The lithography word is derived from the Greek words lithos (stone) and graphos (drawing). Lithography means "drawing with stone." Lithography is a printing method from a flat surface, and the image is marked on the surface using a greasy ink that is repelled by the surface. A flat stone, or metal plate, called a lithographic stone or plate, is used to transfer the image onto a surface or print from the surface for a wide variety of applications. Lithography is one of the main processes used in the manufacturing of integrated circuits (ICs). It is used to pattern the layers of components and interconnects on an IC. In the past, the industry used photolithography to pattern the ICs but recently, due to advances in technology, it was replaced by X-ray lithography.
If you’ve ever wondered how “lithography” gets its name, the answer is surprisingly straightforward. With lithography, a design is drawn on a flat stone or metal plate by applying a greasy substance called a “resist” to certain design parts. The resist is exposed to light, which causes the exposed portions of the plate to be etched away. Thus, “lithography” is a fancy way of saying “stone-printing.”
Lithography is a process used to produce printed circuit boards (PCBs) and integrated circuits (ICs). The photoresist is coated onto a wafer of silicon or other semiconductor material in the most common method. The wafer is exposed to light by a mask (a negative of the desired circuit pattern). The light pattern selectively exposes the photoresist, and the unhardened photoresist is washed away, typically with a solvent or and heated. The remaining resist forms the basis of the printed wiring board of the semiconductor device.
Radiation is used in many different ways in the semiconductor manufacturing process, including as a way to pattern features on the wafer. In the photo at left, optical lithography is used to create a part in a silicon wafer. This process involves exposing a pattern on the mask to light and then transferring it to the wafer using a light-sensitive material. The wafer is etched to eliminate the areas that are not protected by the mask pattern.
Lithography is an essential process in the production of microchips and integrated circuits. There are two main types of lithography: photolithography and electron beam lithography. Photolithography is used to produce the vast majority of current microchip designs. Electron beam lithography is used primarily when minimal features are required.
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