溶液法制备金属氧化物薄膜晶体管的研究进展

金属氧化物薄膜晶体管(MOTFT)因具有迁移率高、可见光透明、工艺简单、可低温制备等优势,在高性能平板显示、可穿戴柔性电子、集成传感器等领域具有广阔的应用前景.主要回顾了溶液法制备MOTFT的研究进展.首先介绍了溶液法制备MOTFT相对于其他方法的优势,如工艺简单、制作成本低、易掺杂;然后阐述了浸涂法、喷雾法、旋涂法、印刷法加工工艺的特点及优缺点,比较了不同溶液加工工艺所制备MOTFT的电学性能;最后指出了目前溶液法制备MOTFT存在的问题,并从有源层材料与结构、栅介质层材料与界面、退火与预处理3个方面详细地讨论了溶液法制备的优化方法.     

溶液法制备环保型高分子聚合物薄膜晶体管

基于一种新型的稠合噻吩-吡咯并吡咯二酮聚合物半导体(PTDPPTFT4),采用溶液法工艺制作了高性能环保型、空穴型有机薄膜晶体管。通过尝试不同的半导体层退火温度及退火时间,优化了有机薄膜晶体管的性能。当采用对二甲苯溶剂,退火温度为190℃,退火时间为60min时,迁移率为2.1cm2·V-1·s-1,电流开关比大于106。通过X射线掠入射角衍射法测试,得到高温退火后聚合物薄膜的结构特点,进而揭示了退火条件改变后,薄膜晶体管拥有高迁移率的原因。     

顶栅共面结构非晶氧化物薄膜晶体管的低成本制备及性能研究

将溶液法制备的不含镓的非晶InAlZnO薄膜和有机聚甲基丙烯酸甲酯薄膜分别作为沟道层和介质层,制备了顶栅共面结构的非晶氧化物薄膜晶体管(TFT)器件,探讨了沟道层中Al含量对器件性能的影响。结果表明：Al对InZnO薄膜中氧空位的形成能起到一定抑制作用,增加Al含量即可降低沟道层中的电子载流子浓度,使得InAlZnO TFT器件阈值电压正向移动、关态电流减小,以有利于器件开关比的提升。此外,基于沟道层中Al含量的调整可通过优化沟道层/介质层界面状态来促进器件阈值电压滞回稳定性的提升。当沟道层中Al含量为30%时,制备的器件具有最佳综合性能。     

氧化物半导体薄膜晶体管的研究进展

简要说明了非晶硅、多晶硅和有机半导体用作薄膜晶体管沟道层的不足,从电学性质、光学性质和制备温度等几方面介绍了氧化物薄膜晶体管在有源阵列驱动显示技术中的优势,并介绍了氧化物沟道层制备工艺的优化和掺杂方法.最后,展望了氧化物半导体薄膜晶体管应用前景.     

基于铟镓锌氧化物的纸基柔性薄膜晶体管器件研究

目前大多数柔性薄膜晶体管(TFT)使用塑料基板替代玻璃基板会导致白色污染加重,本研究采用可降解的纳米纤维素纸作为柔性基板,其具有粗糙度仅为3.12 nm的优异平滑度,且整个器件沉积完后只增加至6.03 nm。更重要的是,该TFT器件通过磁控溅射制备IGZO/Al₂O₃作为有源层,使得器件在室温下无需热退火处理,避免了纳米纸不耐高温的问题。在有源层中,Al₂O₃充当电子桥连接了不连续的铟镓锌氧化物(IGZO),且IGZO有着微弱的结晶,大量的载流子得以沿沟道流通。该纸基器件展示出迁移率为22.5 cm²/(V·s)、开关比高达5.07×10⁶、阈值电压V_th仅为-0.036 V的优异性能,并且有着很好的正偏压和负偏压稳定性。这种纸基TFT在未来的绿色且柔性显示中具有巨大的应用潜力。     

喷墨印刷制备有机薄膜晶体管及其电路的研究进展

有机薄膜晶体管在大面积柔性显示、柔性电子存储等方面具有广阔的潜在应用前景。喷墨印刷技术由于具有工艺简单、成本低廉、微图形数字化、与柔性衬底兼容等优点而成为一种有效的制造有机电子器件工艺方法。文章综述了近年来基于喷墨印刷技术制备有机薄膜晶体管的研究进展,探讨了在制造过程中存在的问题。     

