Structural and electrical properties of gate stack structures containing ZrO2 dielectrics were investigated. The ZrO2 films were deposited by atomic layer chemical vapor deposition (ALCVD) after different substrate preparations. The structure, composition, and interfacial characteristics of these gate stacks were examined using cross-sectional transmission electron microscopy and x-ray photoelectron spectroscopy. The ZrO2 films were polycrystalline with either a cubic or tetragonal crystal structure. An amorphous interfacial layer with a moderate dielectric constant formed between the ZrO2 layer and the substrate during ALCVD growth on chemical oxide-terminated silicon. Gate stacks with a measured equivalent oxide thickness (EOT) of 1.3 nm showed leakage values of 10−5 A/cm2 at a bias of −1 V from flatband, which is significantly less than that seen with SiO2 dielectrics of similar EOT. A hysteresis of 8–10 mV was seen for ±2 V sweeps while a midgap interface state density (Dit) of ∼3×1011 states/cm eV was determined from comparisons of measured and ideal capacitance curves.

Thermal stability of gate stack structures composed of ZrO2 gate dielectrics and silicon electrodes was investigated. The ZrO2 films were deposited by atomic layer deposition, while the polycrystalline silicon electrodes were deposited using different variants of chemical (CVD) and physical vapor deposition (PVD). Zirconium silicide formation was noted in all CVD-electroded samples after subsequent annealing treatments at temperatures above 750 °C, but not in the room temperature PVD-electroded samples, even after gate annealing at 1050 °C. The dependence of zirconium silicide formation on the Si deposition process was explained using thermodynamic arguments which explicitly include the effects of oxygen deficiency of the metal oxide films.

No abstract

Using laboratory scale and full size PEP-I1 vacuum extrusion. Surface composition changes were monitored chamhers. chemical cleaning. glow discharge and thermal through the wet cleaning process as bath compositions and process effects were evaluated using surface analysis by x-rinse water conductivity were adjusted. These coupons ray photoelectron spectroscopy (XPS). These processes were also inserted into a test chamber (Figure 1) to monitor were optimized to reduce surface carbon and thereby changes in surface composition following glow discharge minimize photodesorption gas loads. The relation of processing. Copper discs were also installed at three surface carbon to ion dose was investigated and compared locations in full-scale dipole and quadrupole beam for pure argon. 5% oxygen in argon, and pure hydrogen chambers to monitor thermal and glow discharge plasmas. Argon incorporation was noted only when the processing effects on surface composition (Figure 2). copper was oxidized in the mixed gas. Surfaces, stable in amhient atmosphere. were obtained having surface carbon values less than 10%. These optimized recipes will be used in processing copper vacuum chambers for the PEP-I1 BFactory.