Electronics & Communication Engineering (ECE)
Calcutta Institute Of Technology
Name:-Soumajit Bera Roll No:- 17700322005
VLSI Design Flow: From
Concept to Silicon
This presentation provides an overview of the VLSI design flow, covering the
key stages from system specification to fabrication and testing. The goal is to
equip students and early-career engineers with a concise yet informative
understanding of this complex process.
System Specification and Design
Defining System Requirements Partitioning and Design Styles
The initial stage involves defining the system's functional and The system is then partitioned into smaller, manageable blocks,
non-functional requirements. Functional requirements specify identifying key modules and their interactions. For example, a
performance metrics like clock speed, features, and instruction processor might be divided into an ALU, control unit, memory
set, while non-functional requirements address power interface, etc. The choice of design styles (e.g., full-custom,
consumption, area, cost, and reliability. For instance, designing standard cell, FPGA) and technology node (e.g., 7nm, 5nm)
a processor for a mobile device entails specifying the desired depends on cost, performance, and power considerations. Tools
clock speed, power budget, and instruction set. like SystemC and Simulink assist in this process.
Logic Design and Verification
1 Logic Design 2 Verification Techniques 3 Logic Synthesis
The architectural design is Verification techniques include Logic synthesis converts the RTL
translated into a logical formal verification, which design into a gate-level netlist using
representation using Hardware mathematically proves design tools like Synopsys Design
Description Languages (HDLs) like correctness, and assertion-based Compiler or Cadence Genus.
Verilog or VHDL. For example, one verification, which uses formal Timing constraints (setup time,
might write Verilog code for an methods to check the design against hold time) are applied during this
adder module. Logic simulation and specific properties. Tools like process to ensure proper circuit
functional verification ensure that ModelSim or Synopsys VCS are operation. Optimization for area,
the design meets the specified used for simulation. performance, and power is also
functionality. This involves performed.
developing test benches and writing
test cases to cover all functional
aspects.
Circuit Design and Simulation
Circuit Design Circuit Simulation and Analysis
The logic design is converted into a circuit-level Circuit simulation and analysis are performed using SPICE
representation, involving transistor-level implementation of simulators like HSPICE or Spectre to verify circuit
logic gates. This includes transistor sizing, layout constraints, performance, timing, and power consumption. Sensitivity
and consideration of parasitic effects. For instance, a CMOS analysis is conducted to identify critical parameters. Physical
inverter with specific performance characteristics might be design considerations include layout area, power dissipation,
designed. and signal integrity.
Physical Design: Layout and Placement
Placement and Routing 1
The physical layout of the circuit on the silicon die is
created. Placement involves arranging the circuit
components on the die, while routing connects the 2 Clock Tree Synthesis and Power
components with metal interconnects. Tools like Routing
Cadence Virtuoso or Synopsys IC Compiler are used, Clock tree synthesis evenly distributes the clock signal
taking into account design rules and manufacturing to the circuit, minimizing clock skew. Power routing
constraints. provides power and ground connections to the circuit,
minimizing voltage drop. These steps ensure proper
timing and power delivery.
Verification 3
Design rule checking (DRC) and layout versus
schematic (LVS) verification are performed to ensure
that the layout meets design rules and matches the
schematic. This step guarantees the correctness of the
physical design.
Physical Design: Extraction and Analysis
Parasitic capacitances and resistances are Post-layout simulation and analysis are Signal integrity analysis is performed to
extracted from the layout using tools like conducted using the extracted parasitics to address potential issues like crosstalk, IR
Calibre xACT or StarRC. This step verify circuit performance, including drop, and electromigration. This ensures
accurately models interconnect effects, timing, power, and signal integrity. Any the reliability and functionality of the
which impact circuit performance. performance issues are addressed by circuit.
iteratively refining the layout.
Fabrication and Testing
Fabrication
The integrated circuit is manufactured on a silicon wafer using the wafer fabrication process, which involves
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photolithography, etching, deposition, and other steps. Foundries like TSMC, Samsung, or GlobalFoundries perform
this complex process.
Testing
The fabricated chips are rigorously tested to ensure that they meet the specifications. Functional testing verifies the
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circuit's intended behavior, while parametric testing measures performance parameters. Reliability testing assesses the
chip's long-term durability and stability.
Yield Analysis and Optimization
3 Yield analysis determines the percentage of functional chips produced during fabrication, while process optimization
aims to improve yield and reduce manufacturing defects. This step is crucial for achieving cost-effective production.
Packaging and Assembly
4 After testing, the chips are packaged into appropriate enclosures and assembled into final products. Packaging provides
protection and facilitates connection to other components.
Summary and Future
Trends
Recap
The VLSI design flow comprises several crucial stages, from system
specification and logic design to circuit design, physical design,
fabrication, and testing. Each stage contributes to the development of a
functional integrated circuit.
Emerging Trends
VLSI design is continually evolving, driven by the need for improved
performance, power efficiency, security, and reliability. Emerging
trends include 3D ICs, heterogeneous integration, and AI-driven
design automation.
Collaboration and Learning
Collaboration between different disciplines and continuous
learning are essential for success in the dynamic field of VLSI
design. The ability to adapt to new technologies and design
methodologies is crucial.
