We report for the first time investigations on electroless plated-nickel phosphorus alloy (Ni) contacts to undoped amorphous silicon (a-Si:H). I-V characteristics of electroless NiP were compared with those of Nickel deposited by thermal evaporation. It was found that as-deposited NiP makes a rectifying contact to undoped a-Si:H. The effects of plasma annealing on the contacts were studied. NiP contacts on low pressure chemical vapour deposited a-Si are also reported here. © 1994.

Shreepad Karmalkar

Department of Electrical Engineering

Enakshi Bhattacharya

T. Balaji

S. Satish Kumar

Amorphous materials

Annealing

Chemical vapor deposition

Crystalline materials

Electrons

Electroplating

Evaporation

Nickel alloys

Plasma applications

Silicon

ELECTROLESS PLATED NICKEL CONTACTS

Hydrogenated amorphous silicon

PLASMA ANNEALING

PLASMA ENHANCED CHEMICAL VAPOUR DEPOSITION

Thermal evaporation

ohmic contacts

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Electroless plated nickel contacts to hydrogenated amorphous silicon

Thin Solid Films

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 paper presents an improved procedure for electroplating metal bumps on an array of planar P+-N zener, varactor or rectifier diodes fabricated on a common N-type substrate. The improvements pertain to avoidance of undesirable plating on the substrate periphery and stabilization of the plating current against unpredictable changes in the plating load resistance, when the N-type region is used as the cathode. The former improvement is achieved using a periodic reverse voltage for electroplating, and the latter using a special circuit for automatically adjusting the plating voltage amplitude to compensate for the plating resistance variations. © 2002 Elsevier Science B.V. All rights reserved.

Journal of Materials Processing Technology

An improved procedure for bump plating of planar diodes

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.

A Study of Immersion Processes of Activating Polished Crystalline Silicon for Autocatalytic Electroless Deposition of Palladium and Other Metals

Journal of Applied Physics

Space‐charge limited conduction inn+nn+amorphous hydrogenated silicon films

Applied Physics Letters

Effect of ion‐beam sputter damage on Schottky barrier formation in silicon

Ohmic contacts to n-type silicon having resistivity of the order of 5 Ω-cm and orientation (111) by electroless Ni-P process were investigated under two different conditions, i.e., keeping operating temperature constant and pH variable and vice versa. It was found that the formation of Ni-P alloy during deposition resulted in low resistance ohmic contacts to silicon with increase of P-concentration and with heat-treatment after deposition in both cases; © 1980, The Electrochemical Society, Inc. All rights reserved.

Variation of Contact Resistance of Electroless Ni-P on Silicon with the Change of Phosphorous Concentration in the Deposit

The fabrication of Schottky‐barrier solar cells by electroless nickel plating

Journal of The Electrochemical Society

Electroless Nickel Plating for Making Ohmic Contacts to Silicon

Journal	Thin Solid Films
ISSN	00406090
Open Access	No