Anisotropic liquid phase photochemical copper etch

Abstract

Abstract A copper substrate 30 is immersed in a liquid 34 (e.g. 0.1 molar concentration hydrochloric acid) and illuminated with collimated radiation 24 (e.g. collimated visible/ultraviolet radiation) produced by a radiation source 20 (e.g. a 200 Watt mercury xenon arc lamp). A window 26 which is substantially transparent to the collimated radiation 24 allows the radiated energy to reach the copper substrate 30. An etch mask 32 may be positioned between the radiation source 20 and the substrate 30 (preferably the mask is also in the liquid). The copper substrate 30 and liquid 34 may be maintained at a nominal temperature (e.g. 25 degrees C.). Without illumination, the copper is not appreciably etched by the liquid. Upon illumination the etch rate is substantially increased. A further aspect is the addition of a passivant (e.g. iodine) to the liquid which forms a substantially insoluble passivation layer 36 on the substrate which is removed or partially removed by the radiation 24. Sidewalls 40 are protected from the etchant by vertical passivation layers 42, further increasing the difference between the illuminated and unilluminated etch rates.

Inventors

• 👤 Monte A. Douglas

Bibliographic Details