High-accuracy inspection of defects and profile of wafers by phase measuring deflectometry

Abstract

The demands of the less-defective and high-flatness wafers are urgent in many wafer based technologies ranging from micro-electronics to the current photovoltaic industry. As the wafer becomes thinner and larger to cope with the advances in those industries, there is an increasing possibility of the emerging of crack and warp on the wafer surface. High-accuracy inspection of defects and profile are thus necessary to ensure the reliability of device. Phase measuring deflectometry(PMD) is a fast, cost-effective and high accuracy measurement technology which has been developed in recent years. As a slope measurement technology, PMD possesses a high sensitivity. Very small slope variation will lead to a large variation of the phase. PMD is very possible to have a good performance in the wafer inspection. In this paper, the requirements of the wafer inspection in the industries are discussed, and compatibility of PMD and those requirements is analyzed. In the experimental work, PMD gets the slope information of the wafer surface directly. The curvature or height information can be acquired simply by the derivation or integral of the slope. PMD is proved to make a superior result in high-precision defect detecting and shape measurement of wafer by the analysis of experiment results.

Wafer defect detection by a polarization-insensitive external differential interference contrast module

“…When imaging wafers, the phase distribution of an optical wave reflecting from the wafer indicates its surface topography. Irregularities in the wafer topography indicate defects in the wafer fabrication process [3,4,[9][10][11] and can damage the final semiconductor device. Without imaging phase variations, vital information about the wafer pattern is lost.…”