Robert B. Comizzoli

ELECTRIC FIELD QUENCHING OF PHOTOLUMINESCENCE IN POLY-N-VINYLCARBAZOLE

THERE has been considerable work done on the effect of an applied elect& field on luminescence, particularly with inorganic phosphors [ 11. Bernanose [2] has studied the enhancement effect of previous exposure to light on the electroluminescence in vinylcarbazole, and the dependence on electric field of the optical generation of free carriers in poly-N-vinylcarbazole (PVK) has been demonstrated [3]. In this note the effect of an applied electric field in partially quenching the photoluminescence of PVK is reported. To the authors knowledge, this is the first reporting of an electric field effect on photoluminescence in an organic material. PVK pellets were obtained from two commercial sources. As determined by atomic emission spectroscopy, PVK from one source contained metallic impurities in the several hundred ppm range, while the other source had less than 10 ppm metallic impurity. The effect was observed in both samples but only data from the low metal samples will be presented. Polymer samples were prepared by dissolving the PVK in a 4 : 1 by weight solution of toluene : cyclohexanone. The polymer solution was flow coated onto 1 cm square conducting, transparent tin oxide coated glass substrates, air dried, and baked in air at 70°C for 30 min. Thicknesses were in the 5 to lox cm range, as measured by a micrometer accurate to 1 X cm. The micrometer thickness measurements agreed well with two other estimates of the thickness. If the maximum field to which the samples could be charged is computed from the maximum voltage and measured thickness the result of 1.5 X 106 V/cm agrees well with previous measurements of 1.4 X 106 V/cm[3]. In addition, the surface charge was measured independently of the surface voltage in separate measurements by a technique described elsewhere [4,51. In this way the sample capacitances were measured. Using a dielectric constant of 3.75 [3], the thickness determined by the capacitance measurement was within 15 per cent of that measured with the micrometer. Thus, the micrometer was considered sufficiently accurate and it was used to measure sample thicknesses. The apparatus is shown schematically in Fig. 1. Electric fields of up to 1.5 X 106 V/cm were applied by depositing in the dark on the free PVK surface a positive charge from a high voltage corona discharge in air. Since these techniques for obtaining high electric fields are not well-known outside of electrophotographic research [6, 71, a detailed description of the apparatus for sample charging and voltage measurement

Quantum Efficiency and Photoconductivity in Dye‐Sensitized ZnO‐Resin Binder Layers

Measurements of quantum efficiency and photoconductivity on dye‐sensitized ZnO powder‐organic‐resin binder layers as used in electrophotography show that the carrier range for dye‐sensitized photocurrents is 10 to 100 times lower than that for the intrinsic ZnO photocurrent at 3800 A. The dye‐sensitized photocurrent depends on the square root of light intensity while the photocurrent at 3800 A is linear with intensity. These observations are interpreted in terms of a bimolecular recombination process for the dye‐sensitized photocurrent in which a photoexcited dye molecule injects an electron into the ZnO conduction band and then recaptures ZnO conduction electrons to return to the ground state.

CMOS integrated circuit reliability

Abstract This paper summarizes recently published data on CMOS integrated circuit failure rates, and provides information on the effects of voltage, temperature, device complexity, and packaging on CMOS failure rates. Other factors which can affect failure rate are also indicated, including designs, materials, processes, in-process controls, screening tests, and product maturity. Data on failure rates of NMOS and PMOS integrated circuits are provided to enable comparison with CMOS data. It is concluded that available data do not indicate any consistent reliability difference for CMOS versus NMOS or PMOS integrated circuits. Because of the many advantages of CMOS integrated circuit technology, continued increase in usage of CMOS circuits has been forecast, accompanied by further increases in CMOS integrated circuit reliability.

The Detection of Corrosion Phenomena with pH‐Sensitive Fluorescent Dyes on Aluminum‐ and Gold‐Metallized IC Devices

Corrosion sites on IC devices are often difficult to detect before a significant amount of metallization deterioration occurs. The identification of corrosion sites in their early stages would be a powerful tool in studies of metallized IC device reliability and of corrosion processes themselves. Recently, this laboratory has been investigating metallization corrosion phenomena on IC devices. During these studies we explored the use of pH‐sensitive fluorescent dyes to decorate the IC device surface. After application ofpH‐sensitive fluorescent dye molecules to the surface of the IC test device, an external d‐c bias was applied to the device which activated or deactivated localized fluorescence on the device. We believe this observed behavior relates to corrosion phenomena occurring on the metallization of the IC. Here we report the results of these exploratory experiments conducted on aluminum‐ and gold‐metallized IC test devices.

New methods for detecting structural defects in glass passivation films

Conventional test methods to evaluate the quality of glass passivation overcoats on semiconductor devices are generally inadequate and/or destructive. We have recently devised three new methods that overcome these problems: (1) Sequential selective chemical etching of metal/dielectric structures to detect buried, latent, or partial defects as a function of dielectric layer depth. (2) Electrophoretic cell decoration with uv phosphor particles suspended in an insulating liquid, the sample forming one electrode of the cell. (3) Electrostatic corona charging to selectively deposit surface ions from a high‐voltage dc discharge on the insulating surfaces of the samples, followed by placing of the charged sample in a suspension of charged carbon black particles in an insulating liquid; depending on the polarity of the ions the particles can be deposited on the insulator surface or at the defect sites. The etching method is most suitable in process research studies, and the electrophoretic technique for demarcati...

Reliability Implications of Lateral Alkali‐Ion Migration in MOS Integrated Circuits

At elevated temperatures, as a result of an electric field, alkali‐ion contamination from regions surrounding MOS transistors can increase in concentration at the edges of negatively biased gate electrodes, and can subsequently enter the channel regions of MOS transistors and adversely impact reliability. In contrast to alkali‐ion contamination initially present in the gate oxide or gate electrode material, which can be detected by conventional high‐temperature bias tests of MOS capacitors or transistors, alkali‐ion migration from outside of a transistor into the channel region is more difficult to detect. Electrical characterization of n‐channel MOS transistors with no significant contamination initially present in channel regions, but with alkali‐ion contamination present in regions adjacent to transistors, indicated that lateral alkali‐ ion migration can increase n‐channel transistor subthreshold leakage currents by over three orders of magnitude. Possible sources of lateral alkali‐ion contamination are indicated, and test patterns and screening tests to detect susceptibility to lateral alkali ion migration effects are discussed.

Corona Discharge--Electrostatic Method for Deposition of Powdered Passivation Glass on Semiconductor Devices

Selective deposition of powdered passivating glass on either insulating or conducting regions of a device wafer can be accomplished by first depositing ions from a corona discharge on the insulating regions of the device wafer and then immersing the wafer in an insulating liquid containing a charged suspension of the powdered glass. The method is fast (about 15 s per wafer) and both sides can be coated simultaneously. Advantages compared to other methods are listed. The wafer charging process and the glass deposition process are discussed in terms of the relevant process parameters. Thus far, the main application has been deposition of glass in the grooves of mesa-type thyristors and rectifiers.