MeV ion irradiation effects on semiconductor crystals, GaAs(100) and Si(111) and on an insulating crystal CaF2 (111) have been studiedby the x-ray rocking curve technique using a double crystal x-raydiffractometer. The results on GaAs are particularly interesting. The straindeveloped by ion irradiation in the surface layers of GaAs (100) saturatesto a certain level after a high dose irradiation (typically 1015/cm2), resulting in a uniform lattice spacingabout 0.4% larger than the original spacing of the lattice planes parallelto the surface. The layer of uniform strain corresponds in depth to theregion where electronic energy loss is dominant over nuclear collisionenergy loss. The saturated strain level is the same for both p-type andn-type GaAs. In the early stages of irradiation, the strain induced in thesurface is shown to be proportional to the nuclear stopping power at thesurface and is independent of electronic stopping power. The strainsaturation phenomenon in GaAs is discussed in terms of point defectsaturation in the surface layer.

An isochronal (15 min.) annealing was done on the Cr-doped GaAs attemperatures between 200° C and 700° C. The intensity in the diffractionpeak from the surface strained layer jumps at 200° C < T ≤ 300° C. Thestrain decreases gradually with temperature, approaching zero at T ≤ 500°C.

The strain saturation phenomenon does not occur in the irradiated Si. Thestrain induced in Si is generally very low (less than 0.06%) and isinterpreted to be mostly in the layers adjacent to the maximum nuclearstopping region, with zero strain in the surface layer. The data on CaF2 have been analysed with a kinematical x-ray diffractiontheory to get quantitative strain and damage depth profiles for severaldifferent doses.

Retention and bonding of nitrogen implanted into crystalline Si wereexamined by infrared absorption (ir) and transmission electron microscopy(TEM) after furnace and pulsed laser annealing. Localized Si-N vibrationalmodes for N-N pairs are observed, and the associated ir band intensitiesincrease upon pulsed annealing. Furnace annealing above 600°C decreases their intensity for N-N pairs and fine structure defects appear in TEM.Subsequent laser annealing removes most of the fine structure andreactivates the pair spectrum which we interpret as dissolution of Nprecipitates and pair formation upon quenching from the melt. Any realisticmodel for N in Si must include the formation and consequences of N-Npairs.

In a study to examine the effect of irradiating a number of silica- andcarbon-reinforced composites with high-energy beams, surface analyticaltechniques have proved especially effective in revealing reactions betweenundoped or doped matrices and silica or carbon reinforcements,respectively.

Certain aspects of Rapid Thermal Annealing (RTA) are reviewed. Temperatureconsiderations are discussed. The implant disorder removal rate is measured(5eV removal energy for As induced damage). Shallower defect-free junctionsare obtained using RTA. Results of a ”Round Robin”-RTA annealing arepresented, transient enhanced diffusion is not prominent for As. New resultsfor the concentration enhanced diffusion of As are presented. Diffusion fromthe channeling-tai1 region of shallow boron diffusions is noted as alimiting factor for producing shallow p+-junctions. Other issuesare briefly discussed.

Unlike As, B as well as P implanted into Si exhibits transient, enhanceddiffusion. For example, when P implants are annealed for times of ~1 s attemperatures > 900°C, we observe a large movement of dopant toward thefurnace of the Si wafer which is nearly independent of temperature1050-1200°C. Once the temperature rises above 1200-1250°C the diffusion issimilar to that normally observed. We model the experimental results as atransient, enhanced diffusion of a mobile component, about half the totalphosphorus implant, distributed deeper in the bulk than the total Pdistribution. This mobile component may be linked to a largesuper-saturation of self-interstitials produced by the 50 keV implantation,which are expected to be left deeper in the bulk than the total dopantprofile.

The annealing behaviour of B implants in the millisecond time regime using acombination of swept line beam and background heating is compared withisothermal annealing with heating cycles of a few seconds. Carrierconcentration profiles derived from spreading resistance measurements showthat under annealing conditions which restrict diffusion, millisecondprocessing gives higher activation of B implants than isothermal heating.Transmission electron microscopy shows that millisecond annealing alsoresults in a lower defect density than that following an equivalentisothermal anneal.

