A model of silicon ICs soldered onto a circuit board

Electronic design automation: grand design micro scale

Electronic design automation software for engineers of integrated circuits has to keep pace with a fast-moving range of requirements being created by a dynamic and demanding industry.

Electronics engineers engaged in the design of integrated circuits, systems on chip (SoCs), application-specific integrated circuits (ASICs) and other semiconductors face a complex, time-consuming task. It's one that calls for all the help they can get from electronic design automation (EDA) software when it comes to simulating and testing their wares prior to fabrication, and with the constant flow of innovation in the integrated circuit (IC) market, the producers of software design tools are upping their game in order to keep pace.

"IC manufacturers understand that wasted design cycles are costly, whether on gallium arsenide (GaAs), gallium nitride (GaN), or silicon – [and] as IC process sizes shrink, the complexity of the design grows," says Sherry Hess, vice president of marketing, AWR Group at National Instruments (NI). "EDA tools are necessary to save time, reduce cost, and shorten design cycles, because they automate numerous tasks and provide feedback that enables designers to identify and correct design challenges before entering the costly prototype and manufacturing phase."

Time-saving is also a critical factor. "Our customers claim to speed up the design process by anything from 20-80 per cent depending on the application and [available] resources," explains Valerio Marra, technical marketing manager for Comsol Inc. "Sometimes it is not much, but 20 per cent of a prototype can save a lot of money and even where it [the model] is experimental, you can try to understand what is going on and perform tests. It is not the ultimate solution, but it is a helpful tool."

With silicon manufacturers and device makers looking to pack an increasingly-powerful processing punch into ever-shrinking devices while simultaneously reducing their electricity consumption, building efficient power management into initial semiconductor design has become something of an obsession for the current generation of IC designers, but it is no new concern.

Krishna Balachandran, director of low-power product marketing at EDA software and tools vendor Cadence Design Systems, says that power management has, in fact, been a design issue for at least 15 years. The difference is that only a few mobile application developers and semiconductor companies were previously focused on low energy usage, but now a far broader range of players are taking it more seriously.

Cadence has steadily introduced new power management features into its software, including support for the IEEE 1801 Unified Power Format specification – a common standard to describe lower power design intent in multi-vendor design flows, whose definition was led by Nokia, Texas Instruments (TI), and EDA software specialists Magma Design Automation (Synopsys) and Mentor Graphics.

The latest iteration of the specification – revised in 2013 and additionally supported in EDA software from Mentor Graphics, Synopsys, Aldec, and Docea Power – attempts to improve support for power modelling, implementation and verification through the IC design lifecycle, paying specific attention to the incremental improvement of a design as more implementation detail is added without requiring engineers to rewrite command scripts.

"The idea is to decouple the design from the power information so that the same design could be applied to different power architectures. This would enable low-power and high-speed applications to use different power management techniques," says Balachandran, whose company has also introduced capabilities such as power-aware simulation and emulation to allow designers to experiment with different power modes in order to tune energy consumption in the context of actual software scenarios.

"Depending on the design, emulation can be a hundred times faster than using a software simulator – to verify power intent and run a lot more tests and get better coverage for the device overall. The greater speed allows more scenarios to be explored and so identify power issues in the context of the full system early in the design process."

FreeScale Semiconductor is an international company specialising in the design and production of embedded microcontrollers, microprocessors, digital signal controls, sensors, radio frequency (RF) power, and power management ICs for the automotive, networking, industrial, and consumer markets. Freescale used Cadence's Encounter Digital Implementation software to finalise (or tapeout) the design of its 1.8GHz 64-bit 12-core QorIQ T4240 system-on-chip (SoC) communications processor destined for use in telecommunications and enterprise networking equipment.

Wireless applications

Successful IC design for wireless or mobile communications applications also relies on being able to minimise crosstalk between different frequencies and channels, and stay within limits on spectral emissions and signal interference set by telecommunications standards.

Semiconductor company TriQuint used NI's AWS Microwave Office and Visual System Simulator software tools to design an Edge/GSM power amplifier for use in a mobile handset, accurately characterising the amplifier's circuit performance at system level, and predicting adjacent channel power ratio measurements (ACPR) to minimise the effect of spectral spreading to ensure compliance.

COMSOL Multiphysics finite element analysis (FEA) software is used in a wide diversity of applications – one of which involves the analysis of stress and potential breaking points in flexible printed circuit boards (PCBs) where crosstalk between the layers can adversely affect the strength of the structure and generate heat that degrades the conductivity of the circuit.

