Junction Depth Control

Junction depth control precisely manages the depth of doped regions through optimized implantation and thermal processing to meet device specifications. Definition: Junction depth (Xj) is where dopant concentration equals background concentration, defining the boundary between p-type and n-type regions. Advanced node targets: Source/drain extension Xj < 10nm at leading-edge nodes. Extremely challenging to control. Implant parameters: Ion species, energy, dose, tilt angle, and PAI conditions set the as-implanted profile. Lower energy = shallower initial profile. Thermal budget: Every thermal step after implant causes additional diffusion. Total thermal budget determines final Xj. Anneal optimization: Spike RTA (~1050 C, ~1 sec), flash anneal (~1300 C, milliseconds), or laser anneal (~1400 C, microseconds) activate dopants with minimal diffusion. Ultra-shallow junctions: Combine low-energy implant (sub-keV B), PAI for SPER activation, and minimal thermal budget to achieve Xj < 10nm. Measurement: SIMS depth profiling measures actual dopant profile. Spreading resistance profiling (SRP) for electrically active profile. Abruptness: Sharp junction profile (steep concentration transition) desired for short-channel control. High activation with low diffusion. Process integration: All subsequent thermal steps (oxidation, CVD, anneal) add to junction diffusion. Thermal budget tracking essential. Simulation: TCAD process simulation (Sentaurus, ATHENA) predicts junction profiles through entire process flow.