Are you a student of electronics engineering? If so, perhaps you have been exposed to the preliminary levels of integrated circuits (ICs) involving small-scale integration (SSI) circuits like logic gates or medium-scale integration (MSI) circuits like multiplexers and parity encoders. There is, however, a much bigger world out there involving miniaturisation at levels so great that even a micrometre or a microsecond is consid ered a huge measure! This is the world of VLSI—very large-scale integration. Let’s figure out the opportunities in this field for professionals with subject-matter expertise in electronics.
Where is the demand?
Programmable logic devices, hardware description languages and design tools of today have changed the circuit design process to such an extent that it has become totally independent of the actual device manufacturing issues. According to India Semiconductor Association (ISA), the Indian semiconductor and embedded design industry is expected to earn revenues of $43 billion in 2015—a marked increase from the $5.9 billion it earned in 2008.
In the present scenario, VLSI circuits are designed at one or more locations across the globe and finally manufactured at a different, distant location. This outsourcing aspect of VLSI design is attracting major international players in this field to India. Companies like Intel, Texas Instruments, IBM, Philips, Motorola, SGS-Thompson, Mentor Graphics and Cirrus Logic, to name a few, have already set up their design centres in India. India has some 9500 chip designers working for 300+ companies, and their ranks are swelling by 20 per cent a year. It has a unique advantage with respect to both the talent and market opportunities it provides.
The major recruiters in this fields are Texas Instruments, PMC Sierra, Infineon, Alliance Semiconductor, Analog Devices, Cadence, Synopsys, Mentor Graphics, Celox Networks, Cisco, Control Net, Cypress, DSPG, HCL, Intel, Lucent, Micron Tech, National Semiconductor, Motorola, Philips Semiconductor, Qualcomm, Sasken, C2C, Atrenta, Conexant, Moschip, Cradle Tech, Synplicity, STM, Paxonet, Wipro, TCS, eInfochips, Ishoni Networks and CGCoreEL.
What roles are in demand?
Though there is scope for fast growth in this area, the aspirants have to be competent, hardworking and constant learners. The main job functions are engineering aspects of design, product, test, applications and process. Product engineering and test engineering functions are often combined
efficiently into one role because of the interdependency and overlap of skills and tasks.
C.P. Ravikumar, technical director-university relation, Texas Instruments (TI) India, spoke about the gap between industry requirements and candidate skill sets, selection criteria for fresh recruits and need of specialised knowledge training for aspirants. Excerpts
Do you feel that there is a gap between industry requirements and candidate skill sets?
We do see a gap in areas such as VLSI design and embedded systems software, which are TI India’s focus areas. In particular, getting people in analogue design is a challenge.
What skills are required?
The skill sets are quite varied. I can speak on behalf of TI India, which mainly focuses on VLSI design and embedded software. VLSI design is an area where progresses are rapid. There are two main aspects in VLSI design, namely, front-end and back-end. Front-end design includes digital design using hardware description languages, design verification through simulation and formal verification techniques, synthesis of digital designs to gates, and design for testability. Since SoC (system-on-chip) design today happens through a process of integration of existing IP blocks, the engineers must have a good knowledge of computer architecture, different IPs such as DMA controllers and USB controllers, and bus protocols such as OCP. The VLSI design engineer must have exposure to fundamental concepts as well as familiarity with tools and design flows. Universities, on the contrary, tend to provide an overview of all the aspects of VLSI design. This is one reason why managers may complain that engineers are not production-ready. Having more MS and Ph.D students should help to alleviate this problem. Further, to practice VLSI design, which is mainly orchestrated through automated flows, the engineer must know quite a bit of UNIX utilities and productivity-enhancement tools such as Perl. Analogue design is a competency which requires a deep understanding of mathematical concepts of circuit design, network analysis and control theory. Getting campus-hires for analogue design is a big challenge. Back-end design consists of CMOS library design and characterisation, physical design (floor-planning, placement and routing), design for manufacturability, packaging, test generation and fault simulation. A good understanding of power dissipation in circuits is important from the viewpoint of controlling the dynamic and static power dissipation. Issues such as on-chip variability of transistor parameters and design for manufacturability are becoming important in modern CMOS technologies.
What’s the selection criteria for fresh recruits?
