Electrical Activation Of Boron Research Articles

Effect of Rapid Thermal Processing on Light-Induced Degradation of Carrier Lifetime in Czochralski p-Type Silicon Bare Wafers

The electrical properties of Czochralski silicon (Cz-Si) p-type boron-doped bare wafers have been investigated after rapid thermal processing (RTP) with different peak temperatures. Treated wafers were exposed to light for various illumination times, and the effective carrier lifetime (τ eff) measured using the quasi-steady-state photoconductance (QSSPC) technique. τ eff values dropped after prolonged illumination exposure due to light-induced degradation (LID) related to electrical activation of boron–oxygen (BO) complexes, except in the sample treated with peak temperature of 785°C, for which the τ eff degradation was less pronounced. Also, a reduction was observed when using the 830°C peak temperature, an effect that was enhanced by alteration of the wafer morphology (roughness). Furthermore, the electrical resistivity presented good stability under light exposure as a function of temperature compared with reference wafers. Additionally, the optical absorption edge shifted to higher wavelength, leading to increased free-carrier absorption by treated wafers. Moreover, a theoretical model is used to understand the lifetime degradation and regeneration behavior as a function of illumination time. We conclude that RTP plays an important role in carrier lifetime regeneration for Cz-Si wafers via modification of optoelectronic and structural properties. The balance between an optimized RTP cycle and the rest of the solar cell elaboration process can overcome the negative effect of LID and contribute to achievement of higher solar cell efficiency and module performance.

Doping and Raman Characterization of Boron and Phosphorus Atoms in Germanium Nanowires

Impurity doping is the most important technique to functionalize semiconductor nanowires. The crucial point is how the states of impurity atoms can be detected. The chemical bonding states and electrical activity of boron (B) and phosphorus (P) atoms in germanium nanowires (GeNWs) are clarified by micro-Raman scattering measurements. The observation of B and P local vibrational peaks and the Fano effect clearly demonstrate that the B and P atoms are doped into the crystalline Ge region of GeNWs and electrically activated in the substitutional sites, resulting in the formation of p-type and n-type GeNWs. This method can be a useful technique for the characterization of semiconductor nanowire devices. The B-doped GeNWs showed an increasingly tapered structure with increasing B concentration. To avoid tapering and gain a uniform diameter along the growth direction of the GeNWs, a three step process was found to be useful, namely growth of GeNWs followed by the deposition of an amorphous Ge layer with high B concentration and then annealing.

Effect of Germanium Preamorphization Implant on Boron Deactivation in Silicon Following Multiple-Pulse Flash Annealing

Electrical activation of boron in germanium preamorphized silicon after multiple-pulse flash annealing is studied. As the number of pulses increases, enhanced boron deactivation is observed. This deactivation is attributed to boron precipitation into immobile and electrically inactive clusters due to inefficient removal of end-of-range (EOR) defects with the first pulse. Because subsequent pulses are of the same thermal condition as the first, EOR defects remain and additional pulses serve to deactivate the boron atoms further. However, when preceded with spike anneal condition capable of removing the EOR defects, application of additional pulse results in better activation and lower sheet resistance.

最適入射角度の低速酸素イオンを用いたＳＩＭＳによるボロンのゲート酸化膜突き抜け現象の解析

Accurate SIMS measurement of a boron profile in a SiO2-Si interfacial region under optimum incident angle of low-energy primary oxygen ion beam was made in order to demonstrate the mechanism of boron penetration through gate oxide. Degrees of ionization of Si and boron became almost equal in SiO2 and Si at the 20-degree incident angle with a practical sputtering rate. The estimation of an apparent shift of a boron profile toward surface and the determination of the SiO2-Si interface under measurement conditions achieving matrix-independent degree of ionization of Si were also examined. The SIMS measurement using optimum conditions revealed that the variation of flat band voltages was proportional to the variation of penetrating boron doses in the range of 0.85−1.30 V. It was also found that when a penetrating boron dose was equivalent to a flat band voltage over 1 V, the electrical activation of boron was lower than that of boron ion-implanted in a Si substrate.

