Reticle quality and the capability to qualify a reticle are key issues for EUV Lithography. We expect current and
planned optical inspection systems will provide inspection capability adequate for development and production of 2X
HP masks. We illustrate inspection technology extendibility through simulation of 193nm-based inspection of advanced
EUV patterned masks. The influence of EUV absorber design for 193nm optical contrast and defect sensitivity will be
identified for absorber designs of current interest.
Reticle quality and the capability to qualify a reticle are key issues for EUV Lithography. We expect current and
planned optical inspection systems will provide inspection capability adequate for development and production of 2X
HP masks. We illustrate inspection technology extendibility through simulation of 193nm-based inspection of advanced
EUV patterned masks. The influence of EUV absorber design for 193nm optical contrast and defect sensitivity will be
identified for absorber designs of current interest.
Non-uniformity in reticle CDs can cause yield loss and/or performance degradation during chip manufacturing. As a
result, CD Uniformity (CDU) across a reticle is a very important specification for photomask manufacturing. In addition
the photomask CDU data can be used in a feedback loop to improve and optimize the mask manufacturing process. A
typical application is utilizing CDU data to adjust the mask writer dose and compensate for non-uniformity in the CDs,
resulting in improved quality of subsequent masks.
Mask makers are currently using the CD-SEM for data collection. While the resolution of SEM data ensures its position
as the industry standard, an output map of CDU using the reticle inspection tool has the advantage of denser sampling
over larger areas on the mask. High NA reticle inspection systems scan the entire reticle at high throughput, and are
ideally suited for collecting CDU data on a dense grid.
In this paper, we describe the basic theory of a prototype reticle inspection-based CDU tool, and results on advanced
memory masks. We discuss possible applications of CDU maps for optimizing the mask manufacturing process or in
adjusting scanner dose to improve wafer CD uniformity.
Establishing an effective inspection method for PSM's shifter defects is a very important factor in successful production of PSM under i-line and DUV for 0.25 μm process rules. We have used a PSM with programmed shifter defects to confirm the minimum printable defect size under 0.25 μm rule process environment using i-line and DUV steppers. The same plate was then inspected by a special-detection experimental transmitted and reflected(ETR) and KLA3O1 D/D inspection system which KLA has developed in cooperation with Hitachi to evaluate its detection performance on those printable defects. We report that characteristic of this inspection system, which uses both transmitted and reflected light and special detection algorithm, is an effective tool. We will be able to supply defect free PSM for reliable process of 0.25 μm rule.
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