Effect of Varying Oxidation Parameters on the Generation of C-Dangling Bond Centers in Oxidized SiC
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Abstract SiC is perhaps the most appropriate material to replace Si in power-metal-oxidesemiconductor-field-effect-transistors (MOSFETs), because, unlike the other wide band-gap semiconductors, SiC can be thermally oxidized similarly to Si to form a SiO 2 insulating layer. In our studies of oxidized SiC, we have used electron paramagnetic resonance (EPR) to identify Cdangling bonds generated by hydrogen release from C-H bonds. While hydrogen's effect on SiCbased MOSFETs is uncertain, studies of Si-based MOSFETs indicate that it is important to minimize hydrogen in MOS structures. To examine the role of hydrogen, we have studied the effects of SiC/Si0 2 fabrication on the density of C-related centers, which are made EPR active by a dry heat-treatment. Here we examine the starting and ending procedures of our oxidation routine. The parameter that appears to have the greatest effect on center density is the ending step of our oxidation procedure. For example, samples that were removed from the furnace in flowing 02 produced the smallest concentration of centers after dry heat-treatment. We report on the details of these experiments and use our results to suggest an oxidation procedure that limits center production.
Introduction SiC has both a wide band-gap and high thermal conductivity that make it an attractive replacement for Si in high power, high temperature microelectronic devices. For power metaloxide-field-effect transistors (MOSFETs) in particular, SiC is of interest because unlike the other wide band-gap semiconductors, it can be thermally oxidized similarly to Si in order to create a
Si0 2 insulating layer. In our previous studies of oxidized 3C-SiC, 4H-SiC, and 6H-SiC [1-2], we have observed centers that can be activated by dry heat-treatments at temperatures greater than 800 TC. The gvalues of these centers range from 2.0025 to 2.0029, which is within the range of g-values typical of C-related centers [3-5]. The temperatures at which these centers are generated are significantly greater that those used to generate Si dangling bonds. Thus, we suggest that the centers are unpaired electrons located on C atoms. We have also observed that these centers can be activated by heat-treatment in an ambient that does not contain moisture and passivated in an ambient that contains moisture. Therefore, we suggest that these centers are activated by release of a hydrogenous species from C dangling bonds. Supporting the relation to hydrogen is an experiment in which we heat-treated oxidized samples in dry (
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