Development of generation method of microwave plasmas with an annular slot antenna for large diameter wafer etching

提出了一种新的无磁线圈大直径均匀微波等离子体生成方法。利用环形槽天线和两个环形永磁体，在等离子体约束下，在腔室的圆周上通过电子回旋共振产生高密度等离子体，并向中心区域扩散。我们可以总结如下：(1)在氩气和SF_6气体中成功产生了直径为30cm的均匀微波等离子体，电子密度约为3x10^<10>cm^<-3>。在直径30cm范围内，电子密度均匀性在5%以内，而在电子密度达到最佳均匀性的距离处，蚀刻率在2.5%以内。结果表明，该等离子体源可以成功地用于实际的蚀刻。(2)多晶硅图案的蚀刻曲线表明，多晶硅的蚀刻主要是由自由基驱动的。(3)当施加在衬底上的偏置电压向负方向移动时，在保持均匀性的情况下，刻蚀速率提高了约3倍。在-150V的偏置电压下，蚀刻速率达到400nm/min左右，这似乎可用于半导体器件的制造工艺。

A new generation method for a large diameter and uniform microwave plasma is proposed without magnetic coils. An annular slot antenna and two ring-shaped permanent magnets are used for the generation of high density plasma by electron cyclotron resonance in the circumference of a chamber with the plasma confinement and diffusing to the central region. We can summarize them as follows ;(1) A uniform microwave plasma of 30cm in diameter was success-fully produced in both Ar and SF_6 gases, and the electron density of about 3x10^<10>cm^<-3> was obtained. The uniformity of electron density within 5% over 30cm diameter was obtained, while that of etch rate within 2.5% was observed at the distance where electron density reach the best uniformity. It was found that this plasma source was successfully useful for a practical etching.(2) Results from etching profile of poly-Si pattern suggested that the etching was driven primarily by radicals.(3) As the bias voltage applied to the substrate shifted to the negative direction, the etching rates increased up to about 3 times with the keeping uniformity. The etching rates at a bias voltage of -150V arrived to about 400nm/min which seems to be available for a fabrication process of semiconductor devices.