Monolithically integrated microspectrometer-on-chip based on tunable visible light MEMS FPI

We present a novel microspectrometer-on-chip for the visible spectral region, consisting of a tunable MEMS Fabry-Perot interferometer (FPI) monolithically integrated on a PIN photodiode using IC compatible microfabrication techniques. MEMS FPI is an electrostatically (AC voltage) actuated structure consisting of two parallel atomic layer deposited Bragg mirror stacks of Al2O3/TiO2 with imbedded circular aluminum electrodes on top and the bottom for capacitive tuning capability for the wavelength range of 420–550 nm. The fabrication process flow for the successful completion of the device is presented. The spectral response of the device ranges from 0.1 A/W at λ = 420 nm to 0.2 A/W at λ = 550 nm, with transmission peak width of 8 nm at 540 nm. These results indicate photodiode performance that matches the sensitivity levels typical for commercially available photodiodes in this wavelength range as well as excellent transmission properties of the integrated FPI filter structure, while the monolithical fabrication process offers increased spectrometer robustness and mass production capability.