Most people have heard the term silicon wafer, but unless you are a science or Information Technology professional, you will be forgiven for not knowing what a silicon wafer is. This type of device is most common in the fields of IT, physics and chemistry and known to professionals such as physicists and chemists. The silicon wafer processing is an interesting one.
Technically, this device is a thin, circular disc used in the manufacture of integrated circuits and semiconductors. There are other types such as Gallium Arsenide (GaAs) and SOI, which is silicon on insulator. These types are used in electronics, which require careful manufacturing to ensure high levels of efficiency.
Although the device is tiny, the manufacturing process is tedious and complicated. It is comprised of several sequential processes that are repeated in order to complete photonic or electrical circuits. Examples of their use include the production of central processing units for computers, optical components of computers, LEDs, and radio frequency amplifiers. During fabrication, the appropriate electrical structures are placed within the wafers.
Extensive work precedes the production and several important steps are to be followed preceding the manufacture. In itself, silicon is a unique element, due to its capacity to conduct both electricity and heat in a way that is very controlled. It is otherwise known as a semiconductor. These wafers can become efficient materials in the electronic sphere when they undergo processes such as photolithography and fabrication.
In microelectronics, these wafers are used in creating microchips or integrated circuits. The manufacturer of chips takes great care of many processes such as selecting the most reliable supplier to ensure efficient devices. Top consumer electronics and information technology companies have used SOI wafers to produce their microprocessors. Solar energy technology also uses GaAs, silicon and SOI wafers to create solar cells.
Electrical engineers start the process by designing the circuits and defining the essential functions. Signals, voltages, outputs and inputs are specified. Special software is used to determine these specifications. It is then exported to programs that lay out the designs of the circuits. These programs are similar to those for computer-aided design. During this process, the layers of the wavers are defined.
Firstly, a perfect crystal should be produced from silicon. It must be submerged slowly into a vessel with molten sand. Afterwards, the ingot (cylinder shaped pure silicon) is carefully withdrawn. The ingot is then thinly sliced, using a diamond saw and the sliced sorted, according the thickness of each wafer.
The manufacturers see to defects that occur during the slicing process. If the silicon surface is damaged or cracked after slicing, this is removed using a process known as lapping. If crystal damage is removed, they use etching to do so.
The wafers are checked for flatness and thickness. During this step, they are checked for defects that occurred during the etching and lapping. An automated machine checks the thickness of each disk.
A layer of damage is created in the back by grinding it to approximately thirty-five microns. The wafer is then heated to a temperature of up to more than one thousand degrees Celsius for up to three hours. It is then cooled to below six hundred degrees Celsius.
Uneven surfaces of the wafers need to be polished to create a flat and smooth surface. A final qualification check is done during which the manufacturer ensures the smoothness and thickness. During this check, specifications of the consumer will also be ensured before the products will be ready to produce. The price of wafers is determined based on the thickness and quality.
The wafers are blank when started and then built up in clean rooms. Photosensitive resistance patters are photo masked onto the surface. They are measured in micrometers or fractions right at the beginning of the process; therefore, the density is increased during each step.
It is then exposed to UVB (short-wave) light. The areas that are unexposed are cleaned and etched away. Heated chemical vapors are then deposited onto the required areas and they are baked. The high heat permeates the vapors into the necessary areas. RF-driven sources of ions deposit 0+ or 02+ onto the zones in particular patterns.
The process is repeated several hundreds of times. During each step, the resolution of the circuits is greatly increased. The technology is constantly changing and with new technology comes denser packing of the features.
The semiconductor waves or chips are manufactured at foundry for companies, which sell the chips. The system of silicon wafer processing is an interesting one and when we think about all the ways in which it affects our lives, it is truly amazing.
Jessica entered the Semiconductor Manufacturing field in 1998 and is now the founder of Rogue Valley Microdevices in 2003. As Founder and CEO, Jessica has established the company as a world-class silicon wafer supplier and MEMS (MicroElectroMechanical Systems) Foundry Services.