Control of electric charge at the interface in the RTO and low temperature oxidation of SOI

在硅的快速热氧化（RTO）和低温热氧化过程中，本征应力的不完全松弛导致大量间隙原子的发射。因此，氧化膜的某些性质和界面状态随时间的变化而变化，这使得用通常的线性-抛物线模型来解释氧化行为变得困难。此外，在SOI中，由于埋藏氧化物的存在，导致复杂的应力状态，难以获得高质量的氧化层。在此背景下，我们搭建了适合热氧化过程动态分析的实验装置，建立了研究氧化机理和控制氧化层性质的实验方法。因此，我们在硅的低温热氧化方面获得了许多有趣的基础数据和新的知识和信息。利用原位椭偏仪测量的氧化曲线对氧化参数进行了分析，并通过实验验证了高温热氧化与低温热氧化在氧化机理上的差异。结果表明，硅原子的发射率决定了氧化速率。提出了间隙原子发射的应力相关模型，并进行了实验验证。氧化速率在不同温度和氧化种类下的取向依赖性揭示了本征应力在氧化过程中的作用。在氧化气体中加入适量的NF3可以降低氧化膜的残余应力，改善C-V特性。通过x射线衍射技术，我们发现了不同氧化温度、物质和晶圆取向的不同氧化物结构。

In the rapid thermal oxidation (RTO) and in the low temperature thermal oxidation of silicon, the incomplete relaxation of intrinsic stress leads to the emission of a lot of interstitial atoms. Consequently, some properties of oxide films and the interface states vary from time to time, which causes it difficult to explain the oxidation behavior with the usual linear-parabolic model. Moreover, in case of the SOI,the complex stress states due to the existence of buried oxide makes it difficult to obtain an oxide layr of good quality. From such a background we constructed the experimental apparatus which was suited for the dynamic analyzes of the thermal oxidation process and established an experimental methodology to study the oxidation mechanism and to control the properties of oxide layr. As a consequence, we obtained many interesting basic data and new knowledge and information in the low temperature thermal oxidation of silicon as follows :1.The oxidation parameters were analyzed from the oxidation curves measured ith an in-situ ellipsometer, and the difference in the oxidation mechanism between the high and the low temperature thermal oxidation was experimentally verified.2.It was found that the emission of interstitial silicon atoms ruled the oxidation rate.3.A stress related model for the emission of interstitial atoms was proposed and experimentally confirmed.4.The orientation dependencies of oxidation rates in varied temperature and oxidation species revealed the roles of intrinsic stress in the oxidation process.5.The addition of an appropriate amount of NF3 in the oxidizing gas reduced the residual stress in the oxide films and improved the C-V characteristics.6.By using an X-ray diffraction technique we found different oxide structures depending on the oxidation temperature, species and the wafer orientation.