Takayuki Shingyouji

SEPARATION AND ANALYSIS OF DIFFUSION AND GENERATION COMPONENTS OF PN JUNCTION LEAKAGE CURRENT IN VARIOUS SILICON WAFERS

An analytical method to separate the diffusion and generation components of pn junction leakage currents is developed. The voltage dependence between reverse current and capacitance in pn junctions is measured, and an approximately linear relationship between current density (J) and depletion width (W) is derived. In this relationship, the diffusion component corresponds to linearly extrapolated value of J at W=0, and the generation component corresponds to the rate at which J increases with W as voltage is applied. This method allows both components of the leakage current to be obtained for Czochralski, epitaxial, and intrinsic gettering wafers. Separated diffusion components strongly depend on silicon wafers mainly due to the change of minority carrier density and the diffusion of minority carriers. On the other hand, the generation component increases with increases in the electric field applied to the junction for all wafers. We found that this electric field effect on the generation component can be ...

Degradation of dielectric breakdown field of thermal SiO2 films due to structural defects in Czochralski silicon substrates

We used heat treatment to intentionally introduce various structural defects in Czochralski silicon substrates. The type, size, and number density of the induced defects were surveyed with transmission electron microscopy, and the defects were then incorporated into SiO2 films (10–50 nm thick) during thermal oxidation in dry O2. The effect of the defects on dielectric strength of the SiO2 films was examined with a time zero dielectric breakdown method. Larger platelet oxygen precipitates caused greater decreases of the breakdown field, and precipitates smaller than the SiO2 film thickness did not appreciably reduce the breakdown field. Every large platelet oxygen precipitate incorporated in the SiO2 film caused a degradation. Octahedral oxygen precipitates caused little degradation. The breakdown field was higher than 7 MV/cm and did not depend much on the SiO2 film thickness and precipitate size. We discussed possible mechanisms for the degradation due to both kinds of precipitates. Oxidation‐induced sta...

Effect of bulk microdefects induced in heat‐treated Czochralski silicon on dielectric breakdown of thermal SiO2 films

We examine the effect of bulk microdefects (BMD) intentionally introduced in Czochralski silicon substrates by heat treatment on the dielectric breakdown of thermally grown SiO2 films. Transmission electron microscope observations reveal that the BMD consist of oxygen precipitates, perfect dislocation loops, and faulted dislocation loops. When the BMD are incorporated into the SiO2 film during thermal oxidation, an apparent decrease in the breakdown field is observed. The size of the oxygen precipitates has a clear relationship with the breakdown field: larger oxygen precipitate causes greater degradation. The dislocation loops are unrelated to the breakdown field.

Calculation of Diffusion Component of Leakage Current in pn Junctions Formed in Various Types of Silicon Wafers (Intrinsic Gettering, Epitaxial, Silicon on Insulator)

We derived a general analytical formula for the diffusion component of leakage current in pn junctions formed in various types of silicon wafers such as intrinsic gettering (IG), epitaxial (EPI), and silicon on insulator (SOI) wafers. From this analysis, it can be understood quantitatively that defect regions in IG wafers increase the diffusion current, although heavily doped regions in epitaxial wafers decrease the diffusion current, and in SOI wafers the diffusion current can be considerably reduced when there is a low recombination velocity at the Si/SiO2 interface.

Effect of oxidation ambient on the dielectric breakdown characteristics of thermal oxide films of silicon

This study investigated the dielectric breakdown characteristics of thermal oxide films grown by dry and wet oxidation. Oxide films grown by wet oxidation have lower B‐mode failure rates and higher B‐mode breakdown fields. On the other hand, the reliability of C mode of oxide films does not differ consistently between films grown by dry and wet oxidation. These results indicate that as‐grown defect causing B‐mode failure may shrink or be reduced during wet oxidation.

Study of Si Etch Rate in Various Composition of SC1 Solution

Etching of Si wafer surface in an NH4OH:H2O2:H2O mixture (SC1 solution) is studied in regard to the effect of the composition of the solution. It is clarified that, when H2O2 concentration is constant, the etch rate increases linearly with OH- ion concentration and reaches a saturation etch rate. This saturation etch rate is inversely proportional to H2O2 concentration. Microroughness of Si surface after SC1 treatment is also investigated. It is also found that microroughness is independent of NH4OH concentration when the etch rate is kept constant.

Effects of oxygen-related defects on the leakage current of silicon p/n junctions

The reverse-bias leakage characteristics of silicon pn junctions have been investigated with particular attention to the effects of various types of oxygen-related defects, such as oxygen precipitates, oxidation induced stacking fault, and grown-in defects. The effects of oxygen-related defects on the leakage current of pn junctions in intrinsic gettering wafers and precipitation annealed wafers have been investigated quantitatively, and the field oxidation temperature used to form pn junctions has been found to be an important factor in determining the pn junction leakage current because oxygen-related defects are formed during low temperature field oxidation. It has also been found that grown-in oxidation induced stacking faults degrade the leakage characteristics. Grown-in defects that are well known to degrade the oxide breakdown characteristics were found to have some effects on the increase of the leakage current. In addition, it is recognized that the leakage current of pn junctions formed in wafer...

LOW SURFACE RECOMBINATION VELOCITY ON SILICON WAFER SURFACES DUE TO IODINE-ETHANOL TREATMENT

The above regular paper published in the Japanese Journal of Applied Physics (JJAP) in 1999 should hereafter be regarded as having been negated and nonexistent due to its violation of copyright of a paper published in the Journal of Applied Physics in 1997: J. Appl. Phys. Vol. 81 (1997) pp. 6186-6199 Accurate Method for the Determination of Bulk Minority-Carrier Lifetimes of Mono-and Multicrys-talline Silicon Wafers by Jan Schmidt and Armin G. Aberle

Room Temperature Annealing Behavior of Copper-Related Deep Levels in P-Type Floating Zone Silicon Wafers

Deep level transient spectroscopy analysis of copper-doped p-type floating-zone silicon (FZ-Si) wafer was performed. Five deep energy level states observed in copper-doped silicon (Ev+0.1 eV, Ev+0.15 eV, Ev+0.22 eV, Ev+0.26 eV and Ev+0.43 eV) with concentrations of 1×1011 to 1×1012 cm-3 were detected. We observed that the amplitude of only one peak (deep level at Ev+0.26 eV) dramatically decreased with time during storage at room temperature, but stabilized at a concentration of about 1×1012 cm-3 after 2 days. The other deep level concentrations did not change after two months storage at room temperature. Therefore, it was concluded that room-temperature annealing resulted in a decrease in the deep level at Ev+0.26 eV due to the formation of copper-precipitate related defects and out-diffusion to the silicon surface.

Identification and Quantification of Transition Metal Impurities in Czochralski Silicon Wafers using Microwave Photoconductive Decay Lifetime Measurements

The identification of metallic impurities in p-type silicon has been studied using a microwave photoconductive decay lifetime measurement method at various high injection levels. The light illumination time and carrier injection level dependences of the recombination lifetime show unique characteristics for recombination centers attributed to Fe- and Cr-related levels. The clear identification of iron and chromium is achieved by analyzing the carrier injection level dependence curve and the light illumination time measured before and after the light illumination treatment.