Effect of SiO2 intermediate layer on Al2O3/SiO2/n+-poly Si interface deposited using atomic layer deposition (ALD) for deep submicron device applications

Electrical and reliability characteristics of several Si/Al2O3 (barrier layer)/Si capacitor structures have been investigated. Al2O3 film was deposited by atomic layer deposition (ALD). ALD Al2O3 was found to be a good chemical oxide barrier layer which is important for achieving thin oxide thickness. Formation of a metallic Al cluster was observed at the Al2O3/n+-doped Si interface layer. SiO2 formed by O2 flushing at 400°C for 10 min was found to be very effective to prevent the formation of a metallic Al cluster and to reduce the leakage current to less than 1×10−15 A/μm2 at an applied voltage of 2.0 V. In situ stress–temperature measurement of Al2O3/SiO2/n+-doped poly Si was carried out to evaluate the residual stain of the film. Average interband oscillator energy of the Al2O3 film on SiO2 is greater than that of Al2O3 film on Si(100) by 1.162 eV. Al2O3 films exhibited excellent interface quality, dielectric reliability, and shrinkability. The capacitor using Al2O3 film satisfied the requirement for cell capacitance of 25 fF/cell in 0.30-μm pitched DRAMs.