Norimichi Chinone

Cross-sectional dopant profiling and depletion layer visualization of SiC power double diffused metal-oxide-semiconductor field effect transistor using super-higher-order nonlinear dielectric microscopy

The dopant distribution and depletion layer in a cross-section of a SiC double diffused MOSFET (DMOSFET) is visualized using super-higher-order scanning nonlinear dielectric microscopy (SHO-SNDM), which is a form of scanning probe microscopy. Analysis of the data acquired by SHO-SNDM clarifies the dopant distribution in great detail, which is otherwise difficult to detect using conventional scanning capacitance microscopy or scanning microwave microscopy. Moreover, the newly developed SHO-SNDM method enables us to distinguish the n-type, p-type, and depletion layer regions very clearly, and they are found to be consistent with the general DMOSFET structure.

Lateral resolution improvement in scanning nonlinear dielectric microscopy by measuring super-higher-order nonlinear dielectric constants

Scanning nonlinear dielectric microscopy (SNDM) can be used to visualize polarization distributions in ferroelectric materials and dopant profiles in semiconductor devices. Without using a special sharp tip, we achieved an improved lateral resolution in SNDM through the measurement of super-higher-order nonlinearity up to the fourth order. We observed a multidomain single crystal congruent LiTaO3 (CLT) sample, and a cross section of a metal-oxide-semiconductor (MOS) field-effect-transistor (FET). The imaged domain boundaries of the CLT were narrower in the super-higher-order images than in the conventional image. Compared to the conventional method, the super-higher-order method resolved the more detailed structure of the MOSFET.

Local deep level transient spectroscopy using super-higher-order scanning nonlinear dielectric microscopy

Abstract A new technique for local deep level transient spectroscopy imaging using super-higher-order scanning nonlinear dielectric microscopy is proposed. Using this technique, SiO2/SiC structure samples with different post oxidation annealing conditions were measured. We observed that the local DLTS signal decreases with post oxidation annealing (POA), which agrees with the well-known phenomena that POA reduces trap density. Furthermore, obtained local DLTS images had dark and bright areas, which is considered to show the trap distribution at/near SiO2/SiC interface.

Investigation of solution-processed bismuth-niobium-oxide films

The characteristics of bismuth-niobium-oxide (BNO) films prepared using a solution process were investigated. The BNO film annealed at 550 °C involving three phases: an amorphous phase, Bi3NbO7 fluorite microcrystals, and Nb-rich cubic pyrochlore microcrystals. The cubic pyrochlore structure, which was the main phase in this film, has not previously been reported in BNO films. The relative dielectric constant of the BNO film was approximately 140, which is much higher than that of a corresponding film prepared using a conventional vacuum sputtering process. Notably, the cubic pyrochlore microcrystals disappeared with increasing annealing temperature and were replaced with triclinic β-BiNbO4 crystals at 590 °C. The relative dielectric constant also decreased with increasing annealing temperature. Therefore, the high relative dielectric constant of the BNO film annealed at 550 °C is thought to result from the BNO cubic pyrochlore structure. In addition, the BNO films annealed at 500 °C contained approximate...

Local deep level transient spectroscopy using super-higher-order scanning nonlinear dielectric microscopy and its application to imaging two-dimensional distribution of SiO2/SiC interface traps

We propose a new technique called local deep level transient spectroscopy (local-DLTS), which utilizes scanning nonlinear dielectric microscopy to analyze oxide/semiconductor interface traps, and validate the method by investigating thermally oxidized silicon carbide wafers. Measurements of C-t curves demonstrate the capability of distinguishing sample-to-sample differences in the trap density. Furthermore, the DC bias dependence of the time constant and the local-DLTS signal intensity are investigated, and the results agree to characteristic of interface traps. In addition, the Dit values for the examined samples are estimated from the local-DLTS signals and compared with results obtained using the conventional high-low method. The comparison reveals that the Dit values obtained by the two methods are of the same order of magnitude. Finally, two-dimensional (2D) distributions of local-DLTS signals are obtained, which show substantial intensity variations resulting in random 2D patterns. The 2D distributi...

