The mechanism of leakage current reduction in phosphorus-doped po]ysilicon oxide by high temperature annealing prior to low temperature oxidation was investigated by bias polarity dependence of oxide leakage current, polysilicon grain size measurement, and polysilicon surface observation. Increased phosphorus concentration in polysilicon makes the grains larger and smoothens the surface roughness; consequently, the highest electric field is obtained at the phosphorus concentration of about 6 • 102~ cm-'~. Even at the optimum concentration, leakage current due to field enhancement at the interface between polysilicon oxide and polysilicon is still high. Leakage current can be reduced remarkably by high temperature annealing prior to oxidation, especially at the optimum concentration. The annealing effect is explained by interface flatness improvement due to grain growth during annealing and increase of phosphorus atoms in grains. Phosphorus atom migration from the grain boundaries inside the grains is considered to enhance the grain growth.Thermal oxide grown on heavily doped polysilicon is commonly used as the dielectric of MOS LSI's. Particularly, in a floating polysilicon gate EPROM's and EEPROM cells polysilicon oxide (poly-oxide) hardness to the electric field plays an important role in determining data retention characteristics. However, poly-oxide is well known to be more conductive than bulk silicon oxide, which has been attributed mainly to surface roughness at the poly-oxide/polysilicon interface.A smoother interface is obtained by oxidizing polysilicon at higher temperatures (1), where the viscous flow of the oxide and the small dependence of oxidation rate on polysilicon orientation can moderate the surface roughness generated by oxidation. A similar improvement in the surface roughness is attained by using polysilicon with amorphous structure (2). Also, high temperature annealing just after polysilicon oxidation improves the breakdown field (3). This improvement is explained by the release of stress in the structure, which prevents further flawing induced after the oxidation and thermal cycling.In this paper, the role and mechanism of high temperature annealing prior to oxidation of phosphorus-doped polysilicon is investigated as an effective means of improving the reliability of low temperature oxidized polyoxide. The bias polarity dependence of Fowler-Nordheim tunneling current through poly-oxide, measurement of the polysilicon grain size, and observation of the oxidized polysilicon surface using TEM and replica techniques are reported. ExperimentalPolysilicon films with thickness of 0.40 ~m were deposited by low pressure chemical vapor deposition (LPCVD) at 620~ onto thermally oxidized Si substrates and were doped with phosphorus by diffusion at 900~ from a POC13 source. Prior to oxidation, 0.30 ~m thick CVD oxide films were deposited onto the doped polysilicon films, and annealing was performed at 950 ~ and ll00~ for 10 min in N~ atmosphere. Some of the Si substrates remained unannealed, as shown ...

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We study the level spacing distribution p(s) in the spectrum of random networks. According to our numerical results, the shape of p(s) in the Erdős-Rényi (E-R) random graph is determined by the average degree k and p(s) undergoes a dramatic change when k is varied around the critical point of the percolation transition, k = 1. When k 1, the p(s) is described by the statistics of the Gaussian orthogonal ensemble (GOE), one of the major statistical ensembles in Random Matrix Theory, whereas at k = 1 it follows the Poisson level spacing distribution. Closely above the critical point, p(s) can be described in terms of an intermediate distribution between Poisson and the GOE, the Brodydistribution. Furthermore, below the critical point p(s) can be given with the help of the regularized Gamma-function. Motivated by these results, we analyse the behaviour of p(s) in real networks such as the internet, a word association network and a protein-protein interaction network as well. When the giant component of these networks is destroyed in a node deletion process simulating the networks subjected to intentional attack, their level spacing distribution undergoes a similar transition to that of the E-R graph.

B2O3 and B mixture for ion source material produced B2O2+ and B+ ions of large contents, which can be useful solid source material for B+ ion implantation. Auger electron spectroscopy was employed to investigate the depth distributions of B and O which are components of mainly B2O2+ and B+ ions implanted into Si at the same energy. It is found that only B+ ion can be doped in Si through a SiO2 layer by means of implantation using B2O3 and B mixture for ion source material without mass selection.

The reliability of 100 -200 A poly-oxide grownon heavily doped polysilicon was investigated fmainly by TDDB measurements, compared with -100 A tunnel oxide grown on high dose implanted Si substrate.For the lower phosphorus concentration polyoxide, cumulative failure rate is high at short stress time, slightly depending on stress electric field. The poly-oxide for the higher concentration wears out under the high stress electric field. The wearout phenomenon is considered to be attributed to positive charge generation, due to phosphorus atoms incorporated into poly-oxide. No wearout is observed for tunnel oxide on high dose implanted Si substrate. The TDDB characteristics can be explained by reduction in effective thickness for stoichiometric oxide.