Integrated circuit design - AbsoluteAstronomy.com

Integrated circuit design, or IC design, is a subset of electrical engineering

Electrical engineering

Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical...

and computer engineering

Computer engineering

Computer engineering, also called computer systems engineering, is a discipline that integrates several fields of electrical engineering and computer science required to develop computer systems. Computer engineers usually have training in electronic engineering, software design, and...

, encompassing the particular logic

Boolean logic

Boolean algebra is a logical calculus of truth values, developed by George Boole in the 1840s. It resembles the algebra of real numbers, but with the numeric operations of multiplication xy, addition x + y, and negation −x replaced by the respective logical operations of...

and circuit design

Circuit design

The process of circuit design can cover systems ranging from complex electronic systems all the way down to the individual transistors within an integrated circuit...

techniques required to design integrated circuits, or ICs. ICs consist of miniaturized electronic component

Electronic component

An electronic component is a basic electronic element and may be available in a discrete form having two or more electrical terminals . These are intended to be connected together, usually by soldering to a printed circuit board, in order to create an electronic circuit with a particular function...

s built into an electrical network

Electrical network

An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...

on a monolithic semiconductor

Semiconductor

A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...

substrate by photolithography

Photolithography

Photolithography is a process used in microfabrication to selectively remove parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical "photoresist", or simply "resist," on the substrate...

.

IC design can be divided into the broad categories of digital

Digital

A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

and analog IC design. Digital IC design is to produce components such as microprocessors, FPGAs, memories (RAM

Ram

-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...

, ROM

Read-only memory

Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...

, and flash

Flash memory

Flash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It was developed from EEPROM and must be erased in fairly large blocks before these can be rewritten with new data...

) and digital 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. 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

Radio frequency

Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

IC design. Analog IC design is used in the design of op-amps, linear regulator

Linear regulator

In electronics, a linear regulator is a voltage regulator based on an active device operating in its "linear region" or passive devices like Zener diodes operated in their breakdown region...

s, phase locked loops, oscillators and active filter

Active filter

An active filter is a type of analog electronic filter that uses an amplifier stage. Amplifiers included in a filter design can be used to improve the performance, stability and predictability of a filter. An amplifier prevents the impedance of source or load stages from affecting the...

s. 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

Statistics

Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....

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

Electronic design automation

Electronic design automation is a category of software tools for designing electronic systems such as printed circuit boards and integrated circuits...

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.

Fundamentals

Integrated 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

Silicon

Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

. A method to isolate the individual components formed in the substrate

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...

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

P-n junction isolation

p-n junction isolation is a method used to electrically isolate electronic components, such as transistors, on an integrated circuit by surrounding the components with reverse biased p-n junctions.-Introduction:...

and dielectric isolation. Attention must be given to power dissipation of transistors and interconnect resistances and current density of the interconnect, contacts and vias

Via (electronics)

A via is a vertical electrical connection between different layers of conductors in a physical electronic circuit.- In IC :In integrated circuit design, a via is a small opening in an insulating oxide layer that allows a conductive connection between different layers. A via on an integrated circuit...

since ICs contain very tiny devices compared to discrete components, where such concerns are less of an issue. Electromigration

Electromigration

Electromigration is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applications where high direct current densities are used, such as in...

in metallic interconnect and ESD

Electrostatic discharge

Electrostatic discharge is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits are made from semiconductor materials such as silicon and insulating materials such as silicon dioxide...

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 steps

A typical IC design cycle involves several steps:

Feasibility study and die size estimate
Functional verification
Functional verification
Functional verification, in electronic design automation, is the task of verifying that the logic design conforms to specification. In everyday terms, functional verification attempts to answer the question "Does this proposed design do what is intended?" This is a complex task, and takes the...
Circuit/RTL design
Circuit/RTL simulation
SPICE
SPICE is a general-purpose, open source analog electronic circuit simulator.It is a powerful program that is used in integrated circuit and board-level design to check the integrity of circuit designs and to predict circuit behavior.- Introduction :Unlike board-level designs composed of discrete...

