A Novel Process to Improve the Surface Roughness of RuO[sub 2] Film Deposited by Metallorganic Chemical Vapor Deposition

Abstract

We demonstrate that the surface roughness of metallorganic chemical vapor deposited RuO 2 is significantly decreased by plasma treatment before the deposition of the film. The root mean square (rms) value of the surface roughness is decreased from ~25 to 3 nm by applying O 2 plasma for 5 min prior to the deposition of an ~200 nm thick layer of RuO 2 . Other plasma gases such as H 2 and Ar also decrease the rms value of the surface roughness, but are not as effective as O 2 plasma. The decrease of surface roughness is attributed to the enhancement of nucleation density at the initial stages of film growth. © 1998 The Electrochemical Society. S1099-0062(98)06-055-6. All rights reserved.Manuscript submitted June 15, 1998; revised manuscript received September 10, 1998. Available electronically October 12, 1998. RuO 2 has been chosen as one of the strong candidate materials for an electrode of the high dielectric constant oxides such as barium strontium titanates and lead zirconium titanates, due to such advantages as low electrical resistivity (46 µΩ cm), high interfacial stability with dielectric oxide material, excellent diffusion barrier property against oxygen, and good dry etchability. This motivates many researchers to develop the RuO 2 thin film deposition process. 1-3 While thin films of RuO 2 have been commonly deposited by reactive sputtering process, the development of chemical vapor deposition (CVD) process using metallorganic source gases is now underway. 1,[4][5][6] The CVD process, as compared to the sputtering process, is preferable for obtaining a conformal coverage, which is a critical requirement for the materials to be used in an advanced integrated circuit process. Also, films deposited by CVD show inherently low stress levels as compared to sputter deposited films. However, the RuO 2 films deposited by CVD show extensive surface roughness 1,4 which is detrimental in many applications. This is especially true when the material is used as a lower electrode material. In general, this extensive surface roughness is attributed to large grain size development during deposition, which originates from the low nucleation rate as compared to the grain growth rate. For instance, the average grain size of the RuO 2 deposited by CVD is about 500 nm, which is an order of magnitude larger than that of sputter deposited RuO 2 . 1,4 Apparently, to reduce the surface roughness, one must develop a method to increase the nucleation rate at the initial stages of film growth during the CVD process.In this paper, we propose just such a method to enhance the nucleation rate at the initial stages of film growth. This method is based on utilizing a plasma treatment of the substrate prior to CVD of RuO 2 film, either with or without applying bias voltages. Also, the effects of using different gases, oxygen, hydrogen, and argon, to generate plasma are compared.Experimental Figure 1 shows a schematic diagram of the CVD system that was used for the deposition of the film. The chamber is divided into two parts; the upper pa...

Effect of CO on Ru Nucleation and Ultra-Smooth Thin Film Growth by Chemical Vapor Deposition at Low Temperature

“…12−14 Threedimensional island growth combined with sparse nucleation leads to surface roughness and the deposition of more metal mass than is needed to form a film of sufficient thickness to function as a copper diffusion barrier when compared to a uniformly thick metal film. 15 Growth chemistries that feature small and dense Ru nuclei result in a thinner and smoother metal film than observed when big and sparse island merge with continued Ru deposition. 16 Iodine sources, such as CH 3 I 16,17 and C 2 H 5 I, 17,18 in concert with Ru(EtCp) 2 are shown to enhance the nucleation density dramatically so as to improve film smoothness.…”

“…Metal growth on oxides in general and SiO 2 in particular during CVD typically leads to the formation of three-dimensional islands (Volmer–Weber growth mode) that coalesce into a continuous film for a variety of reasons, including the unfavorable wetting associated with the high surface energy of the metal and the sparse nature of the nuclei from which the three-dimensional islands grow. − Three-dimensional island growth combined with sparse nucleation leads to surface roughness and the deposition of more metal mass than is needed to form a film of sufficient thickness to function as a copper diffusion barrier when compared to a uniformly thick metal film . Growth chemistries that feature small and dense Ru nuclei result in a thinner and smoother metal film than observed when big and sparse island merge with continued Ru deposition .…”

Atomic layer deposition of ruthenium using an ABC-type process: Role of oxygen exposure during nucleation

“…25 In addition to requiring a longer process time, recipes with long nucleation delays can result in films with rough interfaces as a result of island formation during the initial growth. 40,41 It has been claimed that zerovalent precursors lead to deposition after a negligible nucleation delay on a variety of substrates, 37,38,42 although only limited experimental results supporting this claim have been reported so far. Currently, these precursor molecules are being explored for their potential to deposit ultrathin, smooth films.…”

Synthesis, structural, and electrical characterization of RuO2 sol–gel spin-coating nano-films

“…Among many other conductive oxides, RuO 2 exhibits distinct physical and chemical properties and has been used in various applications such as diffusion barriers [1], thin-film resistors [2], bottom electrodes of ferroelectric thin films in dynamic random access memories (DRAMs) [3], and electrochemical capacitors [4]. As one of the most promising electronic ceramics, nanoscale films of RuO 2 can be used for a wide variety of applications because of its semi-metallic conductivity (i.e., 35 lX cm: bulk single crystal) as well as good thermal stability [5], excellent diffusion barrier properties [6,7], and high chemical corrosion resistance [8][9][10]. One of the most promising and important use of RuO 2 is for the applications in organic light emitting devices (OLED), flat panel display and organic solar cells.…”