Polishing Pad Surface Morphology and Chemical Mechanical Planarization

Castillo-Mejia, D.; Kelchner, J.; Beaudoin, Stephen P.

doi:10.1149/1.1649751

Cited by 24 publications

(22 citation statements)

References 30 publications

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“…Mechanic-based models have been widely utilized to calculate the load transferred by the particles and pad onto the wafer as a function of typical CMP parameters. [6][7][8][9][10][11][12] The influence of applied pressure, pad properties, particle size and concentration, wafer hardness, and their interactions on the MRR is also expressed.13 A wafer-level MRR model was proposed by combining a hierarchical model of the particle-wafer-pad interactions and an adhesive wear model. 14 For z E-mail: xuqinzhi@ime.ac.cn in-depth understanding the slurry flow at the wafer-pad interface, 15,16 fluid hydrodynamics with mass transport model was also developed to depict the importance of the slurry flow to the CMP process.…”

mentioning

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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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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“…However, these models did not consider the effect of pad surface roughness (asperity height distribution) on polishing removal rate. There are quite a few other publications considering the effect of pad roughness and other pad properties on polishing removal rate [21,[47][48][49][50][51][52][53][54].…”

Section: Review Of Modeling Of Pad Effects On Polishing Performancementioning

confidence: 99%

Pads for IC CMP

Wang

Paul

Kobayashi

et al. 2007

Microelectronic Applications of Chemical Mechanical Planarization

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The chemical-mechanical polishing or planarization (CMP) process is a complex interplay between the wafer and the consumables involved. The consumables include slurry, pad, conditioner, and so on. During polishing, the pad carries the slurry and delivers it to the wafer surface. It also transmits the normal and shear forces from the polisher to the wafer. Therefore, polishing pad plays a critical role in the CMP process and influences the outcomes such as material removal rate (MRR), within-wafer nonuniformity (WIWNU), wafer-to-wafer nonuniformity (WTWNU), step height reduction efficiency (SHRE), and defect counts.As the CMP process is a combination of mechanical and chemical processes, the polishing pad has to endure repeated mechanical stress and constant chemical attacks. The applied downforce and polishing-induced friction force cause various levels of compression and abrasion. Slurry components such as oxidizers and acids can react with different components of the pads. Thus the polishing pad must have sufficient mechanical integrity and chemical resistance to survive the rigors of polishing. Polishing pads must balance the needs of hardness, modulus for planarity, and strength to resist wear and tear during polishing. Pads must also be able to survive the aggressive slurry chemistry used in CMP polishing without degrading, delaminating, blistering, or warping, since CMP slurries for the polishing of interlevel dielectric (ILD) oxide layers are usually highly alkaline with pH as high as 11, and CMP slurries for the polishing of metal films are highly acidic Microelectronic Applications of Chemical Mechanical Planarization, Edited by Yuzhuo Li

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“…The roughness of a new and a brokenin CMP pad has been analyzed by other researchers (13)(14)(15), but the roughness is not as sensitive a parameter as the asperity radius of curvature for scratching Cu during CMP. Furthermore, there has been some research published on the bulk modulus of the pad (16,17), but the methods used to determine the modulus have been on the macro-scale and they do not provide the statistical variations in the modulus measured at the nano-scale. Figure 3 shows a schematic of a pad in contact with a Cu coating during CMP.…”

Section: Introductionmentioning

confidence: 99%

Breaking-In a Pad for Scratch-Free, Cu Chemical-Mechanical Polishing (CuCMP)

Eusner¹,

Saka²,

Chun³

2010

ECS Trans.

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This paper presents a quantitative analysis of the topography and material properties of new and broken-in CMP pads. Approximately 50 Cu wafers were polished under typical CMP conditions to break-in the pad. The changes in material properties were measured using a Hysitron TriboIndenter and the changes in the topography of the pad were measured using a Tencor P-10 Profilometer.Additionally, SEM micrographs are presented to show the qualitative difference between broken-in and new pad surfaces. Polishing 56 Cu wafers decreased the average pad modulus from 0.66 GPa to 0.34 GPa and the average pad hardness from 0.05 GPa to 0.03 GPa. Furthermore, as a result of breaking-in the pad, the average asperity radius of curvature increased from 16 μm to 93 μm. The increase in the pad asperity radius of curvature decreased the severity of scratching.

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Polishing Pad Surface Morphology and Chemical Mechanical Planarization

Cited by 24 publications

References 30 publications

A Material Removal Rate Model for Aluminum Gate Chemical Mechanical Planarization

A Material Removal Rate Model for Aluminum Gate Chemical Mechanical Planarization

Pads for IC CMP

Breaking-In a Pad for Scratch-Free, Cu Chemical-Mechanical Polishing (CuCMP)

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