Piezoresistive Silicon Diaphragm Doping and Strain Gauge Adhesion Defect Modes
Optimal piezoresistive stability requires heavy surface boron doping above 2e19 cm-3 combined with plasma-activated silane coupling to prevent delamination.
Microvoid Coalescence
Fracture Evolution
A materials failure mechanism drives the growth and linking of microscopic cavities within a metal layer under tensile stress to produce ductile fracture. During microvoid coalescence, small voids that nucleate around secondary phase particles or grain boundary defects grow until they merge with neighboring cavities. This phenomenon is a primary cause of mechanical failure in semiconductor interconnects and solder joints.
Stress Accumulation
Tensile stress applied to a metal line forces plastic deformation to occur around structural inhomogeneities or impurities. As the material stretches, the interface between these impurities and the metal matrix separates, which creates small cavities. Continued mechanical loading causes these cavities to expand in the direction of the stress field.
The remaining metal ligaments between the voids become thinner until they can no longer support the applied load.
Structural Failure
The merger of these growing cavities forms a continuous crack that propagates rapidly across the entire cross-section of the metal line. In microelectronic packaging, this failure mode destroys the electrical connection, resulting in an open circuit or a sudden rise in electrical resistance. Scanning electron microscope analysis of the fractured surface reveals a characteristic dimpled texture that confirms this mechanical failure process occurred.
Prevention Parameter
Controlling the purity of deposition materials and optimizing the thermal processing history minimize the density of initial nucleation sites. Restricting the tensile stress below the yield strength of the metallization layer prevents the initiation of this failure sequence.