Copper Electropolishing in Concentrated Phosphoric Acid: I . Experimental Findings

Vidal, Roberto; West, Alan C.

doi:10.1149/1.2050074

Cited by 74 publications

(73 citation statements)

References 12 publications

(18 reference statements)

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“…In addition, Cu electropolishing in phosphoric acid electrolytes has been a prototype for fundamental studies of electropolishing [7][8][9][10][11][12][13]. Despite intensive investigation, the identity of the solution phase species involved in the rate-determining step remains controversial, with some groups proposing phosphate-containing species and others water [5,7,10,12].…”

Section: Introductionmentioning

confidence: 99%

Water diffusion coefficients during copper electropolishing

Suni

2004

Journal of Applied Electrochemistry

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Cu electropolishing was studied using a rotating disc electrode in a variety of phosphoric acid-based electrolytes, including several with ethanol and other species added as diluents. Diluents allow a wider range of water concentrations and electrolyte viscosities to be accessed and also reduce the removal rate during Cu electropolishing, simplifying possible application to damascene processing. Transient and steady state currents in the mass transfer limited regime are shown to depend on both the number of water acceptor molecules associated with each dissolving Cu ion and on the effective diffusion coefficient of water. Transient analysis samples the bulk transport properties, whereas steady state analysis integrates them through the diffusion layer. Assuming that the effective diffusion coefficients appropriate to transient and steady state behavior are the same, about one water molecule is associated with each dissolving Cu ion. This analysis yields effective diffusion coefficients for water on the order of 10 )9 cm 2 s )1 . However, the data is also consistent with an assumption that six water molecules are associated with each dissolving Cu ion, but the effective diffusion coefficient appropriate for a Levich analysis is somewhat lower than that in the bulk electrolyte. This analysis yields effective diffusion coefficients for water on the order of 10 )8 -10 )7 cm 2 s )1 . The latter interpretation, that six water molecules are associated with each dissolving Cu ion, appears more likely since it provides almost exact agreement with the effective diffusion coefficient reported previously by Vidal and West. In combination with previously published impedance results ruling out a salt film mechanism, the good agreement between the transient and steady state analyses confirm that water is the acceptor species that complexes dissolving Cu ions in phosphoric acid-based electropolishing baths.

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Section: Introductionmentioning

confidence: 99%

Water diffusion coefficients during copper electropolishing

Suni

2004

Journal of Applied Electrochemistry

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“…The pad contains holes that account for 50% of the pad's surface area lack of Cu dissolution inhibition, it would not be possible to planarize a Cu sample. Also, because of the viscosity difference between concentrated phosphoric acid and the potassium phosphate solution, phosphoric acid has a considerably lower current density throughout the whole scan than that of the electrolyte with a pH value of 2 [19]. The optimal chemistry shown by a previous study contains a 1.0 M salt concentration with a pH value of 2 with a BTA concentration as low as 0.001 M [11].…”

Section: Resultsmentioning

confidence: 92%

An investigation of phosphate based ECMP electrolyte performance on feature scale planarization

Shattuck

West

2009

J Appl Electrochem

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Conventional copper chemical mechanical planarization (CMP) techniques are being pushed to their limits by increasing industrial standards caused by device miniaturization and the use of new materials. There is a need to investigate alternative methods of polishing to maintain and/or improve planarization standards while operating at low downforce. In this study, electrochemical mechanical planarization (ECMP) is considered as an alternative and/or an extension to current CMP processes. ECMP is unique due to the combination of an applied voltage to oxidize Cu and an abrasion from a polishing pad, which potentially allows the system to achieve high levels of planarization through the use of an appropriately tailored electrolyte. An electrolyte containing 1.0 M potassium phosphate salt concentration with a pH value of 2 and a benzotriazole (BTA) concentration of 0.001 M was tested for its planarization capability on patterned Cu structures using a custom built ECMP tool. Feature sizes of the Cu structures were varied from 1 to 6 lm. Similar planarization results were achieved using three pad types. All experiments were performed at 0.5 V versus Ag/ AgCl reference. The average step height reduction (SHR) was *840 nm while the decrease in the average metal thickness removed (k avg ) was on the order of *430 nm. Because features were approximately 50% of the substrate area, the total average metal thickness removed was approximately half of the SHR for all three pad types.

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“…The purpose of EP is, in general, to achieve a levelled and brightened surface through anodic dissolution in a suitable electrolyte. Many researchers [5][6][7][8][9][10][11] have noted that Cu and its alloys can be well electropolished in aqueous H 3 PO 4 solutions with H 3 PO 4 concentration from 50 to 100 vol %.…”

Section: Introductionmentioning

confidence: 99%

Electropolishing Behaviour of 73 Brass in a 70 vol % H3PO4 Solution by Using a Rotating Cylinder Electrode (RCE)

Huang

Chen

Sun

2017

Metals

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Abstract:The electropolishing behaviour of 73 brass was studied by means of a rotating cylinder electrode (RCE) in a 70 vol % H 3 PO 4 solution at 27 • C. Owing to the formation of a blue Cu 2+ -rich layer on the brass-RCE, an obvious transition peak was detected from kinetic-to diffusion-controlled dissolution in the anodic polarisation curve. Electropolishing was conducted at the potentials located at the transition peak, the start, the middle, and the end positions in the limiting-current plateau corresponding to the anodic polarisation curve of the brass-RCE. A well-polished surface can be obtained after potentiostatic electropolishing at the middle position in the limiting-current plateau. During potentiostatic etching in the limiting-current plateau, a blue Cu 2+ -rich layer was formed on the brass-RCE, reducing its anodic dissolution rate and obtaining a levelled and brightened brass-RCE. Moreover, a rod climbing phenomenon of the blue Cu 2+ -rich layer was observed on the rotating brass-RCE. This enhances the coverage of the Cu 2+ -rich layer on the brass-RCE and improves its electropolishing effect obviously.

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Copper Electropolishing in Concentrated Phosphoric Acid: I . Experimental Findings

Cited by 74 publications

References 12 publications

Water diffusion coefficients during copper electropolishing

Water diffusion coefficients during copper electropolishing

An investigation of phosphate based ECMP electrolyte performance on feature scale planarization

Electropolishing Behaviour of 73 Brass in a 70 vol % H3PO4 Solution by Using a Rotating Cylinder Electrode (RCE)

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