Physical and electrical analysis of silicon dioxide thin films produced by electron-cyclotron resonance chemical-vapour deposition

Abstract

High-quality silicon dioxide films have been deposited in the temperature range 150–425 °C by electron-cyclotron resonance chemical-vapour deposition (ECR-CVD) using an oxygen plasma with silane introduced downstream. The interface state densities of 10 nm thick films measured by the high-low frequency CV method have values in the range of 3−5×10 10eV −1cm −2. Thirty second anneals in flowing nitrogen in the temperature range 850–950 °C reduced the values to below the sensitivity limit, 2×10 10 eV −1cm −2. The electrical performance of the films has been correlated with their silanol content as determined by Fourier-transform infrared spectroscopy and the surface and interface roughness as determined by atomic-force microscopy. Negative Fowler-Nordheim stress measurements performed on Al-gated capacitors with 19.1 nm thick films deposited at 300 °C and annealed for 30 s at 900 °C exhibited positive charging and interface state generation rates larger than as those of Al-gated capacitors with thermal oxides. The excess generation of both the positive charge and interface states can be described by processes with cross-sections of 3−4×10 −19 cm −2. The nature of the interface traps and the prospects for reducing their concentration by polysilicon gate processing are discussed.