臺灣博碩士論文加值系統

摘要
在有機薄膜電晶體的技術演進中，其載子遷移率表現出來的電性已經迎頭趕上複晶矽薄膜電晶體的電性了。而其中的五環素為電洞導通的有機半導體，載子遷移率最高已高過 1cm2/V s，可說已到了單晶有機的傳輸極限了。不過儘管電性已有大幅改善，但是在接面電阻，導通機制和電性上的不穩定這三個方面還未作有系統的探討。
因而在本論文裡，首先我們會利用四點探測法來了解接面電阻。而四點探測是在上源極和汲極結構時，同時製作上去的， 而非額外多了兩根測電位的探針製作步驟。因此我們用原本兩個電極(源極和汲極)注入並接收電流，另外通道中的兩個電極來感測電壓。這手法跟最近報導的四點探針電晶體很像。而相較於傳統的R對L作圖法求接觸電阻，四點探測主要優點是可在單一顆元件上單獨量到薄膜電阻和各接觸電阻，並使得元件元件間在既存在的電阻差異下更容易對此元件作評估。因此我們可利用它來作進一步作現象分析。
接著我們作變溫量測，此可在遷移率與溫度有關的半導薄膜上作量測。在與溫度相關的遷移率中，蘊育著半導體和傳導機制有關或和缺限分布有關的資訊。有一些模型已提出來解釋這些半導晶體中熱活化的載子遷移率現象，然而“Multiple trapping and release model(MTR)”是最為被大家所廣泛接受的。因此我們再利用橫向電導，可同時來觀測Meyer-Neldel relationship的電性傳輸行為。而我們也適當的利用Multiple trapping and release model(MTR)來解釋變溫量測中過程的熱活化現象。
最後，我們在連續量測中了解到有機薄膜電晶體電性上的不穩定性，進而在定汲極電流的運作下，來探討這五環素有機薄膜電晶體的特性。在此我們也發現極化現象在定電流運作過程中扮演很重要的角色。因此提供簡單的能帶圖來陳述有機薄膜電晶體的特珠殊行為，而這些是載子受到束縳而在臨界電壓和遷移率上的不穩定現象也都一一會被探討。

Abstract

Recent progress in organic thin film transistor (OTFT) technology has led to charge carrier mobility comparable to amorphous silicon. Pentacene, a hole conductor, has shown the highest OTFT mobility(>1 cm2/V s) to date, and has nearly reached the intrinsic transport limit of organic single crystals. Despite the progress in realizing OTFTs with good properties, three important aspects of OTFTs have not been systematically studied: contact resistance, conduction mechanism, and electrical instability.
In this thesis, at first, we use an improved four-probe method for ascertaining contact resistance. The four-probe method is based on the standard OTFT source and drain geometry, but with two additional mid-channel voltage sensing probes. Thus, we use two electrodes to inject and receive current, and two to sense voltage in the OTFT channel. The technique we employ is similar to other recently reported four-probe transistor devices. The major advantage of the four-probe method over conventional RvsL plots is that it allows the film and each contact resistance to be measured independently in a single device, which facilitates assessment of device-to-device variation in these resistances. Hence, we use it to further analyze the phenomenon.
Variable temperature TFT measurements are adapted later. It can be used to determine the temperature dependence of the mobility in a semiconductor thin film. The temperature dependence of the mobility can yield information about the conduction mechanism and trap states in the semiconductor. Several models have been proposed to explain thermally activated mobility in crystalline organic semiconductor films, but the multiple trapping and release (MTR) model is the most widely accepted.. Thus, A Meyer–Neldel relationship was simultaneously observed for electrical transport ,using a transconductance. we properly use the multiple trapping and release model to explain the thermally activated phenomenon from the variable temperature measure..
Finally, we understand the instability of electrical characteristics in a continued series measurements and investigated the characteristics of bottom-contact pentacene-based OTFTs under drain current stress conditions. Here, we find that polarization phenomenon plays an important role during stress, and thus we provide the rough energy band figure to depict these special properties of OTFTs. The effect of these charge trapping instability on the measured threshold voltage and mobility of the transport studies would be discussed.

