To protect wires in some commercial products, manufacturers already spike the silicon dioxide with a little fluorine to drive down the mixture's dielectric constant, Miller says. In a few years, however, the industry will have to break completely with silicon dioxide as the wiring insulator, he says. This problem with silicon dioxide as a wiring insulator cropped up a little sooner than the transistor woes, so chip makers have already gone much further in dealing with it. Research into low-k materials is making progress, Miller says. The challenge of replacing silicon dioxide in transistors looms ahead.
Transistors are the workhorses of integrated circuits.
Applying voltage or current to one of the three terminals of a transistor controls the current moving between the other two. Most commonly used in integrated circuits is the complementary metal oxide semiconductor, or CMOS, transistor. There, a layer of silicon dioxide serves as an electrical insulator, or dielectric, preventing unwanted vertical current flow between the control electrode, known as the gate, and the underlying silicon. That charge accumulation controls the flow of electricity that traverses a thin skin of silicon just beneath the oxide. As circuit devices have shrunk, so too has the area of the gate.