Mechanical grinding is a default technique for sample preparation in electron microscopy. Using this method is used to thin samples down to approx 100 µm.
Since I am building a new condenser aperture holder for our Tecnai F30 microscope and have run out of space for platines, twin aperture and bonding wires I decided to test whether Si3N4 membranes can sustain this mechanical stresses, because the Si wafers carrying these membranes are typically 400 µm thick.
Today in the lab I thinned down a part of a Si wafer carrying a Si3N4 membrane to approx. 180 µm. And the membrane stayed intact during the whole action.
The next image shows the bottom of the Si wafer after grinding.
The next image shows the gold covered top of the Si wafer with the membrane and the aperture holes in it.