Chipmakers have used cross-platform of both EUV exposure and ArF immersion multi-patterning exposure depending on cost effectiveness at each layer. ArF immersion exposure has been required lower linewidth roughness(LWR) to reduce cross matched machine overlay(xMMO) which is the overlay between the different platforms. ArF light sources essentially produce speckle as non-uniform intensity distribution resulting from interference effects generated within a beam. It leads to increase LWR, which results in increasing xMMO. The latest ArF immersion light source, GT66A is introduced a new optical pulse stretcher(OPS) that increases pulse duration to reduce speckle by 30% to improves LWR, which reduces xMMO. This technology will improve chip yield for chipmakers in the processes mixed ArF immersion exposure and EUV exposure.
Multiple patterning ArF immersion lithography has been expected as the promising technology to meet tighter leading edge device requirements. To enhance the resolution and productivity for multiple-patterning application, key light source performances are spectral bandwidth stability and wavelength stability. The increased spectral bandwidth stability contributes to more precise critical dimension (CD) control and improves device yield. The increased wavelength stability can realize accurate focus and improve overlay accuracy. Our new spectral bandwidth control module improves E95 spectral bandwidth stability. The spectral bandwidth has deviations by thermal history with light source operations. It should be always controlled tightly even after a quiescent interval, such as wafer loading. In our laser system, a spectral bandwidth is controlled by adjusting the wavefront of a laser beam using a two-lens optical system within a resonator. A high speed actuator equipped the movable lens enables E95 spectral bandwidth stability to be less variation. New designs of drive mechanism suppress the lens vibration and spectral bandwidth error. This technology enables 3-sigma of E95 spectral bandwidth field average to be under 5 fm. This large shrinkage for E95 spectral bandwidth stability is the key to improve larger focus budgets for a leading edge processes. A new designed line narrowing module (LNM) improves wavelength stability. The wavelength is controlled by changing the rotation of a beam expander prism using actuator. Wavelength stability is improved further by the anti-vibration structure of the actuated prism in the LNM. The new design prism holding mechanisms reduce the mass of actuator load. This increases the stiffness of the system and suppresses the vibration of the prism rotation. New LNM reduce wavelength stability about 20%. The improvement in wavelength stability contributes to accurate focus and overlay. In addition, the lifetime of LNM is extending to reduce the Cost of Operation (CoO) and the light source downtime. A new ArF excimer laser, GT66A, maximizes device yield, process productivity and minimizes the operational costs for chipmakers.
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 user's 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 Gigaphoton's 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.
Laser Produced Plasma (LPP) Extreme Ultra Violet (EUV) light source is expected to be used for next generation
lithography. To realize such performance for industrial use, the main driver laser is one of the key components. Our
source uses a high power pulsed carbon dioxide (CO2) laser as a plasma driver. A master oscillator and a power amplifier
(MOPA) system based on a new configuration of an RF-excited CO2 laser is the key to high efficiency. And multiline
amplification of CO2 laser is efficient to increase the extraction efficiency in the case of short pulse amplification like
this amplification. Numerical result shows the amplification enhancement as 1.3 times higher than the single line
amplification. This report shows its initial performance. Multiline configuration is applied to the master oscillator and the
efficiency of multiline amplification is verified in our experimental amplifier system. We have achieved 10% energy
extraction improvement using 2 lines (P20+P22) as compared to single line (P20).
Laser Produced Plasma (LPP) Extreme Ultra Violet (EUV) light source is expected to be used for next generation
lithography. To realize such performance for industrial use, the main driver laser is one of the key components. Our
source uses a high power pulsed carbon dioxide (CO2) laser as a plasma driver. A master oscillator and a power amplifier
(MOPA) system based on a new configuration of an RF-excited CO2 laser is the key to high efficiency. This pulsed CO2 laser system has started to operate. This report shows its initial performance. Also for a reliable industrial system, the
optical instability caused by vibration and thermal distortion of optics should be suppressed at 20 kW output level. The
primary design of key modules, such as mirrors, for the CO2 laser, and dynamic design concepts are shown in this report.
We have achieved 7.6 kW, 14 nsec, 100 kHz pulsed output in this configuration.
