MEMS-based nanomechanical machining system-on-a-chip: Design, fabrication, and functional testing for feasibility.

摘要

In this research, the design, fabrication, and testing of a nanomechanical machining system on a chip were demonstrated. Many mechanical manufacturing techniques such as embossing, stamping, and molding have become recognized as extremely viable methods of nanomanufacturing. Ultraviolet (UV) lithography resolution is limited in this regime and e-beam and x-ray lithography are very expensive to use and do not offer high throughput. Therefore, a mechanical machining alternative was proposed to address this future device application market requirement. This approach combines scanning probe microscopy (SPM) tip technology with microelectromechanical systems (MEMS) actuator technology to create a novel, top-down, mechanical machining system. This device was called the Nanodrill and this new technology pushes the envelope of MEMS actuator design and is an example of a dynamic SPM tip, opening the pathway for a variety of novel devices in this emerging field.; This research demonstrates successfully the design, fabrication methods, and processes, as well as the actuation systems used in developing the drilling process in smooth polymer films using MEMS as a platform for nanomachining. The MEMS actuator was fabricated using a five-layer, polysilicon surface micromachining process. The actuator is an orthogonal electrostatic comb drive microengine producing 850 nJ of torque rotating a 82 mum pinion gear and capable or rotating at 300,000 rpm. The pinion gear rotates a 58 mum load gear, yielding a 1.5:1 gear reduction, on which the drill tip is fabricated. The drill tips were created by focused ion beam (FIB) milling and are approximately 1mum tall and 500 nm wide. An oxide release process was implemented that created a self-assembling monolayer alkene-based conformal coating that functioned as a lubricant and prevented stiction of the device features to the substrate.; The nanodrill was directly inserted into a Hysitron UB1 nanoindentation system that provided the nanometer and micronewton scale displacement and force resolution required for nanomachining. Drilling tests were performed into 10 mum thick hard-baked photoresist films on a 1 mum pitch spacing up to 1 mum deep, creating machined features with a 2:1 aspect ratio. Photoresist was used since it was an available spin-on polymer that had a very smooth surface. The tips were analyzed by scanning electron microscopy (SEM) and electron dispersive x-ray spectroscopic (EDS) before and after drilling. The analyses of the data show conclusive evidence of material transfer of the polymer from the work piece to the drill tip. EDS analysis of this material also is consistent with that of photoresist showing that the material was in fact machined, which resulted in a built-up edge on the drill tip.; The target applications for this device would be in the areas of nanomachining of single DNA detection sensors, nanonozzles for fuel injectors, micro fluidic channels, reworking and trimming of nanometer scale features of semiconductor electronics and bio-electronics, interconnection vias for vertical cavity surface emitting lasers (VCSELS), and other quantum dot and well devices.