Polarization Effects in Polyimides

Samuelson, Gary L.; Lytle, S.

doi:10.1149/1.2115390

Cited by 8 publications

(8 citation statements)

References 5 publications

(9 reference statements)

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“…Although it was reported that absorbed moisture in the polymer film might yield dielectric moisture polarization, we did not observe any evidence regarding the anomalous C-V hysteresis and increased capacitance ͑or k values͒. 8,20 Accordingly, the stress induced dielectric polarization bound charges in the bulk of dielectric layers may be reasonably presumed to be responsible for the large shift of the C-V curves. ͑Thermal oxide and USG do not exhibit polarization.͒ These bound charges orientated themselves under the influence of the electric field and could be characterized by a shift of the C-V curve in the same direction as that due to mobile ions.…”

Section: Resultscontrasting

confidence: 67%

“…This result may imply that either many mobile ions ͑but not Cu ions͒, or stress induced polarization bound charges, inherently reside in the polymer structure. 8,[16][17][18][19][20][21][22][23][24] A trace of elements ͑such as sodium͒ at a concentration of less than 10 10 cm Ϫ2 was detected in the studied samples from both XPS and TXRF analyses. However, this concentration is two orders of magnitude less than that necessarily required to produce the observed C-V curve shifts.…”

Section: Resultsmentioning

confidence: 99%

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Dielectric and Barrier Properties of Spin-On Organic Aromatic Low Dielectric Constant Polymers FLARE and SiLK

Shiung

et al. 2001

J. Electrochem. Soc.

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This work investigates the dielectric and barrier properties of two species of organic aromatic low dielectric constant ͑low-k͒ polymers, namely, FLARE and SiLK. Experimental results indicate that both of the low-k polymers exhibit acceptable thermal stability with respect to a thermal annealing at 400°C for 8 h in an N 2 ambient. Moreover, they show a good dielectric barrier property against Cu penetration under bias-temperature stressing ͑BTS͒ at 150°C with an applied effective field of 0.8 MV/cm. Nevertheless, an anomalous instability of the capacitance-voltage curve was observed for the first time under BTS. This finding is explained by the proposed model of stress induced dielectric polarization charges within these organic aromatic polymers. The polarization instability may seriously degrade the long term reliability of circuit operations.Interconnect wire parasitics ͑wire resistance R and intra/interlevel capacitance C͒ at 0.18 m begins to dominate not only the overall device delay but also the packing density, reliability, and manufacturing cost of integrated circuits ͑ICs͒. 1 The RC time delay must be reduced by using new materials to alleviate the problem of achieving high performance ultralarge-scale integrated ͑ULSI͒ circuits without compromising the requirements of driving speed, crosstalk tolerance, and dynamic power dissipation imposed by the small feature sizes. 2 The substitution of Cu for Al and its alloys leads to lower electrical resistivity and superior electro/stressmigration resistance, as compared to the conventional Al-based metallization scheme. However, dielectrics with low dielectric constants ͑low-k͒ must be used to reduce the parasitic capacitance, which is dominated by the interline capacitance component in long parallel lines. 3 Therefore, the process integration of Cu-based metallization and low-k dielectrics has been eagerly pursued in the prevalent Cu dual damascene architecture.Although Cu interconnects originally offered the promise of 30% faster devices with fewer metal levels and a lower cost of production, attaining high device yields on chips with Cu interconnects remains the greatest challenge, making low-k the key enabler for high performance. 4 Low-k (kϽ3.0) dielectrics are currently being actively developed and present substantial challenges on both organic ͑carbon-based͒ and inorganic (SiO 2 -based͒ materials using either spin-on ͑SO͒ or chemically vapor deposited techniques. Among various organic polymers, such as fluorinated amorphous carbon, fluorinated polyimides, poly͑arylene ether͒, and benzocyclobutene, aromatic polyether polymers have recently attracted much attention. 1,4,5 These polymers are known to possess a better thermal and mechanical stability than aliphatic polymers, resulting in improved compositional, dimensional, and topographical integrity over continuous high temperature thermal cycles. Moreover, although the integration issues concerning Cu and various low-k dielectrics have been widely addressed, most of those investigations focused on the pure...