Logic simulation
Logic simulation
Logic simulation is the use of a computer program to simulate the operation of a digital circuit. Logic simulation is the primary tool used for verifying the logical correctness of a hardware design. In many cases logic simulation is the first activity performed in the process of taking a hardware...
Floorplanning
Design review
Layout
Integrated circuit layout
Integrated circuit layout, also known IC layout, 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.When...
Layout verification
Static timing analysis
Static timing analysis
Static Timing Analysis is a method of computing the expected timing of a digital circuit without requiring simulation.High-performance integrated circuits have traditionally been characterized by the clock frequency at which they operate...
Layout review
Design For Test
Design For Test
Design for Test is a name for design techniques that add certain testability features to a microelectronic hardware product design. The premise of the added features is that they make it easier to develop and apply manufacturing tests for the designed hardware...

and Automatic test pattern generation
Automatic test pattern generation
ATPG is an electronic design automation method/technology used to find an input sequence that, when applied to a digital circuit, enables automatic test equipment to distinguish between the correct circuit behavior and the faulty circuit...
Design for manufacturability (IC)
Design for manufacturability (IC)
Achieving high-yielding designs in the state of the art, VLSI technology has become an extremely challenging task due to the miniaturization as well as the complexity of leading-edge products...
Mask data preparation
Mask data preparation
Mask data preparation is the step that translates an intended set of polygons on an integrated circuit layout into a form that can be physically written by the photomask writer. Usually this involves fracturing complex polygons into simpler shapes, often rectangles and trapezoids, that can be...
Wafer fabrication
Semiconductor fabrication
Semiconductor device fabrication is the process used to create the integrated circuits that are present in everyday electrical and electronic devices. It is a multiple-step sequence of photolithographic and chemical processing steps during which electronic circuits are gradually created on a wafer...
Die test
Packaging
Integrated circuit packaging
Integrated circuit packaging is the final stage of semiconductor device fabrication per se, followed by IC testing.Packaging in ceramic or plastic prevents physical damage and corrosion and supports the electrical contacts required to assemble the integrated circuit into a system.In the integrated...
Post silicon validation&integration
Device characterization
Tweak (if necessary)
Datasheet generation Portable Document Format
Portable Document Format
Portable Document Format is an open standard for document exchange. This file format, created by Adobe Systems in 1993, is used for representing documents in a manner independent of application software, hardware, and operating systems....
Ramp up
Production
Yield Analysis / Warranty Analysis Reliability (semiconductor)
Reliability (semiconductor)
Reliability of semiconductor devices can be summarized as follows:# Semiconductor devices are very sensitive to impurities and particles. Therefore, to manufacture these devices it is necessary to manage many processes while accurately controlling the level of impurities and particles...
Failure analysis
Failure analysis
Failure analysis is the process of collecting and analyzing data to determine the cause of a failure. It is an important discipline in many branches of manufacturing industry, such as the electronics industry, where it is a vital tool used in the development of new products and for the improvement...

on any returns
Plan for next generation chip using production information if possible

Digital design

Roughly speaking, digital IC design can be divided into three parts.

Electronic system-level design: This step creates the user functional specification. The user may use a variety of languages and tools to create this description. Examples include a C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....

/C++
C++
C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as an intermediate-level language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell...

model, SystemC
SystemC
SystemC is a set of C++ classes and macros which provide an event-driven simulation kernel in C++ . These facilities enable a designer to simulate concurrent processes, each described using plain C++ syntax...

, SystemVerilog
SystemVerilog
In the semiconductor and electronic design industry, SystemVerilog is a combined Hardware Description Language and Hardware Verification Language based on extensions to Verilog.-History:...

Transaction Level Models
Transaction-level modeling
Transaction-level modeling is a high-level approach to modeling digital systems where details of communication among modules are separated from the details of the implementation of functional units or of the communication architecture. Communication mechanisms such as busesor FIFOs are modeled as...

