by induced charge 22 z is a distance from a surface of the semiconductor wafer d is a thickness of the semiconductor wafer and d is a diameter of the semiconductor wafer electric potential caused by accumulated charge 12 may be calculated according to equation 2 below wherein a is the electric potential caused by accumulated charge u03c3 is a surface charge density and u03b5 is a permittivity constant thus induced charge 22 results in a reduction in the total potential above the semiconductor wafer 10 of approximately an order of magnitude the total potential v total above the semiconductor wafer 10 may be calculated according to equation 3 below any other similar approach to calculate the total potential above the wafer analytical or numerical with generalization of the accumulated charge profile is also implied in this invention without any loss of generality back coat 20 should preferably be as thin as possible without adversely affecting its ability to develop induced charge 22 the thickness of back coat 20 will therefore vary depending on the conductive material s included in back coat 20 as well as the method s or technique s by which back coat 20 is applied typical thicknesses of back coat 20 may range from between about a few e g three nanometers and about a few e g three microns one skilled in the art will recognize however that this range is merely illustrative of thicknesses typical of some embodiments of the invention and is not meant to be limiting of the scope of the invention a back coat 20 of any conductive material of any thickness that is capable of developing induced charge 22 is within the scope of the invention fig5 and.