Analysis of electron traps at the 4H–SiC/SiO2 interface; influence by nitrogen implantation prior to wet oxidation

Abstract

Density of interface states, electron traps, and hole traps as a function of the nitrogen density in SiO 2 on SiCInterfaces between 4H-SiC and Si O 2 : Microstructure, nanochemistry, and near-interface traps J. Appl. Phys. 97, 034302 (2005); 10.1063/1.1836004 Study on electron trapping and interface states of various gate dielectric materials in 4H-SiC metal-oxidesemiconductor capacitors Electron states at the SiO 2 / 4H -SiC interface have been investigated using capacitor structures and especially, the influence of excess nitrogen, introduced by ion implantation, at the interface is studied in detail. Implanted and nonimplanted n-type samples with an interfacial concentration of nitrogen of ϳ10 19 cm −3 and 10 16 cm −3 , respectively, were analyzed by capacitance-voltage ͑C-V͒ measurements, performed at different temperatures and probe frequencies, and thermal dielectric relaxation current ͑TDRC͒ measurements performed in the temperature range of 35-295 K. Three main categories of electron states are disclosed, true interface states ͑D it ͒, fast near interface states ͑NIT ox fast ͒ and slow near interface states ͑NIT ox slow ͒. The density versus energy distributions of D it and NIT ox fast have been deduced from the TDRC data and they are shown to give a close quantitative agreement with the shape and frequency dependence of the C-V curves. Further, the amount of NIT ox slow extracted from TDRC is demonstrated to be responsible for the parallel shifts and hysterezis effects occurring in the C-V characteristics. All three categories of electron states are reduced in concentration in the implanted samples. This holds particularly for NIT ox fast with a peak at ϳ0.1 eV below the conduction band edge of 4H-SiC that is suppressed by at least two orders of magnitude relative to the nonimplanted samples. The decrease for D it is also substantial ͑a factor of ϳ10͒ while the loss for NIT ox slow is considerably smaller ͑only ϳ30%͒. The results provide firm evidence that NIT ox fast and NIT ox slow do not originate from the same kind of defect center.

Generation of very fast states by nitridation of the SiO2/SiC interface

“…The existence of near interface oxide traps has been suggested by other evaluation methods. [18][19][20] The existence of fast interface states in the vicinity of the conduction band edge is also suggested by Hall-effect measurements and so on. 9,[21][22][23][24] We proposed a method to evaluate fast interface states that can be neither detected by the conventional high-low nor conductance methods.…”

Study of radiation damage induced by 12 keV X-rays in MOS structures built on high-resistivityn-type silicon

“…As discussed later, the measurements can be approximately described by three interface states D j it (E t ), j = 1, 2, 3. As a function of the band bending É s , assuming that charge carriers are exchanged only with the conduction band, each state j contributes to the capacitance C and the conductance G (Nicollian & Brews, 1982;Pintilie et al, 2010),…”

“…The relation between the bias voltage V G applied at the gate and the band bending É s under steady state conditions (ignoring the 50 mV AC voltage of the capacitance bridge) is (Nicollian & Brews, 1982;Pintilie et al, 2010)…”

Accurate evaluation of interface state density in SiC metal-oxide-semiconductor structures using surface potential based on depletion capacitance

“…The interface state density is characterized by high-low or conductance methods with the maximum frequency of 0.1 $ 1 MHz. [2][3][4][5][6][7][8][9][10][11][12][13][14] The existence of fast interface states has been suggested 15,16 but the fast interface states that respond to the maximum probe frequency are undetectable by these methods. Although increasing the frequency is a method to detect fast states, very high-frequency measurements are not easily obtained because of series resistance and inductance.…”