Conformal Doping of FINFETs: a Fabrication and Metrology Challenge

Whereas the introduction of 3D-dimensional devices such as FINFETs may be a solution for next generation technologies, they do represent significant challenges with respect to the doping strategies and the junction characterization. Aiming at a conformal doping, classical beam implants fail due to the differences in impact angle, ion incorporation efficiency and the effect of wafer rotation. Moreover shadowing represents an additional limitation for larger tilt angles when considering closely spaced FINs. Plasma immersion doping is an alternative approach which holds the promise of conformality but is also quite challenging and relies on secondary processes such as resputtering, deposition and in diffusion etc. Its implementation is compromised by concurrent artifacts, sputter erosion being the most important one. In support of these developments the measurement of the 3D-dopant distribution and the identification of conformality is essential requiring adequate metrology such as Scanning Spreading Resistance Microscopy, SIMS through FINs, resistors and the Tomographic Atomprobe.