Introduction to VLSI Design

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Example: CMOS Inverter Layout

The Gate Poly


The second step is to draw the gate. We will use a vertical polysilicon rectangle to create the channel. Note that the length of the transistor channel will be determined by the width of this poly rectangle.

1. Select poly layer from the LSW

poly

2. From the menu Misc choose Ruler
( Misc --> Ruler )

menu

The ruler is a very handy function. In our case we need to draw the poly rectangle in the middle of the diffusion region. Furthermore, design rules tell us that poly must extend at least by 0.6u (2 Lambda) from edge of the diffusion . To pinpoint the location of the poly gate we can use two rulers. One ruler will be used to determine the horizontal distance of the poly gate from the diffusion edge, while a second ruler will show the minimum amount of poly extension outside the diffusion according to the design rules

3. Draw poly rectangle

poly

The starting point is pinpointed by two rulers. The rectangle function is used to draw a poly rectangle that is 0.6u horizontal and 2.4u vertical.



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Last Updated by Ilhan Hatirnaz on 11/7/1998