The processing of Silicon wafers to produce XMR (AMR / GMR / TMR) sensors involves a good deal of chemistry and physics. In order to alter the surface conditions and properties, it is necessary to use both inert and toxic chemicals, specific and unusual conditions, and to manipulate those conditions with both plasma-state elements and with RF (Radio Frequency) energies. Starting with thin, round wafers of silicon crystal, in diameters of 150, 200 mm, the processes described here build up a succession of layers of materials and geometries to produce thousands of electronic devices at tiny sizes, which together function as sensors. The devices which now occupy the surface of a one-inch square IC would have occupied the better part of a medium-sized room 20 years ago, when all these devices (transistors, resistors, capacitors, and so on) were only available as discreet units.
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