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The AIMS (Aerial Image Measurement Tool) measures approximate aerial images to scanner results by adjusting the
numerical aperture, illumination type and partial parameters. Accordingly, AIMS tool is used generally to verify the
issue points during manufacturing a mask. Normally using a mask for photolithography needs twice verifications. One
is the qualification in the mask shop. The other is verification over the photo process using the mask in the wafer fab. If
evaluated data at AIMS can be trusted about photo process ability including energy latitude (EL), depth of focus (DOF),
CD uniformity (CDU), pattern fidelity and mask defects including repair area, AIMS can function as a first filter before
shipping the mask. That means the AIMS data can be used as a preliminary data in the wafer fab.
So this study is focused on correlation between measured data at AIMS fab 193i and ArF scanner over the photo
process such as EL, DOF, CDU, pattern fidelity and mask defects. First, various patterns are made on attenuated PSM
from 80 to 65nm tech. Next correlations are calculated about EL, DOF and CDU by using same optical conditions,
measurement points and etc at AIMS and Scanner. Also the aerial images from AIMS are compared with scanner results
on defective side how those are matched with each other.
Consequently defect printability and CDU map at AIMS were similar to the scanner. In CDU point of view, AIMS
exceeds the predictive ability of the mask CD SEM. Moreover it means that wafer CDU can be corrected (improved)
independently on the CDU result of the wafer fab by using CDU correctable femto laser tool which reduces
transmittance of the mask. Surprisingly, it is possible. And Aerial image about mask defects including repair area is
useful to predict the problem of the mask, since it is similar to wafer results. But aerial image compared with wafer
image has more difference at 65nm technology node than at 80nm. If adjustment of threshold or measuring method can
be done, prediction of the scanner result will have no matter. In conclusion, predictive results at AIMS over photo
process can be applied as a preliminary data and it can be used to another index verifying the mask quality.
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