Tiznado Hugo, Zaera Francisco
Department of Chemistry, University of California, Riverside, California 92521, USA.
J Phys Chem B. 2006 Jul 13;110(27):13491-8. doi: 10.1021/jp062019f.
The surface chemistry of atomic layer depositions (ALD) of titanium nitride films using alternate doses of TiCl4 and NH3 was characterized by using X-ray photoelectron spectroscopy. The nature of the species deposited by each half-reaction was explored first. Evidence was obtained for the partial loss of chlorine atoms and the reduction of the metal during the adsorption of the TiCl4. Subsequent ammonia treatment removes most of the remaining chlorine and leads to the formation of a nitride. Both half-reactions were proven self-limited, stopping after the deposition of submonolayer quantities of the materials. Repeated ALD cycles were shown to lead to the buildup of thick films. However, those films display a Ti3N4 layer on top of the expected TiN. The data suggest that the reduction of the Ti4+ species may therefore occur during the TiCl4, not NH3, dosing step. The incorporation of impurities in the films was also investigated. Chlorine is only deposited on the surface, and in negligible quantities. This Cl appears to originate from readsorption of the HCl byproduct, and could be removed by light sputtering, heating, or further ammonia treatment. Oxygen incorporation, on the other hand, was unavoidable and was determined to possibly come from diffusion from the underlying substrate.
利用交替剂量的TiCl₄和NH₃进行氮化钛薄膜原子层沉积（ALD）的表面化学性质，通过X射线光电子能谱进行了表征。首先探究了每个半反应所沉积物种的性质。在TiCl₄吸附过程中，获得了氯原子部分损失和金属还原的证据。随后的氨处理去除了大部分剩余的氯，并导致氮化物的形成。两个半反应均被证明是自限性的，在亚单层量的材料沉积后停止。多次ALD循环显示会导致厚膜的形成。然而，这些薄膜在预期的TiN之上显示出一层Ti₃N₄层。数据表明，Ti⁴⁺物种的还原可能因此发生在TiCl₄剂量步骤期间，而不是NH₃剂量步骤。还研究了薄膜中杂质的掺入情况。氯仅沉积在表面，且数量可忽略不计。这种Cl似乎源于HCl副产物的再吸附，可通过轻度溅射、加热或进一步的氨处理去除。另一方面，氧的掺入是不可避免的，并且确定可能来自下层衬底的扩散。
