Koji Kakizaki

High-repetition-rate (6 kHz) and long-pulse-duration (50 ns) ArF excimer laser for sub-65 nm lithography

Development of high-repetition-rate ArF excimer lasers is vital requirement for achieving high throughput and high energy-dose stability in a scanner system. ArF excimer laser, with increasing light pulse duration, can reduce the peak power without the energy-dose change. Then, the spectral bandwidth ΔλFWHM becomes narrower by increasing the number of light round trips in a cavity, and optical damage is reduced from high-peak power. Laser operation exceeding 4kHz is needed for next-generation technologies that can enable high numerical aperture and development of high-throughput scanners. In the present work, we examined the possibilities of achieving a repetition rate to 6kHz from 4kHz in the ArF laser the authors developed, taking the following innovations. The spatial width of discharge region was reduced by about 30%. The uniform gas flow condition between the electrodes was obtained by improving gas flow guides. As a result, we have obtained an average power of 42W, a standard deviation for pulse-to-...

GT40A: durable 45-W ArF injection-lock laser light source for dry/immersion lithography

Last year Gigaphoton introduced a 45-W ArF excimer laser, model GT40A, to semiconductor markets as a light source for 65 nm lithography generation. The GT40A is based on injection lock technology with G-electrode, magnetic bearing and high resolution technologies for high reliability and long lifetime. As a result, GT40A showed the stable performance during the chamber maintenance interval of over 15 billion pulses. In this paper we will report the longterm stability of GT40A.

Development of high coherence high power 193nm laser

We have been developing a hybrid 193 nm ArF laser system that consists of a solid state seeding laser and an ArF excimer laser amplifier for power-boosting. The solid state laser consists of an Yb-fiber-solid hybrid laser system and an Er-fiber laser system as fundamentals, and one LBO and three CLBO crystals for frequency conversion. In an ArF power amplifier, the seed laser passes through the ArF gain media three times, and an average power of 110 W is obtained. As a demonstration of the potential applications of the laser, an interference exposure test is performed.

Reduction of Acoustic Waves Induced by Discharge in High Repetition Rate ArF Excimer Laser Cavity to Obtain Narrow-Bandwidth Laser Light

The suppression of acoustic waves caused by discharge in a laser chamber, which is a technical challenge we face in the development of next-generation 6 kHz ArF lasers for lithography, is studied. In this paper, we describe, firstly, that the acoustic waves produced in an ArF laser medium were observed by a Schlieren method and analyzed by computer simulation. The simulation results successfully explained the gas density fluctuation pattern obtained in Schlieren photographs. On the basis of these results, the inner configuration of a laser chamber for 6-kHz-repetition-rate operation was newly designed. The new laser chamber provided narrow-bandwidth laser light up to a repetition rate of 6 kHz as a result of a marked suppression of acoustic waves.

5 kHz high repetition rate and high power XeCl excimer laser

A 5 kHz high repetition rate excimer laser has been developed. An average laser power of 0.56 kW at 5 kHz operation, which remains stable for 1 s, is obtained. This duty time is limited only by overheating of the switching thyratrons. The 5 kHz operation is attained by some improvements to the gas conditions, the UV‐preionization scheme, and the gas flow speed in the discharge region. The gas is circulated at an effective flow velocity of 137 m/s by a newly developed two‐stage axial blower. The gas conditions are optimized experimentally to achieve 5 kHz operation. To obtain uniform preionization, the locations of pin electrodes for the preionization are determined on the basis of numerical results.

193nm high power lasers for the wide bandgap material processing

Recently infrared laser has faced resolution limit of finer micromachining requirement on especially semiconductor packaging like Fan-Out Wafer Level Package (FO-WLP) and Through Glass Via hole (TGV) which are hard to process with less defect. In this study, we investigated ablation rate with deep ultra violet excimer laser to explore its possibilities of micromachining on organic and glass interposers. These results were observed with a laser microscopy and Scanning Electron Microscope (SEM). As the ablation rates of both materials were quite affordable value, excimer laser is expected to be put in practical use for mass production.