Effects of Abrasive Size and Surfactant Concentration on the Non-Prestonian Behavior of Ceria Slurry in Shallow Trench Isolation Chemical Mechanical Polishing

Kang, Hyun−Goo; Katoh, Takeo; Park, Hyung Soon; Paik, Ungyu; Park, Jea‐Gun

doi:10.1143/jjap.44.l136

Cited by 11 publications

(16 citation statements)

References 9 publications

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“…When the applied pressure is increased, while maintaining the concentration of DADMAC, the ceria particles can penetrate through the adsorbed DADMAC layer and contact the oxide film surface. This is similar to the suggestion of Kang et al 15,16,46 and Shimono et al…”

Section: P39supporting

confidence: 93%

“…Indeed, this DADMAC layer can prevent the interaction between the oxide surface being polished and the ceria abrasives as suggested by Kang et al 15,16,26 and Shimono et al 23 Also, while the adsorption of DADMAC on ceria particles is low and can be considered weak (see below), it can lower the oxide RRs if it reduces the number of reactive species on the ceria surface.…”

Section: Dadmac Adsorption On Siomentioning

confidence: 91%

“…Kang et al 15,16 showed that varying the size (62-290 nm) of the ceria particles and the surfactant (polyacrylic acid) concentration (0-0.8 wt%) in the dispersions can alter the threshold pressure. They reported considerably high threshold pressures of ∼4.5 and ∼6 psi for ∼170 nm and ∼290 nm ceria particles respectively, below which oxide removal rate is low and above which the rate increases rapidly, but still linearly.…”

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confidence: 99%

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Ceria-Based Slurries for Non-Prestonian Removal of Silicon Dioxide Films

Korkmaz

Babu

2014

ECS J. Solid State Sci. Technol.

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A slurry with a non-Prestonian dependence on the polishing pressure can help in minimizing dishing and erosion during shallow trench isolation chemical mechanical planarization. Here, we show that ceria-based slurries containing diallyldimethylammonium chloride (DADMAC) yield a non-Prestonian blanket film polish rate with a low threshold pressure (1-2 psi) when polishing plasma-enhanced chemical vapor (PECVD) tetraethylorthosilicate (TEOS) deposited oxide as well as thermal oxide films. The polishing mechanism of this non-Prestonian slurry was investigated by a series of experiments involving zeta potential measurements, thermogravimetric analysis (TGA) and UV-vis spectroscopy and it was shown that more DADMAC molecules are adsorbed on silica particles (as oxide film representatives) than on ceria particles and the binding strength between DADMAC and silica is much higher than that with ceria surface. Shallow trench isolation (STI) is an ubiquitous complimentary metal-oxide semiconductor isolation process technology. Deposition of an isolation stack that contains 3 to 10 nm thick 1,2 thermally grown pad oxide on top of a silicon substrate followed by the deposition of either plasma-enhanced chemical vapor deposition (PECVD) or low-pressure chemical vapor deposition (LPCVD) nitride layer (10 to 30 nm) 1 is the first step in the STI process. In the next step, active areas and isolation fields are determined by patterning the silicon nitride and silicon dioxide pad layers on the silicon substrate, followed by etching of trenches into the silicon substrate using the oxide/nitride stack as a mask. The trenches are then filled with oxide, employing high density plasma-enhanced chemical vapor deposition (PECVD) process using tetraethylorthosilicate (TEOS) as the source of silicon, because of its high gap-filling capacity. The deposited oxide not only fills the trenches but also generates an overfill, which needs to be removed. This is achieved through planarization of the oxide film topography by chemical mechanical planarization (CMP) using a slurry that produces a high oxide and very low nitride removal rates (RRs).In this STI process, major concerns include dishing within the oxide features resulting from over-polish as well as the erosion of the underlying nitride film and, in some cases, the details of the corner rounding near active areas. Therefore, optimization of the CMP process is crucial in order to achieve complete removal of the oxide on top of the nitride film with good planarity and uniformity and to avoid erosion and dishing during the CMP process. 3,4 One method that can be used to minimize dishing and erosion during STI CMP is to control the polishing performance by using a slurry that shows a non-Prestonian polishing behavior. Non-Prestonian behavior occurs when there is a non-linear relationship between applied polishing pressures and resulting polishing rates. Here we consider only the effect of pressure and not that of the rotational velocity on the blanket film polish rates.Several models were di...

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Section: P39supporting

confidence: 93%

Section: Dadmac Adsorption On Siomentioning

confidence: 91%

mentioning

confidence: 99%

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Ceria-Based Slurries for Non-Prestonian Removal of Silicon Dioxide Films

Korkmaz

Babu

2014

ECS J. Solid State Sci. Technol.

