ZrO2在Si(100)-2×1表面原子层淀积反应机理的密度泛函理论研究

用密度泛函方法研究了ZrO₂在羟基预处理的Si(100)-2×1表面原子层淀积(ALD)初始反应过程的反应机理, ZrO₂的ALD过程包括两个前体反应物ZrCl₄和H₂O交替的半反应. 两个半反应都经历一个相似的吸附中间体反应路径. 比较单羟基Si表面反应的反应焓变, 可以发现双羟基Si表面反应, 由于相邻羟基的存在, 对ZrCl₄的半反应影响较大, 尤其是化学吸附能增加明显. 而对于H₂O的半反应, 单、双羟基Si表面反应的能量变化不是很明显. 使用内禀反应坐标(IRC)方法, 验证了两个半反应存在相似的过渡态结构和反应机理. 另外, 发现随着温度的升高, 吸附络合物的稳定性降低, 其向反应物方向的解吸附变得容易, 而向产物方向的解离难度增加.

Density Functional Theory Study on Surface Reaction Mechanism of Atomic Layer Deposition of ZrO2 on Si(100)-2 × 1

Density functional theory was employed to investigate atomic layer deposition (ALD) mechanism of zirconia on Si(100)-2×1 surface with single and double hydroxyl groups. The ZrO₂ ALD process using ZrCl₄ and H₂O as precursors involves two alternate deposition half-reactions: ZrCl₄ and H₂O half-reactions. Both the half-reactions proceeded through an analogous trapping-mediated mechanism. Compared to the singly hydroxylated Si surfaces, the neighboring hydroxyl of the doubly hydroxylated Si surfaces has a major effect on ZrCl₄ half-reaction, especially the formation of ZrCl₄ intermediate complex, and a minor effect on H₂O half-reaction. Both ZrCl₄ and H₂O half-reactions were found to follow a similar reaction pathway with IRC method. In addition, the intermediate stability was lowered as the surface temperature was raised. However, increasing temperature also enlarged the dissociation free energy barrier, which in turn resulted in increased desorption of adsorbed precursors.