The growth process of LED epitaxial wafers. In the early days of small integrated circuits, thousands of chips were made on each 6? epitaxial wafer. Now, large-scale VLSI with sub-micron line width can only be completed on each 8? epitaxial wafer. One or two hundred large chips. Although the manufacture of epitaxial wafers requires tens of billions of investment, it is the foundation of all electronic industries.

For the growth of silicon crystal pillars, firstly, silicon ore with a relatively high purity needs to be put into the furnace, and pre-set metal substances are added to make the generated silicon crystal pillars have the required electrical properties, and then all the materials need to be mixed After melting, it grows into a single crystal silicon crystal pillar. The following will introduce all the crystal pillar growth processes:

The main program of crystal growth:

1. Melt (MELtDown)

In this process, the bulk polycrystalline silicon placed in the quartz crucible is heated to a melting temperature higher than 1420 degrees Celsius. The most important parameters in this stage are the position of the crucible and the supply of heat. If the power is too high to melt the polycrystalline silicon, the life of the quartz crucible will be reduced. On the contrary, if the power is too low, the melting process will take too long and affect the overall production capacity.

2. Neck Growth

When the temperature of the silicon melt slurry is stable, gradually inject the crystal seed in the direction into the liquid, then pull the seed crystal upward, and reduce the diameter to a certain (about 6mm), maintain this diameter and lengthen it by 10-20cm, so that the To eliminate the dislocation in the seed crystal, the control of this zero dislocation (dislocation-free) is mainly to limit the dislocation to the growth of the neck.

3. Crown Growth

After lengthening the neck, slowly reduce the pulling speed and temperature to gradually increase the diameter of the neck to the desired size.

4. Body Growth

The adjustment of the pulling speed and the temperature change is used to maintain a fixed diameter of the crystal rod, so the crucible must be continuously raised to maintain a fixed liquid level height, so the radiant heat transmitted from the crucible to the crystal rod and the liquid level will gradually increase. This radiant heat source will cause the temperature gradient of the solid-state interface to gradually decrease, so the pulling speed in the growth stage of the ingot must be gradually reduced to avoid the phenomenon of ingot distortion.

5. Tail Growth

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

Cutting:

After the ingot is grown, it can be cut into pieces, that is, epitaxial wafers. Chips, wafers, are the substrates of semiconductor components “chips” or “chips. From the high-purity silicon crystal column (Crystal Ingot) grown by stretching, the round slices cut are called epitaxial wafers (epitaxial wafers). .

Epitaxy:

Arsenic epitaxy can be divided into LPE (liquid phase epitaxy), MOCVD (organic metal vapor phase epitaxy) and MBE (molecular beam epitaxy) depending on the process. LPE has a relatively low technology and is mainly used for general light-emitting diodes, while MBE has a higher technology level and is easy to grow extremely thin epitaxy, with high purity and good flatness, but low mass production capacity and epitaxy growth rate slow. In addition to high purity and good flatness, MOCVD is also faster in mass production capacity and epitaxial growth rate than MBE, so it is now mostly produced by MOCVD.

The process is first to put the GaAs substrate into an expensive organic chemical vapor deposition furnace (simple MOCVD, also known as epitaxial furnace), and then pass through the alkyl compound (methyl or ethylate) vapor of III and II metal elements. With non-metal (V or VI group elements) hydride (or alkyl) gas, at high temperature, a pyrolysis reaction occurs to generate III-V or II-VI group compounds deposited on the substrate to grow a layer A compound semiconductor epitaxial layer with a thickness of only a few microns (1 mm = 1000 microns). A GaAs wafer with an epitaxial layer is often called an epitaxial wafer. After the epitaxial wafer is processed by the chip, it can emit pure monochromatic light, such as red and yellow, when it is energized. Different materials, different growth conditions, and different epitaxial layer structures can change the color and brightness of the emission. In fact, in an epitaxial layer with a thickness of several micrometers, only the quantum well structure with a thickness of several hundred nanometers (1 micrometer = 1000 nanometers) is really luminous.

Reaction formula: Ga(CH3)3 PH3= GaP3CH4