Question

Calculate the mass of boron required to make a silicon crystal with 10^16

/cm^3

doping density, if the initial melt load of silicon is 50 kg. The density of silicon in

the melt is 2.5 g/cm^3

and boron has an atomic weight of 10.8 u. Assume that the

equilibrium segregation coefficient is constant throughout the growth process.

Answer 1

The density of silicon in the melt is 2.5 g/cm³

Volume of the melt = mass/density = 50000/2.5 = 20000 cm³

Number of particles of boron in 20000 cm³ =$10^{16}*20000=2*10^{20}$

1 mole= $6.02*10^{23}$ particles

x moles =$2*10^{20}$ particles

x=$\dfrac{2}{6.02}*10^{-3}$ moles

Mass of boron in x moles= $\dfrac{1}{3}*10^{-3}*10.8=$ $3.6*10^{-3}grams$