Dhanush
- Aug 13, 2020
- 6 min read

Understanding the VLSI Design Flow: A Comprehensive VLSI Flow Chart Guide

Updated: Aug 12, 2023

VLSI technology has been developed mainly to integrate various logic devices such as transistors, and diodes in a smaller area. The concept of #VLSI began after the development of complex semiconductors and communication #technologies. CPU, RAM, ROM, glue logic are the essential properties of an electronic circuit. The VLSI design helps us to integrate entire segments into a single chip.

The #electronics industry has achieved phenomenal growth over the last few decades, mainly due to the rapid advances in large-scale #integration technologies and system design applications. The fundamental concept of VLSI is explained in another article and the link is given in the See also section. Do check it out. In this article, we are going to discuss the VLSI design flow of technology.

Table of contents:

Introduction
What is VLSI ?
VLSI Design Flow
Conclusion

Introduction :

VLSI Full Form (Very Large Scale Integration) technology has revolutionized the electronics industry by enabling the integration of numerous logic devices, such as transistors and diodes, into a single chip. This advancement has paved the way for highly efficient and compact electronic circuits used in various applications, from consumer electronics to aerospace and defense.

What is VLSI?

VLSI stands for Very Large Scale Integration, which refers to the process of integrating a large number of electronic components, such as transistors, resistors, capacitors, and diodes, onto a single semiconductor chip. The integration of these components allows for the creation of complex and sophisticated electronic circuits, enabling increased functionality and reduced physical size.

VLSI (Very Large Scale Integration) technology has been a driving force behind the remarkable growth of the electronics industry. It has allowed for the integration of a large number of electronic components, such as transistors and diodes, onto a single semiconductor chip, enabling the creation of highly efficient and compact electronic circuits. Two crucial aspects of VLSI design are ASIC (Application Specific Integrated Circuit) design and VLSI physical design, which play essential roles in the overall design flow.

ASIC Design Flow in VLSI Flow Chart:

The VLSI design flow begins with formal specifications of the VLSI chip, defining the high-level representation of the system. This is where ASIC design flow comes into play. ASICs are customized integrated circuits designed to perform specific functions, tailored for particular applications. During the architectural design stage, engineers make critical decisions related to ASICs, such as choosing between RISC (Reduced Instruction Set Computer) and CISC (Complex Instruction Set Computer) architectures. These decisions heavily influence the overall performance and functionality of the VLSI chip.

VLSI Physical Design in VLSI Flow Chart:

After the functional design, the logic design proceeds to the VLSI physical design phase. This step involves translating the logical representation of the circuit into a geometrical layout. Engineers use specialized software and tools to convert the abstract circuit diagram into a precise layout with actual dimensions and positions of each component. The physical design ensures that the circuit meets specific performance and power requirements. The physical design includes several steps, such as floor planning, placement, routing, and optimization. Floor planning involves arranging the functional blocks and determining their approximate sizes and locations on the chip. Placement is the process of assigning exact positions to individual components, while routing involves creating interconnections between these components. Optimization aims to improve the layout's overall performance, reducing delays and power consumption.

Fabrication and Beyond:

Once the physical design is complete, the layout data is used to create photo-lithographic masks for the fabrication process. Silicon wafers are used as the base, and various layers of materials are deposited to create the final VLSI chip. After fabrication, the chips undergo rigorous testing to ensure they meet the design specifications before packaging.

The VLSI design flow, illustrated through the VLSI flow chart, involves a series of steps that culminate in the creation of highly sophisticated integrated circuits. ASIC design flow plays a pivotal role in determining the chip's functionality, while VLSI physical design ensures the circuit's optimal performance and power efficiency. As VLSI technology continues to evolve, it will drive further innovation across various industries and solidify its position as a key enabler of modern electronic devices.

VLSI Full Form in Computer:

In the context of computer technology, VLSI Full Form is Very Large Scale Integration. It involves designing and fabricating integrated circuits with millions (and sometimes billions) of transistors, allowing for powerful and feature-rich computing devices.

