Following is what the chip looks like when the cleaning goes well.
This beast is 0.40 mm x 0.45 mm in size. It is from one of the labels sold on eBay at Alien 9662 3''x1'' UHF 6C 915Mhz RFID Wet Inlay Tag Label. That said, the labels that I received look slightly different, for example the "AZ-9662" is missing, and I cannot match the chip features with any diagrams I can find in Alien datasheets. There is some identifier included in the chip design, looks like "HSL3S120SVB1", but I cannot find that by searching. So I dunno -- I suspect the label is just a work-alike, but maybe it really is by Alien.
This chip has none of the deep 3D structures that I found on RFID chips that I looked at earlier, for example HERE, photo panels 4 and 5.
So for visual interest, I played around with the lighting so as to create some of the interesting diffraction colors.
Colors like are shown above only appear when the chip is illuminated with fairly hard illumination and is tipped slightly so that direct reflections can enter the objective.. (Note that the bright "gold" areas in the pretty-colors rendition appear as pure black in the other image, because they're basically just mirrors.) The colors are also best when the 20X NA 0.42 objective is stopped down a bit. The combination of hard lighting and narrow aperture makes nice colors, but it wreaks havoc with imaging the actual structure of the chips. Following is the same section of chip, seen on the left in its pretty-colors rendering and on the right in its boring but accurate setup using highly diffused illumination and face-on perpendicular to the objective.
I really need to emphasize that most of the fine "details" seen in the pretty-colors version are actually stacking artifacts that are caused by apparent subject movement, due to utilized-aperture effects caused by the off-axis direct reflections. Following is an animation showing 6 consecutive images with a focus step of 1.0 micron.
Finally, here is the setup for shooting the pretty-colors version, together with one source frame from the stack. I suggest not trying to make sense of the dark parts, because the shadow cast by the objective and the dark left side of the frame have no direct relationship to each other. What's happening is that the entire field seen by the objective is illuminated, but the direct reflections are entering only one side of the objective where they become especially vulnerable to vignetting from the adjustable aperture positioned above the objective. The dark left side of the frame is an off-center vignette caused by interaction between the on-center added aperture and the very oblique light that was able to enter the objective.
All shot with Mitutoyo 20X NA 0.42 on Raynox DCR-150, using Canon R7 camera. Regular illumination is with 3 flashes diffused through the coating of an LED tube that fits a fluorescent fixture. All are focus-stacked at 1.0 micron. Stereo pair at +-4 degrees (8 degrees total separation). Decapsulation by heat treatment, 10 minutes on a red-hot electric coil, sandwiched between two stainless steel washers. Final cleaning by ultrasound in water with a bit of detergent, before mounting on glass slide using diluted Elmer's Clear washable PVA glue. I'm pretty sure that the fragmented chip is the only one that I tried to clean first by chemical means, an overnight soak in "Goof Off Pro Strength" adhesive remover. That strongly discolored the solution, but did not free the chip. I moved on to using heat, adding two more chips that had not gone through the Goof Off, and treating the set for only 7 minutes. That produced two chips with some black stuff still on them, and the one chip that was clean but fragmented. I cannot be sure what happened, but the coincidence makes me suspicious.
--Rik
