Detailed investigation of the effects of La and Al content on the electrical characteristics and reliability properties of La–Al–O gate dielectrics

The effects of the composition of La–Al–O gate dielectrics on metal–oxide–semiconductor field-effect transistor (MOSFET) characteristics and reliability properties were investigated in detail. It was found that the interface trap density (Dit) was greater for [Al]-enriched La–Al–O than for [La]-enriched La–Al–O. As a result, the drive current and the time-to-breakdown (Tbd) for the gate oxide were lower for [Al]-enriched La–Al–O than for [La]-enriched La–Al–O. It is thought that the large tensile strain at the interface with the Si substrate is responsible for the smaller Dit in the case of [La]-enriched La–Al–O.