Low energy, shallow BF2+ implants were carried out at room or liquid nitrogen temperature into deep pre-amorphized (100) Si for better control of the dopant profile and post-annealing structural defects. Cross sectional and angle polished plan view transmission electron microscopy were used to study the structural quality of the implanted layer, while SIMS provided a chemical profile. Four types of structural defects were observed in BF2+ implanted, pre-amorphized samples following rapid thermal annealing with a halogen lamp. An in-situ ion beam annealing and the presence of F in the Si lattice were related to the creation of the defects. Good correlations between F gettering and TEM observed defects were found to exist. Implantation of B+ into a pre-amorphized Si surface and subsequent rapid thermal annealing was found to produce a wide defect-free surface layer.

B and As implanted Si wafers have been thermally annealed by an array of tungsten halogen lamps at 1000–1200°C for 1–10 sec. Annealing above 1100°C leaves the crystal free of extended defects in all cases as determined by TEM. An enhanced diffusion is observed above normal values characterized by a low activation energy for both As and B samples. This enhanced diffusion is transient and occurs within about one second since the RBS and SIMS dopant profiles are identical for 1 sec and a 10 sec anneal.

The redistribution of indium in silicon has been studied as a function of dose during rapid thermal annealing. The results show little redistribution of indium for doses 1×1015 cm−2. For a 350keV/5×1015 cm−2 indium implant, the annealed sample showed significant indium precipitation and near surface defects. These data are contrasted to an earlier study of a 300keV/1×1015 cm−2 indium implanted silicon sample that was furnace annealed for 30 minutes at 1050°C. The furance annealed sample showed redistribution to both implant damage and the amorphous crystalline interface as well as a tail on the backside of the implant due to interstitial diffusion. This interstitial tail is clearly minimized in the transient annealed sample.

Germanium implantation into Si was conducted to pre-amorphize the-si surface layer prior to a shallow/high dose (42 keV, 2 × 1015 cm−2) BF2 implant. Cross-sectional transmission electron microscopy showed that rapid thermal annealing (RTA) of the amorphous layer (without BF2 ) leaves defect-free material in the implanted region. Only a discrete layer of small (∼300Å) dislocation loops due to straggling ion damage was found to be present at a depth corresponding to the amorphous/crystalline interface. RTA of the amorphous layer with the BF2 creatpd a high density of uniformly. distributed fine defect clusters (∼50Å) in the surface region (0–500Å) in addition to the straggling ion damage. Boron and F profiles obtained by secondary ion mass spectrometry from the unannealed and rapid thermally annealed samples showed the presence of high concentrations of these impurities in the surface region where the fine defect clusters were observed. A comparison of the RTA behavior of the pre-amorphized surface layers (with or without BF2 ) produced by Ge and self-implantation is presented.

A multiple scan electron beam system has been used to anneal silicon implanted with BF2 (25 Kev, 1, 2 and 5 × 1015 ions × cm−2 ). The annealing temperatures range from 1000 to 1200° C and the annealing times from 3 to 18 seconds. The curves of sheet resistance as a function of annealing time show a minimum. The increase in sheet resistance at longer annealing times is due to boron outdiffusion. Junction depths have been measured by spreading resistance and are presented. For implanted doses below 2 × 1015 ions × cm−2 boron outdiffusion limits the sheet resistance value at about 100 R Ωand this minimum value corresponds to an increase in junction depths of about 500 Å. For implanted doses of 5 × 1015 ions ×cm−2, 60 Ω sheet resistance can be obtained, but with about 1000 Å increase in junction depth.

A variety of backside damage techniques are available for gettering heavy-metal contaminants in silicon wafers. These include mechanical damage, ion implantation, thin film deposition, and pulsed–laser surface melting. In each case, strain fields and microscopic defects induced by the processing trap impurities as they diffuse through the wafer during subsequent high–temperature processing steps. We examine the defect structures produced by CW laser gettering, describe the dependence of gettering efficiency on wafer oxygen content and processing conditions, and demonstrate that CW laser processing can be an effective gettering technique even when the number of laser scan lines is reduced to make wafer processing acceptably rapid.

Accurate wafer temperature measurement is very important in the area of material processing. In Short Time Annealing, for example, it is necessary to monitor temperature peaks of up to 1200°C which are only a few seconds in duration. This paper describes a structure consisting of a silicon wafer with a specially attached thermocouple. This structure is capable of reliable high temperature measurements of up to 1200°C and is also capable of surviving repeated cycling at that temperature.

