Chemical Mechanical Planarization Slurry Research Articles

Understanding and mitigating temperature-induced agglomeration in silica-based chemical mechanical planarization (CMP) slurry storage

This study explores the impact of temperature on silica particle agglomeration in Chemical Mechanical Planarization (CMP) slurries during storage. Slurries were stored at 15 °C, room temperature, and 45 °C, and analyzed. ATR-FTIR, RAMAN, SEM, zeta potential, and LPC were employed providing qualitative and quantitative data on slurry stability and agglomeration tendencies. Elevated temperature storage significantly increased agglomeration and large particle counts with particle counts value of ∼1.2×107 Part./ml, likely due to water molecule dehydration leading to destabilization. Low-temperature storage also induced agglomeration but to a lesser extent with particle counts the value of ∼4.0×106 Part./ml compared with the RT (∼2.0×106 Part./ml). Short-term storage yielded soft agglomerates with LPC of ∼(2.0–4.0)×106 Part./ml, while long-term high-temperature storage led to hard agglomerates with LPC of ∼3.0×107 Part./ml. The ATR-FTIR and Raman analysis indicate that the spectroscopic features of the original slurry exhibited changes upon variation of storage temperature from RT to 15 and 45 °C. The study also explored the reversibility of agglomeration post-treatment, indicating a potential mitigation pathway. The results demonstrated an inverse relationship between temperature and dissolved oxygen (DO) in silica slurries. For example. the curves depict a decrease in oxygen content from ∼10 ppm at RT to 7 ppm at 45 °C with increasing aging time. A mechanism outlining the temperature and aging-induced agglomeration was proposed, linking temperature fluctuations and thermodynamic aspects to colloidal stability. These findings offer a robust understanding of temperature-induced agglomeration in silica-based CMP slurry storage, paving the way for developing strategies to alleviate these issues and ensuring consistent CMP performance in semiconductor manufacturing.

Experimental Strategies for Studying Tribo-Electrochemical Aspects of Chemical–Mechanical Planarization

Chemical–mechanical planarization (CMP) is used to smoothen the topographies of a rough surface by combining several functions of tribology (friction, lubrication), chemistry, and electrochemistry (corrosion, wear, tribo-corrosion). The surface layer of interest is structurally weakened by the chemical and/or electrochemical reactions of selected additives in a polishing slurry, and the modified surface is flattened by the abrasion of a polishing pad with or without abrasive particles. The chemically active CMP slurry also serves as a lubricant for polishing and enables planarization at a microscopic level while avoiding the formation of defects at the processed surface. Applications of CMP are wide-ranging in various material-processing technologies and, specifically, it is a critical manufacturing step of integrated circuits. The CMP of metals is a significant part of this processing scheme and is associated with highly complex tribo-electrochemical mechanisms that are now additionally challenging due to various new requirements of the advanced technology nodes. The present review examines the current statuses of experimental strategies for collecting important mechanistic details of metal CMP that are necessary to design and assess CMP consumables. Both traditional and underexplored experimental techniques are discussed with illustrative results, including many previously unpublished findings for certain CMP systems of current interest.

Effect of Ferric Catalyst on Chemical Decomposition of Polyimide-Film-Surface for Enhancing Chemical–Mechanical-Planarization Polishing-Rate

In semiconductor devices, flexible displays and microelectromechanical systems (MEMS), polyimide has been utilized as a protecting layer, interlayer dielectric polymer for thin-film metallization and low-stress polymer for wafer-level packaging. Since, it has low stress, low thermal coefficient of expansion, low moisture, high modulus, good ductility, thermal stability, high glass transition temperature, and low process cost. However, the applications of polyimide required estentially chemical-mechanical-planarization (CMP) of the polyimide-film-surface. that can be challenging to enhance the polishing rate of the polyimide-film-surface because of the hard and covalently bonded nature of the polyimide-film surface.In this study, to enhance chemical dominant CMP, the chemical decomposition of the polyimide-film-surface was performed by hydrolysis reaction between ferric ions and oxygen atoms covalently bonded with pyromellitimide on the polyimide-film-surface during CMP, as shown in Fig. 1. The polyimide-film polishing rate was estimated as a function of ferric catanylst concentration in the CMP slurry;surprisingly, the polyimide film polishing rate(i.e., 1465A/min) peaked at a specific(i.e., 0.05wt%) ferric catalyst concentration, as shown in Fig. 2. This result indicates that the degree of chemical decomposition during CMP could be principally determined by ferric nitrate concentration. The details of both chemical and mechanical dominant polishing mechanisms will be presented. In addition, the evidence of the chemical composition of the polyimide-film-surface will be demonstrated, depending on the ferric catalyst concentation in the CMP slurry. Figure 1

