The main purpose of LED chip manufacturing is to manufacture effective and reliable low-ohm contact electrodes, and to meet the relatively small voltage drop between contactable materials and provide pressure pads for bonding wires, while emitting as much light as possible. The film transition process generally uses the vacuum evaporation method, under 4Pa high vacuum, the material is melted by resistance heating or electron beam bombardment heating, and becomes metal vapor deposition on the surface of the semiconductor material under low pressure.
Generally used P-type contact metals include alloys such as AuBe and AuZn, and AuGeNi alloys are often used as contact metals on the N surface. The alloy layer formed after coating also needs to expose the light-emitting area as much as possible through the photolithography process, so that the remaining alloy layer can meet the requirements of effective and reliable low-ohm contact electrodes and welding wire pressure pads. After the photolithography process, an alloying process is required, and the alloying is usually carried out under the protection of H2 or N2. The time and temperature of alloying are usually determined according to the characteristics of the semiconductor material and the form of the alloy furnace. Of course, the chip electrode process such as blue and green is more complicated, and it is necessary to increase the growth of passivation film and plasma etching process.
In the LED chip manufacturing process, which processes have a more important impact on its photoelectric performance?
Generally speaking, after the completion of LED epitaxial production, its main electrical properties have been finalized, and chip manufacturing will not change its core nature, but inappropriate conditions in the coating and alloying process will cause some electrical parameters to be bad. For example, low or high alloying temperature will cause poor ohmic contact, which is the main reason for high forward voltage drop VF in chip manufacturing. After dicing, if some etching process is performed on the edge of the chip, it will be helpful to improve the reverse leakage of the chip. This is because after cutting with a diamond grinding wheel blade, there will be more debris powder remaining on the edge of the chip. If these stick to the PN junction of the LED chip, it will cause leakage and even breakdown. In addition, if the photoresist on the surface of the chip is not peeled off cleanly, it will cause difficulties and false soldering of the front bonding wires. If it is on the back, it will also cause a high voltage drop. In the process of chip production, the light intensity can be increased by roughening the surface and forming an inverted trapezoidal structure.
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