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Section: Resultscontrasting

confidence: 67%

Section: Resultsmentioning

confidence: 99%

Dielectric and Barrier Properties of Spin-On Organic Aromatic Low Dielectric Constant Polymers FLARE and SiLK

Shiung

et al. 2001

J. Electrochem. Soc.

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“…Results reported here are of potential relevance for applications of polyimides. For example, the kinds of electrochemical phenomena described here may be involved in capacitive polarization phenomena (4). Moreover, the simultaneous transport of ions and electrons can provide totally new ways to exploit or modify the material.…”

mentioning

confidence: 99%

Electrochemistry of Aromatic Polyimides

Mazur

Lugg

Yarnitzky

1987

J. Electrochem. Soc.

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Polyimides derived from condensation of pyromellitic dianhydride with various diamines have been shown to be electrochemically active. Films of these materials coated on the surface of solid electrodes, immersed in electrolyte solutions of dipolar aprotie solvents undergo two distinct reversible redox processes, involving addition of one or two electrons per repeat unit. These processes can be carried out completely and stoichiometrically for films as thick as 20 ~m. Spectrophotometric studies and comparison with model compounds lead to the following conclusions: (i) ion permeability, which is a necessary component of the electrochemical charging and discharging processes, is related to solvent swelling and is, in turn, strongly influenced by the physical history of the polymer, (ii) redox activity involves localized molecular electronic states of the pyromellitic diimide group, (iii) there is no evidence for electronic interactions between pyromellitimide groups along a given polymer chain, and (iv) spectroscopic evidence indicates that weak interactions within the bulk of the polymer give rise to detectable inhomogeneities in optical or electrochemical properties of individual functional groups as a function of the charge on groups in their environment.

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“…This ensures that the exposed Cu electrodes do not oxidize during heating, and that the polymer films do not take up moisture throughout the testing sequence. Ambient moisture can readily be absorbed by a low-κ polymer film to increase polarization in the dielectric and give rise to anomalous C−V hysteresis [24] and increased capacitance [21]. For this reason, the capacitors are annealed at 200°C for 12 hours after being loaded into the test enclosure to dehydrate the low-κ polymer prior to any measurement or stressing.…”

Section: Electrical Testingmentioning

confidence: 99%

Evaluation of Copper Penetration in Low-κ Polymer Dielectrics by Bias-Temperature Stress

et al. 1999

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The industry is strongly interested in integrating low-κ dielectrics with Damascene copper. Otherwise, with conventional materials, interconnects cannot continue to scale without limiting circuit performance. Integration of copper wiring with silicon dioxide (oxide) requires barrier encapsulation since copper drifts readily in oxide. An important aspect of integrating copper wiring with low-κ dielectrics is the drift behavior of copper ions in these dielectrics, which will directly impact the barrier requirements and hence integration complexity.This work evaluates and compares the copper drift properties in six low-κ organic polymer dielectrics: parylene-F; benzocyclobutene; fluorinated polyimide; an aromatic hydrocarbon; and two varieties of poly(arylene ether). Copper/oxide/polymer/oxide/silicon capacitors are subjected to bias-temperature stress to accelerate penetration of copper from the gate electrode into the polymer. The oxide-sandwiched dielectric stack is used to overcome interface instabilities occurring when a low-κ dielectric is in direct contact with either the gate metal or silicon substrate. The copper drift rates in the various polymers are estimated by electrical techniques, including capacitance-voltage, current-voltage, and current-time measurements. Results correlate well with timeto-breakdown obtained by stressing the capacitor dielectrics. Our study shows that copper ions drift readily into fluorinated polyimide and poly(arylene ether), more slowly into parylene-F, and even more slowly into benzocyclobutene. A qualitative comparison of the chemical structures of the polymers suggests that copper drift in these polymers may possibly be retarded by increased crosslinking and enhanced by polarity in the polymer.

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Polarization Effects in Polyimides

Abstract: not Available.

Cited by 8 publications

References 5 publications

Dielectric and Barrier Properties of Spin-On Organic Aromatic Low Dielectric Constant Polymers FLARE and SiLK

Dielectric and Barrier Properties of Spin-On Organic Aromatic Low Dielectric Constant Polymers FLARE and SiLK

Electrochemistry of Aromatic Polyimides

Evaluation of Copper Penetration in Low-κ Polymer Dielectrics by Bias-Temperature Stress

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