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Polymers Used in Microelectronics and MEMs

Polymers Used in Microelectronics and MEMs. An Introduction to Lithography. Integrated Circuits. Micro-electro-mechanical Devices (MEMS). Moore’s Law. Year Processor Transistor Minimum Name Count Feature size 1971 4004 2300 10 micron 1972 8008 3500 10 micron

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Polymers Used in Microelectronics and MEMs

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  1. Polymers Used in Microelectronicsand MEMs An Introduction to Lithography

  2. Integrated Circuits

  3. Micro-electro-mechanical Devices (MEMS)

  4. Moore’s Law Year Processor Transistor Minimum Name Count Feature size 1971 4004 2300 10 micron 1972 8008 3500 10 micron 1974 8080 6000 6 micron 1976 8085 6500 3 micron 1978 8086 29000 3 micron 1982 80286 134,000 1.5 micron 1985 80386 275,000 1.5 micron 1989 Intel486 1.2 million 1 micron 1993 Pentium 3.1 million 800 nanometer 1997 Pentium II 7.5 million 350 nanometer 1999 (Feb.) Pentium III 9.5 million 250 nanometer 1999 (Oct.) Pentium III 28 million 180 nanometer 2000 Pentium IV 42 million 130 nanometer Source: Intel

  5. Industry Road Map

  6. The Drivers in Microelectronics • Cost: more for less! • $1000 bought:16MB in 1993 1000MB in 2000 • A single transistor costs about the same as a single printed word in a local newspaper AMD Athlon chip Local Newspaper 22 million transistors 80 pages x 1600 words per page $200 $0.50 J. Phys. Org. Chem.2000, 13, 767.

  7. The Drivers in Microelectronics • Size • Wafer processing time independent of feature dimension • Printing smaller features or larger wafers allows a greater number of devices to be made in the same amount of time, improving manufacturing yields • Speed • Smaller feature sizes also improve computing speeds by decreasing the travel distance of electrical signals

  8. The Chip-making Process Example – A State-of-the-Art $5 Billion Fab Line Up to 20X 1 Time

  9. Semiconductor Manufacturing

  10. Photolithographic Process • Spin Coat • Expose • Bake • Develop Silicon Substrate • Etch • Strip Process can be repeated up to 30 times: Solvent Intensive!

  11. Imaging Process Handbook of Microlithography, Micromachining and Microfabrication v. 1, P. Rai-Choudhury, ed. SPIE Optical Engineering Press, 1997.

  12. Photolithographic Process Photoresist Substrate Coat Mask h Exposure Negative Positive Develop Etch Strip J. Phys. Org. Chem.2000, 13, 767.

  13. Important Properties of a Photoresist • Resist Thickness (etch resistance) • Solubility for deposition/development • Wettability • Lithographic performance • Sensitivity, contrast • Transparency(more important for 193 nm and beyond)

  14. Optics of Imaging Wavelength 365 nm 248 nm 193 nm 157 nm Notation i-line DUV 193 nm 157 nm mercury KrF ArF F2 excimer Source lamp excimer excimer laser laser laser Feature Size 365+ nm 500 - 100 nm130 - 70 nm* 90 - 45 nm* R = resolution = smallest feature size R   / NA •  is the wavelength of light • NA is the numerical aperture (a function of the optics) Magic!!!!! (aka phase shifting masks…)

  15. “Transitions” in Optical Lithography 365 nm

  16. G- and I-line Resists • Novolac resin • Base-soluble positive resist (TMAH) • Variety of structures and MW’s • Diazonapthaquinone (DNQ) • Photoactive compound (Wolfe Rearrangement) • Inhibits base-dissolution of novolac h -N2

  17. G- and I-line Resists novolacresin & photocatalysis products novolacresin & DNQ 1,000 — 100 — 10 — 1 — 0.1 — Dissolution Rate (nm/sec) novolacresin

  18. G- and I-line Resists • An “engineer’s approach” • Fast N2 outgassing can damage the resist film • Controlled by using a less-intense light source or a less sensitive resist • Wavelength limited resolution (350 nm) • Low contrast (competitive rates of dissolution)

  19. “Transitions” in Optical Lithography 365 nm 248 nm

  20. Evolution from I- and G-Line to 248 nm (DUV) • Demand increases for smaller features:R   / NA • Diazoquinone novolac photoresists lacked sensitivity at 248 nm • Introduced at 0.365 micron (365 nm)

  21. Motivation for Chemical Amplification • Challenges Encountered: • First exposure tools for 248 nm had low output intensity • Need increased sensitivity to avoid use of extremely bright sources, which are expensive • Chemical amplification invented (Frechet, Willison and Ito) Exposure to photons initiates a chain reaction or promotes a cascade of reactions (500-1000) that changes resist solubility in exposed regions

  22. Chemical Amplification • DUV exposure generates catalytic amount of acid from a photoacid generator (PAG) • 1-2 min PEB to trigger deprotection • Catalytic chain length is extremely long • About 500 - 1000 carbonate cleavages per proton J. Phys. Org. Chem.2000, 13, 767. Acc. Chem Res.1994, 27, 150.

  23. Photoacid Generators (PAG) 2,6-Dinitrobenzyl tosylate New fluorinated PAGs

  24. Ionic PAG Mechanism Photolysis of diaryliodonium salts

  25. 2-Nitrobenzyl Ester PAG Mechanism o-Nitrobenzyl Rearrangement

  26. DUV Resists Extremely high contrast Initial resistance inmanufacturing setting Applicable at i-line with sensitizers Levinson, Harry J. Principles of Lithography. SPIE Press, 2001.

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