Generation of a Large Diameter and High Density Processing Plasma

为了满足下一代ULSI加工的要求，利用低混合频率范围内的波传播，开发了一种新的大直径高密度等离子体源概念。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。预测可以通过改变纵波数或外磁场强度来控制功率沉积的径向位置。基于这一原理，设计、构建并测试了一种新的源。通过朗缪尔探针测量验证了等离子体密度径向分布的可控性。用静电探针测量径向波数，证明了低杂波的传播。通过优化功率沉积的径向分布，在230 mm直径范围内均匀度达到* 5%。该等离子体源的绝对等离子体密度约为典型螺旋波等离子体源的一半，但均匀性要好得多。另一方面，新的血浆诊断方法也得到了发展；一种是测量F原子的VUV激光吸收技术，另一种是测量C_xF_y等聚合物质的电子附着质谱技术。这些方法在目前用于ulsi中SiO_2层蚀刻的各种氟碳等离子体中进行了测试，并与我们开发的FT-IR相位调制光谱椭偏仪（PMSE）一起用于表面化学分析的诊断。计划使用这些诊断工具测试我们新的低混合等离子体源，以便在SiO_2蚀刻中实际使用。

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.