L. Santinacci

Electron beam-induced carbon masking for electrodeposition on semiconductor surfaces

Carbon patterns were deposited on Si(100) by electron beam-induced contamination decomposition. The feasibility of using such patterns as a mask for a subsequent electrochemical deposition of Au is studied. We demonstrate that under optimized electrochemical conditions electrodeposition of Au can be blocked selectively by single line carbon deposits in the order of only 1 nm thickness. The lateral resolution of this negative patterning process is in the sub 100 nm range. The principle opens perspectives for high definition patterning of semiconductor surfaces by selective electrodeposition.

Nanoscale patterning of Si(100) surfaces by scratching through the native oxide layer using atomic force microscope

We demonstrate selective electrodeposition of Cu into nanoscratches produced in native oxide covered p-type and n-type Si(100). Nanosize grooves were produced with a diamond-coated atomic force microscope tip at heavy forces. Onto these grooved surfaces, Cu was electrodeposited from a 0.01 M CuSO4+0.05 M H2SO4 electrolyte under various conditions. The results clearly show that these scratches represent activated sites for metal electrodeposition—the surrounding intact oxide layer acts as a highly efficient mask. After optimization of electrochemical parameters, we were able to achieve the deposition of uniform and well-defined structures with a lateral resolution in the 100 nm range. In general, the process opens alternate perspectives for selective electrodeposition and direct patterning of Si surfaces.

Selective palladium electrochemical deposition onto AFM-scratched silicon surfaces

The present work investigates the selective electrochemical deposition of palladium nano-structures into scratches produced through thin oxide layers covering p -Si (1 0 0) surfaces. Using an atomic force microscope equipped with a single-crystalline diamond tip scratches in the 100 nm range were produced through a 10 nm thick dry oxide layer. Pd deposition was carried out in PdCl2 (0.01 g l � 1 )� /HCl (0.1 M) by cathodic potential steps. Investigation of the palladium nucleation and growth processes onto silicon surfaces is presented. Under optimized conditions sub-100 nm palladium structures can be obtained with a very high selectivity. # 2003 Elsevier Ltd. All rights reserved.

Atomic Force Microscopy-Induced Nanopatterning of Si(100) Surfaces

In this study, we investigate the possibilities of selectively electrodepositing Cu on surface defects created in p-type and n-type Si(100) by scratching the surface with the tip of an atomic force microscope (AFM). Nanosized grooves were produced on Si surfaces with a diamond-coated AFM tip at heavy forces. Cu was electrodeposited on these grooved surfaces from a 0.01 M CuSO 4 + 0.05 M H 2 SO 4 electrolyte under various conditions. The results clearly show that defects created on H-terminated p-type Si(100) lead to an enhanced reactivity, i.e., preferential Cu deposition at such defects is possible. However, a much higher degree of selectivity of the deposition is obtained if AFM-induced grooves are produced on surfaces that carry a native oxide layer. The masking effect of this insulator film is demonstrated by selective Cu electrodeposition into scratches on oxide-covered p- and n-type silicon. After an optimization of electrochemical parameters, we achieved the deposition of uniform and well-defined nanostructures. The process presented here opens new perspectives for selective electrodeposition and direct patterning of Si surfaces.

Defect-Free AFM Scratching at the Si / SiO2 Interface Used for Selective Electrodeposition of Nanowires

We demonstrate selective electrodeposition of Pd into atomic force microscopy (AFM) nanoscratches produced in thermal oxide covered p-type Si(100) without creating substantial damage in the silicon substrate. A 10 nm thick thermal SiO 2 film was scratched about 5-7 nm deep with a diamond tip of an AFM. Then, etching in HF was used to remove uniformly 4-5 nm SiO 2 , thus to expose the Si within the nanoscratches while still maintaining an oxide layer on the rest of the surface. Pd was selectively electrodeposited into these scratches. The underlying silicon exhibits no significant damage induced by scratching.

