Jim Leu - Academia.edu (original) (raw)

Papers by Jim Leu

Journal of Alloys and Compounds, Jul 1, 2016

The figure of merit zT was calculated wrong in Figure 4 and 5e of the above manuscript. The corre... more The figure of merit zT was calculated wrong in Figure 4 and 5e of the above manuscript. The correct calculation can be seen in Figure 1 below. Also the maximum zT value is rather 0.30 at 700°C than 0.32 as mentioned in the abstract, introduction and Section 2.2. However, the wrong calculation doesn´t affect the discussion nor the interpretation. Figure 1. Correct calculation of zT for a) Figure 4 and b) Figure 5e in the above manuscript.

Acta Materialia, Mar 1, 2021

Abstract Oriented and nanotwinned copper (nt-Cu) of 3.8 µm thickness was electroplated on a Si wa... more Abstract Oriented and nanotwinned copper (nt-Cu) of 3.8 µm thickness was electroplated on a Si wafer substrate for thermal stress measurement from room temperature to 400 °C by bending beam method. Microstructure transformation in the copper thin film was studied after the thermal process. At 150 °C, the maximum compressive stress reached 150 MPa, and the (111) oriented nanotwinned copper began to transform to (200) orientation. Beyond 150 °C, anisotropic grain growth of (200) grains is faster. For comparison with the random-oriented copper thin films without nanotwins, we discover that the nanotwinned films can withstand a compressive stress of 1.5 times greater than the random copper thin films. This large thermal stress provides the driving force for anisotropic grain growth in the oriented nano-twin Cu, which can reach several hundred µm.

Over the past several years DuPont has been exploring new, rod-like fluorinated polyimides for in... more Over the past several years DuPont has been exploring new, rod-like fluorinated polyimides for interlayer dielectric (ILD) applications. It has been shown that copolymerization is a versatile method for tailoring properties of these rigid polyimides. Initial product offerings from DuPont showed an excellent balance of properties for ILD applications. These materials, however, due to their highly rod-like structure and very low in-plane coefficient of thermal expansion (CTE), actually yielded negative thermal stresses on silicon at the 1 {mu}m thicknesses typical of interlayer dielectrics. More flexible materials with higher CTE typically yield positive stress values which can be undesirably quite high. The dielectric constant of these highly rod-like fluorinated polyimides was also somewhat anisotropic, again due to the rod-like nature and resulting high in-plane orientation of these polyimides. Since a thermal stress on silicon near zero and a more isotropic dielectric constant are likely the most desirable states for an ILD, the highly rod-like polyimide was further optimized by incorporation of a more flexible fluorinated comonomer, 6FDA, at various levels to increase CTE and balance dielectric constant. The various properties of this series of fluorinated polyimides were investigated. The results have shown that it is indeed possible to obtain near zeromore » stress on silicon while attaining more isotropic dielectric constant via structure optimization.« less

Journal of vacuum science and technology, Nov 1, 2018

Low-k dielectric silicon carbonitride (SiC x N y) films are deposited by plasma-enhanced chemical... more Low-k dielectric silicon carbonitride (SiC x N y) films are deposited by plasma-enhanced chemical vapor deposition using a carbon-rich silazane precursor, N-methyl-aza-2,2,4-trimethylsilacyclopentane (SiC 7 NH 17), at 100°C. The post-treatments of SiC x N y films are carried out by thermal annealing and a broadband UV-assisted thermal annealing (UV-annealing) at 400°C for 5 min. Compared to the thermal annealing treatment, UV-annealing can improve both dielectric and mechanical properties of low-k SiC x N y films. Under thermal annealing, SiC x N y films show great thermal stability, but little structural change. In contrast, upon UV-annealing, most of the Si-H and N-H bonds are broken up, which induces more SiN cross-linking and converts Si-C matrix into SiN matrix. The ethylene bridges in Si-(CH 2) 2-Si also remain intact, but the unbridged hydrocarbons in Si-(CH 2) 2-N and Si-CH 2-CH 3 bonds decompose completely during the UV-annealing process. These account for the reduced dielectric constant to k = 3.2 from 3.6 and a 21% enhancement of Young's modulus to 7.4 GPa in the SiC x N y films after UV-annealing. Broadband UV-annealing shows promise as a post-treatment method for enhancing the properties of low-k dielectric barrier, SiC x N y films.

Materials Characterization, Oct 1, 2020

The aim of the study was determination of serum Se concentration and identification of genetic va... more The aim of the study was determination of serum Se concentration and identification of genetic variations in genes related to metabolism of selenium as markers of cancer risks for carriers of BRCA1 gene mutation and individuals with susceptibility to unselected breast cancer.

