The properties of electrical contacts made on porous Si by the electroless Ni plating technique have been studied. It is shown that due to the pore infiltration property of the plating solution, metallization occurs inside the pores over an effective area several times higher than the physical area of the sample. By making variations in the plating bath composition, Ni containing a small amount of P or B as an impurity is plated and excellent ohmic or rectifying contacts on n- or p-type porous Si are obtained. It is further observed that a higher area of contact with comparatively superior electrical properties is obtained when electroless Ni plating is made from the bath which introduces B as the impurity.

S DHAR

S CHAKRABARTI

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Electroless Ni plating on n- and p-type porous Si for ohmic and rectifying contacts

Semiconductor Science and Technology

High-performance rectifying contacts with a rectifying ratio exceeding 1000 are obtained by depositing thin transparent and conducting CdO films on porous silicon (PSi) and annealing at an optimized temperature. The reverse current of 1.5 mm diameter diodes at -10 V in the dark is 26 nA; this increases by three orders of magnitude under exposure to normal tungsten lamp illumination. The results show that CdO-on-PSi diodes will act as very good candidates for making high-efficiency photodiodes.

Large photoresponse of CdO/porous Si diodes

The electrical and optical properties of Cu2S films, deposited on porous Si from a chemical bath, are presented. Annealing of the deposited film in air, at an optimized temperature of 150°C, is shown to be essential to get films with the lowest values of electrical resistivities. The film is more than 60% transparent in the wavelength range of 600-1200 nm. Films deposited on porous Si produce Schottky-like diodes. The best diode characteristics are obtained after annealing the film at 150°C. The diodes show both photoresponse and electroluminescence properties. Luminescence from porous Si, with a top coating of annealed Cu2S, is about 70% of that obtained when no coating was applied. © 1997 American Institute of Physics.

Fulltext

Journal of Applied Physics

Properties of chemically deposited Cu2S films on porous silicon

We present a study of the adhesion and current-voltage characteristics of as-plated electroless nickel deposits on polished crystalline silicon activated using nickel and palladium. A highlight of this study is the derivation of practically significant trends by collating the results of a large number of simple experiments as a function of substrate doping polarity, doping level, plating area, and plating duration. The study reveals that palladium activation is most effective on P+ substrates while nickel activation is most effective on N+ substrates, due to the requirement of substrate holes in the former activation and electrons in the latter. An activation process always improves adhesion, but, in some cases, degrades the electrical properties of the plating-silicon interface, because it introduces an intermediate suicide layer between nickel and silicon. Electroless nickel layer adheres better to nickel activated silicon, than to palladium activated silicon. However, the rectifying nature of the electroless nickel contacts on palladium activated silicon is superior to those on nickel activated silicon. Further, palladium suicide forms at 200°C, which is much lower than the temperature of 400°C required for nickel suicide formation. © 2004 The Electrochemical Society. All rights reserved.

Journal of the Electrochemical Society

Effects of nickel and palladium activations on the adhesion and I-V characteristics of as-plated electroless nickel deposits on polished crystalline silicon

This work reports a study of the adhesion of electroless nickel plating on polished silicon as a function of several plating variables, namely substrate resistivity, activator composition, plating duration, and plating bath temperature. It is shown that an adhesion strength of ∼100 kg/cm2 or more can be obtained, irrespective of the silicon doping, for plating used in semiconductor devices. However, for this purpose, an appropriate silicon activation step is essential, except when the silicon is heavily N-type doped.

Journal of Adhesion Science and Technology

Adhesion of electroless nickel plating on polished silicon

The solution in which Si is immersed for activation prior to autocatalytic electroless deposition (AED) of Ni, Cu, etc. is usually HF-PdCl2-HCl. However, we find that the AED of Pd on polished crystalline Si, which has important applications in modern planar integrated circuit technology, is nonadherent using this activator solution. Our study of the effects of modifying this solution and varying the substrate doping on the Pd deposition during activation and Pd AED adhesion reveals the following. The activation quality and hence AED adhesion depends not on the SiO2 etch rate of the solution but on the composition of the solution Pd complex and the substrate hole concentration. In spite of the highest Pd deposition rate during immersion, the activation quality of n-Si with doping &gt; 1019/cm3 is poor unless a hole-generating stimulus (e.g., illumination) is present. A change in substrate hole concentration influences AED adhesion by altering the substrate potential and/or density of nucleation sites during activation. Similarly, a change in the Pd complex affects AED adhesion by altering the solution Pd potential. Introduction of certain ammonium compounds into the HF-PdCl2-HCl bath creates a specific Pd-ammine complex, most probably Pd(NH3)2 Cl2, which gives Pd AED adhesions of ∼9 and 4 (3) × 106 N/m2 on heavily doped p-Si and lightly doped p(n)-Si, respectively, using a low SiO2 etch rate (∼90 Å/min) and a low temperature (200°C) for Pd nuclei silicidation during activation. Our results regarding the activation mechanism are believed to apply generally to all AED on Si. © 1999 The Electrochemical Society. All rights reserved.

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ISSN	0268-1242