This paper reports the results of the high-rate dry etching of indium gallium zinc oxide (IGZO) at room temperature using BCl3/O2 plasma. We achieved an etch rate of 250 nm/min. We inferred from the x-ray photoelectron spectroscopy analysis that BOx or BOClx radicals generated from BCl3/O2 plasma cause the etching of the IGZO material. O2 initiates the etching of IGZO, and Ar removes nonvolatile byproducts from the surface during the etching process. Consequently, a smooth etched surface results when these gases are added to the etch gas.

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The change of –OH and –CH3 component ratios in Fourier transform-infrared analysis of low-k materials during photoresist (PR) ashing processes were compared to assess the differences in the damages to low-k materials in a reactive ion etch (RIE) chamber and a magnetized-inductively coupled plasma (M-ICP) chamber. In M-ICP, the PR ashing rate was 28.1% higher than that of RIE, but the low-k material damage in M-ICP decreased when typical ashing conditions were used in each machine. The dependences of low-k material damage and PR ashing rate on the pressure, source power, and bias power in the M-ICP chamber were studied. We measured the ion energy distributions using an ion energy analyzer from which the flux could be also obtained. We found that the PR ashing rate increased as the ion flux increased, while the low-k material damage also increased as the ion flux and the incident ion energy increased. However, as the pressure decreased, the ion flux increased dramatically and the ion energy decreased. As a result, the PR ashing rate could be high and the low-k material damage low.

The extreme ultraviolet (EUV) mask using reflective optics has a structure totally different from that of the conventional mask. This study investigated the dry etching characteristics of the EUV mask layer in which TaN and Ru were used as the absorber and buffer layer, respectively. The TaN absorber etching requires high etch selectivity of TaN over Ru to achieve the high EUV reflectivity. In this work, the TaN etching rate was investigated with various halogen gases in the capacitively coupled plasma type etching system. The etching rates with the fluorinated gases were higher than that with the chlorinated gas. Ru could not be etched without oxygen in all of the considered etch gases. The etching rate of TaN and its etch selectivity to Ru were increased with the increase of RF power, pressure and SF6 gas flow ratio. When the real EUV mask specimens were 100% over etched under the highest selectivity etching condition, the Ru buffer layer still remained, which was confirmed by x-ray photoelectron spectroscopy analysis. The surface roughness of etched reflective mirror was very small, and the EUV reflectivity was equivalent to that of the reference mirror (EUV reflectivity is over 60%) which was confirmed by measuring the intensity and the diffracted pattern of 13.5 nm EUV obtained using x-ray charge coupled device camera. The Ru buffer layer could be removed by the O2 plasma used in the posterior photo resist ashing process without affecting the EUV reflectivity.

In this study, we investigated the etching parameter dependence of the reactive ion etch (RIE) lag of nanometer silicon trenches using HBr/O2 plasma in an inductively coupled plasma etcher. As the O2 flow rate, pressure, and source power decreased and the substrate temperature increased, the RIE lag improved. The RIE lag dependence on the O2 flow rate correlated with surface oxidation which gives rise to charging up of positive ions and reduction in silicon etching rate. Increased oxidation, rate resulted in severer RIE lag. These were verified by actinometrical optical emission spectroscopy measurements. On the other hand, the decrease in substrate temperature worsened the RIE lag owing to the remaining etching by-products deposited on the substrate. When the pressure and source power decreased, the RIE lag improved owing to the increase in average ion energy. As the bias power increased, the RIE lag improved, but for excessively high power, the RIE lag deteriorated, as the positive ions could not reach the bottom of the trench due to charging. However, the RIE lag improved at high bias powers when the RF power was pulse-modulated. There was almost no frequency dependence of the RIE lag, but the RIE lag improved when the duty ratio was reduced. The improvement of the RIE lag in the pulsed plasma is thought to be due to the relaxation of the charging up of positive ions by the negative ions generated during the power-off period.