Wh. Brunger et al., DAMAGE CHARACTERIZATION OF ION-BEAM EXPOSED METAL-OXIDE-SEMICONDUCTORVARACTOR CELLS BY CHARGE TO BREAKDOWN MEASUREMENTS, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 13(6), 1995, pp. 2561-2564
Damage in thin (10 nm) oxide layers of metal-oxide-semiconductor varac
tor cells caused by exposures with ions, electrons, and x rays has bee
n electrically characterized by constant-current stress time-dependent
dielectric breakdown and capacitance-voltage measurements. The time-d
ependent dielectric breakdown investigations show measurable damage if
the ions (H+; 74 keV) are allowed to penetrate the resist (300 nm PMM
A) and the poly-Si layer (250 nm) to reach the oxide. This is not the
case if the ions (H-2(+); 74 keV) are stopped inside the poly-Si layer
by use of a thicker (450 nm) resist. Also for electrons and x rays th
e exposure with lithographic doses did not change the time-dependent d
ielectric breakdown curves. The capacitance-voltage measurements demon
strate that electrons and x rays which do penetrate the gate oxide cau
se a flatband voltage shift of nearly 400 mV. This shift could not be
observed if the H-2(+) ions were stopped in the poly-Si buffer layer.
Ions seem to create no secondary effects like x-ray generation which r
each beyond the penetration depth. The measurements were performed in
the unannealed state to detect all possible damage effects including t
hose which can be removed by annealing. (C) 1995 American Vacuum Socie
ty.