Application of surfactant for facilitating benzotriazole removal and inhibiting copper corrosion during post-CMP cleaning

Accepted Manuscript Application of surfactant for facilitating benzotriazole removal and inhibiting copper corrosion during post-CMP cleaning

Jiying Tang, Yuling Liu, Chenwei Wang, Xinhuan Niu, Baimei Tan, Baohong Gao PII: DOI: Reference:

S0167-9317(18)30332-0 doi:10.1016/j.mee.2018.09.005 MEE 10857

To appear in:

Microelectronic Engineering

Received date: Accepted date:

20 July 2018 22 September 2018

Please cite this article as: Jiying Tang, Yuling Liu, Chenwei Wang, Xinhuan Niu, Baimei Tan, Baohong Gao , Application of surfactant for facilitating benzotriazole removal and inhibiting copper corrosion during post-CMP cleaning. Mee (2018), doi:10.1016/ j.mee.2018.09.005

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ACCEPTED MANUSCRIPT Application of surfactant for facilitating benzotriazole removal and inhibiting copper corrosion during post-CMP cleaning Jiying Tanga,b, Yuling Liua,* [email protected], Chenwei Wanga,* [email protected], Xinhuan Niua, Baimei Tana, Baohong Gaoa a

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Tianjin Key Laboratory of Electronic Materials and Devices, School of

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Electronic Information Engineering, Hebei University of Technology,

b

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Tianjin 300130, China

Tianjin Metallurgical Vocation-technology Institute, Tianjin 300400,

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China *

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Corresponding authors.

ACCEPTED MANUSCRIPT Abstract Wafer surface is usually contaminated by organic residues, such as benzotriazole(BTA), after chemical mechanical planarization (CMP). Due to the reason that these organic residuals need to be removed during the

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post-CMP cleaning process as well as keep the copper corrosion

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prevented, it is critically important for some large scale industrial

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applications to develop an effective and low-cost cleaning solution, which will remove the organic residuals and inhibiting corrosion of copper

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surface. In this work, the effect of surfactant based on alkaline chelating

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agent was investigated for BTA removal and copper corrosion during post-CMP cleaning. BTA removal was characterized using contact angle

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measurements and X-ray photoelectron spectroscopy (XPS) analysis. The

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degree of corrosion of Cu surface was characterized by scanning electron microscope (SEM) and electrochemical techniques. The Cu surface

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quality after cleaning was characterized by atomic force microscopy

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(AFM). The defect maps of the 300 mm Cu patterned wafer surface after cleaning were also collected. The experimental results demonstrate that surfactant in the cleaning solution can effectively inhibit the Cu surface corrosion with a lower surface roughness and simultaneously facilitate the removal of BTA residues. The related cleaning mechanism has been studied and proposed based on our experimental results. Keywords:

Post-CMP

cleaning;

Alkaline

cleaning

solution;

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Benzotriazole removing; Copper corrosion

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1. Introduction Chemical mechanical polishing (CMP) is one of the key technologies of integrated circuit manufacture, also it is the only way to [1]

. The Cu surface after CMP is

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provide global and local planarization

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easily contaminated by abrasive particles, copper oxide, organic residue,

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polishing debris, and so on [2]. Especially Benzotriazole (BTA) residual and copper surface corrosion can be two major issues, which have

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significant influences on yield and reliability. BTA usually used as a

organic residues

[2-4]

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corrosion inhibitor in the copper CMP slurry is the primary source of . During the Cu-CMP process, BTA is easily

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combined with Cu ions of Cu wafer surface to form Cu-BTA polymeric

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film, difficult to be removed during the post CMP cleaning, resulting in the Cu surface strongly hydrophobic property.[4]. In previously reported

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works, Cho et al. [5] investigated in detail the effect of CMP operation

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conditions and slurry pH on the formation of resultant Cu-BTA complex. Venkatesh et al.

