LED epitaxial wafer growth process solutions

- Jun 05, 2017-

LED epitaxial wafer growth process solutions

Today, to explore the growth process of LED epitaxial wafers, early in the era of small circuit, each of the 6-chip epitaxial wafer produced thousands of chips, now sub-micron line width of the large VLSI, each 8? Can only complete one or two hundred large chips. The manufacture of epitaxial wafers is tens of billions, but it is the foundation of all electronics industries.


As long as the silicon column grows, it is necessary to place the silicon ore with a relatively high purity in the furnace and add the pre-set metal material so that the resulting silicon column has the required electrical properties and then all the substances Melt and then grow into a single crystal silicon column, the following will be all the crystal into a process to introduce the process:


Long crystal main program:


1, melt (MELtDown)


This process is placed in the quartz crucible in the massive polycrystalline silicon heating system above 1420 degrees Celsius above the melting temperature, the most important parameters of this stage for the crucible position and heat supply, if the use of more Large power to melt the complex silicon, quartz crucible life will be reduced, whereas the power is too low is the process of melting too long, affecting the overall capacity.


2, neck growth (Neck Growth)


When the temperature of the silicon melt is stabilized, the seed is gradually poured into the liquid, and then the seed is pulled up and the diameter is reduced to a constant (about 6 mm), maintaining this diameter and elongating 10-20 cm Elimination of dislocation within the seed crystal, this dislocation-free control is mainly to limit the spread to the growth of the neck.


3, crown growth (Crown Growth)


After long neck, slowly reduce the speed and temperature, so that the diameter of the neck gradually increased to the required size.


4, crystal growth (Body Growth)


The use of speed and temperature changes to adjust the delay to maintain a fixed diameter of the ingot, so the crucible must continue to rise to maintain a fixed level of the liquid, so the crucible reached the crystal bar and the surface of the radiant heat will gradually increase, This radiation heat source will cause the temperature gradient of the solid interface to gradually become smaller, so the growth rate in the crystal bar growth stage must be gradually reduced to avoid the phenomenon of crystal bar twist.


5, tail growth (Tail Growth)


When the crystal grows to a fixed (required) length, the diameter of the ingot must be gradually reduced until it is separated from the liquid surface, which avoids the occurrence of drift and slip caused by thermal stress.

Cutting:


Crystal bar grows after it can be cut into a piece, that is, epitaxial wafers. Chip, wafer, is the semiconductor component "chip or" chip substrate, from the elongated high-purity silicon element crystal column (Crystal Ingot), the cut of the circular sheet called the epitaxial wafer (epitaxial wafers) The


Epitaxy


Arsenic? Epitaxy according to the different process, can be divided into LPE (liquid phase epitaxy), MOCVD (organic metal gas phase epitaxy) and MBE (molecular beam epitaxy). LPE technology is low, mainly for the general light-emitting diodes, and MBE's technical level is high, easy to grow very thin epitaxy, and high purity, good flatness, but low production capacity, epitaxial growth rate SLOW. MOCVD in addition to high purity, good flatness, the production capacity and epitaxial growth rate is also faster than the MBE, so now mostly to MOCVD to produce.


The first step is to put the GaAs substrate into the expensive organic chemical vapor deposition furnace (also known as the epitaxial furnace), and then into the III, II metal elements of the alkyl compounds (methyl or ethyl compounds) vapor And a nonmetallic (V or VI element) hydride (or alkyl) gas, at a high temperature, a pyrolysis reaction takes place to produce a group III-V or II-VI compound deposited on the substrate to grow a layer A semiconductor semiconductor epitaxial layer having a thickness of only a few microns (1 mm = 1000 microns). GaAs films with epitaxial layers are also known as epitaxial wafers. Epitaxial chip processed by the chip, the power can be issued by the color is pure monochromatic light, such as red, yellow and so on. Different materials, different growth conditions and different epitaxial layer structure can change the luminous color and brightness. In fact, in a few microns thick epitaxial layer, the real light is only one hundred nanometer (1 micron = 1000 nm) thick quantum well structure.


Reaction: Ga (CH3) 3 PH3 = GaP3CH4


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