Physical unclonable function for MRAM structures
AssigneeInternational Business Machines Corporation
InventorsRuilong Xie, Alexander Reznicek, Oscar van der Straten, Koichi Motoyama
Life of this patent
Estimating the term…
Abstract
An integrated circuit including a memory array and a physical unclonable function array is obtained by causing metal back sputtering in specific regions of the integrated circuit during ion beam etch. MRAM pillars within the memory array have larger widths than the underlying bottom electrodes while those within the physical unclonable function array have smaller widths than the underlying bottom electrodes. Metal residue deposited over tunnel barrier layers causes random electrical shorting of some of the MRAM pillars within the physical unclonable function array.
Claims20
A method of fabricating an MRAM structure including a physical unclonable function and a memory array, comprising:
- forming a stack comprising a magnetic tunnel junction and a top electrode layer over an interlevel dielectric layer comprising a plurality of bottom electrodes;
- and
- forming first and second arrays of MRAM pillars from the stack by subjecting the stack to etching, thereby:
- causing the MRAM pillars in the first array to have smaller widths than the bottom electrodes in a first region of the interlevel dielectric layer;
- causing electrical shorting of some of the MRAM pillars in the first array;
- and
- causing the MRAM pillars in the second array to have larger widths than the bottom electrodes in a second region of the interlevel dielectric layer.
An integrated circuit comprising:
- a first array of MRAM pillars comprising a first physical unclonable function, the MRAM pillars in the first array adjoining, respectively, a plurality of first bottom electrodes, the MRAM pillars in the first array having smaller widths than the first bottom electrodes;
- and
- a second array of MRAM pillars comprising a memory array, the MRAM pillars in the second array adjoining, respectively, a plurality of second bottom electrodes, the MRAM pillars in the second array having larger widths than the second bottom electrodes.
Dependencies are inferred from the claim text.