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Dopant profiles near the semiconductor–oxide interface are critical for microelectronic device performance. As the incorporation of Si1−xGex into transistors continues to increase, it is necessary to understand the behavior of dopants in Si1−xGex. In this paper, the diffusion and electrical activation of phosphorus within a strained, single-crystal Si0.7Ge0.3 layer on Si during oxidation are reported. Both layers were uniformly doped, in situ, with an average phosphorus concentration of 4 × 1019 atoms/cm3. After high-temperature oxidation, secondary ion mass spectrometry measurements revealed that the bulk of the phosphorus diffuses out of only the SiGe layer and segregates at the oxidizing SiGe–SiO2 interface. Hall effect measurements corroborate the observed phosphorus loss and show that the phosphorus diffusing to the oxidizing interface is electrically inactive. Through density functional theory (DFT) calculations, it is shown that phosphorus interstitials prefer sites near the SiGe–SiO2 interface. Finally, based on a combination of experimental data and DFT calculations, we propose that the phosphorus atoms are displaced from their lattice sites by Ge interstitials that are generated during SiGe oxidation. The phosphorus atoms then migrate toward the SiGe–SiO2 interface through a novel mechanism of hopping between Ge sites as P–Ge split interstitials. Once they reach the interface, they are electrically inactive, potentially in the form of interstitial clusters or as part of the reconstructed interface or oxide. [ABSTRACT FROM AUTHOR]

β-Ga2O3 rectifiers fabricated on lightly doped epitaxial layers on bulk substrates were exposed to CF4 plasmas. This produced a significant decrease in Schottky barrier height relative to unexposed control diodes (0.68 eV compared to 1.22 eV) and degradation in ideality factor (2.95 versus 1.01 for the control diodes). High levels of F (>1022 cm−3) were detected in the near-surface region by Secondary Ion Mass Spectrometry. The diffusion of fluorine into the Ga2O3 was thermally activated with an activation energy of 1.24 eV. Subsequent annealing in the range 350–400 °C brought recovery of the diode characteristics and an increase in barrier height to a value larger than in the unexposed control diodes (1.36 eV). Approximately 70% of the initial F was removed from the Ga2O3 by 400 °C, with the surface outgas rate also being thermally activated with an activation energy of 1.23 eV. Very good fits to the experimental data were obtained by integrating physics of the outdiffusion mechanisms into the Florida Object Oriented Process Simulator code and assuming that the outgas rate from the surface was mediated through fluorine molecule formation. The fluorine molecule forward reaction rate had an activation energy of 1.24 eV, while the reversal rate of this reaction had an activation energy of 0.34 eV. The net carrier density in the drift region of the rectifiers decreased after CF4 exposure and annealing at 400 °C. The data are consistent with a model in which near-surface plasma-induced damage creates degraded Schottky barrier characteristics, but as the samples are annealed, this damage is removed, leaving the compensation effect of Si donors by F− ions. The barrier lowering and then enhancement are due to the interplay between surface defects and the chemical effects of the fluorine. [ABSTRACT FROM AUTHOR]

In this article the theory of Li and Jones is applied to End of Range (EOR) dislocation loops to model the nucleation and evolution of the loops. The model is verified with experimental data and accurately represents the nucleation, growth, and Ostwald ripening stages of dislocation loop evolution.

The results are presented of an investigation into the diffusion of implanted nitrogen in silicon.

Phosphorus diffusion studies can be used to asses the affects of stress on the semiconductor material silicon. Patterned nitride stripes are used to create stress. Uneven diffusion patterns are observed where ion-implanted dislocation loops are smaller and less dense in compressed areas of the nitride film. Finite element stress and diffusion simulations are reliably reproduced in the laboratory.

Studies involving boron, phosphorus and dislocation markers were conducted to compare transient enhanced diffusion (TED) effects which are due to implantation damage producing enhanced diffusion of dopants in silicon. Results indicated that phosphorus is enhanced substantially more than boron during damage annealing. Dislocation growth showed that a number of interstitials greater than the damage dose is captured during these anneals.

Point defect models were studied and compared with experimental results derived from intrinsically doped material. It was shown that point defect models can accurately simulate transient dopant diffusion in intrinsic doping conditions. Furthermore, model parameters approximate low dose silicon implant damage effects and oxidation enhanced diffusion. Pairing coefficients derived from effective binding energies characterize implantation damage effects of boron and phosphorus diffusion.

Vacancy supersaturation was used for diffusion of single quantum well Si1-xGex/Si layers.

