Effect of moisture adsorption on the properties of porous-silica ultralow-k films

Uchida, Yoko; Hishiya, S.; Fujii, Nobutoshi; Kohmura, Kazuo; Nakayama, Takahiro; Tanaka, Hirofumi; Kikkawa, Takamaro

doi:10.1016/j.mee.2006.09.018

Cited by 39 publications

(22 citation statements)

References 8 publications

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“…Cu diffusion and migration in the ILD has been attributed to numerous reliability issues in both interconnects 40,41 and transistors. 42 Moisture penetration into the low-k ILD has also been well documented to contribute to a range of reliability issues including an increase in dielectric constant, 43,44 moisture assisted cracking [45][46][47] and delamination, [47][48][49][50] and degraded electrical reliability (CV stability, leakage, TDDB, and V bd ). [51][52][53] These problems are further exacerbated by the fact that downstream patterning and metallization processes can damage the low-k ILD via breaking bonds, removing terminal organic groups, and densifying the film.…”

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confidence: 99%

Film Property Requirements for Hermetic Low-k a-SiO_xC_yN_z:H Dielectric Barriers

King

Jacob

Vanleuven

et al. 2012

ECS J. Solid State Sci. Technol.

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Continued reduction in resistance-capacitance (RC) delays in nano-electronic Cu interconnect structures will require new materials with increasingly lower dielectric constants (i.e. low-k). Significant reductions in RC delay can be achieved by reducing the dielectric constant of the relatively high dielectric constant Cu capping/etch stop layer. However, this risks comprising the required barrier performance of this material to the diffusion of Cu, H 2 O, and other species. In this regard, critical thresholds for the diffusion of water and solvents through low-k a-SiO x C y N z :H dielectrics of varying composition were investigated using a combination of X-ray reflectivity mass density and positronium annihilation lifetime spectroscopy pore size metrologies. It was observed that hermetic low-k a-SiO x C y N z :H dielectrics were achieved only at mass densities >2.0 g/cm 3 and when the pore diameter was less than twice the molecular diameter of water. The implications of these critical nano-porosity thresholds on continued scaling of low-k diffusion barrier and ILD materials are discussed as well as methods for overcoming these limitations.

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confidence: 99%

Film Property Requirements for Hermetic Low-k a-SiO_xC_yN_z:H Dielectric Barriers

King

Jacob

Vanleuven

et al. 2012

ECS J. Solid State Sci. Technol.

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“…16 The IR absorption band centered ∼3430 cm −1 can be assigned to Si-OH stretching vibration of silanol groups in SiOCH low-k materials. 20 In Figure 3a, an additional 60 sec over-etch in the post-strip step causes an 80% increase of the Si-OH absorption peak height at 3430 cm −1 . This MIR-IR data suggests that the more aggressive plasma chemistry required to strip organic residues also tends to disrupt Si-CH 3 bonds and results in undesirable moisture-adsorbing silanol groups.…”

Section: Resultsmentioning

confidence: 97%

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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“…This band corresponds to -OH ͑H 2 O͒ absorbance ͑3200-3800 cm −1 ͒. 8,9,[17][18][19] Uchida et al 17 studied this region in detail and they decomposed it into three contributions: Si-OH with a H bond due to chemically absorbed H 2 O, isolated Si-OH ͑without an accompanying H bond͒, and H 2 O. However, we could not observe a peak ͑3740 cm −1 ͒ of the isolated Si-OH.…”

Section: Ftir Measurements-mentioning

confidence: 66%

Paramagnetic Defect Generation and Microstructure Change in Porous Low-k SiOCH Films with Vacuum Baking

