微纳电子材料与工艺7薄膜及表征测试

1、北京大学深圳研究生院周航 2022-2-222ZnO薄膜的扫描电镜分析薄膜的扫描电镜分析 3 超薄膜 10 nm 二维纳米薄膜 100 nm 薄膜 3 evHigh mobilityRoom temperature deposited film Amorphous filmControllable carrier concentrationNon-toxic elementsGood reliability Cheap processingTFTs on flexible substrates1. Directly deposit film on flexible substrates (pl

2、astics) and fabricate TFTs.2. Fabricate TFTs on hard substrate (glass) and then transfer the TFTs to flexible substrates (plastics).Currently, most TFTs use -Si or organic TFTs (OTFTs). Two methods are used to fabricate these TFTs on flexible substrates.PET : polyethylene terephthalate Threshold vol

3、tage 1.3VOn/Off ratio 105Sub-threshold voltage swing 0.24 V/decadeField effect mobility 10 cm2V-1S-1gm 0.03 mS/mmHosono et. al., Jpn, J. Appl. Phys., 45, 4303 (2006)JOURNAL OF DISPLAY TECHNOLOGY, VOL. 5, NO. 12, DECEMBER 2009Hosono et. al., Nature, 432, 488 (2004)SiPost-transition metal oxide (n4) E

4、x. Indium oxide, or Tin oxide1.High transparency : available for transparent TFTs2.Room temperature process : available for plastics substrate3.Can be used as electrodes, or channel layers : by adjusting O2 ratio4.High field effect mobility : 10 50 cm2V-1S-1 5.Large area deposition : By sputtering m

5、achine6.Rapid Process 7.Low costAdvantages of the IZO Thin Film TransistorsMobility (m mFE) cm2/V-sFrequency Hz11010010001k100k1Ma-Si TFTAOS TFTLTPSNW TFTOrganicBG nc-Si TFTPure ZnO and In2O3 are crystalline when deposited at room temperatureIn binary oxides, e.g. Zn-In-O and Zn-Ga-O, crystallizatio

6、n is suppressedIncorporation of Ga suppresses formation of oxygen deficiencies IGZOGa2O3ZnOIn2O350cm2/V-s100cm2/V-s=5cm2/V-scrystamorphousIn, Ga, Zn, Sb - major constituents of good transparent conducting oxidescryst Mobility when trap-limited conduction prevails, assuming exp tail states )()()(*GSt

7、rapGSfreeGSfreebtrapfreefreebTLCVQVQVQmmmqfBEmEFlocalized tail statesfreetrapLee et al., APL 98, 2011 Mobility when percolation prevails assuming Gaussian distribution of potential fluctuations22)(2)()(expkTqkTVEqBGSBbPercfmmEEEwheremFqfBEmEFAll traps filledELee et al., APL 98, 2011RegimeKg gRelated

8、 ParametersTLC7.60.7VT = 2V, Ntc = 4x1019 cm-3eV-1Percolation38.90.1VP = 13V, qB = 50 meVLee et al., IEDM 2011Significant absorption due to oxygen vacancies (VO) in IZO by incident photons (430nm)Jeon, Nathan et al., Nature Mats, 2012I-V for different sResponsivity vs Responsivity 1 due to efficient

9、 carrier generation in IZO channel and separation at hetero-interface large photoconductive gain!Jeon, Nathan et al., Adv Mats, 2014Column DecoderRaw DecoderRGBDisplay Pixel DriverSensor PartVDDSelectAmpPhoto TFTTo column (n)Row (n)Row (n+1)GNDdisplay-sensor architecturePhotosensor integrated with i

10、nverted staggered TFT switch and photoresponse with laser pointerJeon, Nathan et al., Nature Mats, 2012Jeon, Nathan et al., Adv Mats, 2014薄膜材料科学（第2版）美 奥林 著； 刘卫国，蔡长龙，梁海锋，等 译工艺部分蒸发镀膜溅射镀膜化学气相沉积溶胶凝胶喷涂热裂解6 S E P T E M B E R 2 0 1 2 | VO L 4 8 9 | N AT U R E | 1 2 9化学气相沉积 (CVD) 根据气压等级分类 1Torr=133Pa常压化学气相沉

