Sunghyun Hwang

Fabrication and characterization of metal-oxide-nitride-oxynitride-polysilicon nonvolatile semiconductor memory device with silicon oxynitride (SiOxNy) as tunneling layer on glass

A nonvolatile semiconductor memory (NVSM) device with a metal-oxide-nitride-oxynitride-polysilicon (MONOS) structure on a rough polysilicon (poly-Si) surface was fabricated using a low-temperature process and poly-Si thin film transistor (TFT) technology on glass. For the fabrication of the NVSM device on glass, plasma-assisted oxynitridation was carried out using nitrous oxide (N2O) as a reactive gas, due to the very rough surface of the poly-Si on glass annealed using an excimer laser. The ultrathin SiOxNy films obtained using the N2O plasma have a very uniform distribution on poly-Si and similar contents of oxygen and nitrogen in the peaks and valleys of the grains. The NVSM devices having a MONOS structure with a tunneling layer of ultrathin SiOxNy on glass have suitable switching and charge retention characteristics for data storage. The results demonstrate that the NVSM device made using low-temperature poly-Si TFT technology on glass reported in this paper can be used in various types of display de...

Spatially varying regularization of deconvolution in 3D microscopy

Confocal microscopy has become an essential tool to explore biospecimens in 3D. Confocal microcopy images are still degraded by out‐of‐focus blur and Poisson noise. Many deconvolution methods including the Richardson–Lucy (RL) method, Tikhonov method and split‐gradient (SG) method have been well received. The RL deconvolution method results in enhanced image quality, especially for Poisson noise. Tikhonov deconvolution method improves the RL method by imposing a prior model of spatial regularization, which encourages adjacent voxels to appear similar. The SG method also contains spatial regularization and is capable of incorporating many edge‐preserving priors resulting in improved image quality. The strength of spatial regularization is fixed regardless of spatial location for the Tikhonov and SG method. The Tikhonov and the SG deconvolution methods are improved upon in this study by allowing the strength of spatial regularization to differ for different spatial locations in a given image. The novel method shows improved image quality. The method was tested on phantom data for which ground truth and the point spread function are known. A Kullback–Leibler (KL) divergence value of 0.097 is obtained with applying spatially variable regularization to the SG method, whereas KL value of 0.409 is obtained with the Tikhonov method. In tests on a real data, for which the ground truth is unknown, the reconstructed data show improved noise characteristics while maintaining the important image features such as edges.

Nonvolatile Poly-silicon Memory Device with Oxide-Nitride-Oxynitride Stack Structure on Glass for Flat Panel Display

This paper explains how non-volatile memory (NVM) devices with an oxide/nitride/oxynitride (ONO) structure on a rough poly-silicon (poly-Si) surface were fabricated and studied using poly-Si thin film transistor (TFT) technology on a glass substrate. When a flat panel display (FPD) such as an organic light emitting diode (OLED) or a liquid crystal device (LCD) displays a static image, the brightness of the panel is altered because of degradation of the driving current. In order to prevent degradation of the driving current, an NVM device can be applied to the compensation circuit for the pixels of a FPD. To fabricate an NVM device on glass, a metal/oxide/nitride/oxynitride/poly-Si (MONOS) structure with an ultra-thin silicon oxynitride (SiOxNy) using nitrous oxide (N2O) plasma as the tunneling layer was used instead of the general methods of oxidation and deposition for ultra-thin silicon dioxide (SiO2). The memory window of a fabricated NVM device which has a MONOS structure with a tunneling layer of ultra-thin SiOxNy at a programming voltage of − 16 V and erasing voltage of + 11 V for a pulse time of 1s is 2.8 V. This is because of programming and erasure of charges in the silicon nitride (SiNx) layer. Because of the properties of NVM device on glass, NVM devices can be used in various FPD.

Effect of charge storage in silicon nanocrystals on needle-like nano-structure for non-volatile memory

In this work, metal-lnsulator-semiconductor (MIS) devices with silicon nitride film as insulator layer have been fabricated on needle-like nano-structures, which can be applicable to non-volatile memory device with increased charge storage capacity over planar structures. We have already reported surface morphologies of needle-like structures and existence of nanocrystals in silicon nitride layer using photoluminescence (PL). In this paper, memory effects are demonstrated by electronic properties of MIS devices with substrate of nano structure. Window sizes of capacitance-voltage (C-V) characteristics in MIS devices on substrates of nano-structure are formed to increase compared to that in MIS device fabricated on planar structure. Therefore, a non-volatile memory device with increased charge storage capacity over planar structure can be realized with the nano-structure.