"I carry one signal, and you carry another one, and that creates crosstalk and interference – and vice versa," explains Marra. "The question with using high frequencies is how much heat that generates. You might decide to use copper, but what happens if conditions change – how does that affect the electrical conductivity of copper, and can you simulate that?"

In other applications of Comsol's software, its MEMS (micro-electrical mechanical systems) module is employed in the design of micromirrors for the digital light processing (DLP) chips used in digital video projection, while the RF module is used to build antenna arrays for GPS chips.

Both EDA and FEA software is expanding to encompass new materials and processes as manufacturers look to lower-cost, more flexible or less power-hungry materials to replace silicon within semiconductors.

"Metals cannot cover everything," adds Marra. "The real opportunity here is to provide customers with the development infrastructure to create their own models, using their own materials."

Silicon alternatives

US light-emitting diode (LED) manufacturer Cree used NI's AWR Microwave Office to design power amplifiers that use gallium nitride (GaN) as the semiconducting material, for example. This includes the CDPA21480 Doherty amplifier, which delivers peaks of 480W and average 80W of RF power for wideband CDMA (WCDMA) networks operating in the 2170MHz UMTS waveband. Engineers were able to optimise the Doherty's performance over a range of power levels using individual source and load-pull measurements on the amplifier, leading to more accurate models that reduced design time by up to 70 per cent using linear frequency domain and harmonic balance simulation through electromagnetic analysis.

CoolCAD Electronics is a custom electronics design firm that specialises in unusual, or non-mainstream, design applications including cryogenic and radiation hard electronics and silicon carbide (SiC) power hardware. The company is working closely with Nasa to develop design tools and methodologies that can help the agency perfect electronic components for use in extreme space environments characterised by very low temperatures and radiation effects.

CoolCAD's SiC Power Electronics Virtual Design Platform is specifically orientated towards SiC devices and ICs, and has been used in circuit and systems simulations carried out by commercial vehicle manufacturers such as General Motors and Ford, and military hardware specialists including General Atomics and Raytheon.

Many ICs also use light to transmit and process signals, with both Phoenix Software and Lumerical Solutions specialising in the supply of photonic circuit design software to manufacturers and research institutions. Lumerical's products are widely used in the design of CMOS image sensors for digital cameras, solar energy and photovoltaic cells, optical networking applications and nanoscale lithographic surface analysis and defect detection in semiconductor manufacturing. In the solar application, the software is used to model plasmon resonance in nanoscale metallic arrays deposited on the surface of thin-film silicon cells to enhance their conversion efficiency.

Cross-industry integration

Hess says that this greater tool integration and 'co-opetition' between EDA vendors is the way forward for the industry, with interoperable 'application specific' products focusing on a specific element such as design synthesis or optimisation algorithms becoming the norm.

Though something that EDA software companies have historically not been especially good at, there are signs that the growing demand for increasingly complex designs from different vertical industries and a broader customer base expanding beyond semiconductor companies is now providing the necessary impetus. NI worked with engineering simulation software vendor Ansys to integrate the latter's high frequency structure simulator (HFSS) into NI's AWR Microwave Office high frequency circuit design package to help designers simulate microwave circuits more quickly and accurately, for example, whilst Synopsys worked with MathWorks to improve their respective design verification capabilities.

Founded in 2010, the Si2's Open process design kit (OpenPDK) Coalition also set itself the task of defining a standard which would allow an agnostic OpenPDK to be created once and then translated into specific EDA tools and foundry formats to aid its portability across different software tools. Si2 (full name: Silicon Integration Initiatives) is an industry body whose members include Globalfoundries, IBM, Intel, Samsung, and STMicroelectronics, as well as Mentor Graphics and Synopsys, all of which are workingto develop reference implementations able to store and process data – database resolution layers, purpose, material and display information – in APIs (application programming interfaces) that can be transferred between EDA tools.

"Integration of thermal tools, design rule checking (DRC), layout versus schematic (LVS), HPC and standards bodies like Si2 with its open PDK – all are making a big difference by removing barriers designers previously faced when moving from one disparate tool to another in order to construct their own design flows/environments to meet the evolving needs of today's RF/microwave ICs," believes Hess.

Marra says that the IC design process has a better chance of being more accurate if results from multiple tests and simulation can be compared and correlated. That includes using more than one EDA/FEA tool for the job: "If you want to be successful [in your design], you have to use all the tools out there, not just rely on one – but that creates another issue, which is that sometimes different tools cannot communicate." 

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