ICMCTF2011 Session TS6: Coatings for Microelectronics and Active Devices

Thursday, May 5, 2011 8:00 AM in Room Tiki Pavilion

Thursday Morning

Time Period ThM Sessions | Abstract Timeline | Topic TS6 Sessions | Time Periods | Topics | ICMCTF2011 Schedule

Start Invited? Item
8:00 AM TS6-1 Improvement of Resistance Switching Behavior by Localizing Filament with Si Injection WOX Switching Layer
Yong-En Syu (National Sun Yat-Sen University, Taiwan)

Metal-insulator-metal (MIM) structures with transition metal oxide (TMO) are typically used to implement resistance random access memory (RRAM) device. The specific structures in this paper are TiN/WOx/Pt and TiN/WSiOx/Pt. A constant voltage forming method is used to induce repeatable bipolar resistance switching behavior. Comparing with the TiN/WOx/Pt structure, the TiN/WSiOx/Pt device exhibits excellent characteristic with good endurance of more than 105 times, long retention time of 104 s in 125℃ and more stable in resistance switching state. Furthermore, the switching mechanism is investigated by current-voltage (IV) curve fitting and material analysis. From the experiment result, the conductive path of the TiN/WOx/Pt RRAM device is disorder due to its filament formed everywhere in the switching layer. In addition, the switching behavior in the TiN/WSiOx/Pt device is regard as point electric filed by localizing filament between the interface of top electrode and insulator. The TiN/WSiOx/Pt device presents a highly stable and excellent memory feature for developing next generation nonvolatile memories.

8:20 AM TS6-2 Mechanism and Characteristic Studies of Resistive Switching Effects on a Thin FeOx-Transition Layer of the TiN/SiO2/FeOx/Fe Structure by Thermal Annealing Treatments
Yao Feng Chang, Chun-Yen Chang (National Chiao Tung University, Taiwan); Ting-Chang Chang (National Sun Yat-Sen University, Taiwan)

Thermal annealing effects and mechanism studies on the resistive switching characteristics of a thin FeOx-transition layer were demonstrated by a TiN/SiO2/FeOx/Fe structure, including bipolar switching behaviors, statistics of set and reset electrical characteristics, and retention. Increase of the thermal budget on the structure shrinks both the operation voltage and variation as well as improves the device operation stability and power dissipation. Cross-section image, crystallinity and composition analyses of the transition layer were examined by tunneling electron microscope, X-ray diffraction and X-ray photon-emission spectra depth profiles, respectively. In addition, the FeOx-contained structure switching mechanism was also studied by statistics of the electrical parameter results. Retention property at room temperature and 85oC keeps both resistance states over 6×104 sec, providing the potential for nonvolatile memory applications.

8:40 AM TS6-3 Integration of Nickel Silicides in VLSI Circuits: A Mateirals Science Perspective
Patrick Desjardins (Ecole Polytechnique, Montreal, Canada)
Silicides formed by the thermally-induced solid-state reaction of a transition metal with Si are widely used in CMOS technology to reduce sheet and contact resistances at poly-Si gates and at implanted contacts. As technology progress allows for the fabrication of continuously smaller devices, roughness and Si consumption become critical issues for contact materials. While CoSi2 still dominates in industrial applications, NiSi, which results in both a smoother contact with less silicon consumption and a lower resistivity, is now used in high-performance circuits. We have utilized a combination of in situ synchrotron x-ray diffraction and ex situ reciprocal space mapping and transmission electron microscopy analyses to characterize the thermally-induced reaction of thin Ni films with Si substrates. Whereas early studies of that solid-state reaction reported the sequential appearance of phases with increasing Si content, the use of sophisticated probes reveals that several highly-textured phases form simultaneously and coexist in thin-film systems. I also demonstrate that texture inheritance between phases, where little atomic motion is required for the transformation to occur, provides a low activation energy pathway which permits the formation of metastable phases in ultrathin systems. The implications of the observed reaction pathways and film microstructure on the integration of NiSi in advanced VLSI circuits are discussed with emphasis placed on the effects of dopants, alloying elements, and substrate orientation on reaction pathways and phase formation temperatures. I conclude by discussing potential technological limitations of NiSi and approaches to circumvent them.
9:20 AM TS6-5 Resistive SwitchingCharacteristics of Ytterbium Oxide Thin Film for Nonvolatile Memory Application
Hsueh-Chih Tseng (National Sun Yat-sen University, Taiwan)
This paper studies the effect between a positive and a negative forming process on resistive switching characteristics of Pt/Yb2O3/TiN RRAM device. The polarity of the forming process can determine the transition mechanism, including bipolar and unipolar. The bipolar behaviors exist after positive forming process. Contrarily, the unipolar behaviors exist after negative forming process. Furthermore, the bipolar switching characteristics of Pt/ Yb2O3/TiN device can be affected by using reverse polarity forming treatment. Not only the set and reset voltage can be reduced, but also the on/off ratio can be improved by using the additional reverse polarity forming treatment.
9:40 AM TS6-11 Study of Micro-Imprint by Electroless Nickel Plating Method
Hsien-Ta Hsu, Ming-Jiing Ho, Tsong-Jen Yang (Feng Chia University, Taiwan)

