Using electron cyclotron resonance sputtering in the deposition of ultrathin Al2O3 gate dielectrics

Abstract

The gate-dielectric characteristics of an ultrathin Al2O3 film deposited by electron cyclotron resonance sputtering are investigated. The sputtering process is classified as operating in either of two deposition modes: a metal mode and an oxide mode. Characteristics of the deposited films, such as their surface morphology, uniformity of thickness, and degrees of interlayer-oxide formation, are presented for both modes. The electrical characteristics of metal-mode Al2O3 films after annealing in a high vacuum (around 10−4 Pa) are looked at in detail. The metal-mode condition and high-vacuum annealing prevents the formation of interlayer oxide and reduces the flat-band voltage (VFB) shift but also produces a rather large capacitance–voltage (C–V) hysteresis loop. A small equivalent oxide thickness of 1 nm, low values for leakage current of around 2×10−3 A/cm2, and a fixed negative-charge density of 7×1010 cm−2 are demonstrated for the metal-mode films. The large C–V hysteresis loop is reducible by oxidation.