Electroless nickel deposition and silicide formation for advanced front side metallization of industrial silicon solar cells

Tous, Loïc; Dorp, Dennis H. van; Russell, Richard; Das, J.; Aleman, Monica; Bender, Hugo; Meersschaut, Johan; Opsomer, Karl; Poortmans, Jozef; Mertens, R.

doi:10.1016/j.egypro.2012.05.006

Cited by 37 publications

(27 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…When a small amount of Ni was present in the Co film, silicide formation became easier than for pure Co. While no silicidation occurred for Ni 3 Co 97 and Ni 15 Co 85 during annealing at 450…”

Section: Resultsmentioning

confidence: 99%

“…[6][7][8][9][10][11][12][13][14][15][16][17] Most of these schemes involve the formation of Ni silicide either from electroless or electrolytic deposited Ni. [8][9][10][11][12][15][16][17] The electrolytic deposition process in these reports typically involves light, so called light induced or light assisted electrodeposition. The formation of silicide lowers the contact resistance between the metal and Si 18 and thus improves the solar cell performance.…”

mentioning

confidence: 99%

See 1 more Smart Citation

A Study on the Electrodeposition and Silicidation of Nickel-Cobalt Alloys for Silicon Photovoltaic Cell Metallization

Huang¹

2015

ECS J. Solid State Sci. Technol.

View full text Add to dashboard Cite

Metallization of silicon solar cells using electroplating is of interest recently as a cheaper replacement of silver screen printing. Light assisted electroplating of Nickel-Cobalt (NiCo) alloys were studied on crystalline silicon (Si) solar cells in this paper. The effect of illumination was investigated in conjunction with the light absorption properties of the plating solution, emission spectrum of the light source as well as the plating current. A solution dependent threshold light intensity was observed, beyond which the solar cells were under reverse bias during electroplating. The detailed compositional depth profiles of the silicide layer were studied along the silicidation reaction using microscopic energy dispersive X-ray spectrum (EDS). A significant improvement in the performance degradation at high temperature thermal stress was observed for solar cells metalized with the ternary silicide. The cost of solar energy compared with fossil fuel is one of the key determining parameters in its adoption by the market. Therefore, ways of saving the manufacturing cost of silicon solar cells are of great interest. The current manufacturing process involves a screenprinting process to metalize the front side with silver paste. While the screen-printing process has been integrated into the process flow with standard tooling, it typically suffers from conversion loss due to the low conductivity of the paste and low line height-width aspect ratio. In addition, the high price of silver potentially limits the cost reduction of the solar cell.Replacing the screen-printed Ag with electroplated high aspect ratio Cu grids has been proposed decades ago.1,2 This method has recently gained more attention due to the high price of Ag and the easy integration of Cu electroplating with laser patterning. The selective emitter formed by the in-situ doping during laser patterning 3-5 further eases the process control for metallization and has the potential to improve the conversion efficiency of the solar cell.Different Cu metallization schemes involving electroplating have been reported. [6][7][8][9][10][11][12][13][14][15][16][17] Most of these schemes involve the formation of Ni silicide either from electroless or electrolytic deposited Ni. [8][9][10][11][12][15][16][17] The electrolytic deposition process in these reports typically involves light, so called light induced or light assisted electrodeposition. The formation of silicide lowers the contact resistance between the metal and Si 18 and thus improves the solar cell performance. Ni and Co silicidation has been extensively studied for the application in complementary metal oxide semiconductor (CMOS) contacts.18-23 The Ni silicidation starts at as low as 300• C for metal rich phases, followed by monosilicide phases around 400• C and silicon rich phases above 800• C. 18 Co silicidation follows a similar phase evolution but at a higher temperature. 24 While the low resistive Co disilicide was originally used in CMOS it suffers from poor nucleation rate and interface roughne...

show abstract

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

A Study on the Electrodeposition and Silicidation of Nickel-Cobalt Alloys for Silicon Photovoltaic Cell Metallization

Huang¹

2015

ECS J. Solid State Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…It is typical for a thin layer of Ni to be deposited as a barrier layer, and annealed at 250°-450°C to form nickel silicide for contact resistance and adhesion purposes [9]. In the event that this layer is formed non-optimally or fails as a diffusion barrier, cells can exhibit catastrophic shunting.…”

Section: Introductionmentioning

confidence: 99%

Electrical characterization of thermally-formed nickel silicide for nickel-copper plated solar cell contacts

