Question

What is the manufacturing process for InGaN diodes?

Answer 1

The manufacturing process of InGaN (diode) LEDs is quite complex, with epitaxy, microstructure control, and packaging heat dissipation being the core. Below is a clear and professional, but not intrusive, complete flow:

Typical Manufacturing Process of InGaN LED Diodes

1. Epitaxy – The Core Step in InGaN LED Manufacturing

Multi-layer structures are grown using MOCVD (Metal-Organic Chemical Vapor Deposition), typically deposited on sapphire (Al₂O₃) or SiC/GaN-on-Si substrates.

Typical structures include:

Low-temperature GaN buffer layer (improves lattice matching)

n-type GaN layer (usually Si-doped)

InGaN multiple quantum well (MQW) (emitting layer)

p-type GaN (Mg-doped)

Current spreading layer (e.g., p-GaN or transparent conductive layer TCE)

Epitaxy determines the light color, brightness, and crystal quality, making it the most valuable step.

2. Epitaxial Wafer Processing and Patterning (Optional)

To improve light extraction and reduce defects, the following can be performed:

PSS patterning of the sapphire substrate (improving light extraction efficiency)

Etching GaN to form a roughened structure (enhancing scattering)

ICP plasma etching to form p/n structure openings

3. Chip Fabrication

The epitaxial wafer is fabricated into an LED chip, including:

(1) Cleaning & Photolithography

Using photoresist to define electrodes and etching areas.

(2) Dry Etching (ICP-RIE)

Etching p-GaN and MQW to expose n-GaN for electrode formation.

(3) Transparent Electrode Layer (TCE) Deposition

Typically, ITO (Indium Tin Oxide) or Ni/Au thin layers are used to improve current spread and light extraction efficiency.

(4) Metal Electrode Deposition

p-side electrode

n-side electrode

Common materials: Ti/Al, Ni/Au, etc. (depending on contact characteristics).

(5) Annealing

Improves ohmic contact performance.

4. Wafer Thinning and Dicing

Epiaxial wafer backside grinding and thinning → laser dicing into individual LED chips.

5. Chip Packaging

Packaging determines heat dissipation, brightness, and reliability.

Common Packaging Forms:

SMD (2835/3030/5630)

COB (Chip on Board)

CSP (Flip Chip Package)

Flip-Chip (Flip Chip Process)

Emitter-on-Substrate (EOS)

Packaging steps generally include:

Die attach (silver paste or solder)

Gold wire bonding (or flip chip bonding)

Adding phosphor (for white light)

Pouring silicone (transparent or diffused)

Molding, testing, and binning

6. Finished LED Testing and Binning

By:

Brightness (lm/W)

Color temperature / Wavelength

Chromaticity coordinates

Voltage (VF)

Strict binning is performed to ensure consistency.

In summary,

the core of InGaN LED manufacturing is MOCVD epitaxial growth + chip microstructure etching + precision packaging and segmentation, which is currently the mainstream process system for blue and green LEDs.

Answer 2

The fabrication process of InGaN diodes involves multiple precision steps, primarily based on the gallium nitride (GaN) material system. Its core lies in forming InGaN/GaN multiple quantum well (MQW) structures through heteroepitaxial growth technology to achieve high-efficiency light emission.

The following is an overview of the key process flows:

1. Material Preparation and Substrate Selection: Sapphire or silicon substrates are typically used, and gallium nitride-based materials are grown via metal-organic chemical vapor deposition (MOCVD).

A buffer layer, an n-type GaN layer, an InGaN/GaN multiple quantum well (active region), and a p-type GaN layer are sequentially grown on the substrate.

2. Photolithography and Etching: Photolithography techniques are used to define the device pattern, such as electron beam lithography to create nanopore arrays to enhance light extraction efficiency.

Inductively Coupled Plasma (ICP) etching or wet etching (such as potassium hydroxide solution) is used to form mesa structures and remove etching damage.

3. Electrode Fabrication

A transparent conductive layer (e.g., indium tin oxide, ITO) is deposited on the p-type layer as the p-electrode, and a metal electrode (e.g., Cr/Pt/Au) is fabricated on the n-type layer.

The electrode and lead are connected via vacuum welding or metallization.

4. Packaging and Testing

A protective adhesive is applied and the chip is sealed to prevent environmental corrosion.

Parameters such as breakdown voltage, leakage current, and luminous efficiency are tested to ensure device performance meets standards.

Technical Challenges and Optimization

Light Extraction Efficiency: Reduce total internal reflection and improve external quantum efficiency through nanopore arrays or photonic crystal structures.

Doping Uniformity: Precisely control temperature and doping concentration to optimize carrier injection efficiency.

Material Compatibility: Explore alternative materials such as p-type ZnO to improve hole injection performance.

Summary

The fabrication of InGaN diodes combines common semiconductor process technologies (such as photolithography and etching) with the unique characteristics of GaN-based materials. Its core lies in achieving high-efficiency light emission through epitaxial growth and structural design. Current technology has enabled the commercialization of blue/green LEDs, but the stability of red LEDs and electronic components still needs further optimization.