Without the ability to detect potential yield-limiting defects in-line, the yield learning cycle is severely crippled, compromising the financial success of chip makers. As design rules shrink, device yield is seriously affected by smaller size particle and patterned defects that were not important in the past. These mechanisms are becoming more difficult to detect with current defect detection tools and techniques. The optical defect inspection tools that are currently available do not adequately detect defects, while scanning electron microscope (SEM) based inspection tools are too slow. With each successive technology node, optical inspection becomes less capable relative to the previous technology. As sensitivity is increased to detect smaller defects, the nuisance defect rate increases commensurately. Line-edge roughness (LER) and subtle process variations are making it more difficult to detect defects of interest (DOI). Smaller defects mean smaller samples available for energy dispersive x-ray analysis (EDX), necessitating an improved or new methodology for elemental analysis. This paper reviews these and some other challenges facing defect metrology at the 45nm technology node and beyond. The challenges in areas of patterned and unpatterned wafer inspection, defect review, and defect characterization are outlined along with proposed solutions. It also provides an overview of several ongoing projects conducted at International SEMATECH Manufacturing Initiative (ISMI) to address these challenges.
Optical second-harmonic generation (SHG)is used as a noninvasive probe of the interfaces of Si nanocrystals (SiNCs)embedded in an SiO2 matrix. We verify experimentally that the second-harmonic polarization P(2) has a quadrupolar form proportional to (E ·∇) E as proposed in recent models based on a locally noncentrosymmetric dipolar polarization averaged over the spherical NC interface. A two-beam sum-frequency geometry is found
to enhance this polarization dramatically compared to a single-beam SHG geometry, yielding strong signals useful for scanning, spectroscopy and real time monitoring. Using this two beam geometry, we have produced non-invasive two dimensional SHG maps with few-micron resolution of 1-micron-thick layers of Si-NCs (3 and
5 nm average diameter)produced by ion implanting Si into SiO2. Samples were scanned over a 5mm x 5mm
area with two non-collinear,orthogonally polarized,amplified Ti:S laser pulses (80 fs,810nm,100 μJ,1 kHz repetition rate) while detecting the generated SH signal in transmission. The SHG signal is sensitive to chemical modification of the Si/SiO2 interface and to local gradients in nanoparticle density.