3.7.4 Charge Centroid Calculation for Accumulation

$T_6 = 1 + \Bigg( \dfrac{q_{i,acc}}{QM0ACC} \Bigg)^{PQMACC} \qquad (3.337)$

$C_{ox,acc} = \begin{cases} \dfrac{3.9 \cdot \epsilon_0}{\Bigg[ TOXP \cdot \dfrac{3.9}{EPSROX} + T_{cen} \cdot \dfrac{QMTCENCV_i}{\epsilon_{ratio}} \Bigg]} &\text{if } GEOMOD \ne 3 \\ \\ \dfrac{3.9 \cdot \epsilon_0}{R \cdot \Bigg[ \dfrac{1}{\epsilon_{ratio}} \cdot ln \Bigg( \dfrac{R}{R - T_{cen}} \Bigg) + \dfrac{3.9}{EPSROX} \cdot ln \Bigg( 1 + \dfrac{T_{oxp}}{R} \Bigg) \Bigg]} &\text{if } GEOMOD = 3 \end{cases}$

$(3.338)$

If $QMTCENCV_i = 0$,

$C_{ox,eff} = C_{ox} \qquad (3.339)$

$C_{ox,acc} = \dfrac{3.9 \cdot \epsilon_0}{EOTACC} \qquad (3.340)$

If $QMTCENCV_i > 0$,

$T_4 = \dfrac{q_{ia}}{QM0} \qquad (3.341)$

$T_5 = 1 + T_4^{PQM} \qquad (3.342)$

$T_{cen} = \dfrac{T_{cen0}}{T_5} \qquad (3.343)$

$C_{ox,eff} = \dfrac{1}{\Bigg[ \dfrac{1}{C_{ox} \cdot \frac{EOT}{TOXP}} + \dfrac{T_{cen} \cdot QMTCENCV_i}{\epsilon_{sub}} \Bigg]} \qquad (3.344)$

Here, $C_{ox,eff}$ is the effective oxide capacitance taking QM effects into account for $V_{gs} > V_{fb}$ and $C_{ox,acc}$ is the effective oxide capacitance taking QM effects into account for $V_{gs} < V_{fb}$.