Fabrication of moly masks by electroetching
First Claim
1. A method of etching a molybdenum foil having a mask area, the method comprising the steps of:
- placing a masking pattern onto the mask area of the molybdenum foil, the masking pattern including bare regions and coated regions;
disposing a cathode at a fixed inter-electrode distance from the mask area;
filling a space between the mask area and the cathode with a liquid electrolyte comprising a 2M-5M aqueous solution of sodium nitrate;
inducing the electrolyte to flow over the mask area;
providing a relatively positive voltage to the molybdenum foil and a relatively negative voltage to the cathode, such that the molybdenum foil is electroetched in the bare regions; and
maintaining the relatively positive molybdenum foil voltage and the relatively negative cathode voltage until the molybdenum foil is etched through to provide openings.
1 Assignment
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Accused Products
Abstract
Masks for microelectronics technology are fabricated by electrochemical etching. Molybdenum sheet or foil is masked with patterned photoresist on one side, and a mating, mirror-image pattern of photoresist is applied on the other side of the foil in exact registration with the first pattern. The foil is immersed in electrolyte (an aqueous solution of sodium nitrate, sodium hydroxide, thiourea, and surfactant) along with nickel anode plates held parallel to the foil surfaces 1-3 cm away. The anode plate is made slightly smaller than the mask area of the foil. When voltage is applied across the cell, the foil is etched through to form vias. The electrolyte is pumped across the surface of the foil and uniform flow velocity over the foil surface is achieved.
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Citations
24 Claims
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1. A method of etching a molybdenum foil having a mask area, the method comprising the steps of:
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placing a masking pattern onto the mask area of the molybdenum foil, the masking pattern including bare regions and coated regions; disposing a cathode at a fixed inter-electrode distance from the mask area; filling a space between the mask area and the cathode with a liquid electrolyte comprising a 2M-5M aqueous solution of sodium nitrate; inducing the electrolyte to flow over the mask area; providing a relatively positive voltage to the molybdenum foil and a relatively negative voltage to the cathode, such that the molybdenum foil is electroetched in the bare regions; and maintaining the relatively positive molybdenum foil voltage and the relatively negative cathode voltage until the molybdenum foil is etched through to provide openings. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus for electroetching molybdenum foil with a liquid electrolyte, the molybdenum foil having two surfaces, the apparatus comprising:
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a container for holding an electrolyte comprising a 2M-5M aqueous solution of sodium nitrate; a cathode disposed within the container and adapted to be immersed in the electrolyte; holding means for holding the molybdenum foil such that the molybdenum foil is disposed within the container and adapted to be immersed in the electrolyte; flow means for inducing electrolyte flow over the molybdenum foil; anode means for applying a relatively positive electrical voltage to the molybdenum foil; and cathode means for applying a relatively negative electrical voltage to the cathode. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A method of etching a metal foil, the foil having two sides together defining a mask area, the method comprising the steps of:
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placing a stationary photoresist mask pattern onto both sides of the mask area of the foil, the photoresist mask pattern including bare regions and coated regions; disposing a cathode on each side of said foil, each cathode at a fixed inter-electrode distance from the photoresist mask pattern; filling a space between the mask area and the cathode with a liquid electrolyte; inducing the electrolyte to flow over the mask area; providing a relatively positive voltage to the foil and a relatively negative voltage to the cathode, such that the foil is electroetched in the bare regions; and maintaining the relatively positive foil voltage and the relatively negative cathode voltage until the foil is etched through to provide openings. - View Dependent Claims (19, 20, 21)
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22. An apparatus for electroetching a metal foil with a liquid electrolyte, the foil having two surfaces, each surface having a stationary photoresist mask, the apparatus comprising:
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a container for holding the electrolyte; two cathodes disposed within the container and adapted to be immersed in the electrolyte; holding means for holding the foil such that the foil is disposed between the two cathodes and adapted to be immersed in the electrolyte; flow means for inducing the electrolyte to flow over the foil; anode means for applying a relatively positive electrical voltage to the foil; and cathode means for applying a relatively negative electrical voltage to the cathode.
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23. A method of etching a metal foil, the foil having a mask area, the method comprising the steps of:
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placing a masking pattern onto the mask area of the foil, the masking pattern including bare regions and coated regions; disposing a cathode at a fixed inter-electrode distance from the mask area; filling a space between the mask area and the cathode with a liquid electrolyte; inducing the electrolyte to flow over the mask area; assuring a substantially uniform electrolyte flow using an hydraulic resistance element; providing a relatively positive voltage to the foil and a relatively negative voltage to the cathode, such that the foil is electroetched in the bare regions; and maintaining the relatively positive foil voltage and the relatively negative cathode voltage until the foil is etched through to provide openings.
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24. An apparatus for electroetching metal foil with a liquid electrolyte, the foil having two surfaces, the apparatus comprising:
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a container for holding an electrolyte; a cathode disposed within the container and adapted to be immersed in the electrolyte; holding means for holding the foil such that the foil is disposed within the container and adapted to be immersed in the electrolyte; flow means which includes all hydraulic resistance element providing a substantially uniform electrolyte flow over the mask area of the foil; anode means for applying a relatively positive electrical voltage to the foil; and cathode means for applying a relatively negative electrical voltage to the cathode.
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Specification