Effects of layers and vias on continuous-wave laser heating and damage of surface-micromachined structures

摘要

The response of microsystem components to laser irradiationnis relevant to processes and applications such as laser processing, op-ntical diagnostics, and optical microelectromechanical systems u0001MEMSu0002ndevice design and performance. The dimensions of MEMS, which are onnthe order of several micrometers, are on the same order as infrared lasernwavelengths, which results in interference phenomena when the partsnare partially transparent. Four polycrystalline silicon structures were de-nsigned and irradiated with 532 and 808 nm continuous wave laser lightnto determine the effects of layers, air gaps, and the presence of a sub-nstrate via on the threshold laser power for damage. The presence of ansubstrate via resulted in lower damage thresholds, and a single-layernstructure had the highest damage threshold for structures irradiated withninfrared light. Structures irradiated with visible wavelength light exhibitednless sensitivity to the underlying via. Optical interference calculations arencarried out to evaluate the absorptance of these structures as a feasiblenexplanation for the observed results. ©