Contents page

Abstract (in Chinese) iii
Abstract (in English) v
Acknowledgements vii
Table of Contents ix
List of Figures xi
List of Tables x

Chapter 1 Introduction
1.1 Overview of Organic Thin Film Transistor 1
1.2 Properties of Pentacene 3
1.3 Operation of Organic Thin Film Transistor 5
1.4 Motivation 6
1.5 Thesis Organization 8

Chapter 2 Devices Fabrication and Four Probe Measurement
2.1 Introduction1 5
2.2 Devices Fabrication and Measurement
2.2.1 Process Flow of Pentacene-Based OTFT Fabrication 17
2.2.2 Electrical Characteristics of Pentacene-Based OTFTs 18
2.3 Result and Discussion
2.3.1 The Growth of Pentacene 22
2.3.2 Four Probe Measurement 25
2.3.3 Sensitivity to Deposition Substrate Temperature 28
2.3.4 The Effect of Scaling 29
2.4Summary 32

Chapter 3 Variable temperature measurements
3.1 Introduction 63
3.2 Variable Temperature Measurements
3.2.1 The Multiple Trapping and Release Model and The Meyer–Neldel Rule
67
3.2.2Experiment Detail 69
3.3 Result and Discussion
3.3.1 The Existence of Meyer–Neldel Rule 70
3.3.2 Sensitivity to Variable Temperature during Measurement 72
3.4 Summary 73

Chapter 4 Electric Instability of Pentacene-Based OTFTs
4.1 Introduction 88
4.2 Instability of OTFTs during current stress
4.2.1 Experiment Detail 89
4.2.2 Result and Discussion 90
4.3 The Recovery after Current Stress and Polarization Phenomenon
4.3.1 Experiment Detail 93
4.3.2 Result and Discussion 93
4.4 Transient Stress Phenomenon in Measurements
4.4.1 Experiment Detail 96
4.4.2 Result and Discussion 97
4.5 Summary 97

Chapter 5 Conclusions and Further Recommendations
5.1 Conclusions 128
5.2Recommendations 130

