Improved fabrication process for Ru/BST/Ru capacitor by liquid source chemical vapor deposition

Tarutani, Masahito; Yamamuka, Mikio; Takenaga, Takashi; Kuroiwa, Takeharu; Horikawa, Tsuyoshi

doi:10.1016/s0040-6090(02)00095-0

Cited by 9 publications

(5 citation statements)

References 8 publications

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“…The other interesting result is that the Ti concentration ratio of the film is not constant but increases slightly up to 40 cycles ͑ϳ12 nm͒ and then saturates to a Ti concentration of approximately 52%. The Mitsubishi group 33 reported a slight increase in the Ti concentration at the Pt/BSTO interface in the case of the BSTO MOCVD on Ru, which is in contrast to the present case. More research on this is certainly necessary.…”

Section: Resultscontrasting

confidence: 96%

“…7b and c. The local increase in Ti concentration of STO or BSTO films at the interfaces with the Ru or Pt has also been reported in the MOCVD of these films. 32,33 Figure 10b shows the cross-sectional bright-field TEM image of an approximately 10 nm thick STO film on Ru substrate. The film was amorphous because of the relatively low deposition temperature.…”

Section: C230mentioning

confidence: 99%

See 1 more Smart Citation

Chemically Conformal ALD of SrTiO[sub 3] Thin Films Using Conventional Metallorganic Precursors

Kwon

Kim

Cho

et al. 2005

J. Electrochem. Soc.

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SrTiO 3 ͑STO͒ thin films were grown on Si wafer, Pt-and Ru-coated Si wafers, respectively, by an atomic layer deposition ͑ALD͒ technique using conventional metallorganic precursors, Sr͑C 11 H 19 O 2 ͒ 2 ͑Sr͑thd͒ 2 ͒ and Ti͑Oi-C 3 H 7 ͒ 4 ͑TTIP͒ as Sr-and Tiprecursors, respectively, with a remote-plasma activated H 2 O vapor as the oxidant at a wafer temperature of 250°C. Patterned Si wafers with contact holes having a diameter of 0.13 and 1 µm depth ͑aspect ratio of 8͒ was used in order to test the film-thickness and cation-composition conformalities over the contact hole surface. The ALD behavior of the STO film was critically dependent on the Sr͑thd͒ 2 source heating temperature. When the Sr source temperature was Ͻ ϳ200°C ͓Sr͑thd͒ 2 melting temperature͔ stoichiometric STO films were deposited with a good process reliability. Excellent film thickness and cation composition conformalities ͑nonuniformity Ͻ3%͒ over the severe contact hole structure were obtained by the optimized precursor supply and deposition conditions. It was also observed that most of the input TTIP precursor molecules did not chemically adsorb on the SrO surface, possibly due to oversaturation of the SrO surface by the Sr͑thd͒ 2 molecules or thermally modified Sr͑thd͒ 2 molecules as a result of the heating process of the Sr͑thd͒ 2 when the Sr-source temperature was Ͼ ϳ200°C. This difficulty resulted in a nonuniform cation composition ratio along the contact hole.High-dielectric constant thin films such as SrTiO 3 ͑STO͒ and ͑Ba,Sr͒TiO 3 ͑BSTO͒ 1-5 have attracted great interest as the capacitor dielectrics of dynamic random access memory ͑DRAM͒ devices. Recently, these materials have also been actively studied for the high-frequency tunable devices, 6,7 decoupling capacitors, 8 and gate dielectric 9,10 applications. Among these, the DRAM capacitor applications require conformal deposition over a 3-dimensional structure with a feature size Ͻ0.1 m in terms of film thickness and composition, which is not required in other applications.The low-temperature ͑Ͻ500°C͒ metallorganic chemical vapor deposition ͑MOCVD͒ process has been extensively studied for producing STO and BSTO thin films for DRAM applications due to its good film step coverage over a severe 3D surface topology, and nondamaging deposition on the underlying electrode stack. 11,12 However, conformal deposition over the entire surface area of such an extreme geometry in terms of the chemical composition as well as the thickness has not necessarily been confirmed even for lowtemperature MOCVD processes. The authors have reported extensive experimental results on the composition and thickness variations of the MOCVD STO and BSTO films deposited at wafer temperatures ranging from 420 to 440°C on a capacitor hole pattern with dimensions of 0.15 ϫ 0.40 ϫ 0.57 ͑depth͒ m 3 where two shower-head-type and one dome-type MOCVD chamber with two different precursor sets were used. 13,14 From the study, it was found that obtaining a conformal composition and film thickness over the 3D geometry using th...