We have investigated the electrical activation of implanted boron in silicon-on-insulator (SOI) material using Hall effect, four-point probe, and secondary ion mass spectrometry. Boron was implanted at energies ranging from 1 keV to 6.5 keV with a dose of 3×1014 cm-2 into bonded SOI wafers with surface silicon thickness ranging from 300 Å to 1600 Å. In one sample set, furnace anneals at 750 °C were performed in a nitrogen ambient for times ranging from 5 min to 48 h. A second sample consisted of isochronal furnace anneals performed from 450 °C to 1050 °C for 30 min. Significantly less activation of boron is observed in SOI at temperatures below 750 °C, regardless of the implant energy and surface silicon thickness. Between 750 °C and 900 °C, the active dose of boron in SOI is similar to that of bulk Si. As the implant energy increases, the fractional activation in thin SOI increases, due to a reduction in boron interstitial clusters (BIC) in the surface Si layer. It is concluded that an increase in the BIC population is the likely source of the low activation observed in SOI. This may be due to an increase in the interstitial supersaturation within the surface Si layer, due to the interface acting as a reflective boundary for interstitials. [ABSTRACT FROM AUTHOR]

Scaling the gate oxide thickness is one of many process development challenges facing device engineers today. Nitrogen implantation has been used to control gate oxide thickness. By varying the dose of the nitrogen implant, process engineers can have multiple gate oxide thicknesses in the same process. Although it has been observed that nitrogen retards gate oxidation kinetics, the physics of how this occurs is not yet well understood. Since the retardation in oxide growth is due to the diffusion of nitrogen and its subsequent incorporation at the silicon/silicon oxide interface, the study of the diffusion behavior of nitrogen in silicon becomes important. Further, it is also necessary to study how this diffusion behavior impacts oxide growth. Models have been developed to explore these issues. The diffusion model is based on ab initio results and is compared to experimental results at two temperatures. The oxide reduction model is based on the diffusion of nitrogen to the surface. The surface nitrogen is coupled to the surface reaction rate of silicon and oxygen to moderate oxide growth. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the interdiffusion of Si/Si0.85Ge0.15/Si single quantum well structures subjected to inert- and oxidizing-ambient annealing. Extraction of diffusion coefficients; Similarity in diffusion profiles of samples processed.

The electrical activation of implanted boron in silicon-on-insulator (SOI) material was investigated using Hall effect, four-point probe, and secondary ion mass spectrometry. The investigation concluded that an increase in the boron interstitial cluster (BIC) population is the likely source of the low activation observed in SOI.

The interdiffusion of a Si/Si[sub 0.85]Ge[sub 0.15]/Si single quantum well heterostructure subjected to thermal annealing in a nitriding ambient was investigated as a function of anneal temperature and time. Nitridation of the silicon surface alters equilibrium vacancy point defect populations throughout the structure, which allows the determination of the point defect species important in interdiffusion. Diffusion coefficients of Ge after nitridation of ∼1x10[sup -14] cm[sup 2]/s for 1100 °C and ∼1x10[sup -13] cm[sup 2]/s for 1200 °C were extracted. The extent of diffusion in a nitriding ambient was much less than in an inert ambient, which indicates minimal vacancy contribution to interdiffusion. This is in contrast to results from previously published studies performed in an oxidizing ambient. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

β-Ga2O3 rectifiers fabricated on lightly doped epitaxial layers on bulk substrates were exposed to CF4 plasmas. This produced a significant decrease in Schottky barrier height relative to unexposed control diodes (0.68 eV compared to 1.22 eV) and degradation in ideality factor (2.95 versus 1.01 for the control diodes). High levels of F (>1022 cm−3) were detected in the near-surface region by Secondary Ion Mass Spectrometry. The diffusion of fluorine into the Ga2O3 was thermally activated with an activation energy of 1.24 eV. Subsequent annealing in the range 350–400 °C brought recovery of the diode characteristics and an increase in barrier height to a value larger than in the unexposed control diodes (1.36 eV). Approximately 70% of the initial F was removed from the Ga2O3 by 400 °C, with the surface outgas rate also being thermally activated with an activation energy of 1.23 eV. Very good fits to the experimental data were obtained by integrating physics of the outdiffusion mechanisms into the Florida Object Oriented Process Simulator code and assuming that the outgas rate from the surface was mediated through fluorine molecule formation. The fluorine molecule forward reaction rate had an activation energy of 1.24 eV, while the reversal rate of this reaction had an activation energy of 0.34 eV. The net carrier density in the drift region of the rectifiers decreased after CF4 exposure and annealing at 400 °C. The data are consistent with a model in which near-surface plasma-induced damage creates degraded Schottky barrier characteristics, but as the samples are annealed, this damage is removed, leaving the compensation effect of Si donors by F− ions. The barrier lowering and then enhancement are due to the interplay between surface defects and the chemical effects of the fluorine. [ABSTRACT FROM AUTHOR]