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Reflecting Thermal Layer for Magnetic Bubble Devices

IP.com Disclosure Number: IPCOM000051887D
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Almasi, GS: AUTHOR

Abstract

Magnetic bubble chips often contain a continuous metallic film located between the garnet bubble domain film and the device pattern used to move the bubble. This metallic layer improves bubble visibility during device development and testing, and also provides better thermal distribution in packaged devices. An insulating layer, such as SiO(2), prevents electrical shorting of the control conductors by the underlying metal sheet. However, as bubble domains are scaled down in size, the SiO(2) thickness is also scaled down, and the number of pinholes and electrical shorts increases. Silicon can be a reflecting insulator, but reproducibility of its thickness and optical constants is a problem.

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Reflecting Thermal Layer for Magnetic Bubble Devices

Magnetic bubble chips often contain a continuous metallic film located between the garnet bubble domain film and the device pattern used to move the bubble. This metallic layer improves bubble visibility during device development and testing, and also provides better thermal distribution in packaged devices. An insulating layer, such as SiO(2), prevents electrical shorting of the control conductors by the underlying metal sheet. However, as bubble domains are scaled down in size, the SiO(2) thickness is also scaled down, and the number of pinholes and electrical shorts increases. Silicon can be a reflecting insulator, but reproducibility of its thickness and optical constants is a problem. In order to solve this problem, the sheet metallic layer is divided into a number of different segments, or tiles, which are separate from one another.

The structure is shown in the figure, where the reflective layer is comprised of a plurality of ""tiles'' 10 located over the bubble domain garnet film. Conductors 12 are the conductors associated with transfer gates 14. The circled regions, denoted A, B, C, and D, indicate regions where pinholes occur in the SiO(2) layer. The reflective tile pattern is approximately 500 angstroms thick.

The separations between tiles 10 are just enough to ensure good optical yield. For example, a 5-micron period bubble device might use 50-micron-wide tiles with 3-micron gaps. The alignment of...