Mechanism of uneven chemical etching of quartz insulating covering layer (SiO2) in the etching windows over outflow sites of magnetoresistive sensors in a plate with ICs chips (Integrated Circuits) was studied. A reason why a significant difference in the rate of SiO2 etching over the northern (N) and south (S) magnetic poles induced in the strip sensors during plasma deposition of magnetoresistive layer (iron-nickel alloy in the ratio of Fe − 18%, Ni − 82% in t a plasma spraying setup UPR-1 ) is analyzed. A mechanism of not full etching of SiO2 windows over the north pole of magnetoresistive sensor is revealed. It leads to through-etching of permalloy layer. The reason for this is significant contribution of interaction energy of the magnetic moment of the molecule etchant of hydrofluoric acid HF with scattering magnetic field of the magnetoresistive sensor. The resultant magnetochemical mechanism of interaction between HF and SiO2 leds to increased chemical interaction of F-HF in molecule over the southern pole of the sensor. This leads to etching of permalloy layer in the southern output areas of the sensors of all the chip plates.