the spot, and then passes through the The fast switching optical pulse output control device controls the output of the light beam. 3. The laser cutting device for LED wafers according to claim 1, wherein the non-diffraction beam generating module comprises an axicon. 4 . The laser cutting device for LED wafers according to claim 1 , wherein the pulse width of the ultrashort pulse laser beam generated by the ultrafast laser is less than 1000 picoseconds. 5. The laser cutting device for LED wafers according to claim 1, wherein the visual detection device comprises a CCD camera. 6. The laser cutting device of LED wafer according to claim 1, characterized in that, the laser pre-segmentation device also includes a semi-reflective half-lens arranged between the visual inspection device and the focusing objective lens, and no diffracted beams are produced. The non-diffraction beam generated by the module first enters the half-mirror, and then partly reflects into the focusing objective lens. 7 . The laser cutting device for LED wafers according to claim 1 , wherein the multiple of the focusing objective lens is greater than 10 times and the numerical aperture is greater than 0.3.