Permanent direct wafer bonding has been an enabling technology for many years, especially in the areas of engineered substrates such as SOI, and in various MEMS or backside illuminated CMOS image sensors (BSI) process flows. With the emergence of new and more challenging bonding requirements and materials, precision and surface condition becomes more critical. One key requirement for a void free and reliable bond is a particle free surface. Residual particulate remaining in the bonding interface can lead to post-bond voids, bond defects and loss of yield. The optimal post cleaning condition is zero particles, and in fact, one of the basic requirements of pre-bond cleaning methods is to be particle neutral, leaving no additional particles after the cleaning process. Historically the critical particle sizes were in the 1um range, but due to continuous feature size reduction, this critical size is today in the area of 90 nm with a strong pressure to reduce below 20 nm. In prior work (reference 1) we have demonstrated a particle neutral cleaning process on 200 mm wafers in a laboratory environment. The cleaning method and MegPie® megasonic apparatus used in prior work is comparable to that used in the current experiments. In the prior experiments, the wafers were intentionally contaminated with large numbers of silicon nitride particles so that particle removal efficiency could be measured and compared to industry standards. In this current work we have moved from laboratory generated artificial contamination to real word production conditions, including the unknown type and quantity of particulate that would be typical to incoming pre bond substrates. The results demonstrate the suitability and repeatability of this non contact cleaning method in real world production consitions. The cleaning tests were performed on an EVG Gemini®FB fully automated fusion bonding system using for cleaning a large area megasonic transducer MegPie® Particle measurement was performed using the KLA-Tencor SP1 Particle Counter and post bond performance was performed using the SAM450 from PVA Tepla Analytical Systems. Reference 1. F. Fournel, L. Bally, D. Dussault, and V. Dragoi, Innovative megasonic cleaning technology evaluated through direct wafer bonding. (ECS 2010)