Patent ID: 7212946

Claim:
A method for accommodating spatially-correlated variation in a process parameter during statistical timing of a circuit, the method comprising: dividing an area of the circuit into a plurality of grid cells; associating an independent random variable with each of the plurality of grid cells; expressing at least one spatially-correlated parameter of a first grid cell as a function of the random variables associated with the first grid cell and at least one neighboring grid cell, wherein the function is expressed as: Δ A=a G ΔX G +a r ΔX r +a sd ΔX c +a ld (Δ X n,1 +ΔX n,2 +ΔX n,3 +ΔX n,4 +ΔX n,5 +ΔX n,6 ), wherein a G is a sensitivity of the process parameter to global variation, ΔX G is a random variable modeling global variation, a r is a sensitivity of the process parameter to independent variation, ΔX r is a random variable modeling the independent variation, a sd is a sensitivity of the process parameter to short distance spatial variation, ΔX c is a random variable associated with the first grid cell, a ld is a sensitivity of the process parameter to long distance spatial variation, and ΔX n,1 through ΔX n,6 are random variables associated with neighboring cells of the first grid cell; and reporting a result of a statistical static timing analysis using the function.