Microchip Construction

The concepts behind microchip construction via photolithography are demonstrated by a simple laboratory experiment by using polymer chemistry. In this experiment, a glass microscope slide acts as the microchip. WE can pattern this "microchip" by layering negative photoresist on the slide using a solution containing monomer, crosslinker, photoinitiator, and dye. We then cover the photoresist with a photomask, which is the negative of a computer-generated image or text printed on transparency film, and illuminate it with UV light. The photoresist in the exposed area polymerizes into a polymer network with a shape dictated by the photomask. The versatility of this technique is exemplified by allowing each strip to fabricate virtually any shape

These regions include a variety of implants and windows in protective cover layers through which connections can be made to the bonding pads. A sequence of steps is required, together with a specific layout pattern, for each of these regions lithographic processes are used to perform these operations and are carried out in succession during circuit fabrication. The major steps in lithography are:
Fabrication of masks (or pattern generation); and Lithography is the technique of transferring the pattern on the mask to a layer of radiation sensitive material (resist) which, in turn, is used to transfer the pattern to the films or substrates through etching I processes. The radiation used may be optical, X-ray, electron beam (e-beam), or ion beam. Each technique involves a specialized

The driving force of diffusion is the concentration gradient. There is a wide range of diffusivities for the various dopant species, which depend on how easy the respective dopant impurity can move through the material. Diffusion is applied to anneal the crystal defects after ion implantation or to introduce dopant atoms into silicon from a chemical vapor source. In the last case the diffusion time and temperature determine the depth of dopant penetration. Diffusion is used to form the source, drain, and channel regions in a MOS transistor. But diffusion can also be an unwanted parasitic effect, because it takes place during all high temperature process