Synergistic effect of LABSA/JFCE combined surfactant system on the removal of particles on copper wafer surface

doi:10.1016/j.matchemphys.2020.123841

Materials Chemistry and Physics

Volume 257, 1 January 2021, 123841

https://doi.org/10.1016/j.matchemphys.2020.123841 Get rights and content

Highlights

•
Adsorption energy of LABSA, JFCE and SiO₂ on copper surface was calculated by periodic DFT computations.
•
JFCE can be used to reduce the possibility of O atoms in LABSA molecules forming Si … •O–H type hydrogen bonding with colloidal silica.
•
Effect and mechanism of composite surfactants were studied by contact angle, PSS, and SEM.
•
When the mass fraction ratio of LABSA/JFCE is 2:3, the synergistic effect on particle removal is the strongest.

Abstract

With the decrease of feature size of integrated circuits, higher requirements are put forward for the surface defects of copper interconnects after chemical mechanical polishing (CMP). Colloidal SiO₂ is used as a common abrasive in the CMP slurry for copper interconnect, which is the main contaminant in the post-CMP cleaning process. The interaction parameters of the anionic surfactant Dodecylbenzenesulfonic acid (LABSA) and the nonionic surfactant fatty alcohol polyethylene ether (JFCE) were calculated. It was determined that when the ratio of LABSA/JFCE compound was 2:3 and the concentration was 1000 ppm, the synergistic effect of the two surfactants was the strongest. The effect of the composite surfactant on the particle removal was verified by scanning electron microscopy (SEM). When the compound ratio of LABSA and JFCE is 2:3, the maximum removal efficiency of particles on copper surface was 97.08%. The reactive sites of LABSA and JFCE were studied at B3LYP/6-31G (d,p) level. Their adsorption energies on copper surface were calculated. It was concluded that under the action of composite surfactant agent, the SiO₂ particles physically adsorbed on the copper surface could be easily desorbed. The theoretical analysis is consistent with the experimental results; the compound cleaning solution is suitable for particle removal in post CMP cleaning.

Introduction

With the decrease of the feature size of GLSI to 14 nm or less, the control of the surface defects of copper interconnection of the integrated circuit becomes more strict [1]. The main purpose of the copper post-CMP cleaning process is to eliminate the residual SiO₂ particles and reaction products on the copper surface [2,3]. The silica is the main kind of the abrasive in CMP slurry of copper interconnection, which is easily adsorbed on copper surface and cause surface defect. It will seriously hinder the improvement of chip yield [4,5].

In semiconductor manufacturing, one of the most widely used alkaline cleaning chemical systems to remove silica particles is: the use of a mixture of ammonium hydroxide (NH₄OH), hydrogen peroxide and deionized water, namely SC-1 solution [6]. Venkatesh et al. [7] proposed that tetramethylammonium hydroxide (TMAH) and arginine can make the copper surface negatively charged. The surface and particles are electrostatically repelled. Thus the alkaline cleaning solution can effectively remove colloidal silica particles on copper surface. Ching-Fa Yeh et al. [8] proposed that hydrofluoric acid and nitric acid can remove silica particles and organic contamination by etching the oxide layer on the copper surface. Lifei Zhang et al. [9] proposed that 0.5 wt% citric acid and non-ionic surfactants have the best removal effect on residual silica particles on copper surface by studying the adhesion between SiO₂ particles and copper in citric acid solution. However, there are few studies on the synergistic effect of compound surfactants on the removal of colloidal silica particles.

In this study, in order to remove the residual silica particles on copper surface, a new type of compound surfactant of anionic surfactant LABSA and nonionic surfactant JFCE was studied. The synergistic effects of LABSA and JFCE were analyzed by experiment and calculations. Molecular dynamics software calculations were used to verify the cleaning mechanism. SEM was used to confirm the cleaning effect of silica particle. Fig. 1 shows the molecular structures of LABSA and JFCE.

Section snippets

Experimental materials and characterization methods

Copper coupons (4 inches) cut from 12 inch copper blanked wafers were used for the cleaning experiments. The cleaning solution for the cleaning of copper surface consisted of different mass fraction of LABSA (500–1500 ppm, C₁₈H₃₀O₃S, 99.9%) and JFCE (500–1500 ppm, C₁₀H₂₂O₂, 99.9%). The surface tension of composite surfactant was measured with contact angle measurement (JC2000D, Shanghai Zhongchen company) to explore the mechanism of different cleaning solution combinations.

During the cleaning

CMC of single surfactant

The minimum concentration of surfactant molecules associated in solution to form micelles is the critical micelle concentration (CMC) [13]. When the concentration of the solution reaches CMC, the surface tension of the solution decreases to the minimum; with the further increase of the surfactant concentration, the surface tension of the solution no longer decreases. A large number of micelles will form.

The pH value and surface tension of the cleaning solution with different mass fractions of

Conclusions

In this paper, the removal effect and mechanism of SiO₂ particles on copper surface by composite surfactants were studied. The interaction parameters of LABSA and JFCE were studied with contact angle meter. The effect of composite surfactants on particle size was researched by particle size analyzer. The removal effect of SiO₂ particles was confirmed using SEM measurement. The electron and Fukui index of the surfactant were verified by molecular dynamics software. The local reactivity of the

CRediT authorship contribution statement

Da Yin: Conceptualization, Methodology, Software, Investigation, Writing - original draft. Siyu Tian: Conceptualization, Software, Validation, Formal analysis, Writing - original draft. Nannan Zhang: Writing - review & editing. Qi Wang: Validation, Formal analysis. Xiaoqin Sun: Writing - review & editing. Mengrui Liu: Writing - review & editing. Shihao Zhang: Writing - review & editing. Baimei Tan: Resources, Writing - review & editing, Supervision.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by the Major National Science and Technology Special Projects (No. 2016ZX02301003-004-007), the Natural Science Foundation, China (No. 61704046), and the Hebei Natural Science Foundation Project (No. F2018202174). The authors also thank the teachers and classmates for their helpful suggestions.

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Citation Excerpt :
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Synergistic effect of LABSA/JFCE combined surfactant system on the removal of particles on copper wafer surface

Highlights

Abstract

Introduction

Section snippets

Experimental materials and characterization methods

CMC of single surfactant

Conclusions

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgements

Appl. Surf. Sci.

Microelectron. Eng.

J. Colloid Interface Sci.

Appl. Surf. Sci.

Appl. Surf. Sci.

Microelectron. Eng.

Construct. Build. Mater.

J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects

Colloid. Surface. Physicochem. Eng. Aspect.

J. Colloid Interface Sci.

Chem. Phys. Lett.

Microelectron. Eng.

J. Mol. Struct.

Mater. Today: Proceedings

J. Mol. Struct.

Dyes Pigments

J. Mol. Struct.