Non-volatile polymer memory for Si IC applications

Abstract

Polymer memory device has attracted great attention for their use in memory applications, due to its low material cost, ease of fabrication and most importantly, the ability to tune the polymer for different memory function. The bistable state of the polymeric materials opens up the field for the use of polymer in the memory applications. Under an electric bias, the sandwiched polymer device between two metal electrodes exhibited two conductivity states. In this thesis, a polymer material which based on the carbazole moiety hole transporting group has been synthesized and its physical and electrical properties were characterized. The polymer containing the carbazole group has demonstrated a write-once read-many-times memory behavior, due to the conformational change under an electric bias. The electrical behavior and its reliability have been demonstrated to be of practical use, and the conformational change that involved was supported by evidence from several material characterization tools. The basic structure of the carbazole containing polymer has been tuned to study the impact of the moiety side chain to its memory behavior. With the incorporating of a larger benzene group in the carbazole containing side chain, the memory behavior changed from that of a write-once read-many-times device to that of a dynamic volatile memory. The change in memory behavior is attributed to the restriction of the conformational change due to the larger benzene group and a greater steric hindrance. When an electron donating oxadiazole group is incorporated with the basic hole donating carbazole group, the donor-acceptor polymer exhibited a rewritable bistable memory behavior. Through the simulation studies and electrical characterization, the rewritable memory behavior is attributed to the charge transfer process between the donor and acceptor pair. After the successful studies on the polymer memory properties, the polymer crossbar memory array was fabricated and studied. Apassive matrix array, as compared to an active matrix, was used in this work for the advantages of simpler circuitry and greater device density. The passive diode-memory device was fabricated with a polymer based diode in series with the basic carbazole polymer exhibiting the WORM memory behavior. The passive device retained the electrical and reliability of the memory device, and in addition, provides a high rectification for the ON state device in the forward and reverse bias sweep. The rectifying memory device has the potential to open up the path for future high density passive matrix crossbar memory array.