Performance and Reliability of ${\rm Gd}_{2}{\rm O}_{3}$ and Stacked ${\rm Gd}_{2}{\rm O}_{3}\hbox{-}{\rm Eu}_{2}{\rm O}_{3}$ Metal-Insulator-Metal Capacitors

Gd
₂
O
₃
-based metal-insulator-metal capacitors have been characterized with single layer (Gd
₂
O
₃
) and bilayer (Gd
₂
O
₃
/Eu
₂
O
₃
and Eu
₂
O
₃
/Gd
₂
O
₃
) stacks for analog and DRAM applications. Although single layer Gd
₂
O
₃
capacitors provide highest capacitance density (15 fF/μm
²
), they suffer from high leakage current density, poor capacitance density-voltage linearity, and reliability. The stacked dielectrics help to reduce leakage current density (1.2×10
^-5
A/cm
²
and 2.7 × 10
^-5
A/cm
²
for Gd
₂
O
₃
/Eu
₂
O
₃
and Eu
₂
O
₃
/Gd
₂
O
₃
, respectively, at -1 V), improve quadratic voltage coefficient of capacitance (331 ppm/V
²
and 374 ppm/V
²
for Gd
₂
O
₃
/Eu
₂
O
₃
and Eu
₂
O
₃
/Gd
₂
O
₃
, respectively, at 1 MHz), and improve reliability, with a marginal reduction in capacitance density. This is attributed to lower trap heights as determined from Poole-Frenkel conduction mechanism, and lower defect density as determined from electrode polarization model.