[4]

reported that tetra methyl ammonium hydroxide

(TMAH) can be used as cleaning solution to effectively remove BTA, however, the TMAH is not an environmentally friendly agent. Manivannan and co-workers

[2]

developed a kind of cleaning agent

consisted of CsOH and KOH as pH adjuster and ethylene glycol as a corrosion inhibitor to almost completely remove BTA. However, this

ACCEPTED MANUSCRIPT approach may also introduce the metallic ion contamination from K+ and Cs+ involved in cleaning agent. Therefore, development of low-cost and environmentally-benign cleaning solution for effective removal for BTA from Cu surface after CMP is still highly desirable. Besides of the surface

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contamination by organic residues, the copper surface corrosion by the

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chemicals used in post-CMP cleaning is also becoming a serious issue. In

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order to solve corrosion problem, various corrosion inhibitors are commonly added to post CMP cleaning solutions such as ethylene glycol , BTA , 1,2,4-triazole (TAZ) and pyrazole [6-9] as protective agents to

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[2]

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effectively inhibit the corrosion of metal surface during post-CMP cleaning.

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Our research group has previously reported an effective alkaline

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chelating agent for BTA removal

[10-14]

. Miao et al.

[10]

and Hong et al. [11]

reported that the developed alkaline chelating agent can effectively

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chelate Cu+/Cu2+ from Cu(I)BTA/Cu(II)BTA, thus producing a stable and

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soluble copper complex ,which would be effectively and readily removed from Cu surface by cleaning solution. Although this developed alkaline chelating agent is very effective for BTA removal of Cu surface, it also simultaneously corrodes the copper surface when used as an alone cleaning agent. Gu et al. [12] and Li et al. [13] and Tang et al. [14] reported a compound cleaning solution including a chelating agent and a nonionic surfactant for BTA removal. The results demonstrated that the developed

ACCEPTED MANUSCRIPT cleaning solution can synergistically enhance the BTA removal. Gu et al. [12]

also investigated the role of surfactant (FA/O I type，O-20) used as a

corrosion inhibitor. In this work, we reported a novel surfactant based on the developed

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alkaline chelating agent for effective BTA removal and concurrent

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corrosion inhibition of Cu surface after CMP. The BTA removal

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effectiveness resulted from chelating agent was experimentally validated by contact angle measurements and XPS analysis, whereas the corrosion

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inhibition performance ascribed to nonionic surfactant was evaluated by

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SEM and electrochemical experiments. The quality of resultant cleaned Cu surface was further checked by using atomic force microscopy (AFM)

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technique. Based on our experimental results, the related mechanism of

has been studied.

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2. Experimental

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surfactant for facilitating BTA removal and inhibiting copper corrosion

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300 mm copper patterned wafers were used to evaluate the cleaning performance in actual production line. The defects scan and review monitoring were performed by a KLA Tencor inspection system and AMAT SEMVision G4 review system, respectively. Cu coupons cut from 300 mm blanket copper wafers were used for all others experiments. Prior to the experiments, the Cu coupons were polished and then dried with nitrogen gas (N2) as the reference. Polishing

ACCEPTED MANUSCRIPT experiments were carried out on E460E polishing equipment (Alpsitec Company, French). The alkaline slurry consists of abrasive with mass fraction of 20.0 %, FA/OII chelating agent with volume fraction of 3.5 %, oxidant with volume fraction of 0.5 %, and FA/O surfactant with volume

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fraction of 3 %. Polishing recipe is as shown in Table 1.

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Table 1 Polishing process conditions.

137 mdaN/cm2

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working pressure head speed

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plate speed

polishing time

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flow rate

55 rpm 65 rpm 300 ml/min 60 s

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HQE-48S PVA brush was used to carry out brushing process for 1

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min with a flow rate of cleaning solution of 2000 mL/min, and then the cleaned samples were dried with N2.The cleaning solution consists of the

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chelating agent and the nonionic surfactant. The alkaline chelating agent

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(FA/O II, shortened as R (NH2)2, Fig.1a) is a multi-hydroxyl and multi-amine organic molecule, which contains more than 13 chelating rings with strong chelating ability for metal ions

[10-14]

