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

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

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

Retention and bonding of nitrogen implanted into crystalline Si were examined by infrared absorption (ir) and transmission electron microscopy (TEM) after furnace and pulsed laser annealing. Localized Si-N vibrational modes for N-N pairs are observed, and the associated ir band intensities increase upon pulsed annealing. Furnace annealing above 600°C decreases the ir intensity for N-N pairs and fine structure defects appear in TEM. Subsequent laser annealing removes most of the fine structure and reactivates the pair spectrum which we interpret as dissolution of N precipitates and pair formation upon quenching from the melt. Any realistic model for N in Si must include the formation and consequences of N-N pairs.

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

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

Unlike As, B as well as P implanted into Si exhibits transient, enhanced diffusion. For example, when P implants are annealed for times of ~1 s at temperatures > 900°C, we observe a large movement of dopant toward the furnace of the Si wafer which is nearly independent of temperature 1050-1200°C. Once the temperature rises above 1200-1250°C the diffusion is similar to that normally observed. We model the experimental results as a transient, enhanced diffusion of a mobile component, about half the total phosphorus implant, distributed deeper in the bulk than the total P distribution. This mobile component may be linked to a large super-saturation of self-interstitials produced by the 50 keV implantation, which are expected to be left deeper in the bulk than the total dopant profile.

The annealing behaviour of B implants in the millisecond time regime using a combination of swept line beam and background heating is compared with isothermal annealing with heating cycles of a few seconds. Carrier concentration profiles derived from spreading resistance measurements show that under annealing conditions which restrict diffusion, millisecond processing gives higher activation of B implants than isothermal heating. Transmission electron microscopy shows that millisecond annealing also results in a lower defect density than that following an equivalent isothermal anneal.

Shallow p+n junctions have been formed through a combination of pre-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 lamp system. 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 activation of the boron, while germanium gives the lowest sheet resistivity, but is responsible for a deep boron tail during implantation. The residual damage is characterized by a plane of dislocation loops centred either close to the boron concentration peak, for B+ implantation into a crystalline substrate, or at the original amorphous-crystalline interface, for pre-amorphized specimens.

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

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

Shallow (0.15-0.2 μm deep) p+ junctions have been formed using boron implanted into silicon which was pre-amorphized using a silicon implant. The implants were annealed using a two-step process; initially the wafers were furnace annealed at 600 °C for 100 min., followed by a rapid isothermal anneal (RIA) at 950-1100 °C for 10 sec. For comparison, some wafers were only given a single-step rapid isothermal anneal at 950-1100 °C for 10 sec. The shallowest junctions were formed when the amorphous silicon layer was deeper than the boron implant, because of the suppression of channelling. When the amorphous/crystalline interface was shallower than the tail of the boron implant, some channeling occurred. This channeling tail exhibited an enhanced diffusion during the single-step RIA which was reduced significantly by the two-step anneal. When the amorphous layer was deeper than the boron implant, the single-step and two-step anneals gave identical results.

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

Solid phase epitaxial regrowth of silicon on sapphire is used to improve the quality of as-received silicon films prior to conventional device processing. It has been shown that this is necessary, especially for layers of 0.3μm and thinner, if the full potential of this particular silicon on insulator technology is to be realised. Si+ ions are implanted at an energy and dose such that all but the surface of the silicon film is rendered amorphous. In this study, the layer is regrown using a rapid thermal annealer operated in the multi-second regime. A second shallower implant followed by rapid thermal annealing produces a further improvement. Characterisation of the material has been principally by cross-sectional transmission electron microscopy. The structures observed after different implant and regrowth treatments are discussed.

We show that post anneals of short duration at high temperature can markedly improve 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 ions in the aligned to random direction, from as-grown values of .07 to .26, to post post-anneal values of .03 to .045. This is the best χmin yet reported for the CaF2:Si system. The post-annealed films also show improved resistance to chemical etching and mechanical stress, and increased dielectric breakdown voltages.

Scanning electron beam annealing has been used to study the annealing of NTD silicon in the temperature range 600-1180°C. The annealing process has been found to be very rapid above 800°C, a 30 second anneal producing highly uniform n-type material. Below this temperature, an initial drop followed by a progressive rise in sample resistivity with increasing anneal time is consistent with phosphorus dopant activation and the formation of a defect-related acceptor complex.

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

The incorporation properties of implanted or deposited Sb into the silicon lattice during laser irradiation with a UV laser has been studied. For both implanted or deposited Sb, we find a maximum substitutional concentration of 2.1 × 1021/cm3 following laser melting and solidification at V ; 6 m/sec. In both cases, substitutional solubility is limited by inter-facial instabilities which develop during regrowth. For the deposited case we observe in addition a much larger cellular microstructure which may result from convection induced instabilities.

In recent years, rapid annealing of GaAs has been employed to activate ion implanted dopants and to produce metal-semiconductor contacts. More recently, rapid heating techniques have been used to anneal heterostructures without degrading requisite high mobilities of SDHT devices. This paper reviews the various annealing regimes which are useful for heat treating GaAs and related compounds. Examples are chosen which illustrate unique and potentially useful features of rapid annealing.

The (0001), (1010), and (2110) faces of Bi have been pulse laser melted at 0.5 J/cm2 with a Q-switched Ruby laser. Nomarski Interference Contrast Microscopy, Channeling, and selective chemical etching have been used to investigate the response to the laser irradiation. The response of the material and the level of damage is shown to be strongly correlated to the critical resolved shear stress characteristics in the particular crystallographic direction studied.

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

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