How to evaluate surface free energies of dense and ultra low-κ dielectrics in pattern structures

Oszinda, Thomas; Schaller, Μ.; Dittmar, Kornelia; Jiang, Le; Schulz, Stefan E.

doi:10.1016/j.mee.2010.06.008

Cited by 5 publications

(2 citation statements)

References 16 publications

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“…2 Other characterization techniques can also yield information about plasma induced damage to low-k materials. [3][4][5][6] These methods, however, are most effective for blanket wafers. Thus, there is a pressing need for a convenient metrology to identify and quantify the damage on the side walls of dielectric trench structures from plasma processing such as photoresist stripping.…”

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confidence: 99%

Evaluation of Plasma Damage to Low-k Dielectric Trench Structures by Multiple Internal Reflection Infrared Spectroscopy

Rimal

Mukherjee

Abdelghani

et al. 2013

ECS Solid State Letters

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Plasma induced damage on a ∼68 nm low-k dielectric trench structure was evaluated and correlated to each plasma processing step using multiple internal reflection infrared spectroscopy (MIR-IR) complemented by XPS and SEM. The plasma stripping process causes significantly more Si-OH and C=O chemical bonding formation and breakage of Si-CH 3 bonds in porous low-k trench structure. Formation and removal of fluorocarbon post-etch residues can be monitored using the IR absorption band at 1530-1850 cm −1 . The Si-OH content provided by MIR-IR metrology can function as a sensitive and reliable quantitative metric for the rapid assessment of plasma induced dielectric damage.Plasma etch damage is the main cause of dielectric degradation of porous low-k materials during fabrication of advanced Cu/low-k interconnects. Highly energetic ions, reactive radicals and vacuum ultraviolet radiation generated during plasma etching have been shown to break Si-CH 3 bonds and form Si-OH (silanol) bonds on the top layer of organosilicate (SiOCH) glass low-k materials. 1 These surfaceanchored silanol groups readily adsorb water (ε ∼80) degrading the effectiveness of the low-k materials. Although electrical characterization (e.g. reliability and leakage current measurements) of fully processed interconnects can reveal dielectric degradation, these methods are costly and cannot pinpoint any particular process causing the damage. 2 Other characterization techniques can also yield information about plasma induced damage to low-k materials. 3-6 These methods, however, are most effective for blanket wafers. Thus, there is a pressing need for a convenient metrology to identify and quantify the damage on the side walls of dielectric trench structures from plasma processing such as photoresist stripping.In this study, we utilized multiple internal reflection infrared spectroscopy (MIR-IR) to monitor water adsorption, carbon stripping and post-etch residues during the formation of trench structures in low-k dielectric materials via plasma etch and strip processes. Fourier transform infrared spectroscopy (FTIR), a fast and non-contact metrology, can provide direct observation of water adsorption and the chemical bonding structure of blanket porous low-k dielectric materials. Recently, applications of FTIR to characterize patterned dielectric wafer were reported. 7-9 MIR-IR spectroscopy can increase detection sensitivity up to 100-fold compared with conventional FTIR because the wafer itself serves as an IR waveguide allowing for multiple detections. 10,11 In this work, a test pattern of ∼68 nm trenches with 128 nm pitch was created through oxide hard mask plasma etching followed by organic residue stripping. Damage to the dielectric in terms of silanol formation was quantified and correlated to each plasma processing step using MIR-IR complemented by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM).

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confidence: 99%

Evaluation of Plasma Damage to Low-k Dielectric Trench Structures by Multiple Internal Reflection Infrared Spectroscopy

Rimal

Mukherjee

Abdelghani

et al. 2013

ECS Solid State Letters

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“…More details on this method and to the application for ULK films are given in recent publications. [30][31][32] According to Wenzel and Cassie, differences in surface roughness can lead to different contact angles for the same surface and hence influence the calculation of the surface free en-ergy by contact angle measurements. 33,34 Since the total roughness for the pristine, the plasma treated, and silylated samples are with roughness of R rms of 0.5 Ϯ 0.1 nm marginal, it can be assumed that the influence of the topography on the contact angle measurement can be neglected, especially since the error of contact angle measurement is very high.…”

Section: Resultsmentioning

confidence: 99%

Chemical Repair of Plasma Damaged Porous Ultra Low-κ SiOCH Film Using a Vapor Phase Process

Oszinda

Schaller

Schulz

2010

J. Electrochem. Soc.

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A vapor phase based silylation process was used to restore plasma damaged porous ultra low-κ SiOCH dielectric films. The process was carried out with 11 different silylation agents. After the processing of blanked wafers, the restoration performance was analyzed by different analytic techniques such as Fourier infrared and Auger electron spectroscopy as well as contact angle, ellipsometric porosimetry, and mercury probe measurements. Quantum mechanic calculations and practical results suggest three repair chemicals having two reactive groups to be most promising. However, a comparable electrical improvement, i.e., κ-value improvement, was achieved with chemicals having one reactive group. The removal of water during the high temperature silylation process is suggested to be the main contributor to the κ-value improvement. The recovery of the surface free energy inhibits or retards water from returning after the silylation process. The chemicals with two reactive groups providing the highest degree of silylation are found to be most appropriate for ultra low-κ dielectric (ULK) recovery. But, depending on the requirement for ULK restoration (e.g., κ-value, surface recovery, etc.), chemicals having one reactive group can be sufficient as well.

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A plasma assisted in situ restoration process for sidewall damaged ULK dielectrics

Koehler

Fischer

Zimmermann

et al. 2016

Microelectronic Engineering

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How to evaluate surface free energies of dense and ultra low-κ dielectrics in pattern structures

Cited by 5 publications

References 16 publications

Evaluation of Plasma Damage to Low-k Dielectric Trench Structures by Multiple Internal Reflection Infrared Spectroscopy

Evaluation of Plasma Damage to Low-k Dielectric Trench Structures by Multiple Internal Reflection Infrared Spectroscopy

Chemical Repair of Plasma Damaged Porous Ultra Low-κ SiOCH Film Using a Vapor Phase Process

A plasma assisted in situ restoration process for sidewall damaged ULK dielectrics

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