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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]

N+ ion implantation to form resistive regions for edge termination at the anode contact periphery was used to maximize the breakdown voltage (VB) of vertical geometry β-Ga2O3 rectifiers. The design was examined via simulations using the Florida object oriented device and process Technology Computer-Aided Design (TCAD) simulator. The configuration of the implanted region was investigated with these simulations and then implemented experimentally. Significant increases of ∼200%–250% in VB were achieved for 50–1000 μm diameter rectifiers with an unbounded resistive region and an implantation depth of ∼0.5 μm. The on-state resistance and on/off ratios of the rectifiers were essentially unchanged by the addition of the implanted regions. An optimized implanted edge termination structure maximizes the breakdown voltage with no associated increase in device resistance in vertical geometry Ga2O3 rectifiers. [ABSTRACT FROM AUTHOR]

The understanding and availability of quantitative measurements of the diffusion of dopants and impurities in Ga2O3 are currently at an early stage. In this work, we summarize what is known about the diffusivity of the common donor dopants, Sn, Ge, and Si, as well as some of the deep acceptors, N, Fe, and Mg, and donors, Ir. Two commonly encountered interstitial impurities are H and F, the former through growth and processing ambients and the latter through its use in plasmas used for stripping dielectrics from Ga2O3. Both are found to have high diffusion coefficients and an effect on electrical conductivity, and H shows anisotropy in its diffusion behavior. Si, Ge, and Sn implanted into bulk β-Ga2O3 at total doses from 2 × 1013 to 2 × 1015 cm−2 and annealed at 1100 °C for 10–120 s in either O2 or N2 ambients showed a significant effect of the annealing ambient on the donor's diffusivity. In the case of O2 annealing, there was extensive redistribution of the Si, Sn, and Ge across the entire dose range, while, in sharp contrast, the use of N2 annealing suppressed this diffusion. The N2 ambient also suppressed loss of dopants to the surface, with >90% of the initial dose retained after annealing at 1100 °C for 120 s, compared to 66%–77% with O2 anneals under the same conditions. [ABSTRACT FROM AUTHOR]

The high breakdown voltage and low on-state resistance of Schottky rectifiers fabricated on β-Ga2O3 leads to low switching losses, making them attractive for power inverters. One of the main goals is to achieve high forward currents, requiring the fabrication of large area (>1 cm2) devices in order to keep the current density below the threshold for thermally driven failure. A problem encountered during the measurement of these larger area devices is the dependence of current spreading on the probe size, resistance, number, and geometry, which leads to lower currents than expected. We demonstrate how a multiprobe array (6 × 8 mm2) provides a means of mitigating this effect and measure a single sweep forward current up to 135 A on a 1.15 cm2 rectifier fabricated on a vertical Ga2O3 structure. Technology computer-aided design simulations using the floods code, a self-consistent partial differential equation solver, provide a systematic insight into the role of probe placement, size (40–4120 μm), number (1–5), and the sheet resistance of the metal contact on the resultant current-voltage characteristics of the rectifiers. [ABSTRACT FROM AUTHOR]

One of the key areas for implementation of high-power Ga2O3 rectifiers is the mitigation of electric field crowding at the edge of the depletion region to avoid premature breakdown. Floating metal field rings (FMRs) are a relatively simple approach for achieving this. We report simulations of the spacing (1–10 μm), width (2–15 μm), number of rings, and also the effect of biasing the rings (0–280 V) and including a field plate at the periphery of the rings on the breakdown voltage of a vertical geometry rectifier with a range of doping concentrations (5 × 1015–4 × 1016 cm−3) in the drift region. Improvements in breakdown voltage of 19%–54% relative to an unterminated rectifier are found with an optimum design of the field rings. The experimental results on rectifiers with different FMR geometries show an RON of 4.5–4.9 mΩ cm2, a turn-on voltage of 0.96–0.94 V, a high on-off ratio of >5 × 106, an ideality factor of 1.03, and a Schottky barrier height of 1.03 eV at room temperature. These devices have similar forward electrical characteristics, indicating that FMRs do not degrade the device rectifying performance. [ABSTRACT FROM AUTHOR]

