What Is Lithography?

by:Rhino     2020-06-01
If you search for its definition online, most of the information you can find explain that it has something to do with artwork particularly the 'method for printing using a stone or a metal plate with a completely smooth surface'. However, in the semiconductor industry, it is a process that is used for device fabrication, a methodology that transfers a pattern from a photomask (also known as reticle) to the surface of a substrate, which is very useful for the production of electronic components such as integrated circuits. There are a number of steps involved in the lithography process for semiconductor production. These are the following: The imposition of structure on a beam - the lithographer imposes structure on a beam of light, by passing it through a 'mask' and this is followed by projecting the image onto a silicon wafer coated with a thin layer of material known as resist. The chemical transformation - the resist covering the substrate undergoes a chemical transformation when exposed to light, a process that alters the solubility of the material and this alteration makes the latent pattern image into a patterned chemical stencil after the application of an appropriate solvent. The deposition - this can be a process where the substrate is placed inside a reactor, to which a number of gases are supplied, which create a chemical reaction, producing a solid material with condenses on all the surfaces inside the reactor. The etching - a process that chemically removes layers from the surface of a substrate; this process is needed to pattern deposited layers - removing the unwanted, leaving behind only the desired traces or patterns. What is photolithography? Many steps in the fabrication process of semiconductor devices should only affect specific sections or areas of a substrate and this is accomplished with the help of photolithography, a process that uses a light-sensitive material called photoresist to create a specific pattern on the surface of a substrate. Some benefits of photolithography: Can transfer the pattern to the substrate very quickly Allows transfer of pattern or shapes that are created using CAD software to the substrate It allows you to fabricate many devices at once, which is very useful particularly in the production of very complex circuits in a short period time. It is highly-efficient and cost-effective while producing even very small pattern in a substrate. Can control the exact size and shape of the entire substrate.
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