In the course of our foray into the world of semiconductor equipment, we discovered why so few people understand semiconductor construction: it's damn complicated.
The process involves hundreds of different steps - some of which require unimaginably high temperatures (more than 1,500°F) and all of which involve unimaginably small features (less than a micron, which is equal to 0.00004 inch; a human hair is roughly 50 microns in diameter). Moreover, all of these steps have to take place in a "clean room," with less than one particle of dust, no larger than 0.3 micron, per cubic foot of air. One particle of dust can render a good chip useless. Needless to say, then, the following primer describes the process in extremely broad strokes.
Unfinished wafers are supplied by the wafer production companies, including Shin-Etsu and MEMC. But the tools that semiconductor manufacturers (like Intel) use to transform their architectures (like x86) into actual chips (like Pentium II) are the dominion of the semiconductor capital equipment companies.
Here are simple explanations and illustrations of the major steps in the "front end" of the semiconductor manufacturing process.
1. DepositionWafers are placed into chambers that are heated to more than 1,500°F. Chemical vapor deposition uses the extreme temperatures to create a chemical reaction that bonds desired material to the surface of the wafer. For example, with oxidation, an oxygen-filled chamber results in a layer of silicon dioxide. Physical vapor deposition, or sputtering, uses ions to propel the material onto the wafer.
Top equipment manufacturers1) APPLIED MATERIALS2) NOVELLUS 3) TOKYO ELECTRON
2. PhotolithographyWafers are coated with photoresist, a resin that softens and loses its resistance to chemical etching when exposed to light. Wafer steppers focus light through a mask (a patterned, opaque piece of glass) onto the photoresist. A chemical bath strips away the softened material, leaving a pattern on the wafer.
Top equipment manufacturers1) NIKON 2) CANON 3) SILICON VALLEY GROUP
3. EtchingEtching tools remove any deposited material on the wafer's surface that is not covered by photoresist. Remaining photoresist is washed away in a chemical bath.Top equipment manufacturers1) LAM RESEARCH 2) APPLIED MATERIALS 3) TOKYO ELECTRON
4. Ion implantation
Dopants, or ion additives, are shot into the wafer, creating the positively and negatively charged regions that act as a conduit through which digital signals are passed (that is, creating the transistor).Top equipment manufacturers1) EATON 2) VARIAN 3) APPLIED MATERIALS
These four steps are repeated to create the desired pattern of transistors. Then alternating layers of aluminum (soon, copper) and insulators are added - using deposition, photolithography, and etching steps similar to those described above - to connect all of the transistors. This is referred to as the
metallizationprocess. Memory chips usually have two metal layers; microprocessors have up to six.
The wafer then moves to the "back end" of the process, where it is divided into hundreds of pieces (or die), wired to metal legs and packaged in a ceramic or plastic housing. The finished integrated circuit undergoes final testing and is ready to be shipped.
SOURCES: COWEN, DATAQUEST