NiCr Films Research Articles

The influence of silicon on properties of deposited Ni-Cr films

Multicomponent alloy thin films based on Ni-Cr with a high silicon content were deposited in a high vacuum onto ceramic flat substrates and investigated. After annealing in air the Ni-Cr-Si films show a high stability. It has been found that the temperature coefficient of resistance has values around zero in a range of the film composition from 5 to 20 at.% Ni, from 20 to 40 at.% Cr and from 50 to 65 at.% Si. This range of the film composition is suitable for the production of metal film resistors by means of sputtering.

Simultaneous preparation of Cr-SiO and NiCr thin film resistors on a single substrate

Using two resistive films on a single substrate has a significant advantage in fabricating thin film hybrid circuits. If the two films have the same sheet resistance, a temperature coefficient of resistance (TCR) of zero can be obtained. The preparation of two films with a sheet resistance ratio of 1:10 gives the possibility of a large increase in the range of values for the resistors prepared. A technological process for preparing Cr-SiO ( R s = 2.0 kΩ/□ ) and NiCr ( R s = 200 Ω/□ ) films is discussed in this paper. Multisource evaporation (evaporation from two sources) is used. The component and R s control are achieved using rate, thickness and R s sensors. First Cr-SiO is deposited and then NiCr. The final metalization is nickel and gold as separate layers. The fabrication of test structure is performed by plasma and conventional wet etching processes. The prepared test structure and the thermal stabilization show that deviation in the TCR for the two films must occur in the same direction from negative topositive for a minimum value to be reached simultaneously. Resistors with two nominal values and a TCR for both films of less than 50 ppm can be made using the technology described.

Ion Beam Mixing of Alternate Layers Of Ni-Nb and Ni-Cr

ABSTRACTAlternating layers of Ni and Nb with a total thickness of 1060Å, and Ni and Cr with a total thickness of 840Å were deposited by electron beam evaporation on silicon. The individual layer thicknesses were adjusted in such a way as to obtain 50/50 at% compositions of Ni-Nb and Ni-Cr; the thicknesses were around 100Å for Ni and 170Å for Nb, and 100Å of Ni and 110Å of Cr. The films were bombarded with 350 keV Cr+ions at a dose of 2 × 10 ions cm. RBS and TEM techniques were used to study the mixing and microstructure. Almost complete mixing and amorphization have been observed for the Ni-Nb system. Ni-Cr film has revealed very little mixing compared to Ni-Nb film and the microstructure remained polycrystalline. Sputter (rf) deposited Ni-Cr film also remained polycrystalline both before and after ion irradiation. The Ni-Cr System appears to be an exception to the structural difference rule for amorphous phase formation by ion irradiation.

Properties of evaporated Ni-Cr films with an aluminum content of about 50%

Films with an aluminum content of about 50% in Ni-Cr were produced as a continuation of investigations on multicomponent thin alloy films based on Ni-Cr, because an additional zero transition for the temperature coefficient of resistance (TCR) of these thin films was indicated in the earlier investigations. The alloy films were evaporated in high vacuum onto ceramic substrates and measurements of the TCR and the stability were carried out. It was found that the TCR is less than ±50 ppm K -1 for aluminum concentrations between 45 and 65 at.%. Such films are suitable for the production of metal film resistors.

Influence of the substrate on the annealing behaviour of sputter-deposited NiCr films

Thin NiCr films of thickness about 30 nm were deposited by magnetron sputtering onto various types of substrate such as (1) polished vitreous carbon, (2) polished vitreous carbon coated with an evaporated carbon film 20 nm thick, (3) (111)-oriented silicon wafers, (4) thermally grown SiO 2 films on silicon and (5) borosilicate glass. Our investigations which involved the combined use of Rutherford ford backscattering and Auger electron spectroscopy showed that, after annealing of the films in air, surface oxidation connected with the known surface segregation of chromium takes place in all cases, whereas a strong oxygen enrichment at the interface was observed only for polished vitreous carbon substrates. It is suggested that this effect is due to a porous and oxidizable interface which is generated during film growth on vitreous carbon substrates.