Full-dimensional variational calculations are reported for the isomerising disilyne molecule, Si2H2. Large-scale calculations using coordinates based on orthogonal satellite vectors permitted the computation of excited vibrational state energies and wavefunctions for all four isomeric forms: dibridged Si(H2)Si, monobridged Si(H)SiH, disilavinylidene H2SiSi, and trans-bent HSiSiH. Energies and wavefunctions have been determined for the lowest 2400 totally symmetric vibrational states; this set includes highly excited states above all three chemically relevant isomerisation barriers - up to about 8300 cm-1 above the (dibridged) ground state. States strongly localised in the dibridged, monobridged, and disilavinylidene regions of the potential energy surface have been found as well as many partially or fully delocalised states. For the trans-bent form, only partially localised states have been identified. Comparisons are made with similar literature calculations on the isovalent acetylene-vinylidene system HCCH/H2CC. [ABSTRACT FROM AUTHOR]

A general, full-dimensional computational method for the accurate calculation of rotationally and vibrationally excited states of tetra-atomic molecules is further developed. The resulting computer program may be run in serial and parallel modes and is particularly appropriate for molecules executing wide-amplitude motions and isomerizations. An application to the isomerizing acetylene/vinylidene system is presented. Large-scale calculations using a coordinate system based on orthogonal satellite vectors have been performed in six dimensions and vibrational term values and wave functions for acetylene and vinylidene states up to ≈23 000 cm-1 above the potential minimum have been determined. This has permitted the characterization of acetylene and vinylidene states at and above the isomerization barrier. These calculations employ more extensive vibrational basis sets and hence consider a much higher density of states than in any variational calculations reported hitherto for this system. Comparison of the calculated density of states with that determined empirically suggests that our calculations are the most realistic achieved for this system to date. Indeed more states have been converged than in any previous study of this system. Calculations on lower lying excited states of acetylene based on HC–CH diatom-diatom coordinates give nearly identical results to those based on orthogonal satellite vectors. Comparisons are also made with calculations based on HH–CC diatom-diatom coordinates. [ABSTRACT FROM AUTHOR]

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]

End of range (EOR) defects are the most commonly observed defects in ultrashallow junction devices. They nucleate at the amorphous-crystalline interface upon annealing after amorphization due to ion implantation. EOR defects range from small interstitial clusters of a few atoms to {311} defects and dislocation loops. They are extrinsic defects and evolve during annealing. Li and Jones [Appl. Phys. Lett., 73, 3748 (1998)] showed that {311} defects are the source of the projected range dislocation loops. In this article, the same theory is applied to 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 density and the number of interstitials trapped by dislocation loops are compared with the experimental results for several annealing times and temperatures. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A general, six-dimensional computational method for the accurate calculation of rotationally and vibrationally excited states of tetra-atomic molecules is developed. The resulting program is particularly appropriate for molecules executing wide-amplitude motions and isomerizations. An application to the Ar[sub 2]HF van der Waals trimer is presented in which the HF intramolecular stretching coordinate is separated out adiabatically and is not treated explicitly. Vibrational term values up to about 100 cm[sup -1] with absolute convergence to better than 0.1 cm[sup -1] are reported. These calculations employ more extensive vibrational basis sets and hence consider a much higher density of states than hitherto. States that sample Ar-Ar-HF linear configurations and approach Ar-HF-Ar linear configurations are characterized for the first time. Results for total angular momentum J = 0 and 1 provide the first accurate calculations of rotational constants for this system. The rotational constants for the HF bending states of Ar[sub 2]HF in the ground and first vibrationally excited states of the HF monomer are in good agreement with experiment, confirming the accuracy of the potential used in this work. [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 n-type dopants, Ge and Sn, were implanted into bulk (−201) β-Ga2O3 at multiple energies (60, 100, 200 keV) and total doses of ∼1014 cm−2 and annealed at 1100 °C for 10–120 s under either O2 or N2 ambients. The Ge-implanted samples showed almost complete recovery of the initial damage band under these conditions, with the disordered region decreasing from 130 to 17 nm after 1100 °C anneals. Fitting of secondary ion mass spectrometry profiles was used to obtain the diffusivity of both Ge and Sn, with values at 1100 °C of 1.05 × 10−11 cm s−1 for Ge and 2.7 × 10−13 cm s−1 for Sn for annealing under O2 ambients. Some of the dopant is lost to the surface during these anneals, with a surface outgas rate of 1–3 × 10−7 s−1. By sharp contrast, the redistribution of both dopants was almost completely suppressed during annealing in N2 ambients under the same conditions, showing the strong influence of point defects on dopant diffusivity of these implanted dopants in β-Ga2O3. [ABSTRACT FROM AUTHOR]

