BASIC KNOWLEDGE – INTEGRATED CIRCUITS What are integrated circuits? Definition, types and more
Our world today is populated by increasingly powerful electronic devices, which all depend on integrated circuits as their fundamental building blocks. This article explains what this all-powerful device is, how it works, how it is made, and the types available. It also looks at IC advantages and disadvantages, and concludes with a review of IC market potential.
On April 11, 1984, Amstrad launched their first personal computer – the Amstrad CPC464. It became a bestselling product, with more than two million units sold in Europe. It brought computing to everyone, and owed its success to its attractive entry price, its simplicity to set up and start using, and an impressive specification. Amstrad founder Lord Sugar recalls how, during the launch, he showed the audience “two giant printed circuit boards (PCBs) covered with over 100 chips”. He continues, ”I then explained how the company was going to achieve a breakthrough in price by condensing the contents of these two PCBs into one tiny IC chip.”
The integrated circuit design was in fact a gate array, which was custom built to Amstrad’s requirements. But the real point of this little story – before getting into any detail – is to introduce the concept of loading ever more electronics functionality onto increasingly diminutive building blocks known as integrated circuits, or simply as an IC, chip or IC chip. It also highlights the impact of doing so; not just on design engineers, but on society in general.
So, given their fundamental importance, this article offers a basic overview of integrated circuits (ICs) and their role in electronics design. Specifically, it looks at:
- 1. What is an integrated circuit (IC)?
- 2. How does an integrated circuit work?
- 3. Types of integrated circuits
- 4. How are integrated circuits made?
- 5. Integrated circuit applications
- 6. Integrated circuit advantages
- 7. Integrated circuit disadvantages
- 8. Integrated circuit market
What is an integrated circuit?
The semiconductor electronics technology that drives all the devices in our factories, cars, homes, and pockets dates from the early Fifties, when the first bipolar transistors entered production. Transistors were fundamental building blocks for logic circuits and computers because they could be used as binary devices that could be switched ON and OFF. They were equally useful in analog circuits such as audio equipment or data acquisition systems because of their amplification capabilities.
Integrated Circuit Definition
Physically, a monolithic integrated circuit (IC) comprises a thin film layer of components – transistors, diodes, resistors, and capacitors, but not inductors – and interconnecting wires, formed onto the surface of a silicon substrate.
Functionally, ICs can be designed as either digital devices such as logic gates or microprocessors, or analog devices like audio or instrumentation amplifiers. Mixed signal devices combining both analog and digital functionality also exist.
The first electronic designs comprised transistors and other discrete components, including diodes, capacitors, resistors, and inductors, assembled onto a PCB which could provide electrical connections between the components as well acting as a mounting base. Simple circuits could be interconnected to achieve larger and more complex functions – but as complexity increased, so did cost, size, temperature, reliability issues and manufacturing challenges. This problem, sometimes known as ‘the tyranny of numbers’, became a technological barrier preventing the full potential of semiconductor technology being applied to more powerful and functional yet smaller devices. To move forward, there had to be a better way of building and connecting transistors in large quantities.
In the mid Fifties, when the world – and the military in particular – had realized the amazing potential of electronic computers, many scientists and engineers were looking for solutions that would not only work technically but could be produced profitably on a commercial scale. Against this background, the integrated circuit was the solution waiting to be invented.
Although there is no consensus on who made the integrated circuit a practical reality, Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor are widely credited as two major developers of the technologies needed.
Kilby was working at Texas Instruments when he developed the idea he called the monolithic principle: trying to build all the different parts of an electronic circuit on a silicon chip. On September 12, 1958, he hand-built the world's first, crude integrated circuit using a chip of germanium (a semiconducting element similar to silicon) and Texas Instruments applied for a patent on the idea the following year.
