ELECTROCHEMICAL COUPLING EFFECTS ON THE CORROSION OF SILICON SAMPLES IN HF SOLUTIONS

Citation
L. Torcheux et al., ELECTROCHEMICAL COUPLING EFFECTS ON THE CORROSION OF SILICON SAMPLES IN HF SOLUTIONS, Journal of the Electrochemical Society, 142(6), 1995, pp. 2037-2046
Citations number
30
Categorie Soggetti
Electrochemistry
ISSN journal
00134651
Volume
142
Issue
6
Year of publication
1995
Pages
2037 - 2046
Database
ISI
SICI code
0013-4651(1995)142:6<2037:ECEOTC>2.0.ZU;2-7
Abstract
Multilevel metallization commonly used in semiconductor manufacturing for VLSI and ULSI circuits production requires low defect densities. I n particular, we could observe in some circumstances, a new defect gen eration owing to a pitting corrosion of the polysilicon substrate duri ng wet processing. Polysilicon pitting corrosion has been investigated in hvdrofluoric solutions (DHF and BHF). The mechanism of corrosion c an proceed by two different modes. First, a purely electroless mechani sm can appear on a nearly homogeneous surface of silicon where a few s ites play the role of micro-cathodes; in that case, surface metallic c ontamination by metal impurities from hydrofluoric solutions is a sour ce of silicon corrosion. A study to characterize all intervening param eters is made using total reflectance x-ray fluorescence (TXRF). Secon d, a spontaneous difference of potential between Pt-Si plots and polys ilicon electrode enhances the short-circuit current. A procedure is de veloped to study this corrosion in relation to real conditions existin g during the wet process. This corrosion is analogous to the anodic di ssolution very near the thermodynamic equilibrium value; then, a very small defect on the structure results in a local variation of potentia l, favorable to pitting or intergranular corrosion. Such a mechanism, at a low value of the overpotential and low current density is known t o be responsible for a preferential etching on crystal lattice defects and leads to surface roughening and pinhole formation.