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Question 19.6: Calculate the capacitance of a metal 4 pad and a metal 4/met...

Calculate the capacitance of a metal 4 pad and a metal 4/metal 3 pad. Assume dimensions of 75 μm × 75 μm and use the capacitance data shown in Fig. 19.50.

19.50
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For a metal 4 pad,

\begin{aligned} C_{t o t} &=75^2 \times 6+75 \times 4 \times 15 &(19.15)\\ &=38.25 fF&(19.16) \end{aligned}

For a metal 4/metal 3 pad,

\begin{aligned} C_{t o t} &=75^2 \times 9+75 \times 4 \times(17+15) &(19.17)\\ &=60.22 fF &(19.18)\end{aligned}

Note that the fringe capacitances of metal 4 and metal 3 are directly added here. This is a rough approximation.

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