Comparison of Ligand Architecture on Vapor Deposition Precursors: Synthesis, Characterization, and Reactivity of Volatile Cadmium Bis-Amidinate Complexes

Abstract

The lack of low-temperature (<200 °C) and easy-to-handle vapor deposition precursors for cadmium has been a limitation for cadmium chalcogenide ALD. Here, the cadmium amidinate system is presented as a scaffold for vapor deposition precursor design because the alkyl groups can be altered to change the properties of the precursor. Thus, the molecular structure affects the precursor stability at elevated temperature, onset of volatility, and reactivity. Cadmium bis-N,N-diisopropylacetamidinate (1) was synthesized and evaluated for its thermal stability, volatility, and reactivity–properties relevant to ALD precursors. Compounds 2, cadmium bis-N,N-diisopropyltertertiarybutylamidinate, and 3, cadmium bis-N,N-diisopropylbutylamidinate, are analogous to 1 and were synthesized by substituting the alkyl group on the bridging carbon during amidinate synthesis. All three compounds are volatile under reduced pressure, and thermal stability studies showed 1 and 3 to be stable at 100 °C in solution for days to weeks, while 2 decomposed at 100 °C within 24 h. Solution phase reactivity studies show 1 to be reactive with thiols at room temperature in a stoichiometric manner. No reactivity with either bis-silyl sulfides or alkyl sulfides was observed up to 110 °C over more than 3 days. Overall, the cadmium amidinate compounds presented here show potential as precursors in ALD/CVD processing, which can contribute to research critical for semiconductor processing.

Synthesis, characterisation and reactivity of a zinc triazenide for potential use in vapour deposition

“…A previous report on Cd( ii ) amidinates presented a reactivity study with triphenylsilanethiol, to mimic a thiol-terminated surface in CdS ALD. 32 The S–H represents the surface-bound thiol while the bulky triphenylsilane-part represents the substrate surface. Thus, mixing solutions of the potential metal precursor and the thiol mimics the ALD half-cycle where the metal precursor is introduced into an ALD chamber to react with the thiol-terminated substrate.…”

Group 11–14 Triazenides : Synthesis, characterization, and thermal evaluation for use in chemical vapor deposition

“…In one such study, amidinates of Cd(II) were reacted with triphenylsilanethiol and the resulting products were characterized and their thermal properties were evaluated. 103 The bulky triphenylsilane is meant to model the substrate surface and the thiol group the surface SH functionality in sulfide ALD.…”

Synthesis, X-ray Diffraction, NMR and Thermolysis Studies of Cadmium Tin Sulfido Complexes

“…The synthesis pathway is related to the synthesis of zinc tin chalcogenido complexes [32] which are accessible by reaction of the zinc complex [(tmeda)Zn(SSiMe 3 ) 2 ] [33] with a diorganotin acetate. Here, we use the cadmium analogue [(tmeda)Cd(SSiMe 3 ) 2 ] as well as similar tmeda-stabilized cadmium silylsulfido complexes [34,35] to generate a Cd-S-Sn structural motif.…”