Chemical Vapor Deposition of  ( Ba , Sr ) TiO3

Abstract

SrTiQ and (Ba, Sr)TiO3 thin films were fabricated on Si and Pt/TaOx/Si substrates by chemical vapor deposition (CVD) using Sr(DPM)2, Ba(DPM)2, Ti(O-i-C3HT)4, and O2 where DPM is dipivaloylmethanate or formally 2,2,6,6-tetramethyl-3,5-heptanedionate. The deposition system was operated in both thermal CVD mode and electron cyclotron resonance (ECR) plasma CVD Mode. Variations in individual Sr and Ti deposition rates with differing deposition conditions were investigated. The SrTiO3 and (Ba, Sr)TiQ films were characterized with a view to discussing the step-coverage, crystal structure, and electrical properties. The step-coverage over the 300 nm wide SiQ lines, with 500 nm height and 500 nm spacing, was 30 to 40 %. The 40 to 100 nm SrTiO3 films~ through the p ostdeposition annealing process, showed dielectric constants > 140 with a leakage current density level <10-' A/cm ~ at 1 V. The prospects for applying the CVD (Ba, Sr)TiO3 films to giga-bit dynamic random access memory storage capacitors are discussed.To maintain sufficient storage capacitance in the future ultralarge scale integrated circuit (ULSI) for use in the 1 Gbit dynamic random access memory (DRAM) and beyond, high permittivity materials are expected to be used as the capacitor dielectrics. (Ba, Sr)TiOa is one dielectric material which has been investigated for this application. 1 Typical deposition methods for this dielectric are RF-magnetron sputtering, 2 and ion-beam sputtering 3 techniques. However, the permittivity of (Ba, Sr)TiOa films is not large enough for application to the I Gbit DRAM with a planar type storage capacitor. Thus, the eonformal nature of thin films fabricated by the CVD technique has attracted special attention for use in side areas of the bottom electrodes in DRAM capacitors to increase the storage capacitance. Figure 1 represents a diagram for CVD system. 4 (Ba, Sr)TiO3 thin films were deposited on Si and Pt/TaOx/ Si 5 substrates, using a source combination of Ba(DPM)2, Sr(DPM)2, Ti(O-i-C3HT)4, and 02. DPM is dipivaloylmethanate (CH(CO . C(CH3)~)~), or formally 2,2,6,6-tetramethyl-3,5-heptanedionate (thd) (CH3-C(CHD2-COCHCO-C(CH3)2-CH3). Vapor from the liquid source (Ti source) and sublimation from the powder sources (Sr and Ba sources) were transported individually with Ar carrier flows and mixed before the reaction chamber. The system was operated in both thermal CVD mode and ECR plasma CVD mode. In the thermal CVD mode, O2 was mixed with the metal source compounds and the reactant vapors were injected toward a rotating substrate of Si or Pt/TaOJSi * Electrochemical Society Active Member. Experimental(preannealed sputtered Pt(50 nm)/Ta(50nm)/Si), 4 in. diam. The vapors with Ar carrier flows were evacuated through the mechanical booster pump. In the ECR-CVD mode, O~ was introduced into the reaction chamber separately through the ECR plasma generator. This 02 plasma was mixed with the metal source compounds in the reaction chamber. The vapors with Ar carrier flows were evacuated through the turbomolecular pump.CVD conditio...

Effect of Bottom Electrode Materials and Annealing Treatments on the Electrical Characteristics of Ba0.47Sr0.53TiO3 Film Capacitors

“…The refractive index for the BST annealed at 550°C approaches a constant value of 1.85, which is close to 1.8, the index of refraction of sputter-deposited amorphous BST. 18,22,23 The refractive indexes of the 650°-and 750°Cannealed BST increase with increasing annealing time and increase to 2.2, which approaches the refractive index (2.3) of microcrystalline BST films. 18,22,23 (The refractive index was previously shown to be affected by composition.…”

“…18,22,23 The refractive indexes of the 650°-and 750°Cannealed BST increase with increasing annealing time and increase to 2.2, which approaches the refractive index (2.3) of microcrystalline BST films. 18,22,23 (The refractive index was previously shown to be affected by composition. 24 ) An ICP study indicates that annealing-induced composition change in the films is not observed as long as the annealing temperature remains <750°C.…”

Thermal Decomposition of Ti(O–iPr)2(dpm)2 in the Gas Phase

“…Although considerable progress has been made in the preparation of BST thin films using MOCVD, the selection of metalorganic compounds continues to be the key problem in the design of the process. [5][6][7] The titanium source compound is generally thought to strongly influence the step coverage of a deposited film. 1) Ti precursors that are commonly used in film deposition are mainly alkoxides and -diketonates, such as Ti(O-iPr) 4 and Ti(O-iPr) 2 (dpm) 2 .…”

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The thermal decomposition of gaseous Ti(O-iPr) 2 (dpm) 2 dpm = bis(2,2,6,5heptadionate)], diluted with either argon or air, was investigated using infrared (IR) and mass spectrometry. The activation energies associated with the dissociation of individual bonds constituting the compound were estimated based on IR data obtained when the compound was heated at different rates.

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Thermal Decomposition Mechanism of Bis(dipivaloylmethanato)strontium Compounds Containing Glyme Adducts

“…[1][2][3] Various deposition techniques such as radio frequency ͑rf͒ sputtering, laser ablation, and metal-organic chemical vapor deposition ͑MOCVD͒ have been proposed for the preparation of the BST and STO thin films, among which MOCVD has received considerable attention because it offers good step coverage, good film uniformity, and high deposition rates. 4,5 However, MOCVD technology is limited by the properties of the film precursors. Precursors of alkaline-earth metal oxides such as Ba and Sr oxides easily deteriorate and yield films with a poor uniformity.…”