IN-LAB PELLICLE METROLOGY CHALLENGES

Transcription

1 IN-LAB PELLICLE METROLOGY CHALLENGES Serhiy Danylyuk RWTH Aachen University , Maastricht

2 Pellicle requirements Pellicle requirem ent HVM Target EUV transmission 90% single pass Spatial non-uniformity of the transmission <0.2% Angular non-uniformity of the transmission <300 mrad Dynamic heat load 5.6 W/cm 2 (250 W IF) *C. Zoldesi, et al., Progress on EUV pellicle development, Proc. SPIE 9048 (2014) Page 2

3 EUV Transmission measurements EUV source plasma-based sources (inherent pulse-to-pulse intensity fluctuation of a few %) Reference signal or very precise dose monitoring Beam splitting Side-view plasma emission monitors In-beam intensity measurements source pellicle detector Detector Diode, CCD, Resists I 0 I Page 3

4 EUV Transmission measurements EUV source plasma-based sources (inherent pulse-to-pulse intensity fluctuation of a few %) Reference signal or very precise dose monitoring Beam splitting (easy only with small samples or near the edge) Side-view plasma emission monitors In-beam intensity measurements source pellicle detector Detector Diode, CCD, Resists I 0 I 0 I Page 4

5 EUV Transmission measurements EUV source plasma-based sources (inherent pulse-to-pulse intensity fluctuation of a few %) Reference signal or very precise dose monitoring Beam splitting Side-view plasma emission monitors In-beam intensity measurements source pellicle detector Detector Page 5 Diode, CCD, Resists I 0 k*i 0 Reference detector I

6 EUV Transmission measurements EUV source plasma-based sources (inherent pulse-to-pulse intensity fluctuation of a few %) Reference signal or very precise dose monitoring Beam splitting Side-view plasma emission monitors In-beam intensity measurements source pellicle detector Detector Diode, CCD, Resists I 0 I Page 6

7 Multilayer based energy monitor for absolute measurement of the 2% Inband power at 13.5 nm st mirror 2nd mirror 1.8 % b.w. 0.4 REFLECTIVITY single REFLECTIVITY double Reference ML-tool E k source 13.5nm2% b. w tool 0 J spect ( ) S J spect 13.5nm 2% Tool tool ( ) d 1 k ( ) d tool T tool 13.5nm Udt R WAVELENGTH [ nm ] p:<euv_kollektor.socomo.mlird-tools.tool_2percent>doubleml.opj ML1 277,3 22,2 AXUV Diode ML2 D=6 mm

8 Transmission measurements: Setup 1 Experimental setup Close-up of filter wheel Setup 1 utilizes DPP EUV source from Bruker/RI and 8 slot filter wheel for fast sample exchange. Page 8

9 Transmission measurements: Setup 2 Scheme of setup (in reflectivity mode) Experimental setup Setup 2 utilizes DPP EUV source from Bruker/RI and two photodiodes each with a Zr filter. It can be used in reflectivity and transmission mode. For detailed information: K. Bergmann, Review of Scientific Instruments 76, (2005) Page 9

10 Results ,5 80 single pulse 8 pulses average 64 pulses average 55,0 Diode signal (mv) Transmission [%] 54,5 54,0 53,5 54,908 0,271% 20 53,0 52,5 10 measurements per point Time (µs) Averaged pulses per measurement The results show that the precision for diode based techniques is mainly limited by the noise of the diode signals. Averaging more pulses improved the results dramatically due to much smoother noise floors. Page 10

11 Transmission (%) BENCHMARKING OF TRANSMISSION MEASUREMENTS Reference pellicle sample (SiNx ~90nm) was used to compare transmission results between RWTH and imec 60% 58% 57.5%+/-0.7% E 0,Pel 56% 56.0% +/-0.3% 54% Transmission Tr pel 52% Pellicle (in proximity to resist) Photoresist E 0 E 0 50% RWTH/ILT imec 11 = E 0,Pel Tr pel Over-all good agreement in transmission measurement result! Small difference is due to subtle difference in wavelength center of ML reflectivity (~0.3nm) in the different tools In both cases transmission of narrowband EUV (ML based) is analyzed with and without pellicle imec detector = photoresist RWTH detector = calibrated photodiode

12 Transmission uniformity measurements The target is 0.2% uniformity, but measured with what res olution? With several millimeters between mask and pellicle only micrometer scale fluctuations are of importance Ray-tracing 50µm mesh source pellicle detector d=10 mm d=180 mm I 0 d 12

13 Transmission uniformity measurements 0.5 mm reference opening Experimental setup Membrane holder fixed to the CCD camera Setup utilises high power EUV source from ILT and custom sample mount Page 13

14 Transmission uniformity measurements Intensity before pellicle Intensity after pellicle (normalized to reference beam) 50 Transmission[%] % band Position [mm] 1,00 Uniformity noise floor s=0.13% for the choosen data stack (10 pictures) CCD signal [counts] Transmission 0,75 0,50 0,25 Reference Membrane Transmission 0,5 0,4 0,3 0,2 0,1 Page Position [mm] 0, Position [mm] 0,0 3,80 3,82 3,84 3,86 3,88 3,90 Position [mm] Knife-edge resolution 48µm

15 Dynamic heat load Current target is 5.6 W/cm 2 for 250 W source (~0.9 W/cm 2 absorbed) For 1 kw source the power density on pellicle will exceed 22 W/cm 2 High power test tool in Aachen Currently using RI source, already providing 2W/cm 2 peak irradiance in 60µm spot Easily upgradable with ILT source, with peak irradiance exceeding 30W/cm 2 without design changes Page 15 *More at the poster P-RE-10

16 Pellicle reflectivity Normally ignored Can, however, for certain materials be in 0.5% range Governed by real part of the refractive index mask pellicle Example : Ru coated 13.5 nm ML mirror for 80 Metrology is already available, specifications? REFLECTVITY [ % ] 10 1 Page 16 0, GI-ANGLE [ ]

17 SUMMARY Current demands to actinic pellicle metrology can be fulfilled with laboratory tools Uniformity specifications should include required resolution of the transmission pellicle map Reflection specification? From actinic metrology point of view there should be no obstacles on the way to HVM introduction of the pellicles.