Thin Solid Films, Aug 1, 2017

Abstract In this study, amorphous silicon carbonitride (SiC x N y ) films were fabricated by radi... more Abstract In this study, amorphous silicon carbonitride (SiC x N y ) films were fabricated by radio frequency (RF) chemical vapor deposition (PECVD) using a single silazane precursor and a low power density (0.15 W/cm 3 ) for better compositional control. The effects of the precursor chemical structure (C/Si ratio, C Si N structure, and vinyl groups) and deposition temperature ( T s ) on the chemical structure and optical properties of SiC x N y films were examined using Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Specifically, two new single precursors; namely, n -methyl-aza-2,2,4-trimethylsilacyclopentane (MTSCP) and 1,3-divinyl-1,1,3,3-tetramethyl-disilazane (DVTMDS) were studied and compared. SiC x N y films deposited using MTSCP involving Si C 3 N rings formed Si N and Si (CH 2 ) 3 crosslinked structures at T s ≤ 100 °C, and were then changed to predominantly Si CH 2 N Si crosslinked structures at T s > 300 °C, leading to a wide range of optical band gap from 5.2 to 3.7 eV. Compared to DVTMDS-deposited SiC x N y films, their relatively higher percentage of Si C N structure accounted for the lower optical band gap and reduced transmission. DVTMDS with di-vinyl groups readily formed a Si (CH 2 ) 2 bridge in SiC x N y films T s ≤ 200 °C, resulting in excellent optical transmittance. The transmittance in the visible wavelengths of 400 °C-deposited SiC x N y film using DVTMDS still showed 85%. Also, tunable refractive index between 1.44 and 2.10 were obtained for SiC x N y films deposited at T s ≤ 400 °C.

ABSTRACT This paper describes the collaboration between university and industry in the evaluation... more ABSTRACT This paper describes the collaboration between university and industry in the evaluation of low dielectric materials for on-chip interconnect applications. The collaboration has established selection criteria and characterization methodologies for materials evaluation of dielectric thin films in the micron range. A review on the concerted efforts of semiconductor industry, materials suppliers, university and consortium in materials and processing evaluation and in improving the interlayer dielectrics (ILD) materials in alignment of SIA Technology Roadmap are described. The characterization techniques of thin films and results of materials evaluation are discussed

Japanese Journal of Applied Physics, Jun 3, 2015

In this paper, we present static thermal analysis of stress and strain on a thin-film transistor ... more In this paper, we present static thermal analysis of stress and strain on a thin-film transistor liquid-crystal display (TFT-LCD) panel and their correlation with light leakage phenomena under high-temperature durability test. Three-dimensional (3D) finite element analysis (FEA) is coupled with experimental parameters of key components of the TFT-LCD panel for the analysis. A strong correlation exists between light leakage and retardation difference induced by stress on triacetyl cellulose (TAC) films. Moreover, shrinkage in stretched poly(vinyl alcohol) (PVA) film and modulus of the adhesive layer are key factors affecting stress distribution and displacement of polarizer stack. An increase in Young's modulus (E) of the adhesive layer effectively reduces polarizer shrinkage and light leakage at the center of the panel. A TAC film with lower Young's modulus and/or coefficient of thermal expansion (CTE) is also an effective solution.

Mrs Bulletin, Oct 1, 1997

Continuing improvement in device density and performance has significantly affected the dimension... more Continuing improvement in device density and performance has significantly affected the dimensions and complexity of the wiring structure for on-chip interconnects. These enhancements have led to a reduction in the wiring pitch and an increase in the number of wiring levels to fulfill demands for density and performance improvements. As device dimensions shrink to less than 0.25 μm, the propagation delay, crosstalk noise, and power dissipation due to resistance-capacitance (RC) coupling become significant. Accordingly the interconnect delay now constitutes a major fraction of the total delay limiting the overall chip performance. Equally important is the processing complexity due to an increase in the number of wiring levels. This inevitably drives cost up by lowering the manufacturing yield due to an increase in defects and processing complexity.To address these problems, new materials for use as metal lines and interlayer dielectrics (ILDs) and alternative architectures have surfaced to replace the current Al(Cu)/SiO2 interconnect technology. These alternative architectures will require the introduction of low-dielectric-constant k materials as the interlayer dielectrics and/or low-resistivity conductors such as copper. The electrical and thermomechanical properties of SiO2 are ideal for ILD applications, and a change to material with different properties has important process-integration implications. To facilitate the choice of an alternative ILD, it is necessary to establish general criterion for evaluating thin-film properties of candidate low-k materials, which can be later correlated with process-integration problems.

Springer series in advanced microelectronics, 2003

As integrated circuit dimensions continue to decrease, RC delay, crosstalk noise and power dissip... more As integrated circuit dimensions continue to decrease, RC delay, crosstalk noise and power dissipation of the interconnect structure become limiting factors for ultra-large-scale integration of integrated circuits. Materials with low dielectric constant are being developed to replace silicon dioxide as interlevel dielectrics. This chapter provides an overview on the basic issues of low-k dielectrics for interconnect applications and serves as

