Characteristics of magnetized inductively coupled plasma source for flat panel display applications

In this study, to improve the plasma uniformity in addition to the plasma density of an inductively coupled plasma source, both permanent magnets and a Helmholtz type axial electromagnet were installed to a conventional planar inductively coupled plasma source and the effects of various magnet combinations on the polysilicon etch rates and etch uniformities were studied. The application of weak axial electromagnetic field to a planar inductively coupled plasma showed increased plasma densities, therefore, increased polysilicon etch rates compared with those by conventional inductively coupled plasmas. However, the application of the electromagnetic field degraded the etch uniformity. By using both an optimized permanent magnets and the axial electromagnet around the chamber wall, we found the improvement of polysilicon etch uniformity in addition to the increase of polysilicon etch rate due to the combination of the better features of both magnets. Among the permanent magnet configurations used with axial electromagnetic field in this experiment, a permanent magnet configuration with two poles/site showed the polysilicon etch uniformity at approximately 3.0% up to 15 G of axial electromagnetic field. The use of the magnetized inductively coupled plasma also decreased the average ion energy to the wall from 20 to 15 eV, therefore, decreased the possible contamination of the substrate caused by sputtering of the chamber wall.