Prediction of scratch generation in chemical mechanical planarization

Chandra, Abhijit; Karra, Pavan; Bastawros, Ashraf F.; Biswas, Rana; Sherman, Peter; Armini, Silvia; Lucca, D.A.

doi:10.1016/j.cirp.2008.03.130

Cited by 66 publications

(52 citation statements)

References 8 publications

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“…27,48 The surface forces have a large effect on the agglomeration of the abrasive particles in the slurry and finally affect the removal rate. 49,50 It has been pointed out that if the particles are at their isoelectric point, the particle aggregates can grow from a nanometer to a micrometer size in a relatively short time, causing undesirable, deep scratches on the wafer surface. 27,49 Although the effects of surface forces were illustrated to contribute to MRR, only few models 8,12,27 have been developed to understand the experimental phenomena.…”

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confidence: 99%

A Material Removal Rate Model for Aluminum Gate Chemical Mechanical Planarization

Chen

2015

ECS J. Solid State Sci. Technol.

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In this work, a new aluminum gate chemical mechanical planarization (CMP) model for material removal rate (MRR) is proposed in high-k metal gate (HKMG) process. Using the basic principles of steady-state oxidation reaction and mechanical abrasion mechanism, the combinational interaction of chemical and mechanical coupled effects on MRR was systematically described by process parameters, pad properties and concentration of oxidizer, and then balanced to construct an overall polishing rate. Because of the great significance of the slurry pH on MRR in CMP process, the effects of surface forces, including the influences of van der Waals (vdW) and double-layer (DL) forces simultaneously acted between the wafer and the particles were investigated. Meanwhile, the influence of particle sizes, abrasive loadings and zeta potentials of the wafer and particles on MRR was also analyzed. It is found that the attractive vdW forces strengthen the MRR, while the DL forces, calculated to be repulsive, lower the MRR. The magnitude of surface forces increases with a smaller particle size compared with the pad-particle force. When zeta potentials of the wafer and particles are considered as a function of slurry pH, the experimental trends for the MRR with slurry pH, applied pressure and abrasive loading were predicted well by the present model. Therefore, the governing equation of aluminum removal reveals some insights into the HKMG CMP process and can be utilized for optimizing and controlling the polishing rate of aluminum gate structures and performing sensitivity analyses of operating parameters. With the steady shrinkage of the feature size and device geometry of modern integrated circuits (ICs), chemical mechanical planarization (CMP) has become the most important process choice for the surface planarization in the fabrication of advanced multilever ICs in microelectronic industry.1 A variety of materials and structures, including copper damascene metallization, oxides in shallow trench isolation (STI) and inter-level dielectrics (ILD), replacement metal gate for high-k metal gate (HKMG) structures and fin field effect transistor (FinFET) devices are polished with different slurries. [2][3][4] In CMP process, a rotating wafer with different types of design structures is pushed against a rotating polishing pad which is immersed in slurries containing chemicals and abrasive particles. Pattern structures on the wafer surface are first chemically passivated by slurry chemicals and then removed by effects of contact interactions of abrasive particles which are trapped between the pad and the wafer. The contact mechanism of the particles in the slurry provides the opportunity to remove the material from the wafer surface at an acceptable production rate. 5The material removal rate (MRR) which has been studied extensively from both a modeling and experimental standpoint depends sensitively on pattern geometry, process parameters, chemical reactions, pad properties and mechanical abrasion. If the CMP process is not properly controlled...

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A Material Removal Rate Model for Aluminum Gate Chemical Mechanical Planarization

Chen

2015

ECS J. Solid State Sci. Technol.

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“…Some sample types were tested multiple times and the results averaged together in an attempt to remove variations between trials. These trials were performed to an initial stress of 4 psi or 27.6 kPa, as this is a common normal pressure applied in CMP [8,12]. Additional trials were performed on new pad samples to view the effects of stress magnitude on the relaxation behavior of the pad material.…”

Section: Compression Stress Relaxationmentioning

confidence: 99%

“…This polishing time is based on the maximum time that a point on the pad is in contact when polishing a wafer. The conditions used in this computation were for a pad diameter of 500 mm and a wafer diameter of 200 mm that is polished for 60 seconds, as these are common specifications for CMP processes [7,8] …”

Section: Planarization Experimentsmentioning

confidence: 99%

Energy dissipation and constitutive modeling for a mechanistic description of pad scratching in chemical–mechanical planarization

Ponte

Meyer

2015

J Mater Sci: Mater Electron

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“…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][14][15][16][17][18] To minimize particle agglomeration, and thus mitigate particle-induced scratching, particle interaction models and such practical methods as magnetically levitated centrifugal pumps have been suggested and developed. 19,20 It has been recently reported, however, that scratches can also be generated without abrasive particles in the slurry, such as in "abrasivefree CMP".…”

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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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Prediction of scratch generation in chemical mechanical planarization

Cited by 66 publications

References 8 publications

A Material Removal Rate Model for Aluminum Gate Chemical Mechanical Planarization

A Material Removal Rate Model for Aluminum Gate Chemical Mechanical Planarization

Energy dissipation and constitutive modeling for a mechanistic description of pad scratching in chemical–mechanical planarization

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

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