Recently observations that high-dose Ge implantations into Si substrates caused the n-type carrier concentration to increase were attributed to residual structural defects after activation annealing [7,12]. However, co-implantation of an n-type impurity is another possibility. The origin of this excess donor concentration has been studied in this work. The possibilities of residual defects versus implantation of impurities have been investigated using two different implanters and materials analysis. Comparison of data from different implanters showed that the concentration of excess donors was sensitive to the implanter configuration. Furthermore, transmission electron microscopy (TEM), Rutherford backscattering channeling (RBS-C), and spreading resistance profiling (SRP) data showed that the excess donor effect was related to impurities rather than residual defects. Secondary-ion mass spectroscopy (SIMS) and SRP measurements confirmed that impurities such as 75As ions were present after implants. This impurity easily explains the excess donor concentration when 75Ge implants are performed into silicon wafers doped with phosphorous.

The oxides of vanadium VO2 and V2O3 are of fundamental and practical interest since they undergo structural phase transitions during which large variations in their optical and electronic properties are observed. In the present work, we report the formation of buried precipitates of V2O3 in sapphire by ion implantation and thermal annealing. It was found that the co-implantation of oxygen and vanadium was required in order to form nanophase V2O3 precipitates. Additionally, these precipitates, which formed only following an anneal of the co-implanted sample under reducing conditions, are coherent with the sapphire lattice. Two epitaxial relationships were observed: (0001)V2O3//(0001) ɑ-Al2O3 and (11-20)V2O3//(0001) ɑ-Al2O3. This finding is in agreement with results obtained elsewhere for thin films of V2O3 deposited on c-axis-oriented sapphire.

The diffusion of implanted chlorine in silicon wafers is studied with neutron activation/accelerator mass spectroscopy (NA/AMS). Depth profiles are obtained from as-implanted and annealed samples. While there is a marked difference between the annealed and as-implanted profiles for the lowest implant dose studied, 1013/cm2, the chlorine from the higher dose implants is virtually immobile. The diffusion of implanted chlorine in silicon is characterized by the apparent absence of indiffusion for the experimental conditions studied. However, outdiffusion is rapid at low concentrations for anneal temperatures of 1100°C and above. This behavior is qualitatively similar to that reported for fluorine in silicon at lower temperatures.

ɑ-SiC crystals were implanted with aluminum to a high dose at room temperature or 800°C. Studies by transmission electron microscopy showed that SiC was amorphized by room temperature implantation but remained crystalline at 800°C. Crystalline aluminum carbide was formed and aluminum redistribution took place in SiC implanted at 800°C. Implanted and unimplanted crystals were oxidized in 1 atm flowing oxygen at 1300°C. Amorphization led to accelerated oxidation of SiC. The oxidation resistance of SiC implanted at 800°C was comparable to that of pure SiC. The oxidation layers formed on SiC implanted at both temperatures consisted of silica embedded with mullite precipitates. The phase formation during implantation and oxidation is consistent with thermodynamic predictions.

The electrochemical properties of O+-implanted Pd measured by cyclic voltammetry in a 0.25 mol dm-3 H2SO4 solution were investigated in relation to their composition and structure. Implantation of 16O+ was performed with doses between 1O17 and 1O18 ions cm-2 at 150 keV, and at nearly room temperature. SIMS, ERD combined with RBS, and XRD were used to analyze the composition depth profile and structure of O+-implanted Pd surface layers. The H atoms were accumulated with a gaussian distribution and carbon materials containing the solid solution of PdCx (x=0.13-0.15) were also formed in the near surface layers during O+-implantation. The distribution of implanted oxygen changed from gaussian to trapezoidal as the dose increased, accompanied by the crystal growth of Pd(OH)2, and simultaneously, the amount of accumulated H atoms increased. The voltammetric measurements revealed that with an increase in the dose, the hydrogen absorption was suppressed at the early stage of sweep cycles, and at the final stage, the redox reaction of both hydrogen and Pd was activated. From these results, we propose that the carbon materials containing the PdCx formed during O+-implantation suppress the hydrogen absorption, and the metallic Pd like a Pd-black formed by the reduction of Pd(OH)2 during voltammetric measurements causes the electrochemical activation of O+-implanted Pd.

