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As DRAM process nodes keep shrinking, the overlay budget becomes tighter, and overlay error showing a more significant effect on yield. This calls for a more accurate and more robust on-product overlay (OPO) measurement approach. In many cases, engineers tune their process to improve yield, especially in the research and development (R&D) phase of a product, but overlay measurability is sensitive to process variation and the measurement window could drift or even disappear after process changes. In the method described in this paper, we use features on the Archer™ imaging-based overlay (IBO) measurement system - such as illumination with tunable wavelength (wave tuner, WT) to optimize illumination wavelength, and dynamic focus mode (DFM) to select best focus position - to produce a more accurate and robust OPO measurement on critical layers in advanced DRAM. With WT, the overlay target has better illumination conditions, resulting in residual improvement of ~60%, and more stable measurements from wafer to wafer and lot to lot. DFM improves measurement accuracy with a more accurate focus position. For products both in R&D and high-volume manufacturing (HVM) phases, WT and DFM are demonstrated to be critical knobs to improve measurability as a function of wavelength and focus position. These features allow further information, such as accuracy heatmaps, residual landscape maps, and focus offset maps to help the user identify key process variations.

In the latest 3D NAND devices there is a larger focus on measurement accuracy control, coupled with more traditional minimization of Total Measurement Uncertainty (TMU). Measurement inaccuracy consumes an increasingly significant part of the overlay (OVL) budget, requiring control and optimization. In this paper we will show the improvement in imaging OVL measurement accuracy using wave tuning (WT) capability combined with advanced algorithms to address 3D NAND process challenges. In addition to new OVL target designs that take advantage of WT capability, we also demonstrate improvement in OVL model residuals through optimization of measurement bandwidth, focus position and number of grab frames. Improvements in precision and tool-to-tool matching are also realized through both optimization of the region of interest (ROI) and splitting measurement areas using a dual-recipe technique.

Shrinking on-product overlay (OPO) budgets in advanced technology nodes require more accurate overlay measurement and better measurement robustness to process variability. Pupil-based accuracy flags have been introduced to the scatterometry-based overlay (SCOL) system to evaluate the performance of a SCOL measurement setup. Wavelength Homing is a new robustness feature enabled by the continuous tunability of advanced SCOL systems using a supercontinuum laser light source in combination with a flexible bandpass filter. Inline process monitoring using accuracy flags allows for detection, quantification and correction of shifts in the optimal measurement wavelength. This work demonstrates the benefit of Wavelength Homing in overcoming overlay inaccuracy caused by process changes and restoring the OPO and residual levels in the original recipe.

We propose a novel hybrid plasmonic polarization rotator based on mode interference. Operating at the telecommunication wavelength of 1.55 μm, the rotation length is very short (3.2 μm), while the polarization conversion efficiency is as high as 99.5%. The total device insertion loss is only 1.38 dB, much smaller than the common level of plasmonic devices. It also has potential to realize integrated waveplates for various polarization states.

An ultracompact and silicon-on-insulator-compatible polarization splitter (PS) is proposed by utilizing asymmetric directional coupling between a hybrid plasmonic waveguide and a strip dielectric waveguide. Owing to the plasmon-assisted asymmetry, birefringence is highly enhanced. Polarization splitting can be realized by strong coupling of one polarization while the other polarization is phase-mismatched. As an example, a PS based on strong TM coupling is demonstrated at the wavelength of 1.55 μm with a coupling length of 4.13 μm. Extinction ratios are 20.9 and 16.4 dB for TM and TE polarizations, respectively. The device is also broadband and fabrication-tolerant.

We report the first observation of near-infrared electroluminescence (EL) in ErYb silicate based metal–insulator–semiconductor (MIS) light-emitting device. The ErYb silicate thin film and the device were fabricated on silicon substrate using the standard silicon technology. The EL spectrum at 1.53 lm was observed under a current density of 1.2 mA/cm 2 . The conduction mechanism of the device was Fowler–Nordheim tunneling and the EL mechanism was attributed to the direct impact excitation of Er ions by the hot electrons produced by the high electric field in the silicate layer.