Silicon-Germanium on Insulator CMP Slurry Designed with Oxidant and Accelerator Heading an Amine Functional Group for Remarkably Enhancing Polishing Rate

High quality single crystal silicon-germanium-on-insulator (SGOI) has a potential to enable the next generationof photonic and electronic devices. However, to utilize an SGOI structure, a high SiGe-film polishing rate isnecessary (i.e., > 200 nm/min) for polishing the facet crystalline SiGe during the fabrication of SiGe on insulatorthrough epitaxial growth processes.In previous studies, amine-based chemicals as SiGe-film polishing rate accelerators have been reported, butthere were limitations in increasing the SiGe-film polishig rate by considering only the chemical reaction of SiGe-film surface. In this study, for the first time, both oxidant(i.e., H2O2) and accelerator with amine functional groups(i.e., triethanolamine) were designed, resulting in a surprising increase in the SiGe-film polishing rate of 270nm/min, as shown Fig. 1a.The SiGe chemical mechanical planarization (CMP) mechanism was clearly demonstrated by preciselyinvestigating both chemical properties(i.e., GeO2 spectra intensity via X-ray photoelectron spectroscopy) andmechanical properties(i.e., electrostatic repulsive force between colloidal silica abrasives and the SiGe-film viaelectrophoretic light scattering). The remarkable enhancement of the SiGe-film polishing rate for oxidant andtriethanolamine was the result of (i) minimizing the loss of degree of SiGe surface oxidation, as shown Fig. 2, (ii)enhancing degree of adsorption of the CMP slurry on the polished SiGe-film surface during CMP, and (iii)decreasing the electrostatic repulsive force between colloidal silica abrasives and the SiGe-film surface, as shownFig 1b. Finally, successful removal of the facets in SiGe on insulator wafers was achieved, securing excellentsurface roughness characteristics. SiGe-film polishing mechanism and the SiGe slurry characteristics will bepresented in detail. Figure 1

Environmentally Friendly Amino Acid-Based Polishing Slurry with Reduced Galvanic Corrosion at Copper/Cobalt Interface for Advanced Cu Interconnect Applications

Chemical mechanical planarization (CMP) is an integral part in semiconductor processing including the back-end-of-line (BEOL) step. A goal of CMP is to uniformly polish the metal interconnects and the liner/barrier materials while minimizing CMP-related defects such as pitting, dissolution, and galvanic corrosion. A variety of azoles are used as corrosion inhibitors such as benzotriazole (BTA) to prevent corrosion defects during polishing. [1,2] These azoles work together with particles in the slurries to polish the overplated metal forming the interconnects. However, azoles are very poorly biodegradable during wastewater treatment and highly toxic to the nitrification process, which requires expensive wastewater treatment challenges.[3,4] Also, it is known that the use of BTA leads to contamination of Cu films by forming undesirable hydrophobic organic residues (e.g., BTA and Cu-BTA complexes),[5] making their removal very difficult during cleaning. To address these challenges aliphatic amino acids were examined as potential corrosion inhibitors to replace problematic azoles in CMP slurries.Three amino acids were considered in a model CMP slurry. These three were chosen for their unique functional groups: methionine, containing a sulfur group, glutamic acid, having an extra carboxylic acid group, and leucine, having a branched hydrocarbon chain. A representative polishing slurry with 35 nm colloidal silica abrasives, 1 wt% hydrogen peroxide as an oxidizer, 0.5wt% arginine as a complexing agent, at pH 8 was used. Three experimental aims were considered (1) corrosion characterization of the three amino acid and BTA electrolytes with linear sweep voltammetry; (2) comparison of the Co and Cu metal removal rate (MRR) in polishing experiments with a proto-type CMP polisher with 8” wafers, and (3) oxidation of the amino acids and BTA in a Fenton assisted electrooxidation reaction. Methionine was most effective in controlling the galvanic corrosion of the Cu-Co couple. The Co and Cu MRR decreased in the presence of three amino acids and showed comparable removal selectivity. The forced degradation of the amino acids under the Fenton-assisted electrooxidation confirmed that they were more readily degraded compared to BTA. Acknowledgments: This work was supported by the Semiconductor Research Corporation grant (Task 3100.001) under the Global Research Collaboration program. References Seo, J., A review on chemical and mechanical phenomena at the wafer interface during chemical mechanical planarization. Journal of Materials Research 2021, 1-23.C. Peethala, H. P. Amanapu, U. Lagudu, and S.V. Babu, J. Electrochem. Soc, 159(6), H582-H588, 2012.D.E. Speed, Chapter 11, Advances in chemical mechanical planarization (CMP) 2nd edition, Babu, S. V., Ed. 2021.G. Li et al. / Chemosphere 241 (2020) 1249932.Seo, J.; Vegi, S. S. R. K. H.; Babu, S.V. ECS Journal of Solid State Science and Technology 2019, 8 (8), P379–P387.

