nota Integrated Circuit Layout

INTEGRATED CIRCUIT LAYOUT

DEFINITION:

Integrated circuit layout, also known IC layout, IC mask layout, or mask design, is the representation of an integrated circuit in terms of planar geometric shapes which correspond to the patterns of metal, oxide, or semiconductor layers that make up the components of the integrated circuit

FUNCTION

• To determine the number of connection layers and floor plans of the components on the wafer.
• To produce the patterns of the masks needed for integrated circuit fabrication process.

TYPES OF LAYOUT

1. Stick Diagram

• A rough sketch of lines/sticks of different colours showing all the different layers of the design.
• The diagram is sketched without any rule and can be designed in a short period of time.

2. Actual Layout

• A true picture of how the composition and size of components to be produced in the IC.
• The exact composition of components according to the size specified by the design rules and take a long time to be designed.

STICK DIAGRAM

• A stick diagram is a cartoon of a layout.
• Does show all components/vias (except possibly tub ties), relative placement.
• Does not show exact placement, transistor sizes, wire lengths, wire widths, tub boundaries.

SIGNIFICANCE OF LAYOUT DESIGN

• IC layout is a way of communication between circuit designer and process engineer.
• It represents the tolerance that will guarantee successful IC fabrication and correct circuit operation.
• Circuit layout is required in generating masks for IC fabrication process.

DESIGN RULES

i) Lambda (λ ) unit

• can define design rules in terms of lambdas.
• can easily be scaled to different fabrication process as fabrication technology advances.
• 1λ = 1/2 minimum feature size,
• e.g, in 0. 6μm process, 1λ=0.3μm.

ii) Micron unit

• 1 micron = 1µm = 1x10^-6 m
• Technology size @ feature size is mentioned in micron unit, e.g. feature size of 0.5 micron implies that the distance between the source and drain is 0.5µm
• A single strand of hair usually has a diameter of 20 to 180µm.