Springer series in advanced microelectronics, 2003

discussing material reaction and process integration. With intense efforts from industry and univ... more discussing material reaction and process integration. With intense efforts from industry and universities, significant progress has been made in the synthesis of fully dense low-k materials with molecular structures to optimize material properties for integration into copper interconnects. Material characterization has been an integral part of low-k development and extensive efforts have been made in metrology development to evaluate material properties for process integration. Since low-k materials are integrated as thin films, their properties can differ appreciably from bulk or thick-film materials. This challenges metrology development for measuring material properties of thin films on a wafer, particularly for porous materials where the porosity further complicates material characterization. In Chap. 2, Ryan et al. describe characterization techniques developed for measuring dielectric, thermal, and mechanical properties of low-k thin films. In Chap. 3, Lin et al. review two new techniques: specular X-ray reflectivity (SXR) and small-angle neutron scattering (SANS) for characterization of porous low-k materials. Two general approaches for synthesis of low-k materials are discussed: in Chap. 4 by Gill et al. on vapor deposition and in Chap. 5 by Endo et al. on plasma-enhanced chemical vapor deposition of polymeric low-k dielectrics. For development of porous low-k materials, the "porogen" approach using a thermally degradable template appears promising in that it can be applied to a wide range of inorganic and organic materials and has good control of the pore size and morphology. The application of the porogen technique to synthesize porous low-k materials is described in Chap. 6 by Volksen et al. In the past several years, significant progress has been made by the semiconductor industry to integrate low-k dielectrics into copper interconnects. In Chap. 10, Waterloos describes process integration of SiLK TM into Cu damascene structures. Complementing the integration chapter, Oehrlein et al. in Chap. 9 discuss the plasma-etching process, a key step in integration of low-k structures. The weak thermal and mechanical properties have raised reliability concerns on thermal stability and structural integrity of low-k structures. Distinct failure mechanisms have been observed in low-k structures during processing or reliability tests, where more work is clearly required to fully understand the impact of low-k integration on interconnect reliability. Two basic issues related to reliability are discussed in this book: in Chap. 7 by Martini and Kelber on metal/polymer interfacial reaction and in Chap. 8 by Faupel et al. on metal diffusion in polymers. Continuing efforts in low-k integration will undoubtedly advance our knowledge on material development, characterization, process integration, and reliability for this exciting class of materials and its technology. While new knowledge and developments are to be expected, we hope that this book provides a basis for readers to understand the current advances in low-k dielectrics for interconnect applications. We sincerely appreciate the efforts from all the authors for their valuable contributions to make this book pos-Preface VII sible. We would like to thank Claus Ascheron from Springer-Verlag for his patience in letting us complete this book properly and Jo Ann Smith for her efforts in working with the manuscript.

Incorporation of porosity into dielectric materials is a viable method to reduce k-value down to ... more Incorporation of porosity into dielectric materials is a viable method to reduce k-value down to < 2.5. A Solid-First TM scheme based on high-temperature porogen, poly (styrene-block-4-vinylpyridine) (PS-P4VP), poly(styrene-block-butadiene-block-styrene) (PS-PB-PS) and methyl-silsesquioxane (MSQ) as the matrix have been employed to prepare porous low-k dielectric in order to circumvent the reliability issues encountered in the integration of as-deposited porous dielectric. The impact of high-temperature porogens, their loadings, and porosities on the moisture uptake and diffusion behavior was investigated using a home-built quartz crystal microbalance (QCM). Three low-k dielectric systems were employed in this thesis to simulate interlayer dielectrics (ILD) at different stages of Solid-First TM integration scheme; namely: (1) MSQ films cured at different temperatures up to 400 o C, (2) MSQ/porogen hybrid films cured at 250 o C with various porogen loadings, and (3) their corresponding porous films burned out at 400 o C. The moisture uptake of porous films cured at 400 o C increased with porosity due to an increase of pore surface area and residual silanol, Si-OH groups. Further

Bismuth selenide (Bi2Se3) and bismuth telluride (Bi2Te3) are well-known compounds for thermoelect... more Bismuth selenide (Bi2Se3) and bismuth telluride (Bi2Te3) are well-known compounds for thermoelectric (TE) cooling and generation applications near room-temperature. The performance of TE materials is quantified by a dimensionless figure of merit, ZT = α2σT/κ, in which α, σ, κ, and T are the Seebeck coefficient, the electrical conductivity, the thermal conductivity, and absolute temperature, respectively. Currently, enhancing the TE power factor (PF = α2σ) of Bi2Se3 and Bi2Te3 thin-films remains a challenge due to the coupling amongst TE material properties and the difficulty of growing stoichiometric films under elevated substrate temperatures (Ts), at which is beneficial for enhancing the σ. In this thesis study, n-type TE Bi2Se3 and Bi2Te3 thin films were grown on SiO2/Si substrates using pulsed laser deposition (PLD). The effects of the structure, composition, and morphology on the TE properties of Bi2Se3 and Bi2Te3 thin films were investigated by controlling background ambient pressures (P) and Ts in PLD depositions. We found that the deposition in relatively high P (≥ 40 Pa) could obtain stoichiometric films at extended Ts up to 300 °C for Bi2Se3 and 340 °C for Bi2Te3, which can reduce the carrier concentration (n) and significantly enhance the Seebeck coefficient (α), following the α~n-2/3 relation approximately. Furthermore, at high Ts- growths, the obtained structures of highly (00l)-oriented – layered of large crystallites led to the substantial increase in the carrier mobility µ and thus improve the σ (= nµe). For example, the stoichiometric Bi2Se3 films grown at grown at 300 °C and 40 Pa with highly (00l) oriented and layered-hexagonal platelets possessed the highest PF of 5.54 µWcm-1K-2, where ׀α׀ = 75.8 µV/K and σ = 963.8 S/cm. Similarly, the stoichiometric Bi2Te3 films grown at Ts = 220–340 °C and PAr = 80 Pa with highly (00l)-oriented and layered structures showed the best properties, with a carrier mobility µ of 83.9 – 122.3 cm2/Vs, an ׀α׀ of 172.8 – 189.7 µV/K, and a remarkably high PF of 18.2 – 24.3 µWcm-1K-2. In contrast, the Te-rich films deposited at Ts ≤ 120 °C with (015)-preferred orientations and columnar–small grain structures or the Te-deficient film deposited at 380 °C with Bi4Te5 polyhedron structure possessed poor properties, with µ < 10.0 cm2/Vs, ׀α׀ < 54 µV/K, and PFs ≤ 0.44 µWcm-1K-2. This study provides a comprehensive understanding the interrelationships between PLD processing conditions, microstructures, and TE properties of Bi2Te3-based thin films, promising for further improving the TE performance of materials and applications. In brief, the morphology of highly (00l) oriented–layered large crystallite structures and the stoichiometry predominantly contribute to the substantial enhancement of µ and ׀α׀, respectively, resulting in remarkable enhancement in PF.

