Atomic Layer Deposition of HfO₂ onto Si Using Hf(NMe₂)₄

Abstract

The temperature window for the atomic layer deposition (ALD) of HfO2 onto Si using Hf(NMe2)4 [tetrakis(dimethylamino)hafnium] as an Hf precursor was determined based on the thermal decomposition characteristics of Hf(NMe2)4, as observed by temperature-programmed decomposition in an ultra-high vacuum. The growth rate of the HfO2 obtained in the temperature window was ca. 1.2 Å/cycle. The prepared film had electrical properties suitable for use in complementary metal–oxide–semiconductor (CMOS) devices, showing an equivalent-oxide thickness (EOT) of 2.5 nm and a leakage current density of 1.3 ×10-6 A/cm2 at -1 V. The leakage current was three orders of magnitude lower than that of SiO2 with the same EOT. The lower current leakage was obtained because N atoms in the Hf(NMe2)4 formed an SiNx interlayer by reaction with the Si substrate during the ALD, as confirmed by in-situ X-ray photoelectron spectroscopy (XPS) and by the analysis of residue on the substrate after the decomposition of the Hf precursor.

Initial Stages of Atomic Layer Deposition of Tantalum Nitride on SiO2 and Porous Low-κ Substrates Modified by a Branched Interfacial Organic Layer: Chemisorption and the Transition to Steady-State Growth

“…One intriguing possibility that might resolve the outlier status of the SiO 2 surface annealed to 550 °C is the following. As indicated above, in previous work on the reaction of Hf[N(CH 3 ) 2 ] 4 with H-terminated Si, the formation of a SiN(CH 3 ) 2 species was suggested. First, if an annealed SiO 2 surface presents Si dangling bonds, in addition to −OH groups, then a highly oxidized Ta species such as (SiO) 3 Ta[N(CH 3 ) 2 ] 2 (cf.…”

“…The second, lower binding energy peak could represent N strongly bound to Ta, 58 or to Si in the substrate. 59 Considering the former, the spontaneous formation of TaN bonds in tantalum dialkylamido compounds has been observed, 54,60 though not for Ta[N(CH 3 ) 2 ] 5 . An expected route to TaN bond formation in Ta[N(CH 3 ) 2 ] 5 would create free CH 2 , an unlikely scenario.…”

“…Alternately, as stated above, the N(1s) peak at ∼397.4 eV could indicate N from a dissociated dimethylamido ligand bound to Si in the substrate, as is observed in the initial stages of HfO 2 ALD using Hf[N(CH 3 ) 2 ] 4 on H-terminated Si. 59 A higher amount of N−Si bonding on the low-κ substrates as compared to that on SiO 2 could be explained by the loss of alkyl groups at elevated temperatures, leaving residual Si atoms on the surface in a potentially more reactive state than the Si atoms in SiO 2 .…”

“…The marginally higher binding energy measured here can be attributed to the likely more oxidized state of the Ta center when it is chemisorbed on an oxygen containing surface. The second, lower binding energy peak could represent N strongly bound to Ta, or to Si in the substrate . Considering the former, the spontaneous formation of TaN bonds in tantalum dialkylamido compounds has been observed, , though not for Ta[N(CH 3 ) 2 ] 5 .…”

Interplay of Precursor and Plasma for The Deposition of HfO2 via PEALD: Film Growth and Dielectric Properties

“…Furthermore, chlorine containing precursors are prone to formation of etching by-products such as HCl that can interfere with the film growth and potentially damage the reactor. [28] As a halide-free alternative, the class of alkylamide containing Hf precursors namely [Hf(NMe 2 ) 4 ], [29][30][31][32] [Hf(NEt 2 ) 4 ], [30,33] and [Hf(NEtMe) 4 ] [30,34] have been commonly been used in thermal ALD processes. These compounds are known to possess limited long term thermal stability under the conditions that are adopted for ALD processes.…”