Reference 132
Vita 141

References

[1] N. Karl, Organic Semiconductors, Landolt Boernstein/New Series Group III, edited by O. Madelung, M. Schulz, and H. Weiss ~Springer, Berlin, Vol. 17, p. 106, (1985).
[2] S. F. Nelson, Y.-Y. Lin, D. J. Gundlach, and T. N. Jackson, “ Temperature- independent transport in high-mobility pentacene transistors”, Appl. Phys. Lett. 72, 1854 ,(1998).
[3] C. D. Dimitrakopolos and D. J. Mascaro, IBM “The dawn of organic electronics” J. Res. Dev. 45, 11 (2001).
[4] H. Sirringhaus, T. Kawase, R. H. Friend, T. Shimoda, M. Inbasekaran, W. Wu, and E. P. Woo, "High-Resolution Inkjet Printing of All-Polymer Transistor Circuits" Sciences 290, 2123 (2000).
[5] W. S. Wong, S. Ready, R. Matusiak, S. D. White, J.-P. Lu, J. Ho, and R. A. Street, “Amorphous silicon thin-film transistors and arrays fabricated by jet printing” Appl. Phys. Lett. 80, 610 (2002).
[6] J. Aizenberg, J. A. Rogers, K. E. Paul, and G. M. Whitesides, "Imaging Profiles of Light Intensity in the Near Field: Applications to Phase-Shift Photolithography ," Appl. Opt. 37, 2145 (1998).
[7] J. A. Rogers, K. Baldwin, Z. Bao, A. Dodabalapur, V. R. Raju, and J. Ewing, “Organic Electronic and Photonic Materials and Devices”, Mater. Res. Soc. Symp. Proc. 660, JJ7.1.7 (2000)
[8]H. Klauk, D. J. Gundlach, J. A. Nichols, C. D. Sheraw, M. Bonse, and T. N. Jackson, Solid State Technol. “Pentacene organic thin-film transistors and IC's”, 43, 63 (2000).
[9]C. D. Dimitrakopolos, S. Purushothaman, J. Kymissis, A. Callegari, and J. M. Shaw, “Low-Voltage Organic Transistors on Plastic Comprising High-Dielectric Constant Gate Insulators” Science 283, 822 (1999).
[10]T. W. Kelley et al., Mater. Res. Soc. Symp. Proc. (2002).
[11] D. Knipp, R. A. Street, B. Krusor, and J. Ho, Mater. Res. Soc. Symp. Proc. “Organic and Polymeric Materials and Devices Optical, Electrical and Optoelectronic Properties” 725, P5.2 (2002).
[12] S. R. Forrest, “Ultrathin Organic Films Grown by Organic Molecular Beam Deposition and Related Techniques “, Chem. Rev. 97, 1793 (1997).
[13] D. Knipp, R. A. Street, B. Krusor, and R. B. Apte, “Reconfigurable hardware mapping for accelerometer-based navigation applications,” Proc. SPIE 3366, 8 (2001)
[14] G. Horowitz, R. Hajlaoui, and P. Delannoy, “Temperature dependence of the field effect mobility of sexithiophene. Determination of the density of traps,” J. Phys. III France, vol. 5, no. 4, pp. 355–371, 1995.
[15] J. Lu, E. Delamarche, L. Eng, R. Bennewitz, E. Meyer, and H.-J. Guntherodt, “Kelvin probe force microscopy on surfaces: Investigation of the surface potential of self-assembled monolayers on gold,” Langmuir, vol. 15, pp. 8184–8188, 1999.
[16] E. M. Suuberg, “Vapor pressures and enthalpies of solution of polycyclic aromatic hydrocarbons and their derivatives,” J. Chem. Eng. Data, vol. 43, no. 3, pp. 486–492, 1998.
[17] E. A. Silinsh and V. Capek, “Organic Molecular Crystals”. New York: AIP, 1994, p. 156.
[18] Christos D. Dimitrakopoulos, D. J Mascaro, “Organic thin film transistors : A review of recent advances ” IBM J. RES. & DEV. 45(1), 11, (2001)
[19]N. Koch, J. Ghijsen, A. Elschner, R. L. Johnson, J. J. Pireaux, J. Schwartz,A.Kahn, “Conjugated organic molecules on metal versus polymer electrodes: Demonstration of a key energy level alignment mechanism”Applied Physics Letters, vol.82, no.1,pp.70-72, 2003.
[20]Y. Kato, I. Shingo, R. Teranmoto, T. Sekitani, T. Someya,H. Kawaguchi, T. Sakurai, “High mobility of pentacene field-effect transistors with polyimide gate dielectric layers” Applied Physics Letters, vol.84, no.19, pp.3789-3791,2004
[21]L. A. Majewski, R. Schroeder,M. Voigt, M. Grell, “High performance organic transistors on cheap, commercial substrates”, Journal of Appplied Physics, vol.37, no.24, pp.3367-3372,2004
[22]D. Knipp, R. A. Street, A, molkel, J. Ho, “Pentacene thin film transistors on inorganic dielectrics: Morphology, structural properties, and electronic transport”, Journal of Appplied Physics, vol.93, no.1, pp.347-355,2003
