a-Si：H TFT SPICE模型的研究
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摘要
薄膜晶体管(Thin Film Transistor的英文缩写是TFT)是近年来显示器上广泛使用的器件，其中a-Si：H TFT(hydrogenateld amorphous siliconTFT非晶硅薄膜晶体管)是发展的主流，常用作有源矩阵液晶显示器的开关元件。随着a-Si：H TFT的广泛应用，其模型的建立就成为非常重要的课题。精确的a-Si：H TFT模型在SPICE模拟中是非常重要的。在国内外已经发表了许多关于a-Si：H TFT物理特性及模型的文章，但仍然不能满足今天先进LCD模拟的需要。
为配合国家十五“863”计划项目“高品质大尺寸a-Si：H TFT-OLED技术研究”工作，本论文重点进行了a-Si：H TFT SPICE模型的研究工作。
本文以底栅结构背沟道阻挡型a-Si：H TFT器件为基础，测试了电流电压(I-V)特性和电容电压(C-V)特性。从电容电压曲线中提取了a-Si：H的掺杂浓度、固定电荷密度、界面态密度等工艺参数。分析了a-Si：H TFT的局域态、亚阈值导电、泄漏电流、表面迁移率调制、栅源和栅漏电容对频率的依赖性，温度特性及应力对阈值电压的影响。本论文以MOSFET为模型基础，对I-V特性进行了理论分析，建立了线性区、饱和区的漏极电流模型，重点建立了精确的亚阈值前区、亚阈值后区漏极电流和截止区的泄漏电流模型。同时：本论文以MIS结构的电容为理论基础，建立了a-Si：HTFT的MIS结构依赖于偏压和频率的电容模型，并提取了阈值电压V_(TO)、迁移率μ0等模型参数。用C语言编程模拟了I-V和C-V特性，测试数据与模拟数据拟合得很好，优于以往的a-Si：H TFT SPICE模型。本论文建立的模型适用于不同工艺结构的a-Si：H TFT器件，对TFT的设计者具有较高的指导价值。
TFT( Thin Film Transistor )is widely used for displays. The main TFT is a-Si:H TFT which is switching device of active matrix liquid crystal display. With the wide application of a-Si:H TFT, the establishment of its models becomes a very important question for study. Accurate a-Si:H TFT models are required for SPICE simulators. Several papers have already been published regarding the physics and the models of a-Si:H TFT, but they are insufficient for today's advanced LCD simulations.
This thesis mainly studied SPICE model for a-Si:H TFT, which is a part of national "863" project, "Study of Large Size and high quality a-Si TFT-OLED technology". The analysis and models are applicable to the simulation of today's optical characterizations of Flat-Panel-Displays.
In this thesis, the new models of a-Si:H TFT are established for SPICE, on the basis of inverted-stagger structure a-Si:H TFT of back channel stopped types. Current-voltage and capacitance-voltage are also tested. From the capacitance curve, the process parameters are extracted, such as dopant concentration, fixed charge density, interface state, etc. This paper analyzed localized state, sub-threshold current, off-leakage current, the field effect mobility, bias- and frequency-dependent capacitance, the threshold voltage change with voltage stress and device temperature, etc. This thesis focuses on the establishment of new drain current models in the linear region, the saturation region, the forward and reverse sub-threshold region, and new off-leakage current models in the off region on based of MOSFET model. In addition, the precise bias- and frequency-dependent MIS capacitance models are established. Some model parameters are extracted, such as threshold voltage(V_(TO)), mobility(μ0) etc. Simulation results by using these models and parameters show good agreement between measured and simulated data. The models are applicable to the a-Si:H TFT devices with different process structures. The modeling procedure is useful to TFT designers.