Lower k and low-leakage silicon carbonitride (SiCxNy) films were fabricated using single precurso... more Lower k and low-leakage silicon carbonitride (SiCxNy) films were fabricated using single precursor by using radio-frequency (RF) plasma-enhanced chemical vapor deposition (PECVD). We explored precursors with (1) cyclic-carbon-containing structures, (2) higher C/Si ratio, (3) multiple vinyl groups, as well as (4) the incorporation of porogen for developing low-k SiCxNy films as etch-stop/diffusion barrier (ES/DB) layer for copper interconnects in this study. SiCxNy films with k values between 3.0 and 3.5 were fabricated at T≦ 200 C, and k~4.04.5 at 300-400 C. Precursors with vinyl groups yielded SiCxNy films with low leakage, excellent optical transmittance and high mechanical strength due to the formation of cross-linked Si(CH2) n-Si linkages.

Thin Solid Films, 2015

Abstract Low-k SiCxNy films were prepared using radio-frequency plasma-enhanced chemical vapor de... more Abstract Low-k SiCxNy films were prepared using radio-frequency plasma-enhanced chemical vapor deposition (PECVD), with only 1,3,5-trimethyl-1,3,5-trivinylcyclotrisilazane (VSZ) as the precursor; VSZ has cyclic Si–N–Si linkages and three pendent vinyl groups. At lower PECVD temperatures, SiCxNy films possess relatively low film densities, indicating the existence of a loose structure or voids within the cross-linked matrix structure. The pore morphology of SiCxNy films deposited at distinct temperatures were examined using grazing-incidence small-angle X-ray scattering, while the chemical bondings and structural information were analyzed using Fourier-transform infrared spectroscopy. At 100 °C, SiCxNy films without porogen displaying 4.9 nm pores and a mean pore spacing of 30.1 nm generated low-density films because Si-(CH2)n-Si and/or Si-(CH2)n-CH3 could be incorporated free volume into the N–Si–C cross-linked structure under plasma deposition. At 300 °C, the N–Si–C cross-linked structure and the some organic phase were disrupted and transformed into a denser structure, reducing pore size (3.5 nm) and losing pore correlation. Thus, low deposition temperatures facilitate the formation of large pores and the ordering of the pores. Post annealing converted the 100 and 300 °C as-deposited SiCxNy films into loose and dense structures, respectively, and maintained slightly reduced pore size and pore correlation in the annealed films.

IEEE Transactions on Device and Materials Reliability, 2020

This study determines the relationship between retention and endurance reliability for a HfOx-bas... more This study determines the relationship between retention and endurance reliability for a HfOx-based resistive random access memory (ReRAM). A TiN (15 nm) / HfOx (6 nm) / Ti (10 nm) / TiN (40 nm) stacked structure is fabricated and tested to verify its basic characteristics and reliability. The high resistance states (HRS) retention behavior is characterized and is found to degrade over 100x on the endured bits because there is a sequential high temperature procedure. The degradation is reduced slightly to a ~30x drop for the endured devices with one single refresh cycle. During the endurance and retention test procedures, the HRS resistance decreases because neutral oxygen vacancy filaments grow and this cannot be reversed. The I-V characteristics for endured devices are also determined. The results show that isothermal treatment causes a gradual SET and RESET process with multiple feasible states. The thermally induced filament degradation model (isolated filament vs. continuous filament) is verified by the relationship between retention and endurance reliability. Design guidance is recommended for an improvement in ReRAM reliability.

Applied Physics Letters, 2020

In this work, SiCxNy-based resistive switching memory by using a single precursor for the back en... more In this work, SiCxNy-based resistive switching memory by using a single precursor for the back end of line (BEOL) integration has been investigated. SiCxNy films were deposited on the aluminum (Al) substrates using plasma enhanced atomic layer deposition (PEALD) method. The effects of SiCxNy chemical structure with respect to resistive switching characteristics have been studied, and the results suggest that the resistive switching mechanism is dominated by the interfacial Schottky junction with SiCxNy composition. This work not only demonstrates a PEALD method in fabricating SiCxNy-based electronics active devices but also provides additional insights into the interaction between the electrical and chemical structures in bi-functional resistive switching or threshold switching behavior. A demonstrated PEALD tool with simple single-precursor for SiCxNy deposition shows excellent feasibility to be used as functional memory and selector devices, further giving the potential pathway fo...

