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

Electroless nickel plating is a very promising process for metallization of silicon solar cells. It can be used to form a seed layer for an electrolytic deposition of copper or silver because it ensures the required adherence, a low contact resistance, and prevent copper from diffusing into the silicon. The nickel plating technique developed in this work consists of a selective electroless nickel–phosphorus (NiP) deposition without the activation step from an alkaline bath containing sodium hypophosphite as a reducing agent and ammonia for pH control. Experimental results of the deposit properties are presented. Thin NiP layers of about 0.1μm on silicon were annealed under different conditions. Rutherford backscattering spectrometry, glancing incidence X-ray diffraction, and scanning electron microscopy were used to obtain information on silicide formation vs temperature. These results were correlated with contact resistivity measurements by the transmission line model. A typical contact resistivity of 10−4Ωcm2 has been obtained.

Section: H744mentioning

confidence: 58%

Electrical and Structural Characterization of Electroless Nickel–Phosphorus Contacts for Silicon Solar Cell Metallization

Boulord

Kaminski

Canut

et al. 2010

“…Equation [1] is the main reaction for the electroless deposition of metallic cobalt (23). One can see from this equation that, as the pH is raised, the reaction is shifted to the right, which prohibits the hydrolysis of NaBH4.…”

Section: Resultsmentioning

confidence: 99%

The Microstructure and Magnetic Properties of Electroless‐Plated Co‐B Thin Films

Chang

Chen

Hung

et al. 1986

Cobalt‐boron alloy films were successfully prepared by electroless plating and characterized by AES, TEM, DSC, and VSM techniques. A bath suitable for room temperature electroless plating was developed. The plating rate was found to be dependent on pH , Co++ concentration, and bath temperature, while the composition of the deposited films was not. The microstructure of the as‐deposited films is characteristic of clusters of aggregating cells and was established to be amorphous with soft magnetic properties. After annealing at 300°C for 1h, the amorphous films were transformed to Co (hcp) phase. normalCoB , Co2B , Co (fcc), stacking faults, and twins were visible for the films subjected to annealing temperatures above 400°C. The saturation magnetization, remanence, and intrinsic coercivity of optimally annealed films are: σs=106 normalemu/normalg , σr=54 normalemu/normalg , and normalHci=250 normalOe . The possible mechanism of autocatalytic reactions, composition, and structure of the films as a function of preparation variables and the detailed transformation during annealing are also discussed.

“…In all the baths, the Pd concentration is the same, and is fixed on the basis of values employed in known baths used extensively for activating different substrates. 6,9,10,20 The conventional HF-PdCl 2 -HCl bath A employs high HF concentration 10 which can strip the important SiO 2 layer present on Si substrates processed using the modern planar integrated circuits technology. This layer acts as a mask during impurity diffusion and as a gate insulator in metal-oxide semiconductor (MOS) devices.…”

Section: Modified Hf-pdcl 2 -Hcl Immersion Systemsmentioning

confidence: 99%

“…Metallization by autocatalytic electroless deposition (AED) is increasingly becoming an important process in semiconductor microelectronics device fabrication. [1][2][3][4][5][6][7][8][9][10][11][12][13] The process is simple, cost-effective, and ideally suited for applications such as via-hole filling 3 and Schottky/ohmic contact formation. 4,8 The process is also being used in combination with electroplating for applications such as metallization of glass packaged devices 4 and surface mount technology.…”

mentioning

confidence: 99%

“…Most earlier studies of AED on silicon (Si) have dealt with either amorphous, 6,7 porous, 8 or heavily etched/abraded crystalline substrates. 9,10 Further, AED studies related to crystalline silicon (c-Si) have mostly centered on Ni and Cu. 10,11 Thus in the context of AED on c-Si, polished substrates and Pd plating have not received sufficient attention except in a preliminary work 12 ; also, the effects of polarity and level of substrate doping on deposit adherence have not been studied.…”

mentioning

confidence: 99%

See 1 more Smart Citation

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

Karmalkar

Banerjee

1999

The solution in which Si is immersed for activation prior to autocatalytic electroless deposition (AED) of Ni, Cu, etc. is usually HF‐PdCl2‐normalHCl . 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 >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‐normalHCl bath creates a specific Pd‐ammine complex, most probably normalPdfalse(NH3)2 Cl2 , which gives Pd AED adhesions of ∼9 and 4 false(3false)×106N/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.