The SO Family:

Image: John Ueland

The letters S and O have lately become a dizzyingly fecund breeding ground of jargon. Here’s the family tree.

SOI: Silicon on insulator. A type of silicon wafer that improves the speed and power consumption of CMOS circuits. It involves making a thin layer of insulator, usually silicon dioxide, buried up to 100 micrometers below the surface. The insulation layer reduces the amount of charge the transistor needs to move in order to switch, and it blocks leaking current. AMD uses lots of SOI; Intel, not so much.

SOS: Silicon on sapphire. Silicon on insulator (see SOI) by other means. In SOS you deposit a thin layer of crystalline silicon atop a wafer of sapphire—otherwise known by its less bejeweled name, aluminum oxide. SOS circuits are usually found in space and military systems, because the sapphire keeps stray currents caused by radiation from messing with the silicon circuits.

SOAN: Silicon on aluminum nitride. A new version of silicon on insulator (see SOI) where you build a silicon wafer with a thin, electrically insulating layer of aluminum nitride buried just below the surface. The aluminum nitride gives electrical benefits similar to those of SOI’s usual insulator, silicon dioxide, but it’s better at drawing heat away from the circuits.

SOG: Silicon on glass, spin-on glass, sea of gates. In general, SOG is some form of silicon on a substrate of glass. From there, things get complicated. The silicon in question could be polycrystalline, the type found at the edges of newer LCD ­panels, where manufacturers are building an increasing amount of circuitry right onto the panel. Or SOG could refer to crystalline silicon that is patterned into a circuit and then bonded to glass. SOG can also mean spin-on glass, a way of applying a thin layer of silicon dioxide insulation to chips using a liquid chemical (see SOD for how that works). And finally, SOG is sometimes sea of gates, a way of minimizing the work of chip construction. A sea-of-gates approach assumes lots of different chips can start out as just a vast grid, or “sea,” of logic gates. The only difference between the chips is in how you wire the gates to each other.

SOA: Silicon on anything. In SOA, a favorite of Philips Electronics, you build a circuit on a silicon wafer, then chemically dissolve away almost the entire wafer, starting from the back side, so that only the part containing the circuitry is left. Finally, you glue this sliver of circuits to “anything.” In practice, “anything” seems to mean glass (see SOG). The glass-silicon combination lets you integrate RF components such as inductors onto the chip. On ordinary silicon chips, integrating inductors is difficult to do, because the silicon tends to soak up the inductor’s signal.

SON: Silicon on nothing. Taking the ­silicon-on-insulator concept to the extreme, ­researchers—mostly at STMicroelectronics—are experimenting with transistors suspended over small pockets of air, one of the best insulators around.

SOIC: Small-outline IC. A rectangular plastic chip package that has connecting pins that stick out from the side in a so-called gull-wing configuration. That is, the pins stick out, then turn down, and then go out again.

SOD: Spin-on deposition. A method of applying a layer of material to a semiconductor wafer. The wafer is spun like a record, and a liquid is poured onto the center. The wafer’s rotation draws the liquid out from the center, so it forms a layer of uniform thickness across the surface. SOD is the method you’d use to apply a spin‑on dielectric, a material used to insulate the on‑chip wiring on some ICs.

SOM: Sulfuric acid–ozone mixture. We bet you thought this was silicon on manganese oxide or some other crystal. But no! It’s actually a nasty chemical brew used to scrub silicon wafers clean in between chip processing steps.

SOC System on a chip. An IC that packs a microprocessor, memory, timers, voltage regulators, and all the other stuff you’d need to build a computer or another electronic system. The reconfigurable version of the chip is, predictably, called a system on a programmable chip, or SOPC.

SOP: System on package. Can’t fit your system on a chip? Make it on separate chips and put them in the same package. And integrate all the capacitors and other components into the package while you’re at it. It’s often confused with system in package (SIP). SIP predates SOP and tends not to squeeze in quite so much non-IC stuff.

Scoring

Fewer than 25 correct Welcome to the club.

25–29 correct: Ph.D.

30–34 correct: Potential game show contestant.

35–39 correct: Übergeek.

40–48 correct: Nobel Prize candidate.

49–50 correct: Liar! (There were only 48.)