Zhensheng Zhang

Efficient field emission from single crystalline indium oxide pyramids

Well-aligned indium oxide pyramids were synthesized on a Ni-coated silicon (100) substrate by a chemical vapor deposition. Scanning electron microscopy and x-ray diffraction investigations show that these pyramids present a tetragonal morphology and single-crystalline cubic bixbyite structure. The size control of the pyramids was achieved by varying the growth temperature. Field-emission characteristics of the as-grown indium oxide pyramids were measured. The field-emission current density of the nanopyramids (average size: ∼180 nm) reached about 1 mA/cm2 at a threshold field of about 6.0 V/μm, which is comparable to that of carbon nanotubes, and can guarantee sufficient luminescence brightness in a flat panel display.

Effects of symmetry of GaN-based two-dimensional photonic crystal with quasicrystal lattices on enhancement of surface light extraction

We demonstrate enhancement of surface light extraction from two-dimensional photonic crystals (2D-PCs) on the electrical injected GaN-based light emitters. The effects of symmetry of PCs on light extraction were studied. 2.5 times enhancement of surface emission was obtained from the PCs with an octagonal symmetric quasicrystal lattice (8PQC) compared to that from a nonpatterned region. Additionally the surface emission from PCs with dodecagonal symmetric quasicrystal lattice (12PQC) exhibited about 1.7 and 1.4 times higher emission than regular PCs with triangular lattice and 8PQC, respectively. Consequently, the 12PQC provides a favorable consideration of 2D-PC in light extraction from light emitting diode.

Shape-controllable synthesis of indium oxide structures: Nanopyramids and nanorods

We describe a vapor-phase route to the controllable synthesis of indium oxide micro-and nanopyramids on the silicon wafer via selective epitaxial vapor-solid growth by a methane-assist thermal reduction method. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy revealed that the pyramids were cubic single crystals with a tetragonal symmetry. The size, morphology, and density of pyramids could easily be controlled by tuning reaction parameters. The method has good compatibility with other procedures involved in the microfabrication processes. Laterally grown indium oxide nanorods on the silicon wafer were also prepared via a vapor-liquid-solid mechanism. Those crystalline In 2 O 3 nanorods were about 100 nm in diameter and 1 μm in length. The as-synthesized indium oxide nanopyramids and nanorods could offer novel opportunities for both fundamental research and technological applications.

Optical critical dimension measurement for 16/14 nm FinFET

Reducing leakage current and improving devices stability become important challenge for CMOS develop under the technology node of 22nm. FinFET has been attractive as the most potential device structure under 22nm. Unique FinFET device structure has the absolute advantage in restraining short channel effect. This paper presents an optical metrology technique OCD for FinFET dimension measurement. This measurement results by OCD, demonstrate the capability of the OCD as an important metrology technique for IC process control.

Optical critical dimension measurement for source/drain structures at advanced node

In modern IC industry, optical critical dimension (OCD) technique has been more and more applied, as one of the most import process control tools. In this work, OCD spectroscopy metrology was used to measure the profiles of 2-D sigma-shaped Source/Drain structures at advanced node. Due to the complexity of the samples, eighteen parameters were investigated and six floating parameters were set up to generate the spectra library. The results were compared with Transmission Electron Microscopy and reference OCD data. The stability of 15-day was evaluated. The results showed good performance of OCD metrology.

Sensitivity study and parameter optimization of OCD tool for 14nm finFET process

Optical critical dimension (OCD) measurement has been widely demonstrated as an essential metrology method for monitoring advanced IC process in the technology node of 90 nm and beyond. However, the rapidly shrunk critical dimensions of the semiconductor devices and the increasing complexity of the manufacturing process bring more challenges to OCD. The measurement precision of OCD technology highly relies on the optical hardware configuration, spectral types, and inherently interactions between the incidence of light and various materials with various topological structures, therefore sensitivity analysis and parameter optimization are very critical in the OCD applications. This paper presents a method for seeking the optimum sensitive measurement configuration to enhance the metrology precision and reduce the noise impact to the greatest extent. In this work, the sensitivity of different types of spectra with a series of hardware configurations of incidence angles and azimuth angles were investigated. The optimum hardware measurement configuration and spectrum parameter can be identified. The FinFET structures in the technology node of 14 nm were constructed to validate the algorithm. This method provides guidance to estimate the measurement precision before measuring actual device features and will be beneficial for OCD hardware configuration.

Nonperiodic binary optical structures for enhancing light extraction of emitters

This paper presents a new method of designing binary optical structures to improve light extraction efficiency for emitters. Using this method a novel binary optical structure is generated. Such structures with an approximate width of 300 nm, are non-period and small enough in size so that they do not generate diffraction orders other than the zero order. They are also insensitive to polarization. They serve as an antireflection layer, sending light outward that would otherwise be absorbed within the device. The experimental devices were GaN based LEDs emitting at 460nm. The non-periodic binary structures and some periodic structures such as triangle-lattice Photonic Crystals (PC), 12-fold Quasi-periodic Photonic Crystals (QPC) are fabricated on the same sapphire side of a LEDs flip chip with a Focus Ion Beam (FIB) for comparison. The surface profile of the structures was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Near field scanning optical microscopy (NSOM) was used to measure the output spectral properties of the devices. Electrical Luminescence (EL) measurements show that the greatest enhancement of emission light intensity was achieved in non-periodic binary structures. This increase was 60~135% at room temperature. It demonstrates that this Non-Periodic Binary Optical Structures will be useful for fabricating high efficient GaN-based LED.