There's a lot of talk about sand and glass becoming Silicon Wafers for use in semiconductor-based integrated circuits (ICs) and solar cells. But this kind of thinking only makes a lengthy and incredibly complicated process seem overly simple. Let's try to shed some light on the process without getting too geeky about it.
One of the best things about producing this wafer is that there is no shortage of raw material. Silicon (Si) is the 2nd most abundantly found element on earth after Oxygen. The duo combine into SiO2 (Silica) to make up a big part of the earth's crust. If there's a glint or glitter in the sand, then that will likely be Silica.
More relevant is the fact that monocrystalline Si turns into a stable electricity conducting material if certain dopants (impurities) are introduced into the crystal structure. The first stage is choosing silica rich sand and processing it to extract and make pure polysilicon chunks. This is done using chemical reactions, and the chunks are often supplied to wafer manufacturers by other producers.
These chunks are the raw material for the crystal pulling stage of the process. They are put into a CZ furnace along with a small amount of dopant like Boron, Antimony, Arsenic and Phosphorus. After the mix turns a melt under the 1420 degree Celsius heat, dissolved oxygen is introduced. To get a well rounded ingot, a seed crystal is lowered into the melt and rotated while it is extracted.
The ingot obtained has the same crystal structure as the seed, but it is not perfectly round and is oversized. It has to be grinded into a specific diameter and shape, and then given a flat or notched to indicate orientation. This is finally where the silicon wafers are created by slicing the ingot using ID (inside diameter) saws.
Even now, this is a rough product much thicker than required and it has saw cuts and other defects. Edge grinding provides rounded edges and makes the wafer more durable. Lapping at this point is used to make it thinner and get rid of the saw marks and any other defects on the front and back of the wafer.
Then the wafer gets polished and cleaned and is finally sent for quality control checks. QA tests in this case cannot be done by workers sitting around measuring the silicon wafers. It needs sophisticated machines that can test not only thickness, but also the total thickness variation (TTV) and other specified parameters like resistivity.
One of the best things about producing this wafer is that there is no shortage of raw material. Silicon (Si) is the 2nd most abundantly found element on earth after Oxygen. The duo combine into SiO2 (Silica) to make up a big part of the earth's crust. If there's a glint or glitter in the sand, then that will likely be Silica.
More relevant is the fact that monocrystalline Si turns into a stable electricity conducting material if certain dopants (impurities) are introduced into the crystal structure. The first stage is choosing silica rich sand and processing it to extract and make pure polysilicon chunks. This is done using chemical reactions, and the chunks are often supplied to wafer manufacturers by other producers.
These chunks are the raw material for the crystal pulling stage of the process. They are put into a CZ furnace along with a small amount of dopant like Boron, Antimony, Arsenic and Phosphorus. After the mix turns a melt under the 1420 degree Celsius heat, dissolved oxygen is introduced. To get a well rounded ingot, a seed crystal is lowered into the melt and rotated while it is extracted.
The ingot obtained has the same crystal structure as the seed, but it is not perfectly round and is oversized. It has to be grinded into a specific diameter and shape, and then given a flat or notched to indicate orientation. This is finally where the silicon wafers are created by slicing the ingot using ID (inside diameter) saws.
Even now, this is a rough product much thicker than required and it has saw cuts and other defects. Edge grinding provides rounded edges and makes the wafer more durable. Lapping at this point is used to make it thinner and get rid of the saw marks and any other defects on the front and back of the wafer.
Then the wafer gets polished and cleaned and is finally sent for quality control checks. QA tests in this case cannot be done by workers sitting around measuring the silicon wafers. It needs sophisticated machines that can test not only thickness, but also the total thickness variation (TTV) and other specified parameters like resistivity.
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