The 800 nm process refers to the manufacturing technology that came into use at leading semiconductor manufacturers from the end of the 1980s onward. At this point, the main difficulties begin to shift from the transistor itself to the interconnect system.
As interconnects shrink, their line resistance increases, while polysilicon is simply not conductive enough as a gate material. The solution is the use of silicides: a metal – usually titanium – is deposited on the gate as well as the source and drain regions and then annealed so that it reacts to form titanium silicide only where it is in contact with silicon. Above the isolation oxide it remains unreacted and is subsequently etched away. Because the same process simultaneously forms low-resistance material on the gate and contact regions while aligning itself automatically, the technique is known as salicide.
The contact holes leading to the first metal layer can also no longer be reliably filled simply by sputtering aluminum. Their depth-to-diameter ratio has become so large that sputtered metal closes the opening at the top before the bottom is completely covered. Instead, tungsten is deposited from the gas phase, conformally filling the holes from the inside, after which the excess material is etched back. The number of metal layers increases to three.
Processors manufactured in 800 nm (selection):
- Intel 486DX2 (1992)
- Intel Pentium (1993)
- AMD Am486 (1993)