为配合国家十五“863”计划项目“高品质大尺寸a-Si：H TFT-OLED技术研究”工作，本论文重点进行了a-Si：H TFT SPICE模型的研究工作。
本文以底栅结构背沟道阻挡型a-Si：H TFT器件为基础，测试了电流电压(I-V)特性和电容电压(C-V)特性。从电容电压曲线中提取了a-Si：H的掺杂浓度、固定电荷密度、界面态密度等工艺参数。分析了a-Si：H TFT的局域态、亚阈值导电、泄漏电流、表面迁移率调制、栅源和栅漏电容对频率的依赖性，温度特性及应力对阈值电压的影响。本论文以MOSFET为模型基础，对I-V特性进行了理论分析，建立了线性区、饱和区的漏极电流模型，重点建立了精确的亚阈值前区、亚阈值后区漏极电流和截止区的泄漏电流模型。同时：本论文以MIS结构的电容为理论基础，建立了a-Si：HTFT的MIS结构依赖于偏压和频率的电容模型，并提取了阈值电压V_(TO)、迁移率μ0等模型参数。用C语言编程模拟了I-V和C-V特性，测试数据与模拟数据拟合得很好，优于以往的a-Si：H TFT SPICE模型。本论文建立的模型适用于不同工艺结构的a-Si：H TFT器件，对TFT的设计者具有较高的指导价值。
TFT( Thin Film Transistor )is widely used for displays. The main TFT is a-Si:H TFT which is switching device of active matrix liquid crystal display. With the wide application of a-Si:H TFT, the establishment of its models becomes a very important question for study. Accurate a-Si:H TFT models are required for SPICE simulators. Several papers have already been published regarding the physics and the models of a-Si:H TFT, but they are insufficient for today's advanced LCD simulations.
This thesis mainly studied SPICE model for a-Si:H TFT, which is a part of national "863" project, "Study of Large Size and high quality a-Si TFT-OLED technology". The analysis and models are applicable to the simulation of today's optical characterizations of Flat-Panel-Displays.
In this thesis, the new models of a-Si:H TFT are established for SPICE, on the basis of inverted-stagger structure a-Si:H TFT of back channel stopped types. Current-voltage and capacitance-voltage are also tested. From the capacitance curve, the process parameters are extracted, such as dopant concentration, fixed charge density, interface state, etc. This paper analyzed localized state, sub-threshold current, off-leakage current, the field effect mobility, bias- and frequency-dependent capacitance, the threshold voltage change with voltage stress and device temperature, etc. This thesis focuses on the establishment of new drain current models in the linear region, the saturation region, the forward and reverse sub-threshold region, and new off-leakage current models in the off region on based of MOSFET model. In addition, the precise bias- and frequency-dependent MIS capacitance models are established. Some model parameters are extracted, such as threshold voltage(V_(TO)), mobility(μ0) etc. Simulation results by using these models and parameters show good agreement between measured and simulated data. The models are applicable to the a-Si:H TFT devices with different process structures. The modeling procedure is useful to TFT designers.
引文
1 杨之廉，申明．超大规模集成电路设计方法学导论．北京：清华大学出版社，1999：124，157-221
2 青木均著．株式会社．1997：1．135，251．267
3 曹培栋．微电子技术基础．北京：电子工业出版社，2001：218-249
4 孙以材．半导体测试技术．北京：冶金工业出版社，1984：405-434
5 Shur M, Hack M. Physics of Amorphous Silicon Based Alloy Field-effect Transistors. J Appl Phys,1984,51(9):3831-3842
6 Shur M S, Slade H C, Jacunski M D, et al. SPICE Models for Amorphous Silicon and Polysilicon Thin Film Transistors. J Electrochem Soc, 1997:144,8,2833
7 Shur M, Hack M, Shaw G. A new analytic model for amorphous silicon thin-film transistors. J Appl Phys, 1989, 1(66):3371-3380
8 Leroux T. Static and Dynamic Analysis of Amorphous Silicon Field Effect Transistors. Solid-State Elec, 1986,29(1):47
9 Khakzar K, Lueder E H. Modeling of Amorphous Silicon Thin Film Transistors for Circuit Simulations with SPICE. IEEE Trans Electron Device, 1992,39(6):1428
