Crystal-originated particles on performance for Nano-generation IC process

Abstract

In this work, we present crystal-originated particles (COPs) always created on ultra-thin gate oxide for recent ultra large-scale integration (ULSI) devices were studied. Various Czochralski (CZ) silicon wafers were prepared by controlling the pulling speed of silicon ingots to determine the relationships between COPs and the breakdown characteristics of the ultra thin-gate oxide. The distribution of COPs, measured by optical shallow defect analysis and the use of a particle counter, was compared with the results of time-independent dielectric breakdown (TZDB), time-dependent dielectric breakdown (TDDB) and stress-induced leakage current (SILC) for gate oxides with thicknesses of 2.5–5 nm. The results reveal no appreciable oxide degradation below an oxide thickness of approximately 3 nm; above this threshold value, the defect density depends strongly on the presence of crystal-originated particles. The COPs are a major factor in the degradation of ultra-thin gate oxide (less than 5 nm) in ULSI devices. The I-V measurements are readily explained by invoking Fowler-Nordheim tunneling effect. It was recently revealed that singularities (crystal-originated “particles”) formed on Si wafers after SC1 cleaning originate from some defects in crystals and were perceived by laser particle counters. In this paper, the size distribution of crystal-originated “particles” is examined in detail by means of repeated SC1 cleanings. It is shown that, as the crystal pulling rate becomes faster, the size distribution of crystal-originated “particles” shifts toward smaller size, and the total number of origins of crystal-originated “particles” increases. Crystal-originated particle (COP) side-wall angles and rates of change in width were measured after treatment in an SC-1 solution by atomic force microscopy (AFM) to determine the shape, size and type of the particles on a polished (100) Si wafer surface.