Horizontal scanning interferometric system for wafer bump inspection of semiconductor packaging process

Abstract

With strong needs of continued miniaturization and high density integration of semiconductor packages, the wafer level package technology leads the semiconductor package trend. For high reliability of the devices, wafer bumps and substrate bumps used for their connection junctions need to be in-line inspected in terms of top-height distribution, coplanarity, and volume uniformity. In this paper, a horizontal scanning interferometric system is proposed for bump shape inspection in three dimensions with large field of view and fast inspection speed based on optomechatronic system design concept. For wafer bumps made of solder and gold under transparent film layer, the specially-designed information extraction algorithms from multiple-peak interferogram acquired with variations of the horizontal position of the reference signal generator are suggested, which are composed of top surface profile and under-layer surface profile detection algorithms. A series of experiments is performed, and the effectiveness of the proposed inspection system is verified experimentally based on acquired test results in detail.