Surface Scanning Inspection Systems Research Articles

Measurement of 100 nm and 60 nm Particle Standards by Differential Mobility Analysis.

The peak particle size and expanded uncertainties (95 % confidence interval) for two new particle calibration standards are measured as 101.8 nm ± 1.1 nm and 60.39 nm ± 0.63 nm. The particle samples are polystyrene spheres suspended in filtered, deionized water at a mass fraction of about 0.5 %. The size distribution measurements of aerosolized particles are made using a differential mobility analyzer (DMA) system calibrated using SRM® 1963 (100.7 nm polystyrene spheres). An electrospray aerosol generator was used for generating the 60 nm aerosol to almost eliminate the generation of multiply charged dimers and trimers and to minimize the effect of non-volatile contaminants increasing the particle size. The testing for the homogeneity of the samples and for the presence of multimers using dynamic light scattering is described. The use of the transfer function integral in the calibration of the DMA is shown to reduce the uncertainty in the measurement of the peak particle size compared to the approach based on the peak in the concentration vs. voltage distribution. A modified aerosol/sheath inlet, recirculating sheath flow, a high ratio of sheath flow to the aerosol flow, and accurate pressure, temperature, and voltage measurements have increased the resolution and accuracy of the measurements. A significant consideration in the uncertainty analysis was the correlation between the slip correction of the calibration particle and the measured particle. Including the correlation reduced the expanded uncertainty from approximately 1.8 % of the particle size to about 1.0 %. The effect of non-volatile contaminants in the polystyrene suspensions on the peak particle size and the uncertainty in the size is determined. The full size distributions for both the 60 nm and 100 nm spheres are tabulated and selected mean sizes including the number mean diameter and the dynamic light scattering mean diameter are computed. The use of these particles for calibrating DMAs and for making deposition standards to be used with surface scanning inspection systems is discussed.

Impact of Chemical and Epitaxial Treatment on Surface Defects on Silicon Wafers

AbstractDefects on polished as well as hot SC1 treated silicon wafers were investigated with an Atomic Force Microscope (AFM) and Surface Scanning Inspection Systems (SSIS). Measurement with two SSIS of different type allows to identify most of the surface defects as non particulate scatterers. AFM of these defects reveals tiny pits or groups of pits. An almost linear relation is found between the geometrical lateral defect dimension and their average size in units of LSE (Latex Sphere Equivalent; an effective measure for the scattering cross section) as reported by one of the SSIS for the defects on wafers treated with hot SC1. Growth rates of about 40 nmLSE/h are observed for the defects during subsequent treatments of wafers with hot SC1. The LSE-size distribution of as-grown defects with a peak at about 105 and 110 nmLSE is obtained for two types of wafer by modeling the defect evolution during hot SC1 treatment. The number of surface flaws ≥ 0.12 μmLSE on a substrate is reduced by two orders of magnitude for epitaxial layers as thin as 1.5 μm.