In the first part of this work, a plan-view TEM study has been made of the time-dependent annealing behavior of end of range (type II) dislocation loops introduced by lxl015/cm2 50KeV Si+ implantation into silicon. The activation energy for loop growth was determined to be 1.0±0.2eV from the Arrhenius plot of loop growth rate versus the reciprocal of annealing temperature. In the second part of this study, a thin boron layer was used as a diffusion monitor. The number of injected interstitials as a result of oxidation was measured by TEM. The diffusivity of boron with and without the presence of loops was studied by fitting experimental SIMS profiles with FLOOPS simulations. The interaction between loops and interstitials was determined to be diffusion limited.

(0001) surfaces of highly oriented pyrolytic graphite (HOPG) were irradiated at 77K with 132Xe+ ions at energies between 50 keV and 900 keV. The ion fluences ranged between 1011 ions/cm2 and 1015 ions/cm2. Scanning tunneling microscopy (STM) was applied to image the irradiation induced defects at the surfaces. In case of orthogonal incidence and small ion fluence each incident ion induces one single hillock at the surface. These hillocks have typical lateral diameters of 2 nm and heights of several à. In many cases measurements of the hillocks with atomic resolution show disordered atomic arrangements. The hillocks are interpreted as the local volume expansion due to surface-near self-interstitials generated in the collision cascades of the ions. The high mobility of these interstitials parallel to the (0001) planes leads to a formation of interstitial clusters which cause the larger hillocks. Irradiation at an angle of incidence of 75° with respect to the surface normal effects a higher density of hillocks due to the higher number of recoils stopped in the uppermost lattice planes. The hillocks are arranged in chains which are aligned in the direction of the incident beam. Each of these chains marks a single collision cascade.

Implanted B and P dopants in Si exhibit transient enhanced diffusion (TED) during initial annealing which arises from the excess interstitials generated by the implant. In order to study the mechanisms of TED, we have used B doping marker layers in Si to probe the injection of interstitials from near-surface, non-amorphizing Si implants during annealing. The in-diffusion of interstitials is limited by trapping at impurities and has an activation energy of -3.5 eV. Substitutional C is the dominant trapping center with a binding energy of 2-2.5 eV. The high interstitial supersaturation adjacent to the implant damage drives substitutional B into metastable clusters at concentrations below the B solid solubility limit. Transmission electron microscopy shows that the interstitials driving TED are emitted from {311} defect clusters in the damage region at a rate which also exhibits an activation energy of 3.6 eV. The population of excess interstitials is strongly reduced by incorporating substitutional C in Si to levels of ∼1019/cm3 prior to ion implantation. This provides a promising method for suppressing TED, thus enabling shallow junction formation in future Si devices through dopant implantation.

SIMS measurements revealed that high energy boron-implantation causes transient enhanced diffusion (TED) of a shallow dopant profile due to Si interstitials even for a relatively low dose of ∼2E13cm-2. By systematic analysis, it is found that this anomalous diffusion is most significant in 700∼800°C annealing, and it takes place in the initial stage (less than 30sec for 800°C) of annealing. Moreover, this anomalous diffusion is more considerable than the enhanced diffusion during oxidation (OED) in practical device fabrication processes. It is found that rapid thermal annealing (RTA) at 1000-1100°C is effective for suppressing the transient enhanced diffusion and realizing a shallow channel profile for deep sub-micron devices.

TMOS devices for power applications use ion-implantation for doped layers. Implant-damage can increase electrical leakage of devices. Transmission electron microscopy was used to study the effect of dose (4E14 - 2E15 cm-2) and energy (20-40 keV) of p+ implants on damage related to leakage in TMOS structures. TEM reveals a high density of boron implant-induced defects such as end-of-range and peak-of-implant damage, boron implant-induced stacking faults and dislocations. End-of-range defects also arise from an arsenic implant, and mask-edge defects arise where arsenic-amorphized Si and crystalline Si meet in the source region. Some defects extend >0.5 μπι into the substrate. The density and the extent of defect penetration decrease with decreasing implant-dose and energy. These data correlate well with the electrical data, which show that Idss leakage decreases with decreasing p+ implant-energy and dose.

The effects of interdiffusion on the band structure of two MxGaUxAs/GaAs single quantum well (SQW) structures were studied using room temperature photoreflectance. Rapid thermal annealing of the SQW structures at temperatures of 800°C, 900°C and 1000°C for times up to 180 seconds resulted in limited interdiffusion. Low dose (1014 cm”2) oxygen implantation reduced the thermal stability of these structures where the extent of the interdiffusion was found to be greater for the implanted samples for identical annealing conditions.

