METHOD FOR EDGE-PLATING COUPLED FILM DEVICES

1,254,575. Electro-plating ferromagnetic films. INTERNATIONAL BUSINESS MACHINES CORP. June 5, 1969 [July 10, 1968), No.28517/69. Heading C7B. A ferromagnetic Ni-Fe alloy film is electroplated on conducting portions of a substrate surface immersed in an aqueous bath comprising 0.084- 0À211 mole/1 of Ni ions and 0À168-0À422 mole/l of Cl ions, e.g. added as NiCl 2 , 0.0054-0.0211 mole/l of Fe ions, e.g. added as FeSO 4 , optionally 0À0006-0À002 mole/l of Cu ions, e.g. added as CuSO 4 , 0À0248-0À0532 mole/l of tartrate ions, e.g. added as NaK tartrate, 0À1-0À3 g/l of saccharin (as 10% aqueous solution) and 0.3-0.6 g/l of a surfactant e.g. (Registered Trade Mark), "Triton" by passing a series of plating current pulses each depositing an alloy layer (e.g. 300 A thick with maximum coercivity 6) on the conducting portions. Up to 0À00362 mole/l of K 2 CO 3 may be dissolved in the bath. The pH of the bath is 3.9-5.8. Each current pulse may have a duration of 6 seconds with the bath being stirred for 4 seconds and subsequently left for 20 seconds between successive pulses. The invention is preferably applicable to edge plating bit lines on a multi-layered device to form a magnetic coupled film memory device, or plating cylindrical forms. The multi-layered device may be prepared by electro-plating a first smoothing Cu film on to a metal layer evaporated on to an insulating layer 3 on a ground plane 2 using a bath and method disclosed in Specification 1, 254, 577; electro-plating a first permalloy film 4 by the method disclosed in Specifications 1, 164, 670 or 1, 139, 987; electroplating a thick Cu film 5 by the method disclosed in Specification 1, 254, 576; electro-plating a second smoothing Cu film, then a second permalloy film 6; annealing the device at 200‹ C. in a magnetic field; photo-etching to form a set of bit lines 8 with resist resin 9 retained on top; then electro-plating the line edges with permalloy film 7 according to the invention.