无羟基Cu（111）上的三甲基铝和氧原子层沉积,ACS Applied Materials & Interfaces

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无羟基Cu（111）上的三甲基铝和氧原子层沉积
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2015-07-23 00:00:00 , DOI: 10.1021/acsami.5b03598
Amir Gharachorlou ₁ , Michael D. Detwiler ₁ , Xiang-Kui Gu ₁ , Lukas Mayr _{2,

3} , Bernhard Klötzer ₂ , Jeffrey Greeley ₁ , Ronald G. Reifenberger _{3,

4} , W. Nicholas Delgass ₁ , Fabio H. Ribeiro ₁ , Dmitry Y. Zemlyanov ₃

Affiliation

使用三甲基铝（TMA）的氧化铝原子层沉积（ALD）在微电子学中具有技术重要性。该方法已经证明在将铜表面保护涂层用于控制光伏器件中的Cu ₂ S膜中Cu的扩散以及液相加氢反应中Cu基纳米颗粒的烧结方面具有很高的潜力。考虑到这一动机，在Cu（111）和Cu ₂ O / Cu（111）表面上研究了TMA与氧气之间的反应。TMA不会吸附在Cu（111）表面上，这一结果与密度泛函理论（DFT）计算相一致，该结果预测TMA在纯Cu（111）上的吸附和分解在热力学上是不利的。另一方面，TMA容易吸附在Cu _2上O / Cu（111）表面在473 K时导致一些表面Cu ¹⁺还原为金属铜（Cu ⁰），并形成铝酸铜，最有可能是CuAlO ₂。该反应受表面氧的量限制。在Cu ₂ O / Cu（111）上进行第一个TMA半循环后，通过扫描隧道显微镜（STM）在表面上观察到了铝酸盐的二维（2D）岛。根据DFT计算，TMA在Cu ₂ O / Cu（111）上完全分解。高分辨率电子能量损失谱（HREELS）用于区分四面体（Al _tet）和八面体（Al _oct）配位的Al ³⁺在表面的adlayers。TMA配料产生的氧化铝膜比配料O ₂含有更多的八面体配位的Al ³⁺（Al _tet / Al _oct HREELS峰面积比≈0.3）（Al _tet / Al _oct HREELS峰面积比≈0.5）。在第一个ALD循环后，TMA在不存在羟基的情况下与Cu ₂ O和氧化铝表面反应，直到第四个ALD循环关闭膜为止。然后，TMA继续与表面Al–O反应，形成化学计量的Al ₂ O ₃。在623 K的O ₂半循环比O ₂更有效地除碳473 K的半个循环或623 K的水半个循环。TMA+ O ₂ ALD的生长速率约为3-4Å/个循环（623 K的O ₂半个循环）。没有观察到在Cu（111）台阶上Al ₂ O ₃优先生长。根据STM，Al ₂ O ₃在Cu（111）平台上均匀生长。

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Trimethylaluminum and Oxygen Atomic Layer Deposition on Hydroxyl-Free Cu(111)

Atomic layer deposition (ALD) of alumina using trimethylaluminum (TMA) has technological importance in microelectronics. This process has demonstrated a high potential in applications of protective coatings on Cu surfaces for control of diffusion of Cu in Cu₂S films in photovoltaic devices and sintering of Cu-based nanoparticles in liquid phase hydrogenation reactions. With this motivation in mind, the reaction between TMA and oxygen was investigated on Cu(111) and Cu₂O/Cu(111) surfaces. TMA did not adsorb on the Cu(111) surface, a result consistent with density functional theory (DFT) calculations predicting that TMA adsorption and decomposition are thermodynamically unfavorable on pure Cu(111). On the other hand, TMA readily adsorbed on the Cu₂O/Cu(111) surface at 473 K resulting in the reduction of some surface Cu¹⁺ to metallic copper (Cu⁰) and the formation of a copper aluminate, most likely CuAlO₂. The reaction is limited by the amount of surface oxygen. After the first TMA half-cycle on Cu₂O/Cu(111), two-dimensional (2D) islands of the aluminate were observed on the surface by scanning tunneling microscopy (STM). According to DFT calculations, TMA decomposed completely on Cu₂O/Cu(111). High-resolution electron energy loss spectroscopy (HREELS) was used to distinguish between tetrahedrally (Al_tet) and octahedrally (Al_oct) coordinated Al³⁺ in surface adlayers. TMA dosing produced an aluminum oxide film, which contained more octahedrally coordinated Al³⁺ (Al_tet/Al_oct HREELS peak area ratio ≈ 0.3) than did dosing O₂ (Al_tet/Al_oct HREELS peak area ratio ≈ 0.5). After the first ALD cycle, TMA reacted with both Cu₂O and aluminum oxide surfaces in the absence of hydroxyl groups until film closure by the fourth ALD cycle. Then, TMA continued to react with surface Al–O, forming stoichiometric Al₂O₃. O₂ half-cycles at 623 K were more effective for carbon removal than O₂ half-cycles at 473 K or water half-cycles at 623 K. The growth rate was approximately 3–4 Å/cycle for TMA+O₂ ALD (O₂ half-cycles at 623 K). No preferential growth of Al₂O₃ on the steps of Cu(111) was observed. According to STM, Al₂O₃ grows homogeneously on Cu(111) terraces.

更新日期：2015-07-23

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