1. Page 1 NSF STC Polymers Used in Microelectronics and MEMs An Introduction to Lithography

2. Polymer Synthesis CHEM 421 Integrated Circuits

3. Polymer Synthesis CHEM 421 Micro-electro-mechanical Devices (MEMS)

4. Polymer Synthesis CHEM 421 Moore’s Law YearProcessorTransistorMinimum NameCountFeature size 19714004230010 micron 19728008350010 micron 1974808060006 micron 1976808565003 micron 19788086290003 micron 198280286134,0001.5 micron 198580386275,0001.5 micron 1989Intel4861.2 million1 micron 1993Pentium3.1 million800 nanometer 1997Pentium II7.5 million350 nanometer 1999 (Feb.)Pentium III9.5 million250 nanometer 1999 (Oct.)Pentium III28 million180 nanometer 2000Pentium IV42 million130 nanometer Source: Intel

5. Polymer Synthesis CHEM 421 Industry Road Map

6. Polymer Synthesis CHEM 421 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 chipLocal Newspaper 22 million transistors80 pages x 1600 words per page $200$0.50 J. Phys. Org. Chem. 2000, 13, 767.

7. Polymer Synthesis CHEM 421 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. Polymer Synthesis CHEM 421 Example – A State-of-the-Art $5 Billion Fab Line The Chip-making Process Up to 20X 1 Time

9. Polymer Synthesis CHEM 421 Semiconductor Manufacturing

10. Polymer Synthesis CHEM 421 Silicon Substrate Expose Strip Etch Develop Bake Spin Coat Process can be repeated up to 30 times: Solvent Intensive! Photolithographic Process

11. Polymer Synthesis CHEM 421 Imaging Process Handbook of Microlithography, Micromachining and Microfabrication v. 1, P. Rai-Choudhury, ed. SPIE Optical Engineering Press, 1997.

12. Polymer Synthesis CHEM 421 Photolithographic Process J. Phys. Org. Chem. 2000, 13, 767. Coat Exposure Develop Strip Etch Photoresist Substrate Mask h Positive Negative

13. Polymer Synthesis CHEM 421 Important Properties of a Photoresist Resist Thickness (etch resistance)Resist Thickness (etch resistance) Solubility for deposition/developmentSolubility for deposition/development WettabilityWettability Lithographic performanceLithographic performance –Sensitivity, contrast Transparency (more important for 193 nm and beyond)Transparency (more important for 193 nm and beyond)

14. Polymer Synthesis CHEM 421 Optics of Imaging 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…) Wavelength Wavelength 365 nm 248 nm 193 nm 157 nm Notation Notation i-line DUV 193 nm 157 nm Source mercury KrF ArF F 2 excimer Source lamp excimer excimer laser laser laser Feature Size Feature Size 365+ nm 500 - 100 nm 130 - 70 nm* 90 - 45 nm*

15. Polymer Synthesis CHEM 421 “Transitions” in Optical Lithography 365 nm

16. Polymer Synthesis CHEM 421 G- and I-line Resists Novolac resinNovolac resin –Base-soluble positive resist (TMAH) –Variety of structures and MW’s Diazonapthaquinone (DNQ)Diazonapthaquinone (DNQ) –Photoactive compound (Wolfe Rearrangement) –Inhibits base-dissolution of novolac h -N 2

17. Polymer Synthesis CHEM 421 G- and I-line Resists Dissolution Rate (nm/sec) 1,000 — 100 — 10 — 1 — 0.1 — novolac resin novolac resin & photocatalysis products novolac resin & DNQ

18. Polymer Synthesis CHEM 421 An “engineer’s approach”An “engineer’s approach” Fast N 2 outgassing can damage the resist filmFast N 2 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) G- and I-line Resists

19. Polymer Synthesis CHEM 421 “Transitions” in Optical Lithography 365 nm 248 nm

20. Polymer Synthesis CHEM 421 Evolution from I- and G-Line to 248 nm (DUV) Demand increases for smaller features:Demand increases for smaller features: R  / NA Diazoquinone novolac photoresists lacked sensitivity at 248 nmDiazoquinone novolac photoresists lacked sensitivity at 248 nm Introduced at 0.365 micron (365 nm)Introduced at 0.365 micron (365 nm)

21. Polymer Synthesis CHEM 421 Motivation for Chemical Amplification Challenges Encountered: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)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. Polymer Synthesis CHEM 421 Chemical Amplification DUV exposure generates catalytic amount of acid from a photoacid generator (PAG)DUV exposure generates catalytic amount of acid from a photoacid generator (PAG) 1-2 min PEB to trigger deprotection1-2 min PEB to trigger deprotection Catalytic chain length is extremely longCatalytic 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. Polymer Synthesis CHEM 421 Photoacid Generators (PAG) 2,6-Dinitrobenzyl tosylate New fluorinated PAGs

24. Polymer Synthesis CHEM 421 Ionic PAG Mechanism Photolysis of diaryliodonium salts

25. Polymer Synthesis CHEM 421 2-Nitrobenzyl Ester PAG Mechanism o-Nitrobenzyl Rearrangement

26. Polymer Synthesis CHEM 421 DUV Resists Levinson, Harry J. Principles of Lithography. SPIE Press, 2001. Extremely high contrast Initial resistance in manufacturing setting Applicable at i-line with sensitizers