Polymer memory and method of its fabrication

#Embodiments of the invention relate to ferroelectric memory, and more specifically to extending the useful life of a ferroelectric memory device by reducing the ferroelectric material degradation during fabrication and operation.

#Memory manufacturers are currently researching and developing the next generation of memory devices. One such development includes technology designed to replace current volatile and non-volatile memory technologies. Important elements of a successor include compactness, low price, low power operation, non-volatility, high density, fast read and write cycles, and long life.

#Current memory technology is predicted to survive into 45 nanometer process generations. This survival is in part based on, for example, exotic storage dielectric materials, cobalt and nickel source and drain regions, copper and low dielectric constant materials for the interconnect levels, and high dielectric constant materials for transistor gates. However, there will thereafter exist a need for new memory materials and technology, particularly for non-volatile memory.

#FIG. 1: illustration of a ferroelectric beta phase polyvinylidene fluoride (PVDF) molecule chain

#FIG. 2: illustration of a top view of a ferroelectric polymer memory device

#FIG. 3: illustration of a schematic cross section of a ferroelectric polymer memory device of an embodiment

#Embodiments of a polymer ferroelectric memory and method of fabrication are described. Reference will now be made in detail to a description of these embodiments as illustrated in the drawings. While the embodiments will be described in connection with these drawings, there is no intent to limit them to drawings disclosed herein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents within the spirit and scope of the described embodiments as defined by the accompanying claims.

#Simply stated, an embodiment of the invention is a polymer ferroelectric memory including an arrangement of layers and deposition process that together mitigate a myriad of functional and fabrication challenges. In particular, and among other features, the design of an embodiment reduces the degradation of the polymer memory due to the polymer's reaction with, and migration or diffusion of, adjacent metal electrode material. Further, the polymer memory of an embodiment is exposed to fewer high temperature or high energy processes that may damage the polymer. It also mitigates the need for additional dielectric layers adjacent to the metal electrodes that, among other detriments, contribute to the parasitic capacitance of the electrodes. The embodiment finally incorporates an immobilized catalyst to improve the adhesion between electrolessly plated electrodes and adjacent layers and particularly between the electrolessly plated electrodes and the ferroelectric polymer.

#As noted, a large portion of the historical research in ferroelectric memory device technology has centered on select crystalline materials such as PZT and SBT. More current trends, however, include utilizing polymer chains that exhibit ferroelectric properties. Polyvinylidene Fluoride (“PVDF”) is a fluoropolymer with alternating CH2 and CF2 groups for which the relative electron densities between the hydrogen and fluorine atoms create a net ionic dipole moment. FIG. 1 illustrates the ferroelectric beta phase PVDF 100, including a chain of carbon 110 and alternating and opposing hydrogen 120 and fluorine 130 pairs. A particular PVDF copolymer is polyvinylidene fluoride trifluoroethylene (“PVDF-TrFE”). The addition of the trifluoroethylene C2HF3 (essentially substituting a hydrogen with a fluorine versus PVDF) in the chain reduces the overall theoretical ionic dipole moment of a ferroelectric PVDF beta phase chain, but increases the likelihood of forming the ferroelectric PVDF beta phase versus the paraelectric PVDF alpha phase during crystallization. The crystalline PVDF-TrFE polymer is ferroelectric in that it can be given a remnant polarization that can be switched in a sufficiently high electric field (i.e., a coercive field). The polarization can be used to store a binary “0” state and a binary “1” state of a memory device fabricated therewith based on the orientation of the polarization.