Sasangan Ramanathan

ALD of Hafnium Oxide Thin Films from Tetrakis(ethylmethylamino)hafnium and Ozone

Hafnium oxide (HfO 2 ) thin films were deposited from tetrakis(ethylmethylamino)hafnium (TEMAH) and ozone (O 3 ) by atomic layer deposition (ALD) on 200 mm silicon wafers. The O 3 half-reaction shows good saturation behavior. However, gradual surface saturation is observed for the TEMAH half-reaction. Within wafer non-uniformity of less than 1% and step coverage of about 100% were achieved for trenches with aspect ratio of around 40:1. The film thickness increased linearly as the number of cycles increased. From susceptor temperatures of 160-420°C, the lowest deposition rate (A/cycle) and the highest refractive index is observed at 320°C. The atomic ratio of hafnium to oxygen determined by Rutherford backscattering is 1:2.04 for the films deposited at 320°C. The carbon and hydrogen content determined by secondary ion mass spectroscopy (SIMS) decreased as the susceptor temperature increased from 200 to 320°C. Lower carbon and hydrogen levels were obtained in the control films made with H 2 O than the films made with O 3 . A reaction mechanism of the TEMAH + O 3 ALD process is discussed. The results show that an O 3 -based ALD HfO 2 deposition is promising for microelectronic applications.

SrBi2Ta2O9 thin films made by liquid source metal-organic chemical vapor deposition

A liquid source metal-organic chemical vapor deposition system was installed to deposit SrBi 2 Ta 2 O 9 (SBT) thin films on sapphire and Pt/Ti/SiO 2 /Si substrates. The process parameters such as deposition temperature and pressure, and ratio of Sr: Bi: Ta in the precursor solutions were optimized to achieve stoichiometric films with good reproducible ferroelectric properties. It was found that the nucleation of SBT started at a deposition temperature close to 500 °C and grain growth dominated at 700 °C and higher temperatures. With increasing deposition temperatures, the grain size of SBT thin films increased from 0.01 μ m to 0.2 μ m; however, the surface roughness and porosity of the films also increased. To fabricate specular SBT films, the films had to be deposited at lower temperature and annealed at higher temperature for grain growth. A two-step deposition process was developed which resulted in high quality films in terms of uniformity, surface morphology, and ferroelectric properties. The key to the success of this process was the homogeneous nucleation sites at lower deposition temperature during the first step and subsequent dense film growth at higher temperature. The two-step deposition process resulted in dense, homogeneous films with less surface roughness and improved ferroelectric properties. SBT thin films with a grain size of about 0.1 μm exhibited the following properties: thickness: 0.16–0.19 μ m; 2 P r : 7.8–11.4 μ C/cm 2 at 5 V; E c : 50–65 kV/cm; I leakage : 8.0–9.5 × 10 −9 Acm −2 at 150 kV/cm; dielectric constant: 100–200; and fatigue rate: 0.94–0.98 after 10 10 cycles at 5 V.

Atomic Layer Deposition of Aluminum Nitride Thin films from Trimethyl Aluminum (TMA) and Ammonia

Aluminum nitride (AlN) thin films were deposited from trimethyl aluminum (TMA) and Ammonia (NH 3 ) by thermal atomic layer deposition (thermal ALD) and plasma enhanced atomic layer deposition (PEALD) on 200 mm silicon wafers. For both thermal ALD and PEALD, the deposition rate increased significantly with the deposition temperature. The deposition rate did not fully saturate even with 10 seconds of NH 3 pulse time. Plasma significantly increased the deposition rate of AlN films. A large number of incubation cycles were needed to deposit AlN films on Si wafers. 100% step coverage was achieved on trenches with aspect ratio of 35:1 at 100 nm feature size by thermal ALD. X-ray diffraction (XRD) data showed that the AlN films deposited from 370 °C to 470 °C were polycrystalline. Glancing angle X-ray reflection (XRR) results showed that the RMS roughness of the films increased as the film thickness increased.

Atomic Layer Deposition of Hafnium Oxide Thin Films from Tetrakis(dimethylamino)Hafnium (TDMAH) and Ozone

Hafnium oxide (HfO 2 ) thin films were synthesized from tetrakis(dimethylamino) hafnium (TDMAH) and ozone (O 3 ) by atomic layer deposition (ALD) on 200 mm silicon wafers. Gradual saturation was observed for TDMAH exposure pulse. However O 3 showed better saturation behavior for O 3 exposure. Yet, 100% step coverage was achieved for ~100nm trenches with aspect ratio of 35. Temperature dependence of the deposition rate was studied at susceptor temperature from 160°C to 420°C. The lowest deposition rate was observed at 320°C. Mercury probe measurements indicated the dielectric constant increased from 16 to 20 as susceptor temperature increased from 200°C to 320°C. Selected comparisons with tetrakis (ethylmethylamino) hafnium (TEMAH) were also made.

