AFM retry
I posted some pictures yesterday from AFM last week. I got back onto the AFM today and re-scanned the megasonics cleaned virginia semiconductor wafers. For each image, the top and bottom panels are the height and ZSensor scans, respectively. All scans are 10um x 10um. I did a linear analysis of the ZSensor data for height data (the red graphs).
225W, 1 run Megasonics
150W, 1 run Megasonics
150W, 2 runs Megasonics
From the height scans, the particles look like they’re about 5-10nm in height and ~100nm in the x-y scale. It looks like 225W Megasonics clean might have removed more stuff than 150W (single AND double runs).
As before, I was still having trouble keeping the AFM in repulsive mode. However, the tracking (scan-rescan) was really good for these images, and I was using a different cantilever (higher k).
According to the aspect ratio these particles are disks. I doubt it.
Great!! This is something that I can send to the manufacturer. Do you have a wafer from Dave that was not sent to Virginia? It would be nice to confirm that they did not make the situation worse.
The lateral size of these particles is exaggerated because the tip must be very dull, or may have picked up something. Maybe you could try a new tip and perhaps zoom in on the particles to see if they look smaller? Realistically, these are probably spherical (or sphere-like). That would give them a lateral size of 5nm, which is below the x-y resolution of the tool. I trust the x-y data to provide density and the z height for size. This would not identify particle clusters, but that’s OK for this data.
We have another set of wafers from SQI that would be great to get a look at. We bought thick (400 micron) and thin (200 micron) wafers and would like to compare to Virginia Semi. Hopefully SQI does not have this particle issue. Dave or I will track down these wafers today, so you have them. Thanks!!
Agreed. I was surprised when I did the height analysis to see that these rather large particles in x-y were actually quite small in z. I think the tip was dull – those tails in image 150W 2 runs might be indicative of that. Plus, I was hitting the surface really hard to try to stay in repulsive mode, so I think that dulled the tip quickly. However, I don’t think the xy measurement should be stretched out THAT much. I’ll redo today – I do have a wafer from Dave to do, as well.