Instrument for measuring accelerations and process of making the same

A process for making an instrument for measuring accelerations having a reset element, a mechano-electric converter and three micromechanical sensors, each consisting of an inert mass and sensitive to a motion in one direction to define multiple directions of sensitivity, integrated in a crystal surface layer, wherein the multiple directions of sensitivity of the sensors point in different directions and do not lie in one plane, comprising the process steps of:

• precipitating a semiconducting epitaxy layer having impurities of one kind onto a silicon wafer doped with impurities of a second kind to form a pn-transition,
• precipitating a passivation layer of silicon nitride on the silicon wafer,
• integrating piezo-resistances on a side of the wafer,
• photolithographic structuring on the front and rear sides of the wafer,
• etching the passivation layer,
• metallizing said front side of said wafer,
• Anisotropic electro-chemical etching of said rear side of said wafer in a KOH-H.sub.2 O etching solution, with the etching process stopping automatically at the pn-transition,
• passivating said rear side of said wafer,
• removing said metallizing layer from said front side,
• anisotropic etching said epitaxy layer on said front side of said wafer, and
• removing said passivation layer on said rear side.