Elsevier

Electrochimica Acta

Volume 45, Issue 20, 23 June 2000, Pages 3263-3268
Electrochimica Acta

Nickel deposition behavior on n-type silicon wafer for fabrication of minute nickel dots

https://doi.org/10.1016/S0013-4686(00)00442-4Get rights and content

Abstract

The present study is a part of our systematic development of mass-scale production processes of nanometer-scale arrays of metal dots on silicon wafer surfaces. Metallic Ni was deposited onto Si(100) wafer surfaces electrolessly or galvanostatically, for surveying appropriate methods for formation of minute structures. Within an electroless bath of simple NiSO4–(NH4)2SO4 solution, metallic Ni was deposited, accompanied by the oxidation of the Si surface. Wet pretreatment of the Si surfaces in HPM (HCl and H2O2 mixture) or in ethanol drastically improved the uniformity of Ni layer and the rate of deposition. The electrolytic deposition with applying a potential at the Si wafer resulted in formation of Ni deposit which were easily peeled off. Based on the knowledge obtained, a two-dimensional array of minute Ni dots (diameter ca. 270 nm) was successfully fabricated.

Introduction

Production of nanostructures on Si wafer surfaces [1], [2], [3] is nowadays of potential request in the currently proceeding development of minute devices such as single electron transistors [4], [5], patterned recording media [6], [7], [8], etc. Fabrication of arrays of nanometer-scale metallic dots will contribute to the realization of ultra high density ROM devices. For depositing metals on Si, wet processes such as electrodeposition [6] and electroless deposition is a very attractive technique for wafer-scale fabrication of fine structures.

We have investigated the mechanism of electroless Ni deposition on Si wafer aiming for fabricating nanometer-scale arrays of metal dots [9], [10], [11]. In those previous reports, we proposed a two-step process composed of treatment for nucleation and that for particle fattening by using two different deposition bathes [11]. A bath without reducing reagent for Ni2+  Ni was used for nucleation, and a bath containing reducing reagent was used for the particle growth, because the particle growth occurs more readily than the nucleation on Si wafer surface when the bath contains the reducing agent. In this process, the nucleation step is obviously the key process in forming metal dots with satisfactory properties.

In the present study, we investigated electrodeposition with external potential control besides electroless deposition because the electrolytically deposited Ni might have different properties from that by electroless deposition.

Another objective of this paper is to examine the effects of wet chemical pretreatment of the HF-treated Si surfaces on the electroless deposition behavior. Pretreatment in strong oxidative environment or even by immersion in ethanol improved the efficiency of electroless deposition and the quality of the deposited layer. These effects are considered to be closely related to the mechanism of reductive Ni depostiion onto Si surfaces, as discussed later.

Section snippets

Experimental

The substrates used were n-type Si(100) wafers (phosphorus-doped with a resistivity of 8–12 Ω cm, Shin-Etsu Handotai Co., Ltd.) for usual experiments. For fabrication of minute dot arrays, the n-Si(100) wafers (phosphorus-doped with a resistivity of 4–6.5 Ω cm) obtained as covered with a CVD-SiO2 resist layer (ca. 450 nm in thickness) with arrays of bores (ca. 270 nm in diameter) was used. These patterned substrates were prepared and supplied by NEC Corporation.

The specimens were cleaned in SPM

Comparison of nickel deposition mechanisms between the electroless and the electrolytic method

Our previous work revealed that Ni deposition in the bath consisting only of NiSO4 and (NH4)2SO4 is accompanied by the formation of a silicon oxide layer between the Si substrate and the Ni deposit [10]. In the case of using the substrate just after the HF treatment, however, Ni nuclei did not cover the Si wafer surface uniformly. Therefore, we carried out some kinds of pretreatment in order to obtain the uniform and adhesive Ni deposits with higher deposition rates, which is described in the

Conclusion

The deposited films of Ni formed by electroless and electrolytic method were compared. In the electrodeposition, there was no oxide layer between Ni deposits and Si substrate, and the Ni deposits were easily peeled off. Whereas in electroless deposition, a silicon oxide layer was formed between the Si substrate and Ni deposits, and a satisfactory adherence was attained. The silicon oxide layer enhanced adherence of deposited Ni nuclei to the wafer surface. Electroless Ni deposition spreaded on

Acknowledgements

The authors would like to thank to Dr Ueno and Dr Kasai, NEC Corporation, for supplying the SiO2 pre-patterned Si wafer. This work was financially supported by the Research for the Future Project ‘Wafer-Scale Formation Process of Nano Dots’, the Japan Society for the Promotion of Science, and by a Grant-in-Aid for Scientific Research on Priority Area of Electrochemistry of Ordered Interfaces from the ministry of Education, Science, Sports and Culture, Japan.

References (11)

  • H. Sugimura et al.

    Thin Solid Films

    (1996)
  • N. Takano et al.

    Electrochim. Acta

    (1999)
  • J. Lohau et al.

    J. Vac. Sci. Technol.

    (1998)
  • T. Tada et al.

    J. Vac. Sci. Technol.

    (1998)
  • L. Guo et al.

    J. Vac. Sci. Technol.

    (1997)
There are more references available in the full text version of this article.

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