Evaluation of chemical mechanical planarization slurry dispersion using a combined scanning mobility particle sizer-optical particle sizer system

A combined scanning mobility particle sizer-optical particle sizer (SMPS-OPS) system was evaluated for measuring the dispersion of a chemical mechanical planarization (CMP) slurry. The dilution rate of one particle per droplet was confirmed to minimize agglomeration. The SMPS and OPS measurements showed similar particle size distributions of 400 nm polystyrene latex particles. The particle size distributions of settled ceria and silica slurries were measured using the SMPS-OPS system. The settled commercial ceria slurry showed a decrease in the number concentration in the top layer. In the bottom layer, increases in the concentration of active particles and in the number of large particles were observed. This indicates that large particles were formed during settling of the slurry. In the silica slurry, there was a change in concentration with depth and little change in number of large particles with settling time. The SMPS-OPS system was able to analyze CMP slurries across a wide range of particle diameters for both active and large particles. Therefore, this system can be helpful for analysis of CMP slurry size.

Size distribution measurement of mixed abrasive slurry for chemical mechanical planarization using an electrospray scanning mobility particle sizer

As the popularity of mixed abrasive slurry (MAS) use in chemical mechanical planarization (CMP) increases, analysis of number concentration and mixing ratios become increasingly important. In this study, the applicability of an electrospray-scanning mobility particle sizer (ES-SMPS) to particle-size analysis of MAS for measuring number concentration and mixing ratio is investigated. Additives to improve the CMP process cause non-volatile residue (NVR) peaks, making it difficult to obtain clear particle-size distributions. Because NVR peaks are affected by the size of the generated droplets, an aerosol generator that produces droplets of different sizes. Compared to atomizers that generate large droplets, an electrospray that generates small droplets minimizes disturbance of NVR peaks, allowing for clear particle-size distributions. Using ES-SMPS, the number concentration and mixing ratio of an MAS were analyzed with no interference from NVR peaks. CMP evaluation of an MAS of a certain number concentration confirmed that using an MAS with a constant number concentration improves the removal rate. Number concentration–based MAS analysis is therefore possible using existing weight concentration–based MAS research and ES-SMPS measurements. Measurement of abrasive number concentrations using ES-SMPS can also provide more realistic information on the number of participating abrasives.

The Effects of Friction and Temperature in the Chemical-Mechanical Planarization Process.

