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

Abstract

The invention discloses a multi-focus femtosecond laser scribing method applied to separation of light emitting diode (LED) device. The multi-focus femtosecond laser scribing method comprises the following steps of: fixing a prepared LED device on a horizontal mobile platform and positioning the prepared LED device in an imaging center of charge coupled device (CCD) imaging equipment; 2, placing a plurality of lenses on a laser light path of a femtosecond laser, and dividing laser into a plurality of focuses; 3, focusing the focuses on parts in a substrate of the LED device at different depths; 4, transversely and longitudinally moving the horizontal mobile platform, and performing femtosecond laser scribing; and 5, shredding the LED device to obtain a single LED device. By the multi-focus femtosecond laser scribing method, a sapphire substrate can be cut by different light beams simultaneously, and effects that the substrate is cut at one time, and a plurality of scratches are caused are achieved, so that a relatively thick sapphire substrate is cut in a mode that low damage is caused, and the LED device is separated.

Description

technical field [0001] 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. Background technique [0002] 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 lig...

AI Technical Summary

Problems solved by technology

However, mechanical thinning and polishing of sapphire will damage the GaN epitaxial layer to a certain extent, thereby reducing the luminous efficiency of light-emitting diodes

At the same time, mechanically thinning and polishing the sapphire substrate will complicate the preparation process of light-emitting diodes, 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 the matching makes it difficult to thin the sapphire substrate to a thickness of about 100 μm

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