The most common n-type dopant, Si, was implanted into bulk (-201) β-Ga2O3 at total doses from 2x1013-2x1015 cm-2 and annealed at 1100 °C for 10-120 secs in either O2 or N2 ambients. Secondary Ion Mass Spectrometry profiling showed a significant effect of the annealing ambient on the Si diffusivity. In the case of O2 annealing, there was extensive redistribution of the Si across the entire dose range, while in sharp contrast, the use of N2 annealing suppressed the Si diffusion. The results are consistent with a defect-assisted process. Excellent fits to the Si profiles were obtained with the FLOOPS simulator, assuming mobile vacancy/defect concentrations as the important factor for the difference in the O2 vs N2 annealing ambients. One possibility is that for N2 anneals, more Ga vacancies are created, enabling interstitial Si to migrate onto a substitutional Ga site where it has low diffusivity. The N2 ambient also suppresses loss of Si to the surface, with >90% of the initial dose retained after annealing at 1100 °C for 120 secs, compared to 66-77% with O2 anneals under the same conditions. [ABSTRACT FROM AUTHOR]

The most common n-type dopant, Si, was implanted into bulk (-201) β-Ga2O3 at total doses from 2x1013-2x1015 cm-2 and annealed at 1100 °C for 10-120 secs in either O2 or N2 ambients. Secondary Ion Mass Spectrometry profiling showed a significant effect of the annealing ambient on the Si diffusivity. In the case of O2 annealing, there was extensive redistribution of the Si across the entire dose range, while in sharp contrast, the use of N2 annealing suppressed the Si diffusion. The results are consistent with a defect-assisted process. Excellent fits to the Si profiles were obtained with the FLOOPS simulator, assuming mobile vacancy/defect concentrations as the important factor for the difference in the O2 vs N2 annealing ambients. One possibility is that for N2 anneals, more Ga vacancies are created, enabling interstitial Si to migrate onto a substitutional Ga site where it has low diffusivity. The N2 ambient also suppresses loss of Si to the surface, with >90% of the initial dose retained after annealing at 1100 °C for 120 secs, compared to 66-77% with O2 anneals under the same conditions. [ABSTRACT FROM AUTHOR]

Studies the behavior of silicon semiconductor devices that are scaled to sub-micron dimensions when exposed to stress. Degradation of device characteristics by generation and propagation of dislocations in the silicon substrate; Comparison of volume of trapped atoms in dislocation loop in nitride films versus nitride films with underlying oxide layers.

Describes the point defect based modeling of low dose silicon implant damage and oxidation effects on phosphorus and boron diffusion in silicon. Comparison with experimental results for intrinsically doped material; Significance of the theory of dopant-defect pairing; Information on the dopant equations used.

Compares transient enhanced diffusion effects between boron and phosphorus of dopants in silicon. Significant enhancement of phosphorus during damage annealing; Indications of dislocation growths; Agreement between dislocation growth saturation time and phosphorus diffusion saturation.

Studies the effects of hydrostatic pressure on dopant diffusion in silicon. Method of the study; Results and discussion; Conclusion.

Two potential energy surfaces for CO2–Ar are obtained by least-squares fitting to the high-resolution spectra of Van der Waals complexes and the second virial coefficients of Ar+CO2 gas mixtures. The potentials incorporate a repulsive wall based on monomer ab initio calculations and the assumption that the repulsion potential is proportional to the overlap of the monomer charge densities. The dispersion energy is represented in a two-site model, with dispersion centers located along the C–O bonds of CO2. The resulting potentials give a good representation of all the experimental data with only three or four adjustable parameters. They are quite different from previous empirical CO2–Ar potentials, which all have either a poor representation of the attractive well or a poor representation of the repulsive wall. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have observed a microwave spectrum of the HeKr+ ion in which all of the observed levels lie within a few cm-1 of either the first or second dissociation limit. We use an ion beam technique in which HeKr+ ions, formed by electron impact, are mass analyzed. Passage of the ion beam through an electric field lens results in selective fragmentation of energy levels lying close to dissociation. Kr+ ions formed in the lens are separated from all other ions by means of an electrostatic analyzer, and are detected with an electron multiplier. Microwave radiation induces transitions which result in population transfer and produce detected changes in the electric field-induced Kr+ fragment ion current. Additional transitions have been detected by a microwave–microwave double resonance method, and we have also made extensive use of the Zeeman effects produced by small applied coaxial magnetic fields to identify the J quantum numbers of the levels involved. Coupled channel calculations of the bound states of the He...Kr+ ion are carried out, fully including all the couplings between different electronic states correlating with He+Kr+ (2P3/2 and 2P1/2). The calculations allow the spectra to be assigned to pure rotational transitions involving levels in the X, A1, and A2 states that lie within 2.5 cm-1 of the dissociation limits. Because of a systematic near degeneracy between vibrational levels in the X and A1 states, the long-range He...Kr+ ion provides a very good example of Hund’s case (e) in the form introduced by Mulliken, in which there are no projection quantum numbers onto the interatomic axis. Mulliken’s case (e) is rather different from the Rydberg case (e) described by Lefebvre–Brion, and this is the first time that Mulliken’s case (e) has been observed. The spectra allow the interaction potential for He...Kr+ to be determined accurately, for the first time, by least-squares fitting of potential parameters to the experimental... [ABSTRACT FROM AUTHOR]

