Transient enhanced diffusion during rapid thermal processing has been reported for most of the common dopants employed for silicon device fabrication. For arsenic a large amount of the available data is fit by a computational model based on accepted diffusion mechanisms. Ion implanted boron on the other hand exhibits anomalous tails and transient motiou. A time dependence of this displacement is demonstrated at lower temperatures. High temperature rapid anneals are shown to reduce some of the anomalous motion observed for low temperature furnace anneals. A model is described that links the electrical activation with the diffusion and describes both the transient diffusion of rapid thermal processing and the large anomalous diffusion reported many years ago for furnace anneals.

The results of a detailed investigation of the diffusion of ion implanted As in Si during Rapid Thermal Annealing (RTA) are reported. A series of experiments has been performed on samples implanted with As in a wide range of concentrations. The use of an improved thermocouple bonding technique enables precise measurement and control of the temperature versus time cycle for each individual sample. The RTA apparatus is designed to perform high vacuum annealing, eliminating the complications associated with point defect generating mechanisms at the surface, which are known to influence the diffusion of impurities in Si. Sample analysis includes depth profiling by SIMS and RBS, and electrical characterization employing VanderPauw and Spreading Resistance measurements.

The resulting profiles have been analyzed via a numerical solution of the diffusion equation subject to the appropriate boundary conditions. With an effective As diffusivity of the form we find good simulation of all measured profiles with the standard values of D0 and D- from SUPREMIII and a one parameter fit to D= Recent results on the redistribution of low dose As implants in heavily phosphorus doped Si illustrate the strong Fermi level dependence. The model has also been successfully used to simulate RTA data in the literature where careful temperature measurements have been made.

Low temperature (600–800&C) thermal treatment subsequent to high temperature short time anneal of As implanted Si has resulted in significant clustering of As atoms in Si. Si wafers implanted with As at a variety of doses and energies were subjected to single and multiple thermal anneals using incoherent tungsten radiation. Sheet resistance (R▩ ), and Rutherford backscattering (RBS) and channeling measurements were carried out on the wafers. The metastable behavior observed in the activation of As was attributed to electrical deactivation of As atoms caused by clustering. From the temperature dependence of the rate of increase in R▩ we extracted a value of 1.1 eV for the activation energy of electronic deactivation of As atoms in agreement with the value obtained earlier for the activation of As clustering. We also report, for the first time, observation of a structure in the Si RBS spectrum which represents a defective layer in Si caused by the clustering As atoms.

Deactivation of ion implanted and rapid thermal annealed (RTA) metastable arsenic in silicon during subsequent furnace annealing has been studied by sheet resistance measurement, Rutherford backs cat t ering/ channeling (RBS), and transmission electron microscopy (TEM). Following RTA, thermal annealing induces deactivation of the dopant which increases the sheet resistivity monotonically with temperature for a very short time, Dislocation loops are formed near the peak of As concentration at post-anneal temperatures of 750°C or higher, where deactivation rate is fast. At lower temperatures deactivation is accompanied by displacement of As atoms, possibly forming clusters.

During the rapid thermal annealing of ion implanted layers, trapped interstitials are responsible for transient enhanced dopant diffusion and the formation of a band of defects at the mean projected ion range. We describe the detailed nature and extent of these effects and show how they can be predicted in practice. We present a model which explains why trapping only occurs with group V implantation and describe double implantation experiments which confirm the model and show how the formation of projected range defects can be suppressed.

It is well known that high surface concentration phosphorus diffusion leads to deeply penetrating “tails” in its concentration profile. At 700 °C the tail diffusivity exceeds that of low concentration phosphorus by a factor of a thousand. Less spectacular, but very significant tailing also affects tioron, making the conventional models contained in commonly available process simulation programs quite inaccurate for boron diffusions with high surface concentrations. We show that the observed tailing can be accounted for by a model whose central assumption is the local equality of dopant and oppositely directed defect fluxes. As predicted by the model, the effect is greatest for normal processing at low temperatures for high surface concentrations. It is minimal for the high temperatures of rapid thermal annealing and unrelated to transient effects.

