All About VSLI

04 June 2021

By: Atreya Tiwari
What is VLSI? Very-large-scale integration (VLSI) is the process of building an integrated circuit (IC) by integrating thousands of transistors into a single chip. The microprocessor is an example of a VLSI device. Before the advent of VLSI technology, most ICs could perform very few functions. VLSI lets IC designers add CPU, ROM, RAM and other glue logic into one chip. With the emergence of VLSI, the number of applications of integrated circuits (ICs) in high-performance computing, controls, telecommunications, image and video processing, and consumer electronics has increased tremendously.In short, it is the backbone of today's electronics. Primary advantages if VLSI • Reduced size for circuits • Increased cost-effectiveness for devices • Improved performance in terms of the operating speed of circuits • Requires less power than discrete components • Higher device reliability • Requires less space and promotes miniaturization What is the scope of VLSI? There are myriad opportunities for jobs in the semiconductor industry. It is imperative for you to understand the various job titles and job profiles that VLSI offers. Additionally, you must be aware of your strengths and personal attributes to choose the right job accordingly. Let us look at the various job opportunities and designations in the VLSI industry. VLSI job opportunities are less but the number of freshers interested in VLSI is also less. We can broadly classify VLSI domain jobs into two categories: 1. Front end: Includes programming of ASIC chips/ FPGAs / CPLDs. This is more of programming in VHDL/Verilog/System Verilog/SystemC and so on. The front end is further subdivided into two categories- Design Jobs and Verification Jobs. Design includes developing logic circuits, placement routing, timings etc; Verification includes developing test environment and debugging of the DUT(RTL developed by designers). Both design and verification in VLSI is challenging with high returns in terms of remuneration. 2. Backend This involves the physical design and physical verification. The number of jobs in the back end is lesser compared to the front end. The work is CMOS level i.e; pre-fabrication level. They talk in terms of nanometers of CMOS transistor gate width. The goal of all semiconductor companies is to reduce the nanometer width. What does a VLSI engineer do? VLSI domain is quite vast and offers different specialisations. Some of the major job titles/profiles are: Design Engineer: Design Engineers are accountable for designing: FPGA – Field Programmable Gate Arrays AMS – Analog Mixed Signal design PCB – Board Design DFT – Design For Test ASIC – Application Specific Integrated Circuit design Custom Designs – Transistor level The design engineer needs to have a deep knowledge of the digital basics and application of the product. Application Engineers: Application Engineers are responsible for supporting the Design and Verification engineers on how to use EDA tools and methodologies. They act as an interface between the R&D and customers. AE engineer's job requires travelling to customer locations, good communication skills and ability to make good presentations and client-company relationships: Field Application Engineer – Pre-sales Corporate Application Engineer – Post-sales Application Consultants Verification Engineer: Verification Engineers are responsible for the Verification of the design implemented by the designers. Majority of the VLSI jobs in India are in the verification department where many foreign companies outsource verification work to India. Verification engineers need a sound understanding of programming, protocols and applications. EDA/CAD engineers: EDA/CAD engineers are responsible for designing and developing the required tools for the implementation of chips. As the number of transistors is from multi-millions to billions advanced, tools are required to develop the chips. Updating yourself with the latest technologies and methodologies is a must in this domain. Marketing and Sales: Marketing and Sales Representative are responsible for selling and promoting the chips generated by the company. A VLSI engineer with an interest in sales and marketing can switch to this department. What are the skills required for a VLSI engineer? 1. Scripting languages – With every job focusing on efficiency, knowledge in at least one scripting language like Python/Perl would help. In RTL design scripting languages help in generating repetitive code and parameterizing designs. In design verification, these would be useful even more in terms of simulation setup, testing, regression and debugs etc.VHDL is used in India, while Verilog is common in America. You should also acquaint yourself with SystemVerilog and verification libraries like OVM/UVM. 2. Fundamentals of analog circuit design – PLLs, CDR (clock and data recovery circuits), ADC/DAC, high-speed signalling and signal integrity concepts (cross talk, jitter, ringing etc) If you are working on a purely digital design, these may not be that significant, but current designs always have several complex clocking schemes and high-speed interfaces which makes an understanding of these important. 3. Fundamentals of digital logic design. These are must to make you think as a chip designer, be able to micro-architect the design in terms of logic blocks, interconnects and synthesizing into right constructs etc. 4. Design Methodologies and flow – Familiarity with design flows and methodologies – RTL design, physical design, STA (Static timing analysis) etc. 5. Power, Performance, Area estimations and trade-offs – Most of the modern chip designs would have a target of meeting highest performance at the lowest power within an optimal area – decided by market requirements and cost. A chip designer will need to trade off several design features/techniques to achieve this. 6. Use of at least one HDL language – Chip designs use an HDL like SystemVerilog or VHDL and having sound knowledge of the language helps you to translate your design into an efficient HDL model. Based on whether you are using the HDL for RTL development or design verification, the skills would vary. Along with the above mentioned technical skills, one must possess qualities like dedication, teamwork, leadership and good interpersonal/communication skills that will make you a successful VLSI engineer. Does VLSI require programming? As a VLSI engineer, you have to convert your ideas into products and each idea that you have needs to be implemented with help of various high-level languages. Good coding knowledge of C is also needed primarily for those who handle processor verification as it is needed to write C based Test Cases to analyze the features and connectivity. 1. Front end VLSI front end which majorly consists of two sub-domains: RTL and ASIC Verification. • RTL coding is related to VHDL, Verilog and SystemVerilog.VHDL and Verilog are mostly used as HDL whereas SystemVerilog is an HDVL. • ASIC Verification where coding is largely with SystemVerilog and methodologies like UVM and OVM. Scripting knowledge on Perl and Python is desired. 2. Back end In the back end of VLSI where it mostly deals with physical design, Analog layout, DFT, There you need to be proficient with scripting languages like TCL or Perl. To summarise: Logic Design - Verilog, VHDL, Tcl, Python, Perl etc. Physical Design - Tcl, Python, Perl, Shell, Awk, Sed etc.