CMOS sensor array with cell-level analog-to-digital conversion for local probe date storage

A scalable CMOS sensing architecture for highly parallel readback of signals from large two-dimensional local probe arrays for AFM(atomic force microscope)-based data storage is presented. The main challenge to the detection scheme comes from the fact that information signals are superimposed on carrier signals that are more than three orders of magnitude higher. In addition, local memories are needed because of carrier variations, and parallel operation requires local data conversion. Therefore, analog-to-digital conversion of the probe signals is performed locally in a two-dimensional scheme fitting the probe array. A scalable prototype array fabricated in a 0.35 µm CMOS technology demonstrates the required functionality and performance for future large arrays of 32 × 32 or more AFM cantilevers.