Imprint lithography has drawn a lot of attention as one of the promising technologies for the transfer of nano/micro-patterns due to its simplicity, low cost and high throughput. Complex-shaped structures such as micro-channels, micro-trenches and non-flat patterns over large areas are commonly required for semiconductor industry. Electroless nickel (EN) plating process is much simpler than e-beam, X-ray lithography, and UV photolithography. The aims of this study are to evaluate the feasibility for the replication of micro-patterns by EN plating method and to examine the effect of additives on the surface morphology by scanning electron microscopy (SEM) and microhardness by nanoindentation. The micro-pattern with line-width 400 nm and pitch 800 nm on silicon substrate ( 24 mm x 24 mm ) can be coated uniformly by EN plating. A blind hole structure of 200 nm in diameter and 300 nm in depth with SiO2 sidewall of 400nm in thickness on 100 mm x 100 mm silicon substrate could be filled with EN. After removal of SiO2 and silicon by 30% KOH aqueous solution, the imprinted columnar array of EN is clearly shown by SEM. Additions of saccharin and SDS wetting agent to EN plating solution are closely related to the smoothness of imprinted surface, but only slightly increases the microhardness of the coating from 6.303 GPa to 6.437 GPa with 15mN loading. Post-treatment of stress relaxation after EN plating is necessary to minimize potential hydrogen embrittlement adverse effect. Excellent pore-filling capability and step coverage of EN plating have been shown during micro-imprint.

10:00 AM TS6-8 Effect of the Thermal Stability and Electrical Behavior of Nickel Silicide by using Nickel Nitride
Chi-Ting Wu, Wen-Hsi Lee, Chia-Yang Wu, Siou-An Yan (National Cheng-Kung University, Taiwan)

Metal silicides have been widely used in ultralarge scale integrated (ULSI) circuits to reduce the contact resistance of source/drain (S/D) in complementary metal-oxide-semiconductor (CMOS) devices. Currently, the most commonly used silicides are TiSi2 and CoSi2. The TiSi2, the transformation from the high resistivity C49 phase to the low resistivity C54 phase is nucleation limited, causing linewidth dependence of the sheet resistance for gate lines narrower than submicrometer dimension. Therefore, CoSi2 and NiSi have emerged as the most promising candidates to replace C54-TiSi2 phase in Self-Aligned Silicide (Salicide) technology.

Nickel mono-silicide (NiSi) with low sheet resistance (Rs), line-width independence and relatively low silicon consumption has received much attention in recent years. The main disadvantage of NiSi is low thermal stability. The formation of NiSi takes place around 350oC, and the phase transition of NiSi to the high resistivity NiSi2 phase occurs at over 700oC, which limits its application. Nickel silicide agglomeration easily occurs at a temperature above 600oC, and the related phase transformation NiSi2 degrades device performance and gives rise to some reliability issues.

In this study, the effects of nickel nitride (NiNx) capping layers on the formation of nickel silicide have been investigated. Using the NiNx replace the capping layer (TiNx) with the anticipation that the resulting materials would be suitable for next-generation CMOS processes. Nickel silicide films using NiNx (N ratio flow of 0~30 sccm) are used in an RTA process. They exhibit advanced thermal stability at 300-800oC/30s, and inhibit surface agglomeration better than the TiNx and non-capping layer nickel silicide. The diffraction peaks of the NiNx films deposited with N2 flow ratios rang from 10~20 sccm has a Ni4N peak, when N2 flow ratios rang from 25~30 sccm has a Ni3N peak. The Ni4N phase is inhibit surface roughness and thermal stability properties better than Ni3N phase. The results of the Ni4N remove rate faster than Ni3N and NiSi and the thermal stability and inhibit surface agglomeration behavior still Ni4N has better than Ni3N on the nickel silicide. Final, the Tafel corrosion rate curves of the NiNx (Ni4N and Ni3N) and nickel thin films in the H2SO4:H2O2=4:1 were investigated.

