Epitaxial regrowth is investigated for layers of InSb and GaAs amorphized by liquid nitrogen temperature ion implants. Experimental criterion for amorphization and limitation of regrowth are correlated with damage calculated by a Boltzmann transport equation approach to ion implant modeling. Conditions for complete epitaxial regrowth as determined by channeled Rutherford backscattering spectrometry are presented with evaluation of residual defects by transmission electron microscopy. Electrical activation following regrowth of GaAs is reported and correlated with calculated damage profiles.

Microdefects in Cr-doped SI LEC (001) GaAs wafers which were implanted with Zn+ or As /Zn and capless-annealed in an As ambient have been studied by means of transmission electron microscopy. Most of the microdefects in Zn +- implanted GaAs specimens were identified as precipitates and stacking fault tetrahedra (SFTs). Every SFT was accompanied by a precipitate at the apex. Most of the precipitates were distributed from Rp to Rp + 2∆Rp. Two types (α and β) of SFTs were differentiated by the arrangement of atoms in the core of the stair-rod partial dislocations bounding the periphery of the SFTs in a polar Frystal. β-SFTs were, however, predominantly formed in Zn+ implanted GaAs specimens. Dual implantation of As+ and Zn+ suppressed the formation of SFTs, but not that of precipitates. The formation of SFTs was found to be influenced by the deviation in stoichiometry.

A comparison has been made between rapid thermal annealing (RTA) and furnace annealing (FA) of implanted GaAs. Hall measurements showed consistently higher electrical activation of n-type (Si-5E12 cm −2) implants with FA and higher electrical activation of p-type (Be-1E14 cm −2) implants with RTA. Photoluminescence (PL) revealed that for RTA temperatures above 950°C some of the Si was going onto As, acceptor sites, thus reducing the net donor concentration. PL for RTA below 950°C showed signs of incomplete recrystallization. By a technique of “dual implantation” of As and Si into GaAs we were able to force the Si onto Ga-sites resulting in a higher donor concentration after RTA.

Ion-beam mixing and rapid thermal annealing (RTA) techniques are used to form shallow and heavily-doped n+ layers in undoped GaAs. RTA reduces surface degradation and improves crystalline quality compared to lengthy thermal cycles, although furnace annealing producesidentical electrical characteristics. Ion-beam mixing has only a small effect on the diffusion of a deposited GeSe film, because the damage created by implantation is repaired during RTA before significant diffusion occurs. We define a threshold temperature representing the onset of significant electrical activation and/or diffusion, and propose a model relating the annealing, activation, and diffusion temperatures for the GeSe/GaAs system. RBS. SIMS, and electrical measurements show that extremely shallow layers with a sheet resistivity as low as 1480/El can be formed in GaAs by diffusion from a GeSe source. This technique has potential application to the formation of shallow ohmic contacts for GaAs integrated circuits.

We report on the structural and electrical properties of (100) InP resulting from the implantation of 180 keV Si+ and subsequent annealing. The radiation damage produced by implantation at substrate temperatures from 77 to 480 K is evaluated using MeV He ion channeling. Varying degrees of recrystallization are found depending on the implant temperature and choice of furnace vs. rapid thermal annealing. Samples implanted at 25°C to a dose of 3.3.1014ions/cm2 continue to display structural disorder regardless of annealing procedures. In contrast, implantation at 200°C to 3.3-1014ions/cm2 produces a low but measurable damage level. Further annealing lowered the disorder to a level similar to that of unimplanted material.

The electrical activation of both low and high fluence ion doses is nearly the same at the optimal conditions for rapid thermal annealing (RTA) or furnace annealing (FA). However the electron mobility is found to be higher after hot implantation and RTA. The electrical profile after hot implantation is wider than the profile after RT implants and FA.

A single crystal silicon layer on an insulator is a desirable structure for applications in electronics. One of the leading processes for achieving such a structure is the formation of a buried oxide layer in silicon by heavy dose oxygen implantation. Characteristics of this material have been reported for implantation by beam scanning. In this work we report on material prepared by wafer scanning at rates such that significant temperature cycling occurs during implantation, and we use TEM and Auger analysis to investigate the differences between these samples and others prepared by the conventional technique of beam scanning. For the implantation and annealing conditions used here, we find more oxygen in the top silicon layer in the case of wafer scanning, and the oxygen concentration increases after annealing at 1150°C for 2 hours, leading to a structure of precipitates throughout the single crystal top silicon layer. For beam scanning, the oxygen concentration decreases after annealing and achieves background levels near the surface, leading to a zone which is free of precipitates.

