Micromechanical sensor fabrication process

摘要

A method for producing micromechanical sensors for the AFM/STM/MFM profilometry is described in which a multiple step mask of cantilever beam and tip is transferred step by step into the wafer substrate by reactive ion etching. A particular highly anisotropic etching step is used for etching and shaping of the tip. This process step uses an Ar/C12 ambient at a pressure of about 100 6bar and a self bias voltage of about 300 V DC. The ratio of pressure to self bias voltage determines the concave shape of the tip side-walls. This etching step is followed by a thermal oxidation step. The oxidation is carried out for a time until the oxidation fronts at the thinnest point of the tip shaft touch each other. A stripping process with buffered hydrofluoric acid gently removes the thermally grown oxide. The oxidation process allows-via oxidation time-a modification of tip height and angle in an extremely controllable manner. To prevent sticking of the tip to the structure to be profiled the ratio of tip diameter to tip height should be about 1:10. Should this ratio be exceeded the tip has to be arranged on a pedestal. The structure, comprising a cantilever beam and a tip on pedestal, can be produced with the same but slightly modified process of the invention.