No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Composition Control and its Electrical Properties of TaNx Thin Films
Abstract
TaN thin films were deposited on Al2O3 wafers by DC reactive magnetron sputtering. The composition control by nitrogen partial flux in the working gas and the electrical properties of the samples were investigated in detail. The results show that the atomic number ratio of Ta to N in the samples can be adjusted from 4 to 0.88, corresponding to the contents of N in the samples from 20 at.% to 53 at.%, by adjusting the nitrogen partial flux from 2% to 6%. The main phases in the TaNx thin films are hexagonal Ta2N, body centered cubic Ta10N and face centered cubic TaN at lower N contents (lower than 28 at.%). However, at higher N contents (higher than 28 at.%), orthorhombic Ta3N5 phase gradually precipitates out from the samples, and the hexagonal Ta2N phase disappears. When the N contents in the samples are lower than 28 at.%, the sheet resistance and resistivity of TaNx thin films are all low. With further increase of the N contents, the sheet resistance and resistivity of TaNx thin films increase sharply. The sheet resistance and the resistivity of the samples can be adjusted from 17 Omega/sq. to 77 Omega/sq., from 344 muOmega ·cm to 1030 muOmega ·cm by adjusting the nitrogen contents, respectively. When the nitrogen contents in the samples are lower than 28 at.%, the TCR of the samples is less than 50 ppm/°C. With further increase of N contents, the TCR of the samples increases sharply up to a few hundred ppm/°C.
... Within the temperature limits of BEOL processing, TaN is an effective diffusion barrier to copper, exhibits small metal diffusion into dielectrics, and displays relatively small changes in resistance when oxidized. [19][20][21] Therefore, any ILO that develops at the TaN interface is likely conductive. For the top electrode, $320 nm of Ag was used. ...
Metals with low enthalpy of oxide formation (ΔHox) are used to examine the influence of the metal/dielectric interface, in the absence of a significant interfacial layer oxide (ILO), on the voltage nonlinearity of capacitance for metal-insulator-metal capacitors. For both atomic layer deposited Al2O3 and HfO2dielectrics,Agelectrode devices show the lowest quadratic electric field coefficient of capacitance (αECC), followed in increasing order by Au, Pd, and Ni. The difference between the metals is greater for thinner dielectrics, which is consistent with increased influence of the interface. In addition, with decreasing dielectric thickness the quadratic voltage field coefficient of capacitance increases, whereas αECC decreases. It is proposed that the thickness dependencies are due to an interaction between vertical compression of the dielectric under an applied bias and the concomitant lateral expansion induced stress that is concentrated near the interface. Through this interaction, the metal interface inhibits lateral expansion of the dielectric resulting in a reduced αECC. Indeed, αECC is found to increase with the increasing lattice mismatch at the metal/dielectric interface, likely due to edge dislocations. Finally, Al, a high ΔHox metal, is found to fit the trend for Al2O3 but not for HfO2, due to the formation of a thin reduced-k ILO at the HfO2/Al interface. These results suggest that minimization of metal/dielectric lattice mismatch may be a route to ultra-low nonlinearity in highly scaled metal-insulator-metal devices.
... TaN is widely used in thin films resistors because of its strong conductivity and high melting point [1][2][3]. The applications of the diffusion barrier layer of TaN films in the microelectronics industry have improved through in-depth research. ...
Tantalum nitrides (TaN) have attracted much attention as a new material of energy exchangers in insensitive detonators, we mainly investigate its ignition law in this paper. Firstly, the paper utilizes numerical simulation to predict the influence of the substrate material, bridge zone thickness, bridge zone length and width on the ignition action. Then its reliability was verified by experiments, which provided technical support for the design of passivated pyrotechnics.
In order to reduce the ignition energy of the tantalum nitride film transducer, a new type of energy exchangers bridge area was designed in this paper, and it was fabricated by MEMS technology. The parameters of ignition voltage, ignition energy, as well as action time were tested. The experimental results showed that in terms of ignition voltage, ignition energy, and action time, the value of the energy exchangers element of the new bridge area was lower than the value of the energy exchangers element of the conventional bridge area. In addition, ignition performance can be reduced by many energy exchangers in the new bridge area.
Structure evolution and electric properties of tantalum nitride (TaN) films deposited on Al2O3-based ceramic and glass substrates by magnetron reactive sputtering were carried out as a function of the N2-to-Ar flow ratio. The TaN thin films on Al2O3-based ceramic substrates grow with micronclusters composed of numerous nanocrystallites, contains from single-phase of Ta2N grains to TaN, and exhibits high defect density, sheet resistance and negative TCR as the N2-to-Ar flow ratio continuously increases. However, the films on the glass substrates grow in the way of sandwich close-stack, contains from single-phase of Ta2N grains to TaN and Ta3N5 phases with the increase of N2-to-Ar flow ratio. These results indicate that the N2-to-Ar flow ratio and surface characteristic difference of substrates play a dominant effect on the structure and composition of the TaN films, resulting in different electrical properties for the films on Al2O3-based ceramic and the samples on glass substrates.
