Effects of impurities on removal of polysilicon in chemical-mechanical polish

The effects of impurities on the removal of doped polysilicon in the chemical-mechanical polishing (CMP) process is discussed. It has been found that the Si-CMP is seriously retarded in the presence of boron impurities. In this paper, effects of several usually used n-and p-type impurities for polysilicon are investigated. Successive polishing was performed to reveal the correlation between the removal rate and the dopant concentration along the depth of polysilicon layer. The removal is seriously retarded for p-type samples and slightly enhanced for n-type samples. After excluding the interference from surface roughness, linear relationship was found between the resultant removal rate and the doping concentration. In this study, electrostatic interaction between the reactant ions and the ionized impurities at the silicon surface is proposed to be the primary factor to change the removal reaction rates. For p-type polysilicon etched in an alkaline aqueous solution, transport of OH⁻ anions is hindered because OH⁻ anions experience a repelling force in front of the negative-charged acceptors. Following the same principle, the removal reaction forn-type polysilicon is enhanced. However, the removal rate forn-type polysilicon is rather limited by surface reaction than by transport of reactant ions. As a consequence, the enhancement of removing n-type polysilicon is not so prominent as compated to the retardation effect found for removal of p-type polysilicon.     

工业用丙烯中烃类杂质的气相色谱分析

用优化后的色谱分析条件 ,分析工业用高纯丙烯中烃类杂质。采用与标准样品对照法进行定性 ;用峰面积外标法进行定量。此法可一次进样较好地分离检测含多组份的烃类物质。方法操作简单 ,省时 ,精确度高 ,重复性好。     

Zone melting of indium phosphide

Bulk indium phosphide crystals have been prepared by zone melting with dislocation densities 104 ≤ N_d ≤ 105 cm^-2. The residual impurity level in nominally undoped crystals and the dopant distribution in Cd-, Sn- and Ge-doped zone melted ingots, as revealed by spark source mass spectrometric analyses, indicate a strong interaction between segregation at the solid/liquid interface and vapor transport. The effective distribution coefficients for Sn and Ge in zone melted InP are k_e(Sn) = 0.3 and k_e(Ge) = 0.4. The free electron concentration measured in the middle section of nominally undoped ingots is N_D-N_A = 1.9 × 10¹⁵ cm^-3 corresponding to a Hall mobility Μ_e = 3263 cm^2V-1sec^-l.     

镍精炼过程中Pb和Zn的热力学探讨

在镍精炼过程中,铅、锌在溶液中以络合离子的形态存在,很难以沉淀的形式除去,给电镍生产带来不利的影响。本文浅析了镍精炼过程中铅和锌的行为及其热力学性质,并提出除去系统中微量Pb、Zn的方法。     

Determination of Trace Impurities in High Purity Lutetium Oxide by Neutron Activation with Aid of Cation-Exchange Separation

Trace impurities including Yb in commercially available LU₂O₃ of high purity were determined by neutron activation followed by cation-exchange separation with α-hydroxyisobutyrate.

After irradiation in reactor, the LU₂O₃, together with about the same quantity of Yb carrier, was dissolved in HC1, and fed to a cation-exchange resin column. Lutetium, Yb, Tm and some other rare earths were eluted successively, using α-hydroxyisobutyrate and citrate solutions as eluants. The addition of Yb carrier facilitated the analysis of Yb which is difficult to separate from Lu, and this permitted the determination of Yb of quantities as small as a few ppm.

The impurities found present in this sample of LU₂O₃ were: 0.26ppm Sc, 395ppm Yb, 150 ppm Tm, 12 ppm Tb and 2.3 ppm Eu.     

Thermodynamic Analyses on Oxygen and Carbon Potentials of Impure Helium

Equilibrium oxygen and carbon potentials of impure He containing small amounts of impurities such as CO, CO₂, CH₄, H₂, H₂O and O₂ at 1,073 and 1,273 K were studied. The calculation of equilibrium composition of impurities was carried out assuming the gas-gas and gas-metal reactions. The diagrams, expressed with atomic oxygen fraction ō/S and atomic carbon fraction [Cbar]/S were represented and showed a wide range of equilibrium oxygen and carbon potentials of impure He. A parameter, (ō-[Cbar])/S showing the difference between atomic oxygen and carbon fraction, was found to give a measure of both oxygen and carbon potentials of gas mixtures. The results of the calculation showed that the oxygen and carbon potentials of the impure He with (ō-[Cbar])/S value of around zero was easily affected by the small variation of the gas composition. The corrosion behaviors of Inconel 617 in various impure He gases at 1,273 K could be explained by (ō-[Cbar])/S values.     

Effect of Oxygen and Carbon Impurities on Lattice Parameter of PuN

The cladding component chemical transport (CCCT) is one of the important modes of the fuel-cladding chemical interaction (FCCI) of LMFBR. In order to explain this phenomenon, a model based on the vapor phase chemical transport of cladding components by iodine was proposed by Johnson et al. and Calais et al. In this study, experimental work has been done to check whether such a mechanism can work due to the free iodine generated by the radiolysis of Csl vapor. As a result, it was confirmed that a significant amount of Fe can be transported via vapor phase from the Fe sheet heated at 430°C to the Mo plate heated at 720 or 800°C. Preliminary comparisons between this study and the in-pile irradiation tests have been made. This result qualitatively supports the appropriateness of the model for the CCCT mechanism based on the vapor phase transport of cladding components by radiation-induced iodine.     

Development of Fluctuation Monitor Type Sodium Ionization Detector

In order to improve the sensitivity and the reliability of the sodium leak detection system used in the fast breeder reactors, a new type SID (sodium ionization detector) has been developed, in which the monitored signal is only the fluctuating component of the current between the filament and the ion collector. The fluctuating component was extracted by a band pass filter and its root mean square value was calculated as the SID signal. Fluctuation characteristics of the output current were studied by its frequency spectrum. The results revealed that the current spectrum was affected by the particle size distribution of the aerosol and was most clearly distinguished from that of the background current in the frequency region of 0.5–10 Hz.

Output characteristics of the fluctuation monitor type SID (FM-SID) were obtained as a function of sodium concentration in the gas. The FM-SID sensitivity was lowered by impurities in the gas, such as oxygen and water vapor. Finally, in comparisons with the conventional DC-SIDs, the background noise level of the FM-SID was much lower and SIN ratio was greatly improved. The detectable sodium concentration level was ten times lower than that of the DC-SID.     

Additive Element Effects on Electronic Conductivity of Zirconium Oxide Film

A theoretical study on the electronic structure of zirconium oxide using a molecular orbital method was carried out to investigate the additive element effects on the electronic conductivity of oxide film formed on Zr-alloys. The atomic clusters used were (MZri₁₂O₈)³⁶⁺(M=Zr, 3d-transition metals and alkali metals). To simulate the electron conduction process in the oxide, calculations for a cluster with oxygen vacancy (V0) were also carried out. The energy gap E_g between electron-occupied and empty levels was evaluated, and the electronic conductivity was estimated qualitatively. Opposite effects on the electronic conductivity were found for additions of 3d-transition metals and alkali metals. The latter increased the electronic conductivity by forming impurity levels with small E_Q. The former, however, induced compressive strain in the oxide, resulting in a lowering of electronic conductivity due to widening of the energy gap at the oxygen vacancy.