Resist Outgassing and its Role in Optics Contamination

Transcription

1 Resist Outgassing and its Role in Optics Contamination Gregory Denbeaux, Rashi Garg, Kim Dean* College of Nanoscale Science and Engineering University at Albany *SEMATECH, Austin, TX Advanced Materials Research Center, AMRC, International SEMATECH Manufacturing Initiative, and ISMI are servicemarks of SEMATECH, Inc. SEMATECH, the SEMATECH logo, Advanced Technology Development Facility, ATDF, and the ATDF logo are registered servicemarks of SEMATECH, Inc. All other servicemarks and trademarks are the property of their respective owners.

2 Introduction Is resist outgassing the dominant cause of optics contamination? Is it the only knob we have left to control contaminants after a tool has been built and wires, stages, lubricants, are already in place? This project uses four techniques to measure the outgassing to ensure accurate calibration: Quadrupole mass spectrometer Pressure rise from ion gauge Mass loss from quartz crystal microbalance Accumulation of outgassed species in thermal desorption tubes Witness plates are used to further verify the measurement techniques and to help determine which molecules are most harmful to the optics

3 EUV ROX System is in Operation (EUV Resist Outgassing and exposure) 10W electrodeless Xe source from Energetiq Based on Z-pinch technology Plasma size of ~350 microns

4 EUV ROX System Loadlock Sample Mass Spectrometer EUV Source

5 EUV ROX System Details QCM Loadlock with computercontrolled sample location (in place of sample) Zr/Si foil 800 l/s Maglev turbo EUV Injection of calibration species Desorption tube 300 AMU Mass spectrometer

6 Calibration of Mass Spectrometer Calibration: The pumping speed of the system was accurately measured The signal on the mass spectrometer was measured compared to an ion gauge calibrated for nitrogen Additionally Species with known cracking patterns and high masses (SF 6 ) are used to calibrate the mass range of the mass spectrometer Injection of known species (methanol, benzene, isobutylene, PGMEA, ) are used to determine the specific signature of each species in this mass spectrometer Injection of known quantities of known species will be used to calibrate the sensitivity of the instrument to each species for those molecules that enter through the 3 mm aperture on the cross beam ionizer Finally, the results have been tested and compared with results from mass loss of a resist measured by a quartz crystal microbalance, pressure rise method, and thermal desorption tube

7 Mass Spectrometer measurement of PMMA Outgassing Methyl Methacrylate (C 5 H 8 O 2 ) at 39 and 41 CO 2 at 44 Methyl Formate (C 2 H 4 O 2 ) at 60

8 1.2E+15 Sample outgassing result (a KRS resist) Methanol CH 4 O at 31, 32, 29, 15 1E+15 molecules/cm^2 8E+14 6E+14 4E+14 Benzene C 6 H 6 at 78 2E Mass Number (AMU) [excluding water] (Sample courtesy of G. Breyta, H. Truong, A. Fornof, G. Wallraff and R. Allen IBM)

9 Incomplete list of outgassed species for testing of optics contamination rates Carbon Dioxide Carbon Monoxide Water Isobutylene Methanol Benzene Methyl Methacrylate Methyl Formate Others??? Do we know ahead of time which species are more likely to contaminate so we can focus our efforts there?

10 Witness Plate Experimental Configuration for Resist Testing Resist sample Resist sample Approximately 2.5 between mirror and resist Not exposed EUV Witness plate Zirconium Filter Witness plate: Si Capped Mo/Si mirror at 6 degrees to the incident wave Exposed to EUV illumination Energetiq Xenon Plasma EUV Source Vacuum chamber ASML proposed a test to expose a 300 mm wafer worth of resist If reflectivity loss is 2% or can be cleaned to meet this reflectivity, the resist is safe for use

11 Reflectivity Measurements Reflectivity Reflectivity of Mo/Si witness plate as a control Wavelength Unexposed peak reflectivity = 68.4% Exposed peak reflectivity = 67% Net 2.0% decrease in peak reflectivity after exposure for the same time as the PMMA Reflectivity Reflectivity of Mo/Si witness plate after PMMA outgassing Unexposed peak reflectivity = 68.6% Exposed peak reflectivity = 66.7% Net 2.8% decrease in peak reflectivity after exposure of 1/4 of 300 mm wafer worth of PMMA Wavelength (nm) Net peak reflectivity loss due to ¼ of a 300 mm wafer is 0.8%; therefore, on extrapolating to a full 300 mm wafer PMMA, the peak reflectivity loss is 3.2% Reflectivity Measurements from Eric Gullikson (CXRO), Steve Grantham (NIST), and Charles Tarrio (NIST) INVENT

12 Summary Ongoing witness plate tests are done using the ASML proposed configuration in progress This will help provide an understanding of which outgassed species are unsafe for the EUV optics Correlate mass spectrometer results with the witness plate tests for different resists A better specification for mass spectrometer outgassing may be available that will be a fast and more accurate measurement of the resists Make a benchmark for passing the resists to be used in EUVL exposure tools How does outgassing change as we change: Dose on resist Increases with dose faster resists are better Dose rate on resist No significant difference we can extrapolate our results to other EUVL exposure tools Angle between resist sample and mass spectrometer head No significant difference, therefore geometry does not matter in our system Thickness of the resist in progress Bandwidth of incoming EUV radiations in progress By measuring outgassing from a resist in direct and reflected beam Effect of resist formulation on outgassing in progress Future Optics contamination with selected species to help develop the understanding needed (with the witness plate results) to come up with a better specification for mass spectrometer outgassing

13 Acknowledgements SEMATECH for funding this work INVENT Resist Team Obert Wood, Warren Montgomery, Chiew-Seng Koay, Robert Brainard, Karen Petrillo, Tom Wallow CNSE Rashi Garg, Chimaobi Mbanaso, Justin Waterman, Yujen Fan, Leonid Yankulin, Alin Anhote, Kevin DeMarco, Molly Jaffe, Matt Waldron, Jeroen Netten Robert Brainard IBM Almaden G. Breyta, H. Truong, A. Fornof, G. Wallraff and R. Allen NIST Steven Grantham and Charles Tarrio from NIST Center for X-ray Optics (LBNL) Eric Gullikson ASML Bill Pierson and Roel Moors Advanced Materials Research Center, AMRC, International SEMATECH Manufacturing Initiative, and ISMI are servicemarks of SEMATECH, Inc. SEMATECH, the SEMATECH logo, Advanced Technology Development Facility, ATDF, and the ATDF logo are registered servicemarks of SEMATECH, Inc. All other servicemarks and trademarks are the property of their respective owners.