Effects of Wet Chemistry Pre-gate Clean Strategies on the Organic Contamination of Gate Oxides for Metal-Oxide-Semiconductor Field Effect Transistor

Abstract

It is known that organic contamination can seriously degrade the electrical performance of gate oxides for metal-oxide-semiconductor field effect transistor (MOSFET) applications. In this paper, organic contamination of wafer surfaces cleaned by different pre-gate clean conditions and subsequently exposed to cleanroom ambience was investigated using time-of-flight secondary ion mass spectroscopy (TOF-SIMS), and the carbon level from thermally decomposed organic species directly trapped in the gate oxides after thermal oxidation and polysilicon deposition was probed using secondary ion mass spectroscopy (SIMS) depth profiling. The C concentration in the oxide-polysilicon gate stack obtained from SIMS depth profiling closely correlates with the total TOF-SIMS peak intensity of organic contaminants detected on post clean wafer surfaces. A quantified carbon concentration on the order of 1012 atoms/cm2 was obtained at the interfaces using SIMS depth profiling calibrated with an implanted C standard. It was found that the susceptibility of wafer surfaces to organic contamination that eventually affects the level of oxide-polysilicon interfacial carbon appears to be highly dependent on the surface termination.