The formation of nearly wavelength-sized laser-induced periodic surface structures (LIPSSs) on single-crystalline silicon upon irradiation with single or multiple femtosecond-laser pulses (pulse duration τ=130 fs and central wavelength λ=800 nm) in air is studied experimentally and theoretically. In our theoretical approach, we model the LIPSS formation by combining the generally accepted first-principles theory of Sipe and co-workers with a Drude model in order to account for transient intrapulse changes in the optical properties of the material due to the excitation of a dense electron-hole plasma. Our results are capable to explain quantitatively the spatial periods of the LIPSSs being somewhat smaller than the laser wavelength, their orientation perpendicular to the laser beam polarization, and their characteristic fluence dependence. Moreover, evidence is presented that surface plasmon polaritons play a dominant role during the initial stage of near-wavelength-sized periodic surface structures in fem...

On the role of surface plasmon polaritons in the formation of laser-induced periodic surface structures upon irradiation of silicon by femtosecond-laser pulses

The present invention is a method of forming large device quality single crystals of silicon carbide. The sublimation process is enhanced by maintaining a constant polytype composition in the source materials, selected size distribution in the source materials, by specific preparation of the growth surface and seed crystals, and by controlling the thermal gradient between the source materials and the seed crystal.

Sublimation of silicon carbide to produce large, device quality single crystals of silicon carbide

A method of fabricating a semiconductor structure including the steps of providing a silicon substrate (10) having a surface (12), forming on the surface (12) of the silicon substrate (10), by atomic layer deposition (ALD), a seed layer (20;20') characterised by a silicate material and forming, by atomic layer deposition (ALD) one or more layers of a high dielectric constant oxide (40) on the seed layer (20;20').

Method for fabricating a semiconductor structure including a metal oxide interface with silicon

During the past decade there has been a rapid growth of interest in poly-Si for the active device layer in thin film transistors (TFTS) for active matrix flat-panel displays. Whilst the early work, demonstrating the high carrier mobility of these devices, employed processing temperatures of approximately 1000 degrees C and quartz susbtrates, this was soon followed by the investigation of lower-temperature processes which were compatible with the use of glass substrates. Some of the key aspects of this work are reviewed in this article: the preparation of the material by direct deposition and by crystallization from a-Si precursors, the characterization of the defect-induced trapping states within the material and their passivation, and the present understanding of the TFT leakage current mechanisms. This work is put into the context of the requirements for active matrix liquid-crystal displays, and, with the understanding and control of poly-Si which has been achieved to date, its application in this area can be expected to increase rapidly in the coming years.

https://iopscience.iop.org/article/10.1088/0268-1242/10/6/001/pdf

Polycrystalline silicon thin film transistors

In producing a thin film transistor, after an amorphous silicon film is formed on a substrate, a nickel silicide layer is formed by spin coating with a solution (nickel acetate solution) containing nickel as the metal element which accelerates (promotes) the crystallization of silicon and by heat treating. The nickel silicide layer is selectively patterned to form island-like nickel silicide layer. The amorphous silicon film is patterned. A laser light is irradiated while moving the laser, so that crystal growth occurs from the region in which the nickel silicide layer is formed and a region equivalent to a single crystal (a monodomain region) is obtained.

Method for producing semiconductor device

During short‐pulse laser crystallization of amorphous silicon on quartz, surface roughening occurs via the freezing of capillary waves excited in the silicon melt. The velocity and viscous damping of these capillary waves is computed and discussed. Volume change of the silicon during solidification appears to drive liquid silicon toward the last areas of solidification. Film thickness variation observed by transmission electron microscopy and atomic force microscopy shows increased film thickness at grain boundaries, and vertices of single pulse irradiated films. This effect is most pronounced within a narrow laser fluence regime wherein large lateral grain growth occurs. For 100 nm thick amorphous silicon films on quartz, this regime extends from approximately 520 to 560 mJ/cm2; standard deviation roughness can be as large as 40 nm. These effects have important implications for large area thin film transistor manufacturing.

Capillary waves in pulsed excimer laser crystallized amorphous silicon

A low temperature process for laser dehydrogenation and crystallization of hydrogenated amorphous silicon (a‐Si:H) has been developed. This process removes hydrogen by laser irradiations at three energy steps. Studies of hydrogen out‐diffusion and microstructure show that hydrogen out‐diffusion depends strongly on film structure and the laser energy density. Both high quality and low leakage bottom gate polycrystalline silicon and a‐Si:H thin film transistors were monolithically fabricated on the same Corning 7059 glass substrate with a maximum process temperature of only 350 °C.

Laser dehydrogenation/crystallization of plasma‐enhanced chemical vapor deposited amorphous silicon for hybrid thin film transistors

A low temperature process for dehydrogenating amorphous silicon using lasers Dehydrogenation occurs by irradiating one or more areas of a hydrogenated amorphous silicon layer with laser beam pulses at a relatively low energy density After the multiple laser pulse irradiation at a relatively low energy density, the laser energy density is increased and multiple irradiation at a higher energy density is performed If after the multiple irradiation at the higher energy density the amorphous silicon hydrogen content is still too high, dehydrogenation proceeds by multiple irradiations at a yet higher energy density The irradiation at the various energy densities can result in the formation of polysilicon due to melting of the amorphous silicon layer As irradiation may be selectively applied to the amorphous silicon, an integral amorphous silicon-polysilicon structure may be formed

Low temperature process for laser dehydrogenation and crystallization of amorphous silicon

Selective dehydrogenation and crystallization are realized by a three‐step incremental increase in laser energy density X‐ray diffraction and transmission electron microscopy show that the polycrystalline grains formed with this three‐step process are similar to those after a conventional one‐step laser crystallization of unhydrogenated amorphous silicon The grain size increases with increasing laser energy density up to a peak value of a few micrometers The grain size decreases with further increases in laser energy density The transistor field effect mobility is correlated to the material properties, increasing gradually with laser energy density until reaching its maximum value Thereafter, the transistors suffer from leakage through the gate insulators A dual dielectric gate insulator has been developed for these bottom‐gate thin film transistors Our structure simplifies fabrication of both high quality amorphous and polycrystalline thin film transistors on the same glass substrate We discuss t

Grain growth in laser dehydrogenated and crystallized polycrystalline silicon for thin film transistors

The invention provides a buffered substrate that includes a substrate, a buffer layer and a silicon layer. The buffer layer is disposed between the substrate and the silicon layer. The buffer layer has a melting point higher than a melting point of the substrate. A polycrystalline silicon layer is formed by crystallizing the silicon layer using a laser beam.

Richard I. Johnson

Papers

Capillary waves in pulsed excimer laser crystallized amorphous silicon

Laser dehydrogenation/crystallization of plasma‐enhanced chemical vapor deposited amorphous silicon for hybrid thin film transistors

Low temperature process for laser dehydrogenation and crystallization of amorphous silicon

Grain growth in laser dehydrogenated and crystallized polycrystalline silicon for thin film transistors

Buffered substrate for semiconductor devices