The design of fluoride-based optical devices for deep ultraviolet applications is discussed. Variations in the band-gap energy and band structure with respect to composition are investigated for Li(1−x)KxBa(1−y)MgyF3 perovskites. The band-gap energy, lattice constant, and band structure of perovskitelike fluorides are estimated based on ab initio calculations within the local-density approximation. The lattice-matched double heterostructure with direct band-gap compounds (Li(1−x)KxBa(1−y)MgyF3 on either LiBaF3 or KMgF3 substrates) is promising for fabrication.

Design of wide-gap fluoride heterostructures for deep ultraviolet optical devices

ArF immersion technology is spotlighted as the enabling technology for below 45nm node. Recently, double exposure
technology is also considered for below 32nm node. We have already released an injection lock ArF excimer laser with
ultra-line narrowed and stabilized spectrum performance: GT61A (60W/6kHz/ 10mJ/0.35pm) to ArF immersion market
in Q4 2006. The requirements are: i) higher power ii) lower cost of downtime for higher throughput iii) greater
wavelength stability for improved overlay and iv) increased lifetimes for lower operation costs.
We have developed high power and high energy stability injection lock ArF excimer laser for double patterning: GT62A
(90W/6000Hz/15mJ/0.35pm) based on the technology of GT61A and the reliability of GigaTwin (GT) platform. A high
power operation of 90W is realized by development of high durability optical elements. Durability of the new optics is at
least 3 times as long as that of the conventional optics used in the GT61A. The energy stability is improved more than
1.5 times of performance in the GT61A by optimizing laser operational conditions of the power oscillator. This
improvement is accomplished by extracting potential efficiency of injection lock characteristic. The lifetime of power
oscillator, which is one of the major parts in cost of ownership, is maintained by using higher output of the power supply.

High-power and high-energy stability injection lock laser light source for double exposure or double patterning ArF immersion lithography

Reliable high power 193nm ArF light source is desired for the successive growth of ArF-immersion technology for 45nm node generation. In 2006, Gigaphoton released GT60A, high power injection locked 6kHz/60W/0.5pm (E95) laser system, to meet the demands of semiconductor markets. In this paper, we report key technologies for reliable mass production GT laser systems and GT60A high durability performance test results up to 20 billion pulses.

https://www.gigaphoton.com/wp-content/uploads/pdf/6520-111_GT60A_Manuscript.pdf

Reliable high-power injection locked 6kHz 60W laser for ArF immersion lithography

An ultra-line-narrowed high-power and high-repetition rate F/sub 2/ laser system has been developed for 157-nm microlithography exposure tools with dioptric projection design. The injection locked system (ILS) consists of a low-power seed laser with ultra-narrow spectral linewidth and a high-gain amplifier. More than 25-W output power, a spectral linewidth below 0.2 pm full-width at half-maximum (FWHM) and an energy stability (3-sigma) below 10% have been obtained at a 5-kHz repetition rate and for a delay time range between the two laser stages of about 15 ns. Directly compared with a master oscillator power amplifier system, the ILS had a better performance related to output energy, energy stability, and laser pulse duration.

An ultra-line-narrowed high-power F/sub 2/ laser for dioptric design microlithography exposure tools

The roadmap of semiconductor fabrication predicts that the semiconductor market will demand 65 nm node devices from 2004/2005. Therefore, an Ultra-Line-Narrowed F2 laser for dioptric projection systems is being developed under the ASET project 'The F2 Laser Lithography Development Project.' The target of this project is to achieve a F2 laser spectral bandwidth below 0.2 pm (FWHM) and an average power of 25W at a repetition rate of 5 kHz. Accurate measurements of the laser spectrum and of the laser wavelength stability are therefore very important. We therefore developed a VUV wavemeter with a Br-lamp to measure the absolute F2 laser wavelength. We obtained 157.631 nm for the main F2 laser transition using the Br-lamp reference lines at 157.4840 nm and 157.6385 nm. We have also developed a VUV high-resolution spectrometer to measure spectral profiles, which was calibrated by 157 nm coherent light source (157CLS). The 157CLS is a very narrow line-width, which can be approximated by delta function. The 157CLS had a line-width of 0.008 pm (Full-Width-At-Half- Maximum, FWHM) and a power of 0.1 mW. The instrument function of the high-resolution spectrometer measured by the 157CLS was 0.10 pm (FWHM). As a result, the deconvolved FWHM of the ultra-line narrowed F2 laser is 0.12 pm, the deconvolved spectral purity containing 95% of the total energy (E95) was less than 0.45 pm.

https://www.gigaphoton.com/wp-content/uploads/pdf/4691_195.pdf

Spectral metrologies for ultra-line-narrowed F2 laser

The roadmap of semiconductor fabrication predicts that the semiconductor market will demand 65nm node devices from 2004/2005. Therefore, an Ultra-Line-Narrowed F2 laser for dioptric projection systems is currently being developed under the ASET project of "The F2 Laser Lithography Development Project". The target of this project is to achieve a F2 laser spectral bandwidth below 0.2pm (FWHM) and an average power of 25W at a repetition rate of 5kHz. The energy stability (3-sigma) target is less than 10%.An Oscillator-Amplifier arrangement at 2kHz was developed as a first step of an Ultra-Line-Narrowed F2 laser system. With this laser system, we did the basic study of the synchronization technology for line narrowing operation using two system arrangements: MOPA (Master Oscillator/Power Amplifier) and Injection Locking. Based on this experience we have developed the 5kHz system. With the 5kHz Line-Narrowed Injection Locking system, we have achieved a spectral bandwidth of 5mJ and an energy pulse to pulse stability of 10%. The feasibility of a 5kHz Ultra-Line-Narrowed F2 Laser for Dioptric Projection Systems has been demonstrated.

Development of a 5 kHz Ultra-Line-Narrowed F2 Laser for Dioptric Projection Systems.

An ultra-line-narrowed, ultra-high-repetition-rate, high-power injection locked F2 laser system for 157 nm exposure tools has been developed. The laser system consists of a low-power oscillator laser having an ultra-narrow spectral bandwidth and a high-gain amplifier with a resonator. The injection locked system achieved a spectral bandwidth 25 W and an energy stability (3-sigma) <10% at a 5 kHz repetition rate, parameters that satisfy requirements of high NA refractive type exposure tools. The jitter reduction between the oscillator laser and the amplifier laser is essential for stable synchronization of two-stage (injection locked and master oscillator power amplifier) laser systems. We solved this problem by a specially developed jitter suppression technique and with long-duration oscillator laser pulses.

http://iopscience.iop.org/article/10.1143/JJAP.42.4325/pdf

Ultra-Line-Narrowed High Power F2 Laser System for Microlithography

To realize an ultranarrow-linewidth and high-output-power F2 laser for next-generation lithography, line narrowing in a F2 laser injection locking system (ILS) that consists of a line-narrowed oscillator and an amplifier with a resonator was investigated. We found out that the time-resolved instantaneous spectrum of the oscillator laser pulse narrows from a start time of discharge and scarcely depends on laser pulse shape. Furthermore, the spectral shape of the ILS is locked to the instantaneous spectral shape of the line-narrowed injection laser when the amplifier discharge starts. We first realized a F2 laser with a linewidth (FWHM) below 0.2 pm and a pulse energy of more than 5 mJ (25 W at 5 kHz repetition rate).

Kazuaki Hotta

Papers

Development of a 5 kHz Ultra-Line-Narrowed F2 Laser for Dioptric Projection Systems.

Ultra-Line-Narrowed High Power F2 Laser System for Microlithography

Line Narrowing and Injection Locking of F2 Lasers