Meanwhile, at another company called Fairchild Semiconductor (formed by a small group of associates who had originally worked for the transistor pioneer William Shockley) the equally brilliant Robert Noyce was experimenting with miniature circuits of his own. In 1959, he used a series of photographic and chemical techniques known as the planar process (which had just been developed by a colleague, Jean Hoerni) to produce the first, practical, integrated circuit, a method that Fairchild then tried to patent. There was considerable overlap between the two men's work and Texas Instruments and Fairchild battled in the courts for much of the 1960s over who had really developed the integrated circuit. Finally, in 1969, the companies agreed to share the idea .
How does an integrated circuit work?
The monolithic integrated circuit concept that emerged comprises a complete circuit or group of circuits – including all the active and passive components and their interconnections - manufactured in a single piece of silicon. The word monolithic is derived from the two Greek words ‘monos’ and ‘lithos’ meaning ‘single’ and ‘stone’ respectively. The word 'monolithic' implies that the circuit is manufactured within a single crystal. This type of IC chip is sometimes described as a planar IC, since it takes the form of a flat surface.
The planar process concept contributes to the realization of integrated circuits by using an integrated circuit drawing that views a circuit in its two-dimensional projection – a plane. This allows the use of photographic processing techniques such as film negatives to mask the projection of light onto exposed chemicals. These facilitate a series of exposures on a substrate (silicon) to create silicon oxide (insulators) or doped regions (conductors). Together with the use of metallization, and the concepts of p–n junction isolation and surface passivation, it is possible to create circuits on a single silicon crystal slice (a wafer) from a monocrystalline silicon boule.
The process involves the basic procedures of silicon dioxide (SiO2) oxidation, SiO2 etching and heat diffusion. The final steps involve oxidizing the entire wafer with an SiO2 layer, etching contact vias to the transistors, and depositing a covering metal layer over the oxide to connect the transistors without manually wiring them together.
Types of integrated circuit
Kilby’s monolithic integrated circuit design concept of the Fifties still underlies most of the IC chips produced today. However, the technology is not ideal for every application, so other fabrication methods exist.
Meanwhile the number of transistors integrated onto a chip has grown exponentially – from the few components on the original devices to nearly 60 billion on a Graphcore Mk2 IPU available in 2020. This is a massively parallel processor designed to accelerate machine intelligence. Such growth has for decades followed Moore’s Law, which says that the number of components on a chip roughly doubles every one to two years. This phenomenon was noticed and described by Gordon Moore in 1965, and has remained true ever since. Apart from his Law, Gordon Moore is notable as a co-founder of the Intel Electronics company, along with the above-mentioned Robert Noyce.
Today, then, the different types of integrated circuit design can be classified by signal type and by fabrication method. Signal types comprise Linear, Digital, and Mixed Signal. Fabrication methods include Monolithic and Hybrid – which further classifies into Thick Film and Thin Film.
A Linear IC operates on continuous, analog signals and provides analog outputs. Applications include amplification, oscillation, mixing, modulation, and others. The first linear ICs were operational amplifiers; modern examples include differential amplifiers, voltage regulators, phase locked loops, analog multipliers, and others.
Digital ICs operate on binary (1 or0) inputs to perform logic functions. Most digital ICs are manufactured using monolithic technology. However, thick and thin film technologies are used for some specific applications. Digital ICs and functions are fundamental to the design of computers and any other machines with decision-making or intelligence capabilities. Functions include flip-flops, counters, and shift registers.
Mixed signal ICs contain both analog and digital circuits. Applications include FM tuners in media players, digital to analog/analog to digital converters, and Ethernet circuits.
Monolithic Integrated Circuits are manufactured or fabricated on a single chip of silicon. All the active and passive circuit components are formed at the same time, using diffusion steps. Monolithic ICs are mostly used in applications where repeatable component characteristics are required, so they are cheap and highly reliable. The operational amplifier IC741 is a classic example of a monolithic IC. It is an 8-pin IC, first developed by Fairchild Semiconductors, and later by companies like Motorola, National Semiconductors, and others.
