What is an Integrated Circuit?
An integrated circuit contains a combination of transistors, resistors and capacitors all on one pea-sized piece of semiconductor material. This enables the shrinking of electronic devices to the point where they are small, intelligent and operate with low power consumption.
ICs are often referred to as chips and they fit into printed circuit boards for easy handling. They are produced in different types of packages, which differ in pin configuration and standardized by business organizations.
History
At the end of the 1950s the transistor had already significantly reduced the size of circuit components such as diodes, resistors and capacitors. But for many electronic devices such as mobile phones and computers, the transistor was still too large, so engineers looked to a much more efficient technology: the integrated circuit.
The IC is considered one of the most important scientific inventions of all time, and its inventor was awarded the Nobel Prize in 2000. Jack Kilby was the first to create a working IC in 1959 while at Texas Instruments. His breakthrough was to vapor deposit gold onto silicon and connect the resulting chips with metal wires, an innovation that eliminated the need for a separate circuit board.
Several other inventors worked on similar concepts at about the same time. For example, in 1949 German engineer Werner Jacobi filed a patent for an integrated circuit-like semiconductor amplifier that lined up five transistors on a single chip in a three-stage arrangement to shrink the components and make hearing aids cheaper to produce.
The IC was soon followed by other innovations, such as Robert Noyce’s invention of the silicon particleboard in which the components were arranged in groups on individual silicon chips instead of being soldered to a separate circuit board. Over the next decades, Small-Scale Integration (SSI) brought dozens of components to a single chip, Medium-Scale Integration (MSI) added hundreds, and Very Large Scale Integration (VLSI) provided tens of thousands of components in an area no larger than a postage stamp.
Functions
The integrated circuit is the basic building block of modern electronics. It is made up of miniature versions of all the basic components that are used in most electronic devices, like transistors, resistors, and diodes. These are then arranged on programmable voltage reference a semiconductor substrate. The resulting integrated circuit is called a chip or microchip. Depending on how it has been designed, the chip can perform several different functions. These functions can be anything from regulating current flow to performing logic gates.
The first step in designing an integrated circuit is known as logic synthesis. Here, macro-level functional descriptions of the circuit elements are recomposed into the required low-level circuit components using a piece of software. Then, the collection ideal diode of these components is simulated to verify that they will function correctly. This includes simulation of the effects of signal crosstalk, added resistance from wiring, and variability in the manufacturing process itself.
Once the design has been analyzed, the IC is fabricated on the semiconductor wafer. It is then encapsulated in a plastic package. There are two types of IC packages: through-hole and surface-mount. The type of IC you choose depends on how it will be mounted to the printed circuit board. Through-hole ICs have longer pins that extend through the IC package and can be soldered to a PCB, while surface-mount ICs have shorter pins that do not extend beyond the edge of the IC package.
Applications
Unlike discrete circuits that used to be assembled using components such as resistors, diodes, transistors and capacitors, IC’s are integrated on a single block of a semiconductor chip mainly made of silicon. IC’s consume less power, cost less and are far more reliable than their predecessors. They can also operate at higher frequencies and speeds. In addition to transistors, IC’s contain other components such as inductors but these are not fabricated inside the IC.
IC’s can be used in a variety of electronic devices such as computers, microprocessors and mobile phones. They can also perform various functions like waveform generation as in oscillators, voltage magnification as in amplifiers and performing binary operations such as AND, OR, NOT etc as in logic gates. They are also used in timing circuits such as timers, pulse generators and frequency counters. IC’s can also function as operational amplifiers which are high gain, differential input and output amplifiers.
The invention of the IC revolutionized electronics and computing during the 1950’s and 1970’s. First engineers were able to put dozens of components together on a chip in what was called Small-Scale Integration (SSI). Later, they began putting together thousands of transistors on a chip in what was known as Medium-Scale Integration (MSI). They eventually reached the point where they could create tens of thousands or even millions of transistors on a chip in what is referred to as Large-Scale Integration or VLSI.
Manufacturing
The IC is the key element of many electronic devices such as cell phones, digital cameras, and computers. It combines transistors, resistors, capacitors, and wiring into one small chip that operates far more efficiently than the vacuum tubes (electronic circuits) that preceded them. These large, bulky vacuum tubes needed to warm up to function and were often damaged by even minor bumps or impacts. Integrated circuits are also smaller, faster and cheaper to produce than the older technology, allowing them to be used in more places.
Using a computer to design a pattern on a photomask, the layout of components and their interconnections is then transferred onto a silicon wafer. This is where the integrated circuit’s real magic happens. The wafer is then etched to expose the desired layer of semiconductor material. Then the patterned layer is doped with certain types of semiconductors (N-type and P-type) to create the necessary transistors, diodes, and other components.
The patterned layer is then etched again to remove excess silicon and metal. A passivation layer is then applied to the surface of the chip to protect it from contamination and moisture. Aluminum is then deposited at certain locations to make electrical contacts. The resulting IC is now ready to be soldered to other ICs or packaged into its final device. For easy handling and to safeguard the IC from harm, it is placed into a protective package that includes a plastic shell or a glass envelope.