Beginning at the 45nm node, the semiconductor industry is moving to high-k gate dielectrics and metal gate electrodes for CMOS logic devices [. Although different approaches of building these devices are being pursued, most of the industry has consolidated behind a gate last approach, in which the transistor is built around a dummy poly polysilicon gate, which is subsequently removed and replaced with a metal gate. Current approaches to removing the dummy poly gate include plasma-based dry processes and liquid-phase wet etching.

Chemical and physical modifications of photoresist and BARC during plasma patterning process on HKMG structure can cause residual defects and yield loss that challenges the subsequent wet cleaning process to resolve this issue. The chemical behavior of materials post dry etching and wet clean was systematically studied by various surface analytical techniques including STEM-EELS, XPS and AES. With a greater understanding of the etching and clean mechanisms, a combined aqueous/solvent cleaning method was developed and tested on a spin clean tool to effectively clean etching by-products. A significant improvement of yield with the application of the new cleaning approach has been observed.

Novel process control methodologies are required for SiGe gate recess structures that are used in IC manufacturing to enhance device performance. Metrology measurements of 28nm SiGe after-etch inspection U-sigma shaped and V-sigma shaped gate structures must be able to track subtle variations for several critical parameters, including SiGe-to-gate width, tip-to-gate width, sigma depth and recess depth. For production process control of these structures, a metrology tool must utilize a nondestructive measurement technique, and have high sensitivity, precision and throughput. This paper explores the capabilities of a new-generation scatterometry critical dimension (SCD) metrology tool to measure critical parameters and serve as a production process monitor for 28nm and beyond complex gate structures. SiGe gate recess; scatterometry; critical dimension; metrologyI.