Advantages of monolithic ICs
- Lower size and weight
- Low cost and short production time
- Highly reliable, due to no soldered joints and fewer interconnections.
- Complex circuits can be fabricated easily to achieve improved functional performance
- As components are fabricated very close to each other, stray signal pickup is eliminated. This allows small signal operation.
- No projections from the chip’s body as all components are fabricated internally.
Disadvantages of monolithic ICs: The internal components’ close proximity also results in poor isolation between them. The chips’ small size means they can only be used for low power applications, and inductors cannot be fabricated.
Hybrid IC chips fabricated using thick or thin film technology can be used when higher power handling is required. These devices are larger than monolithic ICs but smaller than discrete circuits. The passive components like resistors and capacitors are integrated, but the transistors and diodes are connected as discrete components to form a complete circuit. Therefore, commercially available thin- and thick-film circuits are combination of integrated and discrete components.
The essential difference between thin- and thick-film ICs is not their relative thickness but the method of film deposition. They have similar appearance, properties, and general characteristics.
Thin-film IC chips are fabricated by depositing films of conducting material on the surface of a glass or ceramic base. By controlling the width and thickness of the films and by using different materials selected for their resistivity, resistors and conductors are fabricated. Capacitors are produced by sandwiching a film of insulting oxide between two conducting films. Inductors are made by depositing a spiral formation of film.
Thick-film IC chips are sometimes referred to as printed thin-film circuits. In their manufacturing process silk-screen printing techniques are used to create the desired circuits pattern on a ceramic substrate.
ICs produced by thin- or thick-film techniques have the advantage of forming passive components with wider range and better tolerances, better isolation between their components, greater flexibility in circuit design and of providing better high-frequency performance than monolithic ICs.
However, such ICs suffer from the drawbacks of larger physical size, comparatively higher cost and incapability of fabrication of active components.
How are integrated circuits made?
Integrated circuit manufacturing starts by ‘salami slicing’ thin disks called wafers from a long solid pipe of silicon. The wafers are marked out into many identical square or rectangular areas, each of which will make up a single silicon chip (sometimes called a microchip). Thousands, millions, or billions of components are then created on each IC chip by doping different areas of the surface to turn them into n-type or p-type silicon. Doping is done by a variety of different processes.
In one of them, known as sputtering, ions of the doping material are fired at the silicon wafer like bullets from a gun. Another process called vapor deposition involves introducing the doping material as a gas and letting it condense so the impurity atoms create a thin film on the surface of the silicon wafer. Molecular beam epitaxy is a much more precise form of deposition.
A simplified picture of the IC chip manufacturing process can be described in six steps, some of which are repeated.
- 1. Making wafers: these are cut from silicon pipes, as described above.
- 2. Masking: The wafers are heated to coat them in silicon dioxide, and ultraviolet light is used to add a hard, protective layer called photoresist.
- 3. Etching: A chemical is used to remove some of the photoresist, making a template pattern showing the required areas of n-type and p-type silicon.
- 4. Doping: The etched wafers are heated with gases containing impurities to make the areas of n-type and p-type silicon. More masking and etching may follow.
- 5. Testing: Long metal connection leads are run from a computer-controlled testing machine to the terminals on each chip. Any chips that fail testing are marked and rejected.
- 6. Packaging: All the chips that test as OK are cut out of the wafer and packaged into protective plastic bodies, ready for use in computers and other electronic equipment.
Integrated circuit applications
Kilby and Noyce laid the foundations of the IC industry as they sought to solve the ‘Tyranny of numbers’ problem – an issue typically caused as engineers tried to handle ever-larger binary numbers. Accordingly, computers are the most obvious application for ICs – but this does not just mean explicit examples like desktop or laptop PCs, or data center servers. A huge number of devices from widely diverse industries have embedded microprocessors or microcontrollers to provide their functionality and intelligence. There can be up to 3000 microchips in a single car, for example.
