Deep ultraviolet LED chip with vertical structure, manufacturing method and epitaxial structure

Abstract

The invention discloses a deep ultraviolet LED chip with a vertical structure, a manufacturing method and an epitaxial structure. The manufacturing method comprises the following steps: forming the epitaxial structure on a sapphire substrate, wherein the epitaxial structure is provided with a first surface and a second surface, and the second surface is connected with the sapphire substrate; dividing the epitaxial structure into a plurality of epitaxial units arranged in an array, and part of the sapphire substrate is exposed between the adjacent epitaxial units; forming an adhesion layer on the sapphire substrate exposed between the adjacent epitaxial units; bonding and fixing a second substrate above the first surface of the epitaxial structure; stripping the sapphire substrate by laser; and removing the adhesive layer. According to the manufacturing method, the epitaxial structure is divided into the plurality of epitaxial units which are arranged in an array, so that the problem that the epitaxial structure is seriously damaged due to strong impact generated at the moment of high-energy density laser stripping is solved.

Description

technical field [0001] The present application relates to the technical field of semiconductor manufacturing, and more specifically, to a deep ultraviolet LED chip with a vertical structure, a manufacturing method and an epitaxial structure. Background technique [0002] In related technologies, the quantum efficiency of deep ultraviolet LED (Light-Emitting Diode, light-emitting diode) chips is low. Secondly, in order to obtain a better ohmic contact effect for the P-type semiconductor layer, a layer of p-GaN layer needs to be grown on the P-type semiconductor layer as the contact layer. Using the p-AlGaN contact layer will lead to a significant increase in the voltage of the deep ultraviolet LED chip; third, as the Al composition in the quantum well increases, the light emitted by the deep ultraviolet LED chip is mainly in the TM mode (parallel to the light emitting surface), and the TM It is difficult for light to enter the escape cone of the light-emitting surface and ex...

AI Technical Summary

Problems solved by technology

The main reason for choosing sapphire material as the heterogeneous substrate for deep ultraviolet epitaxial growth is that other types of materials (such as AlN, GaN, SiC) that are lattice-matched with deep ultraviolet AlGaN epitaxial layers are expensive and absorb more deep ultraviolet light than sapphire. Large, so generally less used

However, there are still several disadvantages in the flip-chip deep ultraviolet LED chip prepared based on the sapphire substrate epitaxial growth technology: on the one hand, the difference in the refractive index between the sapphire substrate and the air has not yet reached the ideal light extraction efficiency. level, it is necessary to design complex reflectors to improve light extraction; on the other hand, due to the adverse impact of the thicker sapphire substrate on the chip scribing process, the productivity of invisible laser slicing and the yield of chip slitting are greatly reduced; More importantly, since the thermal conductivity of the flip-chip structure has not yet reached an ideal level, it will adversely affect the reliability of the deep ultraviolet LED chip

[0006] For deep ultraviolet LED chips with a vertical structure, the epitaxial layer is mainly composed of AlN or AlGaN with high Al composition. The corresponding luminescent wavelength of AlN material is about 200nm, so only lasers with shorter wavelengths can be used. For example, the 193nm ArF excimer laser can realize the separation of AlN material and sapphire substrate; at the same time, during the laser lift-off process, due to the high melting point and strong adhesion of the metal Al formed by the decomposition of AlN material, the epitaxial layer and the sapphire substrate are separated. It is easy to cause the epitaxial layer to crack when the bottom is separated

In other schemes, Al x Ga 1-x N / Al y Ga 1-y The N superlattice structure is used as a stripping sacrificial layer, and the sapphire substrate is peeled off by using a laser with a wavelength of 248nm or 266nm. The threshold energy range is about 1.0J / mm 2 (The stripped GaN material is only half of its energy, about 0.4-0.6J / mm 2 ), the strong impact generated at the moment of high-energy-density laser lift-off will cause serious damage to the epitaxial layer of the deep-ultraviolet LED chip, and the thick AlN layer used in the epitaxial layer of the deep-ultraviolet LED chip has a serious stress effect. Stripping the lattice will lead to serious chip failure.

If small laser spots are used for continuous stripping, due to the more significant lattice and thermal mismatch of sapphire-AlN-GaN materials, the stress phenomenon in this material system will be more serious. Fragmentation of the epitaxial layer of the deep ultraviolet LED chip will inevitably occur in the splicing area of ​​the unit, resulting in the failure of the entire device, and it is also impossible to obtain a complete unit chip with a larger size

[0007] In addition, for the reverse polarity vertical structure deep ultraviolet LED chip, after the sapphire substrate and the epitaxial structure are peeled off, it is necessary to form an N layer electrically connected to the n-AlGaN layer (N-type semiconductor layer) on the light exit surface. However, after the lift-off process, the N-polar n-AlGaN layer on the light-emitting surface has an ohmic contact effect that is worse than that of the Ga / Al polar n-AlGaN layer, and because the N electrode is located on the light-emitting surface In addition, in order to ensure the light output of the chip, the material of the N electrode is limited to a transparent conductive material, which is more difficult to prepare

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