Experimental observations of dopant diffusion and defect formation are reported as a function of ion energy and implant temperature in Si implanted GaAs. In higher energy implants (>100 keV), little or no diffusion occurs, while at energies less than 100 keV, the amount of dopant redistribution is inversely proportional to energy. The extended defect density shows the opposite trend, increasing with increasing ion energy. Similarly, the diffusion of Si during post implant annealing decreases by a factor of 2.5 as the implant temperature increases from -2 to 40°C. In this same temperature range, the maximum depth and density of extrinsic dislocation loops increases by factors of 3 and 4, respectively. Rutherford Backscattering (RBS) channeling measurements indicate that Si implanted GaAs undergoes an amorphous to crystalline transition at Si implant temperatures between -51 and 40°C. A unified explanation of the effects of ion energy and implant temperature on both diffusion and dislocation formation is proposed based on the known differences in sputter yields between low and high energy ions and crystalline and amorphous semiconductors. The model assumes that the sputter yield is enhanced at low implant energies and by amorphization, thus increasing the excess vacancy concentration. Estimates of excess vacancy concentration are obtained by simulations of the diffusion profiles and are quantitatively consistent with a realistic sputter yield enhancement. Removal of the vacancy rich surface by etching prior to annealing completely suppresses the Si diffusion and increases the dislocation density, lending further experimental support to the model.

Ion irradiation has been carried out to improve wettability of PMMA to water. The polymer was irradiated by argon and oxygen ions, and amount of ions was changed from 1014 ArVcm2 to 5xl016Ar+/cm2. Ions energies were varied from 0.5 keV to 1.5 keV, and oxygen gas was flowed from 0 seem to 6 scan near the polymer surface during ion irradiation. Wetting angle was reduced from 68 degree to 49 degree with increasing Ar+ ion irradiation, to 43 degree with Ch+ ion irradiation, and dropped to 8 degree with Ar+ ion irradiation with flowing 4 seem oxygen gas near the polymer surface. Recovery of wettability in dry air condition, and maintenance of it in dilute HC1 solution were explained in a view of formation of hydrophilic groups due to a reaction between irradiated polymer chain by energetic ion irradiation and flowing oxygen near the surface. Reactions among polymer matrix, energetic ions and oxygen gas to form hydrophilic group by energetic ions were discussed in terms of a two-step reaction, in which the first step is the creation of an unstable polymer chain by the ion irradiation and the second step is a reaction between the radicals and the oxygen gas.

Recently engineered porous materials have been attracted more attentions because of their potential applications in several industrial sectors, such as high efficiency gas separation membrane, catalytic membranes for chemical processing and so on. In spite of their desirable applications, these porous materials have not been realized due to several technical barriers, for example, lack of pore size control. There is a general viewpoint that for conventional gas separation membranes one cannot increase both permeability and permselectivity of the product gas simultaneously. This general viewpoint implies that the conventional methods of gas separation membrane fabrication cannot precisely control the pore size. In this work iodine diffusion property and gas permeation properties of ion beam irradiated polyimides films have been investigated. Small fluence irradiation can raise significantly the iodine penetration in the energy deposition range and permeabilities of the films both for H2 and CH4. After higher fluence irradiation, the implanted layers become stopping layers blocking iodine diffusion into the film and both the permeability for H2 and permselectivity for (H2/CH4) of the film increase hugely. We related the small fluence effects to defects created by irradiation and higher dose effects to the new materials formation of which the pore size is well defined. From these results we can perhaps have a peep at a new way to microporous materials.

Thin films of polystyrene (PS) were modified using oxygen (0+) and helium (He+) ions and analyzed via diffusion and hardness measurements. One micron thick films were modified with 400 keV 0+ and He+ ions. The fluence was varied from 1.7 to 34.0 x 1013 ions/cm2 for both incident ions. Following irradiation, some samples were covered with a probe layer of deuterated PS, and annealed at 170°C. Using forward recoil spectrometry, the diffusion of d-PS and the PS hydrogen loss were measured as a function of incident ion species and dose. For all modified samples, d-PS diffusion was significantly retarded compared to the unmodified case. Atomic force microscopy measurements on the as-cast and irradiated PS samples suggest that the relative hardness of the 0+ modified PS was greater than that of the as-cast PS. The force-displacement curves of the modified PS displayed no hysteresis whereas the as-cast PS had a large hysteresis due to tip penetration and tip-polymer adhesion. These results indicate that ion irradiation decreases transport in PS and increases PS hardness.

