Contamination Removal of EUVL masks and optics using 13.5-nm and 172-nm radiation

Transcription

1 Contamination Removal of EUVL masks and optics using 13.5-nm and 172-nm radiation Takeo Watanabe, Kazuhiro Hamamoto and Hiroo Kinoshita University of Hyogo IEUVI Resist & Contamination TWG Oct.19, 2006 in Barcelona

2 Method of contamination removal (1) Cleaning of EUVL imaging optics (The optics used for EUVL has been aligned in high accuracy. So the cleaning of imaging optics requires in-situ process.) In-situ contamination removal by synchrotron radiation without heating (2) Cleaning of EUVL masks (Both large cleaning area and high speed are required.) Contamination removal by 172-nm-wavelength. Evaluation between before and after removal Contamination thickness Optical thickness measuring system Surface roughness AFM Reflectivity Reflectometer (NewSUBARU BL-10)

3 Online contamination removal by a wavelength of 13.5 nm

4 Contamination adhesion in ETS-1 exposure system M1 M3 M2 Mask Wafer Partial pressure (Pa) Partial pressure in ETS-1 H 2 O N 2 CO C x H y 2 Sample of the multilayer is set on the mask stage, and EUV is irradiated Mass number Total pressure: Pa

5 Thickness of contamination Thickness of contamination (nm) Electron beam current: 200 ma Irradiation time (min.) Deposition rate: 7.5 nm/hr (0.125 nm/min)

6 Reflectivity of multilayer Reflectivity Irradiation time (min.) Multilayer reflectivity of 10% decreased by 4 hours irradiation

7 Surface roughness of multilayer Surface roughness (nm) Irradiation time (min.)

8 Photoelectron intensity for Ta (cps. ev) AES spectrum of contamination of mask O C Ta Photoelectron intensity for C, O, Si (cps. ev) Sputtering time (min.) The ratio of C to O is 96:4

9 Experimental setup of SR cleaning Storage ring M2 mirror M3 mirror (Branch) ETS-1 M1 mirror Photodiode (GaAsP) Contamination testing chamber Incident angle 10 SR Back pressure: Pa adding O 2 during Mask sample TMP Oxygen SR irradiation pressure: Pa

10 Experimental results Normalized reflectivity Normalized storage ring current Pressure: Pa Electron beam current: 130 ma Irradiation: 7 hr Time (min.) Contamination of 0.1-µm-thick was removed. Before cleaning After cleaning

11 Reduction of contamination thickness Reduction in thickness (nm) Removal rate: 0.24 nm/min 7 hr 0 0 1x10 6 2x10 6 3x10 6 4x10 6 5x10 6 6x10 6 7x10 6 8x10 6 Exposure dose (mas) Electron beam current: 130 ma

12 Reflectivity of multilayer (measurement: NS-BL10) Before cleaning contamination multilayer absorber A B C D E After cleaning absorber multilayer absorber Reflectivity E D C B A Reflectivity Wavelength (nm) Wavelength (nm)

13 Offline contamination removal by a wavelength of 172 nm

14 Mask cleaning using 172 nm-excimer VUV/O 3 CO x, H 2,CH z,h 2 O, 172 nm ozone(o 3 ) oxygen(o 2 ) C x H y Active oxygen species(o*) Mo/Si contamination The absorption coefficient to the oxygen molecule at the wavelength of 172 nm is 20 times larger than that at the wavelength of 185 nm of the low-pressure mercury lamp. A high density active oxygen species can be generated.

15 Experimental setup of 172 nm cleaning 172 nm excimer lamp 1mm Stage Intensity 20 mw/cm 2 Distance 1 mm Sample size 8-inch Temperature 25 Environment in the air / in O 2 -rich vacuum O 2 -rich vacuum environment: The initial back pressure of the chamber was 500 Pa by scroll pump, and an O 2 flow kept the pressure at Pa.

16 Results of mask cleaning using 172 nm-excimer lamp (1) Reduction of contamination thickness 30 Removal thickness (nm) in vacuum rate: 2 nm/min. in the air rate: 0.53 nm/min Cleaning time (min)

17 Results of mask cleaning using 172 nm-excimer lamp (2) Reflectivity of multilayer 70% Reflectivity 60% 50% 40% 30% 20% 10% After cleaning Before cleaning 0% Wavelength (nm)

18 Summary (1) From the result of AES, it has been understood that the element of contamination is almost carbon. (2) The effectiveness of the contamination removal for EUVL imaging optics using both in-situ and non-heating method by EUV irradiation in the oxygen atmosphere is confirmed. (3) The effectiveness of the contamination removal for the finished EUVL mask in off-line process using the 172 nmexcimer lamp in the O 2 -rich vacuum atmosphere at the room temperature is confirmed.

19 Thank you for your attention!!

20 Outgassing Measurement in University of Hyogo -Short summary- Takeo Watanabe, Hiroo Kinoshita University of Hyogo IEUVI Resist & Contamination TWG Oct.19, 2006 in Barcelona

21 Setup of novel resist evaluation system 1) Measurements of sensitivity 2) Outgas characteristics 3) Chemical reaction analysis Mo/Si MLs Concave Mirror Simulating six-mirror optics Practical exposure spectrum PC controlled fast speed shutter ( t=11 ms) SR High-sensitive ion counting type Q-mass spectrometer Model HAL/3F/PIC 501 RC, Hiden Analytical, Ltd. Distance 30 mm Mo/Si MLs Two Plane Mirrors Sample

22 Setup of novel resist evaluation system Gate valve Shutter chamber SR Differential pumping Sample Mirror chamber TMP 700L/s Gate valve Gate valve Sample chamber TMP 300L/s Loadlock chamber TMP 300L/s Sample insertion rod

23 By Takeo Watanabe, Univ. of Hyogo 2006 Oct 19 Institute Method Results Molecules/cm mj/cm 2 dose Molecules/cm 2 intensity condition Estimate Rate Molecules/cm 2 Tool (0.4 W/cm 2 ) Intel Synchrotron GC/MS mw/cm SEMATECH Synchrotron GC/MS mw/cm amu ASET Synchrotron Online QMS mw/cm amu BOC Edwards Stand-alone source Online QMS mw/cm 2??-??? amu Univ. of Hyogo Synchrotron Online QMS mw/cm amu amu amu amu amu Excluding 44 amu amu Excluding 44 amu amu Excluding 44 amu