Barrier Chemical Mechanical Planarization Research Articles

Examining amino acids as environmentally friendly corrosion inhibitors for Cu and Co chemical mechanical planarization

Aliphatic amino acids (AAs) were investigated as environmentally friendly alternatives to benzotriazole (BTA) in the chemical mechanical planarization (CMP) process for Cu interconnects. The study evaluated the corrosion resistance, galvanic corrosion, and polishing removal rates (RR) for Cu and Co in a silica-based slurry containing methionine, glutamic acid, and leucine. Corrosion characteristics were determined using linear sweep voltammetry, and the removal rate was assessed by polishing wafers under controlled CMP conditions. Metal surfaces were analyzed by X-ray photoelectron spectroscopy, and scanning electron microscopy. Results indicated that the distinctive functional groups in the amino acids influenced corrosion and polishing behaviors driven by different Cu species in the passivating film layer. Methionine with its sulfur-containing side chain, exhibited exceptional inhibition capabilities by stabilizing Cu(Ⅰ) species compared to Cu(Ⅱ), involving a combination of physisorption and chemisorption. It also effectively controlled Cu-Co galvanic corrosion with a low igc = 0.9 μA/cm². Leucine, with its branched hydrocarbon chain, mitigated Cu corrosion through physisorption (20.5 kJ/mol), but increased galvanic corrosion for Co (igc = 45 μA/cm²). Leucine formed a thin passive layer that easily broke down during the Cu(I) to Cu(II) transition. Glutamic acid, with its additional carboxylic acid group, was not effective as a corrosion inhibitor but showed a relatively low |∆Ecorr| = 5 mV. Metal removal rates of Cu and Co followed the same trend with corrosion results. The selectivity of Cu:Co:TEOS removal with methionine was more comparable than that achieved with other additives, beneficial for Cu barrier CMP.

Synergistic Control on Co/Cu Galvanic Corrosion and Its Application for Co Barrier Chemical Mechanical Planarization in Alkaline Slurry

Selective chelation and protective film formation were synergistically combined to achieve Co/Cu galvanic corrosion control. Chelating agent imionodisuccinic acid and protective film formation agent benzotriazole are strategically chosen for fulfilling the above proposed task in alkaline solution for Co barrier chemical mechanical planarization (CMP). Chronopotentiometry and linear dynamic potential polarization methods are used to investigate the thermodynamics and kinetics of Co and Cu corrosion. A synergistic control of Co/Cu corrosion was accomplished by judiciously balancing the power of selective chelation and protective film formation. This systematic approach can be expanded to systematically design other metal CMP slurries to fulfil the desired polishing performance.

Galvanic corrosion inhibition from aspect of bonding orbital theory in Cu/Ru barrier CMP

In this report, the galvanic corrosion inhibition between Cu and Ru metal films is studied, based on bonding orbital theory, using pyridinecarboxylic acid groups which show different affinities depending on the electron configuration of each metal resulting from a π-backbonding. The sp2 carbon atoms adjacent to nitrogen in the pyridine ring provide π-acceptor which forms a complex with filled d-orbital of native oxides on Cu and Ru metal film. The difference in the d-orbital electron density of each metal oxide leads to different π-backbonding strength, resulting in dense or sparse adsorption on native metal oxides. The dense adsorption layer is formed on native Cu oxide film due to the full-filled d-orbital electrons, which effectively suppresses anodic reaction in Cu film. On the other hand, only a sparse adsorption layer is formed on native Ru oxide due to its relatively weak affinity between partially filled d-orbital and pyridine groups. The adsorption behaviour is investigated through interfacial interaction analysis and electrochemical interaction evaluation. Based on this finding, the galvanic corrosion behaviour between Cu and Ru during chemical mechanical planarization (CMP) processing has been controlled.