Visualization of Gate-Bias-Induced Carrier Redistribution in SiC Power DIMOSFET Using Scanning Nonlinear Dielectric Microscopy

Carrier profiling in the cross section of a gate-biased silicon carbide power double-implanted MOSFET is demonstrated with a newly developed measurement system that utilizes super-higher-order scanning nonlinear dielectric microscopy. Two techniques that have features that complement each other were proposed and demonstrated. In all measurements, the tip-sample voltage difference was cancelled during gate-source voltage (VGS) application. Variation in the VGS-dependent carrier distribution was reasonably determined using both of the proposed techniques.

Evaluation of silicon- and carbon-face SiO2/SiC MOS interface quality based on scanning nonlinear dielectric microscopy

A strong positive correlation was found between the trap density (Dit) at the SiO2/SiC interface and signal variation in a scanning nonlinear dielectric microscopy (SNDM) image. Si-face and C-face SiC wafers with a 45-nm-thick oxide layer were examined by the conventional high-low method and SNDM, which is a type of scanning probe microscopy. The Dit value measured by the high-low method and the standard deviation of normalized SNDM images exhibited a strong positive correlation, which means that the standard deviation of the normalized SNDM image can be used as a universal measure of the SiO2/SiC interface quality. Using this measure, a quick evaluation of Dit using SNDM is possible.

Proposal of local deep level transient spectroscopy using super-higher-order scanning nonlinear dielectric microscopy and 2-dimensional imaging of trap distribution in SiO 2 /SiC interface

A new technique for microscopically evaluating insulator-semiconductor interface traps is proposed. The proposed technique is applied for SiO2/SiC stack structure and 2-dimensional imaging of interface traps is performed.

Nondestructive and Local Evaluation of SiO2/SiC Interface Using Super-Higher-Order Scanning Nonlinear Dielectric Microscopy

SiO2/SiC interface was investigated by using super-higher-order (SHO) scanning nonlinear dielectric microscopy (SNDM) with high spatial resolution. Comparison of non-oxidized and thermally oxidized 4H-SiC wafer (Si-face) revealed that only 5 min oxidation makes the interface quality spatially inhomogeneous. Next four SiC wafers treated under different post oxidation annealing (POA) conditions in NO ambient (three “with” and one “without” POA) were also compared. Using SHO-SNDM, local capacitance-voltage (C-V) curves were obtained. The local C-V curve obtained in sample with POA was more close to ideal C-V curve compared to the C-V curves obtained in the sample without POA. In addition, two-dimensional normalized SNDM images taken on the four SiC wafers were observed, which showed that the spatial deviation of interface state was reduced by the POA treatment. Moreover, standard deviations s of the normalized SNDM images were calculated. Then, very strong correlations between σ and interface-state density Dit as well as channel electron mobility μFE were observed.

Nanoscale linear permittivity imaging based on scanning nonlinear dielectric microscopy

A nanoscale linear permittivity imaging method based on scanning nonlinear dielectric microscopy (SNDM) was developed. The ∂C/∂z-mode SNDM (∂C/∂z-SNDM) technique described herein employs probe-height modulation to suppress disturbances originating from stray capacitance and to improve measurement stability. This method allows local permittivity distributions to be examined with extremely low noise levels (approximately 0.01 aF) by virtue of the highly sensitive probe. A cross-section of a multilayer oxide film was visualized using ∂C/∂z-SNDM as a demonstration, and numerical simulations of the response signals were conducted to gain additional insights. The experimental signal intensities were found to be in a good agreement with the theoretical values, with the exception of the background components, demonstrating that absolute sample permittivity values could be determined. The signal profiles near the boundaries between different dielectrics were calculated using various vibration amplitudes and the boundary transition widths were obtained. The beneficial aspects of higher-harmonic response imaging are discussed herein, taking into account assessments of spatial resolution and quantitation.