Normally, increase the voltage, the cell will run fast, so the delay change small.
for the temperature, high temperataure will inclease the delay value.
So in 90nm, 130nm and above, the corner is defined as follows:
Best case: High V, Low T(0 centi degree),
Typical case: Norm V, Norm T(25 centi degree);
Worst Case: Low V, High T(125 centi degree);
But in the 65nm, 45nm, and below, there is temperature inversion.
that is lower temperature(-25) will have larger delay than the 125 temperature. so in the 65nm and below, another corner is added for simulation