Abstract
This work examines the stability of epitaxial 3C-SiC/Si heterojunctions subjected to heat treatments between 1000 °C and 1300 °C. Because of the potential for silicon carbide in high temperature and harsh environment applications, and the economic advantages of growing the 3C-SiC polytype on large diameter silicon wafers, its stability after high temperature processing is an important consideration. Yet recently, this has been thrown into question by claims that the heterojunction suffers catastrophic degradation at temperatures above 1000 °C. Here we present results showing that the heterojunction maintains excellent diode characteristics following heat treatment up to 1100 °C and while some changes were observed between 1100 °C and 1300 °C, diodes maintained their rectifying characteristics, enabling compatibility with a large range of device fabrication. The parameters of as-grown diodes were J0 = 1 × 10−11 A/mm2, n = 1.02, and +/−2V rectification ratio of 9 × 106. Capacitance and thermal current-voltage analysis was used to characterize the excess current leakage mechanism. The change in diode characteristics depends on diode area, with larger areas (1 mm2) having reduced rectification ratio while smaller areas (0.04 mm2) maintained excellent characteristics of J0 = 2 × 10−10 A/mm2, n = 1.28, and +/−2V ratio of 3 × 106. This points to localized defect regions degrading after heat treatment rather than a fundamental issue of the heterojunction.
Highlights
The advancement in technology for the deposition of silicon carbide on silicon has been evolving, with the 3C polytype being most commonly investigated because device quality films can be grown between 1000 °C and 1380 °C, below the silicon melt temperature[3,4]
Most commonly stacking faults near the interface have been reduced over time and optimization of the initial cleaning, carbonization, and growth steps has resulted in significant improvements in overall film quality[3,20]
While the operational temperature in service is likely to be several hundreds of degrees below 1000 °C, these higher temperatures may well occur in some later fabrication steps. This led us to a systematic investigation into the effect of thermal treatments on the SiC/Si heterojunction in which we developed a sensitive test structure that could be exposed to high temperatures and determine the onset of changes at the heterojunction
Summary
The advancement in technology for the deposition of silicon carbide on silicon has been evolving, with the 3C polytype being most commonly investigated because device quality films can be grown between 1000 °C and 1380 °C, below the silicon melt temperature[3,4]. It was claimed that the carbonization barrier can break down at temperatures roughly above 1000–1100 °C, and that this effect is so prominent that the rectifying n-SiC/p-Si junction is destroyed and the heterojunction becomes electrically shorted[27] It is claimed, the interface instability has crucial consequences for applications exposed to high temperatures such as SiC on Si for harsh environments, or its use as a substrate for growth of III-N compounds and graphene. While the operational temperature in service is likely to be several hundreds of degrees below 1000 °C, these higher temperatures may well occur in some later fabrication steps This led us to a systematic investigation into the effect of thermal treatments on the SiC/Si heterojunction in which we developed a sensitive test structure that could be exposed to high temperatures and determine the onset of changes at the heterojunction. In this study we aim to establish at what temperature we begin to see degradation of the SiC/Si heterojunction and whether it remains of sufficiently high quality and robust at high temperatures to be useful in the above applications
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