Outside dislocations generated from phosphorus implanted silicon layers

The growth, movement and nature of outside dislocation, which propagate from heavily phosphorus (>10¹⁵ ions/cm²) implanted (111), (100), and (110) silicon layers into unimplanted outside regions by a compressive strain induced during 1100° C wet O₂ annealing, are investigated using transmission electron microscopy and x-ray diffraction topography. Outside dislocations are formed, mainly on (111) planes., by the glide motion of dislocation networks formed in implanted layers during early annealing. This results in dislocations extending into the unimplanted areas to different degrees, in the order of, from the largest to smallest, (111), (110), and (100) wafers. In (110) wafers, the [001] oriented dislocations in the implanted regions rise to the surface at the implant and unimplant boundary. On the other hand, the [110] dislocations penetrate into the unimplanted region. Two sets of orthogonal 〈110〉 oriented dislocations generated in (100) implanted wafers behave in the same manner as the [001] dislocations in (110) wafers. Some sources of the compressive strain related to the generation of these dislocations are discussed.     

Electron irradiation assisted annealing of boron and phosphorus implanted silicon layers

Radíatíon annealing due to a 1.0 MeV election beam of intensity 25 μA/cm² was studied in silicon samples implanted with phosphorus and boron ions and annealed at 350–500°C. A significant annealing enhancement as compared to thermal annealing has been observed in phosphorus-implanted samples. In boron-implanted samples, a fast initial rise of electrical activity is followed by a continuous decrease of carrier concentration. The results are interpreted in terms of two competing processes: electron irradiation induced removal of post-implantation defects and introduction of simple electrically active defects.     

Non-monotonic depth distribution of secondary defects in ion implanted layers of silicon

Abstract

The non-monotonic distribution of secondary defects after two-step annealing of silicon implanted with boron ions is investigated using the TEM technique and the method of mercury probe along a bevel which was made chemically. Possible mechanisms of multilayer structure formation are discussed.     

Characterization of ion implanted n+ layers on tetrahedrically textured silicon surfaces

Ion implantation of 2 × 10^{15 31}P⁺/cm² at 10 keV and furnace annealing at 750° C, 1/2 h, have been used to obtain n⁺ -p junctions on (100) silicon samples having tetrahedrically textured surfaces. This texture was obtained by an anisotropic etching in a hot hydra-zine-water mixture. Morphological properties of the surface (dimension, homogeneity and characteristic of the tetrahedrons) have been analyzed and electrical properties of the implanted layers (sheet resistivity, carrier concentration profile) have been measured. The electrical characteristics of the textured samples are similar to those obtained using samples with flat polished surface; the tetrahe-dral structures are not damaged by the implantation process and they keep their antireflecting properties unaltered.     

Athermal effects in ion implanted layers

Abstract

Defect structure and electrical characterization of boron and arsenic implanted layers has been investigated for implantation under athermal (light) excitation. This Photon Assisted (PA) implantation owes its specific properties to an additional electric field acting on charged particles including carriers and charged defects. It was shown that in case of n-type silicon this extra field draws charged vacancies and self-interstitials towards each other and, thus, diminishes transient diffusion of boron. This effect resulted in junctions which are about 20% shallower compared to conventionally processed reference wafers. Experiments using light of an Ar-ion laser and white light of a high pressure Xe arc lamp were compared. Some deactivation of carriers in the deeper laying parts of the p-region was always a by-product.     

Pac studies of ion implanted silicon

The annealing behaviour of radiation induced defects in ion implanted silicon is studied by the perturbed angular correlation method (PAC). Between 700 K and 1000 K the trapping and detrapping of vacancy-oxygen complexes is observed. In annealed p-Si a well defined, axially symmetric electric field gradient (EFG) appears at low temperatures. This EFG is oriented to the surface and not to any crystallographic direction. The size of the EFG depends strongly on the surface charge.     

Photoresponse of ion implanted gallium dopants in silicon

High resolution spectral photoconductivity measurements are reported for a thin Si:Ga layer fabricated by ion implantation. The gallium ions were implanted at an energy of 3 MeV and a dose of 10¹⁴cm⁻². The measured spectral response of the layer was comparable to that of bulk Si:Ga, while the temperature range of the layer's photoresponse showed an increase when compared to that of bulk Si:Ga. These results show that ion implantation can produce useful thin, infrared active layers.     

Damage dependent electrical activation of phosphorus implanted in silicon

Damage profiles for 250-keV self-ion irradiation of gold, determined by (1) stereo electron microscopy measurements of the depth distribution of visible clusters and (2) binary-collision simulations, are presented. Simulations for an amorphous medium, a single crystal (with the ion beam oriented in a nonchanneling direction), and a polycrystal were performed using the MARLOWE code. The calculated damage profiles for the single crystal and the polycrystal both exhibit approximately exponential tails, but have shallower modal depths than the profile for the amorphous medium. The inclusion of room-temperature thermal vibrations in the simulations is found to broaden the profile and suppress long-range channeling. Comparison between simulation and experiment suggests that a screening length somewhat smaller than the Firsov value is appropriate for Au-Au interactions.     