We have measured and interpreted a microwave spectrum of the HeAr+ ion in which all of the observed energy levels lie within 8 cm-1 of the lowest dissociation limit, He(1S)+Ar+(2P3/2). We use an ion beam technique in which the HeAr+ ions are formed by electron impact, accelerated to kilovolt potentials, and mass-analyzed. After passage through an appropriate section of waveguide, the ions enter an electric field lens in which state-selective fragmentation occurs; the Ar+ ions produced in the lens are separated from all other ions by means of an electrostatic analyser and detected with an electron multiplier. Microwave transitions induced in the waveguide section result in population transfer which produces detected changes in the electric field-induced Ar+ fragment current. Many transitions have also been observed by a microwave–microwave double resonance technique. We have observed 68 lines spanning the frequency range 6–170 GHz; no immediately recognizable pattern is apparent. We have measured the Zeeman splitting produced by a small axial magnetic field for almost every line, which enables us to determine the values of the total angular momentum J involved in each transition, and also effective g factors for the two levels involved. We are therefore able to construct a purely experimental pattern of 37 levels lying within 8 cm-1 of the dissociation limit. The data are treated first by means of a conventional effective Hamiltonian in a case (c) basis, which allows electronic and vibrational quantum numbers to be assigned to most of the levels; the assignments are approximate, however, because very strong rotational-electronic coupling undermines the Born–Oppenheimer approximation.A more complete theoretical treatment is then presented, using the coupled-channel method in a case (e) representation to calculate the energy levels without making the Born–Oppenheimer approximation. The microwave transition frequencies and g-factors are... [ABSTRACT FROM AUTHOR]

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]

Provides information on a study which examined the diffusion behavior of nitrogen implanted in silicon. Experimental analysis; Results and discussion.

Sub-bandgap optical pumping with wavelengths of 671, 532, or 447 nm was employed to study traps in AlGaN/GaN high electron mobility transistors. The trap energies were determined from the Arrhenius plots of transient drain current at different temperatures. Prominent states were located around 0.7 eV below the conduction band, and these are commonly reported to be nonradiative traps due to defects trapped on dislocations or possibly Ga interstitials. In addition, traps located at 1.9 and 2.35 eV below the conduction band were found, which have been reported as NGa antisite and VGa-ON complexes, respectively. The postillumination drain current decays were analyzed with a persistent photoconductivity method, and time constants were extracted and associated with the recapture process in the AlGaN barrier and GaN channel layers. [ABSTRACT FROM AUTHOR]

Proton irradiation from the backside of the samples were employed to enhance off-state drain breakdown voltage of AlGaN/GaN high electron mobility transistors (HEMTs) grown on Si substrates. Via holes were fabricated directly under the active area of the HEMTs by etching through the Si substrate for subsequent backside proton irradiation. By taking the advantage of the steep drop at the end of proton energy loss profile, the defects created by the proton irradiation from the backside of the sample could be precisely placed at specific locations inside the AlGaN/GaN HEMT structure. There were no degradation of drain current nor enhancement of off-state drain voltage breakdown voltage observed for the irradiated AlGaN/GaN HEMTs with the proton energy of 225 or 275 keV, for which the defects created by the proton irradiations were intentionally placed in the GaN buffer. HEMTs with defects placed in the two dimensional electron gas (2DEG) channel region and AlGaN barrier using 330 or 340 keV protons not only showed degradation of both drain current and extrinsic transconductance but also exhibited improvement of the off-state drain breakdown voltage. The Florida Object Oriented Device and Process Simulator Technology Computer Aided Design finite-element simulations were performed to confirm the hypothesis of a virtual gate formed around the 2DEG region to reduce the peak electric field around the gate edges and increase the off-state drain breakdown voltage. [ABSTRACT FROM AUTHOR]

