Rajesh Katamreddy

ALD and Characterization of Aluminum Oxide Deposited on Si ( 100 ) using Tris(diethylamino) Aluminum and Water Vapor

© The Electrochemical Society, Inc. 2006. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS). The archival version of this work was published in Katamreddy, R., R. Inman, G. Jursich, A. Soulet, and C. Takoudis, 2006, ALD and characterization of aluminum oxide deposited on Si (100) using tris(diethylamino) aluminum and water vapor: Journal of the Electrochemical Society, v. 153, no. 10, p. C701-C706.

Ti Source Precursors for Atomic Layer Deposition of TiO2, STO and BST

In this study we evaluated several precursors such as tetrakis(dimethylamino) titanium (TDMAT), tetrakis (diethylamino) titanium (TDEAT), tetrakis(ethylmethylamino) titanium (TEMAT) along with novel PrimeTiTM, StarTiTM and TyALDTM for TiO2 ALD application with both water and ozone as the oxidizer. Each precursor is evaluated with respect to some of the important characteristics like growth rate of TiO2 per ALD cycle, range and upper limit of process temperature window, volatility and stability of precursor, chemistry with desired oxidizer etc., that are critical for the selection of the precursor. All amino-compounds had a narrow process window. Precursor decomposition was observed for TDMAT, TDEAT and TEMAT at temperature higher than 225 oC limiting the deposition process at 225 {degree sign}C. On the other hand, TiO2 ALD using PrimeTiTM and StarTiTM is observed up to 325 and 400 {degree sign}C respectively. Finally, photoelectron spectroscopy analysis of some the films will be discussed.

Atomic Layer Deposited Ultrathin HfO2 and Al2O3 Films as Diffusion Barriers in Copper Interconnects

Atomic layer deposited ultrathin HfO 2 and Al 2 O 3 films were studied as diffusion barriers between Cu and Si substrate. The thermal stability of 3 nm thick HfO 2 and Al 2 O 3 films was investigated after annealing at different temperatures for 5 min in N 2 . X-ray diffraction analyses and sheet resistance measurements suggest that both barrier films were thermally stable and the formation of Cu 3 Si started to take place only after annealing at high temperatures. Specifically, our results show that 3 nm thick HfO 2 and Al 2 O 3 diffusion barriers break down after annealing in N 2 at 700 and 750°C, respectively.

Controlling interfacial reactions between HfO2 and Si using ultrathin Al2O3 diffusion barrier layer

The authors investigated the effectiveness of atomic layer deposited (ALD) aluminum oxide barrier layer in controlling the interfacial reaction between ALD HfO2 film and Si substrate. The HfO2 was observed to form silicate and silicide at its interface with Si during 5min postdeposition annealing in Ar at 800 and 1000°C. A 0.5-nm-thick Al2O3 barrier layer was found to control interfacial reactions between HfO2 and Si during annealing at 800°C, but not at 1000°C, whereas a 1.5-nm-thick barrier of Al2O3 was needed to prevent interfacial reaction up to an annealing temperature of 1000°C.

Bis(diethylamino) silane as the silicon precursor in the atomic layer deposition of HfSiOx

Bis(diethylamino) silane is studied and evaluated as a liquid-phase, silicon precursor in the low-temperature atomic layer deposition (ALD) of hafnium silicate films. The depositions were performed using ozone as the oxidizing reagent and tetrakis(diethylamino)hafnium as the source of hafnium in hafnium silicate. The ALD process temperature windows for the deposition of silicon dioxide and hafnium oxide from the aforementioned precursors overlap between 200 and 250°C. This overlap of temperature process windows is especially advantageous as it allows ALD of composite HfSiO x films. The variable compositions of HfSiO x films were prepared by varying ALD pulse sequencing, and excellent tunability of film composition is confirmed using Rutherford backscattering spectroscopy. The morphology of resulting films was also studied using X-ray diffraction. Whereas the SiO 2 films were amorphous after deposition and remained amorphous up to deposition annealing temperatures of 1000°C, the HfO 2 films were amorphous as-deposited but started crystallizing at annealing temperatures above 600°C. The amorphous structure stability in ternary films of HfSiO x was found to depend on the relative amounts of hafnia and silica deposited. For example, films prepared by alternating five cycles of hafnia and one cycle of silica remained amorphous up to 800°C annealing, while films prepared by less than 2:1 alternating hafnia:silica cycles remained amorphous up to 1000°C.

Tuning of Material and Electrical Properties of Strontium Titanates using Process Chemistry and Composition

In this work, we study the compatibility of a highly volatile strontium precursor, HyperSr, which has a low melting point, good thermal stability and good reactivity, with various Ti precursors for atomic layer deposition (ALD) of strontium titanates (STO). Novel Ti precursors studied for STO deposition include PrimeTi & StarTi. We will then discuss the interesting trends in material properties observed in STO films deposited with various compositions. X-ray photoelectron spectroscopic analysis of ALD SrO films showed the presence of carbonate groups in the film. There is the potential that this carbonate species is inherent to the ALD process; however, it has been reported that SrCO3 forms when SrO films are exposed to atmospheric CO2. To isolate the effects of atmospheric exposure on the carbonate formation in the film, a TiO2 capping layer is used on the surface of ALD SrO films and the resulting film structures are analyzed.

