Optical Stressing of 4H-SiC Material and Devices

Kallinger, Birgit; Kaminzky, Daniel; Berwian, Patrick; Friеdrich, J.; Oppel, S.

doi:10.4028/www.scientific.net/msf.924.196

Cited by 3 publications

(2 citation statements)

References 6 publications

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“…In collaboration with an Erlangen metrology company a tool for fast structural characterization of SiC wafers based on UVPL imaging was developed. With this tool SiC wafers up to 200 mm in diameter can be studied in‐line, non‐destructively and without preparative effort within minutes . By scanning the substrate directly after the epi‐process with the UVPL scanner it was possible to predict which devices would later drift due to bipolar degradation, and which devices would exhibit reliable behavior.…”

Section: Development Of Wide Bandgap Semiconductors (Sic Gan Aln)—cmentioning

confidence: 99%

Erlangen—An Important Center of Crystal Growth and Epitaxy: Major Scientific Results and Technological Solutions of the Last Four Decades

Friеdrich

Müller

2019

Crystal Research and Technology

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This article describes the historic development of the Erlangen Crystal GrowthLaboratory CGL from its beginnings in 1974 at the chair of Materials of Electrical Engineering (Department of Material Science) of the University of Erlangen-Nuremberg until its current status as a large department "Materials" of the Erlangen Fraunhofer-Institute for Integrated Systems and Device Technology. Essential developments and scientific achievements in the various fields of crystal growth and epitaxy are presented from the early period until today.

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Section: Development Of Wide Bandgap Semiconductors (Sic Gan Aln)—cmentioning

confidence: 99%

Erlangen—An Important Center of Crystal Growth and Epitaxy: Major Scientific Results and Technological Solutions of the Last Four Decades

Friеdrich

Müller

2019

Crystal Research and Technology

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“…In the paper by Ishigaki et al that investigated the forward bias degradation of approximately 10,000 SiC MOSFET modules, a 10 % increase in V(on) voltage was reported for 2-3% of the modules [3]. Kallinger et al showed that BPDs inside epi-layer on 4H-SiC substrate were optically stressed by applying high UV laser irradiation, which can induce expand 1-SSF from the BPD at the wafer level similar to electrical burn-in testing [4]. Our proposed S-EVC method can detect not only the BPDs inside epi-layer but also the TED-converted BPDs that expand to bar shaped SSFs.…”

Section: Introductionmentioning

confidence: 99%

S-EVC Method for Sorting Wafers with Defects that Extend to Bar Shaped SSFs

Takano¹,

Matsushita²,

Igarashi³

2023

DDF

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In the previous report [1], we proposed the S-EVC (Selective Expansion-Visualization-Contraction) method (Fig. 1) that effectively screens for malignant BPDs (basal plane dislocations) in the drift and buffer layers, which expand to SSFs (Shockley-type stacking faults), leading to forward voltage degradation. The method intentionally utilizes the REDG (recombination enhanced dislocation glide) mechanism by UV (ultraviolet) irradiation in wafer sorting to replace the so-called burn-in (accelerated current stress) process, which is time-consuming during mass production. In the report, triangular SSFs were examined to verify the effectiveness of the method, but they only occupy a much smaller area of the active region on the chip than bar shaped SSFs. In this study, to improve the S-EVC method to be more practical, we focused on the more serious bar shaped SSFs which have a non-negligible impact on electrical characteristics. The bar shaped SSFs are mostly expanded from TED (threading edge dislocation)-converted BPD at or below the substrate epitaxial layer interface. In PL (photoluminescence) observation by a 710 nm LPF (long-pass filter), the TED-converted BPD and the complete TED extended from the bottom of the substrate are observed as the same dark spot, but it was confirmed that both can be distinguished by the presence or absence of their SSF expansion by UV irradiation. In addition, in order to confirm the validity of the S-EVC method even on the virgin epi wafer, UV irradiation was performed on both the aluminum doped PN structured wafer and the virgin epi wafer, and the similar SSF expansion was observed. Meanwhile, the correlation between UV irradiation and forward voltage degradation was quantified using PiN diodes by comparing the glide velocity of 30°Si (g) core partials for bar shaped SSFs by UV irradiation stress with that by current stress.

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Accuracy of EVC Method for the PiN Diode Pattern on SiC Epi-Wafer

Takano,

Morita,

Matsushita

et al. 2024

DDF

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In the previous report, we proposed the EVC (Expansion-Visualization-Contraction) method (Fig. 1) that effectively screens for malignant BPDs (basal plane dislocations) in the epi layer and near substrate interface, which expand to SSFs (Shockley-type stacking faults), leading to forward voltage degradation. The method intentionally utilizes the REDG (recombination enhanced dislocation glide) mechanism by UV (ultraviolet) irradiation in wafer sorting to replace the so-called burn-in (accelerated current stress) process, which is time-consuming during mass production. In this report, to verify the effectiveness of this method, we compared the SSFs expanded by forward biasing the PiN diode (Fig.3) on a wafer with the SSFs expanded by UV irradiating at the same PiN diode area where the metal electrode was removed by etching. The accuracy of the EVC method requires that SSFs expanded by forward biasing should be detected in the same positions as those of SSFs expanded by UV irradiation. Not all BPDs expand at the same time, but the number of expanded SSFs increases over time under constant forward current conditions. In this experiment, the current density was 400 A/cm2 for 8 minutes, and the excessive UV irradiation conditions was 143 W/cm2 for 20 minutes to avoid missing. Missing means the inability to check the SSFs expanded by forward biasing against the SSFs expanded by UV irradiation (Fig.2). For each diode electrode window, the presence or absence of SSFs were determined, and as shown in Table 2, 2 out of 49 window areas were missing, with the EVC method accuracy rate of 96 %.

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Optical Stressing of 4H-SiC Material and Devices

Cited by 3 publications

References 6 publications

Erlangen—An Important Center of Crystal Growth and Epitaxy: Major Scientific Results and Technological Solutions of the Last Four Decades

Erlangen—An Important Center of Crystal Growth and Epitaxy: Major Scientific Results and Technological Solutions of the Last Four Decades

S-EVC Method for Sorting Wafers with Defects that Extend to Bar Shaped SSFs

Accuracy of EVC Method for the PiN Diode Pattern on SiC Epi-Wafer

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