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CN-115377268-B - GaAs-based flip-chip Mini LED chip and preparation method thereof

CN115377268BCN 115377268 BCN115377268 BCN 115377268BCN-115377268-B

Abstract

The invention relates to a GaAs-based flip-chip Mini LED chip and a preparation method thereof. The chip comprises a transparent substrate, a bonding layer, a P current expansion layer and a P ohmic layer which are sequentially arranged from bottom to top, wherein a table top is arranged on the P ohmic layer, the table top sequentially comprises a P wave guide layer, a luminous layer, an N wave guide layer, an N current expansion layer, an N buffer layer and an N ohmic layer from bottom to top, a P electrode is arranged on the P ohmic layer below the table top, an N electrode is arranged on the N ohmic layer on the table top, and electrode pads are arranged right above the P electrode and the N electrode. The solder tin required in the packaging production is combined with the electrode structure through the electrode pad, so that the chip-substrate interconnection is realized without the need of dispensing solder paste on the substrate, the modularized production of the packaged chip is facilitated, and the problems of low chip-substrate welding force, high thermal expansion coefficient, troublesome manufacturing and high production cost in the chip packaging are effectively solved.

Inventors

  • TAN LILONG
  • WU XIANGLONG
  • YAN BAOHUA
  • WANG CHENGXIN

Assignees

  • 山东浪潮华光光电子股份有限公司

Dates

Publication Date
20260505
Application Date
20210519

Claims (8)

  1. 1. The GaAs-based flip-chip Mini LED chip is characterized by comprising a transparent substrate, a bonding layer, a P current expansion layer and a P ohmic layer which are sequentially arranged from bottom to top, wherein a table top is arranged on the P ohmic layer, the table top sequentially comprises a P waveguide layer, a light-emitting layer, an N waveguide layer, an N current expansion layer, an N buffer layer and an N ohmic layer from bottom to top, a P electrode is arranged on the P ohmic layer under the table top, an N electrode is arranged on the N ohmic layer on the table top, and electrode pads are respectively arranged right above the P electrode and the N electrode; The electrode pad structure is Ti/Al/Ni/Pt/Sn, ti/Al/Ti/Pt/Ni/Pt/Sn (1-x-y) Ag x Cu y or Ti/Al/Ti/Pt/Ni/Pt/Sn/In,0.5< X <2,0.1< Y <1; The P electrode structure is Au/AuBe/Au, the N electrode structure is Au/AuGeNi/Au/Pt/Au, the Ti/Al structure in the electrode pad is provided with N pairs, and N is a positive integer; the electrode pad is characterized In that the thickness of a Ti layer In a Ti/Al/Ni/Pt/Sn structure is 50-200nm, the thickness of an Al layer is 200-800nm, the thickness of an Ni layer is 300-1000nm, the thickness of an Sn layer is 6-10 mu m, the thickness of a Ti layer In a Ti/Al/Ti/Pt/Ni/Pt/Sn (1-x-y) Ag x Cu y structure of the electrode pad is 50-200nm, the thickness of an Al layer is 200-800nm, the thickness of an Ni layer is 300-1000nm, the thickness of an Sn (1-x-y) Ag x Cu y layer is 6-10 mu m, the thickness of a Ti layer In a Ti/Al/Ti/Pt/Ni/Pt/Sn/In structure of the electrode pad is 50-200nm, the thickness of an Al layer is 200-800nm, the thickness of an Ni layer is 300-1000nm, the thickness of an Sn layer is 2-4 mu m, and the thickness of an In layer is 3-6 mu m; the preparation method of the GaAs-based flip-chip Mini LED chip comprises the following steps: (1) Sequentially growing an corrosion stop layer, an N ohmic layer, an N buffer layer, an N current expansion layer, an N waveguide layer, a light-emitting layer, a P waveguide layer, a P ohmic layer and a P current expansion layer on a temporary substrate by adopting an MOCVD method to obtain an epitaxial wafer; (2) Coarsening the P current expansion layer to obtain a coarsened surface of the P current expansion layer; (3) Depositing a bonding layer on the coarsened surface of the P current expansion layer, and then polishing the surface of the bonding layer to obtain a polished surface of the bonding layer; (4) Activating the polished surfaces of the transparent substrate and the bonding layer, and then carrying out bonding treatment to obtain an epitaxial wafer bonded with the transparent substrate; (5) Removing the temporary substrate and the corrosion stop layer from the epitaxial wafer obtained in the step (4); (6) Photoetching a mask on the surface of the epitaxial wafer obtained in the step (5), and etching by utilizing an ICP dry method until the P ohmic layer is exposed to form a table top; (7) Manufacturing a P electrode on the P ohmic layer below the mesa, and manufacturing an N electrode on the N ohmic layer on the mesa; (8) Etching a cutting channel between the table tops of the epitaxial wafers obtained in the step (7) by utilizing ICP, and then depositing a protective layer on the surfaces of the epitaxial wafers; (9) Etching the protective layer right above the P electrode and the N electrode to form a P conductive hole and an N conductive hole; (10) P electrode pad and N electrode pad are respectively manufactured above the P conductive hole and the N conductive hole (11) And (3) thinning, invisible cutting, splitting, testing, optical detection and sorting the epitaxial wafer obtained in the step (10) to obtain the GaAs-based flip-chip Mini LED chip.
  2. 2. The GaAs based flip-chip Mini LED chip of claim 1, wherein in step (2), the roughening treatment is wet etching, the roughening time is 30-90s, and the roughening temperature is 20-30 ℃.
  3. 3. The GaAs based flip-chip Mini LED chip of claim 1, wherein in step (2), a mixed solution of sulfuric acid, water, iodine and hydrofluoric acid is used for roughening treatment, wherein in the mixed solution, 2000-3000mL of sulfuric acid, 3000-4000mL of water, 80-100g of iodine and 1500-2000mL of hydrofluoric acid are used.
  4. 4. The GaAs based flip chip Mini LED chip of claim 1, wherein in step (3), the bonding layer is a silicon dioxide layer with a thickness of 2-4 μm, the polishing is a CMP process, and the treated silicon dioxide layer is 0.8-1 μm.
  5. 5. The GaAs-based flip chip Mini LED chip of claim 1, wherein in the step (4), the activation is performed by adopting alkaline liquid medicine or acidic liquid medicine, the bonding temperature is 360-450 ℃, the bonding pressure is 8000-12000kg, the bonding time is 900-1200s, and the transparent substrate is a sapphire substrate.
  6. 6. The GaAs based flip-chip Mini LED chip of claim 5, wherein the mixed solution of hydrochloric acid and hydrogen peroxide is used for activation, and the mixed solution contains 4000-5000mL of hydrochloric acid and 2000-3000mL of hydrogen peroxide.
  7. 7. The GaAs-based flip-chip Mini LED chip of claim 1, wherein in step (5), a mixed solution of ammonia water, hydrogen peroxide and water is used to remove the temporary substrate and the etch stop layer of the bonded wafer, and the volume ratio of ammonia water, hydrogen peroxide and water in the mixed solution is 1:4:5.
  8. 8. The GaAs based flip-chip Mini LED chip of claim 1, wherein in step (9), the protective layer is a silicon dioxide layer.