, Simulink
Simulink
Simulink, developed by MathWorks, is a commercial tool for modeling, simulating and analyzing multidomain dynamic systems. Its primary interface is a graphical block diagramming tool and a customizable set of block libraries. It offers tight integration with the rest of the MATLAB environment and...

and MATLAB
MATLAB
MATLAB is a numerical computing environment and fourth-generation programming language. Developed by MathWorks, MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages,...

.
RTL design: This step converts the user specification (what the user wants the chip to do) into a register transfer level
Register transfer level
In integrated circuit design, register-transfer level is a level of abstraction used in describing the operation of a synchronous digital circuit...

(RTL) description. The RTL describes the exact behavior of the digital circuits on the chip, as well as the interconnections to inputs and outputs.
Physical design: This step takes the RTL, and a library of available logic gates, and creates a chip design. This involves figuring out which gates to use, defining places for them, and wiring them together.

Note that the second step, RTL design, is responsible for the chip doing the right thing. The third step, physical design, does not affect the functionality at all (if done correctly) but determines how fast the chip operates and how much it costs.

RTL design

This is the hardest part, and the domain of functional verification

Functional verification

Functional verification, in electronic design automation, is the task of verifying that the logic design conforms to specification. In everyday terms, functional verification attempts to answer the question "Does this proposed design do what is intended?" This is a complex task, and takes the...

. The spec may have some terse description, such as encodes in the MP3
MP3
MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...

format or implements IEEE floating-point arithmetic. Each of these innocent looking statements expands to hundreds of pages of text, and thousands of lines of computer code. It is extremely difficult to verify that the RTL will do the right thing in all the possible cases that the user may throw at it. Many techniques are used, none of them perfect but all of them useful – extensive logic simulation

Logic simulation

Logic simulation is the use of a computer program to simulate the operation of a digital circuit. Logic simulation is the primary tool used for verifying the logical correctness of a hardware design. In many cases logic simulation is the first activity performed in the process of taking a hardware...

, formal methods

Formal methods

In computer science and software engineering, formal methods are a particular kind of mathematically-based techniques for the specification, development and verification of software and hardware systems...

, hardware emulation

Hardware emulation

In integrated circuit design, hardware emulation is the process of imitating the behavior of one or more pieces of hardware with another piece of hardware, typically a special purpose emulation system. The emulation model is usually based on RTL source code, which is compiled into the format...

, lint

Lint programming tool

In computer programming, lint was the name originally given to a particular program that flagged some suspicious and non-portable constructs in C language source code. The term is now applied generically to tools that flag suspicious usage in software written in any computer language...

-like code checking, and so on.

A tiny error here can make the whole chip useless, or worse. The famous Pentium FDIV bug

Pentium FDIV bug

The Pentium FDIV bug was a bug in the Intel P5 Pentium floating point unit . Certain floating point division operations performed with these processors would produce incorrect results...

caused the results of a division to be wrong by at most 61 parts per million, in cases that occurred very infrequently. No one even noticed it until the chip had been in production for months. Yet Intel was forced to offer to replace, for free, every chip sold until they could fix the bug, at a cost of $475 million (US).

Physical design

Here are the main steps of physical design. In practice there is not a straightforward progression - considerable iteration is required to ensure all objectives are met simultaneously. This is a difficult problem in its own right, called design closure

Design closure

Design closure is the process by which a VLSI design is modified from its initial description to meet a growing list of design constraints and objectives....

Floorplanning: The RTL of the chip is assigned to gross regions of the chip, input/output (I/O) pins are assigned and large objects (arrays, cores, etc.) are placed.
Logic synthesis
Logic synthesis
In electronics, logic synthesis is a process by which an abstract form of desired circuit behavior, typically register transfer level , is turned into a design implementation in terms of logic gates. Common examples of this process include synthesis of HDLs, including VHDL and Verilog...

: The RTL is mapped into a gate-level netlist in the target technology of the chip.
Placement
Placement (EDA)
Placement is an essential step in electronic design automation - the portion of the physical design flow that assigns exact locations for various circuitcomponents within the chip’s core area...

