Characterization of high-K/metal gate using picosecond ultrasonics

Transition from oxide gates to replacement metal gates is well underway and performance benefits have been demonstrated in state-of-the-art microprocessors. High-K/metal gate combination is important for all emerging new applications that require high-performance and low gate-leakage including all silicon and non-silicon nanoelectronic transistors. Picosecond ultrasonic measurements are used as checkpoints during various stages of development and integration of high-K/metal gate. The small spot, non-destructive nature of this technology allows for measurements directly on product wafers and on various line array structures in small measurement sites (30 μm × 30 μm). The technique has shown excellent correlation with cross-section TEM, demonstrating capability for monitoring advanced gate stacks. Picosecond ultrasonics provides high-throughput and can be used for in-line monitoring after the process is transferred to high volume manufacturing.