Introduction to VLSI Design

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Example: CMOS Inverter Layout

Drawing the N-Diffusion (Active)


Now we will start drawing our first transistor. which will be the NMOS transistor of the CMOS inverter. From the schematic, we know that this transistor has a channel width of 1.2u. The width of the transistor will correspond to the width of the active area. We will select the n-diffusion layer and draw a rectangular active area to define the transistor.

1. Select nactive layer from the LSW

nactive

2. From the Create menu in Virtuoso select Rectangle
( Create --> Rectangle )

Menu

3. Draw the box

You are now in rectangle mode. Select the first corner of rectangle in the layout window (you may select any point within the window but try to select a point close to the origin), click once, and then move the mouse cursor to the opposite corner. Using the information bar, draw a box that is 3.6u horizontal and 1.2u vertical. All units are in micrometers by default. To simplify the drawing, a grid of half a lambda is used, that is the cursor moves in 0.15u increments only.

Diffusion



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Last Updated by Ilhan Hatirnaz on 11/7/1998