Optical characteristics of implanted silicon films

The first data are presented on the change (following implantation) in the refractive index and the band structure of silicon on sapphire films. The implantation was effected with phosphor ions of 40 keV and doses from 10¹² to 10¹⁶ cm^–2. An increase following implantation of the refractive index and the energy of the first direct allowed transitions E₁ is noted, indicating changes in the second coordination sphere. The profile E₁(x) is studied pointing to heterogenization effects. The films were annealed with ruby laser pulses of 0.2 J/cm². The same laser was used to study the lux dependence of the injection level _n and surface photo-emf V. Hysteresis in the V(_n) dependence (after the use of maximum intensity of the laser beam) is noted indicating irreversible straightening of the bands at the film surface.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 40–43, May, 1984.     

High concentration effects of ion implanted boron in silicon

The diffusion behaviour of implanted boron in silicon was investigated using the¹⁰B(n,α)⁷ Li nuclear reaction. An anomalous behavior with a strong reduction of the diffusivity above an effective solubility limit at 1.5×10¹⁹, 6×10¹⁹, and 1.1×10²⁰ cm⁻³ was found for annealing temperatures of 800, 900, and 1,000°C, respectively.     

Implications of ion implantation technology on ion implanted active devices in silicon

The use of ion implantation to make integrated devices in silicon implies a good knowledge of the behavior of various parts of the device. This paper deals with three main topics: First the electrical characteristics of implanted diodes are described and their variations as a function of annealing temperature lead to a physical model taking into account the anisotropy of impurity concentration gradients. Second, experimental conditions before, during and after implantation are shown to have a strong influence on the quality of the final device, particularly on the value of the reverse leakage current. Third, effects of bombardment on silicon dioxide layers are studied. It is found that recovery of the layers is generally complete after a 300°C annealing.

Contributions of these various parameters to the overall electrical characteristics of ion implanted self-aligned MOS transistors are finally considered. Substantial increase in the maximum oscillation frequency and reduction of the active surface areas of the device are the most evident advantages of using ion implantation technology.     

Electron-phonon coupling in highly doped n type silicon

The effect of free electrons on the optical phonon of silicon at the center of the Brillouin zone is studied using the Raman scattering technique. Heavy doping gives rise to a continuous electronic Raman scattering and makes the phonon line shape assymetric. The profile factor which is related to the disymetry, is shown to have the signes of the matrix elements of the electron-phonon interaction.     

In-situ electrical measurement in ion implanted amorphous silicon films

Doping in amorphous silicon has been studied by P, B and Si implantation in evaporated silicon films made by electron beam evaporations. After double implantation of P and B, a compensation effect has been observed in implanted amorphous silicon layer.     

Implant redistribution in high-dose ion implanted and annealed silicon

Abstract

Diffusion constants of helium in gold, silver and aluminium are determined from thermal desorption experiments, giving:

Au: D ₀ = 10^?1.0 cm²/sec, ΔH = 1.70 eV

Ag: D ₀ = 10^?1.2 cm²/sec, ΔH = 1.50 eV

Al: D ₀ = 10^+0.1 cm²/sec, ΔH = 1.35 eV

The results are compared to self-diffusion and to the diffusion of other light elements in metals. Possible diffusion mechanisms are discussed.     

Impurity redistribution during laser irradiation in ion implanted silicon

(100) Silicon wafers implanted with 2 × 10^{15 31}P+/cm² at 100 keV have been annealed using a scanning beam of incoherent light. The main results obtained after annealing are: (a) the carrier concentration profile shows a complete dopant activation without diffusion of the implanted ions; (b) the values of carrier mobility are similar to those obtained by furnace annealing; (c) an improvement of minority carrier diffusion length is often observed; (d) a very good damage recovery is obtained. Transmission Electron Microscopy observations show that the residual damage is confined within a region at 0.2 μm depth and consists of dislocation loops of about 50 Å diameter. It is concluded that this technique can be used to obtain very good annealing of implanted layers.     

Rapid thermal process-induced recombination centers in ion implanted silicon

This work presents direct evidence for a correlation between rapid thermal process-induced recombination centers and co-implanted metallic impurities in ion implanted silicon. Experimental evidence includes the dose dependence of the minority carrier diffusion length measured by the SPV technique, SIMS and RBS analysis of high-dose implantations which show the presence of heavy metals, the dependence of the final diffusion lengths on the mass of the implanted ions, as well as the successful modification of an implantation equipment.     

Photoacoustic determination of thermal conductivity of ion implanted silicon

A new method to obtain information about the thermal conductivity of implanted semiconductors is described. Preliminary results are given for implanted silicon at different ions energy.     

Mechanism of light emission in low energy ion implanted silicon

A silicon wafer implanted with a single low energy (42 keV) silicon ion beam results in strong luminescence at room temperature. The implantation results in the formation of various luminescent defect centers within the crystalline and polymorphous regions of the wafer. The resulting luminescence centers (LC) are mapped using fluorescence lifetime imaging microscopy (FLIM). The emission from the ion-implanted wafer shows multiple PL peaks ranging from the UV to the visible; these emissions originate from bound excitonic states in crystal defects and interfacial states between crystalline/amorphous silicon and impurities within the wafer. The LCs are created from defects and impurities within the wafer and not from nanoparticles.