Effects of smoothing on defect printability at extreme ultraviolet wavelengths

Cardinale, Gregory Frank; Ray-Chaudhuri, Avijit K.; Fisher, Aaron; Mangat, P.; Wasson, James R.; Mirkarimi, Paul B.; Gullikson, Eric M.

doi:10.1116/1.1324637

Cited by 8 publications

(6 citation statements)

References 12 publications

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“…We are also investigating other materials that might be capable of enhancing the defect smoothing approach. [23] More recently, a method for multilayer defect repair has been reported, and preliminary modeling and experimental results indicate the concept is feasible. [24] With the efforts in defect reduction during deposition in conjunction with the use of smoothing layers and methods of repairing buried defects, it seems possible that the industry need for defect free EUVL mask blank can be met.…”

Section: Defect Mitigationmentioning

confidence: 99%

EUVL masks: paving the path for commercialization

Mangat

Hector

2001

SPIE Proceedings

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Optical projection lithography has been the principal vehicle of semiconductor manufacturing for more than 20 years and is marching aggressively to satisfy the needs of semiconductor manufacturers for 100nm devices. However, the complexity of optical lithography continues to increase as wavelength reduction continues to 157nm. Extreme Ultraviolet Lithography (EUVL), with wavelength from 13-14 nm, is evolving as a leading next generation lithography option for semiconductor industry to stay on the path laid by Moore's Law.Masks are a critical part of the success of any technology and are considered to be high risk both for optical lithography and NGL technologies for sub-100nm lithography. Two key areas of EUV mask fabrication are reflective multilayer deposition and absorber patterning. In the case of reflective multilayers, delivering defect free multilayers for mask blanks is the biggest challenge. Defect mitigation is being explored as a possible option to smooth the multilayer defects in addition to optimization of the deposition process to reduce defect density. The mask patterning process needs focus on the defect-free absorber stack patterning process, mask cleaning, inspection and repair. In addition, there is considerable effort to understand by simulations, the defect printability, thermal and mechanical distortions, and nontelecentric illumination, to mention a few. To protect the finished mask from defects added during use, a removable pellicle strategy combined with thermophoretic protection during exposure is being developed. Recent migration to square form factor using low thermal expansion material (LTEM) is advantageous as historical developments in optical masks can be applied to EUV mask patterning. This paper addresses recent developments in the EUV mask patterning and highlights critical manufacturing process controls needed to fabricate defect-free full field masks with CD and image placement specifications for sub-70nm node lithography.No technology can be implemented without establishing the commercial infrastructure. The rising cost seems to be a major issue affecting the technology development. With respect to mask fabrication for commercial availability, a virtual mask shop analysis is presented that indicates that the process cost for EUVL masks are comparable to the high end optical mask with a reasonable yield. However, the cost for setting up a new mask facility is considerably high.

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Section: Defect Mitigationmentioning

confidence: 99%

EUVL masks: paving the path for commercialization

Mangat

Hector

2001

SPIE Proceedings

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“…Such EUV sources and corresponding beam steering optics are currently being developed with tremendous effort. [2][3][4][5][6][7][8][9][10][11][12][13] Besides semiconductor microlithography, there are also other applications of EUV radiation, which can strongly profit from the EUVL source and optics developments. For instance, Bonfigli et al demonstrated the generation of surfacenear color centers in LiF crystals positioned in the vicinity of a laser-produced EUV plasma.…”

Section: Introductionmentioning

confidence: 99%

Compact EUV source and Schwarzschild objective for modification and ablation of various materials