: The gates in the netlist are assigned to nonoverlapping locations on the die area.
Logic/placement refinement: Iterative logical and placement transformations to close performance and power constraints.
Clock insertion
Clock Distribution Networks
In a synchronous digital system,the clock signal is used to define a timereference for the movement of data within that system. The clock distribution network distributes the clock signal from a common point to all the elements that need it.Since this function isvital to the operation of a...

: Clock signal wiring is (commonly, clock trees) introduced into the design.
Routing
Routing (EDA)
In electronic design, wire routing, commonly called simply routing, is a step in the design of printed circuit boards and integrated circuits . It builds on a preceding step, called placement, which determines the location of each active element of an IC or component on a PCB...

: The wires that connect the gates in the netlist are added.
Postwiring optimization: Performance (timing closure
Timing Closure
Timing closure is the process by which an FPGA or a VLSI design is modified to meet its timing requirements. Most of the modifications are handled by EDA tools based on directives given by a designer...

), noise (signal integrity
Signal integrity
Signal integrity or SI is a set of measures of the quality of an electrical signal. In digital electronics, a stream of binary values is represented by a voltage waveform. However, digital signals are fundamentally analog in nature, and all signals are subject to effects such as noise,...

), and yield (Design for manufacturability
Design for manufacturability (IC)
Achieving high-yielding designs in the state of the art, VLSI technology has become an extremely challenging task due to the miniaturization as well as the complexity of leading-edge products...

) violations are removed.
Design for manufacturability
Design for manufacturability (IC)
Achieving high-yielding designs in the state of the art, VLSI technology has become an extremely challenging task due to the miniaturization as well as the complexity of leading-edge products...

: The design is modified, where possible, to make it as easy and efficient as possible to produce. This is achieved by adding extra vias or adding dummy metal/diffusion/poly layers wherever possible while complying to the design rules set by the foundry.
Final checking: Since errors are expensive, time consuming and hard to spot, extensive error checking is the rule, making sure the mapping to logic was done correctly
Formal equivalence checking
Formal equivalence checking process is a part of electronic design automation , commonly used during the development of digital integrated circuits, to formally prove that two representations of a circuit design exhibit exactly the same behavior....

, and checking that the manufacturing rules were followed faithfully
Design rule checking
Design Rule Checking or Check is the area of Electronic Design Automation that determines whether the physical layout of a particular chip layout satisfies a series of recommended parameters called Design Rules...

.
Tapeout
Tape-out
In electronics design, tape-out or tapeout is the final result of the design cycle for integrated circuits or printed circuit boards, the point at which the artwork for the photomask of a circuit is sent for manufacture....

and mask generation: the design data is turned into photomask
Photomask
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.-Overview:...

s in mask data preparation
Mask data preparation
Mask data preparation is the step that translates an intended set of polygons on an integrated circuit layout into a form that can be physically written by the photomask writer. Usually this involves fracturing complex polygons into simpler shapes, often rectangles and trapezoids, that can be...

.

Process corners

In semiconductor manufacturing, a process corner is an example of a design-of-experiments technique that refers to a variation of fabrication parameters used in applying an integrated circuit design to a semiconductor wafer. Process corners represent the extremes of these parameter variations...

provide digital designers the ability to simulate the circuit while accounting for variations in the technology process.

Analog design

Before the advent of the microprocessor and software based design tools, analog ICs were designed using hand calculations. These ICs were basic circuits, op-amps are one example, usually involving no more than ten transistors and few connections. An iterative trial-and-error process and "overengineering" of device size was often necessary to achieve a manufacturable IC. Reuse of proven designs allowed progressively more complicated ICs to be built upon prior knowledge. When inexpensive computer processing became available in the 1970s, computer programs were written to simulate circuit designs with greater accuracy than practical by hand calculation. The first circuit simulator for analog ICs was called SPICE

SPICE

SPICE is a general-purpose, open source analog electronic circuit simulator.It is a powerful program that is used in integrated circuit and board-level design to check the integrity of circuit designs and to predict circuit behavior.- Introduction :Unlike board-level designs composed of discrete...

