Electron Beam Recrystallization Research Articles

High rate deposition and electron beam recrystallization of silicon films for solar cells

Silicon films were deposited onto graphite substrates by means of a plasma-enhanced chemical vapor deposition (PECVD) process from trichlorosilane (SiHCl 3) hydrogen gas mixtures at a substrate temperature of 450°C. The plasma was operated at a frequency of 13.56 MHz and a pressure of 500 Pa. Deposition rates of 340 nm min −1 and greater were achieved. The films were examined by optical and scanning electron microscopy, X-ray diffractometry and elastic-recoil detection analysis. The as-deposited films were nanocrystalline. They were then recrystallized by means of a zone melting process realized by a line-shaped electron beam being scanned over the surface. To achieve sufficient wettability during recrystallization, methane (CH 4) was added to the atmosphere at the beginning of plasma-enhanced deposition. The films obtained had a polycrystalline structure with a typical grain size of 100 μm in width (i.e. perpendicular to the direction of scanning) and up to several mm in length. The chlorine content of the silicon films was significantly reduced by recrystallization; impurities of hydrogen and oxygen also decreased, while the carbon content increased.

2 μm thin film c-Si cells on near-Lambertian Al 2O 3 substrates

Near-Lambertian Al 2O 3 substrates, which have the reflectivity of almost 100% and superior optical diffusivity, were newly developed by the doctor-blade technique and 2 μm thin film c-Si cells with the large short-circuit current J SC of 15.6 mA/cm 2 (photocurrent J ph of 17.5 mA/cm 2) were fabricated on the substrates. These cells were prepared by ECR plasma chemical vapor deposition, electron-beam recrystallization, conventional phosphorus diffusion and ITO metallization. The optical confinement in such thin film c-Si cells on the diffuse–reflective substrates was experimentally and theoretically investigated. The theoretical computation presented a strong possibility of higher J SC beyond 30 mA/cm 2.

Recrystallization of polycrystalline silicon films on ceramics by electron beam

The formation of large-grain poly-silicon films on high-reflective alumina ceramics has been investigated by means of electron beam recrystallization technique. Sample structure is Polysilicon layer/buffer layers (SiN x /SiO x ) on Alumina ceramics substrate. These layers are deposited by high-rate Electron Cyclotron Resonance Plasma Chemical Vapor Deposition method. We have found that the SiO x layers act as a thermal buffer and an impurity contamination barrier against the ceramics, and SiN x layer has an important role in obtaining good wettability of molten silicon. We have also found that there are optimal thickness of buffer layers, scanning speed, and electron beam power to obtain good quality grains without agglomeration and cracks.

Improvement in the thickness uniformity of silicon-on-insulator layers formed by dual electron beam recrystallization

Simple modifications to the processing of the capping layer in structures used for the preparation of silicon-on-insulator films by liquid phase recrystallization using the dual electron beam method are shown to reduce nonuniformities in the recrystallized layers. A model has been developed to explain the nature of thickness variations in recrystallized layers in terms of the geometry of the starting structure, the condition of the capping layer and the recrystallization conditions.

Possibilities of electron beam recrystallization of thin films of hydrogenated amorphous silicon (a-Si:H)

Possibilities of electron beam recrystallization of thin films of hydrogenated amorphous silicon (a-Si:H)

Formation of silicon-on-insulator layers by electron beam recrystallization

Abstract This paper outlines the development of the electron beam recrystallization approach to the formation of silicon-on-insulator layers. The technique of recrystallizing seeded layers by a line electron beam has been widely adopted. Present practice in electron beam recrystallization is reviewed, both from materials and process points of view. Applications of silicon-on-insulator substrates formed in this way are described, particularly in three-dimensional integration.

