Brittle and Ductile Fracture Mechanics Analysis of Surface Damage Caused During CMP

Ring, Terry A.; Feeney, Paul; Boldridge, David; Kasthurirangan, Jaishankar; Li, Shoutian; Dirksen, James A.

doi:10.1149/1.2426877

Cited by 45 publications

(30 citation statements)

References 15 publications

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“…25 Average contact pressure at the onset of surface layer yielding.-For frictionless or low frictional contact (0 ≤ μ < 0.3), the maximum shear stress, τ max , for the Hertzian traction distribution is below the surface and the normalized maximum shear stress, τ max /p a , is given by 27 τ max p a = 0.46 ∼ = 0.5 [ 7 ] By the Tresca yield criterion, the surface layer will yield if the maximum shear stress reaches half the yield strength, σ y,l . Thus, the average contact pressure at the onset of surface layer yielding, p s , under elastically deformed asperity will be p s = σ y,l if 0 ≤ μ < 0.3 [ 8 ] As friction increases, however, the location of maximum shear stress will no longer be below the surface but rapidly rises to the surface. It has been shown by Hamilton and Goodman that if the coefficient of friction is greater than 0.3, the location of the maximum von Mises stress also moves to the surface.…”

Section: Pad Scratching Models: Single-asperity Sliding Contactmentioning

confidence: 99%

Pad Scratching in Chemical-Mechanical Polishing: The Effects of Mechanical and Tribological Properties

Kim

Saka

Chun

2014

ECS J. Solid State Sci. Technol.

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In chemical-mechanical polishing (CMP), even the soft pad asperities may, under certain conditions, generate scratches on the relatively hard surfaces being polished. In the present study, contact mechanics models of pad-induced scratching are formulated, and the effects of the hardness of the surface layers and of pad asperities as well as the interfacial friction are elucidated. Additionally, scratch-regime maps are proposed to provide criteria for scratching hard surface layers by the softer pad asperities. Furthermore, scratching indexes are introduced to predict the proportion of asperities in contact that are likely to scratch. The contact mechanics models of scratching have been validated by sliding experiments with two commercial CMP pads (Pad A and IC1000) and various thin-films (Al, Cu, SiO 2 , Si 3 N 4 , TiN and three low-k dielectrics) using deionized water as a "lubricant." Both the theoretical models and the experimental results show that the number of scratches increases as the scratching index exceeds 0.33. Al and Cu layers are found to be more susceptible to pad scratching due to their low hardness and high interfacial friction. The scratch-regime maps provide practical guidelines for mitigating pad scratching in CMP. Chemical-mechanical polishing (CMP), which employs both chemical and mechanical means to remove material from solid surfaces, is a planarization/polishing process. The CMP process is widely used in the manufacture of integrated circuits (IC), computer hard disks, optical glass, and micro-electromechanical systems (MEMS).1-5 Despite its universal usage, a persistent problem in CMP is the scratching of the surfaces being polished. As demands for metal interconnects and surface structures are becoming ever more stringent in integrated circuits, micro-and nano-scale scratching during CMP has lately emerged as a critical problem. 6-8The CMP process is carried out by rotating a wafer over a polishing pad under pressure, while chemical slurry containing hard, abrasive particles is provided at the wafer/pad interface. The basic mechanism of material removal in CMP is by "fine scratching" at the nano-scale by the abrasive particles.9-12 The nano-sized particles, 50-300 nm in diameter, "plow" the surface layer softened by chemical reactions. Such nanometer-scale scratches produce smooth, flat surfaces and thus are preferred.During the polishing process, however, the small abrasive particles may agglomerate due to inter-particle attraction, fluctuations in slurry delivery, and so on. Scratches generated by the agglomerated particles are termed surface defects, and the width of the scratches so generated is an order of magnitude greater than that of the scratches created by individual particles. The abnormally large, hard particles, which may cut the metal interconnects in IC chips and cause malfunctioning of the microelectronic devices, have generally been considered the primary sources of scratching.13-18 To minimize particle agglomeration, and thus mitigate particle-induced scratching, part...

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Section: Pad Scratching Models: Single-asperity Sliding Contactmentioning

confidence: 99%

Pad Scratching in Chemical-Mechanical Polishing: The Effects of Mechanical and Tribological Properties

Kim

Saka

Chun

2014

ECS J. Solid State Sci. Technol.

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“…However, several defects induced by CMP depend on the type of surface being polished. This may be attributed to the effects of various chemicals and abrasive particles as well as the pressure exerted on the wafer surface [7,29]. Defects typically formed during the CMP process include organic residues [29], water marks [30], particle adherence and impingement [31], corrosion pit, and scratches [30,31].…”

Section: Scratch Issues In Cmp Processmentioning

confidence: 99%

“…This may be attributed to the effects of various chemicals and abrasive particles as well as the pressure exerted on the wafer surface [7,29]. Defects typically formed during the CMP process include organic residues [29], water marks [30], particle adherence and impingement [31], corrosion pit, and scratches [30,31]. However, the removal of organic residues and water mark formation are trivial in oxide CMP, but other types of defects, such as scratch formation, are critical, as they affect the yield and reliability of the devices [32].…”

Section: Scratch Issues In Cmp Processmentioning

confidence: 99%

“…Furthermore, Ring et al [29] reviewed the mechanical properties and fracture mechanics of materials in order to understand the surface damage caused during CMP. The resulting failure was predicted by various mechanical wear (or scratching) equations depending upon the assumption of plastic deformation or brittle fracture (Fig.…”

Section: Fig 33mentioning

confidence: 99%

“…Furthermore, the repetitive C-shaped surface showed damage that is tens of nm deep with some individual cracks that were deeper than others, in atomic force microscope (AFM) images. Ring et al [29] explained this phenomenon based on bouncing particle model. The springiness of the pad causes the particle to bounce against the wafer surface.…”

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Scratch formation and its mechanism in chemical mechanical planarization (CMP)

2013

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Chemical mechanical planarization (CMP) has become one of the most critical processes in semiconductor device fabrication to achieve global planarization. To achieve an efficient global planarization for device node dimensions of less than 32 nm, a comprehensive understanding of the physical, chemical, and tribo-mechanical/chemical action at the interface between the pad and wafer in the presence of a slurry medium is essential. During the CMP process, some issues such as film delamination, scratching, dishing, erosion, and corrosion can generate defects which can adversely affect the yield and reliability. In this article, an overview of material removal mechanism of CMP process, investigation of the scratch formation behavior based on polishing process conditions and consumables, scratch formation mechanism and the scratch inspection tools were extensively reviewed. The advantages of adopting the filtration unit and the jet spraying of water to reduce the scratch formation have been reviewed. The current research trends in the scratch formation, based on modeling perspective were also discussed.

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Investigation of Source-Based Scratch Formation During Oxide Chemical Mechanical Planarization

et al. 2013

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Brittle and Ductile Fracture Mechanics Analysis of Surface Damage Caused During CMP

Cited by 45 publications

References 15 publications

Pad Scratching in Chemical-Mechanical Polishing: The Effects of Mechanical and Tribological Properties

Pad Scratching in Chemical-Mechanical Polishing: The Effects of Mechanical and Tribological Properties

Scratch formation and its mechanism in chemical mechanical planarization (CMP)

Investigation of Source-Based Scratch Formation During Oxide Chemical Mechanical Planarization

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