Thin film flip structure Micro-LED chip transferred by adhesive layer, and preparation method thereof

Abstract

The invention provides a thin film flip structure Micro-LED chip transferred by an adhesive layer, and a preparation method thereof. The light extraction efficiency of the chip can be effectively improved. The preparation method comprises the following steps: growing an epitaxial layer on a substrate; depositing a current blocking layer; etching to form a frustum-shaped first frustum-shaped epitaxial layer and a frustum-shaped second frustum-shaped epitaxial layer; forming a p electrode and an n electrode; depositing a plurality of pairs of alternately stacked DBR reflecting layers; evaporating a Ti / Au seed layer on the surface of the epitaxial layer, and electroplating a thick Ni support layer on the seed layer; etching ane isolation groove to manufacture a chip array with a flip structure; etching a micron hexagonal pyramid coarsening structure on the N polar surface of the n-GaN layer; further etching to obtain a nanopillar coarsened structure; coating the graphical temporary substrate with a bonding layer, and selectively bonding with the surface of the n electrode; removing the Ni support layer, and respectively welding the p electrode and the n electrode to the target substrate; and removing the bonding layer to obtain the transferred chip.

Description

technical field [0001] The invention belongs to the technical field of semiconductor light-emitting diodes, and in particular relates to a micro-LED chip with a thin-film flip-chip structure transferred by an adhesive layer and a preparation method thereof. [0002] technical background [0003] Micro-LED has the advantages of high resolution, long life, small size, high brightness and low power consumption. It has important application value in the fields of high-resolution display, optical communication, micro-projector and wearable electronics. The focus of attention of technologically powerful countries. Thin-film flip-chip structure Micro-LEDs are flip-chip-bonded to target substrates with high thermal conductivity through metal bumps, and low-resistance p-type ohmic contact electrodes with high reflectivity are used to reflect the outgoing light of the active layer to avoid horizontal structures The light absorption phenomenon of the metal electrode on the top of the M...

AI Technical Summary

Problems solved by technology

The emission wavelength of a typical blue LED chip is about 450nm. Due to the high refractive index of the GaN material (about 2.5), when the light emitted from the active layer of the LED chip propagates at the GaN / air interface, the wavelength is shortened to about 180nm. At this time, the wavelength is much smaller than The size of the roughened structure, so the traditional roughening method limits the further improvement of the light extraction efficiency of the LED chip

[0005] In addition, the current removal of sapphire substrates mainly uses laser lift-off technology. The laser is incident on the interface between the substrate and the epitaxial layer from the side of the sapphire substrate. Large stress is caused, the spot area of ​​the laser is small, and it can only heat the local position, resulting in uneven heating of the epitaxial wafer during the peeling process, thus forming defects such as pitting and cracks on the epitaxial wafer, which will damage and reduce the Micro-LED device. photoelectric performance

[0006] In addition, the outgoing light of the traditional LED chip will be totally reflected at the interface of the side walls of the chip, and oscillate between the two side walls until it is absorbed by the chip and converted into heat energy, which greatly reduces the light extraction efficiency of the chip; and, the traditional LED In order to facilitate the lateral diffusion of current in the chip, a thick current blocking layer is often set up, but this will easily cause the ITO transparent conductive layer and metal electrodes deposited on the current blocking layer to be faulted at the sidewall of the current blocking layer, which will lead to LED The forward voltage of the chip increases sharply, which reduces the photoelectric performance of the LED chip

Images