Edge Plasma Control Through the Modification of Electrode Protective Materials in a DC Power Bias Environment

As a pitch continues to shrink, dry etching process has become necessary to obtain high aspect ratio in semiconductor industry. However, it is still challenged to form a suitable plasma density and sheath at the edge due to lack of proper rings of a chuck. Rings at the edge of chuck play an important role of controlling a bias using DC power in RF system to make rectangular waveform. A quartz has been widely used as a ring, but it is too weak to protect the edge of plasma, resulting in low yield and unstable plasma. In this work, we achieved the uniform plasma by replacing the quartz with silicon and altering its shape based on an impedance ratio of 1.2. We monitored and evaluated variations in the impedance ratio according to changes in the ring’s thickness and shape. Furthermore, concomitant plasma properties were confirmed through numerical simulation. As a result, the impedance ratio between the center and edge in the plasma varied from 1 to 1.4. It was also verified that ions in the plasma had the enhanced unidirectionality flux as a main factor to fabricate high aspect ratio. This research will contribute to extending the lifespan and improving the yield of semiconductor manufacturing processes in new bias power technology of Rectangular waveform.