LED (Light Emitting Diode), a light-emitting diode (multi-finger LED backlight), is a solid-state semiconductor device that directly converts electricity into light. The heart of the LED is a semiconductor wafer. One end of the wafer is attached to a holder, one end is the negative pole, and the other end is connected to the positive pole of the power supply, so that the entire wafer is encapsulated by epoxy resin. The semiconductor wafer consists of three parts, one part is a P-type semiconductor, in which the hole dominates, and the other end is an N-type semiconductor, where it is mainly electron, and the middle is usually a quantum well of 1 to 5 cycles. When a current is applied to the wafer through a wire, electrons and holes are pushed into the vector sub-well. In the quantum well, the electrons recombine with the holes, and then the energy is emitted in the form of photons. This is the principle of LED illumination. The wavelength of light, which is the color of light, is determined by the material that forms the PN junction.
Process overviewLED (Light Emitting Diode), a light-emitting diode (LED), is a solid-state semiconductor device capable of converting electrical energy into visible light, which can directly convert electricity into light. The heart of the LED is a semiconductor wafer with one end attached to a holder, one end being the negative pole, and the other end connected to the positive pole of the power supply so that the entire wafer is encapsulated by epoxy. The semiconductor wafer consists of two parts, one part is a P-type semiconductor, in which the hole dominates, and the other end is an N-type semiconductor, which is mainly electrons here. But when the two semiconductors are connected, they form a "PN junction" between them. When a current is applied to the wafer through the wire, the electrons are pushed toward the P region. In the P region, electrons recombine with the holes, and then the energy is emitted in the form of photons. This is the principle of LED illumination. The wavelength of light, which is the color of light, is determined by the material that forms the PN junction. It is a display screen for displaying various information such as text, graphics, images, animations, quotes, videos, video signals, etc. by controlling the display mode of the semiconductor light-emitting diodes. Due to its easy control, low-voltage DC drive, rich color performance after combination, long service life, it is widely used in urban projects and large-screen display systems. The LED can be used as a display to display videos and pictures with varying colors under computer control. An LED is a semiconductor that converts electrical energy into visible light.
LED epitaxial film process:In the past ten years, in order to develop blue high-brightness light-emitting diodes, researchers from all over the world have devoted all their efforts. The commercialization of products such as blue and green LEDs and laser diodes LD all illustrate the potential of III-V elements. In the current commercial LED materials and their epitaxial technology, the red and green LED external extension technologies are mostly liquid phase epitaxial growth methods, while the yellow and orange light-emitting diodes are still grown by vapor phase epitaxial growth method. The material is mainly.
In general, the growth of GaN requires a high temperature to interrupt the NH bond of NH3. On the other hand, it is also known from the kinetic simulation that NH3 and MO Gas react to produce non-volatile by-products.
