W-B-N diffusion barriers for Si/Cu metallizations

Reid, J.S.; Liu, R.Y.; Smith, Paul Martin; Ruiz, R.; Nicolet, M.‐A.

doi:10.1016/0040-6090(94)05810-5

Cited by 42 publications

(22 citation statements)

References 17 publications

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“…Considering the as-deposited structure, all the films present an amorphous structure characterised by two broad X-ray peaks of low intensity as already reported [5]. In the single film, W 60 B 17 N 23 , signs of crystalinity were detected, which could be indexed as bcc a-W (ICDD 4-0806).…”

Section: As-deposited Coatingsmentioning

confidence: 66%

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W-B-N sputter-deposited thin films for mechanical application

Louro

Lamni

Lévy

2005

Surface and Coatings Technology

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The structure, composition and hardness of reactively sputtered W-B-N thin films were investigated by XRD, EPMA, and Vickers ultramicroindentation.The chemical composition of the films was changed from W 80 B 20 to W 42 B 9 N 49 by varying the partial pressure of N 2 . All the as-deposited coatings were amorphous, except the W 60 B 17 N 23 film, which showed crystalline peaks, indexed as bcc a-W, overlapping the amorphous feature. This nanocomposite structure lead to a maximum as-deposited hardness of 36 GPa.The coatings were thermally annealed at 850 and 950 8C in Ar/H 2 atmosphere. All the films crystallised with the formation of the bcc a-W and/or the fcc-W 2 N phases, depending on their B and N contents. A small increase in hardness was registered for 850 8C annealing temperature in comparison to the as-deposited state. However, an inverse trend was detected after post-annealing at 950 8C, which was more evident for the high N content films. This behaviour was attributed to the formation of a soft external layer of boron nitride poorly crystallised. D

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Section: As-deposited Coatingsmentioning

confidence: 66%

“…Compared to sputtered Ti-B-N coatings, little research work has been carried out on the W-B-N system. The few exploratory investigations [5][6][7][8] showed that this ternary system is an excellent diffusion barrier, due to a dense amorphous structure, relatively high crystallisation temperature and chemical inertness.…”

Section: Introductionmentioning

confidence: 99%

W-B-N sputter-deposited thin films for mechanical application

Louro

Lamni

Lévy

2005

Surface and Coatings Technology

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“…Many studies used p-n diodes with Cu layers to evaluate different materials for their diffusion barrier properties. [33][34][35][36][37][38][39][40][41][42][43][44][45][46] Among them, Baumann et al 46 studied the impact of Cu on the leakage current of p + -n diode with and without barrier layers. For the case where Cu was in direct contact with 3 Si silicide spikes were clearly observed by TEM-EDS after annealing the device at 120…”

Section: Figures 4a and 4b Show The 200mentioning

confidence: 99%

A Study on the Long-Term Degradation of Crystalline Silicon Solar Cells Metallized with Cu Electroplating

Huang¹,

Reuter²,

Zhu³

et al. 2015

ECS J. Solid State Sci. Technol.

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While using Cu electroplating to metallize silicon cells is of great interest, the long term reliability of such cells have not been well understood. In this paper silicon solar cells metallized with electroplated Cu were thermally stressed. The cell performance was characterized in conjunction with microscopic structure analysis to understand the long-term degradation mechanism and the effect of each different metal layer. The Ni silicide layer had little impact on the performance degradation at 200 • C. Increasing the thickness of a second Ni layer between the silicide and Cu significantly delayed this degradation, acting as a diffusion barrier. A series of cells annealed at different temperatures were used to extrapolate the degradation kinetics. Two different mechanisms were observed. Further silicidation of the second Ni layer was observed and was believed to cause the degradation at a higher temperature of 250 • C. However, this silicidation reaction rate dropped quickly as the temperature decreased and Cu diffusion became the dominant mechanism for cell degradation at temperatures below 200 • C. These two different mechanisms cross over at about 200 • C in this study, where both silicidation and Cu diffusion were observed. An improvement in the cell lifetime by replacing pure Ni with NiCo alloy was studied. In the standard manufacturing process flow of silicon solar cells, the front grids are formed with Ag screen printing. Replacing the screen-printed Ag with electroplated high aspect ratio Cu line has been proposed decades ago.1,2 This method has been of great interest primarily because of the lower conductivity and higher cost of Ag paste. In addition, the plated Cu potentially allows a higher aspect ratio or a smaller shadowing of the front grid and thus enables higher cell efficiencies. More importantly, the most recent development in laser patterning of the front grid allows an easy integration of the electroplating on the selective emitter formed by laser doping. [3][4][5] Different Cu metallization schemes have been reported before. 6,7 The schemes included electroless deposition of Ni and silicidation, [8][9][10] Cu electrodeposition on printed thin seed layer, 11 and electrodeposition of Ni and Cu.12-14 Among them, most of the schemes involve the formation of Ni silicide by annealing either electroless or electrolytic deposited Ni. The main purpose of the silicide is to lower the contact resistance between the metal and emitter and thus to improve the cell performance.Ni silicidation has been extensively studied for the application in complementary metal oxide semiconductor (CMOS) contacts. [15][16][17] Ni 2 Si silicide formation starts at as low as about 300• C, followed by monosilicide phases at around 400• C and silicon rich phases at above 800• C. However, small amount of Ni-richer phases such as Ni 3 Si and Ni 5 Si 2 could be observed at as low as 200• C. 15 All the studies for CMOS applications were performed on extremely thin Ni films fabricated using vacuum deposition. The silicide forme...

