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Proceedings Paper

Etch selectivity of a wet chemical formulation for premetal cleaning
Author(s): Jeremy W. Epton; Deborah L. Jarrett; Ian J. Doohan
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Paper Abstract

This paper examines the relative etching rates of doped and thermal silicon dioxide when using NSSL etchant, comprising of a mixture of ammonium fluoride, water and ammonium dihydrogen phosphate [(NH4)H2PO4] and investigates their dependence on both temperature and mixture composition. The possible reaction mechanism is discussed and compared with the known mechanism for standard buffered oxide etchants (BOE). The observed etch selectivity and mechanisms of BOE and NSSL are also compared with the behavior of a third chemical formulation, referred to as mixed oxide etchant, which comprises of ammonium fluoride (NH4F) solution, diammonium hydrogen phosphate [(NH4)2HPO4] and orthophosphoric acid (H3PO4). It is concluded that no major change in oxide selectivity is observed if either BOE or NSSL etchants are used in the metal pre-clean process.

Paper Details

Date Published: 20 April 2001
PDF: 12 pages
Proc. SPIE 4405, Process and Equipment Control in Microelectronic Manufacturing II, (20 April 2001); doi: 10.1117/12.425245
Show Author Affiliations
Jeremy W. Epton, Rockwood Electronic Materials (United Kingdom)
Deborah L. Jarrett, Rockwood Electronic Materials (United Kingdom)
Ian J. Doohan, National Semiconductor Ltd. (United Kingdom)

Published in SPIE Proceedings Vol. 4405:
Process and Equipment Control in Microelectronic Manufacturing II
Martin Fallon, Editor(s)

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