What is Lithography in VLSI

What is Lithography in VLSI

A wide range of products like smart phones and electrical appliances are shrinking in size and becoming more useful, and they are already a part of our everyday life.

Nikon’s semiconductor lithography technology is helping to shape the progress of semiconductors (semiconductor integrated circuits), which are critical components of these devices. Highly complicated circuit designs etched on a photomask composed of a huge glass plate are reduced using ultra-high-performance lenses and exposed onto a silicon substrate known as a wafer in a semiconductor lithography system.

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What is Lithography in VLSI?

Generally, Lithography is a printing technique that involves putting  a greasy material into the image parts of a flat stone or metal plate so that the ink adheres to them, while the non-image areas are made ink-repellent. With respect to VLSI  process technology, the technique of transferring geometric patterns using  a mask to a thin layer of radiation-sensitive material (called resist) and covering the rest of  the surface of a semiconductor wafer is known as lithography. 

The fabrication of an integrated circuit (IC) in VLSI requires various processes performed on a semiconductor substrate (eg. Silicon) including physical and chemical processes. In general, the various processes are divided into three categories: film deposition, patterning, and semiconductor doping. Films of both conductors (polysilicon, aluminum, copper,etc.) used to connect and insulators (silicon dioxide, silicon nitride,etc) used to isolate transistors and their components. Selective doping of various regions of silicon changes the conductivity of the silicon with the application of voltage. By creating  these structures of  various components, we can build millions of transistors and wire them together to form the complex circuitry of modern microelectronic devices. Fundamentals to all of these processes is lithography.

To build complex structures that make up a billions of transistors and many wires connected, lithography and pattern transfer steps are repeated more times but more typically 20 to 30 times to make one complex circuit. 

What is Lithography in VLSI used for?

Lithography is the heart of the semiconductor production process. It is used to fabricate electrical devices by patterning specified forms of a thin layer on a hard substrate. The direct and monolithic integration of numerous layers on a wafer produces these devices. The most common  lithographic equipment used  for IC fabrication in VLSI  is optical Lithography, commonly known as photo lithography or UV lithography. It is a microfabrication technique for patterning thin films or the bulk of a substrate.The digital CAD output driver  drives a pattern generator that transfers the patterns directly to the photosensitive masks.These , Masks are typically made from glass covered with hard surface materials such as chromium or iron oxide.  A geometric design is transferred from a photomask to a light-sensitive chemical called “photoresist,” or simply “resist,” on the substrate using light.

Conclusion:

Lithography is a procedure that was created in 1796 that involves transferring patterns of desired designs onto a base substrate, usually using masks. The microelectronics industry has matured to the point that it can mass produce miniature products like integrated circuits and nano electro mechanical systems. The industry is always working to create better lithography processes in order to achieve this aim.
Learn more in detail with VLSI courses from the best VLSI training institute, Chipedge. Chipedge provides job oriented courses in Bangalore through online full time and weekend courses. Make sure to check their 

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