Planar Channeling Effects Research Articles

Lattice sites of ion-implanted Cu atoms in diamond

Radioactive 67Cu atoms were accelerated to 60keV at the online isotope separator ISOLDE at CERN, and implanted into a type IIa natural diamond sample to a dose of 2×1012cm−2. The channeling of β−-particles and conversion electrons emitted in the decay of 67Cu and 67Zn∗, respectively, were monitored about the three major axial directions with a two-dimensional position-sensitive detector. The electron emission channeling data were collected from the room-temperature-implanted sample and after annealing at 1200K.The observed channeling patterns were fitted with simulations based on the many beam formalism of electron motion through a crystal lattice. In the as-implanted sample, 25% of the Cu atoms were located a mean, isotropic displacement of 0.25(5)Å from substitutional sites, and the remainder, fR=75%, at sites that gave an isotropic emission yield. Annealing at 1200K results in enhanced axial and planar channeling effects. The fits to the data yield either a fraction f1=45(5)% of Cu atoms located 0.24(4)Å from substitutional sites and fR=57%, or a fraction f1=10(2)% at substitutional sites, a fraction f2=50(5)% at mean isotropic displacement of 0.5Å from substitutional sites, and a ‘random’ fraction fR=40%.

Performance of a Focused-Ion-Beam Implanter with Tilt-Writing Function

An FIB implanter has been developed from a previous FIB lithography system design. Pattern writing with high registration accuracy is performed by a combination of beam-vector scanning and a step-and-repeat stage movement. In order to minimize the axial and planar channeling effects, the ion optical system can be tilted manually up to 7° without venting the workpiece chamber. To correct distortion, a high-speed distortion-correction unit was added. In addition, a sublens and a dynamic-focusing unit were also included for real-time focusing correction. Writing, stitching and overlay accuracies were evaluated by measuring vernier patterns. The stitching error was 0.178 µm (2σ) in the X axis and 0.161 µm (2σ) in the Y axis direction, while the overlay error was 0.170 µm (2σ) in the X-axis and 0.183 µm (2σ) in the Y-axis direction. Ion depth distribution from the implantation of focused Si ions has been measured. The coincidence in SIMS profiles was confirmed for FIBI and conventional ion implantation, when the ion-beam channeling is controlled.

Analysis of planar channeling effects on the threshold voltage uniformity of GaAs metal-semiconductor field-effect transistors using stereographic projection : H MIKAMI, N UCHITOMI, N TOYODA (VLSI Res. Center, Toshiba Corp., Kawasaki, Japan) J. Appl. Phys. (USA), vol. 64, no. 2, pp. 610–613 (15 July 1988)

Analysis of planar channeling effects on the threshold voltage uniformity of GaAs metal-semiconductor field-effect transistors using stereographic projection : H MIKAMI, N UCHITOMI, N TOYODA (VLSI Res. Center, Toshiba Corp., Kawasaki, Japan) J. Appl. Phys. (USA), vol. 64, no. 2, pp. 610–613 (15 July 1988)

Analysis of planar channeling effects on the threshold voltage uniformity of GaAs metal-semiconductor field-effect transistors using stereographic projection

Planar channeling effects on the threshold voltage uniformity of GaAs metal-semiconductor field-effect transistors within 3-in. GaAs wafers have been investigated using the stereographic projection method. This method is very useful for a quantitative understanding of the angular relationship between the direction of an incident ion beam and wafer orientation during implantation. The ratio N(X1)/N(X2) of the peak carrier concentration at a depth of X1 to the carrier concentration of a depth of X2=2X1, obtained from the carrier depth profiles, was employed as a suitable parameter which effectively reflects the variation in the carrier profiles arising from the planar channeling effects. The conclusion, that the most uniform implants are attained at an azimuthal angle of 26.5° when tilting the wafer 10°, was analytically derived from the stereographic projection method and was experimentally confirmed.

A note on obtaining symmetrical angular yield curves in MeV ion channeling

Planar channeling effects can distort the angular yield (dip) curve measured about an axial channeling direction. Two methods for minimizing distortion due to planar channeling are discussed: 1) varying the angles θ and φ of a two-axis goniometer together during the angular scan, and 2) remounting the sample so that a scan of only θ produces an undistorted symmetric dip curve. In practice, remounting the sample is preferred in order to minimize effects due to the mechanical limitations of the goniometer.