Activation of group III combinations in silicon and modifications introduced by nitrogen

A series of experiments were initiated after finding that a supersteep retrograde channel of an n-channel silicon-based field effect transistor would not have an acceptable threshold voltage if created with indium and sufficient nitrogen (4×1014/cm2) present to retard gate oxide growth. A set of combinations of indium, boron, and nitrogen and a set of combinations of gallium, boron, and nitrogen were examined. It was found that nitrogen caused minimal reduction in the electrical activity of boron, greater reduction with indium, and greatest reduction with indium plus boron. Similar results, though of lesser magnitude, were observed with the gallium set. The chemical profiles of the various dopants in combination with each other gave no indication of the active carrier profile associated with each combination. Theoretical criteria were formulated to attempt to correlate atomic level configurations with electrical activity. Ab initio pseudopotential calculations using the Vienna Ab initio Simulation Package followed; the theoretical criteria correlated very well with the observed electrical activity of the various combinations and, to a lesser degree, with the ordering of nitrogen retention as a function of those combinations. The calculations appear to demonstrate the presence of long range interactions.

Orientation and Boron Concentration Dependence of Si Layer Transfer by Mechanical Exfoliation

ABSTRACTMechanical exfoliation strength has been measured in hydrogen implanted <100>, <111> and <110> oriented Si wafers using the crack opening method. The bonding temperature required for exfoliation increases in the order <100>, <111> and <110>. The same method has been applied to study the influence of boron doping on mechanical exfoliation in <100> Si wafers. The required bonding temperature to exfoliate mechanically decreases with increasing doping level independent of the electrical activation of boron. The enhanced crystallization rate of boron doped Si is suggested as a plausible explanation for the result.

Clustering of ultra-low-energy implanted boron in silicon during activation annealing

The clustering kinetics and the electrical activation of boron during the post-implantation activation annealing of ultra-low-energy implanted boron (<1 keV) in silicon has been investigated. By analyzing the boron concentration profiles obtained by means of secondary ion mass spectroscopy (SIMS) non-diffusing boron clusters dissolving with a temperature dependent time constant have been found which exhibit a thermal activation energy of 2.3 eV. The formation of the boron clusters shows at 900°C an incorporation efficiency of boron atoms into clusters of approximately 1. The incorporation efficiency is decreasing with increasing temperature and shows an activation energy of 0.9 eV. The depth profiles of the active boron concentration as measured by spreading resistance profiling was analyzed. The comparison of electrical activation and boron clustering shows that the boron clusters are determining the electrical activation.

Ultra-Low Energy Boron Implants in Crystalline Silicon: Atomic Transport Properties and Electrical Activation

ABSTRACTWe investigated the atomic transport properties and electrical activation of boron in crystalline epitaxial silicon after ultra-low energy ion implantation (0.25–1 keV) and rapid thermal annealing (750–1100 °C). A wide range of implant doses was investigated (3×1012-1×105/cm2). A fast Transient Enhanced Diffusion (TED) pulse is observed involving the tail of the implanted Boron, the profile displacement being dependent on the implant dose. The excess of interstitials able to promote enhanced diffusion of implanted boron occurs, provided the implant dose is high enough to generate a significant total number of point defects. The Boron diffusion following the fast initial TED pulse can be described by the equilibrium diffusion equations.The electrical activation of ultra-shallow implants is hard to achieve, due to the high concentration of dopant and point defects confined in a very shallow layer that significantly contributes to the formation of clusters and complex defects. Provided a correct combination of annealing temperatures and times for these ultra-shallow implants is chosen, however, a sheet resistance 500 Δ/square with a junction depth below 0.1μm can be obtained, which has a noteworthy technological relevance for the future generations of semiconductor devices.

