Theoretical studies on the basic processes of Si thermal oxidation.

在本研究项目中，我们利用第一性原理计算、宏观模拟和二次离子质谱学(SIMS)实验对SiO_2和Si/SiO_2界面的原子化过程进行了深入的研究。用第一性原理计算和联立扩散方程研究了Si/SiO_2界面反应对杂质扩散和Si自扩散的影响。(1)研究了B原子在SiO_2中的扩散机制。我们发现，B原子在SiO_2中形成各种稳定和亚稳定的几何构型，具有点缺陷，这取决于它的荷电状态和周围环境。在具有O间隙的SiO_2中，B原子形成了一个非常稳定的B-O络合物，其中B原子被束缚在O间隙上。我们还发现，在O物种的存在下，B原子从硅衬底扩散到SiO_2层中。一旦B-O复合体…此外，B原子通过SiO_2网络扩散，使该B-O单元具有出人意料的2.1-2.3 eV的小激活能，很好地再现了实验。此外，B-O络合物可以看作是B_&lt；Si&gt；-Si-O络合物，因为人们认为B原子取代了SiO_2中的Si原子。因此，SiO的存在有望促进B的扩散。由于有报道称在Si/SiO_2界面附近SiO含量较高，我们的结果表明在Si/SiO_2界面附近将促进B的扩散。这些结果与随后的SIMS实验结果密切相关，即在Si/SiO_2界面附近观察到了高的Si自扩散系数。(2)考虑了在Si/SiO_2界面产生的SiO分子扩散到SiO_2中以促进两种扩散的效应，模拟了热生长的SiO_2中Si的同时扩散。在此模型的基础上，我们模拟了共注入^&lt；30&gt；Si在^&lt；28&gt；SiO_2中的实验SIMS分布，结果显示在界面附近具有高的扩散系数，该界面被认为是高SiO含量的。实验结果用同步扩散方程模拟，假设SiO的扩散系数增强了Si的扩散系数。结果表明，SiO_2中的Si原子通过在Si/SiO_2界面生成的SiO进行相关扩散。较少

In this research project, we have intensively studied the atomistic process in SiO_2 and at Si/SiO_2 interfaces, by using first principles calculations, macroscopic simulations and secondary ion mass spectroscopy (SIMS) experiments. We have investigated the effect of Si/SiO_2 interface reactions to impurity diffusion and Si self-diffusion in and at Si/SiO_2 interfaces by first principles calculations and by simultaneous diffusion equations. As a result, we have obtained the following remarkable results.(1) We investigated the diffusion mechanisms of boron in SiO_2. We find that a B atom forms various stable and meta-stable geometries in SiO_2 with point defects, depending on its charge state and surrounding environments. In the case of B in SiO_2 with an O interstitial, a B atom forms a very stable B-O complex in which the B atom is bound to the O interstitial. We also found that B atoms diffuse from Si substrates into SiO_2 layers under the existence of O species. Once the B-O complex … More is formed, the B atom diffuses via the SiO_2 network keeping this B-O unit with unexpectedly small activation energies of 2.1-2.3 eV that well reproduce experiments. Moreover, B-O complex can be regarded as the complex of B_<Si>-Si-O complex, since it is believed that B atoms substitute Si atoms in SiO_2. Accordingly, B diffusion are expected to be promoted by the existence of SiO. Since it has been reported that SiO content is high near Si/SiO_2 interfaces, our results imply that B diffusion will be promoted near Si/SiO_2 interfaces. These results are intimately related to the following SIMS experiments that high Si self-diffusivity is observed near Si/SiO_2 interfaces.(2) Simultaneous diffusion of Si in thermally grown SiO_2 is modeled taking into account the effect of SiO molecules generated at the Si/SiO_2 interface and diffusing into SiO_2 to enhance both Si diffusion. Based on the model, we simulated experimental SIMS profiles of co-implanted ^<30>Si in ^<28>SiO_2, which show high diffusivities near the interface that is supposed to have high SiO content. The experimental results were simulated by simultaneous diffusion equations, assuming that the diffusivity of SiO, which enhances the diffusivities of Si. The present result indicates that Si atoms in SiO_2 diffuse correlatively via SiO generated at Si/SiO_2 interfaces. Less