(Invited) Controlling Nano-Scale Chemically Modified Thin Films for Chemical Mechanical Planarization

This is a review paper on the effect of chemicals modified thin films on CMP process development. As the microelectronics manufacturing faces the challenges related to the Beyond Moore’s Scale adaptation, Chemical Mechanical Planarization (CMP) process control becomes much more critical yet difficult simultaneously. The need for planarizing larger scale wafers at an atomic scale precision with superior removal rate selectivity and zero defect focus demands a nano-scale control on the process performance. This study reviews the atomic scale chemical and mechanical interactions on CMP as it applies to traditional as well as the next generation materials in microelectronics manufacturing. Once the behavior of the wafer surface is understood at an atomic level, the process control metrics can be tuned accordingly.In an attempt to come up with the design criteria for the slurry chemistry, chemically modified layer formation is evaluated on conducting, semiconducting and insulating materials as a function of evaluating the nano-scale surface topography and change in surface energy. Metallic films are studied in terms of their corrosion and passivation behavior through macro-scale electrochemical evaluations as well as the surface sensitive characterization techniques such as XRR, XRD and FTIR [1, 2]. In addition, a modeling approach is introduced through Cahn Hilliard Equation (CHE) approximation to the surface energy minimization on the metal-oxide formation by nucleation [3]. Furthermore, removal rate selectivity properties of the semiconductor materials are discussed on conventional and III-V semiconductors and insulators as a function of chemically modified film alteration [4-5]. Some high-end applications such as (i) tungsten T-gate transistors, (ii) new liner/barrier materials [6], (iii) germanium based high-speed, shallow trench isolation transistors and (iv) high-power transistors and LED applications where III/V semiconductors are deliberated. As a new challenge, 3-D implementations of the CMP process, where the chemically modified nano-films impact the materials performance are also introduced. Ozdemir, Basim, G.B. "Effect of Chemical Mechanical Polishing on Surface Nature of Titanium Implants FT-IR and Wettability Data of Titanium Implants Surface After Chemical Mechanical Polishing Implementation," Data, in Brief, 10, P 20-25, 2017. Karagoz, A., and Basim, G.B. “Controlling Germanium CMP Selectivity through Slurry Mediation by Surface Active Agents," ECS Journal of Solid State Science and Technology, CMP Special Issue, 4 (11) P5097-P5104, 2015. Karagoz, A., Sengul, , Basim, G.B., “A Cahn Hilliard Modeling of Metal Oxide Thin Films for Advanced CMP Applications," 225th ECS Meeting – Orlando, Florida, USA, May 11-15, 2014, ECS Transactions, 61 (17) 15-20 (2014). Karagoz, A., Craciun, V., Basim, G.B., “Characterization of Nano-Scale Protective Oxide Films_ Application on Metal Chemical Mechanical Planarization”. ECS Journal of Solid State Science and Technology, 4 (2) P1-P8, 2015. Ozbek, S., Akbar, W., Basim, G.B. “ Optimized Process Design for GaN Chemical Mechanical Planarization” ECS Journal of Solid State Science and Technology, Special Issue on GaN-Based Electronics for Power, RF, and Rad-Hard Applications , 6-11, P S3084-S3092, 2017. Yagan, R., Basim, G.B., “A Fundamental Approach to Electrochemical Analyses on Chemically Modified Thin Films for Barrier CMP Optimization," ECS J. Solid State Sci. Technol. 8-5, P3118-P3127, 2019.

A High Antibacterial Weakly Alkaline Barrier Slurry with the Tunable Selectivity

Barrier chemical mechanical planarization (CMP) is a critical process in the manufacturing of integrated circuits (ICs). Bacterial infestation, the material removal rate (MRR) selectivity and slurry aging are important factors in the evaluation of barrier CMP slurry. In this paper, H2O2 concentration in a lower level was used to adjust the rate selectivity and enhance removal rate on copper to ensure the trench copper thickness reaches the target value. The effects of dodecyl dimethyl benzyl ammonium chloride (DDBAC) and 1,2-Benzisothiazol-3-one (BIT) on bacteria growth were investigated. The total organic carbon analysis and the after-cleaning defect map of the patterned wafer proved the DDBAC and BIT contained in the barrier slurry could prevent bacteria formation within four weeks. The effect of aging on the performance was investigated systematically for the slurry contained containing H2O2, DDBAC and BIT. Aging has been shown to have a small effect on zeta potential, particle size and viscosity of the slurry. The polishing rate and pH decrease with time due to chemical degradation of a part of H2O2. Luckily, the rate selectivity still remains at a high value over time and the barrier slurry after 30d has an effective performance in topography modification.

