448Chapter 710 nm26.5nm(a)Before repair△CD:-8.6%After repairACD:<2.5%Figure 7.40 (a)A dense line/space pattern etched into quartz material by e-beam-inducedprocessing produces an etching resolution of 10 nm.(b)Example of complicated10 nm x 500 nm defect on the mask.Upper left:SEM image before repair.Upper right:AIMS measurement predicting ACD of-8.6%.Lower left:Post-repair SEM image.Lowerright:The same AIMS measurement is performed,and the measured ACD is below 2.5%,indicating a successful repair(reprinted from Ref.130).There are two types of imaging systems:full-field systems and scanningsystems.Schematic diagrams of each imaging system type are shown inFig.7.45.Carl Zeiss SMT GmbH has been developing a full-field-type aerialimage measurement system(AIMS).134 AIMS consists of an incoherent EUVlight from a DPP source,three illumination mirrors,and three mirrors forEUV Mask and EUV Mask Metrology449Depthvs.Y-Aris(a)He*/30 keV(b)H2*/30 keV(c)H2"/15 keVDepth vs.Y-Axis(d)Ga'/15 kev(e)Electron/1 kevFigure 7.41 Trajectories of ions and electrons in the case where the ions and electrons areimplanted into Si bulk(reprinted from Ref.131).D Beam diameterC.:Spherical aberration coefficientRBeam radiusChromatic aberration coefficientM:MagnificationE Acceleration voltageRs:Source size△E:Energy spreada,Beam cone angleFigure 7.42 Typical structure of a GFIS and the FIB beam diameter equation(reprintedfrom Ref.131).imaging the mask pattern on the CCD.On the other hand,Samsung hasdeveloped a scanning EUV reflective microscope (SERM)in order to reducethe system development time and cost.35 A simple scanning system using acoherent source and the diffractive optics of a zone plate lens was applied.Aerial images obtained by these two methods are theoretically equivalent.36An aerial image from the SERM system at Samsung is shown inFig.7.46(b),37 where the phase defect printability on the wafer is well reproduced.A diffraction-limited spot in the scanning system was formed by focusingthe coherent EUV source generated by high-order harmonic generation,using azone plate lens designed and fabricated by CXRO.37 This tool was designed450Chapter 7With shrinkageWithout shrinkagefrom surrounding(c)Figure 7.43 TEM cross-sections of EUVL masks after ion implantation:(a)Hef/30 keV/2x 1015 ions/cm2;(b)Het/30 keV/2 x 1016 ions/cm2;(c)H2+/30 keV/2x 1016 ions/cm2(reprinted from Ref.131).TopSide←8.9nmTopSideQuartzQuartzFigure 7.44 SEM images of a MoSi film after one-line etching with the GFIS system(N2 beam,acceleration voltage=25 kV,probe current=0.1 pA)(reprinted from Ref.132).in 2012 to be used for reviewing defect printability at the 22-nm HP node and cannow be upgraded to use with a high-NA system,which is possible by simplychanging the zone plate and improving the EUV source power.Aerial imagesfrom AIMS are shown in Fig.7.47.The phase defect printability on the waferwas confirmed by an aerial image with a sub-100-nm-size pattern.1387.7 Mask Contamination Protection and Cleaning7.7.1 PellicleContamination during the lithography process is one of the critical issues to besolved for the application of EUVL technology to HVM.139 A pellicle is aphysical particle shield and protective film mounted above the patterned surface