Full custom
Encyclopedia
Full-custom design is a methodology for designing integrated circuit
s by specifying the layout of each individual transistor
and the interconnection
s between them. Alternatives to full-custom design include various forms of semi-custom design, such as the repetition of small transistor subcircuits; 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
s and a small number of ASIC
s.
The main factor affecting the design and production of ASICs is the high cost of mask set
s and the requisite EDA
design tools. The mask sets are required in order to transfer the ASIC designs onto the wafer
.
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
s by specifying the layout of each individual transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
and the interconnection
Interconnection
In telecommunications, interconnection is the physical linking of a carrier's network with equipment or facilities not belonging to that network...
s between them. Alternatives to full-custom design include various forms of semi-custom design, such as the repetition of small transistor subcircuits; 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
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
s and a small number of ASIC
ASIC
ASIC may refer to:* Application-specific integrated circuit, an integrated circuit developed for a particular use, as opposed to a customised general-purpose device.* ASIC programming language, a dialect of BASIC...
s.
The main factor affecting the design and production of ASICs is the high cost of mask set
Mask set
A mask set is a series of electronic data that define geometry for the photolithography steps of semiconductor fabrication. Each of the physical masks generated from this data is called a photomask....
s and the requisite EDA
Electronic design automation
Electronic design automation is a category of software tools for designing electronic systems such as printed circuit boards and integrated circuits...
design tools. The mask sets are required in order to transfer the ASIC designs onto the wafer
Wafer (electronics)
A wafer is a thin slice of semiconductor material, such as a silicon crystal, used in the fabrication of integrated circuits and other microdevices...
.