Sapphire and silicon on SiO 2 substrates are considerably more expensive. Eases automated routing and improves power and clock distribution to modules. Aggressive processes allow the stacking of vias on top of contacts. Silicide used to make direct connection between poly and diffusion, no contact or metal. Trench capacitors allow memory densities of 64Mbit and higher.
Design rules specify geometric constraints on the layout artwork.
Provide a communication channel between the IC designer and the fabrication process engineer. To minimize the area of the circuit. To provide long term reliability of the circuit. More aggressive rules increase performance. Design rules represent a tolerance that ensures high probability of correct fabrication - rather than a hard boundary between correct and incorrect fabrication.