Applications of VLSI:

VLSI technology has found applications in various fields, including:

Aerospace: VLSI is used in aircraft takeoff and landing systems, weather monitoring, and control operations inside aircraft.
Consumer Electronics: VLSI powers smartphones, laptops, tablets, and smart home devices, enhancing their performance and functionality.
Bio-electronics: In the medical field, VLSI technology plays a vital role in developing advanced medical devices and monitoring systems.
Wireless Communication: VLSI chips enable efficient communication in wireless devices, such as smartphones and IoT devices.
Defense: VLSI technology is applied in military equipment and communication systems, ensuring robust and secure operations.

DESIGN OF VLSI FLOW CHART

The VLSI design cycle starts with the formal specifications of a VLSI chip, followed by a series of steps and eventually, produces a packaged chip. The flow chart explains the process that is involved in the physical fabrication of VLSI chips.

VLSI design flow

A brief explanation of the flow chart is given below in the article.

SYSTEM SPECIFICATIONS

The system specifications are nothing but the factors which are to be considered before fabricating a device or constructing any design. The VLSI design process begins with defining the high-level representation of the concerned #system.The specifications of each and every component should be included in the design with the consideration of market requirements and economic viability.

The specification includes the size of the IC, the velocity of the current flow in it, and the maximum amount of power that can be consumed by it. It also consists of the performance and the functionality of #transistors used in it. After determining the specifications, it is followed the architectural design.

ARCHITECTURAL DESIGN

This section serves as the building block of VLSI design. The architectural design stage lays the foundation for the VLSI chip. Here, the overall structure and concept of the integrated circuit are determined. Designers make critical decisions, such as choosing between RISC (Reduced Instruction Set Computer) and CISC (Complex Instruction Set Computer) architectures, deciding on cache size, pipeline structures, and handling floating-point operations.

FUNCTIONAL DESIGN

This represents the functional units involved of the VLSI design and the interconnections between them. The functionality of all units is specified on the basis of their input, output, and time is taken for conduction.This stage is crucial for enhancing the overall chip design and simplifying the fabrication process. It also aids in error detection and debugging.

LOGIC DESIGN

This section can also be stated as Register Transfer Level [RTL] description. This RTL can be expressed in Hardware Description Language such as Verilog, or VHDL.

This logic design takes care of the word widths, register allocation, and also the control flow of the fabrication process.

It also carries out the necessary arithmetic operations. The logic design comprises the Boolean expressions which can be used in the process of simulation and verification.

CIRCUIT DESIGN

Here, the #circuit representation is developed based on the logic design. It is usually expressed in circuit diagrams, that consist of circuit elements such as ICs, transistors, diodes, and the interconnection between them. By considering the speed and power requirement of the fabrication process, the above-mentioned #Booleanexpressions are converted into a circuit design.

PHYSICAL DESIGN

In this step, the circuit diagram is converted into a geometrical design called layout. A Layout is constructed by describing logic components such as diodes, and transistors in their respective geometric models, and also the interconnections between them are also represented by various lines in multiple layers. This is a complex process and so it is operated as an automated function with the help of Layout synthesis tools.

FABRICATION

After constructing the layout, it is verified and enters the fabrication process. A wafer which is about 20 cm long is the base of the fabrication process. Silicon crystals are used to produce wafers. Layout data is converted into photo-lithographic masks. Masks identify the spots, where the elements are needed to be deposited. The wafers are needed to be polished perfectly as the VLSI devices are in small dimensions.

PACKAGING AND TESTING

After fabricating, packaging should be done carefully in such a way, that the chips should ensure all the design specifications without any damage. Chips used in Multi-chip modules are not packaged since they use bare chips. Printed circuit boards use chips that are packaged in the Dual In-Line package and Quad Flat package.

VLSI has been applied in diverse fields such as aerospace, consumer electronics, Bio-electronics, wireless communication, and also in defense. In aerospace, VLSI is applied in the takeoff, and landing of airplanes, weather monitoring, and control of the operations inside the aircraft. The future of the electronics industry is greatly dependent on VLSI technology.

Conclusion:

VLSI technology has been instrumental in the rapid growth of the electronics industry. It allows for the integration of complex logic devices into a single chip, resulting in highly efficient and compact electronic circuits. From system specifications to fabrication, each step in the VLSI design flow contributes to the creation of cutting-edge electronic devices that power modern technologies and shape the future of innovation.

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