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Microelectronics Processing Lithography

Microelectronics Processing Lithography. Photolithography. Photolithography is the sequence of activities needed for transfer a pre-designed pattern to the surface of a semiconductor wafer . The pattern can be registered on a mask, or supplied directly from a computer to a scanning

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Microelectronics Processing Lithography

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  1. Microelectronics Processing Lithography

  2. Photolithography Photolithography is the sequence of activities needed for transfer a pre-designed pattern to the surface of a semiconductor wafer. The pattern can be registered on a mask, or supplied directly from a computer to a scanning radiation source. Photoresist is a photo-sensitive resistant coating used to register an image on the desired surface

  3. Lithography Wafer printing process: • Light sources • Exposure techniques • Photoresist • Mask engineering Novel process • E-beam lithography

  4. The Image

  5. i-line (365 nm) g-line (435 nm) h-line (405 nm) Light Sources: The Hg Lamp

  6. Light Sources

  7. Wafer Exposure Systems

  8. Wafer Exposure Systems

  9. Optics: Basics of Diffraction

  10. Optics: Basics of Diffraction

  11. Optics: Basics of Diffraction

  12. Optics: Basics of Diffraction Assume a circular aperture of radius r0 We define a parameter u as u=(2/)r0sin The far field radiation pattern of the aperture I(u)  I(0) (J1(u)/u)2 J1(u) is the 1st Bessel Function

  13. Optics: Basics of Projection Systems

  14. Optics: Basics of Projection Systems Note that the aperture (or lens) diameter determines the value of 

  15. Optics: Basics of Projection Systems

  16. Rayleigh’s definition of resolution Resolved images Unresolved images Resolution

  17. Numerical Aperture

  18. Inmersion Lithography

  19. NA and Depth of Focus

  20. Depth of focus In-focus Out-of-focus Source: http://emalwww.engin.umich.edu/emal/courses/SEM_lectureCW/SEM_DepthofFocus.html

  21. Example of Depth of Field problem Need a DOF larger than 

  22. Modulation Transfer Function MTF is a function of feature size! MTF= (IMAX-IMIN)/(IMAX+IMIN)

  23. Contact and Proximity Printing(Fresnel diffraction)

  24. Contact and Proximity Printing(Fresnel diffraction)

  25. Contact and Proximity Printing(Fresnel diffraction) =365 nm

  26. Summary of Printing Systems

  27. Critical Dimension Control (Math work on the board)

  28. Photoresist (1)

  29. Photoresist (2)

  30. Photoresist (3) Novolac

  31. PAC Changed due to illumination

  32. (h) soluble on basic solution H2O

  33. Deep UV Resists

  34. Deep UV Resists

  35. Basic Properties of Resists Contrast:

  36. Basic Properties of Resists

  37. Non-ideal Exposure

  38. Critical MTF (CMTF) CMTF is the minimal MTF value of the optical system that results in a fully resolved pattern in the photoresist

  39. Other issues in Photoresist Exposure

  40. Other issues in Photoresist Exposure

  41. Spin-on photoresist t = thickness K = constant S= fraction of solids υ= viscosity ω= angular velocity R = radius Thickness of PR t=KS(/ω2R2)1/3

  42. Constructive interference Destructive interference Other issues in Photoresist Exposure

  43. Mask Engineering

  44. Mask Engineering: OPC With OPC Desired Mask Printed

  45. Mask Engineering: Phase shifting

  46. Optical lithography - Steps required for a pattern transfer (7) Photoresist removal

  47. Spin coat Pre-bake Substrate cleaning Develop Post exposure treatment Expose Plasma de-scum Etch Post bake Strip *Steps in dashed (pink) lines are not always used Flow chart of a typical resist process HMDS 900C 1400C

  48. Equipment (1)

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