SIMS Analyses Applied to Open an Optical Window in 4H-SiC Devices for Electro-Optical Measurements

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.

Determination of 4H-SiC Ionization Rates Using OBIC Based on Two-Photon Absorption 

“…This solution works well, optical power remains high at this point and no scratches are observed on the DUT surface. The DUT is the same circular avalanche diode, with a breakdown voltage of 59 V, as already used in previous studies [5,6,8,12]. It presents a thin and highly doped active layer, which means high electric field devices (> 3 MV.cm -1 ).…”

“…A 100×100 µm 2 optical window was performed using SIMS technique on some diodes ( fig. 3) allowing the optical beam to penetrate towards the drift region of the diode [12]. Figure 4 shows the OBIC signal vs. beam position for different reverse voltages.…”

Temperature Dependence of 4H-SiC Ionization Rates Using Optical Beam Induced Current

“…Since the diode presents a high doping level, its breakdown voltage is very low (59V), and the peripheral protection is realized with a MESA etching. In order to allow optical beam to penetrate towards the active part of the diode, an optical window of 100×100µm 2 has been performed on the metallization using SIMS technique [12]. Figure 3 shows the reverse I-V characteristics of the diode for a temperature ranging from 100K up to 450K.…”

“…The minority carriers currents J n (x p ) and J p (x n )are determined by solving the continuity equations by taking into account the conditions on the limit [11]. From equations (2) and (12), it is possible to determine the ionization rates by fitting the experimental multiplication curve M(V) using numerical solver. In this case, the electric field distribution must be calculated in terms of the reverse voltage V.…”

Optical beam induced current measurements based on two-photon absorption process in 4H-SiC bipolar diodes

“…It is composed by a 2.2µm thick P + layer and a thin epitaxial transition layer P deposited on an N + substrate. An optical window is performed through the metallization (Figure 3a) [11]. These Zener diodes show breakdown voltage of ~60V and have been ever studied by single photon OBIC [12].…”