Semiconductor material preparation:
The foundation of an LED is a semiconductor material, often made from compounds like gallium arsenide (GaAs), gallium nitride (GaN), or other similar materials.
These materials are grown in layers on a substrate using techniques like Metalorganic Vapor Phase Epitaxy (MOVPE) or Molecular Beam Epitaxy (MBE). The choice of material and the specific growth process determine the colour (wavelength) of the emitted light.
Wafer fabrication
Once the semiconductor layers are grown, they form a wafer. This wafer contains numerous individual LED devices that will be later separated.
Additional layers, such as those for creating electrical contacts and improving light extraction, are added to the wafer through various deposition and lithography processes.
Patterning and etching
Photolithography is used to define the shapes and sizes of the individual LED devices on the wafer. A photoresist is applied to the wafer, exposed to UV light through a mask and then developed, leaving behind a pattern.
Etching processes remove material from areas not protected by the photoresist, creating the desired device structures.
Contact formation
Metal contacts are created on the semiconductor layers to allow electrical current to flow into the LED device. These contacts are made using techniques like electron beam evaporation or sputtering.
Die separation
After the LED devices are fully processed on the wafer, they need to be separated into individual chips, also known as "dies."
Various methods like mechanical sawing, laser cutting, or chemical etching can be used to carefully cut the wafer into individual LED chips.
Packaging
Once separated, the LED chips are mounted onto packages that provide mechanical support, thermal management and electrical connections.
The packaging process often includes attaching a lens or encapsulation material to protect the LED chip and shape the light output.
Testing and sorting
Each individual LED chip undergoes rigorous testing to ensure its quality and performance. Parameters such as brightness, colour accuracy and electrical characteristics are evaluated.
Chips that meet the required specifications are sorted into different bins based on their performance characteristics, allowing manufacturers to sell LEDs with different levels of quality.
Assembly into final products
The packaged LED chips can be integrated into various lighting products, such as light bulbs, lamps, fixtures and displays.
Depending on the application, additional components like heat sinks, optics and drivers may be integrated into the final product.
