4.8 Integrated circuit manufacturing: bird's eye view

It will no doubt be helpful if we also take a plane or "bird's eye" view of what this circuit looks like aswell. There are, in fact, some interesting things we can gain by looking at some of them.

We have been looking at the development of the circuit from a cross-sectional point of view, watching theformation of the various levels which make up the finished CMOS inverter. This is, in fact, not the way a circuit designer looksat things. A circuit designer sees things from above, and only worries about the placement of transistors, and how they will beconnected together. In fact, the only factor in the actual design of the layout engineer has any choice on is thetransistor width, W. All other parameters are decided upon beforehand by the process engineer. So what does the layoutengineer see? We start with the n- implant to make the n-tank, as shown in . (You should go back and follow along with the cross-sectional views of the process, aswe review looking at things from the top.)