The line-shaped electron beam annealing system which generates an electron beam of a length of 4 cm and a width af less than 100 um with a high energy density exceeding well over 100 kW/cm2 was developed for the first time with a purpose of SOI processing as its primary application. An pccelaration voltage of up to 20 kV can be used in this system. Seeded single crystalline islands with areas several mm long and 30 to 100 um in width were obtained by a single scan of the electron beam. The electron beam is generated in a pulsed way in the system due to the power restriction of the power supplies. An area of 4×5 cm2 was processed by a single scan of an electron beam at a sample speed of 530 cm/sec and a beam duration of 9.5 msec. The scanning area for one scan is determined by the beam length and the duration of the beam and sample speed.

The present system could give single crystalline silicon films without any grain boundaries. The electron mobility of the electron beam recrystallized films, obtained from FETs made as a vehicle to test the electrical properties of the films, was comparable to that of the bulk silicon. A very rapid migration of silicon atoms in solid polycrystalline silicon films, which is controllable by process parameters, was also found with a migration speed of the order of 1 m/sec in a capped structure. The present electron beam system is useful in studying basic mechanisms of crystal growth in thin films. The system can have a very high throughput, a desirable feature in semiconductor industry. The present system can also be used to study the rapid thermal treatment of materials other than semiconductors including rapidly solidified materials.

Oxygen 0+ ions have been implanted into Si both at room temperature and liquid nitrogen temperature in order to determine the effect of implantation temperature on SiO2 formation. Samples were analysed by RBS with 1.5 MeV He+ ions. The implants of 0+ in Si were done at 150 keV with current densities of ≤10 μA/cm2. For doses of more than 1.5×1018 0+/cm2, in-situ RBS experiments positively indicate a 2:1 oxygen silicon ratio. Increased 0+ doses (for both room temperature and liquid nitrogen temperature) cause the Si02 layers to spread uniformly and symmetrically toward both the surface and the interior. From these results, it is apparent that excess oxygen diffuses toward Si/Si02 interfaces in our experimental situation even at liquid nitrogen temperature.

We demonstrate the formation of buried layers of SiC in (100) single-crystal bulk Si and silicon-on-sapphire by ion implantation of 125-180 keV, (0.56-1.00)×1018 C/cm2 at 30-40 μA/cm2 into samples held at 450-650¼C. The as-implanted and 950°C annealed samples are characterized by differential infra-red absorbance and reflectance, Rutherford backscattering and channeling spectrometry, X-ray diffraction, four-point probe, Dektak profilometry, I-V measurements, spreading resistance and secondary ion mass spectrometry.

Buried insulating silicon nitride layers are formed by a 400°C N+-implantation at 150 keV with fluences from 0.35 to 1×1018 N+/cm2 and subsequent anneal at 1200°C in dry nitrogen. TEM and AES measurements on bevelled samples yield a correlation of ion and damage profiles to local defect structures. Low dose implantation results in polycrystalline precipitates of scaled spherulitic structure. High dose continuous polycrystalline nitride layers have good insulation properties following a 5 hour anneal. During anneal, the common asymmetrical ion depth profile transforms to a nearly rectangular profile. The silicon surface layer contains 106 to 108 dislocations/cm2, which seem to be passivated, since detrimental effects on electronic devices have not been measured.

The annealing of ion implantation damage in silicon by rapid isothermal heating has been monitored by the time resolved reflectivity (TRR) method. This technique was applied simultaneously at a wavelength of 632.8nm and also at 1152nm, where the optical absorption coefficient of silicon is less. The two wavelength method simplifies the interpretation of TRR results, extends the measurement depth and allows good resolution of the position of the interface between amorphous and crystalline silicon. The regrowth of amorphous layers in silicon, created by self implantation and implanted with electrically active impurities, was observed. Regrowth in rapid isothermal annealing occurs during the heating up stage of typical thermal cycles. Impurities such as B, P, and As increase the regrowth rate in a manner consistent with a vacancy model for regrowth. The maximum regrowth rate in boron implanted silicon is limited by the solid solubility.

Single crystal silicon has been implanted with low energy (20 keV) phosphorus ions and a comparison made of furnace annealing (which produces excellent solar cells) and rapid annealing using a radiant incoherent light source. The light source is used to anneal and activate implanted layers in the isothermal mode on a time scale of the order of seconds compared with the much longer furnace annealing times of several hours.

Initial results using the incoherent light source show a high dark current and inferior photoresponse. However a subsequent thermal treatment at 600°C for 10–15 minutes shows that the resultant photoresponse can approach that of the longer time furnace anneal. Transmission electron microscopy shows the formation of large voids (20–100 nm) after the initial annealing phase. These reduce in size after furnace annealing. This photoresponse may be related to this void formation.

