CN102886609A - Multi-focus femtosecond laser scribing method applied to separation of light emitting diode (LED) device - Google Patents

Abstract

A multi-focus femtosecond laser scribing method applied to the separation of LED devices, comprising: Step 1: fixing the prepared LED device on a horizontal moving platform and positioning it at the imaging center of a CCD imaging device; Step 2: Multiple lenses are placed on the laser light path of the laser to divide the laser light into multiple focal points; Step 3: Focus multiple focal points on parts of different depths inside the LED device substrate; Step 4: Move the horizontal platform horizontally and vertically to complete the femtosecond Laser scribing; step 5: splitting the LED device to obtain a single LED device. The invention can cut the sapphire substrate with different light beams at the same time, realize the effect of one-time cutting and multiple scratches, thereby realizing the low-damage cutting of the thicker sapphire substrate, so as to achieve the device separation of the light-emitting diode.

Description

Multi-focus femtosecond laser scribing method applied to separation of LED devices

technical field

The invention belongs to the technical field of semiconductors, in particular to the technical field of gallium nitride-based light-emitting diode wafer laser scribing technology. the

Background technique

Laser scribing technology is widely used in the device separation process of gallium nitride-based light-emitting diode wafers, which is simple, fast and efficient. Now the ordinary nanosecond laser scribing machine can only leave cutting marks with a depth of 20 μm to 50 μm on the sapphire substrate when cutting the sapphire substrate for device separation. In this way, the sapphire substrate with a thickness of about 460 μm needs to be mechanically thinned and polished to a thickness of 70-120 μm before it can be scratched to achieve the purpose of device separation. However, the mechanical thinning and polishing of sapphire will damage the gallium nitride epitaxial layer to a certain extent, thereby reducing the luminous efficiency of the light emitting diode. At the same time, mechanically thinning and polishing the sapphire substrate will complicate the preparation process of the light-emitting diode, thereby increasing the production cost of the device. Moreover, due to the long nanosecond laser pulse, the high temperature generated by its focus on the sapphire substrate will cause a phase change in the sapphire near the laser scratch, which will reduce the light transmittance near the laser scratch, which also affects the performance of the device. light extraction efficiency. On the other hand, due to cost considerations, the epitaxial wafers of GaN-based light-emitting diodes are undergoing industrial upgrading in the direction of large-scale epitaxy such as 4 inches, 6 inches, and even 8 inches. The huge stress caused by matching makes it difficult to thin the sapphire substrate to a thickness of about 100 μm. In this way, a new laser cutting method is needed to perform large-size, low-damage, and high-efficiency laser scribing technology. the

Contents of the invention

The object of the present invention is to provide a multi-focus femtosecond laser scribing method applied to the separation of LED devices, which uses ultrashort-pulse femtosecond lasers to perform low-damage laser cutting on thicker sapphire substrates above 200 μm. At the same time, the laser optical path emitted by the femtosecond laser is designed, and a multi-focus dimming system is introduced in the optical path, so that the laser is dispersed into different beams after passing through the multi-focus dimming system, and focused on different depths of sapphire contrast. In order to achieve the simultaneous cutting of sapphire substrates with different beams, the effect of one-time cutting and multiple scratches can be achieved, so as to achieve low-damage cutting of thicker sapphire substrates and achieve the separation of light-emitting diode devices. The introduction of the multi-focus dimming system can complete the cutting of thicker sapphire substrates only once, thereby reducing production costs. At the same time, because the laser pulse of the femtosecond laser is very short, the sapphire is directly vaporized and decomposed, which reduces the damage of the laser beam to the sapphire and improves the light extraction efficiency. the

The invention provides a multi-focus femtosecond laser scribing method applied to the separation of LED devices, comprising:

Step 1: Fix the prepared LED device on the horizontal moving platform and place it in the imaging center of the CCD imaging device;

Step 2: Place multiple lenses on the laser light path of the femtosecond laser to divide the laser into multiple focal points;

Step 3: focus multiple focal points on different depths inside the LED device substrate;

Step 4: Move the horizontal platform horizontally and vertically to complete the femtosecond laser scribing;

