How are semiconductors fabricated?

How are semiconductors fabricated?

Subject: Science and tech

Section: Awareness in IT and computer

What are semiconductors?

• Semiconductors represent a distinct class of materials that possess some of the electrical properties of both conductors and insulators.
• Like a faucet can be used to control the flow of water, semiconductors can be used to control the flow of electric currents, and with exquisite precision.

 Semiconductor tech: What exactly is India going to manufacture?

• The most important type of a semiconductor is the transistor. 
• At the dawn of the era of modern electronics, the first integrated circuits featured four transistors. 
• Together, they controlled the flow of currents in such a way that the circuits could perform simple arithmetic operations.
• Today, we have single chips boasting billions of transistors.
• Fitting so many transistors on a tiny chip no bigger than a fingernail requires extreme precision and a microscopic eye for detail.
• For instance, the accuracy required is equivalent to dividing a strand of human hair into a thousand segments each of specific width, and further subdividing each segment into a hundred parts.
• This is why fabricating semiconductors involves cutting-edge technology and science.

How are semiconductors made?

• The process starts with an engineer carefully selecting a silicon wafer as the foundation on which the semiconductor will be built. A team puts silicon, sourced from sand, through a meticulous purification process to separate it from other substances, until they have an ultra-pure wafer with impurity levels as low as a few parts per billion. (This percentage is comparable to an error of merely 1 cm when measuring the earth’s diameter.)
• Next is the photolithography process – a crucial step that carves the circuit pattern on the wafer.
• The wafer is coated with a light-sensitive material called a photoresist.
• Then, a mask is held in front of the wafer and light is shined on it.
• The mask contains small gaps in the shape of the circuit pattern.
• The light passes through these gaps and erodes the underlying parts of the photoresist.
• As a result, the photoresist on the wafer ‘acquires’ the pattern of the transistor circuits.
• Following photolithography, engineers use chemical and/or physical techniques to remove the uncarved parts of the photoresist, leaving behind the circuit’s structure on the silicon substrate.
• Then they dope the semiconductor – i.e. deliberately add impurities to specific parts of the semiconductor to alter its electrical properties, and deposit thin layers of materials such as metals or insulators to the wafer’s surface to form electrical connections or insulate components.
• Then the resulting product is packaged – individual chips are separated, encapsulated, and tested to make sure they’re functional and reliable – and finally integrated into electronic devices.

What does the fabrication landscape look like?

• Each step in semiconductor fabrication demands ultra-high precision and harnesses a blend of diverse scientific principles.
• To achieve this, the High NA EUV machine made by the Dutch company ASML uses a cannon to shoot a 50-micrometer blob of liquid tin at 300 km/hr through a vacuum chamber, where laser beams blast it with enough energy to form a plasma that finally emits the requisite wavelength of radiation.
• India boasts a leading role in chip design centered in Bengaluru.

How do semiconductors benefit us?

• Smartphones and computers showcase the pinnacle of semiconductor technology but semiconductors influence nearly every facet of our lives.
• Semiconductors also power ‘smart’ air-conditioners’ ability to regulate the temperature as well as space telescopes’ ability to  capture both awe-inspiring and scientifically interesting images in the depths of the universe, and many other technologies in between