Journal of Alloys and Compounds, Jul 1, 2016

The figure of merit zT was calculated wrong in Figure 4 and 5e of the above manuscript. The corre... more The figure of merit zT was calculated wrong in Figure 4 and 5e of the above manuscript. The correct calculation can be seen in Figure 1 below. Also the maximum zT value is rather 0.30 at 700°C than 0.32 as mentioned in the abstract, introduction and Section 2.2. However, the wrong calculation doesn´t affect the discussion nor the interpretation. Figure 1. Correct calculation of zT for a) Figure 4 and b) Figure 5e in the above manuscript.

Acta Materialia, Mar 1, 2021

Abstract Oriented and nanotwinned copper (nt-Cu) of 3.8 µm thickness was electroplated on a Si wa... more Abstract Oriented and nanotwinned copper (nt-Cu) of 3.8 µm thickness was electroplated on a Si wafer substrate for thermal stress measurement from room temperature to 400 °C by bending beam method. Microstructure transformation in the copper thin film was studied after the thermal process. At 150 °C, the maximum compressive stress reached 150 MPa, and the (111) oriented nanotwinned copper began to transform to (200) orientation. Beyond 150 °C, anisotropic grain growth of (200) grains is faster. For comparison with the random-oriented copper thin films without nanotwins, we discover that the nanotwinned films can withstand a compressive stress of 1.5 times greater than the random copper thin films. This large thermal stress provides the driving force for anisotropic grain growth in the oriented nano-twin Cu, which can reach several hundred µm.

Over the past several years DuPont has been exploring new, rod-like fluorinated polyimides for in... more Over the past several years DuPont has been exploring new, rod-like fluorinated polyimides for interlayer dielectric (ILD) applications. It has been shown that copolymerization is a versatile method for tailoring properties of these rigid polyimides. Initial product offerings from DuPont showed an excellent balance of properties for ILD applications. These materials, however, due to their highly rod-like structure and very low in-plane coefficient of thermal expansion (CTE), actually yielded negative thermal stresses on silicon at the 1 {mu}m thicknesses typical of interlayer dielectrics. More flexible materials with higher CTE typically yield positive stress values which can be undesirably quite high. The dielectric constant of these highly rod-like fluorinated polyimides was also somewhat anisotropic, again due to the rod-like nature and resulting high in-plane orientation of these polyimides. Since a thermal stress on silicon near zero and a more isotropic dielectric constant are likely the most desirable states for an ILD, the highly rod-like polyimide was further optimized by incorporation of a more flexible fluorinated comonomer, 6FDA, at various levels to increase CTE and balance dielectric constant. The various properties of this series of fluorinated polyimides were investigated. The results have shown that it is indeed possible to obtain near zeromore » stress on silicon while attaining more isotropic dielectric constant via structure optimization.« less

Journal of vacuum science and technology, Nov 1, 2018

Low-k dielectric silicon carbonitride (SiC x N y) films are deposited by plasma-enhanced chemical... more Low-k dielectric silicon carbonitride (SiC x N y) films are deposited by plasma-enhanced chemical vapor deposition using a carbon-rich silazane precursor, N-methyl-aza-2,2,4-trimethylsilacyclopentane (SiC 7 NH 17), at 100°C. The post-treatments of SiC x N y films are carried out by thermal annealing and a broadband UV-assisted thermal annealing (UV-annealing) at 400°C for 5 min. Compared to the thermal annealing treatment, UV-annealing can improve both dielectric and mechanical properties of low-k SiC x N y films. Under thermal annealing, SiC x N y films show great thermal stability, but little structural change. In contrast, upon UV-annealing, most of the Si-H and N-H bonds are broken up, which induces more SiN cross-linking and converts Si-C matrix into SiN matrix. The ethylene bridges in Si-(CH 2) 2-Si also remain intact, but the unbridged hydrocarbons in Si-(CH 2) 2-N and Si-CH 2-CH 3 bonds decompose completely during the UV-annealing process. These account for the reduced dielectric constant to k = 3.2 from 3.6 and a 21% enhancement of Young's modulus to 7.4 GPa in the SiC x N y films after UV-annealing. Broadband UV-annealing shows promise as a post-treatment method for enhancing the properties of low-k dielectric barrier, SiC x N y films.

Materials Characterization, Oct 1, 2020

The aim of the study was determination of serum Se concentration and identification of genetic va... more The aim of the study was determination of serum Se concentration and identification of genetic variations in genes related to metabolism of selenium as markers of cancer risks for carriers of BRCA1 gene mutation and individuals with susceptibility to unselected breast cancer.

