Patent ID: 6571628
Filing Date: 2003-06-03
Classification: B81B,G01P,Y10T

Abstract:
A process for manufacturing a Z-axis accelerometer, having a mobile part and an immobile part, comprising:providing a substrate having left and right areas; within the right area, forming a first right pedestal that extends upwards from a first upper surface; within the left area forming a first left trench that extends downwards from said first upper surface; coating with a first protective layer and then patterning the protective layer to define the mobile and immobile parts, said parts being connected by a spring structure intended to inhibit movement of the mobile part in a plane parallel to said upper surface; further patterning said first protective layer to define left and right comb structures, the left comb structure having at least one tooth located over the first left trench and connected to the mobile part, and at least one tooth located outside the first left trench and connected to the immobile part, the right comb structure having at least one tooth located over the first right pedestal and connected to the mobile part, and at least one tooth located outside the first right pedestal and connected to the immobile part; using the protective layer as a mask, etching the substrate, thereby forming: a second left trench within which lie the first left trench and at least two pedestals, one pedestal extending upwards from inside the first left trench and connected to the mobile part, and one pedestal extending upwards from outside the first left trench and connected to the immobile part, and a first right left trench within which lie the first right pedestal and at least two other pedestals, one of the other pedestals extending upwards from within the first right pedestal and connected to the mobile part, and one of the other pedestals extending upwards from outside the first right pedestal and connected to the immobile part; with the protective layer in place, selectively coating all vertical surfaces with a second protective layer; isotropically etching the substrate until the mobile part is released from direct contact with the substrate, remaining connected thereto only through said spring structure; and thereby transforming the left and right comb structures into left and right capacitors each having mobile and immobile plates, said mobile plates being limited by the springs to motion normal to the upper surface, whereby motion by both mobile plates, relative to the immobile plates, results in an increase in capacitance by one of the capacitors and a decrease in capacitance by the other capacitor.