| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS-WeA |
| Session: | PSTD at AVS60: Looking Back and Moving Forward |
| Presenter: | M.A. Lieberman, University of California, Berkeley |
| Correspondent: | Click to Email |
Plasma processing is a crucial technology for fabricating trillions of nanometer-size transistors on a silicon wafer [1]. It evolved from humble beginnings in the early 1900's: the silver-coating of mirrors by physical sputtering in dc glow discharges. The late 1950's - early 1960's saw extensive studies of physical and reactive sputtering in capacitive rf reactors. Isotropic plasma etching, mainly for photoresist stripping, was developed in the late 1960's - early 1970's, and etching of many other important materials was demonstrated. Three key advances in the late 1970's made plasma processing technology indispensable: (a) the discovery of ion-enhanced (anisotropic) etching [2]; (b) the development of SiO2 etching with high SiO2/Si selectivity [3]; and (c) the controlled etching of passivating films, e.g., Al2O3 over Al [4]. Etching discharges evolved from a first generation of "low density" reactors capacitively driven by a single source, to a second generation of "high density" reactors having two power sources, such as ICP's (rf inductive-driven) and ECR's (microwave-driven), in order to control independently the ion flux and ion bombarding energy to the substrate. A third generation of "moderate density" reactors, driven capacitively by multiple frequency sources, is now used, and there is increasing use of pulsed discharges to further control processing characteristics. The inductive reactors were invented 129 years ago [5], while the ECR's and the pulsed technology emerged in the aftermath of World War II [6]. Amazing challenges lie ahead as scale-down of transistor critical dimensions proceeds.
Supported by the Department of Energy Office of Fusion Energy Science Contract DE-SC0001939; special thanks to J.W. Coburn.
[1] H. Abe, M. Yoneda and N. Fujiwara, "Developments of Plasma Etching Technology for Fabricating Semiconductor Devices," Jpn. J. Appl. Phys. 47, 1435 (2008).
[2] N. Hosokawa, R. Matsuzaki and T. Asamaki, "RF Sputter-Etching by Fluoro-Chloro-Hydrocarbon Gases," Jpn. J. Appl. Phys. Suppl. 2, Pt. 1, 435 (1974).
[3] R.A.H. Heinecke, "Control of Relative Etch Rates of SiO2 and Si in Plasma Etching," Solid State Electronics 18, 1146 (1975).
[4] S.I.J. Ingrey, H.J. Nentwich, and R.G. Poulsen, "Gaseous Plasma Etching of Al and Al2O3," USP 4,030,967 (filed 1976).
[5] W. Hittorf, "About the Conduction of Electricity Through Gases," Wiedemanns Ann. Phys. 21, 90 (1884).
[6] H. Margenau, F.L. McMillan Jr, I.H. Dearnley, C.S Pearsall and C.G. Montgomery, "Physical Processes in the Recovery of TR Tubes," Phys. Rev. 70, 349 (1946).