Search

High-K Metal Gate (HKMG) is one of the most significant steps in CMOS manufacturing for 28nm node process and beyond. For Metal Gate step to be accurately controlled the Chemical-mechanical planarization (CMP) method is required for surface planarization. In Al-CMP, the control of metal residue defect and thickness uniformity were crucial to influence the device and yield performance. In this work, different slurry was investigated to control different pattern selectivity and within die uniformity. We found that, different selectivity slurry combined with different polish pad and disk have different effect in within die uniformity. With the same pad disk, for Al/Poly selectivity, slurry A was the twice of slurry B, and Al/Oxide selectivity didn't change at the same time. As a result, poly thickness was improved by 7% when gate height meet target, and over polish risk can be reduced. With another Pad/disk, poly thickness can be improved by 10% when Al residue was all removed clear. Besides, chemical rinse treatment were also investigated to remove Al residue..

The plateau-plateau transition in the integer quantum Hall effect is studied in three Hall bars with different widths. The slopes of the Hall resistance as a function of magnetic field follow the scaling power law as expected in the plateau-plateau transition, and saturate at the low temperature limit. Surprisingly, the saturation temperature is irrelevant with the Hall bar size, which suggests that the saturation of the coherence length is intrinsic.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have a range of unique physics properties and could be used in the development of electronics, photonics, spintronics and quantum computing devices. The mechanical exfoliation technique of micro-size TMD flakes has attracted particular interest due to its simplicity and cost effectiveness. However, for most applications, large area and high quality films are preferred. Furthermore, when the thickness of crystalline films is down to the 2D limit (monolayer), exotic properties can be expected due to the quantum confinement and symmetry breaking. In this paper, we have successfully prepared macro-size atomically flat monolayer NbSe2 films on bilayer graphene terminated surface of 6H-SiC(0001) substrates by molecular beam epitaxy (MBE) method. The films exhibit an onset superconducting critical transition temperature above 6 K, 2 times higher than that of mechanical exfoliated NbSe2 flakes. Simultaneously, the transport measurements at high magnetic fields reveal that the parallel characteristic field Bc// is at least 4.5 times higher than the paramagnetic limiting field, consistent with Zeeman-protected Ising superconductivity mechanism. Besides, by ultralow temperature electrical transport measurements, the monolayer NbSe2 film shows the signature of quantum Griffiths singularity when approaching the zero-temperature quantum critical point.

Superconductor-insulator/metal transition (SIT/SMT) represents a prototype of quantum phase transition, where quantum fluctuation plays a dominant role and dramatically changes the physical properties of low-dimensional superconducting systems. Recent observation of quantum Griffiths singularity (QGS) offers an essential perspective to understand the subtleties of quantum phase transition in two-dimensional superconductors. Here we study the magnetic field induced SMT in ultrathin crystalline Pb films down to ultralow temperatures. The divergent critical exponent is observed when approaching zero temperature quantum critical point, indicating QGS. Distinctively, the anomalous phase boundary of SMT that the onset critical field decreases with decreasing temperatures in low temperature regime distinguishes our observation from previous reports of QGS in various two-dimensional superconductors. We demonstrate that the anomalous phase boundary originates from the superconducting fluctuations in ultrathin Pb films with pronounced spin-orbit interaction. Our findings reveal a novel aspect of QGS of SMT in two-dimensional superconductors with anomalous phase boundary., Evidence of quantum phase transitions is normally difficult to be detected. Here, Liu and Wang et al. report divergent critical exponent in ultrathin Pb films with superconducting fluctuations and spin-orbit interaction, indicating an anomalous quantum Griffiths singularity of superconductor-metal transition.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have a range of unique physics properties and could be used in the development of electronics, photonics, spintronics, and quantum computing devices. The mechanical exfoliation technique of microsize TMD flakes has attracted particular interest due to its simplicity and cost effectiveness. However, for most applications, large-area and high-quality films are preferred. Furthermore, when the thickness of crystalline films is down to the 2D limit (monolayer), exotic properties can be expected due to the quantum confinement and symmetry breaking. In this paper, we have successfully prepared macro-size atomically flat monolayer NbSe

Some theories predict that the filling factor 5/2 fractional quantum Hall state can exhibit non-Abelian statistics, which makes it a candidate for fault-tolerant topological quantum computation. Although the non-Abelian Pfaffian state and its particle-hole conjugate, the anti-Pfaffian state, are the most plausible wave functions for the 5/2 state, there are a number of alternatives with either Abelian or non-Abelian statistics. Recent experiments suggest that the tunneling exponents are more consistent with an Abelian state rather than a non-Abelian state. Here, we present edge-current-tunneling experiments in geometrically confined quantum point contacts, which indicate that Abelian and non-Abelian states compete at filling factor 5/2. Our results are consistent with a transition from an Abelian state to a non-Abelian state in a single quantum point contact when the confinement is tuned. Our observation suggests that there is an intrinsic non-Abelian 5/2 ground state, but that the appropriate confinement is necessary to maintain it. This observation is important not only for understanding the physics of the 5/2 state, but also for the design of future topological quantum computation devices.

The behavior of phase coherence is studied in two-dimensional hole gas through the integer quantum Hall plateau-to-plateau transition. From the plateau transition as a function of temperature, scaling properties of multiple transitions are analyzed. Our results are in good agreement with the assumption of the zero-point fluctuations of the coherent holes, and support the intrinsic saturation of the coherence time at low temperature limit. The critical exponent $p$ can also be determined under the scheme of the zero-point fluctuations. The similarity and difference in experimental observations between quantum Griffiths singularity and plateau transition is discussed. The spin-orbit coupling effect's influence on the plateau transition is explored by comparing the results from different transitions.