[en] High current electrostatic Low-Energy Beam Transport (LEBT) systems are currently being developed for several applications ranging from H- cyclotrons to high intensity linear accelerators. A new design building on the experiences gained from the Spallation Neutron Source (SNS) LEBT system was modeled recently in 2D with PBGUNS. In this paper a 3D treatment is given for this new LEBT design for a 60 mA, 65 kV H- beam. For this type of LEBT 3D modeling is essential to accurately model the deflection of the co-extracted electrons from the beam. The beam chopping and steering for RFQ injection also presents a 3D problem for the otherwise cylindrically symmetric geometry. The modeled LEBT can transport a 60 mA H- beam with 0.2 π mm mrad 1-rms emittance and Twiss parameters that are in accordance with established SNS LEBT specifications

[en] The ability to use large molecular species such as octadecaborane (B₁₈H₂₂) has been investigated at semiconductor device manufacturers as a way to significantly increase wafer throughput relative to standard high current ion implanters. Over the past two years, improvements in the machine design to support the use of B₁₈H₂₂ have led to beam current increases of 50% from 30 pmA to 45 pmA of boron at an equivalent boron energy of 4 keV. This boron energy is required by p⁺ doping of dual poly gate (DPG) structures in DRAM. Beam current has also been significantly improved at the low equivalent boron energies anticipated to be required by 32 nm processes for PMOS source/drain extensions (SDE). For example, at 250 eV equivalent beam energy, a 100% increase in cluster boron beam current has been attained.This paper describes the techniques by which these beam current improvements were accomplished, primarily through the refinement of ion beam optics. Other techniques for increasing overall tool productivity are also described, such as beam utilization and overall operational improvements. Wafer throughputs are presented for critical p⁺ implant processes such as dual poly gate (DPG), source/drain (S/D), source drain extension (SDE) and S/D contact. The higher throughputs resulting from these changes are translated into a cost per wafer (CPW) model and it is demonstrated that an increase in average beam current is the largest contributor to a reduction in CPW.

[en] An important difference between monomer ion beams and heavy molecular beams is a significant reduction in beam angular divergence and increased on-wafer angular accuracy for molecular beams. This advantage in beam quality stems from a reduction in space-charge effects within the beam. Such improved angular accuracy has been shown to have a significant impact on the quality and yield of transistor devices [1,12]. In this study, B₁₈H_x⁺ beam current and angular divergence data collected on a hybrid scanned beam line that magnetically scans the beam across the wafer is presented. Angular divergence is kept below 0.5 deg from an effective boron energy of 200 eV to 3000 eV. Under these conditions, the beam current is shown analytically to be limited by space charge below about 1 keV, but by the matching of the beam emittance to the acceptance of the beam line above 1 keV. In addition, results of a beam transport model which includes variable space charge compensation are presented, in which a drift mode B₁₈H_x⁺ beam is compared to an otherwise identical boron beam after deceleration. Deceleration is shown to introduce significant space-charge blow up resulting in a large on-wafer angular divergence. The divergence effects introduced by wafer charging are also discussed.