Plasma-enhanced atomic layer deposition and etching of high-k gadolinium oxide

Abstract

Atomic layer deposition (ALD) of high-quality gadolinium oxide thin films is achieved using Gd(iPrCp)3 and O2 plasma. Gd2O3 growth is observed from 150 to 350 °C, though the optical properties of the film improve at higher temperature. True layer-by-layer ALD growth of Gd2O3 occurred in a relatively narrow window of temperature and precursor dose. A saturated growth rate of 1.4 Å/cycle was observed at 250 °C. As the temperature increases, high-quality films are deposited, but the growth mechanism appears to become CVD-like, indicating the onset of precursor decomposition. At 250 °C, the refractive index of the film is stable at ∼1.80 regardless of other deposition conditions, and the measured dispersion characteristics are comparable to those of bulk Gd2O3. XPS data show that the O/Gd ratio is oxygen deficient at 1.3, and that it is also very hygroscopic. The plasma etching rate of the ALD Gd2O3 film in a high-density helicon reactor is very low. Little difference is observed in etching rate between Cl2 and pure Ar plasmas, suggesting that physical sputtering dominates the etching. A threshold bias power exists below which etching does not occur; thus it may be possible to etch a metal gate material and stop easily on the Gd2O3 gate dielectric. The Gd2O3 film has a dielectric constant of about 16, exhibits low C–V hysteresis, and allows a 50 × reduction in gate leakage compared to SiO2. However, the plasma enhanced atomic layer deposition (PE-ALD) process causes formation of an ∼1.8 nm SiO2 interfacial layer, and generates a fixed charge of −1.21 × 1012 cm−2, both of which may limit use of PE-ALD Gd2O3 as a gate dielectric.

Reaction Chemistry during the Atomic Layer Deposition of Sc2O3 and Gd2O3 from Sc(MeCp)3, Gd(iPrCp)3, and H2O

“…For the ALD of Gd 2 O 3 and Gd-containing ternary oxide films such as GdAlO 3 , GdHfO x , and GdScO 3 , Gd(MeCp) 3 (MeCp = methyl-cyclopentadienyl), and Gd( i PrCp) 3 ( i PrCp = isopropyl-cyclopentadienyl) precursors have been explored in combination with H 2 O as the oxidizing agent. ,, Niinistö et al reported that Gd 2 O 3 processes using Gd(MeCp) 3 and H 2 O at deposition temperatures of 175–300 °C showed nonideal ALD behavior . By contrast, Vitale et al found that ALD behavior was observed for a Gd 2 O 3 process when Gd( i PrCp) 3 was used in combination with an O 2 plasma at a reactor temperature of 250 °C . However, at higher temperatures above 300 °C, the growth mechanism changed to CVD.…”

Vertical-probe-induced asymmetric dust oscillation in complex plasma

“…When macroscopic dust is introduced into a plasma, the resulting complex plasma system offers the opportunity to simulate, at its most fundamental level, interesting physics pertaining to a host of research areas, including protoplanetary [1] or protostellar [2] development, contamination in plasma enhanced semiconductor atomic layer deposition and etching systems [3], and wall erosion within a fusion device [4]. At low temperature and power, it also provides a basis for the study of entirely new plasma physics.…”

Impact of gadolinium doping into the frustrated antiferromagnetic lithium manganese oxide spinel

“… 35 , 38 Variation in the peaks of Mn 3+ and Mn 4+ can be attributed to the Gd interaction with the Mn ion. Gd 4d core level shows three peaks at 141.12 eV, 146.34 eV, and 153.14 eV assigned to the Gd metal peak (LiMn 1.95 Gd 0.5 O 4 ), Gd-Ox, and Gd satellite peak, respectively, as shown in Figure 4 E. 36 The oxide form supports the presence of Gd(lll) species. 37 The deconvoluted O 1s spectrum displayed in Figure 4 C indicates two peaks at 529.7 and 531.4 eV owing to the surface oxygen present in Mn or Gd Oh sites and Li Td sites, respectively.…”

“… 34 Upon increasing Gd doping, the high intense XRD peak of pristine LMO is shifted to higher 2θ (inset Figure 1 ) due to higher ionic radii of Gd 3+ ion, which further confirms the substitution of Gd ion in place of Mn. 36 Morphological variation in LMO upon Gd doping was observed in the TEM images ( Figures 2 A–2F). In Figure 2 D, Gd04 exhibits minute granular structures due to high Gd doping compared to pristine LMO.…”

“…Figure 4 C shows the binding energies of Mn 3+ are deconvoluted at 641.82 eV (Mn 2p 3/2 ) and 653.58 eV (Mn 2p 1/2 ), whereas Mn 4+ shows deconvoluted peaks at 645.32 eV (Mn 2p 3/2 ) and 657.54 eV (Mn 2p 1/2 ). 36 , 37 Figure 4 G indicates the binding energies of Gd-doped LMO for Mn 3+ at 641.58 (Mn 2p 3/2 ) and 653.26 (Mn 2p 1/2 ) and for Mn 4+ at 645.02 (Mn 2p 3/2 ) and 657.34 (Mn 2p 1/2 ). 35 , 38 Variation in the peaks of Mn 3+ and Mn 4+ can be attributed to the Gd interaction with the Mn ion.…”