Design and characterization of an image acquisition system and its optomechanical module for chip defects inspection on chip sorters

Abstract

Chip sorter is one of packaging facilities in chip manufactory. Defects will occur for a few of chips during manufacturing processes. If the size of chip defects is larger than a criterion of impacting chip quality, these flawed chips have to be detected and removed. Defects inspection system is usually developed with frame CCD imagers. There're some drawbacks for this system, such as mechanism of pause type for image acquisition, complicated acquisition control, easy damage for moving components, etc. And acquired images per chip have to be processed in radiometry and geometry and then pieced together before inspection. These processes impact the accuracy and efficiency of defects inspection. So approaches of image acquisition system and its opto-mechanical module will be critical for inspection system. In this article, design and characterization of a new image acquisition system and its opto-mechanical module are presented. Defects with size of greater than 15μm have to be inspected. Inspection performance shall be greater than 0.6 m/sec. Thus image acquisition system shall have the characteristics of having (1) the resolution of 5μm and 10μm for optical lens and linear CCD imager respectively; (2) the lens magnification of 2; (3) the line rate of greater than 120 kHz for imager output. The design of structure and outlines for new system and module are also described in this work. Proposed system has advantages of such as transporting chips in constant speed to acquire images, using one image only per chip for inspection, no image-mosaic process, simplifying the control of image acquisition. And the inspection efficiency and accuracy will be substantially improved.