The reverse annealing of ion implanted boron, namely, the decrease in the concentration of electrically active boron as the isochronal annealing temperature increases, occurs in the temperature range from 550 to 650°C during conventional furnace heating. In this study, silicon crystals were boron implanted at 50 Kev to a dose of 1×1015 cm-2 followed by both furnace and tungsten-halogen lamp annealing in the reverse annealing temperature range. Cross-sectional Transmission electron microscopic (TEM) technique was used to examine the microstructural changes during annealing as a function of depth. Sheet resistance measurements gave a quick check of the electrical properties, while spreading resistance profiling with shallow angle lapping and Hall measurements reveals the mobility and carrier concentration as a function of depth. Czochralski and Float Zone crystals were studied to examine the effect of oxygen. Tungsten-halogen lamp thermal processing was found to have a more pronounced effect on the annealing of secondary defects than did furnace annealing. The reverse annealing of boron was eliminated completely for lamp annealing time as short as 60 seconds.

The diffusion and activation of implanted boron in silicon during rapid thermal annealing (RTA) has been studied using the analytical techniques of SIMS, TEM, and sheet resistance measurements. Both crystalline and pre-amorphised silicon substrates were investigated. Data analysis in conjunction with a range of numerical models indicates some novel features of boron RTA, as well as accounting for previously observed features. In particular, a large transient diffusion enhancement coupled with an increase of electrical activity, are seen at short anneal times, in the case of crystalline silicon substrates. A non-equilibrium diffusion enhancement of a different type is also seen at much longer times, in both crystalline and pre-amorphised samples implanted to high doses. This second enhancement persists after all the precipitated boron formed on implantation has become substitutional. TEM studies show that the transient enhancement may be associated with the evolution of extended defect structures during the early stages of annealing. Both types of enhancement can be well represented by multiplying the ‘normal’ concentration-dependent diffusivity (with β=0.5) by a factor f>1.

Rapid thermal annealing (RTA) has been used to form Pd2Si by reacting thin layers of Pd metal on As implanted Si. An enhanced growth rate for the Pd2Si has been measured which does not obey the diffusion limited growth kinetics as reported for the furnace reacted Pd2Si. The growing Pd2Si results in As redistribution which is sufficient to displace the shallow p-n junction as the silicide/silicon interface approaches the junction position. The As implanted profile changes little in the Pd2Si region, with As accumulating at the leading edge of the silicide/silicon interface.

A simple, non-destructive technique to characterize the properties of ion-implanted semiconductor wafers is described. The method consists of measuring the infrared attenuated total reflection (ATR) spectrum of the implanted layer/air interface and fitting it with a calculated spectrum which takes account of the free carrier density profile and any possible residual damage and/or amorphization. The results obtained on boron and implanted Si wafers, annealed at different temperatures in a rapid thermal annealer, are compared with their respective SIMS profiles.

The characterization of microstructures is fundamentally important to investigations of amorphization which is induced by ion implantation and recrystallization which occurs by solid-phase, epitaxial regrowth. In this paper, microstructures of amorphized, partially regrown and fully regrown layers are described in terms of extended-defect states of the material. Initial states (i.e. amorphized) and final states (i.e. solid-phase regrown and then reordered) are defined. Transmission electron microscopy and Rutherford backscattering/ion-channeling are the analytical techniques which are used in the characterization.

