Release of Redox Additives Via Megasonic Energy for High Selectivity/Low-Stress STI CMP

Abstract

The advancements in a wide array of semiconductor manufacturing processing have been pivotal for the extension of Moore’s law the Chemical Mechanical Planarization (CMP) process has become an area of focus due to the stringent surface topography requirements. CMP utilizes complex slurry formulations containing abrasive nanoparticles and additives to reduce substrate defectivity and achieve angstrom-level uniformity. One area that has gained significant attention is Shallow Trench Isolation (STI), where the modulation and control of the surface oxidation state of the ceria, specifically the Ce3+ state, is critical to TEOS removal. In the Ce3+ state, defect states (i.e., oxygen vacancies (Ovacs)) on the surface are highly electron deficient (i.e., electrophilic) and allow the nucleophilic substrate to complex. By modulating the electrophilic properties of the particle, the kinetics of surface complexations required for effective TEOS removal can be controlled. This work focuses on developing stimuli-responsive capsules that can be added to STI slurry formulations to promote the controlled release of redox-active additives that can be used to drive the oxidation state of the CeO2 nanoparticle (Ce3+/Ce4+). By encapsulating the additive in a polymeric system, the reactive properties of the slurry are limited until the additive is released. In this work, megasonic action was employed to disrupt the capsules releasing the additives on demand to facilitate the modulation of the CeO2 surface redox states. Results have shown that the addition of a controlled-release capsule with an additive resulted in the increase of Ovacs at the CeO2 surface. This led to an increase from 1800 Å/min to 3450 Å/min using a constant 2.0 W/cm2 continuous flow megasonic flux. Furthermore, the overall defectivity decreased significantly with respect to both particle contamination and surface scratching. Lastly, the nature of the polymeric capsule has been shown to enhance selectivity between TEOS and silicon nitride and preliminarily appears to be megasonic flux dependent.