Ruthenocenes and Half‐Open Ruthenocenes: Synthesis, Characterization, and Their Use as CVD Precursors for Ruthenium Thin Film Deposition

Abstract

Consecutive synthesis methodologies for the preparation of a series of trimethylsilyl and tert‐butyl‐substituted ruthenocenes of the type Ru(η5‐C5H3R1R2)(η5‐C5H3R3R4) (2, R1 = SiMe3, R2 = R3 = R4 = H; 3, R1 = R3 = SiMe3, R2 = R4 = H; 4, R1 = R2 = R3 = SiMe3, R4 = H; 5, R1 = R2 = R3 = R4 = SiMe3; 6, R1 = R3 = tBu, R2 = R4 = H; 7, R1 = R3 = tBu, R2 = SiMe3, R4 = H; 8, R1 = R3 = tBu, R2 = R4 = SiMe3) and Ru(η5‐2,3‐Me2C5H5)(η5‐C5H4R) (10, R = tBu; 12, R = SiMe3) are discussed and their use as a MOCVD precursor for the deposition of ruthenium is reported. The molecular structures of 3, 5–8, 10, and 12 in the solid state are reported. The half‐open ruthenocenes 10 and 12, which are liquids at ambient temperature, exhibit significantly shorter Ru–centroid (η5‐2,3‐Me2C5H5) bond lengths in contrast to ruthenocenes 3 and 5–8. The thermal behavior of all ruthenocenes was studied by thermogravimetric analysis showing that they evaporate without decomposition at atmospheric pressure. In addition, vapor pressure measurements were carried out to obtain profound information about the volatility of the synthesized sandwich compounds. The highest vapor pressures were found for 10 and 12. It was observed that the higher the number of SiMe3 groups, the higher the deposition temperature. All compounds were applied as precursors in MOCVD. The depositions on Si/SiO2 targets were carried out in a vertical cold‐wall CVD reactor between 633 and 688 K with a flow rate of 50 mL min–1 using nitrogen as the carrier gas and oxygen as the coreactant (50 mL min–1). With the tBu‐functionalized ruthenocenes 6 and 10 ruthenium thin films were obtained, while mixed ruthenium/SiO2 layers were formed with 2, 7, 8, and 12. The appropriate layers possess thicknesses between 75–135 nm and are conformal and dense as proven by SEM, EDX spectroscopy, and XPS studies.

Hexacarbonyl (Trimethylsilyl Ethyne) Dicobalt as MOCVD Precursor for Thin Cobalt Layer Formation

“…To get first information on the volatility and the evaporation rate, vapor pressure measurements were carried out using a Mettler Toledo TGA system with a horizontal balance as described elsewhere 30…”

“…The vapor pressure curve of 3 resembles the one recorded for cobaltocene, a commonly used cobalt CVD precursor. Linear regression of the vapor pressure measurements gave characteristic parameter for the dicobalta tetrahedrane 3 with A = 11.8 and B = 3492 according to Equation (1) ( R 2 = 0.998) 30…”

Half-sandwich cobalt complexes in the metal-organic chemical vapor deposition process

“…Chemical vapor deposition experiments using 1-3 as precursors were performed in a home-built vertical cold-wall MOCVD reactor connected to a continuous evaporation system with nitrogen as carrier gas and without any additional reactive gas on silicon wafers with 100 nm thick thermal SiO 2 [46]. The deposition was monitored visually, and the experiment was stopped as soon as a reflective layer was formed.…”

“…The volatility of cobalt(I) complexes [Co(η 5 -C 5 H 5 )(L)(L′)] (1: L, L′ = 1,5-hexadiene; 2: L = P(OEt) 3 , L′ = H 2 C_CHSiMe 3 ; 3: L = L′ = P(OEt) 3 ) was determined by vapor pressure measurements as described in reference [46]. The respective vapor pressure traces of 1-3 are depicted in Fig.…”

Magnesium β-ketoiminates as CVD precursors for MgO formation

“…The appropriate experiments were conducted in a home-built vertical cold-wall CVD reactor equipped with a continuous evaporation system. 29 The MOCVD experiments carried out with 3a,c resulted in the formation of thin, homogeneous MgO lms, when nitrogen (gas ow 50 mL min À1 ) as carrier gas and oxygen as reactive gas (gas ow 40 mL min À1 ) at a 1 mbar pressure were used. For comparison, deposition studies were also carried out solely under N 2 .…”