Cross-section transmission electron microscopy (X-TEM) has been used to illustrate the amornhous/ crystalline (a/c) micromorphology dependence of various low dose Ge+ preamorphizatlon implants in Si. Ge+ Implants were done at room _emperature at energies of 150 and 300 keV in the dose range of 1 to 9E14 cm−2. These implants result in the formation of either a buried or a continuous amorphous layer, with rough a/c interfaces. Nucleation of spanning “hairpin” dislocations during subsequent solid phase epltaxy (SPE) regrowth is known to be related to rough a/c interface morphology. Very low temperature anneals (VLTA),less than 500°C where the rate of SPE is minimal, were utilized to sharpen rough a/c interfaces prior to subsequent SPE regrowth. Sharpening of rough a/c interfaces is shown to result from an unexpected reverse crystalline to amorphous phase transition. This reverse phase transition results in the dissolution of detached microcrystallltes located within the amorphous layer near the a/c interface. Utilization of VLTA interfacial smoothing prior to SPE regrowth therfore, results in the reduction of residual spanning “hairpin” dislocations along with homogenization of the amorphous material.

The damage recovery and electrical activation of PFn+ (1 ≤n ⩽,5) implanted silicon layers during fast thermal annealing has been investigated. The <100> oriented wafers were implanted by glow discharge with 30 keV PFn+ ions at a dose of 2.5–3.1015 ions/cm2 and subsequently annealed using incoherent light pulses in the temperature range 600–1100°C with irradiation times of 1–15 secs.

Our results show that the maximum electrical activity is obtained by about 750°C, 15 sec and the same activity is reached for shorter annealing times and higher temperatures (typically 820°/ 5 sec; 950°C / 1 sec). These values and Rutherford Backscattering analysis reveal that the velocity of regrowth of the PFn+-implantation amorphized layer is lower than in the case of P+ implantation and that the former requires a higher activation energync≃3.4 eV.

TEM analysis reveals precipitates in 820°C/4 s annealed samples with the appearance of dislocation loops at 980°C/4 s annealing. Finally two characterizable defect levels (ETT = EV + 180 meV, ET2 = EV + 542 meV) are seen to remain in the PFn+ implanted samples examined by DLTS, even after annealing at 1100°C.

The rate and direction of regrowth of amorphous layers, created by self-implantation, in silicon-on-sapphire (SOS) have been studied using time resolved reflectivity (TRR) experiments performed simultaneously at two wavelengths. Regrowth of an amorphous layer towards the surface was observed in specimens implanted with 3.1015Si+/cm2 at 50keV and regrowth of a buried amorphous layer, from a surface seed towards the sapphire, was observed in specimens implanted with 1.1015Si+/cm2 at 175keV. Rapid isothermal heating to regrow the layers was performed in an electron beam annealing system. The combination of 514.5nm and 632.8nm wavelengths was found to be particularly useful for TRR studies since the high absorption in amorphous silicon, at the shorter wavelength, means that the TRR trace is not complicated by reflection from the silicon-sapphire interface until regrowth is nearly complete. The dual wavelength method removes ambiguity about the position of the amorphous to crystalline interface and the direction of regrowth. The temperature dependence of the refractive index of silicon leads to large changes in the reflectivity of SOS films as they are heated. The combination of regrowth rate observations and reflectivity measurements during heating has been used to characterize the isothermal heating cycle, avoiding the difficulties of using pyrometers operating at the useful near infra-red wavelengths, where sapphire is transparent.

Variations in the local order of the amorphous phase of Si produced by ion implantation and subjected to rapid thermal annealing were studied using the Raman scattering technique. It was found that the low order amorphous phase was formed independently of implantation ion species for low dose, low energy implantation at room temperature. For high energy, high dose implantation with heavy ions, the ion beam annealing effects were apparent and the higher order amorphous phase was formed. Rapid thermal annealing produced transformation from the low order phase to the high order amorphous phase. The continuous transformation was completed when the detectable crystalline phase regrowth started.

The structure of (111) oriented, unheated oxygen-implanted silicon (dose -7.3×1016cm-2) has been studied by transmission electron microscopy (TEM). The as-implanted material exhibited four structurally different layers: defect-free monocrystaline silicon, amorphous silicon, monocrystalline silicon with a high defect density, and the perfect crystalline substrate. After heat-pulse annealing for 20s at 800°C, 900°C, or 1000°C, the amorphous layer recrystallized resulting in polycrystalline silicon, rich in oxygen. The uniform insulator buried layer was not formed under these specific implantation and annealing conditions.

