Micromechanical Silicon Microbalance

摘要

A micromachined capacitive silicon microbalance has been designed and fabricated. It is intended for weighing masses of the order of 1 g with a resolution and accuracy of about 1 ug. The device consists of a micromachined SOI (silicon-on-insulator) chip which is anodically bonded to a glass plate. The capacitance is formed between two electrodes. The flexible electrode is the SOI layer. The other electrode is metal layer on the glass. The glass electrode is divided into three sections. The sections are used for detecting the tilting of the top electrode due to eccentric loading. The measuring circuit implements electrostatic force feedback which keeps the top electrode at a constant horizontal position irrespective of the mass of the load. First test measurements have demonstrated that an accuracy of about 2 to 3 μg at 1 g can be reached.