Aging model of reactively deposited thin NiCr films

The behaviour of the electrical resistance of thin reactively deposited NiCr films during aging in air is rather complex and is often non-monotonic. A simple model explaining the first stages of the aging behaviour of such films is developed. The main feature of the model is the assumed selective oxidation of the chromium component leading to a simultaneous change in the thickness and composition of the remaining conducting film. By describing the film resistivity in terms of percolation theory and using a relation between the metal composition and the resistivity of the bulk material the aging curves of the resistance can be calculated from its dependence on the film composition, which is determined by the deposition process, and on the aging temperature. Although the model does not include structural effects such as annealing or segregation during aging the change in the aging curves obtained for NiCr films deposited under various conditions can now be calculated in satisfactory agreement with experimental results.

Influence of the substrate on the annealing behaviour of sputter-deposited NiCr films

Influence of the substrate on the annealing behaviour of sputter-deposited NiCr films

Electrical properties and structure in disordered NiCr films

Electrical properties and structure in disordered NiCr films

Electron microscopic and AES studies on thin layers of NiCr

In order to understand the parameters affecting the properties of NiCr resistors prepared by various methods, the annealing properties of NiCr thin films were studied. TEM and electron diffraction were used to determine the structure of the films deposited onto SiO x coated microgrids, while electrical measurements and AES indepth profiling were carried out on the samples deposited under identical conditions onto silica substrates. The effect of a SiO x protective coating on the structural changes was investigated during high temperature annealing in vacuum. In the NiCr samples annealed without a protective layer the selective oxidation of chromium led to a rather metallic type of conduction, while in the protected samples the stabilization of the conduction was observed after the same annealing. By hindering oxidation and surface diffusion processes the protective layer resulted in the development of a more stable structure in the NiCr films.

Allowable power in NiCr film resistors : T. Berlicki and E. Prociow. Electrocomponent Sci. Technol.9, 209 (1982)

Allowable power in NiCr film resistors : T. Berlicki and E. Prociow. Electrocomponent Sci. Technol.9, 209 (1982)

Allowable Power in NiCr Film Resistors

This paper reports the dependence between the power required to cause destruction and the dimensions of resistive films, i.e. the width and thickness. The dependence has been analysed using destruction phenomenon models which consider the increase of temperature of the resistive films and the films defects. Results show that the power value required to cause destruction rises linearly with the width of the resistor films and is exponentially proportional to the sheet resistance.

Directional gas-flow measurement with pyroelectric anemometers (PA)

The directional flow characteristics of pyroelectric anemometers, fabricated using z-cut LiTaO 3 plates, are studied. The heater resistor and the two sensor electrodes were evaporated NiCr films. The ratios of the lengths of the charge-sensing electrodes to the electrode—heater separation distance, β, were 32 and 54. The flow-angle dependence of the differential pyroelectric response was measured. The results yield a cos 1 2 α flow-angle dependence, where α is the fluid flow angle normal to the electrode length. Because of the large value of β, this angular dependence is in close agreement with the empirical formula often used for the hot wire anemometer.

Twenty-five nm features patterned with trilevel e-beam resist

We describe a trilevel e-beam resist process based on the high resolution resist PMMA. This process has been used to form metal features 25 nm wide on thick Si substrates by liftoff. Ni–Cr films patterned in this way have been used as masks for reactive ion etching of Si. The resulting structures were arrays of fins ∠ 30 nm wide and 330 nm high on 95 nm centers with a total length of 3 μm. We also discuss the resolution improvement obtained in a trilevel process based on a higher speed resist, P (MMA/MAA).

Pyroelectric differential thermal analyzer

Abstract A new pyroelectric differential thermal analyzer is devised based on a thin, narrow NiCr film heater and two symmetric electrodes (the sample-electrode and the reference-electrode) simultaneously deposited on thin z-cut LiTaO3 wafer. A NiCr ground plane is used on the other face. A specific study on liquid film vaporization of the Isopropyl alcohol has been examined at low excess temperature. A responsivity of 3.6 volts/calorie was measured with signal accuracy 1 μV.