Composition and growth of thin anodic oxides formed on InP (100)

Thin anodic oxides ( < 100 A) were formed on p-InP (100) in phosphate solution (0.3 M NH 4 H 2 PO 4 ) and in sodium tungstate solution (0.1 M Na 2 WO 4 , 2H 2 O) at different temperatures (25 and 80°C) and potentials (1 8 V). Thickness and composition were determined by different surface-analytical techniques including Auger electron spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and transmission electron microscopy. In general, it has been observed that double-layered films are obtained with an outer In-rich layer. The thickness of the outer layer, oxide morphology and roughness as well as the composition of the duplex structure are strongly dependent on the temperature and the composition of the electrolyte. It has been found that oxides formed in phosphate exhibit a higher stability against dissolution compared with oxides formed in tungstate. The latter contain a large amount of In 2 O 3 , which leads to poor electrical properties.

Electron-Beam Induced Nanomasking for Metal Electrodeposition on Semiconductor Surfaces

The present work investigates the masking effect of carbon contamination patterns deposited by the electron-beam (E-beam) of a scanning electron microscope (SEM) for metal electrodeposition reactions. Carbon contamination lines were written at different electron doses on n-type Si(100) surfaces. Subsequently Au was electrochemically deposited from a 1 M KCN + 0.01 M KAu(CN) 2 solution on the E-beam treated surface sites. The carbon masks as well as the Au deposits were characterized by SEM, atomic force microscopy, and scanning Auger electron spectroscopy. We demonstrate that carbon deposits in the order of 1 nm thickness can he sufficient to achieve a negative resist effect, i.e., can block the electrodeposition of Au completely selectively. The lateral resolution of the process is in the sub-100 nm range. The nucleation and growth of Au deposits and their morphology as well as the selectivity and resolution of the process depend on several factors such as the electron dose during masking, and the applied potential and polarization time during Au deposition. The process opens new perspectives for selective electrodeposition, i.e., for high definition patterning of surfaces with a wide range of materials.

Factors in Electrochemical Nanostructure Fabrication Using Electron-Beam Induced Carbon Masking

Department of Materials Science, LKO, University of Erlangen-Nuremberg, D-91058 Erlangen, GermanyThe present work investigates the fabrication of Au nanostructures using the masking effect of carbon patterns deposited by theelectron-beam~E-beam! of a scanning electron microscope for electrochemical reactions. E-beam induced deposition is based onthe decomposition of residual hydrocarbon species ~molecules from the pump oil! to create a solid deposit at the point of impactof the E-beam. Subsequently, such E-beam deposited matter is used to completely block the electrochemical deposition of Au inthe nanometer scale. In this work, several factors affecting the resolution of the process are studied. Electrochemical conditions aswell as control of the E-beam C-deposit are investigated to optimize the lateral resolution of the process. Especially, it isdemonstrated that the beam energy used for depositing the C-mask plays a crucial role in fabricating Au nanostructures in thesub-50 nm range.© 2004 The Electrochemical Society. @DOI: 10.1149/1.1643744# All rights reserved.Manuscript received April 2, 2003. Available electronically February 5, 2004.

Electron-beam induced carbon deposition used as a mask for cadmium sulfide deposition on Si(100)

The present work investigates the use of carbon masks, deposited on n-type Si(100) surfaces in a scanning electron microscope (SEM), for electrochemical nanopatterning. Carbon contamination lines were written at different electron doses on the n-type Si(100) surfaces and characterized by AFM. Subsequently, deposition of CdS was carried out by electrodeposition of Cd from a 1 mM CdF2+0.05 M NaF solution followed by a chemical treatment in 1 M Na2S. CdS deposits were prepared under various electrochemical conditions and were characterized by SEM, scanning Auger electron spectroscopy and optical techniques including fluorescence and photoluminescence measurements. It is demonstrated that under optimized electrochemical conditions carbon deposits of less than 1 nm thickness and in a width of 100 nm range can act as a negative resist, i.e. can block the deposition of CdS completely and selectively and thus can be used for nanopatterning.

A Semiconductor Nano-Patterning Approach Using AFM-Scratching through Oxide Thin Layers

Abstract : AFM-scratching was performed through thin oxide layer which was either a native oxide layer (1.5 - 2 nm thick) or a thermal oxide layer (10 nm thick). Due to their insulating properties, the SiO2 films act as masks for the metal electrochemical deposition. In the scratched openings copper deposition can take place selectively and thus nano-scale metal lines could be successfully plated onto the p-type silicon substrates. Using particularly, if sufficiently thick thermal oxide has advantages over the native oxide, it allows a H-termination of the Si within the grooves (HF treatment) without eliminating the oxide layer on the rest of the surface.