This study uses a dipole embedded in Al2O3 layer to excite a symmetric surface plasmon polariton (SPP) mode in Au/Al2O3/Au waveguide to investigate its profile properties by using finite-difference time-domain (FDTD) method. The excited dipole decay radiatively direct near-field coupling to SPP mode owing to thin Al2O3 layer of 100 nm. The effects of electric and magnetic field intensity profiles and decay length have been considered and characterized. It is found that dipole location is an important factor to influence the horizontal and vertical profile properties of symmetric SPP mode in Au/Al2O3/Au waveguide. The amplitudes of electric and magnetic field intensity and the wavelengths of metal-insulatormetal (MIM) SPP resonance mode can be tuned by varying dipole location. The horizontal and vertical decay lengths are 19 and 24 nm, respectively. It is expected that the Au/Al2O3/Au waveguide structure is very useful for the practical applications of designing a SPP source.

Polarization manipulation is essential in almost every photonic system ranging from telecommunications to bio-sensing to quantum information. This is traditionally achieved using bulk waveplates. With the developing trend of photonic systems towards integration and miniaturization, the need for an on-chip waveguide type waveplate becomes extremely urgent. However, this is very challenging using conventional dielectric waveguides, which usually require complex 3D geometries to alter the waveguide symmetry and are also difficult to create an arbitrary optical axis. Recently, a waveguide waveplate was realized using femtosecond laser writing, but the device length is in millimeter range. Here, for the first time we propose and experimentally demonstrate an ultracompact, on-chip waveplate using an asymmetric hybrid plasmonic waveguide to create an arbitrary optical axis. The device is only in several microns length and produced in a flexible integratable IC compatible format, thus opening up the potential for integration into a broad range of systems.

After discovery of extraordinary transmission (EOT) subwavelength hole arrays structures patterned on a metal film have generated wide interest as they offer high optical transmission and strong localized electric near-field intensities. However, the large ohmic losses exhibited by SPs in the optical regime represent a fundamental limitation that reduces drastically the practical applicability of EOT properties. Furthermore, not compatible with silicon platform make it difficult for application purposes. As a possible solution to this fundamental problem, gain medium have been introduced to compensate the loss created by metallic film. But the most important yet challenging requirements for gain material are to be silicon compatible and working at telecommunication regime. The aim of this paper is to theoretically study optical amplification of EOT properties in periodic hole arrays incorporating optically pumped gain media. The gain media was selected Erbium/Ytterbium(Er/Yb) silicate that is silicon compatible with photoluminescence peak at telecommunication regime. Use of Er 3+ ions has the advantages of proven, stable, and low-noise operation at the technologically important 1.54 m region. To excite the active material a laser with a maximum power of 372 mW at the wavelength of 1480 nm is applied. Geometrical parameters was obtained by solving the surface plasmon dispersion relation on periodic hole arrays. The condition for lossless propagation was obtained analytically. Simulation results shows that for lossless propagation we will need higher gain value. By considering higher gain values the absorption was approached to zero 30% transmission enhancements was observed at telecommunication wavelength.

A novel and practical polarization rotator is proposed through an asymmetric hybrid plasmonic waveguide. High polarization conversion efficiency (96%) and low insertion loss (1.6 dB) are achieved in a very short rotation length (7.2 μm).

A novel polarization splitting is proposed through plasmonic-dielectric coupling with ultrashort coupling length. Extinction ratios of 20.8 dB and 17.0 dB for TE and TM polarizations are achieved at a coupling length of 4.13 µm.

Hybrid surface plasmon polariton waveguide was fabricated, which has a dimension about 500 nm×575 nm. The visible scattering light covers the whole 4.5-mm-long Au strip. A propagation loss of 20 dB/cm was experimentally demonstrated.

An active metal strip hybrid plasmonic waveguide (MSHPW) using gain materials as loss compensation is proposed with an extremely simple fabrication procedure. Gain materials are introduced either in the low-index layer or in the high-index layer of MSHPW. The effects of waveguide dimensions and material gain coefficients on loss compensation are analyzed at the communication wavelength. For one configuration presented here, a critical material gain as low as 3.8cm(-1) is sufficient for fully compensation of the loss when using a high-index gain material. The active MSHPW with low critical material gain opens up opportunities for practical plasmonic devices in active applications such as amplifiers, sources, and modulators.

An Er/Yb silicate strip loaded waveguide was fabricated for optical amplification purpose. A 2.4-μm-wide SiO2 strip was deposited on top of the Er/Yb silicate active layer. Experiment data showed a 5.5 dB signal enhancement in a 7.8-mm-long waveguide pumped by a laser of 372 mW at 1480 nm. The signal is not saturated and can be further enhanced by increasing pumping power and decreasing waveguide loss. The strong red light emission at 660 nm was also observed due to excited state absorption and Yb3+ participated energy transfer upconversion processes.