Generation of a Large Diameter and High Density Processing Plasma

为了满足下一代超大规模集成电路（ULSI）工艺的要求，利用低杂波频率范围内的波传播，开发了一种新概念的大直径、高密度等离子体源。首先，通过数值模拟分析了等离子体中的波传播和功率沉积特性。据预测，功率沉积的径向位置可以通过改变纵向波数或外磁场强度来控制。基于这一原理，设计、制造并测试了一种新型光源。等离子体密度的径向轮廓的可控性进行了验证，通过朗缪尔探针测量。用静电探针测量径向波数，证明了低杂波的传播。通过优化粉末沉积的径向轮廓，在230 mm的直径上获得了 * 5%的最佳均匀性。该等离子体源的绝对等离子体密度约为螺旋波等离子体源的一半，但其均匀性要好得多.另一方面，还发展了新的等离子体诊断方法，一种是用于测量F原子的真空紫外激光吸收技术，另一种是用于测量聚合物（如C_xF_y）的电子附着质谱技术.这些方法在目前用于ULSI中SiO_2层刻蚀的各种氟碳等离子体中进行了测试，并与我们开发的用于表面化学分析诊断的FT-IR相位调制光谱椭圆偏振仪（PMSE）一起进行了测试。计划使用这些诊断工具测试我们的新的低杂波等离子体源在SiO_2蚀刻中的实际使用。

In order to meet requirements for the ULSI processing in the next generation, a new concept plasma source of large diameter and high density has been developed utilizing the wave propagation in the lower hybrid frequency range. First, the characteristics of wave propagation and power deposition in a plasma has been analyzed by a numerical simulation. It has been predicted that the radial position of the power deposition can be controlled by changing the longitudinal wave number or the external magnetic field strength. Based on this principle, a new source was designed, constructed and tested. The controllability of the radial profile of the plasma density was verified by a Langmuir probe measurement. The propagation of the lower hybrid waves was also proved from a measurement of the radial wave number measured by an electrostatic probe. The best uniformity of * 5% was attained over the diameter of 230 mm by optimizing the radial profile of the power deposition. The absolute plasma density in this plasma source is about a half of the typical value in a helicon wave plasma source, but the uniformity is much better.On the other hand, new plasma diagnostic methods have also been developed ; one is the VUV laser absorption technique for the measurement of F atoms and the other is the electron attachment mass spectroscopic technique for the measurement of polymerized species such as C_xF_y. These method were tested in various fluorocarbon plasmas currently used in the etching of SiO_2 layer in ULSIs together with our developed FT-IR phase modulated spectroscopic ellipsometry (PMSE) for the diagnostics of the surface chemical analysis. It is planned to test our new lower hybrid plasma source using these diagnostic tools for practical usage in the SiO_2 etching.