The LED epitaxial wafer process is as follows:
Substrate - Structural Design - Buffer Layer Growth - N-Type GaN Layer Growth - Multiple Quantum Well Luminescence Layer - P-Type GaN Layer Growth - Annealing - Detection (Photoluminescence, X-Ray) - Epitaxial Wafer
Epitaxial wafer - design, processing reticle - lithography - ion etching - N-type electrode (coating, annealing, etching) - P-type electrode (coating, annealing, etching) - dicing - chip sorting, grading
The details are as follows: Fix: Fix the single crystal silicon rod on the processing table. Slicing: A single crystal silicon rod was cut into thin silicon wafers with precise geometric dimensions. The silicon powder produced in this process is water-sprayed to produce wastewater and silicon slag. Annealing: After the double-station thermal oxidation furnace is purged with nitrogen, it is heated to 300-500 ° C by infrared, and the surface of the silicon wafer reacts with oxygen to form a silicon dioxide protective layer on the surface of the silicon wafer. Chamfering: The annealed silicon wafer is trimmed into a circular arc shape to prevent cracking of the edge of the silicon wafer and generation of lattice defects, and increase the flatness of the epitaxial layer and the photoresist layer. The silicon powder produced in this process is water-sprayed to produce wastewater and silicon slag. Split detection: To ensure the specification and quality of the silicon wafer, it is tested. Waste is produced here. Grinding: The use of grinding tablets to remove the saw marks and surface damage layers made by slicing and wheel grinding, effectively improving the curvature, flatness and parallelism of the single crystal silicon wafer to achieve a specification that can be processed by the polishing process. This process produces waste grinding tablets. Cleaning: The organic impurities on the surface of the silicon wafer are removed by the dissolution of the organic solvent in combination with the ultrasonic cleaning technique. This process produces organic waste gas and waste organic solvent. RCA cleaning: Removal of particulate matter and metal ions from the surface of the wafer by multiple cleaning. The specific process is as follows: SPM cleaning: S2 solution is prepared by using H2SO4 solution and H2O2 solution. The SPM solution has strong oxidizing ability. It can dissolve the metal and dissolve it in the cleaning solution, and oxidize the organic pollutants into CO2 and H2O. . Cleaning the silicon wafer with SPM removes organic contaminants and some metals from the surface of the silicon wafer. This process produces sulfuric acid mist and spent sulfuric acid. DHF cleaning: The natural oxide film on the surface of the silicon wafer is removed with a certain concentration of hydrofluoric acid, and the metal attached to the natural oxide film is also dissolved into the cleaning liquid, and DHF suppresses the formation of the oxide film. This process produces hydrogen fluoride and spent hydrofluoric acid. APM cleaning: APM solution consists of a certain proportion of NH4OH solution and H2O2 solution. The surface of the silicon wafer forms an oxide film (about 6 nm hydrophilic) due to the oxidation of H2O2. The oxide film is corroded by NH4OH, and oxidation occurs immediately after corrosion. Oxidation and corrosion are repeated, so that particles and metals adhering to the surface of the silicon wafer also fall into the cleaning liquid along with the etching layer. Ammonia gas and waste ammonia water are produced here. HPM cleaning: HPM consisting of a certain ratio of HCl solution and H2O2 solution to remove metal contaminants such as sodium, iron, magnesium and zinc on the silicon surface. This process produces hydrogen chloride and spent hydrochloric acid. DHF cleaning: removes the oxide film produced on the silicon surface in the previous process. Grinding test: The quality of the silicon wafer after grinding and RCA cleaning is detected. If it does not meet the requirements, the grinding and RCA cleaning are performed. Corrosion A/B: After mechanical processing such as slicing and grinding, the damaged layer formed by the processing stress on the surface of the wafer is usually removed by chemical etching. Corrosion A is acid corrosion. The damaged layer is removed by mixed acid solution to produce hydrogen fluoride, NOX and waste mixed acid; corrosion B is alkaline corrosion, and the damaged layer is removed with sodium hydroxide solution to produce waste alkali liquor. Some of the silicon wafers in this project use corrosion A and some use corrosion B. Sub-level monitoring: damage detection of the silicon wafer, and the damaged silicon wafer is re-corroded. Rough polishing: The abrasive layer is removed by a single abrasive, and the removal amount is generally 10-20 um. Here, a rough throw waste liquid is produced. Fine polishing: The use of a refiner to improve the micro-roughness of the surface of the wafer, generally less than 1 um, thus to a high flatness wafer. Produce fine polishing waste liquid. Inspection: Check if the silicon wafer meets the requirements, and if it does not, re-polish or RCA cleaning. Detection: Check if the surface of the silicon wafer is clean. If the surface is not clean, brush it up until it is clean.
Packaging: The single crystal silicon polished sheet is packaged.
Before the chip is made into a small chip, it is a relatively large epitaxial wafer. Therefore, the chip fabrication process has a fast cutting process, that is, the epitaxial wafer is cut into small chips. It should be a link in the LED production process.
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