The authors report a power-dividing-based microwave power thin film resistor (MPTFR) that exhibits high operating frequency and high power load. The MPTFR is comprised of substrate, ground electrodes, two TaN resistive films, power dividing circuit and signal input port. The experimental results show that the voltage standing wave ratio of the MPTFR is lower than 1.6 in the band of 3.4–7.4 GHz and 8.2–9.8 GHz. The power load of the MPTFR is 200 W. The experimental data are in good agreement with the electromagnetic simulations.
The main purpose of the present microstructural analysis by transmission electron microscopy (TEM) and X-ray diffraction was to investigate whether amorphous TaN films are a potential candidate as diffusion barrier for Cu wiring used in Si devices. The TaN thin films were prepared by a sputter-deposition technique using Ar and N-2 mixed gas, and the film structure was found to be sensitive to the gas flow ratio of N-2 vs. Ar during sputtering. Polycrystalline TaN films were obtained when the N-2/(Ar+ N2) ratio was smaller than 0.10 and amorphous TaN films were obtained when the ratio was larger than 0.15. Cross-sectional TEM observations revealed that the amorphous films had columnar structure with fine grains and that nano-scaled voids segregated at the boundaries. In addition, two-layered structures were observed in the amorphous TaN films and high density of the grain boundaries was formed close to the substrate. The present results suggested that the amorphous TaN films would not have high resistance against interdiffusion between two different materials because the density of grain boundaries with small voids was extremely high.
It has been shown that single-phase α-Ta, β-Ta, Ta2N, TaN(f.c.c.) and Ta3N5 films can be produced by chemical vapour deposition (CVD). The structure of the microcrystalline deposits has been investigated by transmission electron microscopy.Electrical measurements reveal that the resistivities of CVD films are comparable with those of sputtered films. However, the temperature coefficient of resistivity (TCR) of β-Ta, Ta2N and TaN(f.c.c.) is positive, varying between 30 and . In the case of Ta3N5 the TCR is negative and the resistivity has a value of about 6 μ cm.
The effects of processing parameters on the properties of tantalum nitride thin films deposited by radio frequency reactive sputtering have been investigated. The influence of the N2 partial and (Ar+N2) total gas pressures as well as the sputtering power on the microstructure and electrical properties is reported. Rising the N2 partial pressure, from 2 to 10.7%, induces a change in the composition of the δ-TaN phase, from TaN to TaN1.13. This composition change is associated with a drastic increase of the electrical resistivity over a 7.3% N2 partial pressure. The total gas pressure is revealed to strongly affect the film microstructure since a variation in both composition and grain size is observed when the gas pressure rises from 6.8 to 24.6Pa. When the sputtering power varied between 50 and 110W, an increase of the grain size related to a decrease of the electrical resistivity is observed.
Tantalum nitride thin films were deposited by radio frequency (RF) reactive sputtering at various N2/Ar gas flow ratios and working pressures to examine the change of their electrical resistivity. From the X-ray diffraction (XRD) and four-point probe sheet resistance measurements of the TaNx films, it was found that the change of the crystalline structures of the TaNx films as a function of the N2 partial pressure caused an abrupt change of the electrical resistivity. When the hexagonal structure TaN thin films changed to an f.c.c. structure, the sheet resistance increased from 16 Ω/sq to 1396 Ω/sq. However, we were able to control the electrical resistivity of the TaN thin film in the range from 69 Ω/sq to 875 Ω/sq, with no change in crystalline structure, within a certain range of working pressures. The size of the grains in the scanning electron microscopy (SEM) images seemed to decrease with the increase of working pressure.
TaN–Cu nanocomposite thin films used as materials for TFR (thin film resistor) were prepared by reactive co-sputtering of Ta and Cu in the plasma of N2 and Ar. After deposition, the films were annealed using rapid thermal processing (RTP) at 400 °C for 2, 4, 8 min, respectively to induce the nucleation and grain growth of Cu. The results reveal that temperature coefficient of resistivity (TCR) values will increase with the increase of Cu content for both the as-deposited and annealed films. The increase of nitrogen will result in higher resistivity and more negative TCR. At a constant nitrogen flow rate, the resistivity and TCR may increase or decrease with the increase of annealing time depending on the Cu content. In general, to reach near-zero TCR value, more copper is needed to compensate the negative effect caused by Ta–N. Thus, electrical properties of thin films can be characterized as functions of N2 flow rate, Cu concentration and annealing time.
