New precursors for organometallic chemical vapor deposition of rhodium

Abstract

R. KUMAR and R. J. PUDDEPHATT. Can. J. Chem. 69, 108 (1991).The q-cyclopentadienyl (Cp) and q-ally1 (C3H5) complexes [RhCp(C0)2], [RhCp(cod)] where cod = 1,5-cyclooctadiene, [Rh(q-C3H5)(CO),], and [ R h (~l -c~H~)~] have been shown to be useful precursors for the chemical vapour deposition (CVD) of rhodium films. The rhodium films contain carbon impurities but these can be greatly reduced if CVD is carried out in the presence of hydrogen. The films adhere well to a silicon substrate. Xntroduction There has been much recent interest in the formation of thin films of metals using chemical vapour deposition, CVD (1-3). These films have applications in microelectronics, optical devices, wear protection, and catalysis (4). Advantages of CVD include its ease of use, mild conditions of formation, and high performance of the films. Challenges for chemists include the design and synthesis of volatile precursors which decompose to the desired materials in pure form and under mild thermal or photochemical conditions as required for specific applications, and the determination of the mechanisms of CVD to enable the development of a rational approach to precursor design.Most recent research has been focussed on CVD of gold, palladium, and platinum, noble metals most commonly used in microelectronics (5-9). Rhodium has been much less extensively studied (2, 10). Rhodium films are used in mirror optics, catalysis, and wear protection but, while rhodium has excellent electrical properties and corrosion resistance, its high cost has so far limited its application in microelectronics (11). This paper surveys, some volatile organorhodium complexes, and reports on a study of thermal CVD of rhodium films from these compounds. Other researchers have reported CVD of rhodium using the precursors [Rh2 ( Results and discussionIn this work, the new precursors used were the -q-cyclopentadienyl derivatives [RhCp(cod)] , Cp = p-C5H5, cod = 1 3 -cyclooctadiene, and [RhCp(CO)2] and the q-ally1 derivatives [Rh(q-C3H5)(C0)2] and [Rh(q-C3H5)3]. All were prepared by known procedures (12-15). For reference, some CVD experiments were also carried out with the known precursor [Rh2 t F-C~)Z(CO),] (2). Formation and characterization of rhodium jlmsIn a typical reaction, CVD was carried out in a vertical reactor operating at 10-2-10-3 Torr. The substrate was a silicon wafer, which was heated to 130-270°C. Under these conditions, highly reflective rhodium films were formed and the film thickness typically grew at a rate of -2 pm/h. The films were analyzed by XPS and some typical data are given in Table 1.The rhodium films are rapidly contaminated by exposure to the atmosphere and, in all cases, the films were cleaned before analysis by argon sputtering for 30 s. Even so, the films consistently contained much carbon and oxygen impurities. These impurities were greatly reduced when the CVD was carried out using hydrogen carrier gas (Table 1). For example, using only ~o r r Hz as carrier gas and [Rh(p-C3H5)(CO)2] as precursor, the rhodium content increased...

Chemical Vapor Deposition of Iridium, Platinum, Rhodium and Palladium

“…The decomposition of Rh(allyl) 3 without assistance of hydrogen resulted in amorphous rhodium films contaminated with carbon (about 14 mass%C). 30,31,[72][73][74]82) Additionally, the results coincide in the beneficial effect of hydrogen to reduce contamination (4 mass%C, <2 mass%O). 30,[72][73][74]82) Specifically, the use of hydrogen plasma for the decomposition of Rh(allyl) 3 promoted the formation of pure and crystalline rhodium films (<3 mass%C) at growth rates of about 5 Â 10 À3 nmÁs À1 .…”

Rhodium pyrazolate complexes as potential CVD precursors

“…Other groups have seen dramatic decreases in carbon impurities when H 2 is used as the carrier gas. 10 Films grown using H 2 as the carrier gas had significantly less carbon as shown in Table 7. After removal of the surface contaminants, the Rh concentration was determined to be 58.1% and carbon 41.9%.…”

“…Impurity levels depend strongly on the precursor and carrier gas used. For example, films grown using argon as a carrier gas using [Rh (μ-Cl)(CO) 2 ] 2 at 180°C contain 49% Rh, 24% C, and 27% O, while films grown under the same conditions from [Rh(η 3 -allyl) 3 ] contain 86% Rh and 14% C. 10 In order to explore the potential to grow films with different compositions and/or new morphologies we have investigated the use of precursors which have non-traditional ligands. New CVD precursors should ideally meet several criteria.…”

“…[1][2][3] Thin films of rhodium are used as electrical contacts, 4,5 reflective coatings, 6,7 catalysis, 8,9 and wearresistant coatings for extreme conditions. 2,10 Previous studies have focused on volatile compounds which feature traditional organometallic ligands such as CO, C 2 H 4 , C 5 H 5 , and fluorinated hydrocarbons such as trifluoroacetylacetonate and it has been shown that film quality is dependent on the precursor used. 1,10,11 For example, precursors for the CVD of rhodium films include [Rh(CO) 2 (acac)], [Rh(μ-Cl)(CO) 2 ] 2 , [(η 5 -C 5 H 5 )Rh(η 2 -C 2 H 4 ) 2 ], [Rh(η 3 -allyl) 3 ], [Rh(tfac) 3 ], [Rh 2 (CO) 8 ], and [(η 5 -C 5 H 5 )Rh-(CO) 2 ].…”

“…2,10 Previous studies have focused on volatile compounds which feature traditional organometallic ligands such as CO, C 2 H 4 , C 5 H 5 , and fluorinated hydrocarbons such as trifluoroacetylacetonate and it has been shown that film quality is dependent on the precursor used. 1,10,11 For example, precursors for the CVD of rhodium films include [Rh(CO) 2 (acac)], [Rh(μ-Cl)(CO) 2 ] 2 , [(η 5 -C 5 H 5 )Rh(η 2 -C 2 H 4 ) 2 ], [Rh(η 3 -allyl) 3 ], [Rh(tfac) 3 ], [Rh 2 (CO) 8 ], and [(η 5 -C 5 H 5 )Rh-(CO) 2 ]. [1][2][3]11 Thin films of Rh and Rh 2 O 3 have also been grown by atomic layer deposition (ALD) using organometallic precursors and O 2 as the carrier gas.…”