10 Chen S S, Kuo J B. An Analytical a-Si:H TFT DC/Capacitance Model Using an Effective Temperature Approach for Deriving a Switching Time Model for an Inverter Circuit Considering Deep and Tail States. IEEE Trans Electron Devices, 1994,41(7):1169
11 Servati P, Striakhilev D, Nathan A. Above-threshold Modeling and Parameter Extraction for Amorphous Silicon Thin-film Transistors. IEEE Trans Electron Devices, 2003:1-10
12 Servati P, Nathan A. Modeling of the Static and Dynamic Behavior of Amorphous Silicon Thin Film Transistors. J Vac Sci Technol A, 2002,20(3):1038
13 Servati P. Modeling of Static and Dynamic Characteristicd of a-Si:H TFTs. M A Sc Thesis University of Waterloo, Waterloo:200
14 Iniguez B, Fjeldly T A, shut M S. Thin Film Transistor Modeling. International Journal of High Speed Electronics and Systems, 1999,9(3):703
15 Colalongo L. A New Analytical Model for Amorphous Silicon Thin Film Transistors Including Tail and Deep States. Solid State Electronics, 2001,45(9):1525
16 Hitoshi Aoki. Dynamic Characterization of a-Si TFT-LCD Pixel. IEEE Trans on Electron Devices, 1996, 43(1): 1-8
17 Yue Kuo. Thin Film Transistors-Materials and Processes. Texas A&M University, 2004,1:90-132,140-155
18 方可等．固体物理学[M]．1．重庆：重庆火学出版社，1993，2．256-258．
19 夏建白．现代半导体物理[M]1．2000,1．150-151．
20 Polk D E.J. Non-Crystal Solids. 1971,5.365.21 亢宝位．场效应晶体管理论基础[M]．1．北京：科学出版社，1985，7．181-182．
22 毛友德．非晶态半导体[M]．1．上海：上海交通大学出版社，1986，8．100-101．
23 [日]堀 浩雄，铃木幸治．金轸裕译．彩色液晶显示[M]．1．北京：科学出版社，2003，3．94．
24 Shur M S, Jacunski M D, Slade H C, et al. Analytical Models for Amorphous-Silicon and Poly-silicon Thin-film Transistor for High-definition-display Technology. J of the SID, 1995:3-4.223
25 Slade H C, Shur M S, Deane S C, et al. Physics of Below Threshold Current Distribution in a-Si:H TFTs. Mat Res Soc Symp Proc, 1996:420,257
26 Servati P, Nathan A. Modeling of the Reverse Characteristics of a-Si:H TFTs. IEEE Trans Electron Devicds, 2002,49(5):812
27 Street R A, Thompson M J, Johnson N M. The Electrical Characterization of Surfaces Interfaces and Contacts to a-Si:H. Phil Mag B, 1985,51(1):1
28 Street R A, Thompson M J. Electronic States at the Hydrogenated Amorphous Silicon/silicon Nitride Interface. Appl Phys Lett, 1984,45(7):769
29 Kawachi G, Graeff C F O, Brandt M S, et al. Carrier Transport in Amorphous silicon-based Thin-film Transistors Studied by Spin-dependent Transport. Phys Rev B, 11996,54:7957
30 Nathan A, Austin M, Pereira D. Correlation between Leakage Current and Overlap Capacitance in a-Si:H TFTs. Proc of IEEE Workshop on Charge Coupled Devices and advanced Image Sensor. Japan Karuizawa, 1999,6:10-12,126
31 Angelis T, Dimitriadis C A, Samaras I, et al. Study of Leakage Current in n-channel and p-channel Polycrystalline Silicon Thin-film Transistors by Conduction and Low Frequency Noise Mwasurements. J appl Phys, 1997,82(8):4095
32 Jain S C, Geens W, Mehra A, et al. Injection and Space Charge Limited-currents in Doped Conducting Organic Materials. J Appl Phys, 2001,89(7):3804
33 Jain S C, Geens W, Kumar V, et al. A Unified Model for the Space Charge Limited Currents in Organic Materials Combining Field Dependent Mobility and Poole-Frenkel Detrapping. Mat Res Soc Symp Proc, 2001,665:12,1
34 Park H R, Kwon D, Cohen J D. Electrode Interdependence and Hole Capacitance in Capacitance-Voltage Characteristics of Hydrogenated Amorphous silicon Thin-film Transistor. J Appl Phys, 1998,83(12):8051