Tantalum nitride thin films were deposited on AlN substrates at room temperature with an nitrogen/argon flow ratio (N2/(N2 + Ar)) of 3% by dc-magnetron sputtering technique, and then were annealed at 525 °C in 6.7 × 10−4 Pa. The microstructural and electrical properties of the films were investigated as a function of film thickness. The crystallinity of the films decreased with decreasing film thickness and the sheet resistance of 50 nm-thick tantalum nitride films is approximately 80 Ω/□ suitable for 10 dB application in π-type attenuators. The TCR values increase positively with increasing the thickness and 50 nm thick films exhibit a near-zero TCR value of approximately −6 ppm/K.
Novel bilayer TaN film has been developed using reactive ion DC sputtering. The film has a low resistivity of $80 lX-cm and is more stable compared with high resistivity films with high nitrogen flow rates. Low angle X-ray diffraction results show that the low resistivity TaN film is highly crystallized than that of each individual film deposited in the bilayer design. The crystalline structure and the film resistivity of the bilayer TaN film remain unchanged even when the thickness of each layer is changed, indicating large process window, that is critical for high volume manufacturing.
The aim of this work was to evaluate tantalum nitride thin films fabricated using reactive sputtering with adjusted deposition parameters. Thin TaxN films were deposited reactively on Si wafers using reactive RF magnetron sputtering at various N2/Ar gas ratios. The films were investigated by four-point probe sheet resistance measurement, profilometry, X-ray diffraction, scanning electron microscope, 2 MeV 4He+ backscattering spectroscopy, and atomic force microscopy. As the amount of nitrogen was increased, the phases in the as-deposited films were identified as β-Ta, Ta2N (5% N2-flow), hexagonal TaN (10% N2-flow) and f.c.c.-TaN (15% N2-flow) with resistivities of 166 μΩ cm, 234 μΩ cm, 505 μΩ cm and 531 μΩ cm, respectively. Only the phase obtained at 5% N2-flow showed a reasonable uniformity over the wafer suggesting suitability as thin film resistors. The value of temperature coefficient of resistance (TCR) determined for the Ta2N thin film resistor was −103 ppm/°C.
Electrical and structural properties of tantalum nitride films, deposited on GaAs substrates by a d.c. magnetron sputtering technique at different nitrogen partial pressures for use as resistors in integrated circuits, have been reported. Sheet resistivity measurements indicate that stoichiometric TaN films with stable resistivity values can be obtained if the nitrogen partial pressure is maintained between 10.5 and 20.6%. Structural properties studied using X-ray diffraction indicate the presence of pure Ta, TaN, Ta3N5 or a mixture of Ta–N phases in the films depending on the amount of nitrogen in the sputtering gas. The temperature coefficient of resistivity measured for the films deposited with the nitrogen partial pressure around 13% showed a stable value of −200 ppm K−1. Fabricated TaN thin-film resistors showed resistance values within ±10% of the designed value, suggesting the possibility of integrating these resistors with devices.
Ta/Ta–N multilayer has been developed to control temperature coefficient of resistance (TCR) in a thin-film embedded resistor with the incorporation of Ta layer (+ TCR) inserted into Ta–N layers (− TCR). Electrical and structural properties of sputtered Ta, Ta–N and the multilayer films were investigated. The stable resistivity value of 0.0065 Ω·cm in β-Ta film was obtained, and phase change from fcc-TaN to orthorhombic Ta3N5 in Ta–N films was observed at nitrogen partial pressure of 22%. The multilayer of Si/Ta(60 nm)/Ta3N5(104 nm)/Ta(60 nm)/Ta3N5(104 nm) showed TCR value of − 284 ppm/K, where TCR of Ta was − 183 ppm/K and that of Ta3N5 was − 3193 ppm/K.
TAN resistors are commonly used in RFIC applications and are gaining acceptance in traditional CMOS designs. TAN materials, frequently used in fabrication of Cu interconnects can easily be applied to the fabrication of thin film resistors. Deposition and integration of the films may be well controlled to produce a high precision resistor, and the temperature coefficient of resistance (TCR) characteristics of the film make it ideally suited for application across a large temperature range. While the time zero characteristics of the device are well understood, of equal importance are the device reliability properties. In this paper traditional film characteristics such as resistance distributions and TCR characteristics are presented. A voltage ramp stress is employed to identify the critical current A constant voltage stress at high temperature is utilized for reliability evaluation. Based on the stress results, a reliability degradation model is derived to express the relationship between stress condition, resistance change, and lifetime. The results demonstrate that the TAN thin film resistor is reliable over traditional IC operating ranges. While TAN resistors are robust, application conditions of the resistor typically result in significant resistive joule heating. The joule heating effects on the resistor are included in the resistor degradation model. The effects of the joule heating on reliability for neighboring structures must also be considered. The effective result is that the maximum allowed use current of the resistor might be dictated by the resistive joule heating and not necessarily the resistor reliability itself. The effect of the joule heating on neighboring structures is a subject itself and will not be covered in this paper.