In Situ Reaction Mechanism Study on Atomic Layer Deposition of Intermetallic Co₃Sn₂ Thin Films

Abstract

In this work, a growth mechanism of an intermetallic Co3Sn2 thin film is studied in situ with a quartz crystal microbalance (QCM) and quadrupole mass spectrometer (QMS). The film is deposited by atomic layer deposition (ALD) from CoCl2(TMEDA) and Bu3SnH precursors (TMEDA = N,N,N′,N′-tetramethylethylenediamine). Balanced reaction equations are resolved by fitting the QMS and QCM data, and a step-by-step growth mechanism is determined for the process. During the CoCl2(TMEDA) pulse, only 1-chlorobutane is formed as a byproduct. However, during the Bu3SnH pulse, two byproducts, BuCl and Bu3SnCl, were clearly detected, indicating that two competing reaction pathways exist during that pulse. Preliminary studies on another intermetallic ALD process, Ni3Sn2, revealed that the reactions occur similarly as in the Co3Sn2 process.

Cobalt Metal ALD: Understanding the Mechanism and Role of Zink Alkyl Precursors as Reductants for Low Resistivity Co Thin Films

“…In the beginning, the reaction of gaseous CoCl2(TMEDA) with the surface might be best described by physisorption of CoCl2 with release of the coordinating TMEDA as shown in (I) and suggested in recent ALD literature. 45 When Zn(DMP)2 is then pulsed in after a purge, it may engage in ligand exchange reactions with surface adsorbed CoCl2 producing an intermediate Co(II) aminoalkyl species and ZnCl2 (II). ZnCl2 would leave the surface as a volatile by-product.…”

“…43 To address this crucial drawback, we present for the first time the ALD of metallic, Zn-free Co thin films using, intramolecularly stabilized Zn precursor Zn(DMP)2 44 (DMP = N,N-3-(dimethylamino)propyl) with the Co precursor CoCl2(TMEDA) (TMEDA = N,N,N',N'-tetramethylethylenediamine) that has previously been used for ALD of intermetallic thin films. 45,46 The precursor pair was chosen based on the precedence for the formation of thermally labile Co(DMP)2 species in solution, 47 a bulk reactivity study with the neat reagents, as well as matching thermal properties that facilitate their usage in an F-120 ALD reactor. As a first step, a reactivity screening of several potential precursor combinations (see Scheme 1) comprising the wellknown Zn(Et)2 43 as well as its less known amine stabilized congener Zn(Et)2(TMEDA) 48 is carried out.…”

Highly conductive and stable Co9S8 thin films by atomic layer deposition: from process development and film characterization to selective and epitaxial growth

“…32 The neutral TMEDA adduct ligand makes the non-volatile cobalt(II) chloride volatile, while it has little effect on the deposition chemistry. 32,34 Thermodynamically, the reactions between CoCl2 and H2S producing cobalt sulfide in different possible stoichiometries (Co9S8, CoS, Co3S4, and CoS2) are favorable with similar ∆G values of approximately -125 to -145 kJ/mol of CoCl2 at 180-300 °C (Section S1 in the Supporting Information). Thus, the corresponding ALD surface reactions of our process are also likely to be very favorable.…”

“…32 ) and Co3Sn2 (Ref. 33,34 ) thin films. In this article, CoCl2(TMEDA) is used with H2S to deposit crystalline Co9S8 films with a low resistivity on the order of 100 μΩcm.…”

Cobalt Metal ALD: Understanding the Mechanism and Role of Zinc Alkyl Precursors as Reductants for Low-Resistivity Co Thin Films

“…To address this crucial drawback, we present for the first time the ALD of metallic, Zn-free Co thin films using intramolecularly stabilized Zn precursor Zn­(DMP) 2 (DMP = N , N -3-(dimethylamino)­propyl) with the Co precursor CoCl 2 (TMEDA) (TMEDA = N , N , N ′, N ′-tetramethylethylenediamine) that has previously been used for ALD of intermetallic thin films. , The precursor pair was chosen based on the precedence for the formation of thermally labile Co­(DMP) 2 species in solution and a bulk reactivity study with the neat reagents, as well as matching thermal properties that facilitate their usage in an F-120 ALD reactor. As a first step, a reactivity screening of several potential precursor combinations (see Scheme ) comprising the well-known Zn­(Et) 2 as well as its less-known amine-stabilized congener Zn­(Et) 2 (TMEDA) is carried out.…”