Ultrashallow p-type layers have been formed using an one-wafer type reactor for rapid vapor-phase doping (RVD) with lamp annealing system. Bipolar and MOS transistors were fabricated using the system for the first time. The process includes the injection of the B2H6 diffusion source gas with hydrogen carrier gas at room temperature and rapid thermal annealing using lamps. Ultrashallow boron doping was achieved at 900 for 60 seconds; that is, the junction depths were less the 60 nm with a peak boron concentration of between 1019 and 1020 cm-3. The sheet boron concentrations is controlled by adjusting the flow rate of B2H6. To show the potential of the process, bipolar and MOS transistors were fabricated. The base regions of conventional bipolar transistors were formed by rapid vapor-phase doping. Transistors with 20-nm base and emitter were fabricated and they showed current gain of 150. Shallow source and drain of PMOS transistors were also formed. The threshold voltage roll-off was suppressed down to gate length of 0.22 µm, while devices with BF2-implanted source and drain showed the roll-off below 0.5 µm. Devices with RVD-source and drain thus have drain current 1.5 times higher than those with BF2 ion implantation. RVD provides both good short-channel characteristics and high current drivability.

Single-drain PMOSFET's with a very shallow source and drain were fabricated using a new doping method called rapid vapor-phase doping (RVD). This process is carried out in hydrogen atmosphere using B2H6 as a source gas. By varying flow rate of B2H6 and the doping time, shallow boron doped layers which are suitable for source and drain regions of MOSFET's are formed. The fabricated RVD-PMOSFET's have 50-nm source and drain regions with peak concentration of 41020 cm-3 which were formed under the condition of 800, B2H6 flow rate of 50 ml/min. The junction depth was one third of those formed by conventional low-energy BF2 ion implantation. RVD-PMOSFET's showed normal operation down to poly-Si gate length Lg of 0.18 µm. The advantage of shallow junction was clearly shown by the threshold voltage roll-off characteristics, that is, it was suppressed down to 0.18 µm, whereas in conventional device, roll-off occurred below 0.6 µm. This better short channel behavior suggests that RVD forms shallow source and drain regions with weaker lateral diffusion. This result confirms that RVD is an effective method for forming shallow junctions for MOSFET's.