Silicon wafer manufacturing processes are roughly divided into crystal growth processes and wafer processing processes.
process
process
Polycrystalline silicon is put into a quartz crucible and heated and melted by a graphite heater under reduced pressure in an inert atmosphere.
After that, seed crystals are dipped into the surface of the melt, and silicon single-crystals are grown while controlling the pulling speed of the crystals and the temperature inside the furnace.
CZ method : Czochralski method
process
The single-crystal silicon ingot has a cylindrical shape as shown in the figure.
Crystals for φ300 mm wafers are very large, measuring 2 m in length and weighing over 300 kg.
process
The outer circumference of a single crystal silicon ingot is ground to a specified diameter.
A part of the periphery is processed to form grooves (notches) or planes (orientation flats) to indicate the crystal orientation.
The formed groove (notch).
After that, it is cut to the specified length before slicing.
process
The circumference of the monocrystalline ingot is ground down to a uniform diameter. Based on the resistivity desired by the customer, the ingot is then cut into slices of around 1mm thickness, using an inner-diameter saw or wire saw, to form the wafers.
process
To prevent chipping and cracking during the wafer fabrication process, the edge of the wafer is ground and chamfered in an arc shape with a diamond wheel.
process
The sliced wafers are polished by alumina abrasive in a lapping machine to the desired thickness, while improving the surface parallelism.
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Mechanical damage to the wafer surface resulting from the earlier steps is removed by chemical etching.
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The wafer surfaces are made perfectly flat and given a mirror finish by means of mechano-chemical polishing using colloidal silica.
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High-temperature heat treatment is performed in a vertical furnace to eliminate void defects generated during crystal growth.
At the same time, oxygen precipitates are formed inside the wafer.
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Wafers are physically and chemically cleaned using ultra-pure water and chemicals.
process
Numerous inspections are performed, to check flatness, particles, impurity concentration, specific resistance, etc.
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Wafers are packaged in a clean shipping case, and sealed in a special moisture-proof bag.