1.2 Sizes of Transistors

• In integrated-circuit memory elements, the bit is the circuit element used to store and transfer the electrical charge  that represents one unit of information
• The memory bit is generally a field-effect transistor and capacitor combination where the capacitor stores the charge  and transistor switches/transfers the charge
• The lateral dimensions of semiconductor devices are given in microns
• The resolution of optical microscope is about 0.25 micron, so that electron microscopes are used to reveal the details of IC devices
• 10 angstroms = 1 nm
• Spacing between atoms in a solid is about 2 - 4 angstroms
• As a general rule, all the electronic processes of charge transport in integrated circuits take place within the top 1 micron of the surface
• The number NA of atoms per mole, Avogadro's number is : NA = 6.0220 x 10^23
• The atomic density N of atoms/cm3 is related to NA: N =  NA * pm / A where mass density pm is in gram/cm3 and A is the atomic mass number (# of protons and neutrons)
• In vacuun technology , the basic relation is the ideal gas law: PV = 'vRT = NmkT where P - pressure (N/m2), V - Volume (m3) , T - absolute temperature (K),  Nm = total number of molecules,  'v = number of moles, R = gas constant, k = Boltzmann constant