Optimization of fabrication parameters of barium doped pb(zr0 52ti0 48)o3 thin films on tisi substrates using pulsed laser deposition

BỘ GIÁO DỤC VÀ ĐÀO TẠO TRƯỜNG ĐẠI HỌC BÁCH KHOA HÀ NỘI Phạm Ngọc Thảo TỐI ỨU HĨA Q TRÌNH LẮNG ĐỌNG MÀNG MỎNG Pb(Zr0.52Ti0.48)O3 TRẾN ĐẾ TiN/Si SỬ DỤNG PHƯƠNG PHÁP BỐC BAY XUNG LASER Chuyên ngành : Khoa học kỹ thuật Vật liệu Điện tử LUẬN VĂN THẠC SĨ KHOA HỌC … (Khoa học kỹ thuật Vật liệu Điện tử) NGƯỜI HƯỚNG DẪN KHOA HỌC : TS Nguyễn Đức Minh PGS TS Vũ Ngọc Hùng Hà Nội – 2013 DEDICATION The work has been carried out in the internship program at Solutions in Material Science (SolMateS) company, the Netherlands, from st April to 30th September, 2013 Except where specific references are made, this thesis is entirely the result of my own work and includes nothing that is the outcome of work done in collaboration No part of this work has been or being submitted for other degree, diploma or qualification at this or other university Enschede, September 2013 Pham Ngoc Thao i ACKNOWLEDGEMENTS This work is done in following the internship program at Solutions in Material Science (SolMateS) company from 1st April to 30th September, 2013 I would like to express my gratitude to my supervisor Assoc Prof Vu Ngoc Hung, who offered me the invaluable guidance, supports in my two years study and research at International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology (HUST), Vietnam I am deeply indebted to my supervisor Dr Nguyen Duc Minh (ITIMS & SolMateS), who gave me a precious opportunity to the beautiful city-Enschede, The Netherlands-to join this internship program at SolMateS company I especially wish to thank him about taking professional guidance, and sharing experiences in practical work, giving constructive advices throughout this research and thesis writing I am very grateful to Dr Matthijn Dekkers (SolMateS) for the long support, encouragement and his suggestions for this thesis With his help, I have an opportunity to understand about working in a research enviroment of the commerical company, like SolMateS Special acknowledgments to all members of SolMateS company who created friendly work environment, and gave me encouraging supports Their interest, and hard working to the work impress me so much It is my honor to work with all of them Dear Nicolas, thanks for your great support and kindness Shared office with you is my pleasure Dear Saskia and Francis, I want to say thank to both of you for administration assistance Dear Jan, I have really enjoyed time we spent together in talking about the ships and Dutch culture Dear Steven, thanks for your warm friendship ii I would like to thank sincerely to all the teachers who taught me at ITIMS such Prof Dr Than Duc Hien, Assoc Prof Dr Nguyen Van Hieu, Assoc Prof Dr Nguyen Phuc Duong, Assoc Prof Dr Nguyen Anh Tuan, Dr Tran Ngoc Khiem, Dr Nguyen Van Quy Many thanks to ITIMS employees for always supporting me such Dr Thanh, Dr Toan, Dr Ngoc Anh, Dr Ha, Ms Loan, Ms Lan, Dr Le, Dr Xuan And thanks go to all members of MEMS group such Dr Thong, Dr Hoang, Dr Hien, PhD student Chi, Eng Tai I would also like to thank all friends in The Netherlands: Minh-Giang’s family, Tuan-Hieu’s family, Chung (UvA), Bay (UvA), big cat Tom Aarnink (UT), Boota (UT), Nirupam (UT), Kenan (UT) because of your warm and wonderful encouragement to me Last but not least, I would like to thank to my parents and my sister for their endless love, support, motivations; all of my friends in Viet Nam for their friendship This work was financially supported by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under Grant number 103.02-2011.43, and by the Interreg project "Unihealth" Enschede, September 2013 Pham Ngoc Thao iii TABLE OF CONTENTS DEDICATION .i ACKNOWLEDGEMENTS ii TABLE OF CONTENTS iv LIST OF FIGURES viii LIST OF TABLES .xi CHAPTER THEORETICAL BACKGROUND 1.1 Introduction 1.2 Ferroelectricity .1 1.3 Lead Zirconate Titanate Pb(ZrxTi1-x)O3 (PZT) 1.3.1 Crystal structure .5 1.3.2 Phase diagram 1.3.3 Physical properties of PZT thin film .7 1.3.3.1 Ferroelectric properties 1.3.3.2 Dielectric properties 1.3.3.3 Piezoelectric properties 10 1.4 Approaches to improve the properties of PZT thin films 13 1.4.1 Doping 13 1.4.2 Electrode 15 iv 1.4.3 Buffer layer 16 1.5 Research scopes and Objectives 17 1.6 Summary 19 CHAPTER .20 EXPERIMENTAL PRODUCES 20 2.1 Introduction 20 2.2 Thin film growth 20 2.2.1 General techniques for fabrication 20 2.2.2 