. The chelating

agent AEO-9 (C12H25O(CH2CH2O)9H, Fig.1b) as nonionic surfactant in this work. (a)

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(b)

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Fig.1. The structures of (a) chelating agent [11-12] and (b) surfactant [15]

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The contact angle of Cu surface was measured using JC2000D contact angle analyzer (Shanghai Zhongchen Company).The polished Cu

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coupons were dipped in BTA solution with a concentration of 10 mmol/L for 5 min to effectively grow Cu-BTA film

[10]

, and then rinsed in the

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cleaning solution. To ensure the reliability of the results, each test was repeated for three times. The electrochemical experiments were

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conducted on CHI600e electrochemical workstation to characterize the corrosion degree of Cu surface caused by cleaning solution. The

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electrochemical measurement was performed in a three electrode configuration system with Cu blanket as the working electrode, saturated calomel electrode (SCE) as the reference electrode, and Pt wire as the counter electrode. The electrolyte is the fabricated alkaline cleaning solution. The test time of the open-circuit voltage measurement of each group experiment was 1200 s. Polarization curves were scanned from -0.5 V ~ 0.5 V vs. OCP reference at a scan rate of 5 mV/s

[16]

. Surface

ACCEPTED MANUSCRIPT roughness (sq) of Cu surface after cleaning was measured by 10 µm×10 µm AFM scans on Agilent 5600LS equipment. The chemical states of copper coupons treated with various solutions were studied by X-Ray Photoelectron Spectroscopy (XPS; Thermo Fisher Scientific, ESCALab

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250Xi).

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3. Results and Discussion

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3.1. Effect of FA/OII chelating agent on BTA removal and Cu surface corrosion

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The copper surface dipped in the 10 mmol/L BTA solution for 5 min

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were cleaned for 1 min by the solutions with different FA/OII chelating agent concentrations of 0, 50 ppm, 100 ppm, 150 ppm and 200 ppm, and

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the corresponding pH values were 6.62, 9.82, 10.06, 10.18 and 10.32. The

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contact angle of de-ionized water on Cu surface was measured and the results were presented in Fig.2. The contact angle of post CMP was ~25°,

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which shows it is hydrophilic, and it was taken as reference for this study.

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The contact angle of water on a BTA-treated Cu coupon was found to be ~71°. Cu coupons became hydrophobic after treatment with 10 mmol/L BTA solution for 5 min. After cleaning with DI water the contact angle was 55° which showed Cu surface was still hydrophobic. Upon addition of 100 ppm FA/OII chelating agent, the contact angle was reduced to 44°, which indicated that some BTA has been removed. When the concentration of FA/O II chelating agent was further increased to 150

ACCEPTED MANUSCRIPT ppm and 200 ppm, the contact angle decreased significantly to 32° and 30° respectively, demonstrating a further BTA removal. The contact angle measurement results indicate that FA/O II chelating agent can effectively remove BTA adhered on Cu surface, leading to a change of Cu surface

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from hydrophobility to hydrophility. But when the chelating agent

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concentration was higher than 150 ppm, the contact angle was nearly

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unchanged, implying the optimum BTA removal performance obtained in

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150 ppm chelating agent involved cleaning solution.

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80

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60 50

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Contact Angle (Degree)

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40 30

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20 10

0

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BTA treated

DIW

50

100

150

200

PCMP

FA/OII (ppm)

Fig.2. Contact angle of DI water on Cu surface cleaned by various concentrations of FA/OII chelating agent. In order to further investigate the effect of chelating agent on BTA removal, XPS measurements were performed by an ESCALAB 250 Xi XPS system of Thermo Fisher Scientific. The bare coupon (sample “a”)

ACCEPTED MANUSCRIPT and the Cu coupon treated with 10 mmol/L BTA (sample “b”) and the Cu coupon treated with 10 mmol/L BTA followed by 150 ppm FA/OII chelating agent (sample “c”) were used for the XPS analysis. Fig.3 depicts the complete survey spectra of three types of Cu surfaces. It is

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evident that all three samples have similar spectra with clear Cu2p peaks,

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O1s peak, and C1s peak, but sample “b” contains a distinct N1s peak.