Thin Solid Films, Aug 1, 2017

Abstract In this study, amorphous silicon carbonitride (SiC x N y ) films were fabricated by radi... more Abstract In this study, amorphous silicon carbonitride (SiC x N y ) films were fabricated by radio frequency (RF) chemical vapor deposition (PECVD) using a single silazane precursor and a low power density (0.15 W/cm 3 ) for better compositional control. The effects of the precursor chemical structure (C/Si ratio, C Si N structure, and vinyl groups) and deposition temperature ( T s ) on the chemical structure and optical properties of SiC x N y films were examined using Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Specifically, two new single precursors; namely, n -methyl-aza-2,2,4-trimethylsilacyclopentane (MTSCP) and 1,3-divinyl-1,1,3,3-tetramethyl-disilazane (DVTMDS) were studied and compared. SiC x N y films deposited using MTSCP involving Si C 3 N rings formed Si N and Si (CH 2 ) 3 crosslinked structures at T s ≤ 100 °C, and were then changed to predominantly Si CH 2 N Si crosslinked structures at T s > 300 °C, leading to a wide range of optical band gap from 5.2 to 3.7 eV. Compared to DVTMDS-deposited SiC x N y films, their relatively higher percentage of Si C N structure accounted for the lower optical band gap and reduced transmission. DVTMDS with di-vinyl groups readily formed a Si (CH 2 ) 2 bridge in SiC x N y films T s ≤ 200 °C, resulting in excellent optical transmittance. The transmittance in the visible wavelengths of 400 °C-deposited SiC x N y film using DVTMDS still showed 85%. Also, tunable refractive index between 1.44 and 2.10 were obtained for SiC x N y films deposited at T s ≤ 400 °C.

ABSTRACT This paper describes the collaboration between university and industry in the evaluation... more ABSTRACT This paper describes the collaboration between university and industry in the evaluation of low dielectric materials for on-chip interconnect applications. The collaboration has established selection criteria and characterization methodologies for materials evaluation of dielectric thin films in the micron range. A review on the concerted efforts of semiconductor industry, materials suppliers, university and consortium in materials and processing evaluation and in improving the interlayer dielectrics (ILD) materials in alignment of SIA Technology Roadmap are described. The characterization techniques of thin films and results of materials evaluation are discussed

Japanese Journal of Applied Physics, Jun 3, 2015

In this paper, we present static thermal analysis of stress and strain on a thin-film transistor ... more In this paper, we present static thermal analysis of stress and strain on a thin-film transistor liquid-crystal display (TFT-LCD) panel and their correlation with light leakage phenomena under high-temperature durability test. Three-dimensional (3D) finite element analysis (FEA) is coupled with experimental parameters of key components of the TFT-LCD panel for the analysis. A strong correlation exists between light leakage and retardation difference induced by stress on triacetyl cellulose (TAC) films. Moreover, shrinkage in stretched poly(vinyl alcohol) (PVA) film and modulus of the adhesive layer are key factors affecting stress distribution and displacement of polarizer stack. An increase in Young's modulus (E) of the adhesive layer effectively reduces polarizer shrinkage and light leakage at the center of the panel. A TAC film with lower Young's modulus and/or coefficient of thermal expansion (CTE) is also an effective solution.

Mrs Bulletin, Oct 1, 1997

Continuing improvement in device density and performance has significantly affected the dimension... more Continuing improvement in device density and performance has significantly affected the dimensions and complexity of the wiring structure for on-chip interconnects. These enhancements have led to a reduction in the wiring pitch and an increase in the number of wiring levels to fulfill demands for density and performance improvements. As device dimensions shrink to less than 0.25 μm, the propagation delay, crosstalk noise, and power dissipation due to resistance-capacitance (RC) coupling become significant. Accordingly the interconnect delay now constitutes a major fraction of the total delay limiting the overall chip performance. Equally important is the processing complexity due to an increase in the number of wiring levels. This inevitably drives cost up by lowering the manufacturing yield due to an increase in defects and processing complexity.To address these problems, new materials for use as metal lines and interlayer dielectrics (ILDs) and alternative architectures have surfaced to replace the current Al(Cu)/SiO2 interconnect technology. These alternative architectures will require the introduction of low-dielectric-constant k materials as the interlayer dielectrics and/or low-resistivity conductors such as copper. The electrical and thermomechanical properties of SiO2 are ideal for ILD applications, and a change to material with different properties has important process-integration implications. To facilitate the choice of an alternative ILD, it is necessary to establish general criterion for evaluating thin-film properties of candidate low-k materials, which can be later correlated with process-integration problems.

Springer series in advanced microelectronics, 2003

As integrated circuit dimensions continue to decrease, RC delay, crosstalk noise and power dissip... more As integrated circuit dimensions continue to decrease, RC delay, crosstalk noise and power dissipation of the interconnect structure become limiting factors for ultra-large-scale integration of integrated circuits. Materials with low dielectric constant are being developed to replace silicon dioxide as interlevel dielectrics. This chapter provides an overview on the basic issues of low-k dielectrics for interconnect applications and serves as

