Low‐Frequency Noise and Resistance as Reliability Indicators of Mechanically and Electrically Strained Thick‐Film Resistors

New contemporary applications of thick resistive films are inducing the need to investigate their behaviour under various stressing conditions. On the other hand, there is a growing interest in noise measurements as means of thick‐film resistor quality and reliability evaluation and evaluation of degradation under stress. For these reasons, this chapter presents effects of mechanical, electrical and simultaneous mechanical and electrical straining on performances of conventional thick‐film resistors that are analysed from micro‐ and macro‐structural, charge transport and low‐frequency noise aspects

Thick‐Film Resistor Failure Analysis Based on Low‐Frequency Noise Measurements

The chapter aims to present research results in the field of thick‐film resistor failure analysis based on standard resistance and low‐frequency noise measurements. Noise spectroscopy–based analysis establishes correlation between noise parameters and parameters of noise sources in these heterogeneous nanostructures. Validity of the presented model is verified experimentally for resistors operating under extreme working conditions. For the experimental purposes, thick‐film resistors of different sheet resistances and geometries, realized using commercially available thick‐film resistor compositions, were subjected to high‐voltage pulse (HVP) stressing. The obtained experimental results are qualitatively analysed from microstructure, charge transport mechanism and low‐frequency noise aspects. Correlation between resistance and low‐frequency noise changes with resistor degradation and failure due to high‐voltage pulse stressing is observed

Development of silicon nitride and cermet resistors for use in a binary counter, metal insulator field effect transistor circuit Final report, 1 Dec. 1966 - 31 Mar. 1968

Silicon nitride and cermet resistors for binary counter metal insulator field effect transistor circui

Firing Variables and Strain Sensitivity of Bi2Ru2O7 Thick Resistive Films

In order to provide accurate and semi-real-time information about performances and conditions of various civil engineering structures thick-film resistors are often being used as strain sensors. For that purpose, Ba2Ru2O7 thick resistive films based on compositions with sheet resistivities of 1 kOhm/sq, 10 kOhm/sq and 100 kOhm/sq were evaluated. Resistors were fired at three different peak temperatures (825oC, 850oC and 875oC) and with three different dwelling times (5 min, 10 min and 15 min) in order to correlate influence of firing variables and thick resistive film strain sensitivity by tracking structure-related changes in resistance, gage factor and noise index values. For 10 kOhm/sq composition values of resistance change vs. temperature and temperature coefficient of resistance were measured and calculated

Thick film resistors on dielectrics

This thesis investigates the viability of using thick film materials on a range of thick film dielectrics. They are usually formulated so as to be compatible with 96% alumina substrates. It is sometimes desirable, however, to deposit them on thick film dielectrics. This may produce both technical and commercial advantages. The electrical changes produced and the chemical interactions observed are discussed. It is concluded that viable systems are possible provided the materials are carefully selected. In particular, there is evidence that the presence of barium in a resistor material affects the conduction mechanisms. This means that, in cases where the dielectric contains barium, the effects on the properties of the resistors may be very marked. It is observed, however, that ceramic filled dielectrics with a high content of glasses should form a satisfactory class of dielectric for use as an underlayer for thick film resistors. This conclusion appears to be in agreement with recently published commercial developments. The thesis also discusses materials selection and the preparation of samples and gives detailed results of electrical tests. The figures includes plots of the results of SEM/EDX analyses made on polished cross-sections of samples

Bulk-micromachined mass airflow sensor fabrication and testing methodology for an undergraduate microfabrication course.