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Sample “b” is copper coupon treated only with BTA and it showed a strong peak near 400eV. The peak is attributed to the nitrogen atom of

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BTA. This peak is absent in all the other Cu coupons, which supports the

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contact angle measurements and shows that FA/O II chelating agent can

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effectively remove BTA adhered on Cu surface.

Sample"a" Sample"b" Sample"c"

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C1s

O1s

N1s

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Intensity / cps

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Cu2p

1400

1200

1000

800

600

Binding Energy (eV)

400

200

0

ACCEPTED MANUSCRIPT Fig.3. XPS survey spectra of Cu coupons treated with various solutions: bare coupon (sample “a”), BTA- treated coupon (sample “b”) and BTAtreated coupon followed by FA/OII chelating agent (sample “c”) The existent form of BTA molecule in aqueous solution highly

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depends on the solution pH. In alkaline environment, BTA is present

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mainly in the form of negatively charged BTA-. Due to the interaction

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between the nitrogen atoms of BTA- with the surface Cu atoms, the BTAH molecules easily adsorb on the Cu surface and thus form a surface [6,10-13]

, resulting in a hydrophobic Cu

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polymer complex of [Cu-(BTA)] n

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surface. Insoluble Cu-BTA exist a weak ionization balance in aqueous solution and can form Cu+ and BTA- in alkaline conditions, reaction

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equation can be written as Formula (1).

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Cu - BTA  Cu + + BTA-

(1)

FA/OII chelating agent can remove Cu-BTA mainly based on the

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complexation mechanism. FA/O II chelating agent has a strong chelating

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ability toward copper ions and then produce a stable and soluble copper complex (Eq. (2)).These formed complexes are easily removed by the cleaning solution under the mechanical effect of PVA brush scrubbing [10-14]

. The reaction between FA/O II chelating agent and copper ions

breaks Cu-BTA ionization balance and accelerate the reaction to the right, thus accelerate the dissolution of Cu-BTA. In addition, FA/O II chelating agent also have the same C-N bonds with BTA. Basing on the similar

ACCEPTED MANUSCRIPT miscibility principle of organic solvent, FA/OII chelating agent can dissolve Cu- BTA effectively. R(NH2 ) 2 + Cu +  [Cu(R(NH2 ) 2 )]+

(2)

BTA- is prone to be dissolved when the solution pH is beyond 10 . However, pH is not playing major role in removing Cu–BTA [10]

and Gu et al.

[12]

show that the chelating agent

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polymer. Miao et al.

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[10-11]

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was found to be more efficient when compared to a KOH solution with the same pH by AFM and contact angle experiments, separately.

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Although the FA/OII chelating agent is very effective for BTA

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removal of Cu surface, it also simultaneously corrodes the copper surface because of the reaction between chelating agent and copper ion when sole

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FA/OII chelating agent used as cleaning solution. Fig.4 shows the SEM

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image of the copper surface corrosion cleaned by the cleaning solution.

Fig.4. SEM image of the copper surface corrosion. The copper corrosion caused by the chemical used in post-CMP

ACCEPTED MANUSCRIPT cleaning can be detrimental to the yield and reliability of integrated circuit devices. To evaluate the influence of FA/O II chelating agent on Cu surface corrosion, potentiodynamic polarization measurements of Cu surface treated with different concentrations of FA/O II chelating agent

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were conducted in this work.

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Fig. 5 (a) shows the potentiodynamic polarization curves of Cu

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surface treated with different concentrations of FA/O II chelating agent. The corrosion voltage (Ecorr) and the corrosion current density (Icorr) can

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be estimated from the potentiodynamic polarization curves by Tafel

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extrapolation, as shown in Fig. 5 (b). As shown in Fig. 5, with the concentration of increasing of FA/O II chelating agent, the corrosion

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potential gradually decreased and the corrosion current increased

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significantly, which indicated that anodic reaction was more strong and the corrosion effect of FA/OII chelating agent on the Cu surface was

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more serious with the concentration increasing.

