Setup Surface Cleaning process
After understanding the surface contaminant and detergent selection, now is the time for us to set up a wet surface cleaning process. CMP process for wafer and hard disc substrate is one of the highly demanding processes and the subsequence surface cleaning process does play an important role in overall yield. The wet surface cleaning process is critical as it requires removing the contaminant leftover on the surface. The contaminant may come from the polishing sludge, CMP slurry and environment.
Many details need to be given in order to identify the contaminant source before establishing a reliable surface cleaning process. In most cases, the wet cleaning process is preferred. There are several areas cleaning field engineer should consider.
Detergent use in the wet surface cleaning process
Surface cleaning detergent selection is very important at this stage. Not all surface cleaning detergent performs the same for the wet surface cleaning process. After identifying the surface cleaning detergent, the cleaning field engineer should carry out series of experiments to evaluate the process window and identify the optimised concentration.
PVA sponge roller use for the wet cleaning process
In most case, scrubbing is one of the effecting actions for wet surface cleaning.
And PVA sponge roller is the material commonly used in the wet surface cleaning process. The PVA sponge roller is soft in nature which not causing scratches on the substrate surface and the porous structure also becomes the waterway for detergent flow on the substrate surface.
PVA sponge roller sound simplicity at first glance, however throughout our involvement in the cleaning process, DST is able to supply various design of PVA sponge roller for the dedicate wet surface cleaning process. We could design the different surface structure such as nodular and spline roller, on the other hand, DST also design difference pore size for the dedicate contaminant.
Scrubbing time for the wet surface cleaning process
Longer the scrubbing time, the better the result. This sentence is true to a certain extend. The cleaning field engineer should examine the scrubbing time to allow sufficient time for removing the contaminant from the cleaning of the substrate. In a practical case, a cleaning field engineer could perform several tests of different scrubbing time to find the optimum case.
Re-visit Surface Cleaning Process
A cleaning field engineer is required to re-visit the cleaning process for continual improvement. The surface cleaning monitoring system comes into roles at this moment. Field cleaning engineer should evaluate the monitoring data and identify the common phenomenon or pattern in order to identify the source of the contaminant.
A cleaning field engineer should also audit the wet surface cleaning process with razor-sharp eagle eyes. A minor change of process setup should identify for improvement.
DST Technology is having more than 10 years of experience in the wet surface cleaning process which we are confident to bring benefit to customer and the industry. Feel free to contact DST for further discussion.