WHAT IS AN INTEGRATED CIRCUIT?

The Concept

An integrated circuit (IC) may be thought of as a collection of tiny interconnected switches etched onto a smaller sliver of silicon and encased in a hard plastic or ceramic package. These "switches" control the flow of electronic currents in carefully controlled patterns. Semiconductors are the basic components of virtually all modern electronic devices.

Semiconductors can be designed and packaged to perform a variety of functions. Microprocessor chips can follow the instructions of computer programmers. Specialized arrays help manage data flow. Some memory devices can be erased, while the contents of others are permanent.

The Design & Manufacturing Process

1. depending on its complexity, a semiconductor can take many months —even up to a year — to design. Circuit design begins with a computer-aided design (CAD) system, programmed with standard electronic symbols to represent various circuit elements such as transistors, resistors, capacitors, etc. The CAD system evaluates circuit operation, simulates performance, verifies transistor and circuit parameters, and detects potential temperature voltage, speed, or timing problems.
2. The next step is to create a composite drawing, approximately 400 times larger than the actual size. Electronic symbols are converted into the actual shape of the circuit elements and reproduced in separate, color-coded layers. Each layer is then digitized into a form which can be used to create the mask, or pattern of circuitry, for each layer.
3. To manufacture the design, the logic network much be translated into a series of electronic circuits based on transistors — on/off switches that control the flow of current through a circuit. Various types of silicon transistors respond differently, either enabling current to flow through, or preventing current flow by keeping the transistors turned off.
4. Semiconductor manufacturing is a multi-step process, not unlike the baking of a layer cake. Beginning with a thin silicon wafer up to — in diameter, consecutive layers of complex circuitry are built up, one on top of another, to produce a singe completed wafer, which contains hundreds of similar semiconductor devices. Individual circuits lines are often more than xxx times thinner than a human hair. Because the circuit lines are so small, advanced semiconductors must be manufactured in a highly controlled environment. The manufacturing process can be ruined by a single speck of dust. Therefore, semiconductor "cleanrooms" are designed to prevent impurities from entering the manufacturing process. A series of making and diffusion processes are repeated up to twenty times, using the various patterns necessary to create a particular type of IC. Masking involves the transfer of intricate pattern by exposing unmasked portions of the wafer to light. Then, during diffusion, electrically charged particles are implanted into the silicon to alter its electrical characteristics. This forms negative and positive conducting areas, creating a pathway through which electricity can flow.
5. A final layer of glass-like material is applied to protect the semiconductor from contamination and damage. Each circuit on the wafer is tested for functionality by electronic probes which run more than 10,000 checks in less than a second. The wafer is then sliced into individual chips which undergo further microscopic inspections before packaging.

6. The chips are assembled into a variety of different packaging types. They are bonded with thin wire to leads which provide an interface to the outside world. After packaging, the completed units are subjected to an additional battery of tests to check their electrical performance and ability to withstand extreme environmental conditions.
7. Throughout the manufacturing process, statistical process control (SPC) methods are utilized to ensure that each step of the process stays within operating parameters. In this way, quality is "built in" through real-time control, analysis and adjustment of the process variables.