Development of Lanthanide Precursors as Dopants for Advanced High-k Materials

Abstract

In an effort to replace SiO2 as a gate dielectric, many high-k materials are under evaluation. Rare earth oxides have demonstrated potential to be used as dopants in electronic devices such as gate oxides in CMOS transistors or in DRAM trench capacitors. This interest is motivated by their relatively high-k value and their compatibility with silicon. This work evaluated several lanthanide precursors by TGA and DSC to determine their thermal properties and select promising molecules to be tested in atomic layer deposition (ALD). Then, important process characteristics such as growth rate and process window were then evaluated by ALD. Relatively high growth rates were observed varying from 0.37 A/cycle with Pr(EtCp)3 to 0.65 A/cycle with Dy(iPrCp)3. No obvious trend for the growth rate as a function of the atomic number was found.

Solid-Phase Epitaxy of Perovskite High Dielectric PrAlO3 Films Grown by Atomic Layer Deposition for Use in Two-Dimensional Electronics and Memory Devices

“…) 3 observed here is higher than that reported previously (250 °C) 33 and is higher than the ∼330 °C value reported for Pr(C 5 H 4 Et) 3 . 31 The TGA trace conducted under a nitrogen atmosphere showed a single step weight loss (Figure S1), with <10% nonvolatile residue at 500 °C, consistent with the earlier report.…”

“…The thermogravimetric analysis (TGA) of Pr(C 5 H 4 iPr) 3 indicated that it is more volatile than Pr(C 5 H 4 Et) 3 and PrCp 3 . 33 The ALD growth of Pr 2 O 3 was reported by using Pr(C 5 H 4 iPr) 3 and ozone at 200−250 °C. 33 The growth rate was 0.4 Å/cycle between 200 and 250 °C.…”

“…33 The growth rate was 0.4 Å/cycle between 200 and 250 °C. 33 Recently, volatile lanthanide complexes containing N,N-dimethylaminodiboranate ligands, 34,35 donor-functionalized alkoxide ligands, 36 and guanidinate ligands 37 have been reported, and several were used to deposit selected lanthanide oxides by ALD. However, the deposition of PrO x films from any of these precursors has not been reported.…”

Evaluation of Volatility and Thermal Stability in Monomeric and Dimeric Lanthanide(III) Complexes Containing Enaminolate Ligands

“…9,73 Finally, the ALD growth of Pr 2 O 3 films using Pr(C 5 H 4 iPr) 3 and ozone showed an ALD window from 200 to 250 °C, suggesting that not all lanthanide cyclopentadienyl precursors have high upper temperature limits for self-limited growth. 74 Precursors containing alkoxide, bis(trimethylsilylamide), and amidinate ligands have been evaluated as precursors for the growth of lanthanide oxide films but exhibit problems that include lack of self-limiting growth, low decomposition temperatures, variable reactivity toward water, and impurity incorporation in the films. 29 Precursors containing new ligands such as guanidi-nate 40 and malonate 29 are promising.…”

“…However, the close similarity of the p K a values for water (p K a = 14.00, 15.7) and cyclopentadiene (p K a = 16) may lead to a low reactivity of lanthanide cyclopentadienyl precursors with water in oxide growth. Moreover, the ALD growth of some lanthanide cyclopentadienyl precursors with water does not exhibit self-limited growth. , Finally, the ALD growth of Pr 2 O 3 films using Pr­(C 5 H 4 iPr) 3 and ozone showed an ALD window from 200 to 250 °C, suggesting that not all lanthanide cyclopentadienyl precursors have high upper temperature limits for self-limited growth . Precursors containing alkoxide, bis­(trimethylsilylamide), and amidinate ligands have been evaluated as precursors for the growth of lanthanide oxide films but exhibit problems that include lack of self-limiting growth, low decomposition temperatures, variable reactivity toward water, and impurity incorporation in the films .…”