Direct measurement of l/sub eff/ and channel profile in MOSFETs using 2-D carrier profiling techniques

Abstract

Different two-dimensional (2-D) carrier profiling tools, based on contact-mode atomic force microscopy (AFM), have been used to investigate the details in the lateral and vertical distribution of the carriers in nMOSFET devices with identical channel profile (4e17 atoms/cm/sup 3/) and gate oxide thickness (5.5 nm) but with different S/D architectures, all relevant for 0.25 /spl mu/m CMOS technology. These characterization techniques are: scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM). Two typical 2-D case studies are presented. In the first one, the effective gate length is determined. The measured values are compared with the ones measured by extraction from the electrical characteristics using a modified shift and ratio method. In the second study, the vertical channel profile through the centre of the gate is studied as a function of the gate length. Here, for the first time, transient enhanced diffusion (TED) effects are directly observed. This type of profile information is not accessible using standard 1-D profiling techniques such as SIMS, SRP, or C-V profiling.