CMOS Fabrication Process

Very-large-scale integration (VLSI) Design is the subject that is being taught by every technical university all around the world on graduate or post graduate level. CMOS fabrication process is a very important and essential part of VLSI Design and students must understand this process.The well-established CMOS fabrication technology, requires both n-channel (nMOS) and p-channel (pMOS) transistors to be built on the same chip substrate. Special regions of semiconductor type opposite to the substrate type must be created to accommodate both nMOS and pMOS transistors. These regions are called wells or tubs. A p-well is created in an n-type substrate or, alternatively, an n- well is created in a p-type substrate. In the simple n-well CMOS fabrication technology presented, the nMOS transistor is created in the p-type substrate, and the pMOS transistor is created in the n-well, which is built-in into the p-type substrate. In the twin-tub CMOS technology, additional tubs of the same type as the substrate can also be created for device optimisation. Find the link below for simplified process sequence for the fabrication of CMOS integrated circuits.

1) http://www.youtube.com/watch?v=gBAKXvsaEiw

2) http://www.srmuniv.ac.in/sites/default/files/files/IIunit.pdf