Integrated Circuit is a micro-circuit which is fabricated on a semiconductor chip. This post will discuss what is Integrated Circuit, it’s various types based on Mode of Operation, Fabrication and complexity, its construction, applications, advantages and disadvantages.
What is Integrated Circuit
Integrated Circuit is a micro-circuit which consists of various electronic components like resistors, capacitors, diodes, transistors etc. It is fabricated on a single semiconductor chip. It is abbreviated as IC. IC’s are minute having minimum dimensions of 0.2 mm × 0.2 mm × 0.001 mm. Both active and passive components like transistors, diodes, resistors, capacitors can be fabricated on a single chip.
Fig. 1 – Introduction to IC
However, Inductors and large value Capacitors are not fabricated in an Integrated Circuit. If the Circuit requires Inductors then it is connected externally to an IC. Single IC can function as an Amplifier, Oscillator, Memory, Processor etc.
In the year 1958, Jack Kilby demonstrated his idea of integrating components on a chip. He connected the components using gold wires. Robert Noyce found a practical solution to interconnect the components on a chip. Together, they showed the world that many transistors, resistors, and capacitors could be integrated on a single semiconductor chip.
Fig. 2 – (a) Jack Kilby (b) Robert Noyce
Types of Integrated Circuits
Integrated Circuits are classified into three types:
- Based on Mode of Operation
- Based on Fabrication
- Based on Complexity
Based on Mode of Operation
IC’s are classified into two types based on the Mode of Operation or the signal processed. They are:
- Digital IC or Non-Linear IC
- Analog IC or Linear IC
Digital IC or Non-Linear IC
Digital Integrated Circuits are the logical networks capable of performing mathematical calculations and are commercially available as Memory Chip, Microprocessor, Microcontroller, Counters, Logic gates, Registers etc. The input/ output value is either logical high/low (0 or 1).
Analog IC or Linear IC
Analog Integrated Circuits are the discrete networks, which processes the signals that are continuously variable like an audio signal. The values of voltage or current may vary continuously between minimum and maximum values. They are available commercially as Voltage comparators, regulators, op-amps etc.
Based on Fabrication
IC’s are classified into three types based on the fabrication. They are:
- Monolithic IC
- Thick-Thin Film IC
- Hybrid IC
In Monolithic type of Integrated Circuits, all the active and passive components are formed simultaneously by diffusion process on a single silicon chip. It is followed by metallization process to interconnect the components to obtain the required circuit. They are generally used in low power applications.
Thick-Thin Film IC
These are slightly larger than Monolithic IC’s and passive components like resistors and capacitors are integrated whereas diodes and transistors are connected as discrete components to obtain the required circuit. Thus, Thick-Thin film IC’s incorporate both integrated and discrete components.
Hybrid IC’s are the combination of two or more monolithic IC’s or it is produced using Monolithic IC and Thick-Thin film Integrated Circuit. These are used for high power applications.
Fig. 3 – Image of Silicon Wafer
Based on Complexity
The circuit complexity can be determined by the number of active devices used. Hence Integrated Circuits can be classified in to six types based on the number of components used on a chip. They are:
- Small Scale Integration (SSI)
- Medium Scale Integration (MSI)
- Large Scale Integration (LSI)
- Very Large Scale Integration (VLSI)
- Super Large Scale Integration (SLSI)
- Ultra Large Scale Integration (ULSI)
Small Scale Integration (SSI)
It consists of 10 Transistors or few Gates such as AND, OR, NOT within a single chip.
Medium Scale Integration (MSI)
Large Scale Integration (LSI)
The range is between 100-1,000 Transistors or hundreds of Gates that performs logical operations. LSI is implemented for memory units, ALU etc.
Very Large Scale Integration (VLSI)
VLSI fabrication is used for Processors, Programmable Logic Devices where the Transistor count ranges between 1,000-10,000 or thousands of Gates.
Super Large Scale Integration (SLSI)
SLSI is implemented for circuits which require 10,000-100,000 Transistors within a single package like Microprocessor chips, Microcontrollers etc.
Ultra Large Scale Integration (ULSI)
In this type of fabrication more than 1 Million Transistors are integrated on a single chip. This technique is being used in CPU’s, GPU’s, FPGA’s etc.
Fig. 4 – IC Packages (a) Metal Cap (b) Quad Flat (c) Ceramic (d) Dual in-line
Construction of IC
Manufacturing process of Integrated Circuit begins with formation of Electronic Circuits on the surface of Silicon crystal wafer. The electronic circuits consist of many transistors, Diodes, capacitors, resistors. A thin film layer which forms the wiring for the components is deposited on the wafer. The thin film is coated with Photoresist.
When this material is exposed to ultraviolet light, the circuit pattern from the photo-reticle is projected on the Photoresist. This technique is known as Photolithography. The developed Photoresist acts as a Phot-mask for etching and thin film is further processed to form a single layer circuit.
Fig. 5 – Construction of Integrated Circuit
This process is repeated many times to form a multi layered circuit on a Silicon wafer. Steps are taken to ensure that the patterns fabricated is identical to the design specifications. Silicon Wafer which is processed has to be encapsulated and this marks the final stage in the Integrated Circuit manufacturing process. Encapsulation procedure involves various process like IC bonding, film attaching etc. The chips are then mounted in different types of packages as shown in the Fig. 4.
Applications of Integrated Circuit
The applications of IC’s include:
- They are used in smart phones, mp3 players, laptops, computers.
- IC’s are also used in Television and cameras.
- They are widely used in aircraft and space craft systems.
- IC’s are the basic component used in scientific calculators and digital watches.
- They are used in control systems.
Advantages of Integrated Circuit
The advantages include:
- IC’s are smaller in size and hence the circuit is simplified.
- They are highly reliable as all the circuit components are fabricated.
- Space required by Integrated Circuit is very less.
- Power consumption is less.
- They are economical.
- It has the ability to operate at extreme temperatures.
Disadvantages of Integrated Circuit
The disadvantages are:
- Inductors and high value Capacitors cannot be fabricated.
- Integrated Circuit (IC) cannot produce high power.
- If any component on IC is faulty, then the entire IC has to be replaced.