Philip Tanner

Effects of nitridation in gate oxides grown on 4H-SiC

Experiments have demonstrated that nitridation provides critically important improvements in the quality of SiO2–SiC interface. This article provides results and analysis aimed at developing the much needed understanding of the mechanisms and effects associated with both annealing of pregrown oxides and direct growth in NO and N2O environments. According to the model proposed in the article, nitridation plays a double role: (1) creation of strong Si≡N bonds that passivate interface traps due to dangling and strained bonds, and (2) removal of carbon and associated complex silicon–oxycarbon bonds from the interface. This understanding of the effects of nitridation is experimentally verified and used to design a superior process for gate oxide growth in the industry-preferred N2O environment.

Investigation of nitric oxide and Ar annealed SiO2/SiC interfaces by x-ray photoelectron spectroscopy

Silicon dioxide (SiO2)/silicon carbide (SiC) structures annealed in nitric oxide (NO) and argon gas ambiences were investigated using x-ray photoelectron spectroscopy (XPS). The XPS depth profile analysis shows a nitrogen pileup of 1.6 at. % close to the NO annealed SiO2/SiC interface. The results of Si 2p, C 1s, O 1s, and N 1s core-level spectra are presented in detail to demonstrate significant differences between NO and Ar annealed samples. A SiO2/SiC interface with complex intermediate oxide/carbon states is found in the case of the Ar annealed sample, while the NO annealed SiO2/SiC interface is free of these compounds. The Si 2p spectrum of the Ar annealed sample is much broader than that of the NO annealed sample and can be fitted with three peaks compared with the two peaks in the NO annealed sample, indicating a more complex interface in the Ar annealed sample. Also the O 1s spectrum of the NO annealed samples is narrow and symmetrical and can be fitted with only one peak whereas that of the Ar an...

Slow-trap profiling of NO and N2O nitrided oxides grown on Si and SiC substrates

In this paper, we demonstrate the unique ability of a newly developed slow-trap profiling technique to characterise silicon-based MOS capacitors in strong inversion. We also demonstrate the applicability of the slow-trap profiling technique for the characterisation of oxides grown on SiC. The obtained slow-trap profiles show that NO nitridation eliminates while N2O creates defects acting as slow traps in the case of both Si and SiC substrates. The corresponding effects of nitridation on interface traps and fixed oxide charge are also discussed.

Thickness dependence of the piezoresistive effect in p-type single crystalline 3C-SiC nanothin films

This paper reports, for the first time, the piezoresistive effect of p-type single crystalline 3C-SiC nanothin films grown by LPCVD at low temperature. Compared to thick SiC films, the gauge factors of the 80 nm and 130 nm films decreased remarkably. This result indicates that the crystal defect at the SiC/Si interface has a significant influence on the piezoresistive effect of ultra-thin film p-type 3C-SiC.

Fundamental piezoresistive coefficients of p-type single crystalline 3C-SiC

The orientation dependence of the piezoresistive effect of p-type single crystalline 3C-SiC thin film grown on a (100)Si wafer was characterized. The longitudinal, transverse gauge factors in [100] orientation, and longitudinal gauge factor in [110] orientation were found to be 5.8, −5.2, and 30.3, respectively. The fundamental piezoresistive coefficients π11, π12, and π44 of p-type 3C-SiC were obtained to be 1.5 × 10−11 Pa−1, −1.4 × 10−11 Pa−1, and 18.1 × 10−11 Pa−1, respectively. From these coefficients, the piezoresistive effect in any crystallographic orientation in p-type single crystalline 3C-SiC can be estimated, which is very valuable in designing micro-mechanical sensors.

Charge transport and activation energy of amorphous silicon carbide thin film on quartz at elevated temperature

We report on the temperature dependence of the charge transport and activation energy of amorphous silicon carbide (a-SiC) thin films grown on quartz by low-pressure chemical vapor deposition. The electrical conductivity as characterized by the Arrhenius rule was found to vary distinctly under two activation energy thresholds of 150 and 205 meV, corresponding to temperature ranges of 300 to 450 K and 450 to 580 K, respectively. The a-SiC/quartz system displayed a high temperature coefficient of resistance ranging from −4,000 to −16,000 ppm/K, demonstrating a strong feasibility of using this material for highly sensitive thermal sensing applications.

Piezoresistive Effect of p-Type Single Crystalline 3C-SiC Thin Film

This letter presents for the first time the piezoresistive effect of p-type single crystalline 3C-SiC thin film. The 3C-SiC thin film was epitaxially grown on (100) p-type Si substrate using the low-pressure chemical vapor deposition process. The grown 3C-SiC was doped in situ with aluminum to form p-type semiconductor with carrier concentration of 5×1018 cm-3 and sheet resistance of about 40 kΩ/□. Longitudinal and transverse gauge factors (GFs) of the 3C-SiC in [110] orientation at room temperature (23°C) were 30.3 and -25.1, respectively. These results indicated that the p-type single crystalline 3C-SiC possessed a higher GF than the previously reported results in p-type polycrystalline 3C-SiC.

Electrical Properties of p-type 3C-SiC/Si Heterojunction Diode Under Mechanical Stress

The current mechanism and effects of external transverse stress in the [110] orientation on the electrical properties of a single crystal (100) p-3C-SiC/p-Si heterojunction diode are reported for the first time. It has been observed that the current flow in the heterojunction is due to tunneling through the triangular potential barrier formed due to valence band offset between Si and SiC. The applied stress produces small changes in tunneling current when stress is increased from 0 to 308 MPa. The observed increase in current at 0.24 V is 10% at maximum stress of 308 MPa. The increase of tunneling current when applying stress is explained in terms of stress, which alters the out-of-plane effective mass, and the effective tunneling barrier height of holes in top subbands of p-type Si.

Properties of Nitrided Oxides on SiC

If there is a singular property of silicon that has contributed to its success as a semiconductor material, it is the native oxide, SiO2. This oxide can be thermally grown to form an effective insulating layer as part of the gate in a metal-oxide-semiconductor field-effect transistor (MOSFET) structure. Silicon Carbide also has the ability to grow a similar oxide, and when combined with the bulk properties of wide bandgap, high thermal conductivity and extremely low intrinsic free carrier concentration, will lead to an enormous number of applications. This means that as far as the gate oxide is concerned SiC can be processed in much the same way as Si, the exception being that the processing temperatures are generally higher.

The effect of strain on the electrical conductance of p-type nanocrystalline silicon carbide thin films

This paper presents for the first time the effect of strain on the electrical conductance of p-type nanocrystalline SiC grown on a Si substrate. The gauge factor of the p-type nanocrystalline SiC was found to be 14.5 which is one order of magnitude larger than that in most metals. This result indicates that mechanical strain has a significant influence on the electrical conductance of p-type nanocrystalline SiC, which is promising for mechanical sensing applications in harsh environments.