Optimizing PMOS performance: Enhancing PLDD Implantation by switching from Boron to BF2

In most submicron processes, the p-type lightly doped drain (PLDD) implant is typically performed using a low-energy boron (B) implant, as low as 0.6 keV. Boron, being a light atom, is easily accelerated in the ion beam, resulting in a high projected range and straggle. To achieve the desired implantation profile, a lower energy implant is performed in a deceleration mode, which presents challenges in dose repeatability and energy contamination. These challenges can lead to inconsistencies in device performance, particularly in the PMOS Idsat electrical test (ET) parameter, which may fall out-of-specification (OOS), resulting in low yield, wafer scrap, and higher costs. To address these issues, this study explores the conversion from boron(B) to boron difluoride (BF2), a heavier atom. The BF2 implant process offers several advantages: improved variations and dose control due to the heavier mass of the BF2 molecule, enhanced tool up time and throughput, increased process margin for ET and yield, and superior reliability performance. BF2 implants reduce boron penetration and mitigate damage, leading to better performance in key reliability tests such as Negative Bias Temperature Instability (NBTI), Hot Carrier Injection (HCI), and Time-Dependent Dielectric Breakdown (TDDB). The results indicate that BF2 implants are a preferable choice over boron for advanced semiconductor manufacturing, providing improved process efficiency, yield, and device reliability.