电子材料用铪、锆醇盐类化合物的电化学合成与纯化制备研究

With the silicon chip trending down to sub-10-nm gate regimes, the leakage current of the MOSFET gate increased radically for the quantum tunneling effect. The conventional SiO2 gate has been replaced by a new high-k dielectric material, such as hafnium oxide or hafnium-based silicate, And now the cheap zirconium silicate used for dielectric material is studied. Using hafnium and zirconium metalorganic compound as precursors, the dielectric materials of HfO2, ZrO2 were deposited by using ALD, MOCVD, et al. Currently the metalorganic compound are made from hafnium chloride or zirconium chloride, which exiting the following disadvantages, longer flowsheet, lower yield, high toxicity, et al. So we propose a new method using electrosynthesis and vacuum distillation to produce high-purity Zr or Hf alkoxides. In this project we will study the basic theory on the new method, including: ① electrochemical mechanism of Zr or Hf metal dissolved and forming mechanism of Zr or Hf alkoxides in absolute ethyl alcohol and acetonitrile solution and quatemary ammonium salt solution , and the effects of electroysnthesis conditions on cell voltage, current efficiency and by-product yield; ②establishing the vapor-liquid equilibrium of Zr or Hf alkoxides and related alkoxides of impurities; ③ establishing the vapor pressure equation and discovering thermal decomposition characterization of Zr or Hf alkoxides. The above studies are for not only producing high-purity Zr or Hf alkoxides by using electrosynthesis and distillation methods also choosing MO resources for electronic materials.

随着微电子硅芯片进入纳米时代，量子隧穿效应导致MOSFET栅极漏电流显著增加，高介电的铪氧化物及其伪二元系硅酸盐已经取代传统栅极氧化物Si02，目前正在开发成本更低的锆基氧化物。栅极铪、锆基氧化物主要采用其金属有机物(MO)源的ALD、MOCVD法等制备，但现有制备MO源的卤化物法存在流程长、回收率低、毒性大等缺点，我们提出了电化学合成与精馏纯化制备高纯铪、锆醇盐类化合物的新方法。本课题拟研究新方法的基础理论，包括：① 在无水醇+乙晴溶液+季铵溶液中，金属铪、锆阳极的电化学溶解机理和醇盐形成机制，电解条件对槽电压、电流效率和副反应的影响；②铪、锆醇盐与杂质金属相应的醇盐的多组分体系气-液相平衡规律；③建立高纯铪、锆醇盐的饱和蒸汽压方程及揭示其热分解特性。通过本项目研究，旨在为电化学合成与精馏纯化生产电子材料用高纯铪、锆醇盐产品提供技术原型，也为电子材料用MO源的选择提供理论依据.

本项目以铪、锆为原材料，醇为溶剂，季铵盐为支持电解质，用电化学方法合成粗的铪、锆醇盐，再经常压蒸馏、减压蒸馏得到高纯铪、锆醇盐产品，研究工作主要从它们的电化学合成机理探究、工艺探究和产品表征及热性分析三个方面开展。. 运用线性极化、循环伏安法、计时电流、交流阻抗等电化学测量方法，加上SEM形貌测试和ICP测量技术，研究了铪在含有Et4NBr的无水乙醇、正丁醇、叔丁醇和异丙醇中的电化学溶解行为，锆在含有Bun4NBr和Et4NCl的无水异丙醇、正丁醇体系中的电化学溶解行为和铂在Et4NBr为支持电解质的乙醇中的阴极析氢行为。（1）电化学测量说明铪、锆表面发生点蚀，SEM形貌图辅以证明，击穿之前电极表面都有自发形成的钝化膜，温度和溴离子浓度的升高对点蚀有明显的促进作用。（2）铂在Et4NBr的乙醇体系中的线性极化测量表明析氢主要由两个过程控制，先是复合脱附过程，再是电化学脱附过程。. 电化学合成乙醇铪的最佳条件为：Et4NBr 0.04 mol•L-1, 电解液温度78℃，极距2cm和电流密度100 A•m-2，电流效率高于93%；电化学方法合成乙醇锆和正丁醇锆的电流效率大于100%。. 通过电解所获产物通过真空蒸馏多种铪、锆醇盐产物，其纯度大于99.99%；通过TG/DTG分析，得到的乙醇铪、异丙醇铪的蒸汽压-温度曲线分别为lnp=24.1-9510.3/T和 lnp=31.157−13130.57/T。