Forums
Bruker Media
Community Media
Bruker AFM Probes
SPM Digest
Application Notes
NanoTheater
Website
中文
Brochures & Datasheets
Publications
Probes Catalog
Events
Manuals & Documentation
Presentations
Guide to AFM Modes
News
Journal Club
Webinars & Video
Nanovations
Other
Hello,
I am trying to measure multiple locations across a line-space grating sample to basically get a height profile over a relatively large area. However, I am finding that if I measure a number of locations in a row and then return to a previously measured location I will get different height results.
Basically, an individual scan looks something like this (I am using depth analysis to get the average height of the features at each location):
I'll measure a spot on the sample every 10 microns or so in a row to build up a height profile. I expect the height profile to be something like this:
Below is an example of my actual results. Note that the data was taken in the order indicated, starting at the green dot and finishing at the red dot.
At first the results were more or less as expected, but then when I tried to go back and add more points to the "left side," the heights started to be less than expected. I next tried to repeat some previously measured locations to see what was going on and those measurements were also now lower and significantly different than initially measured. At the final location I measured several times and got similar results that were all different than the initial measurement.
It sort of seems like there is a drift in the data to lower heights, but I don't know why that would be the case.
A few questions:
1. What is the expected repeatability of these type of measurements? (i.e. is what I am trying to do reasonable)
2. Is there a way to improve my measurements to get more repeatable results?
Thanks for any help!
Some technical details:
I am using a DI3000 with TESPA tips in tapping mode.
Measurements are made by engaging, scanning, disengaging in a location, then telling the stage to move a specified number of microns and re-engaging, scanning, disengaging, and so on.
Data analysis: images are flattened, leveled as necessary and depth analyzed to get the height value for each location.
Thanks for your questions.
The image that you provided shows that you are having some tracking issues, noticeably in the left side of the pits, that may be contributing to the histogram data in Depth analysis being a bit choppy. Also, the Histogram Filter Cutoff is set to 0, so any noisy data in the histograms will affect the determination of the peak value.
Try setting your Historgram Filter Cutoff to 5nm, and see if you can clean up the tracking some by adjusting the scan rate, gains and setpoint.
Best,
Mark Hilton
Hi Mark,
Thanks a lot for your response. I've actually been having less trouble with this issue lately; however, I can't really explain why. For unknown reasons, it just stopped being as much of a problem.
Increasing the Histogram Filter Cutoff to >0 during depth analysis is a good recommendation--thanks.
I've consistently noticed that when I scan line/space gratings the left sides of the trenches are noisier. The tracking mostly looks good--at least to my novice eyes. Do you have experience in knowing that this "noise" is typical of a tracking error? I always adjust the amplitude setpoint to improve tracking, but I don't have much experience with changing the gains. Typically, the integral gain is set to 0.8 and the proportional to 1.6 (tapping mode). If you have any advice on how to go about optimizing the gains, I would appreciate it.
Thanks!