The Scatter Works Inc.

Ade Optical Systems Corporation

Craig A Scheer

John C Stover

Yuri A Eremin

In a method for depositing particles onto a substrate a flow of gas containing particles is provided along a flow path that bypasses a deposition chamber. The flow path may direct the flow of the gas containing the particles to a vacuum. To deposit particles onto a substrate in the deposition chamber, the flow path of the gas containing the particles is diverted into the deposition chamber so that particles are deposited onto the substrate. After a desired amount of particles have been deposited onto the substrate, the flow path of the flow of the gas containing the particles is changed to the flow path that bypasses the deposition chamber. A particle deposition system and a method for maintaining particle diameter during deposition of particles onto a substrate also are described.

Particle deposition system with enhanced speed and diameter accuracy

Particles are distinguished from pits, voids, scratches, and other subsurface defects in a surface of a substrate by impinging the defect with polarized light and integrating light scattered by the defect over a wide angular range to produce a total integrated response. Using a P-polarized incident light beam, particles are distinguished from subsurface defects by comparing the total integrated responses, which vary with changes in the incident angle. Alternatively, the defect is impinged with a P-polarized incident beam at a defined incident angle, and is then impinged with an S-polarized beam at the same incident angle. Total integrated responses are measured for both beams and a P-to-S ratio of the responses is calculated. Particles are distinguished from subsurface defects by comparing the P-to-S ratio to a predetermined threshold value which separates particles from subsurface defects.

Method and apparatus for distinguishing particles from subsurface defects on a substrate using polarized light

The method of the present invention accurately measures the diameter of a particle resting on a surface through use of a beam of known wavelength being directed at the surface at an incident angle. Scattered light measurements are taken as the beam contacts the surface and the particle. Scattered light measurements are separated into their respective P and S power components. During all measurements, the beam source remains constant in that it is not moved or adjusted for intensity or polarization. The P and S power components of the background measurements are subtracted from the P and S power components of the particle measurements to give net P and S power components. From the net P and S power components the net P and S components of the differential scatter cross section may be derived as is known in the art. Different ratios may be formed from the differential scatter cross section to eliminate many of the intensity errors inherent in the use of scattered light measurements. These ratios are sensitive to particle diameter but insensitive to absolute light measurements. A model, known in the art for its accuracy, is used to calculate scattered light of the particle. The model results are used to form the same ratios as a function of particle diameter and are then compared to the ratios from the measured data. Based on this comparison, the diameter of the spherical particle is determined.

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Charlotte, NC, United States of America

Craig A Scheer