Chemical-mechanical planarization (CMP) represents the preferred technology in which both chemical and mechanical interactions are combined to achieve global planarization/polishing of wafer surfaces (wafer patterns from metal with a selective layer, in this paper). CMP is a complex process of material removal process by friction, which interferes with numerous mechanical and chemical parameters. Compared with chemical parameters, mechanical parameters have a greater influence on the material removal rate (MRR). The mechanical parameters manifest by friction force (Ff) and heat generated by friction in the CMP process. The Ff can be estimated by its monitoring in the CMP process, and process temperature is obtained with help of an infrared rays (IR) sensor. Both the Ff and the MRR increase by introducing colloidal silica (SiO2) as an abrasive into the selective layer CMP slurry. The calculated wafer non-uniformity (WNU) was correlated with the friction coefficient (COF). The control of Ff and of the slurry stability is important to maintain a good quality of planarization with optimal results, because Ff participates in mechanical abrasion, and large Ff may generate defects on the wafer surface. Additionally, the temperature generated by the Ff increases as the SiO2 concentration increases. The MRR of the selective layer into the CMP slurry showed a non-linear (Prestonian) behavior, useful not only to improve the planarization level but to improve its non-uniformity due to the various pressure distributions. The evaluation of the Ff allowed the calculation of the friction energy (Ef) to highlight the chemical contribution in selective-layer CMP, from which it derived an empirical model for the material removal amount (MRA) and validated by the CMP results. With the addition of abrasive nanoparticles into the CMP slurry, their concentration increased and the MRA of the selective layer improved; Ff and MRR can be increased due to the number of chemisorbed active abrasive nanoparticles by the selective layer. Therefore, a single abrasive was considered to better understand the effect of SiO2 concentration as an abrasive and of the MRR features depending on abrasive nanoparticle concentration. This paper highlights the correlation between friction and temperature of the SiO2 slurry with CMP results, useful to examine the temperature distribution. All the MRRs depending on Ef after planarization with various SiO2 concentrations had a non-linear characteristic. The obtained results can help in developing a CMP process more effectively.

Effect of ammonium halide salts on wet chemical nanoscale etching and polishing of InGaAs surfaces for advanced CMOS devices

Wet surface treatment of InGaAs is crucial for high-performance complementary metal-oxide semiconductor (CMOS) devices as it reduces material loss and oxide formation in the InGaAs layer. In this present study, the surface chemistries of In0.53Ga0.47As during wet chemical etching and the chemical-mechanical planarization (CMP) process in acidic (HCl/H2O2/H2O mixture) and alkaline (NH4OH/H2O2/H2O mixture) solutions were investigated. Elemental oxide formation, surface termination, and stoichiometry after the chemical etching/CMP process were investigated through X-ray photoelectron spectroscopy and atomic force microscopy. In wet chemical etching, the dissolution of the InGaAs elemental oxide was more prominent in acidic HCl mixture solutions compared to alkaline NH4OH mixture solutions. It was observed that the overall surface etching was more aggressive in acidic solution, whereas the alkaline solution provided higher surface roughness (Ra, ∼7.19 nm, scanning area of 5 μm × 5 μm) due to the lower dissolution capacity of indium oxide. The effects of the oxidizer and the slurry pH on the removal rate, Ra, and surface contamination were evaluated after the InGaAs CMP process. A high removal rate (∼110 nm/min) and considerably lower surface contamination were obtained using an alkaline slurry (pH 10). A novel InGaAs CMP slurry is developed by adding different ammonium halide salts to the alkaline slurry for improving surface roughness and removal rate. The addition of ammonium halide salts to an alkaline slurry was very effective in achieving a higher removal rate (∼175 nm/min) and smoother surface (Ra < 0.6 nm) with lower contamination during the InGaAs CMP process.

Study on enhancement and mechanism of K2SO4 in CMP slurries for copper film polishing removal effect

The efficient copper removal of the in the multi-layer copper interconnect copper film chemical mechanical planarization (CMP) process is one of the important indicators for high production efficiency of integrated circuit process. The chemical corrosiveness of polishing slurries to copper is the key factor affecting the copper removal rate. Since the copper polishing slurries are relied too much on the synergistic effect of complexing agent and oxidant for the copper chemical dissolution to achieve efficient removal of copper film, the planarization and corrosion of copper CMP cannot be well improved. In this paper, it was found that adding potassium sulfate (K2SO4) in polishing slurries can improve the copper removal effect of CMP. In this paper, the mechanism of the effect enhancement of K2SO4 was explored with series of characterization experiments. Firstly, the influence of K2SO4 on the increase of electrochemical corrosion degree of copper electrode was studied by electrochemical method. Secondly, based on X-ray photoelectron spectroscopy (XPS) and laser scanning confocal microscope (LSCM), it was determined that the copper surface oxide formation increased after electrochemical corrosion caused by K2SO4. Finally, the efficiency of copper polishing removal of K2SO4 in polishing slurries was verified by CMP experiments, and the dynamic oxidation enhancement mechanism of K2SO4 in polishing slurries for CMP copper removal was analyzed.

