Nanoscale Electrochemical Deposition of Metals on FIB Sensitized p -Type Silicon
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Nanoscale Electrochemical Deposition of Metals on FIB Sensitized p-Type Silicon Adrian Spiegel1, M. Döbeli2 and Patrik Schmuki Dept. of Material Science, LKO, University of Erlangen-Nuremberg, D-91058 Erlangen, GERMANY. 1 Swiss Federal Institute of Technology Lausanne (EPFL), Dept. of Materials Science, LTP, CH-1015 Lausanne, SWITZERLAND. 2 Swiss Federal Institute of Technology Zurich (ETHZ), Inst. of Particle Physics, HPK, CH-8039 Zurich, SWITZERLAND.
ABSTRACT Sub-micrometer copper nanostructures were deposited on p-type silicon (p-Si) by means of a selective electrochemical reaction. Ga+-ions from a focused ion beam (FIB) were used to ‘write’ damage patterns on p-Si; in a subsequent electrochemical reaction Cu was deposited selectively at these defect sites. So far we have been able to obtain Cu structures with a lateral resolution of 300nm, which is also the limit of the FIB currently used. The process may offer advantages over traditional lithographic methods for producing nanometer sized metal structure on Si as no masking steps are required. Also, structures with a lateral resolution in the sub- 100nm region seem possible; so far the process has only been limited by the FIB’s lateral resolution.
INTRODUCTION Electrochemical deposition of metals and alloys onto metallic substrates plays an important role in many modern technologies. In the electronics industry, electrochemical deposition is widely used for applications, such as copper printed circuit boards, through-hole plating, multilayer read/write heads, and thin film magnetic recording media [1, 2]. Usually a photolithographic patterning process followed by metal evaporation, electrodeposition or sputtering is used to produce the desired feature on the surface of the substrate. In comparison, direct patterning approaches have received relatively little attention. However, research in this field suggests that the use of such diverse tools as STMs [3], AFMs [4], FIBs [5], or SEMs [6] may offer advantages over ‘traditional’ photolithographical methods. This is mainly due to the fact that no photoresist is needed to transfer the pattern from a mask to the substrate. We present a novel method for patterned metal deposition on semiconductors based on changing the electrochemical properties of the semiconductor surface in a controlled way. It has been shown that direct patterning by FIB may be used to perform selective electrochemistry leading to porous structures on various semiconductors [7-9]. Subsequent work has led to the selective deposition of metal structures on FIB implanted p-Si [10]. Our research suggests that only the size of the defects created by FIB limits the lateral resolution of the structures; the best FIBs available today are capable of reaching resolutions (defined as full width at half maximum of the beam lateral distribution) of < 10nm. Features of similar size can nowadays only be achieved by electron beam lithography or by methods based on scanning probe microscopes.
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