Ion-implanted bubble circuit function design

Abstract

New transfer designs for 8-μm period bubble memory devices based on ion-implanted propagation patterns are reported. Also, replication in such devices is discussed for the first time. Characterizations are given in the form of plots of bias field versus pulse parameters. These characterizations were obtained on a minicomputer controlled wafer-probe test set. All results reported here were obtained at 40°C. The transfer-in gate transfers bubbles from the high points of a "roof-topped" major line to a standard minor loop turn. The current pulse through the hairpin gates holds the bubbles for approximately one-half of a rotating field cycle, until the ends of the minor loops become attractive. With a drive field of 40 Oe and transfer current of 55 mA, a bias field range of 20 Oe has been achieved with this design. Double transfer at the read line consists of transfer-out to major line cusps followed by a second "invert" pulse to transfer the bubbles on through the unimplanted region to a second roof-topped path. The data order, on the roof-topped side after the invert pulse, is that originally present on the write line. With 40-Oe rotating field, 20 Oe of bias field operating range was obtained for transfer-out with 70 mA of current. The invert-transfer function was achieved with 18 Oe of bias field operating range, using 85 mA of current. Up to 16 Oe margin range was obtained for the invert-replication function in the same gate, but with the current increased to 100 mA. The overlap for transfer-in, transfer-out, and invert-transfer was at least 12 Oe for drive fields between 38 to 50 Oe. A bidirectional transfer gate action was achieved by pulsing a conductor to trap bubbles in 3-μm spaces between the ends of the minor loops and similar bulges incorporated into the major loop propagate path. With currents as low as 35 mA, the gate transferred bubbles in both directions over the bias range common to the minor and major loops, which was 20 Oe with a 40-Oe rotating field.