Development of room-temperature oxidation method of Si due to pulsed hyperthermal atomic oxygen beam

本项目研究了利用脉冲高温原子氧束对硅片进行室温氧化的新方法。一个女人。利用激光诱导氧气爆轰现象产生的脉冲高温（5eV）原子氧束，在Si（001）表面形成氧化物薄膜。实验结果表明，高温离子束在室温下也能形成厚度小于5 nm的氧化膜。这是可以应用于下一代ULSI的厚度。氧化膜的厚度取决于温度和原子氧通量。氧化膜的生长服从抛物线规律。这通过使用X射线光电子能谱（XPS）的氧化物膜的原位厚度测量来证实，其表明氧化时间与厚度之间的线性关系_2。这一结果清楚地表明，生长机制是由原子氧的扩散速率限制。但测得原子氧在SiO_2膜中的扩散激活能低至0.15eV。在微波氧等离子体的非辉光区测得原子氧在SiO_2膜中的扩散激活能为0.5eV，热氧化过程中氧分子的扩散激活能为1.2eV。SiO_2薄膜的形成可能包括在Si/SiO_2界面处施加高压应力所产生的间隙Si原子的逆扩散。为了降低这样高的界面应力，使用氧与少量氟的预混合气体将是有效的。

This project dealt with the new method for room-temperature oxidation of Si wafers "using pulsed-hyperthermual atomic oxygen beam. A broad-. pulsed-, hyperthemial (5eV) atomic oxygen beam, generated by the laser-induced detonation phenomenon of oxygen gas, was applied to formation of thin oxide films on the Si (001) surface. It was clearly observed that the hypertherma.l beam can form thin oxide film (<5 nm) even at the room temperature. This is the thickness can be applied for the next generation ULSIs. The thickness of the oxide film depends on the temperatute and the atomic oxygen flux. It was also observed that the growth of oxide film obeyed the parabolic law. This was confirmed by the in-situ thickness measurement of the oxide film using X-ray photoelectron spectroscopy (XPS) which indicated the linear relationship between oxidation time versus thickness_2. This result clearly showed that the growth mechanism was rate-limited by the diffusion of atomic oxygen. It is, however, measured that the activation energy of diffusion of atomic oxygen in the SiO_2 film was as low as 0.15eV.The activation energy of diffusion of atomic oxygen in the SiO_2 film measure in the out-of-glow region of microwave- generated oxygen plasma was reported to be 0.5eV, and that of molecular oxygen in the thermal oxidation was 1.2eV.The low activation energy on diffusion of atomic oxygen in the SiO_2 film may include the inverse diffusion of interstitial Si atoms which is generated high compressive stresses applied at the Si/SiO_2 interface. In order to reduce such high interfacial stresses, it would be effective to use the premix gas of oxygen with small amount of fluorine.