Surface Planarization of CdZnTe Wafers: Effect of Slurry Formulation and CMP Processing Parameters on Surface Planarity

This study investigates the effect of chemical mechanical planarization (CMP) processing parameters such as platen velocity, the concentration of the oxidizer and abrasive nanoparticle, slurry pH and surfactant types on the surface roughness of cadmium zinc telluride (CdZnTe) substrate. It was found that these parameters have a significant effect on the quality of the polished surfaces. It was found that lower platen velocity, lesser concentration of abrasive particles, basic slurry pH, and addition of anionic surfactant (SDS) into the CMP slurry solution showed improved surface planarity. Optical Surface Profiler and atomic force microscopy (AFM) techniques were used to monitor the surface topography before and after polishing. A notable root-mean-square surface roughness, (Rq), ∼0.9 nm, has been obtained on the polished CdZnTe (CZT) surface over a scan area of 481 × 361 μm2 under the optimized conditions of 60 rpm relative velocity, slurry pH of 9, 3.75 vol% of oxidizer (H2O2) and 1.25 wt% of abrasive (SiO2 nanoparticle). A probable mechanism of the present CMP surface planarization of CZT substrate has been proposed. Unlike the conventional surface planarization processes, which involve two-step lapping followed by CMP for the CZT surfaces, we have developed a single step CMP process to obtain good surface planarity.

Theoretical validation of inhibition mechanisms of benzotriazole with copper and cobalt for CMP and post-CMP cleaning applications

Corrosion inhibitors are essential additives for metal CMP (chemical mechanical planarization) slurries and post-metal CMP cleaning solutions. They effectively address corrosion issues by forming complexes with the metal surfaces, but they sometimes cause organic defects. Hence understanding the interactions between the corrosion inhibitor and metal surface is important. In this study, the formation and stability of the Cu/Co-benzotriazole (BTA) complex on Cu and Co surfaces were experimentally investigated, and the experimental results were theoretically explained through computational calculations. The characteristics of the Cu/Co-BTA complex layer on Cu and Co surfaces were analyzed using sequential EIS, AFM, and contact angle measurements. A Cu/Co-BTA complex layer was formed when the Cu and Co surfaces were exposed to the BTA solution. After a de-ionized (DI) water rinse, the Cu-BTA complex on the Cu surface remained a stable film, whereas the Co-BTA complex layer on the Co surface was removed. Computational calculations provided BTA binding energies, d-band center, and electron charge transfer between BTA and metal surfaces. The BTA binding energy and electron charge transfer to the Co(001) surface were lower than that of Cu(111), which supports the removal of the Co-BTA complex by a DI water rinse in the experimental results.

Fe-substituted silica via lattice dissolution–reprecipitation replacement for tungsten chemical mechanical planarization

Chemical mechanical planarization (CMP) is indispensable for processing of integrated circuit semiconductor devices to attain globally planarized surfaces. One of the critical consumables in the CMP process is a slurry containing abrasives like colloidal silica (SiO2). However, there is a limit to the use of CMP slurries containing SiO2 under acidic conditions due to deterioration of colloidal stability, resulting in defects on the planarized surfaces. Herein, we developed an Fe-substituted SiO2 consisting of single-atom Fe(III), enabling improved colloidal stability over universal pH regions for low-defect tungsten CMP applications. The facile and unique single-atom modification process is proposed by controlling the lattice dissolution–reprecipitation replacement of Fe3+ and Si4+ ions. The physicochemical states of Fe atoms in the surficial lattice of Fe-substituted SiO2 were confirmed through Raman spectroscopy, electron microscopy, x-ray absorption spectroscopy, and energy-dispersive x-ray spectroscopy. Consequently, enhanced performance in W CMP was achieved using Fe-substituted SiO2. Regarding defect performance, defects were reduced from 11 scratches to 0 and 94 other defects to only 7. Additionally, the removal rate increased from 67 to 122 Å/min, and the surface topography improved from 6.6 to 2.9 nm.

