Hermes Microvision Inc.

Chang-Chun Yeh

Jack Jau

Zhong-wei Chen

Yan Zhao

A structure, for defect inspection, is provided, which includes a scanning pad scanned by an electron beam inspection tool and a test key. The structure can be located in the scribe line. A virtual grounding pad is further provided if the test key is located in the dummy pattern regions.

Test device for defect inspection

A method for in-line monitoring of via/contact etching process based on a test structure is described. The test structure is comprised of via/contact holes of different sizes and densities in a layout such that, for a certain process, the microloading or RIE lag induced non-uniform etch rate produce under-etch in some regions and over-etch in others. A scanning electron microscope is used to distinguish these etching differences in voltage contrast images. Image processing and simple calibration convert these voltage contrast images into a 'fingerprint' image characterizing the etching process in terms of thickness over-etched or under-etched. Tolerance of shifting or deformation of this image can be set for validating the process uniformity. This image can also be used as a measure to monitor long-term process parameter shifting, as well as wafer-to-wafer or lot-to-lot variations. Advanced process control (APC) can be performed in-line with the guidance of this image so that potential electrical defects are avoided and process yield ramp accelerated.

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Miaoli, Taiwan

Chang-Chun Yeh