Integrated circuit design in the context of Microprocessors

In integrated circuit design, integrated circuit (IC) layout, also known 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. Originally the overall process was called tapeout, as historically early ICs used graphical black crepe tape on mylar media for photo imaging (erroneously believed to reference magnetic data—the photo process greatly predated magnetic media).

When using a standard process—where the interaction of the many chemical, thermal, and photographic variables is known and carefully controlled—the behaviour of the final integrated circuit depends largely on the positions and interconnections of the geometric shapes. Using a computer-aided layout tool, the layout engineer—or layout technician—places and connects all of the components that make up the chip such that they meet certain criteria—typically: performance, size, density, and manufacturability. This practice is often subdivided between two primary layout disciplines: analog and digital.

Wafer fabrication is a procedure composed of many repeated sequential processes to produce complete electrical or photonic circuits on semiconductor wafers in a semiconductor device fabrication process. Examples include production of radio frequency (RF) amplifiers, LEDs, optical computer components, and microprocessors for computers. Wafer fabrication is used to build components with the necessary electrical structures.

The main process begins with integrated circuit design, where electrical engineers designing the circuit and defining its functions, and specifying the signals, inputs/outputs and voltages needed. These electrical circuit specifications are entered into electrical circuit design software, such as SPICE, and then imported into circuit layout programs, which are similar to ones used for computer aided design. This is necessary for the layers to be defined for photomask production. The resolution of the circuits increases rapidly with each step in design, as the scale of the circuits at the start of the design process is already being measured in fractions of micrometers. Each step thus increases circuit density for a given area.

In electronics and photonics design, tape-out or tapeout is the final stage of the design process for integrated circuits or printed circuit boards before they are sent for manufacturing. The tapeout is specifically the point at which the graphic for the photomask of the circuit is sent to the fabrication facility. The name originates from the use of magnetic tape to send the data to the manufacturing facility.

In integrated circuit design, hardware emulation is the process of imitating the behavior of one or more pieces of hardware (typically a system under design) with another piece of hardware, typically a special purpose emulation system. The emulation model is usually based on a hardware description language (e.g. Verilog) source code, which is compiled into the format used by emulation system. The goal is normally debugging and functional verification of the system being designed. Often an emulator is fast enough to be plugged into a working target system in place of a yet-to-be-built chip, so the whole system can be debugged with live data. This is a specific case of in-circuit emulation.

Sometimes hardware emulation can be confused with hardware devices such as expansion cards with hardware processors that assist functions of software emulation, such as older daughterboards with x86 chips to allow x86 OSes to run on motherboards of different processor families.