| 초록 |
Flexible memories are considered to be an essential component for fully flexible electronic systems, because of their fundamental role in massive data processing, information storage, and inter-device communication. Several researchers have studied flexible organic memories utilizing spin-coating, ink-jet printing, and roll-based processes. However, these memories have had inherent drawbacks, including insufficient performance, low durability, and difficult large-scale integration. Therefore, flexible inorganic memories are regarded as an attractive solution for advanced soft data-storage devices due to their excellent electrical properties, power efficiency, and reliability. In recent years, several innovative approaches have been proposed to transfer high-temperature processed inorganic memories from conventional rigid substrates to polymers. For instance, inorganic-based laser lift-off (ILLO), Ni stressor-based spalling, and direct wafer thinning methods have been reported, however, complicated processing steps such as excimer laser process, electroplating, and wet chemical etching has resulted in low productivity and cost inefficiency. Therefore, a novel method eliminating these issues has to be developed to enable the highly effective transfer of ultrathin inorganic materials. Here in, we report a Mo-based interfacial physical lift-off (IPLO) transfer method to realize flexible crossbar-structured PCM array employing one Schottky diode (SD, selection device) and one conductive filament PCM (CFPCM, storage node). A 32 × 32 parallel array of 1 SD-1 CFPCM for 1 kbit f-PRAM was fabricated on a Mo-based exfoliation layer, and subsequently transferred to a plastic substrate using the IPLO method. To understand the device exfoliation mechanism within competitive phases of the Mo layer, first-principles density-functional theory (DFT) calculations of enthalpies, phonon bands, and adhesive binding energies were performed under high uniaxial tensile strain. In addition, the energy barrier of the Mo phase transformation was computed to study the remaining Mo phase after the strain-induced exfoliation. The exfoliation phenomenon of the Mo-based IPLO was experimentally confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Finally, the f-PRAM was successfully realized using the IPLO transfer method, showing the excellent flexibility of the ultrathin inorganic memory. Reliable flexible memory operations including set/reset switching, RHRS/RLRS, endurance, and retention were confirmed for stable data-storage on a plastic substrate. |
