Pore characteristics of low-dielectric-constant films grown by plasma-enhanced chemical vapor deposition studied by positron annihilation lifetime spectroscopy

The pore characteristics of plasma-enhanced chemical-vapor-deposition (PECV D)-grown low-dielectric-constant (low-k) porous films, grown with dual-freq uency power sources and with a source gas of hexamethyldisiloxane, have bee n studied by positron annihilation lifetime spectroscopy. Six low-k films o f different dielectric constants (2.66-4.13) were prepared by changing the low frequency (380 kHz) power of the PECVD process. The long-lived componen t due to pick-off annihilation of ortho-positronium strongly depends on the low frequency power. Based on the empirical relationship between the ortho positronium lifetime and the cavity volume, average pore volumes were estim ated to be 0.23-0.85 nm(3), The correlation between the pore size and diele ctric constant was discussed.