We reported 1st generation Laser-Produced Plasma source system "ETS" device for EUV lithography one year
ago1). In this paper we update performance status of the 1st generation system. We have improved the system
further, maximum burst power is 104W (100kHz, 1 mJ EUV power @ intermediate focus), laser-EUV conversion
efficiency is 2.5%. Also continuous operation time is so far up to 8 hours with 5% duty cycle is achieved. We have
investigated EUV plasma creation scheme by small experimental device which is facilitated 10Hz operation
(maximum). We have proposed double pulse method to create LPP plasma efficiently. This moment we found out
3.3% conversion efficiency operation condition.
Based on the engineering data of ETS and small experimental device, now we are developing 2nd generation
HVM source; GL200E. The device consists of the original concepts (1) CO2 laser driven Sn plasma, (2) Hybrid
CO2 laser system that is combination of high speed (>100kHz) short pulse oscillator and industrial cw-CO2, (3)
Magnetic mitigation, and (4) Double pulse EUV plasma creation. The preliminary data are introduced in this paper.
We are developing a CO2 laser driven Sn plasma light source for HVM EUVL. This source enables cost-effective high-conversion efficiency (CE >4%) and EUV power scaling. To evaluate light source characteristics we developed a metrology tool for the EUV and for the out of band (DUV, IR) wavelength region.
The EUV plasma light source emits radiation ranging from the EUV to the IR. To evaluate a particular wavelength region, spectral purity filters are used to select the region of interest. For the in-band EUV emission the power, the energy stability and the radiation profile are measured. The power is measured with an attenuating filter and a powermeter. The energy stability is measured with a filterd X-ray diode. The radiation profile is measured with a phosphor plate and a VIS-CCD camera. For the out of band emission, the radiated power is measured with an attenuating filter and a powermeter. The out of band region includes the CO2 laser which is partly scattered by the plasma and reflected towards the IF and needs therefore to be included into the measurement.
We are developing a CO2 laser driven Tin plasma EUV source for HVM EUVL. This approach enables cost-effective EUV power scaling by high-conversion efficiency and full recovery of Tin fuel. The RF-excited, multi 10 kW average power pulsed CO2 laser system is a MOPA (master oscillator power amplifier) configuration and operates at 100 kHz with 20 ns pulse width. The EUV light source is scalable to in-band 200 W IF power with a single 20-kW CO2 laser beam. EUV chamber is kept uncontaminated by using a small size droplet target and effective Tin exhaust by magnetic plasma guiding. Characterization of the plasma flow in uniform magnetic field was studied by monitoring the motion of Tin plasma stream in a large vacuum chamber, depending on the magnetic flux up to 2 T. Topics relevant for HVM source is reported on continuous operation and Tin vapor evacuation.
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 (10.6μm) system, a tin (Sn) target and a magnetic
ion guiding for Sn treatment. We evaluated the characteristics of Sn debris generated by a CO2 laser produced plasma.
Experiments were performed with bulk Sn-plate targets and Mo/Si multilayer mirror samples were used for debris
analysis. We observed very thin and uniform Sn layers of nano/sub-nano size debris particles. The layer deposition rate
at 120mm from the plasma is, without magnetic field, about 30nm per million shots. The fast Sn ion flux was measured
with Faraday cups and the signal decreased by more than 3 orders of magnitude on application of a magnetic field of 1T.
The Sn deposition on the Mo/Si multilayer mirror decreased in small magnetic field space by a factor of 5. In a large
magnetic field space, the effectiveness of the magnetic guiding of Sn ions is examined by monitoring the fast Sn ions.
The ion flux from a Sn plasma was confined along the magnetic axis with a maximum magnetic field of 2T.
We evaluated the characteristics of Sn debris generated by a CO2 laser (10.6μm) produced plasma. Experiments were
performed with bulk Sn-plate targets and Mo/Si multilayer mirror samples were used for debris analysis. We observed
very thin and uniform Sn layers of nano/sub-nano size debris particles. The layer deposition rate at 120mm from the
plasma is, without magnetic field, about 30nm per million shots. The fundamental magnetic field effect has been
confirmed experimentally. The fast Sn ion flux was measured with Faraday cups and the signal decreased by more than 3
orders of magnitude applying a magnetic field of 1T. The Sn deposition on the Mo/Si multilayer mirror decreased in this
case by a factor of 4. The contribution of the remaining neutral Sn particles is under study in order to decrease the
deposition rate.