非晶铟镓锌氧化物薄膜晶体管的制备及其光敏特性研究

基于射频磁控溅射法制备了以非晶铟镓锌氧化物(a-IGZO)作为有源层的底栅顶接触式薄膜场效应晶体管(Thin Film Transistor,TFT),其长/宽比为300μm/100μm。研究了该器件在无激光和在三种不同波长激光照射下的光敏特性。实验表明,器件在波长分别为660、450和405nm三种激光照射下的阈值电压V_th分别为4.2、2.5和0V,均低于无激光时的4.3V,且器件的阈值电压随激光波长减小单调降低,此外,随着激光波长的下降,“明/暗”电流比K由0.54上升到8.06(在VGS=6V且VDS=5V条件下),光敏响应度R由0.33μA/mW上升到4.88μA/mW,可见激光波长越短,可获得更强的光电效应,光灵敏度也更高,该效应表明该器件在光电探测等领域具有广阔的应用前景。     

有机介质层铟锌氧化物薄膜晶体管

利用直流磁控溅射方法在玻璃基板上室温制备非晶铟锌氧化物半导体薄膜,薄膜表面平整。采用旋涂法室温制备聚四乙烯苯酚有机介质层。以铟锌氧化物薄膜作为沟道层、聚四乙烯苯酚作为介质层,成功制备了顶栅结构的薄膜晶体管。测试结果表明,所制备的薄膜晶体管具有饱和特性且为耗尽工作模式,薄膜晶体管的阈值电压为3.8V,迁移率为25.4cm2.V-1.s-1,开关比为106。     

面向有机薄膜晶体管的紫外/红外光退火的溶液法氧化锆薄膜性能研究

首先引入新型油酸配位剂,解决已有溶液法成膜较差的问题,接着引入紫外/红外双光源退火工艺,制备了氧化锆薄膜。与传统的热退火工艺相比,双光源退火能够在较低温度下实现锆盐的分解、还原、氧化,形成高质量氧化锆薄膜。采用紫外分光光度计、原子力显微镜和X射线光电子能谱仪等对制备的氧化锆薄膜进行了表征对比,进而分析了成膜的物理机理。结果表明:所用方法成功实现了低温条件下(<120℃)高质量氧化锆薄膜的制备,薄膜的光学带隙约为5.66 e V,相对介电常数约为22.6,漏电流密度小于10-9 A/cm2@4 MV/cm,表面粗糙度为0.28 nm。最后,基于该氧化锆薄膜绝缘层制备出了低驱动电压的稠合噻吩-吡咯并吡咯二酮聚合物薄膜晶体管,其迁移率为0.50 cm2/(V·s),阈值电压为-0.47 V,电流开关比3.6×107,亚阈值摆幅为0.16 V/dec。     

氧化物薄膜晶体管刻蚀阻挡层PECVD沉积条件研究

为实现氧化物TFT(Indium Gallium Zinc Oxide Thin Film Transistor,IGZO TFT)特性的最优化,采用I-V数据和SEM(Scanning Electron Microscope)图片研究蚀阻挡层(Etch-Stop Layer,ESL)沉积条件与氧化物TFT特性的关系。通过调整沉积温度、正负极板间距、压力和功率,分析了PECVD沉积ESL SiO2的成膜规律,并对所得到的TFT进行了特性分析。发现ESL膜层致密性过差时,后期高温工艺会造成水汽进入IGZO半导体膜层,从而引起TFT特性恶化。而采用高温、高压力等方法取得高致密性的ESL膜层由于高强度等离子体对IGZO本体的还原反应也会致使TFT特性劣化。结果表明,在保证膜层致密性前提下,等离子体对IGZO本体伤害最小的ESL沉积条件才是最优化的ESL沉积条件。     

Alkyl-monosubstituted thiophene/phenylene co-oligomers: Synthesis,thin film preparation,and transistor device characteristics

A novel series of alkyl-monosubstituted thiophene/phenylene co-oligomers (TPCOs) has been synthesized and characterized. The introduction of alkyl chains to TPCOs improved the solubility in organic solvents. Thin films of these compounds were prepared by the vacuum-deposition, solution-cast, and skim methods. Of these, the solution-cast films and skim films consist of highly-ordered structures characterized by molecular bilayers. In particular, the skim method produced a large-sized free-standing thin film. We investigated the carrier transport of the thin films on the field-effect transistor (FET) configurations. These FET devices exhibited typical p-channel characteristics with clear saturation region. The introduction of alkyl monosubstituents is responsible for enhancement in the carrier mobility. The device characteristics are contrasted with those of alkyl-disubstituted compounds.     

