Integrated Circuit Components

INTRODUCTION.

An integrated circuit consists of electronic circuits and components implanted on silicon. It is called an integrated circuit because the base material is silicon as opposed to a discrete circuit which is heterogeneous—ICs range from simple logic modules and amplifiers to complete microcomputers.

HISTORY

In the late 1950s, integrated circuits (ICs) were used in missile control systems. The integrated circuit was patented in 1959 and produced a breakthrough in the technology field.

The first integrated circuits developed in 1959 contained only up to a dozen components on a single chip. The old manufacturing process for ICs was named small-scale integration or SSI. By the mid-1960s, medium-scale integration, MSI, produced ICs with hundreds of components. Later on, the first microcomputers were developed by Large Scale Integration techniques or LSI.

SIGNIFICANCE.

These miniature circuits have been cost-effective, highly reliable with low power requirements and high processing speeds, respond to a wider input range, and produce a wider output range.

Integrated Circuit Features

1. Construction & Packaging

The integrated chip, made up of silicon, is bonded into a set of tiny gold and aluminium wires as they are very small and cast into a flat block of plastic or ceramic which has metal pins on the outside that leads to the wires inside. The solid block keeps the chip cool.

2. Size of an IC

The size of the integrated chip varies between 1 square mm to more than 200 mm.

3. Integration of an IC

Integrated chips like microcontrollers can incorporate a microprocessor, memory, and interface all in the same device.

How Integrated Circuit Works?

N regions are produced by adding dopants to silicon, where they can donate an electron. On the other hand, the P region is produced where dopants can accept an electron. PN junction, being crucial for ICs working, is only 0.000004 inches wide, is produced when P and N regions join.

Within a PN junction, P dopant accepts electrons from N dopant atoms to form Depletion Region. When a positive voltage is applied to the P region, current flows towards the N region. But when the positive voltage is applied to the N region, no current flows. This process forms the basis for the functioning of ICs.

Development Process of Integrated Circuits.

Repairing the silicon wafer

· 1 Silicon cylindrical ingot, 1.5 to 4 inches wide, is held vertically inside a vacuum chamber with a high-temperature heating coil encircling it. The initial temperature is 1400C. As heating coils move down, impurities are carried along with them. At the bottom, no impurity is left. The bottom is then sliced off to get purified silicon.

·2 Wafer slicer produces 0.004-0.01 cm thick silicon wafer from the ingot.

· 3 The surfaces of the wafer are protected from oxidation through the use of silicon dioxide at about 1830°F (1000°C) and high temperature so that oxygen in the form of vapours reacts with silicon.

Masking

·4 In ICs, the design of each layer in the form of a mask, which is clear in some areas, is transferred to the surface of the wafer

·5After being evenly distributed on the wafer, 5 Photoresist materials were baked to remove the solvent.

·6. Beams of electrons, x-rays of light are used to irradiate the photoresist when a coated wafer is placed under the first mask layer. This dissolves only positive photoresists, not a negative one.

· 7 The uncovered areas are then used to produce a layer of P or N regions by doping methods.

Doping — Atomic diffusion

· 8 In this method, a batch of wafers is placed in an oven made of a quartz tube surrounded by a heating element to add dopants to P and N regions.

· The wafers are heated at a temperature of about 1500-2200°F (816-1205°C) so that dopant and gas pass over the wafers and dopant gets deposited on the hot surfaces left exposed by the masking process.

Doping — Ion implantation

·9 In this method, an ionized dopant gas is fired at specific regions where ions penetrate the wafer and remain implanted. Schematically, the whole process resembles firing a beam in a bent cathode-ray tube where dopant is projected at the target area. But it’s a slow process.

Making successive layers

·10 Through the above process, several layers are formed, and silicon dioxide used between layers and components acts as an insulator. This is done through chemical vapor deposition. The surface was sealed by a silicon dioxide layer, contact points were opened by an etching process, and the contact pads were made by aluminium deposition. At this manufacturing process, ICs were tested for electrical functionality.

Making individual ICs

·11 Each chip on a silicon wafer is separated by using a diamond cutter. Those ICs that failed the electrical test or were damaged during the chip separation process are discarded.

·12 The good ICs are individually bonded into their mounting package, and the thin wire leads are connected.

·13 The completed integrated circuits are sealed in plastic bags to be stored or shipped.

Integrated Circuit Design

Following are the categories of IC design:

·       Digital Design

In this design method, the circuit density and efficiency are maximum. The ICs designed using this method work with binary input data, e.g., in computer storage microprocessors. Designing of digital integrated circuits is summarized below.

·        Analog Design

The analog design method is used to formulate oscillators, regulators, and resistors to perfect power dissipation, gain, and resistance.

·       Mixed Design

It employs analog and digital design principles that work as Digital to Analog converters, Analog to Digital converters (D/A and A/D converters), and clock/timing ICs.

Commonly Used ICs

Logic Gate ICs

These are used to get one logical output through different inputs.

Timer ICs

Provide accurate timing cycles with 100% or 50% work cycle.

Operational Amplifiers

With a differential input we get a single-ended amplified output.

Voltage Regulators

It is used to get constant DC output.

How can we dispose or recycle ICs

Significant recycling industries have emerged, intending to dispose of toxic substances like gallium and arsenic and reuse them in other gadgets.

The Future

It is hard to predict the future. Change in technologies can give one to think out of the box. A lot of changes are made until now, and moving on change in architecture, circuit layout and the material of the chip is also new research ideas with which manufacturers are dealing with. Futurists have given an idea that the upcoming generation would be based on biological circuits instead of mineral-based circuits.