Improved bending fatigue life of single crystal silicon micro-beam by phosphorus doping

•The fatigue resistance of the SCS by improving its crystal properties is studied.•The fatigue life of SCS increases with the phosphorus doping concentration.•Phosphorus doping increases the difficulty of the crack initiation and propagation. Focusing on improving the fatigue strength of single crystal silicon (SCS) micro-structures, this paper reports on the effects of phosphorus doping on the bending fatigue properties of a SCS micro-beam. First, a specially designed micro-structure for bending strength tests and a bending test device are presented. Second, the bending fatigue life for six groups of specimens with different phosphorus doping concentrations is tested at room temperature. The results show that the fatigue life has a monotonically increasing relationship with the phosphorus doping concentration. Finally, by analysing the effects of surface roughness and the characteristics of quasi-static fracture surfaces and fatigue fracture surfaces, the mechanism of how phosphorus doping affects the fatigue properties of SCS micro-beam is demonstrated, indicating that phosphorus doping can increase the difficulty of the initiation and propagation for cracks. Research in this work can provide some practical significance for fatigue reliability design of silicon-based MEMS.