Question

2) (a) Calculate the Capacitance per unit area of a MOSCAP with an oxide thickness of 2 , when it is biased in inversion. The oxide is Silicon dioxide, the semiconductor is silicon, and the metal is Copper. (b) Does your answer depend on if the silicon substrate is p-type or n-type? (c) Does your answer depend on the type of metal used.

Answer 1

In Inversion mode

Capacitance per unit area is given as,

In Inversion mode,when MOSCAP is operating in low frequency, Capacitance per unit area is equal to ,and from the formulae we can see that it is independent of type of substrate and type of metal used.

But in Inversion mode,when MOSCAP is operating in high frequency ,Capacitance per unit area is given as

  

For p type,

  

For n type,

  

From formulae shown above we can see that, depend on p type substrate or n type substrate

is surface potential which depend on type of metal

So we can say in high frequency Capacitance per unit area of MOSCAP depend on n type or p type substrate and type of metal used.