The optimal conditions to print the 0.13 μ m line and space are presented for newly constructed x-ray proximity lithography system at Postech Advanced Lithography Center (PALC). The PALC uses the synchrotron light source which is in Pohang Accelerator Laboratory (PAL). The optimal values of the absorber thickness, the bias-width and the spatial blur of the source are investigated with other conditions such as the mask to wafer gap remaining fixed. As a criterion for the optimal aerial image, we introduce hybrid figure of merit(h-FOM) which combines the dose latitude and contrast of the aerial image.