IC chip ubiquity is further driven by their existence as analog as well as digital devices. This considerably increases their ability to interact with the real world, and the number of functions they can fulfil.
Examples of integrated circuit applications include:
- IoT devices
- Industrial machines and robots
- Communications systems
- Domestic appliances
- Medical instrumentation
- Security systems
- Climate control systems
- Cellphones, smart watches, and calculators
- Radar and navigation systems
- Environmental monitoring
- TV and entertainment systems
- Amplifiers for audio, microwave, and other applications
- Railway signaling
Integrated circuit advantages
- With their small size and all components and interconnections ready manufactured on a single chip, integrated circuits eliminate the size, weight, design and assembly time, and reliability issues associated with discrete component implementations.
- IC production costs are low, and they are reliable through having no soldered joints.
- Integrated circuits consume little energy and can be replaced if necessary, and can operate at high temperatures.
- They offer good operating speed due to a lack of parasitic capacitance.
- IC chips operate at low voltages and have limited power ratings. Bulk batch production allows close matching of components and temperature coefficients.
- ICs are suitable for small signal operation since the close proximity of their components as fabricated on the silicon wafer eliminates the possibility of stray electrical pickup.
- There are no external projections as all the components are inside the chip.
- For products like cellphones requiring large production runs, application-specific ICs (ASICs) can be designed to meet the product’s exact requirements while replacing a large number of smaller components. With amortization, this can reduce costs, assembly time and product size, while improving reliability. Mixed signal ASICs can incorporate both analog and digital functions, including sensor interfaces, control outputs, processor, glue logic and all types of memory.
Integrated circuit disadvantages
- IC chips can be expensive, and also liable to failures if roughly handled. They have a limited power rating; most ICs are 10W or less.
- Transformers and inductors cannot be integrated into IC chips; they have to be connected as external components. It is also impossible to fabricate capacitors with values greater than 30 pF. Larger capacitors must be connected externally. Saturation resistance of fabricated transistors is also high.
- High grade PNP assembly is not possible, and attaining a low-temperature coefficient is quite difficult.
Integrated circuit market
An integrated circuit market survey titled ‘Integrated circuits Global Market Report’, published by The Business Research Company, finds that the global integrated circuit market was expected to grow from USD330 billion in 2021 to USD350 billion in 2022 – a CAGR of 5.9 %. The growth is mainly due to companies rearranging their operations and recovering from the COVID-19 impact, which had earlier led to restrictive containment measures involving social distancing, remote working, and the closure of commercial activities that resulted in operational challenges.
The market is then expected to reach USD417.27 billion in 2026 at a CAGR of 4.5 %. The increasing adoption of the Internet of Things (IoT) is expected to make a significant contribution, due to the various benefits of using analog integrated circuits across a wide range of real-time connected devices and applications. Analog IC chips have efficient power consumption features and the signal processing capabilities needed to configure an automated device ecosystem.
Complexity in the design of automotive integrated circuits acts as a major challenge in the integrated circuits market. The structure chain of automotive IC chips is complex when compared to mobile phones and electronic home appliances, such as televisions and remote controllers. This makes developing highly reliable automotive ICs difficult.
Increased use of next-generation mobile networks, such as 4G and 5G, requires new infrastructures. Chipsets such as radio frequency integrated circuits, system on chips (SoCs), application specific integrated circuits, cellular integrated circuits, and millimeter-wave integrated circuits are mainly used in the development of 5G infrastructure, which creates a high demand for integrated circuits. Deployment of 5G as the demand driver that will require semiconductors for infrastructure increased the revenue of semiconductors from USD422.8 billion in 2019 to USD448 billion in 2020.
Asia Pacific was the largest region in the integrated circuits market in 2021, and North America was the second-largest. The regions covered in the integrated circuits market report are Asia-Pacific, Western Europe, Eastern Europe, North America, South America, Middle East, and Africa.