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(-E_A / kT)

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

E_A 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 1100°C.

We know that D = D₀ exp(-E_A / kT)

D₀=10.5 cm²/s

T =1100°C=1100 + 273 = 1373 K

E_A = 3.69 eV / K

K=8.62X10^-5 eV/K

D=2.96X10^-13 cm²/sec