A new low temperature method of forming high quality patterned silicon dioxide (SiO2) layers up to a thickness of 1 μm on silicon substrates is presented. UV pulsed laser excitation in an oxygen environment is utilized. IR absorption spectroscopy, CV and IV measurements are employed to characterize the oxide films and the Si-SiO2 interface. No shift but a significant broadening of the Si-O stretching mode compared with thermally grown oxides is found indicating that the laser grown oxide is stoichiometric but with a higher degree of disorder. From CV measurements we deduce a fixed oxide charge near the Si-SiO2 interface of 6×1010/cm2 for oxides that have been thermally annealed in O2 following the laser induced growth making this material a candidate for applications in semiconductor devices.

We have investigated the annealing of ion implantation damage (in the form of amorphous layers and/or the layers containing only dislocation loops) in silicon and gallium arsenide. The annealing of amorphous layers occurs by solid-phase-epitaxial growth and that of dislocation loops involves primarily loop-coalescence as a result of conservative climb and glide processes. The annealing of disolated loops occurs primarily by a bulk diffusion process. Almost a “complete” annealing of displacement damage is possible for shallow implants provided loop–coalescence does not lead to the formation of cross–grid of dislocations. For deep implants, the free surface cannot provide an effective sink for defects as in the case of shallow implants. Dopant profiles can be controlled to less than 1000 Å in layers having good electrical properties. The enhanced diffusion of dopants is observed probably due to entrapment of point defects in the annealed regions.

We have investigated trap levels in silicon after Thermal Pulse Annealing (TPA). Three different annealing systems consisting of tungsten lamps or a graphite heater have been applied. Trap levels induced in different silicon materials (Cz, FZ, Epi) after TPA have been studied by DLTS and admittance spectroscopy. In boron-doped epitaxial silicon and As+- implanted pn-junctions (Cz grown Si), we have observed a prevalent trap level at concentrations of up to 1015cm−3 (depending on anneal conditions and silicon material). The ionization energy of this trap level is Ev+300meV.

The concentration of the 300 meV-level was studied as a function of the annealing temperature and the quench rate. The thermal pre-processing history strongly affects the trap concentration induced by TPA. The 300 meV-level is almost completely removed by a subsequent furnace anneal at TA > 400°C

Further trap levels are created in boron- and aluminum- doped silicon by Ar+ or 30Si+ implantation and TPA. The defect natures are discussed.

Highly focused Q-switched Nd:VDG fundamental (1.05 micron wavelength IR) and second harmonic (0.53 micron wavelencth green) laser pulses have been shonm to produce bulk defects in single crystal silicon at peak power densities below the vaporization threshold for the IR and below the melting threshold for the green. The defects decrease the encess rinoritv carrier lifetime as measured by junction leakage, junction step recovery, the MOS CV method, bioolar transistor current qain, and pn junction photocurrent. Green pulses have no effect on the thermal oxide dielectric strength or pn junction breakdown voltage at power densities up to the melting threshold. IR pulses begin to lower the junction breakdown voltage below the vaporization threshold and oxide dielectric strength is drastically lowered at or slightly below this threshold. The defect density decreases exponentially into the crystal with effective ranges of 0.7 micron and 1.7 microns for the green and IR respectively. IR absorption is very nonlinear near the vaporization peak power density threshold. The defects are a point type; are unchanged by a subsequent 400°C anneal; and are completely removed by an 800°C anneal. The results suggest some detrimental effects of laser processing of silicon intergrated circuits as well as some new potential applications.

A non destructive SEM observation method has been applied to investigate the extended defects created by pulsed electron beam annealing of arsenic–implanted silicon. The defect study was performed on bevelled samples after irradiation using variable beam fluences for both a 20°C or a 450°C specimen starting temperature. Dislocation generation resulting in subgrain boundaries formation occurs during regrowth of the silicon layer which has been heated up to the melt point or higher. For the rather penetrating electron beam pulse used in this work the subgrain size and their depth extent depend on the beam fluence and the substrate temperature. For 450°C pre‐heated samples, annealing of the arsenic implant is possible without any stable extended defect creation using the 1.0 – 1.2 J.cm−2 fluence range.

