BRYAN SCHACKMUTH, Product Line Manager at Nordson Test & Inspection.
In today’s semiconductor manufacturing industry – in particular the inspection process – there are clear and common productivity and quality control pre-requisites that rank high among the needs of manufacturers. If you’re one such company operating in the semiconductor production ecosystem, then it’s likely that your needs for inspection and testing will mirror those of others in the same industry. Higher throughput, greater accuracy in defect detection, higher resolution, smaller machine footprint and continuous uptime are all desired.
For wafer inspection specifically, among the different technologies that exist – including X-ray (FIGURE 1), infrared, optical (FIGURE 2) and acoustic (FIGURE 3), – not all are created equally, and some have better attributes than others depending on the application. When it comes to X-ray based solutions, thanks to its smaller resolution (typically one micron or less), X-ray is better suited to sampling. Infrared options that use an IR detector have their own drawbacks and struggle to operate in scenarios involving highly doped wafers, while optical solutions inspect the wafer surface, and cannot see inside.
For acoustic inspection, at least with traditional scanning methods, there’s an issue with the use of water. Since the sample is submerged in a tank or bath when the transducer scans it, any crack or other defect in the surface could lead to water entering the sample. This process also necessitates a constant changing and filtering of the water to ensure high purity and safeguard against the unwanted introduction of particles, as well as a drying time upon the wafer’s removal from the water. Additionally, in instances where two wafers have been bonded together but have failed to properly anneal prior to scanning, separation will often occur, demonstrating another limitation of the traditional method. All of that adds to a long and laborious process for manufacturers to endure. However, our new, innovative SpinSAM™ Acoustic system uses waterfall technology (FIGURE 4) that limits the exposure to water versus some competitors that are using water bath or immersion scanning. Nordson offers waterfall on all Acoustic systems, as an option on the lab systems, and standard on production systems.
