Measurements of residual defects and 1/f noise in ion-implanted p-channel MOSFET's

This paper describes the measurements of excess noise and residual defects of extremely low concentrations (<1 × 10
⁹
cm
^-2
) in ion-implanted p-channel MOSFET's. The activation energy and the density of the residual defects after high-temperature annealing were measured using a transient capacitance technique. The test FET's were ion-implanted with fluences of 5 × 10
¹¹
to 4 × 10
¹²
using
³¹
p
⁺
,
¹¹
B
⁺
, or
²⁸
Si
⁺
species. A post-implant anneal was carried out in an N
2
or an Ar ambient for 20 min at various temperatures. For
¹¹
B
⁺
-implanted MOSFET's after annealing above 1000°C, a high residual defect concentration was observed near the conduction band edge; whereas after annealing the defect density as a result of
²⁸
Si
⁺
or
³¹
p
⁺
implantation was equal to that of control MOSFET's. The density-of-state data agree with the equilibrium measurements of excess (
1/f
) noise power. The excess noise was measured as a function of the drain current. The distribution of
1/f
noise power versus potential minimum of holes in the equilibrium condition is similar to that of interface state density. In nonequilibrium operation, a reduction of excess noise was achieved owing to the presence of buried channel created by ion implant.