Diffusion Coefficient

 

 

         Diffusion coefficient tells us how effectively does an impurity atom diffuse through the silicon wafer.

 

         Diffusion coefficient depends exponentially on temperature

 

D = D0 exp(-EA / kT)

 

Where D0 is the frequency factor (in cm2/sec)

EA is the activation energy in eV

T is temperature (in K)

K is Boltzmann constant in eV/K

 

Example: Calculate the diffusion coefficient for boron at 1100C.

 

We know that D = D0 exp(-EA / kT)

D0=10.5 cm2/s

T =1100C=1100 + 273 = 1373 K

EA = 3.69 eV / K

K=8.62X10-5 eV/K

D=2.96X10-13 cm2/sec