MEMS_07-08 guiren resolution enhancement_02

MEMS_07-08 guiren resolution enhancement_02 - Chapter 1...

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Chapter 1 Next generation lithographies and Nanofabrication
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Electromagnetics radiation From www.antonine-education.co.uk/physics_gcse
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Next generation lithographies (NGL) NGL (alternative to DUV photolithography) Extreme UV lithography (EUVL) X-ray lithography Charged particle beam lithography E-beam: Scattering with angular limitation projection lithography (SCALPEL) I-beam: Ion projection lithography (IPL) AFM lithography Nanoprinting Photolithography based on nonlinear optics etc
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Next generation lithographies (NGL) Difference in IC and MEMS: growing IC: Throughput, finer geometry are needed Batch process is a prerequisite MEMS: Modularity, high DOF, height of the feature, incorporating nontraditional materials, replication methods catch the spotlight Batch fabrication is not always a prerequisite Challenges High cost for alternative lithography Technical obstacle for smaller < 100 nm
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Extreme UV lithography (EUVL) Wavelength 10-140 nm Straight forward based on equ. 1.15 and 1.28 Easier operation Can achieve sub-100 nm feature while maintain DOF > 0.5 um Drawback: Strongly be absorbed by virtually all materials Imaging must be done in vacuum All camera optics and mask must be reflective rather than refractive New resist is required
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Extreme UV lithography (EUVL) EUV reflectivity Low reflectivity for near normal incidence at those short wavelength for most materials Multilayer Bragg reflectors with multiple reflecting coating is needed Advantages: No thin membranes are needed as in the case of x- ray lithography, just a solid substrate with required reflective coating and a patterned EUV absorber Due to 4:1 reduction, mask is easier to make Disadvantage: Defect density in the reflective coating need to be so small that there are few techniques available yet to accomplish such defect free films
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X-ray lithography Advantages: Shorter wavelength Large DOF Exposure time and development conditions are not stringent Immune to low-atomic-number (Z) particle contamination (dust) Diffraction effect are generally negligible if λ ~/< 1 nm Proximity mask can be used -> increase mask lifetime Line width decreases with proximity gap -> 150 nm High aspect ratio -> 100 High reproducibility since results are independent of Substrate type Surface reflections Wafer topography
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X-ray lithography Disadvantages: No image reduction -> 1:1 No many manufacturers High cost of sufficiently bright x-ray source Low sensitivity of resist Health? Comparison with others
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X-ray lithography: LIGA LIGA: Lithograpgie Galvanoformung, Abformung Invented ~ 25 ys Exploits all advantages of x-ray lithography Resist can be micrometers - centimeters