Abstract
In this work, bulk Fin field-effect transistors (FinFET) aluminum nanocrystals (Al NCs) flash memory was proposed. It integrates UV-nanoimprint lithography (UV-NIL) for Si fin and gate length patterning, HSQ for isolation, microwave annealing (MWA) for source/drain (S/D) activation, and Al-based memory stacked layer. Al nanowire (NW) and Si fin fabricated by UV-NIL with HSQ stamps is developed. First, in order to pattern the high AR HSQ stamp on ITO/glass substrate, a low e-beam dose exposure combined with heat treatment is used for increasing SiO cross-linking density of HSQ films and enhancing the hardness of HSQ stamp. The antiadhesive layer coated HSQ stamp can be applied for UV-NIL with UV-curable photoresist layer (PAK). UV-NIL with low pressure at room temperature can make the imprinted pattern good replication fidelity with HSQ stamps. After UV-NIL, the patterned PR can be utilized to conducted lift-off or etching process. High aspect ratio of 2.5 with width of 46 nm and width:spacing=1:1 HSQ stamps can be obtained. The Al-base memory structure of Al2O3/Al-rich AlOxNy/AlN/SiO2/n-Si were deposited by rapid thermal processing metal organic chemical vapor deposition (RTP-MOCVD) method. The composition of Al2O3/Al-rich AlOxNy/AlN stacked layers were produced continuously without breaking vacuum by modulating the flow rate of trimethylaluminum (TMA) and ammonia (NH3) and deposition temperature. Furthermore, the Al-rich AlOxNy matrix was deposited at various temperatures to adjust the stoichiometry of AlOxNy to reduce trapped state generation during the stress cycling for good electrical performance. The P/E speed, retention time, and endurance cycling of memory devices were also investigated.We also performed low temperature MWA experiments with different anneal power and time to study the boron dopant profiles and the activation in Si fin. First, in order to characterize atomic and carrier profiles in Si p-n junctions, the secondary ion mass spectroscopy (SIMS) measurement is used to derive atomic concentration data. Further, the selective etching method by using HF-HNO3-CH3COOH (HNA) solution is used to obtain the activated dopant profile. The etching thickness is measured by atomic force microscope (AFM). So, the calibration of the etch rate of p-Si thickness as a function of the carrier concentration is established. The junction depth and the activated dopant profile can be obtained. Comparing with the SIMS data and activated dopant profile, the electrical activity can be found. Further, in order to investigate the electrical properties of Si fin NWs after BF2 implantation and MWA, the transfer length method (TLM) analysis was also employed to obtain the contact resistivity between Al/Ni metal and Si fin and resistivity of Si fin. For FinFET isolation between gate and Si substrate, the flowable oxide of HSQ is used by simple spin-coated method followed by step-like heating to remove solvent and change the molecular structure to SiO2-like material. During step heating process, the HSQ would fill in the trench between Si fins without the chemical mechanical polishing (CMP) process.Finally, the UV-NIL for Si fin and gate length patterning, HSQ for isolation, microwave annealing for S/D activation were integrated with gate-last method to fabricate bulk FinFET device. The Al-NC memory stacked layer of Al2O3(10 nm)/Al-rich AlOxNy(8 nm)/AlN(3 nm)/SiO2(2 nm) were deposited by RTP-MOCVD system on 15 nm Si fin. The final bulk FinFET Al NCs flash memory can be fabricated. The electrical characteristics are also investigated and correlated to SEM and TEM analysis of the device.