Pyroelectric anemometers: preparation and flow velocity measurements

A new class of pyroelectric anemometers is described based on a thin, narrow NiCr film heater and two symmetric electrodes simultaneously deposited on a thin z-cut LiTaO 3 wafer. A NiCr ground plane is used on the other face. An a.c. voltage drives the heater to produce a thermal current at 2× the voltage frequency. This thermal current produces an a.c. electrical current at each electrode. The differential signal is a measure of the average temperature difference between the two electrodes. In the absence of a fluid flow velocity, U(∞), the signal is zero. When the fluid does flow, the signal is proportional to U 1 2 (∞) as expected and is proportional to the drive power squared. Flows as low as 1 cm/min in N 2 have been measured.

Effect of trimming on the structure of NiCr thin films

The exact matching of NiCr thin film resistors can be made by trimming using current pulses. The effects of current pulses -by several orders of magnitude larger than the nominal value -on the structure of the thin films were studied. The temperature rise of the thin NiCr film during trimming was monitored by a low heat capacity and time constant thin film Pt resistance thermometer, deposited over the NiCr film and separated by a 200 /~m SiO 2 insulator film. The resistance of the NiCr film changed abruptly rising its temperature above 670 K. Structural changes of the thin films deposited on a microgrid were s t id ied in situ by a transmission electron microscope during trimming. Results of experiments are described and possible processes of resistance changes ate discussed. Acta Physica .4cademiae Scientiarum Hungaricae 49, 1980

Matrix effect in SIMS analysis using an O2+ primary beam

We have observed large matrix effects in the secondary ion emission from alloys when bombarded with an O+2 beam. Binary alloys of Ni with Cr, Fe, and Cu were studied. Chromium, which reacted most strongly with oxygen, induced the largest enhancement of the Ni+ ionization probability. Iron enhanced the Ni+ ionization probability to a lesser extent, whereas copper resulted in a decrease of the Ni+ ionization probability. Ni also induced a small enhancement of the ionization probability of Cr. We find a strong correlation of the mean free energy of formation of the metal-oxide bond with the observed trends in the ionization probabilities. These matrix effects can cause artifacts in the depth profiling of metal film structures where interdiffusion at the interface leads to the formation of alloys or intermetallic compounds. This is indeed observed when interfaces of Ni–Fe and Ni–Cr films are studied by SIMS.

Resistance stabilization of Ni-Cr films by surface oxide formation

Resistance stabilization of Ni-Cr films by surface oxide formation

Systematic studies of α-particle elastic scattering and proton induced X-ray emission on NiCr thin film resistors

Systematic studies of α-particle elastic scattering and proton induced X-ray emission were conducted on NiCr films, and an accuracy of the order of 2.8% was obtained for Ni/Cr atomic ratio determination. The enhancements over the Rutherford cross-sections were determined for the mean cross-sections of 1.0–4.0 MeV α-particle elastic scattering on chromium and nickel. Deviations from Rutherford predictions are reported, and similar measurements on other selected elements are proposed. The semiempirical cross-section data of Johansson for K α X-ray production by protons were verified by measuring the nickel/chromium ratio as a function of proton energy.

Composition and temperature coefficient of resistance of Ni-Cr thin films

Thin films of Ni-Cr have previously been found to have an anomalous maximum in the temperature coefficient of resistance (TCR) values in the thickness range 100–150 Å. The region of high TCR on the higher thickness side (170–230 Å) of this maximum was studied. Films were evaporated from a given amount of the evaporant material under high vacuum ((1–8) × 10 −4 Pa) in series of depositions at 0.5–1.5 Å s −1. Their thickness-composition profiles were analysed using Auger electron spectroscopy in conjunction with sputtering and their TCR and electrical resistivity values were compared. It was shown that under certain conditions the anomalous TCR maximum could be avoided. Thinner films and films deposited at slower rates had higher resistivities and higher total contents of oxygen and carbon. Ni-Cr films of low (less than 100 ppm °C −1) TCR were obtained at all thicknesses studied when the sum of the total atomic contents of chromium, oxygen and carbon reached 50–55%. This effect is attributed to potential barriers due to chromium oxide and carbide in the grain boundary region.