260 of about 700 u00e5 of low temperature silicon oxide is deposited on the top side of the wafer followed by about 1100 u00e5 of low stress silicon nitride 262 which are deposited on both sides of the wafer followed by 1 micron of low temperature silicon oxide 264 also deposited on both sides of the wafer the sandwich structure is designed so that it is possible to preserve a thin layer of silicon oxide on top of the cantilever for protection the oxide nitride oxide sandwich structure on the top side of the wafer is patterned and etched using standard photolithography and etching steps to produce a contact hole 270 as shown in fig1 referring to fig1 another photoresist layer is applied and developed on the top side of the wafer with a protective photoresist applied on the bottom side of the wafer followed by a long oxide etch and then a nitride etch to remove the top oxide layer 264 and the underlying nitride layer 262 in region 272 after removing all photoresist a protective photoresist is applied to the top side of the wafer followed by oxide and nitride etches of the oxide and nitride layers 264 and 262 on the bottom side of the wafer a cross section of the wafer at this point is shown in fig1 referring to fig1 a metal layer 266 is sputtered onto the wafer and.