Control of the photoresist etch uniformity in inductive discharge with magnetic resonance wireless power transfer

As chamber and wafer sizes increase to improve productivity, generating a uniform plasma with a large-area plasma source is a key challenge. To control the uniformity of photoresist (PR) etching, an inductively coupled plasma (ICP) source using magnetic resonance wireless power transfer is developed. An inner-powered antenna (PA) connected to a power generator and an outer resonant antenna (RA) connected to a variable capacitor are installed on the chamber. Three resonance regimes are identified as the self-resonance frequency of the RA is adjusted: non-resonance regime, PA and RA current ratio 1:1 regime, and resonance regime. In each regime, the electron energy probability function is measured and the electron kinetics is investigated. In addition, the radial distribution of ion flux is measured and compared to the PR etching results to control etch uniformity through plasma uniformity adjustment. The residual PR thickness shows the opposite profile to the ion flux profile in each regime. Another way to control the PR etch uniformity in addition to the three regimes is the cyclic regime, which is a continuous change of the resonance regime, the PA and RA current ratio 1:1 regime, and the non-resonance regime. At this cyclic regime, the PR thickness is lower by the non-resonance regime at the center region, and lower by the resonance regime in the edge region. In this cyclic regime, it is possible to add a control knob to control PR etch uniformity by adjusting the ratio of time each condition is sustained within the cycle. These experimental results present perspectives for the controllability of an ICP source using the magnetic resonance wireless power transfer and for improving the uniformity of PR etching.