Point Defect-Based Modeling of Transient Diffusion of Boron Implanted in Silicon Along Random and Channeling Directions

ABSTRACTA point defect-based model, which has been developed to describe diffusion and electrical activation of boron in crystalline silicon during post-implantation annealing, is used to simulate the anomalous diffusion of boron implanted into silicon along the random and [100] channeling directions. The model predictions are compared to data measured by Chu et al.

Electrical Activation of Boron in B+ + C+ Implanted Si during RTA with Different Heating Rates

ABSTRACTSilicon samples were single implanted with B+ (5 x 1014 cm−2, 50 keV) or co-implanted with C+ (5 x 1015 cm−2, 55 keV). Rapid thermal annealing (RTA) with heating rates (HR) of 1°C/s and 100°C/s with dwell time duration from 2 s to 15 min was used for B activation and the results compared with those provided by conventional furnace annealing (FA) for 30 min. In single implanted samples it was found that below 600°C or above 800°C the activation always increases with the annealing time. However, in the temperature range of 600-800°C and annealing times longer than 60 s a fraction of the initially activated B concentration deactivates. For temperatures in the range of 700-800°C the deactivation is followed again by another activation period. There is no noticeable difference between the activation yields after RTA with high HR for 15 min or FA for 30 min. In the C co-implanted samples the activation of boron saturates after few minutes. In addition the deactivation process is significantly reduced. A model assuming interaction of the B atoms with point defects and the C atoms with Si self- interstitial atoms is proposed to explain the results.

Inactivation of implanted impurities during buried Si 3N 4 layer formation

The electrical activity of boron and phosphorus atoms in silicon layers previously implanted with nitrogen ions was investigated. The behavior of implanted impurities (boron and phosphorus) depends on the dose of implanted nitrogen, previous thermal treatment, dose and energy of boron and phosphorus ions. The decrease of electrical activity is connected with accumulation of impurity atoms on sinks as silicon nitride inclusions, grain boundaries in polycrystalline silicon. It is proposed that impurity affected distribution profiles are influenced elastic force fields appearing as a result of creation of silicon nitride inclusions. The conclusion was drawn that the distribution profile formation is connected with the mobility of impurity atoms during irradiation.

Transient diffusion of boron implanted in SI along random and channeling directions

We have studied anomalous diffusion of boron implanted into silicon along the [100] channeling direction versus random directions for 5, 10, and 40 keV, 2 × 10 14 cm 2 boron implantations. Three different annealing conditions, 800 °C for l h, 900 °C for 30 min, and 1000 °C for 10 s, were studied. Anomalous diffusion was observed for all implants annealed at all conditions. The amount of enhanced diffusion is 10–50% higher in the implants along the channeling direction than along the random directions. We attribute the mechanism of the diffusion enhancement to the annealing of ion implantation damage. The difference of diffusion enhancement between channeled implants and random implants are due to the difference in damage profile of the two different implants. Electrical activity of boron is observed for random and for channeled implantations, and the shape of the Hall profile agrees with that of SIMS.

Electrical activation of boron-implanted silicon during rapid thermal annealing

The electrical activation of boron implanted in crystalline and preamorphized silicon has been investigated during rapid thermal annealing performed with halogen lamps. Samples implanted with B+ fluences ranging between 5×1014 and 1×1016cm−2 and treated at temperatures between 900°C and 1100°C have been examined. When boron is implanted in crystalline Si, activation proceeds slowly atT<1000°C and cannot be completed in times typical of rapid thermal annealing (a few tens of seconds). The analysis of carrier profiles indicates that the time constant for activation is strongly affected by local damage and dopant concentration. If the total boron concentration exceeds equilibrium solubility, precipitation occurs concomitant to activation, even if the substitutional boron fraction is still lower than equilibrium solubility. ForT≧1000°C complete activation is obtained in times of about 10 s. In the case of preamorphized Si the activation occurs very quickly, during the recrystallization of the amorphous layer, for all the examined temperatures.