35 Shur M, Hack M, Shaw G, et al. Capacitance-voltage Characteristics of Amorphous silicon Thin-film Transistors. J Appl Phys, 1989,66(7):3381
36 Oh S Y, Ward D E, Dutton R W. Transient Analysis of MOS Transistors. IEEE Trans Electron Device, 1980,27(8):1571
37 Meyer J E. MOS Models and Circuit Simulation. Rcs Rev, 1971:32,42
38 Shur M, Hack M, shaw J G, et al. Capacitance-Voltage Characteristics of Amorphous Silicon Thin-film Transistors. J Appl Phys, 1989,66(7):338139 Bahadur B. Liquid Crystals Applications and Uses. 1993,(1):405
40 Ibaraki N, Kigoshi M, Fukuda K, et al. Threshold Voltage Instability of a-Si:H TFT's in Liquid Crystal Displays. J Non-Crystalline solids, 1989,115:138-140
41 Dawson R M A, Kane M G. Pursuit of Active Matrix Organic Light Emitting Diode Displays. Digest of Techincal Papers SID International Symp San Jose, 2001,6:5-7,372
42 Servati P, Prakash S, Nathan A, et al. Amorphous Silicon Driver Circuits for OLED displays. J Vac Sci Technol A, 2002,20(4): 1374
43 Karim K S, Nathan A. Readout Circuit in Active Pixel Sensors in Amorphous silicon Technology. IEEE Electron Device Lett,2001,22(10):469
44 Cerdeira, Estrada M, Garcia R, et al. New Procedure for the Extraction of Basic a-Si:H TFT Model Parameters in the Linear and Saturation Regions. Solid-State Electronics, 2001,45:1077
45 邵丙铣，郑国祥．集成电路的分析与设计．上海：复旦大学出版社，2002：214-223
2 青木均著．株式会社．1997：1．135，251．267
3 曹培栋．微电子技术基础．北京：电子工业出版社，2001：218-249
4 孙以材．半导体测试技术．北京：冶金工业出版社，1984：405-434
5 Shur M, Hack M. Physics of Amorphous Silicon Based Alloy Field-effect Transistors. J Appl Phys,1984,51(9):3831-3842
6 Shur M S, Slade H C, Jacunski M D, et al. SPICE Models for Amorphous Silicon and Polysilicon Thin Film Transistors. J Electrochem Soc, 1997:144,8,2833
7 Shur M, Hack M, Shaw G. A new analytic model for amorphous silicon thin-film transistors. J Appl Phys, 1989, 1(66):3371-3380
8 Leroux T. Static and Dynamic Analysis of Amorphous Silicon Field Effect Transistors. Solid-State Elec, 1986,29(1):47
9 Khakzar K, Lueder E H. Modeling of Amorphous Silicon Thin Film Transistors for Circuit Simulations with SPICE. IEEE Trans Electron Device, 1992,39(6):1428
10 Chen S S, Kuo J B. An Analytical a-Si:H TFT DC/Capacitance Model Using an Effective Temperature Approach for Deriving a Switching Time Model for an Inverter Circuit Considering Deep and Tail States. IEEE Trans Electron Devices, 1994,41(7):1169
11 Servati P, Striakhilev D, Nathan A. Above-threshold Modeling and Parameter Extraction for Amorphous Silicon Thin-film Transistors. IEEE Trans Electron Devices, 2003:1-10
12 Servati P, Nathan A. Modeling of the Static and Dynamic Behavior of Amorphous Silicon Thin Film Transistors. J Vac Sci Technol A, 2002,20(3):1038
13 Servati P. Modeling of Static and Dynamic Characteristicd of a-Si:H TFTs. M A Sc Thesis University of Waterloo, Waterloo:200
14 Iniguez B, Fjeldly T A, shut M S. Thin Film Transistor Modeling. International Journal of High Speed Electronics and Systems, 1999,9(3):703
15 Colalongo L. A New Analytical Model for Amorphous Silicon Thin Film Transistors Including Tail and Deep States. Solid State Electronics, 2001,45(9):1525
16 Hitoshi Aoki. Dynamic Characterization of a-Si TFT-LCD Pixel. IEEE Trans on Electron Devices, 1996, 43(1): 1-8
17 Yue Kuo. Thin Film Transistors-Materials and Processes. Texas A&M University, 2004,1:90-132,140-155
18 方可等．固体物理学[M]．1．重庆：重庆火学出版社，1993，2．256-258．
19 夏建白．现代半导体物理[M]1．2000,1．150-151．
20 Polk D E.J. Non-Crystal Solids. 1971,5.365.21 亢宝位．场效应晶体管理论基础[M]．1．北京：科学出版社，1985，7．181-182．