基于纳米多晶硅薄膜晶体管分裂漏MAGFET制作和特性

A split-drain magnetic field-effect transistor （MAGFET） based on a nano-polysilicon thin film transistor （TFT） is proposed, which contains one source, two drains and one gate. The sensor chips were fabricated on （100） high resistivity silicon substrate by CMOS technology. When drain-source voltage equals 5.0 V and length and width ratio of the TFT channel is 80 μm/160 μm, the current and voltage magnetic sensitivities of the split-drain MAGFET based on the TFT are 0.018 mA/T and 55 mV/T, respectively. Through adopting nano-polysilicon thin films and nano-polysilicon thin films/high resistivity silicon heterojunction interfaces as the magnetic sensing layers, it is possible to realize detection of the external magnetic field. The test results show that magnetic sensitivity of the split-drain MAGFET can be improved significantly.     

Improved thermal stability in photochromism-based optically controllable organic thin film transistor

Thermally induced structural change in photoisomerization molecules is a serious obstacle to the development of optically controllable organic field-effect transistors (OFETs). This is because the thermal relaxation of molecular structures degrades photo-induced change in drain current and removes the memory function. To deal with this issue, a naphthopyran (NP) derivative, namely 3,13-dihydro-3-(4-triphenylaminyl)-3,13-diphenylbenzopyrano[5,6-a]carbazole (NP-TPAC) was tested that displays pseudo p-type photochromism at room temperature. The NP-TPAC-doped poly(triarylamine) (PTAA) film exhibited a reversible change in transistor properties; the drain current was reduced by ultraviolet (UV) and returned to its original value by visible (VIS) light irradiation. Importantly, no change in the drain current was observed at room temperature for more than 30 h under dark conditions. This was because the open-ring trans–trans (TT) isomer of NP-TPAC is thermally stable owing to the CH-π interaction and the steric force exerted by the phenyl ring of the carbazole unit onto the double bond responsible for the thermal back reaction. In other words, the thermal stability of photochromism-based optical devices can be greatly improved by adopting an appropriate molecular design.     

有机薄膜晶体管直流电流-电压模型的研究

通过对有机薄膜晶体管(OTFT)电流-电压特性的研究,建立了一种用于电路模拟的仿真程序(SPICE)的OTFT直流电流-电压模型,所用的参数都可从实验特性曲线中提取。对一种基于并五苯(Pentacene)的底栅顶接触(TC)结构的OTFT的实验曲线进行参数提取,并利用所得的参数与建立的模型进行仿真,得到的输出特性和转移特性曲线与实验结果无论在线性区还是在饱和区都具有较强的一致性,验证了本文所建模型及参数的准确性。建立的模型能够准确描述OTFT的直流特性,可用于有机电路的SPICE仿真。     

A molecular probe layer modified organic thin film transistor on flexible platform for next generation cyanide sensor

Organic thin film transistor (OTFT) based cyanide (CN⁻) sensor can be of an intense interest due to its simple operation, high sensitivity, system on chip (SoC) integration capacity and applicability towards environmental safety. So, mechanical flexibility of such sensors can extend them to conformable, bio-compatible and wearable applications. In our recent work, a novel OTFT based highly sensitive and mechanically flexible platform was developed to detect CN⁻ in aqueous medium. The sensor was fabricated on a flexible polyethylene terephthalate (PET) substrate by simple spin coating and operated at a very low voltage of −3 V. For the sensing element, a chemically active dansyl-dervatized-triazole linked glucopyranosyl conjugate (DTGC) was used as a molecular probe on the semiconducting poly (3-hexylthiophene) P3HT layer in the device structure. The fabricated sensor was characterized electrically while using an aqueous solution of tetrabutylammonium cyanide (TBAC) as an analyte. Significant changes in device characteristics including 0.4 V shift in threshold voltage, 0.2 cm²v⁻¹s⁻¹ increment in mobility and 2 μA increase in drain current were observed for the OTFT based sensor with presence of CN⁻ analyte. The concentration of the CN⁻ was then varied and thus the minimum detection limit was found to be 1 μM. The sensor also exhibited excellent mechanical flexibility with its stable operation even up to a bending with 5 mm of bending radius. The sensing mechanism of the developed sensor has been explained through the possible charge transfer phenomena from the host semiconductor due to a chemical reaction between the probe layer and the analyte. The sensititvity and chemical reactivity of the molecular probe to the CN⁻ were further confirmed from the microscopic studies and the change in the visual appearance (colour) of the probe with the presence of aqueous CN⁻.     