Initial Study on the Polishing Performance of Silica Abrasive Size in Copper Barrier Chemical Mechanical Planarization (CMP)

In this study, two types of copper barrier metal slurries used. We analyze the abrasive particle size by light scattering and SEM. Under different particle size distribution, polishing performance discussed. As a result, the material removal rate is higher even in smaller abrasive mean size and defects are not problematic in a certain pitch size for yield.

A Fundamental Approach to Electrochemical Analyses on Chemically Modified Thin Films for Barrier CMP Optimization

Chemical Mechanical Planarization (CMP) process development for 10nm nodes and beyond demands a systematic understanding of atomic-scale chemical and mechanical surface interactions for the control of material removal, selectivity, and defectivity. Particularly the CMP of barrier/liner films is challenging with new materials introduced to better adhere the contact metal at the interface and limit the probability of metal diffusion to the transistors. The relative selectivity of the CMP removal rates of the barrier materials against the contact metal needs to be controlled depending on the integration scheme. This paper focuses on understanding the barrier CMP process selectivity on the model W/Ti/TiN applications through electrochemical evaluations and chemically modified thin film analyses. Ex-situ electrochemical evaluations are conducted on the W/Ti/TiN system to evaluate the passivation rates in various slurry formulations as a function of the slurry chemistry and the abrasive particle solids loading. Results of the passivation rates are compared to the removal rate selectivity and the post CMP surface quality on blanked W, Ti, and TiN films. A new methodology for CMP slurry formulations through ex-situ electrochemical analyses is outlined for new and more challenging barrier films while simultaneously highlighting an approach for corrosion prevention on the metallic layers.

Role of Dispersant Agent on Scratch Reduction during Copper Barrier Chemical Mechanical Planarization

The chemical mechanical planarization (CMP) has been one of the major manufacturing process to provide global and local surface planarizations in integrated circuits (IC) fabrications. Defects such as micro-scratches generated during CMP can lead to severe circuit failure, which affects yield. In the present work, ethoxylated decylalchohol (EDA) was used as dispersant agent to prevent the particles agglomeration to reduce scratches. Firstly, the effect of EDA on particle size distribution (PSD) of the slurry was investigated by dynamic light scattering (DLS) method. Then the effect of EDA on large particle counts (LPC) was studied through a dual sensor single particle optical sensing (SPOS) analysis method. The wetting ability of slurries as a function of EDA concentration was also studied. Finally, the defect scan tool and scanning electron microscope (SEM) reviewer were used to identify the scratch defects. The results show that the addition of EDA into the slurry can enhance the dispersity of colloidal silica abrasives and significantly reduce the number of large particles in the slurry, the SEM review results show that the scratch counts remarkably decreases with EDA concentration increasing. It can be demonstrated that the EDA can effectively reduce the scratch counts.

Improvement of Barrier CMP Performance with Alkaline Slurry: Role of Ionic Strength

With the development of ultra-large scale integrated circuits, chemical mechanical planarization (CMP) has been one of the most critical processes to achieve global planarization. The ionic strength of slurry is one of the key factors influencing the material removal rate and surface quality during CMP process. In this paper, potassium nitrate was used to enhance ionic strength in baseline slurry, and the removal mechanism of copper and TEOS (tetraethylorthosilicate) were investigated. The results showed that, when the potassium ionic strength was 100mM, TEOS and copper removal rate can reach 768Å/min and 395Å/min respectively, and the removal rate selectivity ratio was 1.98 which can match well with the industrial production requirement. On pattern wafer, after polishing 60s, the dishing and erosion were amended to be 570 ± 50Å and 195 ± 30Å respectively, and the number of total defects was about 9. Such results provide guiding significance for industrial production.

