Plate wave oscillator systems in silicon for sensing in liquids

The design of silicon oscillator systems that can be used for sensing in liquids is presented. The basis of the design is a silicon-nitride plate wave device in combination with automatic-gain-controlled electronic amplifiers. The fabrication of very thin silicon-nitride membranes is technologically easier than the fabrication of very thin silicon membranes. Therefore, if the plate wave devices require a low plate velocity, the use of silicon-nitride membranes is preferred. An advantage of the low-pressure chemical vapor deposition process is the possibility of adding extra silicon, yielding low-stress membranes. The IDT/ZnO/aluminum/nitride layered structure allows the design of very thin plates with a high piezoelectric coupling constant, thus lowering the overall insertion loss of the device. Examples of applications of the system are given.<>