Influence of Copper Interconnect Characteristics on Chemical Mechanical Planarization

HASH(0x1ab9ef20)

林正裕(Jeng-Yu Lin)

指導教授 ： 萬其超

國立清華大學/工學院/化學工程學系/博士(2008年)

https://doi.org/10.6843/NTHU.2008.00305

摘要

Cu electroplating and chemical mechanical planarization (CMP) are two related roles in damascene process. In the first part of this dissertation, the influence of characteristics of IC Cu interconnects on CMP performance was investigated from Chapter 2 to 4. The effect of various frequencies of pulse current (PC) on the crystal orientation of Cu deposit was investigated in Chapter 2. When PC frequency was lower than 100 Hz, high (111)/(200) ratio after annealing was achieved, which enhanced the corrosion resistance, resulting in minimizing the amount of void defects after CMP process. However, the behaviors of additives used in filling features depend on the pulse frequency. While using PC at lower pulse frequency in plating, more PEG would be displaced by SPS, which implies that the mechanism of superfilling would be disrupted as PC at lower pulse frequency is applied to filling features. We therefore proposed a modified deposition approach comprising direct current (DC) and PC, which can reduce the void defects after CMP process based on the above experimental results. We also developed a mathematical model to determine the switched time from DC to PC.
To achieve superfilling, several organic additives are usually employed in plating bath. These organic additives may result in incorporation of nonmetal impurities in Cu deposits. So, the effect of impurities distribution in Cu deposit on corrosion of Cu deposit during CMP process was studied in Chapter 3. The corrosion behavior was investigated by electrochemical and surface analytical techniques. Energy Dispersive X-ray (EDX) attached to Focus Ion Beam (FIB) was utilized to analyze the distribution of impurities. As more impurities were accumulated at grain boundary, the Cu oxide film formed on Cu deposit tended to be porous while immersed in CMP slurry. Therefore, corrosion was enhanced. The correlation between corrosion behavior and distribution of impurity was established in this chapter.
In Chapter 4, the reaction which caused the formation of localized defects between the interface between Cu deposit and tantalum nitride (TaN) barrier layer was studied. The experimental results of potentiodynamic polarization and secondary ion mass spectroscopy (SIMS) demonstrate that galvanic corrosion was not the dominant factor for such localized defects in our system, most impurities, such as carbon (C) and chloride ion (Cl-), aggregated near the interface between Cu deposit and TaN barrier layer. As a result, the correlation between localized defects at the Cu/TaN interface and the distribution of impurities was proposed herein.
In the second part of this dissertation, our studies at columbia university, we used a combined microfluidic, electrochemical device to characterize the adsorption and desorption behaviors of chemicals in solutions used for planarization techniques from Chapter 5 to 7. In Chapter 5, the adsorption and desorption kinetics of glycine and benzotriazole (BTA) in peroxide-based solution have been studied. The changes in time in the open circuit potential (OCP) of the working electrode were recorded. The OCP response demonstrates a transition consisting of two stages in the presence of BTA and glycine. During the first ~ 10 s, the OCP response seems to follow the behavior of a glycine-only solution. After that, the BTA adsorption behavior dominates. The desorption of glycine is characterized by a 10 ~ 20 s delay in changes in the OCP, followed by an abrupt change to the OCP. Desorption kinetics in the presence of BTA are considerably more complex. The interplay between glycine and BAT in peroxide-based solution at short times is discussed.
In Chapter 6, the removal kinetics of organic residues remaining after CMP were studied. Citric acid at various pH values, ranging from 2 to 9, was investigated as the cleaning solution. The optimized pH value of the citric-acid cleaning solution seems to be 5. The in situ electrochemical methodology is effective for preliminary evaluation or optimization of cleaning solutions. In addition, the electrochemical methodology may be utilized in screening inhibitors used in CMP process for their susceptibility to post-process cleaning.
Recently, electrochemical mechanical planarization (ECMP) is considered a potential replacement or complement to conventional CMP techniques. ECMP can operate at very low downforces (<1.0 psi), without slurry particles or oxidizers, and can also be tailored to achieve specific dissolution rates via applied potential. In Chapter 7, a possible ECMP electrolyte was developed through the modification of a phosphate based electrolyte, by the use of BTA. The pH value, electrolyte molarity, and BTA concentration were determined and studied by a rotating disk electrode and a microfluidic device. The 1 M pH 2 phosphate based electrolyte containing 0.01 M BTA is suitable for Cu EMP due to demonstration of inhibition effect, electrolyte stability, applicable dissolution rate, and quick adsorption ability of BTA. The planarization efficiency calculated from the removal rate with and without abrasion also demonstrates that the phosphate based electrolyte containing 0.01 M BTA has potential for use during Cu ECMP.

關鍵字

electroplating ； HASH(0x1abade30) ； CMP ； HASH(0x1abadf70) ； corrosion ； HASH(0x1abae0b0) ； slurry

並列摘要

無資料

並列關鍵字

HASH(0x1abae1c0) ； HASH(0x1abae260) ； HASH(0x1abae2d0) ； HASH(0x1abae370) ； HASH(0x1abae3e0) ； HASH(0x1abae480) ； HASH(0x1abae4f0)

參考文獻

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4. R. J. Contolini, S. T. Mayer, R. T. Graff, L. Tarte and A. F. Bernhardt, “Electrochemical Planarization of ULSI Copper”, Solid State Technol., 40, 155 , 1997.

6. Y. Morand, “Copper Metallization for Advanced IC: Requirements and Technological Solution”, Microelectron. Eng., 50, 391, 2000.

7. R. J. Contolini, A. F. Bernhardt and S. T. Mayer, “Electrochemical Planarization for Multilevel Metallization”, J. Electrochem. Soc., 141, 2503, 1994.