基于表面勢(shì)的非晶銦鎵氧化鋅薄膜晶體管緊湊模型的研究
發(fā)布時(shí)間：2018-09-17 13:50
【摘要】：以非晶銦鎵氧化鋅(a-IGZO)為代表的非晶金屬氧化物半導(dǎo)體被視為下一代薄膜晶體管(TFTs)技術(shù)的有力候選者。在多個(gè)產(chǎn)業(yè)領(lǐng)域,特別是有源矩陣有機(jī)發(fā)光二極面板(AMOLED)與柔性電路,a-IGZO TFTs有著廣闊的應(yīng)用前景。a-IGZO TFTs工作的物理機(jī)制不同于早期的硅基器件�；谄洫�(dú)特的物理機(jī)制,建立緊湊模型以理解材料創(chuàng)新對(duì)TFTs電學(xué)性能的影響,并最終用于輔助集成電路的設(shè)計(jì),對(duì)促進(jìn)和發(fā)展AMOLED和集成電路產(chǎn)業(yè)有著深遠(yuǎn)意義。本文的主要內(nèi)容是分析a-IGZO TFTs的物理機(jī)制,考慮載流子簡(jiǎn)并的情況,建立基于表面勢(shì)的a-IGZO TFTs直流(DC)和電容緊湊模型,并使模型具備嵌入電路仿真器的條件。分析材料的能帶結(jié)構(gòu)與帶隙缺陷,為建立數(shù)學(xué)模型提供了清晰的理論依據(jù)。由于電負(fù)性的差異,a-IGZO的導(dǎo)帶由銦離子的s軌道相互交疊構(gòu)成,價(jià)帶由氧離子的2p軌道構(gòu)成,導(dǎo)致a-IGZO導(dǎo)帶附近的帶尾局域態(tài)密度要遠(yuǎn)小于氫化非晶硅(a-Si:H)等共價(jià)半導(dǎo)體。同時(shí),a-IGZO的價(jià)帶頂附近存在高密度深缺陷態(tài),易使費(fèi)米能級(jí)釘扎而難以移動(dòng)至價(jià)帶附近,因而a-IGZO TFTs多見于n型器件。結(jié)合這兩點(diǎn)可以說明,在a-IGZO TFTs中,施加足夠正的柵壓就可使費(fèi)米能級(jí)進(jìn)入導(dǎo)帶。因此,提出的模型必須考慮簡(jiǎn)并傳導(dǎo)機(jī)制。基于理論分析,本文指明了玻爾茲曼統(tǒng)計(jì)的局限性,給出適用于非簡(jiǎn)并和簡(jiǎn)并狀態(tài)的自由電荷和陷阱電荷濃度公式。結(jié)合泊松方程和高斯定理,運(yùn)用數(shù)學(xué)變換和Lambert W函數(shù),非迭代地求解出亞閾值區(qū)和積累區(qū)的表面勢(shì)。利用光滑函數(shù)與施羅德級(jí)數(shù)修正,得到了一個(gè)完整的、高精度的表面勢(shì)解析模型。模型結(jié)果與數(shù)值迭代解進(jìn)行了比較,絕對(duì)誤差可控制在10-8V范圍內(nèi)。利用表面勢(shì)計(jì)算結(jié)果,基于Pao-Sah雙重積分公式,建立了a-IGZO TFTs的直流緊湊模型,包括亞閾值電流與積累區(qū)電流。遷移率模型基于實(shí)際的載流子傳輸機(jī)制,主要包括陷阱限制傳導(dǎo)(TLC)機(jī)制和滲流導(dǎo)電(PM)機(jī)制兩種,其遵循冪律函數(shù)關(guān)系,并且考慮了聲子散射與表面粗糙散射對(duì)遷移率的退化。在核心電流模型的基礎(chǔ)上,融入了載流子速度飽和與溝道長(zhǎng)度調(diào)制兩個(gè)高階效應(yīng)。基于薄層電荷模型(CSM)與對(duì)稱正交方法(SQM),求解出各個(gè)端電荷的表達(dá)式,建立了考慮簡(jiǎn)并機(jī)制的a-IGZO TFTs的電容緊湊模型。該模型滿足電荷守恒與電容非互易性的條件,能夠很好地描述器件的動(dòng)態(tài)行為。綜上所述,提出的a-IGZO TFTs直流模型與電容模型都是以器件內(nèi)部物理機(jī)制為基礎(chǔ)的。通過與數(shù)值迭代解或?qū)嶒?yàn)數(shù)據(jù)多方面的比較,模型有效性得到了有力的支持。該模型物理概念清晰,算法簡(jiǎn)單明了,易于嵌入電路仿真器。
[Abstract]:Amorphous metal-oxide semiconductors, represented by amorphous indium gallium oxide (a-IGZO), are considered as potential candidates for the next generation of thin film transistor (TFTs) technology. In many industrial fields, especially active matrix organic light-emitting bipolar panel (AMOLED) and flexible circuit (a-IGZO TFTs) have broad application prospects. The physical mechanism of a-IGZO TFTs is different from that of silicon based devices. Based on its unique physical mechanism, a compact model is established to understand the impact of material innovation on the electrical properties of TFTs, which is ultimately used to assist the design of integrated circuits. It is of great significance to promote and develop the AMOLED and IC industry. The main content of this paper is to analyze the physical mechanism of a-IGZO TFTs, consider the degeneracy of carriers, establish a compact model of a-IGZO TFTs DC (DC) and capacitance based on surface potential, and make the model have the condition of embedded circuit simulator. The energy band structure and band gap defects of the materials are analyzed, which provides a clear theoretical basis for the establishment of mathematical models. Because of the difference in electronegativity, the conduction band of a-IGZO is composed of the S-orbitals of indium ions and the valence band is composed of the 2p orbitals of oxygen ions. The local density of states near the a-IGZO conduction band is much smaller than that of covalent semiconductors such as hydrogenated amorphous silicon (a-Si:H). At the same time, there are high density and deep defect states near the top of valence band of a-IGZO, which makes it difficult to move to the valence band due to the pinning of Fermi level, so a-IGZO TFTs is more common in n-type devices. Combined with these two points, it can be concluded that in a-IGZO TFTs, Fermi level can enter the conduction band by applying enough positive gate voltage. Therefore, the proposed model must consider the degenerate conduction mechanism. Based on theoretical analysis, this paper points out the limitation of Boltzmann statistics, and gives the free charge and trap charge concentration formulas suitable for nondegenerate and degenerate states. Combined with Poisson's equation and Gao Si's theorem, the surface potentials of sub-threshold region and accumulation region are solved without iteration by means of mathematical transformation and Lambert W function. By using smooth function and Schroeder series correction, a complete and high precision analytical model of surface potential is obtained. The results of the model are compared with the numerical iterative solution. The absolute error can be controlled in the range of 10 ~ (-8) V. Based on the results of surface potential calculation and Pao-Sah 's double integral formula, a direct current compact model of a-IGZO TFTs is established, including subthreshold current and accumulative current. The mobility model is based on the actual carrier transport mechanism, including trapping restricted conduction (TLC) mechanism and percolation conductive (PM) mechanism. The mobility model follows the power law function and considers the degradation of phonon scattering and surface rough scattering to mobility. Based on the core current model, two higher order effects, carrier velocity saturation and channel length modulation, are incorporated. Based on the thin layer charge model (CSM) and symmetric orthogonal method (SQM), the expressions of each end charge are solved, and a compact capacitance model of a-IGZO TFTs with degenerative mechanism is established. The model satisfies the condition of non-reciprocity between charge conservation and capacitance, and can describe the dynamic behavior of the device well. In conclusion, the proposed a-IGZO TFTs DC model and capacitance model are based on the internal physical mechanism of the device. Compared with numerical iterative solution or experimental data, the validity of the model is strongly supported. The physical concept of the model is clear, the algorithm is simple and clear, and it is easy to embed the circuit simulator.