The subject of VLSI design is quite vast. It is not fair to expect both breadth and depth from a fresh recruit. At the undergraduate level, we expect a good understanding of fundamental concepts. Our campus recruitment is based on a written test and an interview. The written test is separate for hardware and software engineers. The hardware paper has a section on aptitude, a section on digital design and a section on analogue design—we ask the students to select any one section between digital and analogue design. The software paper has two parts—an aptitude section and a section on software. Candidates who fare well in the written test are shortlisted for interview. From my experience, the interviews are mostly based on problem-solving exercises and test the conceptual understanding rather than rote learning. We don’t pay too much importance to the B.Tech project done by the student. For postgraduate students, our process is similar, except that we may go into the M.Tech project/MS thesis/Ph.D thesis. For candidates with a Ph.D background, we also ask for a presentation where we invite our experts.
How important is specialised knowledge training for aspirants?
Specialised knowledge is useful for the engineers to grow inside the company. More than the knowledge itself, the ability to learn is a more important aspect. This learning can happen from peers, from publications, from attending meetings and conferences, etc. Many of our engineers express their desire to take up higher studies and this is encouraged.
Though most of the entry-level job profiles involve code entry, verification, synthesis and system-level engineering works, the possibility of role diversification moving ahead is huge.
The roles are defined depending on the requirements of the job. Typically, a design engineer takes specifications, defines architecture, designs circuits, runs simulations, supervises layout, tapes out the chip to the foundry and evaluates the prototype once the chip comes back from the factory. The design role itself offers further classification. For example, when the marketing team tells a company what product to design for the market, the architecture team is responsible for defining the chip design. You may work in such a team as a chip architect. As an RTL designer, you may be involved in designing the functions or modules of the chip which are required to perform the well-defined tasks described by the architecture team. This design is written in a high-level logic description language such as Verilog or VHDL.
If you find interest in optimising the existing standard cell library for performance and/or power by optimising circuit design or design/layout of custom cells like adders and shifters, synthesising the logic description into a circuit description or producing a document referred to as a ‘netlist,’ you may start as a circuit designer. As a physical designer, on the other hand, your responsibilities will include placement and routing of digital blocks and chip-level integration. You have to take the netlist and perform a ‘layout’ of the chip. This layout can be used to produce ‘masks,’ which are then used to manufacture the chip on a silicon wafer.
You may get involved in a project during the design phase as a product engineer and ensure manufacturability; develop characterisation plan, assembly guidelines, quality assurance and reliability plan; and also evaluate the chip through characterisation, reliability qualification and manufacturing yield point of view (statistical data analysis). You will be responsible for production release as well as for customer returns, failure analysis and corrective actions including design changes during the post-production phase.
In a test or verification engineering role, you will have to generate and run tests on the chip to ensure proper functionality. It involves development of behavioural models, test benches and simulation environments, module integration, complete functional and regression test suites, functional coverage analysis and a reusable test infrastructure.
Applications engineers define new products from a system point of view at the customer’s end, based on the input received from marketing. They need to ensure that the chip works in the designed system or used by the customers, and complies with appropriate standards (such as Ethernet, SONET and WiFi). They will be responsible for all customer technical support, firmware development, evaluation boards, datasheets and other product documentation such as application notes, trade shows, evaluation reports, software drives and so on.
There are also some highly specialised functions like process engineering and packaging engineering. Process engineering involves new wafer process development, device modeling, and other research and development projects. A packaging engineer, on the other hand, develops precision packaging technology and new package designs for the chips, characterises new packages and performs modeling of the new designs. Compared to other roles discussed earlier, there are no quick rewards in these jobs! If you are highly trained in semiconductor devices and willing to experiment, and do not mind wearing bunny suits (the clean-room uniforms used in all fabs), these jobs are for you.
Supportive functions like CAD engineering also demands importance. A CAD engineer is responsible for acquiring, maintaining or developing all CAD tools used by a design engineer. Most companies buy commercially available CAD tools for schematic capture, simulation, synthesis, test vector generation, layout, parametric extraction, power estimation and timing closure; but in several cases, these tools need some type of customisation. A CAD engineer needs to be highly skilled in the use of these tools, to write software routines to automate as many functions as possible and have a clear understanding of the entire design flow.
For those of you who are already enjoying the brainteasers in designing and testing the chips with all the innovation and rapid development, this field may provide unlimited scope to grow. Let’s check whether VLSI is rewarding not just from the intellectual point of view but also from the ‘pocket’ point of view.
