AFM – Megasonics
I got some wafers from Chris last week(?) that had undergone different Megasonics cleaning treatments by the manufacturer. We’re trying to figure out if these treatments are actually cleaning the wafers. I’ve been having trouble getting the AFM to stay in the “right” mode for imaging with these wafers. However, I have gotten some images. Keep in mind that these are attractive (not repulsive) mode images. All are the ZSensor channel (a more accurate representation of height) and the wafers are from the center of the batch.
1 run Megasonics, 150W; 5x5um scan
Not much on the surface.
1run Megasonics 225W, 5x5um scan
Some large features (~50 nm) and relatively lots of smaller dots (<10nm?).
1run Megasonics 225W, 10x10um scan; different day
Here, there are lots of large features (~50-300nm), but also notice the streaks in the image, which indicate that the phase was jumping around.
I’m not sure if these are helpful, but this gives everyone an idea of what out of the box wafers probably look like. I’m trying to get these AFM issues worked out this week so I can be more confident of the images.
This data does not really makes sense based on the process conditions. It’s not reasonable that the 150W treatment would have almost no particles, while a wafer cleaned at 225W would be covered with junk. There must be particulate hidden in the 150W image. I’m also a little suspicious of the particles in last image, since they all have the same shape. Something must be stuck to the tip.
That said, we really need to figure this stuff out soon, so please let me know how I can help. Right now we have a number of samples that need to be scanned so we can make production decisions. We also cannot do much more characterization of the new sputter system, without getting some AFM data. We have a preliminary oxide process on the new tool that looks great with ellipsometry, however, if we go with it and find out later that it’s a rough mess, we will have wasted considerable effort. We are making some preliminary test samples with this oxide now, but are flying blind…