Number Determination of Successfully Packaged Dies Per Wafer Based on Machine Vision

Packaging the integrated circuit (IC) chip is a necessary step in the manufacturing process of IC products. In general, wafers with the same size and process should have a fixed number of packaged dies. However, many factors decrease the number of the actually packaged dies, such as die scratching, die contamination, and die breakage, which are not considered in the existing die-counting methods. Here we propose a robust method that can automatically determine the number of actual packaged dies by using machine vision techniques. During the inspection, the image is taken from the top of the wafer, in which most dies have been removed and packaged. There are five steps in the proposed method: wafer region detection, wafer position calibration, dies region detection, detection of die sawing lines, and die number counting. The abnormal cases of fractional dies in the wafer boundary and dropped dies during the packaging are considered in the proposed method as well. The experimental results show that the precision and recall rates reach 99.83% and 99.84%, respectively, when determining the numbers of actual packaged dies in the 41 test cases.