We are developing a high power CO2 laser system for a LPP EUV light source. Recent theoretical and experimental data
demonstrate the advantages of the combination of a CO2 laser with a Sn target including the generation of a high CE and
low debris plasma with low energy ions and low out-of-band radiation. Our laser system is a short pulse CO2 MOPA
(Master Oscillator Power Amplifier) system with 22 ns pulse width and multi kW average power at 100 kHz repetition
rate. We achieved an average laser power of 8 kW with a single laser beam having very good beam quality. A EUV in-band
power of 60 W at the intermediate focus was generated irradiating a rotating tin plate with 6 kW laser power.
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 target and a magnetic ion guiding for
tin treatment. The laser system is a master oscillator power amplifier (MOPA) configuration. We have achieved an
average laser output power of 10 kW at 100 kHz by a single laser beam with good beam quality. EUV in-band power
equivalent to 60 W at intermediate focus was produced by irradiating a tin rotating plate with 6 kW laser power. 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 ion guiding. Effectiveness of the magnetic ion guiding is examined by
monitoring the motion of fast Sn ion in a large vacuum chamber with a maximum magnetic flux density of 2 T.
A laser produced plasma light source for a small field exposure tool (SFET) has been developed at the EUVA Hiratsuka
R&D center. The light source consists of the following components: The drive laser of the xenon plasma source is a
short-pulse, high-power KrF laser that has been developed in cooperation with Gigaphoton Inc. and Komatsu Ltd. The
laser has an unstable resonator and produces a maximum output power of 580W at 4kHz repetition rate. The xenon
target is a 50 micrometer diameter liquid jet with a speed of about 35 m/s. The source has been designed to generate
0.5W in-band power at the intermediate focus (IF) at a collecting solid angle of pi sr. The source includes automatic
control, e.g. jet and plasma position control, and an electrical interface for the exposure tool. The performance of the
source at IF has been evaluated by Canon Inc. This paper explains source performances. Especially, results of IF
parameters like image size, position stability and out of band radiation are presented.
A small field exposure tool (SFET) is currently being built in Japan by the Extreme Ultraviolet Lithography System Development Association (EUVA) and Canon Inc. The laser plasma light source of SFET has been developed at the EUVA Hiratsuka R&D center. The drive laser of the xenon plasma source is a short-pulse, high-power KrF laser, that has been developed in cooperation with Gigaphoton Inc. and Komatsu Ltd. The laser has a maximum output power of 580W at 4kHz repetition rate. The xenon target is a 50 micrometer diameter liquid jet with a speed of about 30 m/s. The source has been designed to generate 0.5W in-band power at the intermediate focus at a collecting solid angle of pi sr. The set-up of the source at the Hiratsuka R&D center has been completed and the source is now being evaluated.
We previously succeeded in fabricating 60-nm line-and-space (L/S) patterns with fluorine-containing silsesquioxane-type (F-SSQ) resist, BARRIERTA® J25V immersion fluid, and NovecTM HFE-7200 rinse liquid using our two-beam interferometer. In the study reported here, we tried to fabricate a finer resist pattern with this immersion fluid, but 40-nm L/S could not be resolved because of the T-top shapes produced under the same conditions. The cause of the T-top shape was photo-acid generator (PAG) leaching into HFE-7200, which in effect caused the resist layer to swell. When FluorinertTM FC-84 with the CF3 functional group, which has the lowest reactivity, was used as a rinse liquid, the resolution of 40- and 32-nm L/S without T-top shape was achieved. Next, to fabricate finer patterns, we considered improving the molecular structure to raise the refractive index. As a result of an examination based on perfluoroalkane, which has high transparency, we found that it is effective to reduce the fluorine atom concentration, transform the molecular structure to a steric structure without reducing molar refractivity, and attach a functional group such as a cyclohexyl or chloro group. Finally, with the high-refractive index immersion fluid, we attempted to fabricate 28-nm L/S. Although we tried pattern fabrication with two immersion fluid candidates, transfer of the interference patterns to the resist has not been confirmed at this time. However, since we checked that the light did reach the resist, we speculate that it will be possible to fabricate 28-nm L/S by making a minor change.
A two-beam interference lithography system based on a line-selected F2 laser has been developed. Resist patterns with a 60nm line and space (L&S) resolution were produced by the interferometer by F2 immersion lithography. The F2 laser performance had been especially optimized for this application. The spectral emission at the 157.53nm line was less than 1% of the main line emission at 157.63nm. The main line had a deconvolved spectral bandwidth of 0.84 pm (full width at half maximum (FWHM)). The degree of horizontal linear polarization was above 0.73 and the visibility of spatial coherence was larger than 0.83 at a pinhole distance of 0.1mm.
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