Springer series in advanced microelectronics, 2003

discussing material reaction and process integration. With intense efforts from industry and univ... more discussing material reaction and process integration. With intense efforts from industry and universities, significant progress has been made in the synthesis of fully dense low-k materials with molecular structures to optimize material properties for integration into copper interconnects. Material characterization has been an integral part of low-k development and extensive efforts have been made in metrology development to evaluate material properties for process integration. Since low-k materials are integrated as thin films, their properties can differ appreciably from bulk or thick-film materials. This challenges metrology development for measuring material properties of thin films on a wafer, particularly for porous materials where the porosity further complicates material characterization. In Chap. 2, Ryan et al. describe characterization techniques developed for measuring dielectric, thermal, and mechanical properties of low-k thin films. In Chap. 3, Lin et al. review two new techniques: specular X-ray reflectivity (SXR) and small-angle neutron scattering (SANS) for characterization of porous low-k materials. Two general approaches for synthesis of low-k materials are discussed: in Chap. 4 by Gill et al. on vapor deposition and in Chap. 5 by Endo et al. on plasma-enhanced chemical vapor deposition of polymeric low-k dielectrics. For development of porous low-k materials, the "porogen" approach using a thermally degradable template appears promising in that it can be applied to a wide range of inorganic and organic materials and has good control of the pore size and morphology. The application of the porogen technique to synthesize porous low-k materials is described in Chap. 6 by Volksen et al. In the past several years, significant progress has been made by the semiconductor industry to integrate low-k dielectrics into copper interconnects. In Chap. 10, Waterloos describes process integration of SiLK TM into Cu damascene structures. Complementing the integration chapter, Oehrlein et al. in Chap. 9 discuss the plasma-etching process, a key step in integration of low-k structures. The weak thermal and mechanical properties have raised reliability concerns on thermal stability and structural integrity of low-k structures. Distinct failure mechanisms have been observed in low-k structures during processing or reliability tests, where more work is clearly required to fully understand the impact of low-k integration on interconnect reliability. Two basic issues related to reliability are discussed in this book: in Chap. 7 by Martini and Kelber on metal/polymer interfacial reaction and in Chap. 8 by Faupel et al. on metal diffusion in polymers. Continuing efforts in low-k integration will undoubtedly advance our knowledge on material development, characterization, process integration, and reliability for this exciting class of materials and its technology. While new knowledge and developments are to be expected, we hope that this book provides a basis for readers to understand the current advances in low-k dielectrics for interconnect applications. We sincerely appreciate the efforts from all the authors for their valuable contributions to make this book pos-Preface VII sible. We would like to thank Claus Ascheron from Springer-Verlag for his patience in letting us complete this book properly and Jo Ann Smith for her efforts in working with the manuscript.

Incorporation of porosity into dielectric materials is a viable method to reduce k-value down to ... more Incorporation of porosity into dielectric materials is a viable method to reduce k-value down to < 2.5. A Solid-First TM scheme based on high-temperature porogen, poly (styrene-block-4-vinylpyridine) (PS-P4VP), poly(styrene-block-butadiene-block-styrene) (PS-PB-PS) and methyl-silsesquioxane (MSQ) as the matrix have been employed to prepare porous low-k dielectric in order to circumvent the reliability issues encountered in the integration of as-deposited porous dielectric. The impact of high-temperature porogens, their loadings, and porosities on the moisture uptake and diffusion behavior was investigated using a home-built quartz crystal microbalance (QCM). Three low-k dielectric systems were employed in this thesis to simulate interlayer dielectrics (ILD) at different stages of Solid-First TM integration scheme; namely: (1) MSQ films cured at different temperatures up to 400 o C, (2) MSQ/porogen hybrid films cured at 250 o C with various porogen loadings, and (3) their corresponding porous films burned out at 400 o C. The moisture uptake of porous films cured at 400 o C increased with porosity due to an increase of pore surface area and residual silanol, Si-OH groups. Further

Bismuth selenide (Bi2Se3) and bismuth telluride (Bi2Te3) are well-known compounds for thermoelect... more Bismuth selenide (Bi2Se3) and bismuth telluride (Bi2Te3) are well-known compounds for thermoelectric (TE) cooling and generation applications near room-temperature. The performance of TE materials is quantified by a dimensionless figure of merit, ZT = α2σT/κ, in which α, σ, κ, and T are the Seebeck coefficient, the electrical conductivity, the thermal conductivity, and absolute temperature, respectively. Currently, enhancing the TE power factor (PF = α2σ) of Bi2Se3 and Bi2Te3 thin-films remains a challenge due to the coupling amongst TE material properties and the difficulty of growing stoichiometric films under elevated substrate temperatures (Ts), at which is beneficial for enhancing the σ. In this thesis study, n-type TE Bi2Se3 and Bi2Te3 thin films were grown on SiO2/Si substrates using pulsed laser deposition (PLD). The effects of the structure, composition, and morphology on the TE properties of Bi2Se3 and Bi2Te3 thin films were investigated by controlling background ambient pressures (P) and Ts in PLD depositions. We found that the deposition in relatively high P (≥ 40 Pa) could obtain stoichiometric films at extended Ts up to 300 °C for Bi2Se3 and 340 °C for Bi2Te3, which can reduce the carrier concentration (n) and significantly enhance the Seebeck coefficient (α), following the α~n-2/3 relation approximately. Furthermore, at high Ts- growths, the obtained structures of highly (00l)-oriented – layered of large crystallites led to the substantial increase in the carrier mobility µ and thus improve the σ (= nµe). For example, the stoichiometric Bi2Se3 films grown at grown at 300 °C and 40 Pa with highly (00l) oriented and layered-hexagonal platelets possessed the highest PF of 5.54 µWcm-1K-2, where ׀α׀ = 75.8 µV/K and σ = 963.8 S/cm. Similarly, the stoichiometric Bi2Te3 films grown at Ts = 220–340 °C and PAr = 80 Pa with highly (00l)-oriented and layered structures showed the best properties, with a carrier mobility µ of 83.9 – 122.3 cm2/Vs, an ׀α׀ of 172.8 – 189.7 µV/K, and a remarkably high PF of 18.2 – 24.3 µWcm-1K-2. In contrast, the Te-rich films deposited at Ts ≤ 120 °C with (015)-preferred orientations and columnar–small grain structures or the Te-deficient film deposited at 380 °C with Bi4Te5 polyhedron structure possessed poor properties, with µ < 10.0 cm2/Vs, ׀α׀ < 54 µV/K, and PFs ≤ 0.44 µWcm-1K-2. This study provides a comprehensive understanding the interrelationships between PLD processing conditions, microstructures, and TE properties of Bi2Te3-based thin films, promising for further improving the TE performance of materials and applications. In brief, the morphology of highly (00l) oriented–layered large crystallite structures and the stoichiometry predominantly contribute to the substantial enhancement of µ and ׀α׀, respectively, resulting in remarkable enhancement in PF.

