What is an IC chip?
Integrated circuits are the brains of modern intelligent electrical devices.
They have become synonymous with technology because devices become faster and more clever as they advance.
Some of the recent developments you might have heard of are the M1 and M2 chips. Wanting to know more about IC chips? Let’s find out below.
What Is an IC Chip?
In a nutshell, an IC chip is a semiconductor circuit built to fit in a tiny chip. Also known as a microchip or chip, this semiconductor device primarily consists of fabricated transistors.
And they are the brains of most modern digital computers.
Integrated Circuit Elements
Besides transistors, one integrated circuit can contain millions or billions of components (diodes, resistors, and capacitors). Since the chip is a tiny device, these electronic components are microscopic.
And they connect via thin aluminum or copper webs in the semiconductor wafer.
IC Chip Generations
Ever since the invention of the IC in 1958, the goal among chip designers and manufacturers has been to fit as many transistors per chip while making them smaller.
Gordon Moore observed these improvements in 1965 and came up with the observation of transistors doubling per chip every two years. So as the years progressed, chips have advanced through these generations.
- Small Scale Integration (SSI): Houses tens to hundreds of transistors per chip with 1-12 logic gates
- Medium Scale Integration (MSI): Contains hundreds of transistors per chip with 13-99 logic gates
- Large Scale Integration (LSI): Houses thousands to several hundred thousands of transistors per chip with 100-9,999 logic gates
- Very Large Scale Integration (VLSI): This single chip has up to a million transistors and 10,000-99,999 logic gates
- Ultra Large Scale Integration (ULSI): Modern ICs fall under this category. They contain over a million transistors per chip and hundreds of thousands of logic gates, making them the highest-density devices.
A computer motherboard with multiple chips
Types of IC Chips
Integrated circuits can either have an analog, digital, or mixed design.
Analog (Linear) Chips
These microchips produce a continuously variable output that changes depending on the input electrical signal. The continuous variation implies the chip can output an infinite number of states.
And when you plot the instantaneous output vs. the input, you’ll get a straight line, hence the name linear.
An operational amplifier (analog chip)
These chips are typical in radio & audio frequency amplifiers and sensors. They have few electronic components, and you can program them to turn other devices off or on after reaching a preset threshold.
Digital Chips
Digital chips operate using two discrete levels: a logic 0 (low) and a logic 1 (high). The building blocks that enable these binary operations are logic gates.
These chips are typical in personal computers, mobile phones, modems, networking devices, etc.
Mixed Design Chips
Mixed circuit design chips incorporate both the analog and digital circuits described above. So they can function as analog-to-digital converters, digital-to-analog converters, timers, and clocks.
Analog-to-digital converter chips
Typical IC Chips
These are the most common chips in use today.
Logic Gate Chips
Logic gates form combinational circuits that generate logical outputs based on several input signals. You can package them in an IC to create counters, timers, shift registers, latches, etc. And most come in DIP, SSOP, or SOIC packages.
A shift register
Timers
Timer ICs usually contain logic gates with precise timing cycles and a 50% or 100% duty cycle.
Microprocessors, Microcontrollers, and FPGAs
These are arguably the most sophisticated IC chips on the market. They contain millions or even billions of transistors per chip and come in different size/complexity configurations.
For instance, there are 8-bit microcontrollers for dev boards and 64-bit microprocessors to run complex computer operations.
The simpler microcontrollers usually have few connection pins in QFP, QFN, or DIP packages. But the complex FPGAs and microcontrollers must have thousands of pins to power and connect the internal components. So you’ll mostly find them with BGA or LGA packages.
A computer processor with an LGA package
Operational Amplifiers
These chips are high-gain voltage amplifiers that produce a single-ended output from a differential input.
Sensors
Digital sensors are analog chips that can generate a continuously variable output. They include gyroscopes, accelerometers, digital thermometers, etc.
Voltage Regulators
These integrated circuits generate a constant DC output regardless of the DC input changes.
Typical IC Packages
Another way to differentiate chips is by using their packages, which include the following.
- Quad Flat Package (QFP): These packages contain pins on all chip sides. And they can range from eight to 70+ per side. QFP pins have a gull-wing shape and a 0.4-1 mm spacing between them.
A chip with a QFP
- Quad Flat No-Lead (QFN): These leadless packages are usually tiny and have thermally conductive pads to enhance their heat dissipation properties.
