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二氧化铪(HfO2)纳米晶态薄膜的自组装制备-贺中亮-2009

2013年06月17日 11:52 贺中亮 点击:[]

 

 作者姓名  贺中亮
 中文论文题名  二氧化铪(HfO2)纳米晶态薄膜的自组装制备
 外文论文题名  SYNTHESIS OF NANOCRYSTALLINE HAFNIUM OXIDE THIN FILM BY SELF-ASSEMBLED MONOLAYER METHOD
 论文提交日期  2009-06-20
 学位年度  2009
 中文论文关键词  HfO2薄膜,OTS自组装层,液相沉积,图案化
 外文论文关键词  HfO2 thin films, OTS-SAMs, liquid phase deposition, pattern

 

中文论文文摘


    随着金属氧化物半导体(MOS)器件尺寸的缩小,栅介质等效氧化物层厚度已缩小至纳米量级,这时电子的直接隧穿效应加剧,严重影响器件的稳定性和可靠性,因此需要寻找新型高k栅介质材料来替代传统的SiO2栅极材料。铪(Hf)系氧化物由于具有高的k值,好的热稳定性,成为当前高k栅介质的研究热点。
     本文研究了一种低温水溶液中制备纳米晶态薄膜材料的新的合成方法。将自组装分子膜(Self-Assembled Monolayers, SAMs)技术与液相沉积技术(Liquid Phase Deposition, LPD)相结合,利用功能化自组装膜层对前驱体溶液的诱导作用,在玻璃基底表面制备出与基底结合紧密、结构致密均一的HfO2晶态薄膜及图案化薄膜。
    首先对十八烷基三氯硅烷(OTS)在玻璃基底表面自组装成膜过程进行了研究。接触角测试仪、原子力显微镜(AFM)和扫描电子显微镜(SEM)的测试结果表明:沉积时间对于自组装膜层的生长影响显著,沉积时间增加,膜层的接触角明显增大,膜层质量提高。沉积反应开始1分钟后,OTS自组装分子膜就已经在整个基底表面形成,表面接触角的急剧增大。20分钟后,成膜过程趋于稳定,接触角不再有明显变化,膜层平整致密光滑。
    OTS自组装分子层形成后,对其进行紫外光照射改性。接触角测试及红外光谱(FT-IR)分析的结果表明:照射时间对于膜层的表面亲水性能影响很大,照射时间增加,亲水性能明显提高。紫外照射30分钟后,自组装分子层表面接触角已小于5°,由原来的强疏水性转变为良好的亲水性,说明OTS自组装膜层表面已被羟基化。
    利用功能化自组装膜层的诱导作用,在前驱液中沉积制备出具有晶体结构的二氧化铪薄膜。对二氧化铪薄膜的这种液相自组装法制备进行了比较系统的工艺研究和理论探讨。利用X射线衍射仪、扫描电镜(SEM)、原子力显微镜(AFM)等测试手段对所制备薄膜的结构、相组成和表面形貌进行了分析考察。研究结果表明:当前驱液中铪浓度在5mmol/L,盐酸浓度在0.3mol/L,沉积温度为70℃的实验工艺条件下,在空气中经过600℃煅烧2小时成功制备出结晶良好具有立方相晶型的二氧化铪薄膜,且薄膜表面平整,结构致密均一,与基底结合牢固。
    根据上述实验条件进一步对二氧化铪薄膜进行图案化制备。在光掩模的掩饰下采用紫外光在OTS自组装层表面刻蚀不同的图案,利用液相自组装技术在OTS模板表面沉积HfO2图案化薄膜。由扫描电镜(SEM)、原子力显微镜(AFM)、能谱仪(EDS)等测试分析表明:利用紫外光刻蚀制备出了图案化OTS自组装层,通过诱导沉积成功制备出了HfO2图案化薄膜,薄膜表面图案清晰,粗糙度较小,与基板结合力较强。

 

外文论文文摘


 

    With the decrease of the MOS devices size, the thickness of equivalent oxide of MOSFET lowers to nanometer magnitude, the electron tunneling is becoming serious enough to endanger the stability and reliability of devices. It is an urgent task now to seek a novel high-k dielectric material to substitute the traditional SiO2 gate dielectric in microelectronic industry. The Hf and oxide have currently become a hot point of study due to their high-k value and good thermal stabilization.
    A new thin film synthesis method was investigated in this paper for preparing nanocrystalline thin films at the low temperature in an aqueous solution. By the combination process of Self-Assembled Monolayers (SAMs) technique and the Liquid Phase Deposition (LPD) method, the nanocrystalline titanium dioxide thin films were successfully deposited on the glass substrates modified by the self-assembled monolayers. The as-deposited hafnium oxide patterned thin films were uniform, dense, with excellent adherence.
Firstly, the growth and the process of octadecyl-trichloro-silane (OTS) self-assembled monolayers on the hydroxylated glass substrates were investigated in the present study. The characterization results of water contact angle, atomic force microscopy and scanning electron microscopy, indicated immersion time had the significant effects on the growth and surface structure of self-assembled layers on the glass substrates. As the deposition time increases the surface contact angle of OTS-SAMs became larger and the layers quality improved highly. After 1 minute deposition, OTS-SAMs have been formed on the whole substrate. After 20 minutes, the water contact angle turned larger sharply and got to maximum. The growing process tended to stable. There were no obvious changes after that. The layers were smooth and dense.
    The OTS-SAMs were exposed to UV-light irradiation for functionalization. The test results of the surface water contact angle and Fourier-transform infrared spectroscopy (FT-IR) indicated irradiation time had a great effect on the hydrophile ability of the OTS-SAMs. The hydrophile ability would improve obviously with irradiation time increasing. After 30 minutes irradiation, the water contact angle had been less than 5°, indicating the surface of OTS-SAMs had been well hydroxylated.
    At last, self-assembled monolayers with functional hydrophilic hydroxyl groups on the glass substrates were used as templates for the deposition of HfO2 thin films from aqueous solutions. The process and influence factors of HfO2 thin films prepared on OTS-SAMs were systematically investigated. The phase composition, microstructure and surface morphology of as-deposited HfO2 thin films were studied via XRD, SEM and AFM. The results indicated that HfO2 thin films could be fabricated under the following experiment parameters: the cubic-phase nanocrystalline HfO2 thin films successfully prepared were annealed at 600 °C for 2 hours in the air. The optimal experiment conditions were the precursor solution containing 5mmol/L Hf(SO4)2•4H2O and 0.3mol/L HCl, the deposition temperature at 70 °C. The surface of thin films was smooth, uniform and dense. It had good adherence with the substrate.
    On the basis of the above-mentioned experimental results, the HfO2 thin films were further done with the pattern preparation. Different kinds of micro-patterns were created on the octadecyltrichlorosilane (OTS) self-assembled monolayers utilizing UV lithography with the cover of photomask, The HfO2 pattern films have been formed on silanol SAMs by the liquid-phase deposition (LPD) method. The test results of scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy disperse spectroscopy (EDS) indicated the HfO2 pattern films with distinct patterns were successfully prepared. By UV sculpture, OTS self-assembled monolayers with patterns were prepared. Through the inducing deposition, the HfO2 pattern thin films were successfully prepared. The patterns on the surface of thin films were clear, the line edge roughness was small and they had the greater adherence with the substrate.

 

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