Surface Transformation of Spin-on-Carbon Film via Forming Carbon Iron Complex for Remarkably Enhanced Polishing Rate.

To scale down semiconductor devices to a size less than the design rule of 10 nm, lithography using a carbon polymer hard-mask was applied, e.g., spin-on-carbon (SOC) film. Spin coating of the SOC film produces a high surface topography induced by pattern density, requiring chemical–mechanical planarization (CMP) for removing such high surface topography. To achieve a relatively high polishing rate of the SOC film surface, the CMP principally requires a carbon–carbon (C-C) bond breakage on the SOC film surface. A new design of CMP slurry evidently accomplished C-C bond breakage via transformation from a hard surface with strong C-C covalent bonds into a soft surface with a metal carbon complex (i.e., C=Fe=C bonds) during CMP, resulting in a remarkable increase in the rate of the SOC film surface transformation with an increase in ferric catalyst concentration. However, this surface transformation on the SOC film surface resulted in a noticeable increase in the absorption degree (i.e., hydrophilicity) of the SOC film CMP slurry on the polished SOC film surface during CMP. The polishing rate of the SOC film surface decreased notably with increasing ferric catalyst concentration. Therefore, the maximum polishing rate of the SOC film surface (i.e., 272.3 nm/min) could be achieved with a specific ferric catalyst concentration (0.05 wt%), which was around seven times higher than the me-chanical-only CMP.

Application of an Electrospray Scanning Mobility Particle Sizer to Mixed Abrasive Slurry for Chemical Mechanical Planarization

Application of an Electrospray Scanning Mobility Particle Sizer to Mixed Abrasive Slurry for Chemical Mechanical Planarization

Urea as a complexing agent for selective removal of Ta and Cu in sodium carbonate based alumina chemical–mechanical planarization slurry

This work reports urea as a promising complexing agent in sodium carbonate-based alumina slurry for chemical?mechanical planarization (CMP) of tantalum and copper. Ta and Cu were polished using Na2CO3 (1 wt. %) with alumina (2 wt. %) in the presence and absence of urea. The effect of slurry pH, urea concentration, applied downward pressure and platen rotational speed were deliberated and the outcomes conveyed. Prior to the addition of urea, the Ta removal rate (RR) was observed to increase with pH from acidic to alkaline, having a maximum RR at pH 11. However, Cu RR decreases with increasing pH with minimum RR at pH 11. With the addition of urea in the slurry, a Cu to Ta removal rate selectivity of nearly 1:1 was encountered at pH 11. The addition of urea simultaneous boosts the Ta RR and suppresses Cu RR at pH 11, as it adsorbs on the metal surface. Potentiodynamic polarization was conducted to determine the corrosion current (Icorr) and the corrosion potential (Ecorr). Electrochemical impedance spectroscopy of both metals was carried out in the proposed formulation and the obtained outcomes are elaborated.

Entegris will acquire CMC in $6.5 billion deal

Entegris has struck a deal to acquire CMC Materials in a transaction valued at about $6.5 billion. CMC, which until last year was known as Cabot Microelectronics, is the world’s leading producer of chemical mechanical planarization (CMP) slurries, used to smooth the surfaces of circuit-laden silicon wafers between semiconductor chip fabrication steps. It has annual sales of about $1.2 billion. Entegris has annual sales of about $2.1 billion of both equipment and chemicals used in chip production. In announcing the deal, Entegris CEO Bertrand Loy said the combination will create “the industry’s most comprehensive and innovative end-to-end electronic materials offering.” Mike Corbett, a managing partner at the electronic materials consulting firm Linx Consulting, says the purchase will make Entegris a top-five player, by sales, in materials and gases for semiconductor wafer fabrication, along with Linde, Air Liquide, DuPont, and Merck KGaA. Moreover, Corbett says, Entegris’s materials portfolio will be both

