Challenges of Finer Particle Detection on Unpatterned Silicon Wafers

As the size of yield‐limiting particles has significantly decreased with the decrease in the feature size of leading‐edge ULSI devices, a clear need has arisen for a system capable of detecting particles of far below 50 nm in diameter on the surface of silicon wafers. If we employ a shorter wavelength (266 nm or below) laser for the laser‐scanning wafer inspection system, its sensitivity level can be raised to the range of 20 to 30 nm in diameter on smooth surfaces. However, so far, silicon surface morphology, such as crystal originated pits (COPs), micro‐scratches, microroughness, as well as residual chemical contamination on the surface of a mirror‐finished wafer, prevents the detector sensitivity from being raised to such a high level. Therefore, before further raising the particle detection sensitivity of the system, we must establish technologies for obtaining a super‐smooth silicon surface by employing scratch‐free precision surface polishing, COP‐free crystal growing/annealing, and microroughness/p...