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We present a low-temperature post-processing module, utilizing polyimide as a sacrificial layer and novel materials such as PECVD SiC and metals (sputtered aluminium and titanium) as structural layers. The use of spin-on polyimide allows an all-dry final release step overcoming stiction problems often encountered in wet sacrificial etching processes. The spinning and curing procedure has been tailored to the specific needs of the IC-compatible post-process module. For the patterning of the polyimide, thin films of aluminium, PECVD silicon oxide or silicon carbide are employed as a mask layer. Anisotropic etching of the mask film and of the polyimide layer is accomplished by RIE. After patterning the structural layer, sacrificial etching of the polyimide is done using an isotropic dry etch process in high-density oxygen plasma. An underetch rate of 4 μm min−1 is achieved. Compatibility with different structural materials is tested and test structures are designed and realized in a fully post-processing surface micromachining module.

Nanometer-thick amorphous boron (a-B) layers were formed on (100) Si during exposure to diborane (B 2 H 6 ) in a chemical vapor deposition (CVD) system, either at atmospheric or reduced pressures, at temperatures down to 500°C. The dependence of the growth mechanism on processing parameters was investigated by analytical techniques, such as transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS), in conjunction with extensive electrical characterization. In particular, devices fabricated by B deposition effectively demonstrated that p + doping of the silicon substrate can be achieved within 10 nm from the surface in a manner that is finely controlled by the B 2 H 6 exposure conditions. High-quality, extremely ultrashallow, p + n junctions were fabricated, and their saturation current was tuned from high Schottky-like values to low deep pn junction-like values by the increasing of the deposited B layer thickness. This junction formation exhibited high selectivity, isotropy, spatial homogeneity, and compatibility with standard Si device fabrication.

Varactor diode-based circuit topologies, which can act as high-Q "distortion-free" tunable capacitive elements, are presented. These diodes are implemented in a novel ultra low-loss silicon-on-glass technology, with resulting measured Q's of over 200 at 2 GHz. The measured IM3 improvement compared to traditional single varactor tuning techniques is greater than 30 dB.

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