IC design can be divided into the broad categories of digital and analog IC design. Digital IC design is to produce components such as microprocessors, FPGAs, memories (RAM, ROM, and flash) and digital ASICs. Digital design focuses on logical correctness, maximizing circuit density, and placing circuits so that clock and timing signals are routed efficiently. Analog IC design also has specializations in power IC design and RF IC design. Analog IC design is used in the design of op-amps, linear regulators, phase locked loops, oscillators and active filters. Analog design is more concerned with the physics of the semiconductor devices such as gain, matching, power dissipation, and resistance. Fidelity of analog signal amplification and filtering is usually critical and as a result, analog ICs use larger area active devices than digital designs and are usually less dense in circuitry.
Modern ICs are enormously complicated. A large chip, as of 2009 has close to 1 billion transistors. The rules for what can and cannot be manufactured are also extremely complex. An IC process as of 2006 may well have more than 600 rules. Furthermore, since the manufacturing process itself is not completely predictable, designers must account for its statistical nature. The complexity of modern IC design, as well as market pressure to produce designs rapidly, has led to the extensive use of automated design tools in the IC design process. In short, the design of an IC using EDA software is the design, test, and verification of the instructions that the IC is to carry out
FundamentalsIntegrated circuit design involves the creation of electronic components, such as transistors, resistors, capacitors and the metallic interconnect of these components onto a piece of semiconductor, typically silicon. A method to isolate the individual components formed in the substrate is necessary since the substrate silicon is conductive and often forms an active region of the individual components. The two common methods are p-n junction isolation and dielectric isolation. Attention must be given to power dissipation of transistors and interconnect resistances and current density of the interconnect, contacts and vias since ICs contain very tiny devices compared to discrete components, where such concerns are less of an issue. Electromigration in metallic interconnect and ESD damage to the tiny components are also of concern. Finally, the physical layout of certain circuit subblocks is typically critical, in order to achieve the desired speed of operation, to segregate noisy portions of an IC from quiet portions, to balance the effects of heat generation across the IC, or to facilitate the placement of connections to circuitry outside the IC.
Design stepsA typical IC design cycle involves several steps:
1.Feasibility study and die size estimate
4.Circuit/RTL simulation Logic simulation
9.Static timing analysis
11.Design For Test and Automatic test pattern generation
12.Design for manufacturability (IC)
13.Mask data preparation
17.Post silicon validation
19.Tweak (if necessary)
20.Datasheet generation Portable Document Format
23.Yield Analysis / Warranty Analysis Reliability (semiconductor) 24.Failure analysis on any returns
25.Plan for next generation chip using production information if possible Digital designRoughly speaking, digital IC design can be...