【學(xué)位授予單位】：暨南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN321.5
本文編號(hào)：2246120
[Abstract]:Amorphous metal-oxide semiconductors, represented by amorphous indium gallium oxide (a-IGZO), are considered as potential candidates for the next generation of thin film transistor (TFTs) technology. In many industrial fields, especially active matrix organic light-emitting bipolar panel (AMOLED) and flexible circuit (a-IGZO TFTs) have broad application prospects. The physical mechanism of a-IGZO TFTs is different from that of silicon based devices. Based on its unique physical mechanism, a compact model is established to understand the impact of material innovation on the electrical properties of TFTs, which is ultimately used to assist the design of integrated circuits. It is of great significance to promote and develop the AMOLED and IC industry. The main content of this paper is to analyze the physical mechanism of a-IGZO TFTs, consider the degeneracy of carriers, establish a compact model of a-IGZO TFTs DC (DC) and capacitance based on surface potential, and make the model have the condition of embedded circuit simulator. The energy band structure and band gap defects of the materials are analyzed, which provides a clear theoretical basis for the establishment of mathematical models. Because of the difference in electronegativity, the conduction band of a-IGZO is composed of the S-orbitals of indium ions and the valence band is composed of the 2p orbitals of oxygen ions. The local density of states near the a-IGZO conduction band is much smaller than that of covalent semiconductors such as hydrogenated amorphous silicon (a-Si:H). At the same time, there are high density and deep defect states near the top of valence band of a-IGZO, which makes it difficult to move to the valence band due to the pinning of Fermi level, so a-IGZO TFTs is more common in n-type devices. Combined with these two points, it can be concluded that in a-IGZO TFTs, Fermi level can enter the conduction band by applying enough positive gate voltage. Therefore, the proposed model must consider the degenerate conduction mechanism. Based on theoretical analysis, this paper points out the limitation of Boltzmann statistics, and gives the free charge and trap charge concentration formulas suitable for nondegenerate and degenerate states. Combined with Poisson's equation and Gao Si's theorem, the surface potentials of sub-threshold region and accumulation region are solved without iteration by means of mathematical transformation and Lambert W function. By using smooth function and Schroeder series correction, a complete and high precision analytical model of surface potential is obtained. The results of the model are compared with the numerical iterative solution. The absolute error can be controlled in the range of 10 ~ (-8) V. Based on the results of surface potential calculation and Pao-Sah 's double integral formula, a direct current compact model of a-IGZO TFTs is established, including subthreshold current and accumulative current. The mobility model is based on the actual carrier transport mechanism, including trapping restricted conduction (TLC) mechanism and percolation conductive (PM) mechanism. The mobility model follows the power law function and considers the degradation of phonon scattering and surface rough scattering to mobility. Based on the core current model, two higher order effects, carrier velocity saturation and channel length modulation, are incorporated. Based on the thin layer charge model (CSM) and symmetric orthogonal method (SQM), the expressions of each end charge are solved, and a compact capacitance model of a-IGZO TFTs with degenerative mechanism is established. The model satisfies the condition of non-reciprocity between charge conservation and capacitance, and can describe the dynamic behavior of the device well. In conclusion, the proposed a-IGZO TFTs DC model and capacitance model are based on the internal physical mechanism of the device. Compared with numerical iterative solution or experimental data, the validity of the model is strongly supported. The physical concept of the model is clear, the algorithm is simple and clear, and it is easy to embed the circuit simulator.
【學(xué)位授予單位】：暨南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN321.5
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