A chip with a QFN
- Pin Grid Array (PGA): As the name suggests, PGAs have pins protruding from the chip. And instead of soldering them to the board like QFP and QFN, these packages mount on a CPU socket. So you can remove or mount them quickly without any tools.
An old computer CPU with a PGA package
- Land Grid Array (LGA): This package is the opposite of PGA. Instead of having pins on the chip, these ICs have flat pads with leads on the CPU sockets. PGAs have pinned chips with flat contact pads on the CPU socket.
A computer chip with an LGA package
- Ball Grid Array (BGA): This package consists of tiny balls for soldering on the PCB. Since the balls are small, the BGAs have high-density connection points for powering and transferring electrical signals. They don’t need dedicated sockets but are more challenging to replace in case of device failure.
A chip with a BGA package
- Dual Inline Package (DIP): Rectangular chips with two parallel rows of pins to insert into PCB holes (thru-holes) or breadboards. The leads have a 0.1-inch spacing, and the DIP package dimensions depend on the pin count.
A chip with a DIP
- Chip Scale Package (CSP): CSP is similar to BGA. But the surface-mounting area must not exceed 1.2 times the die area. And it must have a single die.
- Multi-Chip Module Package (MCM): This package contains several pins or terminals for integrating multiple chips, dies, or other discrete components.
Microchip Fabrication Process
Creating a microchip is complex because the transistors, resistors, capacitors, and other internal components are microscopic. Plus, the entire circuit sits in a single piece of silicon. But we’ll simplify this process into these eight steps.
Wafer Production
The process begins by growing pure silicon crystals into long cylinder shapes, then slicing them into thin wafers. This slicing is similar to salami slicing. Chips emerge from these thin wafers after they get cut into tiny pieces.
A silicon wafer
Silicon gets extracted from sand. But to get pure silicon, heat the sand until it melts to form an uncontaminated liquid.
The liquid undergoes solidification using the crystallization process to create ingots. These long cylinders (ingots) get sliced into thin wafers.
But the surface after slicing is rough and has defects. So the wafers get polished to prevent electronic circuit precision issues.
Masking
The silicon wafers created in the previous step are not conductive. So this step is necessary to make them semiconductive.
Oxygen or water vapor gets sprayed on the surface to create a uniform oxide layer. This film protects the wafer surface and prevents current leakage within the circuits.
Photolithography
This process draws the circuit on the wafer surface. And it is similar to developing a photo from a film because it uses light. In this case, the photomask is the film because it holds the computer-designed circuit pattern.
A silicon wafer undergoing photolithography
But you cannot develop the circuit directly on the oxide layer. So a thin photoresist layer gets added above the silicon oxide.
So when you place the photomask above the wafer and shine light above it, the photoresist responds to light, imprinting a circuit pattern.
Etching
Chemical etching removes the unwanted photoresist to leave the circuit pattern. Some chip makers use plasma or gas for dry etching.
Regardless, this process leaves a template pattern that shows the sections to place the p-type and n-type silicon transistors.
Remember, the wafers have markings that separate the individual chips into multiple rectangular and square areas. So photolithography and etching only occur in these areas.
A silicon wafer after etching
Deposition/Doping and Ion Implantation
With the designs etched on the surface, the wafers undergo heating using gasses with impurities to form the n-type and p-type silicon junctions.
This doping process produces multiple components, which can be in the thousands, millions, or billions (depending on the etched surfaces).
Wiring
The doped semiconductors (transistors) can only work if electricity flows through them.
So wire them according to the circuit pattern. The process involves depositing a thin metal film in the semiconductor wells.
Although copper is more electrically conductive than aluminum, aluminum is the best material to use for wiring.
Copper diffuses into silicon, altering its electrical properties, which damages the transistors.
But aluminum does not kill the semiconductors. It is easily workable and sticks to the silicon oxide layer.
Energy Dispersive Spectroscopy Testing
This testing process sorts out defective chips from functional ones. Each wafer can only hold a certain number of chips.
The ratio of the prime or flawless chips to the maximum number of chips forms the yield percentage.
Commercial Circuit Packaging
The flawless silicon chips get clipped from the wafer and undergo packaging into either of the options we looked at earlier.
A silicon die being extracted from a wafer
Packages create electrical connections from the silicon die to the outer components through printed circuit boards. Also, they protect the chip from external elements.
The package forms what we usually see and know as the black chip.
Wrap Up
Integrated circuits are integral to intelligent device functioning, and you can find them in almost all electronics and machines.
So any electronics engineer must understand their types, packages, how to make them, etc. And this article covers all that information. We hope it has been insightful.