Thin Film Processing with Ecr and Downstream Oxygen Plasmas


Downstream oxygen plasmas are used routinely to etch and strip resist materials in integrated circuit (IC) process sequences. Differences in the electrical damage incurred in thin (26 nm) silicon dioxide films on silicon due to the afterglow of rf and microwave oxygen plasmas appear to be due to higher energy VUV emission and to a greater density of positive ions in the case of rf excitation at downstream distances less than 35 cm. The high flux of oxygen ions in electron cyclotron resonance (ECR) plasmas also permits reasonable silicon oxidation rates at low temperature. Oxidation rates ofsilicon in ECR oxygen plasmas at temperatures between 250 and 450 C are comparable to those obtained for thermal oxidation in dry oxygen at temperatures above 850 C. Although oxidation rates are adequate under floating, anodic or cathodic bias conditions, only oxides grown under floating or anodic conditions display comparable chemical, physical and electrical properties to those of thermal oxides.

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The downstream plasma stripping and oxide damage results are from the M.S. thesis of Scott Bell (currently at AMD, Sunnyvale), and the ECR oxidation results are from the Ph.D. thesis of Dan Carl (currently at IBM, Burlington). Robert Porteous is gratefully acknowledged for assistance with the double probe measurements. The author is also grateful to Mike Lieberman (U.C. Berkeley) for collaboration on the ECR studies and John Davies and Janice McOmber (Branson/IPC) for many helpful discussions on the downstream plasma stripping studies. The ECR oxidation work was supported by National Science Foundation Grants No. ECS-8517363 and No. ENG-8710988, Department of Energy Grant No. DE-FG03-87ER13727, and a contract from IBM Corporation, General Technology Division, Burlington, VT. The downstream oxygen plasma studies were supported by Branson/IPC and the California State MICRO program.

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Hess, D.W. Thin Film Processing with Ecr and Downstream Oxygen Plasmas. MRS Online Proceedings Library 236, 191–198 (1991).

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