Multi-objective optimization of tungsten CMP slurry for advanced semiconductor manufacturing using a response surface methodology

In this study, a response surface methodology (RSM) coupled with a face center cube design (FCD) was used to optimize the three principal components (i.e., Fe(NO3)3, H2O2, and SiO2 abrasives) in polishing slurries for a W barrier chemical mechanical planarization (CMP) process. The experimental ranges of the three components were 10–50ppm of Fe(NO3)3, 0.3–0.9wt% of H2O2, and 1–5wt% of SiO2 abrasives. Based on the experimental data from the FCD, the second-order models for the material removal rate (MRR) of the W and Oxide films were fitted; these were determined to be statistically valid and reliable. We have achieved the optimal conditions for the three components where the MRR is maximized and the selectivity between the W and Oxide MRRs is ~1. The predicted MRR and selectivity at the optimal conditions were well correlated with the results of a confirmation run, which was conducted by using the W barrier CMP process with W-patterned wafers. In addition, we employed a particular RSM called dual-response optimization in order to investigate the tradeoff between the MRR and selectivity. Based on the tradeoff information, process engineers can conduct the optimization of the three components more flexibly.

The optimization of FA/O barrier slurry with respect to removal rate selectivity on patterned Cu wafers**Project supported by the Special Project Items No. 2 in National Long-Term Technology Development Plan (No. 2009ZX02308), the Natural Science Foundation of Hebei Province (No. F2012202094), and the Doctoral Program Foundation of Xinjiang Normal University Plan (No. XJNUBS1226).

Because the polishing of different materials is required in barrier chemical mechanical planarization (CMP) processes, the development of a kind of barrier slurry with improved removal rate selectivity for Cu/barrier/TEOS would reduce erosion and dishing defects on patterned Cu wafers. In this study, we developed a new benzotriazole-free barrier slurry named FA/O barrier slurry, containing 20 mL/L of the chelating agent FA/O, 5 mL/L surfactant, and a 1:5 concentration of abrasive particles. By controlling the polishing slurry ingredients, the removal rate of different materials could be controlled. For process integration considerations, the effect of the FA/O barrier slurry on the dielectric layer of the patterned Cu wafer was investigated. After CMP processing by the FA/O barrier slurry, the characteristics of the dielectric material were tested. The results showed that the dielectric characteristics met demands for industrial production. The current leakage was of pA scale. The resistance and capacitance were 2.4 kω and 2.3 pF, respectively. The dishing and erosion defects were both below 30 nm in size. CMP-processed wafers using this barrier slurry could meet industrial production demands.

Next generation barrier CMP slurry with novel weakly alkaline chelating agent

To strengthen the device performance with the pattern wafer by enhancing the Cu polishing rate and improve the surface roughness with the Cu lines, a new weakly alkaline chelating agent with a barrier slurry is developed to meet the process demand of the advanced barrier chemical mechanical planarization (CMP). This new chelating agent has a stronger chelating ability and a lower pH value than the previous generation-FA/O I chelating agent researched before. Without an unstable oxidant agent added in the polishing slurry, it is difficult to enhance the copper polishing rate during the barrier CMP. The stronger chelating ability of the new chelating agent could increase the copper polishing rate along with controlling the Cu/Ta/TEOS removal rate selectivity to meet the requirements of the IC fabrication process. Thus it has solved the problem of excessive roughness due to the lower polishing rate, avoiding reducing the device performance with the pattern wafer. The new chelating agent with its lower pH value could make it possible to protect the low-k dielectric under the barrier layer from structurally breaking. The CMP experiment was performed on the 12 inch MIT 854 pattern wafers with the barrier slurry containing the new weakly alkaline chelating agent. By the DOE optimization, the results indicate that as the new chelating agent concentration in the slurry was up to 2.5 mL/L, the copper polishing rate is about 31.082 nm/min. Meanwhile, the wafer surface has a rather low roughness value of 0.693 nm (10 × 10 μm), the correction ability with the above slurry is adapted to the next generation barrier CMP and the k value of the low-k dielectric seems to have no k-shift. All the results presented show that the new weakly alkaline chelating agent with its superior performance can be used for the advanced barrier CMP.