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“…Dishing takes place if the oxide material inside the trenches is polished, especially at the low pressures created by contact with the polishing pad. One efficient method that can minimize dishing is to use a non-Prestonian polishing slurry [5][6][7] which causes negligible removal below a threshold applied downward pressure. Recently, it was shown that a ceria-based slurry containing 15 mM diallyldimethyl ammonium chloride (DADMAC) as an additive resulted in non-Prestonian oxide removal 7 with negligible removal below ∼2 psi applied pressure.…”

mentioning

confidence: 99%

AFM-Based Study of the Interaction Forces between Ceria, Silicon Dioxide and Polyurethane Pad during Non-Prestonian Polishing of Silicon Dioxide Films

Korkmaz

Vahdat

Trotsenko

et al. 2015

ECS J. Solid State Sci. Technol.

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A colloidal AFM-based method was used to understand the role of diallyldimethyl ammonium chloride (DADMAC) molecules in non-Prestonian silicon dioxide removal obtained using ceria-based slurries. A series of force-distance measurements between silicon dioxide films, polyurethane IC1000 polishing pad and ceria abrasives in liquid media with and without DADMAC molecules were made. It was shown that at 15 mM concentration, DADMAC molecules yield non-Prestonian behavior by interfering between ceria particles and the oxide film. The effects of the DADMAC additive on the removal rates of the oxide films and their corresponding coefficients of friction (COFs) values were also investigated. Finally, the correlation between AFM force measurements, removal rates and COF values measured during polishing are discussed. Interestingly, below a threshold COF value of ∼0.23 to 0.24, corresponding to a threshold down pressure of ∼2psi for both 15 mM and 25 mM DADMAC concentration, no oxide film removal was observed. Chemical Mechanical Planarization (CMP) is a critical step during the fabrication of ultra large scale integrated circuits (ULSICs) in the semiconductor industry. Since the feature dimensions of current ICs are continually scaling down (latest technology node of 14 nm was recently announced by Intel corp.), the demands on surface planarity of various films have become more stringent. An improved understanding of polishing mechanisms can help to achieve the desired polishing requirements. These requirements include minimizing defects such as surface roughness, micro-scratches, etc. 1,2One of the main applications of CMP in the front-end-of-the-line is shallow trench isolation (STI) fabrication. The STI 3 structure isolates two adjacent semiconductor device components (transistors, diodes, etc.) preventing electrical current leakage between them. Application of CMP for fabricating these STI structures has been widely studied. However, precise end-point detection during the fabrication of these structures remains a challenge. As a result, due to the non-uniform polishing of the oxide film across the wafer, 4 over-polishing time is almost always required to remove any residual oxide from the nitride areas. This can result in considerable dishing in the oxide-filled trenches in the STI structure. Dishing takes place if the oxide material inside the trenches is polished, especially at the low pressures created by contact with the polishing pad. One efficient method that can minimize dishing is to use a non-Prestonian polishing slurry [5][6][7] which causes negligible removal below a threshold applied downward pressure. Recently, it was shown that a ceria-based slurry containing 15 mM diallyldimethyl ammonium chloride (DADMAC) as an additive resulted in non-Prestonian oxide removal 7 with negligible removal below ∼2 psi applied pressure. Based on the measurements of the adsorption strength of DADMAC molecules on ceria and silica surfaces, using various techniques including thermo-gravimetric analysis (TGA) and UV-visible sp...

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“…Zeta potential behavior of ceria in presence and absence of silicate ions[2] Zeta potential behavior of silicon nitride[3] Zeta potential behavior of Silica[4] …”

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confidence: 99%

STI Post CMP Cleaning Solution Development

et al. 2008

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Shallow Trench Isolation (STI) is the standard isolation method for fabrication of submicron CMOS devices. Ceria based slurries are often used for the chemical mechanical planarization (CMP) of STI structures. It is essential therefore, to clean the structure after the CMP process to remove the ceria and other organic residues, usually resulting from the slurry. In this paper, post CMP cleaning of STI wafers with a specially formulated clean solution has been discussed.

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Effects of Abrasive Size and Surfactant Concentration on the Non-Prestonian Behavior of Ceria Slurry in Shallow Trench Isolation Chemical Mechanical Polishing

Cited by 11 publications

References 9 publications

Ceria-Based Slurries for Non-Prestonian Removal of Silicon Dioxide Films

Ceria-Based Slurries for Non-Prestonian Removal of Silicon Dioxide Films

AFM-Based Study of the Interaction Forces between Ceria, Silicon Dioxide and Polyurethane Pad during Non-Prestonian Polishing of Silicon Dioxide Films

STI Post CMP Cleaning Solution Development

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