Complex MEMS: a fully integrated TOF micro mass spectrometer

Abstract

A fully integrated mass spectrometer on one chip is presented. This miniaturized mass spectrometer (MMS) is predestinated for mobile measurements, portable applications as well as continuous process monitoring. MEMS technology allows all critical structures to be fabricated by a one mask anisotropic deep silicon etch. Hence, the MMS is very cost efficient due to its mass producibility. Its small size (5 mm × 10 mm) reduces the vacuum requirements by a few orders of magnitude, so that a one stage pumping system achieves the necessary vacuum. The operation is based on electron impact ionization and a time-of-flight mass filter. The electron beam for ionization is supplied by the electron source, which operates with a high density microwave plasma. The integrated ion optics extracts and focuses the beam into the mass separator, where short ion pulses diverge based on their mass-to-charge ratio. An energy filter keeps the ion beam monochromatic before it is recorded at the detector. Mass spectra of different gas compositions measured with the MMS are presented.