Light-emitting diode (LED) substrate lift-off method

Abstract

The invention provides a light-emitting diode (LED) substrate lift-off method, which comprises the steps of: providing an LED substrate, wherein the LED substrate comprises a substrate and an epitaxial layer which is arranged on the substrate; bonding the epitaxial layer on a transfer substrate; thinning the substrate in the LED substrate by adopting a femtosecond laser system, wherein the femtosecond laser system focuses femtosecond pulse laser in the substrate, a light spot formed through focusing is a linear light spot and the length of the linear light spot is larger than or equal to the diameter of the LED substrate; and removing the remaining substrate by adopting a physicochemical polishing method to expose the epitaxial layer. The LED substrate lift-off method has the advantages that the heat produced in the lift-off process can be prevented from damaging the epitaxial layer, the rate of non-defective products is improved and the luminous efficiency is improved.

Description

technical field [0001] The invention relates to a stripping method of an LED substrate, in particular to a method for stripping an LED substrate by using a femtosecond laser. Background technique [0002] As we all know, the LED wafer is grown on the sapphire or silicon carbide substrate by vapor deposition method based on the light-emitting active layer of gallium nitride-based materials. At present, the size of the common LED wafer is 2 inches to 4 inches. The development of the LED industry, the reduction of LED prices and the improvement of luminous efficiency have driven the popularization of LED chips, which has also driven various technologies used in the LED field. [0003] In the current market, the generally popular planar structure LED chips (positive and negative electrodes on the same side of the substrate) have problems such as small light-emitting area and current crowding effect, while vertical structure LED chips (positive and negative electrodes on the uppe...

AI Technical Summary

Problems solved by technology

However, due to its longer pulse time (usually nanoseconds), it needs to consume more energy to break chemical bonds, and the heat generated will be very large, and the heat-affected zone is relatively large

The laser action area will be accompanied by severe thermal diffusion, which will generate strong shock wave stress, which will cause cracks or pits, and not only easily damage the nitrogen with a thickness of only a few microns in the direction perpendicular to the peeling surface. Gallium epitaxial layer will also damage the surrounding chips in the horizontal direction

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