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Prevention of a Silicon Surface Staining During Silicon Dioxide Etching

IP.com Disclosure Number: IPCOM000093468D
Original Publication Date: 1967-Oct-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Wong, MC: AUTHOR

Abstract

A stain forms on the exposed silicon surfaces during the etching of the silicon dioxide passivation layer with a buffered hydrofluoric acid solution in a semiconductor device manufacturing process. Diffusion into the stained areas results in erratic PN junctions with irregularities or diffusion pipes. Silicon surfaces with high diffusion dopant concentrations, especially P-type, are more susceptible to staining. Semiconductor process yields are consequently reduced. The staining problem can be solved by preventing current flow, photon-induced or otherwise, between the front and back sides of the silicon wafer during the silicon dioxide etching step.

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Prevention of a Silicon Surface Staining During Silicon Dioxide Etching

A stain forms on the exposed silicon surfaces during the etching of the silicon dioxide passivation layer with a buffered hydrofluoric acid solution in a semiconductor device manufacturing process. Diffusion into the stained areas results in erratic PN junctions with irregularities or diffusion pipes. Silicon surfaces with high diffusion dopant concentrations, especially P-type, are more susceptible to staining. Semiconductor process yields are consequently reduced. The staining problem can be solved by preventing current flow, photon-induced or otherwise, between the front and back sides of the silicon wafer during the silicon dioxide etching step. The anodic current flow is minimized or substantially alleviated by either etching the silicon dioxide with the standard buffered hydrofluoric acid etch in absolute darkness or by masking all exposed silicon areas, which are otherwise in direct contact with the etchant, with a suitable wax or other acid resistant coating material. The masking material is conveniently removed by a solvent after the silicon dioxide etching step.

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