Wafer

A wafer is a thin slice of semiconductor, usually Silicon, used for the fabrication of ICs and Photovoltaic Cells.

Substrate

A substrate is a solid surface on which a thin film or layer of another material is applied.

The wafer serves as the substrate for microelectronic devices built in and upon the wafer.

For Intel Core i7 Wafer, it’s a 300mm wafer, 280 chips, 32nm technology. Each chip is 20.7 x 10.5mm