The basic principle of LED epitaxial wafer growth before LED chip generation is: on a substrate substrate (mainly sapphire and SiC, Si) heated to a suitable temperature, the gaseous substance InGaAlP is controlled to be transported to the surface of the substrate for growth. A specific single crystal film is produced. At present, the LED epitaxial wafer growth technology mainly adopts the organic metal chemical vapor deposition (MOCVD) method.
MOCVD Metal-Organic Chemical Vapor Deposition (MOCVD), a new technology for preparing compound semiconductor single-film films proposed by Rockwell Corporation in 1968. This equipment integrates precision machinery, semiconductor materials, vacuum electronics, fluid mechanics, optics, chemistry, and computer multidisciplinary. It is a state-of-the-art optoelectronic special equipment with high degree of automation, high price, and high technology integration. It is mainly used for GaN ( The epitaxial growth of nitriding semiconductor materials and the fabrication of blue, green or ultraviolet light-emitting diode chips are among the most promising specialized devices in the optoelectronics industry.
The production process of LED epitaxial wafers in the production process of LED chips is complicated:
1. After the epitaxial wafer is finished, randomly select nine points for each epitaxial wafer to test. Good products meet the requirements, others are defective products (high voltage deviation, short wavelength or long wavelength, etc.).
2. The epitaxial wafer of the good product should be an electrode (P pole, N pole). Next, the epitaxial wafer is cut by laser, and then 100% bifurcation, and fully automated inspection according to different voltage, wavelength, and brightness to form an LED chip (square chip).
3. Finally, visual inspection is carried out to remove the defects or the wear of the electrodes. These are the latter crystals. At this time, there are chips on the blue film that do not meet the shipping requirements, and these become side pieces or pieces. Epitaxial wafers of defective products are generally not used for square chips, and they are directly used as electrodes (P pole, N pole), and do not need to be sorted. These are the LED wafers currently on the market.
The success of epitaxial wafer technology requires the following three conditions:
1. Accurate mastery of the equipment. MOVCD is important because of the high cost, maintenance intervals and the preparation of accessories.
2. Mastering the principle of epitaxy, the growth of materials requires three basic skills: physics, materials science and analytical techniques. To master these, the growth of materials can have certain capabilities.
3. Persevering experimental spirit, the extension results need to wait perseveringly, because in addition to the basic analysis, the observation and record of the results, the analysis of the results of LED chips, need patience and perseverance.
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