Aggressive line width and other features of interest in advanced-technology node designs are achieved by using
pattern-related resolution enhancement techniques (RET) coupled with mask transmission effects. Mask
transmission effects, such as phase shift, are controlled by physical parameters, including mask blank material
characteristics and mask architecture. In the case of advanced phase shift masks, the uniformity of transmitted
phase, affected by both material properties and thickness, can become a dominant factor in achieving the final
wafer CD targets.
While traditional mask inspection tools are capable of detecting geometrical variation, detecting phase
non-uniformity effects requires complementary, slow analytical tools. AMAT's IntenCDTM is a novel application
for advanced PSM masks which can be used for CD variation control in mask qualification. IntenCD captures
mask CD variations in the aerial image regardless of the geometrical or physical aspect of its origin, producing a
high-definition CDU map of the reticle. In this paper, we focus on a case study encountered at MP Mask where a
PSM mask was sent to the fab to confirm large CD variations on a printed wafer due to mask etching process
issues. Conventional defect inspection was not capable of detecting this excursion. The effect was clearly related
to phase layer thickness as verified using an Atomic Force Microscope (AFM) tool. We show how the novel
IntenCD application integrated into the aerial image mask inspection tool enables accurate prediction of CD
variation in the aerial image due to mask phase errors.