I once crashed the scanning tip of a scanning electron microscope into the sample when my attention wandered for a few seconds while I was adjusting the focus. The lab techs had made it very, very clear to me beforehand that I was never to let the tip and sample get less than a few centimeters (I forget the exact value, but it was specified) apart, because the scanning tip was very expensive and fragile. My moment of inattention ended up costing the lab $10,000, and me any possible friendships with the lab staff.
One lesson is, “Be careful!” but that is tough to actually put into practice. It’s precisely when you’re not being careful that you need the advice the most. A more actionable piece of advice might be, “Regard scanning and thinking as two separate tasks. Plan out where you’re going to scan, then stop thinking. Then scan. Then think again. Do not think and scan at the same time.”
The ‘scanning tip’ of an SEM? Do you mean the pole piece? It’s not at all a ‘scanning tip’ in the same sense as an AFM or STM. Like, there’s no reason for an SEM to get closer than a few millimeters from the sample.
A crash like that could only happen if you’re moving the stage… were you trying to focus by moving the piece around instead of adjusting the electron optics?
I guess every SEM I’ve used has had very specific, easy-to-follow instructions on how to avoid crashing.
Yes, my mistake, it was indeed the pole piece. Not something that’s supposed to be in close proximity like with an AFM. If I had broken an AFM tip it would’ve been less of a problem, because those are expected to wear out every so often.
It was a few years ago, but I remember that we were doing e-beam lithography, and that did make it necessary to move the stage around. I think the idea was that our circuit was pre-drawn using software, after which we could just put the diagram into the SEM computer and it would scan around and draw the pattern we wanted. But in order to set this up, it was necessary to precisely locate the initial position of the stage in (x, y, z) so that our pattern would be drawn at the correct location on the silicon. And this meant we had to actually move the stage around, instead of just using the optics to focus on different parts. And due to things like differences in the wafer housing thickness, and other users who had moved the stage, that included moving it up and down.
ETA: All this was done before turning on the electron beam itself, since that would’ve started burning up the resist. The initial setup was done using a low-power optical microscope inside the SEM.
The best technique I use for “being careful” is to imagine the ways something could go wrong (e.g., my fingers slip and I drop something, I trip on my feet/cord/stairs, I get distracted for second, etc.). By imagining the specific ways something can go wrong, I feel much less likely to make a mistake.
In the HUGR, I’ve included the advice “learn the sad stories of your lab as soon as possible”—the most painful mistakes others, past and present, have made in the course of action. Helpful as a specific “ways things can go wrong” list.
I once crashed the scanning tip of a scanning electron microscope into the sample when my attention wandered for a few seconds while I was adjusting the focus. The lab techs had made it very, very clear to me beforehand that I was never to let the tip and sample get less than a few centimeters (I forget the exact value, but it was specified) apart, because the scanning tip was very expensive and fragile. My moment of inattention ended up costing the lab $10,000, and me any possible friendships with the lab staff.
One lesson is, “Be careful!” but that is tough to actually put into practice. It’s precisely when you’re not being careful that you need the advice the most. A more actionable piece of advice might be, “Regard scanning and thinking as two separate tasks. Plan out where you’re going to scan, then stop thinking. Then scan. Then think again. Do not think and scan at the same time.”
The ‘scanning tip’ of an SEM? Do you mean the pole piece? It’s not at all a ‘scanning tip’ in the same sense as an AFM or STM. Like, there’s no reason for an SEM to get closer than a few millimeters from the sample.
A crash like that could only happen if you’re moving the stage… were you trying to focus by moving the piece around instead of adjusting the electron optics?
I guess every SEM I’ve used has had very specific, easy-to-follow instructions on how to avoid crashing.
Yes, my mistake, it was indeed the pole piece. Not something that’s supposed to be in close proximity like with an AFM. If I had broken an AFM tip it would’ve been less of a problem, because those are expected to wear out every so often.
It was a few years ago, but I remember that we were doing e-beam lithography, and that did make it necessary to move the stage around. I think the idea was that our circuit was pre-drawn using software, after which we could just put the diagram into the SEM computer and it would scan around and draw the pattern we wanted. But in order to set this up, it was necessary to precisely locate the initial position of the stage in (x, y, z) so that our pattern would be drawn at the correct location on the silicon. And this meant we had to actually move the stage around, instead of just using the optics to focus on different parts. And due to things like differences in the wafer housing thickness, and other users who had moved the stage, that included moving it up and down.
ETA: All this was done before turning on the electron beam itself, since that would’ve started burning up the resist. The initial setup was done using a low-power optical microscope inside the SEM.
Upvoted especially for noticing that “Be careful!” is unhelpfully vague, and bothering to think of a usably specific piece of advice.
The best technique I use for “being careful” is to imagine the ways something could go wrong (e.g., my fingers slip and I drop something, I trip on my feet/cord/stairs, I get distracted for second, etc.). By imagining the specific ways something can go wrong, I feel much less likely to make a mistake.
In the HUGR, I’ve included the advice “learn the sad stories of your lab as soon as possible”—the most painful mistakes others, past and present, have made in the course of action. Helpful as a specific “ways things can go wrong” list.