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Outline

Outline. Why Advanced Lithography? Advances in “Conventional Lithography” Light Source Phase Shift Immersion Lithography Double Expose Other Lithography methods NGL = New Generation Lithography EBL = E-Beam Lithography NIL = Nano-Imprint Lithography FIB = Focused Ion Beam Tools in MNFU.

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Outline

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  1. Outline • Why Advanced Lithography? • Advances in “Conventional Lithography” • Light Source • Phase Shift • Immersion Lithography • Double Expose • Other Lithography methods • NGL = New Generation Lithography • EBL = E-Beam Lithography • NIL = Nano-Imprint Lithography • FIB = Focused Ion Beam • Tools in MNFU Amit Zeidler

  2. Short History (not by date…) Amit Zeidler

  3. Advances in “Conventional Lithography” • Light Source • Phase Shift • Immersion Lithography • Double Expose Amit Zeidler

  4. Rayleigh’s definition of resolution Resolved images Unresolved images Advances in “Conventional Lithography” • Rayleigh’s definition of resolution Amit Zeidler

  5. Advances in “Conventional Lithography” • Light source • Hg lamp  i-line ( = 365 nm)  Minimum structure ~ 350 nm • Typical 100 to 300 mJ/cm2.  5 to 10 years of heavy use for Lens damage • DUV (KrF Laser)   = 248 nm  Minimum structure ~ 150 nm • Typical 5 to 20 mJ/cm2.  5 to 10 years of heavy use for Lens damage • 193 (ArF Laser)   = 193 nm  Minimum structure ~ 90 nm with immersion lithography: ~ 45 nm • Typical 10 to 40 mJ/cm2.  1 to 2 years of heavy use for Lens damage • “2 photons effect”  “milky glass”  reduction of transmission. • 157 (Laser)   = 157 nm • 2 to 3 months of heavy use for Lens damage • Lens becomes “consumable”, Lens costs 106 us$  Project failed. Amit Zeidler

  6. Advances in “Conventional Lithography” • Phase Shift • Was already used during the use of different Light sources • Drastically improved the resolution: • i-line ( = 365 nm)  Minimum structure ~ 200 nm • DUV ( = 248 nm)  Minimum structure ~ 110 nm • 193  Minimum structure ~ 90 nm Amit Zeidler

  7. Advances in “Conventional Lithography” Amit Zeidler

  8. Advances in “Conventional Lithography” Amit Zeidler

  9. Advances in “Conventional Lithography” • Double Expose • Resolution Limit is the pitch • Very expensive method: • Method: • Align & Expose odd lines • Develop and Etch • Align & Expose even lines • Develop and Etch • 2 times process • Alignment requirements are extremely high! • 193  Minimum structure ~ 45 nm Amit Zeidler

  10. Other Lithography methods • NGL = New Generation Lithography • EUV (Extreme UV,  ~ 10 to 50 nm) • There are teams in the world working on this option. • Glass is not transparent, Lenses are mirrors. • Requires vacuum chamber. • X-ray (Photons,  ~ 1 Å to 10 nm) • There are teams in the world working on this option. • There is no effective focusing lenses for X-Rays • Requires vacuum chamber. • E-Beam (Electrons,  ~ 0.1 Å) • A lot of experience in the industry (mask making) and in research. • Very slow process. • Requires vacuum chamber. • NIL • FIB (Ions,  << 0.1 Å) Amit Zeidler

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  13. Why Electron Beam? • General features of EBL • Advantages • Resolution depends on e-beam size, can reach ≤5nm • Diffraction is not limiting the resolution • Direct writing, no need for mask, easy to modify pattern and writing conditions • Disadvantages • Throughput is low –difficult expose large areas • Backscattered electrons affect exposition in radius of few microns- need for proximity correction • Application for charge-sensitive structures problematic Amit Zeidler

  14. “To be good in e-beam lithography means to be good in SEM imaging.” Short summary of SEM technology • Motivation Amit Zeidler

  15. Short summary of SEM technology • Principal sketch of e-beam writer Amit Zeidler

  16. Short summary of SEM technology • Lenses for electrons • Either magnetic or electrostatic fields can be used to focus electrons just as glass lenses are used to focus rays of light. Amit Zeidler

  17. Short summary of SEM technology • Beam blanker and Stigmator Stigmator Amit Zeidler

  18. Short summary of SEM technology • Focus / Stigmation / Other aberrations - + Focus Spherical aberration 0 Chromatic aberration Amit Zeidler

  19. Short summary of SEM technology • Focus / Stigmation Correction • Astigmatism in X • Astigmatism in Y • Bad Focus • Good image Amit Zeidler

  20. Short summary of SEM technology • Signal generation in excited volume Amit Zeidler

  21. Short summary of SEM technology • Higher voltage enables higher lithography resolution 10KV 25KV 50KV Amit Zeidler

  22. Some Process issues - Proximity 400nm 1.400nm 580nm 1.4µm PMMA on Si-substrate Amit Zeidler

  23. Some Process issues - Proximity trajectories energy deposition Double Gaussian energy distribution Important Note: It’s just a Model! energy deposition is not directly related to proximity effect But:proximity function has qualitatively the same shape asenergy distribution with respect to lateral distances Amit Zeidler

  24. for some material better fit for some material no good fit Some Process issues - Proximity standard proximity approach choice of prox. function depends on material and on resist contrast proximity approach withadditional exp.-function Amit Zeidler

  25. Some Process issues - Proximity • Results of EBL proximity Amit Zeidler

  26. E-Beam + Lithography What is EBL? Amit Zeidler

  27. What is EBL? • E-Beam • Just had a few slides about. • Lithography • Similar to optical lithography (OL) • There are positive and negative resists. • Some major differences: • Resists are sensitive to electrons and not to photons – different chemistry • One exception: SU-8 • EBL: Beam “Writing” vs. OL: uniform field illumination • EBL: Direct Writing from file vs. OL: Mask exposure • EBL: Effect of secondary electrons vs. OL: Effect of reflections – standing waves • EBL: Stage and Beam movement vs. OL: Stage movement • OL – Step and Scan: Mask moves in very high synchronization with stage Amit Zeidler

  28. EBL Methods • EBL Writing Strategies Amit Zeidler

  29. Some Process issues - Resist types • Resist contrast = Slope in resist * Raith GmbH, internal information ** http://www.nanophys.kth.se/nanophys/facilities/nfl/resists/ma-N240X-pdfs/ 13-MicroEngin_elsner.pdf *** Rishton et al., JVST B 5 (1), 1986, pp.135-41 Amit Zeidler

  30. Conventional lithography Third Dimension! Conventional lithography Some Examples • 18 nm line width • 3Dimensional Lithography (SU-8) Positive resist Amit Zeidler

  31. Currently Dutch Development Company: http://www.mapperlithography.com Amit Zeidler

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  37. FIB Amit Zeidler

  38. Tools in MNFU • FIB Amit Zeidler

  39. Tools in MNFU • I-Line Stepper Amit Zeidler

  40. Tools in MNFU • Writing Electron Microscope JSM-6400 Amit Zeidler

  41. Tools in MNFU • e-Line - Writing Electron Microscope of Raith Amit Zeidler

  42. Tools in MNFU • NIL • Not Yet but planned to be the next tool Amit Zeidler

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