Deposition of Iridium Thin Films Using New IrI CVD Precursors

Abstract

Noble metal thin films have been extensively studied by both the traditional and microelectronics industries for potential applications such as anti-corrosion and anti-oxidation coatings, [1] or in the manufacture of bottom electrodes for high-density memory devices and ferroelectric capacitors. [2] Iridium is considered to be one of the best of these transition metal elements as it possesses a high work function, a stable conductive oxide phase, IrO 2 , and excellent electrical properties. [3] Although physical sputtering seems to be a good choice of method for depositing such iridium metal-containing thin films, CVD will eventually become the preferred method as it has several major ad-vantages, i.e., good conformal coverage, selective deposition on the substrate surface, the capacity for scale-up production with high throughput, and the ability to produce meta-stable materials at low temperatures. [4] The CVD of iridium has been achieved using Ir III reagents, such as tris-acetylacetonato and tris-allyl complexes Ir(acac) 3 and Ir(C 3 H 5 ) 3 , [5] of which the commercially available Ir(acac) 3 is the better choice due to its excellent air stability, but its high melting point and low volatility limit its possible use as the industrial standard. A second type of the source reagent consists of an Ir I metal complex, such as (MeCp)Ir (COD), [6] (hfac)Ir(COD), [7] [Ir(COD)(l-OMe)] 2 , [8] [Ir (COD)(l-OAc)] 2 , and [Ir(CO) 2 -(l-S t Bu)] 2 . [9] Among these Ir I source reagents, the monomeric metal complexes (MeCp)Ir(COD) and (hfac)Ir-(COD) seem to be more useful for CVD due to their enhanced vapor pressure and the negligible possibility of dimer dissociation during vapor phase transport.In this work, we report the synthesis of three new Ir I 1,5cyclooctadiene complexes, in which the anionic ligand is carefully selected in order to ensure formation of the stable metal chelate interaction, while two CF 3 substituents are introduced onto the ligand to improve the volatility of the final metal complexes, [10] making them more suitable for CVD investigations. Moreover, as these complexes differ only slightly in their molecular structure, systematic studies using these iridium precursor compounds will allow us to find the best CVD reagent in the series, and permit an understanding of other parameters that may influence the typical deposition processes.For synthesis of the required iridium compounds, three CF 3 substituted anionic ligands (keim)H, (hfda)H, and (amak)H were first prepared according to the procedures documented in the literature, [11] then the iridium source complexes, namely (keim)Ir(COD) (1), (hfda)Ir(COD) (2), and (amak)Ir(COD) (3) (Scheme 1), were obtained by mixing the corresponding sodium salt of anionic ligand, which was generated in situ from the reaction with NaH, and the iridium chloride starting material [Ir(COD)(l-Cl)] 2 in THF solution at room temperature. After a typical work-up of the reaction mixture, further purification of these compounds was carried out using vacuum sublima...

Chemical Vapor Deposition of Iridium, Platinum, Rhodium and Palladium

“…25) Cyclooctadienyl complexes, named (keim)Ir(1,5-COD), (hfda)Ir(1,5-COD) and (amak)Ir(1,5-COD), were synthesized by introducing fluorinated ligands (keim)H, (hfda)H and (amak)H to improve volatility and make them attractive for CVD of iridium. 40) Differing only slightly in their molecular structure, these three complexes sublimed without decomposition at 323-333 K under 26.6 Pa. The first two complexes were found to be air-stable.…”

Study of Emissivity of MOCVD Iridium Film with Different Topography

“…This leads to an increased supply of precursor. In the deposition at 540 °C, the supply of Ir(acac) 3 is not enough from the kinetics control, the closer to the precursor direction, the faster grow will be, and bigger size grains will fabricated. Compared to the deposition at 480 °C, the deposition is kinetics control, the precursor supply is sufficient from every region of the substrate, therefore, the grain growth is even.…”

“…IV. CONCLUSIONS The emissivity of different topographies of iridium films which were obtained using Ir(acac) 3 (1.216×10…”

“…Among which, metallo-organic chemical vapor deposition (MOCVD) can be processed under much lower deposition temperatures, therefore aroused widespread concern. From a few iridium organic compound precursors studied previously, iridium(III) acetylacetonate (Ir(acac) 3 ) has become one of the most popular [11][12][13][14][15]. In addition, it is much easier to deposit coating/film on special shaped pieces.…”

“…Considering its expensive value and brittleness, the fabrication of iridium through chemical vapor deposition (CVD) process is found essential [3][4][5][6][7][8][9][10]. Among which, metallo-organic chemical vapor deposition (MOCVD) can be processed under much lower deposition temperatures, therefore aroused widespread concern.…”