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Benefits of anti-fuse NVM in 28nm high-K metal gate

Posted: 28 Oct 2011 ?? ?Print Version ?Bookmark and Share

Keywords:high-K metal Gate? non-volatile memory? Anti-fuse? e-fuse?

Tampering using invasive techniques such as scanning electron microscope (SEM) passive voltage contrast likewise has difficulty isolating the anti-fuse bitcell within the crosspoint memory array. Furthermore, it is difficult using chemical etching or mechanical polishing to locate the anti-fuse oxide breakdown.

Storage capacity options
Because of its area scalability, Anti-fuse technology provides a wide variety of storage capacity options from a few kilobits all the way to several megabits. For applications requiring over 4kbits of storage, the anti-fuse solution is ideal because it simply adds storage bitcells without the associated overhead of adding a complete module of bitcells and control. Typically a small capacity memory module is dominated by overhead. Newer generation of anti-fuse memory architectures are providing storage capacities upward of 4 megabits of storage, sufficient for storing processor boot code securely and with the added advantaged of faster access compared to external NVM code storage. Furthermore, in applications where the contents of memory change infrequently, the OTP memory can function as MTP by storing new data in over-provisioned memory cells.

 anti-fuse technology

Figure: This cross section of a Kilopass 2T bitcell shows the uniqueness of the anti-fuse technology. To write data, an elevated voltage applied to the 2T cell causes a breakdown of the gate oxide shown in the green circle. The breakdown converts an open to a low-resistance path. The gate oxide breakdown is very difficult to detect with conventional reverse engineering methods and the technology, which requires no special processing, can scale with each new standard CMOS process generation.

Extended temperature range
Finally, with a wide operating temperature range anti-fuse technology provides the rugged operating characteristics needed for designs going into industrial applications. Anti-fuse has an operating temperature range between -40C and 125C. The ability of anti-fuse to operate at these temperature extremes provides designers building consumer electronics device a robust NVM storage solution.

Conclusion
The various commercially available embedded NVM technologies each have a set of applications that they serve well. At process geometries above 90nm, embedded flash provides high-density storage for applications with frequently changing data. Pseudo-flash OTP/MTP is appropriate at 90nm and above for apps that require a small to medium NVM with a limited write endurance. E-fuse is a cost-effective single foundry solution for applications that require a very small amount of OTP storage at process geometries above 40nm. For applications that require small to medium storage capacity but must scale below 90nm to the latest process geometry, anti-fuse OTP offers an optimum solution.

About the author
Andre Hassan is field marketing and applications director at Kilopass. He is an industry veteran with over 20 years of semiconductors and systems experience. Hassan brings a broad business experience in marketing, sales and operations, as well as depth in multiple engineering disciplines. Prior to Kilopass, he held senior management and engineering positions at Sigmatel, Monolithic System, S3, Sun Microsystems and Digital Equipment.

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