Microreplicated Conditioners for Cu Barrier Chemical-Mechanical Planarization (CMP)

Removal rates of low-k SiCOH dielectric and scratch defect density of Cu barrier CMP on a soft polyurethane pad with conditioning are characterized and compared between conventional diamond tip conditioner and two types of microreplicated diamond-coated conditioners. Data collected from high volume manufacturing environment demonstrate stable and uniform SiCOH removal rates plus lower scratch density with up to 1000 wafer passes on the soft pad with the microreplicated conditioners, relative to the conventional diamond tip conditioner. Scratch defects are categorized based upon their length and severity. The formation mechanism for each type of scratches are hypothesized. Groove depth and asperity height of soft pads are analyzed in order elucidate the observed differences in removal rates and scratch density with various different pad conditioners.

Alkaline barrier slurry applied in TSV chemical mechanical planarization

We have proposed a TSV (through-silicon-via) alkaline barrier slurry without any inhibitors for barrier CMP (chemical mechanical planarization) and investigated its CMP performance. The characteristics of removal rate and selectivity of Ti/SiO2/Cu were investigated under the same process conditions. The results obtained from 6.2 mm copper, titanium and silica show that copper has a low removal rate during barrier CMP by using this slurry, and Ti and SiO2 have high removal rate selectivity to Cu. Thus it may be helpful to modify the dishing. The TSV wafer results reveal that the alkaline barrier slurry has an obvious effect on surface topography correction, and can be applied in TSV barrier CMP.

Electrochemical Characterizations and CMP Performance of Ru Slurry

Currently, the manufacture of integrated circuits and fabrication of electronic devices requires the use of various types of chemical mechanical polishing compositions to selectively remove different metal, barrier, dielectric, low-k, ultra-low-k and other films at desirable rates to achieve the global planarization goal on the surfaces of patterned wafers. For more advanced node processing and applications, the copper metal lines are getting thinner and narrower, which leads to increased resistivity and causes electrical signal loss in the interconnection lines of the fabricated electronic devices. Therefore, new barrier layer materials other than Ta, TaN, Ti and TiN have been introduced in order to reduce the electrical signal loss beyond 20nm node applications. Ruthenium (Ru) has been used and tested as one of the new promising barrier layer materials. The introduction of Ru as a new barrier layer further complicates electrochemical and chemical reactions involved in a barrier chemical mechanical planarization process. Our studies focused on discovering the effects of key chemical components used in the CMP polishing compositions for polishing copper/ruthenium films and the effects of such polishing compositions on corrosion current, open circuit potential, galvanic corrosion and AC impedance on both ruthenium and copper films. The chemical mechanical polish results are reported together with these electrochemical studies. Using electrochemical studies, the effects of corrosion inhibitors on galvanic corrosion behavior at the Cu/Ru interface enables a more effective selection of suitable corrosion inhibitors for polishing Cu/Ru films.

