Analysis of Dislocation Structures in 4H‐SiC by Synchrotron X‐Ray Topography

Abstract

SUMMARY Current 4H‐SiC wafers contain certain amount of dislocations, stacking faults, and other lattice‐defects. These defect structures evolve during various processes for power device fabrication. It is very important to examine evolutions of dislocation structures during power device processes, as well as the effect of dislocations on performances of fabricated power devices. Since lattice defects can be observed at only subsurface regions selectively by Berg–Barrett X‐ray topography, we have applied this useful observation technique to 4H‐SiC technology to solve various technological issues. Appearances of scratch‐like surface morphology after epi‐film growth on very flat substrate surface by chemomechanically polish were examined by this technique, and the mechanism was discussed. Analyses of dislocation structure evolutions during epi‐film growth and also basal‐plane dislocation glide by recombination of electrons and holes were discussed. Effects of threading‐screw dislocations on reliability of MOS structures and on current leakage in pn‐junction under reversed bias condition were investigated and discussed. Various important suggestions for 4H‐Sic industries were obtained.

Cathodoluminescence and EBIC investigations of stacking fault expansion in 4H-SiC due to e-beam irradiation at fixed points

“…Additionally, it helps to understand the extremely small activation energy for the REDG in 4H-SiC because in this case to enhance the dislocation glide the kink formation energy should be only lowered. If the activation energy for the kink migration is indeed very low, this allows a fresh look on the results obtained previously [13,14], which showed that SSFs introduced under a mechanical shear stress at elevated temperatures did not expand due to subsequent LEEBI despite the fact that the expansion of SSFs under irradiation and under mechanical shear stress was driven by the similar dislocations, namely Si-core 30 • PDs [22][23][24]. If one takes into account that, as theory predicted [46,47], the barrier for the kink migration can be of about 30-60 meV for some core configurations (e.g.…”

“…It has been well established that SSFs can be introduced at room temperature in power devices at high forward currents [3-8, 18, 21] or under electron beam or optical irradiation [10][11][12][13][14][15][16][17]. As the SSF expansion in 4H-SiC under mechanical shear stress was observed only at temperatures exceeding 250 • C [13], their expansion at room temperature suggests a strong effect of excess carriers on the mobility of partial dislocations (PDs) driving the SSF expansion (Si-core 30 • PDs [22][23][24]). For the dislocation glide in semiconducting covalent crystals an intrinsic potential barrier, the so-called Peierls potential, should be overcome.…”

Методы Рентгеновской Дифракционной Топографии (О Б З О Р)

“…Метод Берга-Барретта успешно был использован для изучения структурных дефектов в различных кристаллах, например, взаимодействия дислокаций в цинке [38], оценке качества сильнопоглощающих кристаллов [39,40], исследования дефектов в многослойных эпитаксиальных силовых приборах на основе кремния [41]. Рентгеновская монохроматическая топография Берга−Барретта с использованием синхротронного излучения (СИ) явилась эффективным методом исследования дислокаций и дефектов упаковки в силовых устройствах на основе карбида кремния и их влияния на производительность этих устройств [42,43].…”

Kink Migration along 30° Si‐Core Partial Dislocations in 4H‐SiC

“…It has been well established that SSFs can be introduced at room temperature in power devices at high forward currents [3][4][5][6][7][8]19,22] or under electron beam or optical irradiation. [10][11][12][13][14][15][16][17] As the SSF expansion in 4H-SiC under mechanical shear stress was observed only at temperatures exceeding 250 °C, [13,18] their expansion at room temperature suggests a strong effect of excess carriers on the mobility of partial dislocations (PDs) driving the SSF expansion (Si-core 30°PDs [23][24][25] ). For the dislocation glide in semiconducting covalent crystals an intrinsic potential barrier, the so-called Peierls potential, should be overcome.…”