Material Deposition into Porous Silicon Template

Porous silicon (PSi) is often fabricated by the electrochemical etching of silicon in a fluoride-based solution [1-4]. One of the unique properties of PSi layer is the ability to precisely tune the pore size and morphology through the variation of the silicon dopant type and level and controlling the applied anodic current and etching time. The compatibility of PSi with existing silicon processing technology adds another advantage. A wide range of materials including metals, conducting polymers, oxides, magnetic alloys and semiconductors can be deposited inside the pores of PSi templates by different techniques including; the electrochemical deposition, immersion plating and electroless deposition, sol-gel and chemical vapor deposition. Such deposition strategies would lead to various surface morphologies such as nanowires or nanorods, nanotubes, nanorings, nanodots and heterogeneous nano-macrostructures. The dimensions of as-formed hybrid structures can be controlled by regulating the shape and pore size of PSi template as well as the deposition conditions.

In this work, we used PSi as a template-directing synthesis of various metallic and polymeric nano-macrostructures. Firstly, preparation of various shapes and morphologies of PSi templates are given. Examples of chemical and electrochemical deposition of metals and conducting polymers are provided. We then focus on understanding of the mechanism of Cu deposition by the immersion plating method using the XPS sputter depth profiling into PSi template as a case study and discuss the processing issues associated with its deposition inside the nanoscale pores under the open-circuit condition.

Various pore diameters ranging from < 5 nm up to > 1 µm are accessible in PSi layers. Typical examples of SEM images of PSi templates, mainly ordered 5 µm macropores, 120 nm medium-sized pores and 20 nm mesopores are presented in Fig.1 [5]. Results of the synthesis and characterization of the obtained PSi-deposited materials will be presented and thoroughly discussed during the conference.

Keywords: Porous silicon; electrochemical deposition; immersion plating; Cu deposition; conducting polymer

References

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