Lower k and low-leakage silicon carbonitride (SiCxNy) films were fabricated using single precurso... more Lower k and low-leakage silicon carbonitride (SiCxNy) films were fabricated using single precursor by using radio-frequency (RF) plasma-enhanced chemical vapor deposition (PECVD). We explored precursors with (1) cyclic-carbon-containing structures, (2) higher C/Si ratio, (3) multiple vinyl groups, as well as (4) the incorporation of porogen for developing low-k SiCxNy films as etch-stop/diffusion barrier (ES/DB) layer for copper interconnects in this study. SiCxNy films with k values between 3.0 and 3.5 were fabricated at T≦ 200 C, and k~4.04.5 at 300-400 C. Precursors with vinyl groups yielded SiCxNy films with low leakage, excellent optical transmittance and high mechanical strength due to the formation of cross-linked Si(CH2) n-Si linkages.

Thin Solid Films, 2015

Abstract Low-k SiCxNy films were prepared using radio-frequency plasma-enhanced chemical vapor de... more Abstract Low-k SiCxNy films were prepared using radio-frequency plasma-enhanced chemical vapor deposition (PECVD), with only 1,3,5-trimethyl-1,3,5-trivinylcyclotrisilazane (VSZ) as the precursor; VSZ has cyclic Si–N–Si linkages and three pendent vinyl groups. At lower PECVD temperatures, SiCxNy films possess relatively low film densities, indicating the existence of a loose structure or voids within the cross-linked matrix structure. The pore morphology of SiCxNy films deposited at distinct temperatures were examined using grazing-incidence small-angle X-ray scattering, while the chemical bondings and structural information were analyzed using Fourier-transform infrared spectroscopy. At 100 °C, SiCxNy films without porogen displaying 4.9 nm pores and a mean pore spacing of 30.1 nm generated low-density films because Si-(CH2)n-Si and/or Si-(CH2)n-CH3 could be incorporated free volume into the N–Si–C cross-linked structure under plasma deposition. At 300 °C, the N–Si–C cross-linked structure and the some organic phase were disrupted and transformed into a denser structure, reducing pore size (3.5 nm) and losing pore correlation. Thus, low deposition temperatures facilitate the formation of large pores and the ordering of the pores. Post annealing converted the 100 and 300 °C as-deposited SiCxNy films into loose and dense structures, respectively, and maintained slightly reduced pore size and pore correlation in the annealed films.

IEEE Transactions on Device and Materials Reliability, 2020

This study determines the relationship between retention and endurance reliability for a HfOx-bas... more This study determines the relationship between retention and endurance reliability for a HfOx-based resistive random access memory (ReRAM). A TiN (15 nm) / HfOx (6 nm) / Ti (10 nm) / TiN (40 nm) stacked structure is fabricated and tested to verify its basic characteristics and reliability. The high resistance states (HRS) retention behavior is characterized and is found to degrade over 100x on the endured bits because there is a sequential high temperature procedure. The degradation is reduced slightly to a ~30x drop for the endured devices with one single refresh cycle. During the endurance and retention test procedures, the HRS resistance decreases because neutral oxygen vacancy filaments grow and this cannot be reversed. The I-V characteristics for endured devices are also determined. The results show that isothermal treatment causes a gradual SET and RESET process with multiple feasible states. The thermally induced filament degradation model (isolated filament vs. continuous filament) is verified by the relationship between retention and endurance reliability. Design guidance is recommended for an improvement in ReRAM reliability.

Applied Physics Letters, 2020

In this work, SiCxNy-based resistive switching memory by using a single precursor for the back en... more In this work, SiCxNy-based resistive switching memory by using a single precursor for the back end of line (BEOL) integration has been investigated. SiCxNy films were deposited on the aluminum (Al) substrates using plasma enhanced atomic layer deposition (PEALD) method. The effects of SiCxNy chemical structure with respect to resistive switching characteristics have been studied, and the results suggest that the resistive switching mechanism is dominated by the interfacial Schottky junction with SiCxNy composition. This work not only demonstrates a PEALD method in fabricating SiCxNy-based electronics active devices but also provides additional insights into the interaction between the electrical and chemical structures in bi-functional resistive switching or threshold switching behavior. A demonstrated PEALD tool with simple single-precursor for SiCxNy deposition shows excellent feasibility to be used as functional memory and selector devices, further giving the potential pathway fo...