3-D Capability Turns CD-SEM Into Metrology System
Alexander E. Braun, Senior Editor -- Semiconductor International, 1/1/2000
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Applied Materials (Santa Clara, Calif.) has introduced its VeraSEM 3-D, which is described as the first production-worthy CD-SEM system to provide three-dimensional imaging technology. The system's 3-D stereoscopic imaging is taken from multiple angles, tilting electronically at very high speeds, resulting in up to 10 times better resolution at the slope than top view. In less than a minute, the imaging system delivers an in-line monitoring of slope angle and shape, which otherwise would have taken considerably longer in off-line analysis.
The new system provides not only CD measurements, but a view of the slope and shape of the most aggressive features, including 1:14 high-aspect ratio contact holes and trenches. By detecting variations in these critical structures in-line, it allows the fast identification of process problems that otherwise would be undetectable using traditional CD-SEM technology. The system can image sidewall profiles of device features down to 0.10 µm. This could have a positive result in yields and costs, by enabling the early detection of process excursions.
Tighter control of slope changes in DUV resists to allow better focus control, detection of negative slopes and T tops, and detection of the smallest foot are some of the other applications. Copper applications also could benefit from these capabilities, since maintaining slope is critical in preventing voiding effects in dual-damascene structures.
Unlike other profile viewing techniques, such as cross-section SEMs, the system does not require off-line destructive testing procedures, reducing the need for test wafers. The in-line system allows rapid monitoring of wafers between process steps and automatically alerts operators to marginal or out-of-spec conditions.
Sidewall imaging capability enables the introduction of automatic classification of all process-induced excursions, leading the way to a closed correction loop with the tools it controls. The system will accept both 200 mm and 300 mm wafers, is fully automated, and provides high throughput shared database, offline programming and online data analysis. The system should reduce destructive testing, while providing better control of copper fill processes and shorter corrective cycle times by correlating shape profile to process anomalies.
Applied Materials www.appliedmaterials.com