Tanbara

Kamigaki

2010

J. Electrochem. Soc.

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We studied in detail the paramagnetic defect generated in the porous low-k SiOCH films, which is called the T b center with the oxygen-carbon mixed back bonds. We baked the SiOCH films in vacuum from 600 to 1000°C, which could correspond to temperature elevation at a local area in cases of UV or electron-beam curing and Joule heating in circuits. The amount of the T b center increased abruptly around 775°C by electron spin resonance spectroscopy, at which we observed 30% volume shrinkage by ellipsometry and network change from a cage link to a ring link by Fourier transform IR spectroscopy. These phenomena might be due to the crush of microholes wrapping Si-CH 3 end groups. Therefore, we consider that the generation of the T b center suggests the quality change of the porous low-k SiOCH films for the ultralarge-scale integration reliability.As device densities increase in ultralarge-scale integration ͑ULSI͒ semiconductor chips, the signal propagation delay in multilevel interconnects becomes more critical for device performance. SiOCH films ͑silicon oxide containing hydrocarbon groups, k = 3.0͒ have been used for the low-dielectric-constant ͑low-k͒ dielectrics of the most advanced ULSI interconnects because of their high compatibility with the silicon process. 1 Recently, the nanometer level pores in a SiOCH film have been introduced to reduce k ͑Ͻ2.7͒. 2 The porous low-k SiOCH films have a lower mechanical strength than the conventional dielectric films. So, the porous SiOCH films were cured by UV light exposure or electron-beam ͑EB͒ irradiation to enhance mechanical strength. 3,4 However, the defects, called the T b centers having oxygen-carbon mixed back bonds, can be generated in the porous SiOCH films by excess UV/EB curing. 3,5-7 The generation of paramagnetic defect ͑T b center͒ is thought to be one of the ULSI interconnect reliability issues. In this work, we investigated in detail the behavior of the T b center in the porous low-k SiOCH films using vacuum baking instead of UV/EB curing. UV curing ͑high energy photon; about 5 eV͒ corresponds to local annealing, and vacuum baking ͑low energy phonon; at most 0.1 eV͒ corresponds to uniform annealing. Both processes are thought to give rise to the same microstructure change. We used an electron spin resonance ͑ESR͒ technique to detect the defects, ellipsometry to measure the film thickness and refractive index, and Fourier transform infrared ͑FTIR͒ spectroscopy to analyze the atomic network in the porous low-k SiOCH films. ExperimentalSample preparation.-The 500 nm thick, porous low-k SiOCH films ͑k = 2.6͒ were deposited on 300 mm ͑100͒ silicon wafers ͑10-15 ⍀ cm͒ with plasma-enhanced chemical vapor deposition. The film composition was determined to be Si:O:C:H = 1.0:1.7:0.9:2.9 by Rutherford backscattering analysis. 7 To actualize the defects in the low-k films, the samples were baked up to 1000°C in the vacuum chamber ͑15-25 Pa͒, where the samples were maintained at a certain setup temperature for 30 min and taken out below 300°C.Characterization.-The ESR m...

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Effect of moisture adsorption on the properties of porous-silica ultralow-k films

Cited by 39 publications

References 8 publications

Film Property Requirements for Hermetic Low-k a-SiO_xC_yN_z:H Dielectric Barriers

Film Property Requirements for Hermetic Low-k a-SiO_xC_yN_z:H Dielectric Barriers

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

Paramagnetic Defect Generation and Microstructure Change in Porous Low-k SiOCH Films with Vacuum Baking

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Effect of moisture adsorption on the properties of porous-silica ultralow-k films

Cited by 39 publications

References 8 publications

Film Property Requirements for Hermetic Low-k a-SiOxCyNz:H Dielectric Barriers

Film Property Requirements for Hermetic Low-k a-SiOxCyNz:H Dielectric Barriers

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

Paramagnetic Defect Generation and Microstructure Change in Porous Low-k SiOCH Films with Vacuum Baking

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Film Property Requirements for Hermetic Low-k a-SiO_xC_yN_z:H Dielectric Barriers

Film Property Requirements for Hermetic Low-k a-SiO_xC_yN_z:H Dielectric Barriers