Development of Automatic Detection Machine for Contaminants on Wafer and Crystal Originated Particles (COP) in Wafer with Nano-meter order

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In this study, an experiment and a theoretical analysis to detect the small particles adhering to a wafer and the crystal originated particles (COPs) existing in the wafer, whose diameters are approximately 0.1μm, are carried out successfully. The technology to separate COPs from detected particles is also carried outThe intensity distribution of light scattered by particles and COPs is calculated using the Maxwell equation under the assumption that they are illuminated by laser light. The finite difference time domain (FD-TD) method is used to solve the Maxwell equation. On the basis of the above mentioned results, it is theoretically verified that both particles and COPS larger than 0.1 μm in diameter are detected and recognized independentlyFor the experiment, both particles and COPs are detected when an Ar-ion laser is illuminated perpendicularly downward onto the wafer, and the obliquely scattered light is detected using a photomultiplier tube No.1. Only particles are detected when a YAG laser is illuminated obliquely with an incident angle of 77ー and the light scattered perpendicularly upward is detected using a photomultiplier tube No.2. On the basis of the two detected signals, the particles and COPs can be recognized independentlyThe experiment was conducted using two types of wafers. One is a wafer made by a Czochralski (CZ) method, which is known as a wafer with COPs, and the other is a wafer made by a floating zone (FZ) method, which is known as a non-COP wafer. COPs are detected on the CZ wafer but not on the FZ wafer. On the basis of this experimental result, it is experimentally verified that COPs can be detected.by this detection methodThe experimental results coincide with the theoretical results