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(a)

10

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-0.28

-0.30

9

8

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Ecorr (V)

-0.26

-0.32

11

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-0.24

7

6

-0.34

0

Icorr (μA)

-0.22

50

100

150

200

FA/O II (ppm)

(b) Fig.5. (a) Potentiodynamic polarization curves of the Cu surfaces treated with various concentration of chelating agent (b) values of corrosion potential and corrosion current.

ACCEPTED MANUSCRIPT 3.2. Effect of AEO-9 on BTA removal Fig. 6 shows the effect of AEO-9 surfactant on the surface tension of cleaning solution while the FA/OII chelating agent concentration is fixed to 150 ppm. It could be seen that the surface tension dramatically

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declined from 78 to 44 mN/m when the concentration of AEO-9

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surfactant increased from 0 to 100 ppm. The surface tension decreased to

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29.1 mN/m when the concentration of AEO-9 surfactant increased to 1000 ppm and then remains relatively constant, implying the optimum

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concentration of AEO-9 surfactant in the cleaning solution was about

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1000 ppm (the critical micelle concentration (CMC) value of AEO-9 is in

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the literature is approximately 0.10 mmol/m3 [17]).

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70

60

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Cleaning Solution' Surface Tension (mN/m)

80

50

40

30

20 0

500

1000

1500

2000

2500

3000

AEO-9 surfactant (ppm)

Fig.6. Effect of AEO-9 surfactant on the surface tension of cleaning

ACCEPTED MANUSCRIPT solution. Fig.7 shows the contact angle values of DI water on the BTA treated Cu coupons cleaned by various concentrations of AEO-9 surfactant (0, 500ppm, 1000ppm, 1500ppm, and the corresponding pH values

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were10.18, 10.16, 10.14, 10.13) while the FA/OII chelating agent

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concentration is fixed to 150 ppm for 1min. When the AEO-9 surfactant

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concentration was increased to 1000 ppm, the contact angle of Cu surface was decreased to 29°, suggesting that the introduction of AEO-9

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surfactant in cleaning solution can synergistically promote the BTA

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removal.

90

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80

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60

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50 40 30

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Contact Angle (Degree)

70

20 10

0 BTA treated

DIW

500

1000

1500

PCMP

AEO-9 surfactant (ppm)

Fig.7. Contact angle of DI water on Cu surface cleaned by various concentrations of AEO-9 surfactant while the FA/OII chelating agent concentration is fixed to 150 ppm.

ACCEPTED MANUSCRIPT Surfactant has the strong permeation and wetting abilities. Nonionic surfactant is not ionized and it is not likely to introduce additional ionic contamination in the wafer cleaning process

[18]

. The surfactant used in

our experiments is AEO-9, which is a kind of fatty alcohol

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polyoxyethylene ether composed of hydrophilic EO chain and

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hydrophobic carbon chain. The carbon chain length (Nc = 12) of AEO-9 is

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short, surface tension (~29.1 mN/m) is very low and penetrability is strong. It can effectively penetrate into the gap between the Cu-BTA

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residual and copper surface during the process of scrubbing. On the one

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hand, the hydrophobic carbon chains of AEO-9 adsorb on the surface of Cu-BTA, while hydrophilic EO chains of AEO-9 full stretch in water.

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And Cu-BTA residual is coated with AEO-9 surfactant to form wrappage.