(Simulation Program with Integrated Circuits Emphasis). Computerized circuit simulation tools enable greater IC design complexity than hand calculations can achieve, making the design of analog ASIC

Application-specific integrated circuit

An application-specific integrated circuit is an integrated circuit customized for a particular use, rather than intended for general-purpose use. For example, a chip designed solely to run a cell phone is an ASIC...

s practical. The computerized circuit simulators also enable mistakes to be found early in the design cycle before a physical device is fabricated

Semiconductor fabrication

Semiconductor device fabrication is the process used to create the integrated circuits that are present in everyday electrical and electronic devices. It is a multiple-step sequence of photolithographic and chemical processing steps during which electronic circuits are gradually created on a wafer...

. Additionally, a computerized circuit simulator can implement more sophisticated device models and circuit analysis too tedious for hand calculations, permitting Monte Carlo analysis and process sensitivity analysis to be practical. The effects of parameters such as temperature variation, doping concentration variation and statistical process variations can be simulated easily to determine if an IC design is manufacturable

Design for manufacturability (IC)

Achieving high-yielding designs in the state of the art, VLSI technology has become an extremely challenging task due to the miniaturization as well as the complexity of leading-edge products...

. Overall, computerized circuit simulation enables a higher degree of confidence that the circuit will work as expected upon manufacture.

Coping with variability

A challenge most critical to analog IC design involves the variability of the individual devices built on the semiconductor chip. Unlike board-level circuit design which permits the designer to select devices that have each been tested and bin

Bin

Bīn may refer to:* Pungi, a South Asian double clarinet* Veena, a North Indian stick zither* 宾 , a Chinese character meaning guest, visitor...

ned according to value, the device values on an IC can vary widely which are uncontrollable by the designer. For example, some IC resistors can vary ±20% and β of an integrated BJT

Bipolar junction transistor

|- align = "center"| || PNP|- align = "center"| || NPNA bipolar transistor is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons...

can vary from 20 to 100. To add to the design challenge, device properties often vary between each processed semiconductor wafer. Device properties can even vary significantly across each individual IC due to doping gradients. The underlying cause of this variability is that many semiconductor devices are highly sensitive to uncontrollable random variances in the process. Slight changes to the amount of diffusion time, uneven doping levels, etc. can have large effects on device properties.

Some design techniques used to reduce the effects of the device variation are:

Using the ratios of resistors, which do match closely, rather than absolute resistor value.
Using devices with matched geometrical shapes so they have matched variations.
Making devices large so that statistical variations becomes an insignificant fraction of the overall device property.
Segmenting large devices, such as resistors, into parts and interweaving them to cancel variations.
Using common centroid device layout to cancel variations in devices which must match closely (such as the transistor differential pair of an op amp).

Vendors

The four largest companies selling electronic design automation

Electronic design automation

Electronic design automation is a category of software tools for designing electronic systems such as printed circuit boards and integrated circuits...

tools are Synopsys

Synopsys

Synopsys, Inc. is one of the largest companies in the Electronic Design Automation industry. Synopsys' first and best-known product is Design Compiler, a logic-synthesis tool. Synopsys offers a wide range of other products used in the design of an application-specific integrated circuit...

, Cadence

Cadence Design Systems

Cadence Design Systems, Inc is an electronic design automation software and engineering services company, founded in 1988 by the merger of SDA Systems and ECAD, Inc...

, Mentor Graphics

Mentor Graphics

Mentor Graphics, Inc is a US-based multinational corporation dealing in electronic design automation for electrical engineering and electronics, as of 2004, ranked third in the EDA industry it helped create...

, and Magma

Magma Design Automation

Magma Design Automation is a software company in the electronic design automation industry. The company was founded in 1997 and maintains headquarters in San Jose, California, with facilities throughout North America, Europe, Japan, Asia and India....

External links

CAD – IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems

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