Limiting Step Involved in the Thermal Growth of Silicon Oxide Films on Silicon Carbide

Abstract

Thermal growth of silicon oxide films on silicon carbide in O 2 was investigated using oxygen isotopic substitution and narrow resonance nuclear reaction profiling. This investigation was carried out in parallel with the thermal growth of silicon oxide films on Si. Results demonstrate that the limiting steps of the thermal oxide growth are different in these two semiconductors, being diffusion limited in the case of Si and reaction limited in the case of SiC. This fact renders the growth kinetics of SiO 2 on SiC very sensitive to the reactivity of the interface region, whose compositional and structural changes can affect the electrical properties of the structure. DOI: 10.1103/PhysRevLett.89.256102 PACS numbers: 81.65.Mq, 61.82.Fk, 68.35.Fx, 77.55.+f In semiconductor device applications involving high power, frequency, voltage, and/or temperature, Si use is limited by its physical properties. An example is the relative narrow band gap (1.1 eV) that prevents Si devices from operating at high temperatures. The polar crystal silicon carbide (SiC) appears to be the wide band-gap material of choice since besides the wider gap (2.9 eV for the 6H polytype) SiC has other desired properties such as high thermal conductivity, breakdown voltage, and saturated electron drift velocity. It is also the only known compound semiconductor on which SiO 2 can be grown thermally. On the other hand, the properties of the SiO 2 =SiC interface lead to electrical characteristics worse than those of SiO 2 =Si, while the scatter of the available data [1] suggests poor interface control. Investigations of the thermal oxide film on SiC in its different regions have been pursued [2 -7], indicating that in the surface and bulk regions the oxide is similar to that grown on Si [4,8,9], that the interface is less abrupt [5,10], and that incompletely oxidized C or Si are found near the interface [2,3,6,7,[11][12][13][14]. However, a thorough understanding of the phenomena taking place during the thermal growth of SiO 2 on SiC is still missing.Growth of SiO 2 on SiC is much slower than on Si, presenting more scattered data [15][16][17] and differences along the polar directions [ 0001 and (0001) in the hexagonal polytypes]. Several authors have tried to model the kinetics of the thermal growth of SiO 2 on SiC [15,17,18], mostly within the framework of the Deal and Grove model [19], which satisfactorily describes the thermal growth of SiO 2 on Si in dry O 2 for oxide thicknesses above 20 -30 nm. This model is based on a stationary flux of O 2 , the only mobile species, across the growing oxide and on reaction with Si to form SiO 2 only at an abrupt interface. These efforts were curve fittings which did not consider the reaction mechanisms and limiting steps characteristic of the SiO 2 =SiC system. The elucidation of the oxidation mechanismsidentification of the limiting steps and the mobile species and how they are transported during oxide thermal growth-is necessary to develop an oxidation model for SiC allowing prediction and control of the ...

Abrupt model interface for the 4H(1000)SiC-SiO2 interface

“…Moreover, the channel mobilities of SiC-based MOS devices are much lower than expected from the bulk value [4,5]. Despite numerous experimental studies, an atomicscale understanding of the origin of these drawbacks has to a large extent remained elusive [6][7][8][9][10][11]. To address these issues, it is important to achieve a clearer picture of the atomic structure at the SiC/SiO 2 interface.…”

Identification of the Carbon Dangling Bond Center at the4H−SiC/SiO2Cantin1, Bardeleben2, Shishkin3 et al. 2004Phys. Rev. Lett.922691View full textAdd to dashboardCite

“…Experimental information on these processes is still very limited and additional experiments are clearly required. We know from nuclear reaction analysis that the interface reaction between oxygen and SiC is the limiting step in the oxidation process [7]. This leads to very different oxidation kinetics for the C(000-1) and Si(0001) interfaces contrary to the Si case where the oxygen diffusion through the SiO 2 layer is the limiting process.…”

Variation of interface trap level charge density within the bandgap of 4H-SiC with varying oxide thickness

“…The extracted D it values near the mid-bandgap of 4H-SiC remain stable for all oxides with thicknesses in the range of 10 9 -10 10 cm −2 eV −1 . It is observed from table 1 that the fixed oxide charge density is continuously increasing with oxide thickness, which means that for a long time oxidation bulk charges of oxide (due to removal of C species during thermal oxidation [18][19][20]) will be more effective. The value of D it near the conduction band edge has been found to be of the order of 10 12 cm −2 eV −1 for thicker oxides and for thinner oxides D it comes out in the range of 10 10 cm −2 eV −1 .…”