22 毛友德．非晶态半导体[M]．1．上海：上海交通大学出版社，1986，8．100-101．
23 [日]堀 浩雄，铃木幸治．金轸裕译．彩色液晶显示[M]．1．北京：科学出版社，2003，3．94．
24 Shur M S, Jacunski M D, Slade H C, et al. Analytical Models for Amorphous-Silicon and Poly-silicon Thin-film Transistor for High-definition-display Technology. J of the SID, 1995:3-4.223
25 Slade H C, Shur M S, Deane S C, et al. Physics of Below Threshold Current Distribution in a-Si:H TFTs. Mat Res Soc Symp Proc, 1996:420,257
26 Servati P, Nathan A. Modeling of the Reverse Characteristics of a-Si:H TFTs. IEEE Trans Electron Devicds, 2002,49(5):812
27 Street R A, Thompson M J, Johnson N M. The Electrical Characterization of Surfaces Interfaces and Contacts to a-Si:H. Phil Mag B, 1985,51(1):1
28 Street R A, Thompson M J. Electronic States at the Hydrogenated Amorphous Silicon/silicon Nitride Interface. Appl Phys Lett, 1984,45(7):769
29 Kawachi G, Graeff C F O, Brandt M S, et al. Carrier Transport in Amorphous silicon-based Thin-film Transistors Studied by Spin-dependent Transport. Phys Rev B, 11996,54:7957
30 Nathan A, Austin M, Pereira D. Correlation between Leakage Current and Overlap Capacitance in a-Si:H TFTs. Proc of IEEE Workshop on Charge Coupled Devices and advanced Image Sensor. Japan Karuizawa, 1999,6:10-12,126
31 Angelis T, Dimitriadis C A, Samaras I, et al. Study of Leakage Current in n-channel and p-channel Polycrystalline Silicon Thin-film Transistors by Conduction and Low Frequency Noise Mwasurements. J appl Phys, 1997,82(8):4095
32 Jain S C, Geens W, Mehra A, et al. Injection and Space Charge Limited-currents in Doped Conducting Organic Materials. J Appl Phys, 2001,89(7):3804
33 Jain S C, Geens W, Kumar V, et al. A Unified Model for the Space Charge Limited Currents in Organic Materials Combining Field Dependent Mobility and Poole-Frenkel Detrapping. Mat Res Soc Symp Proc, 2001,665:12,1
34 Park H R, Kwon D, Cohen J D. Electrode Interdependence and Hole Capacitance in Capacitance-Voltage Characteristics of Hydrogenated Amorphous silicon Thin-film Transistor. J Appl Phys, 1998,83(12):8051
35 Shur M, Hack M, Shaw G, et al. Capacitance-voltage Characteristics of Amorphous silicon Thin-film Transistors. J Appl Phys, 1989,66(7):3381
36 Oh S Y, Ward D E, Dutton R W. Transient Analysis of MOS Transistors. IEEE Trans Electron Device, 1980,27(8):1571
37 Meyer J E. MOS Models and Circuit Simulation. Rcs Rev, 1971:32,42
38 Shur M, Hack M, shaw J G, et al. Capacitance-Voltage Characteristics of Amorphous Silicon Thin-film Transistors. J Appl Phys, 1989,66(7):338139 Bahadur B. Liquid Crystals Applications and Uses. 1993,(1):405
40 Ibaraki N, Kigoshi M, Fukuda K, et al. Threshold Voltage Instability of a-Si:H TFT's in Liquid Crystal Displays. J Non-Crystalline solids, 1989,115:138-140
41 Dawson R M A, Kane M G. Pursuit of Active Matrix Organic Light Emitting Diode Displays. Digest of Techincal Papers SID International Symp San Jose, 2001,6:5-7,372
42 Servati P, Prakash S, Nathan A, et al. Amorphous Silicon Driver Circuits for OLED displays. J Vac Sci Technol A, 2002,20(4): 1374
43 Karim K S, Nathan A. Readout Circuit in Active Pixel Sensors in Amorphous silicon Technology. IEEE Electron Device Lett,2001,22(10):469
44 Cerdeira, Estrada M, Garcia R, et al. New Procedure for the Extraction of Basic a-Si:H TFT Model Parameters in the Linear and Saturation Regions. Solid-State Electronics, 2001,45:1077
45 邵丙铣，郑国祥．集成电路的分析与设计．上海：复旦大学出版社，2002：214-223