Concentration, chemical bonding, and etching behavior of P and N at the SiO2/SiC(0001) interface

Abstract

Phosphorous and nitrogen are electrically active species at the SiO2/SiC interface in SiC MOSFETs. We compare the concentration, chemical bonding, and etching behavior of P and N at the SiO2/SiC(0001) interface using photoemission, ion scattering, and secondary ion mass spectrometry. Both interfacial P and N are found to be resistant to buffered HF solution etching at the SiO2/SiC(0001) interface while both are completely removed from the SiO2/Si interface. The medium energy ion scattering results of etched phosphosilicate glass/SiC not only provide an accurate coverage but also indicate that both the passivating nitrogen and phosphorus are confined to within 0.5 nm of the interface. Angle resolved photoemission shows that P and N are likely situated in different chemical environments at the interface. We conclude that N is primarily bound to Si atoms at the interface while P is primarily bound to O and possibly to Si or C. Different interface passivating element coverages and bonding configurations on different SiC crystal faces are also discussed. The study provides insights into the mechanisms by which P and N passivate the SiO2/SiC(0001) interface and hence improve the performance of SiC MOSFETs.

Mechanism of phosphorus passivation of near-interface oxide traps in 4H–SiC MOS devices investigated by CCDLTS and DFT calculation

“…The trap passivation mechanism by phosphorus is only partially understood. It has been reported that, at the interface as well as in the bulk PSG layer, P is primarily bound to O atoms, which are themselves bonded to Si or C atoms [46]. This suggests that the trap passivation mechanism due to P may be related to re-arranging the critical interfacial dielectric layer, relieving interface stress and possibly allowing better passivation of the dangling bonds [46].…”

“…It has been reported that, at the interface as well as in the bulk PSG layer, P is primarily bound to O atoms, which are themselves bonded to Si or C atoms [46]. This suggests that the trap passivation mechanism due to P may be related to re-arranging the critical interfacial dielectric layer, relieving interface stress and possibly allowing better passivation of the dangling bonds [46]. Accordingly, the effect of phosphorus on near-interface traps can be summarized by the following theories reported in the literature: (1) the P atoms act as a network former and result in reconstruction of the oxide network in SiO 2 (Si-Si bonds elimination) [26,28,46] (2) C related defects are removed by the P doping of SiO 2 [28,[47][48][49] where threefold carbon atoms at the interface are replaced by a P=O group [28].…”

“…This suggests that the trap passivation mechanism due to P may be related to re-arranging the critical interfacial dielectric layer, relieving interface stress and possibly allowing better passivation of the dangling bonds [46]. Accordingly, the effect of phosphorus on near-interface traps can be summarized by the following theories reported in the literature: (1) the P atoms act as a network former and result in reconstruction of the oxide network in SiO 2 (Si-Si bonds elimination) [26,28,46] (2) C related defects are removed by the P doping of SiO 2 [28,[47][48][49] where threefold carbon atoms at the interface are replaced by a P=O group [28]. In this regard, it has been reported recently that POCl 3 annealing can form a peculiar -O 3 PO structure which can act as a carbon absorber [48,49] For the Si interstitial (Si i ), it should be noted that this defect has a complex structure consisting of several electrically active centers: two Si-Si bonds, one threefold oxygen, and one five-fold Si [15].…”

Impact of design and process variation on the fabrication of SiC diodes

“…Nitrogen (N) acts as an n-type dopant in SiC, and after N 2 O annealing there may be some counter doping of the pdoped regions (created by aluminium dopants) by N [15,16] . These p regions are used underneath the Schottky contact in the termination region.…”

Advanced SiC/Oxide Interface Passivation

“…For example, this polarize charge can change a "normally-off" device to a "normally-on" device. X-ray photoelectron spectroscopy (XPS) results [34,35] reveal that PSG layers cannot be removed completely by etching in BOE if is grown on 4H-SiC while opposite is true for the layer grown on Si. After BOE etching in the case of SiC, a 2-3-nm Si-C-O-P interfacial layer can still be seen which is equivalent to a phosphorous areal density of 2 × 10 .…”