Anisotropic liquid phase photochemical copper etch
First Claim
1. A method to anisotropically etch copper, said method comprising:
- (a) submersing a surface of said copper in a liquid; and
(b) illuminating portions of said surface with radiation to produce illuminated areas andsubstantially unilluminated areas of said surface, wherein said illuminated areas are etched at a substantially greater rate than said unilluminated areas.
1 Assignment
0 Petitions
Accused Products
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° 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.
34 Citations
24 Claims
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1. A method to anisotropically etch copper, said method comprising:
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(a) submersing a surface of said copper in a liquid; and (b) illuminating portions of said surface with radiation to produce illuminated areas and substantially unilluminated areas of said surface, wherein said illuminated areas are etched at a substantially greater rate than said unilluminated areas. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method to etch copper on a VLSI semiconductor substrate, said method comprising submersing said copper in a liquid and illuminating said copper with radiation.
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23. A method to anisotropically etch copper on an integrated circuit, said method comprising:
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(a) submersing a surface of said copper in 0.1% molar concentration hydrochloric acid; and (b) illuminating portions of said surface with radiation, whereby said illuminated portions of said surface are etched at a substantially greater rate than the unilluminated portions of said surface. - View Dependent Claims (24)
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Specification