Andre Martinez

Surface profile measurement with a dual-beam optical system

A system for the noncontact measurement of surface profiles is reported. Instead of measuring the absolute displacement profile, we measure its derivative, the velocity profile. This is done by measuring the difference in the focus errors between two laser spots. Data processing is then used to recover the displacement information. The system has demonstrated sensitivities of the order of nanometers on soft plastic surfaces. It also permits the real-time measurement of surface profiles in dynamic conditions. Thus it has special applicability to magnetic and optical disks. Results of measurements on several substrates are described.

Addressing the Problems of Agglomeration, Surface Roughness and Crystal Imperfection in Soi Films

We have designed and experimentally tested, under a wide variety of laser recrystallization conditions, a reliable encapsulation structure that prevents agglomeration and enables recrystallization of SOT films over a 100% wafer area. Our experiments indicate that the wetting characteristics of the structure can also improve the surface planarity of the recrystallized silicon. We also report a dramatic reduction in defect density and the non - occurrence of the characteristic branched subgrain boundary pattern under appropriate conditions of laser recrystallization.

Defect measurements in digital optical disks

A method of characterizing defects on an unrecorded optical disk is described. Information on the density of defects is obtained by analyzing the statistical distribution of the widths of the pulses obtained when playing back an unrecorded disk. It was shown that disk quality, as measured by bit error rates on actual recording, can be correlated with defect densities measured in this manner. The same method can also be used to characterize defects on uncoated substrates. It was demonstrated that defects on tellurium coated disks are largely the result of defects on the uncoated substrates.

Formation of Facets at the Solid-Melt Interface in Silicon

We have done experimental and theoretical studies of the origins of facet formation at the solid-liquid interface in laser-beam-melted silicon films. Two laser beams were used to produce a molten zone with a closely controlled thermal profile in a thin single-crystal film of silicon, and the liquid-solid interface was observed in situ. A transition to a faceted structure was found to occur under conditions of near thermal equilibrium. The solidliquid interface was also studied theoretically by means of molecular dynamics simulations, incorporating pair- and three-body terms in the interaction potential. Similarly to the experimental system, the solid-melt interface in the simulated system breaks up into facets defined by (111) planes. The melt region in the vicinity of the faceted planes exhibits a certain degree of ordering due to the influence of the crystalline potential.

Twin Stabilzed Planar Growth of Soi Films

The microstructure of beam recrystallized silicon-on-insulator (SOI) films is strongly dependent on nucleation and growth processes during zone-melt propagation. In general, the recrystallization takes place along the (100) plane and in the direction and in this case subgrain boundaries form the only major defects in the material. We have, however, identified stable growth regimes that produce predominantly twin boundaries, when the SOl films recrystallize with their surface parallel to the (110) planes. The twin formation process is attributed to growth twinning characteristic for f.c.c. and diamond structures. It has been established that the majority of these boundaries consist of coherent twins. In this manner (110) textured SOl films can be grown which contain almost entirely twin boundaries as structural defects. The crystallography of coherent twin boundaries in SOI films and their dependence on growth parameters is presented.