Organometallic Ruthenium Source Reagents for CVD

Abstract

There has been considerable interest in the deposition of highly conductive ruthenium and RuO 2 thin films for use in the manufacture of integrated circuits. Various ruthenium organometallic complexes have been proposed as CVD source reagents, including ruthenocene [1] and its alkyl substituted derivative complexes such as Ru(C 5 H 4 Et) 2 , [2] and metal carbonyl complexes such as Ru(CO) 3 (C 6 H 8 ), (C 6 H 8 = 1,3-cyclohexadiene), [3] Ru(CO) 4 (hfb), [4] (hfb = hexafluoro-2-butyne), [(C 5 H 5 )Ru(CO) 2 ] 2 , and Ru 3 (CO) 12 ; [5] tris-b-diketonate complexes such as Ru(acac) 3 , Ru(tfac) 3 , and Ru(tmhd) 3 , (tfac = 1,1,1-trifluoro-2,4-pentandionate and tmhd = 2,2,6,6-tetramethyl-3,5-heptanedione); [6] alkenyl and alkene complexes such as bis(2,4-dimethylpentadienyl)-ruthenium, bis(2,4-dimethyloxapentadienyl)ruthenium, [7] (g 6 -C 6 H 6 )Ru(g 4 -C 6 H 8 ), and Ru(C 3 H 5 ) 2 (COD), (COD = 1,4-cyclooctadiene). [8] Although some of these compounds are liquids, or relatively volatile low-melting point solids, which are amenable to sublimation for gas-phase transport into the CVD reactor, most of them possess fairly high melting points, high decomposition temperatures, or are thermally unstable and react with moisture and oxygen when exposed to air, making them difficult to store and handle.Accordingly, there is an urgent need for low-melting point, highly volatile, and relatively stable ruthenium compounds as source reagents for various CVD applications, such as the preparation of ruthenium metal bottom electrodes and barrier layers for integrated circuits. [9] More specifically, these CVD source materials may find applications in fabricating the BST-based Gb-scale dynamic random access memory (DRAM), and for manufacturing Ru pillars and Ta 2 O 5 /Ru capacitors in embedded DRAM technology. [10] The complexes which possess the required physical properties are a series of new Ru II complexes with the general formula Ru(CO) 2 (diketonate) 2 . These complexes are easily prepared in excellent yields from the direct reaction of excess b-diketone, such as hexafluoroacetylacetone (hfacH) or 2,2,6,6-tetramethyl-3,5-heptanedione (tmhdH), and Ru 3 (CO) 12 in a sealed stainless steel autoclave at an elevated temperature, according to a modification of the method for Ru(CO) 2 (acac) 2 . [11] The resulting products are purified by reduced-pressure distillation or vacuum sublimation, followed by recrystallization from methanol at ±20 C.The 13 C NMR spectra for the complexes Ru(CO) 2 (hfac) 2 (1) and Ru(CO) 2 (tmhd) 2 (2) show the presence of one signal for Ru-bound CO ligands and two distinct CO signals from the b-diketonate ligands, suggesting that the molecule consists of an octahedral structure composed of two b-diketonate ligands and two CO ligands arranged in the cis-disposition. The structure of these complexes is further confirmed by single-crystal X-ray analysis of 1 (Fig. 1). The Ru±CO distances (1.896(3) and 1.900(4) ) are slightly shorter than that of the parent carbonyl complex Ru 3 (CO) 12 (av. 1.93 ). [12] The Ru±...

Synthesis and Electrochemical Studies of Ruthenium(II) Dicarbonyl Bis(ferrocenyl‐β‐diketonates)

“…1975 and 2050 cm –1 appeared, which are characteristic for cis ‐oriented carbonyl ligands of a Ru(CO) 2 entity. [14b] This arrangement was also confirmed by single X‐ray structure analysis ( vide infra ). For the respective 1,3‐diketonates correspondingly strong vibrations are found in the range of 1400–1550 cm –1 ( 3a : ν C=C , 1402 cm –1 ; ν CO , 1516 and 1544 cm –1 ; 3b : ν C=C , 1404 cm –1 ; ν CO , 1516 and 1530 cm –1 ) confirming their O,O '‐chelate binding to Ru II ,.…”

“…The neutral species exhibits the typical pattern of a Ru(CO) 2 fragment with two CO bands (see earlier, Experimental Section) , . As compared to dicarbonyl β‐diketonate ruthenium(II) complexes, i.e.…”

“…Such type of Ru II species have been characterized crystallographically only to a lesser extent for, i.e. cis ‐[Ru(CO) 2 (hfac) 2 ] and cis ‐[Ru(CO) 2 (tfac) 2 ] (hfac = hexafluoroacetylacetonato,[14a] tfac = 1,1,1‐trifluoro‐2,4‐pentadionato[14b]). In contrast to these compounds, which both crystallize in the centrosymmetric triclinic space group P 1, 3a crystallizes in the orthorhombic Sohncke space group P 2 1 2 1 2 1 .…”

“…The Ru–CO [1.867(11) and 1.870(10) Å] and Ru–O [2.032(7)–2.078(7) Å] bond lengths of 3a agree well with the values observed for cis ‐[Ru(CO) 2 (hfac) 2 ] and cis ‐[Ru(CO) 2 (tfac) 2 ]. [14a], [14b] As displayed in Figure , the cyclopentadienyl ring of one of the Fc substituents is in plane with respect to the β‐diketonate ligand (red colored), while for the second one (green and yellow colored) a minor deviation is observed. In the solid state of 3a there are no mentionable dispersion interactions (sandwich‐, parallel‐displaced sandwich‐ or T‐shape‐type) between aromatic fragments as well as no unusually short intermolecular atomic distances below the sum of the van der Waals radii.…”

“…[Ru(CO) 2 (β‐diketonate) 2 ] featuring as substituents solely organic groups in positions 1,3 of the organic ligands, the more electron‐donating ferrocenyls in 3a , b cause a bathochromic shift of the ν CO bands. [14b]…”