The fabrication process of silicon devices has evolved over the last 25 years into a mature, reproducible and reliable integrated circuit manufacturing technology. While the focus in this course is on individual devices, one must realize that the manufacturability of millions of such devices on a single substrate is a minimum requirement in today’s industry. Silicon has evolved as the material of choice for such devices, for a large part because of its stable oxide, silicon dioxide (SiO2), which is used as an insulator, as a surface passivation layer and as a superior gate dielectric.
The scaling of MOSFETs started in the seventies when the initial 10 micron gatelength of the devices was gradually reduced by about a factor two every five years, while today (1997) MOSFETs with a quarter micron gatelength are manufactured on a large scale. This scaling is expected to continue well beyond the year 2000, as devices with a gatelength smaller than 100 nm have already been demonstrated. While the size reduction is a minimum requirement when scaling MOSFETs, successful scaling also includes the reduction of all the other dimensions of the device so that the device indeed delivers superior performance. Devices with record gate lengths are typically not fully scaled, so that several years go by until the large scale production of such device takes place.
The combination of complementary MOSFETs in logic circuits also called CMOS circuits has the unique advantage that carriers only flow through the devices when the logic circuit changes its logic state. Therefore there is no associated power dissipation if the logic state must not be changed. The use of CMOS circuits immediately reduces the overall power dissipation by a factor ten, since less that one out of ten gates of a large logic circuit switch at any given time.