High-dose arsenic and phosphorus ion implanted silicon was annealed either by a CW CO2 or a pulsed Nd:YAG laser creating supersaturated dopant concentrations up to 3·1021 cm−3. The relaxation of these metastable electrically active atoms was investigated during thermal post-annealing at temperatures between 600 and 1000°C for times between 3 and 106 s. In heavily doped samples which contain residual damage after laser annealing, a very fast first relaxation phase is observed followed by a much slower second phase. In samples without residual damage only this second slower phase is seen. Carrier concentration profile measurements show that the saturation concentration after the relaxation depends only on temperature and corresponds to the concentration in thermal equilibrium. Using reaction kinetics a cluster model is proposed which demonstrates that in As doped layers the most probable number of As atoms in one cluster depends on temperature (4 As atoms at 700°C, 3 As atoms at 800 - 1000°C). In P doped layers the most probable clusters contain 3 P atoms at temperatures between 700 and 900°C.

The irreversible thermal annealing behaviour of paramagnetic oxygen vacancy defects (E' centers) induced by 40 keV Ne+ and 140 keV Kr+ ion implantation in amorphous SiO2 has been studied by means of electron paramagnetic resonance. The reversible E'l⇆ B2 defect transformation occurring via a hole injection/trapping process under ionising radiation (190 keV H+) is used as a means of distinguishing a reversible modification of the defect charge state from irreversible annealing of oxygen vacancies. Irreversible thermal recovery is shown to occur between 500 and 900°C. Both conventional and tungsten lamp heater annealing results are compared to predictions based on Simpson and Sosin's model for diffusional recombination of spatially correlated Frenkel pairs and to a simple model for unimolecular recombination. The annealing behaviour observed is accounted for assuming a gaussian distribution in activation energy for diffusion.

A simple relationship for rapid thermal annealing exposure time for the case of annealing of boron and arsenic high dose shallow implants is found from first principles. The percentage of redistribution is found to be intrinsically dependent on exposure time and rate of temperature rise in the heat pulse. An upper bound of pulse rising rate for a given percentage tolerance in redistribution is also found. Extensive SIMS analysis shows very good agreement of these formulae with experimental data.

Silicon wafers (100) orientation, were implanted with 3 × 1015 and 1 × 1016 PF5 at 30 keV by glow discharge and subsequently annealed by a commercially available lamp set-up. The annealing temperatures were in the range 620–980°C with irradiation times of 4–7 sec.

Sheet resistivity and Hall measurements together with anodic oxidation stripping have been used to determine the mobility and the carrier concentration profiles; the residual damage and the presence of precipitates were investigated by Rutherford Backscattering (RBS) and Transmission Electron Microscopy (TEM).

Comparison between the as-implanted dopant depth distribution and the carrier concentration profiles of the annealed samples shows the evolution of the electrically active, substitutional dopant fraction, at increasing annealing temperatures. It is found that the maximum electrical activity is obtained at 720°C; between 720°C and 820°C a process of reverse annealing takes place and the sheet resistivity increases by a factor of about 3. By annealing at temperatures higher than 820°C the substitutional dopant fraction increases again to its maximum value and it is possible to observe the presence of diffusion tails.

Finally, RBS, TEM, and Deep Level Transient Spectroscopy (DLTS) were used to investigate the depth location and the evolution of the damage after annealing.

semiconductor doping. This paper surveys some of the equipment developed at Eaton Corporation in response to the proliferation of ion implanted devices. Developments in both high current (~10mA) and medium current (~1mA) implanters will be discussed.

The evolution of dedicated equipment for the production of buried oxide layers (silicon on insulator technology) will also be reviewed.

Contamination of implanted surfaces by metals and dopants is a significant limitation to the use of high-dose implantation for semiconductor IC fabrication. RBS, SIMS, SRP, chemical etching and IC device parameter measurements have been used to characterize contaminated surfaces implanted with modern, production-type implanters. Levels of dopant cross -contamination of the order of 10% of the primary dose have been observed. A systematic study of the effects of As, P, B and Sb implanted Si has shown measurable effects on diffusion profiles and junction depths at contamination levels as low as 0.01% of the primary dose. These effects are particularly serious for fast-diffusing contaminants in slow-diffusing primary dopants (such as P contamination in As implants). Evidence has been found for both sputtering and ‘vaporization’ mechanisms for transfer of contaminants from implanter surfaces to the wafer target. The effectiveness of machine design choices and process procedures (such as wafer clamp design, post-implant chemical cleans, and the use of screen oxides) in minimizing the effects of contamination are discussed.