et al. 2007

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In recent years technological developments in the area of extreme ultraviolet lithography (EUVL) have experienced great improvements. So far, intense light sources based on discharge or laser plasmas, light guiding and imaging optics, as well as detection devices are already available. Currently, the application of EUV radiation apart from microlithography, such as metrology, high-resolution microscopy, or surface analysis comes more and more into focus. The aim is to make use of the strong interaction between soft x-ray radiation and matter for surface-near probing, modification or structuring techniques. In this contribution, we demonstrate the surface-near direct structuring of different polymeric materials as well as lithium fluoride crystals using EUV radiation with a wavelength of 13.5 nm. The setup consists of a table-top EUV source based on a laser-induced plasma and a modified Schwarzschild objective with a resolution down to 130 nm. The mirrors of the employed objective were coated with Mo/Si multilayers, providing a transmittance of around 42 % (reflectivity ~65 % @ 13.5 nm per mirror). With a demagnification factor of 10 small foci are generated, leading to spot diameters of 30 µm in plasma imaging mode and down to 1 µm in mask imaging mode, respectively. The EUV energy density of ~100 mJ/cm² obtained in the focus is sufficient to observe direct photo-etching of polymers, e.g. PMMA. Thus, material interaction studies are currently in progress. The investigations revealed already that in contrast to common excimer laser ablation there are no incubation pulses when using EUV radiation. For lower energies the ablation rate is found to be linear with respect to the applied dose, whereas for higher energies a saturation behavior is observed. By EUV irradiation of LiF samples surface-near defects within the crystal lattice are formed. These color-centers (mainly F 2 -and F 3 + -color centers) are known to be stable at room temperature. They are able to emit characteristic radiation in the visible range after optical excitation with a wavelength around 450 nm. In the future structured areas of such color centers could be used as laser-active gain medium in distributed feedback lasers. For measuring the radiation resistence of Mo/Si mirrors, the setup was used as a top-illuminated microscope at 13.5 nm. By placing the analyzing Mo/Si mirror into the image plane of the objective, the change in reflectivity due to irradiation at a fluence of 20mJ/cm 2 could be observed.

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“…Phase defects would change in line width in the printed image. [1][2][3][4][5][6][7] It has been reported that a phase defect with a surface bump of 2 nm height and full width at half maximum (FWHM) of 60 nm, which is a critical size for printable defects, causes an unacceptable line width change of 20 %, to 35 nm line (140 nm on the masks). 2,4 It is very important to closely inspect and reduce the phase defects with a small height.…”

Section: Introductionmentioning

confidence: 99%

“…Near-normal incident deposition and ion-assisted deposition techniques have been evaluated as a smoothing technique for the mitigation of phase defects in the multilayer. 1,4,6,[8][9][10][11][12][13][14] Recently, repair techniques for the phase and amplitude defects have been developed using focused ion beams (FIB) and electron beams (EB). 4,14 The smoothing technique and the repairing technique, however, have not yet been sufficient investigated for cross sectional multilayer stack image.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of programmed phase defects on EUV multilayer blanks

et al. 2003

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Programmed phase defects for EUV multilayer blanks were successfully fabricated in specified sizes and at known locations using a newly developed simple technique; depositing CrN film on a 6025 glass substrate or a Si wafer, generating CrN patterns of isolated lines and/or dots by EB lithography, and depositing Mo/Si multilayer of 40 bi-layers by ion beam sputtering over the CrN patterns. In this way, programmed bump defects were created on the multilayer surface over the CrN pattern.The programmed defects were observed by TEM and AFM, revealing behavior of the multilayer growth on the CrN patterns. The observed images show that height and full width at half maximum (FWHM) of the bump on the multilayer surface strongly depended on the CrN pattern, as well as on incident angle of the sputtered molecular flux to the substrate surface. The multilayer coating at near-normal incidence provides a significant amount of smoothing near the CrN patterns. A programmed phase defect of 1.7 nm in height and 60 nm in width was thus obtained on the multilayer surface using a dot pattern as the minimum size, which corresponded to a critical defect for EUV lithography at the 45 nm node. This paper describes a simple fabrication process of the programmed phase defects on EUV multilayer blanks, the evaluation results for the programmed phase defects, and growth behaviors of multilayer surface on top of various patterns (seed of the defects).

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Effects of smoothing on defect printability at extreme ultraviolet wavelengths

Cited by 8 publications

References 12 publications

EUVL masks: paving the path for commercialization

EUVL masks: paving the path for commercialization

Compact EUV source and Schwarzschild objective for modification and ablation of various materials

Fabrication of programmed phase defects on EUV multilayer blanks

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