An upward facing probing mechanism using mercury probe contacts for accurate automatic multi-site measurements of a semiconductor wafer, especially of ultra-shallow ion implanted layers on a semiconductor wafer held top surface facing downward. A fixed force is applied to the wafer regardless of the thickness of the wafer through the of use of a regulated pressure piston. Incorporated are a plurality of spring-loaded rod assemblies to support the floating probe head to position the probe head face into full contact with the wafer surface accurately placing all mercury contacts on the surface of the wafer regardless of the inclination of the wafer as a result of the even support of the probe head by the spring-loaded rod assemblies. Included is a mechanism to refresh the mercury contacts for each probing with full containment and recovery of the mercury used in each probing.