Microstructural and Electrical Characteristics of Rapid Thermally Processed (Ba1—xSrx)TiO3 Thin Films Prepared by Metalorganic Solution Deposition Technique

Barium strontium titanate thin films including barium titanate BaTiO3 and strontium titanate SrTiO3 end members were fabricated on Pt-coated silicon and bare silicon substrates by metalorganic solution deposition (MOSD) technique using acetate precursors. Polycrystalline (Ba 1-x Sr X )TiO 3 thin films were obtained by rapid thermal annealing at 700 °C for 60s. The films were characterized for electrical properties in terms of dielectric permitivity, dissipation factor, and dc leakage current characteristics. A peak in dielectric constant was observed for (Ba 0.6 Sr 0.4 )TiO3 composition at room temperature. The typical measured small signal dielectric constant and dissipation factor for 0.5 μm-thick (Ba 0.6 Sr 0.4 )TiO3 films at 100 kHz were 450 and 0.012, respectively. (Ba 0.6 Sr 0.4 )TiO3 thin films exhibited a high voltage dependent tunability of 47% at an applied electric field of 0.5 MV/cm. The interfacial properties of Au/(Ba 0.6 Sr 0.4 )Ti0 3 /Si structure were examined by high frequency C-V measurements. A charge storage density of 39.6 fC/μm 2 and leakage current density of less than 10 -8 A/cm 2 were obtained for (Ba 0.6 Sr 0.4 )TiO 3 thin films at an applied electric field of 100 kV/cm.

Characteristics of ALD HfSiO/sub x/ using new Si precursors for gate dielectric applications

We have successfully developed a process for ALD HfSiO/sub x/ that can provide excellent compositional control by using new Si precursors, Si/sub 2/Cl/sub 6/ (HCDS) and SiH[(CH/sub 3/)/sub 2/]/sub 3/ (tDMAS). In addition, comparisons of electrical properties of HfSiO/sub x/ using two Si precursors have been performed. CMOSFET with HfSiO/sub x/ using HCDS results in better reliability characteristics than tDMAS. Superior electron and hole mobility (100% and 90% of universal curve at 0.8MV/cm) are also achieved with HCDS. Consequently, HCDS has the potential to be used as a Si precursor for ALD HfSiO/sub x/.

Characterization of Ba0.6Sr0.4TiO3 thin films with Mg additive fabricated by Metalorganic decomposition technique

Abstract We report for the first time Ba0.6Sr0.4TiO3 (BST 60/40) thin films with Mg additive fabricated by Metalorganic decomposition technique on platinum coated silicon substrates using acetate-alkoxide precursors.[1] The structural and electrical properties of the BST thin films were greatly changed by additions of Mg. The surface morphology of the films was smooth with a dense microstructure. The typical small signal dielectric constant and the loss factor for a 0.4 μm thick undoped BST films were 450 and 0.013, respectively, at an applied frequency of 100 kHz. The dielectric loss was significantly reduced by the Mg content. The tunability (ΔC/C0) was found to change from 20.7% to 5.8% as the Mg additive content was changed from 0 to 20 mol%. The films exhibited high resistivity of the order of 1012 Ω-cm even up to an applied electric field of 100 kV/cm.

Mass production worthy HfO/sub 2/-Al/sub 2/O/sub 3/ laminate capacitor technology using Hf liquid precursor for sub-100 nm DRAMs

For the first time, we successfully demonstrated MIS capacitor with ALD (Atomic Layer Deposition) grown HfO/sub 2/-Al/sub 2/O/sub 3/ laminate film using Hf liquid precursor (Hf(NEtMe)/sub 4/) with EOT of 22.5 /spl Aring/ and acceptable leakage currents (1.0 fA/cell at 1.65 V) which is comparable to the smallest reported value. Advantages of Hf(NEtMe)/sub 4/ liquid precursor for DRAM capacitor dielectric are excellent step coverage (94% on high aspect ratio(>40:1)) and reasonable throughput (over two times higher than that of HfCl/sub 4/ solid precursor). This study will provide practical solution for chip-making industry in terms of mass production worthy process for sub-100 nm DRAM capacitor.

Advances in ALD Equipment for sub-40nm Memory Capacitor Dielectrics: Precursor delivery, Materials and Processes

In DRAM, maintaining the cell capacitance more than 25 fF/cell with shrinking cell capacitance area has been accomplished with the introduction of higher k oxides as the capacitor dielectric. Higher k materials include Al2O3, HfO2, ZrO2 or a combination of HfO2/Al2O3/HfO2 and ZrO2/Al2O3/ZrO2. These materials can satisfy DRAM device requirements down to the 50 nm node. However, for sub 40nm DRAM technology nodes, precursor delivery challenges are far greater and require unique precursor delivery methodology to ensure >90% conformality in high aspect ratio DRAM capacitor structures, while maintaining higher productivity. The precursor delivery problem is due to the very low vapor pressures of the precursors for advanced high k dielectrics.. This paper highlights the progress made in ALD equipment development offering solutions for critical problems facing sub 40nm DRAM technology nodes. Particularly, this paper describes a unique pulsed vaporization technology (TriJet®) coupled with a high performance ALD reactor that offers solution for next generation high k film deposition without compromising productivity.

Atomic level solutions® for advanced microelectronic applications

Atomic Layer Deposition (ALD) has successfully been applied to advanced microelectronic applications importantly for conformal coatings on high aspect ratio devices. However, traditional ALD is limited in deposition rate because the ability to bring precursors rapidly to the surface. In this paper we review recent results for precursor delivery using advanced vaporization (Trijet) as well as recent advances in Pulsed CVD (AVD®) using art elements held in common with ALD technology. These and other advances - such as Multiple Single Wafer configurations allow ALD application for continued scaling under conditions of improved process control and higher productivity. Key applications include: capacitors (dielectrics and electrodes), transistors and contacts. This paper reviews these technological advances in the context of their applications.