Chapter 2
Background
2.1 Related work on process variation
2.1.1 Early work
Manufacturing variations have been a main source of random properties of pre-
cisely designed ICs. Even though process variations were very small in 20th
century fabrication technology, they could affect precise analog design and they
were addressed by a number of researchers [27,41,55,66]. Three of the early
works in identification of random variations stand out.
In 1982, Shyu et al. [66] studied effects of random variations on MOS capac-
itors. They identified the capacitor edge and the oxide thickness fluctuation as
two sources of randomness in MOS capacitors. The variations in the physical
properties lead to a random capacitance. They analytically derived the relation-