High-Performance Ge MOS Capacitors by $\hbox{O}_{2}$ Plasma Passivation and $\hbox{O}_{2}$ Ambient Annealing

Very promising capacitance-voltage (C-V) characteristics of capacitors on both p- and n-type Ge substrates are demonstrated by using an in situ O
₂
plasma passivation and an O
₂
ambient annealing. The capacitors exhibited a small equivalent oxide thickness of ~1.5 nm and a low D
_it
(<; 6 * 10
¹¹
cm
^-2
eV
^-1
) energy distribution covering the major part of the Ge bandgap (>; 0.51 eV). The surface potential modulation efficiency was estimated to be ~80% from Hatband to strong inversion on both types of Ge. C-V hysteresis was less than 10 mV with positive bias up to 1.5 V. A low gate leakage current density of <; 9 * 10
^-8
A/cm
²
at V
_FB
± 1 V indicates high quality of the HfO
₂
/GeO
₂
gate stacks. Excellent comprehensive properties suggest that a combination of O
₂
plasma passivation and O
₂
ambient annealing provides a promising technology for GeO
₂
-based CMOS devices.