Time-resolved reflectivity techniques for dynamic studies of electron beam recrystallization of silicon-on-insulator films

A time-resolved reflectivity (TRR) technique has been developed for dynamic studies of swept beam heating of silicon-on-insulator (SOI) materials. The method exploits the temperature dependence of the reflectivity of SOI films to allow noncontact temperature measurement with high spatial and temporal resolution. This technique is of considerable practical importance for beam processing, since it allows the temperature distribution induced by a beam being scanned across a specimen to be determined. The temperature distribution produced by a line electron beam swept across a SOI specimen was experimentally measured and found to be consistent with a theoretical prediction. The TRR technique can also be used to study melting and will prove useful for characterizing zone melting recrystallization, where thermal modeling is often inadequate for the complex structures involved.

Scanning ion microscopy and microsectioning of electron beam recrystallized silicon on insulator devices

Structures fabricated during the development of a process for making three-dimensionally interconnected integrated circuits using electron beam recrystallization of silicon on insulator have been microsectioned and examined in the scanning ion microscope. This provided detailed information, not accessible by standard analysis techniques, concerning the effects of processing at specific sites in the structures.

Electron beam recrystallization of plasma-sprayed silicon substrates

Polycrystalline silicon substrates of 5–8 cm2 area and 0.5–3 mm thickness have been recrystallized by electron beam glazing. The grain size as well as the Hall mobility increases dramatically from 50 μm to 1 mm or more and from 5 to 320 cm2/V s, respectively.

Multilevel construction of seeded-laterally epitaxial silicon films on insulator

A new seed structure, partially thickened silicon films on insulator (PTS), is proposed for multilevel seeded-laterally epitaxial silicon films on insulator (SOI). Two-level seeded-laterally epitaxial silicon films on thick SiO2 (2.5 μm) were successfully fabricated, using the PTS structure in conjunction with the electron-beam technique. The SOI surface flatness after recrystallization was also improved by the PTS. Through computer simulation of the electron-beam recrystallization process, it is determined that the PTS structure enhances the lateral heat conduction within the SOI. This is important in smoothly melting the seed and field SOI regions.

Direct observation of growth front movement in electron beam recrystallization of silicon layer on insulator

A high-speed movie technique was used to investigate the growth front movement during electron beam recrystallization of thin silicon layers on insulating material. In a laterally epitaxial growth process, it was clearly observed that the molten zone shape dramatically changes across a seed opening, which is due to nonuniformity in heat dissipation toward the substrate in the vicinity of the seed opening. The molten zone width and velocities of the melt front and growth front were quantitatively analyzed using digital film motion analysis. The growth front velocity was found to drastically change by ∼30% across the seed opening.

Perforation seed structure in electron beam recrystallized silicon-on-insulator films

A novel perforation seed structure in electron beam recrystallization of silicon-on-insulator (SOI) films has been proposed, in which seed regions typically with rectangular shapes are separately arranged along a line, so that voids are not generated in the films during the melting and recrystallization process. The structure was designed based on investigation of the void generation mechanism and its optimum dimensions were determined experimentally from viewpoints of the void suppression effect and the crystalline quality of the SOI films.

Highly controllable pseudoline electron-beam recrystallization of silicon on insulator

A new electron-beam annealing technique, an amplitude modulated pseudoline electron beam, has been proposed for recrystallization of large-area silicon layers on insulating materials (SOI). The technique utilizes an amplitude modulated sinusoidal wave for high-frequency beam oscillation. Through computer simulation of the temperature distribution for the sample surface, precise control of the position probability density profile of the line beam proved to be essential in realizing wide and uniform annealing. An optimum oscillation waveform was determined from the simulation. A large-area SOI, 4 mm ⧠, was successfully recrystallized.