Pulsed laser deposition (PLD) .22 2.2.2.1 Mechanisms of PLD 23 2.2.2.2 Experimental setup 24 2.3 Patterning process of PBZT thin film capacitors 26 2.4 Characterization techniques 28 2.4.1 Structural analysis 28 2.4.2 Morphological analysis 30 2.4.3 Electrical characterization .30 2.4.3.1 Ferroelectric properties .30 2.4.3.2 Dielectric properties 33 2.4.4 Mechanical characterization 33 2.5 Summary 34 v CHAPTER .36 OPTIMIZATION OF DEPOSITION TEMPERATURE 36 3.1 Introduction 36 3.2 Structure and morphology 36 3.3 Electrical properties .39 3.3.1 Ferroelectric properties 39 3.3.1.1 Hysteresis loops .39 3.3.1.2 Fatigue behavior 40 3.3.1.3 Effect of applied field 43 3.3.2 Dielectric properties .44 3.4 Mechanical properties 45 3.5 Effect of poling process .48 3.6 Summary 50 CHAPTER .52 OPTIMIZATION OF ELECTRODE THICKNESS 52 4.1 Introduction 52 4.2 Structure and morphology 53 4.3 Electrical properties .56 4.3.1 Ferroelectric properties 57 4.3.1.1.Hysteresis loops 57 4.3.1.2 Fatigue behavior 58 vi 4.3.2 Dielectric properties .60 4.4 Mechanical properties 61 4.5 Summary 62 CHAPTER .64 CONCLUSION AND SUGGESTION FOR FUTURE WORK 64 5.1 Conclusion 64 5.2 Suggestions for future works .65 REFERENCE 66 vii LIST OF FIGURES Figure 1.1: Schematic diagram of the phase transition in a ferroelectric material Figure 1.2: The formation of 180○ and 90 ○ ferroelectric domain walls in a tetragonal perovskite ferroelectric; Ed: depolarizing field, Ps: spontaneous polarization Figure 1.3: Hysteresis loop and domain switching Figure 1.4: Schematic illustration of the poling process Figure 1.5: Schematic of cubic ABO3 perovskite .5 Figure 1.6: Phase diagram PZT solid solution Figure 1.7 : Axes including normal (1-3) and shear directions (4-6) .10 Figure 1.8 : (a) Capacitor and cantilever structures; 3D-upward displacements of (b) capacitor and (c) cantilever The LDV measurements were performed 11 Figure 1.9: The example of the relationship between dielectric constant, d33 coefficient and Zr/Ti ratio of PZT films .12 Figure 1.10: (a) The dependence of 2Pr values of PZT films as a function of the thicknesses of LNO buffer layers; (b) The d33values of PZT films as a function of the thicknesses of LNO buffer layers 17 Figure 1.11: The chapter structure of thesis The main achievements of each chapter are summarized below the titles .18 Figure 2.1: (a) Flow diagram for the PZT thin film was deposited by Sol-gel processing; (b) The HRSEM of PZT thin film 21 Figure 2.2: A schematic construction of PLD system .25 viii Figure 2.3: Flow diagram for process of PZT film capacitors 27 Figure 2.4: The PANalytical X’Pert PRO system to identify phases of a crystalline material at IMS Group-Mesa+, University of Twente, Netherlands 29 Figure 2.5: A construction of SEM 30 Figure 2.6: Ferroelectric polarization (P–E) hysteresis loop of a PBZT thin film capacitor 31 Figure 2.7: The typical signal of fatigue excitation 32 Figure 2.8: A Polytec MSA-400 micro–scanning laser Doppler vibrometer system at IMS Group-Mesa+, University of Twente, Netherlands 33 Figure 2.9: Schematic view of the measurement set-up for the d33 coefficient 34 Figure 3.1: Micrographs of PBZT films on TiN/Ti/SiO2/Si substrates at different deposition temeperatures 37 Figure 3.2: The SEM cross-sections of PBZT thin-film capacitor (a) at 535 ○C, (b) at 550 ○C, (c) at 565 ○C, (d) at 575 ○C temperature 38 Figure 3.3: XRD patterns of PBZT thin films at different deposition temperatures: (a) full scale and (b) zoom scale of (111) peak 39 Figure 3.4: PBZT films deposited on TiN/Ti/SiO2/Si susbtrates by PLD technique: (a) Hysteresis loops at different temperatures; and (b) The temperature dependence of the remanent polarization (P r) and coercive field (Ec) 40 Figure 3.5: (a) The SEM image of external failure; (b) The fatigue behavior of Pt/PBZT/TiN capacitor at 400 kV/cm applied field at 565 ○C temperature The insets show the electric field as a funtion of switching cycles 41 ix Chapter Optimization of Electrode Thickness kHz) and at pulse height of 400 kV/cm These results indicate that the remanent polarization (P r) almost remain these value until 106 switching cycles, and then the degradation can be found from 10 to 108 cycles The fatigue behaviors at various deposition temperatures are considerably different on 80 nm thickness of TiN electrode (Fig.4.7(a)) On 100 nm thickness of TiN electrode 15 10 10 Pr (C/cm ) Pr ( C/cm ) On 80 nm thickness of TiN electrode 15 @535 @550 @565 -5 -10 @535 @550 @565 -5 -10 -15 10 -15 10 10 10 10 10 10 10 Number of cycles 10 10 10 10 10 10 10 10 10 10 Number of cycles On 100 nm thickness of TiN electrode (with RTA) On 150 nm thickness of TiN electrode 20 15 15 10 Pr (C/cm ) 2 Pr (C/cm ) 10 @535 @550 @565 -5 @535 @550 @565 -5 -10 -10 -15 -15 10 10 10 10 10 10 10 10 -20 10 10 Number of cycles 10 10 10 10 10 10 Number of cycles 10 10 Figure 4.7: Remanent polarization Pr of Pt/PBZT/TiN capacitors on various electrode thicknesses as a function of cumulative switching cycles In contrast, the small difference of fatigue behaviors at various deposition temperature on 100 nm thickness of TiN electrode (Fig.4.7(b)) and 100 nm thickness of TiN electrode (with RTA) (Fig.4.7(c)) can prove the stability of these electrodes at these temperatures In addtion, to get a good comparison of fatigue behaviors on different thickness of TiN, the results of Pr values as a function of switching cycles at 535–565 ºC on 150 nm thickness with underlying 300 kV/cm are still shown again 59 Chapter Optimization of Electrode Thickness 4.3.2 Dielectric properties A relationships between the dielectric constant (ε) and dielectric loss (tanδ) values versus the different temperatures on various electrode thicknesses are shown in Fig.4.8 These experiments are measured at room temperature (25 ºC), kHz frequency with an small ac signal (4 kV/cm) and the dc bias sweeping from –300 to +300 kV/cm and then back to –300 kV/cm On 80 nm thickness of TiN electrode On 100 nm thickness of TiN electrode 2000 1400 1200 0.15 1100 0.30 (b) 1800 0.25 1600 0.20 1400 0.15 1200 0.10 1000 0.05 Dielectric loss, tan 1300 Dielectric constant,  0.20 Dielectric loss, tan Dielectric constant,  (a) 800 1000 535 540 545 550 555 560 565 0.10 535 540 545 560 565 0.00 On 150 nm thickness of TiN electrode 1200 0.20 0.19 0.10 1000 0.05 (d) 1150 0.18 1100 0.17 1050 0.16 Dielectric loss, tan  0.15 1200 Dielectric constant,  (c) Dielectric loss, tan  Dielectric constant,  555 Temperature ( ) On 100 nm thickness of TiN electrode (with RTA) 1400 550 0 Temperature ( ) 800 535 540 545 550 555 560 565 1000 0.00 535 540 545 550 555 560 565 0.15 Temperature ( ) Temperature ( ) Figure 4.8: The ε and tanδ values versus temperatures on different thicknesses of electrodes On 80 nm thickness of TiN electrode (Fig.4.8(a)), and 150 nm thickness of TiN electrode (Fig.4.8(d)), the ε values at various temperatures have not shown the large distinction Namely, these dielectric constant values are over 1000 with the dielectric loss in the range of between 0.10 and 0.16 The opposite trends can be found by the results between 100 nm thickness of TiN electrode and 100 nm thickness of TiN electrode (with RTA) The movement upward of the εr value appears on 100 nm thickness of TiN electrode 60 Chapter Optimization of Electrode Thickness (Fig.4.8(b)), in fact, the lowest value of εr is 741 at 535 ºC temperature and its increase to over 1173 and 1087 at 550 and 565 ºC, respectively Whereas, the downward trend can be shown in sample on 100 nm thickness of TiN electrode (with RTA) electrode (Fig.4.8(c)), the value of εr declines from 1135 to 742 in range of 535–575 ºC temperate deposition Their dielectric loss (tanδ) of samples on both two kinds of electrodes fluctuates in 0.12–0.30 values Hence, due to the difference of these dielectric constants, the suitable relationship between the electrode thickness and deposition temperature is necessary to further research 4.4 Mechanical properties The displacements (δ) of the ferroelectric thin-film capacitors were derived under a sinusoidal ac voltage of 3V (or Vp-p peak to peak) and at kHz frequency with using the capacitor of 300 m x 300 m in size As the discussion in Chapter 3, the effective out-of-plane piezoelectric coefficient (d33,f) was then calculated as the ratio between the δ and 3V (applied voltage in experiment) Piezoelectric constant d33 (pm/V) 60 50 40 On 80 nm TiN electrode On 100 nm TiN electrode On 100 nm TiN electrode (RTA On 150 nm TiN electrode 30 535 540 545 550 555 560 565 Temperature ( C) Figure 4.9: Piezoelectric constant d33,f as a function of temperatures on different thicknesses of electrodes In Fig.4.9 show the relationship between of d33,f values and various temperatures on different thicknesses of TiN electrode The decrease trends with 61 Chapter Optimization of Electrode Thickness increasing temperatures can be found in all of samples on thinner thickness (