Use of Darkfield Laser Technology in Monitoring Particles Generated by Process Tools in Cu Pillar Bumping & Wafer Edge Inspection

Abstract

In recent years, the semiconductor industry has witnessed an increasingly fast adoption rate of Cu pillar bumps for a variety of devices including memory, logic, processors, and FPGA. Cu pillar bumps provide several advantages over their counterparts, among which are tighter pitch, large number of I/Os as well as better heat dissipation. Due to the constant drive for miniaturization, the size and pitch of these bumps are getting smaller and smaller. As the sizes shrink, the need to minimize size and number of particles generated by the process tools increases. Unwanted particles generated by tools such as sputtering or etch can create killer defects driving down yields. The purpose of this paper is to examine how a darkfield laser technique can be used to monitor process tools for the amount of particles they generate. Determination of excessive particle density could trigger a chamber clean. After the chamber is cleaned, particle density needs to be re-characterized before releasing tool into production. Figure 1 shows the working principal of this sensor and figure two shows an example of maps generated by the inspection tool. Particle and haze data generated on a monitor wafer allows engineers to maintain process tools at optimal cleaning levels.