EUV mask stack optimization for enhanced imaging performance

Setten, Eelco van; Oorschot, Dorothe; Man, Cheuk-Wah; Dusa, Mircea V.; Kruif, Robert de; Davydova, Natalia; Feenstra, Kees; Wagner, Christian; Spies, Petra; Wiese, N.; Waiblinger, M.

doi:10.1117/12.864247

Cited by 11 publications

(8 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Rigorous simulations show an increase (decrease) of the measured CD at wafer level for increasing (decreasing) absorber thickness, with embedded oscillations showing a period of about half the exposure wavelength 9 . This effect has also been confirmed experimentally via wafer print studies 10 . As a conclusion, a direct proportionality between CD and absorber thickness variation can be expected, which will affect the overall dependence of the shadowing effects on the absorber height across the scanner illumination field.…”

Section: Shadow Dependence On Absorber Heightmentioning

confidence: 58%

Scanner arc illumination and impact on EUV photomasks and scanner imaging

et al. 2014

View full text Add to dashboard Cite

The combination of a reflective photomask with the non-telecentric illumination and arc shaped slit of the EUV scanner introduces what are known as shadowing effects. The compensation of these effects requires proper biasing of the photomask to generate the intended image on the wafer. Thus, the physical pattern on the mask ends up being noticeably different from the desired pattern to be written on the wafer. This difference has a strong dependence on both the illumination settings and the features to be printed. In this work, the impact of shadowing effects from line and space patterns with a nominal CD of 16nm at wafer was investigated with particular focus on the influence of pattern orientation and pitch, illumination pupil shape and fill (coherence) and absorber height. CD, best focus shift and contrast at best focus are utilized in detail in order to study the impact of the shadowing effects. All the simulation cases presented employ a complete scanner arc emulation, i.e. describe the impact of the azimuthal angle component of the illumination arc as in the NXE:3300 scanner and as it can be emulated by the AIMS™ EUV.

show abstract

Section: Shadow Dependence On Absorber Heightmentioning

confidence: 58%

Scanner arc illumination and impact on EUV photomasks and scanner imaging

et al. 2014

View full text Add to dashboard Cite

show abstract

“…It was shown experimentally [1] that it impacts CDU of 27 nm dense lines with a sensitivity of about 1.8 nm / nm. This sensitivity can be reduced if the absorber height is chosen in a minimum or a maximum of CD swing curve [5], [2] .…”

Section: Figurementioning

confidence: 99%

“…The Absorber height is also important for Optical Proximity Correction (OPC). In particular, the wellknown shadowing effect [5], [10] is largely determined by the absorber height and optical absorber parameters. The shadowing effect increases with height of the absorber.…”

Section: Figurementioning

confidence: 99%

See 1 more Smart Citation

Experimental approach to EUV imaging enhancement by mask absorber height optimization

