Effect of Reticle CD Uniformity on Wafer CD Uniformity in the Presence of Scattering Bar Optical Proximity Correction

Amplification of reticle linewidth variations in imaging is examined through direct measurements of the mask error factor (MEF), which typically is used to describe this undesirable effect. The error observed in the aerial image linewidth is decoupled from the error in the resulting resist profile linewidth with the introduction of two separate mask error factors, namely the aerial image MEFaerial and the resist MEFresist. These MEF’s are evaluated from systematic aerial image measurements and resist profile measurements on printed wafers respectively. In many cases the noise in the metrology tools used in the experiment, combined with the very high quality of the test reticle used, limit the statistical confidence of our results. However useful insight is gained on the role of the non-linearity of the resist in reducing the error observed at the wafer (MEFresist) in comparison to the error observed in the aerial image (MEFaerial). It is found that 180nm lines (k1=0.38) have a MEFaerial≅1.5 and a MEFresist≅1. The effect of scattering bars OPC on the MEF for features sizes 180nm and 220nm (k1 factors of 0.38 and 0.47 respectively) is generally small and on the order of <10%.