Papers by Keyword: OBIC

Abstract: This paper presents micro-OBIC measurements performed at different biasing on two power devices protected by a combination of P⁺ rings embedded in a JTE Zone. Thanks to the micro-OBIC micrometer spatial resolution, small gaps can be visible on OBIC profiles. Thus, the spatial variation of the micro-OBIC signal accurately reflects the topology of the periphery protection: combination of JTE and rings and channel stopper. These measurements agree with the electric field distribution (calculated by finite element method) along the structure.

Abstract: This paper presents micro-OBIC measurements performed at different voltages on two devices protected by narrow field rings. At the surface of the device #1, a polyimide layer was deposited during the fabrication process. On the contrary, passivation layer was removed on device #2. Thanks to the micro-OBIC micrometer spatial resolution and the spot size carefully focused, small gaps in the range of 1 μm can be visible on OBIC profiles. Thus, the variation of the μ-obic accurately reflects the topology of each ring.

Abstract: This paper presents OBIC measurements performed at near breakdown voltage on two devices with different JTE doses. Overcurrent has been measured either at the JTE periphery or at the P⁺ border. Such overcurrent is present due to the electric field enhancement near the breakdown voltage. This hypothesis is proved by the electroluminescence. TCAD simulation of two different JTE doses yielded similar results to the OBIC measurements.

Abstract: Optical Beam Induced Current (OBIC) measurements are performed on 4H-SiC avalanche diodes with a very thin and a highly doped active region. A pulsed green laser, with a wavelength of 532 nm, illuminates a reverse biased diode leading to generate electron-hole pairs in the space charge region. Comparison between the 4H-SiC bandgap and the incident photon energy shows that single photon absorption process can be neglected and two-photon absorption process dominates in this case. Ionization rates are then extracted from multiplication curve in a high electric field range (3 to 5 MV.cm^–1). Results are in good agreement with previous ones obtained on the same diodes using single photon absorption process.

Abstract: The behavior of 4H-SiC power devices in severe environment with varying temperature is a key characteristic indicating their reliability. This paper shows the dependence of the ionization rates of 4H-SiC with respect to temperature. Optical Beam Induced Current (OBIC) measurements have been performed on PN junctions to determine the multiplication coefficient for temperature varying between 100 and 450K. That allows extracting the ionization rates by fitting the curves of multiplication coefficient.

Abstract: Optical Beam Induced Current (OBIC) measurements have been performed on 4H-SiC avalanche diodes with very thin and highly doped avalanche region. The light source used in this study is an Ar-laser with a wavelength of 351 nm which results in a mixed carrier injection. From these measurements, impact ionization coefficients for 4H-SiC have been extracted in the electric field range from 3 to 4.8 MV/cm. In combination with ionization coefficients in our previous paper extracted from diodes with lowly doped avalanche region, we propose a set of parameters of impact ionization coefficients for 4H-SiC, applicable to a wide electric field range.

Abstract: 4H-SiC vertical bipolar power diodes have been fabricated with bilayer metallic anode contact based on an Al-Ti-Ni ohmic contact and a thick Al over-metallization. An optical window of 100 × 100 μm2 has been created through the anode contact with a SIMS Cameca IMS 4F equipment using Cs+ primary ions at 10 kV and with a beam spot size of 100 nm. The current/voltage characteristics of the diodes show that the SIMS process does not induce an increase of the leakage currents in forward nor in reverse bias. OBIC UV photogeneration occurs under the optical window and not under the contact metal.

Abstract: High voltage SiC semiconductor devices have been successfully fabricated and some of them are commercially available [1]. To achieve experimental breakdown voltage values as close as possible to the theoretical value, i.e. value of the theoretical semi-infinite diode, it is necessary to protect the periphery of the devices against premature breakdown due to locally high electric fields. Mesa structures and junction termination extension (JTE) as well as guard rings, and combinations of these techniques, have been successfully employed. Each of them has particular drawbacks. Especially, JTE are difficult to optimize in terms of impurity dose to implant, as well as in terms of geometric dimensions. This paper is a study of the spreading of the electric field at the edge of bipolar diodes protected by JTE and field rings, by optical beam induced current.