Complexing Between Additives and Ceria Abrasives Used for Polishing Silicon Dioxide and Silicon Nitride Films

Wang, Liangyong; Liao, Bo; Zhang, Song; Liu, Weili; Feng, Songlin; Huang, David; Babu, S. V.

doi:10.1149/1.3519883

Cited by 7 publications

(5 citation statements)

References 16 publications

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“…We also observed that the addition of ascorbic acid changed the color of the ceria slurry from white to reddish brown and made it unstable. Similar results were observed by Wang et al 54 with other chemical additives including ethylenediaminetetraacetic acid and gluconic acid and was attributed to the blocking of active Ce 3+ .…”

Section: Resultssupporting

confidence: 90%

Cleaning Solutions for Removal of ∼30 nm Ceria Particles from Proline and Citric Acid Containing Slurries Deposited on Silicon Dioxide and Silicon Nitride Surfaces

Gowda

Seo

Ranaweera

et al. 2020

ECS J. Solid State Sci. Technol.

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A previously developed aqueous cleaning solution (4.2 mol l−1 each of H2O2 and NH4OH) was found to be ineffective in cleaning oxide/nitride surfaces after contamination with ceria particles from slurries containing proline or citric acid. However, a cleaning solution consisting of 1 wt% ascorbic acid, 1 wt% ammonium carbonate and 50 ppm triton X-100 at pH 12, aided by ultrasonic cleaning, removed these ceria particles, even those as small as ∼30 nm, from both oxide and nitride surfaces with efficiencies >99% as determined by AFM imaging. Fourier transform infrared (FTIR) spectroscopy results indicated that ceria particles treated with these additives can also bind with oxide/nitride surfaces through Si–O–C and Si–O–H bonds, in addition to any Ce–O–Si, where the C and H atoms are from the additives adsorbed on the ceria particles. All these bonds are broken effectively by the nucleophilic attack of hydroxyl anions in the cleaning solution while triton X-100 in the cleaning solution reduces adhesion between the particles and the film surface and facilitates cleaning via a wetting mechanism. More importantly, ascorbic acid and ammonium carbonate prevent particle redeposition by complexing with the removed particles and blocking the active Ce3+ species on their surface.

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Section: Resultssupporting

confidence: 90%

Cleaning Solutions for Removal of ∼30 nm Ceria Particles from Proline and Citric Acid Containing Slurries Deposited on Silicon Dioxide and Silicon Nitride Surfaces

Gowda

Seo

Ranaweera

et al. 2020

ECS J. Solid State Sci. Technol.

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“…In addition, it was also proposed that the specific form of an amino acid (depending on the pKa value) plays a vital role in blocking the chemically active sites on ceria, 25 presumably Ce 3þ species, 8,9 and silicon nitride 26 surfaces. Recently Wang et al 27 proposed a model in which a chemical complex is formed between amino acids containing an additional carboxyl group and ceria abrasives to explain nitride RRs suppression. They predicted a six ligand complex between the oxygen atoms of the two carboxyl groups of the additive and cerium.…”

Section: Resultsmentioning

confidence: 99%

Silicon Nitride Film Removal During Chemical Mechanical Polishing Using Ceria-Based Dispersions

Dandu¹,

Peethala²,

Amanapu³

et al. 2011

J. Electrochem. Soc.

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The role of abrasives and additives in ceria-based dispersions on the removal rate of silicon nitride film during chemical mechanical polishing is discussed. Our results suggest that ceria abrasives give high silicon nitride removal rates due to the reactivity of Ce 3þ on the surface of the ceria abrasives with the suboxide formed on the silicon nitride surface by hydrolysis. Also, it was observed that the nitride removal rates were suppressed to <2 nm/min when either the hydrolysis of the nitride to oxide is hindered or the Ce 3þ on the surface of the ceria abrasive is completely blocked by the adsorption of the additives. However, the two polymer additives, poly(4-vinyl pyridine) and poly(acrylic acid-co-diallyldimethyl ammonium chloride), do not suppress the silicon nitride RR even though they adsorb on the ceria particle surface and we propose an alternate removal mechanism for this case.Chemical mechanical planarization (CMP) applications like shallow trench isolation 1 require silicon dioxide to be polished much faster than the underlying silicon nitride, while in replacement gate technology, 1 silicon nitride and silicon dioxide need to be polished stopping on polysilicon. In contrast, both silicon dioxide and silicon nitride removal rates (RRs) need to be suppressed during the fabrication of micro-electro-mechanical systems (MEMS). 1 In order to achieve these wide ranging removal rate selectivities, ceria-based dispersions with a variety of different additives, namely amino acids (proline, 2,3 glutamic acid, 4 picolinic acid, 4 arginine, 5,6 lysine, 5,6 and ornithine 7 ), amines (pyridine, imidazole, and piperazine), 4,8 and polymers [poly(acrylicacid-co-diallyldimethylammonium chloride) or PAD (Ref. 9) for short, or poly(4-vinylpyridine) or PVP (Refs. 9 and 10) for short] were investigated.The blanket silicon nitride film polishing results obtained using these additives and two types of commercially available ceria particles, one from Ferro Material Systems (d m 180 nm) and the other from Rhodia Inc. (d m 60 nm), are presented in the second column in Tables I and II, respectively. Of these, the RRs with glutamic 4 and picolinic 4,7 acids and PVP (Refs. 9 and 10) are new results that were obtained using the G & P polisher in our laboratory and the others were taken from Refs. 5,6,8, 9 and 11. It can be seen that the dispersions containing amines and amino acids suppress the silicon nitride film RRs to <2 nm/min (Refs. 2-6, 9, 10) while those containing PVP and PAD do not alter the RRs. 9,10 The fourth column in each of these tables contains new data obtained from experiments discussed later in this paper.Ceria-based dispersions are known to produce high silicon dioxide RRs. Recently, 7,9 we found that the abrasive-free filtrates obtained by filtering additive-free ceria (both from Rhodia and Ferro) dispersions contain Ce 3þ species. These presumably originate from the surface of the ceria particles 12 and, hence, will be in dissolution-deposition equilibrium 13 with the surface species. Several authors 7,...

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“…These particles were also used and described in our earlier investigations. 18,19 The oxide RRs were determined by measuring the thickness of the films before and after polishing using a Filmetrics F-20 interferometer. The RRs were calculated from the average of the change in the thickness measured at 20 points across a diameter of the wafer, and the standard deviation reported was based on the data from total of 40 locations obtained from two different polished wafers.…”

Section: Methodsmentioning

confidence: 99%

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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Complexing Between Additives and Ceria Abrasives Used for Polishing Silicon Dioxide and Silicon Nitride Films

Cited by 7 publications

References 16 publications

Cleaning Solutions for Removal of ∼30 nm Ceria Particles from Proline and Citric Acid Containing Slurries Deposited on Silicon Dioxide and Silicon Nitride Surfaces

Cleaning Solutions for Removal of ∼30 nm Ceria Particles from Proline and Citric Acid Containing Slurries Deposited on Silicon Dioxide and Silicon Nitride Surfaces

Silicon Nitride Film Removal During Chemical Mechanical Polishing Using Ceria-Based Dispersions

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

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