Patent ID: 7031794

Claim:
An overlay control system comprising: a plurality of process machines; a data collection tool wherein said data collection tool measures overlay error from a run of a lot through a process machine and generates overlay error measurement data; a data processing tool for processing said overlay error measurement data, said processing including generating an overlay control table wherein said overlay control table comprises current layer overlay correction value, C n , previous layer overlay correction value, P n , overlay measurement error value, O n , residual overlay error value, R n , fine tuning value, F n , and average process offset value, K for a lot n, wherein the data processing tool sends the overlay control table to an operator for use in manual overlay correction or to a smart overlay control servo for use in automatic overlay correction; and an in-line equipment servo wherein said in-line equipment servo obtains previous layer correction and fine tuning values from said smart overlay control servo for a lot on a process machine, calculates an overlay correction using said previous layer overlay correction and said fine tuning values, and sends said overlay correction to said process machine, wherein for said lot n, the overlay control table is generated using the following algorithm: C n = P n + F n−1 O n R n n = 1 C 1 = P 1 + K O 1 R 1 = K − O 1 n = 2 C 2 = P 2 + F 1 O 2 R 2 = F 1 − O 2 n = 3 C 3 = P 3 + F 2 O 3 R 3 = F 2 − O 3 n = 4 C 4 = P 4 + F 3 O 4 R 4 = F 3 − O 4 n = 5 C 5 = P 5 + F 4 O 5 R 5 = F 4 − O 5 n = 6 C 6 = P 6 + F 5 O 6 R 6 = F 5 − O 6 n = k C k = P k + F k−1 O k R k = F k−1 − O k n = k + 1 C k+1 = P k+1 + F k O k+1 R k+1 = F k − O k+1 F n n = 1 F 1 = R 1 n = 2 F 2 = ½ * (R 1 + R 2 ) n = 3 F 3 = ⅓ * (R 1 + R 2 + R 3 ) n = 4 F 4 = ⅓ * (R 2 + R 3 + R 4 ) n = 5 F 5 = ⅓ * (R 3 + R 4 + R 5 ) n = 6 F 6 = ⅓ * (R 4 + R 5 + R 6 ) n = k F k = ⅓ * (R k−2 + R k−1 + R k ) n = k + 1 F k+1 = ⅓ * (R k−1 + R k + R k+1 ) wherein said variables C n , P n , O n , R n , F n , and K are defined as above and P 1 =0 and K value is supplied with initial data for n=1.