Compact in-line EUV Laser Plasma Reflectometer for the measurement reflectivity and uniformity of EUV Lithography Mask Blank Multilayer Coatings Rupert C. C. Perera & James H. Underwood EUV Technology, Martinez, CA 94553 www.euvl.com
About EUV Technology EUV Technology manufactures custom R&D instrumentation for the utilization and analysis of short wavelength electromagnetic radiation soft x-rays EUV. We specialize in metrology and calibration tools for EUV lithography. The first LPR1016 Reflectometer was purchased by EUV LLC on behalf of International SEMATECH, delivered and installed at Lawrence Livermore National Laboratory in September 2000. www.euvl.com
Goal To provide a method of quality control of mask blanks by defining a process monitoring concept that meets the needs of mask blank production. Test, calibration and quality control equipment that can be installed and used on the shop floor. Accuracy sufficient to monitor and evaluate the entire coating process at the customers manufacturing facility without the mask blank ever having to leave the clean environment. Difficult to achieve high yield without fast feed back. Specifications for EUV mask blanks No printable defects Wavelength controlled to within λ ± 0.4 Å Reflectance uniform across the wafer to within 1%
EUV Technology offers two Reflectometer models: Model No. LPR1016: In-line Reflectometer for the Metrology of EUV Mask Blank Coatings using a Laser Plasma Source. Model No. LPR1016-FS1515: Stand-alone Reflectometer with a Clean Vacuum Robotic Sample Transfer System for the Metrology of EUV Mask Blank Coatings using a Laser Plasma Source
Specifications of the EUV Reflectometer Model No. LPR1016 Measurement area: Up to 200 mm diameter wafer/ 150 mm square blanks with positioning accuracy of 0.1 mm Designed to measure reflectivity at 85 degrees angle Fab compatible. Measurement spot size: less than 2 mm diameter Wavelength range: 10 to 16 nm Wavelength accuracy: 0.0025 nm (0.02%) Reflectivity accuracy: better than 1% compared to reflectivity standard measured at ALS Data rate: 1 point/sec or greater at 1 laser shot per point Can obtain a complete reflectance measurement in 30 seconds 120,000 shots per target change (over 3000 samples without changing the laser target). Footprint of the instrument is about 1.0 m by 1.0 m. User friendly LabView based software to control the instrument and to analyze the reflectance measurements.
Specifications of the EUV Reflectometer Model No. LPR1016-FS1515 Measurement area: 150 mm X 150 mm mask blanks with positioning accuracy of 0.1 mm Substrate thickness: 6 mm Footprint of the instrument is about 2.0 m by 2.0 m. Extremely reliable MESC compatible vacuum mask blank handling robot (MCBF of 10,000,000) to transfer the mask blanks from a standard container. Other specifications are same as for the Model No.LPR1016
Path Operating principle of our EUV Reflectometer Model No. LPR1016 Target (Au) Beam Grating Detector package MIE Laser
User friendly software was designed to be used in a cluster tool Written in LabView. Fully integrated with LDD control system. Measurement recipe is wafer selectable just like deposition recipe is. Allows both full automation and manual control.
Reflectometer is installed on a spare port of the LLNL LDD cluster tool to allow tight integration and automated measurement Reflectometer (top view) Wafer position during deposition Load lock (side-view) Robot Chuck Top view Mo/Si target Load-lock vacuum chamber Robot Ion gun Can measure one wafer while the next is coated. Automated measurement of every blank possible. Small footprint, self contained system: Fab compatible.
Integration of LPR 1016 with the LLNL LDD cluster tool The LPR is compact. It contains two sub-systems Top - The reflectometer Bottom - Mask inspection enclosure Measurements at fixed near-normal incidence only Scanning capability across substrate using translation stage Particles/debris mitigated by optical design, baffles and filters
EUV Reflectometer Model No. LPR1016 reflectance measurements agree with the ALS: 70% Reflectance 60% 50% 40% 30% 20% 10% 20 LPR scans ALS Measurement area: 200 mm Data rate about 2 points/sec Data to be obtained at 1 laser shot per point Less than 30 sec per measurement. 0% 122 124 126 128 130 132 Wavelength (Angstrom)
Recent results from LPR1016: 72 consecutive multilayer reflectivity measurements - P. Kearney (LLNL) 10/02 134.5 134.45 LPR measurements ALS Measurement Wavelength (A) 134.4 134.35 134.3 134.25 0.655 0.66 0.665 0.67 0.675 0.68 Reflectance
Only EUV reflectivity measurement facility in the world clean enough for mask blanks wafers do not leave the clean environment for measurement Defect levels on wafers with both single and multiple (20 ) wavelength scans were statistically indistinguishable from samples that remained in the load-lock. They all had average added defect levels of 0.004 cm -2 (1 added defect).
Conclusions Demonstrated performance of the commercially available inline EUV Reflectometer Model No.LPR1016 Wavelength to ± 0.1 Å Reflectance to ± 0.5% Add no printable defects Fab compatible Set up time is considerably faster (about 10 sec) Turn around time is even faster (about 5 min) Time per measurement (about 1 min) comparable to SR facilities Can be installed and used on the shop floor Laser Plasma Reflectometry is clearly a viable option for mask measurement Need SR facilities like ALS, HIT, PTB etc. to make accurate EUV measurements and for standardization. The Laser Plasma Reflectometers are now commercially available!