LED epitaxial wafer and quality identification method

LED epitaxial wafers and quality identification methods The production process of epitaxial wafers is very complicated, and the inspection process is also more complicated. The basic method is to randomly select nine points for each epitaxial wafer for testing. The deviation is large, the wavelength is too short or too long, etc.). Good-quality epitaxial wafers will start to make electrodes (P pole, N pole), and then use laser to cut the epitaxial wafer, then *** sorting, according to different voltage, wavelength, brightness for fully automated sorting, that is, forming led chip (square chip). Then we need to conduct a visual inspection to sort out the defective or worn electrodes. These are the scattered crystals in the back. At this time, if there is a chip on the blue film that does not meet the normal shipping requirements, it will naturally become a side piece or a **. The epitaxial wafers of poor products (mainly because some parameters do not meet the requirements) are not used to make square wafers, but directly make electrodes (P pole, N pole), and do not perform sub-inspection, which is the LED circle on the market. Slices (there are also good things, such as square slices, etc.). 'Semiconductor manufacturers mainly use polished Si wafers (PW) and epitaxial Si wafers as raw materials for ICs. Epitaxial wafers began to be used in the early 2000s, which have certain electrical characteristics that standard PWs do not have and eliminate many surface/near-surface defects introduced during crystal growth and subsequent wafer processing.　　 Historically, epitaxial wafers were produced by Si wafer manufacturers and used for their own use. The amount used in ICs was not large. It required a thin single crystal Si layer to be deposited on the surface of the single crystal Si wafer. Generally, the thickness of the epitaxial layer is ~μm, and the thickness of the substrate Si is μm (mm diameter piece and μm (mm piece). 　　Epitaxial deposition can process multiple pieces at a time (simultaneously) or a single piece. Single piece reactors can be used. Produce the best quality epitaxial layer (good thickness, resistivity uniformity, fewer defects); this epitaxial wafer is used for the production of mm 'frontier' products and all important mm products.