Electrical properties of ultrathin HfO2 films for replacement metal gate transistors, fabricated by atomic layer deposition using Hf(N(CH3)(C2H5))4 and O3

Abstract

Ultrathin HfO2 gate dielectric was fabricated by atomic layer deposition (ALD) technology using tetrakis(ethylmethylamino)hafnium {Hf[N(CH3)(C2H5)]4}, with O3 as an oxidant for use in replacement metal gate transistors. From secondary ion mass spectrometry analyses, the ALD process temperature was very important for the fabrication of high-quality HfO2 films. The dielectric constant with 275 °C deposition was higher than that at 200–250 °C. Furthermore, the VFB with 200 °C deposition was about 0.1–0.15 V lower than that at 275 °C, due to formation of high residual impurity concentrations, such as carbon, in the HfO2 films. The leakage current densities in the 275 °C case were reduced by about five orders with respect to reference SiO2 films. From these results, it was judged that the ALD process temperature of 275 °C was suitable for the fabrication of ultrathin HfO2 gate dielectrics necessary to improve the leakage current characteristics.

Atomic Layer Deposition of HfO2 Thin Films Employing a Heteroleptic Hafnium Precursor

“…[9] As discussed in the Introduction, the decomposition depends on the reactor design and process conditions. [7][8][9]11] This prompted us to carry out a comparative study using the compounds 1 and 2 with the same reactor and under identical process conditions to avoid any ambiguity. Apart from the ALD window, the surface-controlled selfterminated ALD growth behavior, and the linear dependence of film thickness on the number of ALD growth cycles, characterize a typical ALD process.…”

“…[9,10] Among the different Hf amides, the tetrakis-ethylmethylamido-hafnium (TEMAH) complex has been investigated in detail with various co-precursors such as H 2 O or O 3 . [7][8][9][10][11] There are various reports on the decomposition temperature of this precursor during an ALD process, and it was surmised that the decomposition depends on the reactor design and the process conditions. [7,8,11] A recent report highlighted that parasitic growth is associated with ALD using [TEMAH]/H 2 O owing to the limited thermal stability of the precursor.…”

“…[7][8][9][10][11] There are various reports on the decomposition temperature of this precursor during an ALD process, and it was surmised that the decomposition depends on the reactor design and the process conditions. [7,8,11] A recent report highlighted that parasitic growth is associated with ALD using [TEMAH]/H 2 O owing to the limited thermal stability of the precursor. [9] Surprisingly, the ALD characteristics of the other two closely related amides, namely tetrakisdiethylamido-hafnium (TEAH) or tetrakis-dimethylamidohafnium (TMAH), had not, until recently, been reported in detail.…”

Effects of Low Temperature O2 Treatment on the Electrical Characteristics of Amorphous LaAlO3 Films by Atomic Layer Deposition

“…Figure 6 shows the leakage current density scaling of both the as-deposited and post annealed LaAlO 3 films, compared with that of thermal SiO 2 films (27) and of HfO 2 films (28). The leakage current density of the oxygen post annealed capacitors is about four orders magnitude lower than that of thermal SiO 2 films, and one order magnitude higher than that of HfO 2 films.…”

Hafnium carbide formation in oxygen deficient hafnium oxide thin films

“…This concentration is comparably low to known carbon concentrations for ALD-grown films, which are in the range of 7·10 19 /cm³. 17 The source of carbon impurities in the here described experiments is residual graphite from the UHV chamber due to the use of carbon spray. The Hf source itself does not contain carbon contaminations as ruled out by SIMS studies.…”