The electrical switching phenomenon of a phase change memory using nitrogen doped Sb₂Te₃

In order to increase the sheet resistance of Sb₂Te₃ (ST) thin fdms, nitrogen-doped Sb₂Te₃ (N-doped ST) thin films were deposited using DC magnetron sputtering. The nitrogen gas flow rate was changed from 0 seem (ST(O)) to 6 seem (ST(6)) during the deposition. The sheet resistances of N-doped ST films rapidly increased as the nitrogen gas flow rate increased. Phase-change random access memory (PRAM) test cells were fabricated using N-doped ST thin films. The threshold voltages of ST(O) and ST(6) PRAM test cells were 1.09 and 0.70 V, respectively. The mismatch problem of 1^st and 2^nd sweeping was hypothesized to be caused by poor adhesion and Te segregation between the ST film and TiN.