An AC field-effect study of TCE-oxidised SiO<inf>2</inf>-Si interface states

Surfaces of 10 Omega cm, n-type (111) silicon wafers were oxidised in trychloroethylene (TCE) ambient. MOS test devices were prepared to characterise the Si-SiO2 interface by AC field-effect and C-V methods. The AC field-effect mobility mu FE as a function of frequency showed a small temperature dependence of relaxation times (8-4 mu s) in the temperature range 240-370K. The dominant energy level ET was found to be 0.04 eV below the conduction band edge and the effective capture cross-section of interface traps was found to be about 10-1 cm2. C-V measurements on the same structure showed that the normal distribution of interface state density NSS increased towards the conduction band edge from the mid-gap energy. The effect of TCE tends to reduce the density of interface states NSS as well as shift the energy of shallow traps ET towards the conduction band edge.