A new theoretical model for ozone generation from air is proposed. This model considers the dependency of the ozone dissociation rate by electron impact on the electric field strength, in addition to ozone decomposition processes through the reactions with nitrogen oxides. Assuming a stationary and uniform discharge in time and space, ozone concentrations obtained experimentally under various discharge gap widths and gas pressures are in good agreement with the analytical results. It is concluded that the discharge condition of a narrow gap and accordingly an optimized high gas pressure is one of the most effective means of efficient ozone generation for an air-fed ozone generator.

Experimental and theoretical investigations have been carried out on the ozone generation characteristics of oxygen-fed ozone generators with various discharge gap lengths. In this paper, a new theoretical model considering the dependence of ozone dissociation rate by electron impact on the electric field strength is suggested. Assuming a stationary and uniform discharge in time and space, ozone concentrations obtained experimentally under various discharge power densities and gas pressures are well explained by this model. It is concluded that the operation under a high electric field has a potential advantage in producing high-concentration ozone efficiently because of the reduction in the population density of low-energy electrons which decompose generated ozone.

A photoresist removal method for liquid crystal display manufacturing, using highly concentrated ozone gas and water vapor, has been developed. This method overcomes limitations of conventional ozone processing for resist removal, and obtains a resist removal rate over 1 m/min at substrate temperatures lower than 100°C. In our experiment, ozone gas was bubbled into water, and water vapor concentration in the gas phase was controlled by the water temperature (T w ). The influence of treatment parameters, such as substrate temperature (T s ), water vapor concentration, and residence time ͑͒, on the removal rate has been experimentally examined. The treatments were performed at T s ϭ 25-83°C, T w ϭ 27-92.5°C, ϭ 0.5-2 min, ozone concentration ͓O 3 ͔ 0 ϭ 4.2-10.7 vol % ͑90-230 g/m 3 ͒, gas flow rate 1-12.5 slm, and total pressure 100 kPa. The observed removal rate was 1.4 m/min for a sample with a dry etching treatment at T s ϭ 83°C, T w ϭ 90°C, and ͓O 3 ͔ ϭ 10.7 vol %. It was also shown that the difference between the water and the substrate temperatures, T w Ϫ T s , was a critical parameter for determining the removal rate. The removal rate in this process is more than ten times greater than that of the conventional ozone processing, such as ozone gas ashing and ozonized water treatment. A higher removal rate was realized by optimizing the amount of condensed water with respect to a resist oxidation rate and the diffusion rate of ozone into the resist in the water.Surface cleaning and resist stripping processes in semiconductor and liquid crystal display ͑LCD͒ manufacturing use a large amount of chemicals such as sulfuric acid, hydrogen peroxide, and an amine-based organic solvent. An alternative cleaning process without these chemicals could reduce the cost of chemicals and the amount of water for rinsing the substrate after the chemical treatment. A toxic chemicals-free process also has the benefit of lower environmental impact in the recent trend for stricter regulations for environmental protection.Photoresist plays an important role for constructing electric devices precisely, and must be completely removed after an etching and/or ion implantation process. Although oxygen plasma ashing is widely used for removing a hard-baked and/or an ion-implanted resist, several problems occur, such as a dielectric breakdown by charged particles, 1 or nonuniformity of the treatment for 300 mm wafers. A mixture of an amine-based solvent is also used for resist stripping, especially in LCD factories. This method features higher performance with over 1 m/min and a lower process temperature of about 80°C. However, the removal rate is strongly affected by a baking process, and the surface tends to generate thin film residue, which is difficult to rinse off. 2 Ozone is one of the most powerful oxidants, and it has the potential to realize an ecofriendly and economical process for the resist and/or organic residue removal. A resist removal process using ozone gas had already been investigated. In the ozone gas ashing, it is require...

A method of removing the photoresist using ozone gas with acetic acid vapor has been developed. Glass substrates ͑size 100 ϫ 100 mm 2 ͒ coated with I-line resist were treated under the conditions of substrate temperature, (T S ) 27-50°C; acetic acid vapor, 2-18 vol %; ozone, 0-9.3 vol % ͑0-200 g/m 3 ͒; total gas flow rate, 2 L/min; and gas pressure, 100 kPa. A previous ozone treatment with oversaturated water vapor or sprayed water overcame the limitation of ozone diffusion into the resist by the control of the water film on the resist. In this study, pure acetic acid vapor has been first applied for the resist removal by ozone in order to improve the oxidation rate of the resist, because acetic acid is an inactive solvent in the ozonization, and the solubility of ozone is much higher than water. It was observed that the resist removal rate increased with acetic acid and ozone concentration, and reached at 6 m/min at T S ϭ 50°C, which was about six times greater than that of the previous ozone treatment. Metal corrosion of molybdenum and aluminum electrodes was found negligible during the ozone treatment with acetic acid vapor. The mechanism of resist removal without the metal corrosion by ozone with acetic acid vapor is also discussed, based on the solubility of ozone in acetic acid and the corrosion current in ozonized solutions.

This study is devoted to an investigation of the energy consumption and byproduct generation of the nonthermal plasma-chemical NO-reduction process. Nitrogen gas with a 200 ppm NO impurity has been processed at a pressure of 1.3 atm in a silent discharge reactor with a gap spacing of 50 µm. Detailed measurements of NO, NO 2 and N 2 O concentrations at the reactor outlet were carried out and analysed by means of the created model. On the basis of the proposed three-collision reaction mechanism of N 2 O generation the byproduct-suppression effect has been predicted and experimentally confirmed. An extremely low energy consumption (less than 150 eV per molecule) for NO reduction by the discharge nonthermal plasma has been attained.