Yasunori Goto

Infrared Defect Dynamics of Irradiation Induced Complexes in CZ Silicon - C-Rich Case

Irradiation induced complexes of C-rich case in silicon crystal were examined by the highly sensitive and accurate infrared absorption spectroscopy. Low impurity concentration and high quality crystal was used and low dose was employed to make the reaction simple. Almost all possible absorption lines were revealed and their absorbance determined. The conversion coefficient from absorbance to the complex concentration was estimated by the plausible assumptions. The reaction was discussed in terms of concentration rather than absorbance. Intra-group reaction, chain reaction of successive addition of oxygen or self-interstitial, reaction yield and competition between the parallel reactions were described.

Observation of impurity diffusion defect in IGBT using a laser terahertz emission microscope technique

Abstract This paper describes a technique for observing impurity diffusion defects in IGBTs using laser terahertz emission microscopy (LTEM). In this method, femtosecond laser pulses are applied to the p-n junction of a trench IGBT structure and terahertz (THz) waves emitted from the wiring connected to the p-n junction are observed by a photoconductive antenna. Furthermore, covering the measurement sample with aluminum foil blocks opposite-phase THz waves emitted from the sample and improves the detection sensitivity of the THz waves emitted from the IGBT wiring. This technique enables impurity diffusion defects, which were created by deliberately omitting a portion of the resist pattern used in the IGBT emitter n+ ion implantation process, to be recognized as contrast differences on an LTEM image.

Infrared Absorption from Low Carbon Concentration, Low Dose, Annealed CZ Silicon

Complexes formed by low dose irradiation with electron (1015-16/cm2) and He (5x1012- 5x1013/cm2) in the relatively low carbon concentration (1016/cm3) MCZ silicon were investigated by highly sensitive and quantitative IR absorption analysis. CiOi and VO were the main complexes in all cases. The concentration of these complexes was about 1015/cm3, or 10% of included carbon in the highest case. Loss of almost equal amount of Cs was observed. The concentration of CiOiI was one order of magnitude lower. Upon annealing, these lines weakened and almost disappeared at 400 oC. There were some absorption lines introduced by the annealing. VO2 was strongest among them and CsOi related structure was also confirmed. There were absorption lines at 954.9 and 962.6 cm-1 appeared after annealing at 300 oC.

A 3D analysis technique for detecting trace metal contamination

Abstract A 3D analysis technique for detecting trace metal contamination has been developed. Trace metal contamination is contained in a site-specific failure on a semiconductor device. In this research, first, a sample extracted from the plane direction is observed in a 3D perspective using the STEM (Scanning Transmission Electron Microscope) method, which is less affected by chromatic aberration. With this method, a failure point can be localized at the sub-μm level. Next, the sample was thinned from the cross-sectional direction by the FIB (Focused Ion Beam) method and observed in a 3D perspective using the STEM method. By repeating the STEM and FIB methods, it was possible to fabricate a sample to a thickness of 0.1 μm, without missing any failure points. Moreover, element analysis (1 nm ϕ) by the EDX (Energy Dispersive X-ray) method made it possible to detect trace metal contamination (10−20 g or less) contained in the failure point.

Simultaneous observation of two dimensional electron gas and polarization in AlGaN/GaN heterostructure using scanning nonlinear dielectric microscopy

The AlGaN/GaN heterostructure has two-dimensional electron gas (2DEG) and electric polarization. We observed both of them simultaneously in the cross section of the AlGaN/GaN heterostructure by scanning nonlinear dielectric microscopy (SNDM), which can visualize both carrier and polarization distributions. The AlGaN/GaN heterostructure was cross-sectioned at an angle of 20° from the [0001] axis and, hence, the perpendicular components of the polarizations of AlGaN and GaN were observed. Moreover, the 2DEG distribution was confirmed in a range of ~10 nm at the AlGaN/GaN interface.

Defect analysis concerning variation in characteristics of PIN diode for Hybrid Vehicles.

Variation in voltage forward (Vf) characteristics was observed in test PIN diodes for Hybrid Vehicles (HV). By employing the SR, PL and DLTS methods of defect analysis, therefore, difference in carrier concentrations was produced in the I region where carbon-related defects exist (such as Ci-Cs and Ci-Oi), which is thought to be responsible for Vf variation. Using the FT-IR method of measuring minute quantities of impurities in wafers to enable measurement of carbon concentration according to ingot position (1e14 (top)-4e15 (bottom)cm -3 ) indicates that arranging ingot positions may be a way to lower Vf variation.

Estimation of radiation-induced complex concentration in CZ-Si by IR absorption spectroscopy

Introduction Irradiation-induced complexes are used to fabricate switching devices for hybrid cars [1]. We have established the highly sensitive infrared absorption (IR) measuring method of the absorption lines from the complexes down to 10 in unit of absorbance and detected most kinds of complexes induced in low dose irradiated device grade Si substrates [2]. It is helpful if the complex concentration can be estimated from the absorbance, but there have been few attempts. In this paper we try to estimate the complex concentration.