What is a semiconductor?

What is a semiconductor?

According to the conductivity, all items in life can be approximately split into three categories: conductors, semiconductors, and also insulators.

This is well comprehended. Items are either conductive, not conductive, or a little conductive. This type of product is for physicists to play in a various area.

Too outright conductive and also non-conductive materials are not interesting, and the conductivity of points that alter under different situations is interesting.

Items are classified according to their electrical conductivity.

Insulators: conductivity is very low, in between 20-18S/ centimeters ~ 10-8S/ cm, such as merged silica and also glass.

Conductor: high conductivity, between 104S/cm ~ 106S/cm, such as aluminum, silver, and also various other metals.

Semiconductor: conductivity is in between insulators as well as conductors.

Common essential semiconductors in nature are silicon and also germanium. It is said that germanium-based semiconductors than silicon-based semiconductors were uncovered and also used earlier, however the natural advantage of silicon is economical! The common sand and crushed rock in nature include a huge amount of silicon.

Despite the fact that there is a lot of silica sand in nature, it has a lot of contaminations and also way too many problems to be used straight, as well as it needs to be fine-tuned.

How to refine? One word - burn!

As we found out in chemistry, a redox response is executed.

① SiC + SiO2 → Si+ SiO2 + CARBON MONOXIDE( gas).

② Si + 3HC → SiHCl3 + H2.

③ SiHCl3 + H2 → Si + 3HCl.

After three high-temperature chemical reactions, we have solid silicon, but it is polycrystalline silicon this time around.

What is polycrystalline silicon?

Like when we peel off an orange, there are several cloves in it, and also different cloves taste different, so we have to select the most effective tasting one as well as choose it to allow the cloves grow alone!

How to make a little solitary crystal mature alone?

Physicists are still extremely brilliant. They developed a way to expand single crystals, called the Tchaikovsky method, and probably, the technique is called hereafter researcher.

There is additionally an instinctive name in the sector called the Tila method!

Growing solitary crystals is to pull the smaller sized crystals upwards! After that the long ingots will certainly be reduced with a mechanical blade, cut into an item of the disc, and it comes to be a wafer.

This is how the wafers are created.

Although we obtain the wafer, currently, the electrochemical residential properties of single-crystal silicon are not yet, can not be utilized straight to do the chip. Designers then discover methods to modify the electrochemical buildings of single-crystal silicon.

How to transform single-crystal silicon?

First extensive understanding of the element silicon, in the periodic table, silicon in the 14th placement, the outer layer of the silicon atom has 4 electrons, specifically, and the surrounding 4 atoms share 4 pairs of electrons. The structure of this common electron pair is called covalent bonding; each electron set includes a covalent bond.

Unexpectedly someday, a physicist thought of an issue, if silicon does not share electrons with silicon, what would occur if other materials were added?

The physicist added arsenic eventually, and a wonder happened.

Arsenic has five electrons in its outer layer, four of which discover their method to the silicon object, and an additional electron is left alone as well as ends up being a hobo, strolling around. Since the electron has an electrical cost, it alters the conductivity of silicon.

Now, the arsenic atom gives another electron to silicon, so the arsenic atom is called the giver.

The adversely billed service providers boost after the silicon has even more totally free electrons, as well as silicon comes to be an n-type semiconductor.

Similarly, physicists wondered, given that they could add the electron-rich arsenic aspect, could they additionally add the electron-poor boron atom?

Since the outermost layer of the boron atom has just 3 electrons, one much less than silicon, the covalent bond that was initially two pairs of electrons currently ends up being just one set of electrons, with another vacant setting, and also comes to be a positively charged opening.

At this point, the silicon-based semiconductor is called a p-type semiconductor.

The various atoms contributed to the silicon single crystal develop the N-type semiconductor and also the P-type semiconductor.

When we have single-crystal silicon and also can figure out just how to oxidize the surface of the single-crystal silicon to silicon dioxide, silicon dioxide can be used as an insulator for numerous gadget frameworks or as a barrier layer for diffusion or ion injection throughout device manufacture.

For example, in the construction of a p-n junction, a silicon dioxide film can be utilized to specify the region of the crossway.

With the theoretical understanding of p- and also n-type semiconductors, it is possible to have fun with some complexity as well as customize the surface of the silicon dioxide to make the graphics we desire, such as drawing a feline, pulling a blossom, and so on. The means to transform the surface area of the wafer is lithography!

Lithography that does not make use of a premium lithography equipment? I heard that this devices is powerful ... How concerning the initial take a look at the principle of lithography.

With making use of a rewriter, spin-coating a layer of UV-sensitive products externally of the wafer is called a photoresist. Will take the wafer from the spin coating equipment after cooking between 80ºC ~ 100ºC to drive off the solvent in the photoresist and solidify the photoresist to strengthen the adhesion of the photoresist and wafer. Next off, a UV light source reveals the wafer through a formed mask plate. Then, buffered hydrofluoric acid is used as the acid etchant to get rid of the silicon dioxide surface area that is not secured by the photoresist. Ultimately, a chemical solvent or plasma is utilized to oxidize the removed photoresist.

After photolithography, the silicon surface is revealed to the outdoors, at which time physicists include various other elements to this silicon surface by different techniques, called ion injection.

Because after the shot of B or As ions, these ions are included in the silicon family members after transforming the silicon family members custom, the electrochemical residential or commercial properties of silicon are changed, and also the semiconductor is called an extrinsic semiconductor.

The joint developed by the contact in between a P-type semiconductor and an N-type semiconductor is called a p-n joint!

After the doping is completed, we require to locate a means to draw out the properties of this semiconductor, so the surface area of this semiconductor is metalized, ohmic contact, and adjoin are completed in the next metallization action, PVD or CVD can form the metal movie.

With the completion of metallization, the p-n junction prepares to work!