Government or public-sector players offer a starting salary in the range of Rs 8000 to Rs 10,000 per month (excluding allowances) for diploma holders and Rs 15,000 to Rs 20,000 for degree holders. The private sector is always ready to offer more lofty figures for candidates with a suitable exposure. The ability to handle multitasking jobs may be a defining factor. For a typical fresher, the starting salary is Rs 300,000 upwards per year depending on the company, the need and the skill level demonstrated. Design engineers are the most sought after because of the industry’s emphasis on continuous new product development, miniaturisation and innovation in integration.
Typically, a master’s degree holder can expect about 10 per cent higher than the one with a bachelor’s. As you gain experience, this field offers one of the best growth potentials, both on the technical as well as management ladder. Though the global recession has hugely affected the starting salaries in the private sector at present, last year the average pay package ranged between Rs 700,000 and Rs 1.5 million per annum for professionals with four to five years of experience.
How to get the entry pass?
First of all, let’s make it clear that for working in this field it is not mandatory to have an engineering degree or diploma in electronics engineering, electrical engineering or computer science. These certainly are the obvious qualifications to earn, but graduate or postgraduate degree in physics also qualifies one to work as an engineer. The physics of semiconductor devices is the fundamental basis of VLSI.
As is always the case, “the earlier, the better.” If you ever tinkered with a broken radio set, you have already started. Academically, the right time to acquaint yourself with various specialisations of electronics is when you are in the second or third year of engineering. You can choose your electives so that you can concentrate more on specific subjects. A fresh engineering graduate has several opportunities to use his engineering skills in the VLSI world. As mentioned earlier, primarily, the work profiles can be classified as design engineers, product engineers, test engineers, process engineers or applications engineers. Of course, there are other important people like CAD engineers too who keep developing (or maintaining) all the important CAD tools and systems.
Irrespective of which job function you choose, there are certain basic skills required to break into this field. A VLSI engineer is expected to know the physics of semiconductor devices, linear systems, probability and random variables, engineering mathematics (Fourier, Laplace and Z transforms), circuit analysis and engineering electromagnetics. In addition to these solid Verilog/VHDL skills, familiarity with front-end design cycle, synthesis and simulation tool knowledge, sound digital design fundamentals and nonetheless knowledge of microprocessors would be an advantage for any aspiring candidate.
Where to start?
VLSI circuits are everywhere—your personal computer, your cellphone, your brand new state-of-the-art digital camera or for that matter any electronic gadget you dream to buy. Actually, this field involves packing of more and more logic devices into progressively smaller areas. So the circuits that would have taken board-full of space can now be put into a small space few millimetres across!
The best way to start work on VLSI is to know VLSI designing tools. VLSI has been around for a long time, but as a side effect of advances in the world of computers, there has been a dramatic proliferation of tools that can be used to design VLSI circuits. Also, obeying Moore’s law, the capability of an IC has increased exponentially over the years in terms of computing power, utilisation of available area and yield. The combined effect of these two factors is that designers can now put diverse functionality into an IC, opening up new frontiers. Examples are embedded systems, where intelligent devices are placed inside everyday objects, and ubiquitous computing, where small computing devices proliferate to such an extent that even the shoes you wear may actually do something useful like monitoring your heartbeats!
How to deal with VLSI circuits?
Keep in mind that digital VLSI circuits are predominantly CMOS-based. So the way normal blocks like latches and gates are implemented, is different from what you have seen before. However, the behaviour remains the same. All the miniaturisation involves new things to consider. A lot of thought has to go into actual implementation as well as design.
Let us look at some of the external factors responsible for the functionality of the circuit—large complicated circuits running at very high frequencies have to tackle the delays in propagation of signals through gates and wires. This is a big problem even for areas a few micrometres across. The operational speed is so large that as the delays add up, these can actually become comparable to clock speeds.
Another effect of high operation frequencies is increased consumption of power. This has two-fold effect: devices drain batteries faster, and heat dissipation increases. Coupled with the fact that surface areas decrease, heat poses a major threat to the stability of the circuit itself.
Laying out the circuit components is a task common to all branches of electronics. The speciality in VLSI layout is number of possible ways available to do this; there can be multiple layers of different materials on the same silicon, there can be different arrangements of the smaller parts for the same component and so on.
The power dissipation and speed in a circuit present a trade-off; if you try to optimise on one, the other is affected. The choice between the two is determined by the way you choose to layout the circuit components. Layout can also affect the fabrication of VLSI chips, making it either easy or difficult to implement the components on the silicon.
How to proceed with designs?
