5 was 200 angstroms thick the layer in example 6 was 50 angstroms thick gold was then sputtered at 50 w forward power to produce a layer 1000 angstroms thick chromium serves as an adhesion layer for the gold the combined chromium gold thickness of the wafers used in example 6 was measured to be 1052 angstroms on a dektak ii surface profile measuring device at this point the chromium gold was in direct contact with the sio 2 substrate only in the areas that were to form the microelectrodes leads and contact pads and on photoresist in all other areas the chromium gold on photoresist was removed by a lift off procedure the metallized wafers were immersed in warm acetone in which soft baked positive photoresist is soluble for 75 minutes for the wafers used in examples 1 to 5 and 5 minutes for the wafers used in example 6 the wafers used in examples 1 to 5 were briefly sonicated in acetone to remove the metal between microelectrodes dried and then cleaned of residual photoresist in a planar oxygen plasma etching chamber at 200 w forward power in 50 mtorr oxygen for 60 sec the wafers used in example 6 was blasted with acetone from a paasche air brush with n 2 at 70 psi sonicated for 30 minutes in acetone then rinsed with acetone and methanol before drying the wafers were then cleaned in a mixture of hot aqueous 6 by volume h 2 o 2 14 by volume aqueous nh 3 rinsed in deionized water greater than 14 megaohm cm and spun dry the wafers were then baked at 180 u00b0.