Polycrystalline silicon

About: Polycrystalline silicon is a research topic. Over the lifetime, 19554 publications have been published within this topic receiving 198222 citations. The topic is also known as: polysilicon & poly-Si.

Process and apparatus for manufacturing polycrystalline silicon, and process for manufacturing silicon wafer for solar cell

Abstract: An object of the present invention is to provide a process and apparatus for the continuous flow production of polycrystalline silicon from metallic silicon or silicon oxide as a raw material and also for the manufacture of a wafer by using it, which process and apparatus permit the mass production at a low cost. The above object can be attained by the manufacture of polycrystalline silicon and a silicon wafer for a solar cell by the following steps: (A) smelting metallic silicon under reduced pressure, carrying out solidification for the removal of the impurity components from the melt, thereby obtaining a first ingot, (B) removing the impurity concentrated portion from the ingot by cutting, (C) re-melting the remaining portion, removing boron and carbon from the melt by oxidizing under an oxidizing atmosphere, and blowing a mixed gas of argon and water to carry out deoxidization, (D) casting the deoxidized melt into a mold, and carried out directional solidification to obtain a second ingot, and (E) removing the impurity concentrated portion of the ingot obtained by directional solidification by cutting.

Method of fabricating field effect transistor having polycrystalline silicon gate junction

Abstract: A field effect transistor includes a polycrystalline silicon gate having a semiconductor junction therein. The semiconductor junction is formed of first and second oppositely doped polycrystalline silicon layers, and extends parallel to the substrate face. The polycrystalline silicon gate including the semiconductor junction therein is perfectly formed by implanting ions into the top of the polycrystalline silicon gate simultaneous with implantation of the source and drain regions. The semiconductor junction thus formed does not adversely impact the performance of the field effect transistor, and provides a low resistance ohmic gate contact. The gate need not be masked during source and drain implant, resulting in simplified fabrication.

Seed selection through ion channeling to modify crystallographic orientations of polycrystalline Si films on SiO2: Implant angle dependence

Abstract: Polycrystalline silicon films 4800 A thick deposited by low pressure chemical vapor deposition at 620 °C on oxidized silicon wafers have been amorphized by implantation with 210‐keV Si28 ions to a dose of 1015 cm−2 at 0°, 1°, 3°, 5°, or 7° from normal incidence and subsequently recrystallized at 700 °C. The as‐deposited film was {110} textured with the 〈110〉 directions within ±20° of the surface normal. After the 0°, 1°, or 3° implant and subsequent recrystallization, most of the 〈110〉 directions were confined to within ±4° of the corresponding implant direction. For the 5° and 7° implants, the 〈110〉 directions in the recrystallized layers became randomly oriented; that is, the films lost their {110} texture. These results can be explained by the process of seed selection through ion channeling (SSIC): the grains that survived the 0°, 1°, or 3° implant due to ion channeling acted as seeds during recrystallization. The fact that the direction of the 〈110〉 axes in the recrystallized films was coincident wit...

Purely Intrinsic Poly-silicon Films for n-i-p Solar Cells

Abstract: Polycrystalline silicon films have been prepared by hot wire chemical vapor deposition (HWCVD) at a relatively low substrate temperature of 430° C at a high growth rate (>5 A/s) by optimizing the hydrogen dilution of the silane feedstock gas, the gas pressure and the wire temperature. The optimized material has 95% crystalline volume fraction with complete coalescence of grains. The grains with an average size of 70 nm have a preferential orientation along the (220) direction. Large structures up to 0.5 µ m could be observed by atomic force microscopy (AFM). An activation energy of 0.54 eV for the electrical transport and a low carrier concentration (<1011 cm-3) confirmed the intrinsic nature of the films. A white light photoconductivity of 1.9×10-5 Ω-1 cm-1, a high minority carrier diffusion length of 334 nm and a low (<1017 cm-3) defect density ensure that the poly-Si:H films possess device quality. A very small temperature dependence of the Hall mobility (0.012 eV) indicates negligible barrier to carrier transport at the grain boundaries. A single junction n-i-p cell incorporating HWCVD poly-Si:H in the configuration n+-c-Si/i-poly-Si:H/p-µc-Si:H/ITO yielded 3.15% efficiency under 100 mW/cm2 AM1.5 illumination and a current density of 18.2 mA/cm2 was achieved for only 1.5 µ m thick i-layer.