MEMS

ABSTRACT: A technique is described for assembly of multiple batches of micro components onto a single substrate. The substrate is prepared with hydrophobic alkanethiol-coated gold binding sites. To perform assembly, a hydrocarbon oil is applied to the substrate and wets exclusively the hydrophobic binding sites in water. Micro components are then added to the water, and assembled on the oil-wetted binding sites. Moreover, assembly can be controlled to take place on desired binding sites by using an electrochemical method to de-activate specific substrate binding sites. By repeatedly applying this technique, different batches of micro components can be assembled to a single substrate sequentially. As a post assembly procedure, electroplating is incorporated into the technique to establish electrical connections for assembled components. Important issues presented are: substrate fabrication techniques, electrochemical modulation by using suitable alkanethiol (dodecanethiol), electroplating of tin and lead alloy and binding site design simulations. Finally, we demonstrate a two-batch assembly of silicon square parts, and electrical connectivity by electroplating contacts to surface-mount light emitting diodes.

ABSTRACT: A double-sided micromachining process for silicon-based device fabrication is developed that allows the use of capacitively coupled reactive ion etching (RIE) equipment for high-aspect-ratio etching. The effects of the masking materials and RIE conditions are discussed. Based on the experimental results, a 1000-A-thick Al film sufficiently protects the unexposed substrate while allowing the etching of a 350-m-deep hole with an area of 33 mm2 when etching with SF6/CHF3/O2plasma. A 2000-m-long and 100-m-wide (with layers of Al/SiO2/Si and thickness of 0.1/2.2/40 m, respectively) cantilever beam is achieved. A silicon etch rate up to 2.5 to 2.8 m/min is obtained and an anisotropy of A=0.5 (A=1-V/H, where V is the horizontal undercut and H is the etch depth) is obtained. The technique is developed mainly for bulk micromachining of silicon or composite silicon cantilever structures.