LED epitaxial film growth is the basic principle: add LED epitaxial wafers at a thermal temperature of the substrate to a suitable substrate (mainly sapphire and, SiC, Si), the gaseous substances controlled InGaAlP transported to the substrate surface, the growth of the specific single-crystal films. LED epitaxial wafer growth techniques currently used mainly metal organic chemical vapor deposition method.
LED wafer substrate material is a semiconductor lighting industrial technology development the cornerstone. Different substrate materials require different growth techniques LED epitaxial wafers, chip processing technology and device packaging technology, LED substrate material determines the line of semiconductor lighting technology.
LED wafer substrate material selection features:
1, structural characteristics, and epitaxial materials and substrates of the same or similar crystal structure, lattice constant mismatch is small, good crystallinity, defect density
2, interface characteristics, and is conducive to the nucleation and epitaxial materials and strong adhesion
3, chemical stability, in the epitaxial growth temperature and atmosphere, do not break down and corrosion
4, thermal properties, including good thermal conductivity and thermal mismatch of the small
5, good conductivity, can be made into the upper and lower structures
6, optical performance, the production of the light emitted by the device substrate absorb the
7, good mechanical properties, easy processing devices, including thinning, polishing and cutting, etc.
8, low prices.
9, large size, the general requirements of not less than 2 inches in diameter.
10, easy to get regular shape substrate (unless there are other special requirements), and extension of facilities similar to the substrate hole tray was not easy to form irregular shaped vortex that affect the epitaxial quality.
11, without affecting the extension of the premise of quality, LED substrate machinability as the follow-up chip and package to meet the processing requirements.
The choice of substrate to meet the above eleven is a very difficult. Thus, the present can only be changed through the epitaxial growth technology and device processing adjustments to adapt to different substrates of semiconductor light emitting device LED R & D and production.
LED epitaxial wafer technology
Substrate>> structure DESIGN "> buffer layer growth>> N-type GaN layer growth>> multiple quantum well light-emitting layer growth>> P-type GaN layer growth>> annealing>> test (ray fluorescence, X-ray)>> extension pieces
Wafer>> design, processing, mask>> Lithography>> ion etching>> N-type electrode (coating, annealing, etching)>> P-type electrode (coating, annealing, etching)>> Dicing >> chip sorting, grading
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