(A) study on the ferroelectricity after chemical treatment on the interface between bottom electrode TiN and HZO

Abstract

With the advent of the Big Data era, memory demand is expected to increase by five times within 10 years. Memory semiconductor integration, computing performance, power, and cost should be improved to store and utilize a large amount of data, but there are limitations of memory such as DRAM and NAND Flash that are currently commercially available, so new materials and various types of memory research are being conducted. Among them, memory research using ferroelectricity has recently been most widely conducted. Hafnium oxide is a material that is actively used in research such as FeFET, FeRAM, FeCap, etc. because it can be sizable compared to the existing PZT-based ferroelectric materials and is suitable for the CMOS process. In this paper, research was conducted using the MFM capacitor structure to improve ferroelectricity by applying chemical treatment to the interface between the lower titanium nitride electrode and the hafnium zirconium oxide. Based on chemical treatment methods such as HF, BOE, H2O2, and SC-1, ferroelectric changes according to MFM's current-electric field, capacitance-electric field, and polarization-electric field were compared. Interface energy was compared by DIW contact angle measurement. By GIXRD and FE-TEM analysis, crystal structure of halide zirconium oxide were analyzed and measurement was conducted by AFM analysis. Based on the analysis results, BOE is applied to remove some of the natural oxide film on the titanium nitride surface and make the surface hydrophilic, while creating a nitrogen-rich interface to even hafnium zirconium oxide crystal growth. After that, additional condition was selected that by applying SC-1 additionally, the roughness of the interface is intentionally degraded to increase the stress of the interface. And a method was selected that help hafnium zirconium oxide crystal growth by applying hydrogen peroxide to even out the titanium oxide layer. Through the above three methods, the amount of ferroelectricity improvement was compared for each condition by manufacturing 5 nm, 10 nm, and 15 nm and each cases by increasing wake up cycles. In conclusion, a BOE treatment method capable of improving ferroelectricity by 3.6 times compared to the conventional one at a thickness of 5 nm and a method of treating SC-1 after BOE were finally proposed.