Transcript Slide 1
Overview • Economic Impact of Plasma Processes used in Microelectronics • What is Plasma? • Manufacturing Computer Chips • Plasma Etching and Deposition • The Future: Energy and Nanotechnology Economic Impact • $227B: The 2005 global revenue of semiconductor chip producers. – e.g., Intel, AMD, Samsung,… FUNDAMENTALS OF SEMICONDUCTOR FABRICATION, May and Sze • About one-half of the procedures to make a chip require the use of plasmas. Other Uses of Plasma Lighting Plasma Television Source: www.plasmacoalition.org/publications.htm Biomedical E. coli Environmental Plasma: an ionized gas consisting of atoms, electrons, ions, molecules, molecular fragments, and electronically excited species (informal definition) www.geo.mtu.edu/weather/aurora/ www.plasmacoalition.org Plasma: the “fourth state of matter” plasma Temps > 10,000oK energy (electrons+ions) >99% of the matter in the universe gas (steam) solid (ice) energy energy liquid (water) Often, electrical energy is used to create a plasma - - + battery Simple Plasma Generation - adding energy to gas ”sputtering” - Argon + Mercury @ ~0.004 atm. + - A common fluorescent light contains around 10,000,000,000,000 electrons and ions - + +- - +- - - +- - - +- - + High Voltage - + - + Source: www.plasmacoalition.org This is also at the heart of high power gas lasers. Argon Electron (-) Argon ion (+) Microfabrication: Making Computer Chips Computer chips are made like a layered cake, but with the unwanted parts of each layer removed. To create the complex 3-dimensional structure, a sequence of adding a layer and etching away the unwanted parts is repeated many times – as shown next: Microfabrication: Starting with the Wafer Microfabrication: Plasma Deposition of Glass (SiO2) Microfabrication: Application of Photoresist (Film) Microfabrication: Gas Plasma Laser Patterning of Photoresist photomask Microfabrication: Developing the Photoresist Film (Etch Mask) Microfabrication: Plasma Etching of Glass Microfabrication: Etching of Photoresist (Ashing) Microfabrication: Deposition of Metal (Wires): Plasma Sputtering and Electroplating Microfabrication: Polishing Excess Metal (CMP) Microfabrication: Repeat this sequence: The first four layers Plasma Etching Equipment www.kostas.neu.edu Plasma Etching Vacuum Chamber Cl2 Chlorine Plasma Cl2 SiCl2 Cl+ SiCl2 Cl + High Voltage at Radio Frequency Plasma Etching Plasma Etching Wet Etching (in acid) Cl+ Cl wafer wafer negative voltage Si(s) + 2Cl(g)+ ion energy SiCl2(g) The directional ion energy drives the chemical reaction only at the bottom of the microscopic feature. In wet chemistry, the chemical reaction occurs on all surfaces at the same rate. Very small features can not be microfabricated since they eventually overlap each other. Scanning Electron Microscope Photographs of Plasma Etched Microstructures: 500 times smaller diameter than a hair Jason M. Blackburn, David P. Long, Albertina Cabañas, James J. Watkins Science 5 October 2001: Vol. 294. no. 5540, pp. 141 - 145 Plasma Deposition (of SiO2) Etching in Reverse SiH4 S O2 H2 SiHx O 2 H2+H2O H2O Plasma Deposition Equipment Source: S.A. Campbell (Oxford Press, 2001) The Future “Transistor Elements for 30nm Physical Gate Lengths and Beyond,” B. Doyle, et al. 20 atoms wide! http://developer.intel.com/technology/itj/index.htm Energy, Nanotechnology, and the Environment High-efficiency solar cells using silicon nanodots Low-cost solar cells http://www.me.umn.edu Low power microplasmas for hand-held toxic gas sensors Conclusion • Plasma, the fourth state of matter, plays a crucial role in the microelectronics industry Plasma enables us to create extremely small circuits Faster, smarter, and cheaper electronics • Plasma science and engineering help us understand how plasmas behave and allow us to harness the potential of plasma for new and exciting technologies Questions and Comments Coalition for Plasma Science www.plasmacoalition.org Speaker Contact Information: Jeffrey A. Hopwood Professor of Electrical and Computer Engineering Tufts University Medford, Massachusetts [email protected]