K. Schmid

Backscattering measurements and surface roughness

Abstract The backscattering spectra of He + particles in the MeV range measured on rough and polished silicon surfaces show different line-shapes. The surface edge of the spectrum of a rough sample (roughness about 3000 A) was distinctly smoother than that of a polished sample. This behaviour can be explained by a simple model.

Electrical and backscattering measurements of arsenic implanted silicon

Measurements of doping concentration and mobility of arsenic implanted silicon at high energies and at low energies with following drive-in diffusion are presented. The electrical measurements are compared with and supported by backscattering measurements. Tails which are present after short time anneals vanish during drive-in diffusion. A temperature of at least 825°C is required to fully activate the arsenic and to obtain the same mobility as in diffused samples. Backscattering data reveal an anomaly in the annealing behavior of the damage. After prolonged annealing As shows some accumulation at the surface. For drive-in diffusions lattice location experiments were performed.

A universal goniometer for channeling experiments

Abstract A goniometer was designed to rotate a sample around four different axes. A horizontal shifting motion was also included, and provision for rotation of a cooled semiconductor detector around the scattering center was made. The movements are done by stepper motors and the pulses measured at the detector are correlated to a multichannel analyzer working at multiscaling mode. The resolution of the equipment is 0.023°. The geometry of the goniometer provides an easy and exact adjustment of a crystal in respect to an ion beam. Two different adjustment procedures will be compared.

Determination of the critical dose for different mass ions implanted into silicon

A simple theoretical model for the mass dependence of the critical dose of ion implanted silicon is reported in which the energy into atomic processes is considered as a basic quantity for the determination of the number of displaced target atoms. Backscattering experiments on samples implanted at an energy of 150 keV at low temperatures with B, Ne, P, Kr, Sb will be presented. The annealing behavior of damage distributions is investigated both by back-scattering of 1.3 MeV He ions and by electrical measurements for the dopant ions B, P, and Sb. A correlation between the different results for the critical dose is evaluated.

Damage dependent electrical activation of boron implanted silicon

The important role of damage dependent electrical activation in the case of boron implanted silicon layers is whown by comparing measured acceptor concentration profiles in differently amorphized silicon layers. It is shown that the amorphous layer is completely recrystallized after a 650° C anneal for 10 min and the implanted boron is electrically active. In the heavily damaged but not amorphous region underneath the amorphous layer the implanted boron is hardly electrically active after this temperature treatment. At higher annealing temperatures the electrical activity increases, but 900° C are required for complete activation of the implanted boron. These results indicate that the process to activate the implanted boron electrically is strongly damage dependent. We thus found a new contribution to the understanding of the annealing behavior of implanted layers.

The investigation of lateral damage effects of ion-implanted layers by back-scattering techniques☆

Abstract Using a particle beam of small diameter the back-scattering technique can be applied to the microanalysis of small geometries. By moving a sample in steps of 5 μm with respect to the beam, lateral properties of the surface layers can be investigated. Particle beams of He + ions with diameters of 5–100 μm have been used. We found that the width of a damaged area which was defined by SiO 2 masking during ion implantation was smaller than the width of the window in the mask itself. A wire for masking was placed at a distance of 1 mm from the surface of the sample. In this case lateral annealing of the implanted area was observed, which might be due to an effect of the scanning ion beam.

Experimental data about dechanneling and channel stopping power

Abstract The dechanneling probability for a He+ particle beam which is used for backsattering experiments was investigated at various experimental parameters. These parameters used to get a relation between dechanneling probability and disorder density are stripping depth, annealing temperature, element and dose of the particles which caused the lattice defects by implantation. The relation between the stopping power for a He+ particle beam incident along a random direction and incident along a (100) channel direction was measured on epitaxial layers of silicon on spinel and silicon on sapphire.

A simple spectrum monitor for E × B velocity filters

Abstract A simple spectrum monitor for E × B filters in ion implantation systems is described. It permits a dynamic control of ion-optical parameters such as focus and extraction voltage and proves to be beneficial in optimizing the machine performance by improved control of gas flow and beam qualities. The spectrum monitor is realized by modulating the electric field of the E × B filter by means of transformer and displaying the ion current at the target vs the modulating voltage.

The simple use of a digital multimeter for beam current integration

Abstract A schematic drawing illustrates the use of a digital multimeter or voltmeter as a current integrator. Using digital measuring instruments without voltage to frequency conversion the effective integration will be performed only during the integration time of the instrument. If the measuring time, however, is long compared to the cycle time of the integration this disadvantage can be ignored.