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Vapor‐deposited amorphous silicon films of 4000 A thickness have been epitaxially crystallized on (100) silicon substrates by pulsed Nd : YAG laser radiation of 125‐nsec duration at power levels of 90–120 MW/cm2. The epitaxial layers were found to be defect free when examined by transmission electron microscopy and Rutherford backscattering. Patterned arrays of epitaxial crystal were produced by overlapping individual 39‐μm laser pulse spots.

A description is given of the design and testing of a directly heated, stable, electron source utilizing a single‐crystal lanthanum hexaboride (LaB6) cathode. The emitter mounting fixture consists of an adjustable molybdenum base unit supported on gas‐impervious alumina or machinable glass. Single‐crystal cathode rods are securely clamped and positioned between vitreous carbon jaws that are resistively heated. The complete assembly is designed to be a direct ’’plug‐in’’ substitute for the conventional tungsten thermionic filaments used in electron‐beam instruments. The cathode current density for 〈110〉 axial orientations is found to be ten times higher than that for 〈100〉 orientations under equivalent conditions, a value of 50 A cm−2 being measured at 1500°C with an observed lifetime in excess of 300 h. Optimum vacuum conditions for high lifetime and stable operation are in the range 1×10−6 Torr and lower. Comparison values for the emission at various temperatures from other borides, and tungsten, are als...

135 nsec pulses ofλ = 1.06μm light from a Nd: YAG laser have been used to form Schottky barriers by irradiation of a 500A thick metal film on n-type silicon. Large area barriers were fabricated by over-lapping individual 30μ diameter laser pulses of from 4 to 12 J/cm2. The barrier height was 0.73 ± 0.03 V, independent of the laser power. The barrier quality, as assessed by measurement of the forward current characteristic, decreased with laser power to a value of n = 1.5 at 12 J/cm2.

Laser annealing of silicon in the pulsed, high energy density mode results in melting and rapid epitaxial resolidification. The incorporation of dopant atoms in the resultant crystals in excess of the retrograde solubility maximum provides firm evidence for the occurence of nonequilibrium, impurity trapping processes at the solid-liquid interface during crystal growth.

Dielectrically isolated single crystals of large extent may be fabricated by zone melting a thin silicon sheet that is encapsulated between SiO 2 layers. The material, however, contains a lineage structure of subgrain boundaries that we demonstrate arises via cellular growth at the trailing edge of the molten zone.

Lasers have long established a permanent position in manufacturing.1–5 They are used to cut hard and brittle materials, to weld metallic objects rapidly and efficiently, to harden locally surfaces of metals, and to drill microscopic holes in materials as diverse as rubber and steel. High power electron beams are routinely used for spot welding and to a lesser extent for cutting and drilling.

Data are reported for n-MOSFET's fabricated in laser crystallized poly-Si on amorphous insulating substrates. The dependence of electrical characteristics on the effective channel length in the range of 100 to 0.3 µm and on channel width from 120 to 20 µm is presented. The electron surface mobility is found to increase as the channel length is reduced, approaching that of devices in single-crystalline silicon. The source-to-drain leakage current, negligible for long channels, rapidly increases for channels shorter than ≃ 3 µm. This excessive current results from grain boundary diffusion of As from source and drain during high temperature fabrication steps.

The charge collected within the SiO 2 layer of an MOS capacitor during bombardment with kilovolt electrons is approximately proportional to the field in the oxide. We have used this proportionality to form SEM images of the field distribution in MOSFET channels.

Polycrystalline silicon films on SiO2 and Si3N4 may be processed by tightly focused, overlapping laser pulses to yield large‐grained (1–5μm) material. In individual nonoverlapping spots the large grains are arranged in concentric rings whose origin is clarified in this letter.

Extensive seeded epitaxial growth of crystalline Si over SiO2 was achieved by an oscillatory regrowth method applied to rectangular Si pads recessed into a thick SiO2 film. Narrow (≃5 μm) via holes linked the pads with the bulk (100) Si substrate. Oriented single crystals propagated as far as 500 μm from the seeding area, following the long term advance of a scanned focused laser beam.

We have reacted thin Pt, Pd, and Ni films with single‐crystal Si using Q‐switched Nd : YAG laser pulses of 100‐nsec duration in the power range 18–50 MW cm−2. The layers are laterally very uniform in thickness but are not single phase. Average composition of the reaction product layer can be changed over a wide range by varying film thickness and laser power. The microstructure of the reacted layers indicates that reaction occurs via surface melting, mixing, and rapid resolidification.

The redistribution of antimony impurity atoms implanted in (111) and (100) substrates was studied as a function of the power density of Q-switched YAG laser radiation (λ = 0.53μm) used to recrystallize 4700Å films of amorphous silicon vapor deposited over blanket and patterned Sb buried layer structures. Results for fully crystallized layers show impurity profiles ranging from a sharp interface displaced outward slightly relative to the as-grown interface, to complete redistribution of antimony into the deposited layer. Studies of patterned buried layer structures indicate that epitaxial crystallization can be achieved on (111) and (100) substrates without serious damage to the surface topography necessary for subsequent mask alignment.

Thin Pt, Pd and Ni films have been reacted with single crystal Si, using Q‐switched Nd:YAG laser pulses of 100 nsec duration in the power range 18–50 MW cm−2, to produce layers that are laterally very uniform in thickness but are not single phase. Average composition and thickness of the reaction product layer can be changed over a wide range by varying starting film thickness and laser power. The microstructure of the reacted layers indicates that reaction occurs via surface melting, mixing and rapid resolidification. Molybdenum and Nb films have been reacted with Si at powers of approximately 90 WM cm−2.

