MEMS (Micro Electro Mechanical Systems) Mass Spectrometry and Portability

Miniature analytical devices have recently become a growing area to produce handheld, field-portable instrumentation. Because of the difficulty to micromachine optical components and features with small aberrations, it is necessary to incorporate new doped silicon micro-electro-mechanical system (MEMS) methods. This technique allows for precise manufacturing of small electrical and mechanical device assemblies.

The micromechanical spectrometers and ion optical components are fabricated using deep reactive ion etching (DRIE) on highly n-doped (0.01 ohm-cm) silicon-on-insulator (SOI) wafers to form the micromechanical and electromechanical structures. The wafer is then diced and flip-chip bonded to an insulating substrate for components that operate at high voltages (>1 kV). An automated and directed pick and place microassembly assembly tool with MEMS end-effectors and high precision robotics is used to assemble the micro ion-optical devices. This assembly system provides a high degree of flexibility in terms of three-dimensional assembled structures and assembly precision. Ion and electron-optical assemblies are tested for electrical breakdown from 760 to 1x10^-7 torr. The mass spectrometers and ion lens assemblies are then tested for ion manipulation accuracy.

We have created and tested ten new MEMS based ion optical assemblies. This list includes the Bradbury-Nielsen Gate, cylindrical ion trap, time-lag focusing TOF, reflectron optics, einzel lens, electron beam collimator, periodic focusing, and ion mobility. Data has been presented showing the resolution, attenuation, and performance of each of these devices. With the ability to utilize multiple substrates such as Pyrex, sapphire, and aluminum nitride, we can make ion lenses that can withstand an applied potential >2kV before breakdown. These devices have been created with <5um feature sizes and <250nm position accuracy. The angular alignment of the assembled structures is shown to be less than 1 degree.