Electrical activation of low-fluence boron implantation in silicon studied by PCV in combination with SIMS

The thermally induced electrical activation of boron implanted in silicon at fluences ≦1013 cm−2 was studied by the combination of secondary ion mass spectrometry (SIMS) and pulsed capacitance voltage (PCV). After annealing at 900°C for 30 min boron is completely ionized and the contribution of electrically active defects to the electrical profile is negligible. For partly annealed samples (T<900°C) the degree of electrical activation of boron decreases with increasing boron concentration due to the presence of residual defects. The experimental data can be described qualitatively by the first-order kinetics if the influence of residual crystal defects on the electrical activation is considered.

Raman Spectroscopy for Nondestructive Depth Profile Studies of Ion Implantation in Silicon

Raman spectra of B+, , and Si+ ion implanted silicon as a function of incident angle are presented. In addition to providing data on the physical and chemical structure of the bulk sample, it is shown that by varying the angle of incidence of the laser on the sample to obtain depth resolution, it is possible to measure depth profiles of implantation damage, annealing, and electrical activation of boron in substitutional sites. Although the range of penetration depths as a function of is limited by the high refractive index of silicon, depths in the range of ∼50 to ∼500 nm are accessible with wavelengths from an Ar+ laser. This technique is of particular interest for nondestructive characterization of submicron pn junctions for VLSI applications.

A Structural and Electrical Comparison of BCl and BF 2 Ion‐Implanted Silicon

The molecular ions and are implanted into <100> silicon at an energy of 16 keV per boron atom in the dose range of to form shallow p+/n junctions. Cross‐sectional transmission electron microscopy shows that chlorine is at least four times as effective as fluorine in amorphizing silicon. The increase in thickness of the amorphous layer, however, has a small effect in the reduction of axial channeling of boron as measured by secondary ion mass spectrometry. After annealing for 30 min at 900°C, diffusion of interstitial boron is enhanced by chlorine relative to fluorine, whereas the electrical activity of boron is inhibited. Diodes made with both and implantations have comparable I‐V characteristics with low reverse‐bias junction leakage currents that are not affected by a band of dislocation loops which remain near the original amorphous‐crystalline interface.

Annealing of ion-implanted silicon by an incoherent light pulse

Annealing of boron-implanted silicon by a single 15-μsec pulse from a flash lamp has been observed. The required energy density was 27 J/cm2 incident on the silicon. Electrical activity of boron was comparable to that in thermally annealed samples.

Anomalous migration of fluorine and electrical activation of boron in BF+2-implanted silicon

Fluorine distribution profiles for silicon implanted with 150-keV 1×1015-cm−2 BF+2 at room temperature or at −110 °C have been measured by SIMS as a function of anneal temperature. Anomalous migration of fluorine during annealing is observed, and is explained in terms of recrystallization and impurity-gettering effects. Electrical carrier distribution profiles of room-temperature BF+2-implanted silicon, measured by differential Hall effect methods, demonstrate that boron is electrically activated by epitaxial recrystallization during 550 °C annealing. However, a damaged region near the crystalline-amorphous interface remains after recrystallization. This damaged layer is apparently responsible for the fluorine gettering.

Ionization assisted annealing of boron implanted silicon

Abstract Electrical activity of boron implanted silicon layers has been extensively studied by many authors.1-7 Ionization is known to affect the transformation processes of simple lattice defects8,9 and similar influence was also observed for silicon implanted layers being annealed with ionization generated by uv light, laser beams or high energy electrons.10-13 In all these experiments a substantial increase in a recrystallization rate was observed.

2114. On electrical activity of boron and phosphorus implanted in silicon: Yu N Shutov et al,Izv VUZ Fiz, No 4, 1975, 118–119 ( in Russian)

2114. On electrical activity of boron and phosphorus implanted in silicon: Yu N Shutov et al,Izv VUZ Fiz, No 4, 1975, 118–119 ( in Russian)