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The formed wrappage can be easily taken away under the action of PVA brush. On the other hand, the surfactant completely spreads over the

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copper surface and makes the copper surface from hydrophobic to

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hydrophilic. The adhesion between BTA and copper surface can be reduced due to the adsorption of surfactant, thus Cu-BTA residual is easily removed by PVA scrubbing. Cu-BTA residual and copper complex and surfactant would be swept away by cleaning solution under the mechanical effect of PVA brush scrubbing. The schematic diagram is shown in Fig. 8. CMP process involves both chemical interactions and mechanical

ACCEPTED MANUSCRIPT interactions. Under the action of CMP, Cu-BTA film is damaged and most Cu-BTA film can be removed, leaving only a small amount of Cu-BTA residual which needs to be removed during post-CMP cleaning. Fig. 8a presents a schematic diagram of Cu-BTA residual adsorbed on copper

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surface. Only one Cu-BTA residual is shown in the figure, and actually

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there may be more than one. Fig. 9b shows the surfactant coating

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Cu-BTA residual and spreading over the copper surface. R (NH2)2 represent FA/OII chelating agent can chelate Cu ions from Cu-BTA and

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Cu oxide respectively to form stable and soluble copper amine complex

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ion [Cu(R(NH2)2)]+. Under the action of mechanical force created by PVA brush and water, reactants would be flushed away. The schematic diagram

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is shown in Fig. 8c. Due to permeation and wetting abilities, surfactant

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facilitates the removal of Cu-BTA by chelating agents.

(a)

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(b)

(c)

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Fig. 8. Mechanism of Cu-BTA residual removal.

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3.3. Effect of AEO-9 on Cu surface corrosion Fig. 9 (a) shows the potentiodynamic polarization curves of Cu surface treated with different concentrations of AEO-9 surfactant in cleaning solution with a fixed FA/OII chelating agent concentration of 150 ppm. The corrosion voltage (Ecorr) and the corrosion current density (Icorr) can be estimated from the potentiodynamic polarization curves by Tafel extrapolation, as shown in Fig.9 (b). When the concentration of

ACCEPTED MANUSCRIPT AEO-9 surfactant was lower than 1000 ppm in cleaning solution, an increase in Ecorr and a decrease in Icorr can be achieved with increasing AEO-9 surfactant concentration, suggesting a weak Cu surface corrosion. However, when the concentration of AEO-9 surfactant was more than

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1000 ppm, the change of Ecorr and Icorr was almost ignorable with

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increasing AEO-9 surfactant. The electrochemical measurement results

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demonstrated that AEO-9 surfactant can effectively inhibit the corrosion resulted from FA/O II chelating agent on Cu surface owing to the

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formation of AEO-9 surfactant protective layer film on Cu surface.

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However, a suitable AEO-9 surfactant concentration should be adopted for effectively enhancing corrosion inhibition of Cu surface and

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simultaneously avoiding secondary pollution from surfactant.

0.4

0 ppm 500 ppm 1000 ppm 1500 ppm 2500 ppm

-0.2

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E (V vs. SCE)

0.0

CE

0.2

-0.4

-0.6

-0.8 -7.5

-7.0

-6.5

-6.0

-5.5

-5.0 2

Log(I, A/cm )

(a)

-4.5

-4.0

-3.5

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(b)

Fig.9. The electrochemical curve of different concentration of surfactant

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(a)Cu potentiodynamic polarization curves of Cu surfaces (b) values of corrosion potential and corrosion current.

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Fig. 10 shows the SEM image of the copper surface cleaned by compound cleaning solution（FA/OII chelating agent + AEO-9 surfactant）.

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Fig.4 shows the SEM image of the copper surface cleaned by sole FA/O II cleaning solution. Comparing Fig.11 with Fig.4, we can see that the Cu surface corrosion was inhibited. This indicates that AEO-9 surfactant can mitigate the corrosion caused by the FA/OII chelating agent.

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Fig.10. SEM image of the copper surface cleaned by compound

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cleaning solution.

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AEO-9 surfactant can pass through the Cu-BTA residual, spreading on the copper surface, and forming a layer of protective film to prevent

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the chelating agent reacting with Cu ion, thus avoiding Cu surface

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corrosion by chelating agent.

defect map

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3.4. Effect of compound cleaning solution on surface roughness and

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Copper coupons after Cu-CMP, treated with BTA solutions, were further treated with different cleaning solutions and the AFM images of the treated surfaces are presented in Fig. 11(a-d). These images were obtained with a scan range of 10 µm×10 µm. The surface roughness after Cu-CMP was 7.26 nm, while the surface roughness treated with BTA solutions was obviously increased to 15.6 nm. The surface roughness was decreased to 4.41 nm after brushing by FA/O II chelating agent.

