MRAM write error categorization with QCKBD

A new test pattern, quadruplet checker board (QCKBD), is proposed which enables to evaluate magnetic crosstalk from the neighbor write lines. At first, some conventional test patterns changing the write points were applied to categorize magnetic random access memory (MRAM) write errors. But magnetic crosstalk from the neighbor write lines could not be isolated by these conventional tests since magnetic crosstalk error was caused when the neighbor cell is written. Whereas the QCKBD results from 4Kb test vehicles show that magnetic crosstalk restricts the write margin. By changing the cell structure in order to suppress magnetic crosstalk, the write margin is improved from 3.3 to 7.3