Deep ultra-violet (DUV) laser and short pulse lasers are used for laser processing, because they can decrease the heat effect for process materials. We are developing a hybrid ArF excimer laser that is consists of a solid-state laser, multi wavelength conversion and ArF excimer amplifier. This laser can generate DUV light of 193 nm wavelength short pulse width. In this research, we demonstrated laser drilling on ultra-high temperature structural material that is silicon carbide ceramic matrix composites (SiC-CMC) using high peak power DUV laser. The removal rate was 150 nm/shot with 460 ps pulse. This rate was more than 4 times higher than ArF excimer laser (20 ns pulse width). The HAZ was also reduced by using high peak power DUV light source.
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.
The Argon Fluoride (ArF) immersion lithography is now shifting to mass production phase for below 45nm node. For a
laser light source in this node, narrower and more stable spectrum performance is required. We have introduced GT61A
ArF laser light source (60W/6kHz/10mJ/0.35pm) with spectrum E95 stabilization system which meets these
requirements. The narrow and stabilized spectrum performance was achieved by developing an ultra line narrowing
module and Bandwidth Control Module (BCM). It contributes to the reduction of differences of the spectrum during
exposure over a wafer, wafer to wafer, during machine lifetime and machine to machine for every light source. Stable
laser performance is obtained for mass production. The GT61A integrated on a common and already reliability-proven
GigaTwin (GT) platform, and its inherited reliability is proved with the availability over 99.5% in the field.
KEYWORDS: Molybdenum, High power lasers, Laser systems engineering, Laser applications, Light sources, Systems modeling, Semiconductors, Lithography, Electrodes, Pulsed laser operation
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.
Mass production in 193 nm lithography is now starting and its target node is moving from 90 nm to 65 nm. The main performance requirement of ArF excimer laser in this situation is high power with ultra narrow spectrum for higher throughput. The other hand, higher reliability and lower cost of ownership (CoO) are strongly hoped in mass production because CoO of ArF excimer laser is still higher than that of KrF excimer laser. We have already reported the 4 kHz ArF excimer laser for mass production, model G42A, which has an 20 W of average power, spectral bandwidth less than 0.3 pm (FWHM) and a spectral purity less than 0.75 pm (E95). We applied some technologies to G42A for achieving the high reliability and long lifetime. As a result, G42A showed the stable performance during the lifetime of over 10 billion pulses. In this paper, we report the long-term stability of G42A. And also, we introduce the reliability data of G40A series, which is the previous 4 kHz ArF excimer laser model.
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 has been 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 0.2 pm (FWHM) and an average power of 25 W at a repetition rate of 5 kHz. The energy stability (3-sigma) target is less than 10%. Simultaneously, it is also required to establish the technology of evaluating the optical performance. An Oscillator-Amplifier arrangement at 2 kHz was developed as a first step of an Ultra-Line-Narrowed F2 laser system. With this laser system, we achieved 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 5 kHz system. With the 5 kHz Line-Narrowed Injection Locking system, we have achieved a spectral bandwidth of <0.2 pm with an output energy of >5 mJ and a pulse to pulse energy stability of <10%. The feasibility of a 5 kHz Ultra-Line-Narrowed F2 Laser for Dioptric Projection Systems has been demonstrated.
We have developed an ultra-line-narrowed, high-repetition-rate, high-power injection-locked F2 laser system for 157 nm dioptric projection systems under the ASET project “F2 Laser Lithography Development Project”. A spectral bandwidth of < 0.2 pm (FWHM), an output power of > 25 W, and an energy stability (3-sigma) of < 10 % at 5 kHz repetition rate was successfully obtained by using a low-power ultra-line-narrowed oscillator laser and a high-gain multi-pass amplifier laser. These parameters satisfy the requirements of exposure tools. A numerical simulation code that can simulate the spectral dynamics of the F2 laser under different operation modes such as free running operation, line-narrowed operation, and injection-locked operation, has also been developed. Using this simulation code, it is found that the instantaneous spectral bandwidth narrows monotonously during the laser pulse, and a narrower spectral output can be obtained by seeding the tail area of the line-narrowed F2 laser pulse. And the line-narrowing operation of the oscillator laser and the behavior of the injection-locked laser system can be predicted very precisely with this simulation code. The development of F2 laser for microlithography will be accelerated by this new simulation code.
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.
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 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 0.2 pm (FWHM) and an average power of 25 W at a repetition rate of 5 kHz. The energy stability (3-sigma) target is less than 10%. An Oscillator-Amplifier arrangement at 2 kHz 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 5 kHz system. With the 5 kHz Line-Narrowed Injection Locking system, we have achieved a spectral bandwidth of < 0.2 pm with an output energy of > 5 mJ and an energy pulse to pulse stability of 10%. The feasibility of a 5 kHz Ultra-Line-Narrowed F2 Laser for Dioptric Projection Systems has been demonstrated.
The Association of Super-Advanced Electronics Technologies (ASET) started The F2 Laser Lithography Development Project in March 2000, to clarify solutions of base F2 lithography technologies. In this project, we are developing an ultra line-narrowed F2 laser light source for exposure tools tat are employing dioptric projection optics. We have developed an intermediate engineering injection- locking laser system that has an oscillator laser and an amplifier to study the feasibility of an ultra line-narrowed F2 laser. A spectral bandwidth of <0.2pm (FWHM) at a repetition rate of 1000Hz and an average power of 14W has been achieved with this laser system. The laser output performance dependence on the relative delay between oscillator laser and amplifier is also measured.
It is predicted that the semiconductor market will demand 70 nm devices from 2004 or 2005. Hence, F2 laser microlithography systems have to be developed according to this time frame. At ASET, 'The F2 Laser Lithography Development Project' started in March 2000, as a 2-year project to fulfill this market requirement. The final target of this project is to achieve a F2 laser spectral bandwidth of 0.2 pm (FWHM) at a repetition rate of 5000 Hz and an average power of 25 W. These specifications meet the demand of dioptric projection system. We have done a feasibility study for a high efficiency line narrowing design to achieve the ultra narrow spectral bandwidth and the high output power. In addition, we have developed an intermediate engineering laser system consisting of an oscillator laser and an amplifier. With this laser system we have performed the line-narrowed operation using two arrangements: Master Oscillator Power Amplifier (MOPA) and Injection Locking. With this Oscillator-Amplifier system and have achieved a spectral bandwidth (convoluted) of FWHM <0.2 pm with both systems: MOPA and Injection Locking. The maximum output energy was >20 mJ for MOPA and >15 mJ for Injection Locked operation.
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