A metastable Pt-Si phase of approximately PtSi 2 stoichiometry has been formed by msec duration irradiation of Pt films on silicon with a free running Nd:YAG laser. The silicide forms epitaxially on (111) silicon, exhibits low (50–60 μΩcm) resistivity, and excellent surface smoothness. The alloying reaction occurs at the Pt-Si interface and proceeds towards the free Pt surface. Neither the composition nor the structure of the metastable phase corresponds to previously reported Pt-silicides.

Beam processing can be applied to thin, polycrystalline silicon films on amorphous substrates to: a( increase grain size, b( produce single, isolated crystals, and c( to produce oriented single crystals. Specific methods for these tasks are outlined. Crystal growth and heat flow consideration appropriate to each are presented.

We have grown high quality epitaxial Si films from amorphous deposited layers using pulsed and CW Nd:YAG lasers. Pulsed irradiation produced epitaxial growth by melting and resolidification. The regrowth is relatively insensitive to interfacial and incorporated impurities of C, O, and Ar. Gallium dopants in the amorhous film redistribute within the melt and are zone refined towards the surface during solidification. Gallium left within the regrown layer exceeds the maximum equilibrium solid solubility by an order of magnitude. Continuous wave irradiation can produce epitaxial regrowth in the solid phase providing that the silicon is deposited on an atomically clean substrate. No Ge dopant redistributed has been observed in this regime.

Silicon crystals that have been annealed by both Cw and pulsed laser irradiation have been examined by scanning, charge collection microscopy. In this technique, the short circuit current across a laser annealed diode is employed as the video signal in a scanning electron microscope, which provides a source of focused carrier injection. Repetitively pulsed, overlapping spot arrays show excellent uniformity on a scale large compared to the laser spot size, but exhibit inhomogeneity in the 1 to 10 μm range. Specifically, 1 μm ripple is observed in diodes annealed at laser powers near the surface melting of the sample surface. In well‐annealed material, the periphery of each laser spot is the region of best charge collection. Measurement of collection efficiency vs. injection depth yields estimates of carrier lifetime in the laser melted an resolidified layer. These are always small, of order 1 nsec. Finally, we have observed conversion of p‐type silicon surfaces to n‐type following CW laser annealing.

Laser induced melting and resolidification of single crystal silicon introduces electrically active point defects. The electrical properties of laser processed silicon were monitored by capacitance transient spectroscopy (DLTS) and thermally stimulated capacitance (TSCAP) measurements. Removal of residual defects by thermal annealing occurs between 500°C and 700°C. More importantly, the defects are passivated by reaction with atomic hydrogen in the temperature range of 100–300°C.

Silicon layers evaporated on crystalline Si have been crystallized by Q-switched Nd:YAG laser irradiation. A strong correlation was observed between the density of a-Si films and the quality of the epitaxial regrowth from the liquid phase. Dense films crystallized epitaxially in a wide range of laser energy densities. Layers with 20% lower density, as determined by spectroscopic ellipsometry, had higher crystallization thresholds and suffered from severe pitting of the surface. Coalescence of the excess void volume into microbubbles, stabilized by gaseous contaminants, is responsible for the surface degradation.In polycrystalline films on amorphous insulating substrates laser melting changes the grain distribution. Rapid melting and solidification of small diameter spots creates concentric rings of large crystallites. This characteristic pattern is explained by a simple model, based on the kinetics of crystallization.

The growth of device-worthy silicon crystals on insulating substrates would have a revolutionary impact upon microelectronics, and is consequently the object of intense effort. This article reviews recent progress in the application of laser and electron beams and incoherent light to this end. In every case, radiant energy is employed to melt a precursor material, from which device-worthy layers are produced during resolidification. Techniques include seeded and unseeded growth, partial and complete encapsulation of the liquid layer, and oscillation of the solid-liquid interface. Considerations of liquid zone stability, temperature gradient control, and interface morphological stability are central to each technique. Progress in this field has been rapid and several techniques have been successfully demonstrated.

Seeded epitaxial growth of Si over SiO2 is demonstrated in two types of structures. In the first case, rectangular pads of deposited Si were recessed into a thick SiO2 film. Narrow (≃ 5μm) via holes in SiO2 linked the pads with the bulk Si substrates. In the second embodiment, SiO2 patterns were recessed into the Si wafers which were then covered with a continuous 0.5μm poly-Si layer. In both cases, nearly planar geometries were maintained by use of local oxidation and etching techniques. Silicon was recrystallized with a focused Ar+ laser beam. Depending on the scanning conditions and the Si pattern geometry, single crystal growth propagated between 30 and >500μm. The factors influencing the extent and quality of the crystallized regions are discussed.

Laser melting of crystalline silicon introduces electrically active defects which are observed by capacitance transient spectroscopy. The electrical activity of these point defects is neutralized by reaction with atomic hydrogen at 200 °C.

Measurement of thermionic electron emission values for pointed LaB6 single‐crystal emitter cathodes has shown that 〈110〉 axial orientations yield emission values ten times higher than 〈100〉 orientations at 1545 °K. Minimum values were obtained for the 〈510〉 directions. These findings seem encouraging in achieving perhaps two orders of magnitude higher emission fluxes as compared to tungsten emitters.

Pt‐Si alloy layers are formed during 130‐nsec pulsed irradiation of Pt coated Si with light from a Nd : YAG laser. The alloys form via surface melting and resolidifaction. Laser processing of arsenic of ion implanted, p‐type silicon results in formation of a p‐n+/Pt‐Si structure that exhibits rectifying electrical behavior. This structure arises because the As and Pt impurities are zone refined to different extents during resolidification of the molten surface layer.