Breaking down the job description: The Physical Design Engineer

The job title seems quirky, doesn’t it? It sounds like a complicated profile- evasive, and coveted. Here we are, back with the breaking down the job description series to help you understand and prepare better for this role.

You may haven’t noticed, but this is one of the major positions available in almost all the top IT companies in the world of technology. Who is responsible for converting the code to design? Who designs all the chips we take for granted?

Welcome to the world of physical design.

What is the physical design?

We design different algorithms through computer codes. But these computer codes are functionally right. To convert the algorithms to exact scenarios in the form of digital circuits- a new core comes into the picture called Digital Design.

Digital design, in short, involves the usage of hardware description languages in converting the high-level algorithms into gate-level architectures.

But it is also another incarnation of algorithmic coding. But physical design is a whole new domain- it is a new ball game altogether.

In layman terms, Physical design deals with placing the logical building blocks of a circuit designed on a virtual breadboard. Sounds simple right? Maybe, if we want to build a simple adder. But consider making a 555 timer, oh well that sounds grueling. But the joy extends with the complexity of the challenge.

The process involves a synthesizable circuit design as the input and a “ready for fabrication” design as output.

• It starts with the planning of the entire structure- striking an uncanny resemblance to the blueprint of a city.
• Placement refers to physically representing the gates on the surface- usually a dotted spreadsheet of the software. It can be considered analogous to deciding where the town hall, offices and housing colony must be built in the city.
• Routing is connecting the gates using the myriad of metal layers present- each categorically giving predetermined wire delays. It is like the roads, bridges, subways in a city required for a commute.

Who is a physical design engineer?

Evidently, a physical design engineer is anonymous to a city planner. He/She plans the Integrated Circuit layout. The engineers typically work on processors, and controller architectures- called Application Specific Integrated Circuits (or ASICs).

But it just does not end there. They go on to optimize the circuit up and beyond, trying to increase its performance, until the design breaks. The varied technologies- from the outdated 180nm to the currently trending 7nm are the bread and butter of a physical design engineer. These refer to the channel length of the transistors. Other responsibilities include the synthesis of clock trees for easy routing, reducing delays and clearing the glitches.

The development of the IC starts with planning, placement, and routing (PnR) through the multiple metal layers. The constrained development environment allows the testing of different corner cases. The synthesizable hardware description code is known as the netlist which the physical design engineer takes as ignition. After PnR, the resistances and capacitances of the design are calculated using RC extraction. This allows for a calculation of the bandwidth, quality factor, corner points.

The optimized output is called the layout of the design. Signing off takes verification of the layout and the packaging of the design.

What should I pursue to follow the footsteps towards becoming a Physical Design Engineer?

Companies usually look for relevant education in the field of electronics and computer architecture. A bachelor’s in -

1. Electronics and communication engineering
2. Electronics and computer engineering
3. Electrical engineering

give a head start.

But the bachelor’s degree does not give much insight. Relevant laboratory courses are non-existent. A master’s degree by thesis allows research and exposure to tools required. It also provides insight at abstract concepts. It is a true pleasure to look at the small MOS transistors revealing their actual forms. The foundation- analog electronics and VLSI with special focus on MOS transistors is a must. Knowledge of the ASIC design flow is important.

The analytical study must include:

• Small-signal analysis
• Static timing analysis
• Passive circuits
• Transients
• Collective understanding of signal processing tools like Laplace transform.

Apart from these, a stronghold on the fundamentals of digital electronics and microprocessors is necessary. It is advisable to opt for advanced design courses if an opportunity presents itself- this could include advanced IC design, advanced VLSI, etc.

So, what do you need to have to become the perfect handyman?

The tools to be known are usually specific to the requirements. EDA vendors provide PnR tools for synthesis and optimization. Apart from that knowledge of HDL languages like Verilog is crucial.

Tutorials are present for EDA specific tools in the respective vendor websites for reference. However, hands-on experience can be obtained only if the license is available. Usually, educational institutions have licensed machines available. Knowledge of Linux operating systems is an added advantage.

Job Positions

Specific job positions to physical design are currently available in all leading corporations having a business in the ASIC industry. Given the challenges involved, it caters to stringent screening procedures. Here are some of the top companies in this field:

• Intel
• Google
• Qualcomm
• Synopsys
• AMD

The list goes on, and a quick LinkedIn job search would return you an ample of intriguing opportunities!

What do you need apart from the skills?

Perseverance. Patience. These two in abundance always helps. It is challenging yet satisfying to create something which is eventually getting integrated into everyone’s day to day technology (like mobile phones) shortly. But with this comes a bout of responsibility. The ability to keep a serene mind and collective approach to solutions is the key. This work conditions the mind to usually approach towards a list of easy hacks. It does not always work. Tailor-made solutions are found to be advantageous.

Play around with circuits. Circuits are dramatic and unpredictable until proven through observation. Get the creative cap on and try to think like a kid- having a limited space to accommodate all his toys without breaking any of them and retrieving them easily.

Electronics is one of the enduring branches of science. Building a chip is every electronics student’s dream. If it is yours too, do not think twice before moving towards physical design engineering.

P.S: I forgot to mention the sharp eyesight to keep up with the tiny nodes. Good luck with that!

This article was first published in The Research Nest blog here.

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