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Section: Resultscontrasting

confidence: 96%

Section: C230mentioning

confidence: 99%

Chemically Conformal ALD of SrTiO[sub 3] Thin Films Using Conventional Metallorganic Precursors

Kwon

Kim

Cho

et al. 2005

J. Electrochem. Soc.

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“…It was previously found that the preannealing of the Ru electrode in vacuum ͑ϳ3 mTorr͒ at 750°C for 1 min before the ALD of STO greatly improved the electrical performance of the as-deposited thin films. This was also reported for the CVD of STO films on Ru electrodes by Tarutani et al 20 Therefore, all Ru electrodes were vacuum-annealed prior to ALD.…”

Section: Ald Of Sto Films With Plasma-activated H 2 O Vapor and Xps S...mentioning

confidence: 53%

Atomic Layer Deposition and Electrical Properties of SrTiO[sub 3] Thin Films Grown Using Sr(C[sub 11]H[sub 19]O[sub 2])[sub 2], Ti(Oi-C[sub 3]H[sub 7])[sub 4], and H[sub 2]O

Kwon

Lee

Han

et al. 2007

J. Electrochem. Soc.

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Atomic layer deposited SrTinormalO3 (STO) thin films were grown using Sr(normalC11normalH19normalO2)2 and Ti(Oi-normalC3normalH7)4 with a remote plasma activated or thermal normalH2O vapor as oxidant at growth temperatures ranging from 190to270°C . The as-grown films were amorphous and showed a low effective dielectric constant of ∼20 with a low leakage current density ( <10−7A∕cm2 at 1V ). The chemical binding status of the Sr ions varied with the degree of crystallization of the STO film. A reasonable film growth rate and stoichiometric cation composition were obtained when the vaporization temperature of Sr-precursor was <200°C with the thermal normalH2O vapor. The low density of the as-grown film induced a large shrinkage in the film thickness which caused microcracking of the crystallized films during postannealing, even with the increased normalH2O supply. Adoption of thin (∼5nm) crystallized seed layer before the main layer STO growth improved the microstructure after the crystallization and the leakage current performance. As a result of the process optimization, the best electrical properties of an STO film grown on a Ru electrode were 0.45nm for the equivalent oxide thickness and 1×10−3A∕cm2 for the leakage current density at 1V .

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“…The authors revisited an earlier report of the ALD and MOCVD of STO films,70, 83 and found that the Sr(tmhd) 2 precursor was usually vaporized at temperatures higher than its melting temperature (∼200 °C) to achieve a high enough vapor pressure. However, this was also a viable condition for the oligomerization of the precursor molecules of which the chemical reactivity with H 2 O should be degraded significantly compared to that of the monomer molecules 76.…”

Section: Resultsmentioning

confidence: 95%

Capacitors with an Equivalent Oxide Thickness of <0.5 nm for Nanoscale Electronic Semiconductor Memory

Kim

Lee

Han

et al. 2010

Adv Funct Materials

204

144

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The recent progress in the metal‐insulator‐metal (MIM) capacitor technology is reviewed in terms of the materials and processes mostly for dynamic random access memory (DRAM) applications. As TiN/ZrO2‐Al2O3‐ZrO2/TiN (ZAZ) type DRAM capacitors approach their technical limits, there has been renewed interest in the perovskite SrTiO3, which has a dielectric constant of >100, even at a thickness ∼10 nm. However, there are many technical challenges to overcome before this type of MIM capacitor can be used in mass‐production compatible processes despite the large advancements in atomic layer deposition (ALD) technology over the past decade. In the mean time, rutile structure TiO2 and Al‐doped TiO2 films might find space to fill the gap between ZAZ and SrTiO3 MIM capacitors due to their exceptionally high dielectric constant among binary oxides. Achieving a uniform and dense rutile structure is the key technology for the TiO2‐based dielectrics, which depends on having a dense, uniform and smooth RuO2 layer as bottom electrode. Although the Ru (and RuO2) layers grown by ALD using metal‐organic precursors are promising, recent technological breakthroughs using the RuO4 precursor made a thin, uniform, and denser Ru and RuO2 layer on a TiN electrode. A minimum equivalent oxide thickness as small as 0.45 nm with a low enough leakage current was confirmed, even in laboratory scale experiments. The bulk dielectric constant of ALD SrTiO3 films, grown at 370 °C, was ∼150 even with thicknesses ≤15 nm. The recent development of novel group II precursors made it possible to increase the growth rate largely while leaving the electrical properties of the ALD SrTiO3 film intact. This is an important advancement toward the commercial applications of these MIM capacitors to DRAM as well as to other fields, where an extremely high capacitor density and three‐dimensional structures are necessary.

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Improved fabrication process for Ru/BST/Ru capacitor by liquid source chemical vapor deposition

Cited by 9 publications

References 8 publications

Chemically Conformal ALD of SrTiO[sub 3] Thin Films Using Conventional Metallorganic Precursors

Chemically Conformal ALD of SrTiO[sub 3] Thin Films Using Conventional Metallorganic Precursors

Atomic Layer Deposition and Electrical Properties of SrTiO[sub 3] Thin Films Grown Using Sr(C[sub 11]H[sub 19]O[sub 2])[sub 2], Ti(Oi-C[sub 3]H[sub 7])[sub 4], and H[sub 2]O

Capacitors with an Equivalent Oxide Thickness of <0.5 nm for Nanoscale Electronic Semiconductor Memory

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