Metallic Copper Thin Films Grown by Plasma‐Enhanced Atomic Layer Deposition of Air Stable Precursors

Abstract

The authors, report here on the deposition of metallic copper thin films by plasma-assisted atomic layer deposition (ALD) with an air stable and volatile precursor À [Cu((Py)CHCOCF 3 ) 2 ] 2 (Py ¼ pyridine) À that stands out due to its facile synthesis and easy handling under ambient conditions. Copper thin films are obtained by decomposing [Cu((Py)CHCOCF 3 ) 2 ] 2 in hydrogen plasma in a concomitant deposition and recrystallization process. The thermal stability of the precursor prevents thermally induced decomposition, which allows precise control over thickness and film homogeneity. Electrical measurements of the as-deposited samples show clear interdependence of sheet resistance on the substrates surface roughness, thereby, films with higher roughness show higher resistance. Combined X-Ray photoelectron spectroscopy of Cu 2p peak and Cu LMM peak, as well as resistivity values of 58 V & À1 confirm the high quality of copper films without the need of further annealing steps under reducing atmosphere.

Synthesis of β‐Ketoiminato Copper(II) Complexes and Their Use in Copper Deposition

“…As evidenced by SEM (scanning electron microscopy), the deposits are covered with separated spherical particles of Cu or CuO (sample A, substrate temperature 400°C, size 25 Ϯ 5.6 nm), whereas deposit C (reactive gas oxygen, substrate temperature 500°C) is composed of particles with an aspherical appearance of size distribution 39.4 Ϯ 20.3 nm. The island growth observed by the CVD experiments using 6 as precursor, is comparable with the layer topography obtained from copper(I) and copper(II) complexes of type [Cu(OCRCHC(Me)NCH 2 CH 2 NX 2 )(μ-OAc)] 2 [8] (R = Me, Ph; X = OMe, NMe 2 ), [Cu((py)CHCOCF 3 ) 2 ] 2 (py = pyridine) [73] and [Cu(hfac)(η 2 -H 2 C=CHC(CH 3 ) 3 ] [74] (hfac = 1,1,1,5,5,5hexafluoro-2,4-pentanedionate). The particle island growth characteristic for samples A-C might be based on the high thermal stability of 6 as evidenced by TG studies and hence the growth rate of the precursor might be adversely affected resulting in the formation of separated particles instead of layers.…”

“…In contrast, sample C exhibits more aspherical particles with larger diameters (39.4 Ϯ 20.3 nm) compared to sample A (25 Ϯ 5.6 nm) (Figure 8, Table 4), although the substrate temperature was maintained at 500°C, but oxygen was used as reactive gas during the deposition experiment (Table 4). The observed surface topography of samples A-C differs from deposition experiments performed with complexes such as [Cu(OCRCHC(Me) NCH 2 CH 2 NX 2 )(μ-OAc)] 2 [8] (R = Me, Ph; X = OMe, NMe 2 ), [Cu(hfac) 2 TMEDA] [10] (TMEDA = N,N,N',N'-tetramethylethylenediamine), [Cu((py)CHCOCF 3 ) 2 ] 2 (py = pyridine) [73] and [Cu(hfac)(η 2 -H 2 C=CHC(CH 3 ) 3 ]. [74] The films obtained from the latter precursors show closed Cu layers with a particulate surface, in contrast, complex 6 displays island growth (Figure 8), which can be ascribed to the lattice mismatch between copper and silicon, [73,75,76] or to the high thermal stability as well as decreased volatility of 6.…”

“…The morphology of samples D and E deviate from those ones obtained by using copper complexes as CVD and spin-coating precursors, for example, [Cu(OCRCHC(Me) NCH 2 CH 2 NX 2 )(μ-OAc)] 2 [8] (R = Me, Ph; X = OMe, NMe 2 ), [Cu(hfac) 2 TMEDA], [10] [Cu(OAc) 2 ], [27] [Cu((py) CHCOCF 3 ) 2 ] 2 [73] or [Cu(hfac)(η 2 -CH 2 =CHC(CH 3 ) 3 )], [74] resulting in closed layer formation with a granular surface, whereas sample D exhibit solely aspherical particles at the top of the substrate and sample E did not result in any layer formation.…”

Plasma Enhanced Atomic Layer Deposition of Plasmonic TiN Ultrathin Films Using TDMATi and NH3

“…Such a peak is indicative of four possible chemistries: 1) SiO2 which has an O 1s peak at 532.9 eV, 2) organic C-O Unique from traditional plasmonic metals, TiN has variable optical properties in the near-IR and visible regions. One method of tuning the optical properties is through high-temperature annealing in vacuum, which results in a more metallic film, a down-shift in ε 1 and may reduce ε 2 [3,29,30]. However, high-temperature anneals are not ideal for all applications and, therefore, having a low-temperature post-deposition treatment to achieve varied optical properties is advantageous.…”

“…However, high-temperature anneals are not ideal for all applications and, therefore, having a low-temperature post-deposition treatment to achieve varied optical properties is advantageous. One alternative to high-temperature annealing is plasma post-treatment, which has been demonstrated previously with ALD metal films to modify the surface and decrease resistance [29]. Yun et al [30] report a H 2 /N 2 plasma post-deposition treatment that reduced surface oxygen contamination as well as carbon contamination throughout ALD TiN films that had been exposed to air for 30 days.…”