Effects of aging time in hydrogen peroxide-glycine-based Cu CMP slurry

Hydrogen peroxide is widely used as an oxidizer in metal chemical mechanical planarization (CMP) slurry due to its strong oxidizing ability and being a non-metal product. However, hydrogen peroxide is unstable and easily decomposes into water and oxygen molecules. In this experiment, the aging of a hydrogen peroxide-glycine-based Cu CMP slurry was investigated in terms of the chemical concentration and CMP performance. Ultraviolet–visible–near-infrared spectroscopy was used to measure the change of hydrogen peroxide concentration with slurry aging. As the slurry aging time was increased, the removal rate decreased for several reasons. With slurry aging, not only decreases of hydrogen peroxide concentration but also decreases of pH and glycine decomposition were observed. Therefore, the removal rate was suppressed due to complex factors, including the decreased oxidizing ability with decreased hydrogen peroxide concentration, decomposition of the glycine chelating agent, and decrease in pH. This study suggests the necessity of monitoring slurry aging and management for optimizing CMP process performance.

Scavenger with Protonated Phosphite Ions for Incredible Nanoscale ZrO2-Abrasive Dispersant Stability Enhancement and Related Tungsten-Film Surface Chemical-Mechanical Planarization.

For scaling-down advanced nanoscale semiconductor devices, tungsten (W)-film surface chemical mechanical planarization (CMP) has rapidly evolved to increase the W-film surface polishing rate via Fenton-reaction acceleration and enhance nanoscale-abrasive (i.e., ZrO2) dispersant stability in the CMP slurry by adding a scavenger to suppress the Fenton reaction. To enhance the ZrO2 abrasive dispersant stability, a scavenger with protonate-phosphite ions was designed to suppress the time-dependent Fenton reaction. The ZrO2 abrasive dispersant stability (i.e., lower H2O2 decomposition rate and longer H2O2 pot lifetime) linearly and significantly increased with scavenger concentration. However, the corrosion magnitude on the W-film surface during CMP increased significantly with scavenger concentration. By adding a scavenger to the CMP slurry, the radical amount reduction via Fenton-reaction suppression in the CMP slurry and the corrosion enhancement on the W-film surface during CMP performed that the W-film surface polishing rate decreased linearly and notably with increasing scavenger concentration via a chemical-dominant CMP mechanism. Otherwise, the SiO2-film surface polishing rate peaked at a specific scavenger concentration via a chemical and mechanical-dominant CMP mechanism. The addition of a corrosion inhibitor with a protonate-amine functional group to the W-film surface CMP slurry completely suppressed the corrosion generation on the W-film surface during CMP without a decrease in the W- and SiO2-film surface polishing rate.

Fenton Reaction for Enhancing Polishing Rate and Protonated Amine Functional Group Polymer for Inhibiting Corrosion in Ge1Sb4Te5 Film Surface Chemical-Mechanical-Planarization

A Fenton reaction and a corrosion inhibition strategy were designed for enhancing the polishing rate and achieving a corrosion-free Ge1Sb4Te5 film surface during chemical-mechanical planarization (CMP) of three-dimensional (3D) cross-point phase-change random-access memory (PCRAM) cells and 3D cross-point synaptic arrays. The Fenton reaction was conducted with 1,3-propylenediamine tetraacetic acid, ferric ammonium salt (PDTA–Fe) and H2O2. The chemical oxidation degree of GeO2, Sb2O3, and TeO2 evidently increased with the PDTA–Fe concentration in the CMP slurry, such that the polishing rate of the Ge1Sb4Te5 film surface linearly increased with the PDTA–Fe concentration. The addition of a corrosion inhibitor having protonated amine functional groups in the CMP slurry remarkably suppressed the corrosion degree of the Ge1Sb4Te5 film surface after CMP; i.e., the corrosion current of the Ge1Sb4Te5 film surface linearly decreased as the corrosion inhibitor concentration increased. Thus, the proposed Fenton reaction and corrosion inhibitor in the Ge1Sb4Te5 film surface CMP slurry could achieve an almost recess-free Ge1Sb4Te5 film surface of the confined-PCRAM cells, having an aspect ratio of 60-nm-height to 4-nm-diameter after CMP.