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.

Specimen size effect on tensile strength of surface-micromachined polycrystalline silicon thin films

Abstract: A new tensile tester using an electrostatic-force grip was developed to evaluate the tensile strength and the reliability of thin-film materials. The tester was constructed in a scanning electron microscope (SEM) chamber for in situ observation and was applied for tensile testing of polycrystalline silicon (poly-Si) thin films with dimensions of 30-300 /spl mu/m long, 2-5 /spl mu/m wide, and 2 /spl mu/m thick. It was found that the mean tensile strengths of nondoped and P-doped poly-Si are 2.0-2.8 and 2.0-2.7 GPa, respectively, depending on the length of the specimens, irrespective of the specimen width. Statistical analysis of these size effects on the tensile strength predicted that the location of the fracture origin was on the edge of the specimen, which was Identified by the SEM observation of the fracture surface of the thin films.

Defects in silicon

Abstract: The method of obtaining pure polycrystalline silicon is described, followed by short accounts of how this material is converted into single-crystal form either by the Czochralski (CZ) pulling method or the float-zone (FZ) method. It is shown that the silicon contains various impurities including oxygen, carbon, boron and possibly hydrogen. The defects and impurities often show a nonhomogeneous distribution in the form of helical swirls. Heat treatment of silicon-containing oxygen leads to the clustering of this impurity. At 450 degrees C there is formation of small complexes that act as shallow donors. Investigations using IR and ESR spectroscopy have so far failed to determine the atomic configuration of the defects. Heating at higher temperatures causes wide-scale precipitation of oxygen. There are interactions with carbon and there can be formation of silicon carbide precipitates. Contamination from Cu, Au, Fe, etc., can occur during these treatments and methods for gettering these metals are discussed, involving dislocations and silica precipitates. Low-temperature irradiations produce vacancies and self-interstitials which combine with impurities to form complexes on heating from 4K to 300K. Evidence is presented to illustrate the possible charge states of self-interstitials. Damage produced by fast neutrons is discussed next, followed by a brief account of neutron transmutation doping whereby neutrally occurring 30Si is converted to 31P by the capture of thermal neutrons. Some aspects of high-temperature diffusion are discussed and attempts are made to correlate the data with that derived from the irradiation studies.

Modeling and optimization of monolithic polycrystalline silicon resistors

Abstract: The processing parameters of monolithic polycrystalline silicon resistors are examined, and the effect of grain size on the sensitivity of polysilicon resistivity versus doping concentration is studied theoretically and experimentally. Because existing models for polysilicon do not accurately predict resistivity dependence on doping concentration as grain size increases above 600 A, a modified trapping model for polysilicon with different grain sizes and under various applied biases is introduced. Good agreement between theory and experiments demonstrates that an increase in grain size from 230 to 1220 A drastically reduces the sensitivity of polysilicon resistivity to doping levels by two orders of magnitude. Such an increase is achieved by modifications of the integrated-circuit processes. Design criteria for the optimization of monolithic polysilicon resistors have also been established based on resistivity control, thermal properties, and device geometry.

A method of fabricating a TFT-EL pixel

Abstract: A method of making a 4-terminal active matrix electroluminescent device that utilizes an organic material as the electroluminescent medium is described. In this method, thin film transistors are formed from polycrystalline silicon at a temperature sufficiently low such that a low temperature, silica-based glass can be used as the substrate.

Preparation of Pb(Zr,Ti)O3 thin films on electrodes including IrO2

Abstract: The development of ferroelectric memory devices requires an improvement of the fatigue properties of ferroelectric thin films. Pb(Zr,Ti)O3(PZT) thin films obtained by the sol‐gel method on Pt/Ti electrodes have reduced residual polarization by continuous polarization reverses about of 108 cycles. The electric characteristics such as fatigue properties have mostly depended on electrode materials. We propose Ir, IrO2, and these layer films as electrode materials and evaluate electric characteristics of PZT thin film capacitors. PZT thin films using Ir/IrO2 and Pt/IrO2 electrodes show no fatigue up to 1012 cycles of ±5 V switching pulses. Moreover, good properties of PZT capacitors, not only on SiO2 but also on polycrystalline silicon, were obtained by using IrO2.