電子ビームによる大面積シリコン薄膜再結晶化技術

Recent progress of SOI growth by electron beam recrystallization is described. Emphasis was placed on pseudo-line electron beam (PLEB) technique with lateral seeded epitaxy.Through computer simulation of the temperature distribution of the sample during electron beam irradiation, amplitude modulation of a high frequency oscillation wave is proved to be useful for obtaining large area SOI.Agglomeration of SOI near seed region can be suppressed by using a seed structure with tape-red edge and narrow seed width of 2 μm, which leads to realization of single crystalline SOI with well controlled crystallographic orientation. A large area SOI growth, 4 mm_??_, is successfully carried out. [J. Cryst. Soc. Jpn. 28, 83 (1986) ] .

Self-radiation damage in Gd 2Ti 2O 7

The effects of self-radiation damage from alpha decay in Gd 2Ti 2O 7 were investigated by studying specimens doped with 244Cm. The radiation-induced microstructure consists of individual amorphous tracks from both the alpha-recoil particles and the spontaneous fission fragments. The eventual overlap of the tracks at higher doses leads to a completely amorphous state. The self-radiation damage increases the volume, dissolution rate, and fracture toughness. Electron-beam recrystallization of the amorphous state results in the formation of fine microcrystallites on the order of 0.05 μm in size.

Electron-Beam Recrystallization of Silicon Layers on Silicon Dioxide

ABSTRACTRecent progress of SOI growth by electron beam recrystallization is described. Transient temperature profile on the recrystallizing sample surface was analyzed experimentally by direct observation with a thermovision, which is essential for the understanding of crystal growith mechanism. SOI growth was performed by a spot beam annealing and a pseudo-line shaped beam annealing. The line shaped electron beam has been proved to be useful for large area crystallization.Emphasis was placed on lateral seeded recrystallization of silicon layer evaporated in an ultra high vacuum. Silicon layers with the seed area grown epitaxially during the evaporation and above 1 μm thickness were successfully recrystallized, resulting in reproducible lateral epitaxiy. The pseudo-line shaped electron beam formed by very high frequency oscillation enabled dimensional enlargement of lateral epitaxial growth. crystalline properties were characterized by analyses of Rutherford backscattering and electron channeling pattern.

A Comparison of Cw Laser and Electron-Beam Recrystallization of Polysilicon in Multilayer Structures

ABSTRACTA thermal model for beam-induced melting of polysilicon in polysilicon/insulator/silicon structures has been used to compare CW Ar+ laser and electron-beam melting processes. The laser melting process exhibits a decreasing recrystallization threshold power and an increasing substrate melting threshold power with increasing insulator thickness. The decrease in recrystallization threshold with increasing insulator thickness is generally smaller for electron beams because of their deep penetration. The substrate melting threshold is approximately independent of insulator thickness for e-beams since no change in the power absorption occurs on melting of the polysilicon. As a result, the process window between the onset of recrystallization and melting of the substrate is narrower for e-beams than for laser beams. Also, essentially no window will exist between the onset of melting over a seed and substrate melting under an oxide if lateral epitaxy is performed with an electron beam.

Thermoelastic stress analysis of pulsed electron beam recrystallization of ion-implanted silicon

The time and spatial dependence of the temperature rise produced in ion-implanted silicon subjected to pulsed electron beam bombardment has been numerically calculated. The temperature profiles generated were then used to calculate the thermoelastic stresses produced by the deposited energy. Experimental measurements of the incident energy density thresholds for fracture of the silicon have beem compared with damage threshold levels suggested by this analysis. The temperature calculations have been qualitatively verified by diffusion profile measurements as compared with calculated profiles based on dopant diffusion in liquid silicon. The shear forces produced by the large temperature gradients have been proposed as the primary cause of fracture which occurs at high beam fluences.

Electron beam recrystallization of chemically vapor deposited polysilicon films

Electron beam recrystallization of chemically vapor deposited polysilicon films

Single crystal InSb thin films by electron beam re-crystallization : N. F. Teede, Solid-St. Electron.10 (1967), p. 1069

Single crystal InSb thin films by electron beam re-crystallization : N. F. Teede, Solid-St. Electron.10 (1967), p. 1069