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Use of ALD thin film Bragg mirror stacks in tuneable visible light MEMS Fabry-Perot interferometers
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2012
Year
Short Wavelength OpticOptical MaterialsEngineeringAld Fpi ProcessingOptical TestingInterferometryThin Film Process TechnologyOptical PropertiesFpi ProcessInstrumentationGraded-reflectivity MirrorsMaterials SciencePhotonicsFpi Fabrication ProcessDepth-graded Multilayer CoatingApplied PhysicsGlass PhotonicsThin FilmsOptoelectronics
This paper discusses the use of ALD thin films as Bragg mirror structure materials in MEMS Fabry-Perot interferometers in the visible spectral range. Utilizing polyimide sacrificial layer in the FPI fabrication process is also presented as an alternative method to allow higher temperature (T= 300 °C) ALD FPI processing. ALD Al<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub> thin films grown at T= 110 °C are optically characterized to determine their performance in the UV - visible range (λ>200nm) and effects of the ALD temperature on the thin film stacks and the FPI process is discussed. Optically simulated 5-layer Bragg mirror stacks consisting of ALD Al<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub> for wavelengths between 420 nm and 1000 nm are presented and corresponding MEMS mirror membrane structures are fabricated at T= 110 °C and tested for their release yield properties. As a result, the applicable wavelength range of the low-temperature ALD FPI technology can be defined.