Metal-Oxide-Semiconductor Characteristics of Zr-Oxynitride Thin Film on 4H-SiC Substrate

Abstract

Sputtered Zr on 4H-SiC substrate and followed by simultaneous oxidation and nitridation in nitrous oxide ambient at various temperatures (400-900 • C) for 15 min have been systematically investigated. The structural and electrical properties of the samples were evaluated. Energy-filtered transmission electron micrographs demonstrated that an interfacial layer (IL) of 1.44 to 4.20 nm had been formed in between a bulk oxide of 14.63 to 18.53 nm and the SiC substrate, depending on the temperature. The calculated activation energies for the bulk oxide, which was Zr-oxynitride, IL, and total oxide growth were −0.0335 eV, 0.1543 eV, and −0.0078 eV, respectively. Supportive results were obtained from X-ray diffractometer, Raman spectrometer, and atomic force microscope. The electrical results revealed that 500 • C oxidized/nitrided sample has demonstrated the highest breakdown field and reliability. This was attributed to the lowest total interface trap, effective oxide charge, and highest barrier height between conduction band edge of oxynitride and semiconductor.The current progress in semiconductor industry is mainly focusing in four parallel directions, which include downscaling of circuit elements on an inexpressible scale, reducing its power consumption, increasing operation speed, and tolerance-temperature range. 1, 2 To realize next generation metal-oxide-semiconductor (MOS)-based devices for high power and/or high radiation, integration of functional gate oxides on wide bandgap (WBG) semiconductors are of interest. 3-7 Silicon carbide (SiC) has several merits over other WBG semiconductors due to its commercial availability and ability to grow native oxide (SiO 2 ). 8, 9 Amongst many SiC polytypes, 10, 11 4H-SiC offers a wide bandgap of 3.26 eV, high breakdown field strength of ∼3 MV/cm, high saturation electron drift velocity of ∼2×10 7 cm/s, and high thermal conductivity of ∼3.7 W/cm • C. 9, 12, 13 Demonstration of these properties makes SiC-based MOS devices potentially suited for operation under harsh conditions.In order to fabricate these devices, the gate oxide must be able to bear a high transverse electric field and to possess a good reliability, so that leakage current through the gate oxide could be minimized. To date, thermally nitrided-SiO 2 on SiC is still considered as the first choice gate oxide. 7, 14-21 Nonetheless, its low dielectric constant (κ) value of 3.9, as compared to SiC with κ value of 10, could cause oxide breakdown and reliability issues. According to Gauss law: 22The high electric field strength in SiC of ∼3 MV/cm, would give a high electric field of ∼7.69 MV/cm in SiO 2 , in which, it is equivalent to a factor of ∼2.56 times higher electric field being imposed on the gate oxide than on the SiC. Consequently, the gate oxide may electrically break down much earlier than the SiC substrate thus depletes the objective of using SiC as the primer substrate for high power, high temperature, and/or high radiation applications. An approach to circumvent this is to supersede the relatively lo...

Properties of thermally oxidized and nitrided Zr-oxynitride thin film on 4H–SiC in diluted N2O ambient

“…Two peaks located at 204 cm À1 and 777 cm À1 are originated from 4HeSiC substrate and it can be detected in all investigated samples. For as-deposited Zr metal on SiC substrate, Raman spectrum was not detectable except for the two characteristics SiC spectra (not shown) [3,9]. This indicates that the metal layer is an amorphous phase, which is in agreement with XRD results that have been presented in Section 3.4.…”

“…12(a)e(d) in order to identify the characteristic peaks of tetragonal phase of ZrO 2 (t-ZrO 2 ). It has been described elsewhere [3,9] that a very strong intensity of diffraction peak at 35.5 and a minor peak at 43.2 (not shown) were recorded in all investigated samples, in which the peaks are well matched with 4HeSiC(004) (ICDD card number 00-022-1317). The featureless pattern of as-deposited Zr metal on SiC has been verified elsewhere [3,9] that the sample is amorphous structure (not shown).…”

“…It has been described elsewhere [3,9] that a very strong intensity of diffraction peak at 35.5 and a minor peak at 43.2 (not shown) were recorded in all investigated samples, in which the peaks are well matched with 4HeSiC(004) (ICDD card number 00-022-1317). The featureless pattern of as-deposited Zr metal on SiC has been verified elsewhere [3,9] that the sample is amorphous structure (not shown). Upon oxidation and nitridation at temperatures of 500 C in different N 2 O concentrations, crystalline structure is revealed in all investigated films.…”

“…The E g value of SiC substrate is obtained from literature [2,52]. [3,9,53,54]. A typical EFTEM image of two crystalline planes is clearly shown in Fig.…”

“…One of the main strengths of SiC over other WBG semiconductors is its ability to grow native oxide (SiO 2 ) [3,4]. Nonetheless, there are numerous woes associated with the SiO 2 thin film or gate based on SiC, namely high SiO 2 eSiC interface-trap density and high electric field [5,6].…”