Tatsuo Enami

Billion-level durable ArF excimer laser with highly stable energy

We have succeeded in the development of the ArF excimer laser with high performance and durability, by researching and developing of the spectral measurement and gas control technologies, laser chamber with radio frequency preionizer, the high repetition rate solid state pulse power module and the optimized highly durable optical module. As regards spectral measurement technologies, the true instrumental function of a monitor etalon have been measured by our developed 193nm coherent light source. Spectrum of ArF laser could be obtained precisely by deconvolution performed using the covolved spectrum of the ArF laser and the measured instrumental function of the monitor etalon. As for gas control technologies, the influence of impurities given to the ArF laser performance was bigger about 5-20 times compared with the KrF one. And we have paid attention that low concentration Xe gas has effect to the triple output energy. The durability test of 2 billion pulses has been done for the first time in the world. The developed ArF laser kept the integrated energy stability less than +/- 0.6 percent and spectral band-width of FWHM less than 0.8 pm. The result showed, developed laser has an enough performance for lithography even after the pulse number exceeds 2 billion pulses.

High-spectral-purity and high-durability kHz KrF excimer laser with advanced rf preionization discharge

We present the performance and durability of the newest model of the KrF excimer laser for microlithography KLES-G10K. The laser achieves 10 W of output power with 0.7 pm bandwidth at 1000 Hz with newly developed solid state pulsed power module and the high precise narrowing module. The durability of laser tube achieves 5 billion pulses with the new radio frequency preionization scheme, which reduces consumption of fluorine gas and maintenance of laser tube drastically.

Performance Improvement of a Discharge-Pumped ArF Excimer Laser by Xenon Gas Addition

The effect of xenon (Xe) gas addition to a discharge-pumped ArF excimer laser was examined. When the partial pressure of the Xe gas was changed over a wide range, the output energy of the ArF excimer laser was found to become maximum at the Xe partial pressure of 20 mTorr and to be about three times higher than that without Xe addition. It was shown that Xe gas addition was effective in increasing the initial electron density which was produced in the preionization process, and that the increase of the initial electron density then produced a tendency to make the main discharge in the laser uniform in the direction of the optical axis.

Ultra line-narrowed ArF excimer laser G42A for sub-90-nm lithography generation

193-nm lithography is going to move from pre-production phase to mass production phase and its target node become narrowing from 90 nm to 65 nm. In these situations, the laser manufacture needs to provide the high durable ArF excimer laser, which has superior spectrum performance. Gigaphoton has already introduced 4 kHz ArF laser (model G41A) to 193-nm lithography market, which produce 20 W and spectrum bandwidth of 0.35 pm (FWHM). G41A has showed high reliability and long lifetime over 5 billion pulses. In this paper, we report on the 4 kHz ArF excimer laser for mass production, model G42A, which has 20 W, spectral bandwidth less than 0.3 pm (FWHM) and a spectral purity less than 0.75 pm (E95).

Ultranarrow-bandwidth 4-kHz ArF excimer laser for 193-nm lithography

We have developed a 4-kHz ArF excimer laser with ultra-narrow bandwidth, which is applicable to high-NA scanners for sub-0.13-micrometers microlithography. In this paper, we describe a 4-kHz ArF excimer laser for mass production: the model G40A, which has an output power of 20 W and energy dose stability of less than +/- 0.3% (20-ms window) at 4 kHz. This dose stability is comparable to the performance of an existing 2-kHz ArF excimer laser, the model G20A. The new laser also has the following specifications: a long pulse duration of over 40 ns, spectral bandwidth of less than 0.35 pm (FWHM), and spectral purity of less than 1.0 pm (95%). These characteristics are better than those of the G20A. A lifetime test of over 7 billion pulses has been conducted at 4-kHz operation. The new laser has maintained an energy dose stability of less than +/- 0.3% (20-ms windows) and demonstrated performance suitable for mass production even after over 7 billion pulses.

