A novel fabrication method for titania resistive switching device.

The titania showing reversible resistive switching are attractive for today's semiconductor technology in nonvolatile random-access memories. A novel fabrication method for titania resistive switching device with vertical structure is proposed. First, the Pt electrode was fabricated the bottom using conventional photolithography and chemical etching technique. Next, the titania thin films with the thickness about 50 nm was deposited on the bottom electrode by electron beam evaporation (EBE). Then, the trench of photoresist for electrode deposit was etched with mild chemical process to preserve the original structure of titania layer. After that, the platinum was deposited in the trench of photoresist using ion sputter. A final lift-off process to define the Pt top electrodes was performed with acetone in an ultrasonic bath to remove the resist. The resistive bistability was observed in this device. The on-threshold voltage is +1.5 V and the off-threshold voltage is -0.6 V. The resistance ratio between the two stable states of the device including Al electrode is approximately 1 x 10(3), the state is nonvolatile and the retention-time test performed over an hour in sweeping mode measurement. The results indicate the forming and rupture of conductive channel relate to the defects and distributing of oxygen vacancy. This method is low-cost, high-yielding, and easy to implement, which is applicable to the fabrication of nonvolatile memories.