**3. Classification of lithographic techniques**

There are many techniques through which micro/nano patterning could be possible. They are,

	- **◦** Ion beam Lithography
	- **◦** Micro-contact printing
	- **◦** Nano-imprint lithography
	- **◦** Scanning Probe lithography

### **3.1. Photolithography – A conventional and classical method**

Lithography consists of patterning substrate by employing the interaction of beams of photons or particles with materials. Photolithography is widely used in the integrated circuits (ICs) manufacturing. The process of IC manufacturing consists of a series of 10-20 steps or more, called mask layers where layers of materials coated with resists are patterned then transferred onto the material layer.

A photolithography system consists of a light source, a mask, and an optical projection system. Photoresists are radiation sensitive materials that usually consist of a photo-sensitive com‐ pound, a polymeric backbone, and a solvent. Resists can be classified upon their solubility after exposure into: positive resists (solubility of exposed area increases) and negative resists (solubility of exposed area decreases). Fig. 1 shows the schematic of lithographic process in order to make the pattern on the desired substrate.
