Strong Phase Shzft Mask Manufacturing Error Impact625The yield computed within a CDiIPE ellipse is lower than the yield calculated within a CDIIPE rectangle as can be seen in figures of Table 2, column 3. Several reticle specifications were simulated, see Table 1. The reticle specification was optimized to obtain 100% CDIIPE yield. The reticle with specification #4 with 30PW = 4.5 n d p e r side, 30PD = 1" and 3oP = 1% will also provide good yield margins presented in Table 2.Table 2. Normalized distribution functions and CD versus IPE scattering plots used for the CD-yield and combined CDIIPE yield calculation illustrate statistical simulation results prcsented in Table 1. Normalized CD distribution functions. CD yield is calculated as an integral of a distribution function within CD = (65+/-5) nm shown by a doted box. CD-yield CD. vs. IPE scattering plots. CDIIPEyield presented in Table 2 is calculated as a ratio of the failing events (outside a dotted box) to the total number of samplinas, CDIIPE-yield65nm lzneVariables presented in Table 1Spec #I : = 179" 3uPD=5' 3oPI= 10% 3oPW-0 = 3oPW-180 = 9 nml per side- 80%- 78%pztch$ 1 160nm 1-10-50510CD [nm]IPE [nm]CD-yield Spec #4 = 179" 3oPD = 1" 3oPI= 1% 3oPW-0 = 3oPW-180 = 4.5 n d per side- 100%CDIIPE-yield- 99 6%65nm line in 160nm pitch-10-7.5-5 -2.5 IPE02.557.510CD [nm][nm]The realistic reticle may not produce 100% wafer CDIIPE yield within the photo process CD tolerance. The calibration of reticle control parameters and illumination conditions have to be done before doing the imaging simulation. It was found that the match between simulated and empirical CDs is achieved with the reticle specification fabricated with the specification #5 from the Table 1 (30PW = 5 nm/per side, 30PD = 5" and 3oPI = 5%). Figure 5 compares the cumulative probabilities of the wafer CD distribution (circles) with simulated CD distributions (curves) obtained with two virtual181
