Reduction Of Plasma-induced Damage Research Articles

Reduction of plasma-induced damage in n-type GaN by multistep-bias etching in inductively coupled plasma reactive ion etching

Plasma-induced damage was reduced by multistep-bias etching that involved a stepwise decrease of the etching bias power (Pbias) and subsequent annealing. The depth of damage at Pbias = 60 W was determined to be 60 nm from the capacitance–voltage characteristics of Ni/Al2O3/etched-GaN metal-oxide-semiconductor diodes. The damaged layer was removed by subsequent etching at Pbias = 5 W and 2.5 W. The residual and shallow damage induced by the low Pbias was then recovered by subsequent annealing at 400 °C. The multistep-bias etching of inductively coupled plasma reactive ion etching was thus confirmed to be effective for achieving a high etching rate with low damage.

Reduction of plasma-induced damage in SiO2 films during pulse-time-modulated plasma irradiation

Use of a pulse-time-modulated (TM) plasma is an effective way to reduce vacuum ultra-violet (VUV) radiation damage in SiO2 films because such a plasma can reduce the quantity of high-energy electrons while maintaining the electron density during the off time of the TM plasma. To understand the effects of VUV radiation, we measured the VUV-induced current in SiO2 films using a simple on-wafer monitoring technique. We found that the plasma-induced-current in the SiO2 films strongly depended on the VUV photon energy. Under the same conditions, the density of E′ centers in SiO2 films also depended on the photon energy. That is, the plasma-induced currents in the SiO2 films detected by on-wafer monitoring corresponded to the density of E′ centers (dangling bonds) in the films. By using a TM plasma, the plasma-induced current and the E′ center density in SiO2 films can be reduced during the plasma-off time. Consequently, use of a TM plasma can eliminate VUV radiation damage. These results also confirm that our developed on-wafer monitor can predict plasma-induced damage.

Reduction of plasma-induced damage by electron beam excited plasma CVD

The electron beam excited plasma (EBEP-) CVD has succeeded in making nano-crystaline films. On the other hand, the existence of the plasma-induced damage by EBEP-CVD has been confirmed using the hydrogen plasma by measuring the photoluminescence (PL). After plasma exposure, broad band peak appears in the region of 1.0–0.78 eV (1.2–1.6 μm), and intensity of bound exciton peak with energy of 1.093 eV, which is measured and the non-irradiated silicon has been decreased. The same experiment was also performed with RF plasma and the peak appeared not only for EBEP but also for conventional RF plasma. The damage peak tends to disappear over 420°C of the substrate temperature. The damage recovery analysis has been done in relation to the annealing temperature of the substrate after the plasma exposure. Exciton peak has been increased by increasing the temperature especially at 350°C. Furthermore, plasma-induced peak intensity has been decreased at temperature higher than 500°C. Similar peak has been observed in the samples irradiated with high-energy protons. Therefore, positive ions in the plasma are thought to be the source of the damage of the silicon. The origin of the plasma-induced defect in Si is also considered. According to these results, the electric potential of substrate was controlled in order to avoid collision with positive ions in the plasma. When it was set to zero, plasma-induced peaks did not appear.