VLSI Technology : Design Flow

VLSI Technology

                             With the advent of discrete semiconductor devices such as bipolar transistors, unijunction transistors, field effect transistors, etc., miniaturization started in full-swing, replacing bulky systems that used vacuum tubes. Vacuum tubes are even now used in high power applications. Since the invention of the first IC (Integrated Circuit) in the form of a Flip Flop by Jack Kilby in 1958, our ability to pack more and more transistors onto a single chip has doubled roughly every 18 months, in accordance with the Moore’s Law. Gradually, attempts were made to integrate several circuits, be it analog or digital, in a single package. These attempts succeeded in producing both analog and digital ICs, as well as mixed signal ICs. Analog ICs offered operational amplifiers, multipliers, modulators/demodulators, etc., while digital ICs integrated AND, OR, XOR gates and so on

             Chips falling under the category of small scale integration (SSI) contain up to 10 independent gates in a single package. Example of SSI includes flip flops, decoder, Multiplexer.With the improvement in technology, 10-100 gates is integrated in a single substrate that comes under the category of Medium scale integration (MSI).Example of MSI includes RAM, Adders, registers etc.In the mid of 1970s, Technology improves again and 1000 gates is integrated in a single substrate, which is called LSI.Example of LSI includes digital clock, calculators etc.Finally in 80s,comes the VLSI(Very large scale integration),which comprises of Thousands of gates in a single package. Personal Computer chips comes down in this category. VLSI circuits are everywhere ... your computer, your car, your brand new state-of-the-art digital camera, the cell-phones. Since then Integration has been growing in a very highly manner and currently millions of gates is occupying in a single package going into ULSI, System level integration and SOC. VLSI is dominated by the CMOS technology. The output switching levels from CMOS ICs is higher than TTL.CMOS having very less power consumption than TTL.74 Series (74LS) comes under the category of TTL

      

        FIELD OF VLSI 

               

               VLSI  DESIGN 

                      VLSI Design today is the most happening field in Electronics. This is a highly specialized field that has the power of integrating billions of transistors on a Silicon Chip.VLSI chiefly comprises of Front End Design and Back End design these days. While front end design includes digital design using HDL, design verification through simulation and other verification techniques, the design from gates and design for testability, backend design comprises of CMOS library design and its characterization. It also covers the physical design and fault simulation.

      VLSI IC DESIGN FLOW

                                      

                                         

                                

              Front End Design Flow

Back End Design Flow