ACCEPTED MANUSCRIPT Interestingly, the Cu surface roughness can be further decreased to 1.39 nm in the co-presence of 1000 ppm AEO-9 surfactant and 150 ppm FA/O II chelating agent, indicating their synergistic effect to significantly decrease the Cu surface roughness.

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(b)

Sq = 7.26 nm

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nm

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(a)

(d)

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(c)

Sq = 15.6

Sq = 4.41 nm

Sq = 1.39

nm

Fig.11. AFM images of the copper coupons: (a) after Cu-CMP, (b) treated with BTA, (c) after cleaning by150 ppm FA/OII chelating agent,

ACCEPTED MANUSCRIPT (d) after cleaning by 1000ppm AEO-9 surfactant and 150ppm FA/OII chelating agent. 300 mm Cu patterned wafers based on 55 nm feature size were used to evaluate the cleaning performance in actual production line. Before the

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cleaning, the polishing was performed on Applied Materials Reflexion

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LK 300mm system which was designed for a three-step CMP approach:

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platen one was configured for bulk Cu removal, platen two for complete Cu removal at low removal rate and platen three for barrier and oxide

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buffer removal. The polishing pad for the barrier CMP was used FUJIBO

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H7000HN. The slurry used for barrier CMP contained 20wt% colloidal silica abrasives. Ethoxylated decylalchohol (EDA) was use as dispersant

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agent for scratch reduction [19].

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Fig. 12 shows the defect map of wafer surface after cleaning by using various cleaning solutions. It was clearly seen that the sum of the defects

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was very high after cleaning with only deionized water (DIW) with a

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value of 16571（Fig. 12 (a)）. However, the total number of the defects significantly reduced to 728 after cleaned by using a cleaning solution composed of FA/O II chelating agent and AEO-9 nonionic surfactant（Fig. 12 (b)）. Comparing Fig.12 (b) with Fig. 12 (a), it revealed that the efficiency of the compound cleaning solution on defect removal was obvious. After cleaning, the total number of the defects had decreased from 16571 to 728. Fig. 12 (c) showed the defect map of the wafer

ACCEPTED MANUSCRIPT cleaned by the commercial cleaning solution. Comparing Fig.12 (b) with Fig. 12 (c), it can be seen that the compound cleaning solution was not as good as the commercial one. However, the commercial cleaning solution is citric acid, with the improvement of the semiconductor integrated

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circuit, acid chemicals have exposed many disadvantages, such as it is

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harmful to the low K dielectric and the new barrier materials. The issues

the main trend of development. (b)

(c)

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(a)

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can be well solved by using alkaline chemicals, so alkaline chemical is

Fig.12. Defect map of the wafer surface after cleaning by using various

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cleaning solutions: (a) after cleaning by DIW, (b) after cleaning by compound cleaning solution (c) after cleaning by commercial cleaning solution.

Conclusions In summary, the effect of surfactant on facilitating benzotriazole removal and corrosion inhibition during post-Cu CMP cleaning was

ACCEPTED MANUSCRIPT investigated experimentally. The contact angle experiments and XPS analysis showed that FA/O II chelating agent can effectively remove BTA and AEO-9 nonionic surfactant can synergistically facilitate the BTA removal. The electrochemical experiments and SEM demonstrated that

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the surfactant can effectively inhibit copper surface corrosion caused by

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the chelating agent. AFM analysis and defect map of the wafer surface

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revealed that compound cleaning solution has better effect than the cleaning solution only consisted of single chelating agent. The

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mechanisms of the synergistic effect of surfactant and chelating agent for

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effective BTA removal and corrosion inhibition of metallic Cu surface

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Acknowledgments

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was discussed and proposed on the basis of our experimental results.

