Bubble Memory Chip Research Articles

Fabrication of bubble memory chips

Investigations have been made on the fabrication of accurate and uniform T-bar circuits. Chrome masks are preferable to emulsion masks, and furthermore, a minimum exposure and intimate contact have been demonstrated to be necessary for accurate and uniform pattern imaging on the AZ1350 resist. A newly developed chemical etchant, a nitric acid-base solution without ferric chloride, can almost eliminate undercutting of permalloy elements. Application of spin-on-glass prior to Permalloy evaporation can result in excellent step coverage at the places where T-bar circuits overlap conductors. Large memory chips having a capacity of 16 × 103bits and a storage density of 105bits/cm2have successfully been fabricated.

An all-permalloy bubble memory with control functions based on drive-field operation

A small experimental bubble memory chip with the major-minor loop organization has been designed and tested under laboratory conditions. As distinct from the conventional current-controlled memories, the necessary functions are operated by a temporary change of rotation of the drive field. Using this method a design is possible for which in practice only one mask is needed. The transfer gates, used in the control elements, are discussed extensively as also are the generator- and annihilator-locks, which are necessary for chip selection. The specific properties of this memory are compared with those of a current-controlled memory.

1024 bit bubble memory chip

A 1024-bit bubble memory chip having a storage density of 1.5 × 106bits/in2has been designed, fabricated, and tested. The chip organization consists of two identical, independent, 512-bit major-minor-loop configurations. All device functions have been operated at the chip level at 500 kHz. The bubble chip has been mounted in a ceramic module assembly containing a sense amplifier chip, the in-plane field coils, and the permanent-magnet bias field. All device functions have been operated at the module level at 100 kHz, and the nonvolatility capability has been established.

Magnetic bubble memory chip design

The choice and organization of bubble-circuit functions in the design of a magnetic bubble mass memory chip are discussed with emphasis on factors such as circuit function compatibility and performance, circuit density, and processing simplicity. A specific major-minor organized chip design is described which uses rotating field driven propagation, $-sign transfer gates, all T-bar minor loops, a nucleate generator with chevron merging port, a chevron based replicator/ annihilator and a chevron guard rail expander detector. The overall operating characteristics of chips having 20 510 bits of storage capacity have been measured and a bias field margin of 12 Oe is typically obtained with a 25 Oe, 100 kHz rotating field.