Step 5: Splitting the LED device to obtain a single LED device. the

Wherein the femtosecond laser output laser center wavelength range is 200nm-1600nm, pulse width range is 1fs-1000fs, repetition frequency is 1MHz-1000MHz, average power range is 1mw-100W. the

Wherein the number of lenses and focal points is 1-10. the

Wherein the plurality of focal points are uniformly distributed at different depths inside the substrate. the

The focus diameter mentioned therein is 100nm-5μm. the

Description of drawings

In order to enable the examiner to further understand the structure, features and purpose of the present invention, the following detailed description in conjunction with the accompanying drawings and preferred specific embodiments is as follows, wherein:

Fig. 1 is the flow chart of the multi-focus femtosecond laser scribing method that the present invention is applied to LED device separation;

Fig. 2 is the schematic diagram of multi-focus femtosecond laser cutting principle of the present invention;

Fig. 3 is a schematic diagram of a focusing structure of a multi-focus femtosecond laser. the

Detailed ways

Please refer to Figures 1 to 3, the present invention provides a multi-focus femtosecond laser scribing method applied to the separation of LED devices, including:

Step S10: Fix the prepared LED device 400 on the horizontal moving platform 500, then adjust the CCD focus of the optical path system so that the back of the LED device 400 is located at the imaging center of the CCD imaging device 200 (see FIG. 2); adjust the horizontal moving platform 500 Parallel to the runway of the LED device 400 . the

Step S20: placing a plurality of lenses 300 on the laser optical path of the femtosecond laser 100 to divide the laser light into multiple focal points, the central wavelength range of the laser output by the femtosecond laser 100 is 200nm-1600nm, and the pulse width range is 1fs-1000fs, The repetition frequency is 1MHz-1000MHz, the average power range is 1mw-100W, the number of the lens 300 and the focal point is 1-10 (the number of the lens 300 provided in this embodiment is two, the lens 301 and the lens 302), the number The focal points are uniformly distributed at different depths inside the substrate, and the diameter of the focal points is 100nm-5μm;

Step S30: by adjusting the position of the lens 300, multiple focal points 401 and focal points 402 (referring to Fig. 3, the present embodiment provides two focal points 401, 402) are focused on the positions of different depths inside the substrate of the LED device 400; The laser energy is uniform at the focal point. the

Step S40: After the adjustment is completed, turn on the laser switch, use a stepping motor to control the horizontal movement platform 500 to move horizontally and vertically, and complete the femtosecond laser scribing process of the LED device 400;

Step S50: After the dicing is completed, protect the LED device 400 with a protective film, place it on a splitting machine, adjust the X and Y axes of the splitting machine to be parallel to the running track of the LED device 400, and split to obtain a single LED device. Thus, the dicing and splitting process of the LED device 400 is completed. the

The above is only a specific implementation mode in the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technology can easily think of changes or replacements within the technical scope disclosed in the present invention. All should be covered within the scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims. the

Claims (5)

1. A multi-focus femtosecond laser scribing method applied to the separation of LED devices, comprising: Step 1: Fix the prepared LED device on the horizontal moving platform and place it in the imaging center of the CCD imaging device; Step 2: Place multiple lenses on the laser light path of the femtosecond laser to divide the laser into multiple focal points; Step 3: focusing multiple focal points on parts at different depths inside the LED device substrate; Step 4: Move the horizontal platform horizontally and vertically to complete femtosecond laser scribing; Step 5: Splitting the LED device to obtain a single LED device. 2. The multi-focus femtosecond laser scribing method applied to the separation of LED devices as claimed in claim 1, wherein the laser center wavelength range of the femtosecond laser output is 200nm-1600nm, and the pulse width range is 1fs-1000fs, The repetition frequency is 1MHz-1000MHz, and the average power range is 1mw-100W. 3. The multi-focus femtosecond laser scribing method applied to the separation of LED devices as claimed in claim 1, wherein the number of said lenses and focus points is 1-10. 4. The multi-focus femtosecond laser scribing method applied to the separation of LED devices as claimed in claim 1, wherein the multiple focus points are uniformly distributed at different depths inside the substrate. 5. The multi-focus femtosecond laser scribing method applied to the separation of LED devices as claimed in claim 1, wherein said focus diameter is 100 nm-5 μm.

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