Full-custom design is a methodology for designing
integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
s by specifying the layout of each individual
transistor
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...
and the interconnections between them. Alternatives to full-custom design include various forms of semi-custom design, such as the repetition of small transistor subcircuits;
[{{cite book , title = The VLSI handbook , author = Rajneesh kaswan , publisher = CRC Press , year = 1999 , isbn = 0-8493-8593-8 , url = https://books.google.com/books?id=0r5LihlMogkC&q=%22full+custom+design%22&pg=PT853 ] one such methodology is the use of
standard cell libraries (standard cell libraries are themselves designed using full-custom design techniques).
Full-custom design potentially maximizes the performance of the chip, and minimizes its area, but is extremely labor-intensive to implement. Full-custom design is limited to ICs that are to be fabricated in extremely high volumes, notably certain
microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...
s and a small number of
ASICs.
As of 2008 the main factor affecting the design and production of ASICs was the high cost of
mask set
A photomask is an opaque plate with holes or transparencies that allow light to shine through in a defined pattern. They are commonly used in photolithography and the production of integrated circuits (ICs or "chips") in particular. Masks are used ...
s (number of which is depending on the number of IC layers) and the requisite
EDA EDA or Eda may refer to:
Computing
* Electronic design automation
* Enterprise Desktop Alliance, a computer technology consortium
* Enterprise digital assistant
* Estimation of distribution algorithm
* Event-driven architecture
* Exploratory ...
design tools. The mask sets are required in order to transfer the ASIC designs onto the
wafer
A wafer is a crisp, often sweet, very thin, flat, light and dry biscuit, often used to decorate ice cream, and also used as a garnish on some sweet dishes. Wafers can also be made into cookies with cream flavoring sandwiched between them. They ...
.
See also
*
Electronics design flow
References
Integrated circuits