et al. 2013

Self Cite

View full text Add to dashboard Cite

EUV lithography performance is improved significantly by optimizing and fine-tuning of the EUV mask. The EUV mask is an active element of the scanner optical system influencing main lithographic figure of merits such as image contrast, critical dimension uniformity (CDU), focus and overlay. The mask stack consists of Mo/Si multilayer acting as a bright field and a patterned absorber stack. In this work we will concentrate on investigation of EUV absorber.Absorber topography that is pronounced compared to the imaging wavelength of 13.5 nm, will give rise to various mask 3d effects such as shadowing or dependence of CD on feature orientation, best focus shift of different resolution structures, etc. [1] [2] . Light interference in the absorber layer results in swinging behavior of various lithography metrics as function of the absorber height [5] . Optimization of the mask absorber allows mitigating mask 3d effects and improving imaging performance. In particular, reduction of the absorber height mitigates the shadowing effect and relaxes requirements on Optical Proximity Correction (OPC), but can result in smaller Process Window due to lower imaging contrast and larger best focus shifts.In this work we will show results of an experimental approach to absorber height optimization. A special mask with 27 different absorber heights in the range 40-70 nm is manufactured by Toppan Photomasks. EUV reflectivity spectra are measured for the different absorber heights and an experimental swing curve is constructed.For each absorber height various resolution features are present on the mask. Lines of 27 nm and 22 nm are imaged on the wafer using the ASML EUV scanner NXE:3300B with an NA of 0.33. The experimental CD swing curve is constructed as well as HV change as a function of absorber height. The impact of the absorber height on Exposure Latitude (EL) and Dose to Size (D2S) is investigated. EL improves with increasing absorber height in some cases, however there is no clear EL gain for a 70 nm absorber compared to for example 52 nm absorber. D2S does show a clear trend through absorber height. In particular, D2S can be reduced by absorber height reduction: e.g. for 52 nm absorber D2S is 5% or 1 mJ/cm 2 smaller compared to 70 nm.The experimental results are used for calibration and verification of rigorous mask 3d simulations. This knowledge is crucial for accurate OPC of production masks and allows for accurate litho simulations of EUV user cases as a basis for lithography roadmaps towards High Volume Manufacturing and High NA EUV.EUV absorber behavior is determined by phase shifts Reflectivity Swing Curve X 8% k 6% 4% 2% awrmiim mm 55 6.5 75 85 9.5 10.5 Ab orbe heieht,A /2n Light retardation in the matter 4 phase shift Substrate: LTEM EUV mask n -refraction index of absorber 46, 53, 60, 67.5, 75, 82 (for n = 0.95) 180° phase shift between bright field and dark field: A h 67.5 (for n=0.95) 1. Figure 1 Two types of phase shifts in EUV mask: (a) Interference between reflection at the top of the absorber and from the multil...

show abstract

“…[1] To achieve massproduction by using EUVL, lots of researches are in progress such as EUV source, defect control, roughness reduction and so on. [2][3][4][5][6][7] Especially, defect control is one of the biggest problems. [8][9][10] The usage of the extreme ultraviolet (EUV) pellicle is regarded as the solution for defect control.…”

Section: Introductionmentioning

confidence: 99%

Impact of deformed extreme-ultraviolet pellicle in terms of CD uniformity

Kim

Yeung

Barouch

et al. 2015

Photomask Japan 2015: Photomask and Next-Generation Lithography Mask Technology XXII

View full text Add to dashboard Cite

The usage of the extreme ultraviolet (EUV) pellicle is regarded as the solution for defect control since it can protect the mask from airborne debris. However some obstacles disrupt real-application of the pellicle such as structural weakness, thermal damage and so on. For these reasons, flawless fabrication of the pellicle is impossible. In this paper, we discuss the influence of deformed pellicle in terms of non-uniform intensity distribution and critical dimension (CD) uniformity. It was found that non-uniform intensity distribution is proportional to local tilt angle of pellicle and CD variation was linearly proportional to transmission difference. When we consider the 16 nm line and space pattern with dipole illumination (σc=0.8, σr=0.1, NA=0.33), the transmission difference (max-min) of 0.7 % causes 0.1 nm CD uniformity.Influence of gravity caused deflection to the aerial image is small enough to ignore. CD uniformity is less than 0.1 nm even for the current gap of 2 mm between mask and pellicle. However, heat caused EUV pellicle wrinkle might cause serious image distortion because a wrinkle of EUV pellicle causes a transmission loss variation as well as CD nonuniformity. In conclusion, local angle of a wrinkle, not a period or an amplitude of a wrinkle is a main factor to CD uniformity, and local angle of less than ~270 mrad is needed to achieve 0.1 nm CD uniformity with 16 nm L/S pattern.

show abstract

EUV mask stack optimization for enhanced imaging performance

Cited by 11 publications

References 9 publications

Scanner arc illumination and impact on EUV photomasks and scanner imaging

Scanner arc illumination and impact on EUV photomasks and scanner imaging

Experimental approach to EUV imaging enhancement by mask absorber height optimization

Impact of deformed extreme-ultraviolet pellicle in terms of CD uniformity

Contact Info

Product

Resources

About