Stick diagram and Layout Diagram
A stick diagram is a diagrammatic representation of a chip layout that helps to abstract a model. Stick diagrams are used to convey the layer information with the help of a color code.
“A stick diagram is a cartoon of a layout!!!”
The designer draws a freehand sketch of a layout, using colored lines to represent the various process layers such as diffusion, metal, and polysilicon.
For example, in the case of nMOS design,
• Red color is used for n-diffusion
• Green for polysilicon
• Blue for metal
• Yellow for an implant, and black for contact areas.
Stick Diagrams Rules
- If the same layer crosses each other, it makes contact.
- If the different layers just cross, it doesn’t make contact but if contact has to be made, it must be in the form of a dark-shaded circle.
- If polysilicon crosses the n-type of diffusion, then the nMOS enhancement transistor is formed.
- Cross mark has to be used on Vdd and Vss rails in order to create n-well and p-well contact for PMOS devices and NMOS devices respectively.
- PMOS devices must be placed in the pull-up part(above the line) and NMOS devices in the pull-down part(below the line) in the CMOS design style.
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