This work was supported by the Major National Science and Technology

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Special Projects (No. 2016ZX02301003-004-007), National Natural

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Science Foundation of China (NSFC61504037, 61704046); the Natural Science Foundation of Hebei Province (F2015202267); Scientific Innovation grant for Excellent Young Scientists of Hebei University of Technology under grant (No. 2015007)

ACCEPTED MANUSCRIPT References [1] Yair Ein-Eli, and David Starosvetsky, Review on copper chemical-mechanical polishing (CMP) and post-CMP cleaning in ultra large

system

integrated

(ULSI)-An

electrochemical

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Electrochimica Acta, 52 (2007) 1825-1838.

perspective,

and Jin-Goo Park, Characterization of

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Srinivasan Ramanathan,

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[2] Ramachandran Manivannan, Byoung-Jun Cho, Xiong Hailin,

non-amine-based post-copper chemical mechanical planarization cleaning

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ACCEPTED MANUSCRIPT [7] Zhenyu Chen, Ling Huang, Guoan Zhang, Yubing Qiu, and Xingpeng Guo, Benzotriazole as a volatile corrosion inhibitor during the early stage of copper corrosion under adsorbed thin electrolyte layers, Corrosion Science, 65 (2012) 214-222.

PT

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Juan Wang, Liying Han, Chenqi Yan, and Jin Zhang, Effect of a novel chelating agent on defect removal during post-CMP cleaning, Applied Surface Science, 378 (2016) 239-244. [12] Zhangbing Gu, Yuling Liu, Baohong Gao, Chenwei Wang, and Haiwen Deng, A novel compound cleaning solution for benzotriazole removal after copper CMP, Journal of Semiconductors, 36 (2015) 106001-1-106001-6.

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Jiang, Yan Wang, and Shengjun Tian, Study on the Weakly Alkaline

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ACCEPTED MANUSCRIPT (2017) 270-275. [19] Yanlei Li, Yuling Liu, Chenwei Wang, Xinhuan Niu, Tengda Ma, and Yi Xu, Role of Dispersant Agent on Scratch Reduction during Copper Barrier Chemical Mechanical Planarization, ECS Journal of Solid State

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ACCEPTED MANUSCRIPT Fig.1. The structures of (a) chelating agent [11-12] and (b) surfactant [15]

Fig.2. Contact angle of DI water on Cu surface cleaned by various

PT

concentrations of FA/OII chelating agent.

RI

Fig.3. XPS survey spectra of Cu coupons treated with various solutions:

SC

bare coupon (sample “a”), BTA-treated coupon (sample “b”) and

NU

BTA-treated coupon followed by FA/OII chelating agent (sample “c”).

MA

Fig.4. SEM image of the copper surface corrosion.

D

Fig.5. (a) Potentiodynamic polarization curves of the Cu surfaces treated

PT E

with various concentration of chelating agent (b) values of corrosion

CE

potential and corrosion current.

AC

Fig.6. Effect of AEO-9 surfactant on the surface tension of cleaning solution.

Fig.7. Contact angle of DI water on Cu surface cleaned by various concentrations of AEO-9 surfactant while the FA/OII chelating agent concentration is fixed to 150 ppm.

ACCEPTED MANUSCRIPT Fig. 8. Mechanism of Cu-BTA residual removal.

Fig.9. The electrochemical curve of different concentration of surfactant (a) Cu potentiodynamic polarization curves of Cu surfaces (b) values of

RI

PT

corrosion potential and corrosion current.

SC

Fig.10. SEM image of the copper surface cleaned by compound cleaning

NU

solution.

MA

Fig.11. AFM images of the copper coupons: (a) after Cu-CMP, (b) treated with BTA, (c) after cleaning by150 ppm FA/OII chelating agent, (d) after

D

cleaning by 1000ppm AEO-9 surfactant and 150ppm FA/OII chelating

PT E

agent.

CE

Fig.12. Defect map of the wafer surface after cleaning by using various

AC

cleaning solutions: (a) after cleaning by DIW, (b) after cleaning by compound cleaning solution (c) after cleaning by commercial cleaning solution.