A simple model for solute trapping during rapid solidification is presented in terms of a single unknown parameter, the interfacial diffusivity Di. A transition from equilibrium segregation to complete solute trapping occurs over roughly an order of magnitude in growth speed, as the interface speed surpasses the maximum speed with which solute atoms can diffuse across the interface to remain ahead of the growing crystal. This diffusive speed is given by Di/λ, where λ is the interatomic spacing, and is typically of the order 10 meters per second. Comparison is made with experiment. The steady–state speed of a planar interface is predicted by calculating the free energy dissipated by irreversible processes at the interface and equating it to the available driving free energy. A solute drag term and an intrinsic interfacial mobility term are included in the dissipation calculations. Steady–state solutions are presented for Bi–doped Si during pulsed laser annealing.

We report on an investigation of the temperature and concentration dependent kinetic competition between solid phase epitaxy and complex formation and precipitation in arsenic–implanted Si(100). Crystallization kinetics were monitored using time–resolved reflectivity during cw laser irradiation or furnace heating; microstructural changes were evaluated using cross–sectional TEM. At low temperatures and high As concentrations, complex formation and precipitation substantially alter the SPE kinetics. At higher temperatures competing interactions are less significant, and SPE becomes the dominant process. The kinetic competition between these processes is discussed with respect to the vacancy model for SPE.

Recently it has been proposed that solid silicon at the melting temperature is amorphous. There is no known case of a solid for which an amorphous structure is the equilibrium state. Silicon thin films on insulating substrates, when heated radiantly, melt inhomogeneously and provide an accessible high temperature system for a study of a solid coexisting with its melt. Using the intensity, energy distribution and polarization of Raman scattering from silicon lamellae, we have proved that the equilibrium phase is in fact crystalline. Furthermore, we give strong evidence that the solid regions have {100} texture at Tm.

The behaviour of thin liquid films is known to be dominated by surface tension forces. We show that the crystallization of thin liquid films requires that two wetting angle conditions be simultaneously satisfied: (i) relating to the liquid–vapour interface and (ii) relating to the crystal–liquid interface. The balance between capillary pressure and thermal gradient forces shows that the equilibrium freezing point of thin films is actually depressed below the bulk freezing point. The magnitude of the effect is 1°K in an 800 Å thick film. These observations suggest that small–scale thickness fluctuations may be responsible for the initiation of sub–grain boundaries in the growth of crystalline silicon films.

Single crystalline germanium islands on SiO2 have been formed by zone melting with graphite strip heaters. Two types of geometrical patterns for islands were successfully used to obtain large single crystalline islands. Most germanium islands were found to be single crystal and the predominant orientation was (100). Electron concentrations of 1016 - 1018/cm3 with Hall mobility of 3 × 103 − 1 × 103 cm2 /Vsec were obtained for single crystalline germanium islands. Gallium Arsenide layers, grown by molecular beam epitaxy, on the germanium islands were found to emit photoluminescence, the intensity of which was almost comparable to that of gallium arsenide layers on bulk germanium crystals.

It is well known that crystal growth and defect propagation occur along the local thermal gradient at a liquid - solid interface, It is shown here that this property can be used to greatly reduce the density of structural defects in zone crystallized silicon thin films on amorphous substrates, A solidification front perpendicular to the direction of zone motion has its in - plane component of the thermal gradient parallel to the direction of zone motion. In this case, the defects, once nucleated, propagate along this zone path and the defect density reaches a steady state value. By using striped polysilicon patterning and a solidification front tilted relative to the molten zone path, a defect-free region is shown to occur. It is also shown that defects, once nucleated, are swept laterally from the region of interest and are terminated at the stripe boundary Methods of forming a tilted interface are proposed and demonstrated for CO2 laser crystallization.

We report and analyze the breakup of a crystalline silicon surface into solid and molten faceted segments by radiative heating. Melting starts at discrete sites since there is a nucleation barrier requiring superheating of the surface. Once started, the melt remains localized and does not encompass the entire surface because of the changes in optical properties of Si upon melting. It is estimated that superheating by <0.5 K should be sufficient to stabilize faceted melt regions spaced 200 μm apart. The preliminary measurements, however, indicate superheating by several degrees.

Two CVD techniques producing monocrystalline SOI films, silicon-on sapphire (SOS) and Epitaxial Lateral Overgrowth (ELO), are described and the nature of the crystallographic defects in the films is discussed. The geometrical structure of SOI devices, device properties, dynamic characteristics, capacitance, and radiation hardness are then examined with emphasis on evaluating the potential of SOI technologies in future applications.