Fabrication of Pt-Si Schottky diodes using soft lithographic patterning and selective chemical vapor deposition

This work demonstrates the feasibility of using soft lithographic patterning in conjunction with additive metallizatian to fabricate micron-scale electronic devices. Specifically, the fabrication of platinum/platinum silicide/silicon Schottky diodes is demonstrated using a unique combination of soft lithographic patterning and additive metallization techniques. The diode architecture provides a useful means through which to demonstrate the specific characteristics and general utility of this fabrication technique. A 30 x 10 array of micron-scale diode features was patterned on a silicon substrate using a polymeric film prepared by micromolding in capillaries (MIMIC), a soft lithographic patterning technique. Following etching to remove oxide from the substrate surface, metallization by selective platinum chemical vapor deposition (CVD) was used Co form rectifying contacts to the substrate, The polymeric film successfully served both as an oxide etch resist before metallization and as a deposition-inhibiting surface for the selective deposition of platinum. The selectivity of the deposition was confirmed by secondary ion mass spectrometry (SIMS). Electrical characterization of the metallized areas showed expected diode behavior. Rutherford backscattering (RBS) and Auger sputter-depth profiling revealed the presence of significant amounts of both Pt and Si at the surface of the platinum film, suggesting that, silicide formation accompanies the thin film growth. An unusual feature of the platinum-silicon microstructures obtained in this work was the presence of a platinum concentration gradient within the film instead of the well-defined interfaces between intermetallic phases that are typically seen in platinum silicide layers. A backscattering simulation was used to extract the elemental depth profiles from the RES data.