Level set methods have previously been successfully implemented in interface propagation for etching and deposition processes. In this article, the authors show that level set methods can be used to model solid phase epitaxial regrowth. The model incorporates orientation dependence of regrowth as found by Csepregi et al. [J. Appl. Phys. 49, 3906 (1978)]. The orientation dependent velocity data are taken from Csepregi’s paper and fitted to a polynomial function to give the growth velocity for level set methods. Simulations show the capability of our model in predicting the pinching of the corners in <111> direction and humplike shape in <100> direction. This is confirmed by the transmission electron microscope pictures from recent papers. This modeling holds special interest because of the different diffusivities of boron in amorphous and crystalline silicon (approximately five orders of magnitude difference) and because of the various defects forming at the pinching corners which could lead to higher leakage current in scaled devices. The level set model is implemented in FLOOPS. [ABSTRACT FROM AUTHOR]

In order to investigate the B and Ge interaction in silicon, an implant/anneal experiment is performed. The initial Si pre-amorphization step defines the amorphous layer depth and the end-of-range point defect distributions for all samples. The following Ge implant provides a low Ge content, thus minimizing the strain and the band gap narrowing effects on the diffusion of the subsequent B implant. The control sample received Si and B implants. The annealed profiles of the control samples show B profile broadening consistent with the transient enhanced diffusion. The B tail diffusion in the Ge implanted samples is almost identical to that of the control samples, indicating that Ge does not act as a trap for the BI pair. The GeB complex, suggested in literature, was used to explain the higher profile peak magnitude in Ge implanted samples. [ABSTRACT FROM AUTHOR]

The effect of proton irradiation on the off-state drain breakdown voltage of AlGaN/GaN high electron mobility transistors (HEMTs) grown on Si substrates was studied by irradiating protons from the backside of the samples through via holes fabricated directly under the active area of the HEMTs. There was no degradation of drain current nor enhancement of off-state drain voltage breakdown voltage observed for HEMTs irradiated with 275 keV protons, for which the defects created by the proton irradiation were intentionally placed in the GaN buffer. HEMTs with defects positioned in the 2 dimensional electron gas channel region and AlGaN barrier using 330 keV protons not only showed degradation of both drain current and extrinsic transconductance but also exhibited an improvement of the off-state drain breakdown voltage. Finite-element simulations showed the enhancement of the latter were due to a reduction in electric field strength at the gate edges by introduction of charged defects. [ABSTRACT FROM AUTHOR]

This study investigates the effectiveness of flash-assist rapid thermal processing in dissolving the end of range damage inherent to preamorphizing implants. A series of silicon wafers is preamorphized with a Ge implant and subsequently implanted with B. The wafers are then subjected to a flash anneal, a rapid thermal anneal, or both annealing processes. The flash anneal results in higher defect densities and trapped interstitials than the rapid thermal anneal. Defect dissolution has been previously reported to have an activation energy between 4 and 5 eV. This work demonstrates that the defect dissolution during flash-assist rapid thermal processing is mediated by a 2.2±0.05 eV activation energy. [ABSTRACT FROM AUTHOR]

In this work, a series of 13 boron implants were performed into Czochralski silicon substrates with doses of 2 × 10[sup 14]-1.6 × 10[sup 15] cm[sup -2] at energies of 10-80 keV. The boron was deliberately clustered with a 750°C anneal of 10 or 30 min and the electrical activation of the boron implants was determined following a second anneal at 750 or 850 °C with a Hall effect system with certain samples also being analyzed with a spreading resistance technique. Analysis of the reactivation rates allows for the determination of the net energy to boron reactivation to be approximately 3.0 eV assuming the reactivation process is mediated by release of a boron interstitial with a migrational energy of 0.3 eV. This results in a critical binding energy of approximately 2.7 eV from the process limiting the dissolution of the most stable boron-interstitial cluster. [ABSTRACT FROM AUTHOR]

Boron is introduced into silicon via implantation to form p-type layers. This process creates damage in the crystal that upon annealing causes enhanced diffusion and clustering of the boron layer. Reactivation of the boron is not a well-understood process. In this letter we experimentally investigate the effect of the annealing ambient on boron reactivation kinetics. An oxidizing ambient which injects silicon interstitials is compared to an inert ambient. Contrary to published theory, an excess of interstitials does not accelerate the reactivation process. [ABSTRACT FROM AUTHOR]

Investigates the effects of low-dose Si implantation damage on diffusion of low-concentration P and As in Si wafers. Implantation of dopants at a low dose; Observation of an enhanced diffusion of P; Monitoring of the effective diffusivity of P at various annealing temperatures.