Shallow p+n junctions have been formed through a combination ofpre-amorphization of the silicon surface by implantation of 28Si, 33Ar, or 73Ge, low energy implantation of boron or BF2+, and rapid thermal annealing (RTA) in a tunqsten halogen lampsystem. Both pre-amorphization and RTA are required to form a shallow(<0.25 μm) junction, for either boron or BF2+. Arqon pre-amorphization results in poor electrical activationof the boron, while germanium gives the lowest sheet resistivity, but isresponsible for a deep boron tail during implantation. The residual damageis characterized by a plane of dislocation loops centred either close to theboron concentration peak, for B+ implantation into a crystallinesubstrate, or at the original amorphous-crystalline interface, forpre-amorphized specimens.

Short time anneal experiments were performed in a specially developedannealing system based on a bank of Tungsten-Halogen lamps. The annealingprocess during the temperature transient was studied as a function of theillumination time with the system operating in the constant maximum powerregime. By using this procedure it was shown that electrical activation ofall elements (B, P, As) considered in this study is completed within thetransient period without noticeable diffusion. Redistribution of theimplanted profiles was only observed for longer times after the steady statetemperature was reached. Pre-amorphization with Argon is found tosignificantly alter and retard the annealing behaviour.

We report on a systematic study of the doping profiles resulting from rapidthermal annealing of boron and BF2+-implanted silicon samples that were preamorphized by Si+ implantation. A two-step process consisting of an initialsolid phase epitaxial regrowth followed by a brief (~5 sec) high temperature(1050ଌ) anneal produces extremely shallow (<1500Å) junctions with lowdefect concentrations. The quality of the epitaxial regrowth is verysensitive to implant conditions and impurity effects as deduced fromtime-resolved reflectivity measurements. Using the best conditions forimplantation and solid phase crystallization, we have obtained boron-dopedregions with sheet resistivities of 40 Ω/ and BF2-doped regionsof resistivity 60 Ω/.

Shallow (0.15-0.2 μm deep) p+ junctions have been formed using boronimplanted into silicon which was pre-amorphized using a silicon implant. Theimplants were annealed using a two-step process; initially the wafers werefurnace annealed at 600 °C for 100 min., followed by a rapid isothermalanneal (RIA) at 950-1100 °C for 10 sec. For comparison, some wafers wereonly given a single-step rapid isothermal anneal at 950-1100 °C for 10 sec.The shallowest junctions were formed when the amorphous silicon layer wasdeeper than the boron implant, because of the suppression of channelling.When the amorphous/crystalline interface was shallower than the tail of theboron implant, some channeling occurred. This channeling tail exhibited anenhanced diffusion during the single-step RIA which was reducedsignificantly by the two-step anneal. When the amorphous layer was deeperthan the boron implant, the single-step and two-step anneals gave identicalresults.

Enhanced dopant diffusion during RTA depends upon whether the followingphysical phenomena occur individually or in combination: (1) amorphizationof the Si, (2) damage-induced dislocation formation, (3) damage annealing,(4) self-interstitial trapping, (5) solubility enhancement. RTA of B incrystalline or preamorphized Si presents significantly differentenvironments for enhanced diffusion. In preamorphized Si, enhanced Bdiffusion is modeled as increased B solubility following SPE. In addition, adifferent intrinsic diffusivity is observed which corresponds to B diffusionin preamorphized Si. Anomalous diffusion of B and As from high dose implantscan be modeled with the same mechanism -- self-interstitial trappingfollowing SPE.

