What Is a Microchip IC?
Microchips are the building blocks of modern technology. They’re used in computers, guided missiles and “smart bombs,” hand-held communication devices, televisions, aircraft and motor vehicles.
During the last several decades, engineers have striven to shrink microchips and their components so that more and more can fit on each chip. Nevertheless, there are real physical limits to further miniaturization based upon conventional engineering principles.
IC Process
A microchip — also known as a computer chip or an integrated circuit (IC) — is a set of miniature electrical circuits printed on a flat piece of semiconductor material, such as silicon. It contains transistors, which act as miniature electrical switches that can turn current on and off. The pattern of these switches is etched into the semiconductor, along with intricate connections that facilitate the flow of electric signals. Once the wafer is complete, it’s tested using specialized automated test equipment to determine whether each individual chip functions correctly. Those that fail are removed and marked, while those that pass are placed into the supporting packages that allow them to be plugged into circuit boards.
Modern chips contain billions of transistors in an area the size of a fingernail. This amazing level of integration is made microchip ic possible by technological advances that have allowed the etching of smaller and smaller components on ever-smaller areas.
The first step in making a microchip is to deposit a layer of silicon dioxide on the surface of a wafer. That’s followed by a coating of photoresist, which is patterned to expose soft parts of the chip to light and hardens those areas. A series of deposition, etching and removal processes are used to build up the component circuitry on the chip.
Conducting paths between the different components etched into the chip are created by overlaying it with a thin layer of metal, such as aluminum. The lithography and etching processes are used again to remove all but the thin conducting pathways, which can be encased in glass insulators.
IC Materials
A microchip carries thousands, sometimes billions of transistors on a tiny silicon wafer that is smaller than a human fingernail. This is because circuitry takes place on a microscopic scale, with features measured in nanometers (nm) – a millionth of a millimeter.
A pure form of silicon provides the base, or substrate, for all ICs. The silicon is chemically doped to provide the n and p regions that make up the components of an integrated circuit. The n-type dopants are phosphorus and arsenic, while the p-type dopants are boron and gallium.
The resulting “chip” is separated into hundreds of individual units, or dies, by scoring a crosshatch pattern on the surface with a fine diamond and then applying stress to cause each chip to separate. The bad chips are discarded, and the good ones bonded into their mounting packages.
These packages can be as simple as the Dual In-Line Package (DIP) that has two rows of pins extending perpendicularly from the body of the chip, or they can be complex and rugged like the plastic quad flat no-lead package (QFN). There are also surface-mount packages, which have their contact terminals (pins) arranged on a side of the packaging that is designed to sit on a circuit board for soldering.
The encapsulant material that holds the die is often made of an epoxy blend. This is because it is durable and can offer a beneficial mix of properties, including thermal performance. The die-attach adhesive is normally a liquid or film format that is specifically designed and intended not to outgas, since any outgassed material that redeposits on bond pads could degrade their quality.
IC Design
The first step in the IC design process is functional design, which involves creating a high-level description of the chip’s requirements. It includes deciding what architecture to use, choosing between a RISC and CISC processor, determining the number of ALUs (Arithmetic Logic Units) needed, and defining the data and control flow. This information is then turned into a logical design in a hardware description language.
This logical design is then mapped into a physical geometric representation by the physical design stage. This step can be difficult because it is not easy to balance the tradeoffs of size, cost, and performance. For example, longer wires require more space on the chip and can introduce parasitic effects such as resistance, capacitance, inductance, and crosstalk. This phase also includes floorplanning and partitioning, laying out the major block structures of the chip, and performing a clock tree synthesis.
Once the physical layout is done, a GDS file is generated and sent to the fabrication house for manufacturing. During this phase, critical parameters that affect performance and manufacturability are verified using quality tools. This is called signoff and allows the IC to be sent to production.
The final step in the IC design process is to test and verify the resulting logical circuit. This is done on emulation and simulation platforms to ensure that the IC meets all of its requirements and functions correctly.
IC Applications
When you dream up a clever microcircuit, get it sculpted in a sliver of silicon and then unleash that little creation, the results can be spectacular. Such is the story of the Signetics NE555 timer, designed by Hans Camenzind.
Before the advent of integrated circuits (ICs), electronic devices were constructed from discrete transistors and other components that required a lot of space and power. The chips that came to market after the first microprocessors in 1961, tantalum capacitor however, made it possible for computers to be built into much smaller and lighter gadgets than could have been imagined just five years earlier.
ICs work by combining semiconductors with microelectronics components such as transistors, diodes and resistors on a piece of silicon that’s divided into many small pieces called wafers. When a voltage is applied to a chip, it turns on the transistors and creates an electric current.
A chip can have anywhere from one to billions of transistors. The transistors act as miniature electrical switches, and a pattern of those switches can be etched in a wafer to create an entire microprocessor, for example.
Some ICs focus on logic or memory; others combine both or other capabilities into what are known as system-on-a-chip (SoC) ICs. Other types of ICs include application-specific ones, which can be customized for a particular device such as medical equipment or automotive components.