Controlled and Selective Aggregation of Submicrometer Cu-Crystallites on FIB Sensitized p -Si
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Controlled and Selective Aggregation of Submicrometer Cu-Crystallites on FIB Sensitized p-Si Adrian Spiegel1 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. ABSTRACT Electrochemical deposition of metals and alloys onto metallic substrates plays an important role in many modern technologies. Usually, a photolithographic patterning process is used to produce the desired feature on the substrate surface. An alternative method to patterned metal deposition on semiconductors is presented here: it is based on changing the electrochemical properties of the semiconductor by controlled surface defect creation. A focused ion beam (FIB) was used to introduce defects into p-Si, followed by a selective electrochemical reaction to produce metal structures in the sub-micrometer range. In this work we study the selective deposition behavior of Cu on FIB sensitized surface locations and show that crystallite growth follows a three- dimensional growth law. Crystallites grow very rapidly in a first phase and reach a size of roughly 200nm after 5s. Factors determining nucleation, growth, and coalescence of metal clusters are identified and investigated.
INTRODUCTION Deposition of metals and alloys onto semiconductors by electrochemical means has become increasingly important for many modern technologies. Mainly the electronics industry depends on electrochemical deposition for the production of such diverse products as printed circuit boards, through-hole plating, multilayer read/write heads, thin film magnetic recording media, and others [1, 2]. In most processes photolithographic techniques are used in combination with metal evaporation, sputtering, or electrodeposition to produce these features. In comparison, direct patterning approaches have so far received relatively little attention. Recent research suggests however, that promise may lie in such diverse techniques as STMs [3], AFMs [4], FIBs [5], or SEMs [6]. Their advantage over traditional techniques is due to the absence of photoresist usually needed to transfer the desired layout from a mask onto the sample surface. Our work presents a novel method for direct maskless electrochemical metal deposition onto p-type semiconductors. Previous research has shown that the electrochemical properties of a semiconductor may be altered by introducing damage at its surface. Direct patterning by FIB was used to perform selective electrochemistry leading to porous structures on various semiconductors [7-9]. Subsequent work has led to selective deposition of metal structures on FIB implanted p-Si [10]. Structures as fine as 300nm have been written, and our results indicate that lateral resolution is only limited by the FIB used for writing the defect patterns; the best FIBs used today are capable of reaching resolutions (defined as full width at half maximum of the beam lateral distribution) of < 10nm. Only e
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