Improved performance and specific results are reported for several test and prototype extreme ultraviolet (EUV) light sources developed for next-generation lithography. High repetition rate and high-power CO2 laser-produced plasma sources operating on tin droplet targets are described. Details of laser architecture, source chambers and system operation are given. Stable output power, efficient light collection, and clean EUV transmission could be achieved for hours of operation. We review progress during integration of light sources with collector mirrors reaching EUV power levels at intermediate focus of 60 W and 45 W, respectively, with duty cycles of 25% and 40%. Far-field EUV images of the collected light were recorded to monitor the source output performance during extended tests of collector longevity and debris protection with system operation time exceeding 50 h. Development results on EUV spectra, out-of-band (OOB) radiation, and ion debris obtained with dedicated metrology setups are also described. Angle-resolved measurements with ion energy analyzer and Faraday cups reveal the contributions of individual ion charge states in related spectra. Our laser-produced EUV light source technology has now reached a level of maturity in full integration where prototype sources can be delivered and pilot line introduction can be prepared.
This paper is devoted to the development of laser produced plasma (LPP) EUV source architecture for advanced
lithography applications in high volume manufacturing of integrated circuits. The paper describes the development
status of subsystems most critical to the performance to meet scanner manufacturer requirements for power and
debris mitigation. Spatial and temporal distributions of the radiation delivered to the illuminator of the scanner are
important parameters of the production EUV tool, this paper reports on these parameters measured at the nominal
repetition rate of the EUV source. The lifetime of the collector mirror is a critical parameter in the development of
extreme ultra-violet LPP lithography sources. Deposition of target material and contaminants as well as sputtering
and implantation of incident particles can reduce the reflectivity of the mirror coating substantially over time during
exposure even though debris mitigation schemes are being employed. We report on progress of life-test experiments
of exposed 1.6sr collectors using a Sn LPP EUV light source. The erosion of MLM coating is caused mostly by the
high-energy ions generated from the plasma. In this manuscript the ion distribution measured at small (14 degree)
and medium (45 degree) angles to the laser beam are presented. The measurements show that the chosen
combination of the CO2 laser and Sn droplet targets is characterized by fairly uniform angular ion energy
distribution. The maximum ion energy generated from the plasma is in the range of 3-3.5 keV for all incident angles
of the collector. The measured maximum energy of the ions is significantly less than that measured and simulated
for plasmas generated by short wavelength lasers (1 μm). The separation of ions with different charge states was
observed when a retarding potential was applied to the Faraday Cup detector.
Laser produced plasma (LPP) systems have been developed as a viable approach for the EUV scanner light source for
optical imaging of circuit features at sub-32nm and beyond nodes on the ITRS roadmap. This paper provides a review
of development progress and productization status for LPP extreme-ultra-violet (EUV) sources with performance goals
targeted to meet specific requirements from leading scanner manufacturers. We present the latest results on power
generation, stable and efficient collection, and clean transmission of EUV light through the intermediate focus. We
report on measurements taken using a 5sr collector optic on a production system. Power transmitted to intermediate
focus (IF) is shown. The lifetime of the collector mirror is a critical parameter in the development of extreme ultraviolet
LPP lithography sources. Deposition of target material as well as sputtering of the multilayer coating or
implantation of incident particles can reduce the reflectivity of the mirror coating during exposure. Debris mitigation
techniques are used to inhibit damage from occuring, the results of these techniques are shown. We also report on the
fabrication of 5sr collectors and MLM coating reflectivity, and on Sn droplet generators with droplet size down to 30μm
This paper provides a review of development progress for a laser-produced-plasma (LPP) extreme-ultra-violet (EUV) source with performance goals targeted to meet joint requirements from all leading scanner manufacturers. Laser produced plasma systems have been developed as a viable approach for the EUV scanner light source for optical imaging of circuit features at sub-32nm and beyond nodes on the ITRS roadmap. Recent advances in the development of the system, its present average output power level and progress with various subcomponents is discussed. We present the latest results on peak EUV and average EUV power as well as stability of EUV output, measured in burst-mode operation at the nominal repetition rate of the light source. In addition, our progress in developing of critical components, such as normal-incidence EUV collector and liquid-target delivery system is described. We also report on dose stability, plasma position stability and EUV distribution at the output region of the source. This presentation reviews the experimental results obtained on systems with a focus on the topics most critical for an HVM source.
The capability to scale LPP power by further development of the high power CO2 drive laser in order to increase duty cycle and duration of continuous light source operation is shown. Production systems with thermal management and capable of 5 sr light collection are being assembled and tested. A description of the development of a normal-incidence ellipsoidal collector is included. Improvements in substrate quality lead to increased EUV reflectance of the mirror. Results on the generation of liquid tin droplets as target material for efficient plasma generation are also described. The droplet generator serves as a key element in the precise and spatially stable delivery of small quantities of liquid tin at high repetition rates. We describe a protection module at the intermediate focus (IF) region of the source and imaging of the EUV distribution using a sub-aperture collector and a fluorescent screen. A path to meet requirements for production scanners planned well into the next decade is also presented.