A study on the comparison of CMP performance between a novel alkaline slurry and a commercial slurry for barrier removal

Chemical mechanical planarization (CMP) is a vital process for the fabrication of advanced copper multilevel interconnects schemes. The formidable challenge in barrier CMP is that the copper lines suffer from dishing and erosion. There have been several efforts to reduce both dishing and erosion by extensive experimental investigations. However, most of the slurries applied in CMP processes are acidic and containing some kinds of inhibitors. In this paper, we have proposed a novel alkaline slurry without any inhibitors (namely slurry A) for barrier CMP and investigated its CMP performance by comparison with a commercial slurry (namely slurry B). The CMP performance is evaluated in terms of surface roughness, dishing and erosion values. The CMP results obtained from the roughness maps of copper blanket wafers show that the Cu films polished by slurry A has lower surface roughness values and good surface quality than that polished by slurry B. CMP data obtained from patterned wafers show that the amounts of dishing increases with the increment of line width, while the erosion has a slight decrease with increasing line width, the tendency is apparently the same by using the two different slurries, but slurry A provides a lower dishing and erosion values. The root mean square (RMS) roughness within 10 × 10 μm2 area of copper lines after being polished by slurry A and slurry B is 0.125 and 0.225 nm, respectively. By comparison, the alkaline barrier slurry has a good planarization performance and can be useful for barrier CMP.

An advanced alkaline slurry for barrier chemical mechanical planarization on patterned wafers

We have developed an alkaline barrier slurry (named FA/O slurry) for barrier removal and evaluated its chemical mechanical planarization (CMP) performance through comparison with a commercially developed barrier slurry. The FA/O slurry consists of colloidal silica, which is a complexing and an oxidizing agent, and does not have any inhibitors. It was found that the surface roughness of copper blanket wafers polished by the FA/O slurry was lower than the commercial barrier slurry, demonstrating that it leads to a better surface quality. In addition, the dishing and electrical tests also showed that the patterned wafers have a lower dishing value and sheet resistance as compared to the commercial barrier slurry. By comparison, the FA/O slurry demonstrates good planarization performance and can be used for barrier CMP.

Integrated Product and Process For Copper and Barrier CMP

Chemical mechanical planarization (CMP) of copper and barrier interconnects are significant value-adding steps in semiconductor manufacturing. There are a number of materials, designs, processes, and requirements to achieve a successful system. Variables that impact CMP include the selection of the polishing tool, pad, slurry, conditioner, ring, cleans and the elements of polishing processes including down-force, flow rate, time, temperature, friction, conditioning, and cross-contamination. Given the multiplicity of semiconductor design, materials, and processes, it is not surprising that CMP varies from fab to fab. We describe in this Paper, Cabot Microelectronics' approach to helping our customers develop an integrated system of slurry, pad, and auxiliary processes to achieve improved CMP process performance, yields, and costs.

구리 CMP 후 연마입자 제거에 화학 기계적 세정의 효과

Cleaning is required following CMP (chemical mechanical planarization) to remove particles. The minimization of particle residue is required with each successive technology generation, and the cleaning of wafers becomes more complicated. In copper damascene process for interconnection structure, it utilizes 2-step CMP consists of Cu and barrier CMP. Such a 2-steps CMP process leaves a lot of abrasive particles on the wafer surface, cleaning is required to remove abrasive particles. In this study, the chemical mechanical cleaning(CMC) is performed various conditions as a cleaning process. The CMC process combined mechanical cleaning by friction between a wafer and a pad and chemical cleaning by CMC solution consists of tetramethyl ammonium hydroxide (TMAH) / benzotriazole (BTA). This paper studies the removal of abrasive on the Cu wafer and the cleaning efficiency of CMC process.

Development of Barrier Slurry for Improved Electrical Performance

As device dimensions shrink to the sub-65 nm regime, a greater demand is placed upon the barrier polishing process. Therefore the ability to modulate the barrier chemical mechanical planarization performance window by process and formulation synergy can provide tunability at advanced technology nodes to meet stringent electrical, topography, and defect requirements. This study introduces one approach in achieving the synergy between barrier polishing slurry and the development of a robust process. The system investigated has demonstrated desirable uniformity control and greater margin for polishing. Extensive layer testing (more than 10 wafer lots) has consistently shown better within-wafer (resistance) spread compared to process of record, with improvement above 30% for all layers. The slurry also shows a more gradual fluctuation over a 20 s polish time range. A marathon run has also shown consistent polishing rate performance over the pad life with comparable defect density and characteristics.