Examines the interaction of implantation-induced dislocation loops in crystals and interstitials in silicon. Experiments under dry oxidation conditions; Consideration of the interaction as a diffusion limited process; Agreement of simulations with secondary ion mass spectroscopy.

Determines the effect of nonamorphizing silicon implantation damage on phosphorus diffusion. Use of the two-dimensional technique to compare damaged and nondamaged areas; Measurement of junction depth under stripes of varying widths; Analysis of the decaying profile of junction depth as a function of increasing stripe width.

Investigates phosphorus (P) diffusion in isoconcentration backgrounds under inert conditions of silicon (Si). Implantation of P at low doses in Si wafers; Use of secondary ion mass spectrometry to measure wafer profiles; Employment of P diffusivity on dopant-type concentrations.

Nitrogen implantation is commonly used in multigate oxide thickness processing for mixed signal complementary metal-oxide-semiconductor and System on a Chip technologies. Current experiments and diffusion models indicate that upon annealing, implanted nitrogen diffuses towards the surface. The mechanism proposed for nitrogen diffusion is the formation of nitrogen-vacancy complexes in silicon, as indicated by ab initio studies by J. S. Nelson, P. A. Schultz, and A. F. Wright [Appl. Phys. Lett. 73, 247 (1998)]. However, to date, there does not exist any experimental evidence of nitrogen-vacancy formation in silicon. This letter provides experimental evidence through positron annihilation spectroscopy that nitrogen-vacancy complexes indeed form in nitrogen implanted silicon, and compares the experimental results to the ab initio studies, providing qualitative support for the same. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

All activity in modeling transient diffusion behavior relies on knowledge of the inert intrinsic diffusivities of dopants in Si. The measurements upon which these values are based were conducted over 15 years ago. Since then, the quality of wafers used in industrial applications has significantly changed. This will affect the effective diffusivity through changes in trap concentrations. The reliability of measurement techniques has also changed dramatically from tracer and staining methods to secondary ion mass spectrometry (SIMS) measurements that are dominant today. Finally, our understanding of diffusion behavior has changed significantly. For example, we now understand that the extraction of diffusivities from implanted samples with no pre-anneal includes a significant transient effect. We have measured the inert intrinsic diffusivities of As, B, P, and Sb in different substrates in defect-free Czochralski and float zone wafers and epitaxially grown layers. All samples underwent a 30 min anneal at 1000 °C in dry oxygen in order to grow a cap oxide and eliminate transient enhanced diffusion. We performed SIMS analysis on an initial batch of samples to evaluate the different factors that may affect the diffusivity in a nonideal manner and concluded that there are no transient effects but that surface effects are important. Hence, for the fast moving dopants (B, P) we restrict our data extraction to the deep implants. Our data show that B and P diffusivities are different than the values commonly assumed in the literature at low temperatures. We compare our results to previously published data in light of the factors mentioned here. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Boron, a p-type dopant, experiences transient enhanced diffusion (TED) via interstitials. The boron TED and {311} dissolution rates are explored as a function of implant energy dependence. Silicon implants of 10[sup 14]/cm[sup 2] at various energies were used to damage the surface of a wafer with an epitaxially grown boron marker layer. Samples were annealed at 750 °C for 15-135 min to observe the diffusion exhibited by the marker layer and to correlate this with the dissolution of {311} type defects. The diffusion enhancement depends strongly on implant energy but the {311} dissolution rate is weakly dependent. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Transient enhanced diffusion (TED) below the amorphization dose threshold is thought to be caused by the release of interstitials from {311} defects. The interstitials are annihilated by diffusion to and then recombination with the surface of the wafer. This would suggest that the layer of {311} defects formed from an implantation and anneal would dissolve from the surface down. Cross-section transmission electron microscopy (TEM) was used to investigate this hypothesis. It is shown that the {311} defects dissolve uniformly across the layer, and the width of the layer does not change until the {311} defects nearly completely dissolve. The total population was also measured using plan-view TEM, so that the dissolution and distribution functions could be plotted from the same annealing conditions. These data suggest that surface is not the limiting factor in the interstitial removal from {311} defects. © 1998 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]