Karas

Kim

Michaelson³

et al. 2015

2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC)

View full text Add to dashboard Cite

Plated copper is being considered as an alternative to screenprinted silver for the front contacts of crystalline silicon solar cells. Generally, a thin nickel layer, annealed to form nickel silicide is used to improve contact resistance and adhesion of the contact to silicon. Nickel layers can also be used to prevent the detrimental diffusion of copper into the cell. One challenge to the commercialization of plated copper contacts is the potential for this nickel barrier to fail, causing catastrophic local electrical shunts of the cell. In this work, we monitor shunting during a thermal stress test to evaluate the adequacy of nickel diffusion barrier layers and identify different mechanisms by which Ni-Cu plated cells may become shunted.

show abstract

“…4 Upon sintering, a low-resistivity, Ohmic contact is formed which enables the use of optimum, lowly-doped homogeneous emitters. 5 Cu serves as electrical conductor and the Ag (or Sn) capping layer enables the soldering of the individual cells, during panel assembly.…”

mentioning

confidence: 99%

Light-Induced Electrochemical Deposition of Ni for Si Solar Cell Processing

Dorp

Sniekers

Bonneux

et al. 2014

ECS Solid State Letters

Self Cite

View full text Add to dashboard Cite

This work outlines the general electrochemical features of the Ni light-induced deposition process. Typical observations for the deposition on textured solar cells are discussed and compared to planar n-Si (100) electrodes. The electrochemical measurements clearly show that after nucleation, Ni-on-Ni deposition is favored over Ni-on-Si, resulting in hemispherical growth. This observation is attributed to a kinetic effect and may be a disadvantage for the growth of ultra-thin contacting layers. In addition, the simultaneous metallization of fingers and busbars shows a significant non-uniformity due to an inevitable variation in current distribution which leads to an enhanced deposition rate for the narrowest features.The front side metallization of industrial silicon solar cells is currently based on screen printed silver (Ag) contacts which are fired through the front anti-reflection coating (ARC). One of the disadvantages of producing conductive lines with this method is that the resistivity of these lines is high as compared to bulk metal, mainly due to the use of glass based filling materials. 1 The fact that Ag contributes significantly to the costs of the metallization process and the troublesome printing of narrow lines, induced the development of alternative routes. 2 More recently, alternative processes are being developed that use a metal silicide as contacting layer and Cu as the main conductor. 3 In previous work we reported on the development of a relatively simple metallization scheme for crystalline silicon solar cells consisting of: 1) defining the front-contact pattern by laser ablation of the ARC; 2) deposition of Ni/Cu/Ag in a single plating sequence; and, finally, 3) sintering in N 2 for nickel silicidation. 4 Upon sintering, a low-resistivity, Ohmic contact is formed which enables the use of optimum, lowly-doped homogeneous emitters. 5 Cu serves as electrical conductor and the Ag (or Sn) capping layer enables the soldering of the individual cells, during panel assembly.Unlike the more expensive physical vapor deposition (PVD) techniques, electrochemical metallization allows for self-aligned deposition, i.e. deposition occurs selectively on areas where the semiconductor is exposed to solution. A common technique used for depositing contact layers is light induced plating (LIP). 6-9 So far, little attention has been focused on the (photo)electrochemistry of the solar cell metallization process. In this letter we discuss the basic electrochemistry of n-type Si (100) in nickel-containing solutions and light-induced deposition on pyramid-textured silicon solar cells. The implications of kinetic effects during contact/seed layer deposition are discussed. ExperimentalFor the Ni bath a nickel sulphamate solution (Rohm and Haas) and boric acid (Merck, p.a. grade) was used. The concentration was fixed to 0.62 M for both components. The pH of the solution was 3.9.The electrochemical measurements were performed using a standard three-electrode setup with the Si substrate as the working electrode, a Pt cou...

show abstract

Electroless nickel deposition and silicide formation for advanced front side metallization of industrial silicon solar cells

Cited by 37 publications

References 8 publications

A Study on the Electrodeposition and Silicidation of Nickel-Cobalt Alloys for Silicon Photovoltaic Cell Metallization

A Study on the Electrodeposition and Silicidation of Nickel-Cobalt Alloys for Silicon Photovoltaic Cell Metallization

Electrical characterization of thermally-formed nickel silicide for nickel-copper plated solar cell contacts

Light-Induced Electrochemical Deposition of Ni for Si Solar Cell Processing

Contact Info

Product

Resources

About