The Strain Gauges on the SOI Structures

In this work the parameters of the strain gauges made on the “silicon on insulator” structures are investigated. Industrial silicon-on-sapphire structures and the Si/CaF2/Si (100) structures, obtained by molecular beam epitaxy, as a substrate were used. The piezoresistors were created by the ion implantation of the boron ions with the equal process conditions: volume concentration, accelerating voltage, topological layout and geometric dimensions. The rapid thermal annealing were used to eliminate radiation defects and to activate impurity atoms in the epitaxial silicon layer of both structures. It was found that resistance stabilization of the epitaxial silicon layer in the Si/CaF2/Si structures took significantly less time than in the silicon-on-sapphire structures, which indicates a higher structural perfection of the epitaxial silicon layers on the CaF
2
/ Si substrate. The piezoresistors formed on the Si/CaF
2
/Si structures had the same sensitivity as the piezoresistors based on the silicon-on-sapphire structures. The experimental dependences of the resistance on the applied load are linear and in a quality manner coincide with the calculated dependences. With the same parameters of the piezoresistors, quality of Si layers on the CaF
2
/Si substrate is higher, and their cost is significantly lower than the silicon-on-sapphire structures. It is important to note that, despite the lower sensitivity compared to the piezoresistors based on the monolithic silicon, the piezoresistors based on the SOI structures have a higher working temperature and radiation resistance.