10:20 AM TS6-9 Inkjet-Printed High-k Nanocomposite Dielectric Film for OTFT Applications
Chao-Te Liu, Wen-Hsi Lee, Tsu-Lang Shih, Hsueh-Jen Yan (National Cheng-Kung University, Taiwan)
The preparation of nanocomposite as the gate insulating film was achieved by blending cross-linked Poly(4-vinylphenol) of polymer and high-k TiO2 nano-particles to enhance the permittivity of the dielectric and reduce operating voltage of devices. In order to well disperse the TiO2 particles and increase doping concentration higher than 1 wt%, we utilize pearl mill to crumble the agglomerations and dispersant to stabilize the nano-particles in the polymer matrix for inks. In this paper, the dielectric film with the admixture was made by inkjet printing to avoid the photography process. By studying the characteristics of insulating films at different parameters of ink-jet printing, including voltage, frequency and waveform, we successfully printed dielectric layout, accomplishing the purpose of directly-patternable and low roughness after curing at 190°C, when the solid content of TiO2 about 3 wt% in the ink. Finally, we realized a low leakage current density in the nanocomposite dielectric and high current ratio in the pentacene-TFTs device with top contact structure. These devices exhibited p-channel TFT characteristics with a high field-effect mobility (a saturation mobility of ~0.49 cm2V-1s-1) and a low voltage operation (<6 V), indicating that these NC-dielectric materials can be used in low-cost and high-performance printable electronics.
10:40 AM TS6-10 Resistive Switching Characteristics of Gallium Oxide for Nonvolatile Memory Application
Jheng-Jie Huang (National Sun Yat-Sen University, Taiwan)
In this study, we fabricated the resistance random access memory (RRAM) of Ti/GaOx/Pt structure and the device present a bipolar resistance switching characteristics. The gallium oxide of control sample was sputtered in Ar atmosphere, and demonstrates a bistable resistance ratio of about 2 orders by I-V sweeping. Additionally, the gallium oxide layer of proposed sample was sputtered in a mixed ambient of Ar and oxygen to increase the oxygen ion quantity, and the resistance ratio can be enhanced to 3 orders. Endurance and retention results indicate that the proposed memory device has excellent device reliability, and the multi-level phenomenon can be applied for multi-bit storage. The X-ray photoelectron spectroscopy (XPS) was employed to verify the influence of oxygen content on the resistance switching characteristic.
11:00 AM TS6-6 Study of Sputter Deposited SiO2/Co/Pt/SiO2 Multilayers for Magnetic Storage
Rajan Walia (Indian Institute of Technology, Roorkee, India); Amit Kumar Chawla, Ramesh Chandra, R. Jayaganthan (Indian Institute of Technology Roorkee, India)

Conventional Co alloy based recording media are unable to fulfill the requirement of high density magnetic recording up to 1 Tbit/ in2 due to phenomenon like superparamagnetism. L10 CoPt is a potential candidate due to its large Ku value of 107 ergs/cm3. The high Ku value of CoPt allows smaller and thermally stable grains (of size 3nm) against superparamagnetism[1]. Such small grain size is able to increase the areal density beyond 1 Tbit/ in2. However, as deposited CoPt film shows fcc phase. To achieve the desired phase, high deposition temperature or postdeposition annealing at temperature higher than 600°C is required [2-4]. High deposition temperature increases the grain size which effectively reduces the signal-to-noise ratio. L10 CoPt–SiO2 nanocomposite provides control the CoPt grain size and intergranular magnetic interaction [5]. However, the effects of SiO2 addition on chemical ordering and magnetic properties of Co/Pt multilayers will be interesting to probe.

In this study we have prepared different set of thin films containing different number of multilayers of Co and Pt with SiO2 as a buffer and capping layer on Si (100) substrates. Deposition were made in a custom built DC/RF sputtering chamber by varying number of multilayers of SiO2 /Co/Pt/SiO2. In each set of thin films thichkness of various layers were kept fixed while the number of multilayers were varied. Samples were annealded up to (400oC -700oC) in Ar atmosphere. Structural studies of these films were done by X-ray diffraction and Field Emission Scanning Electron Microscopy, Atomic Force Microscopy and Transmission Electron Microscopy while magnetic measurements were done by SQUID (Superconducting Quantum Interference Device) magnetometer. Structural properties of as deposited thin films show the formation of fcc phase of CoPt nanoparticles while annealing at higher temperatue shows the change in the crystal structure. Magnetic Measurements show the high value of coercivity for both longitudinal as well as in perpendicular direction.

1. R. Sbiaa and S. N. Piramanayagam, Recent Patents on Nanotechnology 1, 29 (2007).

2. Y. Xu, Z. G. Sun, Y. Qiang, and D. J. Sellmyer, J. Magn. Magn. Mater. 266, 164 (2003).

3 O. Kitakami, Y. Shimada, K. Oikawa, H. Daimon, and K. Fukamichi, Appl. Phys. Lett. 78, 1104 (2000).

4. C. Chen, O. Kitakami, S. Okamoto, and Y. Shimada, Appl. Phys. Lett. 76, 3218 (2000).

5. C. Chen, O. Kitakami, S. Okamoto, and Y. Shimada, IEEE Trans. Magn. 35, 3466 (1999).

Time Period ThM Sessions | Abstract Timeline | Topic TS6 Sessions | Time Periods | Topics | ICMCTF2011 Schedule