Papers by Keyword: Ion-Implantation

Abstract: In this work, we focus on the electrical characterization of Ni Schottky contact on n-type heavily doped (N_D>10¹⁹ cm⁻³) 4H-SiC layer, achieved by P-ion implantation. In particular, the forward current–voltage characterization of Schottky diodes showed a reduced turn-on voltage for the Ni/heavily-doped 4H-SiC if compared to a reference Ni/4H-SiC Schottky contact fabricated under similar conditions but without implant. Moreover, it was observed the predominance of a thermionic-field-emission (TFE) mechanism for the current transport through the interface. From a current-voltage-temperature (I-V-T) study, the temperature-dependence of the Schottky barrier and doping concentration were evaluated, obtaining a reduction of the barrier (from 1.77 to 1.66 eV), while the doping concentration maintains constant around 1.96×10¹⁹ cm^-3. This study provides useful insights for a deeper comprehension of the electrical behavior of Ni contacts and can have possible applications in 4H-SiC Schottky diode technology.

Abstract: The impact of different p-well designs upon the transient performance, in particular, the turn-off losses and short-circuit capability, of a >10 kV SiC n-IGBT is assessed. We find that in addition to improved transient performance, a substantial reduction in the depth of p-well implants can be achieved, if an extensively optimized retrograde approach is utilized. A conventional p-well consisting of a uniformly doped deep implant (doping concentration of ~3×10¹⁷ cm^-3 and depth of >1.5 µm) exhibits considerable turn-off switching losses without offering any short circuit capability. However, an optimized retrograde p-well consisting of a variable doping profile and depth as shallow as 0.7-0.8 µm results in much reduced turn-off losses with excellent short-circuit capability. Shallow implants are desirable to lower the development cost and processing challenges. The retrograde p-well is therefore highly promising for the development of >10 kV class of SiC IGBTs.

Abstract: In this article, mathematical models and processes of introducing homogeneous ultrasonic oscillations and mechanical stresses into silicon wafers in the direction of their thickness are developed and investigated, and mathematical models of the movement of interstitial defects in silicon wafers created by the processes of ion-beam transients at the transitions of ion-beam transitions and hidden dielectric layers using the action of ultrasound oscillations and mechanical stresses, both in the process of implantation of impurities and before the annealing of plates upon activation of the impurities are developed and investigated.

Abstract: A p-well consisting of a retrograde doping profile is investigated for performance improvement of >10kV SiC IGBTs. The retrograde p-well, which can be realized using low-energy shallow implants, effectively addresses the punch-through, a common issue in high-voltage vertical architectures consisting of a conventional p-well with typical doping density of 1e17cm^-3 and depth 1μm. The innovative approach offers an extended control over the threshold voltage. Without any punch-through, a threshold voltage in the range 6V-7V is achieved with gate-oxide thickness of 100nm. Gate oxide thickness is typically restricted to 50nm if a conventional p-well with doping density of 1e17cm^-3 is utilized. We therefore propose a highly promising solution, the retrograde p-well, for the development of >10kV SiC IGBTs.

Abstract: The technique of stone-in-place casting has been established in jewelry production for three decades. However, the process is not widely used since it is limited to precious stones with high hardness and high stability at high temperature. This experiment tested tourmaline, which is a semi-precious gemstone having less hardness and less stability compared with precious stones. The objective was to achieve the conditions of a lost-wax casting process with tourmaline placed in waxes in the casting process. The experiment was divided into two parts. The first part was to understand the tolerance of tourmaline under the heating conditions. Natural tourmaline stones were investigated and compared inclusions tested at a temperature of 700°C. Tourmaline with ion-implantation was also heated to 700°C for comparison. The second part was to test tourmaline in-place casting with tree conditions of flask casting at 550°C, 625°C, and 700°C. The results showed that stones were able to tolerate as much as at 700°C. The inclusion growth of ion-implantation under heating to 700°C also observed the growth of inclusion in the same way as untreated tourmaline. The casting condition at 550°C showed better results. The highest probability of stones breaking after casting occurred in bezel settings.

Abstract: In this work we carried out electrical characterization of n-GaAs implanted at 300 K with high energy (100 MeV) ²⁸Si and ¹²⁰Sn ions to a fluence of 1x10¹⁸ ions/m² using current–voltage (I-V) measurements. The as implanted samples and samples annealed in the temperature range 373-1123 K have been investigated. Resistance of the samples obtained from I-V curves recorded over the temperature range 110K-270K indicate that the samples implanted with ²⁸Si and annealed up to 623 K and the samples implanted with ¹²⁰Sn and annealed up to 723K shows tunnel assisted hoping conduction mechanism. In the other hand, ²⁸Si implanted samples annealed to 723K and 823K and ¹²⁰Sn implanted samples annealed to 823K and 923K the electrical conduction mechanism is dominated by thermal hoping between closed defect states.

Abstract: In this work, a partial amorphization is introduced to form a Nickel silicide ohmic contact for 4H-SiC bottom electrode. In a conventional Nickel silicide electrode, a carbon agglomeration at the silicide/SiC interface has been occured, and contant resistance between Ni silicide and SiC substrate became larger. For the reduction of the contact resistance, the partial amorphization of surface of SiC substrate was introduced. By this partial amorphization, the space position of the carbon agglomeration is controlled, and contact resistance can be reduced. As a result, with an amorphous 100 nm line pattern, a reliable contact resistance of 1.9×10^-3Ωcm² was realized.

Abstract: Room-temperature photoluminescence (PL) properties of the Tb³⁺ ion implanted non-stoichiometric silicon nitride (SiN_x:Tb³⁺) and silicon dioxide (SiO_x:Tb³⁺) were studied. The films were deposited by plasma-enhanced chemical vapor deposition (PECVD) and then annealed at different temperatures for 1 hour in flowing N₂ after the Tb ion-implantation. Results show that there are four intense PL peaks due to the intra-4f transitions of Tb³⁺ in the wavelength from 470 nm to 625 nm for both kinds of films. Moreover, the PL intensity of Tb³⁺:SiN_x is much higher than that of Tb³⁺:SiO_x. The less oxygen content of the SiN_x film and, more importantly, the faster recombination lifetime of Tb³⁺ ion in SiN_x film are the main reasons. This result shows that SiN_x:Tb³⁺ can be used for silicon-based light emission materials.