Polystyrene (PS) was irradiated with 2 MeV He+ ions to a fluence of 3.3×1019 ions/m2. A cross-section of the irradiated layer was subjected to hardness measurements across the section using a nanoindentation technique. Results showed that hardness increased as a function of irradiation depth and showed a maximum value of 12 GPa at a depth of approximately 6.5 μπι, for a total ion penetration range of 9 μιη, as compared to a hardness of 0.45 GPa for unirradiated PS. The hardness variation with depth followed the trend for Linear Energy Transfer (LET) for ionization from the energetic ions to substrate atoms. This investigation showed for the first time how hardness varies as a function of depth for ion-irradiated polymers; this variation approximately follows the ionization LET profile, suggesting that cross-linking in the polymers could be proportional to ionization.

A study has been made of the carbon formation in the surface layer of Ag-, W- and Pd-ions implanted polyimide films. The doses of 130 KeV Ag-ions and 190 KeV W-ions ranged from lxlO16 to 5×1017 atoms/cm2. The doses of 100 KeV Pd-ions ranged from 5×1016 to 2×1017 atoms/cm2. The carbon structure in implanted layers was characterized by laser Raman spectroscopy (LRS). Non-implanted polyimide film has very strong intensity of fluorescence, and the intensity of all W-, Ag- and Pd-ions implanted specimens decreases with the increase in dose. The intensity of Raman spectra for both W- and Ag-ions implanted specimens increases with the increase in dose. For Pd-ion implanted specimens, the Raman spectrum of carbon is hardly observed even with a high dose. Raman spectra for W- or Ag-ions implanted specimens with a high dose show that the diamond-like carbon (DLC) exist in the implanted layers. It is found that the DLC structures in the W- and Ag-ions implanted layers have graphite-like and amorphous-like structures, respectively. We propose that transparency carbon structure in implanted layers is generated by Pd-ion implantation. It is concluded that marked DLC formation in surface layer of polyimide films can be caused by Ag- or W-ions implantation except Pd-ion implantation, and carbon structure in implanted layers depends strongly on the implanted elements.

Total reflection X-Ray Fluorescence (TXRF) is a glancing x-ray analytical technique which is used primarily to measure surface metal contamination on semiconductor substrates. This is a review of Total reflection X-Ray Fluorescence (TXRF) applications for silicon semiconductor processing. In addition, some comments are made about the future of TXRF, and in particular, synchrotron radiation TXRF (SR-TXRF)

Heavy Ion Backscattering Spectrometry (HIBS) is a tool for measuring surface contamination at levels much lower than previously achievable with ion beam analyses. Many areas of materials research and development require very low levels of impurities, with advanced microelectronics as the best example. HIBS uses low-energy, heavy ions for analysis, taking advantage of the increased backscattering yield which can be obtained from high Z ion beams at low energy. Background due to increased yield from the substrate is eliminated by a thin carbon foil as part of the detector, with a thickness chosen to range out ions scattered from the substrate and allow only ions scattered from impurities heavier than the substrate to reach the detector. Our research system, using 150-200 keV N+ beams and a single time-of-flight detector optimized for large solid angle, has achieved a sensitivity ranging from ∼5×1010 atoms/cm2 for Fe to ∼1×109 atoms/cm for Au on Si, without preconcentration. A stand-alone HIBS prototype which we have developed for SEMATECH is expected to reach detection limits of -5×10 atoms/cm for Fe and -1×10 atoms/cm for Au on Si. In this paper we discuss in detail the factors which affect sensitivity for HIBS.

As the typical feature size of silicon integrated circuits, such as in VLSI technology, has become smaller, the surface cleanliness of silicon wafers has become more important. Hence, detection of trace impurities introduced during the processing steps is essential. A novel technique, consisting of a “Charged Particle Energy Filter (CPEF)” used in the path of the scattered helium ions in the conventional Rutherford Backscattering geometry, is proposed and its merits and limitations are discussed. In this technique, an electric field is applied across a pair of plates placed before the detector so that backscattered particles of only a selected energy range go through slits to strike the detector. This can be used to filter out particles from the lighter substrate atoms and thus reduce pulse pileup in the region of the impurity signal. The feasibility of this scheme was studied with silicon wafers implanted with 1×1014 and 1×1013 14pe/cm2 at energy of 35 keV, and a 0.5 MeV He+ analysis beam. It was found that the backscattered ion signals from the Si atoms can be reduced by more than three orders of magnitude. This suggests the detection limit for contaminants can be improved by at least two orders of magnitude compared to the conventional Rutherford Backscattering technique. This technique can be incorporated in 200–300 kV ion implanters for monitoring of surface contaminants in samples prior to implantation.