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“…Figure 2 shows the dependence of the Si content and the deposition thickness per cycle on the SiH 4 /NH 3 ratio. In this experiment, SiH 4 and NH 3 were simultaneously supplied in the sequence of the TDMAT pulse for 5 s and the SiH 4 /NH 3 pulse for 10 s. The Si content increases as the SiH 4 /NH 3 ratio increases and is saturated at 23 at. %.…”

mentioning

confidence: 99%

“…Amorphous refractory ternary metals such as ͑Ti, Ta, W͒-Si-N, W-B-N do not have fast diffusion paths such as a grain boundary present in polycrystalline materials and are promising candidates for these applications. 3,4 These diffusion barriers need to be deposited with good step coverage, especially on the sidewall, as the aspect ratio of contact/via/ trench increases.…”

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confidence: 99%

Metal–organic atomic-layer deposition of titanium–silicon–nitride films

Min

Park

Kang

1999

Applied Physics Letters

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Titanium-silicon-nitride films were grown by metal-organic atomic-layer deposition at 180°C. When silane was supplied separately in the sequence of a tetrakis͑dimethylamido͒ titanium pulse, silane pulse, and ammonia pulse, the Si content in the deposited films and the deposition thickness per cycle remained almost constant at 18 at. % and 0.22 nm/cycle, even though the silane partial pressure varied from 0.27 to 13.3 Pa. Especially, the Si content dependence is strikingly different from the conventional chemical-vapor deposition. The capacitance-voltage measurement revealed that the Ti-Si-N film prevents the diffusion of Cu up to 800°C for 60 min.Step coverage was approximately 100% even on the 0.3 m diam hole with slightly negative slope and 10:1 aspect ratio. © 1999 American Institute of Physics. ͓S0003-6951͑99͒01137-7͔As the minimum feature size of semiconductor devices shrinks, the Cu diffusion barrier must be effective even when it is as thin as 10 nm because thick diffusion barriers leave little space for Cu, and thus, nullify the advantage of Cu metallization.1,2 In this respect, more effective Cu diffusion barrier materials with a thinner thickness are required. Amorphous refractory ternary metals such as ͑Ti, Ta, W͒-Si-N, W-B-N do not have fast diffusion paths such as a grain boundary present in polycrystalline materials and are promising candidates for these applications.3,4 These diffusion barriers need to be deposited with good step coverage, especially on the sidewall, as the aspect ratio of contact/via/ trench increases.Metal-organic atomic-layer deposition ͑MOALD͒ achieves near-perfect step coverage and can control precisely the thickness and composition of grown films. 5 We have already demonstrated that TiN film could be grown with excellent conformality by MOALD using tetrakis͑ethylmethyl-amido͒titanium and NH 3 .6 However, MOALD of a ternary system may not be as easy to demonstrate as much as it is for a binary system and may not be understood straightforwardly in terms of chemical composition and growth kinetics. Therefore, in the present study, we have developed a MOALD technique for ternary Ti-Si-N films using a sequential supply of Ti͓N͑CH 3 ͒ 2 ͔ 4 ͓tetrakis͑dimethylamido͒ titanium: TDMAT͔, silane (SiH 4 ), and ammonia (NH 3 ), and evaluated the Cu diffusion barrier characteristics of a 10 nm Ti-Si-N film with high-frequency small-signal capacitance-voltage (C -V) measurements.A MOALD apparatus was used to grow Ti-Si-N films, which is schematically similar to the one described previously. 6 All the films were grown on SiO 2 ͑100 nm͒/Si wafers at the substrate temperature of 180°C and with the reactor pressure maintained at 133 Pa. TDMAT was delivered from the bubbler ͑30°C͒ to the reactor using Ar ͑70 sccm͒ as a carrier gas. Also, the flow rates of NH 3 and SiH 4 ͑forming gas with 10% SiH 4 /90% Ar͒ diluted in Ar were fixed at 70 sccm. The film thicknesses were measured by the surface profilometer. The composition of the grown film was analyzed using 9.0 MeV Cl 5ϩ elastic recoil detection...

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W-B-N diffusion barriers for Si/Cu metallizations

Cited by 42 publications

References 17 publications

W-B-N sputter-deposited thin films for mechanical application

W-B-N sputter-deposited thin films for mechanical application

A Study on the Long-Term Degradation of Crystalline Silicon Solar Cells Metallized with Cu Electroplating

Metal–organic atomic-layer deposition of titanium–silicon–nitride films

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