[23] S. M. Sze, Physics of Semiconductor Devices, 2nd ed. Wiley, New York,1981.
[24] P. V. Necliudov, M. S. Shur, D. J. Gundlach, and T. N. Jackson, “Contact resistance extraction in pentacene thin film transistors” Solid-State Electron. 47, 259 (2002).
[25] R. A. Street and A. Salleo, “Contact effects in polymer transistors” Appl. Phys. Lett. 81, 2887 (2002).
[26] J. A. Merlo and C. D. Frisbie, “Field effect conductance of conducting polymer nanofibers” J. Polym. Sci., Part B: Polym. Phys. 41, 2674 (2003).
[27] H. E. Katz, J. Johnson, A. J. Lovinger, and W. Li, "Naphthalenetetracarboxylic diimide-based n-channel transistor semiconductors: structural variation and thiol-enhanced gold contacts" J. Am. Chem. Soc. 122, 7787 (2000).
[28] V. Podzorov, V. M. Pudalov, and M. E. Gershenson, “Field-effect transistors on rubrene single crystals with parylene gate insulator” ,Appl. Phys. Lett. 82, 1739 (2003).
[29] J. A. Merlo and C. D. Frisbie, “Field effect conductance of conducting polymer nanofibers” J. Polym. Sci., Part B: Polym. Phys. 41, 2674 (2003).
[30] C.-Y. Chen and J. Kanicki,”Gated Four Probe a-Si:H TFT Structrue:Anew Technique to Measure the Intrinsic Performance of a-Si:H TFT” IEEE Electron Device Lett. 18, 340 (1997).
[31] Sirringhaus, H.; Brown, P.J.; Friend, R.H.; Nielsen, M.M.; Bechgaard, K.; Langeveld-Voss,B.M.W.;et.al.”Microstructure–mobility correlation in self-organised, conjugated polymer field-effect transistors” Synthetic Metals Volume: 111-112, June 1, 2000, pp.129-132
[32]C.D.Dimitrakopoulos, D.J.Mascaro,“Organic thin-film transistors:A review of recent advances, IBM Journal of Research and Development, Organic electronics”, vol.45 no.1,pp.11-27,2001
[33] The pentacene project, http://www.research,ibm.com/leem/pentacene.html.
[34] D. Knipp, R. A. Street, A. Volkel, and J. Ho, “Pentacene thin film transistors on inorganic dielectrics: Morphology, structural properties, and electronic transport”, J. Appl. Phys. 93, 347 (2003).
[35] D. J. Gundlach, T. N. Jackson, D. G. Schlom, and S. F. Nelson, “Solvent-induced phase transition in thermally evaporated pentacene films” Appl. Phys. Lett. 74, 3302 (1999).
[36] P. V. Necliudov, M. S. Shur, D. J. Gundlach, and T. N. Jackson, “Contact resistance extraction in pentacene thin film transistors” Solid-State Electron. 47, 259 (2002).
[37] J. Zaumseil, K. W. Baldwin, and J. A. Rogers, “Contact resistance in organic transistors that use source and drain electrodes formed by soft contact lamination” J. Appl. Phys. 93, 6117 (2003).
[38] H. Klauk, G. Schmid, W. Radlik, W. Weber, L. Zhou, C. D. Sheraw, J. A. Nichols, and T. N. Jackson, “Contact Resistance in Organic Thin Film Transistors” ,Solid-State Electron. 47, 297 (2003).
[39] C.-S. Chiang, C.-Y. Chen, J. Kanicki, and K. Takechi, “Investigation of intrinsic channel characteristics of hydrogenated amorphous silicon thin-film transistors by gated-four-probe structure”Appl. Phys. Lett. 72, 2874 (1998).
[40] I. Kymissis, C. D. Dimitrakopoulos, and S. Purushothaman, “High-performance bottom electrode organic thin-film transistors” Trans. Electron Devices 48, 1060 (2001)
[42] E.J. Meijer, C. Tanase, “Switch-on voltage in disordered organic field-effect transistors” Appl. Phys. Lett. 80, 3838 (2002).
[43] M. Matters, D. M. de Leeuw, P. T. Herwig, “Bias-stress induced instability of organic thin film transistors” Synth. Met. 102, 998 (1999).
[44] M. Shur and M. Hack, “Physics of amorphous silicon based alloy field-effect transistors” J. Appl. Phys. 55, 3831 (1984).
[45] S. Luan and W. Neudeck, “An experimental study of the source/drain parasitic resistance effects in amorphous silicon thin film transistors” J. Appl. Phys. 72, 766 (1992).
[46] H. Sirringhaus, N. Tessler, D. S. Thomas, P. J. Brown, and R. H. Friend, Adv. Solid State Phys. 39, 101 (1999).
[47] G. Horowitz, R. Hajlaoui, D. Fichou and A. El Kassmi, “Gate voltage dependent mobility of oligothiophene field-effect transistors” J. Appl. Phys. 8,3202, (1999).
