AVS 46th International Symposium
    Nanometer-scale Science and Technology Division Friday Sessions
       Session MS+PS-FrM

Paper MS+PS-FrM1
Effect of CH@sub 3@F/C@sub 4@F@sub 8@ Ratio on the SiO@sub 2@-to-Si@sub 3@N@sub 4@ Selectivity in a Self-Aligned-Contact Etching Process for Giga-bit DRAM

Friday, October 29, 1999, 8:20 am, Room 611

Session: Diagnostics and Processes in Etching
Presenter: S.C. Park, Hyundai Electronics Industries Co. Ltd., Korea
Authors: S.C. Park, Hyundai Electronics Industries Co. Ltd., Korea
J.S. Kim, Hyundai Electronics Industries Co. Ltd., Korea
J.J. Lee, Hyundai Electronics Industries Co. Ltd., Korea
K.T. Kim, Hyundai Electronics Industries Co. Ltd., Korea
D.D. Lee, Hyundai Electronics Industries Co. Ltd., Korea
Y.S. Seol, Hyundai Electronics Industries Co. Ltd., Korea
I.H. Choi, Hyundai Electronics Industries Co. Ltd., Korea
Correspondent: Click to Email
Effect of CH@sub 3@F/C@sub 4@F@sub 8@ ratio on the SiO@sub 2@-to-Si@sub 3@N@sub 4@ selectivity in a self-aligned-contact(SAC) oxide etching process was investigated using an inductively coupled plasma. As published in other studies, the SiO@sub 2@-to-Si@sub 3@N@sub 4@ selectivity usually increases as the CH@sub 3@F/C@sub 4@F@sub 8@ ratio increases.@footnote 1@ However, we found out in this work that the selectivity gradually increases to a specific peak and sharply drops as the CH@sub 3@F/C@sub 4@F@sub 8@ ratio continuously increases. Moreover, the selectivity was extremely poor at the valleys between the word lines (and in some cases, the nitride layer was even 'punched through'), while the selectivity was very high at the top shoulder of word line at a certain CH@sub 3@F/C@sub 4@F@sub 8@ ratio. It was found from the XPS and SEM analysis that the fluorocarbon film was built up without any bonding state change, as the CH@sub 3@F/C@sub 4@F@sub 8@ ratio increased. The increase in the selectivity with increasing CH@sub 3@F/C@sub 4@F@sub 8@ ratio should be related with the amount of the fluorocarbon polymer deposition on the surface of Si@sub 3@N@sub 4@ barrier.@footnote 2@ However, the analysis of the fluorocarbon films could not completely explain the sharp drop in the selectivity and the extremely low selectivity at the valley between the word lines. Further studies showed that step coverage of the polymer film formed during the SAC oxide etching was very poor as the contact size decreased and the CH@sub 3@F/C@sub 4@F@sub 8@ ratio increased. In this case, less amount of the fluorocarbon gases should enter the contact hole and less amount of fluorocarbon polymer should be deposited on the Si@sub 3@N@sub 4@ etch barrier. This will eventually result in the sudden drop in the selectivity. @FootnoteText@ @footnote 1@ Y. Iijima and H. Okano, Jpn. J. Appl. Phys, Vol. 36, 5498 (1997) @footnote 2@ N.R. Rueger and G.S. Oehrlein, J. Vac. Sci. Technol. A 15, 1881 (1997