Planar channeling effects in a batch process ion implanter

In batch process implantation systems, the presence of platen rotation and the possible use of domed platens produce averaging effects which complicate the design of implant geometries to minimize channeling. Data is presented for both flat and domed platens with different wafer orientation (twist) angles. Evidence is shown that channeling effects can be equivalently reduced for both flat and domed geometries.

Planar and residual channeling of Si+ implants in GaAs

The influence of planar channeling on the atomic profiles of low-dose Si+ implants into GaAs is demonstrated as a function of wafer rotation angle, ion beam incidence angle, wafer crystallinity, and thickness of dielectric coating on the surface of the wafer during implantation. Use of a controlled wafer rotation angle or implantation through a dielectric layer results in reproducible profiles free of planar channeling effects. However, even these implants still show a significant profile ‘‘tail’’ that is absent for implants into preamorphized material, thus suggesting the existence of significant residual channeling in GaAs.

Channeling phenomena in off-axis ion implanted (001) silicon

(001) silicon wafers were implanted in random conditions with 8 × 10 13 cm −2, 60 keV silicon ions. The samples were given a tilt angle of 8° from the [001] direction to avoid axial channeling and rotation angles of 0°, 20°, 70° and 90° to evidence (110) planar channeling effects, the 0°, 90° conditions denoting parallelism between (110) planes and the ion beam direction. An unforeseen more marked ion channeling was detected by double-crystal X-ray diffraction for the 70° rotated wafer compared with the ones observed for the 0° and 90° cases. Considering the errors in the sample alignment procedure and the deviations of wafer reference flats from 〈110〉 directions, the experimental results could be explained with the simple concept of crystal transparency to the ion beam for the incidence conditions used.

Planar channeling effects in Si(100)

Effects of axial and planar channeling in Si(100) crystals on junction depth and sheet resistance control are studied for the case of shallow junction implants. Whole-wafer sheet resistance mapping, SIMS and spreading resistance profiling are used to characterize the effects of tilt and azimuthal angle variations for electrostatic and mechanical-scan implanters. Additional effects studied include critical angle variations with atomic mass and ion energy, beam scan angles for electrostatic-scan systems, implants through thin dielectric layers, wafer flexing over heat-sink pads and errors in crystal orientation. Planar and axial channel critical angles are modeled for B, P and As implants into Si(100) for energies between 20 and 200 keV. System requirements for avoidance of direct channeling effects are reviewed for IC production conditions.

Depth profiling light nuclei in single crystals: A combined nuclear reaction and RBS technique to minimize unwanted channeling effects

The difficulties of depth profiling in single crystals, using MeV light ion beams, are discussed with particular emphasis on planar channeling effects. Depth profiling of 18O self-diffused crystals (corundum, Al 2O 3; forsterite, Mg 2SiO 4) via the 18 O(p, α) 15N nuclear reaction is used as an illustration. The effects on the alpha spectrum of channeling the proton beam along major axes and planes are described. There is a high probability that planar channeling effects distort the spectra strongly when the proton beam is incident on the crystals off axis but with any azimuthal orientation. A simple routine procedure is presented to minimize such unwanted effects, based on a combined use of nuclear reaction depth profiling and RBS techniques.

Computer simulation of deflection effects for relativistic charged particles in a curved crystal

A computer analysis of planar channeling effects for 1.0 and 6.6 GeV protons and axial effects for 1.0 and 5.5 GeV π --mesons in a thin curved Au crystal has been performed. Effective beam deflection is obtained for positively charged particles, while negative particles exhibit a wide angular distribution on leaving the curved crystal.

A structure modeling of metal-silicide layers by using axial and planar channeling techniques

Planar channeling effects are studied in such well-oriented polycrystalline layers as NiSi 2 and Pd 2Si layers formed on single crystalline Si. Crystalline perfection of such layers is discussed by using the energy- and angular dependences of the axial and planar channeling yields. It has been shown that, in suitable conditions, the energy dependence of the planar yield is more sensitive to the spread of crystallite orientations in polycrystals than that of the axial one.