ABSTRACT
Dopant impurities play a key role in semiconductor device operation, as they directly inuence the electrical properties of different regions. The dopant concentration directly affects the parameters such as the threshold voltage in metal-oxide semiconductor (MOS) very large scale integration (VLSI) transistors and breakdown voltage of the devices fabricated. During silicon crystal growth, the impurity atoms with ko value (i.e., equilibrium segregation coefcient) less than 1 are rejected by the advancing solid at a greater rate than they can diffuse into the bulk of the melt. Most values for the commonly used impurity dopant species for silicon are below this unity value, which means that during the crystal growth process, the dopant species are rejected into the silicon melt. With melt-crystal, at the beginning of the solidication process at a given crystal solid-melt interface, segregation takes place, and the rejected impurity atoms begin to accumulate in the melt layer near the growth interface and diffuse in the direction of the bulk of the melt [1]. An impurity concentration gradient develops ahead of advancing crystal.