11、积 （APCVD, 760 Torr）次大气压化学气相沉积 （SACVD, 10760Torr）低压化学气相沉积 （LPCVD, 0.110 Torr)超低压化学气相沉积 （ULPCVD, 0.1 Torr) 化学气相沉积 (CVD) 根据能量供给方式分类 热激活式化学气相沉积 （TACVD） 等离子体增强CVD （PECVD, RF-,MW-.DC, ECR-PECVD, Remote Plasma, et al) 光辅助式化学气相沉积 （Photo-assisted CVD)磁控溅射成膜质量高，成本贵，速率较低喷涂热裂解成本低，但成膜均匀性不佳II-VI半导体都是直接跃迁型由于ZnO的组成

12、元素Zn和O蒸汽压不同，因而制备符合化学计量比的完美ZnO单晶比较困难，导致高密度的空位和晶格缺陷较宽的禁带宽度导致氧空位（施主态）的形成能较低，为n型p-type dopantsLi, Na，N，Pn-type dopantsAl掺杂元素掺杂元素掺杂量掺杂量(at.%)(at.%)电阻率电阻率(10(10-4-4cm)cm)载流子浓度载流子浓度（10102020cmcm-3-3) )Al1.5Inemm载流子迁移率依赖弛豫时间，弛豫时间与电荷漂移速率及平均自由程相关，这些参数又依赖于晶格缺陷散射机制 晶格散射 中性杂质散射 离化杂质散射 晶界散射影响电学性

13、能的因素Petritz模型-在多晶薄膜总，传到机制主要是由晶界而不是晶粒内特性控制。晶界含高密度界面态，它们俘获自由载流子，形成界面势垒，并能散射自由载流子N1和N2分别为晶内和晶界的载流子数量Mott模型-在非晶材料中，电子跃迁过程是主要的传导机制。电子能跃迁到相隔几个原子的原子上非晶材料的电导机制基片温度氧分压溅射功率薄膜厚度沉积后退火处理掺杂量例：磁控溅射掺杂氧化锌AZO基片温度()/掺杂浓度电导率（-1cm-1）氧分压(10-3Pa)电导率（-1cm-1）溅射功率电导率（-1cm-1）电导率（-1cm-1）薄膜厚度(nm)结晶改善Al2O3生成结晶恶化掺杂改善透射率波长吸收透过反射 紫

14、外截止特性：强吸收性有价带到导带的跃迁决定 a Tauc plot shows the quantity h (the energy of the light) on the abscissa and the quantity (h)1/r on the ordinate, where is the absorption coefficient of the material. The value of the exponent r denotes the nature of the transitionr = 1/2 for direct transitionsr = 2 for indir

15、ect allowed transitionsTauc, J. (1968). Optical properties and electronic structure of amorphous Ge and Si. Materials Research Bulletin 3: 3746. doi:10.1016/0025-5408(68)90023-8介电函数实部介电函数虚部等离子频率（在此频率下，电子与电场发生共振）1.在非晶硅太阳能电池中，ITO 与a-Si之间通常沉积一层SnO2， 以阻止In向a-Si层扩散。AZO优于ITO。2.金属氧化物太阳能电池Substrate: GlassIT

16、OPEDOT:PSSAlLightPoly(3-hexylthiophene-2,5-diyl) 6,6-Phenyl-C61 butyric acid methyl ester ZnO NWs051015201.01.1 Plain ZnOARIsc(mA/cm2)Time (hrs)Equationy = a + b*xWeightNo WeightingResidual Sum of Squares2.61616E-92.43136E-9Adj. R-Square0.995410.98885ValueStandard ErrorPlainInter

17、cept0.001078.08138E-6Slope-2.61143E-55.34812E-7ZnOARIntercept0.001138.74345E-6Slope-1.74859E-55.86942E-7Decay of an organic solar cell with time under constant UV illumination.Measurements taken under AM 1.5 conditionsUV-Protection2.Self-Cleaning3.ZnO Nanowires can be functionalised be using acetic

18、acidZnO Nanowires can be functionalisedAs grownFunctionalisedZn Source (415 C) ZnO:C (850 -1000C )Required Growth temperature on gold coated silicon substrate (750 C)ZnO nanoparticles and nanowire/tetrapods can form in the vapour. The vapour is a mixture of Zn, ZnO, N2, O2.Catalytic growth terminates when (a) Lack of reactant (Zn or O ) in the vapour (b) Temperature is lowe