Solid phase epitaxial regrowth of silicon on sapphire is used to improve thequality of as-received silicon films prior to conventional deviceprocessing. It has been shown that this is necessary, especially for layersof 0.3μm and thinner, if the full potential of this particular silicon oninsulator technology is to be realised. Si+ ions are implanted atan energy and dose such that all but the surface of the silicon film isrendered amorphous. In this study, the layer is regrown using a rapidthermal annealer operated in the multi-second regime. A second shallowerimplant followed by rapid thermal annealing produces a further improvement.Characterisation of the material has been principally by cross-sectionaltransmission electron microscopy. The structures observed after differentimplant and regrowth treatments are discussed.

We show that post anneals of short duration at high temperature can markedlyimprove the quality of CaF2 films grown by molecular beam epitaxy(MBE) on Si (100). Anneals at 1100°C for 20 sec in an Ar ambient improved χmin, the ratio of backscattered 1.8 MeV He4 ionsin the aligned to random direction, from as-grown values of .07 to .26, topost post-anneal values of .03 to .045. This is the best χmin yet reportedfor the CaF2:Si system. The post-annealed films also showimproved resistance to chemical etching and mechanical stress, and increaseddielectric breakdown voltages.

Scanning electron beam annealing has been used to study the annealing of NTDsilicon in the temperature range 600-1180°C. The annealing process has beenfound to be very rapid above 800°C, a 30 second anneal producing highlyuniform n-type material. Below this temperature, an initial drop followed bya progressive rise in sample resistivity with increasing anneal time isconsistent with phosphorus dopant activation and the formation of adefect-related acceptor complex.

From studies of time-resolved reflectivity and microstructural changes, wehave obtained direct evidence of CO2 laser-induced melting abovea threshold energy density. Results of the optical measurements,transmission electron microscopy, and secondary ion mass spectrometry arereported. The measurements show that melt depths as deep as 1 μm can beachieved with pulsed CO2 laser radiation. By using differentialabsorption between layers with different free-carrier densities, we findthat a CO2 laser can be used to melt regions which are embeddedin the material. It is likely that this observed phenomenon is impossible toobtain with a visible or ultraviolet laser.

The incorporation properties of implanted or deposited Sb into the siliconlattice during laser irradiation with a UV laser has been studied. For bothimplanted or deposited Sb, we find a maximum substitutional concentration of2.1 × 1021/cm3 following laser melting andsolidification at V ; 6 m/sec. In both cases, substitutional solubility islimited by inter-facial instabilities which develop during regrowth. For thedeposited case we observe in addition a much larger cellular microstructurewhich may result from convection induced instabilities.

In recent years, rapid annealing of GaAs has been employed to activate ionimplanted dopants and to produce metal-semiconductor contacts. Morerecently, rapid heating techniques have been used to anneal heterostructureswithout degrading requisite high mobilities of SDHT devices. This paperreviews the various annealing regimes which are useful for heat treatingGaAs and related compounds. Examples are chosen which illustrate unique andpotentially useful features of rapid annealing.

The (0001), (1010), and (2110) faces of Bi have been pulse laser melted at0.5 J/cm2 with a Q-switched Ruby laser. Nomarski InterferenceContrast Microscopy, Channeling, and selective chemical etching have beenused to investigate the response to the laser irradiation. The response ofthe material and the level of damage is shown to be strongly correlated tothe critical resolved shear stress characteristics in the particularcrystallographic direction studied.

We have used the heavy ion elastic recoil technique to study B distributionchanges during Co and Ti di silicide formation on B implanted single crystalSi wafers. B diffuses to the interface of TiSi2 and Si and to thesurface of CoSi2.

The rapid annealing of Be implanted GaAs has produced electrical activationsof 70% for doses of 5 × 1014 cm−2 and hole profilessimilar to the as implanted distribution. Si implanted GaAs has also beeninvestigated using doses of 1 and 2 × 1014 cm−2 withsheet resistivities of 40 Ω/square after rapid thermal annealing. GaAs hasbeen annealed with W-Si on the surface for the application of self alignedgate FET technology. Temperature cycles upto 850°C are required to activatethe implanted dopant. Such cycles do not cause inter diffusion between theW-Si and GaAs or deterioration of the metallisation surface morphology.