Hi
If we have a wafer that is already patterned, we need to localize the fiducials on on it at first. Their positions, as reported in interferometer increments, will define an arbitrary-unit scale across the wafer that depends on wavelength. In that case, not knowing lambda is not a problem as long as it remains the same during stepping that wafer. For a new wafer, I would recommend to expose and etch a "zero-layer" on it (like in HKUST) with a conventional mask and contact alignment.
Regards,
Ferenc
On 1/25/22 23:07, David Lanzendörfer wrote:
Hi Ferenc Awesome! I'm looking forward to hearing your results! I wonder how we can get a somewhat reproducible result and how we can calibrate the distance measuring setup... Any idea?
Cheers -lev
On Tuesday, January 25, 2022 10:05:33 PM WET Ferenc Éger wrote:
Hello List,
I just found a laser diode with a built-in photodetector in my home. I will play with it and report in the upcoming days. Since these are used in optical drives, they are supposed to be atom-cheap. What is evident right now is that the diode's temperature has to be controlled to keep the wavelength constant.
Regards,
Ferenc
On 1/25/22 21:42, Jacob Lifshay wrote:
On Tue, Jan 25, 2022, 12:05 David Lanzendörfer
leviathan@libresilicon.com wrote: Hi Ferenc Good point with the precision issue...
Do you know of any good off-the-shelf laser distance measuring sensor which has a sufficient resolution for determining the exact distance (with an acceptable tolerance), so that we can do the fine adjustment?it isn't off-the-shelf but you could likely easily build one based off of laser-diode self-mixing: https://youtu.be/MUdro-6u2Zg
Jacob
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