Static information storage and retrieval – Floating gate – Particular connection
Reexamination Certificate
2000-06-15
2001-11-06
Nelms, David (Department: 2818)
Static information storage and retrieval
Floating gate
Particular connection
C365S185010, C365S185040
Reexamination Certificate
active
06314023
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to the field of integrated circuits and more particularly to a mechanism and method for enabling redundancy and electrical identification using non-volatile programming elements.
RELATED ART
Semiconductor memory and microprocessor devices are typically fabricated with additional or redundant memory elements that can be selectively enabled for yield enhancement purposes. Typically, these redundant elements are enabled using conductive fuses that are selectively cut or otherwise severed with a high energy beam. Historically, such fuse elements have been implemented in polysilicon or aluminum. Processes for cutting polysilicon or aluminum are well developed.
As device speeds have increased, however, it has been necessary to replace conventional interconnect materials (i.e., aluminum) with more conductive materials, such as, for example, copper. Unfortunately, the replacement of aluminum interconnects with copper has resulted in the use of copper fuses in those devices with redundant elements. Conventional methods of cutting aluminum fuses are not typically sufficiently effective in cutting copper fuses.
It is theorized that the high energy beams that are efficient in destroying aluminum fuses may result in copper fuses that reform after the fuse disconnect operation resulting in an unwanted conductive path. This mechanism of copper re-fusing results in unreliable redundancy and electrical identification. Therefore, it would be desirable to implement a mechanism in process that would support electrical identification and redundancy, improve the efficiency of the redundancy mechanism, and without significantly increasing the size of the device (die), or the complexity of the processes to fabricate the device.
In addition, the use of metal fuses leaves exposed metal after the laser repair operation which may result in a long-term liability concern. Furthermore, copper or other metal fuse processes are typically not scalable with a reduction in process device sizes. Therefore, as a technology is reduced in size, the redundant elements occupy an increasingly large percentage of the device size. It would therefore be desirable if the implemented solution provided a scalable solution that scaled with the device technology. In addition, conventional methods of eliminating fuses may be incompatible with organic interleave dielectric because the heat generated by the fuse elimination process could undesirably alter the characteristics of the ILD.
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Auduong Gene N.
Motorola Inc.
Nelms David
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