Asymmetric fluid-structure dynamics in nanoscale imprint lithography

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Chapter 3: Active Stage DesignThe practical development of the SFIL process requires that the baselayers are thin and uniform. An active stage machine is currently being designedand implemented to allow scientific studies of the imprinting process. Thismachine will have independent, high-resolution actuators and a feedback controlsystem to squeeze the etch barrier fluid prior to UV exposure. The requirementsand embodiment of such an active stage system are presented in this chapter.3.1 OPTIMIZING BASE LAYER THICKNESS, ORIENTATION ALIGNMENT,AND THROUGHPUTThe ideal imprint process would lead to an etch barrier with a zero base layerthickness. However, a zero base layer thickness cannot be obtained in finite timewith finite pressure. From the analysis in chapter 2, it can be seen that for a finitepressure an infinite time is required to obtain a zero base layer thickness.Experimental results from the multi-imprint machine support this theoreticalresult in that base layers below 100 nm have been very difficult to achieve. Inreality, there is a tradeoff between throughput and base layer thickness since athinner base layer would require more time to achieve. If a base layer of uniformthickness and of the order of the imprinted features (typically 200 nm) isobtained, then a preliminary etching can eliminate the base layer without affectingthe fidelity of the imprinted features. Therefore, a base layer thickness in therange of 100 to 200 nm would provide an optimal solution to both throughputrequirements and imprinted feature fidelity.In the initial test beds for SFIL development, a coarse, micron-level precalibrationstage ensures that any initial orientation misalignment of the template41
orientation stages relative to the substrate is within the range of motion for thetemplate orientation stage to self-correct during the filling and squeezing process.In the multi-imprint stepper, there are no means to determine if the template andsubstrate are parallel during the imprint process, orientation correction is basedondesign of flexures that self-correct during the squeezing process. Base layerthickness is determined experimentally for various loading conditions andcontrolled by moving the template towards the wafer until a specified load ismeasured, which corresponds to the desired base layer thickness.The template orientation stages are passively, selectively compliant.These flexure stages have been implemented to minimize angular misalignmentbetween the template and wafer. The flexure stages provide the advantage ofhaving repeatable linear response through small displacements without generatingparticles. However, a problem with thick, wedge-shaped base layers remains as amajor challenge to SFIL research. Furthermore, the current process reliesheavily on force sensing to determine the film thickness during the filling andsqueezing process. There is not enough correlative data to determine absolutegap thickness and orientation information from force measurements. Therefore, itis highly desirable to be able to characterize the absolute base layer thickness inreal-time. An active stage design may be necessary to investigate solutions tothese challenges.3.2 ACTIVE STAGE COMPONENTSTo achieve a repeatable, uniform base layer thickness in the range of 100to 200 nm, it may be necessary to have an active stage to provide precise controlover the base layer thickness as well as orientation alignment between the42
Page 3 and 4: Asymmetric Fluid-StructureDynamics
Page 5 and 6: AcknowledgementsFirst of all, I wou
Page 7 and 8: Table of ContentsList of Tables ...
Page 9 and 10: 6.2.3 Control Software ............
Page 11 and 12: List of FiguresFigure 1.1 Optical m
Page 13 and 14: Figure 6.9 Force due to fluid press
Page 15 and 16: The exponential escalation in the c
Page 17 and 18: 1.2.1 Optical Lithography Process O
Page 19 and 20: patterns to the desired specificati
Page 21 and 22: 1.3 STEP AND FLASH IMPRINT LITHOGRA
Page 23 and 24: transferlayerwaferStep 1: Spin-coat
Page 25 and 26: the etch barrier fluid has an infin
Page 27 and 28: Researchers at the University of Te
Page 29 and 30: stage development. Design requireme
Page 31 and 32: minimum and maximum base layer thic
Page 33 and 34: square plate with fluid completely
Page 35 and 36: 7. The fluid is assumed incompressi
Page 37 and 38: ⎛ ∂ ⎞⎜τdz ⎟dxdy⎝+ τ
Page 39 and 40: where V 1 and V 2 correspond to U 1
Page 41 and 42: ddx⎛⎜h⎝3dp ⎞ ∂h⎟ = 12µ
Page 43 and 44: dhdtLzhθh αh βxx αx = 0 x βFig
Page 45 and 46: C2hhtanθ2 21= αxαxβxαxβ( ) (
Page 47 and 48: ⎛⎜ hD⎜⎝6C ⎞1tanθ⎟24µh
Page 49 and 50: at the plate edges. Freeland obtain
Page 51 and 52: For the case of 10 psi of pressure,
Page 53: are the same as the width of the tr
Page 57 and 58: Wafer ChuckAir SolenoidMounting Pla
Page 59 and 60: The one degree-of-freedom template
Page 61 and 62: Figure 3.7 Initial and final desire
Page 63 and 64: 7645321Figure 3.8 Active stage prot
Page 65 and 66: Chapter 4: Real-Time Gap Sensing Vi
Page 67 and 68: R( λ)( 4πnd/ λ)2 2 −2αd−αd
Page 69 and 70: Rate Monitoring and is adapted for
Page 71 and 72: 10090807060PSD504030201000 500 1000
Page 73 and 74: the multi-imprint and active stage
Page 75 and 76: 5.2.2 Composite Stiffness and Dampi
Page 77 and 78: ( )2πR−1.5clamping length of 1.5
Page 79 and 80: 65actuator height, micron432100 0.1
Page 81 and 82: time marching is required to minimi
Page 83 and 84: 5.4 SQUEEZE FILM DYNAMICS OF INCLIN
Page 85 and 86: force, lb504540353025201510500 0.05
Page 87 and 88: improve upon these results by tunin
Page 89 and 90: Again, Figure 5.12 shows that a bas
Page 91 and 92: optically flat quartz plate coated
Page 93 and 94: optic probe was illuminated with a
Page 95 and 96: Figure 6.3 Screenshot of control so
Page 97 and 98: 6.3 EXPERIMENTAL PROCEDUREExperimen
Page 99 and 100: film thickness, nm40003800360034003
Page 101 and 102: Figure 6.6 shows that the force due
Page 103 and 104: similar. In Figures 6.7 and 6.8, th
Page 105 and 106:
500045004000film thickness, nm35003
Page 107 and 108:
Figure 6.13 shows the force-time pl
Page 109 and 110:
⎛ n ⎞in the FFT that is not ind
Page 111 and 112:
when measuring thin layers in the r
Page 113 and 114:
is a major milestone. The next step
Page 115 and 116:
7.2.4 Control schemeThe ultimate go
Page 117 and 118:
Assuming the liquid perfectly wets
Page 119 and 120:
ase h (for a semi-circular notch,h
Page 121 and 122:
Chou, S. Y., P .R. Krauss, and P. J
Page 123 and 124:
Tripp, J. H. 1983. Surface roughnes
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Asymmetric fluid-structure dynamics in nanoscale imprint lithography

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