氧分压对铟镓锌氧薄膜晶体管性能影响

采用标准的液晶显示屏基板制备工艺制备出铟镓锌氧薄膜晶体管(IGZO-TFT),通过调节IGZO薄膜工艺中氧分压,研究不同氧分压对TFT器件电学性能的影响。实验结果表明,所有器件都展现出良好的电学特性,随着氧分压从10%增加到50%,TFT的阈值电压由0.5 V增加到2.2 V,而亚阈值摆幅没有发生变化。在栅极施加30 V偏压3600 s后,随着氧分压的增加,阈值电压向正向的漂移量由1 V增加到9 V。经过分析得出高氧分压的IGZO-TFT器件中载流子浓度低,建立相同导电能力的沟道时所需要栅极电压会更大,阈值电压会增加。而在金属-绝缘层-半导体(MIS)结构中低载流子浓度会导致有源层能带弯曲的部分包含更多与电子陷阱相同的能态,栅介质层(GI)会俘获更多的电子,造成阈值电压漂移量较大的现象。     

异质诱导生长的酞菁铜薄膜晶体管的研究

因酞菁薄膜平面具有多电子共轭大π键结构,本文采用异质诱导的方式对酞菁薄膜的生长特性进行了改善研究。采用高掺杂硅为栅极,氧化硅为绝缘层,生长α-四噻吩或p-六联苯薄膜为异质诱导层,制备了酞菁铜有机薄膜晶体管。利用原子力显微镜研究薄膜生长特性,并对比研究了2种诱导层对薄膜晶体管性能的影响。实验结果表明:α-四噻吩上生长的酞菁铜薄膜,形貌呈片状,而p-六联苯上生长的酞菁铜薄膜,形貌呈针状,均与单层酞菁铜棒状形貌不同。同时,α-四噻吩与p-六联苯薄膜上生长酞菁铜后,两者晶体管电性能都有不同程度的提高,均比单层酞菁铜提高了1~2个数量级,表明α-四噻吩或p-六联苯对酞菁铜薄膜均有诱导效应,可以获得高性能的有机薄膜晶体管。     

High-resolution inkjet-printed organic thin film transistor array with commercially applicable source-drain electrode process

High-resolution inkjet printing of an organic thin film transistor (OTFT) array for mass-production is still regarded as an immature technology due to the difficulty in controlling the dimension of pattern and registry with other layers in commercial large-scale substrates. Especially, in the case of on organic gate insulator (OGI) in an inkjet-printed OTFT array, it is impossible to use plasma pre-treatment of the OGI for the hydrophobicity required for high-resolution inkjet printing of an organic semiconductor (OSC) due to its non-selectivity between organic layers, both inside and outside the channel area. A novel and commercially applicable process of the source-drain (SD) electrode prior to inkjet printing of the OSC in the bottom contact structure not only allowed a selective plasma treatment for high-resolution inkjet printing of OSC on OGI without the extra photolithographic process, but also protected the channel interface from the harmful outcomes of wet or plasma processes. This method enabled uniform electrical characteristics of more than 300 thousand pixels of an OTFT array for a backplane. Based on these results, a 5.7 inch electrophoretic display (EPD), with a high resolution of 140 dots per inch (DPI), on a plastic substrate was successfully demonstrated.     

Stable growth of large-area single crystalline thin films from an organic semiconductor/polymer blend solution for high-mobility organic field-effect transistors

We developed an effective and steady solution-processing technique for a small molecule–type semiconductor, C₁₀–DNBDT–NW, by adding an amorphous PMMA polymer to produce stable growth of a two-dimensional large-area single-crystalline thin film by effective phase separation at a crucially faster processing speed compared to the case without the addition of a polymer. By using this solution-processing technique, it is noteworthy that the single-crystalline films of C₁₀–DNBDT–NW/PMMA exhibit the highest and average mobilities of 17 and 10.6 cm²/Vs, respectively. Furthermore, we also show the limitations of two-dimensional continuous growth of a single-crystalline film in terms of the solution technique.     

Influence of oxygen on the parameters of a thin film copper phthalocyanine field effect transistor

The influence of oxygen on the electrical parameters of a copper phthalocyanine thin film field effect transistor was investigated by means of temperature‐modulated field effect spectroscopy. It was found that both the dark electrical conductivity and threshold voltage of the source–drain current versus gate voltage dependence were changed after oxygen exposure. Both effects can be effectively utilised for gas sensing. Copyright © 1999 John Wiley & Sons, Ltd.