[48] Y.Y. Lin, D.J. Gundlach, and T.N. Jackson, “Contact dependence. of. -sexithienyl thin film transistor characteristics,” Mat. Res. Soc. Symp. Proc. 413, 413 (1996).
[49] K. Terada and H. Muta, “A New Method to Determine Effective. MOSFET Channel Length”, Jap. J. Appl. Phys. 18, 953 (1979).
[50] J.G.J. Chern, P. Chang, R.F. Motta and N. Godinho, "A. New Method to Determine MOSFET Channel Length," IEEE Elect. Dev.Lett. 1, 170 (1980).
[51] T. van Woudenbergh, P.W.M. Blom, M.C.J.M. Vissenberg and J.N. Huiberts, “Temperature dependence of the charge injection in poly-dialkoxy-p-phenylene vinylene”, Appl. Phys. Lett. 79, 1697 (2001).
[52]Y. Shen, M.W. Klein, D.B. Jacobs, J.C. Scott and G.G. Malliaras, “Mobility-Dependent Charge Injection into an Organic Semiconductor” Phys. Rev. Lett. 86, 3867 (2001).
[53]G. Horowitz and M. E. Hajlaoui, “Mobility in Polycrystalline Oligothiophene Field-Effect Transistors Dependent on Grain Size” Adv. Mater. 12, 1046 (2000)
[54] J. Kanicki, “Amorphous and Microcrystalline Semiconductor Devices”, Materials and Device Physics, Artech House, Inc., Norwood, (1992), Vol. 2.
[55] H. Sirringhaus, P. J. Brown, R. H. Friend, M. M. Nielsen, K. Bechgaard, B. M. W. Langeveld-Voss, A. J. H. Spiering, R. A. J. Janssen, E. W. Meijer, P. Herwig, and D. M. De Leeuw, “Two-dimensional charge transport in self-organized, high-mobility conjugated polymers” Nature (London) 401, 685 (1999).
[56]L. Torsi et al. “Charge transport in oligothiophene field-effect transistors”,Phys Rev B57(4),2271,1998.
[57]S.F. Nelson et al. “Temperature-independent transport in high-mobility pentacene transistors”, Appl.Let. 72(15), 1854,1998.
[58]G. Horowitz et al, “Temperature Dependence of the Field-Effect Mobility of Sexithiophene. Determination of the Density of Traps”. Appl. Phys. Let. 5, 355, 1995.
[59]A.R. Brown et al, “Benzodithiophene Rings as Semiconductor Building Blocks”. Science 270,972,1995.
[60]G Horowitz,“Organic Field-Effect Transistors” Adv. Mater. 10(1998) 365.
[61]A.R. Brown. C.P. Jarrett, D.M. de Leeuw, and M. Matters, “Field-effect transistors made from solution-processed organic semiconductors” synth. Met. 88(1997)37.
[62]S.F.Nelson, Y.Y. Lin,D.J. Gundlach, and T,N. Jackson, “Temperature-independent transport in high-mobility pentacene transistors” Appl. Phys. Lett. 72(1998)1854
[63]M. Matters, D.M. de Leeuw, M.J.C.M. Vissenberg, C.M. Hart, P,T. Herwig, T. Geuns, C.M.J. Mutsacrs, and C.J. Drury, “Organic Feld-efect transistors and all-polymer integrated Circuits” Optical Materials, Proceedings of the E-MRS 12,189,(1999)
[64]H. Sirringhaus, N. Tessler, and R.H. Friend,“Integrated optoelectronic devices based on conjugated polymers” Science 280(1998)1741
[65]M.J. Powell et al. “Time and temperature dependence of instability mechanisms in amorphous silicon thin-film transistors” , Appl. Phys. Let. 54 (14),1323,1989
[66] Guangming Wang, James Swensen, Daniel Moses, and Alan J. Heeger, “Increased mobility from regioregular poly(3-hexylthiophene) field-effect transistors” Journal of Applied Physics, Vol 93, no. 10
[12] Sung Kyu Park,Yong Hoon Kim, Jeong In Han, Dae Gyu Moon, and Won Keun Kim; “High-Performance Polymer TFTs Printed on a Plastic Substrate” ; IEEE TRANSACTIONS ON ELECTRON DEVICES
[13] K.P. Pernstich, S. Haas, D. Oberhoff, C. Goldmann, D.J. Gundlach, B. Batlogg, A.N. Rashid and G. Schitter, ”Threshold voltage shift in organic field effect transistors by dipole monolayers on the gate insulator”,Journal of Applied Physics, vol.96, no. 11, 2004.
[14 ] 22
[69] J. H. Lin ”The Analysis of Process Improvement and Reliability Characteristic of Spin-On Organic TFT”, Graduate thesis.
[70] Mohamed S. A. Abdou, Francesco P. Orfino, Yongkeun Son, and Steven Holdcroft; “Interaction of Oxygen with Conjugated Polymers: Charge Transfer Complex Formation with Poly(3-alkylthiophenes) ” ; J. Am. Chem. Soc. 1997, 119, 4518-4524
[71] A. Ullmann, W. Fix, H. Rost, and W. Clemens “Stability of polythiophene –based transistors and circuits” Journal of Applied Physics Vol 94, no. 4, 2003