Measurement of attraction force between AFM tip and surface of dielectric thin films with DC-bias

The attraction force between the AFM tip and the surface of sputtered dielectric thin films (SiO2 and ZrO2) was measured with atomic force microscope (AFM) by applying DC-bias between the AFM tip and the n-Si substrate. Under 0 electric field, there exists van der Waals interaction between the AFM tip and the surface of dielectric films. When DC voltages are applied, the attraction force increases obviously for thin SiO2 (5.2 nm) and ZrO2 (6.8 nm) films due to the columbic interaction between them. A parallel-plate model has been developed to evaluate the ideal columbic tip-surface force for SiO2 and ZrO2 films. Contrary to the calculation result, the columbic force for ZrO2 film (6.8 nm) is lower than that for SiO2 film (5.2 nm), indicating the poor dielectric properties of the ZrO2 film. The poor dielectric properties of ZrO2 film should be due to the interfacial SiOx-containing layer formed between ZrO2 and Si, supporting the conclusion reached in the literature that the interfacial SiOx-containing layer can deleteriously influence the dielectric properties of high-k films.