Reduction of UV-Induced Damage Using a Controllable Electron Temperature Plasma Source

Ultraviolet (UV) light emitted from plasma can affect the threshold voltage and subthreshold swing of transistors, ultimately degrading their electrical performance. Lowering the electron temperature in the plasma is an effective approach to suppress UV emission, especially in the vacuum ultraviolet (VUV) range. In this study, the UV emission characteristics of an ultra-low electron temperature (ULET) plasma are examined. The ULET plasma is generated using an inductively coupled plasma (ICP) source equipped with a DC-biased grid to control the electron temperature. As the electron temperature decreases from 2.7 eV to 0.3 eV in an argon plasma, a significant reduction in UV emission intensity (at 309.9 nm) is observed, while the electron density remains stable. This suggests that at lower electron temperatures, the number of high-energy electrons capable of initiating excitation reactions is reduced, thereby decreasing UV emission and suppressing etch reactions. These low UV emission characteristics help to minimize UV-induced damage. When photoresist (PR) wafers are exposed to plasma, the UV-induced etch rate is significantly reduced as the electron temperature is lowered from 2.2 eV to 0.6 eV. These findings offer a promising approach for the precise fabrication of semiconductor devices, minimizing damage caused by UV radiation.