Know the fundamentals of both analogue and digital design processes. You may start with a typical design flow of any one of them. For example, a digital design flow to get the end product is: specification→architecture→RTL cod-ing→RTL verification→synthesis→ backend→tape out to foundry. Here the end product is a wafer with repeated number of identical ICs.
Today, all digital designs start with a designer writing a hardware description of the IC (using hardware description language, or HDL) in Verilog/VHDL. A Verilog or VHDL program essentially describes the hardware (logic gates, flip-flops, counters, etc), the functionality and circuit block interconnects. Various CAD tools are available to synthesise a circuit based on the HDL. The most widely used synthesis tools come from two CAD companies: Synposys and Cadence.
Without going into details, you may consider VHDL as ‘C’ of the VLSI industry. VHDL stands for ‘VHSIC hardware definition language,’ where VHSIC stands for ‘very high-speed integrated circuit.’ This language is used to design the circuits at a high level, in two ways. It can either be a behavioural description, which describes what the circuit is supposed to do, or a struc tural description, which describes what the circuit is made of. There are other languages for describing circuits, such as Verilog, which work in a similar fashion. Both forms of description are then used to generate a very low-level description that actually spells out how all this is to be fabricated on the silicon chips. This results in the manufacture of the intended IC.
For an analogue design, the flow may vary to some extent, like specifications→architecture→circuit design→ SPICE simulation→layout→parametric extraction/back annotation→final design→tape out to foundry.
As operational amplifiers,filters or power management chips. For more complex analogue chips such as data converters, the design is done at the transistor level, building up to the cell level, then the block level and finally integrated at the chip level. Not many CAD tools are available for analogue design even today and thus analogue design remains a difficult art. SPICE remains the most useful simulation tool for analogue as well as digital design.
Where to apply skills?
Now, it’s time to address the real-world need. Know where to apply your skillsets. For example, analogue While digital design is highly automated now, very small portion of analogue design can be automated. There is a hardware description language called ‘AHDL’ for analogue design but it is not widely used as it does not accurately give the behavioural model of the circuit because of the complexity of the analogue behaviour of the circuit. Many analogue chips are termed as ‘flat’ or non-hierarchical designs. This is true for small-transistor-count chips such designs are mostly used for smalltransistor-count precision circuits such as amplifiers, data converters, filters, phase-locked loops and sensors. In digital design, the progress in the fabrication of ICs has enabled designers to create fast and powerful circuits in smaller and smaller devices. This also means that one can pack a lot more of functionality into the same area. The biggest application of this ability is found in the design of application-specific integrated circuits (ASICs). These ICs are created for specific purposes—each device is created to do a particular job.
The most common application area for an ASIC is DSP— signal filters, image compression, etc. To go to extremes, consider the fact that the digital wristwatch normally consists of a single IC doing all the time-keeping as well as extra features like games and calendar. Systems-on-a-chip (SoCs), on the other hand, are highly complex mixed-signal circuits (digital and analogue on the same chip). Network processor chips and wireless radio chips are examples of SoCs.
It is possible that your awareness about most of the aforementioned terms is from a notional perspective only. But the industry needs something extra—actual hands-on experience is indispensable. Remember, there are a number of directions you can take while choosing a career in VLSI, and they are closely related to each other. So be a go-getter, dig all the possibilities to gain a practical exposure.
At the same time, be up-to-date about the latest technological trends to get an edge over your competitors. For example, reconfigurable computing is a very interesting development in microelectronics. It involves fabricating circuits that can be reprogrammed on the fly. Try to know how reconfigurable computing involves specially fabricated devices called FPGAs, that when programmed act just like normal electronic circuits without using a microcontroller running with EEPROM inside. This fantastic ability to create modifiable circuits again opens up new possibilities in microelectronics.
You may even explore how ASIC designing creates miniature devices that can do a lot of diverse functions. With an impending boom in this kind of technology, what the industry needs is a large number of people who can design these ICs. This is where one may cross the threshold between a chip designer and a systems designer at a higher level.
You will require extensive training in this field. If you have passion for chip designing and want to learn it, you need not disappoint. All IITs and other prestigious engineering institutes have included VLSI as an important part of their course curriculum.
So don’t panic over the current job scenario, the time’s perfect to resurrect your thought process. There’s plenty of time at hand. Devote your time to become an expert in VLSI. It will definitely bring ‘very large’ opportunities in the future.
The author is a research analyst cum journalist at EFY