Description

GaAs-based flip-chip Mini LED chip and preparation method thereof Technical Field The invention relates to a GaAs-based flip-chip Mini LED chip and a preparation method thereof, and belongs to the technical field of LED chip manufacturing. Background The Mini LED device is used as a novel display device, and has the advantages of low power consumption, high resolution, high contrast, high reliability, wide color gamut and the like, and has very wide application in the field of display screens. However, the low substrate replacement yield in the GaAs-based flip-chip Mini LED production process and low warehouse-in yield cause high price, so that the quick popularization of GaAs-based Mini LED products is severely restricted, the product yield is improved, the enhancement of light efficiency is always a subject actively explored by industry personnel, meanwhile, the packaging technology in the industry chain has a plurality of problems, such as chip welding, and the main technical scheme of the chip welding of the miniature flip-chip Mini LED is spot solder reflow soldering. However, the existing spot solder reflow soldering has the problems of weak welding force, high thermal expansion coefficient, troublesome preparation and the like caused by high void ratio, and researchers are always trying to improve the reflow soldering process and the solder paste composition to solve the problems. The Chinese patent document CN112242477A discloses an easy-to-weld flip Mini/Micro-LED chip, a preparation method and a packaging method thereof, wherein the chip comprises a substrate, a light-emitting structure arranged on the substrate, an electrode arranged on the light-emitting structure and a welding layer arranged on the electrode. The Mini/Micro-LED chip is easy to weld and package, and has high packaging efficiency, high yield and low cost. However, the existence of the common Sn alloy formed by the easy diffusion of solder tin and the electrode layer in the patent leads to the rapid decline and even falling off of the reflow soldering thrust of the chip electrode. The Chinese patent document CN112467007A provides a Mini LED chip and a manufacturing method thereof, wherein the Mini LED chip is positioned between a first type semiconductor layer and a first bonding electrode and is not connected with the first bonding electrode through a corresponding auxiliary extension electrode, namely, the auxiliary extension electrode is not manufactured on the exposed surface of the first type semiconductor layer at the electrode contact hollowed-out position, so that the problem of occupation area of the enlarged electrode contact hollowed-out area caused by the existence of the auxiliary extension electrode is avoided, the large area of a light-emitting area is ensured, and the light-emitting efficiency of the Mini LED chip is improved. The patent has the problems of poor current expansion, poor electrode coverage and easiness in fault, and influences the reliability in the subsequent use. In addition, because of lattice mismatch, overlarge dislocation defects and other problems, the GaAs-based LED cannot directly grow epitaxy on a sapphire substrate, and a substrate replacement process is required to be completed through wafer bonding, so that low substrate replacement yield is always a main problem faced in the industry. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a GaAs-based flip-chip Mini LED chip and a preparation method thereof. The invention combines the problems of troublesome solder paste welding in the middle stream package in the industrial chain, difficult high-precision lamination of the chip-solder paste-substrate, weak welding force of the chip-substrate, high thermal expansion coefficient and the like, and prepares the electrode pad on the Mini LED, thereby providing a novel method for effectively solving the problems in the package. The technical scheme of the invention is as follows: The GaAs-based flip-chip Mini LED chip comprises a transparent substrate, a bonding layer, a P current expansion layer and a P ohmic layer which are sequentially arranged from bottom to top, wherein a table top is arranged on the P ohmic layer, the table top sequentially comprises a P waveguide layer, a light-emitting layer, an N waveguide layer, an N current expansion layer, an N buffer layer and an N ohmic layer from bottom to top, a P electrode is arranged on the P ohmic layer below the table top, an N electrode is arranged on the N ohmic layer on the table top, and electrode pads are respectively arranged right above the P electrode and the N electrode; The electrode pad structure is Ti/Al/Ni/Pt/Sn, ti/Al/Ti/Pt/Ni/Pt/Sn (1-x-y)AgxCuy or Ti/Al/Ti/Pt/Ni/Pt/Sn/In,0.5< X <2,0.1< Y <1. According to the invention, the P electrode structure is preferably Au/AuBe/Au, and the N electrode structure is preferably Au/AuGeNi/Au/Pt/Au. According to the invention, the Ti/Al structure in the elec