Back-end Design Tools (Physical Design):Porting Designs to New Processes

Porting Designs to New Processes

Larry:

Pretty much. Maybe they'll add some features. Moving a design to a later process is called porting.

Some EDA tools help port (migrate) a chip design or cell library to a new process. Many processes are known as process shrinks, where only the feature size changes.

Suppose we go from, say, a 0.18-micron process to a 0.13-micron process. We shrink the smallest feature size (gate length). Most cell libraries are scaled to the smallest feature size. So every other transistor dimension is shrunk proportionally.

However, not all parameters (the resistances, capacitances, and other electrical properties) scale so nicely. The transistors and gates all have to be recharacterized to establish the new operating values.

Some EDA tools do most of the resizing and characterization automatically. They simultaneously ensure that the circuits meet all the design rules and constraints.

The automation of the resizing, recharacterizing and change control of process libraries reduces the manual work. An IC manufacturer or foundry may use several processes (e.g., 0.25, 0.18, 0.13 micron, etc.) at the same time. Some EDA companies specialize in the porting and maintenance of libraries.

Porting a design or library to an entirely new process is a more complex process. It may involve a new foundry, new process steps, or more layers—not just a shrink. The same EDA tools help with this migration and library development as well.

Analog circuits tend to use larger transistors than digital circuits. Digital circuit processes rapidly shrank below 1.0 micron (submicron). Processes below about 0.18 micron are referred to as deep submicron (DSM).

Nora:

So these ICs are always in a state of migration?

Larry:

The libraries are, more so than the chips. Well, Nora, that's about all I can tell you about the back-end design tools.

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