In July 1995, National Science Foundation Award # 9551869 funded the development of a new inter-disciplinary microfabrication course under the primary leadership of Dr. Kevin Walsh at the University of Louisville. Along with this award, the completed construction of a new building in 1996 that contained a class 1000/100 cleanroom laboratory facilitated the development of the course. Moreover, curricula had to be completed to provide students with practical, hands-on experience in building Micro Electro-Mechanical Systems (MEMS) devices using processes and methodologies introduced in the course. Dr. Walsh wanted to include a mass airflow sensor in his portfolio of total possible devices students could build in the cleanroom lab for the course. This document describes the design of a bulk-micromachined, monolithic, mass airflow sensor with a thermally-isolated, thin-film, dielectric, microbridge/diaphragm design. In addition, several fabrication methodologies were explored, as well as a means to test and evaluate the sensors for this undergraduate class laboratory. The mass airflow sensor architecture chosen was based upon a closed-loop-control,microelectronic thermal (hot-wire) anemometer design, which was first developed and presented by Johnson, Higashi, et. al. at Honeywell in the mid 1980s [2]. Two separate photomask sets were developed using L-Edit™ software (by Tanner Research), with each set including multiple geometric variations of a dual/triple microbridge/cantilever flow sensor structure to be suspended over a precision, anisotropically-etched pit, integrated onto a (100) silicon substrate. Four primary structural fabrication strategies were explored to produce the thin-film material for the flow sensors: (1) RF planar magnetron sputter-deposited 1 m m -thick silicon nitride microbridges/cantilevers; (2) anodically-bonded-and-machined 20-30 m m -thick borosilicate glass diaphragms; (3) spin-on-glass microbridges/cantilevers; and (4) low-stress, 0.5 m m -thick, LPCVD silicon nitride microbridges/cantilevers. Four resistor metallizations were separately evaluated: permalloy (Ni81Fe19), chromium, titanium, and platinum. A process was developed and documented to successfully fabricate flow sensors with low stress LPCVD silicon nitride microbridges/cantilevers. DC planar magnetron sputterdeposited platinum thin-film resistors (with a ~120 nm-thick RF planar magnetron sputterdeposited chromium adhesion layer), with nominal thicknesses of ~56 – 70 nm, were delineated by photolithographic imaging techniques. The resistors had measured Temperature Coefficients of Resistance (TCR) in the range of 1.93 – 2.25 x10-3 W /W /°C at 25 - 125 °C. Anisotropic KOH etching of the (100)-oriented silicon substrate was utilized to release the flow sensor microbridge/cantilever microstructures. After designing and building a flow sensor test machine capable of controlled volumetric air flow rates of up to ~15 SLPM (0.54 m/s), nominal sensor sensitivities (SV) of up to 0.67 mV/SLPM (20.4 mV/(m/s)) were measured. The sensitivities varied somewhat depending upon resistor values set in the flow sensor heater-driver circuit and the insertion depth of the devices within the flow channel

Realization of fully distributed RC networks using thick film technology

The problems associated with the fabrication of Fully Distributed RC (FDRC) networks using thick film techniques have been discussed. Also, a comprehensive investigation into the fabrication of fully distributed RC networks has been carried out in which a series of resistor-dielectric ink combinations were examined for compatibility. The investigations resulted in the successful fabrication of thick film FDRC devices. It must be mentioned, however, that the conventional methods of trimming could not be used in view of the fact that the first resistor layer of the FDRC network is completely covered with a layer of dielectric and that the physical shape and size of the distributed network should not be changed by trimming. The high voltage pulse trimming technique was therefore examined in detail since it neither required accessibility to the surface of the resistor nor did it change the physical shape of the resistors. A suitable electronic circuit was designed for this purpose and was used to adjust the values of several fully distributed RC components. The manufactured thick film FDRC devices was examined in various electronic networks such as multivibrators, phase shift oscillators and active filters with successful results

Vanadium Oxide Microbolometers with Patterned Gold Black or Plasmonic Resonant Absorbers

High sensitivity uncooled microbolometers are necessary to meet the needs of the next generation of infrared detectors, which seek low power consumption and production cost without sacrificing performance. Presented here is the design, fabrication, and characterization of a microbolometer with responsivity enhanced by novel highly absorptive coatings. The device utilizes a gold-doped vanadium oxide film in a standard air bridge design. Performance estimations are calculated from current theory, and efforts to maximize signal to noise ratio are shown and evaluated. Most notably, presented are the experimental results and analysis from the integration of two different absorptive coatings: a patterned gold black film and a plasmonic resonant structure. Infrared-absorbing gold black was selectively patterned onto the active surfaces of the detector. Patterning by metal lift-off relies on protection of the fragile gold black with an evaporated oxide, which preserves gold black\u27s near unity absorptance. This patterned gold black also survives the dry-etch removal of the sacrificial polyimide used to fabricate the air-bridge bolometers. Infrared responsivity is improved 70% for mid-wave IR and 22% for long-wave IR. The increase in the thermal time constant caused by the additional mass of gold black is a modest 15%. However, this film is sensitive to thermal processing; experimental results indicate a decrease in absorptance upon device heating. Sub-wavelength resonant structures designed for long-wave infrared (LWIR) absorption have also been investigated. Dispersion of the dielectric refractive index provides for multiple overlapping resonances that span the 8-12 ?m LWIR wavelength band, a broader range than can be achieved using the usual resonance quarter-wave cavity engineered into the air-bridge structures. Experimental measurements show an increase in responsivity of 96% for mid-wave IR and 48% for long-wave IR, while thermal response time only increases by 16% due to the increased heat capacity. The resonant structures are not as susceptible to thermal processing as are the gold black films. This work suggests that plasmonic resonant structures can be an ideal method to improve detector performance for microbolometers

Index to 1984 NASA Tech Briefs, volume 9, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1984 Tech B Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Retention and application of Skylab experiences to future programs

The problems encountered and special techniques and procedures developed on the Skylab program are described along with the experiences and practical benefits obtained for dissemination and use on future programs. Three major topics are discussed: electrical problems, mechanical problems, and special techniques. Special techniques and procedures are identified that were either developed or refined during the Skylab program. These techniques and procedures came from all manufacturing and test phases of the Skylab program and include both flight and GSE items from component level to sophisticated spaceflight systems