| abstract |
An anisotropic liquid phase photochemical etch is performed by submersing a substrate 30 (e.g. copper) in a liquid 34 containing an etchant (e.g. hydrochloric acid) and a passivant (e.g. iodine), the passivant forming an insoluble passivation layer 36 (e.g. Cul) on the surface, preventing the etchant from etching the surface. The passivant and its concentration are chosen such that the passivation layer 36 has a solubility which is substantially increased when it is illuminated with radiation 38 (e.g. visible/ultraviolet light). Portions of the surface are then illuminated with radiation 38, whereby the passivation layer 36 is removed from those illuminated portions of the surface, allowing the etch to proceed there. Portions of the surface not illuminated are not etched, resulting in an anisotropic etch. Preferably, an etch mask 32 is used to create the unilluminated areas. This etch mask 32 may be formed on the surface or it may be interposed between the surface and the radiation source. |