Atomic Layer Deposition of Rare-earth Oxide Thin Films for High-k Dielectric Applications

Many different organolanthanide molecules are being proposed as metal sources for depositing metal and metal oxide layers for semiconductors by atomic layer deposition (ALD). These precursors need particular physical and thermal properties to be used in the semiconductor manufacturing process. For example, the precursors need to have high volatility, reactivity, and thermal stability. Atomic layer deposition (ALD) is the preferred method for depositing metal oxide thin films where precise control of film composition and structure are highly desired. ALD deposition methods are very promising; however, new high-k metal oxide films will require new precursors to meet the very stringent requirements of the semiconductor process.

Atomic layer deposition of HfO2, Al2O3, and HfAlOx using O3 and metal(diethylamino) precursors

Tetrakis-diethylamino hafnium (TDEAH), tris-diethylamino aluminum (TDEAA), and ozone were used for the atomic layer deposition (ALD) of HfO 2 , Al 2 O 3, and HfAlO x films. The ALD rates were measured to be 1.1 A/cycle for HfO 2 and 1.3 A/cycle for Al 2 O 3 . The ALD temperature windows were found to be between 200 and 325 °C for TDEAA, and between 200 and 275 °C for TDEAH. The overlap of these ALD windows between 200 and 275 °C is critical for ALD of the composite film, HfAlO x . In addition to the overlapping ALD temperature windows, the two metal precursors have similar thermal characteristics, as shown by TGA and differential scanning calorimetry. As-deposited films and films postannealed at 600 and 800 °C films were analyzed using Fourier transformed infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy, and x-ray diffraction (XRD) techniques. FTIR spectra revealed interfacial oxide growth during deposition of both HfO 2 and Al 2 O 3 whose thickness increased with annealing temperature. The FTIR data also indicated hydroxyl and nitrate groups in the films; these species were removed after annealing in Ar at a temperature of ⩾600 °C. Both FTIR and XRD results indicated the crystallization of pure HfO 2 after annealing at temperatures as low as 600 °C. On the other hand, pure Al 2 O 3 remained amorphous after annealing at temperatures up to 800 °C. XRD data of the composite HfAlO x film show that films deposited by alternating five cycles of HfO 2 and one cycle of Al 2 O 3 remained amorphous after annealing at 600 °C. Rutherford backscattering analysis of HfAlO x deposited with a varied number of alternating HfO 2 and Al 2 O 3 cycles demonstrated a strong correlation between the cyclic dosage of TDEAA and TDEAH and the film composition.

Investigation of Local Coordination and Electronic Structure of Dielectric Thin Films from Theoretical Energy-Loss Spectra

Quantum mechanical simulations were performed to calculate the valence electron energy-loss spectra (VEELS) for hafnium oxide, hafnium silicate, silicon oxide and silicon systems using the full potential Linearized Augmented Plane Wave (LAPW) formalism within the Density Functional Theory (DFT) framework. The needed energy-loss function (ELF) was derived from the calculation of the complex dielectric tensor within the random phase approximation (RPA). The calculated spectra were compared with experimental scanning transmission electron microscopy (STEM)/EELS of atomic layer deposited (ALD) HfO 2 on Si(100) to evaluate their use as a “fingerprint” method that can be used to distinguish among various polymorphs of HfO 2 thin films and relate the fine structure to the electronic structure and local bonding environment. Calculated low-loss spectra are found to be in satisfactory agreement with experimental data. Also, the combination of such theoretical calculations and experimental data could be of key importance in our understanding of fundamental issues of these systems. Compared to energy-loss near edge structure (ELNES) or core energy-loss spectra, the ELF calculated for low-loss spectra is computationally less expensive and can prove useful for prompt analysis.

Erratum: ALD and Characterization of Aluminum Oxide Deposited on Si ( 100 ) Using Tris(diethylamino) Aluminum and Water Vapor [ J. Electrochem. Soc. , 153 , C701 (2006) ]

D Erratum: ALD and Characterization of Aluminum Oxide Deposited on Si„100... Using Tris(diethylamino) Aluminum and Water Vapor [J. Electrochem. Soc., 153, C701 (2006)] Rajesh Katamreddy, Ronald Inman, Gregory Jursich, Axel Soulet, and Christos Takoudis American Air Liquide, Chicago Research Center, Countryside, Illinois 60525, USA Departments of Chemical Engineering and Bioengineering, University of Illinois at Chicago, Chicago, Illinois 60607, USA