Semiconductor International, June 2008

Alexander Braun

"Paul Ter Beek, senior product manager for opaque and transparent thin-film products at Rudolph Technologies (Flanders, N.J.), thinks that the key to meeting measurement requirements is implementing a metrology method that allows high sample rates and non-destructive measurements of the basic core -- the transistor's workfunction. "All we've done in past decades is measure derived parameters to support that workfunction's control," he said. Most common parameters for process control systems are thickness, composition, CD and stress. Advanced devices also require spatially resolved parameters, such as shape and compositional gradient. In even relatively simple OCD cases, there are issues with sidewall angles that cannot currently be measured accurately. This is a signal-to-noise ratio problem, pertaining to the limited response received from variations in sidewall angle, making signal-to-noise performance critically important."

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