Particle detection method including comparison between sequentia

Details Particle detection method including comparison between sequentia Particle detection method including comparison between sequentia

1987-08-07

1988-08-23

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

356431, G01N 2100

Patent

active

047663243

ABSTRACT:
A particle detection method for matching particles detected in two scans of a surface taken at different times in which particles having a light scattering intensity above a collection threshold are first detected and the measured position and scattering intensity therefor stored in a computer memory. Corresponding first and second measured positions from the respective first and second scans are determined by forming a triangle from selected first detected particles and finding those second detected particles which form a variant triangle with matching perimeter and area. From these matching first and second particles a transformation is found for mapping first measured positions to corresponding second positions and vice versa. Areas around corresponding positions of particles having a scattering intensity above a display threshold are examined for matching particles. If not found, the area is reexamined at a reduced threshold. Matching particles are considered to be the same, while unmatched particles are considered to be either added or removed. The method provides an accurate count of particles for process contamination analysis.

REFERENCES:
patent: 4378159 (1983-03-01), Galbraith
patent: 4541011 (1985-09-01), Mayer et al.
patent: 4681442 (1987-07-01), Wagner
Tullis, Barclay J., "A Method of Measuring and Specifying Particle Contamination by Process Equipment", Microcontamination, Nov. 1985-Jan., 1986, three parts.
Gise, Peter, "Applications of Laser Scanning for Wafer and Photoplate Inspection" Microcontamination, Oct./Nov., 1983, pp. 41-44 and 62.
Gise, Peter, "Principles of Laser Scanning for Defect and Contamination Detection in Microfabrication," Solid State Technology, Nov., 1983, pp. 163-165.

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