Fabrication of Silicon based electronic devices

Electronics and semiconductor industry rely much on Silicon since it is very cheap and readily available. Silicon wafers are manufactured initially. Silicon oxidizes at room temperature in a normal atmosphere. As you increase the temperature, thickness of the oxide layer increases. By lithographic techniques, wafers are manufactured. In MEMS technology, optical lithography is employed. Here a photosensitive layer is spun onto the wafer. Then it is exposed to ultraviolet light through a mask. A developer is then used to remove photosensitive layer which leaves a pattern on the wafer. Etching is performed on these patterned wafers. Both dry and wet etching can be employed. Wet etching is isotropic. MEMS technology use plasma etching systems which enable pits to be fabricated with vertical walls. Silicon wafers are now doped by the method, either diffusion or ion implantation. Diffusion is a process in which the wafers are subjected to an atmosphere containing the desired dopant at a high temperature. In ion implantation, dopant ions are accelerated toward the wafers with sufficient energy. Next step is annealing- heating to high temperatures. Now thin film has to produce by chemical vapour deposition. Last stage is bonding and packaging which are used to protect against excessive movement. Bond should be mechanically strong and different techniques are used for this. Some of them are gluing, glass bonding, eutectic bonding, fusion bonding and anodic bonding.