Post Plasma Etch Residue Removal Using CO[sub 2]-Based Mixtures: Mechanistic Considerations

A possible way to realize a 22.5 nm 1⁄2 pitch and beyond BEOL interconnect structures within the low-kmaterial is the partial-trench via first with self-aligned double patterning (SADP) integration approach. A scheme of this BEOL integration stack with the different materials used after patterning is described in Figure 1. In BEOL processing, fluorocarbon-containing plasma is commonly used to pattern silica-based dielectric layers. During the patterning of the low-kdielectric layer, a thin layer of fluoropolymer (CFx-type residues) is intentionally deposited on the dielectric sidewalls and TiN hardmask to ensure anisotropic etching and prevent/minimize dielectric degradation. This polymer layer must be removed from the sidewall and the via bottom prior to the subsequent processing steps to achieve good adhesion and coverage of materials deposited in the etched features. The compatibility requirement is even more stringent for advanced low-kdielectrics, i.e. materials with lowerk-value and higher porosity. The post etch residue (PER) amount and properties are specific and depend on the stack structure and the plasma that is used for patterning. The low-kmaterials and hardmasks that are used in this work are respectively an organo-silicate glass (OSG) type of low-kmaterial withk= 2.4 (~20 % open porosity) and low-stress TiN. Recent results clearly showed the presence of a highly fluorinated layer deposited on the trench sidewalls during the plasma etch based on a fluorocarbon plasma [1-3]. Commodity aqueous cleaning solutions, such as diluted HF, do not efficiently remove the sidewall polymers without etching the underlying layer (lift-off). Therefore, there is a need for commercially available chemicals that can be easily tuned to deal with the different requirements. This study focuses on the use of FOTOPUR® R 2300 mixed with H2O2 for polymer residue removal selectively to other materials (presented in the stack) such as MHM, metals (Cu, W), and porous low-k dielectrics. We will show that TiN etch can be easily tuned by changing the concentration of H2O2.

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Optimized Wetting Behavior of Water-Based Cleaning Solutions for Plasma Etch Residue Removal by Application of Surfactants

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.187.201 ◽

2012 ◽

Vol 187 ◽

pp. 201-205 ◽

Cited By ~ 1

Author(s):

Nicole Ahner ◽

Sven Zimmermann ◽

Matthias Schaller ◽

Stefan E. Schulz

Keyword(s):

Surface Energy ◽

High Surface ◽

Application Of Surfactants ◽

Plasma Etch ◽

Promising Alternative ◽

Wetting Behavior ◽

Residue Removal ◽

Wet Chemical ◽

Low K ◽

Etch Residue

Wet chemical plasma etch residue removal is a promising alternative to low-k dielectric degrading plasma cleaning processes. With decreasing feature dimensions the wetting behavior of the liquid on low energetic surfaces present after dielectric patterning will be an important issue in developing wet cleaning solutions. High surface energy liquids may not only be unable to wet low energetic surfaces, but can also cause nonwetting of small structures or pattern collapse. The improvement of the wetting behavior of a cleaning liquid by lowering its surface energy by the addition of surfactants is the strategy followed in this study. We show that with choosing the appropriate rinsing solution a wet chemical process using surfactant aided cleaning solutions compatible to the materials used in BEOL (porous low-k, copper, barriers) can be found. The results show a distinct improvement of the wetting behavior of the modified solutions on several low energetic solid surfaces like copper or polymers deposited during dry etching.

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Wetting Behavior of Plasma Etch Residue Removal Solutions on Plasma Damaged and Repaired Porous ULK Dielectrics

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.219.193 ◽

2014 ◽

Vol 219 ◽

pp. 193-196

Author(s):

Nicole Ahner ◽

Sven Zimmermann ◽

Nicole Köhler ◽

Stephan Krüger ◽

Stefan E. Schulz

Keyword(s):

Integrated Circuits ◽

Dry Etching ◽

Plasma Etch ◽

Plasma Damage ◽

Wetting Behavior ◽

Residue Removal ◽

Via Holes ◽

Processing Regimes ◽

Interconnect System ◽

Etch Residue

Porous ultra low constant materials (ULK) for isolation within the interconnect system of integrated circuits are a promising approach to reduce crosstalk and RC-delays due to shrinking feature sizes [1]. Due to their porosity and the integration of carbon rich species like methyl groups into the Si-O-Si backbone of currently fabricated PECVD SiCOH dielectrics those materials are highly sensible towards plasma processing, e.g. dry etching or resist stripping [2]. Metal hard mask approaches, e.g. using TiN hard masks are widely used to prevent the resist stripping plasma directly attacking the low-k material [3]. To reduce further plasma damage like carbon depletion and formation of polar silanol groups the development of less aggressive etching processes is in the focus of research and development activities. Nevertheless dry etching will attack the sidewalls and cause a material degradation. That is why repair processes, mainly based on silylation, are considered to follow the patterning step to reintegrate carbon rich species and to recover the dielectric’s properties [3]. Subsequently to dry etching and repairing the dielectric the wet chemical plasma etch residue removal process is performed. Besides material compatibility and effectiveness in residue removal the wetting behavior of the applied cleaning solutions towards the surface which has to be cleaned is crucial, especially looking on wetting issues like the incomplete wetting of very small via holes or pattern collapse. In this study we investigate in which way different silylation based repair processing regimes are affecting the wettability of the dielectric by water based cleaning solutions using contact angle based surface energy calculations.

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Determination of Surface Energy Characteristics of Plasma Processed Ultra Low-K Dielectrics for Optimized Wetting in Wet Chemical Plasma Etch Residue Removal

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.195.110 ◽

2012 ◽

Vol 195 ◽

pp. 110-113

Author(s):

Nicole Ahner ◽

Sven Zimmermann ◽

Matthias Schaller ◽

Stefan E. Schulz

Keyword(s):

Moisture Absorption ◽

Plasma Processing ◽

Reaction Products ◽

Plasma Etch ◽

Promising Alternative ◽

K Value ◽

Oh Groups ◽

Residue Removal ◽

Low K ◽

Etch Residue

The integration of porous ultra low dielectric constant materials (ULK) for isolation within the interconnect system of integrated circuits is a promising approach to reduce RC-delays and crosstalk due to shrinking feature sizes [1]. Actually the focus is on porous CVD-SiCOH materials, which consist of a Si-O-Si backbone and organic species (e.g. CH3) to lower polarizability and prevent moisture uptake to remarkably decrease the k-value [2]. The integration of porous low-k materials is very challenging, especially looking at patterning, resist stripping and etch residue removal, where commonly plasma processing has been applied. But plasma processing of ULK materials, especially using oxygen plasmas, is known to degrade electrical, optical and structural material properties by removing carbon from the film and densification of the surface near areas of the ULK [5]. Carbon depletion may also lead to the incorporation of-OH groups, which easily form silanols and therefore increase moisture absorption and k-values [2]. Besides the development of nondamaging plasma processes, wet cleaning is a promising alternative to avoid ULK damage while removing organic plasma etch residues. Additionally wet cleaning steps are always necessary to remove inorganic residues, which do not form volatile reaction products and can therefore not be removed by plasma processing.

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