Low-pressure chemical vapor deposition of pureb layers on silicon for p+n junction formation

Ultrashallow junctions were fabricated by chemical vapor deposition of pure boron (PureB) at 95 torr as opposed to atmospheric pressure deposition. The low pressure deposition process with hydrogen as carrier gas demonstrated to be a viable process for fabricating ideal diodes with low saturation current and no detrimental effects. The minimum deposition temperature for forming an ideal diode is 500°C. In the 500°C to 700°C temperature regime, the saturation current density decreases with increasing deposition temperature. Diodes fabricated with PureB deposition at 400°C show a superposition of p⁺n and Al-to-Si Schottky-like behavior. Depositing PureB at 95 torr results in a thicker layer than at atmospheric pressure, implying that hydrogen desorption from silicon surface is limiting in the reaction mechanism of the PureB deposition.