Semiconductor market demand for improved performance at lower cost continues to drive enhancements in excimer
light source technologies. Increased output power, reduced variability in key light source parameters, and improved
beam stability are required of the light source to support immersion lithography, multi-patterning, and 450mm wafer
applications in high volume semiconductor manufacturing. To support future scanner needs, Cymer conducted a
technology demonstration program to evaluate the design elements for a 120W ArFi light source. The program was
based on the 90W XLR 600ix platform, and included rapid power switching between 90W and 120W modes to
potentially support lot-to-lot changes in desired power. The 120W requirements also included improved beam
stability in an exposure window conditionally reduced by 20%. The 120W output power is achieved by efficiency
gains in system design, keeping system input power at the same level as the 90W XLR 600ix. To assess system to
system variability, detailed system testing was conducted from 90W – 120W with reproducible results.
Semiconductor chip manufacturing is on the verge of a new production process node driving critical feature sizes below 100 nm. The next generation of 193 nm Argon Fluoride laser, the NanoLith<SUP>TM</SUP> 7000, has been developed in response to this recent technology development in the lithography industry. The NanoLith<SUP>TM</SUP> 7000, offering 20 Watts average output power at 4 kHz repetition rate, is designed to support the highest exposure tool scan speeds for maximum productivity and wafer throughput. Technology improvements to support the move from pilot production to full production will be described. With core technology defined and performance to specification established, attention turns to cost of operation, which is closely tied to module lifetime and reliability. Here we present results of the NanoLith<SUP>TM</SUP> 7000 system lifetest tracking all optical performance data over a 4.4 Billion shot. The system is operated in firing modes ranging from 1-4 kHz, and up to 75% duty cycle. Overall system performance measured to date both in the lab and in the field suggests that this laser meets all the production requirements for 193 nm lithography.
The next generation 193 nm (ArF) laser has been designed and developed for high-volume production lithography. The NanoLith<SUP>TM</SUP> 7000, offering 20 Watts average output power at 4 kHz repetition rates is designed to support the highest exposure tool scan speeds for maximum productivity and wafer throughput. Fundamental design changes made to the laser core technologies are described. These advancements in core technology support the delivery of highly line-narrowed light with <EQ 0.35 pm FWHM and <EQ 0.95 pm at 95% included energy integral, enabling high contrast imaging from exposure tools with lens NA exceeding 0.75. The system has been designed to support production lithography, meeting specifications for bandwidth, dose stability (+/- 0.3% in 20 ms window) and wavelength stability (+/- 0.05 pm average line center error in 20 ms window) across 2 - 4 kHz repetition rates. Improvements in optical materials and coatings have led to increased lifetime of optics modules. Optimization of the discharge electrode design has increased chamber lifetime. Early life-testing indicates that the NanoLith<SUP>TM</SUP> core technologies have the potential for 400% reduction of cost of consumables as compared to its predecessor, the ELX-5000A and has been discussed elsewhere.
Highly line-narrowed F<SUB>2</SUB> laser operation in the VUV has been achieved for the first time by means of a master oscillator/power amplifier laser design. Different concepts have ben investigated experimentally for the master oscillator (MO) in order to obtain narrowband spectra. The diffraction grating based design showed to be limited to a FWHM of approximately 0.4 pm. The spectral FWHM of the MO could be further reduced to below 0.3 pm with a double etalon-based resonator. Single pass amplification was employed to increase the beam energy density of the beam up to 50 mJ/cm<SUP>2</SUP>. The spectral FWHM of the amplified light is slightly larger than the FWHM of the correspondent MO radiation, indicating saturation and/or inhomogeneous broadening of the F<SUB>2</SUB> amplifier medium. Experimental data obtained from broadband operation and ASE measurements suggests that the free running bandwidth of F<SUB>2</SUB> lasers result form spectral gain-narrowing of the laser medium.
Exposure tools for 193nm lithography are expected to use Argon-Fluoride lasers at repetition rates of at least 2kHz. We are showing that, by revisiting several key technologies, the performance and reliability of ArF lasers at 2 kHz are trending towards a level comparable to KrF lasers.
Designers of DUV lithographic lenses are faced with serious materials problems relating to compaction and color-center formation in fused silica, especially at 193 nm. However, these problems, while less sever, are not negligible at 248 nm. Compaction appears to be the more serious, since it degrades imaging performance and effectively sets the lifetime limit for the lens. Previous damage studies have clearly shown that fused silica compacts as a function of the parameter grouping (NI<SUP>2</SUP>/(tau) ), where (tau) is the pulsewidth. This fact has strongly influenced the design of the excimer laser light source by stressing repetition rate over pulse energy as a way of achieving high average power, and by driving the optical pulsewidth to be as long as possible. These studies, however, have emphasized the dependence of damage rates on the energy density I(mJ/cm<SUP>2</SUP>), whereas the optical pulsewidth (tau) has been given only cursory attention and has not been well controlled during the damage experiments. In this paper we report the results of an experiment to more clearly establish the functional dependency of compaction on laser pulsewidth.
The present day notion of the extensibility of KrF laser technology to ArF is revisited. We show that a robust solution to ArF requirements can be met by significantly altering the laser's core technology-discharge chamber, pulsed power and optics. With these changes, a practical ArF tool can be developed. Some of the laser specifications are: Bandwidth: 0.6 pm (FWHM) 1.75 pm (95% Included Energy); Average Power: 5 W; Repetition Rate: 1000 Hz; Energy Stability (3(sigma) ): 20% (burst mode) 8% (continuous); Pulse Width: 25 ns.