Step Coverage and Composition of Pb(Zr, Ti)O₃ Capacitors Prepared on Sub-Micron Three-Dimensional Trench Structure by Metalorganic Chemical Vapor Deposition

Abstract

Pb(Zr, Ti)O3 (PZT) films were deposited into sub-micron trench structure consisting of SiO2/TiAlN/Ti/SiO2/Si to investigate their thickness and composition conformality by pulsed-metalorganic chemical vapor deposition (MOCVD) using liquid delivery source-supply system. Bis(dipivaloylmethanato)lead [Pb(DPM)2], tetrakis(1-methoxy-2-methyl-2-propoxy)zirconium [Zr(MMP)4] and tetrakis(1-methoxy-2-methyl-2-propoxy)titanium [Ti(MMP)4] were used as Pb, Zr and Ti source materials, respectively. In Arrhenius plot, the slopes of the straight lines for the constituents Pb, Zr and Ti in PZT film were almost the same at a lower deposition temperature (Td) region as well as a higher Td one. This means the composition change in the film against the Td can be suppressed by using Pb(DPM)2-Zr(MMP)4-Ti(MMP)4-O2 source system. From the results of Arrhenius plot, the Tds were fixed on 450 and 540°C as lower and higher temperatures, respectively. At both Tds, the sidewall-bottom step coverage (SCs-b) was approximately 70 %, while the sidewall step coverage (SCsw) reached excellent values above 90 %. It is suggested that low SCs-b value was caused by crystallization of the PZT films at the bottom of the trench because underlayer of the film at this area was not SiO2 but crystalline TiAlN. On the other hand, no significant composition fluctuation was observed along the depth direction of the sidewall. These results mean that the film deposited at 540°C had almost the same level in terms of thickness and composition conformality as that deposited at 450°C.

Growth of ternary PbTiOx films in a combination of binary oxide atomic layer depositions

“…The isotropic flow of precursor molecules accounts for the good step coverage of MOCVD in contrast to most physical vapor deposition processes with a straightforward flight of elements from a point source to the substrate. In the case of 3D deposition of binary oxide films, such as HfO 2 and Ta 2 O 5 for capacitor applications, the homogeneity of film thickness is central, while uniformity in cation composition becomes an additional issue for multicomponent films. Recent studies have indicated a serious problem in that multicomponent oxide films deposited over 3D structures by MOCVD exhibit nonuniformity in cation composition, although film thickness appears to be uniform over the complex structure.…”

“…Recent studies have indicated a serious problem in that multicomponent oxide films deposited over 3D structures by MOCVD exhibit nonuniformity in cation composition, although film thickness appears to be uniform over the complex structure. [1][2][3][4] In MOCVD, surface reaction limiting deposition, where the deposition rate depends only on the substrate temperature, has been a common approach to achieving a homogeneous 3D coverage. However, at a mutual deposition temperature, not every precursor necessarily decomposes under the surface-reaction limiting condition.…”

“…9,10 Due to ongoing reductions in the feature size and switching voltage, a conformal deposition of very thin films on 3D capacitor structures was required. 1,2 Thin films of PbTiO x were deposited in a combination of two self-limiting binary processes of ALD-TiO x and PbO. 11,12 The deposition rates of the cations and the incubation period were investigated as a function of the input of precursors using planar substrates.…”

Trial for Making Three Dimensional PZT Capacitor for High Density Ferroelectric Random Access Memory

“…Pb(C 11 4 [tetrakis (1-methoxy-2-methyl-2-propoxy) zirconium, Zr(MMP) 4 ] (Asahi Denka Kogyo K. K.), and Ti(OC(CH 3 ) 2 CH 2 OCH 3 ) 4 [tetrakis(1-methoxy-2-methyl-2-propoxy)titanium, Ti(MMP) 4 ] (Asahi Denka Kogyo K. K.) were used as the respective Pb, Zr, and Ti source materials [10,11]. Ethylcyclohexane and O 2 gas were used as a solvent and as an oxidant, respectively.…”

Microstructural analysis of integrated pin-shaped two-dimensional and three-dimensional ferroelectric capacitors from micro-focused synchrotron X-ray techniques

“…Thus, in the replacement of conventional planar capacitors, recent developments have been oriented toward integration of three-dimensional capacitors (Goux, Russo et al, 2005;Scott, 2005a,b;Scott et al, 2005;Nagel et al, 2004;Joshi, 2004;Narayan, 2003;Zambrano, 2003;Johnson et al, 2003). Lead zirconate titanate (PbZr 1Àx Ti x O 3 , PZT) is the most used ferroelectric material for planar capacitors and is also used for three-dimensional capacitor scaling (Nagai et al, 2006(Nagai et al, , 2005; Koo et al, 2005;Kim et al, 2005;Funakubo et al, 2005). Nevertheless, much attention is also focused on the integration of strontium bismuth tantalate (SrBi 2 Ta 2 O 9 , SBT) in threedimensional capacitors or in nanotubes (Morrison et al, 2003).…”