Polycrystalline silicon films were transient preannealed, As implanted, and transient post-annealed at peak temperatures up to 1250°C for times up to 17.5 seconds. Structural changes occurring during post-annealing were examined by transmission electron microscopy. These results were correlated to Rutherford Backscattering and sheet resistance results. The grain size, which increased from 5–20 to 150–300 nm during preannealing, did not increase during post-annealing. During early stages of post-annealing, As diffused along grain boundaries and generated dislocation sources at grain boundary surfaces. Subsequently, as annealing progressed, a fine, As-rich cellular network structure propagated into the grains until the structure of an entire grain was transformed into a fine cellular network at the longest annealing times. Residual stresses in the film were relieved during formation of the network structure. The sheet resistance of preannealed samples, in comparison with non-preannealed samples with similar implantation and final transient anneals, was lower at shorter annealing times due to the larger grain size, which increased mobility, and the reduced grain boundary area, which trapped less As. It was also lower at longer annealing times due to the formation of the cellular network structure. In subsequent furnace stability tests for 30 minutes at 700–900°C, the sheet resistance increased less for preannealed than for non-preannealed samples.

DLTS measurements show that majority-carrier traps exist after quartz-lamp, rapid-thermal annealing (RTA) activation of B+ and BF2+ ion implants in n-type silicon. Levels at Ec-0.17, 0.27, 0.44 and 0.57 eV annealed out with an additional 20 minute isochronal anneal at 550°C in argon. A stable defect at 0.37 eV existed at temperatures above 750°C. DLTS measurements of a Schottky diode on n-type silicon after only RTA indicated that electron traps could be introduced into n-type silicon by the RTA alone.

Ion implantation of 27Al+ and 31p+ ions into monocrystalline s-SiC films was conducted in order to acquire p-type and n-type conducting layers, respectively. Implant energies ranging from 110 to 190 keV and fluences from 7 × 1013 to 9 × 1014 cm-2 were used. In order to activate each dopant specie, rapid thermal annealing (RTA) was employed. A decrease in sheet resistance with increasing annealing temperature for both type layers was observed up to 1800°C. After annealing at this highest temperature for 300 s in 1 atm. Ar, the percent of activated and ionized n-type and p-type dopant was ≅20% and ≅0.5%, respectively, as determined by room temperature capacitance-voltage measurements. Recrystallization of both heavily damaged and amorphized layers occurred as a result of the use of the aforementioned annealing process. Unlike SPE regrowth in other compound semiconductors, no microtwins were present in the regrown bulk as observed by XTEM. SIMS analyses also showed that there was essentially no redistribution of P and moderate redistribution of Al from the corresponding as-implanted profiles after annealing.

The annealing behavior of B or N dual implants in 1-SiC thin films has been studied using cross-sectional transmission electron microscopy (XTEM), secondary ion mass spectroscopy (SIMS), and four point probe electrical measurements. A high resistivity layer was produced after annealing the B implanted-amorphous layer in the temperature range from 1000°C to 1500°C for 300 a; however, the resistivity rapidly decreased as a result of annealing at higher temperatures. The reasons for these changes in resistivity and the lack of p-type conduction at all annealing temperatures in these B implants include: (1) possible compensation of the native n-type carriers, (2) reduction in the B concentration via formation of B-containing precipitates between 1300°C and 1600°C and out diffusion of this species at and above 1600°C, and (3) creation of additional n-type carriers.

No precipitates or defect structure was observed in N implanted-annealed samples. The resistivity of this non amorphous n-type layer decreased with increasing annealing temperatures from 700°C to 1800°C. Furthermore n-p junction diodes were fabricated for the first time in β-SiC via N implantation into samples previously in situ doped with 8 × 1018/cm3 Al coupled with rapid thermal annealing at 1200°C for 300 a. A typical diode ideality constant and a saturation current for these diodes was 3.4 and 9 × 10-10 A/cm2, respectively.