Output stabilization technology with chemical impurity control on ArF excimer laser

Based on accurate gas analysis technology it has been found that both gas purity and gas control are key factors in optimizing the performance of ArF excimer lasers. The study of the behavior of gas impurities inside the laser chamber showed that impurities built up not only during laser operation but also during rest periods. In-situ gas analysis and controlled impurity gas addition clarified that hydrogen fluoride and oxygen impurities, are the main causes for the decrease of laser output energy. Based on our experiments, a modified gas composition was chosen for the ArF laser that significantly improved its output characteristics.

Development of a 2 kHz F_2 Laser for 157 nm Lithography

We have developed a 2 kHz repetition rate discharge-pumped molecular fluorine laser oscillating at 157 nm. It has achieved an average power of 22 W at the repetition rate of 2 kHz with a newly developed solid-state pulse power module which has a maximum input energy of 6 J/pulse. The multi-kilohertz F2 laser is a key device for 157 nm lithography aimed at the design rule of below 0.10 microns.

Extending green technology innovations to enable greener fabs

Semiconductor manufacturing industry has growing concerns over future environmental impacts as fabs expand and new generations of equipment become more powerful. Especially rare gases supply and price are one of prime concerns for operation of high volume manufacturing (HVM) fabs. Over the past year it has come to our attention that Helium and Neon gas supplies could be unstable and become a threat to HVM fabs. To address these concerns, Gigaphoton has implemented various green technologies under its EcoPhoton program. One of the initiatives is GigaTwin deep ultraviolet (DUV) lithography laser design which enables highly efficient and stable operation. Under this design laser systems run with 50% less electric energy and gas consumption compared to conventional laser designs. In 2014 we have developed two technologies to further reduce electric energy and gas efficiency. The electric energy reduction technology is called eGRYCOS (enhanced Gigaphoton Recycled Chamber Operation System), and it reduces electric energy by 15% without compromising any of laser performances. eGRYCOS system has a sophisticated gas flow design so that we can reduce cross-flow-fan rotation speed. The gas reduction technology is called eTGM (enhanced Total gas Manager) and it improves gas management system optimizing the gas injection and exhaust amount based on laser performances, resulting in 50% gas savings. The next steps in our roadmap technologies are indicated and we call for potential partners to work with us based on OPEN INNOVATION concept to successfully develop faster and better solutions in all possible areas where green innovation may exist.

Extremely high-NA high-throughput-scanner-compatible 4-kHz KrF excimer laser for DUV lithography

KrF excimer laser lithography has applications for the less-than-130-nm-design rule by improving the exposure technology, i.e., super-resolution technology. We therefore developed a 4-kHz KrF excimer laser which corresponds to the next generations high throughput and high number of aperture (NA) scanner requirements, and achieved low cost of operation (CoO) for this light source for mass production uses. We estimated the basic performance requirements of our device, and developed the necessary high repetition rate operation technology that corresponds to a high throughput scanner, and achieved 4-kHz/30-W laser output. We also developed pulse stretching technology for ultra line narrowing, which can accommodate the high NA lens, and achieved more than 30 ns pulse width (Tis). We can thus expect less than 0.45-pm spectral bandwidth (FWHM). Moreover, the relation of the repetition rate operation and main module life was evaluated, and the optimal repetition frequency, which considers CoO, was adopted.

Development of kHz F/sub 2/ laser for 157 nm lithography

We have been developing a high repetition rate discharge-pumped molecular fluorine laser for 157 nm microlithography. We have developed a high repetition rate solid state pulsed power module (SSPPM) up to 800 Hz. This laser adopts a stable resonator composed of a MgF/sub 2/ high reflection plane mirror and a MgF/sub 2/ output coupler, which show high transmittance and durability for VUV light. To avoid attenuation of the 157 nm radiation due to the absorption of O/sub 2/, all the optical path including optics and detectors are continually flushed by pure nitrogen at least below 100 ppm O/sub 2/ concentration.