Multi-beam Inspection (MBI) Development Progress and Applications

In order to successfully develop and manufacture semiconductor chips, in-line inspection is extremely important. Optical and e-beam inspection are the two major defect inspection approaches used for semiconductor manufacturing. As critical dimensions continue to shrink with each new technology, killer defects are becoming smaller and smaller, reducing the effectiveness of optical inspection, which is resolution limited. A growing number of defect types are just not detectable with optical inspection. A partial solution is to adjust inspection parameters to run "hot", but then the few defects of interest that are captured are buried in large numbers of nuisance defects. E-beam inspection (EBI), in addition to it's unique role of detecting buried defects using voltage contrast (VC), is able to detect these smaller defects, but suffers from throughput constraints. This is because of EBI's substantially smaller pixel size, which takes much longer to tile across the wafer surface, and a lower sampling frequency, because electrons aren't as prevalent as photons. In R&D, this is not as much of a limitation, with EBI commonly deployed as a metric for many physical defects beyond optical inspection resolution as well as lithography related use cases such as process window qualification (PWQ) and EUV print check. However, EBI's adoption during yield ramp and high volume manufacturing (HVM) is limited by these throughput constraints. To address this issue, HMI is developing multi-beam inspection (MBI) systems [1,2]. This latest paper covers three new topics. First, new milestones were achieved in the last year, including simultaneous operation of all beams and defect detection while in this mode, will be reviewed. Second, the importance of minimizing cross-talk between beamlets for MBI and the cross-talk performance of our latest tool is discussed. Finally, simulations of the anticipated throughput gains achievable for a range of physical and voltage contrast inspections for the current system are presented. These throughput gains vary widely and are useful in prioritizing certain inspections over others for practical use, as well as understanding the limiting factors for laggard inspections. Potentially some of these factors can be alleviated. Going forward, the plan is to continue to aggressively increase the number of beamlets while simultaneously further improving the resolution. Overall the HMI MBI program is on track with tool shipments to select customers in the very near future.