Top 5 Reasons for Silicon Uses in Electronics as a Semiconductor Material

With the term ‘electronics’, there are many things you can associate, especially the electronic circuit board components like transistors, diodes, ICs and so on.  If you are completely aware of these components, you must be aware of the prevailing silicon uses in the manufacturing of these components as well.

What is Silicon?

Silicon is a semiconductor material with an atomic number of 14, located in the group 4 of the periodic table. Pure Amorphous silicon was first prepared by Jones Jacob Berzelius in 1824, whereas crystalline silicon was first prepared by Henry Etienne in 1854.

What are semiconductors?

Semiconductors are nothing but materials with insulating properties in pure form and conducting properties when doped or added with impurities. Semiconductors usually have a band gap (energy required for electrons to break free from covalent bond) between insulators (maximum band gap) and conductors (minimum band gap). The conduction or flow of charge in semiconductors is due to the movement of free electrons or holes.

If you are familiar with the periodic table, you must be aware of the groups in a periodic table. Semiconductor materials are usually present in the group 4 of periodic table or also present as a combination of group 3 and group 6, or as a combination of group 2 and group 4 as well. The most widely used semiconductors are Silicon, Germanium and Gallium-Arsenide.

So, what makes Silicon as the most preferred semiconductor material in electronics?

The following are the top most reasons:

1. Abundance of Silicon

The foremost and most prominent reason for silicon’s popularity as a material of choice is its abundance. Next in line with oxygen which is about 46% in the earth’s crust, Silicon forms about 28% of the earth’s crust. It is widely available in the form of sand (silica), and quartz.

2. Silicon Manufacturing

The silicon wafers that are used for the production of ICs and electronic components are manufactured using effective and economical techniques. Pure silicon or poly silicon is obtained by the following steps:

• Quartz is made to react with coke to produce metallurgical silicon in an electric furnace.
• The metallurgical silicon is then converted to trichlorosilane (TCS) in fluidized bed reactors.
• Subsequently, TCS is purified by distillation, and then decomposed onto hot silicon filaments in a reactor, along with hydrogen. Finally, the resultant is a poly-silicon rod.

The poly-silicon rod is then crystallized using Czochralski method to obtain silicon crystals or ingots. These ingots are finally cut into wafers using ID cutting or wire cutting methods.

All the above processes facilitate the achievement of required diameter, orientation, conductivity, doping concentration and oxygen concentration needed for the production of silicon wafers.

3. Chemical Properties

Chemical properties refer to those properties in regard to which the reaction of materials with others is defined. The chemical properties depend directly on the atomic structure of the element. Crystalline Silicon used mostly in electronics, consists of a diamond like structure. Each unit cell consists of 8 atoms in a bravais lattice arrangement. This makes pure silicon highly stable at room temperature when compared to other materials like Germanium.
Thus, pure silicon is least affected by water, acid or steam. Also, at higher temperature in a molten state, silicon easily forms oxides and nitrides and even alloys.

4. Silicon Structure

The physical properties of Silicon also contribute to its popularity and usage as a semiconductor material.

• Silicon possesses a moderate energy band gap of 1.12eV at 0 K. This makes silicon a stable element when compared to Germanium and reduces the chance of leakage current. The reverse current is in nano-amperes and is very low.
• Crystalline structure of Silicon consists of face centric cubic lattice structure with 34% packing density. This allows easy substitution of impurities’ atoms in the empty places of the lattice. In other words doping concentration is quite high, about 10^21atoms/cm^3.

This also enhances the possibility of adding impurities like oxygen as the interstitial atoms within the crystal lattice. This provides a strong mechanical strength to the wafers against different kinds of stresses like thermal, mechanical or gravitational.

• Forward voltage for silicon diodes is 0.7 V, which is higher when compare to Germanium diodes. This makes them more stable and enhances silicon uses as rectifiers.

5. Silicon Dioxide

The last but not the least reason for the huge popularity of silicon, is the ease with which it forms oxides. Silicon dioxide is the most widely used insulator in IC technology owing to its extremely stable chemical nature when compare to other oxides like Germanium, which is water soluble and decomposes at a temperature of 800 degree Celsius.

Silicon Dioxide can be grown thermally using oxygen over silicon wafers at higher temperature or deposited using Silane and Oxygen.

Silicon dioxide is used:

• In IC fabrication techniques like etching, diffusion, ion implantation, etc.
• In Dielectrics for the electronic devices.
• As an Ultrathin layer for MOS and CMOS devices. This has infact increased the wide popularity of CMOS devices with high input impedance.
• In 3D devices in MEMs technology.

So, these are the top most reasons for the increasing usage of silicon in electronics. We hope that by now you might have got a clear understanding and apt reasoning as to why silicon is used as a semiconductor material for developing electronics based projects. Here is a simple yet intriguing question for you: Why is Silicon not used in LEDs and photo diodes?

Photo Credits:

• Silicon Uses by thomasnet
• Silicon abundance in nature by cleanroom
• Silicon manufacturing by sunedisonsilicon
• Silicon structure by chemistryinamaterialworld
•  Silicon Dioxide by green-planet-solar-energy