 photolithography, also termed optical lithography or uv lithography, is a process used in microfabrication to pattern parts of a thin film or the bulk of a substrate. it uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical "photoresist", or simply "resist," on the substrate. a series of chemical treatments then either engraves the exposure pattern into, or enables deposition of a new material in the desired pattern upon, the material underneath the photo resist. for example, in complex integrated circuits, a modern cmos wafer will go through the photolithographic cycle up to 50 times. photolithography shares some fundamental principles with photography in that the pattern in the etching resist is created by exposing it to light, either directly (without using a mask) or with a projected image using an optical mask. this procedure is comparable to a high precision version of the method used to make printed circuit boards. subsequent stages in the process have more in common with etching than with lithographic printing. it is used because it can create extremely small patterns (down to a few tens of nanometers in size), it affords exact control over the shape and size of the objects it creates, and because it can create patterns over an entire surface cost-effectively. its main disadvantages are that it requires a flat substrate to start with, it is not very effective at creating shapes that are not flat, and it can require extremely clean operating conditions. == history == the words 'photo', 'litho', and 'graphy' all have greek origins with the meanings 'light', 'stone' and 'writing'. as suggested by the name, lithography is a printing method where photo suggests the method uses the properties of light to create the prints. joseph nicephore niepce was one of the first people to produce a photograph using such properties. in 1826, niepce used bitumen of judea (a form of asphalt) on a pewter plate to create the image and then mixed lavender oil and minerals to keep the image in place. years later in 1935, louis minsk developed the first negative photoresist, which relied on the solubility of chemicals to determine what part of the surface would remain raised and what parts would dissolve away where the dissolved areas created the image. five years later, otto suess developed the positive photoresist, which worked in the opposite manner - all the remaining raised surfaces created the image. it wasn't until 1954, when louis plambeck jr. developed the dycryl polymeric letterpress plate, that the process of photo making quicker. .{{cite web | title=lithography | url=http://www.lib.u
Lithography_(microfabrication) Microtechnology