Youichi Sasaki

Laser-produced plasma source development for EUV lithography

We are developing a laser produced plasma light source for high volume manufacturing (HVM) EUV lithography. The light source is based on a high power, high repetition rate CO2 laser system, a tin droplet target and a magnetic plasma guiding for collector mirror protection. This approach enables cost-effective high-conversion efficiency and EUV power scaling. The laser system is a master oscillator power amplifier (MOPA) configuration. We have achieved a maximum average laser output power of more than 10 kW at 100 kHz and 20 ns pulse by a single laser beam with good beam quality. EUV in-band power and out-of-band characteristics are measuring with high power CO2 laser and Sn droplet target configuration. This light source is scalable to more than 200 W EUV in-band power based on a 20-kW CO2 laser. Collector mirror life can be extended by using droplet target and magnetic plasma guiding. Effectiveness of the magnetic plasma guiding is examined by monitoring the motion of fast Sn ion in a large vacuum chamber. The ion flux from a Sn plasma was confined along the magnetic axis with a maximum magnetic flux density of 2 T.

Power up: 120 Watt injection-locked ArF excimer laser required for both multi-patterning and 450 mm wafer lithography

193nm ArF excimer lasers are widely used as light sources for the lithography process of semiconductor production. At first, ArF excimer lasers have been used in semiconductor productions at the 90nm node and recently ArF excimer lasers have begun to be used for the 32nm node, by the progress in the immersion technology and the double-patterning technology. Furthermore, considering current status of development of the lithography technology using a next-generation light source, or extreme ultraviolet (EUV) light source, the start of mass production with the next-generation light source is estimated to start from 2015. Therefore, there is a need for extension of 193nm immersion lithography technology. By using the multi-patterning and double-patterning technology, design rules below limit at single exposure is possible. However, throughput is reduced due to increased lithography processes. In order to improve a decrease in throughput, a high power ArF excimer laser and larger size wafer (450mm in diameter) is needed. We have developed a new high power laser with the concept of eco-friendly. In this paper, we will introduce technologies used for our latest ArF excimer laser having tunable output power between 90W and 120W and report its performance data.

Technology for monitoring shot-level light source performance data to achieve high-optimization of lithography processes

Gigaphoton has developed a new monitoring system that provides shot-level light source performance data to FDC systems during exposure time. The system provides basic monitoring data (e.g. Energy, Wavelength, Bandwidth, etc.) and beam performance data, such as Beam Profile, Pointing, Divergence, Polarization can also be monitored using a new metrology tool called the Beam Performance Monitor (BPM) module. During exposure time the system automatically identifies the start and end timing of the wafer and each shot based on the burst of firing signals from the scanner, and stores the measured data in sequence. The stored data is sorted by wafer or by shot, and sent to REDeeM Piece which in turn converts the data to the users protocol and send it to the FDC system. The user also has the option to directly view or download the stored data using a GUI. Through this monitoring system, users can manage light sources data at the shot or reticle level to facilitate optimization of performance and running cost of the light source for each process. This monitoring system can be easily retrofitted to Gigaphotons current ArF laser light sources. The beam splitter of the BPM was specially designed to bend only a small fraction of the source beam, so we are able to simply install the BPM without the need for special optical alignment.

Ultra line narrowed injection lock laser light source for higher NA ArF immersion lithography tool

The GT61A ArF laser light source with ultra line narrowed spectrum, which meets the demand of hyper NA (NA > 1.3) immersion tool, is introduced. The GT61A aims at improving spectrum performance from value E95 0.5pm of GT60A. The spectrum performance 0.3pm or less was achieved by developing an ultra line narrowing module newly. Moreover, in 45nm node, since it indispensably requires OPC (optical proximity correction) and a narrower process window, improved stabilization of spectrum performances was performed by bandwidth control technology. Newly designed Bandwidth Control Module (BCM) includes high accuracy measurement module which support the narrower bandwidth range and active bandwidth control module. It also contributes to the reduction of the tool-to-tool differences of the spectrum for every light source.

Seismic Evaluation Method of a Process Computer System for Nuclear Power Plants.

In order to maintain the functional capability of a process computer system used in nuclear power plant, it is necessary to keep both structural integrity and information processing function during design earthquake.Based on failure mode analysis of the process computer system against the earthquake, a method of evaluating functional capability of process computer system is proposed. In this method, the acceleration responses of computer equipment are calculated by FEM and compared with the allowable accelerations obtained by the seismic proving test. The proposed method is examined its usefulness in evaluating the functional capability of an actual process computer system in a nuclear power plant and its validity is verified.