The gas flow is then changed to pure nitrogen and the temperature of the furnace increased. This causes the B2O3 layers on the BN wafers to evaporate.
The B2O3 molecules then strike the polished surface of the silicon wafers where they react to form a SiO2 (glass) - B surface layer. With continued heating, some of the B diffuses into the silicon wafer providing the electrically active "doping" require to form a transistor.
