Selective chemical etching in microelectronics fabrication
US5800726A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 26, 1995 |
| Grant date | Sep 1, 1998 |
| Priority date | — |
| Expiry date | Jul 26, 2015 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC23F1/30
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
The present invention relates to a chemical etchant for etching metals in the presence of one or more metals not to be etched, the etchant comprising 10-25 gms EDTA, 15-35 gms K.sub.2 HPO.sub.4 and 25-45 gms oxalic acid in a liter of 30% H.sub.2 O.sub.2. More particularly, in the fabrication of interconnections for microchip structures, the present invention addresses the removal of intermediate adherent layers, e.g., Ti--W, without damaging other microchip structures made of other metals, such as Al or Al--Cu test pads; Cu and phased Cr--Cu layers; and Sn--Pb solder bumps. The use of potassium phosphate in the hydrogen peroxide+EDTA bath has been found to significantly reduce the attack on the metal not to be etched. Furthermore, the use of oxalic acid in the bath prevented the deposition of tin oxide on the substrate adherent layer metal, thus facilitating its complete removal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.